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International audience; New titanium complexes of general formula [Ti(OR)2(OiPr)2], containing functionalized alkoxido ligands, were developed for the selective catalytic dimerization of ethylene to 1-butene using a combined High Throughput Screening (HTS) / Design of Experiment (DoE) approach. First, a library of 19 ligands was elaborated and a primary screening spotted the phosphorus-functionalized alkoxido ligands as most promising. A second, more focused library containing 8 alkoxidophosphane ligands was then developed. A longer linear spacer between the alkoxido and the phosphorus functions, as in [Ti(19)2(OiPr)2], was found beneficial for this catalytic reaction. After identification of the best co-catalyst (AlEt3) and co-ligand (OnBu), final optimization of the reaction conditions was performed using a design of experiments (DoE) approach. The complex [Ti(19)2(OnBu)2] was shown to selectively dimerize ethylene in 1-butene (C4(α)=93 % (99+%)) at 30 bar C2H4 and 55 °C with AlEt3 as co-catalyst, resulting in very high activity and selectivity for a molecular titanium catalyst (13000 g gTi−1 h−1, 93 % 1-butene).

In order to examine the possibility to promote cooperative effects on catalytic activity and selectivity in ethylene dimerization through ligand design, the bisphosphino-iminato ligands syn-L and a...

Metal-organic frameworks (MOFs) with controllable shapes and sizes show a great potential in Li-S batteries. However, neither the relationship between shapes and specific capacity nor the influence of MOF particle size on cyclic stability have been fully established yet. Herein, MIL-96-Al with various shapes, forming hexagonal platelet crystals (HPC), hexagonal bipyramidal crystals (HBC), and hexagonal prismatic bipyramidal crystals (HPBC) were successfully prepared via co-solvent methods. Density functional theory (DFT) calculations demonstrate that the HBC shape with highly exposed (101) planes can effectively adsorb lithium polysulfides (LPS) during the charge/discharge process. By changing the relative proportion of the co-solvents, HBC samples with different particle sizes were prepared. When these MIL-96-Al crystals were used as sulfur host materials, it was found that those with the smaller size of HBC shape deliver the higher initial capacity. These investigations establish that different crystal planes have different adsorption abilities for LPS, and that the MOF particle size should be considered for a suitable sulfur host. More broadly, this work provides a strategy for designing sulfur hosts in Li-S batteries. This article is protected by copyright. All rights reserved.

In combination with methyllithium, a 2,6-bis(amino)phenol zinc complex 1 was used in the ring-opening polymerization of δ-valerolactone in the absence or presence of benzyl alcohol and showed high efficiency, mainly producing cyclic and linear polyvalerolactones, respectively. On the basis of homopolymerization, the ring-opening copolymerization of e-caprolactone and δ-valerolactone was investigated. The P(CL-co-VL) random copolymers, PCL-b-PVL and PVL-b-PCL diblock copolymers, were prepared by varying the feeding strategy (premixing or sequential feeding). The copolymer composition was adjusted by varying the feeding ratio of two monomers. The structure and thermal properties of obtained polymers were characterized by GPC, 1H-NMR, 13C-NMR, MALDI-TOF mass spectroscopy, and DSC, respectively.

Potentially bidentate ditopic ligands containing a N-heterocyclic carbene (NHC) donor associated with an ether or an amine have been prepared and coordinated to NiII centers. The influence of the length of the alkyl chain, –(CH2)2– or –(CH2)3– connecting the ether or the amine group to the heterocycle was examined. In the analogous AgI complexes [Ag{Im(Dipp)(C3OMe)-κ1CNHC}2]Cl (8), 9 and 10, in the neutral NiII complexes with a C3 spacer trans-[NiCl2{Im(Dipp)(C3OMe)-κ1CNHC}2] (5a), 6, and 7, and in the cationic cis-[Ni{Im(Dipp)(C3OMe)-κ1CNHC}2(NCMe)2](PF6)2 (15) and cis-[Ni{Im(Mes)(C3OMe)-κ1CNHC}2(NCMe)2](PF6)2 (16), the ligand is monodentate. [(ImH)(Dipp)(C3OMe)][NiX3{Im(Dipp)(C3OMe)-κ1CNHC}] (14a, X = Cl) and (14b, X = Br) are rare examples of complexes of the type [NiX3(NHC)]–. For comparison, [NiBr2{(Im)(Dipp)(C2NMe2)-κ2,CNHC,Namine}] (24) and [NiBr2{(Im)(Dipp)(C3NMe2)-κ2,CNHC,Namine}] (25) contain a six- or a seven-membered κ2CNHC,Namine chelate, respectively. Various NiII complexes were evaluated as precatalysts for ethylene oligomerization. The structures of the carbene (Dipp)(C3OMe)imidazole-ylidene (4) and of the complexes 5a, 7, 8, [(ImH)(Dipp)(C3OMe)]2[NiCl4] (11a), [(ImH)(Dipp)(C3OMe)]2[NiBr4] (11b), [(ImH)(Me)(C3OMe)]2[NiCl4] (13), 14b, 16·NCMe, [Im(H){C(Me)(=NDipp)}(C3OMe)]2 [NiCl4] (18), [AgCl{Im[C(Me)=NDipp](C3OMe)}-κ1CNHC] (19), [AgCl{Im(Dipp)(C3NMe2)-κ1CNHC}] (23), 24, 25 and trans-[NiCl2{Im(Dipp){CH2CH2C(O)OEt}}2] were analyzed by X-ray diffraction

International audience; Metallotropism of the M[N(SiMe3)2]2 metal fragment in the tautomeric system IAR⇌ACR involving imidazolium salts/N‐heterocyclic carbenes with remote aminide/amine substituents, respectively, is manifested by its CNHC carbophilicity (R=tBu, M=Co, Fe) or NRaminido nitrogenophilicity (R=Cy, M=Co, Fe; R=Mes, M=Fe) and has been rationalized on the basis of steric and electronic effects. The thermolysis products of the [M{N(SiMe3)2}2]/ IAR⇌ACR system are also substituent‐dependent, leading to a rearranged aminide‐functionalized aNHC Co2 complex of an unprecedented type or to ring‐opened metallaketenimines; they are postulated to originate from different metalloisomers. The results are interpreted on the basis of the X‐ray diffraction analysis of 11 new compounds.

Tritopic NCNHC N' ligands containing a central N-heterocyclic carbene (NHC) donor flanked by two chemically-different nitrogen donors (Nimine and Namine ) were evaluated as potential tridentate pincer-type ligands in NiII complexes. The imidazolium chloride [(ImH){C(Me)=NDipp}(C2 NMe2 )]Cl (1) and the ammonium-imidazolium dichlorides [(ImH){C(Me)=NDipp}(C2 NHMe2 )]Cl2 (4) and [(ImH){C(Me)=NDipp}(C3 NHMe2 )]Cl2 (5), differing by the length (C2 or C3 ) of the alkyl spacer were used as precursors. Oxidative addition of 1 to [Ni(cod)2 ] afforded the dinuclear bis-NHC NiII complex [Ni2 Cl2 {μ-C(Me)=NDipp-κ2 Nimine ,C}{μ-Im(C2 NMe2 )-κ3 Namine ,CNHC ,Nimid }{Im[C(Me)=NDipp](C2 NMe2 )-κ1 CNHC }] (2) resulting from partial ligand rearrangement. A dinuclear byproduct 3 was also isolated. The salt [NiCl{Im[C(Me)=NDipp](C2 NMe2 )-κ3 Nimine ,CNHC ,Namine }]2 [NiCl4 ] (6) containing two Nimine CNHC Namine pincer NiII complex cations was obtained from 4. In contrast, the reaction of closely related 5 yielded [NiCl{Im[C(Me)=NDipp](C3 NMe2 )-κ2 Nimine ,CNHC }{μ-Im[C(Me)=NDipp](C3 NMe2 NiCl3 }-κ2 Namine ,CNHC }] (7 a), a dinickel(II) complex that contains a Nimine ,CNHC -chelating and a bridging κ2 Namine ,CNHC ligand. The molecular structures of 2, 3, 6, 7 a⋅THF, 7 b, an isomer of 7 a, and 8⋅CH2 Cl2 have been determined by single-crystal X-ray diffraction. Our results emphasize the often-underestimated importance of seemingly minor changes in the length of the spacers connecting a NHC donor group to its N-bound lateral functionalities.

Selective copper(I) to palladium(0) transmetallation of P-donors from the rigid N,N'-diphosphanyl-imidazol-2-ylidene C3 H2 [NP(tBu)2 ]2 (PCNHC P) was observed when known [Cu3 (μ3 -PCNHC P,κP,κCNHC ,κP)2 ](OTf)3 was reacted with [Pd(PPh3 )4 ]. When 1.2 equivalents of [Pd(PPh3 )4 ] was used, the product [Cu2 Pd(μ3 -PCNHC P,κP,κCNHC ,κP)2 ](OTf)2 (2(OTf)2 ) was obtained, which features a CuI -CuI -Pd0 chain and appears to be the first linear heterotrinuclear complex with d10 -d10 interactions between Pd0 and CuI . When the Cu3 precursor was reacted with 3.0 equivalents of [Pd(PPh3 )4 ], the complex [CuPd2 (μ3 -PCNHC P,κP,κCNHC ,κP)2 ](OTf)2 (3(OTf)2 ) was obtained, which, on the basis of magnetic measurements, DFT calculations, and computed nuclear shieldings, was formulated as containing a Pd0 -CuI -Pd0 chain with an electron hole delocalized over the whole cation, including the metal chain. Similarly, selective transmetallation of the P-donors in [Ag3 (μ3 -PCNHC P,κP,κCNHC ,κP)2 ](OTf)3 from silver to palladium (originating from [Pd(PPh3 )4 ]) gave the linear chain [Ag2 Pd(μ3 -PCNHC P,κP,κCNHC ,κP)2 ](OTf)2 (5(OTf)2 ), which on the basis of NMR spectroscopy comprises an AgI -AgI -Pd0 metal core. However, X-ray diffraction data collected on various samples of 5(OTf)2 were modeled with 50:50 metal disorder at the terminal positions, corresponding to a (AgI /Pd0 )-AgI -(AgI /Pd0 ) formulation. Upon standing in solution, 5(OTf)2 transformed to 6(OTf)2 , the regioisomer of 5(OTf)2 in which the Pd center has migrated to the central position of an AgI -Pd0 -AgI chain. Prolonged standing in CH2 Cl2 or by reaction with [PtCl2 (NCMe)2 ] converts complex 6(OTf)2 to the AgI /PdII complex [Ag2 PdCl2 (μ3 -PCNHC P,κP,κCNHC ,κP)2 ](OTf)2 (7(OTf)2 ). The structural data of 2(OTf)2 , 3(OTf)2 , and 7(OTf)2 establish significant heterometallophilic interactions.

The imidazolium chloride [C3H3N(C3H6NMe2)N{C(Me)(=NDipp)}]Cl (1; Dipp=2,6-diisopropyl phenyl), a potential precursor to a tritopic NimineCNHCNamine pincer-type ligand, reacted with [Ni(cod)2] to give the NiI-NiI complex 2, which contains a rare cod-derived η3-allyl-type bridging ligand. The implied intermediate formation of a nickel hydride through oxidative addition of the imidazolium C−H bond did not occur with the symmetrical imidazolium chloride [C3H3N2{C(Me)(=NDipp)}2]Cl (3). Instead, a Ni−C(sp3) bond was formed, leading to the neutral NimineCHNimine pincer-type complex Ni[C3H3N2{C(Me)(=NDipp)}2]Cl (4). Theoretical studies showed that this highly unusual feature in nickel NHC chemistry is due to steric constraints induced by the N substituents, which prevent Ni−H bond formation. Remarkably, ethylene inserted into the C(sp3)−H bond of 4 without nickel hydride formation, thus suggesting new pathways for the alkylation of non-activated C−H bonds.

The development of bifunctional non-noble metal electrocatalysts demonstrating high activity and stability for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is of great significance for renewable and clean energy. In this work, we report hierarchically structured integrated Fe-MoS2/Ni3S2/NF (NF = nickel foam) materials prepared by a facile in situ solvothermal method, and among them, the Fe-doped MoS2 was assembled into spine-like nanorods. The optimized electrocatalyst (denoted as Fe-MoS2/Ni3S2/NF-2) demonstrated excellent activity and durability for performing the HER and OER in an alkaline electrolyte (pH = 14) with low overpotentials of 130.6 mV and 256 mV (vs. RHE) at a current density of 10 mA cm-2, as well as no significant loss in catalytic performance even after 2000 cyclic voltammetry (CV) cycles. An outstanding durability of 180 h could be achieved for OER. The overall water splitting made up of the two-electrode system with Fe-MoS2/Ni3S2/NF-2 as both the anode and the cathode required a voltage of only 1.61 V to drive a current density of 10 mA cm-2 along with an outstanding long-term stability of 20 h, displaying its great potential for application in water splitting. The effective construction of multi-component synergistic structures shows a good pathway for high-performance electrocatalysis and energy storage.

The emergence of N-heterocyclic carbenes as ligands across the Periodic Table had an impact on various aspects of the coordination, organometallic, and catalytic chemistry of the 3d metals, including Cu, Ni, and Co, both from the fundamental viewpoint but also in applications, including catalysis, photophysics, bioorganometallic chemistry, materials, etc. In this review, the emergence, development, and state of the art in these three areas are described in detail.

Tridentate 2,6-bis(imino)phenol (L1−L4) and 2,6-bis(amino)phenol (L5−L8) ligands and their corresponding zinc chloride complexes (1–8) have been synthesized and well characterized by FT-IR, 1H and 13C NMR, elemental analysis and single-crystal X-ray diffraction analysis. It was found that zinc complexes (1–4) with 2,6-bis(imino)phenol ligands were inactive for the ring-opening polymerization (ROP) of e-caprolactone (e-CL) even if they were activated by methyllithium. Zinc complexes (5–8) with 2,6-bis(amino)phenol ligands were proved to be highly efficient initiators for the ROP of e-CL in combination with 4 equiv. of methyllithium. The ROP of e-CL in the absence or presence of benzyl alcohol, including the influence of monomer ratio, reaction temperature and the substituents in the ligands, were investigated. The structure and thermal properties of obtained polymers were analyzed by NMR and MALDI-TOF mass spectra, DSC and TGA, respectively.

A comparative study of the reactivity of the carbonylmetalates {m}− = [MoCp(CO)3]− (Cp = η5-C5H5) and [Mo(η5-C5H4NMe2)(CO)3]− toward d10 complexes of the group 11 metals, [Cu(NCMe)4](BF4), AgBF4 and [N(n-Bu)4][AuBr2], has allowed the characterization of new heterometallic hexa- and octanuclear clusters with the same general formula [M{m}]n (M = Cu, Ag, Au). In these cyclic oligomers, the value of n depends of the coinage metal. Thus, the hexanuclear cluster [Cu3{Mo(η5-C5H4NMe2)(CO)3}3] (17) has a planar metal core, formed by a copper triangle with edge-bridging molybdenum atoms. The octanuclear “star shape” clusters [Ag4{Mo(η5-C5H4NMe2)(CO)3}4] (19) and [Au4{Mo(η5-C5H4NMe2)(CO)3}4] (21) contain a square silver or gold core, respectively, edge-bridged by molybdenum atoms. In these three clusters, the 2-D raft-type structure of their metal core, which is ν2-triangular for Cu3Mo3 and of a square-in-a-square-type for the octanuclear Ag4Mo4 and Au4Mo4 clusters, allows for d10–d10 metallophilic interactions. Th...

Monodeprotonation of the 2,6-bis(di-tert-butylphosphinomethyl) pyridine (tBuPNtBuP) at the α-lutidinyl-CH2 position with 1 equiv of KCH2C6H5 and concomitant dearomatization of the heterocycle afforded K(tBuP*NatBuP) (tBuP*= di-tert-butyl vinylic P donor, tBuP = PtBu2, Na = anionic amido N donor); its transmetalation with [CrCl2(THF)2] afforded the CrII complex [Cr(tBuP*NatBuP)Cl] (A). The X-ray diffraction analysis of A established a slightly distorted square-planar coordination geometry at the metal center and confirmed retention of the dearomatized coordinated ligand. The catalytic activity of A in ethylene oligomerization was studied and compared with that of the related CrII complexes [Cr(tBuP*NaCNHC)Cl] (B) and [Cr{Cr(tBuP*NatBuP*)Cl}2] (C) previously reported [Chem. Commun., 2015, 51, 10699 and Dalton Trans., 2016, 45, 2800, respectively].

The reaction of 2,6-bis(di-tert-butylphosphinomethyl)pyridine (tBuPNtBuP) with 1 molar equiv of KCH2C6H5 or LiCH2SiMe3 gave M(tBuP*NatBuP) (M = K, Li; P* = vinylic P donor, tBuP = PtBu2, Na = anionic amido N donor) after monodeprotonation of the α-lutidinyl-CH2 and concomitant dearomatization of the heterocycle. Evidence is provided that the anion tBuP*NatBuP may exist as Z- and E-isomers, interconvertible by rotation about the Cα-N–Cα-P exocyclic formal double bond. Thus, the two isomers of K(tBuP*NatBuP), i.e., [K{(Z)-(tBuP*NatBuP-κP*,κNa,κP)}(THF)], 1-Z·(THF), and [K{(E)-(tBuP*NatBuP-κNa,κP)}(THF)], 1-E·(THF), cocrystallized from THF in a 4:1 ratio. However, in the presence of DME, the isomerically pure [K{(E)-(tBuP*NatBuP-κNa,κP)}(DME)2], 1-E·2(DME), was crystallized. The α-picolinyl-CH2 moiety in RPNCNHC (N = substituted 2-picoline, RP = PCy2, R = Cy; RP = PtBu2, R = tBu; CNHC = N-heterocyclic carbene) was similarly deprotonated with concomitant dearomatization using LiN(SiMe3)2. This afforded the co...

The influence of the potentially chelating imino group of imine-functionalized Ir and Rh imidazole complexes on the formation of functionalized protic N-heterocyclic carbene (pNHC) complexes by tautomerization/metallotropism sequences was investigated. Chloride abstraction in [Ir(cod)Cl{C3 H3N2 (DippN=CMe)-κN3}] (1 a) (cod=1,5-cyclooctadiene, Dipp=2,6-diisopropylphenyl) with TlPF6 gave [Ir(cod){C3 H3N2 (DippN=CMe)-κ(2) (C2,Nimine )}](+) [PF6 ](-) (3 a(+) [PF6 ](-)). Plausible mechanisms for the tautomerization of complex 1 a to 3 a(+) [PF6 ](-) involving C2-H bond activation either in 1 a or in [Ir(cod){C3 H3 N2 (DippN=CMe)-κN3}2](+) [PF6 ](-) (6 a(+) [PF6 ](-)) were postulated. Addition of PR3 to complex 3 a(+) [PF6 ](-) afforded the eighteen-valence-electron complexes [Ir(cod)(PR3){C3 H3N2 (DippN=CMe)-κ(2) (C2,Nimine )}](+) [PF6 ](-) (7 a(+) [PF6 ](-) (R=Ph) and 7 b(+) [PF6 ](-) (R=Me)). In contrast to Ir, chloride abstraction from [Rh(cod)Cl{C3H3N2 (DippN=CMe)-κN3}] (1 b) at room temperature afforded [Rh(cod){C3 H3N2 (DippN=CMe)-κN3}2](+) [PF6 ](-) (6 b(+) [PF6 ](-)) and [Rh(cod){C3 H3N2 (DippN=CMe)-κ(2) (C2,Nimine )}](+) [PF6 ](-) (3 b(+) [PF6 ](-) ) (minor); the reaction yielded exclusively the latter product in toluene at 110 °C. Double metallation of the azole ring (at both the C2 and the N3 atom) was also achieved: [Ir2 (cod)2 Cl{μ-C3H2N2 (DippN=CMe)-κ(2) (C2,Nimine ),κN3}] (10) and the heterodinuclear complex [IrRh(cod)2 Cl{μ-C3H2N2 (DippN=CMe)-κ(2) (C2,Nimine ),κN3}] (12) were fully characterized. The structures of complexes 1 b, 3 b(+) [PF6 ](-) , 6 a(+) [PF6 ](-) , 7 a(+) [PF6 ](-), [Ir(cod){C3HN2 (DippN=CMe)(DippN=CH)(Me)-κ(2) (N3,Nimine )}](+) [PF6 ](-) (9(+) [PF6 ](-)), 10⋅ Et2 O⋅toluene, [Ir2 (CO)4 Cl{μ-C3H2N2 (DippN=CMe)-κ(2) (C2,Nimine ),κN3}] (11), and 12⋅2 THF were determined by X-ray diffraction.

Substituted benzodiazepines of the general formula 2,2′-di(R)-5,6,6′,7′,8,13-hexahydro-5′H-spiro-benzo[2,3][1,4]diazepino[6,5-h]quinoline-7,8′-quinoline [R = H (L1), Me (L2), and Cl (L3)] were synthesized by the condensation reactions between 1,2-phenylenediamine and (2R)-5,6,7-trihydroquin-8-ones. Treatment of these compounds with two equivalents of C2H5MgBr or AlMe3 afforded the corresponding yellow magnesium complexes [R = H (C1) and Me (C2)], and the red aluminum complexes [R = H (C3), Me (C4) and Cl (C5)], respectively. The molecular structures of L1 and L3 and of complexes C1, C3 and C4 were determined by the single crystal X-ray diffraction study. L1 and L3 contain two 2R-substituted-5,6,7-trihydroquin-8-one groups fused with benzodiazepine through one-carbon or two-carbon atoms, respectively. The magnesium complex C1 displays a dinuclear bromomagnesium bridged by the ligand as the “pas de deux” arrangement, while aluminum complexes (C3 and C4) show bis(dimethylaluminum)benzodiazepines. In the presence of BnOH, the magnesium complexes showed efficient activities toward the ring-opening polymerization (ROP) of e-caprolactone (e-CL) with TOF up to 8100 h−1 at 60 °C; while the aluminum complexes also initiated high conversion of e-CL by ROP. Introduction to the international collaboration The international collaboration between Professor Wen-Hua Sun at the Institute of Chemistry, Chinese Academy of Sciences (CAS), China, and Professor Pierre Braunstein at the Institute of Chemistry (UMR 7177 CNRS), University of Strasbourg, France, started in 2005 through the sharing of common scientific interests in the development of transition metal complexes as homogeneous catalysts. Prof. Sun was first a Visiting Professor at the University of Strasbourg in 2005, and Prof. Braunstein visited the Institute of Chemistry (CAS) giving a Molecular Science Forum Lecture in 2006. Supported by the Scientific Exchange Programme of the French Embassy in Beijing, Chinese graduate students from Sun's group moved into Braunstein's group as bilateral PhD candidates from 2007 to 2011. A PhD student from Sun's group also came to Strasbourg as a post-doctoral fellow. Furthermore, Profs. Sun and Braunstein successfully organized the “Sino-Franco-German Trilateral Symposium on Homogeneous Catalysis” in October 2007 in Beijing and in October 2010, the Symposium “Future of sciences, sciences for the future: Chemistry and its interfaces with biology and physics” was organized in Paris under the auspices of the CAS, French Academy of Sciences and German National Academy of Sciences Leopoldina. On this occasion, a special issue of C. R. Chim. was published (2011, issue 9). International exchanges and mutual visits are actively maintained between the two groups and Prof. Braunstein recently spent one month in China (mainly Beijing). Overall, Braunstein has supervised 16 Chinese PhD students and post-docs.

The stepwise reaction of a zwitterionic ligand, 4-methylamino-6-methyliminio-3-oxocyclohexa-1,4-dien-1-olate (QH2) with [Pt2(μ-Cl)2(ppy)2] (Hppy = 2-phenylpyridine) afforded a mononuclear complex, [Pt(ppy)(QH)] (1), and a dinuclear complex, [{Pt(ppy)}2(μ-Q)] (2). Using [Pd2(μ-Cl)2(ppy)2] in the second step resulted in the formation of a heterodinuclear complex, [{Pt(ppy)}(μ-Q){Pd(ppy)}] (3), which is the first heterodinuclear complex bridged by a quinonoid ligand. Single crystal X-ray diffraction analysis revealed that all three complexes adopted double-decker structures in the crystal. For 1, intermolecular N–H⋯O interactions between uncoordinated N–H and O groups in two adjacent square-planar mononuclear units led to the formation of hydrogen-bonded dimers, which stacked to form a herringbone structure with a double-decker tetranuclear motif. For 2 and 3, dinuclear units bridged by Q2− formed a double-decker motif similar to that of 1, but a tetranuclear chain in the herringbone pattern was characteristic of the dinuclear complexes. Pt⋯Pt (or Pt⋯Pd) distances were more than 3.5 A, twice the van der Waals radii of Pt, suggesting weak electronic metal–metal interactions in the crystal structures. Thus, the different colours observed (brown, purple, and dark green for 1, 2, and 3, respectively) mainly originated from the molecular structures. In fact, the three complexes exhibited colourful solutions of yellow, red, and green. UV-vis absorption spectroscopy and time-dependent density-functional theory (TD-DFT) calculations revealed that colour variations occurred depending on the electronic states composed of metal ions and the quinonoid ligand.

The controlled and intact deposition of molecules with specific properties onto surfaces is an emergent field impacting a wide range of applications including catalysis, molecular electronics, and quantum information processing. One strategy is to introduce grafting groups functionalized to anchor to a specific surface. While thiols and disulfides have proven to be quite effective in combination with gold surfaces, other S-containing groups have received much less attention. Here, we investigate the surface anchoring and organizing capabilities of novel charge-neutral heterocyclic thioether groups as ligands of polynuclear nickel(II) complexes. We report on the deposition of a cubane-type {Ni4} (= [Ni(μ3-Cl)Cl(HL·S)]4) single-molecule magnet from dichloromethane solution on a Au(111) surface, investigated by scanning tunneling microscopy, X-ray photoelectron spectroscopy, and low-energy electron diffraction, both immediately after deposition and after subsequent post-annealing. The results provide strong evidence for partial decomposition of the coordination complex upon deposition on the Au(111) surface that, however, leaves the magnetic {Ni4Cl4n} (n = 1 or 2) core intact. Only post-annealing above 480 K induces further decomposition and fragmentation of the {Ni4Cl4n} core. The detailed insight into the chemisorption-induced decomposition pathway not only provides guidelines for the deposition of thioether-functionalized Ni(II) complexes on metallic surfaces but also reveals opportunities to use multidentate organic ligands decorated with thioether groups as transporters for highly unstable inorganic structures onto conducting surfaces, where they are stabilized retaining appealing electronic and magnetic properties.

The chromium(II) complexes [CrCl2(t-BuNHC,P-κC)2] (1), [CrCl2(MesNHC,P-κC)2] (2), [CrCl2(DippNHC,P-κC)2] (3), and [CrCl2(P,NHC,P-κC)2] (4) containing the N-phosphanyl- or N,N′-diphosphanyl-substituted N-heterocyclic carbene (NHC) hybrid ligands t-BuNHC,P (1-(di-tert-butylphosphino)-3-tert-butylimidazol-2-ylidene), MesNHC,P (1-(di-tert-butylphosphino)-3-mesitylimidazol-2-ylidene), DippNHC,P (1-(di-tert-butylphosphino)-3-(2,6-diisopropylphenyl)imidazol-2-ylidene), and P,NHC,P (1,3-bis(di-tert-butylphosphino)imidazol-2-ylidene), respectively, were prepared from CrII ([CrCl2(thf)2]) or CrIII ([CrCl3(thf)3] or [Cr(Me)Cl2(thf)3]) precursors. The solid-state structures of these four complexes show square-planar CrII centers, with two trans chloride and two monodentate CNHC donors. Alkylation of 3 and 4 with [Mg(benzyl)2(thf)2] led to the formation of the σ complexes [Cr(benzyl)3(DippNHC,P-κC,κP)] (5) and [Cr(benzyl)3(P,NHC,P-κC,κP)] (6), respectively, with five-coordinate distorted-square-pyramidal CrIII coordin...

The reaction of [Ir(cod)(μ-Cl)]2 (cod = 1,5-cyclooctadiene) with 2 equiv of the ketophosphine Ph2PCH2C(O)Ph in the presence of TlPF6 afforded the hydrido, phosphino-enolate Ir(III) complex [IrH(cod){Ph2PCH ··· C( ··· O)Ph,κP,κO}{Ph2PCH2C(O)Ph,κP}]PF6 (4), which results from the room temperature activation of a C–H bond from the PCH2 moiety. The distorted octahedral coordination environment around the metal centre in 4 contains the cod ligand, the P atom of the monodentate ketophosphine and the P,O donor atoms of a chelating phosphino-enolate ligand acting as a 3-electron donor. The hydride ligand was located on the difference Fourier map obtained by single-crystal X-ray diffraction studies and is trans to the enolate oxygen and cis to the two, mutually cis P atoms. The reaction of this complex with NaH in THF led to the isolation of the Ir(I) complex [Ir(cod){Ph2PCH ··· C( ··· O)Ph,κP,κO}{Ph2PCH2C(O)Ph,κP}] (5). The penta-coordination environment around the metal centre in 5 includes the cod ligand, one 3-electron donor P,O chelating phosphino-enolate ligand and a P-bound Ph2PCH2C(O)Ph ligand containing an uncoordinated ketone function. The structures of 4·CH2Cl2 and 5·C7H8 have been determined by X-ray diffraction analysis.

The reactivity of dichloroplatinum(II) complexes containing thioether-functionalized bis(diphenylphosphanyl)amines of formula (Ph2P)2N(CH2)2SR (R = (CH2)5CH3, CH2Ph) toward group 6 carbonylmetalates Na[M(CO)3Cp] (M = Mo or W, Cp = cyclopentadienyl) was explored. Reactions with two or more equivalents of Na[M(CO)3Cp] (M = Mo or W) afforded the trinuclear complexes of general formula [PtPh{M(CO)3Cp}{?-P(Ph)N(CH2CH2SR)(PPh2)-?3P,P,S}M(CO)2Cp] (3 M = Mo, R = (CH2)5CH3; 4 M = Mo, R = CH2Ph; 9 M = W, R = (CH2)5CH3; 10 M = W, R = CH2Ph), the structure of which consists of a six-membered platinacycle condensed with a four-membered M-P-N-P cycle, together with small amounts of isomeric PtM2 clusters [PtM2(CO)5Cp2{(Ph2P)2N(CH2CH2SR)-?2P,P}] (5 M = Mo, R = (CH2)5CH3; 6 M = Mo, R = CH2Ph; 11 M = W, R = (CH2)5CH3; 12 M = W, R = CH2Ph) in which the ligand (Ph2P)2NR solely chelates the Pt atom or bridges an M-Pt bond as in [PtM2(CO)5Cp2{?-(Ph2P)2N(CH2CH2SR)-?2P,P}] (7 M = Mo, R = (CH2)5CH3; 8 M = Mo, R = CH2Ph; 13 M = W, R = (CH2)5CH3; 14 M = W, R = CH2Ph). The synthesis of the trinuclear complexes 3, 4, 9, and 10 entails an unexpected P-phenyl bond cleavage reaction and phenyl migration onto Pt. When only 1 equiv of Na[M(CO)3Cp] (M = Mo or W) was used, the heterodinuclear products of monosubstitution [PtCl{M(CO)3Cp}{Ph2PN(R)PPh2-P,P}] (15 M = Mo, R = (CH2)5CH3; 16 M = Mo, R = CH2Ph; 17 M = W, R = (CH2)5CH3; 18 M = W, R = CH2Ph) were obtained, which are the precursors to the bicyclic products 3, 4, 9, and 10, respectively. Density functional calculations were performed to study the thermodynamics of the formation of all the new complexes, to evaluate the relative stabilities of the isomeric chelated and bridged forms, and to trace the mechanism of formation of the phosphanido-bridged products 3, 4, 9, and 10. It was concluded that Pt(II) complexes containing a thioether-functionalized short-bite ligand, [PtCl2{Ph2PN(R)PPh2}], react with Na[M(CO)3Cp] to yield first heterodinuclear Pt-M and then heterotrinuclear PtM2 complexes resulting from the activation of a P-C bond in one of the PPh2 groups and phenyl migration to Pt. The critical role of an intramolecular thioether group was demonstrated. (Chemical Equation Presented).

In this Account, we discuss diverse aspects of the structural and chemical properties associated with phosphanido-bridged triangular platinum clusters, in particular the 44 valence electron cluster [Pt3(μ-PPh2)3Ph(PPh3)2] (1). Various structural isomers of this cluster have been obtained as a function of the crystallization solvents and X-ray diffraction analyses established that their Pt–Pt separations span a large range of distances, one of them witnessing a record change of 0.56 A, from 3.074(1) to 3.630(1) A, when going from one structural isomer to another. These “closed” and “open” triangular forms of 1 can be readily and reversibly interconverted, simply by changing the crystallization solvents. Their reactions with electrophilic reagents, such as protons and isolobal d10 metal fragments, which led to heterometallic, tetranuclear clusters, as well as with oxidants and silanes are discussed. It was found that the reductive coupling between the phenyl ligand and a phosphanido bridge in 1, which restores a PPh3 ligand in the coordination sphere of the cluster and thus represents the reverse of the transformation of a PPh3 ligand in PPh2 and Ph that occurs upon thermal activation of a Pt(0) precursor containing PPh3 ligands, is promoted by iodine oxidation or by protonation. We also present the structure of the new 44 valence electron mixed-metal palladium–platinum triangular cluster [PdPt2I2(μ2-I)(μ-PPh2)(PPh3)3] (3), which was obtained by oxidative-addition of a PdII–I bond of [PdI2(PPh3)2] at the Pt0 center of [Pt(C2H4)(PPh3)2].

With the aim to favour formation of ‘pincer’-type IrIII complexes containing two NHC donor moieties, we have used a pro-ligand with a bis-CF3-substituted phenylene backbone in order to prevent unwanted backbone cyclometallation. The potential of this new ‘pincer’ pro-ligand, 1,1′-(4,6-bis(trifluoromethyl)-1,3-phenylene)bis(3-butyl-1H-imidazol-3-ium) iodide (3), is demonstrated by the synthesis and structural characterisation of the ‘pincer’ IrIII bis carbene benzenide complex (4).

Transamination of [Co{N(SiMe3)2}2]2 with C6H4(NHSiiPr3)2 gave the centrosymmetric trinuclear [{CoterN(SiMe3)2(μ-η-[o-C6H4(κNSiiPr3)2])}2Coint] (1) (Coter, Coint=terminal, internal Co, respectively), with 3-coordinate Coter, and Coint “sandwiched” between the o-phenylenes of the two ligands; experimental and computational data support CoII centres and ditopic o-amido-imino-cyclohexen-allyl ligands; magnetic studies reveal intermetallic ferromagnetic interactions and single-molecule magnet (SMM) character. One-electron reduction of 1 yielded the salt [K(18-crown-6)(THF)2][{CoterN(SiMe3)2(μ-η-[o-C6H4(κNSiiPr3)2])}2Coint] (4) with the anion isostructural to 1. The centrosymmetric Fe complex [{FeterN(SiMe3)2(μ-η-[o-C6H4(κNSiiPr3)2])}2Feint] (5), analogous to 1, was also obtained.

Since the synthesis of the first arene ruthenium complexes in 1967, various groups have systematically investigated the chemistry of this family of complexes because of their appealing structural diversity, related to the ways in which the arene ligand can be functionalized, their role as versatile stereochemical controlling elements in areas such as catalysis, chemical and photochemical sensing, biology and supramolecular chemistry, and their potential as metalloligands. This review is focused on the recent developments of arene ruthenium complexes towards both supramolecular chemistry and biology. Arene ruthenium complexes can form various supramolecular structures with applications as chemical/photochemical sensors, in medicine and for drug transport inside the cell. Recent developments in the chemistry of arene ruthenium complexes will likely give access to a variety of metal-based drugs/sensors within the next few years.

The synthesis of Pd(II) and Ni(II) alcohol-functionalized N-heterocyclic carbene (NHC) complexes was explored to examine the possible influence of the functional arm attached to the NHC backbone on their structure and reactivity and, in the case of a Ni(II) complex, on its catalytic properties in ethylene oligomerization. Starting from the alcohol-functionalized imidazolium salt [ImDiPP(C2OH)]Cl (2), the new functionalized NHC palladium(II) complex [PdCl(acac){ImDiPP(C2OH)-CNHC}] (3) was synthesized and fully characterized. Two byproducts, [PdCl{μ-ImDiPP(C2O)-CNHC,O}]2 (4) and trans-[PdCl2{ImDiPP(C2OH)-CNHC}2] (5), formed during the synthesis of 3, were also fully characterized. Acids promoted the transformation of 3 into the new CNHC-bound complex [PdCl(μ-Cl){ImDiPP(C2OH)-CNHC}]2 (6), unveiling the lability of the acac ligand and the resistance of the Pd-NHC bond to acids. Complex 6 reacted with a base to afford complex 4, in which alkoxide coordination to Pd(II) has occurred to generate a CNHC,O chelate. The stability of 3 was also assessed under basic conditions, and the new complex [Pd(acac){ImDiPP(C2O)-CNHC,O}] (7) was characterized. The new nickel(II) alcoholate-functionalized NHC complex [NiCl{μ-ImDiPP(C2O)-CNHC,O}]2 (8) was synthesized by the reaction of the imidazolium salt 2 with n-BuLi and [NiCl2(dme)]. The reaction of 8 with HCl regenerates the imidazolium and alcohol functions to give [ImDiPP(C2OH)]2[NiCl4] (9). The mixed-metal Ni(II)-Li(I) complexes [Ni2{μ-ImDiPP(C2O)-CNHC,μ-O}4Li]BF4 (10), [Ni2{μ-ImDiPP(C2O)-CNHC,μ-O}4Li]Cl (11), and [Ni{ImDiPP(C2O)-CNHC,μ-O}2LiBr] (12) were isolated and characterized. However, it was not possible to synthesize a Ni(II) alcohol-functionalized NHC complex in high yield. Small amounts of the square-planar complex [NiCl2{ImDiPP(C2OH)-CNHC}2] (13) could be isolated, and this complex was characterized by single-crystal X-ray diffraction. In 13, only the CNHC atom of the alcohol-functionalized NHC ligand is bound to the metal. The structures of the imidazolium salt 2·2H2O and of the complexes 3, 4, 4-polymorph, 5, 6·CH2Cl2, and 8-13 were established by single-crystal X-ray diffraction.

A reaction of the 44 electron cluster [Pt3(μ-PPh2)3Ph(PPh3)2] (1) with wet AgBF4 afforded the cationic cluster [Pt3(μ2-OH)(μ-PPh2)2(PPh3)3]BF4 (3(BF4)) which slowly transformed into [Pt3(μ2-Cl)(μ-PPh2)2(PPh3)3]BF4 (4(BF4)) upon recrystallization from CH2Cl2. These 44 electron clusters have been characterized by 31P{1H} NMR, and the crystal structure of 4(PF6) has been determined by X-ray diffraction, as well as that of [Pt3(μ-PPh2)2I2(PPh3)3] (5), which was obtained by recrystallization of the known cluster [Pt3(μ2-I)(μ-PPh2)2(PPh3)3]I (2(I)) from toluene and represents a neutral formula isomer of the latter. In addition, we have prepared the adducts of cluster 1 containing the moieties [Cu(NCMe)2]+ and [Au(PPh3)]+ in 6 and 7, respectively, and on the basis of their spectroscopic data, it was concluded that these complexes have similar structures to that previously established for the adduct of 1 with Ag(TFA) (TFA = OC(O)CF3), [Pt3{μ3-Ag(TFA)}(μ-PPh2)3Ph(PPh3)2] (8). The cationic clusters in 3(BF4) and 4(BF4) react with Ag(TFA) to afford cationic adducts in [Pt3{μ3-Ag(TFA)}(μ2-X)(μ-PPh2)2(PPh3)3]BF4 (9(BF4), X = OH; 10(BF4), X = Cl). The structure of the mixed-metal cluster [Pt3(μ3-AgBF4)(μ2-I)(μ-PPh2)2(PPh3)3]BF4 (11(BF4)), obtained by reaction of the complex 2(I) with AgBF4, was determined by X-ray diffraction.

The ligands azobenzene (az) and the zwitterionic 4-(isopropylamino)-6-(isopropyliminio)-3-oxocyclohexa-1,4-dien-1-olate (Q) were used to synthesize the mononuclear complex [(Q-H)Pt(az-H)] (1), and the dinuclear complex [(Q-H)Pt(μ-az-2H)Pt(Q-H)] (2). Structural characterization of the complexes shows a distorted-square-planar environment around the Pt(II) centers and localization of the double bonds within the Q-H ligand on metal coordination. Furthermore, the N═N azo bond is elongated in the metal complexes in comparison to free az, owing to π back-bonding from Pt(II) to az. Complexes 1 and 2 display multiple reversible reduction steps in their cyclic voltammograms. The complexes also exhibit strong absorptions in the visible region, the position and intensity of which can be influenced by the chromophore [(Q-H)Pt]. UV–vis–near-IR spectroelectrochemical studies show that the absorption of these complexes in the visible as well as the near-IR region can be controlled by electron transfer steps. Depending o...

The potentially pincer-type N-heterocyclic (NHC) precursor salt 1,3-bis((E)-1-((2,6-diisopropylphenyl)imino)ethyl)-1H-imidazol-3-ium chloride, 3(Cl–), was prepared by reaction of N-(2,6-diisopropylphenyl)acetimidoyl chloride (1) with N-(1-(1H-imidazol-1-yl)ethylidene)-2,6-diisopropylaniline (2). Attempts to crystallize 3(Cl–) at different temperatures afforded single crystals of 3(Cl–)·MeCN from MeCN and the mixed salt 4 from toluene, in which 2H+(Cl–) and 3(Cl–) have cocrystallized. Deprotonation of 3(Cl–) yielded 1,3-bis[1-(2,6-diisopropylphenylimino)ethyl]imidazol-2-ylidene (5), the first bis(imino)-N-heterocyclic free carbene, and a novel product, 6, resulting formally from the insertion of the carbene carbon atom of 5 into the C–H bond of the N═CHN moiety of 2 and formation of a new C–C bond. The structures and NMR spectra of 4 and 6 indicate that loss of one N-substituent from the bis(imino) NHC core by exocyclic imidazole N–C bond cleavage is relatively easy. Reaction of 5 with [Ir(μ-Cl)(cod)]2 in ...

The coordination chemistry of the DPPA-type functional phosphine bis(diphenylphosphino)(N-thioether)amine N(PPh2)2(CH2)3SMe () and its monosulfide derivative, (Ph2P)N{P(S)Ph2}(CH2)3SMe (1·S), towards Ni(II) precursors has been investigated. The crystal structures of N{P(S)Ph2}2(CH2)3SMe (1·S2), [NiCl2{(Ph2P)2N(CH2)3SMe-P,P}] (2), [NiCl2((Ph2P)N{P(S)Ph2}(CH2)3SMe-P,S)] (3), [Ni((Ph2P)N{P(S)Ph2}(CH2)3SMe-P,S)2]NiCl4 (3'), [Ni((Ph2P)N{P(S)Ph2}(CH2)3SMe-P,S)2](BF4)2 (4), and [Ni((Ph2P)NH{P(S)Ph2}-P,S)2]Cl2 (5) have been determined by single-crystal X-ray diffraction. In all of the complexes with the hybrid ligand 1·S, P,S-chelation to the Ni(II) center is observed. Despite the stability generally associated with five-membered ring chelation, easy migration of this LL'-type P,S-chelating ligand from one metal center to another was observed, which accounts for the reversible ligand-redistribution reaction occurring in the equilibrium between the neutral, diamagnetic complex [NiCl2LL'] and the paramagnetic ion-pair [Ni(LL')2][NiCl4]. Detailed investigations by multinuclear NMR, UV/Vis, and FTIR spectroscopic methods and DFT calculations are reported. Each of the formula isomers 3 and 3' can be selectively obtained, depending on the experimental conditions.

Three types of hybrid phosphorus-imidazolium salts, 1-methyl-3-(3-((diphenylphosphino)methyl)benzyl)-1H-imidazol-3-ium hexafluorophosphate (2·PF6), 1-methyl-3-(3-(di-tert-butylphosphinooxy)phenyl)imidazolium iodide (8a), and 3-(3-((diphenylphosphoryl)methyl)phenyl)-1-methyl-1H-imidazol-3-ium iodide (11) have been prepared and used as precursors to phosphine-NHC, phosphinite-NHC, and phosphoryl-NHC metal complexes, respectively. The structure of 11 has been determined by X-ray diffraction. The Ag(I) and Ir(I) complexes of the phosphine-NHC ligand, [Ag(μ-P-NHC,κC,κP)]2(PF6)2 (3) and [Ir(cod)(μ-P-NHC,κC,κP)]2(PF6)2 (4), were obtained and characterized by NMR, ESI-MS, elemental analysis, and X-ray diffraction. Both complexes are dinuclear and dicationic, with two P-NHC ligands bridging the two metal centers. The presence of the P donor led for 3 to an unprecedented structure compared to that of related Ag(I) complexes with trans spanning bis-NHC ligands. Complex 4 is the first example of a dinuclear iridium complex with a hybrid P-NHC ligand. The new hydrido, Ir(III) pincer-type complex [IrH(CNHCCCNHC)(MeCN)]PF6 (7) is suggested to have a square-pyramidal structure. The tetranuclear Ag(I) complex with the phosphinite-NHC ligand, [Ag2(μ3-I)(μ-PO-NHC,κP,κCNHC)]2 (9a) has a cubane-type structure, with alternating silver and iodine apexes and two PO-NHC ligands bridging opposite edges of the Ag4 tetrahedron. The Ir(III) pincer complexes [IrH(I)(PO-NHC,κP,κC,κCNHC)(Me)] (10a) and [IrH(I)(PO-NHC,κP,κC,κCNHC)(n-Bu)] (10b), with Me or n-Bu substituents on the nitrogen atom, respectively, have been prepared and characterized. Ag(I) and Cu(I) complexes with the phosphoryl-NHC ligand are reported and the centrosymmetric structure of the latter, [Cu(OP-NHC,κCNHC)2(μ-I){Cu(μ-I)}]2 (13), was established by X-ray diffraction and consists of a central Cu2(μ-I)2 rhombus connected by single iodide bridges to two Cu(OP-NHC,κCNHC)2 moieties. The Ir(III) hydride pincer complexes 10a,b were tested as catalyst precursors for the C-H bond activation of alkanes. Although their efficiency was significantly lower for transfer dehydrogenation from cyclooctane (coa) to t-butylethylene (tbe) than that of known PCP-Ir systems, these results represent the first attempts to study the catalytic properties of hybrid P-NHC iridium pincer complexes.

In order to investigate further the chemoselectivity of reactions involving the μ-orthometalated, metal–metal bonded dinuclear Pt(I) complex [Pt2(μ-o-C6H4PPh2)(μ-PPh2)(PPh3)2](Pt–Pt) (1), it was reacted with HCl and HI using various stoichiometries. The first step was the breaking of the metal–carbon bond and the formation of C–H and Pt–X bonds. When a 1:1 ratio was used, the complexes [Pt2X(μ-PPh2)(PPh3)3](Pt–Pt) (2, X = Cl; 3, X = I) have been obtained but the use of a 2:1 ratio resulted instead in the formation of the complexes [Pt2(μ-H)(μ-PPh2)X2(PPh3)2](Pt–Pt) (4, X = Cl; 6, X = I). The latter transformed into [Pt2(μ-X)(μ-PPh2)X2(PPh3)2] (5, X = Cl; 7, X = I) in the presence of an additional equivalent of HX. The cis,cis- and cis,trans-isomers of 7 were also obtained by oxidation of 3 with one equivalent of iodine. Whereas compounds 4, cis,cis-5, and cis,trans-7 have been characterized in solution, the complexes 2·1/2C7H8, 3, 6 and cis,cis-7 have been isolated and structurally characterized by X-ray diffraction.

The synthesis and full characterization of the unprecedented open-shell Cr(II) benzyl organometallic complexes [Cr(NHC)2(benzyl)2] (2) and [Cr(NHC*)(benzyl)2] (3) (NHC = N,N′-diisopropylimidazol-2-ylidene; NHC* = N,N′-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) from [Cr(benzyl)3(THF)3] and [CrCl2(THF)2]/[Mg(benzyl)2], respectively, uncovered unusually acute angles (93° in 2 and 76° in 3) at the sp3 benzylic C of the coordinated benzyl ligands. Detailed theoretical analyses (DFT and CASPT2) of the four- and three-coordinate Cr(II) species were performed to elucidate the physical origin of the benzyl bending and led to the recognition of a noncovalent, intramolecular polarization-induced metal–arene (PIMA) interaction as being responsible for it. The energetic contribution from a single PIMA interaction is estimated to be ca. 50 kJ/mol. A comparison with the origin of the angular distortions in the d0 [Zr(benzyl)4] complex will also be presented. Sharing the common origin of an induced-dipole charge densi...

International audience; The coordination of two heterofunctional P,P,S ligands of the N-functionalized DPPA-type bearing an alkylthioether or arylthioether N-substituent, (Ph2P)2N(CH2)3SMe (1) and (Ph2P)2N(p-C6H4)SMe (2), respectively, toward cobalt dichloride was investigated to examine the influence of the linker between the PNP nitrogen and the S atoms. The complexes [CoCl2(1)]2 (3) and [CoCl2(2)]2 (4) have been isolated, and 3 was shown by X-ray diffraction to be a unique dinuclear, zwitterion containing one CoCl moiety bis-chelated by two ligands 1 and one CoCl3 fragment coordinated by the S atom of a thioether function. The FT-IR, UV-vis, and EPR spectroscopic features of 3 were analyzed as the superposition of those of constitutive fragments identified by a retrosynthetic-type analysis. A similar approach provided insight into the nature of 4 for which no X-ray diffraction data could be obtained. A comparison between the spectroscopic features of 4 and of its constitutive fragments, [CoCl(2)2]PF6 (7) and [H2']2[CoCl4] (8) (2' = NH2(p-C6H4)SMe), and between those of 4 and 3 suggested that 4 could either have a zwitterionic structure, similar to that of 3, or contain a tetrahedral dicationic bis-chelated Co center associated with a CoCl4 dianion. Magnetic and EPR studies and theoretical calculations were performed. Doublet spin states were found for the pentacoordinated complexes [CoCl(1)2]PF6 (5) and 7 and anisotropic quadruplet spin states for the tetrahedral complexes [CoCl3(H1')] (6) (1' = NH2(CH2)3SMe) and 8. A very similar behavior was observed for 3 and 4, consisting in the juxtaposition of noninteracting doublet and quadruplet spin states. Antiferromagnetic interactions explain the formation of dimers for 6 and of layers for 8. The EPR signatures of 3 and 4 correspond to the superposition of low-spin nuclei in 5 and 7 and high-spin nuclei in 6 and 8, respectively. From DFT calculations, the solid-state structure of 4 appears best described as zwitterionic, with a low-spin state for the Co1 atom.

New imino-imidazole ligands bearing a pendant donor function L were synthesized in excellent yields. The corresponding nickel(II) complexes [NiCl2(imino-imidazole-L)]n (L = (CH2)2SMe (2a), (CH2)2OMe (2b), (CH2)2NEt2 (2c), (CH2)2PPh2 (2d), (C6H4)-p-OMe (2e), (CH2)3OMe (2f), (CH2)3CH3 (2g); n = 1, 2) were prepared and characterized by FT-IR spectroscopy and elemental analysis. Furthermore, the coordination geometry around the metal center in the dinuclear complex 2a and the mononuclear complexes 2c and 2e was unambiguously established by single crystal X-ray diffraction. All complexes have been evaluated for the oligomerization of ethylene in the presence of EtAlCl2 or MAO (methylaluminoxane) as cocatalyst, and mostly dimers and trimers were produced. Better activities were observed with EtAlCl2 as cocatalyst than with MAO.

Theoretical methods (B3LYP, M06, and CCSD(T)) have been used to study the kinetics and thermodynamics of ethyl migratory insertion in a series of square-planar [(X∧Y)Ni(ethyl)(ethylene)] complexes (X∧Y = anionic bidentate ligand). The results are discussed qualitatively using general trans-influence arguments. When X ≠ Y, the reactions of the two possible isomers have been compared. The results reveal that when one of the coordinating groups exerts a strong trans influence (STI) and the other a weak trans influence (WTI), as in a STI∧WTI chelating ligand such as a phosphino-enolate (P∧O), one of the two isomers has an activation energy for ethylene insertion (i.e., ethyl migration) that is much less than that calculated for symmetrical bidentate ligands of either the WTI∧WTI or STI∧STI types. Specifically, a low activation energy is found when an ethyl group, coordinated trans to the STI group, migrates to the ethylene coordinated trans to the WTI group. The converse pathway in the STI∧WTI system, wherein...

We compare the electronic structure of a quinonoid zwitterionic type molecule adsorbed on both gold and graphene on copper substrates. This (6Z)-4-(butylamino)-6-(butyliminio)-3-oxocyclohexa-1,4-dien-1-olate, C6H2( ⋯ NHR)2( ⋯ O)2 where R = n-C4H9, film is made of small molecules with a large intrinsic dipole of 10 Debyes. We find that the photoemission and inverse photoemission final states are well screened for these dipolar molecules on gold. This is not observed when they are adsorbed on graphene on copper. This weaker screening results in a larger highest occupied molecular orbital to lowest unoccupied molecular orbital gap for the molecules on graphene.

We describe a stepwise synthesis of the hydrido, N-heterocyclic dicarbene iridium(III) pincer complex [Ir(H)I(C(NHC)CC(aNHC))(NCMe)] (3) which features a combination of normal and abnormal NHC ligands. The reaction of the bis(imidazolium) diiodide [(CH(imid)CHCH(imid))]I(2) (1) with [Ir(μ-Cl)(cod)](2) afforded first the mono-NHC Ir(I) complex [IrI(cod)(CH(imid)CHC(NHC))]I (2), which was then reacted with 2 equiv. of Cs(2)CO(3) in acetonitrile at 60 °C for 40 h to yield 3. These observations support our previously proposed mechanism for the formation of hydrido, N-heterocyclic dicarbene iridium(III) pincer complexes from the reaction of bis(imidazolium) salts with weak bases involving a mono-NHC Ir(I) intermediate. We describe the reactivity of the mono-NHC Ir(I) complex 2 under various conditions. By changing the reaction solvent from MeCN to toluene, we observed the cleavage of the imidazol-2-ylidene ring and the formation of an iminoformamide-containing mono-NHC Ir(I) complex [IrI(cod){[NHCH=CHN(Ad)CHO]CHC(NHC)}] (4). Complex 4 was also prepared in high yield from the reaction of 2 with strong bases (potassium tert-butoxide or potassium hexamethyldisilazane), via the initial formation of the complex [IrI(cod)(CH(NHC)CHC(NHC))] (5), which contains a coordinated NHC moiety and a free carbene arm, followed by subsequent hydrolysis of the latter. The bis(imidazolium) salt 1 can be deprotonated by strong bases to form the bis(carbene) ligand C(NHC)CHC(NHC) (6), which readily reacts with [Ir(μ-Cl)(cod)](2) to give the dinuclear complex [{IrI(cod)}(2)(μ-C(NHC)CHC(NHC))] (7), in which the N-heterocyclic bis(carbene) ligand bridges the two metals through the carbene carbon atoms.

The Pd(II) complex [PdCl(2)(1)] [1 = ({oxazolin-2-yl}methyl)diphenylphosphine] was obtained by the 1:1 reaction of 1 with [PdCl(2)(NCPh)(2)]. Although this neutral complex is stable in the solid-state and in solution, it reacts with the dinuclear complex [CoCl(2)(μ-1)](2) to afford the heterometallic zwitterionic complex [{PdCl(1)}(+)(μ-1)(CoCl(3))(-)] (2). Under inert atmosphere, two equivalents of 1 reacted with [NiCl(2)(dme)] to give trans-[NiCl(2)(1)(2)] (3) in CH(2)Cl(2) but cis-[NiCl(2)(1)(2)] (4) in CHCl(3). When the latter reaction was performed in air, trans-[NiCl(2)(5)(2)] (6) [5 = ({oxazolin-2-yl}methyl)diphenylphosphine oxide] was obtained. All metal complexes, 2, 3, 4 and 6, have been structurally characterized by X-ray diffraction. Complexes 3, 4 and 6 have been evaluated as precatalysts for ethylene oligomerisation in the presence of AlEtCl(2) as cocatalyst. Complexes 3 and 6 yielded a turnover frequency (TOF) of 60,700 and 62,600 mol of C(2)H(4)/((mol of Ni)·h), respectively, in the presence of 10 equiv. of AlEtCl(2). In the presence of only 6 equiv. of cocatalyst, these Ni complexes yielded TOF values of 41,500 and 58,000 mol of C(2)H(4)/((mol of Ni)·h), respectively.

Reactions of [Ru(PPh3)3(CO)(H)Cl] with the zwitterionic p-benzoquinonemonoimine-type ligands 4-(n-butylamino)-6-(n-butylimino)-3-oxocyclohexa-1,4-dien-1-olate (Q1), 4-(isopropylamino)-6-(isopropylimino)-3-oxocyclohexa-1,4-dien-1-olate (Q2), and 4-(benzylamino)-6-(benzylimino)-3-oxocyclohexa-1,4-dien-1-olate (Q3) in the presence of a base led to the formation of mononuclear complexes [Ru(PPh3)2(CO)(H)(Q1–H)] (1a and 1b), [Ru(PPh3)2(CO)(H)(Q2–H)] (2a and 2b), and [Ru(PPh3)2(CO)(H)(Q3–H)] (3a and 3b), respectively. The positional isomers (a and b) that were formed in each case were separated by preparative TLC. The structural characterization of 2a and 3a·MeCN helped to identify the isomers, and established the distorted octahedral coordination geometry around the ruthenium center. The bond lengths in the complexes are consistent with localization of the double bonds in Q2–H and Q3–H in both their monodeprotonated and metal-coordinated forms. The Ru–C–O(carbonyl) bond angle is almost linear. Cyclic voltammetry of the complexes showed one oxidation and one reduction process. These are predominantly centered on the quinonoid ligands, which shows their redox-noninnocent character. Studies of transfer hydrogenation with 2a as a precatalyst showed that, in the presence of KOH, acetophenone could be converted to 1-phenylethanol within 10 h in over 90 % yield.

A range of new N-heterocyclic carbene complexes of iron(II) and cobalt(II) have been conveniently obtained by the aminolysis of bis[bis(trimethylsilyl)amido]iron and -cobalt precursors with imidazol(in)ium salts. Whereas sterically less hindered salts produced the tetrahedral complexes [M(carbene)2Cl2] (M = Fe), bulkier salts gave the three-coordinate [M(carbene){N(SiMe3)2}Cl] (M = Fe, Co), which serve as versatile precursors to a range of derivatives; mechanistic aspects of the reaction are discussed.

The reaction of the functional, zwitterionic quinonoid molecule (6E)-4-(butylamino)-6-(butyliminio)-3-oxo-2-(1,1,2,2-tetracyanoethyl)cyclohexa-1,4-dien-1-olate, [C(6)H-2-{C(CN)(2)C(CN)(2)H}]-4,6-(···NH n-Bu)(2)-1,3(···O)(2) (2), which has been previously prepared by regioselective insertion of TCNE into the C-H bond adjacent to the C···O bonds of the zwitterionic benzoquinone monoimine (6E)-4-(butylamino)-6-(butyliminio)-3-oxocyclohexa-1,4-dien-1-olate, C(6)H(2)-4,6-(···NHn-Bu)(2)-1,3-(···O)(2) (1), with 2 equiv of [Pt(C(2)H(4))(PPh(3))(2)], afforded the Pt(0) complex [Pt(PPh(3))(2)(4)] (6) (4 = 2-HCN; (6E)-4-(butylamino)-6-(butyliminio)-3-oxo-2-(1,2,2-tricyanoethenyl)cyclohexa-1,4-dien-1-olate), in which a tricyanoethenyl moiety is π-bonded to the metal. A metal-induced HCN elimination reaction has thus taken place. The same complex was obtained directly by the reaction of 1 equiv of the Pt(0) complex [Pt(C(2)H(4))(PPh(3))(2)] with the olefinic ligand [C(6)H-2-{C(CN)═C(CN)(2)}]-4,6-(···NHn-Bu)(2)-1,3-(···O)(2)) (4), previously obtained by the reaction of 2 with NEt(3) in THF. A similar reactivity pattern was observed between 2 and 2 equiv of the Pd(0) precursor [Pd(dba)(2)] in the presence of dppe, which led to [Pd(dppe)(4)] (7), which was also directly obtained from 4 and 1 equiv [Pd(dba)(2)]/dppe. In contrast to the behavior of the TCNE derivative 2, the reaction of the TCNQ derivative (6E)-4-(butylamino)-6-(butyliminio)-2-(dicyano(4-(dicyanomethyl)phenyl)methyl)-3-oxocyclohexa-1,4-dien-1-olate, [C(6)H-2-{C(CN)(2)p-C(6)H(4)C(CN)(2)H}]-4,6-(···NHn-Bu)(2)-1,3-(···O)(2)) (3), with 2 equiv of [Pt(C(2)H(4))(PPh(3))(2)] led to formal oxidative-addition of the C-H bond of the C(CN)(2)H moiety to give the Pt(II) hydride complex trans-[PtH(PPh(3))(2){N═C═C(CN)p-C(6)H(4)C(CN)(2)-2-[C(6)H-4,6-(···NHn-Bu)(2)-1,3-(···O)(2))}] (8). The molecular structures of 3, 4, 6·0.5(H(2)O), and 8·3(CH(2)Cl(2)) have been determined by single-crystal X-ray diffraction.

The reaction of 1,3-bis(imidazolyl)benzene with excess 1-bromoadamantane at 170 °C for 14 h afforded 1,3-bis(1-adamantylimidazolium)benzene dibromide (1), which was characterized by IR, NMR, and X-ray diffraction. Metathetical anion exchange with excess sodium iodide yielded the N-heterocyclic dicarbene precursor 1,3-bis(1-adamantylimidazolium)benzene diiodide, (CHimidCHCHimid)I2 (2), in high yield. The reaction of [Ir(μ-Cl)2(cod)]2 (cod = 1,5-cyclooctadiene) with 2 in the presence of 2.2 equiv of Cs2CO3 in refluxing acetonitrile led to the formation of the unsymmetrical iridium(III) hydride pincer complex [Ir(H)I(CNHCCCaNHC)(NCMe)] (3), which contains a C2-bound NHC ligand and a C5-bound NHC ligand. Recrystallization of 3 from ClCH2CH2Cl/Et2O generated the dihalide Ir(III) pincer complex [IrX2(CNHCCCaNHC)(NCMe)], where X = mixture of I and Cl (4). Its formation probably involves initial formation of an iridium chloro iodo intermediate via solvent-induced substitution of the hydride ligand of 3 by chlorid...

To gain a deeper knowledge of the nature of the species formed in situ by reaction of a catalyst precursor complex and typical cocatalysts used for ethylene oligomerization or polymerization, the Cr(III) complex fac-[Cr(NPN)Cl3] (1; NPN = bis(2-picolyl)phenylphosphine) was reacted with MAO and partial methylation to give the mononuclear complex fac-[Cr(NPN)Cl2.23Me0.77] (2) was observed, whereas reaction with AlMe3 in toluene led to partial halide abstraction and produced the dinuclear, chloride-bridged dicationic complex [{fac-Cr(NPN)Me(μ-Cl)}2][AlMexCl4–x]2 (3·[AlMexCl4–x]2), in which the metal centers are bridged by two chloride ligands. The complex fac-[Cr(NPN)Cl2Et] (4) was isolated in high yield from the reaction of 1 with AlEt3 and contains a rare example of CrIII–Et function. Upon treatment of 1 with EtAlCl2, the dinuclear Cr(III) complex [{fac-Cr(NPN)}2(μ-Cl)3][AlCl4]3 (5·[AlCl4]3) was obtained, which contains three bridging chlorides. Thus, under the conditions investigated, MAO and AlEt3 behave...

Reactions between an N,N′-adamantyl-substituted bis(imidazolium) diiodide (CHimidCHCHimid)I2 (1) and the dinuclear iridium(I) complex ([Ir(μ-X)(cod)]2 [X = Cl, I (prepared in situ)] in the absence ...

We have now obtained unusualmixed nickel/sodium polynuclear complexes and identifiedremarkablestructural effects ofthe sodiumcations associatedwith the reagent used to deprotonate the alcohol function. Inaddition to their intrinsic novelty, such observations arerelevant to the possible in situ formation of unexpected andpossibly overlooked active species in catalytic reactions.The dinuclear complex [Ni(m-Cl)(HL)]

The reactions of selected primary amines with the unsaturatedheterodimetallic complex [(η-C 5 Me 5 )Ni(μ-CO)Mo(CO) 2 -(n-C 5 H 5 )](Ni ... -Mo) (1a) were investigated. Primary amines react with this heterodimetallic complex to form unstable adducts, which are in equilibrium with the free amine and complex 1a in solution. Complex 1b, the nickel-tungsten analogue of 1a, reacts similarly with benzylamine. The position of the equilibrium shifts in favour of the adducts at low temperature, and crystals of the allylamine and benzylamine complexes [(η-C 5 Me 5 )(RNH 2 )Ni-Mo(CO) 3 (η-C 5 H 5 )]. (2a, R = C 3 H 5 ; 4a, R = PhCH 2 ) could be isolated. Their structures were established by single-crystal X-ray diffraction studies. The primary amines in complexes 2a and 4a are each coordinated, by means of their respective nitrogen atoms, to the nickel atom and thus provide the first structurally characterised examples of primary amine organometallic nickel complexes. The bonding of the amine to the heterodimetallic centre is in contrast to what has been observed with phosphorus-containing 2-electron donor ligands, in which the phosphane ligand is coordinated to the group 6 metal atom. A measure of the Ni-N bond dissociation enthalpy for the (benzylamine)nickel-tungsten complex 4b was obtained from a VT 1 H NMR spectroscopic study and was found to be -149 ± 10 kJ mol -1 . N-Bonded hydrogen atoms in both 2a and 4a exhibit intermolecular hydrogen-bonding interactions in the solid state with carbonyl oxygen atoms of adjacent molecules. These molecules exist as loosely bound dimers in the solid state. Complex 2a (C 21 H 27 MoNNiO 3 ) crystallises in the monoclinic space group P2 1 /n with a = 10.1922(2), b = 11.1538(3), c = 18.8053(4) A, β = 90.777(2)° and Z = 4. Complex 4a (C 25 H 29 MoNNiO 3 ) also crystallises in the monoclinic space group P2 1 /n with a = 12.0840(4), b = 10.9490(4), c = 17.4930(6) A, β = 90.396(3)° and Z = 4.