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The chemistry of discrete molecular chains constituted by metals in low oxidation states, displaying metal-metal proximity and stabilized by suitable metal-bridging, assembling ligands comprising at least one soft donor atom is comprehensively reviewed; complexes with a single (hard or soft) bridging atom (e.g., μ-halide, μ-sulfide, or μ-PR2etc.) as well as "closed" metal arrays (that fall in the realm of cluster chemistry) are excluded. The focus is on transition metal-based systems, with few excursions to cases combining transition and post-transition elements. Most relevant supporting ligands have neutral C, P, O, or S donor (mainly, N-heterocyclic carbene, phosphine, ether, thioether) or anionic donor (mainly phenyl, ylide, silyl, phosphide, thiolate) groups. A supporting-ligand-based classification of the metal chains is introduced, using as the classifying parameter the number of "bites" (i.e., ligand bridges) subtending each intermetallic separation. The ligands are further grouped according to the number of donor atoms interacting with the metal chain (called denticity in the following) and the column of the Periodic Table to which the set of donor atoms belongs (in ascending order). A complementary metal-based compilation of the complexes discussed is also provided in a concise tabular form.

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...

Whereas the bis(imine)imidazolium salt 1·Cl is a potential precursor to a NimineCNHCNimine pincer-type ligand, it reacted with [Pt(cod)2] to give the PtII NHC hydrido complex 3, in which chloride coordination and CNHCNimine chelation is preferred over pincer formation. Unexpectedly, reaction of 1·BF4 with [Pt(cod)2] afforded the unprecedented, 56 CVE tetrahedral cluster [Pt4(μ-H)(cod)4]BF4 (7), which was fully characterized. Imidazolium salts are ubiquitous sources of the much studied NHC ligands and not expected to lead to the formation of metal clusters.

This review summarizes the syntheses, crystal structures and applications of metal complexes with a specific zwitterionic thiolate ligand, 4-(trimethylammonio)benzenethiolate (Tab). The chemistry of Tab with transition metals (Fe, Co, Ni, Pd, Cu, Ag, Au, Zn, Cd, Hg), main group metals (In, Pb, Bi) and in heterometallic systems is described. The most significant structural features of the metal/Tab complexes are summarized and trends are discussed as a function of nuclearity and coordination numbers. The reactivity of specific metal/Tab complexes towards N- and P- donor ligands, organic acids, inorganic anions and metal ions is discussed. The luminescence and dielectric properties of the metal/Tab complexes and their applications as fluorescent biosensors and precursors to metal nanoparticles and catalysts for organic transformations are also illustrated.

Aliphatic polyesters are a class of biorenewable, biocompatible, and biodegradable materials. The ring-opening polymerization (ROP) of lactones is one of the most powerful methods to access these materials. A novel series of benzoheterocyclic urea catalysts has been synthesized and characterized. When employed in the ROP of δ-valerolactone (δ-VL) in combination with 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD), a fast and “living”/controlled feature was observed in both solvent-free polymerization and solution polymerization, which was proved by kinetic and chain extension experiments. With benzyl alcohol as an initiator, polyvalerolactones (PVLs) were obtained with different molecular weights and narrow molecular weight distributions. In addition, the PVLs with different topological structures were prepared by varying the initiators. The structure and thermal properties of resulting polymers were determined by NMR, GPC and DSC analyses. A possible mechanism was also proposed on the basis of NMR analysis.

Light-up luminescence sensors have been employed in real-time in situ visual detection of target molecules including volatile organic compounds (VOCs). However, currently employed light-up sensors, which are generally based on the aggregation-induced emission (AIE) or solvent-induced energy transfer effect, exhibit limited sensitivity for light-up detection and poor recycling performances thereby significantly hindering their industrial applications. Inspired by the low-temperature enhanced luminescence phenomenon, we herein propose and show that a guest-lock-induced luminescence enhancement mechanism can be used to realize the ultrafast light-up detection of target VOCs. Through introduction of chlorinated hydrocarbons to lock the molecular vibrations within a designed [Cu4I4]-based metal-organic framework (MOF), luminescence intensity could be enhanced significantly at room temperature. This guest-lock-induced luminescence enhancement is brought about by weak supramolecular interactions between the host framework and the guest molecules, allowing highly sensitive and specific detection of the guest vapor with ultrafast response time (

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

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.

Regioselective photodimerization of trans-4-styrylpyridine (4-spy) derivatives is performed using pseudorotaxane-like Zn-based metal organic frameworks MOFs as templates. The formation of rctt-HT (head-to-tail) dimers is achieved by confining pairs of coordinated 4-spy derivative ligands within hexagonal windows and then irradiating them with UV light. It is also possible to achieve a photodimerization reaction where two different substituted 4-spy ligands are included in such a MOF material. The ether bond formation is employed to protect the sensitive -OH group of HO-spy and the methyl group of CH3 O-spy is subsequently removed after the formation of cyclobutane derivative in the CH3 O-spy-based MOF. Introducing substituents at the 2- or 3-position of the phenyl group of 4-spy does not significantly affect the rate of the dimerization process except in the case of the strongly electron-withdrawing nitro group where the rate is significantly decreased. These results are in striking contrast to the mixtures of photoproducts and low yields obtained by untemplated photodimerization in organic solvents.

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.

N-Heterocyclic carbene (NHC) ligands are attracting worldwide interest because of their considerable scope and potential in coordination/organometallic chemistry, catalysis and materials science and this is reflected by the exponential growth in the number of relevant publications. The focus of this review is on the synthesis, structures and reactivity of 3d metals complexes with bis-NHC, tripodal NHC and tetrapodal NHC ligands. These metals are particularly relevant because of their generally lower cost and availability. The literature coverage includes the year 2015. This review is organized in six major sections, five of them are dedicated to each of the families of NHC ligands covered (chelating NHC, bridging NHC, chelating and bridging NHC, tripodal NHC and tetrapodal NHC ligands). Each section is in turn divided into subparts, one for each 3d metal. The seventh section is concerned with the catalytic applications, and we first examine C–H and C–C bond formation, the latter including polymerization, oligomerization and cross coupling reactions (Suzuki, Heck…). This is followed by C–N, C–O, C–B, C–Si, C–S and C–Br bond formation reactions. Reduction reactions and the conversion of sugars into 5-hydroxymethylfurfural are also discussed. After the Conclusion, a paragraph provides an update of the most recent articles that appeared in the literature after completion of the review.

The use of the dialkene divinyltetramethyldisiloxane (dvtms) allows easy access to the reactive 16-valence-electron complexes [Fe0(L-L)(dvtms)] (L-L = dppe (1,2-bis(diphenylphosphino)ethane; 1), dppp (1,2-bis(diphenylphosphino)propane; 2), pyNMeP(iPr)2 (N-(diisopropylphosphino)-N-methylpyridin-2-amine; 4), dipe (1,2-bis(diisopropylphosphino)ethane; 5)) and [Fe0(L)2(dvtms)] (L = PMe3; 3) by a mild reductive route using AlEt2(OEt) as reducing agent. In contrast, by the same methodology, the 18-valence-electron complexes [Fe0(L-L)2(ethylene)] (L-L = dppm (1,2-bis(diphenylphosphino)methane; 6), dppa (1,2-bis(diphenylphosphino)amine; 7), dppe (8)) were obtained, which do not contain dvtms. In addition, a combined DFT and solid-state paramagnetic NMR methodology is introduced for the structure determination of 5. A comparative study of the reactivity of 1, 2, 4–6, and 8 with 3-hexyne highlights emerging mechanistic implications for C–C coupling reactions using these complexes as catalysts.

Molecular films of quinonoid zwitterions, of the general formula C6H2([horiz bar, triple dot above]O)2([horiz bar, triple dot above]NHR)2, have been shown to display electronic properties highly dependent on the nature of the N-substituent R when deposited on gold substrates. The different spacing and organization of the molecules can lead to molecular films with semi-metal or dielectric behavior. With the long term goal to establish how packing effects in the solid state correlate with properties as thin films, we first attempted to identify by X-ray diffraction analysis candidate molecules showing suitable packing arrangements in the crystalline state. To this end, we have prepared a series of new functionalized, enantiopure or sterically-hindered quinonoid zwitterions and established the crystal structure of those with R = CH2–CH2–Ph (6), CH2–CH2–CH2–Ph (7), CH2–CH2–CH2–CH2–Ph (8), CH2–CH2–CH(Ph)–Ph (9), CH(CH3)–Ph (12), CH(CH2–CH3)–Ph (13), CH2–((4–CH3)–C6H4) (15), CH2–((4–NH2)–C6H4) (19) and CH2–CH2–((3,4–(OCH3)2)–C6H3) (24). An analysis of the crystal packing of three molecules, 5, 13 and 15, selected as illustrative examples for comparisons, was carried out and it was unexpectedly found that these chemically very similar molecules gave rise to different packing in the bulk, with resulting thin films showing different electronic properties. Various methods have been used for the characterization of the films, such as synchrotron radiation-based FTIR spatial spectra-microscopy, which provided an anchoring map of zwitterion 15 on a patterned substrate (Au/SiO2) showing its selective anchoring on gold. This is one of the best examples of preferential anchoring of a zwitterion and the sole example of spatial localization for a quinonoid zwitterion thin film. We have also used combined photoemission and inverse photoemission spectra and the data were compared to occupied and unoccupied DFT density state calculations.

The ring-opening polymerization (ROP) of lactones is an effective method for the preparation of biocompatible and biodegradable aliphatic polyesters, for which the development of efficient organocatalysts with high activity and good controllability is highly desirable. A series of novel pyridyl-urea catalysts has been synthesized and applied in the solvent-free ROP of lactones and trimethylene carbonate. Combined with 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD), the pyridyl-urea/MTBD systems showed a fast and living/controlled behavior in the ROP, generating polymers with narrow molecular weight distributions. The influences of catalyst structure, type of base, pyridyl-urea/base ratio, feed ratio of monomer/initiator and reaction temperature on the catalytic properties were investigated. A possible mechanism was proposed on the basis of NMR titration and dilution experiments.

International audience; The addition of various dipolar molecules is shown to affect the temperature dependence of the spin state occupancy of the much studied spin crossover Fe(II) complex, [Fe{H2B(pz)2}2(bipy)] (pz = pyrazol-1-yl, bipy = 2,2'-bipyridine). Specifically, the addition of benzimidazole results in a re-entrant spin crossover transition, i.e. the spin state starts in the mostly low spin state, then high spin state occupancy increases, and finally the high spin state occupancy decreases with increasing temperature. This behavior contrasts with that observed when the highly polar p -benzoquinonemonoimine zwitterion C6H2(...NH2)2(...O)2 was mixed with [Fe{H2B(pz)2}2(bipy)], which resulted in locking [Fe{H2B(pz)2}2(bipy)] largely into a low spin state while addition of the ethyl derivative C6H2(...NHC2H5)2(...O)2 did not appear to perturb the spin crossover transition of [Fe{H2B(pz)2}2(bipy)].

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.

Solvothermal reaction of Zn(NO3)2 with 2,9-bis-(2-pyridine-3-yl-vinyl)-[1,10]phenanthroline (3-bpep) and furan-2,5-dicarboxylic acid (2,5-H2FDC) afforded a one-dimensional (1D) coordination polymer {[Zn2(3-bpep)2(2,5-FDC)2]·1.5H2O}n (1), which undergoes regioselective photocycloaddition to yield another 1D coordination polymer {[Zn2(3-bpep)(trans,rctt-3-bpbpycb)0.5(2,5-FDC)2]·H2O}n (2) in a single-crystal-to-single-crystal manner under UV light irradiation. The reverse process from 2 to 1 can be achieved by heating 2 at 240 °C. Such a photocycloaddition/thermocycloreversion cycle results in an interesting reversible dielectric switching.

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...

A mononuclear bis(NHC)/Au(I) (NHC=N-heterocyclic carbene) cationic complex with a rigid bis(phosphane)-functionalized NHC ligand (PC(NHC)P) was used to construct linear Au3 and Ag2 Au arrays, a Au5 cluster with two intersecting crosslike Au3 arrays, and an unprecedented Cu6 complex with two parallel Cu3 arrays. The impact of metallophilic interactions on photoluminescence was studied experimentally.

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.

A thermal component to the soft x-ray induced spin crossover transition exists in the switching of a spin crossover compound (complex [Fe{H2B(pz)2}2(bipy)] (pz = pyrazol-1-yl, bipy = 2,2'-bipyridine) combined with the dipolar molecular additives (zwitterionic p-benzoquinonemonoimine C6H2([Formula: see text])2([Formula: see text])2). The addition of the zwitterionic molecule locks the Fe(II) complex in a largely low spin state configuration over an unusually broad temperature range that includes temperatures well above the thermal spin crossover temperature of 160 K. It is demonstrated here that the process of exciting the [Fe{H2B(pz)2}2(bipy)] moiety, in the presence of with C6H2([Formula: see text])2([Formula: see text])2, to an electronic state characteristic of the high spin state though incident x-ray fluences, has a thermal activation energies are determined to 14-18 meV for a range of mixing ratios from 1:2 to 1:10. Those activation energies are also significantly reduced as compared to values of 60-80 meV found for nanometer thin films of [Fe{H2B(pz)2}2(bipy)] on SiO2.

The double aminolysis reaction of [Co{N(SiMe3)2}2] by the salt 1-(6-((dicyclohexylphosphaneyl)methyl)pyridin-2-yl)-3-(2,6-diisopropylphenyl)-1H-imidazol-3-ium bromide, which contains one phosphane, one pyridine and one imidazolium groups, of formula [o-Cy2PCH2(C5H3N)(o-C3H3N2DiPP)]Br and abbreviated as (CyPNpyrCim)Br, was previously shown to afford the Co(II) complex [Co(CyP*NaCNHC)Br] (1) containing a dearomatised picolyl moiety in the tridentate, anionic donor ligand CyP*NaCNHC (Na = anionic amido, P* = vinylic P donor). We now report that formation of 1 is preceded by an intermediate tentatively assignable to the 5-coordinate Co(II) complex [Co(CyPNpyrCNHC){N(SiMe3)2}Br] (2). The reaction of 1 with LiCH2SiMe3 afforded the dark purple, paramagnetic [Co(CyP*NaCNHC)CH2SiMe3] (3) with a low spin d7 CoII; the electronic configurations of 1 and 3 were corroborated by EPR spectroscopy. Addition of excess (≥4 equiv.) H2SiPh2 to a solution of 1 gave the diamagnetic [Co(CyP(SiHPh2)NCNHC)Br] (4) following Si–H activation and silylation of the ligand backbone at the α-CHP. Reduction of CoII to CoI by silanes is uncommon.

Homo (Au3)- and heterotrinuclear coinage metal complexes (Au2Ag and Au2Cu) ligated by the first tritopic carbanionic N-heterocyclic carbene (NHC) have been prepared by deprotonation of ditopic NHC digold complexes and structurally characterized by single-crystal X-ray diffraction.

Iridium(III) complexes with a trifunctional pincer ligand containing protic N-heterocyclic carbene (pNHC), pyridine, and imine donor groups were obtained in two sequential steps: (i) protonation of 2-(1-(2,6-diisopropylphenylimino)ethyl)-6-(1-imidazolyl)pyridine (LCH; the superscript specifies the position of the tautomerizable H atom in the imidazole ring) with HBF4·Et2O to give the imidazolium salt [HLCH]+[BF4]− (protonation always occurs at the imidazole N atom) and (ii) metalation of the latter with [Ir(cod)(μ-Cl)]2 to give the hydrido pincer complex [Ir(H)(Cl)(NCMe){LNH-κ3Nimine,NPy,CNHC}]+[BF4]− (3+[BF4]−). Substitution of MeCN in 3+[BF4]− by treatment with triisopropylphosphine gave the analogue [Ir(H)(Cl)P(i-Pr)3{LNH-κ3Nimine,NPy,CNHC}]+[BF4]− (4+[BF4]−). Chloride abstraction from 3+[BF4]− by AgBF4 gave [Ir(H)(NCMe)2{LNH-κ3Nimine,NPy,CNHC}]2+[BF4–]2 (52+[BF4–]2). The centrosymmetric dinuclear Ir(III) complex [Ir(H)(NCMe){μ-(LCH−H)-κ3Nimine,NPy,C2,κN3}]22+[B(C6F5)3F–]2 (62+[B(C6F5)3F–]2) was obtain...

The coordination behavior 1,3-diisopropylimidazole-2-thione (diprimt) (1) toward BiI3 was studied and the resulting dinuclear adduct [Bi(thf)(diprimt)(μ-I)I2]2 (2) was fully characterized. The potential of this complex as a transmetallation agent was demonstrated by transferring the diprimt ligands to Pd(OAc)2, which resulted in a unique dinuclear Pd(II) complex, [PdI(diprimt)(μ-I)(μ-diprimt)PdI2] (3), containing a bridging and a terminally-coordinated diprimt ligand. The structural features of both complexes demonstrate stronger donor properties of diprimt compared to other thiones.

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 relative lability and transmetallation aptitude of trialkylphosphine and NHC donors, integrated in semi-rigid hybrid ligands attached to [Ag4Br4] pseudo-cubanes, lies in favor of the NHC and is used to selectively access unprecedented NHC complexes with heterobimetallic cores, such as Ag-Cu (4(Cy)) and Ag-Ir (5(tBu)). These can be viewed as an arrested state before the full transmetallation of both donors, which gives the homodinuclear Cu (3(Cy)) and Ir (6(Cy)) complexes. The observed NHC transmetallation aptitude and reactivity urges caution in the common notion that views the NHC as a universal spectator.

International audience; Silver(I) and copper(I) complexes containing neutral bis(N-heterocyclic carbene) (NHC) ligands and coordinated or non-coordinated chloride, bromide, iodide, or tetrafluoroborate anions, were synthesised. The nature of the anions impacts deeply the structural features of the complexes in the solid-state and neutral cubane-, neutral coordination polymer-, or dicationic bridged-type architectures have been characterised. The structures of (1,3-bis(3′-butylimidazol-2′-ylidene)benzene)disilver(I) dichloride (2a), bis(μ-1,3-bis(3′-butylimidazol-2′-ylidene)benzene-κ-C)tetra-μ3-bromotetrasilver(I) (2b), bis(1,3-bis(3′-butylimidazol-2′-ylidene)benzene)disilver(I) tetrafluoroborate (2d) in 2d·CH2Cl2, (1,3-bis(3′-butylimidazol-2′-ylidene)benzene)dicopper(I) dichloride (3a) and (1,3-bis(3′-butylimidazol-2′-ylidene)benzene)dicopper(I) dibromide (3b) were established by X-ray diffraction.

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 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).

A series of three-coordinate N-heterocyclic carbene bis(trimethylsilyl)amide complexes of cobalt, [Co{N(SiMe3)2}2(NHC)] (NHC = N,N′-diarylimidazolin-2-ylidene, aryl = 2,6-diisopropylphenyl, SIPr (1), aryl = mesityl, SIMes (2); κ1-N,N′-diphosphanylimidazol-2-ylidene, PCP (5); κ1-N-phosphanyl-N′-2,6-diisopropylphenylimidazol-2-ylidene, PC (6); cyclic alkyl amino carbene :C(Cy)CH2CMe2N-2,6-Pri2C6H3, cAACCy (7)) were prepared by the reaction of [Co{N(SiMe3)2}2] with the corresponding NHCs. The complexes exhibited interesting transamination reactivity in reactions with bulky 2,6-diisopropylaniline (NH2(DiPP)), where adjustment of the stoichiometry and reaction conditions resulted in the substitution of one or two N(SiMe3)2 ligands by the anilido ligand NH(DiPP), giving [Co{N(SiMe3)2}{NH(DiPP)}(NHC)] (NHC = N,N′-bis(2,6-diisopropylphenyl)imidazol-2-ylidene, IPr (8)) and [Co{NH(DiPP)}2(NHC)] (NHC = SIPr (9); IPr (10); PCP (11)). X-ray crystallography revealed trigonal-planar coordination geometry at Co for all o...

N-Arylimine-functionalised protic NHC (pNHC) Ir(i) and Ir(iii) complexes are obtained directly from neutral or cationic Ir(i) imidazole complexes using excess [Ir(cod)(μ-Cl)]2 or TlPF6, respectively. N-Arylimine-functionalised imidazolium salts lead to imidazole or pNHC complexes by competing N-H or C-H bond activation depending on the type of imidazolium counterion.

We report a facile, one-step green synthesis of two new star-shaped compounds containing three or six pendant carbonate groups with terminal alkynes. The reaction occurs under 1 atm CO2 and proceeds optimally at room temperature. These multialkynyl-carbonate-functionalized benzenes represent readily accessible precursors to more complex dendritic materials.

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).

New non-symmetrical, redox-active imino NHC pyridine pincer ligands, 2-(R1-imidazol-2-ylidene)-6-(R2NCH)-pyridine (R1 = 2,6-diisopropylphenyl (DiPP), R2 = 2,4,6-trimethylphenyl (Mes), 4B; R1 = R2 = DiPP, 4C), have been accessed by a ZnII-promoted modular synthesis involving the quaternization of R1-imidazole by [Zn(κNimineκNpyridine)(2-(R2NCH)-6-bromo-pyridine)Cl2], followed by ZnII removal and deprotonation of imidazolium pro-ligands. Redox active forms of 4B were implicated in the two complexes obtained by its reaction with FeBr2/KC8; metrical data analysis pointed to the occurrence of radical anionic and dianionic redox states of 4B.

Ligand design has met with considerable success with both categories of hybrid ligands, which are characterized by chemically different donor groups, and of N-heterocyclic carbenes (NHCs). Their spectacular development and diversity are attracting worldwide interest and offers almost unlimited diversity and potential in e.g. coordination/organometallic main group and transition metal chemistry, catalysis, medicinal chemistry and materials science. This review aims at providing a comprehensive update on a specific class of ligands that has enjoyed much attention in the past few years, at the intersection between the two categories mentioned above, that of hybrid NHC ligands in which the functionality associated with the carbene donor is of the oxygen-donor type. For each type of oxygen-donor present in such chelating (Section 1) or bridging (Section 2) hybrid ligands, we will examine the synthesis, structures and reactivity of their metal complexes and their applications, with a special focus on homogeneous catalysis (Section 3). Thus, hydrogenation, C–H bond activation, C–C, C–N, C–O bond formation, hydrolysis of silanes, oligomerization, polymerization, metathesis, hydrosilylation, C–C bond cleavage, acceptorless dehydrogenation, dehalogenation/hydrogen transfer, oxidation and reduction reactions will be successively presented in a tabular manner, to facilitate an overview and a rapid identification of the relevant publications describing which metals associated with a given oxygen functionality are most suitable. The literature coverage includes the year 2015.

International audience; The reactivity of the N-functionalized DPPA-type ligands (Ph2P)2N(p-Z)C6H4 [Z = H (1a), SMe (1b), OMe (1c)] with AgBF4 was investigated and revealed an unexpected influence of the para substituent Z of the N-aryl ligand. In acetone, the mononuclear bis-chelated [Ag{(1a–1c)-P,P}2]BF4 (2a·BF4–2c·BF4) and dinuclear bridged [Ag2{μ2-(1a–1c)-P,P}2](BF4)2 [3a·(BF4)2–3c·(BF4)2] complexes were obtained with a 1 : 2 and 1 : 1 AgBF4/ligand molar ratio, respectively. While the molecular structures of 2a·BF4 and 2b·BF4 determined in the solid-state by X-ray diffraction revealed their mononuclear nature and the absence of cation/anion interaction, complexes 3b·(BF4)2 and 3c·(BF4)2 form 2D coordination polymers through intermolecular Ag–S or Ag–O interactions, respectively, involving the N-function of the respective DPPA-type ligand, and display direct interactions between one BF4 anion and both Ag(I) cations. Surprisingly, the equimolar reaction between ligands 1a–1c and AgBF4 in CH2Cl2 led to different proportions of the dinuclear complexes 3a·(BF4)2–3c·(BF4)2 and clusters [Ag3(μ3-Cl)2{μ2-(1b–1c)-P,P}3]BF4 (4b·BF4–4c·BF4), depending on the nature of the para substituent Z of the N-aryl ligand. The trinuclear complexes resulted from C–Cl bond activation of the chlorinated solvent and were characterized by NMR spectroscopy and X-ray diffraction, and could be selectively produced by addition of 2/3 equiv. of [NMe4]Cl to the corresponding dinuclear complexes or by a one-pot procedure involving the correct amount of each reagent. A series of experiments and kinetic NMR investigations were performed to gain further insight into the formation of the trinuclear Ag3Cl2 core clusters.

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.

A highly active nickel catalyst with a hybrid P,N ligand is successfully used for the first time for the polymerization of a thiophene monomer with sterically very demanding side groups. The performance of this catalyst is by far not achievable with commercially available standard catalysts. Polythiophenes with special side chain patterns can thus be made with predetermined molecular weight, low dispersity, and high regioregularity, which enable the preparation of various large crystalline superstructures for the investigation of anisotropic optoelectronic properties in the absence of π-π interactions.

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 series of alcohol-functionalized NHC gold(I/III) complexes of the types [(L)Au(Cl or NTf2)] and [(L)AuCl3] (L = IPrEtOH, (1, 4, 5), IMesEtOH (2, 6), IMeEtOH (3, 7)) was readily synthesized and characterized by NMR spectroscopy and single-crystal X-ray diffraction. The catalytic activity of the new complexes was assessed and compared with that of other gold catalysts, in the tandem 3,3-rearrangement–Nazarov reactions of enynyl acetate and the rearrangement reaction of alkynyloxirane. The new complexes appeared to be dual-site catalysts in both transformations, thanks to the presence of the primary alcohol function tethered to the NHC ligands.

Two regioisomeric, non-symmetric P(C2)P(N)-imidazoles, t-Bu2PNCH=CHNC(PPh2) (L1, P(C2) = PPh2, P(N) = P(t-Bu)2) and Ph2PNCH=CHNC[P(t-Bu)2] (L2, P(C2) = P(t-Bu)2, P(N) = PPh2), respectively, show dramatic differences in the reactivity of the N-bound phosphine group; the L2 isomer is extremely sensitive to P-N bond cleavage by nucleophiles, and when coordinated to the PdCl(Me) fragment it undergoes facile interchange of one P(N) phenyl with the methyl originating from Pd.