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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.

Discovering and constructing novel and fancy structures is the goal of many supramolecular chemists. In this work, we propose an assembly strategy based on the synergistic effect of coordination and covalent interactions to construct a set of octahedral supramolecular cages and adjust their degree of distortion. Our strategy innovatively utilizes the addition of sulfur atoms of a metal sulfide synthon, [Et4N][Tp*WS3] (A), to an alkynyl group of a pyridine-containing linker, resulting in a novel vertex with low symmetry, and of Cu(I) ions. By adjusting the length of the linker and the position of the reactive alkynyl group, the control of the deformation degree of the octahedral cages can be realized. These supramolecular cages exhibit enhanced third-order nonlinear optical (NLO) responses. The results offer a powerful strategy to construct novel distorted cage structures as well as control the degree of distortion of supramolecular geometries.

Reactions of the phosphanyl-gold(I) precursor [(AuCl)2(bdppmapy)] (1; bdppmapy = N,N-bis(diphenylphosphanylmethyl)-2-aminopyridine) with Na2S in a 1:1 or 1:2 molar ratio gave rise to one tetradecanuclear and one octanuclear Au(I) sulfido cluster, [Au14S6(bdppmapy)5]Cl2 (2) and [Au18S8(bdppmapy)6]Cl2 (3), respectively. The former displays a new structural framework in gold cluster chemistry. Compounds 2 and 3 showed strong green luminescence and were employed as excellent imaging probes to selectively light up the lysosomes of living cells. Their long-term tracking of lysosomes can be achieved for up to 36 h, while tracking with commercial Lyso-Tracker Red under the same conditions was limited to 3 h. Our work demonstrated the possibility of constructing novel gold(I) sulfido clusters supported by special P-N hybrid ligands and the potential application of these clusters as long-term selective trackers of lysosomes in bioimaging.

Finding diverse and tunable molecular structures is relevant toward the design of functional nanostructures. The photoluminescence of complex [Au2Cl(μ-P-C-κP,κC,κN)]3 (1), featuring a ligand-suppor...

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.

We present well resolved ( Δ ν ∼ = 3 cm−1) Infrared Multiple Photon Dissociation (IR-MPD) spectra of [Co4(CO)n(dppa-H+)]− (n = 3–10, dppa = NH(PPh2)2) in the carbonyl stretching range when isolating these species at low temperatures (26 K and below). We utilize IR-MPD in conjunction with DFT calculations to investigate the influence of CO ligands on structure and spin multiplicity of the Co4 core. The recorded spectra reveal multiple bands of CO stretching vibrations which shift by reduction of CO coverage. This indicates a corresponding change of coordination motifs, and we find a conclusive interpretation of all recorded IR features in the case of the saturated n = 10 compound, likely in a singlet state as in solution. We tentatively postulate a singlet/triplet to quintet spin-flip upon removal of the first one or two CO ligands (from n = 10 to n = 9, 8) as well as a conceivable isomerization at a particular CO coverage (n = 6).

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 linear, two-coordinate and isostructural heteroleptic [M(IPr){N(SiMe3)2}] (IPr = 1,3-bis(diisopropylphenyl)-imidazol-2-ylidene), formally MI complexes (M = Co, 3; Fe, 4) were obtained by the reduction of [M(IPr)Cl{N(SiMe3)2}] with KC8, or [Co(IPr){N(SiMe3)2}2] with mes*PH2, mes* = 2,4,6-tBu3C6H2. The magnetism of 3 and 4 implies CoII and FeII centres coupled to one ligand-delocalized electron, in line with XPS and XANES data; the ac susceptibility of 4 detected a pronounced frequency dependence due to slow magnetization relaxation. Reduction of [Fe(IPr)Cl{N(SiMe3)2}] with excess KC8 in toluene gave the heteronuclear ‘inverse-sandwich’ Fe–K complex 7, featuring η6-toluene sandwiched between one Fe0 and one K+ centre.

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)].

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...

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 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.

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 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.

Four Au-(μ-phosphinite)-In units assemble to form an unprecedented Au2In2 12-membered metallacycle which intersects at the In centres an 8-membered ring containing two In-μ-phosphinate linkages, resulting in a tricyclic structure. Thermal treatment of this complex and of its Ag(I) analog affords Au-In-P and Ag-In-P nanomaterials, respectively.

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].

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.

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 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.

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...

The heterofunctional and rigid ligand N,N'-diphosphanyl-imidazol-2-ylidene (PCNHCP; P = P(t-Bu)2), through its phosphorus and two N-heterocyclic carbene (NHC) donors, stabilizes trinuclear chain complexes, with either Au3 or AgAu2 cores, and dinuclear Au2 complexes. The two oppositely situated PCNHCP (L) ligands that "sandwich" the metal chain can support linear and rigid structures, as found in the known tricationic Au(I) complex [Au3(μ3-PCNHCP,κP,κCNHC,κP)2](OTf)3 (OTf = CF3SO3; [Au3L2](OTf)3; Chem. Commun. 2014, 50, 103-105) now also obtained by transmetalation from [Ag3(μ3-PCNHCP,κP,κCNHC,κP)2](OTf)3 ([Ag3L2](OTf)3), or in the mixed-metal tricationic [Au2Ag(μ3-PCNHCP,κP,κCNHC,κP)2](OTf)3 ([Au2AgL2](OTf)3). The latter was obtained stepwise by the addition of AgOTf to the digold(I) complex [Au2(μ2-PCNHCP,κP,κCNHC)2](OTf)2 ([Au2L2](OTf)2). The latter contains two dangling P donors and displays fluxional behavior in solution, and the Au···Au separation of 2.8320(6) Å in the solid state is consistent with metallophilic interactions. In the solvento complex [Au3Cl2(tht)(μ3-PCNHCP,κP,κCNHC,κP)](OTf)·MeCN ([Au3Cl2(tht)L](OTf)·MeCN), which contains only one L and one tht ligand (tht = tetrahydrothiophene), the metal chain is bent (148.94(2)°), and the longer Au···Au separation (2.9710(4) Å) is in line with relaxation of the rigidity due to a more "open" structure. Similar features were observed in [Au3Cl2(SMe2)L](OTf)·2MeCN. A detailed study of the emission properties of [Au3L2](OTf)3, [Au3Cl2(tht)L](OTf)·MeCN, [Au2L2](OTf)2, and [Au2AgL2](OTf)3 was performed by means of steady state and time-resolved photophysical techniques. The complex [Au3L2](OTf)3 displays a bright (photoluminescence quantum yield = 80%) and narrow emission band centered at 446 nm with a relatively small Stokes' shift and long-lived excited-state lifetime on the microsecond timescale, both in solution and in the solid state. In line with the very narrow emission profile centered in the violet-blue region, fabrication of organic light-emitting devices (OLEDs) comprising the [Au3L2](OTf)3 complex demonstrated its usefulness as a deep-blue emitter in solution-processed OLEDs. Electrochemical and Raman spectroscopic studies were also performed on [Au3L2](OTf)3. Experimental results were rationalized by means of Wave-Function Theory (WFT) and Density Functional Theory (DFT). MP2 calculations gave a satisfactory description of the structures of the cationic complexes [Au3L2](3+) and [Au2L2](2+) and pointed to Au···Au interactions having an electrostatic component owing to the dissimilar charge distribution in the chain caused by the heterofunctional ligand. The nature of the emitting states and their geometric distortions relative to the ground states in [Au3L2](3+) and [Au2L2](2+) was studied by DFT, revealing contraction of the Au···Au distances and coordination geometry changes by association of the dangling P donor, respectively.

International audience; Driven by the huge potential of engineering the molecular band offset with highly dipolar molecules for improving charge injection into organic electrics, the anchoring of various N-alkyl substituted quinonoid zwitterions of formula image file: c5nj03251b-t1.tif (R = iPr, Cy, CH2CH(Et)CH2CH2CH2CH3,…) on gold surfaces is studied. The N–Au interactions result in an orthogonal arrangement of the zwitterions cores with respect to the surface, and stabilize adsorbed compact rows of molecules. IR spectroscopy is used as a straightforward diagnostic tool to validate the presence of ultra-thin molecular films. When combined with computational studies, IR measurements indicate that the presence of a CH2 group in α position to the nitrogen atom is important for a successful anchoring through N–Au interactions. The presence of such a flexible CH2 spacer, or of aryl groups, enables π-interactions with the surface, making possible the anchoring of enantiopure or sterically-hindered zwitterions. X-ray diffraction analyses indicate that the intermolecular spacing within a row of molecules can be modulated by the nature of the alkyl substituent R. This modulation is directly relevant to the electronic properties of the corresponding molecular films since these zwitterions are expected to form rows on gold surfaces similar to those observed in the bulk crystalline state.

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.

Substitution of a trans chloride ligand in the N-heterocyclic carbene (NHC) AuIII complexes (NHC)AuCl3 in the presence of AgNTf2 yields a new family of (NHC)AuCl2(NTf2) complexes. They display a moderate stability in solution but are stable once crystallized. These new organogold(III) complexes could be fully characterized by NMR, IR, and single crystal X-ray diffraction. They exhibit in 13C{1H} NMR an unusually upfield-shifted resonance associated with the carbene center.

The adsorption of molecular films made of small molecules with a large intrinsic electrical dipole has been explored. The data indicate that such dipolar molecules may be used for altering the interface dipole screening at the metal electrode interface in organic electronics. More specifically, we have investigated the surface electronic spectroscopic properties of zwitterionic molecules containing 12π electrons of the p-benzoquinonemonoimine type, C(6)H(2)(···NHR)(2)(···O)(2)(R = H (1), n-C(4)H(9) (2), C(3)H(6)-S-CH(3) (3), C(3)H(6)-O-CH(3) (4), CH(2)-C(6)H(5) (5)), adsorbed on Au. These molecules are stable zwitterions by virtue of the meta positions occupied by the nitrogen and oxygen substituents on the central ring, respectively. The structures of 2-4 have been determined by single crystal X-ray diffraction and indicate that in these molecules, two chemically connected but electronically not conjugated 6π electron subunits are present, which explains their strong dipolar character. We systematically observed that homogeneous molecular films with thickness as small as 1 nm were formed on Au, which fully cover the surface, even for a variety of R substituents. Preferential adsorption toward the patterned gold areas on SiO(2) substrates was found with 4. Optimum self-assembling of 2 and 5 results in ordered close packed films, which exhibit n-type character, based on the position of the Fermi level close to the conduction band minimum, suggesting high conductivity properties. This new type of self-assembled molecular films offers interesting possibilities for engineering metal-organic interfaces, of critical importance for organic electronics.

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 the unique structural and electronic arrangement in the heptanuclear polyiodobismuthate [Bi(7)I(24)](3-) which displays striking similarities with the Anderson-type structures found in polyoxometalates. This main group element anion is part of the complex [Bi(OAc)(2)(thf)(4)](3)[Bi(7)I(24)] (1) which has been characterized by X-ray crystallography. We investigated the structure, stability, and bonding of [Bi(7)I(24)](3-) using relativistic dispersion-corrected density functional theory in combination with a quantitative energy decomposition and electron localization function analysis in order to better understand the main features of this isopolyanion. A comparative analysis of the properties of [Bi(7)I(24)](3-) and previously reported high-nuclearity [Bi(n)X(3n+m)](m-) anions, in the gas phase and in solution, has been performed, in the latter case to track the macroscopic solvent effects. [Bi(7)I(24)](3-) is the largest building block in the class of trianionic iodobismuthates and the sole heptanuclear framework in the family of iodobismuthates.

New Cu(I) and Ag(I) complexes containing a chelating bis(N-heterocyclic carbene) ligand, in which an aryl group acts as a spacer between the NHC donor groups, have been prepared by deprotonation of the bis-imidazolium salt 1,1′-((4,6-dimethyl-1,3-phenylene)bis(methylene))bis(3-methyl-1H-imidazol-3-ium) bis(hexafluorophosphate) ((H2L)(PF6)2). Their structures, determined by X-ray diffraction, reveal a short separation (2.611(4) A (Cu) and 2.747(7) A (Ag), respectively) between the metal center and the C2 arene carbon of the ligand, whose metalation would result in pincer-type complexes. However, DFT calculations indicate that these distances do not correspond to C–H–M bonding interactions. Furthermore, whereas Ag(I) NHC complexes are typically used as transmetalation reagents, we report here an unusual example of the reverse situation consisting of a Cu(I) to Ag(I) transfer of NHC ligands.

The new heterometallic complexes [Mo2Pd2(η5-C5H4CH2CH2SCH2CH3)2(CO)6(PEt3)2] (5), trans-[Pt{Mo(η5-C5H4CH2CH2SCH2CH3(CO)3}2(CNt-Bu)2] (6) and trans-[Pt{Mo(η5-C5H4CH2CH2SCH2CH3)(CO)3}2(NCPh)2] (7) and the mononuclear complex (8) have been prepared from the new carbonylmetallate Li[Mo(η5-C5H4CH2CH2SCH2CH3)(CO)3]·2DME (4). Whereas the first three complexes are analogous to the known complexes [Mo2Pd2(η5-C5H5)2(CO)6(PEt3)2] (1a), trans-[Pt{Mo(η5-C5H5)(CO)3}2(CNt-Bu)2] (2) and trans-[Pt{Mo(η5-C5H5)(CO)3}2(NCPh)2] (3), respectively, their cyclopentadienyl ligands have been functionalized by a dialkyl sulfide group with the aim to anchor these compounds on gold surfaces. Two approaches have been used to anchor the heterometallic complex on the surface and generate monolayers. The first process consisted of depositing cluster 5 by spin coating on a gold surface. The second was the immersion of a gold surface into a cluster solution. For both procedures, the resulting deposits were analysed by STM (scanning tunneling microscopy), ellipsometry and XPS (X-ray photoelectron spectroscopy). For the layers obtained by spin coating of a solution of cluster 5, it was found that the cluster is not attached to the surface, but only deposited on it. In contrast, after immersion of a gold substrate into a solution of 5 or 6, anchoring of the complexes was clearly evidenced by XPS via the chemical shift of the S–2p binding energy toward lower binding energies.

The controlled stoichiometry of heterometallic carbonyl clusters make them attractive precursors for the stabilization of bare metal alloy clusters for magnetic applications. The mixed-metal molecular cluster [RuCo3(H)(CO)12] has been functionalized with the phosphane-thiol ligand Ph2PCH2CH2SH to allow subsequent anchoring on a gold surface. The resulting tetrahedral cluster [RuCo3(H)(CO)11(Ph2PCH2CH2SH)] (1) has been characterized by X-ray diffraction and the P-monodentate ligand is axially bound to a cobalt center and trans to the ruthenium cap. This synthesis also yielded the product of oxidative coupling, in which two SH groups were coupled intermolecularly to give a disulfide ligand that links two tetrahedral cluster units in [{RuCo3(H)(CO)11(Ph2PCH2CH2S)}2] (2). This cluster has also been characterized by X-ray diffractions studies. After deposition of 1 on a Au(111) surface by self-assembly, the carbonyl ligands were stripped off by thermal annealing in ultra-high vacuum (UHV) to form a metallic species. X-ray photoelectron spectroscopic measurements performed as a function of the annealing temperature show that the cobalt and ruthenium centers converge towards metallic character and that the stoichiometry of the alloy is retained during the annealing process. Preliminary X-ray absorption spectroscopy (XAS) synchrotron experiments indicate that clusters 1 and 2 behave similarly, which is consistent with the retention of their tetrahedral units on the gold surface after transformation of the thiol function or breaking of the disulfide bond to form Au--S bonds, respectively, has occurred.

Heterodinuclear silyl complexes of the type [(OC)3(R3Si)Fe(μ-PPh 2 )Pt(CO)(PPh3)], which contain a Fe(μ-P)Pt triangular core, were previously reported to undergo an unprecedented dyotropic-type rearrangement involving migration of the silyl group from iron to platinum with concomitant 1,2 migration of CO from Pt to Fe. In the resulting complexes of formula [(OC) 4 Fe(μ-PPh 2 )Pt(SiR 3 )(PPh 3 )], the Si atom occupies a cis position at the planar Pt center with respect to the phosphido bridge. DFT calculations were employed to elucidate the mechanism of this intramolecular silyl migration reaction. When the Fe-Pt precursor complex is [(OC)3(R3Si)Fe(μ-PPh2)Pt(PPh3)2], the reaction sequence involves (i) the substitution of PPh 3 by CO at Pt, (ii) the concerted migration of CO and SiR 3 , and (iii) the cis-trans isomerization at Pt. The calculations support the exergonic character of the overall process. An explanation for the experimental observation of only one product isomer being formed is possible via frontier molecular orbital analysis. Consistent with the experimental findings, the transition states of the migration (a species with a triply bridged intermetallic bond) and isomerization steps were found to be energetically within reach at room temperature. Additional support for the suggested mechanism also comes from the fact that relative silyl migration activities could be rationalized by the means of quantum chemistry.

The reaction of the iron metalate [Fe{Si(OMe)3}(CO)3(dppm-P)]− (1b) with [Ru(CO)3Cl(μ-Cl)]2 afforded the heterodinuclear complex [(OC)3{(MeO)3Si}Fe(μ-dppm)Ru(CO)3Cl)] (Fe–Ru) (3) in which a long Fe–Ru separation of 2.956(1) A has been crystallographically evidenced. It was shown by density functional theory (DFT) calculations to correspond to the minimum-energy structure. Upon treatment of the corresponding hydrido complex [HFe{Si(OMe)3}(CO)3(dppm-P)] (1a) with [Ru(CO)3Cl(μ-Cl)]2, the chloride-bridged tetranuclear hydrido complex [(OC)3{(MeO)3Si}Fe(H)(μ-dppm)Ru(CO)2Cl(μ-Cl)]2 (4) was formed in which the Fe and Ru centers are only linked via bridging dppm ligands.

The products of the reaction between N,N'-diphosphanylimidazol-2-ylidene (P-C-P) and gold(I) precursors depend on the nature of the anions associated with the latter. In contrast to the reported reaction with [Au(tht)2(OTf)], the use of [AuCl(tht)] led to the new hexanuclear complex 1, which features a Au6(μ3-P-C,κC,κN,κP)3 skeleton. The reaction of lithium imidazolide (P-C-Li) and [AuCl(tht)] also afforded 1, together with an unusual salt of the general formula [Au5Cl(μ3-P-C-κP,κC,κN)3]2[AuCl2]2 (2), which contains [Au5(μ3-P-C-κP,κC,κN)](+) subunits. In the solid state, one of these Au5 cations is associated with an [AuCl2](-) anion, while two other cations interact through their unique dicoordinated N-Au-N center with a [AuCl2](-) anion, with the charge of the resulting monocation being compensated for by another [AuCl2](-) anion to give a Au12 salt. Remarkably, the latter displays seven different bonding types at Au(I): C-Au-C, N-Au-N, P-Au-P, Cl-Au-Cl, C-Au-N, P-Au-Cl, and Au···Au.

International audience; The condensation reaction between two chemically different tetranuclear cubane-like clusters [Ni(μ3-Cl)(Cl)(HL)]4 (1; HL=2-methyl-1-(pyridin-2-yl)propan-2-ol) and [Ni(μ3-OH)(Cl)(HL)]4 (2) provides new access to higher nuclearity complexes, as shown with the synthesis of the octanuclear complex [Ni8(μ3-Cl)3(μ3-OH)5(μ-Cl)2Cl6(HL)7] (3). In one instance, we also isolated the heptanuclear complex [Ni7(μ3-Cl)2(μ3-OH)6Cl4(H2O)2(HL)6]Cl2 (4). Magnetic properties measured by superconducting quantum interference device (SQUID) susceptometry evidenced S=8 and S=5 ground states for complexes 3 and 4, respectively. In particular, alternating current (ac) susceptometry evidenced slow relaxation of the magnetisation for complex 3, and suggests a similar behaviour at sub-kelvin temperatures for complex 4.

International audience; Deprotonation of 1-arylimidazoles (aryl = mesityl (Mes), 2,6-diisopropylphenyl (Dipp)), with n-butyl lithium afforded the corresponding derivatives (1-aryl-1H-imidazol-2-yl)lithium (1a, Ar = Mes; 1b, Ar = Dipp) in good yield. Reaction of 1a with 0.5 equiv. of [Ir(cod)(μ-Cl)]2 yielded two geometrical isomers of a doubly C2,N3-bridged dinuclear complex [Ir(cod){μ-C3H2N2(Mes)-κC2,κN3}]2 (3), 3H–H, a head-to-head (H–H) isomer of CS symmetry, and 3H–T, the thermodynamically preferred head-to-tail (H–T) isomer of C2 symmetry. The metallated carbon of the 4 electron donor anionic bridging ligands has some carbene character, reminiscent of the situation in N-metallated protic NHC complexes. Displacement of cod ligands from 3H–H and 3H–T afforded the tetracarbonyl complexes [Ir(CO)2{μ-C3H2N2(Mes)-κC2,κN3}]24H–H and 4H–T, respectively. The reaction with PMe3, which gave only one complex, [Ir(CO)(PMe3){μ-C3H2N2(Mes)-κC2,κN3}]2 (5), demonstrates that the isomerization of the central core Ir[μ-C3H2N2(Mes)-κC2,κN3]2Ir from H–H to H–T on going from 4H–H to 5 is readily triggered by phosphine substitution under mild conditions. Oxidative-addition of MeI to 5 afforded the formally metal–metal bonded d7–d7 complex [Ir2(CO)2(PMe3)2(Me)I{μ-C3H2N2(Mes)-κC2,κN3}2] (6). The blue [Ir(C2H4)2{μ-C3H2N2(Mes)-κC2,κN3}]2 (7) and purple [Rh(C2H4)2{μ-C3H2N2(Dipp)-κC2,κN3}]2 (9) tetraethylene complexes were also obtained with only a H–T arrangement of the bridging ligands. Although only modestly efficient in alkane dehydrogenation, complex 7 was found to be a more active pre-catalyst than 3H–T, 4H–T and 5, probably because of the favorable lability of the ethylene ligands. From cyclic voltammetry, exhaustive coulometry and spectroelectrochemistry studies, it was concluded that 3H–T undergoes a metal-based one electron oxidation to generate the mixed-valent Ir(I)/Ir(II) system. The energy of the intervalence band for the orange dirhodium complex [Rh(cod){μ-C3H2N2(Mes)-κC2,κN3}]2 (8) is shifted toward lower energies in comparison with 3H–T, reflecting the decrease of the energy with the intermetallic distance. It was concluded from the EPR study that the Ir and Rh centres contribute substantially to the experimental magnetic anisotropy and thus to the singly occupied molecular orbital (SOMO) in the mixed-valent Ir(I)/Ir(II) and Rh(I)/Rh(II) systems. The molecular structures of 3H–H, 3H–T, 8 and 9 have been determined by X-ray diffraction.

The reactions of TCNE- and TCNQ-functionalized (TCNE: tetracyanoethylene and TCNQ: 7,7',8,8'-tetracyanoquinodimethane) zwitterionic benzoquinonemonoimines with a Cu(I)-BIAN complex (BIAN = bis(o,o'-bisisopropylphenyl)acenaphthenequinonediimine) have been investigated and found to follow a diversity of interesting patterns. The complexes [Cu(BIAN)(NCMe)(L2)]BF4 (2) and [Cu(BIAN)(L2)2]BF4 (4) were obtained by reacting [Cu(BIAN)(NCMe)2]BF4 (1) with one and two equivalents of L2, respectively. Following similar procedures, the complexes [Cu(BIAN)(NCMe)(L3)]BF4 (6) and [Cu(BIAN)(L3)2]BF4 (7) were obtained by reaction of 1 with L3. The reaction of 2 with 0.5 equiv. of 4,4'-bipyridine afforded [{Cu(BIAN)(L2)}2(μ-4,4'-bipyridine)](BF4)2 (3). The complexes were characterized by multinuclear NMR, IR and UV-Vis spectroscopic techniques, mass spectrometry, cyclic voltammetry and elemental analysis. The molecular structures of complexes 3 ·4CH2Cl2 and 4 ·CH2Cl2 were determined by single crystal X-ray diffraction. An unexpected coordination polymer [Cu((L2-))2]∞ (5) was also structurally characterized, which contains Cu(II) centres chelated by two N,O-bound ligands resulting from the monodeprotonation of L2.

We describe the synthesis of novel quinonemonimines Cu(II) coordination complexes, of the type: Download : Download full-size image which, in addition to their intrinsic interest, have potential application in optical recording. The following key parameters have been highlighted: (i) the presence of coordinating arms on the quinonoid core of the ligand leads to octahedral complexes with increased solubility, (ii) the presence of Cu(II) as a metal centre leads to a favourable exothermic decomposition, (iii) the presence of quinonoid moieties results in the optical absorption to be in the desired wavelength range. To cite this article: P. Braunstein et al., C. R. Chimie 9 (2006).

The reactivity of isolobal molybdenum carbonylmetalates containing a 2-boratanaphthalene, [Mo(η 5 -2,4-MeC 9 H 6 -BMe)(CO) 3 ] - (5a) and [Mo(η 5 -2,4-MeC 9 H 6 BNi-Pr 2 )(CO) 3 ] - (5b), a 1-boratabenzene, [Mo(η 5 -3,5-Me 2 C 5 H 3 BNi-Pr 2 )-(CO) 3 ] - (8), or a functionalized cyclopentadienyl ligand, the new metalate [Mo(η 5 -C5H4Ph)(CO)3]- (7) and [Mo(η 5 -C 5 H 4 NMe 2 )(CO) 3 ] - (9), toward palladium (I and II) or platinum (I and II) complexes, such as trans-[PdCl 2 (NCPh) 2 ], [Pd 2 (NCMe) 6 ](BF 4 ) 2 , trans-[PtCl 2 (PEt 3 ) 2 ], and [N(n-Bu) 4 ] 2 [Pt 2 Cl 4 (CO) 2 ], has been investigated, and this has allowed an evaluation of the influence of the π-bonded ligands on the structures and unprecedented coordination modes observed in the resulting metal-metal-bonded heterometallic clusters. The new 58 CVE planar-triangulated centrosymmetric clusters, [Mo 2 Pd 2 (η 5 -C 5 H 4 Ph) 2 (CO) 6 (PEt 3 ) 2 ] (11), [Mo 2 Pd 2 (η 5 -2,4-MeC 9 H 6 BNi-Pr 2 ) 2 (CO) 6 ] (12), [Mo 2 -Pd 2 (η 5 -3,5-Me 2 C 5 H 3 BNi-Pr 2 ) 2 (CO) 6 ] (13), [Mo 2 Pd 2 (η 5 -C 5 H 4 NMe 2 ) 2 (CO) 6 (PEt 3 ) 2 ] (15), [Mo 2 Pt 2 (η 5 -C 5 H 4 NMe 2 ) 2 (CO) 6 -(PEt 3 ) 2 ] (16), and [Mo 2 Pt 2 (η 5 -C 5 H 4 NMe 2 ) 2 (CO) 8 ] (20), have been characterized by single-crystal X-ray diffraction. Their structural features were compared with those of the 54 CVE cluster [Re 2 Pd 2 (η 5 -C 4 H 4 BPh) 2 (CO) 6 )] (4), previously obtained from the borole-containing metalate [Re(η 5 -C 4 H 4 BPh)(CO) 3 ] - (2), in which a 2e-3c B-C ipso -Pd interaction involving the π-ring was observed. As an extension of what has been observed in 4, clusters 12 and 13 present a direct interaction of the boratanaphthalene (12) and the boratabenzene (13) ligands with palladium. In clusters 11, 15, 16, and 20, the π-ring does not interact with the palladium (11 and 15) or platinum centers (16 and 20), which confers to these clusters a geometry very similar to that of [Mo 2 Pd 2 (η 5 -C 5 H 5 ) 2 (CO) 6 (PEt 3 ) 2 ] (3b). The carbonylmetalates [Mo(π-ring)(CO) 3 ] - are thus best viewed as formal four electron donors which bridge a dinuclear d 9 -d 9 unit. The orientation of this building block in the clusters influences the shape of their metal cores and the bonding mode of the bridging carbonyl ligands. The crystal structure of new centrosymmetric complex [Mo(η 5 -C 5 H 4 Ph)(CO) 3 ] 2 (10) was determined, and it revealed intramolecular contacts of 2.773(4) A between the carbon atoms of carbonyl groups across the metal-metal bond and intermolecular bifurcated interactions between the carbonyl oxygen atoms (2.938(4) and 3.029(4) A, as well as intermolecular C-H···π Ar (C=C) interactions (2.334· (3) and 2.786(4) A) involving the phenyl substituents.

Dinuclear, divalent acetylacetonato (acac) complexes of the type [M(acac){mu-C6H2(--NR)4}M(acac)] (M = Ni, Pd) have been prepared by the reaction of the corresponding bis(acac) metal precursor with 2,5-diamino-1,4-benzoquinonediimines C6H2(NHR)2(=NR)2 (4a, R = CH2-t-Bu; 4b, R = CH2Ph; 4c, R = Ph), which are metalated and become bridging ligands, also like in the complex [(C8H11)Pt{mu-C6H2(--NCH2-t-Bu)4}Pt(C8H11)] (6) obtained by the reaction of 4a with [PtCl2(COD)]. The complexes were fully characterized, including by X-ray diffraction for [Ni(acac){mu-C6H2(--NCH2Ph)4}Ni(acac)] (9b) and [Pd(acac){mu-C6H2(--NCH2-t-Bu)4}Pd(acac)] (10a). The coordination geometry around the metal ions is square-planar, and a complete electronic delocalization of the quinonoid pi system occurs between the metal centers over the two N--C--C--C--N halves of the ligand. The nature of the N substituent explains the differences between the supramolecular stacking arrangements found for [Ni(acac){mu-C6H2(--NR)4}Ni(acac)] (9a; R = CH2-t-Bu; 9b, R = CH2Ph). The Ni complexes were evaluated as catalyst precursors for ethylene oligomerization in the presence of AlEtCl(2) or MAO as the cocatalyst, in particular in order to study possible cooperative effects resulting from electronic communication between the metal centers and to examine the influence of the N substituent on the activity and selectivity. These catalysts afforded mostly ethylene dimers and trimers.

The dinuclear complex Fe2(μ2-η2-S2)(CO)6 (1) has been reacted with the bis(amino)stannylene Sn(μ-Nt-Bu)2SiMe2 (2) to form the new 1:1 complex Me2Si(μ-Nt-Bu)2SnFe2(μ3-S)2(CO)6 (4). The ‘double-star’ shape of its Fe2S2Sn central core (X-ray structure analysis, multinuclear NMR) contains a tetracoordinated tin atom, which provides a spirocyclic connection between the Fe2S2 butterfly and the four-membered SnN2Si cycle. The reaction can thus be described as an insertion of the divalent tin into the sulphur–sulphur bond of the Fe2(μ2-η2-S2)(CO)6 precursor. All distances and angles in 4 are in accordance with tin being in the formal oxidation state +4. The Sn–N bonds in this cluster can serve as excellent targets for the subsequent addition of thiols (sulphanes). Indeed, these bonds are highly reactive and when HS(CH2)2SH is allowed to react with 4, the cluster is destroyed and the spiro-cyclic tin sulphide Sn[S2(CH2)2]2 is the only isolable reaction product. If HS(CH2)2SH is replaced by Me3Si(CH2)2SH, the 1:1 adduct Me2Si(μ-Nt-Bu)[μ-N(H)t-Bu]Sn{S(CH2)2SiMe3}(μ3-S)2Fe2(CO)6 (6a) is isolated. This new cluster contains a five-coordinate tin atom (three S and two N donors) and has several functional groups (X-ray structure analysis, NMR). The proton of the thiol reagent Me3Si(CH2)2SH has migrated to one of the nitrogen atoms as a result of selective S–H addition across an Sn–N bond, while the Fe2S2Sn core remains intact. To the best of our knowledge, no other tin compound displaying two nitrogen and three sulphur ligands has been structurally described before. To cite this article: M. Veith et al., C. R. Chimie 8 (2005).

The phosphinooxazoline ligands 9−12 have been prepared and used to examine and compare the catalytic properties of their corresponding Ni(II) complexes in ethylene oligomerization. The molecular structure of rac-2-[1‘-(diphenylphosphanyl)ethyl]-4,4-dimethyl-4,5-dihydrooxazole (10) has been determined by X-ray diffraction. The paramagnetic Ni(II) complexes [NiX(μ-X)(P,N)]2 (19, X = Br, P,N = 2-[(diphenylphosphanyl)methyl]-4,4-dimethyl-4,5-dihydrooxazole (9)); 20, X = Cl, P,N = 9; 21, X = Cl, P,N = 10); 22, X = Cl; P,N = 2-[(diphenylphosphanyl)methyl]-4-(R)-phenyl-4,5-dihydrooxazole (12)); 23, X = Br, P,N = 12) and [NiCl2(P,N)] (24; P,N = 2-[1‘-(diphenylphosphanyl)-1‘-methylethyl]-4,4-dimethyl-4,5-dihydrooxazole (11)) were prepared in yields of 79−90%, and 19 and 24 have been characterized by X-ray diffraction. The former is a dinuclear complex with distorted-trigonal-bipyramidal geometry around the Ni(II) centers, whereas 24 is a mononuclear, tetrahedral complex, which underlines the strong influence of a ...

Short-bite ligand cluster stabilization is achieved in the tetrahedral clusters [Co4(μ-CO)3 (CO)7(μ-dppy)] (1a−c), obtained in high yields by reactions of [Co4(CO)12] with 1 equiv of the diphosphine ligands dppy, Ph2PCH2PPh2 (dppm), Ph2PNHPPh2 (dppa), or (Ph2P)2N(CH2)3Si(OEt)3 (dppaSi), respectively. The structure of 1a has been determined by X-ray diffraction, and the P atoms occupy axial positions on the basal face, transoid to a Co−Co bond. Clusters 1a−c were reacted with phenylacetylene to afford the corresponding butterfly clusters [Co4(μ-CO)2(CO)6(μ-dppy)(μ4-η2-PhC2H)] (2a−c) by insertion of the alkyne into a Co−Co bond of the precursor. This was established by an X-ray diffraction study of [Co4(μ-CO)2(CO)6(μ-dppm)(μ4-η2-PhC2H)] (2a). In an alternative synthetic procedure, the alkyne cluster [Co4(CO)10(μ4-η2-PhC2H)] (3), prepared from [Co4(CO)12] and phenylacetylene, was reacted with the diphosphines dppy. This led in good yields to butterfly clusters, isomeric with 2a−c in terms of the position of ...

It is shown that phosphinooxazolines such as (2-oxazoline-2-ylmethyl)diphenylphosphine 1 can be used as P,N assembling ligands for the synthesis of heterometallic complexes. These were obtained in a stepwise manner from the iron carbonyl complexes containing one, [Fe(CO)4(PCH2-oxazoline-P)] 2, or two, trans-[Fe(CO)3(PCH2-oxazoline-P)2] 6, P-bound phosphinooxazoline ligands. These metalloligands were then reacted with metal complexes. With 2, complete ligand transfer from Fe to the second metal (Pd) was sometimes observed. The metal–metal bonded complex [(OC)4Fe(μ-PCH2-oxazoline-P,N)PdCl2] 3 was of limited stability, whereas the trinuclear complex trans-[{(OC)4Fe(μ-PCH2-oxazoline-P,N)}2CoCl2] 4, in which 2 functions as a N-donor metalloligand toward the tetrahedral Co(II) centre, was stable and could be fully characterised by X-ray diffraction. This complex catalyses the oligomerization of ethylene to give linear α-olefins in the range C4–C26, with a maximum of the Schulz-Flory distribution around C6. The complex [{(OC)4Fe(μ-PCH2-oxazoline-P,N)}2HgI2] 5 was also prepared from 6. With the metalloligand 6, the Fe→Pd and Fe→Co metal–metal bonded compounds trans-[(OC)3Fe(μ-PCH2-oxazoline-P,N)2Pd(NCMe)](BF4)28 and trans-[(OC)3Fe(μ-PCH2-oxazoline-P,N)2CoCl2] 9 were obtained.

We describe the synthesis and reactivity towards metal cations of metalloligands that contain a Fe–Hg–Fe chain-like core consisting of two iron carbonyl fragments bonded to a central mercury atom and linked to a donor function available for further metal complexation. Free rotation of these fragments about the Fe–Hg–Fe metal–metal σ bonds allows greater adaptability to the nature and stoichiometry of the added metal complex. The structures of the chain complexes [Hg{Fe[Si(OMe) 3 ](CO) 3 (dppm-E)} 2 ] ( 6 , E = S; 7 , E = O) with pendent phosphine sulphide or oxide moieties were determined by single crystal X-ray diffraction. To cite this article: W. Schuch et al., C. R. Chimie 6 (2003) 000–000 .

The new cluster [Cp2MoFe2(μ3-S)2(CO)6] (1) was obtained by the reaction of [Fe2(μ2-η2-S2)(CO)6] with [Cp2MoH2]. Its “double-star” shape was established by single crystal X-ray diffraction analysis. It possesses a pseudo mirror plane passing through the Mo atom and the middle of the Fe–Fe bond. This cluster and the known tetranuclear cluster [Cp2Mo2Fe2(μ3-S)2(CO)8] (2) have been used as precursors for the formation of thin films, using the Metal Organic Deposition (MOD) process on silicon or borosilicate glass substrates. After thermal treatment of the films, the mixed-metal oxide phase Fe2MoxOz (3