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We describe the synthesis and the molecular and electronic structures of the complex [Mo 2 Me 2 {μ-HC(NDipp) 2 } 2 ] (2; Dipp=2,6-iPr 2 C 6 H 3 ), which contains a dimetallic core with an Mo-Mo quadruple bond and features uncommon four-coordinate geometry and has a fourteen-electron count for each molybdenum atom. The coordination polyhedron approaches a square pyramid, with one of the molybdenum atoms nearly co-planar with the basal square plane, in which the trans coordination position with respect to the Mo-Me bond is vacant. The other three sites are occupied by two trans nitrogen atoms of different amidinate ligands and the methyl group. The second Mo atom occupies the apex of the pyramid and forms an Mo-Mo bond of length 2.080(1) Å, consistent with a quadruple bond. Compound 2 reacts with tetrahydrofuran (THF) and trimethylphosphine to yield the mono-adducts [Mo 2 Me(μ-Me){μ-HC(NDipp) 2 } 2 (L)] (3⋅THF and 3⋅PMe 3 , respectively) with one terminal and one bridging methyl group. In contrast, 4-dimethylaminopyridine (dmap) forms the bis-adduct [Mo 2 Me 2 {μ-HC(NDipp) 2 } 2 (dmap) 2 ] (4), with terminally coordinated methyl groups. Hydrogenolysis of complex 2 leads to the bis(hydride) [Mo 2 H 2 {μ-HC(NDipp) 2 } 2 (thf) 2 ] (5⋅THF) with elimination of CH 4 . Computational, kinetic, and mechanistic studies, which included the use of D 2 and of complex 2 labelled with 13 C (99 %) at the Mo-CH 3 sites, supported the intermediacy of a methyl-hydride reactive species. A computational DFT analysis of the terminal and bridging coordination of the methyl groups to the Mo≣Mo core is also reported., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The low-electron-count cationic platinum complex [Pt(ItBu')(ItBu)][BAr F ], 1, interacts with primary and secondary silanes to form the corresponding σ-SiH complexes. According to DFT calculations, the most stable coordination mode is the uncommon η 1 -SiH. The reaction of 1 with Et 2 SiH 2 leads to the X-ray structurally characterized 14-electron Pt II species [Pt(SiEt 2 H)(ItBu) 2 ][BAr F ], 2, which is stabilized by an agostic interaction. Complexes 1, 2, and the hydride [Pt(H)(ItBu) 2 ][BAr F ], 3, catalyze the hydrosilation of CO 2 , leading to the exclusive formation of the corresponding silyl formates at room temperature., (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

To clarify the nature of the Mo-Carene interaction in terphenyl complexes with quadruple Mo-Mo bonds, ether adducts of composition [Mo2 (Ar')(I)(O2 CR)2 (OEt2)] have been prepared and characterized (Ar'=Ar(Xyl) 2 , R=Me; Ar'=ArMes2, R=Me; Ar'=Ar(Xyl2), R=CF3) (Mes=mesityl; Xyl=2,6-Me2 C6 H3, from now on xylyl) and their reactivity toward different neutral Lewis bases investigated. PMe3 , P(OMe)3 and PiPr3 were chosen as P-donors and the reactivity studies complemented with the use of the C-donors CNXyl and CN2 C2 Me4 (1,3,4,5-tetramethylimidazol-2-ylidene). New compounds of general formula [Mo2 (Ar')(I)(O2 CR)2 (L)] were obtained, except for the imidazol-2-ylidene ligand that yielded a salt-like compound of composition [Mo2 (Ar(Xyl2))(O2 CMe)2 (CN2 C2 Me4)2]I. The Mo-Carene interaction in these complexes has been analyzed with the aid of X-ray data and computational studies. This interaction compensates the coordinative and electronic unsaturation of one of the Mo atoms in the above complexes, but it seems to be weak in terms of sharing of electron density between the Mo and Carene atoms and appears to have no appreciable effect in the length of the Mo-Mo, Mo-X, and Mo-L bonds present in these molecules., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The bis(hydride) dimolybdenum complex, [Mo2(H)2{HC(N-2,6-iPr2C6H3)2}2(thf)2], 2, which possesses a quadruply bonded Mo2(II) core, undergoes light-induced (365 nm) reductive elimination of H2 and arene coordination in benzene and toluene solutions, with formation of the Mo(I)2 complexes [Mo2{HC(N-2,6-iPr2C6H3)2}2(arene)], 3⋅C6H6 and 3⋅C6H5Me, respectively. The analogous C6H5OMe, p-C6H4Me2, C6H5F, and p-C6H4F2 derivatives have also been prepared by thermal or photochemical methods, which nevertheless employ different Mo2 complex precursors. X-ray crystallography and solution NMR studies demonstrate that the molecule of the arene bridges the molybdenum atoms of the Mo(I)2 core, coordinating to each in an η(2) fashion. In solution, the arene rotates fast on the NMR timescale around the Mo2-arene axis. For the substituted aromatic hydrocarbons, the NMR data are consistent with the existence of a major rotamer in which the metal atoms are coordinated to the more electron-rich C-C bonds., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

New zincocenes [ZnCp'(2)] (2-5) with substituted cyclopentadienyl ligands C(5)Me(4)H, C(5)Me(4)tBu, C(5)Me(4)SiMe(2)tBu and C(5)Me(4)SiMe(3), respectively, have been prepared by the reaction of ZnCl(2) with the appropriate Cp'-transfer reagent. For a comparative structural study, the known [Zn(C(5)H(4)SiMe(3))(2)] (1), has also been investigated, along with the mixed-ring zincocenes [Zn(C(5)Me(5))(C(5)Me(4)SiMe(3))] (6) and [Zn(C(5)Me(5))(C(5)H(4)SiMe(3))] (7), the last two obtained by conproportionation of [Zn(C(5)Me(5))(2)] with 5 or 1, as appropriate. All new compounds were characterised by NMR spectroscopy, and by X-ray methods, with the exception of 7, which yields a side-product (C) upon attempted crystallisation. Compounds 5 and 6 were also investigated by (13)C CPMAS NMR spectroscopy. Zincocenes 1 and 2 have infinite chain structures with bridging Cp' ligands, while 3 and 4 exhibit slipped-sandwich geometries. Compounds 5 and 6 have rigid, eta(5)/eta(1)(sigma) structures, in which the monohapto C(5)Me(4)SiMe(3) ligand is bound to zinc through the silyl-bearing carbon atom, forming a Zn--C bond of comparable strength to the Zn--Me bond in ZnMe(2). Zincocene 5 has dynamic behaviour in solution, but a rigid eta(5)/eta(1)(sigma) structure in the solid state, as revealed by (13)C CPMAS NMR studies, whereas for 6 the different nature of the Cp' ligands and of the ring substituents of the eta(1)-Cp' group (Me and SiMe(3)) have permitted observation for the first time of the rigid eta(5)/eta(1) solution structure. Iminoacyl compounds of composition [Zn(eta(5)-C(5)Me(4)R)(eta(1)-C(NXyl)C(5)Me(4)R)] resulting from the reactions of some of the above zincocenes and CNXyl (Xyl=2,6-dimethylphenylisocyanide) have also been obtained and characterised.