An Unsaturated Four-Coordinate Dimethyl Dimolybdenum Complex with a Molybdenum-Molybdenum Quadruple Bond.
We describe the synthesis and the molecular and electronic structures of the complex [Mo2Me2{μ-HC(NDipp)2}2] (2; Dipp=2,6-iPr2C6H3), 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 [Mo2Me(μ-Me){μ-HC(NDipp)2}2(L)] (3⋅THF and 3⋅PMe3, respectively) with one terminal and one bridging methyl group. In contrast, 4-dimethylaminopyridine (dmap) forms the bis-adduct [Mo2Me2{μ-HC(NDipp)2}2(dmap)2] (4), with terminally coordinated methyl groups. Hydrogenolysis of complex 2 leads to the bis(hydride) [Mo2H2{μ-HC(NDipp)2}2(thf)2] (5⋅THF) with elimination of CH4. Computational, kinetic, and mechanistic studies, which included the use of D2and of complex 2 labelled with13C (99 %) at the Mo-CH3sites, 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.
Instituto de Investigaciones Químicas (IIQ), Departamento de Química Inorgánica and Centro de Innovación en Química Avanzada (ORFEO-CINQA), Consejo Superior de Investigaciones Científicas (CSIC) and Universidad de Sevilla, Avda. Américo Vespucio, 49, 41092, Sevilla, Spain.
Natalia
N
Curado
Instituto de Investigaciones Químicas (IIQ), Departamento de Química Inorgánica and Centro de Innovación en Química Avanzada (ORFEO-CINQA), Consejo Superior de Investigaciones Científicas (CSIC) and Universidad de Sevilla, Avda. Américo Vespucio, 49, 41092, Sevilla, Spain.
Mario
M
Carrasco
Instituto de Investigaciones Químicas (IIQ), Departamento de Química Inorgánica and Centro de Innovación en Química Avanzada (ORFEO-CINQA), Consejo Superior de Investigaciones Científicas (CSIC) and Universidad de Sevilla, Avda. Américo Vespucio, 49, 41092, Sevilla, Spain.
Jesús
0000-0002-5155-1262
J
Campos
Instituto de Investigaciones Químicas (IIQ), Departamento de Química Inorgánica and Centro de Innovación en Química Avanzada (ORFEO-CINQA), Consejo Superior de Investigaciones Científicas (CSIC) and Universidad de Sevilla, Avda. Américo Vespucio, 49, 41092, Sevilla, Spain.
Celia
C
Maya
Instituto de Investigaciones Químicas (IIQ), Departamento de Química Inorgánica and Centro de Innovación en Química Avanzada (ORFEO-CINQA), Consejo Superior de Investigaciones Científicas (CSIC) and Universidad de Sevilla, Avda. Américo Vespucio, 49, 41092, Sevilla, Spain.
Amor
A
Rodríguez
Departament de Química Inorgànica and Institut de Química Teòrica i Computacional, Universitat de Barcelona, Martí i Franquès 1-11, 08028, Barcelona, Spain.
Eliseo
E
Ruiz
Departament de Química Inorgànica and Institut de Química Teòrica i Computacional, Universitat de Barcelona, Martí i Franquès 1-11, 08028, Barcelona, Spain.
Santiago
S
Álvarez
Instituto de Investigaciones Químicas (IIQ), Departamento de Química Inorgánica and Centro de Innovación en Química Avanzada (ORFEO-CINQA), Consejo Superior de Investigaciones Científicas (CSIC) and Universidad de Sevilla, Avda. Américo Vespucio, 49, 41092, Sevilla, Spain.
Ernesto
E
Carmona
agostic interactions; alkyl complexes; dimolybdenum; kinetics; theoretical calculations