Hexakis(trimethylphosphine)molybdenum chemistry: dinitrogen, ethylene, butadiene, η-cyclopentadienyl, and related derivatives

Protonated diolefin complexes: Model systems for C;h activation via metal complexation

“…The protonated diolefin complexes of Co, Rh, and Ir 2a-c and 2a'-c', while similar in their dynamic behaviour to complexes of Fe [13], Mo [37] as well as Mn [17] recently described in the literature, are nevertheless unique in exhibiting three different structures A, B, and D in the ground state, depending on the metal or the substituents at the auxiliary ligand. The fluxional behaviour (1,4-H shift) is only observed for the coordinatively unsaturated 16e species, while for the CO and C1-adducts only the static form D is observed at room temperature, indicating that the suprafacial 1,4-H shift can only take place via a free coordination site at the metal, thus confirming the proposed mechanism.…”

Different Approaches to Mid-Valent, Paramagnetic Half-Sandwich Complexes of the Heavier Group 6 Metals

“…CpMoH(PMe 3 ) 3 was first reported by Brookhart et al 67 as an uncrystallizable wax, impure from cyclopentadiene oligomers, obtained from the oxidative addition of CpH to Mo(PMe 3 ) 6 . We have generated this compound from CpMoCl(PMe 3 ) 3 and LiBEt 3 H, eq.…”

“…The complete substitution of carbonyl ligands with phosphine donors should accomplish this goal, as illustrated for instance by the greater reactivity of Mo(PMe 3 ) 6 relative to Mo(PMe 3 ) x (CO) 6-x in C-H bond activation processes. 67 Half-sandwich Mo(II) complexes of the CpMoXL 3 type frequently contain p acidic ligands (mostly L = CO, but also L = carbene, L 2 = diene or XL = allyl), [68][69][70] or moderately acidic ligands such as phosphites. 71 Fully phosphine-substituted examples were limited to X = H. 67 We wanted to access similar derivatives where X = p-donor ligand, with the idea of destabilizing a saturated structure by filled-filled repulsion and stabilizing the unsaturated one by p-donation, 72 73 Thus, the easily available CpMoX(CO) 3 compounds are not suitable precursors to fully phosphine-substituted CpMoXL 3 .…”

“…67 Half-sandwich Mo(II) complexes of the CpMoXL 3 type frequently contain p acidic ligands (mostly L = CO, but also L = carbene, L 2 = diene or XL = allyl), [68][69][70] or moderately acidic ligands such as phosphites. 71 Fully phosphine-substituted examples were limited to X = H. 67 We wanted to access similar derivatives where X = p-donor ligand, with the idea of destabilizing a saturated structure by filled-filled repulsion and stabilizing the unsaturated one by p-donation, 72 73 Thus, the easily available CpMoX(CO) 3 compounds are not suitable precursors to fully phosphine-substituted CpMoXL 3 . This left us with the use of a reductive route on the CpMo(III) compounds that we had just synthesized (see previous section) according to eq.…”

Imido–hydrido complexes of Mo(iv): catalysis and mechanistic aspects of hydroboration reactions

“…To further identify the potential catalytically active species in the hydroboration reactions, stoichiometric reactions between complex 2, unsaturated organic molecules and HBR (R = Cat, Pin) were studied. At ambient temperature, NMR scale reaction of 2 with HBCat results, within minutes, in the formation of a new tris( phosphine) complex, which was tentatively formulated as the agostic borane complex Mo(H) 2 27 Despite the instability, the agostic compound 15 can be generated on preparative scale in 82% yield by the reaction of the dihydride 2 with one equivalent of HBCat at −30°C and can be stored at this temperature under inert atmosphere for several days. On the other hand, treatment of the dihydride complex 2 with ketones resulted in complex reaction mixtures.…”