From μ3- to μ- agostic methyl coordination: NMR and solid state study of donor ligands uptake by the triangular cluster anion [Re3(μ-H)3(μ3-CH3)(CO)9]-

[Re3(μ-H)3(μ3-CH3)(CO)9]- (1) reacts with CO at 273 K to quantitatively give the [Re3(μ-H)3(μ-CH3)(CO)10]- derivative (2) through conversion of methyl group from triply doubly-bridging coordination. An NMR isotopic perturbation experiment demonstrates unsymmetrical bridging on Re-Re bond, and a fast exchange, in solution, between one agostic two terminal CH bonds. This is agreement X-Ray diffraction analysis performed single crystals 2. In solution room temperature 2 decomposes CH4 elimination, which also observed when treated affording [Re3(μ-H)2(CO)12]- anion. The opening triple coordination 1 occurs other different L ligands, yielding syn anti isomers unsymmetrically bridged complexes general formula [Re3(μ-H)3(μ-CH3)(CO)9(L)]- (L = MeCN, PMePh2, THF). kinetic thermodynamic stabilities these vary nucleophilicity ligand polarity solvent. particular, strong nucleophile PMePh2 affords quantitative anion into isomer, stable THF for several days. On contrary, weak nucleophiles, such as MeCN or THF, equilibrium mixtures containing residual amounts 1. adducts are hours, while decompose fastly neat mainly cluster [Re3(μ-H)4(CO)9(MeCN)]-. suggests that stabilization after methane evolution follows path respect reaction CO.