Inorganic Chemistry, Vol.54, No.20, 9810-9820, 2015
Electronic Structure and Multisite Basicity of the Pyramidal Phosphinidene-Bridged Dimolybdenum Complex [Mo-2(eta(5)-C5H5)(mu-kappa(1):kappa(1),eta(5)-PC5H4)(eta(6)-(C6H3Bu3)-B u-t)(CO)(2)(PMe3)]
The title phosphinidene complex could be sequentially protonated with HBF4 center dot OEt2 or [H(OEt2)(2)](BAr'(4)) to give the phosphido-bridged derivatives [Mo2Cp (mu-kappa(1):kappa(1),eta(5)-HPC5H4)(eta(6)-HMes*)-(CO)(2)(PMe3)]X and then the hydrides [Mo2Cp (mu-kappa(1):kappa(1),eta(5)-HPC5H4)(eta(6)-HMes*)-(CO)(2)(PMe3)]X2 (X = BF4, BAr'(4); Ar' = 3,5-C6H3(CF3)(2); Mes* = 2,4,6-(C6H2Bu3)-Bu-t). Density functional theory (DFT) calculations revealed that the most favored site for initial electrophilic attack is the metallocene Mo atom, but attachment of the electrophile to the phosphinidene P atom gives more stable products. This was in agreement with all other reactions investigated, which invariably involved the attachment of the added electrophile at the P site. Thus, the title compound reacted with S8 at 223 K to give the thiophosphinidenebridged complex [Mo2Cp (mu-kappa(1):kappa(1),eta(5)-HPC5H4)(eta(6)-HMes*)-(CO)(2)(PMe3)], a poorly stable molecule which reacted with Mel at room temperature to give the corresponding thiolatophosphido derivative, isolated as [Mo2Cp (mu-kappa(1):kappa(1),eta(5)-HPC5H4)(eta(6)-HMes*)-(CO)(2)(PMe3)](BAr'(4)) (P-S = 2.128(4) angstrom) after anion exchange with Na(BAr'(4)). Reaction of the title compound with MeI proceeded smoothly to give the corresponding methylphosphido derivative, isolated analogously as [Mo2Cp (mu-kappa(1):kappa(1),eta(5)-HPC5H4)(eta(6)-HMes*)-(CO)(2)(PMe3)] (BAr'(4)). The related complex [Mo2Cp (mu-kappa(1):kappa(1),eta(5)-HPC5H4)(eta(6)-HMes*)-(CO)(2)(PMe3)](BAr'(4)) (P-C(Me) = 1.841(5) angstrom) could be prepared analogously from the neutral precursor [Mo2Cp {mu-kappa(1):kappa(1),eta(5)-HPC5H4}(eta(6)-HMes*)-(CO)(2)(PMe2Ph)]. In contrast, reaction of the title complex with ethylene sulfide involved opening of the C2S ring and formation of new P-C and Mo-S bonds (1.886(7) and 2.493(2) angstrom, respectively), with displacement of the PMe3 ligand, to give the phosphido-thiolato complex [Mo2Cp{mu-kappa(2)(P,S):kappa(1)(P),eta(5)-P(C2H4S)C5H4}(eta(6)-HMes*)(CO)(2)]. All these derivatives of the title complex displayed an unusual trigonal pyramidal-like environment around the bridging P atom, with the added electrophile placed in the Mo2P plane as a result of the directionality of the relevant frontier orbital of the phosphinidene complex, according to DFT calculations.