Chemistry of CS2- and SCNPh-adducts of the pyramidal phosphinidene-bridged complex [Mo2Cp(μ-κ1:κ1,η5-PC5H4)(CO)2(η6-HMes*)(PMe3)].

The title complex reacted readily with CS2 and SCNPh to give the phosphinidene-cumulene adducts [Mo2Cp{μ-κ1P:κ1S,η5-P(CS2)C5H4}(CO)2(η6-HMes*)(PMe3)] and [Mo2Cp{μ-κ1P:κ1S,η5-P(C(NPh)S)C5H4}(CO)2(η6-HMes*)(PMe3)] respectively (Mes* = 2,4,6-C6H2tBu3), as a result of the formal insertion of the C[double bond, length as m-dash]S bond of the heterocumulene into the metallocene Mo-P bond of the phosphinidene complex. The newly formed species bear a pyramidal P atom with a lone electron pair involved in fast inversion, and displayed strong nucleophilicity which enabled easy addition at the P site of carbon-based electrophiles and chalcogen atoms, while the uncoordinated S and N atoms were also competitive nucleophilic sites in these complexes. These air-sensitive materials readily added an O2 molecule in the solid state, to give the corresponding derivatives [Mo2Cp{μ-κ1O:κ1S,η5-OP(O)(C(X)S)C5H4}(CO)2(η6-HMes*)(PMe3)] (X = S, NPh), and the CS2 adduct reacted selectively with S8 in solution to give the sulfide derivative [Mo2Cp{μ-κ1P:κ1S,η5-P(S)(CS2)C5H4}(CO)2(η6-HMes*)(PMe3)], which was stabilized through methylation, thus yielding the cationic complex [Mo2Cp{μ-κ1P:κ1S,η5-P(S)(C(SMe)S)C5H4}(CO)2(η6-HMes*)(PMe3)]+. The CS2 adduct could be methylated selectively at either the P or C[double bond, length as m-dash]S sites, depending on the reagent used, to give respectively the cationic complexes [Mo2Cp{μ-κ1P:κ1S,η5-PMe(CS2)C5H4}(CO)2(η6-HMes*)(PMe3)]+ or [Mo2Cp{μ-κ1P:κ1S,η5-P(C(SMe)S)C5H4}(CO)2(η6-HMes*)(PMe3)]+. Further methylation could be accomplished through reaction with [Me3O]BF4 to give the dipositive cation [Mo2Cp{μ-κ1P:κ1S,η5-PMe(C(SMe)S)C5H4}(CO)2(η6-HMes*)(PMe3)]2+. In contrast, the SCNPh adduct was only methylated at the P site to yield the phosphanylthioformamidato complex [Mo2Cp{μ-κ1P:κ1S,η5-PMe(C(NPh)S)C5H4}(CO)2(η6-HMes*)(PMe3)]+, but was readily protonated at the N site upon reaction with (NH4)PF6, to give the phosphanylthioformamide-like derivative [Mo2Cp{μ-κ1P:κ1S,η5-P(C(NHPh)S)C5H4}(CO)2(η6-HMes*)(PMe3)]+. In the presence of Na(BAr'4), this adduct was even able to displace chloride from the solvent (dichloromethane) to give the corresponding chloromethyl derivative [Mo2Cp{μ-κ1P:κ1S,η5-P(CH2Cl)(C(NPh)S)C5H4}(CO)2(η6-HMes*)(PMe3)]+. The structures of the new complexes were analyzed using spectroscopic, diffractometric and, in some cases, density functional theory methods.