Phosphinidene-Bridged MoMn Derivatives of the Thiophosphinidene Complex [Mo2Cp2(μ‑κ2:κ1,η6‑SPMes*)(CO)2] (Mes* = 2,4,6‑C6H2tBu3)

The title complex (1) reacted with [Mn2(CO)10] under visible–UV irradiation (toluene solution and quartz glassware) to give a mixture of the phosphinidene complex [MnMoCp­(μ-κ1:κ1,η6-PMes*)­(CO)4], the cluster [Mn2Mo2Cp2(μ-κ1:κ1,η6-PMes*)­(μ3-S)­(CO)8], and the thiophosphinidene complex [MnMoCp­(μ-κ2:κ1,η4-SPMes*)­(CO)5], in yields of ca. 60, 20, and 10% respectively (Mes* = 2,4,6-C6H2tBu3). The major product follows from formal replacement of the SMoCp­(CO)2 fragment in 1 with a Mn­(CO)4 fragment, and displayed multiple bonding to phosphorus (Mn–P = 2.1414(8) Å); the tetranuclear cluster results from formal insertion of a Mn2(CO)6 fragment in 1, with cleavage of P–S and P–Mo bonds, to render a μ3-S bridged Mn2Mo core bearing an exocyclic phosphinidene ligand involved in multiple bonding to one of the Mn atoms (Mn–P = 2.140(2) Å); the thiophosphinidene complex (Mn–P = 2.294(1) Å) formally results from addition of sulfur and carbon monoxide to the major MnMo product, a transformation which actually could be performed stepwise, via the MnMo thiophosphinidene complex [MnMoCp­(μ-κ2:κ1,η6-SPMes*)­(CO)4]. When the photolysis of 1 and [Mn2(CO)10] was performed in tetrahydrofuran solution and using conventional glassware, then the V-shaped cluster [Mn2MoCp­{μ-κ1:κ1:κ1,η5-P­(C6H3tBu3)}­(CO)8] was obtained selectively (Mo–Mn = 3.2910(5) Å, Mn–Mn = 2.9223(5) Å), which unexpectedly displays a cyclohexadienylidene-phosphinidene ligand resulting from H atom abstraction at the aryl ring of the precursor. Density functional theory calculations on the complexes [LnM­(μ-κ1:κ1,η6-PMes*)­MoCp] (MLn = MoCp­(CO)2, Mn­(CO)4, Co­(CO)3) revealed that the degree of delocalization of the metal–phosphorus π-bonding interaction over the Mo–P–M chain is significantly conditioned by the heterometal fragment MLn, it being increased in the order Mn ≤ Mo < Co.