Structure, Bonding, and Reactivity of Binuclear Complexes Having Asymmetric Trigonal Phosphinidene Bridges: Addition of 16-Electron Metal Carbonyl Fragments to the Dimolybdenum Compounds [Mo2Cp(μ-κ1:κ1,η5-PC5H4)(CO)2L] and [Mo2Cp2(μ-PH)(CO)2L] (L = η6-1,3,5-C6H3tBu3)

The phosphinidene-bridged complexes [Mo2Cp(mu-kappa(1):kappa(1),eta(5)-PC(5)H4)(CO)2L] and [Mo2Cp2(mu-PH)(CO)(2)L] (Cp = eta(5)-C5H5; L = eta(6)-1,3,5-C(6)H3(t)Bu(3)) react readily with [Fe-2(CO)(9)] or the solvate complexes [M(CO)(5)(THF)] (M = Cr, Mo, W; THF = tetrahydrofuran) to give, as a result of the addition of the corresponding 16-electron M(CO)n fragments to their multiple Mo-P bonds, the trinuclear derivatives [FeMo2Cp(mu(3)-kappa(1):kappa(1):kappa(1),eta(5)-PC(5)H4)(CO)6L], [(MMoCp)-Cp-2(mu(3)-kappa(1):kappa(1):kappa(1),eta(5)-PC(5)H4)(CO)7L][FeMo2Cp2(mu(3)-PH)(CO)(6)L], and [MMo2Cp2(mu(3)-PH)(CO)(7)L]. The PH-bridged complexes display a distorted tetrahedral environment around their P atom, according to X-ray diffraction studies on the Fe, Cr, and W compounds, whereas the PC5H4-bridged ones display an unusual trigonal-pyramidal geometry around the P atoms (sum of M-P-M angles 359.6 degrees for the Fe compound). The latter species were stable toward hydrolysis, whereas the trinuclear PH-bridged complexes underwent easy hydrolysis of their P-Mo(metallocene) bonds to give the corresponding PH2-bridged derivatives [FeMoCp(mu-PH2)(CO)(6)L] and [MMoCp(mu-PH2)(CO)(7)L] (M = Cr, Mo, W).