Heterometallic Derivatives of the Unsaturated Methyl-Bridged Complex [Mo2(η5-C5H5)2(μ-CH3)(μ-PCy2)(CO)2]. Photochemical Generation of Methylidyne-Bridged Clusters

The photochemical reactions of the methyl-bridged complex [Mo2CP2(mu-CH3)(mu-PCy2)(CO)(2)] (1) (Cp = eta 5-C5H5) with the carbonyl complexes [M(CO)6] (M = Cr, Mo, W) and [MnCP'(CO)(3)] (CP' eta(5)'-C5H4CH3) give the corresponding electron-precise methylidyne-bridged derivatives [MMO2CP2(mu(3)-CH(mu-PCy2)(CO)(7)] (Mo-Mo = 2.9340(13) angstrom for M = W) and [MnMo2CP2CP'(mu(3)-CH)(mu-PCy2)(CO)(4)] (Mo-Mo = 2,9678(6)angstrom in good yields. Under similar conditions, the reaction of 1 with [Ru-3(CO)(12)] gives the 46-electron methylidyne-bridged Cluster [Mo2RuCP2(mu(3)-CH)(mu-PCy2)(CO)(5)] (Mo-Mo 2.6824(7) angstrom, along with a small amount of the rnethoxy-bridged analogue [Mo2RUCP(2)(mu(3)-OCH3)(mu-PCy2)(CO)(5)]. A related iron species [FeMo2CP2(mu(3)-OCH3) (mu-PCy2)(CO)51 (Mo-Mo = 2.667(1) angstrom) can be prepared in moderate yield from the reaction of the 30-clectron methyl complex [Mo2CP2(mu-kappa(1) :eta(2)- CH3)(mu-PCy2)(mu-CO)] and [Fe-2(CO)(9)]. Compound 1 reacts with [Fe-2(CO)(9))] at room temperature to give the acetyl-bridged cluster [FeMo2)CP2(mu(3)-kappa(1):eta(2) :kappa(1)-C(O)CH3}{mu-PCy2)(CO)(5)] (Mo-Mo = 2.8474(5) angstrom) in high yield, which undergoes full cleavage of the acetyl C-0 bond UNDER thermal or photolytic activation to give the oxoethylidyne derivative [FeMo2CP2(mu(3)-CCH3)(mu-PCy2)(O)(CO)(4)] (Mo-Mo = 2.8469(4) angstrom). Under photochemical conditions, however, compound 1 reacts with [Fe2(CO)(9)] to give the methylidyne-bridged compound [FeMo2CP2(mu(4)-CH)(mu-PCy2)(CO)(8)] (Mo-Mo = 2.8351(7) angstrom as major species. This 60-electron cluster displays a butterfly Mo2Fe2 core with no agostic interactions of the methylidyne ligand.