Chemistry of phosphido-bridged dimolybdenum complexes. Part 3. Reinvestigation of the reaction between [Mo₂(η-C₅H₅)₂(CO)₆] and P₂Ph₄; X-ray structures of [Mo₂(η-C₅H₅)₂(µ-PPh₂)₂(CO)₂], [Mo₂(η-C₅H₅)₂(µ-PPh₂)₂(µ-CO)], and trans-[Mo₂(η-C₅H₅)₂(µ-PPh₂)₂O(CO)]

Abstract

The thermal reaction of [Mo2(η-C5H5)2(CO)2] with P2Ph2 in toluene gives [Mo2(η-C5H5)2(µ-PPh2)2-(CO)2] in high yield. An X-ray diffraction study shows a Mo–Mo double bond [2.712(2)Å] symmetrically bridged by two PPh2 groups, with a planar Mo2P2 core. Under u.v. irradiation, further decarbonylation occurs to give [Mo2(η-C5H5)2(µ-PPh2)2(µ-CO)], in which two PPh2 groups and a carbonyl ligand bridge a Mo–Mo triple bond of length 2.515(2)Å. Oxidation of either of these complexes gives cis- and trans-[Mo2(η-C5H5)2(µ-PPh2)2(CO)]; the structure of the trans isomer has been determined by X-ray diffraction. Protonation of [Mo2(η-C5H5)2(µ-PPh2)2(CO)2] occurs across the metal–metal bond to give [Mo2(η-C5H5)2(µ-H)(µ-PPh2)2(CO)2][BF4].