Structure of the dinuclear compound [Mo 2(C 5H 5) 2(CO) 4(μ-Ph 2PCH 2PPh 2)] in the crystal and in solution

Abstract

The synthesis of [Mo 2(η-C 5H 5) 2(CO) 4(μ-dppm)] ( 1) (dppm = Ph 2PCH 2PPh 2) from the parent hexacarbonyl, its spectra, and X-ray structure are reported. The Mo, Mo bond [3.327(1) Å] is significantly longer than in known related compounds such as the corresponding t BuPHCH 2PH t Bu compound [3.2109(4) Å] or the parent hexacarbonyl [3.235(1) Å]. The previously reported t BuPHCH 2PH t Bu compound and the dppm compound ( 1) have different conformations about the Mo Mo bond in the crystal, having gauche and anti arrangements of the cyclopentadienyl ligands, respectively. Compound ( 1) exists in solution in these two rotameric forms in equilibrium, interconvertingrapidly enough above room temperature to give NMR coalescence. The equilibrium between these rotamers was studied by variable temperature 1H and 31P NMR spectroscopy.