P−C and C−H Bond Cleavages in the Photochemical Reactions of [Fe2(η5-C5H5)2(CO)4] with Bis(diphenylphosphino)methane

The photochemical reactions of [Fe 2 Cp 2 (CO) 4 ] (Cp = η 5 -C 5 H 5 ) and the bidentate ligand Ph 2 PCH 2 PPh 2 give a complex mixture of products. These include the known complexes [Fe 2 Cp 2 (μ-CO) 2 (μ-Ph 2 PCH 2 PPh 2 )] and cis -[Fe 2 Cp 2 (μ-PPh 2 ) 2 (CO) 2 ], as well as the new species [Fe 2 Cp(μ-η 5:κ 1 -C 5 H 4 CH 2 PPh 2 )(μ-CO) 2 (CO)], cis -[Fe 2 Cp 2 (μ-H)(μ-PPh 2 )(CO) 2 ], [Fe 2 Cp(μ-η 5:κ 1 -C 5 H 4 CH 2 PPh 2 )(μ-H)(μ-PPh 2 )(CO)], trans -[Fe 2 Cp 2 (μ-H)(μ-PPh 2 )(CO)(PMePh 2 )], and [Fe 2 Cp 2 (μ-PPh 2 ) 2 (μ-CO)]. An intermediate species, trans -[Fe 2 Cp 2 (μ-CO) 2 (CO)(κ 1 -Ph 2 PCH 2 PPh 2 )], having an intact diphosphine ligand coordinated through one of the P atoms, can be detected at the early stages of the reaction. Separate experiments indicate that the latter species is the precursor of the unique diphosphine-bridged complex, but of none of the other products. The above results indicate that different P−C (diphosphine) and C−H (cyclopentadienyl) bond cleavage processes are operative under the conditions examined, as well as novel C−C bond formations. The structures of the new complexes are analyzed on the basis of the corresponding IR and NMR ( 1 H, 31 P, and 13 C) data, as well as a single-crystal X-ray study on the (diphenylphosphinomethyl)cyclopentadienyl complex [Fe 2 Cp(μ-η 5:κ 1 -C 5 H 4 CH 2 PPh 2 )(μ-CO) 2 (CO)]. A reassessment of the 31 P chemical shifts for cis - and trans -[Fe 2 Cp 2 (μ-PPh 2 ) 2 (CO) 2 ] is also made.