Structural investigations on new iron-acyl derivatives of B(C6F5)3

Reactions between [Fe(η-C5H5)(MeCO)(CO)(L)], L = PPh3 (1), PMe3 (2), PPhMe2 (3), PCy3 (4), CO (5), and B(C6F5)3 give new complexes [Fe(η-C5H5){MeCOB(C6F5)3}(CO)(L)] L = PPh3 (7), PMe3 (8), PPhMe2 (9), PCy3 (10), CO (11), where B(C6F5)3 coordinates selectively to the O-acyl groups. Hydrolysis of 7 gives [Fe(η-C5H5){HOB(C6F5)3}(CO)(PPh3)] (6). The X-ray structures of 6, 8 and 11 have been determined. Calculations, using density functional theory, demonstrate that the charge transfer to the acyl group on Lewis acid coordination is more significant in the σ than the π system. Both effects lead to a lengthening of the acyl C–O bond thus π populations cannot be inferred from the distance changes.