Metal–carbonyl and metal–nitrosyl complexes. Part XVI. Comparison of the molecular structures of dicarbonyl(π-cyclopentadienyl)[bis-(trifluoromethyl)phosphino]iron, [(π-C5H5)Fe(CO)2P(CF3)2], and its oxidation product, [(π-C5H5)Fe(CO)2P(:O)(CF3)2], as determined by X-ray crystallography

Abstract

The molecular geometries of the complexes [(π-C5H5)Fe(CO)2P(CF3)2](1) and [(π-C6H6)Fe(CO)2P(:O)(CF3)2](2) have been determined by X-ray crystal-structure analysis. Mean P–C bond lengths [1·878(8) in (1), 1·887(6)A in (2)] demonstrate that the covalent radius of phosphorus is essentially the same in both complexes, but the difference in the Fe–P bond length [2·265(3) in (1), 2·191 (3)A in (2)] is interpreted in terms of increased Fe→P dπ–dπ back bonding in (2). The P–O bond length in (2) is 1·478(5)A. Both complexes crystallize in the monoclinic system, space group P21/c, with Z= 4; unit-cell dimensions are: (1), a= 8·602(7), b=11·924(9), c= 12·859(9)A, β= 112·75(9)°; (2), a= 11·938(8). b= 7·603(6), c= 13·818(9)A, β= 100·97(8)°. The crystal structures were elucidated by Fourier and full-matrix least-squares methods from diffractometer data. The analyses converged at R 4·8%[1882 reflections, (1)] and 4·5%[1777 reflections, (2)].