Two molybdenum pentacarbonyl complexes with electroneutral phosphane ligands: [bis(morpholin-4-yl)(pentafluoroethyl)phosphane-κP]pentacarbonylmolybdenum(0) and pentacarbonyl[(pentafluoroethyl)bis(piperidin-1-yl)phosphane-κP]molybdenum(0).

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The crystal structures of the title compounds, [Mo{(C4H8NO)2P(C2F5)}(CO)5], (1a), and [Mo{(C5H10N)2P(C2F5)}(CO)5], (2a), were determined as part of a larger project that focuses on the synthesis and coordination chemistry of phosphane ligands possessing moderate (electroneutral, i.e. neither electron-rich nor electron-deficient) electronic characteristics. Both complexes feature a slightly distorted octahedral geometry at the metal center, due to the electronic and steric repulsions between two of the four equatorial CO groups and the pentafluoroethyl group attached to the phosphane ligand. Bond length and angle data for (1a) and (2a) support the conclusion that the free phosphane ligands are electroneutral. For complex (1a), the Mo-P, Mo-Cax and Mo-Ceq(ave) bond lengths are 2.5063 (5), 2.018 (2) and 2.048 (2) Å, respectively, and for complex (2a) these values are 2.5274 (5), 2.009 (3) and 2.050 (3) Å, respectively. Geometric data for (1a) and (2a) are compared with similar data reported for analogous Mo(CO)5 complexes.