cis-Tetracarbonylbis(tricyclohexylphosphine)molybdenum(0) and pentacarbonyl(tricyclohexylphosphine)molybdenum(0).

In the present redetermination of the complex cis-tetracarbonylbis(tricyclohexylphosphine)molybdenum(0), (I), [Mo(C(18)H(33)P)(2)(CO)(4)] or cis-eta(1)-[P(C(6)H(11))(3)](2)Mo(CO)(4), the Mo atom has a distorted octahedral geometry with a large P-Mo-P angle of 104.8 (1) degrees. A strong trans influence on the carbonyls in (I) is seen in a shortening of the Mo-C and a lengthening of the C-O distances opposite the phosphines compared with those that are cis. This influence is greatly diminished in the complex pentacarbonyl(tricyclohexylphosphine)molybdenum(0), (II), [Mo(C(18)H(33)P)(CO)(5)] or eta(1)-[P(C(6)H(11))(3)]Mo(CO)(5), the core of which has a slightly distorted C(4v) geometry.