Cis-Tetracarbonylbis(Tricyclohexyl-Phosphine)Molybdenum(0) And Pentacarbonyl(Tricyclohexylphos-Phine)Molybdenum(0)

In the present redetermination of the complex cis-tetra-carbonylbis(tricyclohexylphosphine)molybdenum(0), (I), [Mo(C18H33P)(2)(CO)(4)] or cis-{eta (1)-[P(C6H11)(3)](2)}Mo(CO)(4), the Mo atom has a distorted octahedral geometry with a large PD 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(C18H33P)(CO)(5)] or {eta (1)-[P(C6H11)(3)]}Mo(CO)(5), the core of which has a slightly distorted C-4 nu geometry.