Steric contributions to the solid-state structures of bis(phosphine) derivatives of molybdenum carbonyl. X-ray structural studies of cis-Mo(CO)4[PPh3-nMen]2 (n = 0, 1, 2)

Article abstract of DOI:10.1021/ic00131a055

The crystal and molecular structures of three cis-Mo(CO)₄(PR₃)₂ compounds - PR₃ = PMe₂Ph (1), PR₃ = MePh₂ (2), and PPh₃ = PR₃ (3) - have been determined to provide data for assessing the influence of steric effects on the stability and reactivity of such molecules. In the order 1, 2, 3, the following changes occur: 〈P-Mo-P = 94.78 (5), 92.52 (5), 104.62 (7)°; r(Mo-P) = 2.529 (3), 2.555 (5), 2.577 (2) A?. The irregularity in the angle changes is probably due to the rotational orientations of the ligands in 1 and 2 and may be characteristic of the solid state only. Crystallographic data are as follows. 1: P2₁2₁2₁ with a = 8.203 (1) A?, b = 9.795 (1) A?, c = 27.604 (4) A?, V = 2217 (1) A?³, Z = 4. 2: Pc with a = 9.648 (2) A?, b = 10.670 (3) A?, c = 14.065 (1) A?, β = 98.22 (1)° V = 1433 (1) A?³, Z = 2. 3: P1 with a = 11.522 (1) A?, b = 16.909 (3) A?, c = 9.633 (2) A?, α = 98.05 (2)°, β = 110.29 (1)°, γ = 99.95 (1)°, V = 1693 (1) A?³, Z = 2. The steric and electronic factors that may affect the molecular structures are discussed, and it is shown that steric factors play a key role (affecting also the chemical reactivity) but not in a quantitatively predictable way.