Structural characterizations of cis-Mo(CO)4(PPhMe2)(NHC5H10) and cis-Mo(CO)4(PPhMe2)(PPh3) and their solution reactivities toward carbon monoxide

Article abstract of DOI:10.1021/ic00134a075

The crystal and molecular structures of cis-Mo(CO)₄(PPhMe₂)(HNC₅H₁₀) (1) and cis-Mo(CO)₄(PPhMe₂)(PPh₃) (2) have been determined and are discussed in terms of the influence of structural and steric factors on the reactivities of cis-Mo(CO)₄L₂ molecules. Compound 1 forms monoclinic crystals in space group P2₁/c with a = 13.764 (3) ?, b = 10.693 (2) ?, c = 13.585 (2) ?, β = 98.99 (2)°, V = 1974 (1) ?³, and Z = 4. The structure was refined to R₁ = 0.038. Compound 2 forms monoclinic crystals in space group P2₁/n with a = 9.487 (1) ?, b = 17.757 (2) ?, c = 16.920 (1) ?, β = 98.72 (1)°, V = 2817.5 (5) ?³, and Z = 4. The structure was refined to R₁ = 0.030. The ¹³C NMR spectra have also been recorded, and they show that ³¹P-¹³C couplings are in the ranges 7.8-9.8 Hz for the cis arrangement and 24.2-31.3 Hz for the trans arrangement and that chemical shifts are increasingly downfield as the Mo-C bond lengths become shorter. Relative rates of reaction of the cis-Mo(CO)₄LL′ compounds with CO to give Mo(CO)₅PMe₂Ph are found to correlate well with steric factors.