Reactions of co-ordinated ligands. Part 32. The reaction of sulphur nucleophiles with cationic molybdenum alkyne complexes: alkyne rotation and the molecular structures of the complexes [Mo(SC6H4NO2-p){P(OMe)3}(η2-MeC2Me)(η-C5H5)] and [Mo(SC6H4SPh-o)(CO)(η2-MeC2Me)(η-C5H5)]
Abstract
Treatment of [Mo{P(OMe)3}2(η2-MeC2Me)(η-C5H5)][BF4] with NaSR (R = Me, p-NH2C6H4, p-MeOC6H4, p-MeC6H4, C6H5, or p-NO2C6H4) leads to displacement of P(OMe)3 and formation of [Mo(SR){P(OMe)3}(η2-MeC2Me)(η-C5H5)]. Similar reactions afforded [Mo(SePh){P(OMe)3}-(η2-MeC2Me)(η-C5H5)] and [Mo(SMe){P(OMe)3}(η2-ButC2H)(η-C5H5)]. Barriers to rotation of the but-2-yne ligand present in these complexes are related to electronic effects of the substituents on the thiolate ligand. The molecular structure of [Mo(SC6H4NO2-p){P(OMe)3}(η2-MeC2Me)-(η-C5H5)] has been established by single-crystal X-ray crystallography. Crystals are monoclinic, space group P21/n with a= 8.968(3), b= 20.104(9), c= 11.452(5)Å, β= 95.77(3), and Z= 4. Using 3 601 reflections measured on a four-circle diffractometer at 200 K, the structure has been refined to R 0.028, R′ 0.032. The molecule adopts the familiar three-legged piano stool geometry, in which the but-2-yne ligand is orientated such that the central C–C bond lies approximately parallel to the Mo–P vector. In contrast, [Mo(CO)(η2-MeC2Me)2(η-C5H5)][BF4] reacts with NaSMe to give the complexes [Mo(SMe)(CO)(η2-MeC2Me)(η-C5H5)] and [Mo2(CO)4(µ-MeC2Me)(η-C5H5)2], whereas the corresponding reaction with [Mo(NCMe)(η2-MeC2Me)2(η-C5H5)][BF4] affords [Mo(SMe)-(η2-MeC2Me)(η-C5H5)]. Reaction of sodium dimethyldithiocarbamate with [Mo(NCMe)(R1C2R2)2-(η-C5H5)][BF4](R1= R2= Me or R1= But, R2= H) gives the monoalkyne complexes [Mo(S2C–NMe2)(η2-R1C2R2)(η-C5H5)]. In contrast the anion [SC6H4SPh-o]– affords a separable mixture of [Mo(SC6H4SPh-o)(η2-R1C2R2)2(η-C5H5)] and [[graphic omitted]Ph-o)(η2-R1C2R2)(η-C5H5)]. Reaction of the S,S′-bidentate species with carbon monoxide gives [Mo(SC6H4SPh-o)(CO)(η2-MeC2Me)-(η-C5H5)], which was structurally identified by X-ray crystallography. Crystals are orthorhombic, space group P212121(no. 19) with Z= 4 in a unit cell of dimensions a= 9.852(3), b= 11.486(4), and c= 18.476(6)Å. From 1 714 independent intensities measured at 292 K the structure has been refined to R 0.059, R′ 0.041. The molecule adopts a piano stool geometry with the but-2-yne lying parallel to the Mo–CO vector. The dithioaryl ligand is monodentate.