Reactions of the complexes [WI2(CO)(NCMe)(η2-RC2R)2](R = Me or Ph) with dithiocarbamates and related ligands, and the X-ray crystal structure of [WI(CO)(S2CNC4H8)(η,2-MEC2Me)2]
Abstract
The complexes [WI2(CO)(NCMe)(η2-RC2R)2](R = Me or Ph) react with 1 equivalent of S2CX–[X = NMe2, NEt2, N(CH2Ph)2, OEt, NC4H8, or NC5H10] in CH2Cl2 or Et2O at room temperature eventually to give the new bis(alkyne) complexes [WI(CO)(S2CX)(η2-RC2R)2]. Infrared spectral studies of the reaction of [WI2(CO)(NCMe)(η2-MeC2Me)2] with 1 equivalent of Na[S2CNEt2]·3H2O in CH2Cl2 suggest the formation of several intermediates including those with monodentate dithiocarbamate attached to tungsten. X-Ray single-crystal studies wen carried out on the compound [WI(CO)(S2CNC4H8)(η2-MeC2Me)2](9). Crystals of (9) are monoclinic, space group P21/n, in a unit cell of dimensions a= 9.256(8), b= 17.685(14), c= 10.962(11)Å, and β 90.5(1)°. The structure was refined to R= 0.061 for 2 097 reflections above background. The co-ordination geometry around the tungsten is octahedral with the two parallel cis-but-2-yne ligands trans to a sulphur and an iodide with the other sulphur of the dithiocarbamate and the carbonyl ligand occupying the axial sites. Variable-temperature 1H n.m.r. studies show complex (9) to he fluxional in solution. The complexes [WI2(CO)(NCMe)(η2-RC2R)2] also react with 2 equivalents of S2CX–[R = Me, X = NMe2, NEt2, N(CH2Ph)2, OEt, NC4H8, or NC5H10; R = Ph, X = NEt2 or OEt] to give the monoalkyne complexes [W(CO)(S2CX)2(η2-RC2R)]. 13C N.m.r. spectroscopy shows that the alkyne ligands in the bis(alkyne) complexes [WI(CO)(S2CX)(η2-RC2R)2] are donating an average of three electrons each to the metal, whereas the alkyne ligand in [W(CO)(S2CX)2(η2-RC2R)] is donating four electrons to the tungsten.