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.