SYNTHESIS AND REACTIONS OF BUT-2-YNE COMPLEXES OF TUNGSTEN(II) CONTAINING PYRIDINE-2-THIONATE (SC5H4N) - CRYSTAL-STRUCTURE OF [W(CO)(NCME)(SC5H4N)-(ETA-2-MEC2ME)2][BPH4]

The complex [WI2(CO)(NCMe)(eta2-MeC2Me)2].0.5CH2Cl2 reacted with an equimolar amount of K[SC5H4N] (SC5H4N = pyridine-2-thionate) to give [WI(CO)(SC5H4N)(eta2-MeC2Me)2] 1. Two equivalents of K[SC5H4N] yielded the mono (but-2-yne) complex [W(CO)(SC5H4N)2(eta2-MeC2Me)] 2. Complex 1 reacted with a slight excess of Na[BPh4] in acetonitrile to afford the cationic bis(but-2-yne) complex [W(CO)(NCMe)(SC5H4N)(eta2-MeC2Me)2][BPh4] 3 which has been crystallographically characterised: monoclinic, space group P2(1)/n, Z = 4. a = 19.806(21), b = 13.498(13), c = 15.289(13) angstrom, and beta = 117.4(1)-degrees. The structure was refined to R = 0.064 for 21 02 reflections above background. The coordination geometry about the tungsten may be considered to be octahedral, with the nitrogen and sulfur atoms of the pyridine-2-thionate ligand and the two cis and parallel but-2-yne ligands occupying the equatorial sites with the carbonyl and acetonitrile ligands in the axial sites. The reaction chemistry of 3 with neutral mono- and bi-dentate donor ligands is discussed. The barrier to but-2-yne rotation of several of the complexes was investigated by variable-temperature H-1 NMR spectroscopy, and C-13 NMR spectroscopy was used to suggest the number of electrons donated by the but-2-yne ligands to the tungsten in these complexes.