Synthesis and reactions of but-2-yne complexes of tungsten(II) containing pyridine-2-thionate (SC5H4N): crystal structure of [W(CO)(NCMe)(SC5H4N)(η2– MeC2Me)2][BPh4]

Abstract

The complex [WI₂(CO)(NCMe)(η²– MeC₂Me)₂]·0.5CH₂Cl₂ reacted with an equimolar amount of K[SC₅H₄N](SC₅H₄N = pyridine-2-thionate) to give [WI(CO)(SC₅H₄N)(η²– MeC₂Me)₂]1. Two equivalents of K[SC₅H₄N] yielded the mono(but-2-yne) complex [W(CO)(SC₅H₄N)₂(η²– 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)(η²– MeC₂Me)₂][BPh₄]3 which has been crystallographically characterised: monoclinic, space group P2₁/c, Z= 4, a= 19.806(21), b= 13.498(13), c= 15.289(13)Å, and β= 117.4(1)°. The structure was refined to R= 0.064 for 2102 reflections above background. The co-ordination 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 ¹H NMR spectroscopy, and ¹³C NMR spectroscopy was used to suggest the number of electrons donated by the but-2-yne ligands to the tungsten in these complexes.