The synthesis, fluxional properties and X-ray crystal structure of [WI(CO)(C4H3N2S)(η2-MeC2Me)2] (where [C4H3N2S]− = pyrimidine-2-thionate)

Abstract Reaction Of [WI 2 (CO)(NCMe)(η 2 -MeC 2 Me) 2 ]· 1 2 CH 2 Cl 2 with one equivalent of K[C 4 H 3 N 2 S] (C 4 H 3 N 2 S = pyrimidine-2-thionate) in diethyl ether at room temperature affords the monoiodide product [WI(CO)(C 4 H 3 N 2 S)(η 2 -MeC 2 Me) 2 ] ( 1 ) in high yield. The molecular structure of 1 has been crystallographically determined and is best described as a distorted octahedron, with one of the but-2-yne ligands lying trans to the iodide and both of them occupying the axial positions, and the remaining alkyne, carbon monoxide and the sulphur and nitrogen atoms of the pyrimidine-2-thionate ligand occupying the equatorial positions. Variable-temperature 1 H NMR spectroscopic studies have shown the complex [WI(CO)(C 4 H 3 N 2 S)(η 2 -MeC 2 Me) 2 ] ( 1 ) to be fluxional. 13 C NMR spectroscopy indicates that the alkyne ligands donate a total of six electrons to the tungsten in 1 .