Synthesis, crystal structures and spectroscopic properties of cationic carbyne complexes of molybdenum and tungsten supported by tripodal nitrogen, phosphorus and sulphur donor ligands

Abstract

Reaction of the tridentate ligands HCpy 3 or Ppy 3 (py=2-pyridyl) with Cl(CO) 2py 2MCPh (M=Mo, W) in THF at elevated temperature followed by metathesis with NaBPh 4 in CH 3CN affords [( η 3-Xpy 3)(CO) 2MCPh] + (M=W, X=P ( 2), HC ( 3); M=Mo, X=P ( 4)) in high yield. Interaction between 1,1,1-tris(diphenylphosphinomethyl)ethane (CH 3C(CH 2PPh 2) 3) or 1,4,7-trithiacyclononane (TTCN) and Cl(CO) 2py 2WCPh in the presence of AgPF 6 in refluxing CH 3CN gives [{CH 3C(CH 2PPh 2) 3}(CO) 2WCPh]PF 6 ( 5) and [(TTCN)(CO) 2WCPh]PF 6 ( 6), respectively. These complexes exhibit intense absorption bands at 320–340 nm and weak absorptions in the 400–500 nm region, while excitation at 330 nm in dichloromethane give intense orange to red emission. The structure of the product ( 1) from reaction of Ppy 3 with Cl(CO) 2py 2WCPh was established by X-ray crystallography and shows that only two of the pyridine rings in Ppy 3 are bound to the metal center. The crystal structures of 2·EtOH and 3·EtOH show that the W–N distance trans to the carbyne moiety is significantly longer than those which are cis, and this is attributed to the strong trans influence of CPh compared to CO.