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 HCpy3 or Ppy3 (py = 2-pyridyl) with Cl(CO)2py2M=CPh (M = Mo, W) in THF at elevated temperature followed by metathesis with NaBPh4 in CH3CN affords [(n3-Xpy3)(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 (CH3C(CH2PPh2)3) or 1,4,7-trithiacyclononane (TTCN) and Cl(CO)2py2W≡CPh in the presence of AgPF6 in refluxing CH3CN gives [{CH3C(CH2PPh2)3}(CO) 2W=CPh]PF6 (5) and [(TTCN)(CO)2W≡CPh]PF6 (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 Ppy3 with Cl(CO)2py2W=CPh was established by X-ray crystallography and shows that only two of the pyridine rings in Ppy3 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. © 1998 Elsevier Science S.A. All rights reserved.