SYNTHESIS, CRYSTAL-STRUCTURES AND SPECTROSCOPIC PROPERTIES OF CATIONIC CARBYNE COMPLEXES OF MOLYBDENUM AND TUNGSTEN SUPPORTED BY TRIPODAL NITROGEN, PHOSPHORUS AND SULFUR DONOR LIGANDS

Reaction of the tridentate ligands HCpy(3) or Ppy(3) (py = 2-pyridyl) with Cl(CO)(2)py(2)M=CPh (M = Mo, W) in THF at elevated temperature fo llowed by metathesis with NaBPh4 in CH3CN affords [(eta(3)-Xpy(3))(CO) (2)M=CPh](+) (M = W, X = P (2), HC (3); M = Mo, X = P (4)) in high yie ld. Interaction between 1,1,1-tris(diphenylphosphinomethyl)ethane (CH3 C(CH2PPh2)(3)) or 1,4,7-trithiacyclononane (TTCN) and Cl(CO)(2)py(2)W= CPh in the presence of AgPF6 in refluxing CH3CN gives [{CH3C(CH2PPh2)( 3)}(CO)(2)W=CPh]PF6 (5) and [(TTCN)(CO)(2)W=CPh]PF6 (6), respectively. These complexes exhibit intense absorption bands at 320-340 nm and we ak 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)(2)py(2)W=CPh was established by X-ray crystallography and shows that only two of the py ridine rings in Ppy(3) are bound to the metal center. The crystal stru ctures of 2 . EtOH and 3 . EtOH show that the W-N distance trans to th e carbyne moiety is significantly longer than those which are cis, and this is attributed to the strong trans influence of CPh compared to C O. (C) 1998 Elsevier Science S.A. All rights reserved.