Chemistry of di- and tri-metal complexes with bridging carbene or carbyne ligands. Part 25. Protonations of tolylmethylidyne ligands bridging tungsten–chromium, –cobalt, and –platinum bonds and the X-ray crystal structure of [PtW{µ-σ:η3-CH(C6H4Me-4)}(CO)2(PMe3)2(η-C5H5)][BF4]

Abstract

The Complex [Cr(thf)(CO)(NO)(η-C₅H₅)](thf = tetrahydrofuran), generated in situ from [Cr(CO)₂(NO)(η-C₅H₅)] by u.v. irradiation, reacts with [W(CC₆H₄Me-4)(CO)₂(η-C₅H₅)] to afford the dimetal compound [CrW(µ-CC₆H₄Me-4)(CO)₃(NO)(η-C₅H₅)₂]. Protonation of the latter, and the complexes [CoW(µ-CC₆H₄Me-4)(CO)₃(η-C₅H₅)(η-C₅Me₅)] and [PtW(µ-CC₆H₄Me-4)(CO)₂(PR₃)²(η-C₅H₅)](PR₃= PMe₃, PMe₂Ph, or PMePh₂), with HBF₄·Et₂O affords the salts [MW{µ-σ:η³-CH(C₆H₄Me-4)}(CO)₂(L_n)(η-C₅H₅)][BF₄][ML_n= Cr(CO)(NO)(η-C₅H₅), Co(CO)(η-C₅Me₅), or Pt(PR₃)₂]. N.m.r. data (¹H, ¹³C-{¹H}, ¹³P-{¹H}, and ¹⁹⁵Pt-{¹H}) for the new compounds are reported and discussed. A single-crystal X-ray diffraction study was made on the compound [PtW{µ-σ:η³-CH-(C₆H₄Me-4)}(CO)₂(PMe₃)₂(η-C₅H₅)][BF₄]. In this salt the Pt–W bond [2.795(1)Å] is bridged by the CH(C₆H₄Me-4) group in such a manner that two carbons of the aryl ring form an η₂ attachment to the tungsten so that the µσCH(C₆H₄Me-4) group as a whole adopts an η³-bonding mode to the tungsten and a to the platinum [W–C 2.166(14), 2.406(14), and 2.602(13)Å; Pt–µ-C 2.053(14)Å]. The tungsten atom carries a cyclopentadienyl ligand and a terminally bound CO group, while the remaining carbonyl semi-bridges the metal–metal bond [W–C–O 155.1 (14)°]. The platinum atom is in an essentially planar environment, ligated by the two PMe₃ groups, the tungsten atom, and the bridging carbon atom. Crystals are monoclinic (space group P2₁/c); the structure has been refined to R 0.054 for 3 430 reflections measured to 2θ= 50° at room temperature.