Preparation and reactions of cyclo-tetra-µ-lithio-tetrakis[bis(η-cyclo-pentadienyl)hydrido-molybdenum] and -tungsten] and some bis(η-cyclopentadienyl) derivatives of molybdenum and tungsten

Abstract

The dihydrides [M(η-C₅H₅)₂H₂](M = MO or W) react in toluene with n-butyl-lithium to give the tetramers [{M(η-C₅H₅)₂HLi}₄]. The tetramers react with PhCH₂Br or PhCOX [X = Cl, OMe, or (M = W)H] giving [M(CH₂Ph)₂(η-C₅H₅)₂] or [M(η-C₅H₅)₂(COPh)H] respectively. With carbon dioxide the monocarbonyls [M(η-C₅H₅)₂(CO)] are formed in high yield. The tetramer (M = W) reacts with acetyl chloride or benzophenone giving the compounds [W(η-C₅H₅)₂(COMe)H] or [W(η-C₅H₅)₂{C₆H₄(COPh-p)H] respectively. These compounds in carbon tetrachloride give the chloro-analogues [W(η-C₅H₅)₂(COMe)Cl] and [W(η-C₅H₅)₂{C₆H₄(COPh-p)}Cl]. The molybdenum tetramer with carbon monoxide gives both the monocarbonyl [Mo(η-C₅H₅)₂(CO)] and the cyclopentenyl compound [Mo(η-C₅H₅)(η³-C₅H₇)₂(Co)₂] The products of reaction between the dihydrides [M(η-C₅H₅)₂H₂] and methyl- or phenyl-lithium appear to be identical to those formed from LiBuⁿ. With ZnR₂(R = Et or Buⁿ) the dihydrides give polymeric compounds [{M(η-C₅H₅)₂Zn}_n]. The compounds [M(η-C₅H₅)_2–(COPh)Cl](M = Mo or W), [W(CH₂SiMe₃)₂(η-C₅H₅)₂], [M(η-C₅H₅)₂(C₆F₅)₂](M = Mo or W), and [Mo(η-C₅H₅)₂(η³-C₃H₄Me)][PF₆] are also described.