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

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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.