Preparation and properties of metallacyclopentane and dineopentyl derivatives of molybdenocene and tungstenocene. X-Ray crystal and molecular structure of bis(η-cyclopentadienyl)molybdenacyclopentane

Abstract

The interaction of [Mo(η-C₅H₅)₂I₂] with the appropriate dilithium reagents yields the metallacyclopentane derivatives [[graphic omitted]H₂)(η-C₅H₅)₂](1), [[graphic omitted]H₂}(η-C₅H₅)₂](2), and [[graphic omitted]H₂)(η-C₅H₅)₂](3). Structures for these compounds are proposed on the basis of elemental analysis, n.m.r. and mass spectrometry. The crystal structure of the molybdenum parent compound (1) has been determined from X-ray diffractometer data and refined by least squares. Crystals of (1) are Monoclinic, space group P2₁/c, with unit-cell parameters a= 11.352(2), b= 7.665(1), c=16.111(3)Å, β= 121.37(2)°, and Z= 4; R= 0.047 based on 1 272 observed reflections. The structural details are discussed also in terms of their chemical significance. Carbonylation of (1) yields cyclopentanone; compounds (1)–(3) give, by thermal decomposition, the corresponding olefins as the major products in addition to small amounts of olefins derived from metallacycle fragmentation. The dineopentyl derivatives [M(CH₂CMe₃)₂(η-C₅H₅)₂](M = Mo or W) have been prepared and their thermal decomposition has been investigated. No isolable metallacyclobutane has been obtained.