Cyclic hydroborate complexes of metallocenes. IV. Weak Unsupported single hydrogen bridges in Cp2Zr{μ-HB(X)CH2Ph}{(μ-H)2BX} (X = C5H10, C4H8)

Article abstract of DOI:10.1021/ic981347u

The compounds Cp₂Zr{(μ-H)(BC₅H₁₀)CH ₂Ph}{(μ-H)₂BC₅H₁₀}, 1, and Cp₂Zr{(μ-H)(BC₄H₈)CH ₂Ph}{(μ-H)₂BC₄H₈}, 2, were prepared in yields of 59percent and 51percent, respectively, from the the unsupported Zr-H-B bridge in complexes 1 and 2. However, NMR spectra at room temperature indicate that the hydrogen bridge is dissociated into Cp₂ZrH{(μ-H)₂BC₅H₁₀} and B(C₅H₁₀)CH₂Ph in the case of complex 1, and Cp₂ZrH{(μ-H)₂BC₄H₈} and B(C₄H₈)CH₂Ph in the case of complex 2. It is possible to pump away the B(C₄H₈)CH₂Ph from solid 2 at room temperature, leaving behind Cp₂ZrH{(μ-H)₂BC₄H₈}. These results suggest that the Zr-H bond acts as an electron pair donor to trivalent boron in the formation of 1 and 2. Crystal data for Cp₂Zr{(μ-H)(BC₅H₁₀)CH ₂Ph}{(μ-H)₂BC₅H₁₀}: monoclinic, P2₁/m (No. 11), a = 9.392(5) A?, b = 13.250(4) A?, c = 9.841(6) A?, β = 95.70(4)°, Z = 2. Crystal data for Cp₂Zr{(μ-H)(BC₄H₈)CH ₂Ph}{(μ-H)₂BC₄H₈}: orthorhombic, Pbca (No. 61), a = 18.1630(10) A?, b = 19.0497(10) A?, c = 13.0393(10) A?, Z = 8.