Phosphinomethyl complexes of zirconium: Preparation, complexation capabilities, and structural and chemical characteristics

Article abstract of DOI:10.1021/om50006a012

Syntheses of Cp₂Zr(Cl)CH₂PPh₂ (1) and Cp₂Zr(CH₂PPh₂)₂ (4) are described as is the X-ray crystal structure determination of the latter: monoclinic, space group P2₁/a, a = 17.377 (1) ?, b = 12.844 (1) ?, c = 13.250 (1) ?, β = 96.084 (6); V = 2940.6 (3) ?³, Z = 4. As was found earlier for 1, the geometry about Zr is normal, and no Zr-P interaction is evident. Reduction of 1 with Na/Hg produces a fairly stable paramagnetic Zr(III) species formulated as Cp₂ZrCH₂PPh₂. The latter is monomeric and, similar to a simple Zr(III) alkyl model compound, decomposes in solution mostly via intermolecular H transfer from a Cp ring to Zr-bound carbon. Mechanisms for the chemistry of these Zr(III) species are suggested on the basis of an isotopic labeling study. Reaction of 1 with Cr(CO)₅THF produces crystalline Cp₂Zr(Cl)CH₂PPh₂Cr(CO)₅: monoclinic, space group P2₁/n, a = 11.346 (9) ?, b = 13.696 (7) ?, c = 17.609 (13) ?, β = 99.88 (6)°, V = 2696 (3) ?³, Z = 4. Reaction of 4 with (norbornadiene)Cr(CO)₄ produces Cp₂Zr(μ-CH₂PPh₂)₂Cr(CO) ₄, containing a severely hindered six-membered ring in a twist-boat conformation: monoclinic, space group P2₁/n, a = 12.932 (5) ?, b = 16.966 (3) ?, c = 19.160 (5) ?, β = 97.88 (3) ?, V = 4164 ?³, Z = 4. Both Cr complexes display relatively normal Zr and Cr geometric environments with no unexpected interactions evident.