1,2-Bis(dimethylphosphino)ethane (dmpe) alkyl compounds of zirconium(IV) and hafnium(IV). Crystal structures of ZrMe₄(dmpe)₂ and Zr(CH₂PH)₄(dmpe)

The reaction of ZrCl₄(dmpe)₂ [dmpe = 1,2-bis(dimethylphosphino)ethane] with excess MgMe₂ gives the dialkyldichloro-complex ZrMe₂Cl₂(dmpe)₂, whereas interaction with excess LiMe gives the tetra-alkyl ZrMe₄(dmpe)₂. N.m.r. data indicate a rigid structure for the latter molecule at -60 °C, while the X-ray crystal structure shows the molecule, which has crystallographic C₂ symmetry, to have dodecahedral geometry with the methyl groups at the (B) sites and the phosphines at the (A) sites: Zr-C 2.440(6), Zr-P 2.814(1) Å. Alkylation of ZrCl₄(dmpe)₂ with excess LiCH₂SiMe₃ leads to the six-co-ordinate complex Zr(CH₂SiMe₃)₄(dmpe); the analogous compound Zr(CH₂Ph)₄(dmpe) can be prepared from Zr(CH₂Ph)₄ and dmpe. The X-ray crystal structure of Zr(CH₂Ph)₄(dmpe) shows a severely distorted octahedral geometry consisting of three σ-benzyl groups and one partially π-bonded benzyl group: Zr-C(σ) 2.264(7)-2.368(5), Zr-C_α(π) 2.359(6), Zr ⋯ C_β(π) 2.788(8), Zr-P 2.862(4), 2.885(4) Å. The preparations and characterizations of some hafnium analogues are also described.