Formation of a σ-cyclobutyl-platinum bond by the intramolecular activation of a cyclobutylphosphine. Synthesis and structure of

When the hydrobromide adduct of di-t-butylcyclobutylmethylphosphine, P(t-Bu)₂(CH₂CHCH₂CH₂CH₂) · Hbr is combined with K[PtCl₃(C₂H₄)] and LiBr in ethanol and heated at reflux for 5 h, the σ-cyclobutyl complex {A figure is presented} forms. The complex also forms from {A figure is presented} in boiling ethanol. The structure of {A figure is presented} was deduced from spectroscopic and analytical data and confirmed by X-ray analysis of a single crystal. The complex crystallizes in the tetragonal system in space group C¹²_4ν-I4₁cd (a = b = 19.658(7) Å, c - 15.805(6) Å, A = 113 K) with 8 molecules per unit cell. The final agreement index for R(F²) is 0.075 for the 2403 unique data (including F₀² < 0). Bond lengths in the five-membered chelate ring PtPC(3)C(10)C(11) are PtP 2.198(4), PC(3) 1.875(18). C(3)C(10) 1.53(2), C(10)C(11) 1.57(2), C(11)Pt 2.079(17) Å. The remaining cyclobutyl bond distances are C(11)C(12) 1.56(2), C(12)C(13) 1.51(3), C(10)C(13) 1.53(3) Å. The PtBr bond distances are 2.510(2) and 2.612(2) Å for bromine cis- and trans- to atom C(11), respectively.