STRUCTURE OF ETHYLCYCLOBUTADIENE)(TRIPHENYLSTIBINE)PLATINUM(II)

The title compound [PtCl2 (C(4)Me(4))(SbPh(3))] (1) crystallizes from methylene chloride/n-hexane in the monoclinic space group P2(1)/n with lattice constants a = 8.303(1) Angstrom, b = 17.378(2) Angstrom, c = 17.640(2) Angstrom, beta = 90.86(1)degrees, Z = 4. The crystal structu re was solved by the heavy atom method. The refinement converged to a final wR2 = 0.051 for 4310 reflections (R1 = 0.024 for 3810 observed r eflections). In the solid state the exactly planar cyclobutadiene liga nd is asymmetrically coordinated with respect to the Pt atom having tw o shorter and two longer Pt-C bonds (Pt-C distances in the range 2.105 (4) Angstrom - 2.195(5) Angstrom). The methyl carbon atoms show a rema rkable difference concerning the bend out of the C-4 plane, away from the Pt atom (out-of-plane displacement in the range of 0.083(6) Angstr om to 0.401(6) Angstrom). The Pt-Sb bond length amounts to 2.5911(4) A ngstrom. The Pt-Cl bonds in 1 are longer than those in the correspondi ng stibine-free complex [PtCl2(C(4)Me(4))] (2) (2.449(1) Angstrom/2.45 8(1) Angstrom, 2.335(2) Angstrom/2.323(3) Angstrom). This corresponds to a low-frequency shift of the (PtCl) stretching and deformation mode s in 1 compared to that observed in 2.