Meshing ability of bulky tertiary phosphine. X-ray structure of cis-bis(di-t-butil-phenylphosphine)-di-chloro-platinum(II).

The square-planar platinum(I1) complex PtClz(P(~-Bu)2Ph)c~o, ntaining two bulky phosphines cis to each other, has been studied by X-ray diffraction methods. The crystals are monoclinic of space group P21/c,w ith a = 11.21 1 (1) A, b = 14.621 (1) A, c = 18.157 (2) A, p = 102.38 ( 2 ) O , and 2 = 4. The structure was solved by Patterson and Fourier methods and refined by least squares to a conventional R factor of 0.059, on the basis of 2427 intensities above background. The square-planar coordination is very distorted with P-Pt-P and Cl-Pt-CI angles of 107.3 (4) and 84.2 (3)O, respectively. The mean Pt-P and Pt-C1 distances are 2.358 (6) and 2.333 ( 5 ) A. The stability of the complex, in spite of the cis relation of the two phosphines, is explained as having recourse to the variable-aperture cone model. The substituent orientation about the Pt-P bonds allows for a good fitting of protrusions and hollows without severe steric hindrance.