π-Complexes of platinum(II) with unsaturated hydrocarbons. Part II. Crystal and molecular structure of trans-dichloro-(π-di-t-butylacetyl-ene)-p-toluidineplatinum(II)

The compound [PtCl2(ButCCBut)(MeC6H4NH2)] forms monoclinic crystals, a= 9·812(2), b= 9·790(2), c= 10·611(3)Å, β= 95·30(2)°, space group P21/m. There are two molecules, each with a plane of symmetry perpendicular to the platinum co-ordination plane, in the unit cell. After refinement of the positional and aniso-tropic thermal parameters, by use of 1380 independent structure amplitudes with |Fo| 10σ(Fo), R was 0·038.The crystal structure contains discrete molecules linked in chains by pairs of N–H⋯Cl hydrogen bonds (N⋯Cl 3·38 Å). The co-ordination around platinum is square-planar, and the acetylene ligand is co-ordinated by a π-type bond, the CC bond making an angle of 85° with the co-ordination plane. The CC bond [1·24(2)Å] is slightly longer than a normal triple bond, and the CC–But angles (162 and 165°) differ from 180°, indicating that the acetylenic bond after co-ordination is no longer a pure triple bond, but has some double-bond character. The changes in the acetylene caused by co-ordination are not large, and since the Pt–C distances [average 2·16(1)Å] are relatively long, it appears that the π-type bond in this complex is not strong. The Pt–Cl bonds are of normal length, but the Pt–N bond (which is trans to the acetylene) is longer [2·10(1)Å] than the radius sum.