Structural studies of precursor and partially oxidized conducting complexes. VIII. A neutron diffraction investigation of rubidium tetracyanoplatinate (2:1) sesquihydrate, Rb2[Pt(CN)4].1.5H2O

The crystal and molecular structure of rubidium tetracyanoplatinate (2:1) sesquihydrate, Rb2[Pt(CN)4] . 1.5H2O(RbTCP), has been determined by a single-crystal neutron-diffraction study. The compound RbTCP crystallizes with eight formula units in the space group C/sub 2h/6-C2/c with monoclinic cell dimensions a = 12.693 (8) A, b = 12.809 (8) A, c = 13.642 (9) A, and β = 112.22 (4)0. The centrosymmetric space group C2/c was verified by a very satisfactory least-squares refinement. A total of 4108 reflections was averaged to yield 2875 independent reflections (2417 with F02 greater than 1sigmaF02). The structure solved by direct methods and refinement, using full-matrix least-squares techniques, has produced a final R(F02) value of 0.068 using all data. The structure consists of a bent Pt metal atom chain [bond angle 170.97 (4)0] in which the asymmetric unit contains two crystallographically distinct Pt(CN)42- groups, two Rb+ ions, and two H2O molecules (one O and one H atom are in disorder). An inversion center occurs at Pt(1), and a twofold rotation axis is present along the b axis of the cell (on which Pt(2) lies). While Pt(1) resides on the c axis, Pt(2) is displaced 0.270 (1) A normal to c. This bent Pt-Pt chain appears to result from an asymmetric electrostatic environment about Pt(2) involving Rb+.../sup delta-/N identical with C interactions. The role of Rb+ ion coordination and hydrogen bonding in this structure is discussed. The importance of RbTCP as a precursor in the formation of partially oxidized tetracyanoplatinate (POTCP) complexes is presented in a discussion of POTCP complexes of rubidium