X-Ray crystal structure analyses of [PtCl2{(t-Bu)2P(CH2)2P(t-Bu)2}] (I) and [PtCl2{(t-Bu)2P(CH2)2P(t-Bu)2}, C6H5C1] (II) have been carried out. Crystals of I belong to monoclinic system: a=20.595(3), b=7.917(3), c=14.885(2) Å, β=109.03(1)°, space group P21/c with Z=4. II forms monoclinic crystals, P21/c: a=14.873(2), b=13.193(2), c=15.314(2) Å, β=98.75(1)°, Z=4. Both structures, solved by the heavy-atom method, have been refined anisotropically by least-squares procedure to R=0.067 and 0.078 for I and II respectively. There is no essential difference between the structures of [PtCl2{(t-Bu)2P(CH2)2P(t-Bu)2}] molecules in I and II. The coordination around the platinum atom is square-planar; Pt–P=2.262(3) and 2.265(3) Å and Pt–Cl=2.374(4) and 2.365(4) Å. The molecule has a pseudo-C2 symmetry: the platinum atom and the center of the C–C bond in the P–C–C–P lie on this pseudo-C2 axis.