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The crystal and molecular structure of cadmium( II) NN-diethyldithiocarbamate has been determined from threedimensional X-ray data and refined by anisotropic least-squares methods to a final R value of 0.084. Crystals are monoclinic, space group P2Jc. with a = 10.1 66, b = 10.746, c = 16.71 7 A, 13 = 11 1" 53'. In the solid state the complex is binuclear, the two halves of the molecule being related by a centre of symmetry, and should be formulated as [Cd2(S2CNEt2)4]. Two of the four NN-diethyldithiocarbamate groups act as bridging ligands, giving rise to a puckered eight-membered ring which comprises two cadmium, four sulphur, and two carbon atoms. The two symmetry-related cadmium atoms are five-co-ordinate, the co-ordination polyhedron being intermediate between a tetragonal pyramid and a trigonal bipyramid. The five cadmium-sulphur bond distances range from 2.536 to 2.800 A.

Die Molekül‐ und Kristallstrukturen der Titelverbindungen (I) (RG P21/c, Z=4), (II) (RG C2/c, Z=8), (III) (X: N0; RG P21/n, Z=4) und (III) (X: C102; RG P21/c, Z=4) werden mittels Röntgenanalysen bestimmt und diskutiert.

It is shown that ligand 1, designed to span trans‐positions, under appropriate conditions also gives cis‐mononuclear complexes of platinum (II). The structure of cis‐[PtCl2 (1)] (2) has been determined by single‐crystal X‐ray diffraction. The major distortion from square planar coordination is the P‐Pt‐P angle of 104.8°. Values of valence angles within the bidentate ligand indicate that this part of the molecule is very strained. Two phenyl groups, one on each phosphorus, lie almost parallel to each other separated by ca. 3.2–3.3 Å. The 1H‐NMR. data for this compound show that the π‐phenyl interactions observed in the solid state occur also in solution. The preparation and NMR.‐spectroscopic properties of trans‐ and cis‐[PtH(PPh3) (1)] [BF4] are reported.