PREPARATION, STRUCTURES, AND FLUXIONAL BEHAVIOR OF ORGANOLITHIUM DERIVATIVES OF A 1,5-DIPHOSPHADITHIATETRAZOCINE AND THEIR COMPLEXES WITH PLATINUM(II) AND PALLADIUM(II)

The reaction of the diphosphadithiatetrazocine 1,5-Ph4P2N4S2 with orga nolithium reagents RLi (R = Me, Bu(t), Ph, CH2PPh2) in THF generates L i[Ph4P2N4S2R]. An X-ray structural determination shows that the phenyl derivative is a dimer [Li(Ph4P2N4S2Ph).THF]2 with a step-shaped struc ture. The phenyl group is attached to sulfur, and each lithium atom is coordinated, almost symmetrically, to two nitrogen atoms on the oppos ite side of the P2N4S2 ring and to one nitrogen atom of the other P2N4 S2 ring. A single THF molecule completes the coordination sphere of th e lithium atoms. The crystals of [Li(Ph4P2N4S2Ph).THF]2 are triclinic, space group P1BAR, with a = 13.189(10) angstrom, b = 13.355(8) angstr om, c = 11.760(5) angstrom, alpha = 90.67(4)degrees, beta = 114.15(4)d egrees, gamma = 114.05(5)degrees, V = 1683(2) angstrom3, and Z = 2. Th e final R and R(w) values were 0.072 and 0.060, respectively. Li-7 and P-31 NMR investigations of [Li(Ph4P2N4S2R).THF]2 (R = Me, Bu(t), Ph, CH2PPh2), as a function of temperature and concentration in THF, show that these dimers are fluxional and provide evidence for a second spec ies, which is tentatively identified as a symmetrical dimer with two m olecules of THF coordinated to each lithium atom. The treatment of Li[ Ph4P2N4S2Me] with iodomethane gives the S,S'-dimethyl derivative 1,5-P h4P2N4S2Me2 and the reaction of Li[Ph4P2N4S2R] with MCl2(PEt3)2 (M = P t, Pd) produces metal complexes of the type trans-MCl(PEt3)2(Ph4P2N4S2 R) (M = Pt, R = Me, Bu(t), Ph, CH2PPh2; M = Pd, R = Me) in which the m etal and the R group are attached to opposite sulfur atoms. A variable -temperature P-31 NMR study of these metal complexes reveals an intram olecular dynamic exchange of the inequivalent PEt3 groups, which is at tributed to rotation about the metal-sulfur bond. The activation energ y for this exchange is ca. 45 kJ mol-1 and is essentially independent of the nature of the R group attached to the other sulfur atom or the identity of the metal. The reaction of Li[Ph4P2N4S2Me] with cis-PtCl2( PPh3)2 in THF at 65-degrees-C produces Pt(PPh3)2(eta2-Ph4P2N4S2-S,S') and Pt(PPh3)(eta1-THF-O)(Ph4P2N4S2) in an approximately 2:3 molar rati o.