TETRAHEDRAL VERSUS SQUARE-PLANAR NIS4 CORE IN SOLID-STATE BIS(DITHIOIMIDODIPHOSPHINATO) NICKEL(II) CHELATES - CRYSTAL AND MOLECULAR-STRUCTURES OF NI[(SPR(2))(SPPH(2))N](2) (R=PH,ME)

Bis(dithioimidodiphosphinato) nickel(II) chelates, Ni[(SPR(2))(SPPh(2) )N](2) (R = Ph (1), Me (2)) were prepared by metathesis reactions betw een NiCl2 . 6H(2)O and the corresponding potassium dithioimidodiphosph inate, in methanol. Compound 1 crystallizes in the triclinic space gro up P-1, a = 13.336(2), b = 18.580(2), c = 18.670(2) Angstrom, alpha = 90.10(2), beta = 93.00(2), gamma = 98.21 (2)degrees, Z=4, and contains two independent molecules in the unit cell. Compound 2 crystallizes i n the monoclinic space group P2(1)/c, a = 13.161(2), b = 10.737(5), c = 12.101(4) Angstrom, beta = 108.38(2)degrees, Z=2. In both compounds the 1,3-dithiophosphorus ligands act as symmetrical monometallic bicon nective (isobidentate chelating) units and the resulting NiS2P2N rings are non-planar. Compound 1 contains a tetrahedral NiS4 core (mean Ni- S 2.299 Angstrom, S-Ni-S 111.9 degrees (endocyclic), 108.2 degrees (ex ocyclic)), while compound 2 exhibits a square-planar NiS4 core (mean N i-S 2.239 Angstrom, S-Ni-S 98.3 degrees (endocyclic), 81.1 degrees (ex ocyclic)). The structures are discussed in relation to previously repo rted Ni(II) derivatives of 1,1-dithiophosphorus ligands.