Novel xanthate complexes of nickel. X-ray structure of [NiBr(S2CO-i-Am)(PPh3)] at 150 K

Nickel(II) isopropylxanthate complexes of composition Ni2(-L)2(S2CO-i-Pr)2]·xCHCl3 (1) and (2) {HL = thiophenol or 4-methylthiophenol, x = 1/2 or 1/3} and Ni(bpy)(S2CO-i-Pr)]Br (3) {bpy = 2,2-bipyridine} have been synthesized and characterized by elemental analyses, electronic and i.r. spectroscopy, magnetic moment studies and conductivity measurements. The results show that (1) and (2) are non-electrolytes, square-planar, binuclear nickel(II) complexes bridged via two L1– ligands, while compound (3) is ionic (1:1); the donor atom arrangement around the nickel(II) centre is tetrahedral with an NiS2N2 chromophore. The geometry of the Ni(bpy)(S2CO-i-Pr)]+ cation has been optimized using MM+ calculations. The crystal and molecular structure of NiBr(S2CO-i-Am)(PPh3)], as an example of an i-Am derivative of a starting complex for preparation of all the above compounds, has been determined. X-ray analysis of the complex reveals distorted square-planar geometry at the metal centre with an S2PBr donor set.