Dimeric versus monomeric nickel(II) complexes with tetraorganodichalcogenoimidodiphosphinato ligands: Crystal structures of Ni2[(OPPh2)2N]4 · CH2Cl2, Ni[(OPPh2)2N]2(DMF)2 · 2H2O and [KNi[(SPPh2){OP(OEt)2}N]3]2

Nickel(II) complexes of the type Ni [(XPR2) (YPR2 ') N]2 [X = S (1) or O (2), Y = O, R = Ph, R' = OEt] and Ni2[(OPPh2)2N]4 (3) were prepared by reacting either anhydrous NiCl2 or NiCl2 · 6H2O with the potassium salt of the appropriate tetraorganodichalcogenoimidodiphosphinic acid, in 1:2 molar ratio. Recrystallization of 3 from dimethylformamide resulted in Ni[(OPPh2)2N]2(DMF) (4). Reaction between NiCl2 and K[(SPPh2){OP(OEt)2}N] in an 1:3 molar ratio resulted in the ionic species KNi[(SPPh2){OP(OEt)2}N]3 (5). Compounds 1-5 were characterized by IR, electronic spectroscopy and mass spectrometry. The molecular structures of 3 · CH2Cl2, 4 · 2H2O and 5 were determined by single-crystal X-ray diffraction. A dimeric structure was found in case of complex 3 · CH2Cl2, with both monometallic biconnective and homobimetallic triconnective [(OPPh2)2N]- units, while an octahedral environment around nickel was established in the monomeric complex 4 · 2H2O by monometallic biconnective [(OPPh2)2N]- and DMF ligands, respectively. The crystal of the ionic species 5 contains discrete tetranuclear units in which the phosphorus ligands act heterobimetallic, either (O,O,S)-triconnective or (S,O,O,OEt)-tetraconnective, and (N,O,O,S)-heterotrimetallic tetraconnective, resulting in an octahedral environment around nickel and a square-pyramidal one around potassium, respectively. Powder X-ray diffraction studies on 5 are in agreement with the single-crystal investigation. © 2008 Elsevier Ltd. All rights reserved.National Council of University Research Administrators NATO B2 Consiliului National al Cercetarii Stiintifice din Invatamantul Superior: A-358/2006This work was supported by the National University Research Council of Romania (CNCSIS Grant: A-358/2006). S.I. is grateful for financial support in form of the Scientific and Technical Research Council of Turkey (TUBITAK) - NATO B2 fellowship. Appendix A -