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The reaction of the monooxidised imidodiphosphinate ligand Ph2P(Se)NHPPh2 with NiCl2·6H2O in the presence of tBuOK afforded [NiPh2P(Se)NPPh2-Se,P2] (1), which was characterized by UV-Vis, IR and NMR spectroscopies. X-ray crystallographic studies on a single crystal of 1 revealed the trans Ni(Se,P)2 arrangement in the solid state, showing a bis-chelating type of coordination. The diamagnetic 31P NMR peaks of 1 in CDCl3 were interpreted as "deceptive" triplets, due to the conservation of the square-planar trans-isomer of 1 in solution. The structure of 1 exhibits a center of symmetry, with the two five-membered Ni-Se-P-N-P rings being equivalent. The higher electronegativity of Se compared to P is considered as the likely cause of the P-N bond length differences observed in the chelating rings of 1. During the reaction between NiCl2·6H2O and the ligand Ph2P(Se)N(S)-CH(CH3)PhPPh2, single crystals were obtained, the analysis of which by X-ray crystallography showed the formation of trans-[NiPh2P(Se)NPPh2-Se,PPh2P(Se)N (H)PPh2-Se,P]Cl·CH2Cl2·H 2O (2). Complex 2 contains one Ni-Se-P-N(H)-P and one Ni-Se-P-N-P ring. Structural comparison between 1 and 2 makes possible to establish structural effects due to the protonation/deprotonation of the rings at their N atom. © 2009 Elsevier Ltd. All rights reserved. |
