PARAMAGNETIC SIGMA-BONDED PHENYLNICKEL(II) MACROCYCLIC SYSTEMS - NUCLEAR-MAGNETIC-RESONANCE IDENTIFICATION OF (SIGMA)-PHENYL)NICKEL(II) 5,20-DIPHENYL-10,15-BIS(P-TOLYL)-21-THIAPORPHYRIN AND (SIGMA-PHENYL)NICKEL(II) N-METHYLTETRAPHENYLPORPHYRIN

Addition of the phenyl Grignard reagent to toluene or dichloromethane solutions of nickel(II) monohalide complexes of 5,20-diphenyl- 1 0, 1 5-bis(p-tolyl)-2 1 -thiaporphyrin (SDPDTPH) and N-methyltetraphenylporphyrin (NCH3TPPH) at -70-degrees-C resulted in formation of paramagnetic (sigma-phenyl)nickel(II) derivatives which were characterized by means of H-1 NMR and H-2 NMR. The coordination of the phenyl ligand has been proven by the unique downfield pattern of three phenyl resonances in the respective H-2 NMR spectra of (SDPDTP)Ni(II)(C6D5) (1) and (NCH3TPP)Ni(II)(C6D5) (2) (1, ortho 616, meta 170.0, para 76.0; 2, ortho 568, metal 148.0, para 62.8; -70-degrees-C, in ppm vs TMS in toluene). The (sigma-phenyl)nickel(II) derivatives are in the high-spin paramagnetic electronic state: d(xy)2d(xz)2d(yz)2d(z2)1d(x2-y2)1. The protons of the nickel-bound phenyl group display substantial hyperfine shifts which are dominated by the sigma-contact contribution. A contact shift pattern established for phenyl ligand resembles that of pyridine in a large variety of nickel(II) pyridine complexes as both ligands are isoelectronic. A homolytic cleavage of the Ni(II)-C bond has been observed for (SDPDTP)Ni(II)(C6H5) in toluene with formation of (SDPDTP)Ni(I). The decomposition of (NCH3TPP)Ni(II)(C6H5) in toluene results in formation of (TPP)Ni(II), due to the demethylation.