Preparation and Properties of Monoalkylnickel(II) Complexes Having a Phenoxo, Benzenethiolato, Oximato, β-Diketonato, or Halo Ligand

Abstract

Abstract Thirteen complexes of a type NiR(Y)Ln (R=CH3 (Me), C2H5 (Et); Y=OC6H5, p-cyanophenoxo, 8-phenylphenoxo, 8-quinolinolato, OCOEt, OCOPh, acetophenone oximato, acetylacetonato, benzoylacetonato, Cl; L=trie thy lphosphine (PEt3), 2,2′-bipyridine (bpy)) have been prepared by reactions of dialkylnickel(II) complexes NiR2L2 (1) with the corresponding active hydrogen compounds HY. Reactions of 1 with R′COY (Y=OC6H5, OCOC6H5, Cl) also afford the NiR(Y)Ln type complexes with formation of unsymmetrical ketones RCOR′. Reactions of 1 with alcohols lead to dehydrogenation of alcohols to afford aldehydes or ketones. The NiR(Y)Ln type complexes have been characterized by elemental analysis and spectroscopies (IR, NMR, visible). NMR spectra of trans-NiMe(OCOPh)(PEt3)2, NiMe(acetophenone oximato)(PEt3) (11), NiMe(benzoylacetonato) (PEt3) show temperature dependence, indicating occurrence of rapid dynamic reactions on NMR time scale in these complexes. The acetophenone oximato ligand in 11 is proposed to serve as an oxa-, aza-π-allylic ligand on the bases of IR and NMR spectroscopies. NiEt(OCOC2H5)(bpy) (8), NiEt(OCOC6H5)(bpy), and NiEt(Cl)(bpy) (14) undergo disproportionation reaction to give NiEt2(bpy) and NiY2(bpy) type complexes. Diethyl ketone is also produced during the disproportionation of 8. Reactions of 14 with olefins having electron-withdrawing substituents afford NiCl2(bpy) and Ni(olefin)2(bpy).