Synthesis and reactivity studies on alkyl–aryloxo complexes of nickel containing chelating diphosphines: cyclometallation and carbonylation reactions

Nickel alkyl–aryloxo complexes of composition Ni(R)(OC6H32,6-Me2)(PP) (R=CH2SiMe3, CH3, CH2CMe2Ph; PPPPr2i(CH2)nPPr2i, n=2 (dippe) or 3 (dippp)) have been synthesized. While the (trimethylsilyl)methyl and the methyl derivatives are stable in solution at room temperature, the bis-neophyl (R=CH2CMe2Ph) complexes undergo a cyclometallation reaction that leads to the metallacycles H4)(PP) together with 2,6-dimethylphenol. The alkyl–aryloxo complexes cleanly react with carbon monoxide giving products resulting from CO insertion and reductive elimination, i.e. Ni(CO)2(PP) and the corresponding 2,6-dimethylphenyl carboxylates quantitatively.