Metal phosphinohydrazone complexes

Abstract

The reaction of benzophenone hydrazone with chlorodiphenylphosphine in the presence of triethylamine affords the monophosphino derivative Ph2C=N-N(H)PPh2(1). The lithiation of 1 with one equivalent of MeLi produces the stable salt Ph2C=N-N(Li)PPh2, and the addition of the second equivalent of MeLi results in the lithiation of the aromatic ring of the Ph2C group followed by the cyclization to lithium-substituted diazaphosphinine. The treatment of the latter with chlorotrimethylsilane furnishes 1,4-diphenyl-2-trimethylsilyl-1,2-dihydrobenzo-[d][1,2,3]diazaphosphinine. Phosphinohydrazone 1 gives 2: 1 complexes with cobalt and nickel bromides, which were characterized by X-ray diffraction. The migratory insertion of the Ph2P group into the N-N bond was not observed in phosphinohydrazone derivatives, as opposed to phosphinohydrazides M-NR-NR-PPh2 (M is metal).