Phosphorus hydrazides as building blocks for potential photoaffinity labels. Synthesis and co-ordination chemistry of perfluoroaryl azide conjugates of phenylphosphonothioic dihydrazide

Abstract

The phosphorus hydrazide PhP(S)(NMeNH₂)₂1 reacted with the azido functionalized aldehyde 4-N₃C₆F₄CHO to give a mixture of Schiff-base adducts with one or two perfluoroaryl azido substituents on 1. However, the reaction with R′CHO (R = 4-O₂NC₆H₄, 3-O₂NC₆H₄ or 2,4-Me₂C₆H₃) resulted in a considerable selectivity of incorporating one aromatic substituent in the terminal hydrazide unit of 1via Schiff-base coupling to produce PhP(S)(NMeNH₂)(NMeNCHR′)(R′= 4-O₂NC₆H₄3, 3-O₂NC₆H₄4 or 2,4-Me₂C₆H₃5). These mono-Schiff-base adducts 3–5 undergo further Schiff-base coupling with azidotetrafluorobenzaldehyde to produce the azido-functionalized phosphorus hydrazides PhP(S)-(NMeNCHC₆F₄N₃)(NMeNCHR′)(R′= 4-O₂NC₆H₄7, 3-O₂NC₆H₄8 or 2,4-Me₂C₆H₃9). The ligating properties of the representative phosphorus hydrazides 2 and 9 with palladium (II) were investigated. The crystal structure of the complex [PdCl₂{PhP(S)(NMeNH₂)(NMeNCHC₆F₄N₃-4)}] reveals that the palladium(II) is bound in a chelating cis arrangement to the phosphorus chalcogenide and the hydrazine nitrogen via a five-membered metallacyclic framework: monoclinic, space group P2₁/n, a= 7.826(10), b= 18.051 (20), c= 18.330(3)Å, β= 98.196(7)°, Z= 4, R= 0.038 and R′= 0.053.