New perspectives in phosphonodithioate coordination chemistry. Synthesis and X-ray crystal structure of trans-bis-[ O-ethyl-(4-methoxyphenyl)phosphonodithioato] nickel(II)

Abstract

Attempts to optimise the synthesis of a new class of nickel(II) dithiolene complexes starting from 1,3-dialkylimidazolidine-2-thione-4,5-dione ( 1) and Lawesson's reagent ( 2) have afforded a new and easy one-step synthesis of phosphonodithioate nickel(II) complexes. This consists of the direct reaction between NiCl 2 and Lawesson's reagent in the appropriate alcohol R′OH (R=Me, Et, i-Pr, Bu, Bz) as solvent, to give the bis-[ O-alkyl/aryl-(4-methoxyphenyl)phosphonodithioato] nickel(II) complexes ( 5a– e) with high yields (64–91%). Among them, trans-bis-[ O-ethyl-(4-methoxyphenyl)phosphonodithioato] nickel(II) ( 5b) was characterised by means of X-ray diffraction measurements on a single crystal. The compound crystallises in the triclinic, P 1 ̄ space group with a=6.4840(7), b=7.6032(9), c=13.055(2) Å, α=99.481(9), β=99.43(1), γ=104.487(9)° and Z=1. The compound is centrosymmetric and exhibits discrete monomeric units with the ligand acting as S,S-bidentate. To explain the reactivity of Lawesson's reagent, the formation of 4-methoxyphenyldithiophosphorane ( 6) as intermediate has been suggested. The reaction was also tested for Pd(II) and Pt(II), but in these cases the yields were not as satisfactory as for Ni(II).