Complexes of functionalised phosphine ligands. Part 1. Complexes of FeIII, CoIII, NiII and ReV with tridentate Schiff bases having PNO, NNO and NNS donor sets. Crystal structures of 2-(Ph2PC6H4NCH)C6H4OH and [Co{2-(Ph2PC6H4CHN)C6H4O}2][PF6]

Abstract

The Schiff bases 2-[Ph₂P(CH₂)_nNCH]C₆H₄OH (n= 3, HL¹ or 2 HL²), 2-(RCHN)C₆H₃(OH)X-4 (R = 2-Ph₂PC₆H₄, X = H HL³; R = 2-C₅H₄N, X = H HL⁴; R = 2-C₅H₄N, X = Cl HL⁵) were synthesised from the appropriate amine and aldehyde. On deprotonation these all functioned as tridentate monoanionic ligands to give complexes [FeL₂]⁺ and [CoL₂]⁺ with Fe^III and Co^III and neutral complexes of stoichiometry NiL₂ with Ni^II. The iron complexes were examined by Mössbauer spectroscopy which indicated the presence of two iron sites in [FeL¹₂]⁺ with a spin-state equilibrium dependent on both temperature and the counter ion. The complex [FeL³₂]⁺ showed a single iron site, again with a spin state dependent on counter ion and temperature. The crystal structures of HL³ and [CoL³₂]⁺ have been determined. The distortions in free HL³ predispose it for co-ordination in a fac geometry to the Co with cis-PPh₂ groups, and the changes occurring on co-ordination are discussed in detail. Reaction of RCHO (R = 2-Ph₂PC₆H₄ or 2-C₅H₄N) with 2-aminobenzenethiol gave stable thiazoles R[graphic omitted]-2 which did not ring open to give tridentate ligands even on reaction with base and/or metal ions.