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]

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 FeIII and CoIII and neutral complexes of stoichiometry NiL2 with NiII. The iron complexes were examined by Mossbauer 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.