Rhodium Complexes of Tetradentate Tripodal Tripyridyl Ligands: Phosphate, Phosphate Monoester, and an Unexpected Acetimidamide Species

The complexes [Rh(N₄)Cl₂]ClO₄ (N₄ = tpa, pmea, pmap, tepa) and [Co(pmea)Cl₂]ClO₄ have been prepared and characterised (tpa = tris(2-pyridylmethyl)amine, pmea = bis[(2-pyridyl)methyl]-2-[(2-pyridyl)ethyl]amine, pmap = bis[2-(2-pyridyl)ethyl]-(2-pyridylmethyl)amine, and tepa = tris[2-(2-pyridyl)ethyl]amine), and the X-ray crystal structures of [Rh(pmea)Cl₂]ClO₄, [Co(pmea)Cl₂]ClO₄‧0.61H₂O, and [Rh(tepa)Cl₂]ClO₄ are reported. Reaction of the rhodium complexes with Na₃PO₄ and Na₂C₆H₅PO₄ gives chelated phosphate and phenylphosphate complexes for all but the [Rh(tpa)Cl₂]+ starting material, as evidenced by Hi Res Mass Spectrometry and ³¹P NMR spectroscopy. Reaction of the in situ-generated [Rh(pmap)Cl(MeCN)]²+ ion with bis(cyclohexylammonium)-t-butylphosphate gives Rh(pmap)Cl(N-cyclohexylacetimidamide)₂, which results from attack of cyclohexylamine at the nitrile C atom of coordinated MeCN. The X-ray crystal structure of this complex is reported.