Substitution and derivatization reactions of a water soluble iron(ii) complex containing a self-assembled tetradentate phosphine ligand

Abstract

Facile substitution reactions of the two water ligands in the hydrophilic tetradentate phosphine complex cis-[Fe{(HOCH₂)P{CH₂N(CH₂P(CH₂OH)₂)CH₂}₂P(CH₂OH)}(H₂O)₂](SO₄) (abbreviated to [Fe(L¹)(H₂O)₂](SO₄), 1) take place upon addition of Cl⁻, NCS⁻, N₃⁻, CO₃²⁻ and CO to give [Fe(L¹)X₂] (2, X = Cl; 4, X = NCS; 5, XN₃), [Fe(L¹)(κ²-O₂CO)], 6 and [Fe(L¹)(CO)₂](SO₄), 7. The unsymmetrical mono-substituted intermediates [Fe(L¹)(H₂O)(CO)](SO₄) and [Fe(L¹)(CO)(κ¹-OSO₃)] (8/9) have been identified spectroscopically en-route to 7. Treatment of 1 with acetic anhydride affords the acylated derivative [Fe{(AcOCH₂)P{CH₂N(CH₂P(CH₂OAc)₂)CH₂}₂P(CH₂OAc)}(κ²-O₂SO₂)] (abbreviated to [Fe(L²)(κ²-O₂SO₂)], 10), which has increased solubility over 1 in both organic solvents and water. Treatment of 1 with glycine does not lead to functionalisation of L¹, but substitution of the aqua ligands occurs to form [Fe(L¹)(NH₂CH₂CO₂-κ²N,O)](HSO₄), 11. Compound 10 reacts with chloride to form [Fe(L²)Cl₂] 12, and 12 reacts with CO in the presence of NaBPh₄ to form [Fe(L²)Cl(CO)](BPh₄) 13b. Both of the chlorides in 12 are substituted on reaction with NCS⁻ and N₃⁻ to form [Fe(L²)(NCS)₂] 14 and [Fe(L²)(N₃)₂] 15, respectively. Complexes 2·H₂O, 4·2H₂O, 5·0.812H₂O, 6·1.7H₂O, 7·H₂O, 10·1.3CH₃C(O)CH₃, 12 and 15·0.5H₂O have all been crystallographically characterised.