Synthesis, coordination studies and redox properties of a novel ditertiary phosphine bearing two ferrocenyl groups

The new ferrocenyl substituted ditertiary phosphine {FcCH2N(CH2PPh2)CH2}2 [Fc = (η5-C5H4)Fe(η5-C5H5)] (1) was prepared, in 72% yield, by Mannich based condensation of the known bis secondary amine {FcCH2N(H)CH2}2 with 2 equiv. of Ph2PCH2OH in CH3OH. Phosphine 1 readily coordinates to various transition-metal centres including Mo0, RuII, RhI, PdII, PtII and AuI to afford the heterometallic complexes {RuCl2(p-cym)}2(1) (2), (AuCl)2(1) (3), cis-PtCl2(1) (4), cis-PdCl2(1) (5), cis-Mo(CO)4(1) (6), trans,trans-{Pd(CH3)Cl(1)}2 (7) and trans,trans-{Rh(CO)Cl(1)}2 (8). In complexes 2, 3, 7 and 8 ligand 1 displays a P,P′-bridging mode whilst for 4–6 a P,P′-chelating mode is observed. All new compounds have been fully characterised by spectroscopic and analytical methods. Furthermore the structures of 1, 2 · 2CH2Cl2, 3 · CH2Cl2, 4 · CH2Cl2, 6 · 0.5CHCl3 and 8 have been elucidated by single crystal X-ray crystallography. Electrochemical measurements have been undertaken, and their redox chemistry discussed, on both noncomplexed ligand 1 and representative compounds containing this new ditertiary phosphine.

Graphical abstractThe new ferrocenyl functionalised ditertiary phosphine 1 along with some transition metal complexes of this ligand were prepared and studied by multinuclear NMR spectroscopy, single crystal X-ray diffraction and cyclic voltammetry. Solution and structural studies show that 1 can function as a chelating or bridging ligand upon metal coordination.Figure optionsDownload full-size imageDownload as PowerPoint slide