MOESSBAUER STUDIES ON FERROCENE COMPLEXES. IX. PHOSPHAFERROCENES AND THEIR PROTONATED DERIVATIVES

Article abstract of DOI:10.1016/S0022-328X(00)99302-1

A number of mono- and di-phosphaferrocenes have been synthesised and their NMR (1H, 31P) and Moessbauer spectra measured.The presence of a phosphorus atom in the cyclopentadienyl (Cp) moiety causes a reduction of about 0.3 mm s^-1 in the quadrupole splitting (QS) compared with that of ferrocene.The effect appears to be additive, as does the effect of Cp ring substituents.Thus 2,5-diphenylphosphaferrocene (I), 3,3',4,4'-tetramethyldiphosphaferrocene (II) and 2,2',5,5'-tetraphenyldiphosphaferrocene (III) have QS values of 2.03, 1.82 and 1.52 mm s^-1, respectively.III dissolves readily and reversibly in triflic acid (CF3SO3H) to give a phenyl ring protonated species.The Moessbauer spectrum of the frozen solution shows a significant increase in QS to 1.77 mm s^-1 which is interpreted in terms of iron participation in the stabilisation of the ? complex.H/D exchange reactions and oxidation of phosphaferrocenes are briefly reported together with an improved synthesis of the important precursor, 1,2,5-triphenylphosphole.