Phosphinomethylation of [1'-(diphenylphosphino)ferrocenyl]-methylamines as a route to unsymmetric ferrocene diphosphine ligands
Abstract
[1'-(Diphenylphosphino)ferrocenyl]methylamine (1) reacts with Ph2PH/(CH2O)(x) or [Ph2P(CH2OH)(2)]Cl to give mixtures of Ph(2)PfcCH(2)NHCH(2)PPh(2) and Ph(2)PfcCH(2)N(CH2PPh2)(2) in which the triphosphine dominates (fc = ferrocene-1,1'-diyl). To avoid unwanted two-fold phosphinomethylation, the amine group in 1 was alkylated.
As expected, the reaction of the N-methyl analogue Ph(2)PfcCH(2)NHMe (5), obtained by reductive methylation of the aldehyde Ph(2)PfcCHO, with [Ph2P(CH2OH)(2)]Cl, only led to the diphosphine Ph(2)PfcCH(2)N(Me)CH2PPh2 (6). The diphosphine was structurally characterized and further reacted with [PdCl2(MeCN)(2)] and [PdCl(Me)(cod)] (cod = eta(2):eta(2)-cycloocta-1,5-diene), affording the respective trans-chelate complexes [PdCl(X){Ph(2)PfcCH(2)N(Me)CH2PPh2-kappa P-2,P'}] (7a: X = Cl; 7b: X = Me), which were also structurally authenticated by X-ray diffraction analysis.