Imino-bridged bisphosphaalkenes (2,4-diphospha-3-azapentadienes)

Nitrogen-bridged bidentate phosphaalkene ligands

Nitrogen-bridged bidentate phosphaalkenes reveal several exceptional properties as a new class of P=C-unsaturated diphosphinoamine (PNP) ligands: N–Si bond cleavage of the first N-silylimino-bridged bis-phosphaalkene (R2C=P)2NSiMe3 (R = iPrMe2Si) with chlorides of AgI, AuI, and RhI leads to complexes of the 5c-6π-heteropentadienide imidobisphosphaalkene anion; double Cl– transfer from PtCl2 and PdCl2 to coordinated phosphaalkene phosphorus atoms of P-diphenylphosphanylamino phosphaalkenes R2C=PN(R')PPh2 (R' = Me3Si or iPrMe2Si; R = tBu, 1-Ada) furnishes unprecedented bis-chelate P-chloroylid complexes M[R2CP(Cl)N(R')PPh2]2 (M = Pd, Pt); CO- and RhI-induced coupling of two P-diphenylphosphanylamino phosphaalkenes under disilylketene elimination provides trigonal–bipyramidal RhIII complexes with novel tetradentate dianionic “PNP–C–PNP” ligands R2C[P(–)N(R')PPh2]2.

Phosphaalkenylidene bridged ferrocenes

The lithiation of ferrocenylphosphane Fc-PH(2) (Fc = -C(5)H(4)FeC(5)H(5)) has been reinvestigated and both Fc-PHLi and Fc-PLi(2) have been identified by NMR-spectroscopy. The lithiated phosphanides have been converted to the corresponding mono and bis(silylated) species the latter of which gave synthetic access to an oligomer in which three ferrocene units are symmetrically connected by phosphaalkene units. The charge distribution within this oligomer and its isomers has been analyzed using DFT calculations which indicates that the iron atom of the central metallocene unit is slightly more positive than the terminal ones. These findings are supported experimentally by Mößbauer spectroscopy and cyclic voltammetry.