Reactivity of iron complexes containing monodentate aminophosphine ligands – Formation of four-membered carboxamido-phospha-metallacycles

Treatment of [FeCp(CO)(2)Cl] with 1 equiv of the amidophosphine ligands Li[R(2)PNR′] (R = Ph, iPr, R′ = iPr, tBu, Cy) afforded complexes of the type [FeCp(CO)(κ(2)(C,P)-(C[bond, double bond]O)–NiPr-PPh(2))] (1a), [FeCp(CO)(κ(2)(C,P)-(C[bond, double bond]O)-NtBu-PPh(2))] (1b), and [FeCp(CO)(κ(2)(C,P)-(C[bond, double bond]O)-NCy-PiPr(2))] (1c) in 40–50% yields. Complex 1a was also formed when [FeCp(CO)(2)(PPh(2)NHiPr)](+) (2) was reacted with 1 equiv of KOtBu. These complexes feature a four-membered carboxamido-phospha-ferracycle as a result of an intramolecular nucleophilic attack of the amidophosphine ligand on coordinated CO. Upon treatment of 1a with the electrophile [Me(3)O]BF(4) the aminocarbene complex [FeCp(CO)(κ(2)(C,P)[bond, double bond]C(OMe)-NiPr-PPh(2))](+) (3) was obtained bearing an aza-phospha-carbene moiety. Upon treatment of cis,trans,cis-[Fe(CO)(2)(Ph(2)PNHiPr)(2)(Br)(2)] (4a) and cis,trans,cis-[Fe(CO)(2)(Ph(2)PNHtBu)(2)(Br)(2)] (4b) with KOtBu the carboxamido-phospha-ferracycles trans-[Fe(CO)(2)(κ(2)(C,P)-(C[bond, double bond]O)-NiPr-PPh(2))(Ph(2)PNHiPr)Br] (5a) and trans-[Fe(CO)(2)(κ(2)(C,P)-(C[bond, double bond]O)-NtBu-PPh(2))(Ph(2)PNHtBu)Br] (5b) were formed in moderate yield. Finally, representative structures were determined by X-ray crystallography.