N-tert-Alkyl-Substituted N-Heterocyclic Carbenes with a 1,1’-Ferrocenediyl Backbone

Abstract

1,1’-Diaminoferrocene (1) was converted to α-aminonitriles fc[NHC(CN)MeR’]2 (fc=1,1’-ferrocenediyl; 2 a: R’=Me, 2 b: R’=Ph, 2 c: R’=tBu) by reaction with ketones MeC(O)R’ in the presence of NaCN/HOAc or to the diimine fc(N=CPh2)2 (3) by condensation with Ph2CO. Treatment of 2 a–c or 3 with MeLi furnished fc(NHR)2 (4 a: R=tBu, 4 b: R=CMe2Ph, 4 c: R=CMe2tBu, 4 d: R=CMePh2) after aqueous work-up. The formylative cyclisation of 4 a–d to fc[(NR)2CH][BF4] (5H[BF4]) was possible only for R=CMe3 (a) and CMe2Ph (b). The reaction of these formamidinium compounds with NaN(SiMe3)2 afforded the N-heterocyclic carbenes fc{[N(CMe3)]2C:} (5 a) and fc{[N(CMe2Ph)]2C:} (5 b). 5 a was converted to the thiourea derivative 5 aS with elemental sulfur. 5 a and 5 b slowly decompose in solution by alkene elimination, affording the respective formamidine fc(NRCH=N) (6 a: R=CMe3, 6 b: R=CMe2Ph). 6 a was transformed to fc{[N(CMe3)][N(CPh3)]CH}[BF4] (5eH[BF4]) with Ph3C[BF4].