Steric control of the reduction of carbodiimides by samarium(ii) and the synthesis of very crowded samarium(iii) complexes

Abstract

Reduction of N,N′-di(2,6-diisopropylphenyl)carbodiimide (DippNCNDipp) by [SmL₂(thf)₂] (1) (L = N,N′-bis(2,6-diisopropylphenyl)formamidinate, DippNC(H)NDipp) in PhMe gave [Sm(L)₃] (2) in good yield. An analogous reaction of 1 with N,N′-dimesitylcarbodiimide (MesNCNMes) gave [SmL₂(MesNC(H)NMes)] (3). In contrast, reduction of N,N′-dicyclohexylcarbodiimide (CyNCNCy) by 1 in PhMe gave mixture of products from which [SmL₂(CyNC(CH₂Ph)NCy)] (4) and [SmL₂(CyNC(H)NCy)] (5) were isolated by fractional crystallisation. Using thf as the reaction solvent, solely compound 5 was crystallised. Reactions of [Sm(L)₂(CCPh)(thf)] (6) with the carbodiimides RNCNR (R = Cy, Mes) gave [Sm(L)₂(RNC(CCPh)NR)] (R = Cy (7) or Mes (8)) which are analogues of 4. No reaction was observed between 6 and DippNCNDipp.