Carborane‐Substituted Bis(phosphino)hydrazines: Selective Formation of Six‐ and Twelve‐Membered P,N Heterocycles

Abstract

Six‐ and twelve‐membered heterocyclic carborane‐substituted bis(phosphino)hydrazines 1 and 2 were obtained selectively. Compound 1 was obtained as the major product in a 1:1 reaction, when the dilithiated o‐carborane was added to 1,2‐bis(dichlorophosphino)‐1,2‐diethylhydrazine, whereas the reverse addition led to 2 as the main product (2:2 reaction). Compound 1 was obtained only as the rac isomer, 2 as the RP,SP,SP,RP isomer. The rhodium(I) complex of 1, rac‐[{RhCl(η4‐C8H12)}2{cyclo‐1,2‐(NEt)2‐3,6‐(PCl)2‐4,5‐(ortho‐C2B10H10)‐κP,κP′}] (3), shows dynamic behavior due to a temperature‐dependent equilibrium. Preliminary studies showed the rhodium(I) complex generated in situ from 1 and [Rh(cod)2]BF4 (cod = 1,5‐cyclooctadiene) to be an active catalyst in the hydrogenation of dimethyl itaconate.