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

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 R-P,S-P,S-P,R-P isomer. The rhodium(I) complex of 1, rac-[{RhCl(eta(4)-C8H12)}(2){cyclo-1,2-(NEt)(2)-3,6-(PCl)(2)-4,5-(ortho-C2B10H10)-kappa P,kappa P '}] (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.