New chelating nitrogen ligands and their application to the catalytic reduction of nitrobenzene to aniline. X-ray structure of [Rh(CO)2(BBOM)] (HBBOM = bis(2-benzoxazolyl)methane)

The use of two novel chelating nitrogen ligands of the bis(azaheteroaryl)methane type is reported. Two complexes were synthesized: [Rh(CO)2(BBOM)] and [Pd(HBBOM)2](NO3)2 (HBBOM = bis(2-benzoxazolyl)methane), the first of which was completely characterized by X-ray crystallography. The dimethylated compound α,α-dimethyl-bis(2-benzothiazolyl)methane was also synthesized by an original procedure and used as a promoter in the [Ru3(CO)12]-catalyzed reduction of nitrobenzene to aniline. It gave much better conversions and selectivities with respect to the non-methylated HBBOM, probably due to the fact that the latter can be deprotonated when coordinated to the metal.