Interaction of benzene-1,2-diamines with isocyanide complexes of palladium(II): Insight into the mechanism.

Reactivity of 4-toluidine ( 2 ) and 4,5-dimethylbenzene-1,2-diamine ( 3 ) were compared in coupling with the palladium- bis (isocyanide) complex cis -[PdCl 2 (CNXyl) 2 ] (Xyl = 2,6-Me 2 C 6 H 3 , 1 ), mixed isocyanide/diaminocarbene species cis -[PdCl 2 (CNXyl){C(NHXyl) NH(4-C 6 H 4 CH 3 )}] ( 4 ), and cis -[PdCl(CNXyl){ C (NHXyl) NHC 6 H 2 (Me) 2 N H 2 }]Cl ( 5 ). In these Pd(II)-mediated reactions, 4,5-dimethylbenzene-1,2-diamine ( 3 ) was significantly more reactive than 4-toluidine ( 2 ), leading to the first mixed bis (diaminocarbene) complex cis -[PdCl{ C (NHR) NHC 6 H 2 X 2 N H 2 }{C(NHXyl) NH(4-C 6 H 4 CH 3 )}]Cl ( 6 ) containing two different diaminocarbene ligands. Complex 6 was isolated and characterized by elemental analyses (C, H, N), HRESI + -MS, IR, 1 H and 13 C{ 1 H} NMR spectroscopies, and single-crystal X-ray diffraction. [ABSTRACT FROM AUTHOR]