Net Heterolytic Cleavage of B–H and B–B Bonds Across the N–Pd Bond in a Cationic (PNP)Pd Fragment

The use of weakly coordinating anions BArF4 (where ArF = 3,5-(CF3)2C6H3) and CB11H12 allows one to access clean reactions of the [(PNP)Pd]+ fragment (PNP = bis(2-iPr2P4̅-Me-phenyl)amido) with the B–H bond in catecholborane (CatBH) and catecholdiboron (CatBBCat). In both cases, a net heterolytic cleavage of B–H or B–B takes place, with the nitrogen atom of PNP being a recipient of a boryl fragment. The resultant products [(PN(BCat)P)PdH]+ (2) and [(PN(BCat)P)PdBCat]+ (3) were isolated as either BArF4 or CB11H12 salts and fully characterized. They are susceptible to hydrolysis, with the B–N bond hydrolyzing selectively and rapidly at RT to give [(PN(H)P)PdH]+ (1) and [(PN(H)P)PdBCat]+ (4). Notably, 4 and 2 are isomers, but they do not interconvert even under thermolysis at 90 °C. The Pd–B bond in 4 can be further hydrolyzed more slowly, to give 1. On the other hand, a Pd–B bond was formed from the Pd–H bond in 2 by reaction with excess CatBH (and evolution of H2), producing 3.