Synthesis of Os Hydride Complexes Supported by the Diarylamido/Bis(phosphine) PNP Ligand and Attempts at Using (PNP)Ru and (PNP)Os Complexes in C–H Borylation Catalysis

This manuscript describes the synthesis of Os complexes supported by the diarylamido/bis(phosphine) PNP pincer ligand. Compound (PNP)OsH(CO) (3-Os) was prepared by analogy with the previously reported 3-Ru. However, attempts to make (PNP)OsH₃ (4-Os) analogously to 4-Ru resulted in the formation of an unexpected compound (5-Os) that is a product of addition of a BH₃ unit across the Os–N bond in 4-Os. Nonetheless, 4-Os was prepared via an alternative route. Unlike 4-Ru, 4-Os appears to be a classical trihydride. Compounds 3-Ru, 3-Os, 4-Os, 4-Ru, and 5-Os were tested as potential catalysts for (a) dehydrogenative borylation of terminal alkynes (DHBTA) and (b) dehydrogenative borylation of benzene. No catalytic C–H borylation was observed for any of them, but all of them catalyzed unselective hydroboration of 4-MeC₆H₄CCH.