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

This manuscript describes\nthe synthesis of Os complexes supported\nby the diarylamido/bis(phosphine) PNP pincer ligand. Compound (PNP)OsH(CO)\n(<b>3-Os</b>) was prepared by analogy with the previously reported <b>3-Ru</b>. However, attempts to make (PNP)OsH<sub>3</sub> (<b>4-Os</b>) analogously to <b>4-Ru</b> resulted in the formation\nof an unexpected compound (<b>5-Os</b>) that is a product of\naddition of a BH<sub>3</sub> unit across the Os–N bond in <b>4-Os</b>. Nonetheless, <b>4-Os</b> was prepared via an alternative\nroute. Unlike <b>4-Ru</b>, <b>4-Os</b> appears to be a\nclassical trihydride. Compounds <b>3-Ru</b>, <b>3-Os</b>, <b>4-Os</b>, <b>4-Ru</b>, and <b>5-Os</b> were\ntested as potential catalysts for (a) dehydrogenative borylation of\nterminal alkynes (DHBTA) and (b) dehydrogenative borylation of benzene.\nNo catalytic C–H borylation was observed for any of them, but\nall of them catalyzed unselective hydroboration of 4-MeC<sub>6</sub>H<sub>4</sub>CCH.