Synthesis and Chemistry of Dihydridoborate Group 7 Metal Complexes with Varied N,E-Chelated Ligands (E = O, NH, or S).

Several dihydridoborate group 7 metal complexes have been synthesized and their structural aspects have been described from various N,S-, N,N-, and N,O-chelated borate species, such as Na[(H 3 B)mp] (mp = 2-mercaptopyridyl), Na[(H 3 B)amt] (amt = 2-amino-5-mercapto-1,3,4-thiadiazolyl), Na[(H 3 B)hp] (hp = 2-hydroxypyridyl), Na[(H 2 B)bap] (bap = bis(2-aminopyridyl)), and Na[(H 2 B)bdap] (bdap = bis(2,6-diaminopyridyl)). Room temperature photolysis of [M 2 (CO) 10 ] (M = Mn or Re) with these borate species afforded dihydridoborate complexes [(CO) 3 M(μ-H) 2 BHL] 1 - 6 ( 1 , M = Mn, L = mp; 2 , M = Re, L = mp; 3 , M = Mn, L = amt; 4 , M = Mn, L = hp; 5 , M = Mn, L = ap; 6 , M = Mn, L = dap, ap = 2-aminopyridyl, dap = 2,6-diaminopyridyl). In complexes 1 - 3 , the corresponding (H 2 BHL) units are coordinated to the metal centers through the (κ 3 -H,H,S) mode. However, in complexes 4 and 5 (or 6 ), the connection is via (κ 3 -H,H,O) and (κ 3 -H,H,N) modes of coordination, respectively. Complexes 1 and 5 underwent hydroboration reactions with terminal alkynes that yielded trans -hydroborated species [Mn(CO) 3 (μ-H) 2 (NC 5 H 4 E)B(PhC═CH 2 )] ( 7 , E = S; 8 , E = NH). Density functional theory (DFT) calculations have been carried out to investigate the electronic structures of these dihydridoborate species as well as the nature of bonding in them.