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

Abstract

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[(H3B)mp] (mp = 2-mercaptopyridyl), Na[(H3B)amt] (amt = 2-amino-5-mercapto-1,3,4-thiadiazolyl), Na[(H3B)hp] (hp = 2-hydroxypyridyl), Na[(H2B)bap] (bap = bis(2-aminopyridyl)), and Na[(H2B)bdap] (bdap = bis(2,6-diaminopyridyl)). Room temperature photolysis of [M2(CO)10] (M = Mn or Re) with these borate species afforded dihydridoborate complexes [(CO)3M(μ-H)2BHL] 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 (H2BHL) units are coordinated to the metal centers through the (κ3-H,H,S) mode. However, in complexes 4 and 5 (or 6), the connection is via (κ3-H,H,O) and (κ3-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(NC5H4E)B(PhC═CH2)] (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.