Group VIII coordination chemistry of a pincer-type bis(8-quinolinyl)amido ligand.

This paper provides an entry point to the coordination chemistry of the group VIII chemistry of the bis(8-quinolinyl)amine (BQA) ligand. In this context, mono- and disubstituted BQA complexes of iron, ruthenium, and osmium are described. For example, the low-spin bis-ligated Fe(III) complex [Fe(BQA)(2)][BPh(4)] has been prepared via amine addition to FeCl(3) in the presence of a base and NaBPh(4). Complexes featuring a single BQA ligand are more readily prepared for Ru and Os. Auxiliary ligands featuring a single BQA ligand, along with two other L-type donor ligands, allow for a variety of ligand types to occupy a sixth coordination site. Representative examples include the halide and pseudohalide complexes trans-(BQA)MX(PPh(3))(2) (M = Ru, Os; X = Cl, Br, N(3), OTf), as well as the hydride and alkyl complexes trans-(BQA)RuH(PMe(3))(2) and trans-(BQA)RuMe(PMe(3))(2). Electrochemical studies are discussed that help to contextualize the BQA ligand with respect to its neutral counterpart 2,2',2''-terpyridine (terpy) in terms of electron-releasing character. Bidentate ligands have been explored in conjunction with the BQA ligand. Thus, the bidentate, monoanionic aryl(8-quinolinyl)amido ligand 3,5-(CF(3))(2)-(C(6)H(3))QA has been installed onto the (BQA)Ru platform to provide (BQA)Ru(3,5-(CF(3))(2)-(C(6)H(3))QA)(PPh(3)). A bis(phosphino)borate ligand stabilizes the five-coordinate complex [Ph(2)B(CH(2)PPh(2))(2)]Ru(BQA). Finally, access to dinitrogen complexes of the types [(BQA)Ru(N(2))(PPh(3))(2)][PF(6)], [(BQA)Ru(N(2))(PMe(3))(2)][PF(6)], and [(BQA)Os(N(2))(PPh(3))(2)][PF(6)] is provided by exposure of the sixth coordination site under a N(2) atmosphere.