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 (BOA) ligand. In this context, mono- and disubstituted BOA complexes of iron, ruthenium, and osmium are described. For example, the low-spin bis-ligated Fe(III) complex [Fe(BQA)(2)][BPh4] has been prepared via amine addition to FeCl3 in the presence of a base and NaBPh4. Complexes featuring a single BOA ligand are more readily prepared for Ru and Os. Auxiliary ligands featuring a single BOA 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(PPh3)(2) (M = Ru, Os; X = Cl, Br, N-3, OTf), as well as the hydride and alkyl complexes trans-(BQA)RuH(PMe3)(2) and trans-(BQA)RuMe(PMe3)(2). Electrochemical studies are discussed that help to contextualize the BOA 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 BOA ligand. Thus, the bidentate, monoanionic aryl(8-quinolinyl)amido ligand 3,5-(CF3)(2)-(C6H3)QA has been installed onto the (BQA)Ru platform to provide (BQA)Ru(3,5-(CF3)(2)-(C6H3)QA)(PPh3). A bis(phosphino)borate ligand stabilizes the five-coordinate complex [Ph2B(CH2PPh2)(2)]Ru(BQA). Finally, access to dinitrogen complexes of the types [(BQA)Ru(N-2)(PPh3)(2)][PF6], [(BOA) Ru(N-2)(PMe3)(2)][PF6], and [(BQA)Os(N-2)(PPh3)(2)][PF6] is provided by exposure of the sixth coordination site under a N-2 atmosphere.