| Popis: |
Di- and tri(3-methylindolyl)methanes and related pyrrolyl-based ligands have strong electron-withdrawing ability and reduced N•M π-donation when coordinated in the η1–N bound mode since the nitrogen lone pair is delocalized over the aromatic system. Thus, complexes based on these frameworks are potentially ideal for generation of tripodal monomeric electrophilic metal centers. This dissertation reports the synthesis and characterization of Lewis acidic aluminum and gallium complexes using di- and tri(3-methylindolyl)methanes, tris(pyrrolyl-α-methyl)amine, and isonitriles. In chapter 2, the synthesis and characterization of the first extensive series of isonitrile complexes of aluminum and gallium are reported. The new complexes are R3M•C≡NtBu (M = Al: R = tBu (1a), Me (1c), iBu (1e), Et (1f); M = Ga: R = tBu (1b), Me (1d)); R3M•C≡N(2,6-dimethylphenyl) (M = Al: R = tBu (2a), Me (2c), iBu (2e), Et(2f); M = Ga: R = tBu (2b), Me (2d)). All 12 of the new complexes have been characterized by 1H and 13C NMR spectroscopy, and seven of these complexes (1a, 1b, 1d, 2a, 2b, 2c, and 2d) have been characterized by X-ray crystallography, which confirms the structures as donor-acceptor complexes with one isonitrile bound to a metal trialkyl. These isonitrile complexes serve as models of unknown non-classical CO complexes of aluminum and gallium, and are presumed to model the intermediates for CO insertion into Al–C and Ga–C bonds. Enthalpies of formation for these complexes were determined using Isothermal Titration Calorimetry (ITC) in collaboration with Drs. Bob Flowers and Joe Teprovich at Lehigh University. In chapter 3, the synthesis and characterization of group 13 complexes with 3-methylindole (L1), di(3-methylindolyl)phenylmethane (L2), and tri(3-methylindolyl)methane (L3) are reported. Within this report are the first examples of μ2-η1:η1-N-indolyl moieties bridging group 13 elements, specifically aluminum in the complexes; [L1AlR2]2 (R = Me (7a), Et (7b), iBu (7c)), (L2Al2Me4) (8), (L3Al3R6) (R = Me (9a), Et (9b)), (L3Al3HiBu5) (9c). These complexes have been characterized by 1H and 13C NMR spectroscopy and elemental analysis. X-ray crystallography confirmed the presence of the bridging 3-methylindolyl group in 7a, 8, 9a, 9b, and 9c where there is one 3-methylindolyl moiety per aluminum. Complexes 7a-7c are observed as isomers in solution with a 60:40 ratio of anti:syn. NMR spectroscopic data suggests interconversion between syn and anti isomers for 7a-7c in solution. In chapter 4, the synthesis and spectroscopic characterization of four- and five-coordinate complexes of aluminum and gallium are reported. This includes the synthesis of four-coordinate anionic aluminum and gallium complexes of tri(3-methylindolyl)methane, four-coordinate neutral aluminum complexes of tri(3-methylindolyl)imidazolylmethane (L4), and five-coordinate aluminum and gallium complexes of tris(pyrrolyl-α-methyl)amine (L5). These complexes include: [(L3MX)][Li(THF4)] (M = Al: X = Cl (3a), H (4a), D (4b), tBu (4c); M = Ga: X = Cl (3b)); (L4AlR) (R = Me (5a), Et (5b), iBu (5c), tBu (5d); (L5M(HNMe2)) (M = Al (6a), Ga (6b)). These complexes have been characterized by 1H and 13C NMR spectroscopy. X-ray crystallography confirmed the structures of 3b, 6b and 7a. These complexes serve as precursors to potential three- or four-coordinate neutral, Lewis acidic, group 13 compounds although initial attempts to generate these were unsuccessful. |
