Synthesis and Catalytic Applications of Platinum(II) and Palladium(II)-PTA and DAPTA Complexes
Doctor of Philosophy
Date of Defense
Janet Braddock-Wilking, PhD
The cage-like tertiary phosphine, 1,3,5-triaza-7-phosphaadamantane (PTA) has recently received interest because of its water-solubility, air-stability, non-ionic, non-surfactant, and basic nature. These properties can solubilize transition metal complexes in the aqueous phase. A related air-stable derivative, N,N’-diacetyl-1-3-5-triaza-7-phosphaadamantane (DAPTA) has greater water-solubility than PTA, however, its coordination chemistry has not been significantly explored. This study involved the synthesis and characterization of a series of novel air-stable and water-soluble four-coordinated dialkyl, dialkynyl, dihalo, and halo(alkyl) complexes of platinum and palladium bearing PTA and DAPTA ligands. The alkyl complexes of the type MX(R)P2 (M = Pt, Pd; X = Cl, Br, I; R = Me, Et; P = PTA, DAPTA) were obtained as the trans-isomers whereas the dialkyl or dihalo complexes of the type MX'2P2 (X' = Me, Br) were isolated as cis-isomers except trans-MI2P2. The complexes were characterized by multinuclear NMR, IR, MS, and elemental analysis experiments. X-ray crystallographic studies were performed on some of the complexes and confirmed a square planar geometry. The complex, cis-PtMe2(PTA)2 was found to be a very effective catalyst in hydrosilylation reactions of alkenes, alkynes, and a ketone using a variety of tertiary hydrosilanes including siloles and silafluorenes, with good regioselectivity and relatively low catalyst loading. The hydrosilylation reaction of terminal alkynes formed the β-trans isomer as the major product and the α-isomer as a minor product. This study is the first example of using a transition metal PTA complex as a pre-catalyst for hydrosilylation reactions. The Suzuki-Miyaura and Sonogashira cross-coupling reactions are some of the most common C-C bond forming reactions. The complex, trans-PdCl(Me)(PTA)2 was found to be effective in catalyzing Suzuki-Miyaura cross-coupling reactions of a series of haloarenes with phenylboronic acid with minimal homo-coupling, especially in isopropanol solvent. The previously reported complex, cis-PdCl2(PTA)2 was found to catalyze Sonogashira cross-coupling reactions of haloarenes with terminal alkynes effectively with minimal side reactions in piperidine in the absence of Cu(I) salts. The effects of substituents and leaving groups in both kinds of cross-coupling reactions have been investigated.
Acharya, Sitaram, "Synthesis and Catalytic Applications of Platinum(II) and Palladium(II)-PTA and DAPTA Complexes" (2012). Dissertations. 345.