The heterolytic splitting of dihydrogen
Subtitle: ruthenium hydrogenation catalysts and an acidity scale.
Contributors: University of Toronto.  Dept. of Chemistry.
Published: 2005
Language: eng
Number of pages: 190
Description: Equilibrium constants KDM for reactions between acids and bases of phosphorus-containing compounds including phosphonium salts, iron hydrides and ruthenium dihydrogen complexes in CD2Cl 2 (DM) at room temperature are determined by use of 31P and 1H NMR spectroscopy. A continuous scale of pKDM  values covering the range 9.7 to -3 is created with acidic compounds [HPR3]BF4 and [FeH(CO)3(PR 3)2]BF4 in CD2Cl2. The crystal structures of [FeH(CO)3(PCy2Ph)2]BF 4 and Fe(CO)3(PCy2Ph)2 are obtained. The new dihydrogen complexes, [Ru(H2)Cl(PPh3)2 (dach)]BF4 (dach = (1R, 2R)-(-)-diaminocyclohexane) and [Ru(H2)Cl{tmeP2(NH)2}]BF4, are prepared and their crystal structures are reported. Their pKDM  values are determined to be 8.6 and 6.8, respectively.The heterolytic splitting of dihydrogen in new ruthenium complexes is utilized for the catalytic hydrogenation of the polar bonds in ketones and nitrites.The complex RuHCl{enP2(NH)2} (en = -NHCH2 CH2NH-) is an active catalyst for nitrile hydrogenation. This catalyst, in combination with Ru(H2)2H2(PCy 3)2, a known catalyst for nitrile hydrogenation, provides very efficient conversion of benzonitrile to benzylamine. The mechanism of the nitrile hydrogenation is proposed. These catalysts are extremely moisture sensitive. The crystal structures of a possible deactivated form of the catalysts, RuH(PhCONH){enP2(NH)2} and RuH(PhCONH){tmeP2(NH) 2}, are reported. The new complex RuH(BH4){enP2(NH) 2} is prepared by RuHCl{enP2(NH)2} and NaBH 4 and its crystal structure was obtained. This is a poor nitrile hydration catalyst.The new tetradentate ligands PPh2C6H4CH=NCMe 2CMe2N=CHC6H4PPh 2 {tmeP2N2} and PPh2C6H 4CH2NHCMe2CMe2NHCH2C 6H4PPh2 {tmeP2(NH)2}, and their ruthenium complexes, trans-RuHCl{tmeP2N 2} and trans-RuHCl{tmeP2(NH)2} (as two isomers), are prepared. The reaction of trans-RuHCl{tmeP 2(NH)2} with KOtBu produces the novel hydridoamido complex RuH{tmeP2NNH}. The reaction of the amido complex with H2 gives, by the heterolytic splitting of dihydrogen, exclusively the dihydridoamine complex trans-Ru(H)2 {tmeP2(NH)2}. The reaction of the amido complex with D2 is also studied. The complex RuH{tmeP2NNH} catalyzes the hydrogenation of acetophenone and a mechanism involving an outer sphere H+/H- transfer to the ketone is proposed.An improved route for the preparation of the phosphine-ketone PPh 2CH2CH2(C=O)Me from PPh2H and CH 2=CH(CO)Me provides an economical and efficient route to the phosphine-hydrazone PPh2CH2CH2(C=N-NH2)Me. The mixture of ruthenium complexes produced from the phosphine-hydrazone catalyzes the hydrogenation of acetophenone to 1-phenylethanol efficiently. The synthesis, structure and preliminary testing of the new precatalyst RuHCl((S, S)-PPM)(PPh3) for ketone hydrogenation are described.
Notes: Advisor: Robert Morris

Thesis (Ph.D.)--University of Toronto, 2005.

Electronic version licensed for access by U. of T. users.

Source: Dissertation Abstracts International, Volume: 66-06, Section: B, page: 3127.