This thesis describes a broad range of coordination and organometallic chemistry on a series of ruthenium and rhodium complexes towards the aim of activating unsaturated N Ξ N, C=O, and C=C bonds. The dinitrogen complex [RuTp(pzP)(N2)]BPh4 (5) (where Tp= tris(pyrazolyl)borate, and PzP= 1-(2-diphenylphosphinoethyl)pyrazole) was synthesized via displacement of the chloride ligand from the complex [RuTp(pzP)Cl] (1). It was found that N2 coordination proceeded through an unusual oxidation/reduction cycle with the Ru(III) intermediate, [RuTp(pzP)CI]BF4 (6), isolated upon reaction of 1 with AgBF4 in THF. Investigations of the coordination chemistry of the related Tp complex [RuTp(Bp)PPh3] (4) (where Bp= bis(pyrazolyl)borate), resulted in several unusual reactions occurring on the Bp chelate. Reaction of 4 with AgBF4 gave the unusual product [RuTp(BpF')PPh3] (6), which had the Bp B-hydride substituents replaced by fluoride substituents from the BF4 anion, (i.e. BpF,). Alternatively, reaction of 4 with AgOTf, or SOCb, led to the synthesis of the products [RuTp(BpoH)PPh3]OTf (34), and [RuTp(BpoH)PPh3]Cl (35), respectively, which have a single hydroxyl substituent substituted in place of the two B-hydrides to yield a highly unusual neutral borane chelate (BpOH). A series of ruthenium tris(pyrazolyl)methane (Tpm) complexes [RuTpm(PPh3)2Cl]BPh4 (44.BPh4) RuTpm(PPh3CI2] (46), [RuTpm(PPh3)2CI]BPh4 (44.BPh4) [RuTpm(PPh3)(MeCN)Cl]BPh4 (50), [RuTpm(PPh3HMeCN)](BF4)2 (51), [RuTpm(PPh3)(MeCNh](BF4)2 (52), and [RuTpm(MeCNhCI]BPh4 (54.BPh4) were synthesized. These complexes varied in the number of labile acetonitrile ligands they contained, the net charge of the complex, and the presence or absence of strongly coordinating phosphine coligands on the complex. The influence of these properties on the catalytic activity of the complexes for the transfer hydrogenation of acetophenone was investigated. It was shown that the net charge and number of labile MeCN donors on the complex had little influence on the activity of the catalyst. It was also observed that the catalyst [RuTpm(MeCN)2CI]BPh4 (54.BPh4), which does not contain a strongly coordinating PPh3 ligand, would rapidly decompose during catalysis. A series of bis(tert-butylthiomethyl)pyridyl (SNS tBU ) pincer complexes [Ru(SNStBU)(PPh3)Cb] (65), [Ru(SN StBU)(PPh3)(MeCN)CI]BPh4 (66), [Ru(SNStBU)(PPh3)(MeCN)2](BF4h (67), and [Ru(SNStBU)(MeCN)Cb] (68) were synthesized and their as catalysts for the transfer hydrogenation of acetophenone was investigated. The activity of these complexes for as transfer hydrogenation catalysts was shown to increase as the number of labile coligands on the complex increased, with an extremely high transfer hydrogenation activity obtained using 68. The catalytic activity of 68 is one of the fastest to be reported in the literature, achieving a superlative TOF (turnover frequency) of 87360 h- I. The coordination of SNStBu in 66 and the related complexes [Ru(SNS (MeCN)2CI]BPh4 (70), and [Ru(SNS)(MeCN)2CI]2[??-Ag(MeCN)2]2(BF4)4(71) was observed to yield a range of different conformational isomers. These isomers were studied in detail using low temperature NMR and 20 NOESY and COSY IH_1H correlation experiments. The complex 71 was also characterized crystallographically and was shown to have an unusual tetrametallic macrocyclic structure with two [Ru(SNS)(MeCN)2C1r moieties bridged by two [Ag(MeCN)2r ions through a chloro and thioether donor group. The hydrogenation of unsaturated olefinic bonds was achieved using a series of Rh N-heterocyclic carbene (NHC) complexes of the type [Rh(L)(COD)]BPh4 (where L= and NHC-pyrazolyl chelate). A series of NHC-pyrazoly ligands (L) were synthesized that contained varying degrees of steric bulk on the pyrazolyl and NHC donor group. The influence of these steric parameters on the rhodium complex structure and activity of the complexes as catalysts for the hydrogenation of styrene was investigated. It was found that increasing the steric bulk around Rh decreased the activity of the catalyst.
| Identifer | oai:union.ndltd.org:ADTP/258612 |
| Date | January 2008 |
| Creators | Page, Michael John, Chemistry, Faculty of Science, UNSW |
| Publisher | Publisher:University of New South Wales. Chemistry |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | http://unsworks.unsw.edu.au/copyright, http://unsworks.unsw.edu.au/copyright |
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