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Synthesis and Coordination Chemistry of Novel Water Soluble Diphosphines: Application to Ruthenium Catalyzed Aqueous Nitrile Hydration
AdvisorFrost, Brian J.
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This thesis investigates the synthesis and characterization of two novel 1,3,5-triaza-7-phosphaadamantane (PTA) diphosphine derivatives. Preparation involved the addition of chlorophosphines to lithiated PTA (PTA-Li). Two novel bicyclic diamino chlorophosphines were isolated for the synthetic approach. The chlorophosphine ClP(NiPr)2(CH2)2 (3) is previously reported, however citation used to give spectroscopic data was not observed to do so and is therefore reported herein. Compounds PTA-PiPr2 (4) and PTA-P(NiPr)2(CH2)2 (5) were isolated in good yields (56-73%). Both 4 and 5 exhibited moderate to slight water solublility (10 g/L and ~10 mg/mL, respectively). The corresponding dioxides, (O)PTA-(O)PiPr2 (6) and (O)PTA-(O)P(NiPr)2(CH2)2 (7), were also prepared and characterized. These were obtained by the addition of H2O2 to PTA-PiPr2 (4) and PTA-P(NiPr)2(CH2)2 (5). Isolated tungsten tetracarbonyl complexes [W(CO)4(PTA-PiPr2)] (8) and [W(CO)4(PTA-P(NiPr)2(CH2)2)] (9) were useful in attributing electronic characteristics of 4 and 5. Ruthenium arene complexes of PTA-PiPr2 (4) exhibit monodentate, chelating, and bridging coordination modes. Whereas coordination of PTA-P(NiPr)2(CH2)2 (5) to ruthenium arene and cyclopentadienyl complexes were difficult to ascertain. The ruthenium arene complexes and in situ generated catalysts incorporating ligands 4 and 5 were identified as catalytically active toward benzonitrile hydration. Isolated air-stable, water-soluble ruthenium arene complexes were further investigated for a variety of nitriles featuring methoxy, nitro, pyridyl, benzyl, and alkyl functional groups. Conversion of these nitriles to the corresponding amides was carried out in water, at 100°C, and under air. Synthesis and characterization of the dimeric complex [(n6-C6H5CH3)RuCl2(k1-(P)PTA-CHPhNHPh)] and [(n6-C6H5CH3)RuCl(k2-(P,N)PTA-CHPhNHPh)]Cl (12) will also be reported. Hemilability of this and two other similar complexes, [(n6-C6H5CH3)RuCl(k2-(P,N)PTA-CH(p-C6H4OCH3)NHPh)]Cl (13b) and [(n6-C6H5CH3)RuCl(k2-(P,N)PTA-CPh2NHPh)]Cl (14b), was investigated by two pathways. The use of MeOH and CH2Cl2 resulted in separate coordination modes for 14 only. The observed coordination was k2-P,N and k1-P, respectively. Pursuit of hemilability characterization for these complexes identified them as instable in solution. A series of unsuccessfully isolated PTA diphosphine derivatives will also be presented. The two major problems associated with these were the observance of unidentified singlets and incomplete separation from residual PTA. Three major types of chlorophosphine (ClPC2, ClPO2, ClPN2) were used. Both phosphite and bicyclic diamino PTA diphosphines were water soluble.