Thesis (M. Phil.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Thesis (Ph. D.)--University of Hong Kong, 1971.

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2006. / Includes bibliographical references. Also available in electronic version.

Thesis (Ph. D.)--Stanford University, 2002. / Includes bibliographical references (leaves 122-126).

The existence of numerous phosphorus containing functional groups gives phosphorus chemistry its enormous breadth. The range of functional groups stems from phosphorus’ ability to vary its coordination and valance. Phosphorus containing compounds have shown applications in agriculture, biological systems and chemical warfare. High refractive index polymers are used in lenses, fingerprint recognition and optical coatings. However, often these devices rely on to the materials available. Phosphorus rich polymers have shown promise due to the high level of polarisability. A range of poly(phosphate ester)s and polyphosphonates have been synthesised and their thermal and optical properties tested. Some of the samples prepared boast the highest refractive indices for these types of compounds. Polymers synthesised via a polycondensation mechanism usually possess a high dispersity, one way to introduce control is via a ring opening polymerisation (ROP). Novel aromatic phosphonate monomers have been prepared and attempted to polymerise. Monomer, catalyst and copolymerisation scope for aliphatic phosphonate ROP has also been explored. Organocatalysts are becoming increasingly popular in ring opening polymerisation literature, one of the most popular organocatalysts is triazabicyclodecene (TBD). TBD is a dual activating catalyst as it activates both the initiator and monomer via a basic and acidic moiety respectively. Phosphates also have dual activating substituents. A range of aromatic phosphates have been successfully synthesised with varying electron withdrawing/ donating groups. These catalysts were then screened against the polymerisation of β-butyrolactone and their catalytic activity investigated.

Master of Science / Department of Agronomy / Nathan O. Nelson / Phosphorus (P) loss from non-point agricultural sources has been identified as a main contributor to degraded surface water quality throughout the United States. Excessive P inputs to surface waters can lead to eutrophication, increased water treatment costs, and negative health impacts. Therefore, agricultural best management practices (BMP) that promote water quality, through minimizing P loss, must be identified. Studies outlined in this thesis aim to determine the impacts of cover crops and P fertilizer placement on P loss in surface runoff and nutrient cycling in a no-till corn (Zea mays)-soybean (Glycine max) rotation and provide insight into how cover crop species selection and termination method affects potential P loss from crop tissue. The first study examined combined effects of cover crop and P fertilizer placement on total P, dissolved reactive P (DRP) and sediment losses in surface runoff from natural precipitation events. This large-scale field study was conducted near Manhattan, Kansas, at the Kansas Agricultural Watershed (KAW) Field Laboratory during the 2016 and 2017 cropping years. Two levels of cover crop [no cover crop (NC) and cover crop (CC)] and three levels of P fertilizer management [no P (CN), fall broadcast P (FB), and spring injected P (SI)] were used. Flow-weighted composite water samples were collected from precipitation events generating greater than 2.0 mm of surface runoff. Results from this study found the CC treatment increased DRP losses compared to NC in both cropping years; however, CC reduced sediment loss by over 50% compared to NC. Application of P fertilizer increased DRP losses compared CN in both cropping years, although SI resulted in lower quantities of DRP loss compared to FB. In addition, this study found that CC reduced biomass and yield of corn compared to NC and therefore decreased nutrient uptake, removal, and deposition during the 2017 cropping year. However, no negative impacts of CC on biomass or yield were observed during the 2015 (corn) and 2016 (soybean) cropping years. Application of P fertilizer increased the concentration of Melich-3 P and total P in the top 0-5 cm of soil compared to CN; however, no differences between P fertilizer management practice were observed for concentrations of Melich-3 P at 5-15 cm. A greenhouse-based study determined the impacts of cover crop species (brassica, grass, and legume), termination method (clipping, freezing, and herbicide), and time after termination (1, 7, and 14 days after termination) on total P and water-extractable P (WEP) release from cover crop biomass. Freezing increased WEP concentration of crop tissue by more than 140% compared to clipping and herbicide. Additionally, at 7 and 14 days after termination, both concentration of WEP and fraction of WEP compared total P increased compared to 1 DAT. Findings from these studies suggest the use of cover crops may unintentionally result in greater DRP losses in surface runoff. However, addition of a cover crop can dramatically reduce erosion losses. In addition, cover crop species selection can directly impact the quantity of P being taken up and released by crop tissue. Understanding the impact of crop species selection may help create new BMPs which aim to reduce P loss.

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Chapter 1 reviews the literature concerning the principal synthetic routes to hydroxyphosphine transition-metal complexes and their reactions, which have led to the formation of some unusual diphosphoxane derivatives. The preparation and characterization of aminophosphine complexes of chromium, molybdenum, and tungsten are presented in Chapter 2. The phosphorus-nitrogen bond is readily cleaved by HC1 gas and other aqueous acids, to afford phosphorus-chlorine and phosphorus-oxygen bonded derivatives. The chromium and tungsten aminophosphine complexes have been found to be particularly useful for the preparation of chlorodiphenylphosphine derivatives. In addition their reactions with alcohols have also been investigated. The study of aminophosphine complexes has been extended to Pt(II) derivatives in Chapter 3. Cleavage of the phosphorus-nitrogen bond in these complexes is again observed to proceed smoothly with gaseous HC1 and aqueous HC1, but not with other aqueous acids. Treatment of the chlorodiphenylphosphine complex, cis-[PtC12(PPh2C1)2], with sodium sulphide afforded a four-membered metallacycle. A similar four-membered metallacycle was also obtained by refluxing the hydroxyphosphine complex, cis-[PtC12(PPh2OH)2], in toluene for 12h. Other reactions of the hydroxyphosphine complex with chlorodiphenylphosphine and dichlorophenyl- phosphine led to the formation of six-membered ring systems. The molecular structure of the complex [NHEt3] [Pt(C?CPh)(Ph2PO)2 (Ph2POH)] has been established by X-ray crystallography and reveals an unsymmetrical hydrogen-bridged system. Some of the complexes have been characterised via their 1,2-dithiolene derivatives. Treatment of cis-[PtC12(PNEt2Ph2)2] with diphenacyl sulphone in the presence of silver(I) oxide afforded the metallathietane-3, 3-dioxide complex, L2Pt-CHR-S (O)2-CHR (L=Ph2PNEt2; R = C(O)Ph). The final chapter describes the preparation of some Rh(I) and Ir(I) aminophosphine complexes. Their oxidative addition reactions with methyl iodide, tetracyanoethylene, dioxygen, and HC1 gas have been investigated. In addition, some interesting metal-mercury bonded complexes were prepared by the treatment of trans-[IrC1 (CO) (PNEt2Ph2)2] with mercuric halides, HgX2 (X=C1, Br or I). Satellite peaks due to mercury-199 coupling (I=1/2, 16.9%) were readily observed in the 31P-{1H} n.m.r. spectra.

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Master of Science / Department of Agronomy / Colby J. Moorberg / Soil profile phosphorus (P) distribution is known to influence rooting dynamics. However, it’s unknown if P placement in long-term no-till management influences root development in high P-testing soils. The research objective was to compare impacts of P placement on corn (Zea mays, L.) root development. Replicated field trials were conducted in Manhattan, KS on a long-term, strip-tilled, corn-soybean-wheat rotation. Five P treatments were applied to the corn rotation for 11 years and included a control (0 kg), 22 kg starter and 67 kg broadcast (BC+ST), 90 kg broadcast (BC), 22 kg starter and 67 kg deep band (DB+ST), and 90 kg deep band (DB) of P₂O₅ per hectare. This study was conducted in 2015 and 2016 – years 10 and 11 of the long-term study, respectively. All treatments tested above 20 ppm P, with highest concentrations at 10-15 cm for DB, and 0-5 cm for all other treatments. Root length treatment differences were observed primarily in the upper 35 cm during vegetative growth. In 2015, both total root length (TRL) and root length by depth were significantly less for starter P treatments. Though no TRL differences were observed in 2016, BC+ST exhibited reduced root length compared to BC across multiple depths. The BC and DB treatments had similar root growth in 2015. In 2016, greater TRL and root length across multiple depths were observed for BC compared to DB. Although grain yield was not affected, this study showed that P placement in high testing soils impacts root development, particularly during vegetative growth.