Phosphate ester linkages are omnipresent in nature and are found in many biologically important molecules such as DNA, RNA and ATP. Many enzymes that hydrolyze phosphate esters are activated by metal ions. Since the structure of biological enzymes can be quite complicated, it is often useful to work with simpler artificial metalloenzymes to help elucidate the mechanisms by which phosphate ester hydrolysis is activated by metals. / In principle, simple dinuclear metal complexes could hydrolyze phosphate esters by double Lewis acid activation or by a combination of single Lewis acid activation and metal-hydroxide activation. These two mechanisms are kinetically indistinguishable. In this study, two different phosphate substrates are used to distinguish these mechanisms. / Lanthanide (iii) salts have proven extraordinarily effective in accelerating the rate of phosphate ester hydrolysis by several orders of magnitude. Consequently, there has been much effort in recent years to develop a ligand that would bind lanthanides so as to further improve their ability to hydrolyze phosphates. These efforts have met with limited success. Reported here is a dinuclear lanthanide (iii) complex which hydrolyzes BNPP (bis p-nitrophenyl phosphate) with unprecedented reactivity at pH 7.0 and 25°C. / A mononuclear copper (ii) 6,6'-diamino-2,2 '-bipyridyl complex is synthesized which gives one of the fastest rate accelerations reported for hydrolyzing 2',3 '-cAMP. A hydrogen bonding mechanism is proposed for the acceleration of the rate of hydrolysis of the cyclic phosphate.

The development of non-amino acid routes for the construction of peptides remains a challenge. The main goal of this study is to develop a new transition metal-mediated route to synthesize alpha-amino acid and peptide derivatives from imines and carbon monoxide. The proposed approach requires the sequential insertion of CO and imine into late transition metal sigma-bonds. / In Chapters 2 and 3, the ability of the palladium complex L2Pd(CH 3)N(R)=C(H)R'+ X- [L2 = chelating nitrogen ligands, X- = non-coordinating counteranion] to mediate the insertion of imines is examined. While L 2Pd(CH3)N(R)=C(H)R'+ X- is inert towards imine insertion into a palladium-methyl bond, the addition of CO to L2Pd(CH3)N(R)=C(H)R '+ X- yields the palladium-acyl complex L2Pd(COCH3)N(R)=C(H)R' +X-, which subsequently reacts to form the novel product of imine insertion: (L2)Pd[eta2-CH(R ')NRCOCH3]+X-. This demonstrates that these palladium complexes can undergo the novel sequential insertion of carbon monoxide and imine into the palladium-carbon bond in a manner directly analogous to that observed in olefin/CO alternating co-polymerizations. Examination of the mechanism of imine insertion (Chapter 3) demonstrates that, unlike olefins, imines undergo a concerted migration from the sigma-imine complex to form the product of imine insertion. The X-ray structure of the insertion complex 2.6b suggests the unique combination of amide bond formation, carbonyl oxygen chelation, and resonance stabilization of the chelate ring provides the stabilization required for this reaction to occur. / The product of CO/imine insertion is found to be inert towards reaction with carbon monoxide (Chapter 4). However, the addition of CO to its chloride analogue, generated via the oxidative addition of N-acyl iminium salts Tol(H)C=N(CH 2Ph)COPh+Cl- to Pd2(dba) 3•CHCl3 in the presence of 2,2'-bipyridine, results in the formation of 2-imidazolinecarboxylate derivatives (Chapter 5). Mechanistic studies reveal that imidazoline formation occurs via CO insertion into Pd--C bond of (bipy)Pd[eta2-CH(R' )NRCOR″]+Cl-, generating a palladium-bound alpha-amino acid derivative, which is followed by coupling with imine. This reaction is extended into a novel one pot palladium-catalyzed coupling of imine, carbon monoxide and acid chloride into 2-imidazolinecarboxylate derivatives. The described methodology provides a facile route to access the biologically relevant imidazoline derivatives through the sequential insertion of CO and imine into palladium-alkyl bonds.

The vibrational spectra (IR, Raman) of (eta6-C 6H5CO2CH3)Cr(CO)3, (eta 6-C6H5CO2CH3)Cr(CO) 2(CS), [Pt(NH3)4][PtCl4] (MGS), [Pt(ND 3)4] [PtCl4] (MGS-D), [Pt(NH 3)4][PtBr4] (MGS-Br), ReH7(dppe) (dppe = 1,2-bis(diphenylphosphino)ethane) and CpCo(C64H4) (Cp = cyclopentadiene) have been studied under pressures up to ∼45 kbar. The magnitude and direction of the pressure-induced shift of the Raman-active nu(CO) and nu(CS) vibrational modes of (eta6-C6H 5CO2CH3)Cr(CO)3 and (eta6 -C6H5CO2CH3)Cr(CO) 2(CS) indicate an increase in the amount of pi-backbonding to the CO and CS ligands, under pressure, the increase being greater to the CO ligand than to the CS ligand. Wavenumber vs. pressure plots revealed a phase transition in both the tricarbonyl and thiocarbonyl complexes between 10--15 kbar. For CpCo(C64H4), discontinuities in the wavenumber vs. pressure plots at 10 kbar indicate a phase transition at this pressure, most likely involving rotation of the Cp ring. Insertion of the Co atom into the cage does not occur under compression; a shift to higher wavenumbers was observed for all the Raman and IR vibrational modes of CpCo(C64H4) and the parent fulleride, C 64H4. Phenyl ring rotation is thought to occur in ReH 7(dppe) under compression. Three pressure regions, from ambient pressure to ∼16 kbar, between 16 and 29 kbar and above 29 kbar, were identified from the wavenumber vs. pressure plots. A broad, weak feature in the ER spectrum appears from 5 kbar, increasing in intensity with increasing pressure. This peak has been assigned to the nu(HH) mode of a coordinated dihydrogen ligand, Re(eta2-H2). Ring rotation may assist the pressure-induced dihydride-dihydrogen interconversion. The pressure-tuning IR study of MGS and its derivatives probed the intermolecular interactions, in particular the interactions of the NH3 groups and investigated the hypothesis that hydrogen bonding of the type N- H&cdots;Cl exists in MGS. Splitting of the IR bands at ambient pressure, and

Self-consistent field multiple scattering (SCF-MS) calculations have been performed on the aluminium trihalides, AlX$ sb3$ (X = F, Cl, Br, I) and their dimers, Al$ sb2$X$ sb6$ and on the large organometallic compounds diphenyltin(IV) dichloride and diphenyllead(IV) dichloride monomers and dimers. All these molecules have nuclear quadrupole resonance (n.q.r.) active nuclei and strong or weak intermolecular halogen interaction. In addition, diphenyltin(IV) dichloride has a Mossbauer active $ sp{119}$Sn nuclei to study the isomer shift and quadrupole splitting. Calculations used the Vosko-Wilk-Nusair(VWN) exchange-correlation potential in addition to Slater's X$ alpha$ exchange potential and also a quasi-relativistic wavefunction for the heavy nuclei in these molecules. The VWN and X$ alpha$ n.q.r. results are compared for the aluminium trihalides. The non-relativistic and relativistic calculations which are very important for the hyperfine interactions are compared for diphenyltin(IV) dichloride and the calculated relativistic Mossbauer isomer shift and quadrupole splitting agree well with experiment. The electric field gradients, which are very sensitive to the charge distribution around the nuclei in the molecules, gave very important information, using the n.q.r. and Mossbauer results, about the intermolecular halogen interactions in these molecules, supporting the conclusions arrived at using the one-electron energies and the HOMO-LUMO gap, and from the wavefunction contours and density maps. The relative Lewis acidity order and ionization potentials are also studied in the aluminium trihalides. Qualitative interpretation and agreement with experiment were found whenever experiment was available. Electronic structure and n.q.r. comparison of the diphenyltin(IV) dichloride and diphenyllead(IV) dichloride monomers and dimers lead to the conclusion that the diphenyltin(IV) dichloride is a monomer and the diphenyllead(IV) dichloride is a polymer.

In early work this chemiluminescence was confused with that from the oxygen atom - nitric oxide reaction. Indeed it has turned out that their spectra and mechanisms are quite similar, so that an understanding of the 0-NO reaction (which was investigated first) will facilitate understanding of the O3-No reaction. [...]

Vapour concentrations of methanol and ethanol over benzene solutions, and over saturated solutions of cobalt(II) thiocyanate in alcohol-benzene solutions were 0 measured at 25 c, by gas-chromatography. The activity of the alcohol in each solution was thereby found. [...]

The preparation of the first complex compound of BF3, BF3, NH3, was reported by Gay-Lussac and Thenard (1) more than 150 years ago. Some time afterwards the first SiF4 complex, SiF4.2NH3, was prepared (2). In 1890, Besson (3) isolated crystalline SiF4.PH3, but a temperature of -22° and a pressure of SO atmospheres were necessary. This is the only SiF4 complex reported containing a phosphorus electron-pair donor molecule and none have been reported with sulfur electron-pair donor molecules. [...]

<p> Detailed herein are the synthesis, characterization, and reactivity of three isolable four-coordinate iridium(I) monohydride complexes. Iridium(I) monohydrides containing the simple formula HIrL₃ have been postulated as reactive intermediates for over four decades escaping definitive evidence. The judicious use of the C&ndash;H activation resistant methyleneadamantyl phosphine P(CH₂¹Ad)(<i>i</i>-Pr)₂ (abbreviated L^mAd) and phosphinite P(O¹Ad)(i-Pr)₂ (abbreviated L^oAd) ligands allowed for the successful isolation and characterization of several four-coordinate iridium(I) monohydride complexes.</p><p> These electron-rich monohydride complexes rapidly deprotonate protic reagents, such as H₂N(2,6-(<i>i</i>-Pr)₂C₆H₃) and C₆F₅OH, and activate N&ndash;H, O&ndash;H, and H&ndash;H bonds. The sequential addition of 12-crown-4 with 1.0 equ. of a strong lewis base, i.e. Li(CH₃)₃CLi to cyclometallated complexes H₂Ir(&kappa;²-<i> P,C</i>-L^oAd)(L^oAd) and H₂Ir(&kappa;²-<i>P,C</i>-L^mAd)(L^mAd) produces four-coordinate anionic complexes [Li(12-c-4)][HIr(&kappa;²-<i>P,C</i>-L^mAd)(L^mAd)] and Li[12-c-4)2][H₃Ir(&kappa;²-P,<i>C</i>-L^oAd)(L^oAd)], respectively.</p><p> Herein we also report the X-ray characterization of coordinated alkanes, <i> n</i>-hexane and <i>n</i>-heptane, forming two cobalt metal complexes. A continued effort to isolate and characterize alkane &sigma;-complexes stems from the desire to control alkane C&ndash;H bond transformations, a significant synthetic challenge with high economic benefit.</p><p> Support for a distinct &eegr;²-H,C &sigma;-type interaction with <i>n</i>-hexane or <i>n</i>-heptane was provided by DFT and AIM analysis computations as well as <i>r</i>_bp parameter calculations. The diamagnetic complex, Co(SiMe₃)(CNAr^Mes2)₃ forms from the addition of (CH₃)₃SiCl to the zwitterionic complex (&kappa;²-PPN)(Co(CNAr^Mes2)₃ (PPN = (C₆H₅)₃P=N=P(C₆H₅)₃). Crystallization of Co(SiMe₃)(CNAr^Mes2)₃ with 5% v/v of C₆H₆ in <i> n</i>-hexane or <i>n</i>-heptane at -35 &deg;C under an argon atmosphere produces single crystals of the respective alkane &sigma;-complexes. When <i>n</i>-nonane (C₉H₂₀) is employed as the crystallization solvent, the unsaturated Co(SiMe₃)(CNAr^Mes2)₃ forms single crystals of Ar_1/7Co((SiCH₃)₃)(CNAr^Mes2)₃ which were manipulated in single crystal to single crystal (SC-SC) dinitrogen intercalation experiments, resulting in full occupancy and binding of dinitrogen to the cobalt metal center. Persistent in the solid-state are weak Van der Waals interactions from the CNAr^Mes2 ligands to the bound alkanes, <i>n</i>-hexane and <i>n</i>-heptane, possibly mimicking a clathrate-type entrapment mechanism. Distinct from clathrate networks is the strategic placement of a highly Lewis acidic cobalt center of proper electronic structure to engage in bonding.</p>

The phenomenon of mutual protective action in dual systems of hydrous oxides has been studied extensively at The Rice Institute. A variety of systems has been studied and in many of these systems each oxide prevents or retards the crystallization of the other. The degree of mutual protection varies from system to system and also depends upon the temperature level at which the dual gels have been heated. The system BeO-In2O 3 was first studied in 1947 by Watt by x-ray diffraction techniques. Marked mutual protection was observed in this system in two composition zones. Only the diffraction pattern of cubic In2O3 was observed for any sample containing In2O3, agreeing with the observations of Ensslin and Valentiner. Extensive sorption-desorption studies have been made by the author on the system BeO-In2O3, heat-treated for 2 hours at 500&deg;. From these studies surface areas, specific adsorptive capacities, differential and integral heats of adsorption, and pore size distributions were obtained. Enhanced adsorptive capacities, surface areas, and differential and integral heats of adsorption were observed in the same composition zones which had previously shown protection against crystallization. It is noted that there are two major regions of increased surface area and adsorptive capacity, at a region corresponding to 40--60% BeO and at a region corresponding to 90% BeO. The enhanced surface area and adsorptive capacity has been explained on the basis of mutual protection against crystallization, utilizing the concept of adsorption of one oxide on the other in the solid state. The differential and integral heats of adsorption as a function of composition at various values of the relative pressurer show two maxima exist, one between 30% BeO and 60% BeO, the other between 80% BeO and 90% BeO. These are essentially the same composition ranges in which there is mutual protection against crystallization and an increase in surface area and adsorptive capacity. If these zones correspond to smaller crystal size, and it will be shown that this is the case, the increase in heat of adsorption may be explained on the basis of increase of heterogeneity of the surface, due to a larger predominance of cracks, crevices, sharp edges and the like for an assembly of smaller crystals. The purpose of the present investigation is an attempt to elucidate the structure of these gels, especially in the zones of mutual protection.

On the basis of their electrical conductivities solids may be divided into three classes: metals, insulators, and semiconductors. Metals at room temperature have a high electronic conductivity which decreases with increasing temperature, while insulators have an extremely low ionic conductivity which increases rapidly with temperature. Semiconductors, like metals, conduct electronically, but their resistance at room temperature is much higher than that of metals and has a negative temperature coefficient. A solid may be a member of more than one class. For example, it is believed that if most semiconductors were prepared in an extremely pure state, they would behave as insulators. On the other hand, insulators to which some excess cation or anion has been introduced exhibit both electronic and electrolytic conductivities in some cases. However, there is evidence to indicate that a few solids have a true "intrinsic" semiconduction which is independent of their impurity content.