(I) Zinc complexes as synthetic analogues for carbonic anhydrase and as catalysts for hydrogen production and carbon dioxide functionalization (II) Application of lithium silylamides in the synthesis of transition metal isocyanide compounds from their ca

The multidentate alkyl ligand, [Tptm] ([Tptm] = tris(2-pyridylthio)methyl), provides an organometallic counterpart to the more common tripodal ligands, [Tp] ([Tp] = tris(pyrazolyl)hydroborato) and [Tm] ([Tm] = tris(2-mercapto-imidazolyl)hydroborato). A wide range of [Tptm] zinc complexes have been synthesized, enabling a diverse range of both stoichiometric and catalytic chemical transformations including the production of H 2 and the functionalization of CO2.;The [Tptm] ligand has been used to isolate the first mononuclear alkyl zinc hydride complex, [kappa3-Tptm]ZnH. The hydride complex may be easily synthesized on a multigram scale via reaction of the trimethylsiloxide complex, [kappa4-Tptm]ZnOSiMe 3, with PhSiH3. The hydride complex, [kappa3-Tptm]ZnH, provides access to a variety of other [Tptm]ZnX derivatives. For example, [kappa3-Tptm]ZnH reacts with (i) R 3SiOH (R = Me, Ph) to give [kappa4-Tptm]ZnOSiR 3, (ii) Me3SiX (X = Cl, Br, I) to give [kappa 4-Tptm]ZnX and (iii) CO2 to give the formate complex, [kappa4-Tptm]ZnO2CH.;The bis(trimethylsilyl)amide complex, [kappa 3-Tptm]ZnN(SiMe3)2, which has been prepared directly via the reaction of [Tptm]H with [ZnN(SiMe3)2]2, reacts with CO2 to give the isocyanate complex, [kappa 4 Tptm]ZnNCO. The formation of the isocyanate complex results from a multistep sequence in which the initial step is insertion of CO2 into the Zn-N(SiMe3)2 bond to give the carbamato derivative, [Tptm]Zn[O2CN(SiMe3)2], followed by rearrangement to [kappa4-Tptm]ZnOSiMe3 with the expulsion of Me3SiNCO, which further reacts to give [kappa4-Tptm]ZnNCO. An important discovery is that the rate of the final metathesis step, to give [kappa4-Tptm]ZnNCO, is enhanced by CO2. Specifically, insertion of CO2 into the Zn-O bond of [kappa 4-Tptm]ZnOSiMe3 gives the carbonate complex [kappa 4-Tptm]Zn[O2COSiMe3], which is more susceptible towards metathesis than is the siloxide derivative.;Additionally, [kappa3-Bptm*]ZnO2CH (Bptm* = bis(2-pyridylthio)(p-tolylthio)methyl) has been synthesized using the tridentate [Bptm*] ligand, which has only two chelating pyridyl arms, forbidding a kappa4 coordination. It serves as a room temperature catalyst for the hydrosilylation of CO 2, resulting in more rapid CO2 functionalization compared to the [Tptm] system. [kappa3-Tptm]ZnH and [kappa 3-Bptm*]ZnO2CH provide the first two examples of zinc complexes that catalyze the hydrosilylation of CO2. These results provide evidence that, in suitable ligand environments, inexpensive and abundant non-transition metals can perform reactions that are typically catalyzed by precious metal-containing compounds.;Thimerosal, [(ArCO2)SHgEt]Na, an organomercurial utilized since the 1930s as a topical antiseptic, and more recently as a vaccine preservative, previously was not structurally characterized. Therefore, the molecular structures have been determined for thimerosal, its protonated derivative, (ArCO2H)SHgEt, and its mercurated derivative, [(Ar CO2HgEt)SHgEt]2, using single crystal X ray diffraction. 1H NMR spectroscopic studies indicate that the appearance of the 199Hg mercury satellites of the ethyl groups is highly dependent on the magnetic field and the viscosity of the solvent; this observation is attributed to relaxation caused by chemical shift anisotropy. The relative signs of the Hg-H coupling constants (i.e. 2J Hg-H and 3JHg-H) have been determined by virtue of the fact that the inner pair of satellites appears as a singlet at 400 MHz. Reactivity studies involving (ArCO2H)SHgEt provide evidence that the Hg-C bond is kinetically stable with respect to protolytic cleavage. Finally, a series of known dithiol compounds have been synthesized for use as mercury chelating agents. (Abstract shortened by UMI.).