Thesis (M.S.)--University of North Carolina at Wilmington, 2003. / Includes bibliographical references (leaves : [85]-87).

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: porous material; crystal engineering. Includes bibliographical references (p. 92-95).

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The complexes Cp(,2)M(SH)(,2), where M = Ti and Zr, have been prepared and treated with S(,8) and >N-S(,x)-NN = benzimidazolyl, phthalimidyl and x = 1, 2, to give the metallacyclohexasulfanes Cp(,2)MS(,5). Reaction of Cp(,2)TI(SH)(,2) with >N-SR, where >N = phthalimidyl, succinimidyl, gave the complexes Cp(,2)Ti(S(,2)R)(,2) (R = CHMe(,2)) and Cp(,2)Ti(SR)(S(,3)R) (R = Ph, 4-C(,6)H(,4)Me). The thiolates Cp(,2)Ti(Cl)SR and Cp(,2)Ti(SR)(,2) (R = CHMe(,2), CMe(,3), Ph, 4-C(,6)H(,4)Me) were prepared for comparison. Treatment of the complexes Cp(,2)MCl(,2) with anhydrous solutions of Li(,2)E(,x) gave the complexes Cp(,2)ME(,5), where M = Ti, Zr, Hf and E = S, Se. The compounds (RCp)(,2)TiS(,5) (R = Me, SiMe(,3)),CH(,2)Cp(,2)TiS(,5), and (Me(,5)Cp)CpTiS(,5) were prepared similarly. Reaction of Li(,2)S(,x) with (Me(,5)Cp)(,2)MCl(,2) gave the metallacyclotetrasulfanes (Me(,5)Cp)(,2)MS(,3). The complex Cp(,2)Ti{S(CH(,2))(,3)S} was synthesized. Variable temperature ('1)H NMR studies established the barriers ((DELTA)G('(NOT=))) for ME(,x) and TiS(,2)C(,3) ring reversal in the above complexes. The crystal structures of Cp(,2)Ti(SPh)(S(,3)Ph), Cp(,2)MS(,5), and (Me(,5)Cp)(,2)TiS(,3) are discussed.

This Thesis describes some theoretical studies on ligated and bare clusters. Chapter 1 gives a review of the two theoretical models, Tensor Surface Harmonic Theory (TSH) and Jellium Model, accounting for the electronic structures of ligated and bare clusters. The Polyhedral Skeletal Electron Pair Theory (PSEPT), which correlates the structures and electron counts (total number of valence electrons) of main group and transition metal ligated clusters, is briefly described. A structural jellium model is developed in Chapter 2 which accounts for the electronic structures of clusters using a crystal-field perturbation. The zero-order potential we derive is of central-field form, depends on the geometry of the cluster, and has a well-defined relationship to the full nuclear-electron potential. Qualitative arguments suggest that this potential produces different energy level orderings for clusters with a nucleus with large positive charge at the centre of the cluster, enabling the spherical jellium model to be applied to alkali metal clusters seeded with magnesium and zinc. Analysis of the effects of the non-spherical perturbation on the spherical jellium shell structures leads to the conclusion that for a cluster with a closed shell electronic structure a high symmetry arrangement which is approximately or precisely close packed will be preferred. It also provides a basis for rationalising those structures, which have been predicted using ab initio calculations, of clusters with incomplete shell electronic configurations In Chapter 3, the geometric conclusions derived in the structural jellium model are developed in more detail. Alkali metal clusters with closed shell electronic configurations according to the jellium model adopt geometries of high symmetry and based on the T_d , O_h and I_h point groups. For high nuclearity clusters alternative high symmetry structures can occur and those which are either the most close packed or spherical are predicted to be the most stable. When the jellium closed shell "magic numbers" coincides with one of these high symmetry structures then the cluster will be particularly stable. The group theoretical consequences of the Tensor Surface Harmonic Theory are developed in Chapter 4 for[ML₂]_n, [ML₄]_n and [ML₅]_n clusters where either the xz and yz or x²-y² and xy components to L^π_d and L^δ_d do not contribute equally to the bonding. The closed shell requirements for such clusters are defined and the orbital symmetry constraints pertaining to the interconversion of conformers of these clusters are described. In Chapter 5 Stone's Tensor Surface Harmonic methodology is applied to high nuclearity transition metal carbonyl cluster compounds with 13-44 metal atoms. Two limiting bonding situations are identified and represented in terms of general electron counting rules. If the radial bonding effects predominate the clusters are characterised by 12n_s+Δ_i valence electrons, where Δ_i is the characteristic electron count of the interstitial moiety. If radial and tangential bonding effects are important then the total number of valence electrons is 12n_s+2(s_s+s_i-l), where s_s and s_i are the number of skeletal bonding molecular orbitals associated with surface (s_s) and interstitial (s_i) moieties. Chapter 6 develops a new theoretical framework to account for the bonding in the high nuclearity ligated clusters with columnar topologies. The wave functions of columnar metal clusters can be expressed as an expansion based on the particle on the cylinder problem. This bonding analysis is applied to clusters containing columns of triangles and squares. In Chapter 7 the origin of non-bonding orbitals in molecular compounds is reviewed and analysed using general quantum mechanical considerations. A combination of the pairing theorem and a group theoretical analysis leads to a definition of the number of the non-bonding molecular orbitals in co-ordination, polyene and cluster compounds. The non-bonding molecular orbitals have been generated by defining the nodal characteristics of the relevant orbitals and evaluating the solutions under the appropriate boundary conditions. The stereochemical role of nonbonding molecular orbitals in co-ordination compounds is also discussed.

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The synthesis and characterization of pyridinyl &alpha / -diimine Pd(II) complexes having a functionalized hydrocarbon attached to the imino nitrogen was performed. The catalytic activity of these complexes were then evaluated in the polymerization of ethylene and in the Heck coupling reaction of methyl acrylate with iodobenzene.<br /> <br /> Unconjugated &beta / -diimine complexes of palladium were also synthesized and their activities towards ethylene polymerization and the Heck coupling of methyl acrylate and iodobenzene also evaluated and compared to that of the &alpha / -diimine complexes. Three of the &alpha / -diimine complexes synthesized showed activity towards ethylene polymerization, these being the complexes bearing the allyl, styrene and phenol functionalities. &omega / -Carboxylato complexes which were also synthesized showed no activity towards ethylene polymerization.<br /> <br /> The polymer produced was found to be high density linear polyethylene with an average PDI of 2.54 with Mn values ranging between 3.42 and 6.90 x 10-5 and Mw values ranging between 6.05 and 17.6 x 10-5.<br /> <br /> The complexes bearing the allyl, styrene and phenol functionalities, as well as the &omega / -carboxylato complexes active in the Heck coupling reactions of methyl acrylate with iodobenzene. None of the unconjugated &beta / -diimine complexes prepared showed any activity towards ethylene polymerization even at high Al/Pd ratios. The activity of these complexes towards the Heck arylation reaction was comparable to that of the &alpha / -diimine complexes showing similar activities.