Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Chemistry

Supervisor

John F. Corrigan

Abstract

N-Heterocyclic carbenes (NHCs) are strong σ-donating ligands and thus, promising candidates for decorating and stabilizing metal-phosphide nanoclusters. While much research has been focused on the coordination of NHC ligands to different coinage metal centers in order to synthesize mononuclear organometallic complexes, their application in nanocluster chemistry has been relatively unexplored. The work described in this thesis involves employment of NHC ligands for stabilizing coinage metal t-butylthiolate and silylphosphido complexes. These complexes are promising molecular precursors for formation of larger NHC-stabilized nanoclusters.

In particular, the ligation of NHCs to [CuStBu] and [AgStBu] was developed as an alternative to PR3 ligands as solubilizing reagents for these coordination polymers in order to form polynuclear copper and silver t-butylthiolate clusters. 1,3-Di-isopropylbenzimidazol-2-ylidene (iPr2-bimy) and 1,3-di-isopropyl-4,5-dimethylimidazol-2-ylidene (iPr2-mimy) were ligated to [CuStBu] and [AgStBu] forming [Cu4(StBu)4(iPr2-bimy)2] (1), [Cu4(StBu)4(iPr2-mimy)2] (2), [Ag4(StBu)4(iPr2-bimy)2] (5) and [Ag5(StBu)6][Ag(iPr2-mimy)2] (6). For comparison, the trialkyl phosphines PnPr3 and PiPr3 were also used to solubilize [AgStBu] and [CuStBu] to form copper and silver t-butylthiolate clusters. [Cu4(StBu)4(PnPr3)2] (3), [Cu4(StBu)4(PiPr3)2] (4), [Ag4(StBu)4(PnPr3)2] (7), and [Ag6(StBu)6(PiPr3)2] (8) were thus formed upon reaction with [CuStBu] and [AgStBu]. The synthesized complexes have been characterized via spectroscopic and crystallographic methods. The molecular structures of the clusters, which can vary according to the ligand type, are described.

Moreover, the facile preparation and structural characterization of [M6{P(SiMe3)2}6] (M = Ag, Cu) is reported. These complexes show limited stability towards solvent loss at ambient temperature; however, NHC ligands were used to synthesize more thermally stable metal-silylphosphido compounds. iPr2-bimy and 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IPr) are found to be excellent ligands to stabilize silylphosphido-copper compounds that show higher stability when compared to [Cu6{P(SiMe3)2}6] (9).

Furthermore, iPr2-bimy is found to be an excellent ligand for the stabilization of silver–phosphorus polynuclear complexes. The straightforward preparation and characterization of the clusters [Ag12(PSiMe3)6(iPr2-bimy)6] (13) and [Ag26P2(PSiMe3)10(iPr2-bimy)8] (14) are described, representing the first examples of such structurally characterized, higher nuclearity complexes obtained using this class of ligands.

Lastly, iPr2-bimy and IPr were successfully utilized in the facile preparation of four gold silylphosphido complexes: [IPrAuP(Ph)SiMe3](15), [IPrAuP(SiMe3)2] (16), [(iPr2-bimy)AuP(Ph)SiMe3] (17), and [(iPr2-bimy)AuP(SiMe3)2](18). Furthermore, reactivity of the P−Si bond in 15 and 17 was explored via the addition of PhC(O)Cl. The product of such reactions was the formation of [(IPrAu)2PPhC(O)Ph][AuCl2] (19) and PPh(C(O)Ph)2 (20), respectively, as well as the elimination of ClSiMe3.


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