Reaction Chemistry of the Heavier Group 14 Carbene Analogues, M[Ar(Me6)]2, with Small Molecules Mediated by Synergistic Effects (M=Germanium, Tin; Ar(Me6)=C6H3-2,6-(C6H2-2,4,6-(CH3)3)2).

摘要

This dissertation describes the reaction chemistry of heavy carbene analogs with several small molecules. First, the reaction of the diarylgermylene, Ge(ArMe6)2, with isocyanides was shown to give the corresponding Lewis adduct species, (ArMe6) 2GeCNR (R = But, Me, C6H 11) in which the isocyanide ligand displays a decreased C-N stretching frequency consistent with an n – π* back-bonding interaction. Density functional theory confirms that the HOMO is a Ge-C bonding combination that involves the lone pair of electrons at the germanium atom and the C-N π* orbital of the isocyanide ligand. It was shown that the germylene – tert-butylisocyanide complex, (ArMe6) 2GeCNBut, undergoes facile C-H bond activation to produce a new diarylgermanium hydride/cyanide species and isobutene via heterolytic cleavage of the N-But bond, while the methylisocyanide adduct easily inserted into one of the germanium – ligand bonds to yield (ArMe6)Ge(μ-CNMe)(Ar Me6) or (ArMe6)GeC(NHMe)C(NCH 2)C(ArMe6)μ-N)Me if an excess of isocyanide is used. In addition, the back-bonding interaction between isocyanides and the germanium alkyne analog, AriPr 4GeGeAriPr4, were also investigated using density functional theory.;The ability of the germylene, Ge(ArMe6) 2, to insert into E-H bonds was also explored in several reactions. The germylene inserted into the N-H bond of hydrazines, to form (Ar Me6)-2Ge(H)N2H2R (R = H, Me, Ph) but this insertion is blocked when the substituted N,N dimethylhydrazine was used and only the Lewis adduct species was isolated. The crowding at the terminal nitrogen atom of the dimethyl-substituted hydrazine molecule blocks the close association of a second molecule of hydrazine which facilitates the proton transfer. Reaction of Ge(ArMe6) 2 with various inorganic acids (HCN, HN3, and HBF4) led to the facile oxidation of the germanium atom to yield the corresponding Ge(IV) products (ArMe6)2Ge(H)X (X = CN, N3, F). The base stabilized, cationic germanium complex [(Ar Me6)2GeH(OH2)][SO3CF 3] was prepared by treating Ge(ArMe6) 2 with triflic acid. The reactions presented provide an efficient method of installing a variety of functional groups at a germanium center, and can utilized in the preparation of germanium complexes which are analogous to lighter carbon species. The tin species, Sn(ArMe6) 2, is also oxidized by HBF4 to the Sn(IV) complex, (Ar Me6)2Sn(H)F, which is in stark contrast to the reaction of the stannylene with ammonia, which yields H(ArMe6 ) and [(ArMe6)Sn(μ-NH2)] 2.;The synthesis of the low valent In-In bonded indium amide dimer [(In{N(Dipp)SiMe 3})2(μ2-η1:η 1 C5H5)(μ2-η1:η 2 C5H5)] is also described. The complex was synthesized by the addition of [LiN(Dipp)(SiMe3)]2 to In(η5-C5H5), which, via a disproportionation reaction, led to the product. The structure of the amide features a unique bridging of the In-In bond via two cyclopentadienyl ligands and has a relatively short metal-metal distance of 2.7146(3)Å. The complex is a unique example of a low valent indium amido species stabilized by monodentate amide ligands.