Dissertation/Thesis Abstract

Synthesis and Reactivity of Low Valent Group 13 and 14 (Semi)metal Complexes
by Tan, Gengwen, Dr.Nat., Technische Universitaet Berlin (Germany), 2015, 173; 10698444
Abstract (Summary)

Low-valent main group chemistry is one of the main research topics in contemporary organometallic chemistry. In this dissertation, the syntheses of monovalent Group 13 and divalent Group 14 (semi)metal compounds as well as their reactivities towards small molecules and transition metal reagents were investigated. In the first part of the dissertation, a distinctively different reaction feature between the NHSis L1(X)Si: (L1 = PhC(NtBu)2, X = Cl, OtBu, NMe2) and L2Si: (L2 = CH(C=CH2)(CMe)(NAr)2, Ar = 2,6-iPr2C6H3) towards copper(I) reagents was demonstrated. The reaction of the NHSis L1(X)Si: and L1Si:(O):SiL1 with Cu(I) precursors afforded only the second isolable examples of NHSi copper(I) complexes. In contrast, the zwitterionic NHSi ligand L2Si: is capable of activating the Cu−O and Cu−H bonds of (IPr)CuX (X = OtBu, OH, H and OC6F5; IPr = (CHNAr)2, Ar = 2,6-iPr2C6H3) affording the silyl copper(I) complexes L2Si(X)Cu(IPr). The latter are active for CO2 reduction to CO, and the comparison of the activity indicates that the stronger the nucleophilicity of the silyl group, the higher the activity of the silyl copper(I) complex for CO2 reduction to CO. In the second part of the dissertation, the compounds L2(H)Si(CH2)NHC (NHC = 3,4,5-trimethylimidazol-2-yliden-6-yl) and L3Si(=E)OH(dmap) (L3 = CH(MeCNAr)2, Ar = 2,6-iPr2C6H3; E = S, Se; dmap = 4-dimethylaminopyridine) were employed as ligands for Ni(0, II) and Cu(I) complexes, respectively. The former compound serves as an elegant precursor to realize the first mixed NHSi-NHC chelate ligand supported Ni(II) complex [L3Si:(CH2)NHC]NiBr2. The reduction of the Ni(II) complex to Ni(0) complexes as well as its catalytic properties for Kumada-Corriu type cross-coupling reactions were investigated. The complexes L3Si(=E)OH(dmap) were facilely deprotonatd by (MesCu)4 (Mes = 2,4,6-Me3C6H2) affording the two novel dimeric copper(I) complexes [L3Si(=E)OCu]2, which are efficient precatalysts for aziridination reaction. In the third part of this dissertation, the chemistry of germylene-, aluminum(I)- and gallium(I)-hydrides was investigated. The novel germylene hydride LCyGeH (LCy = cyclo-C6H8-1-NAr-2-C(Ph)NAr, Ar = 2,6-iPr2C6H3) was utilized to activate CO2 affording the formate compound LCyGeOCH(=O). In addition, a plausible mechanism for the conversion of the formate into methanol with NMe3·AlH3 as a hydrogen source was proposed based on the results from the model reaction of L3GeOCH(=O) with L3AlH2. The Al(I)-monohydride complex bisNHC-Al(H)[Fe(CO)4] (bisNHC = bis-(N-Ar-imidazole-2-ylidene)methylene, Ar = 2,6-iPr2C6H3) turned out to be highly reactive and capable of activating the α-C−H and C−O bonds of cyclic ethers. In contrast, the Ga(I)-monohydride complex bisNHC-Ga(H)[Fe(CO)4] could be successfully isolated. The pronouncedly different reactivity between the Al(I)- and Ga(I)-monohydride species towards cyclic ethers is likely attributed to the higher electronegativity of gallium versus aluminum which leads to a stronger Ga−H bond.

Indexing (document details)
Advisor: Driess, Matthias
School: Technische Universitaet Berlin (Germany)
School Location: Germany
Source: DAI-C 81/1(E), Dissertation Abstracts International
Subjects: Inorganic chemistry, Organic chemistry
Keywords: Organometallics
Publication Number: 10698444
ISBN: 9781392424131
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