Dissertation/Thesis Abstract

Introducing Bis(silylene) and Bis(germylene) Pincer Type Ligands in Catalysis
by Gallego Mahecha, Daniel, Eng.D., Technische Universitaet Berlin (Germany), 2015, 232; 10698436
Abstract (Summary)

Inspired by the application of pincer ligands in catalysis and the coordination abilities of N-heterocyclic silylenes and germylenes toward late transition metals, a combination of these systems was investigated for the synthesis of novel bis(silylene) and bis(germylene) pincer ligands. First, the novel pincer ligands based on N-heterocyclic silylenes and germylenes (LE–X–EL, E = SiII, GeII; L = N,N’-di-tert-butylchloro(phenylamidinate); X = 4,6-di-tert-butyl-resorcinolate, 2-bromo-4,6-di-tert-butylresorcinolate, N,N’-diethylpyridine-2,6-diamide), denominated as GeCHGe, GeCBrGe, SiNSi, and GeNGe were synthesized and accessed in high and gram scale yields. Their chemical properties were compared with traditional phosphine pincer ligands tBu-PCHP and iPrN-PCHP (CH = 4,6-di-tert-butylresorcinolate, tBu-P = P(tBu)2, iPrN-P = P(iPr-N(CH2)2NiPr)), the latter being more electronic related with the bis(metallylene) pincer ligands. The coordination toward late transition metals was evaluated with the synthesis of the iridium(III) complexes of type [ECE]IrHCl(coe); nickel(II) complexes of type [ECE]NiBr; and iron(II) and iron(0) complexes of type κ2E,E’-[ENE]FeCl2 and [ENE]Fe(PMe3)2, respectively. The novel ligands and their complexes were fully characterized by spectroscopic methods such as 1H, 13C{1H}, 29Si{1H}, 31P{1H} NMR, 2D NMR correlation 1H-1H COSY, 1H-13C HSQC, 1H-13C HMBC, single crystal X-ray diffraction analysis, 57Fe Mössbauer, IR, ESI or APCI mass spectrometry, and elemental analysis. The series of novel metal complexes were tested as precatalysts in different catalytic reactions: borylation of arenes with the [ECE]IrHCl(coe); Sonogashira cross-coupling reaction with the nickel complexes [ECE]NiBr; and hydrosilylation of ketones with the iron complexes [ENE]Fe(PMe3)2. Mechanistic evaluation of the different reactions led to a general understanding of the catalytic cycles in each case. The unprecedented isolation of reaction intermediates and mechanistic details for such reactions are discussed and described. The results presented in this dissertation contribute to broaden the application scope of N-heterocyclic metallylenes as steering ligands in the catalytic arena.

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: Pincer ligands
Publication Number: 10698436
ISBN: 9781392713297
Copyright © 2020 ProQuest LLC. All rights reserved. Terms and Conditions Privacy Policy Cookie Policy