EXPLORING AND EXPLOITING NOVEL [TM-Mʹ] HETEROBIMETALLIC COMPLEXES

Abstract

This thesis describes the chemistry of a series of ruthenium-main group metal heterobimetallic complexes. The work comprises of three distinct areas; a brief survey of E-H activation chemistry by the known [Ru-Zn] species [Ru(IPr)2(CO)(ZnEt)][BAr4F ] 1.12, the synthesis and thermal reactivity towards H2 and CO of novel [Ru-Al] and [Ru-Sn] complexes and, lastly, the preparation and photochemical reactivity of new [Ru-Zn] and [Ru-Al] species featuring Z-acceptor ligands.

The previously reported stoichiometric reactivity of [Ru(IPr)2(CO)(ZnEt)][BAr4F] 1.12 towards B-H and Si-H bonds has been extended and efforts undertaken to develop this for the catalytic reduction of alkenes. Side-by-side comparisons with [Ru(IPr)2(CO)H][BAr4F ] 1.11, provide some evidence for enhanced reactivity of the [Ru-Zn] complex, but of not enough significance to warrant prolonged study.

The heterobimetallic complexes [Ru(C6H4PPh2)2(PPh2C6H4AlMe(THF))H] 3.1 and [Ru(PPh3)(C6H4PPh2)(PPh2C6H4SnMe2)] 3.2 form upon reaction of [Ru(PPh3)(C6H4PPh2)2H][Li(THF)2] with AlMe2Cl and SnMe3Cl respectively following elimination of LiCl and CH4. The reaction pathways to formation of 3.1 and 3.2 were probed by variable temperature NMR studies and a range of intermediates detected in both cases. 3.1 reacts with H2 at 60 ℃ to afford [Ru(PPh3)2(PPh2C6H4AlMe)H3] 3.3, whereas 3.2 reacts with H2 at room temperature to yield [Ru(PPh3)2(PPh2C6H4SnMe2)H3] 3.4. The reaction of CO with 3.2 affords the acylated phosphine complex [Ru(CO)2(C(O)C6H4PPh2)(PPh2C6H4SnMe2)] 3.5 through a series of intermediates characterised by 13CO labelling in conjunction with NMR studies.

CO reacts with 3.1 to give [Ru(AlMePhos)(CO)3] 4.4, featuring the novel Z-accepting ligand AlMePhos ((o-C6H4PPh2)2AlMe). An analogue, [Ru(ZnPhos)(CO)3] 4.3 was prepared by reacting CO with the di-zinc complex [Ru(PPh3)(C6H4PPh2)2(ZnMe)2] 4.2. The reactivity of both 4.3 and 4.4 with E-H bonds (E = H, Si, B, C) is discussed. Upon photolysis with H2, 4.3 loses CO and adds H2 over the [Ru-Zn] bond to afford [Ru(ZnPhos)(CO)2(μ-H)2] 4.5. Photolysis of 4.4 under H2 yields the asymmetric product [Ru(AlMePhos)(CO)2(μ-H)H] 4.6. The experimental studies have been performed in conjunction with collaborative computational investigations. The reactivity of silanes, boranes and phenylacetylene with 4.3 and 4.4 was limited in success. Reaction of 4.4 with B(C6F5)3 affords the methyl abstracted compound [Ru(AlPhos)(CO)3][MeB(C6F5)3] 4.7 featuring the cationic [(o-C6H4PPh2)2Al]+ or AlPhos ligand.

Date of Award	29 Mar 2023
Original language	English
Awarding Institution	University of Bath
Supervisor	Michael Whittlesey (Supervisor) & David Liptrot (Supervisor)