Mechanistic insights into dehydrocoupling of amine boranes using dinuclear zirconocene complexes

Abstract

Catalytic dehydrocoupling of H3B·NMe2H using the in situ system Cp2Zr(Cl)(µ-Me3SiC3SiMe3)Zr(Cl)Cp2 (1)/MeLi was studied as a model for previously reported dehydropolymerisation of H3B·NMeH2. NMR and UV-Vis spectroscopic monitoring of the precatalyst...

Cooperative approaches in catalytic hydrogenation and dehydrogenation

“…mechanistic information relies instead on computational studies. Some systems capable of MLC have been proposed to operate via non-cooperative single-site 22,23 or outer-sphere [24][25][26][27] pathways during catalysis. This tutorial review focuses on the conventional mechanisms proposed, but it is important to recognise that this is an ongoing area of study in the literature.…”

“…It is important to note that the presence of two metals does not necessitate bifunctional reactivity as one of the metals might not be involved, with the reaction proceeding via a monometallic single-site mechanism. 22,23 We have limited the examples included here to those for which there is mechanistic evidence to support both metals playing a functional role in catalysis.…”

“…69 These systems had modest catalytic activities for the dehydrogenation of H 3 BÁ NHMe Reiß, Beweries and co-workers have investigated a number of dizirconium systems in dehydrogenation of H 3 BÁNHMe 2 . 22 Detailed experimental and computational studies reveal the most active system [{ZrClCp 2 } 2 (m-Me 3 SiC 3 SiMe 3 )]/MeLi operates via a single-site mechanism in which all reactions take place at a single Zr centre. In contrast, the mode of activity of the slower, single-component catalyst [Zr 2 (m-H)(m-C 2 SiMe 3 )Cp 2 ] (22) does invoke MMC.…”

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“…Beweries, Reiß and coworkers reported on "Mechanistic Insights into Dehydrocoupling of Amine Boranes using Dinuclear Zirconocene Complexes". [6] In these studies, they were interested in modelling some single reaction steps for the dehydrocoupling and used the complex Cp 2 Zr(py)(η 2 -Me 3 SiC 2 SiMe 3 ) which, after dissociation of the alkyne and pyridine, serves as a generator for [Cp 2 Zr]. Reacting Cp 2 Zr(-CH 2 SiMe 3 )(-C � CSiMe 3 ) with Cp 2 Zr(η 4 -butadiene), they obtained a dinuclear hydridebridged zirconocene complex (Scheme 4).…”

“…While photochemistry and electrochemistry for binuclear complexes was described on several occasions, the related trinuclear complexes are less studied. Hexaphenyl-5,6,11,12,17,18-hexaa-zatrinaphthylene-tris-titanocene (Cp 2 Ti) 3 HATN(Ph) 6 shows six oxidation and three reduction waves in the voltammogram. The spectra in solution and the electrochemically formed oxidation products showed electronic transitions in the UV, visible and the NIR ranges.…”