Toward Transition-Metal-Templated Construction of Arylated B-4 Chains by Dihydroborane Dehydrocoupling

Carsten Lenczyk (1) , Dipak Kumar Roy (1, 2) , Kai Oberdorf (1) , Joern Nitsch (1) , Rian D. Dewhurst (1) , Krzysztof Radacki (1) , Jean-François Halet (3) , Todd B. Marder (1) , Matthias Bickelhaupt (4, 5, 6) , Holger Braunschweig (1)

1 JMU - Julius-Maximilians-Universität Würzburg
2 IITI - Indian Institute of Technology Indore
3 ISCR - Institut des Sciences Chimiques de Rennes
4 ACMM - Department of Theoretical Chemistry and Amsterdam Centre for Multiscale Modeling (ACMM) VU University Amsterdam
5 VU - Vrije Universiteit Amsterdam [Amsterdam]
6 Radboud University [Nijmegen]

The reactivity of a diruthenium tetrahydride complex towards three selected dihydroboranes was investigated. The use of [DurBH ] (Dur=2,3,5,6-Me C H) and [(Me Si) NBH ] led to the formation of bridging borylene complexes of the form [(Cp*RuH) BR] (Cp*=C Me ; 1 a: R=Dur; 1 b: R=N(SiMe ) ) through oxidative addition of the B-H bonds with concomitant hydrogen liberation. Employing the more electron-deficient dihydroborane [3,5-(CF ) -C H BH ] led to the formation of an anionic complex bearing a tetraarylated chain of four boron atoms, namely Li(THF) [(Cp*Ru) B H (3,5-(CF ) C H ) ] (4), through an unusual, incomplete threefold dehydrocoupling process. A comparative theoretical investigation of the bonding in a simplified model of 4 and the analogous complex nido-[1,2(Cp*Ru) (μ-H)B H ] (I) indicates that there appear to be no classical σ-bonds between the boron atoms in complex I, whereas in the case of 4 the B chain better resembles a network of three B-B σ bonds, the central bond being significantly weaker than the other two.

Keywords: B-H activation; boron; dehydrocoupling; ruthenium; transition metal

Domains: Chemical Sciences; Organic chemistry

Carsten Lenczyk, Dipak Kumar Roy, Kai Oberdorf, Joern Nitsch, Rian D. Dewhurst, et al.. Toward Transition-Metal-Templated Construction of Arylated B-4 Chains by Dihydroborane Dehydrocoupling. Chemistry - A European Journal, 2019, 25 (72), pp.16544-16549. ⟨10.1002/chem.201904772⟩. ⟨hal-02438529⟩