Boron Insertion into the N≡N Bond of a Tungsten Dinitrogen Complex

Lisa C Haufe; Lukas Endres; Merle Arrowsmith; Rüdiger Bertermann; Maximilian Dietz; Felipe Fantuzzi; Maik Finze; Holger Braunschweig

doi:10.1021/jacs.3c06259

Boron Insertion into the N≡N Bond of a Tungsten Dinitrogen Complex

J Am Chem Soc. 2023 Nov 8;145(44):23986-23993. doi: 10.1021/jacs.3c06259. Epub 2023 Oct 24.

Authors

Lisa C Haufe^{1

2}, Lukas Endres^{1

2}, Merle Arrowsmith^{1

2}, Rüdiger Bertermann^{1

2}, Maximilian Dietz^{1

2}, Felipe Fantuzzi³, Maik Finze^{1

2}, Holger Braunschweig^{1

2}

Affiliations

¹ Institute for Inorganic Chemistry, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg, Germany.
² Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg, Germany.
³ School of Chemistry and Forensic Science, University of Kent, Park Wood Rd, Canterbury CT2 7NH, United Kingdom.

PMID: 37875434
DOI: 10.1021/jacs.3c06259

Abstract

The 1,3-addition of 1,2-diaryl-1,2-dibromodiboranes (B₂Br₂Ar₂) to trans-[W(N₂)₂(dppe)₂] (dppe = κ²-(Ph₂PCH₂)₂), which is accompanied by a Br-Ar substituent exchange between the two boron atoms, is followed by a spontaneous rearrangement of the resulting tungsten diboranyldiazenido complex to a 2-aza-1,3-diboraallenylimido complex displaying a linear, cumulenic B=N=B moiety. This rearrangement involves the splitting of both the B-B and N=N bonds of the N₂B₂ ligand, formal insertion of a BAr boranediyl moiety into the N=N bond, and coordination of the remaining BArBr boryl moiety to the terminal nitrogen atom. Density functional theory calculations show that the reaction proceeds via a cyclic NB₂ intermediate, followed by dissociation into a tungsten nitrido complex and a linear boryliminoborane, which recombine by adduct formation between the nitrido ligand and the electron-deficient iminoborane boron atom. The linear B=N=B moiety also undergoes facile 1,2-addition of Brønsted acids (HY = HOPh, HSPh, and H₂NPh) with concomitant Y-Br substituent exchange at the terminal boron atom, yielding cationic (borylamino)borylimido tungsten complexes.