N-H deprotonation of a diaminodialkoxido diborane(4) - a structural study on bifunctional Lewis acids/bases and their dimerisation to B(sp 2 ) 2 B(sp 3 ) 2 N 2 six membered rings.

Authors :: Drescher W
Kleeberg C
Source :: Dalton transactions (Cambridge, England : 2003) [Dalton Trans] 2021 Sep 28; Vol. 50 (37), pp. 13149-13157. Date of Electronic Publication: 2021 Sep 28.
Publication Year :: 2021
Abstract: The N-H deprotonation of the diaminodialkoxido diborane(4) pinB-Bdab (1) (pin: (OCMe <subscript>2</subscript> ) <subscript>2</subscript> , dab: 1,2-(NH) <subscript>2</subscript> C <subscript>6</subscript> H <subscript>4</subscript> ), is crucial for the electrophilic N -functionalisation towards unsymmetrical diborane(4) reagents. An N-H deprotonated diborane(4) comprises Lewis basic nitrogen atoms and at the same time Lewis acidic boron atoms. This bifunctionality governs its reactivity and structural chemistry. Whilst bases such as Na(hmds), t BuLi or Li(tmp) readily effect a single deprotonation of 1, the second deprotonation is less straightforward and cleanly only achieved with Li(tmp) as a strong but little nucleophilic base. The N-H deprotonated diborane(4) derivatives readily dimerise to give B(sp <superscript>2</superscript> ) <subscript>2</subscript> B(sp <superscript>3</superscript> ) <subscript>2</subscript> N <subscript>2</subscript> six-membered ring Lewis base adducts. The structural chemistry of this class of compounds was studied in detail in the solid state by single crystal X-ray diffraction as well as in solution by NMR spectroscopy.

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