Extremely Facile Transformations of Tris(3, 5‐dimethylpyrazolyl)borate: a Bidentate Nitrogen Ligand and a C2‐Chiral Cation. Issue 20 (23rd June 2015)

• Record Type: Journal Article
• Authors: Daryanavard, Marzieh; Armstrong, David; Lough, Alan J.; Fekl, Ulrich
• Is Part Of: European journal of inorganic chemistry. Issue 20(2015)
• Page Start: 3232
• Page End: 3235
• Publication Date: 2015-06-23
• Subjects: Borates -- Boranes -- Frustrated Lewis pairs -- Aryldiazonium cations -- Tris­(pyrazolyl)borates; Chemistry, Inorganic -- Periodicals; Organometallic chemistry -- Periodicals; Bioinorganic chemistry -- Periodicals; Solid state chemistry -- Periodicals; 546
• DOI: 10.1002/ejic.201500424
• Languages: English
• ISSNs: 1434-1948

Abstract

Abstract: Two novel transformations are reported for the well‐known hydridotris(3, 5‐dimethylpyrazolyl)borate (Tp* – ). The uncommon Lewis base abstractor aryldiazonium cation (ArN2 + ; Ar = p ‐Br‐C6 H4, p ‐MeO‐C6 H4 ) if used in equimolar amounts, removes a hydride from Tp* – in acetone to produce the formal acetone adduct of tris(3, 5‐dimethylpyrazolyl)borane (pz*3 B· C3 H6 O, compound1 ). Frustrated Lewis pair (FLP) like behavior is thus found for a tris(pyrazolyl)borane. If 2 equiv. of ArN2 + are used, 3, 5‐dimethylpyrazolate is now being abstracted from1, and the resulting intermediate bifunctional borane adds another equivalent of acetone to form cation2 + {[pz*2 B· (C3 H6 O)2 ] +, obtained as2 ‐BF4 }, a boronium cation that is the formal addition product of 2 equiv. of acetone to the bis(3, 5‐dimethylpyrazolyl)borinium cation. Compounds1 and2 + are characterized by 1 H, 13 C, and 11 B NMR spectroscopy, mass spectrometry, and single‐crystal X‐ray diffraction. Compound1 is potentially useful as a charge‐neutral bidentate chelate ligand with controlled sterics, and2 + is a C 2 ‐chiral cation. Abstract : Although aryldiazonium cations have been known for a very long time, they are still good for surprises. Aryldiazonium cations ArN2 + react with hydridotris(3, 5‐dimethylpyrazolyl)borate (commonly used as a ligand) to remove a hydride and to form short‐lived intermediate tris(3, 5‐dimethylpyrazolyl)borane, which is trapped as the acetone adduct. If 2 equiv. of ArN2 + are used, 3, 5‐dimethylpyrazolate will additionally be abstracted, followed by acetone trapping.