Diverse reactivity of a tricoordinate organoboron L₂PhB: (L = oxazol-2-ylidene) towards alkali metal, group 9 metal, and coinage metal precursors

Abstract

The reactivity of a tricoordinate organoboron L2PhB: (L = oxazol-2-ylidene) 1 towards metal precursors and its coordination chemistry were comprehensively studied.

Umpolung at Boron: Ancillary‐Ligand‐Induced Formation of Boron‐Based Donor Ligands from Phosphine‐Boranes

“…The absence of resonances between 0 and −40 ppm in the 1 H NMR spectrum suggests that no hydrido ligand is coordinated in 3 b‐CN . The broad resonance at −37.5 ppm in the 11 B{ 1 H} NMR spectrum is high‐field‐shifted compared to 3‐CO (Table ) and other reported borylene complexes, which is probably due to the different charges of the complexes and the different ligands in trans position to the boron atom: 3‐CO is neutral and has a CO ligand trans to the borylene ligand, whereas in the case of 3 b‐CN the complex is anionic and the stronger σ donor CN − is trans to the boron‐based donor group.…”

“…[17] Althought he reactivity of transition metal boryl and borylene complexes has been discussed extensively, [18][19][20] examples of base-stabilized borylenes and their transition metal complexes are still rare. [21][22][23][24] More interestingly,t he transformation of A into D is in line with af ormal umpolung from aL ewis acidic boron centre, stabilized by ap hosphine (R 3 P!BH 3 ), to aL ewis base that donates electrons to at ransition metal centre (M ! BH{PR 3 } 2 ).…”

“…Instead, ab road resonance at 43.9-49.0 ppm and al ow-intensity doublet of doublets at 95.3 ppm are detected,w hich is in line with symmetrization to ac omplex with two sets of magnetically equivalent phosphorus atoms. The absence of resonances between 0a nd À40 ppm in the 1 HNMR spectrums uggests that no hydrido ligand is coordinated in 3b-CN.T he broad resonance at À37.5 ppm in the 11 B{ 1 H} NMRs pectrum is high-field-shifted compared to 3-CO (Table 1) and otherreported borylene complexes, [21][22][23] which is probably due to the differentc harges of the complexes and the different ligandsi n trans positiont ot he boron atom: 3-CO is neutral and has a CO ligand trans to the borylene ligand,w hereas in the case of 3b-CN the complexi sa nionic and the stronger s donor CN À is trans to the boron-based donor group.…”

Serendipitous Observation of AlI Insertion into a C−O Bond in L2PhB (L=Oxazol‐2‐ylidene)

“…In previous studies on the reactivity of 2 , we observed a facile dissociation of one of the oxazol‐2‐ylidenes from the boron center of 2 in its reaction with [IrCl(COD)] 2 . This result prompted us to investigate if similar dissociation could occur in the presence of 1 .…”

A Tale of Two Elements: The Lewis Acidity/Basicity Umpolung of Boron and Phosphorus

“…[35] Similarly,species based on oxazol-2-ylidene ligands of formulations L 2 BH were prepared and reported by Kinjo et al [36] Theoxazol-2-ylidene derivative (Me 2 H 2 C 3 N(Me)O) 2 )BPh (25;S cheme 5) can be readily protonated with acid and coordinated to metals to give Cr(CO) 5 ,A uCl, and (NHC)Au + derivatives. [37] More recently, such borylenes have served as precursors to diborylene dications [38] and azaborabutadienes. [39] Scheme 4.…”