Synthesis and Structure of Boron Compounds Bearing Tridentate Ligands with 1,3-Bicarbonylbenzene Skeleton

Abstract

In order to examine differences in structure due to the electronic nature of the oxygen ligand, several organoboron compounds bearing ester 8a–8c and amide 13a and 13b ligands were prepared and crystallographically analyzed. In the ester ligand systems, the pinacolato derivative 8a and catecholato derivative 8b took a pentacoordinate structure, while fluorenyl derivative 8c took a tetracoordinate structure instead of pentacoordinate due to the strong electrophilic nature of the boron atom. In contrast to the ester ligand systems, no pentacoordinate species were found in the amide ligand systems. The pinacolato derivative 13a is tricoordinated, and catecholato derivative 13b is tetracoordinated. These results could be due to the steric effect of the diisopropylamide ligand together with the electronic effects. The VT NMR study and the DFT calculations reveal that the energy difference between the tetracoordinate and pentacoordinate structure in 8c is very small, and indicated that the electronic nature and steric effects of the ligand greatly affect the coordination state of the boron atom.

Generation of triplet carbenes by oxidation of an allene compound

“…The geometries and relative stabilities of the singlet and triplet states of 8a (A = S) and 8b (A = NMe) were calculated at the B3PW91/6‐31G(d) level . The triplet states ( 8a T and 8b T , respectively) were found to be favored over the corresponding closed‐shell singlet states ( 8a CS and 8b CS , respectively) for both compounds (Δ E ST = E CS − E T = 12.6 and 14.0 kcal/mol for 8a and 8b , respectively).…”

9-Borafluorenes: Synthesis, Properties, and Reactivity

“…The formation of metal halide byproducts provides a driving force for the reaction and can be easily removed due to their poor solubility in nonpolar solvents. It has been demonstrated that treating 9-halo-9-borafluorenes ( 2 or 45 ) with lithium (di- tert -butylboryl)­methylamide, 2,4,6-tri tert -butylphenyl lithium (Mes*Li), Li­[P­( t Bu) 2 ], potassium bis­(trimethylsilyl)­amide (K­[N­(SiMe 3 ) 2 ]), , 2,4,6-tris­(trifluoromethyl)­phenyl lithium (Mes F Li), , LiF, t BuONa, t BuOK, bis­(methylthio)­lead [Pb­(SCH 3 ) 2 ], chloromercuri­ferrocene (FcHgCl) and bis­(cyclopentadienyl)­zirconium­(IV) dimethyl (Cp 2 ZrMe 2 ) can generate the corresponding 9-borafluorenes ( 66 – 75 ) in moderate to good yields (Table , entries 1–12).…”

Mono- and Polynuclear Boron Dications

“…In particular, reaction of BCl 3 with [Li 2 (ttp)] (ttp: tetra(p-tolyl)porphyrin) gives the corresponding diboryl complex, which can be reduced with two equivalents of a Na/K alloy to yield the dichlorodiboranyl complex. A subsequent chloride abstraction with Na[BAr 60 [26] 2+ can be also viewed as a borenium dimer linked through a B(sp 2 )B(sp 2 ) bond. Unfortunately, structural characterization of [26] 2+ could not be accomplished due to the high Lewis acidity of the molecule.…”

“…A subsequent chloride abstraction with Na[BAr 60 [26] 2+ can be also viewed as a borenium dimer linked through a B(sp 2 )B(sp 2 ) bond. Unfortunately, structural characterization of [26] 2+ could not be accomplished due to the high Lewis acidity of the molecule.…”