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The solution-phase thermolysis of (formazanate)boron dihydrides (LBH2; 2) results in the formation of aminoborane compounds (4) via a series of boron-to-ligand intramolecular hydride transfer reactions. Monitoring the reactions by NMR spectroscopy allowed identification of several intermediates, and a reaction mechanism is proposed. In the case of a ligand with an N-Mes substituent it was possible to characterize an intermediate (7b-i) during this transformation that shows an unexpected cyclohexadiene moiety, which results from hydride transfer to the ortho-position of the mesityl substituent. Two consecutive boron-to-ligand hydride transfers eventually result in reductive N-N bond cleavage to give triazaboroles as the final product. [ABSTRACT FROM AUTHOR]

The solution-phase thermolysis of (formazanate)boron dihydrides (LBH2; 2) results in the formation of aminoborane compounds (4) via a series of boron-to-ligand intramolecular hydride transfer reactions. Monitoring the reactions by NMR spectroscopy allowed identification of several intermediates, and a reaction mechanism is proposed. In the case of a ligand with an N-Mes substituent it was possible to characterize an intermediate (7b-i) during this transformation that shows an unexpected cyclohexadiene moiety, which results from hydride transfer to the ortho-position of the mesityl substituent. Two consecutive boron-to-ligand hydride transfers eventually result in reductive N-N bond cleavage to give triazaboroles as the final product. [ABSTRACT FROM AUTHOR]

The cationic tantalum complex {[η6-Ar-CMe2-η5-C5H4]TaPr}[B(C6F5)4] (1; Ar = 3,5-Me2C6H3) serves as a starting materialfor a series of neutral, monocationic, and dicationic derivatives.The cationic hydride {[η6-Ar-CMe2-η5-C5H4]TaH}[B(C6F5)4] (2) that results from hydrogenolysisof 1inserts the di- and trisubstituted olefins cyclopenteneand 2-methyl-2-pentene; it reacts with styrene to give the 2,1-insertionproduct, for which the Ta–CH(Me)Ph group is bound in a σ3-allylic fashion. A neutral complex is obtained from 1by reaction with Br–, and a dicationicderivative is available by hydride abstraction from 2using the Lewis acidic trityl cation. All compounds described hereretain the unusual ansa-(η5-cyclopentadienyl,η6-arene) coordination mode of the ligand that stabilizes theformally Ta(III) center. X-ray structures and DFT calculations showthat the metal–arene interaction contains a significant πback-donation component (arene←Ta(III)) that differs only slightlyin the series, despite the variation of charge at the metal center. [ABSTRACT FROM AUTHOR]

Reactions of N,N-dimethylaniline, N-isopropylaniline, 1,4-C6H4(CH2NHtBu)2,and benzyldimethylamine with the Lewis acid B(C6F5)3have been studied. In the case of N,N-dimethylaniline the combination of the Lewisacid and base forms an almost completely noninteracting frustratedLewis pair, while the corresponding reactions of N-isopropylaniline and benzyldimethylamine with B(C6F5)3afford the adducts (PhNHiPr)B(C6F5)3(1) and PhCH2NMe2B(C6F5)3(2), respectively. 1,4-C6H4(CH2NHtBu)2reacts with 2 equiv of B(C6F5)3to give rise to an inseparablemixture of the mono- and bis-amine–borane adducts as well asan iminium salt derived from hydride abstraction from a benzylic carbonof the diamine. Subsequent selected reactions of the Lewis acid/basecombinations with H2afforded [PhNMe2H][HB(C6F5)3] (3), [PhCH2NMe2H][HB(C6F5)3] (4), and [1,4-C6H4(CH2NH2tBu)2][HB(C6F5)3]2(5). Reactions with CO2gave PhCH2NMe2CO2B(C6F5)3(6), [PhNiPrH2][PhNiPrCO2B(C6F5)3] (8), [1,4-C6H4(CH2NH2tBu)(CH2NtBuCO2B(C6F5)3] (9), and [C5H6Me4NMeH]2[1,4-C6H4(CH2NtBuCO2B(C6F5)3)2] (10). Interestingly, the species 4also reacts with CO2to give [PhCH2NMe2H][HCO2B(C6F5)3] (7). Species 8reacts with HSiEt3to yield [PhNiPrC(OSiEt3)OB(C6F5)3] (11). The adduct 2also reacts with ethene, 2,4-hexadiyne, and the alkynesHCCR (R = n-Bu, Ph, tBu,SiMe3) to give the 1,2- addition products PhCH2NMe2CH2CH2B(C6F5)3(12), PhCH2NMe2C(CCMe)=CMeB(C6F5)3(13), and the ammoniumalkynylborate salts [PhCH2NMe2H][RCCB(C6F5)3] (R = n-Bu (14a), Ph (14b), tBu (14c), SiMe3(14d)). In contrast, the reactionof 1-hexyne with the Lewis pair PhNMe2and B(C6F5)3affords the trans-1,2-addition productPhNMe2C(C4H9)=CH(B(C6F5)3) (15). This chemistry demonstratesthe generality of such FLP chemistry, extending it to N-based Lewisbases and thereby expanding the scope for applications of FLP chemistry. [ABSTRACT FROM AUTHOR]