We demonstrate that trimethylamine borane can exhibit desirable piezoelectric and pyroelectric properties. The material was shown to be able operate as a flexible film for both thermal sensing, ...thermal energy conversion and mechanical sensing with high open circuit voltages (>10 V). A piezoelectric coefficient of d33≈10–16 pC N−1, and pyroelectric coefficient of p≈25.8 μC m−2 K−1 were achieved after poling, with high pyroelectric figure of merits for sensing and harvesting, along with a relative permittivity of ϵ33σ≈
6.3.
Pyroelektrisches Boran: Plastizität und mechanische Flexibilität von Trimethylaminboran wurden genutzt, um einen piezo‐ und pyroelektrischen Film herzustellen, der für Sensor‐ und Energieanwendungen geeignet ist.
The reaction of phosphorus(III) esters with pinacolborane generates phosphines via the action of an NHC-copper(I) catalyst. This gives access, within minutes, to 12 P–H bonded species, including ...secondary and primary phosphines as well as PH3, in excellent conversions. These phosphines can be subsequently applied in the copper(I)-catalyzed hydrophosphination of heterocumulenes in a telescoped, one-pot fashion. This approach yielded 12 phosphaureas, 3 phosphaguanidines, and 2 phosphathioureas in moderate to excellent yields without the need to handle toxic, pyrophoric, or gaseous P–H bond containing compounds. The crystal structures of two of the phosphaureas, PhP(C(O)NHPh)2 and P(C(O)NHPh)3, are presented.
The Front Cover shows a photograph taken by Dr. Mary F. Mahon on a visit to the subantarctic. Three Royal penguins strut past a sleeping elephant‐seal on Macquarie island. The somnolent, chunky seal ...represents the calming effect of a sterically demanding ring‐expanded N‐heterocyclic carbene−copper fragment on the reactivity of three exuberant boryl anions, depicted as the penguins. This summarises the ability of the (6‐Dipp)Cu moiety to support three boryl anions; −Bcat, −Bneop, and −Bhex (6‐Dipp=:C({Dipp}NCH2)2CH2, Dipp=2,6‐iPr2−C6H3; cat=1,2‐O2C6H4; neop=(OCH2)2C(CH3)2; hex=OC(CH3)HCH2C(CH3)2O). These species are readily synthesised and are far more stable than their 5‐membered N‐heterocyclic carbene analogues, providing convenient access to tame boryl birds‐in‐hand for the wider synthetic community. More information can be found in the Research Article by M. F. Mahon, D. J. Liptrot and co‐workers.
A tandem double Friedel−Crafts reaction of indoles and nonsymmetrical divinyl ketones has been achieved. The tandem reaction forms complex 6-5-7-tricyclic indoles in excellent yields. The reaction is ...completely regioselective and offers high levels of syn diastereoselectivity. The reaction is also seen to be sensitive to substrate structure and catalyst.
The transition metal tetra‐ and trinorbornyl bromide complexes, M(nor)4 (M=Fe, Co, Ni) and Ni(nor)3Br (nor=1‐bicyclo2.2.1hept‐1‐yl) and their homolytic fragmentations were studied computationally ...using hybrid density functional theory (DFT) at the B3PW91 and B3PW91‐D3 dispersion‐corrected levels. Experimental structures were well replicated; the dispersion correction resulted in shortened M−C bond lengths for the stable complexes, and it was found that Fe(nor)4 receives a remarkable 45.9 kcal mol−1 stabilization from the dispersion effects whereas the tetragonalized Co(nor)4 shows stabilization of 38.3 kcal mol−1. Ni(nor)4 was calculated to be highly tetragonalized with long Ni−C bonds, providing a rationale for its current synthetic inaccessibility. Isodesmic exchange evaluation for Fe(nor)4 confirmed that dispersion force attraction between norbornyl substituents is fundamental to the stability of these species.
Gecko‐Komplexe: Eine dispersionskorrigierte DFT‐Analyse von Übergangsmetall(IV)‐Komplexen des Norbornyl‐Liganden, M(nor)4 (M=Co, Fe, Ni) und Ni(nor)3Br, belegt, dass anziehende Dispersionskräfte zwischen den starren Liganden entscheidend für die Stabilisierung der ungewöhnlich hohen Oxidationsstufen sind.
The facile heterodehydrocoupling of a range of primary or secondary amines and even ammonia with pinacolborane (HBPin) was accomplished using {Ar
Me
6
Sn(μ-OMe)}
2
(1, Ar
Me
6
= C
6
H
3
-2,6-(C
6
H
2
...-2,4,6-Me
3
)
2
) as pre-catalysts for a catalytically active tin(
ii
) hydride. The more sterically hindered pre-catalyst
2
, {Ar
iPr
4
Sn(μ-OMe)}
2
(Ar
iPr
4
= C
6
H
3
-2,6-(C
6
H
3
-2,6-iPr
2
)
2
) facilitated the dehydrocoupling only of primary amines with HBPin, and at an increased rate relative to the less crowded {Ar
Me
6
Sn(μ-OMe)}
2
. Also presented is {Ar
Me
6
Sn(μ-NEt
2
)}
2
(3), which can be converted into the structurally characterizable {Ar
Me
6
Sn(μ-NEt
2
)(μ-H)SnAr
Me
6
} (4)
via
the addition of pinacol borane. This, alongside stoichiometric studies, give insight into the mechanism of the catalysis.
{Ar
Me
6
Sn(μ-OMe)}
2
(
1
, Ar
Me
6
= C
6
H
3
-2,6-(C
6
H
2
-2,4,6-Me
3
)
2
) and {Ar
iPr
4
Sn(μ-OMe)}
2
(
2
, Ar
iPr
4
= C
6
H
3
-2,6-(C
6
H
3
-2,6-iPr
2
)
2
) facilitate the dehydrocoupling of ammonia, 1° and 2° amines with HBpin.
2
catalyzes the reactions faster than
1
but is limited to 1° amines. Synthesis and characterization of a tin(
ii
) amide and amide-hydride give insight into the catalytic mechanism.
Reactions between PhSiH3 and alkali-metal diamidoalkylmagnesiates (M{N(SiMe3)2}2MgBu, M=Li, Na, K) provide either selective alkyl metathesis or the formation of polyhydride aggregates contingent upon ...the identity of the Group1 metal. In the case of M{N(SiMe3)2}2MgBu, this reactivity results in a structurally unprecedented dodecametallic decahydride cluster species.
Both homo‐ and heteroleptic alkyl and amide complexes of the Group 2 elements Mg and Ca are shown to be active for the catalytic dehydrocoupling of Me2NH⋅BH3. Reactions of either magnesium dialkyls ...or the β‐diketiminate complex HC{(Me)CN(Dipp)}2MgnBu with four or two equivalents of Me2NHBH3, respectively, produce compounds containing the H3BNMe2BH2Me2N− ion, which coordinates to the magnesium centers through MgN and Mg⋅⋅⋅HB interactions in both the solution and solid states. Thermolysis of these compounds at 60 °C produces the cyclic product (H2BNMe2)2 and, it is proposed, magnesium hydrido species by an unprecedented δ‐hydride elimination process. Calcium‐based species, although less reactive than their magnesium‐based counterparts, are found to engage in similar dehydrocoupling reactivity and to produce a similar distribution of products under thermally promoted catalytic conditions. A mechanism for these observations is presented that involves initial production and insertion of H2BNMe2 into polarized MN bonds as the major BN bond‐forming step. The efficacy of this insertion and subsequent β‐ or δ‐hydride elimination steps is proposed to be dependent upon the charge density and polarizing capability of the participating Group 2 center, providing a rationale for the observed differences in reactivity between magnesium and calcium.
Alkaline release: Stoichiometric and catalytic reactions of alkaline earth (Mg and Ca) alkyls and amides with Me2NH⋅BH3 result in the formation of the corresponding amidoborane derivatives and dehydrogenative coupling of two amine–borane fragments under mild conditions (see graphic).
Dehydrocoupling reactions between the boranes HBpin and 9‐borabicyclo3.3.1nonane and a range of amines and anilines ensue under very mild reaction conditions in the presence of a simple ...β‐diketiminato magnesium n‐butyl precatalyst. The facility of the reactions is suggested to be a function of the Lewis acidity of the borane substrate, and is dictated by resultant pre‐equilibria between, and the relative stability of, magnesium hydride and borohydride intermediates during the course of the catalysis.
Leicht zu verkuppeln: Dehydrokupplungen zwischen den Boranen HBpin oder 9‐Borabicyclo3.3.1nonan und Aminen oder Anilinen verlaufen unter milden Reaktionsbedingungen in Gegenwart eines einfachen β‐Diketiminato‐Magnesium‐n‐butyl‐Präkatalysators (siehe Bild). Die Reaktion wird durch die Lewis‐Acidität des Boransubstrats gefördert, und Vorgleichgewichte zwischen Magnesiumhydrid und Borhydrid bestimmen den Reaktionsverlauf.
Reactions of TEMPO (2,2,6,6‐tetramethyl‐1‐piperidinyloxy) with magnesium hydride species initiate oxidative hydrogen release, which may be elaborated to a catalytic regime within a manifold ...constructed about sequential TEMPO‐mediated redox and MgO/SiH metathesis processes.
Mit Tempo zum Ziel: Reaktionen von TEMPO (2,2,6,6‐Tetramethyl‐1‐piperidinyloxy) mit Magnesiumhydridspezies initiieren die katalytische Freisetzung von Wasserstoff über sequenzielle TEMPO‐vermittelte Redox‐ und Mg‐O/Si‐H‐Metatheseprozesse (siehe Schema). Dies ist das erste Beispiel eines katalytischen Ein‐Elektronen‐Transfers mit einem s‐Block‐Metall.
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