The past decade has witnessed some remarkable advances in our appreciation of the structural and reaction chemistry of the heavier alkaline earth (Ae = Mg, Ca, Sr, Ba) elements. Derived from ...complexes of these metals in their immutable +2 oxidation state, a broad and widely applicable catalytic chemistry has also emerged, driven by considerations of cost and inherent low toxicity. The considerable adjustments incurred to ionic radius and resultant cation charge density also provide reactivity with significant mechanistic and kinetic variability as group 2 is descended. In an attempt to place these advances in the broader context of contemporary main group element chemistry, this review focusses on the developing state of the art in both multiple bond heterofunctionalisation and cross coupling catalysis. We review specific advances in alkene and alkyne hydroamination and hydrophosphination catalysis and related extensions of this reactivity that allow the synthesis of a wide variety of acyclic and heterocyclic small molecules. The use of heavier alkaline earth hydride derivatives as pre-catalysts and intermediates in multiple bond hydrogenation, hydrosilylation and hydroboration is also described along with the emergence of these and related reagents in a variety of dehydrocoupling processes that allow that facile catalytic construction of Si-C, Si-N and B-N bonds.
The past decade has witnessed some remarkable advances in our appreciation of the structural and reaction chemistry of the heavier alkaline earth (Ae = Mg, Ca, Sr, Ba) elements.
This article provides a comprehensive overview of piezo‐ and ferro‐electric materials based on organic molecules and organic–inorganic hybrids for mechanical energy harvesting. Molecular (organic and ...organic–inorganic hybrid) piezo‐ and ferroelectric materials exhibit significant advantages over traditional materials due to their simple solution‐phase synthesis, light‐weight nature, thermal stability, mechanical flexibility, high Curie temperature, and attractive piezo‐ and ferroelectric properties. However, the design and understanding of piezo‐ and ferroelectricity in organic and organic–inorganic hybrid materials for piezoelectric energy harvesting applications is less well developed. This review describes the fundamental characterization of piezo‐ and ferroelectricity for a range of recently reported organic and organic–inorganic hybrid materials. The limits of traditional piezoelectric harvesting materials are outlined, followed by an overview of the piezo‐ and ferroelectric properties of organic and organic–inorganic hybrid materials, and their composites, for mechanical energy harvesting. An extensive description of peptide‐based and other biomolecular piezo‐ and ferroelectric materials as a biofriendly alternative to current materials is also provided. Finally, current limitations and future perspectives in this emerging area of research are highlighted. This perspective aims to guide chemists, materials scientists, and engineers in the design of practically useful organic and organic–inorganic hybrid piezo‐ and ferroelectric materials and composites for mechanical energy harvesting.
Mechanical Energy Harvesters: The review overviews the recent developments in piezoelectric and ferroelectric organic molecules and organic–inorganic hybrid materials for energy harvesting applications. The advantage of them lies in their solution‐phase synthesis, light‐weight nature, thermal stability, mechanical flexibility, and high polarization that enables them to serve as efficient generators. These aspects are discussed in detail, and future directions indicated.
London dispersion forces are the weakest component of Van der Waals interactions. They arise from attractions between instantaneously induced dipoles on neighbouring atoms. Their relative weakness, ...in particular for light atoms, such as hydrogen, has led to their importance being largely ignored in discussions of molecular stability and reactivity. This Review highlights the influence of these attractive forces — usually between C–H moieties in ancillary ligands — on the physical and chemical properties of organometallic and inorganic molecules. We feature recent examples of organic species that have informed current thinking and follow with a discussion of several prominent inorganic and organometallic complexes wherein dispersion forces have been explicitly identified or calculated. These forces strongly influence the behaviour of such complexes and often have a defining structural role. Attention is also drawn to several compounds in which significant attractive dispersion forces are probably present but have not been investigated.Despite its relative weakness, the London dispersion force can strongly influence physical and chemical properties of molecules. This Review highlights how structure and reactivity of organometallic and inorganic molecules are greatly affected by the cumulative effect of this force.
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.
Pyroelectrics are borane: Plasticity and mechanical flexibility in trimethylamine borane are harnessed to generate a piezoelectric and pyroelectric flexible film for sensing and energy harvesting applications.
An acyclic aluminyl anion Jackson, Ross A; Matthews, Aidan J. R; Vasko, Petra ...
Chemical communications (Cambridge, England),
04/2023, Letnik:
59, Številka:
35
Journal Article
Recenzirano
Odprti dostop
The potassium aluminyl complex K
2
Al{N(Dipp)SiMe
3
}
2
2
was synthesised
via
reduction of AlI{N(Dipp)SiMe
3
}
2
(Dipp = 2,6-i-Pr
2
C
6
H
3
). This represents the first example of an aluminyl anion ...supported by an acyclic ligand framework. Attempts to yield the same structure with a larger ligand framework, {N(Dipp)Si(i-Pr)
3
}, led to C-H cleavage. K
2
Al{N(Dipp)SiMe
3
}
2
2
behaves as a nucleophilic source of aluminium; reaction with an electrophilic β-diketiminate supported magnesium(
ii
) iodide forms a monomeric, acyclic magnesium aluminyl complex.
The potassium aluminyl, K
2
Al{N(Dipp)SiMe
3
}
2
2
has been synthesised. Reaction with HC{(CH
3
)C(Dipp)N}
2
MgI(OEt
2
) forms HC{(CH
3
)C(Dipp)N}
2
MgAl{N(Dipp)SiMe
3
}
2
, a monomeric, acyclic, magnesium aluminyl complex.
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.
BoNd‐forming catalysis: 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 reaction is facilitated by the Lewis acidity of the borane substrate, and is dictated by resultant pre‐equilibria between magnesium hydride and borohydride.
A β-diketiminato
-butylmagnesium complex is presented as a selective precatalyst for the reductive hydroboration of organic nitriles with pinacolborane (HBpin). Stoichiometric reactivity studies ...indicate that catalytic turnover ensues through the generation of magnesium aldimido, aldimidoborate and borylamido intermediates, which are formed in a sequence of intramolecular nitrile insertion and inter- and intramolecular B-H metathesis events. Kinetic studies highlight variations in mechanism for the catalytic dihydroboration of alkyl nitriles, aryl nitriles bearing electron withdrawing (Ar(EWG)CN) and aryl nitriles bearing electron donating (Ar(EDG)CN) substitution patterns. Kinetic isotope effects (KIEs) for catalysis performed with DBpin indicate that B-H bond breaking and C-H bond forming reactions are involved in the rate determining processes during the dihydroboration of alkyl nitriles and Ar(EDG)CN substrates, which display divergent first and second order rate dependences on HBpin respectively. In contrast, the hydroboration of Ar(EWG)CN substrates provides no KIE and HBpin is not implicated in the rate determining process during catalysis. Irrespective of these differences, a common mechanism is proposed in which the rate determining steps are deduced to vary through the establishment of several pre-equilibria, the relative positions of which are determined by the respective stabilities of the dimeric and monomeric magnesium aldimide and magnesium aldimidoborate intermediates as a result of adjustments to the basicity of the nitrile substrate. More generally, these observations indicate that homogeneous processes performed under heavier alkaline earth catalysis are likely to demonstrate previously unappreciated mechanistic diversity.
The synthesis, isolation and full characterisation of a Cu(IPr)(OC(H)(CF
3
)
2
) (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) complex are reported. This new Cu(
i
) complex is a versatile ...synthon and can activate numerous X-H bonds including C-H, N-H and S-H bonds. Cu(IPr)(OC(H)(CF
3
)
2
) was investigated as a pre-catalyst in several catalytic reactions.
A simple synthetic route gives access to well-defined Cu(
i
)-alkoxide complexes that prove stable to air and can be used as pre-catalysts.
PDF
![An air-stable [Cu(NHC)(OR)]...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/1359-7345/small "An air-stable [Cu(NHC)(OR)] (R = C(H)(CF)) complex for C-H, N-H and S-H bond activation")