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Multiple Bonding (multiple + bonding)

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Chemistry100%

Selected Abstracts

Calculated Enthalpies for Dimerisation of Binary, Unsaturated, Main-Group Element Hydrides as a Means to Analyse Their Potential for Multiple Bonding

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2003
Hans-Jörg Himmel
Abstract Herein, the dimerisation of subvalent, binary, main-group element hydrides with the potential for multiple bonding is studied using both hybrid DFT (B3LYP) and ab initio [MP2 and CCSD(T)] methods. The [2+2] cycloaddition is an important and characteristic reaction of derivatives of ethylene. A comparison of dimerisation reactions for several compounds with the potential for multiple bonding should, therefore, shed light on the properties of these species. Our study includes the hydrides E2H2 (E = B, Al, Ga, N P or As), E2H4 (E = C, Si or Ge) and ENH4 (E = B, Al or Ga) and their dimers. Several isomeric forms of the monomers and dimers have to be considered. The trends within a group and a period are established and the factors responsible for them are discussed. It turns out that, generally, the enthalpies for dimerisation increase for heavier homologues, reflecting that the most important factor is the reduced strength of the E,E bonds in the monomers prior to dimerisation and, to some degree, also the reduced ring strain in the cyclic dimers. The exceptions are the dimerisations of B2H2 and Al2H2, both of which lead to the tetrahedral E4H4 species (E = B or Al). Dimerisation of Al2H2 is associated with a smaller enthalpy than that for the dimerisation of B2H2. Comparisons and analyses are made complicated because of the changes in the structures of the isomeric global minima between homologues. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

Calculated Enthalpies for Dimerization of Binary, Unsaturated, Main-Group Element Hydrides as a Means to Analyse Their Potential for Multiple Bonding.

CHEMINFORM, Issue 31 2003
Hans-Joerg Himmel
No abstract is available for this article. [source]

An Alternative Way of Characterizing the Bonding in Compounds Featuring Main-Group Elements and with the Potential for Multiple Bonding: On the Dissociation of Binary Main-Group Hydrides.

CHEMINFORM, Issue 18 2003
Hans-Joerg Himmel
No abstract is available for this article. [source]

Calculated Enthalpies for Dimerisation of Binary, Unsaturated, Main-Group Element Hydrides as a Means to Analyse Their Potential for Multiple Bonding

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2003
Hans-Jörg Himmel
Abstract Herein, the dimerisation of subvalent, binary, main-group element hydrides with the potential for multiple bonding is studied using both hybrid DFT (B3LYP) and ab initio [MP2 and CCSD(T)] methods. The [2+2] cycloaddition is an important and characteristic reaction of derivatives of ethylene. A comparison of dimerisation reactions for several compounds with the potential for multiple bonding should, therefore, shed light on the properties of these species. Our study includes the hydrides E2H2 (E = B, Al, Ga, N P or As), E2H4 (E = C, Si or Ge) and ENH4 (E = B, Al or Ga) and their dimers. Several isomeric forms of the monomers and dimers have to be considered. The trends within a group and a period are established and the factors responsible for them are discussed. It turns out that, generally, the enthalpies for dimerisation increase for heavier homologues, reflecting that the most important factor is the reduced strength of the E,E bonds in the monomers prior to dimerisation and, to some degree, also the reduced ring strain in the cyclic dimers. The exceptions are the dimerisations of B2H2 and Al2H2, both of which lead to the tetrahedral E4H4 species (E = B or Al). Dimerisation of Al2H2 is associated with a smaller enthalpy than that for the dimerisation of B2H2. Comparisons and analyses are made complicated because of the changes in the structures of the isomeric global minima between homologues. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

The charge capacitance of the chemical bond: Application to bonds containing metals

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 3 2009
Asbjørn Holt
Abstract The charge capacitance of metal containing complexes are studied. For molecules with multiple bonding between the metal atoms it is found that the charge capacitance is correlated to the maximum bond order, natural bond order, and to some extent the effective bond order. Furthermore the charge capacitance of some methylidene metal dihydride complexes are studied. These molecules have agostic interactions of varying strength, and it is concluded that this strength is very well reflected in the charge capacitances of the systems. In accordance with the definition of agostic interactions it is therefor concluded that the charge capacitance holds information about the strength of covalent interactions. The effect therefore on the agostic interactions upon substitution of one of the hydrogen atoms with fluorine in the methylidene metal complexes is studied, and found to reduce the agostic interactions. It is also demonstrated that there is an agostic interaction in an ArCrCrAr complex. The distance dependence of the charge capacitance is also discussed. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 [source]

Triple-Bond Covalent Radii

CHEMISTRY - A EUROPEAN JOURNAL, Issue 12 2005
Pekka Pyykkö Prof.
Abstract A system of additive covalent radii is proposed for ,2,,4 triple bonds involving elements from Be to E,112 (eka-mercury). Borderline cases with weak multiple bonding are included. Only the elements in Group 1, the elements Zn,Hg in Group 12 and Ne in Group 18 are then totally excluded. Gaps are left at late actinides and some lanthanides. The standard deviation for the 324 included data points is 3.2 pm. Alkuaineille Be,(E,112) on määrätty ,2,,4 -kolmoissidoksille luonteenomaiset kovalenttiset säteet, rajatapaukset mukaan lukien. Vain ryhmän,1 alkuaineet, ryhmän,12 alkuaineet Zn,Hg, ryhmän,18 Ne sekä osa lantanoideista ja myöhemmät aktinoidit on tällöin kokonaan jätetty tarkastelun ulkopuolelle. Aineisto käsittää 324 pistettä ja tulosten standardipoikkeama on 3.2 pm.Abstract in German:Ein System additiver kovalenter Radien für ,2,,4Dreifachbindungen fast aller Elemente von Be bis E,112 (Eka-Quecksilber) wird vorgestellt. Grenzfälle mit schwachen Mehrfachbindungen wurden mit einbezogen. Die Elemente in Gruppe,1, Zn,Hg in Gruppe,12, Ne, die meisten Lantanide und einige Actinide wurden wegen mangelnder Daten nicht berücksichtigt. Die Standardabweichung für die 324 verwendeten Datenpunkte beträgt 3.2 pm. [source]