Alane bonds

Financial support was provided by the National Science Foundation (Grant CHE-94-13128). Prof. Alan Bond and Mr. Richard Webster provided advance information concerning their studies on the electrochemistry of pyridine 2,6-dithioesters and related substances84. 

Fritz Scholz is a Professor at the University of Greifswald, Germany. Following studies of chemistry at Humboldt University, Berlin, he obtained a Dr. rer. nat. and a Dr. sc. nat. (habil-itation) from that University. In 1987 and 1989, he worked with Alan Bond in Australia. His main interest is in electrochemistry and electroanalysis. He has published more than 300 scientific papers, and he is editor and coauthor of the book Electroanalytical Methods (Springer, 2002, 2005, 2010, and Russian Edition A BINOM, 2006), coauthor of the book Electro-... 

Alan M. Bond Department of Chemistry, Monash University, Clayton VIC 3168, Australia, alan.bond sci.monash.edu.au... 

School of Chemistry, Monash University, Clayton South, VIC 3800, Austraha e-mail Alan.Bond monash.edu... 

According to the Haaland model, an increase of the Lewis acid-base interaction is accompanied by a decrease of both the R—Al—R bond angles and the Al—R bond distances. However, comparisons are possible only for adducts containing the same alane to exclude any steric or electronic effects of... 

Bis(diamino)alanes (R2N)2A1H were used for the hydroalumination of terminal and internal alkenes [18, 19]. TiCb and CpjTiCb are suitable catalysts for these reactions, whereas CpjZrCb exhibits low catalytic activity. The hydroaluminations are carried out in benzene or THF soluhon at elevated temperatures (60°C). Internal linear cis- and trans-alkenes are converted into n-alkylalanes via an isomerization process. Cycloalkenes give only moderate yields tri- and tetrasubstituted double bonds are inert. Hydroaluminahon of conjugated dienes like butadiene and 1,3-hexa-diene proceeds with only poor selechvity. The structure of the hydroaluminahon product of 1,5-hexadiene depends on the solvent used. While in benzene cyclization is observed, the reaction carried out in THF yields linear products (Scheme 2-10). 

This interpretation was supported by further investigations by GiacomelH and coworkers [73]. Racemic 4-phenyl-l-hexene was kineticaUy resolved by isomerization of the double bond using a catalyst system consisting of Al Buj, (R)-N,N-di-methyl-l-phenylethylamine and Ni(mesal)2. Very poor enantioselectivities (ee < 0.3%) were observed for both the isomerization product and the unreacted alkene. The authors note that it is essential to first react the alane with the chiral amine. No... 

The reaction between a Lewis acid R3M and a Lewis base ER3 is of fundamental interest in main group chemistry. Synthetic and computational chemists have investigated the influence of both the Lewis acid and the base on the solid state structure and the thermodynamic stability of the corresponding adduct, that is usually expressed in terms of the dissociation enthalpy De. This led to a sophisticated understanding of the nature of dative bonding interactions. In particular, reactions of boranes, alanes and gallanes MR3 with amines and phosphines ER3, typically leading to adducts of the type R3M <— ER3, have been studied.10... 

Steric interactions between bulky substituents such as t-Bu, leading to larger C-E-C bond angles, obviously affect the Lewis basicity caused by the increased -character of the electron lone pair. However, the strength of the Lewis acid-base interaction within an adduct as expressed by its dissociation enthalpy does not necessarily reflect the Lewis acidity and basicity of the pure fragments, because steric (repulsive) interactions between the substituents bound to both central elements may play a contradictory role. In particular, adducts containing small group 13/15 elements are very sensitive to such interactions as was shown for amine-borane and -alane adducts... 

Selected Bonding Parameters [pm, °] of Alane Stibine Adducts R3A1 <- SbR3... 

In contrast to these trends observed for borane-stibine adducts, the M-Sb bond lengths of alane-, gallane- and indane-stibine adducts are significantly elongated compared to the sum of the covalent radii (J>cov(AlSb) 266 J>cov(GaSb) 267 J>cov(InSb) 285 pm),48 as is expected for dative bonds. 

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