Brian G. McBurnett

An indium(II)-indium(II) compound with intramolecular donor-acceptor bonds

Abstract The diindium compound {2,6-(Me 2 NCH 2 ) 2 C 6 H 3 }(Cl)In–In(Cl){(2,6-Me 2 NCH 2 ) 2 C 6 H 3 }( 2 ) has been prepared via the reaction of [(2,6-Me 2 NCH 2 ) 2 C 6 H 4 ]InCl 2 with Li 2 [(C 4 H 4 BN( i Pr) 2 ]. By means of X-ray crystallography, it was established that four N→In donor-acceptor bonds are made to the unsuspended In–In moiety: monoclinic, space group C 2 /c, with a =21.913 (6), b= 8.364 (1), c =17.877 (3) A, α =90, β =117.21 (2), γ =90°, V =2914 (1) A 3 and Z =4.

Direct evidence for the β-hydride elimination mechanism in the decomposition of triethylgallium on GaAs(100)

Abstract Decomposition of the surface ethyl group formed by dissociative adsorption of triethylgallium (TEGa) on GaAs(100) is investigated using temperature programmed desorption. Deuterium labeling indicates that decomposition of the surface ethyl group proceeds exclusively through a β-hydride elimination reaction mechanism without any scrambling between α- and β-hydrogens. For undeuterated TEGa (TEGa-d0), the surface ethyl group decomposes and desorbs simultaneously as C2H4 and H2 at 600 K. For perdeuterated TEGa (TEGa-d15), the desorption of C2D4 and D2 occurs at a slightly higher temperature (630 K). Partially deuterated TEGa (TEGa-d6), with deuterium on the α-carbons, results in H2 and C2H2D2 as desorption products at 600 K. A kinetic isotope effect of 8 ± 5 kJ mol−1 for hydride versus deuteride transfer is determined, which is consistent with cleavage of the CβH bond in the transition state, and with tunneling.

AZIDO AND AMIDO DERIVATIVES OF ALUMINIUM(III)

Abstract The piperidinyl-substituted aluminium azide, [(pip)2AlN3]2 (5) (pip = piperidinyl, has been synthesised via the reaction between [(pip)2AlCl]2 and one equivalent of NaN3. A related pyrrolyl derivative, [(Me2N(H))Al(pyr)3] (7) (pyr = pyrrolyl, was prepared via the dimethylamine elimination reaction between [Al2(NMe2)6] and six equivalents of pyrrole. A third aluminium amido complex, [Li(Al(NHtBu)4)]2 (9), has been isolated from the salt elimination reaction between AlCl3 and an excess of LiNHtBu. all three compounds have been characterised by X-ray crystallography; compounds 5 and 9 are dimeric in the solid state, whereas 7 is monomeric.

Homolysis versus β-hydride elimination in the decomposition of trialkylgallium on GaAs(100)

Abstract The decomposition of various surface alkyl groups on GaAs(100), which were generated by dissociative adsorption of the corresponding trialkylgallium precursors R 3 Ga (R=Me, Et, Et- d 5 , n Pr , i Pr , n Bu and t Bu ), was studied by temperature programmed desorption. Two elimination pathways were observed, homolysis and β-hydride elimination. The former reaction results in the formation of alkyl radicals and the latter gives alkene and H 2 as products. On GaAs(100), both reactions are observed in the decomposition of all surface alkyl groups, except for methyl that reacts by homolysis. For each surface alkyl group, homolysis always occurs at slightly lower temperature than β-hydride elimination. Experiments with perdeuterated triethylgallium reveal that surface Et groups do not undergo coupling with coadsorbed deuterium on the surface to form ethane, and that ethane forms in subsequent wall reactions that involve Et radicals. The activation energy E a for homolysis followed the trend Me>Et> n Pr> n Bu> i Pr> t Bu , which reflects the strength of alkyl–surface bonds as well as the increased stability of the alkyl radical. The E a for β-hydride elimination follows closely the E a for homolysis and exhibits similar behavior in terms of magnitude and trend, i.e. Et> n Pr> n Bu≈ i Pr> t Bu , suggesting that breaking the alkyl–surface bond contributes to the activation energy for both homolysis and β-hydride elimination reactions. The alkyl–surface bond energy (Δ H h ) and the heat of reaction for β-hydride elimination (Δ H β ) for all surface alkyls are calculated from the desorption temperatures of their products.

Binuclear tin and germanium calix[4]arenes

Ditin(II) and digermanium(II) calix[4]arenes, [Butcalix]M2 (1, M = Sn; 2, M = Ge) have been prepared by treatment of [Butcalix]H4 with M(NR2) (R = Me or Me3Si); the reaction of [Butcalix]Li4 with SnCl4 affords the mixed valence ditin derivative [Butcalix]Sn2Cl2 3.

Novel zwitterionic complexes of Ti(IV) via reaction of Lewis acids M(C6F5)3 (M = B, Al) with a titanium diene complex (η5-C5Me4SiMe2NtBu)Ti(1,3-pentadiene)

The reaction of (η5-C5Me4SiMe2NtBu)Ti(1,3-pentadiene) with B(C6F5)3 or Al(C6F5)3 in 1:1 mole ratio in hexane solution at room temperature results in the formation of titanium borate or aluminate zwitterions which both feature stabilisation of the Ti(IV) centre by two agostic Ti⋯H–C interactions.