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New KIT Phone numbers from January 01, 2011: Please note that our phone numbers have been extended from four to five digits.
New Collaborative Research Centre “Kooperative Effekte in homo- und heterometallischen Komplexen (3MET)”

The preparation and structures of new heteronuclear [1.1.1]propellanes E2Si3Mes6 have been reported (Mes = 2,4,6-Me3C6H2), together with their electronic properties, photochemically controllable radical-type reactivities, and reaction products thereof.

In recent collaborative papers with the groups of Dietmar Stalke and David Scheschkewitz we reported on experimental charge density distribution in [Mg{(pz*)3C}2], (pz* = 3,5-dimethylpyrazolyl), containing two non-coordinating sp3 carbanionic lone-pairs (Figure a) and the transfer of a disilenyl moiety to aromatic substrates and lateral functional group transformation in aryl disilenes (Figure b), respectively.

The
icing on the cake: We have recently
reported on the successful synthesis of the first
pentasilapropellane, Si5Mes6 (Mes = 2,4,6-trimethylphenyl), which consists of an archetypal
[1.1.1] cluster core featuring two ligand free, “inverted
tetrahedral” bridgehead silicon atoms. The separation between
the latter is much longer, and the bond strength is much weaker, than
usually observed for a regular Si-Si single bond. A detailed analysis
of the electronic characteristics of Si5Mes6 revealed a low-lying excited triplet state, indicative for some
biradical(oid) character. Reactivity studies provided evidence for
both closed-shell and radical type reactivity, confirming the unusual
nature of the stretched silicon silicon bond in this “non-classical”
molecule (this contribution has been highlighted recently)

In a
recent collaborative paper with the group of Holger Braunschweig we
reported on the reduction chemistry of
ferrocenylborol: One electron reduction of
1-ferrocenyl-2,3,4,5-tetraphenylborole results in a radical anion
with 5 electrons in the borole ring. Both EPR spectroscopic investigations
and spin density calculations confirm the formation of a borol
radical (see picture). Further one-electron reduction stimulates an
intramolecular [(C5H5)Fe]
migration from the cyclopentadienyl anion to the borole dianion.

Radical-Type
Reactivity of Metalla[1.1.1]propellanes of Group 14: The preparation and structures of new metal-terminated
bicyclo[1.1.1]pentastannanes are reported,
together with preparative and electrochemical studies on their
reduction chemistry.
We have
recently reported on the utility of multifunctional, k1Si:k3S-coordinated
tris(methimazolyl)silanide ligands [Si(mtMe)3]- for the stabilisation of a triangulo palladium cluster [Pd3{Si(mtMe)3}2]
(see picture) consisting of very unusual m3-capping SiR3 donors. Differences to
the corresponding platinum chemistry were supported by NMR spectroscopy and DFT
calculations.
This article is part of the ‘Emerging Investigators’ themed issue for Chem. Commun.

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