Interstellar Molecules – A Guide for New Chemistry
Herbert W. Roesky, University of Goettingen, Institute of Inorganic Chemistry,
Tammannstrasse 4, 37077 Goettingen, Germany
UKB Kamenice 5, A11/ 132, on 7.10.2010 at 14:00
The interstellar space is one of the most remarkable chemical laboratories in the
universe. The existence of a number of species with low valent elements has been
characterized by scientists from astrophysics. Therefore it is a challenge for a
chemist to prepare compounds with low valent elements in the laboratory and study
their chemistry. Moreover to stabilize these species to be stable at room
temperature for further reactions.
We were able to prepare and study the chemistry of aluminum(I), silicon(I), silicon(II),
germanium(I), germanium(II), and tin(II) compounds. The low valent state can be
arrested by using sterically bulky ligands or base stabilizing procedures.
Methods for the preparation of compounds with the following composition
NHC•SiCl2 (NHC = N-heterocyclic carbene), LSi(II)H (L = monovalent amidinate),
LSi(II)F, LSi(I)-Si(I)L will be given, and their reactions with phosphorus, ketones,
alkines, partly- and per-fluorinated aromatics, 2,3-dimethylbutadiene, azobenzene,
and diazo compounds are reported. In the case of germanium and tin the
monohydrides of composition LM(II)H (L = ß-diketiminate, M = Ge, Sn) have been
prepared. Due to the larger radius of the M(II) in comparison with the M(IV) cations,
the compounds show an increased reactivity. For example LGeH and LSnH react
below room temperature with CO2 under insertion into the metal-hydrogen bond.
Comparable reactions with M(IV) species need an additional transition metal
catalyst.
Furthermore, perfluorinated aromatics can be converted selectively to the
monohydrides using Group 14 hydrides with low valent elements.
The X-ray structures and bonding properties of these new species will be discussed.