A duo of chemists from the Institute of Inorganic Chemistry at the University of Heidelberg has synthesized and characterized the first species of silicon(IV) with a square-planar configuration.
Silicon(IV) with a square-planar configuration represents a transition state. Image credit: Ebner & Greb, doi: 10.1016/j.chempr.2021.05.002.
“Silicon is the second most abundant element in the Earth’s crust, constituting 28 weight % as tetrahedral silicon(IV),” said University of Heidelberg’s Dr. Lutz Greb and Dr. Fabian Ebner.
“As a classical semi-metal, it possesses properties of both metals and non-metals, and belongs to the carbon group on the periodic table.”
“Due to the high stability of a tetrahedron, other structures are not known in silicon(IV).”
“Considered purely geometrically, the two-dimensional equivalent to a tetrahedron is a square.”
“These configurations are already known for carbon but, a square-planar structure has not yet been produced in the field of silicon(IV) chemistry, even after over 40 years of intensive effort.”
To create square-planar silicon(IV), the scientists grew a monocrystal and irradiated it with a finely focused beam of X-rays.
“The diffraction of the X-rays when encountering the atoms of the monocrystal led to an unmistakable pattern from which it is possible to calculate the position of the atom nuclei,” they said.
“This measurement enabled us to show that they were dealing with molecules with square-planar silicon(IV).”
“Further studies with spectroscopic methods supported this configuration.”
According to the team, square-planar silicon(IV) has unexpected physical and chemical properties, e.g. color in a naturally colorless class of substances.
“Synthesizing this configuration from the components we chose is comparatively simple once you have understood the key conditions,” Dr. Ebner said.
“Surprisingly, the square-planar silicon(IV) molecule constitutes a stable, isolable compound at all.”
“Due to the high reactivity, there are many conceivable ways of decomposition,” Dr. Greb said.
“Still, we have always believed that it is possible to isolate this compound.”
The team’s paper was published in the journal Chem.
Fabian Ebner & Lutz Greb. An isolable, crystalline complex of square-planar silicon(IV). Chem, published online June 9, 2021; doi: 10.1016/j.chempr.2021.05.002