Pyörimisnivelet

Pyörimisnivelet refers to the theory and concept of isolating and determining the number of electron pairs in molecules, particularly in organometallic compounds. This concept, also known as the spinning top model or Berry pseudorotation, was introduced by Richard B. Bereman and Donald M. Gerloch in the 1970s.

The theory is based on the idea that an organometallic compound with a trigonal bipyramidal or square pyramidal geometry can undergo a Berry pseudorotation, a type of structural change where the ligand attachment to the metal center appears to be translating around the metal atom as a "spinning top." The pyörimisnivelet corresponds to the physical analogue of this dynamic behaviour as a fixed point on a hypothetical circular perpendicular plane from which an imaginary line connects the central metal point to the space coordinates of all the ligands in the molecule.

This theory is important in the context of organometallic chemistry as it helps to explain the behavior of certain organometallic compounds. The understanding of pyörimisnivelet contributes significantly to comprehending the true nature of the positioning of lone-pairs in the pseudo-tetrahedral arrangement of compounds without ambiguity.