The inversion of tetrahedral p-block element compounds: general trends and the relation to the second-order Jahn–Teller effect

Abstract

The tetrahedron is the primary structural motif among the p-block elements and determines the architecture of our bio- and geosphere. However, a broad understanding of the configurational inversion of tetrahedral...

Calix[4]pyrrolato gallate: square planar-coordinated gallium(iii) and its metal–ligand cooperative reactivity with CO2 and alcohols

“…† In comparison, constraining the non-cyclic tetrapyrrolato gallate, which has an effectively tetrahedral ground state, to square planarity costs 166 kJ mol À1 . 20 This nicely illustrates the substantial support of the macrocyclic calix [4]pyrrolato ligand and its electronic properties (s-accepting, p-donating) 39 as being crucial for the experimental realization of this conguration.…”

“…1B). 19,20 These features equip the compounds with biphilic properties, ideal for element-ligand cooperative reactivity 21–23 toward various functional groups (Fig. 1A).…”

Ligand-enforced geometric constraints and associated reactivity in p-block compounds

“…75,76 The origins of the high Lewis acidity have been thoroughly-discussed with referenced to Walsh analysis elsewhere, and are therefore not reproduced here. 77 Highlighting consequences for reactivity, the adjacency of a low-lying vacant p-orbital and heteroatoms or other electron-dense components of an anionic ligand unlocks metal-ligand cooperativity that can be harnessed for catalytic reactivity (Fig. 5d) such as dehydropolymerization of phosphine-boranes.…”

“…Despite early calculations showing the lower energy barrier required for the planarization of four-coordinate silicon species compared to carbon, experimental realization of planarization for the heavier group 14 elements has only occurred recently. 77, When considering unusual geometries in group 14 compounds, it is instructive to consider the inversion pathways for tetrahedral molecules. The inversion of methane has been extensively investigated computationally, [112][113][114] finding that it occurs not through a planar D 4h transition state but rather a distorted C s transition state (Fig.…”

“…115 The square planar inversion of heavier tetrahedral p-block compounds was more recently investigated computationally, finding low barriers for a number of these compounds. 77,98 While square planar inversion is not the most favorable pathway for most of the element hydrides, 98 depending on the substituents the planar transition state can be significantly stabilized. 77 This allows some insight into how a planar group 14 compound can be stabilized on an electronic basis.…”