Thallophilic interactions and Tl–aryl π-interactions are competitive with cation–cation repulsion: [LTl2L]2+ dications as salts of weakly co-ordinating anions

Abstract

The synthesis and characterization by single-crystal X-ray diffraction of two thallium salts of the non-co-ordinating anion [B{3,5-(CF3)2C6H3}4] are reported. They possess Tl-Tl contacts supported by Tl-aryl interaction. This cation association overcomes both electrostatic repulsion and cation-anion size and charge matching considerations in the [LTl2L](2+) dications so formed.

Electronic Effects of Ligand Substitution on Spin Crossover in a Series of Diiminoquinonoid-Bridged FeII2 Complexes

“…These isomer shifts and quadrupole splittings are consistent with low-spin Fe II , and as such we assign this site to the low-spin center of an [Fe HS -Fe LS ] species. 56 Upon further decreasing temperature to 80 K, we observed the continuation of this trend, revealing the additional decrease of the high-spin Fe II site in [Fe HS -Fe HS ] to 31(10) and 36(7)% for 3 and 4, respectively, whereas both the high-and low-spin Fe II sites in [Fe HS -Fe LS ] increased to 33(1) and 35(11)% for 3 and 31(1) and 33(8)% for 4, respectively. Moreover, in the cases of 1 and 2, the data were best fit considering only two quadrupole doublets each, corresponding to the high-and lowspin centers of an [Fe HS -Fe LS ] species, with no evidence for [Fe HS -Fe HS ].…”

“…55 Here, the site with a smaller ΔE Q was shown to correspond to the [Fe HS -Fe LS ] complex, stemming from the distortion of the high-spin Fe II coordination sphere imposed by spin crossover of the second Fe II center. 55a,56 Finally, the third doublet, which accounts for 34(1), 33(2), 19(2), and 19(1)% of the spectra for 1−4, respectively, exhibits parameters of δ = 0.44(1)−0.45(1) mm/s and ΔE Q = 0.45(1)−0.62(2) mm/s (blue lines in Figure 5). These isomer shifts and quadrupole splittings are consistent with low-spin Fe II , and as such we assign this site to the low-spin center of an [Fe HS -Fe LS ] species.…”

Thallophilic Tl(i)–Tl(i) contacts mediated by Tl–aryl interactions. A computational study

“…15 The studies on 1 consist of single point calculations using the crystal structure. 6 Ab initio calculations on the model system were performed at the CCSD(T) 16 , BD 17 , MP2 18 and SCS-MP2 19 levels. In all wavefunction calculations reported here, all 21 valence electrons of the Tl atoms were correlated.…”

“…Calculations on systems with aurophilic bonds suggest that these relativistic effects provide at least 15% of the aurophilic attraction. 5 Metallophilic bonds involving thallium atoms (thallophilic), one of which was the subject of a recent experimental study, 6 have been observed at distances between 3.4-3.8 Å. 7 In comparison, twice the van der Waals and covalent radii of Tl are 3.92 Å and 2.96 Å, respectively.…”

“…tki Me3iPr3 Tl (β-triketimine = tki; the substituents on the imine carbon atoms are indicated, followed by an indication of the N-aryl substituents, which in all cases are ortho, hence tki Me3iPr3 = HC{MeCN(2-iPrC6H5)3}) with BArF counter ions, where BArF=[{3,5-(CF3)2C6H3}4B] -has been found to form dimers with Tl-Tl distances of 3.65 Å in the crystal geometry 6 (Figure 1). The [(tki Me3iPr3Tl )2] ·[BArF]2 system is an interesting case as the β-triketimine ligands are neutral, meaning the dimer without counter ions has a charge of 2+.…”