Structural Transformations and Spin-Crossover in [FeL2]2+  Salts (L = 4-{tertbutylsulfanyl}-2,6-di{pyrazol-1-yl}pyridine) - the Influence of Bulky Ligand Substituents.

Structural Transformations and Spin-Crossover in [FeL2]2+ Salts (L = 4-{tertbutylsulfanyl}-2,6-di{pyrazol-1-yl}pyridine) - the Influence of Bulky Ligand Substituents.
Chemistry. 2020 Oct 19;:
Authors: Kulmaczewski R, Bamiduro F, Shahid N, Cespedes O, Halcrow MA
Abstract
4-(Tert-butylsulfanyl)-2,6-di(pyrazol-1-yl)pyridine (L) was obtained in low yield from a one-pot reaction of 2,4,6-trifluoropyridine with 2-methylpropane-2-thiolate and sodium pyrazolate in a 1:1:2 ratio. The materials [FeL2][BF4]2·solv (1[BF4]2·solv) and [FeL2][ClO4]2·solv (1[ClO4]2·solv; solv = MeNO2, MeCN or Me2CO) exhibit a variety of structures and spin-state behaviors including thermal spin-crossover (SCO). Solvent loss on heating 1[BF4]2·xMeNO2 (x ≈ 2.3) occurs in two steps. The intermediate phase exhibits hysteretic SCO around 250 K, involving a "reverse-SCO" step in its warming cycle at a scan rate of 5 Kmin-1. The reverse-SCO is not observed in a slower 1 Kmin-1 measurement, however, confirming its kinetic nature. The final product [FeL2][BF4]2·0.75MeNO2 was crystallographically characterized, and shows abrupt but incomplete SCO at 172 K which correlates with disorder of an L ligand. The asymmetric unit of 1[BF4]2·yMe2CO (y ≈ 1.6) contains five unique complex molecules, four of which undergo gradual SCO in at least two discrete steps. Low-spin 1[ClO4 ]2·0.5Me2CO is not isostructural with its BF4- congener, and undergoes single-crystal-to-single...

Source: Chemistry - October 19, 2020 Category: Chemistry Authors: Kulmaczewski R, Bamiduro F, Shahid N, Cespedes O, Halcrow MA Tags: Chemistry Source Type: research