Selective coordination of cyanate and thiocyanate in the end-on mode: synthesis, structures and properties of [NiII2L(μ1, 1-NCO)]+ and [NiII2L(μ1, 1-NCS)]+ (L2− = macrocyclic N6S2 ligand). (28th March 2018)

• Record Type: Journal Article
• Authors: Jeremies, Alexander; Gruschinski, Sina; Schmorl, Sara; Severin, Tobias; Kersting, Berthold
• Is Part Of: New journal of chemistry. Volume 42:Number 10(2018)
• Page Start: 7630
• Page End: 7639
• Publication Date: 2018-03-28
• Subjects: Chemistry -- Periodicals; Chimie -- Périodiques; 540
• DOI: 10.1039/c8nj00114f
• Languages: English
• ISSNs: 1144-0546

Abstract

Abstract : The complex [Ni2 L] 2+ exhibits a pre-organized binding pocket, whose walls direct the coordination of pseudohalide ions via repulsive CH⋯π interactions. Abstract : The ability of the dinickel complex [Ni2 L] 2+ supported by the binucleating hexaaza-dithiophenolate macrocycle (L) 2− to bind linear (OCN −, SCN − ) and bent triatomic anions (NO2 − ) has been examined. The complexes [NiII2L(μ1, 1 -NCO)]BPh4 (3 ) and [NiII2L(μ1, 1 -NCS)]BPh4 (4 ) have been synthesized by addition of KOCN or KSCN to [NiII2L](ClO4 )2 (1 ) and characterized by IR, ESI-MS, UV-vis, SQUID magnetometry, X-ray crystallography (3 ) and computational studies. [Ni2 L][ClO4 ]2 (1 ) binds cyanate and thiocyanate ions specifically end-on via their N atoms yielding face-sharing bis(octahedral) N3 Ni(μ-S2 )(μ1, 1 -X)NiN3 core structures (X = NCO or NCS), while no reactions occur with NO2 − . The X-ray structure of3 * and accompanying DFT calculations imply that the selective binding of the pseudohalide ions is governed by repulsive host–guest CH⋯(anion)π interactions.3 and4 exhibit an S = 2 ground state that is attained by competing antiferromagnetic and ferromagnetic exchange interactions via the thiolato and cyanato (or thiocyanato) bridges, respectively, with a value for the magnetic exchange coupling constant J of 12.6 and 9.8 cm −1 ( H = −2 JS 1 S 2 ). The affinity of1 for cyanate determined by absorption spectrometry in MeCN/MeOH (1/1 v/v) at I = 0.01 M is ca. two orders of magnitude higher than for thiocyanate (log K 11 = 3.92(1) (3 ), 2.16(1) (4 )). The value for3 was found to compare favorably well with the equilibrium constant derived by isothermal titration calorimetry.