The influence of H-bonding on the ‘ambidentate’ coordination behaviour of the thiocyanate ion to Cd(ii): a combined experimental and theoretical study

Abstract

Two new trinuclear hetero-metallic copper(II)-cadmium(II) complexes [(CuL)2Cd(NCS)2] (1) and [(CuL(R))2Cd(SCN)2] (2) have been synthesized using [CuL] and [CuL(R)] as "metalloligands" (where H2L = N,N'-bis(salicylidene)-1,4-butanediamine and H2L(R) = N,N'-bis(2-hydroxybenzyl)-1,4-butanediamine) respectively. Both the complexes were characterized by elemental analysis, various spectroscopic methods and single crystal XRD. Complex 1 is an angular trinuclear species, in which two terminal four-coordinate square planar "metalloligands" [CuL] are coordinated to a central Cd(II) through double phenoxido bridges along with two mutually cis nitrogen atoms of terminal thiocyanate ions. In complex 2, which is linear, in addition to the double phenoxido bridge, two SCN(-) coordinate to the trans positions of the central octahedral Cd(II) via S atoms. Theoretical calculations on the energetic difference between the two possible coordination modes of the thiocyanate anion to the Cd atom reveal that N-coordination is preferred over S-coordination in agreement with the much greater abundance of the reported N-bonded structures. In 2, there is a strong N-H···NCS-Cd H-bonding interaction, the binding energy of which is computed to be approximately -9.3 kcal mol(-1), which is sufficient to compensate the 9.0 kcal mol(-1) of energetic cost due to the unusual Cd-SCN coordination mode.

Key Role of Size and Electronic Configuration on the Sign and Strength of the Magnetic Coupling in a Series of Cu2Ln Trimers (Ln = Ce, Gd, Tb, Dy and Er)

“…These studies established that the α-methylation on the N 2 O 2 donor Schiff base ligand has a key role in determining the structures of the resulting compounds [40][41][42][43][44][45][46]. However, such studies have not been performed with lanthanide-containing trinuclear coordination clusters for these complexes.…”

Trinuclear complexes of [CuL] (H2L = N,N′-bis(salicylidene)-1,4-butanediamine) with HgX2 (X−= N3− and NCO−): Facile crystallization with Z′ = 1 and Z′ = 0.5 for both complexes

“…The Schiff-base ligand (H 2 L), and it's Cu(II) complex, [CuL] were synthesized using the reported procedures [20,21]. When a methanolic solution of [CuL] is added slowly to the top of an aqueous solution of sodium azide or sodium cyanate and mercuric chloride in a layer tube, a solid powder-like product appears instantaneously near the junction of the two solutions and within ca.…”

“…The yellow solid mass was collected by filtration and then washed with cold methanol. 5 mmol (1.47 g) of this yellow solid, H 2 L was dissolved in 10 mL methanol by heating over a water-bath for 10 min and then added to a methanolic solution (20 mL) of Cu(ClO 4 ) 2 Á6H 2 O (1.852 g, 5 mmol) to prepare the ''metalloligand'' [CuL] [20,21]. The precursor ''metalloligand'' [CuL] (0.714 g, 2 mmol) was dissolved in methanol (10 mL) and it was slowly poured above a water solution (5 mL) of HgCl 2 (0.271 g, 1 mmol) and sodium azide (0.130 g, 2 mmol) or sodium cyanate (0.130 g, 2 mmol) in two separate layer tubes for complexes 1 and 2, respectively (Scheme 1).…”

Syntheses, crystal structures and density functional theory investigations of copper(ii) complexes bearing tridentate Schiff base ligands derived from 8-aminoquinoline

“…Several non-covalent interactions involving the π-system of coordinated pseudohalides has been analyzed both theoretically and exploring the Cambridge structural database. [43][44] We have used several theoretical models to analyze the π-π and C-H/π interactions that are shown in Fig. 5.…”

“…Consequently, the relevance of these non-covalent interactions is broadly analysed by a large number of researchers using combined theoretical and experimental investigations [22][23][24][25][26][27][28] and currently it is an interesting topic of research.…”