Experimental and Theoretical Study of the Features of Zinc(II) and Cadmium(II) Complexation with the Substituted closo‐Hydridoborate Anion [2‐B10H9(OH)]2−

Abstract

AbstractHerein, we studied the experimental and theoretical foundations of the process of zinc(II) and cadmium(II) complexation with 2‐hydroxido‐nonahydrido‐closo‐decaborate(2−) anion [2‐B10H9(OH)]2− in the presence of azaheterocyclic ligands L (L=2,2′‐bipyridyl (bipy), 1,10‐phenanthroline (phen), and 2,2′‐bipyridylamine (bpa)), which can be used as model system for obtaining complexes with the required composition and structure. The first examples of mixed‐ligand Zn(II) and Cd(II) complexes with [2‐B10H9(OH)]2− coordinated by the metal atom were isolated selectively. The structures of zinc(II) complexes [Zn(bipy)2(2‐B10H9(OH)‐κ2H1,O)] ⋅ 2CH3CN (1 ⋅ 2CH3CN) and [Zn(phen)2(2‐B10H9(OH)‐κ2H9,O)] ⋅ 2CH3CN (2 ⋅ 2CH3CN), as well as two cadmium(II) bond isomers [Cd(bipy)2(2‐B10H9(OH)‐κ2H1,O)] (4 a) and [Cd(bipy)2(2‐B10H9(OH)‐κ2H9,H10)] (4 b) bound into a dimeric pair in the complex [Cd(bipy)2(2‐B10H9(OH))] (4), and cadmium(II) complex [Cd(bpa)2(2‐B10H9(OH)‐κ2H7,H10)] (7) were solved by single‐crystal X‐ray diffraction (XRD). Density functional theory (DFT) calculations show that for cadmium(II) the formation of both multicenter BH−Cd−HB and BO(H)−Cd−HB bonds is equally probable. The affinity of zinc(II) for oxygen leads to preferential formation of complexes via BO(H)−Zn−HB bonds than BH−Zn−HB bonds. The M−B(H) bonding was found to be presumably electrostatic in nature, which could be the reason of topological isomerism of zinc(II) and cadmium(II) decaborates.