Octahedral Niobium Thiocyanato Complexes Containing [Nb6Cl9O3] Cluster Core: Syntheses, Crystal Structures and Evidences of NCS Ligand Exchange

• Published in: Journal of cluster science Vol. 20; no. 1; pp. 213 - 223
• Main Authors: Naumov, N. G., Cordier, S., Ovoschnikov, D. S., Naumov, D. Y., Artemkina, S. B., Perrin, C., Fedorov, V. E.
• Format: Journal Article
• Language: English
• Published: Boston Springer US 01.03.2009; Springer Nature B.V
• Subjects: Aqueous solutions; Catalysis; Cesium; Chemistry; Chemistry and Materials Science; Chlorine; Clusters; Crystal structure; Crystallization; Crystals; Data collection; Hydrochloric acid; Inorganic Chemistry; Investigations; Isomers; Ligands; Nanochemistry; Niobium; Original Paper; Physical Chemistry; Potassium; Radiation; Substitution reactions; Symmetry; Thiocyanates; Ligand exchange; Niobium; Cluster compounds; Crystal structure
• ISSN: 1040-7278; 1572-8862
• DOI: 10.1007/s10876-008-0223-4

Two isomers ( cis and trans ) of [Nb 6 Cl 9 O 3 (NCS) 6 ] 5– niobium cluster complexes characterized by an ordered arrangement of oxygen and chlorine ligands over the 12 inner positions in the cluster core were prepared by reaction of Cs 2 LaNb 6 Cl 15 O 3 and ScNb 6 Cl 13 O 3 solid state compounds with aqueous solution of potassium thiocyanate. The cis and trans isomers (idealized C 2 v and D 3 symmetry, respectively) crystallize with counter cations and water molecules to form the following salts: Cs 4.75 K 0.25 [Nb 6 Cl 9 O 3 (NCS) 6 ] · 5.5H 2 O ( 1 ) and Cs 2.5 K 2.5 [Nb 6 Cl 9 O 3 (NCS) 6 ] · 2H 2 O ( 2 ), respectively. The trans isomer is ordered in structure 1 (s.g.: C 2/ c ), while in the structure of 2 (s.g.: Pnma ), the cis isomer is randomly disordered over two positions that correspond one to each other by a mirror plane. Interestingly, the treatment of thiocyanato complexes cis and trans with hydrochloric acid led to substitution of (NCS) – ligands by Cl – and to formation of soluble complexes [Nb 6 Cl 9 O 3 Cl 6 ] 5– . The cesium salt of trans -[Nb 6 Cl 9 O 3 Cl 6 ] 5– was crystallized as Cs 5 [Nb 6 Cl 15 O 3 ] · CsCl · 7H 2 O ( 3 ) and structurally characterized. Indeed, the formation of soluble [Nb 6 Cl 9 O 3 (NCS) 6 ] 5– intermediates is a necessary step towards the formation of soluble anions.