Nuclearity Controlled Cyanide‐Bridged Bimetallic Cr III –Mn II Compounds: Synthesis, Crystal Structures, Magnetic Properties and Theoretical Calculations

• Published in: Chemistry : a European journal 2004-12, Vol.10 (23), p.6130-6145
• Main Authors: Toma, Luminita, Lescouëzec, Rodrigue, Vaissermann, Jacqueline, Delgado, Fernando S., Ruiz‐Pérez, Catalina, Carrasco, Rosa, Cano, Juan, Lloret, Francesc, Julve, Miguel
• Format: Article
• Language: English
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.200400611

The preparation, X‐ray crystallography and magnetic investigation of the compounds PPh 4 [Cr(bipy)(CN) 4 ] ⋅ 2 CH 3 CN ⋅ H 2 O ( 1 ) (mononuclear), [{Cr(bipy)(CN) 4 } 2 Mn(H 2 O) 4 ] ⋅ 4 H 2 O ( 2 ) (trinuclear), [{Cr(bipy)(CN) 4 } 2 Mn(H 2 O) 2 ] ( 3 ) (chain) and [{Cr(bipy)(CN) 4 } 2 Mn(H 2 O)] ⋅ H 2 O ⋅ CH 3 CN ( 4 ) (double chain) [bipy=2,2′‐bipyridine; PPh 4 + =tetraphenylphosphonium] are described herein. The [Cr(bipy)(CN) 4 ] − unit act either as a monodentate ( 2 ) or bis‐monodentate ( 3 ) ligand toward the manganese atom through one ( 2 ) or two ( 3 ) of its four cyanide groups. The manganese atom is six‐coordinate with two ( 2 ) or four ( 3 ) cyanide nitrogens and four ( 2 ) or two ( 3 ) water molecules building a distorted octahedral environment. In 4 , two chains of 3 are pillared through interchain Mn‐N‐C‐Cr links which replace one of the two trans ‐coordinated water molecules at the manganese atom to afford a double chain structure where bis‐ and tris‐monodenate coordination modes of [Cr(bipy)(CN) 4 ] − coexist. The magnetic properties of 1 – 4 were investigated in the temperature range 1.9–300 K. A Curie law behaviour for a magnetically isolated spin quartet is observed for 1 . A significant antiferromagnetic interaction between Cr III and Mn II through the single cyanide bridge [ J =−6.2 cm −1 , the Hamiltonian being defined as Ĥ =− J ( Ŝ Cr(1) ⋅ Ŝ Mn + Ŝ Cr(2) ⋅ Ŝ Mn )] occurs in 2 leading to a low‐lying spin doublet which is fully populated at T