Cyanooxo molybdenum(IV) complexes with 2-pyrazinecarbonitrile and 2-pyrazinecarboxylate: Crystallographic and spectroscopic studies reveal metal-assisted nitrile hydrolysis

摘要

The pH-control of a reaction between tetracyanooxomolybdate(IV) and 2-pyrazinecarbonitrile (pcn), in aqueous-ethanolic solution under ambient conditions, affords the Mo(W) mixed-ligand complex anions [Mo(CN)(4)O(pcn)](2-) (1) or [Mo(CN)(4)O(Hpca)](2-) (2) with a monodentately bound 2-pyrazinecarboxylic acid (Hpca), resulting from metal-assisted organonitrile hydrolysis. The acid undergoes slow rearrangement to a bidentate mode in [Mo(CN)(3)O(pca)](2-) (3), which is confirmed by means of UV-Vis spectroscopy. The nitrile hydrolysis, favored by the basic conditions, has been ascertained by elemental analyses as well as IR, H-1 and C-13 NMR spectroscopy. The use of Hpca instead of pcn in the synthetic procedure results in the direct formation of [Mo(CN)(3)O(pca (3) with the bidentate 2-pyrazinecarboxylate. The coordination versatility of 2-pyrazinecarboxylate toward cyanooxomolybdenum(IV) complexes is demonstrated by the IR and UV-Vis spectroscopy of solids with [Mo(CN)(4)O(H pCa)](2-) and [Mo(CN)(3)O(pca)](2-) ions, and the definitive evidence for the structure of [Mo(CN)(3)O(pca)](2-) is provided by single-crystal X-ray crystallography. The chemical formulations of all the complexes, isolable as [PPh4](+) salts, have been verified with microanalyses, spectroscopic measurements and X-ray crystal structures of 1 and 3. (C) 2008 Elsevier Ltd. All rights reserved.