Synthesis and crystal structures of salen-type Cu(ii) and Ni(ii) Schiff base complexes: application in [3+2]-cycloaddition and A3-coupling reactions. (23rd July 2018)

• Record Type: Journal Article
• Authors: Agrahari, Bhumika; Layek, Samaresh; Ganguly, Rakesh; Pathak, Devendra D.
• Is Part Of: New journal of chemistry. Volume 42:Number 16(2018)
• Page Start: 13754
• Page End: 13762
• Publication Date: 2018-07-23
• Subjects: Chemistry -- Periodicals; Chimie -- Périodiques; 540
• DOI: 10.1039/c8nj01718b
• Languages: English
• ISSNs: 1144-0546

Abstract

Abstract : The synthesis and characterisation of two new salen-type Schiff base complexes of the type [Cu(L)]·0.5H2 O and [Ni(L)], and their application in the synthesis of 5-substituted 1 H -tetrazoles and propargylamines are described. Abstract : The synthesis of two new salen-type Schiff base complexes of the type [Cu(L)]·0.5H2 O, 1, and [Ni(L)], 2, from the reaction of a 6, 6′-[(1 E, 1′ E )-(cyclohexane-1, 2-diylbis(azanylylidene))bis(methanylylidene)bis(3-(diethylamino)phenol)] salen-type Schiff base ligand (H2 L) with Cu(OAc)2 ·H2 O and Ni(OAc)2 ·4H2 O in methanol at room temperature, respectively, is described. The complexes are isolated as coloured crystalline solids and characterized by elemental analysis, FT-IR spectroscopy, UV-visible spectroscopy and single crystal X-ray diffraction studies. The paramagnetic nature of complex1, having g iso = 2.076, was confirmed by EPR studies, which indicated a distorted square planar geometry of the complex. In contrast to this, the nickel complex was found to be diamagnetic in nature and it was additionally characterized by 1 H NMR. The crystal structures of complexes1 and2 confirm the distorted square planar geometry of both the complexes. Complex1 was found to be a better catalyst for the synthesis of a series of 5-substituted 1 H -tetrazoles from nitriles and sodium azide via [3+2]-cycloaddition and for the A 3 -coupling reaction of aldehydes, secondary amines and terminal alkynes with a low catalyst loading (0.7 and 0.9 mol%, respectively) as compared to complex2 . Complex1 is novel in the sense that, being a homogeneous catalyst, it can be recovered almost quantitatively in both reactions and recycled up to four times to afford good yields of the corresponding products.