Oxovanadium(V) and Cobalt(III) Complexes of Dithiocarbazate-Based Schiff Base Ligands: Formation of a Thiadiazole Ring by Vanadium-Induced Cyclization of the Coordinated Ligand

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• 作者：Subodh Kanti Dutta ; Satyabrata Samanta ; Dipesh Ghosh ; Ray J. Butcher ; and Muktimoy Chaudhury
• 刊名：Inorganic Chemistry
• 出版年：2002
• 出版时间：October 21, 2002
• 年：2002
• 卷：41
• 期：21
• 页码：5555 - 5560
• 全文大小：107K
• 年卷期：v.41,no.21(October 21, 2002)
• ISSN：1520-510X

文摘

S-Methyl 3-((2-hydroxyphenyl)methyl)dithiocarbazate (H₂L¹) and its bromo derivative (H₂L²), which are traditionallybiprotic tridentate (ONS) ligands, behave in an unprecedented manner when allowed to react with [VO(acac)₂]under an oxidative environment in acetonitrile-water medium containing a catalytic amount of alkali metal ion. Theproducts obtained are oxovanadium(V) compounds [VOL(L_cyclic)] (L = L¹, 1a, and L², 1b) that contain one moleculeof ligand which undergoes metal-induced cyclization to form a thiadiazole ring. Compound 1a crystallizes in thetriclinic space group P with a = 9.1830(9) Å, b = 9.4165(12) Å, c = 12.700(2) Å, = 100.988(8)^o, =100.195(7)^o, = 78.774(8)^o, V = 1046.3(2) ų, and Z = 2. With cobalt(III), however, the products [CoL(HL)]·H₂O(L = L¹, 2a, and L², 2b) have hydrogen-bonded dimeric structures with each ligand virtually carrying 1.5 units ofnegative charge as confirmed by X-ray crystal structure analysis of 2a. It also crystallizes in triclinic space groupP with a = 12.0842(8) Å, b = 13.5251(9) Å, c = 14.1960(10) Å, = 78.122(6)^o, = 73.888(6)^o, = 78.255(6)^o, V = 2154.7(3) ų, and Z = 4. In solution, 2a is a symmetric molecule as indicated by ¹H NMR, involving acharacteristic hydrogen-bonded O-H-O broad feature in the downfield (at 14.5 ppm) connecting both monoprotonated(LH^-) and deprotonated (L^2-) forms of the ligand-a situation somewhat analogous to the classic H-F-H case asobserved in bifluoride ion.