Homo- and Heterometal Complexes of Oxido鈥揗etal Ions with a Triangular [V(V)O鈥揗O鈥揤(V)O] [M = V(IV) and Re(V)] Core: Reporting Mixed-Oxidation Oxido鈥揤anadium(V/IV/V) Compounds with Valence Trapped Struc

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• 作者：Kisholoy Bhattacharya ; Manoranjan Maity ; Sk Md Towsif Abtab ; Mithun Chandra Majee ; Muktimoy Chaudhury
• 刊名：Inorganic Chemistry
• 出版年：2013
• 出版时间：August 19, 2013
• 年：2013
• 卷：52
• 期：16
• 页码：9597-9605
• 全文大小：369K
• 年卷期：v.52,no.16(August 19, 2013)
• ISSN：1520-510X

文摘

A new family of trinuclear homo- and heterometal complexes with a triangular [V(V)O鈥揗O鈥揤(V)O] (M = V(IV), 1 and 2; Re(V), 3] all-oxido鈥搈etal core have been synthesized following a single-pot protocol using compartmental Schiff-base ligands, N,N鈥?bis(3-hydroxysalicylidene)-diiminoalkanes/arene (H₄L¹鈥揌₄L³). The upper compartment of these ligands with N₂O₂ donor combination (Salen-type) contains either a V(IV) or a Re(V) center, while the lower compartment with O₄ donor set accommodates two V(V) centers, stabilized by a terminal and a couple of bridging methoxido ligands. The compounds have been characterized by single-crystal X-ray diffraction analyses, which reveal octahedral geometry for all three metal centers in 1鈥?b>3. Compound 1 crystallizes in a monoclinic space group P2₁/c, while both 2 and 3 have more symmetric structures with orthorhombic space group Pnma that renders the vanadium(V) centers in these compounds exactly identical. In DMF solution, compound 1 displays an 8-line EPR at room temperature with g and A values of 1.972 and 86.61 脳 10^鈥? cm^鈥?, respectively. High-resolution X-ray photoelectron spectrum (XPS) of this compound shows a couple of bands at 515.14 and 522.14 eV due to vanadium 2p_3/2 and 2p_1/2 electrons in the oxidation states +5 and +4, respectively. All of these, together with bond valence sum (BVS) calculation, confirm the trapped-valence nature of mixed-oxidation in compounds 1 and 2. Electrochemically, compound 1 undergoes two one-electron oxidations at E_1/2 = 0.52 and 0.83 V vs Ag/AgCl reference. While the former is due to a metal-based V(IV/V) oxidation, the latter one at higher potential is most likely due to a ligand-based process involving one of the catecholate centers. A larger cavity size in the upper compartment of the ligand H₄L³ is spacious enough to accommodate Re(V) with larger size to generate a rare type of all-oxido heterotrimetallic compound (3) as established by X-ray crystallography.