Synthesis of homobimetallic molybdenum(VI) complex of bis(2-hydroxy-1-naphthaldehyde)malonoyldihydrazone and its reaction with electron and proton bases |
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| Authors: | Ram A. Lal Sanjesh Choudhury Aziz Ahmed Rosmita Borthakur Mrityunjaya Asthana Arvind Kumar |
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| Affiliation: | 1. Department of Chemistry, North-Eastern Hill University, Shillong 793022, Meghalaya, India;2. Institute of Chemistry, Academia Sinica 128, Academia Road, Sec.2 Nankang, Taipei 115, Taiwan, ROC |
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| Abstract: | The diamagnetic dioxomolybdenum(VI) complex [(MoO2)2(CH2L)(H2O)2]H2O (1) has been isolated in solid state from reaction of MoO2(acac)2 with bis(2-hydroxy-1-naphthaldehyde)malonoyldihydrazone (CH2LH4) in 3:1 molar ratio in ethanol at higher temperature. The reaction of the complex (1) with electron donor bases gives diamagnetic molybdenum(VI) complexes having composition [Mo2O5(CH2LH2)]·2A·2H2O (where A = pyridine (py, 2), 2-picoline (2-pic, 3), 3-picoline (3-pic, 4), 4-picoline (4-pic, 5)). Further, when the complex (1) is allowed to react with protonic bases such as isonicotinoylhydrazine (inhH3) and salicyloylhydrazine (slhH3), reduction of molybdenum(VI) centre occurs leading to isolation of homobimetallic molybdenum(V) complexes [Mo2(CH2L)(inh)2(H2O)2] (6) and [Mo2(CH2L)(slh)2] (7), respectively. The composition of the complexes has been established by analytical, thermo-analytical and molecular weight data. The structure of the molybdenum(VI) complexes (1)–(5) has been established by electronic, IR, 1H NMR and 13C NMR spectral studies while those of the complexes (6) and (7) by magnetic moment, electronic, IR and EPR spectral studies. The dihydrazone is coordinated to the metal centres in staggered configuration in complex (1) while in anti-cis configuration in complexes (2)–(7). The complexes (6) and (7) possess magnetic moment of 2.95 and 3.06 BM, respectively, indicating presence of two magnetic centre in the complexes per molecule each with one unpaired electron on each metal centre without any metal–metal interaction. The electronic spectra of the complexes are dominated by strong charge transfer bands. All of the complexes involve six coordinated molybdenum centre with octahedral arrangement of donor atoms except in the complex (6), in which the molybdenum centre has rhombic arrangement of ligand donor atoms. The probable mechanism for generation of oxo-group in the complexes (2)–(5) involving coordinated water molecule has been proposed. |
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