Synthesis and characterization of molybdenum(V,VI) complexes derived from bis(2-hydroxy-1-naphthaldehyde)malonoyldihydrazone

Abstract

Monometallic molybdenum(VI) complexes [MoO₂(CH₂LH₂)] · H₂O (1), [Mo₂O₄(CH₂LH₂)₂(A)₂] (A = py (2), 2-pic (3), 3-pic (4) and 4-pic (5)) and molybdenum(V) complexes [Mo(CH₂LH₂)(inh)] · H₂O (6) and [Mo(CH₂LH₂)(slh)] (7) of bis(2-hydroxy-1-naphthaldehyde)malonoyldihydrazone (CH₂LH₄) have been synthesized and characterized by various physico-chemical and spectroscopic studies. The compositions of the complexes have been established by elemental analyses and molecular weight determination. The structural assessment of the complexes has been done on the basis of data obtained from molar conductances, magnetic moment studies, electronic, infrared, electron paramagnetic resonance (EPR), proton nuclear magnetic resonance, and ¹³C proton nuclear magnetic resonance spectroscopic studies. The molar conductance values for the complexes in DMSO suggest that they are non-electrolytes. The magnetic moment values for 6 and 7 correspond to one unpaired electron while the remaining complexes are diamagnetic. Complexes 1, 6, and 7 have six-coordinate octahedral stereochemistry around molybdenum, while 2–5 are eight-coordinate dodecahedral around the metal centers. EPR spectral features suggest that 7 is less symmetrical than 6.

Keywords:

• Bis(2-hydroxy-1-naphthaldehyde)malonoyldihydrazone
• Molybdenum(VI,V) complexes
• Isonicotinoylhydrazine
• Salicyloylhydrazine
• Magnetic moment and spectroscopic studies

Acknowledgments

The authors are thankful to the Head, SAIR, North-Eastern Hill University, Shillong-793022, Meghalaya, India, for ¹H NMR and ¹³C NMR spectroscopic studies. Further, they would like to thank Head, SAIF, IIT Madras, for EPR studies and Head, SAIF, CDRI, Lucknow, for C, H, N analyses. One of the authors (R.A. Lal) thanks University Grants Commission, New Delhi, India, for financial assistance through major research project.