Metal chelates of bioinorganic and catalytic relevance: Synthesis, magnetic and spectral studies of some mononuclear and binuclear oxovanadium(IV) and dioxotungsten(VI) complexes involving Schiff bases derived from 4-butyryl-3- methyl-1-phenyl-2-pyrazolin-5-one and certain aromatic amines

Abstract

Synthesis of two series of metal chelates: (i) mononuclear chelates of compositions, [VO(L₁)₂].H₂O and [WO₂(SCN)(C₂H₅OH)₂(L₁)], (where L₁ H = N-(4'-butyrylidene-3’-methyl-1'-phenyl-2'-pyrazolin-5'-one)-<i>p</i>-anisidine(BUMPHP-PAH, I), N-(4’-butyrylidene- 3'-methyl-1 '-pheny l-2'-pyrazolin-5' -one)-o-phenitidine (BUMPHP-OPH, II), N(4' -butyrylidene-3' -methyl-1' -phenyl-2' -pyrazolin-5' -one)-<i>m</i>-phenetidine (BUMPHP-MPH, II I) or N-(4' -butyrylidene-3'methyl- 1' -phenyl-2' -pyrazolin-5' -one)-III-toluidine (B UMPHP-MTH, IV) or N-(4' -butyrylidene-3 ' -methyl-1' -phenyl-2'pyrazolin-5'-one)-p-tolui dine (BUMPHP-PTH V), [VO(L₂)].H₂O, and [WO₂(SCN)(L₂H)] (where L₂H₂ = N,N'-bis-(4'-butyrylidene-3' -methyl-1' -phenyl-2' -pyrazolin-5'-one)-<i>o</i>-phenylenediamine (BUMPHP-OPHDH₂, VI) or N,N'-bis-(4'-butyrylidene-3' -methyl-1' -phenyl-2' -pyrazolin-5'-one)-<i>m</i>-phenylenediamine (BMPHP-MPHDH₂, VII) and VO(L₂')(H₂O)] (where L₂' H₂ N,N'-bis-(4'-butyrylidene-3' -methyl-1' -phenyl-2' -pyrazolin-5'-one)-<i>o</i>-phenylenediamine (BMPHP-MPHDH₂, VII), and (ii) binuclear chelates of compositions, [{VO(H₂O)(OH)}₂ (L₃)] and [{WO₂(SCN)(H₂O)}₂ (L₃) ], where L₃H₂ = N ,N' -bis-(4-butyrylidene-3-methyl-1-phenyl-2-pyrazolin-5-one)-p-phenylenediamine (BMPHP-PPHDH₂, VIII ) or N,N'-bis-(4-butyrylidene-3-methyl-l-phenyl-2-pyrazolin-5-one)-benzidine (BMPHP-BZH₂, IX) are described. The resulting chelates have been characterized by elemental analyses, molar conductance, decomposition temperature and magnetic measurements, electron spin resonance/ ¹H-NMR, infrared and electronic spectral studies. The oxovanadium(IV)

compounds with ligands, BUMPHP-PPHDH₂ and BUMPHP-BZH₂ exhibit subnormal magnetic moments. Structures involving ... V=O··· V=O··· chain for oxovanadium(IV) complexes, and tentative structures involving <i>cis-</i>WO₂ have been proposed for dioxotungsten(VI) complexes.