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Indian Journal of Chemistry Vol. 25A. March 1986. pp. 27<)-280 Complexes of Co(ll). Ni(ll). Cu(ll). Zn(II). Cdrl l). UO~ -t- and V0 2 + with o-(N-y.-PhenyL 2-hydroxy- benzylideneimino)benzoic Acid (Miss) SHOBHA SHARMA. ASHOK GAHLOT & R K MEHTA' Department of Chemistry. Lmversity of Jodhpur. Jodhpur 34200 I Receiced 12 Norember 1984; reiised and accepted 18 N 01 emher 1985 The dissociation constants of O-(N-l-phenyl. 2-hydroxybenzyl- idencimino) benzoic acid (H,BB) and stability constants of its chelatcs with C'ot l l). Nit l l), Cu(ll). Zrul l). Cdtl l), uo~ + and VO U have been determined in aqueous medium (/I = 0.01 M. 0.05 M and 0.1 M NaClO .•) using Calvin's extension of Bjerrurn's method. /j,Go. /j,H" and /j,S' of the chelates have been evaluated using Gibbs- Helmholtz equation. The electronic and IR spectra and magnetic moments indicate octahedral stereochemistry for VO' ". Co(ll). Ni(1I) and Cu(ll) chclares. The stability constants of the chelates of o-(N-'l.- phenyl. 2-hydroxybenzylideneimino) benzoic acid with Co(ll). Ni(ll), Cu(II), Zn(IJ), Cd(IJ), UO~+ and V02+ have been evaluated using Calvin's extension of B · . hd 1 2 jerrum s met 0 '. o-(N-'l.-PhenyI. 2-hydroxybenzylideneimino) be- nzoic acid (H 2 BB) was synthesized by the method reported earlier 3A : m. p. 180 . The following mixtures (total volume 40 mij were prepared and titrated against carbonate-free 0.1 M sodium hydroxide solution at 25 .35 and 45 and the titration curves were found to be of usual shapes: (A) 10.Oml (O.OIM) H2BB+4.0ml (0.IMNaCI0 4 ) +26.0 ml water: (8) 10.0 ml (0.01 M) H2BB +4.0 ml (0.1 M NaCI0 4 ) + 10.0 ml (0.01 M) metal ion solution + 16.0 ml water; (C) 20.0 ml (0.01 M) H2BB +4.0 ml (0.1 M NaCI0 4 )+ 10.0 ml (0.0 I M) metal ion solution +6.0 ml water. The pK 1 and pK 2 values of the ligand were found to be 4.41 and 10.01 at 25.4.10 and 9.83 at 35 and 3.84 and 9.55 at 45 . respectively. These values suggest that the ligand is a biprotic one. The metal-ligand stability constants were read from the formation curves drawn by plotting n versus -log[A 2 -]. The refinement was done by computational method". The values obtained by different methods are in agreement and their average values are summarized in Table I. The order of stabilities, V02+ > UO~ + > Cu(IJ) > Ni(lI) > Co(ll) > Zn(lI) > Cd(II), is in accordance with the Irving- Williams rule". The values of overall changes in free energy (L'1GO). enthalpy (L'1HO) and entropy (L'1S» have been evaluated using Gibbs-Helmholtz equation 7 (Table I). L'1GO values of all the chelates are more negative at 45 than those at 35 or 25 . It is further observed that L'1Ho is positive in all the cases which suggests that the reactions are endothermic. The positive values of L'1S' for all the chelates indicate that the entropy term is favourable for their formation. The metal chelates were obtained as crystalline solids by an earlier method". The solid Co(ll). Ni(ll). Cu(II). and V0 2 + chelates and their adducts were found to be paramagnetic (Table I) and the rest diamagnetic. The octahedral Nirl l) complexes show higher magnetic moment <j I (J as given by the term V\3 (I - 4 i./ I0 Dq). This can also be explained on the basis of Oh symmetry involving a high degree of orbital contribution due to three-fold orbital degeneracy of 3 A 2~ ground state. The electronic spectrum in benzene of the Corl l) chclates consists of three bands at 8.525. 17.200 and 20,600 em I which can be assigned to the transitions 4Tl~(F)-' 4T2~(F). 4TI~(F)_.4 A 2~(F) and 4TI~(F) Table I Average Stability Constants. Thermodynamic Functions and Magnetic Moments of Metal Chelatcs of 0-( :"J-::t-Phenyl. 2-hydroxybenzylideneiminolbenlOic Acid (H 2BB) Metal log K, log 1(, -1\(;" (kLmol) /j,/f' /j,S" 1 ' ,11 ion (k.l.rnolj (kJ dcg. m.M) 25 35 45 25 35 45 25 35 45 at 35 C mol at 10X'" at 35 C VO'+ 11.19 11.55 11.XO <)4<) 9.112 10.17 12H2 134.2<) 140.2<) 5X.07 0.2475 IX~ UO~ + 10.85 11.13 11.55 9.03 9.35 9.60 120.63 127.50 135.12 95.26 0.1046 Cu(II) 10.15 10.47 10.75 g.61 lU!5 9.00 IIH.40 124.0H 13122 72.5x 0.1672 1.97 Ni(lI) 9.4X 9.90 10.11 7.H!! !!.1O X.5' 110.36 115.89 123.30 H2.56 0.1082 3.51 Co(ll) H.nO !!.90 <).30 6.lIO 7.07 7.20 9X.72 104.6!! 11003 69.86 0.1131 4.D Zn(II) H.W H.H2 <).17 5409 SH.21 61.19 51.71 0.0211 Cd(ll) X.IO K.53 X 73 52.3!! 56.20 5H.45 38.11 0.0587 2-:")
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