Basak, Gaurgopal

Bhattacharyya, B. C.

Bhowal, S. K.

English

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INDIAN J. CHEM., VOL. 14A, MAY 19764. VOGEL, A. I., A text book of practical organic chemistry(Longmans, Green, London), 1956: 7~O.. .5. VOGEL, A. I., A text book of quantitatioe inorganic analysis(Longmans, Green, London), 1956, 177. .6. JAHAGIRDAR, D. V. & KHANOLKAR, D. D., J. inorg, HIlCZ.cs-«, 35 (1973). 921.7. VAN-UlTERT, E. G & HAAS, C. G., J. Am. chem, ss«;75 (1953), 451.Steric Effect in Ni(I1) & Co(ll) Complexes ofMethyl Substituted N-Benzoyl-N-phenyl-hydroxylamines (N-phenylbenzohydroxamicAcids)B. C. BHATTACHARYYA & S. K. BHOWALDepartment of Chemistry, Jadavpur UniversityCalcutta 700032andGAURGOPAL BASAKDepartment of Chemistry, New Alipore CollegeCalcutta 700053Received 7 April 1975; accepted 26 July 1975Positions of the methyl substituents in some methylsubstituted N_benzoyl_N_phenylhydroxylamines acids(N-phenylbenzohydroxamic acids) are found to exert asteric influence in the formation of their Ni(II) andCo(II) complexes. When the methyl group is presentin 3-, 4-, 3'- or 4'-position, no steric hindrance isobserved and the complexes obtained are hi~hly poly-meric and octahedral. However, methyl substitutionin the 2- or 2'- or in both the positions exert Iar gesteric hindrance which results in a si~nificant reduc-tion in the de~ree of polymerization yieldin~ trimericoctahedral Ni(U) complexes. The complexes have beencharacterized by cryoscopic, magnetic moment andabsorption spectral studies. The tendency of poly-merization is ~reater in the case of Co(Il) complexes,but N-0-tolyl-2-methylbenzohydroxamic acid (HgandII) yields only a dimeric pentacoordinated Co(II)complex.HYDROXAMIC acid derivatives (R'COXR"OH)are known to be excellent reagents for thespectrophotometric determination of vanadiumt-s.Majumdar and Das" have earlier pointed out thatthe specificity of N-o-tolyl-benzohydroxamic acid(I, R = H; Rl = 2' -CH3) towards vanadium arisesout of the steric influence of the ortho-substitutedmethyl group in the N-phenyl ring. Molecularmodels show that this steric effect is likely to be ofimportance in the formation of the 1:2 complexesof some bivalent met.als which are very muchprone to attain hexacoordination through polymeri-zation of the 1:2 species. In order to test thevalidity of this idea, Ni(II) and Co(II) complexesof some hvdroxamic acid derivatives have beenisolated and characterized on the basis of analytical,electronic spectral, molecular weight and magneticmoment data.N-(o-Tolyl)-2-methylbenzohydroxamic acid (II, R= 2' -CRa; RI = 2-CH3) was prepared accordi ng tothe method of Pal and coworkers", Other ligancls,viz. N-phenyl-2-methylbenzo-(III, R = 2-CHs; Rl354:I, Rs H ; R,= 2-CH3II ,R=2-CH3; Rf2-CH)m ,R=2-CH3;R,= HDr ,R=H; ..R =) -CH3JI: ,R=3- CH3 .R, s H:vI: ,R=H , ~=4-CH31llI ,1'1=4--CH3;R,s H=H)-; N-(m-tolyl)-b::nzo-(IV, R = H; Rl = 3-CHa)-;N -phenyl-3-methylbenzo-(V, R = 3' -CR3; RI = H)-;N-(P-tolyl)-benzo-(Vl, R = H; Rl = 4'-CH3)-; andN-phenyl-4-methylbenzo-(VII, R = 4-CH3; Rl= H)-hydroxamic acids were prepared by the litera-ture method-.Ni(IJ) complexes - A solution of ~iCI2.6H20(1 g) in ethanol (20 ml) was added to a hot solutionof the ligand (2-2·1 g), also in ethanol (30 ml). Asaturated aqueous solution of sodium acetate (2-2·5g) was added to the above mixture. In the casesof Iizands IV, V, VI and VII and the unsubstitutedNvphenylbenzohydroxamic acid, immediate precipi-tation of the compounds occurred. The compoundswere filtered, washed with ethanol and dried in air.With ligands I, II and III, l-owever, the complexeswere obtained by diluting the ethanol solution withwater. These were then filtered, washed with hot.water, dried in air and recrystallized from benzene-ligroin (60-80°) mixture.Co(II) complexes - A solution of CoCI2.6H2.O(1 g) in acetone (50 m1) was added to the ligandsolution (2-2·1 g in about 20 m1 of acetone). Anaqueous solution of so.iium hydroxide (1 M) wasadded dropwise with constant stirring t.ill the c1eep-blue colour changed to wine-red. The solution wasthen diluted with wat er. In the case of ligands Iand II, equal volume of and excess of water wereadded respectively to obtain the complexes. Theseparated crystals were filtered, washed with waterand finally recrystallized from acetone (for ligand I)and benzene-ligroin (60-80°) (for ligand II).The complex with ligand III changed into aninsoluble form on precipitation from acetone solutionby the addition of water. However, a complexsoluble in benzene could be isolated by diluting theacetone solution with about 20 ml of benzene andthen washing the solution 2-3 times with water.This benzene solution was dried with anhydroussodium sulphate, diluted with ligroin (60-80°) andkept in a deep-freeze overnight. The precipitatedcomplex was then filtered, washed with ligroin anddried in air. But this complex also slowly changedto the insoluble form in the solid state and as suchNOTESTABLE 1- MELTING POINT, ELECTRONIC SPECTRAL, MOLECULAR WEIGHT AND MAGNETIC MOMENT DATA OF Ni(II) ANDCo(II) COMPLEXESComplex* Decomposi-tion point(OC)Ni(III), 170Ni(I)! 167Ni(II)2 178Ni(II\2PYlI 206Co(III)lI 191Co(I)2 145Co(II)J 154Electronic spectra Mol. weight Magneticmoment(BM)3·133·1730483·244·404-674·41SolventBenzenePyridineBenzenePyridineBenzenePyridineAmax (nrn] (€m~x)665 (7-8), 780 (sh), 1020-30 (6·2)620-25 uzs; 780 (3·2), 1000-10 (13·1)665 (6·7), 800 (sh), 1020-30 (8·0)625 (12·7), 780 (H), 1000-10 (11·7)670-75 (7·0), 810 (sh), 1010 (8·2)630 (12-8), 780 (3·3), 1000 (11·6)1466 (1532)t1405 (1532)t1695 (1616)tBenzene 750 (sh), (8·3)Pyridine 560 (43·3), 1000 (6·0)*1, II and III are the ligands as numbered in the text.[Calculated for trimer.!CalcuI2.ted for dimer.983 (1078)!molecular weight and spectra in benzene could not Thus, it may be concluded that the phenylhy-be taken. droxami~ aci~ derivatives have the tendency to formNi(U) complex of the ligand II yielded a pyridine poly:me~lc NI(II) complexes and the degree of poly-adduct on dissolving the former in a minimum menzation depends on the position of methylquantity of the latter and keeping tile solution for su.bstitue~t. It is very high where the methyl sub-2 days after dilution with excess water. Light-blue stituent, In both the phenyl rings, is not suitablycrystals obtained were filtered, washed with water placed to exert any steric influence (ligands IV, V,and dried in a desiccator over CaCI2• The TG curve VI and VI!): Wnere the su~sti.tuted methyl groupof this compound shows a single break at 143° which I~ In a position to exert steric mfl~ence (ligands I,corresponds to the loss of two pyridine molecules II and III),. the ~eg.ree of polymerization is largelysimultaneously. re.d.uced glvmg relatively weaker trimeric complexesAll the compounds were characterized by ele- which can be broken down by a strong coordinatinzmental analysis. solvent like pyridine. 0Magnetic measurements at room temperature The tendency of polymerization is observed towere carried out using a Gouy balance calibrated be much greater in the case of Co(I!) complexes withwith Hg[Co(NCS)cJ. Cryoscopic measurements were the ligands r. I! and II!. The cryoscopic datamade in sodium-dried benzene. Hilger Uvispeck and (Table 1) of the Co(Il) complex with ligand II inSpectromom 201 spectroph?tometers were used for be~zene suggest a dimeric structure for the complexthe electronic spectral studies. unlike the corresponding Ni(II) complex. TheA Chevenard- Jounier thermobalance ADAMEL nature of the visible absorption spectrum of thistype CTTB No. 107 was used to rec?rd the change Co(II) complex in benzene is different from thein weight of the substance as a function of tempera- corresponding Ni(I!) complex and the magneticture. The rate of heating was maintained at 58 per moment value is slightly lower than that expectedmin. for an octahedral configurations. This complex,Ni(II) complexes with ligands IV, V, VI and VII thus, may be concluded to be five-coordinated. It(class A complexes) are found to. be hi~hly inS?l~lble may be pointed out that some dirneric five-coordi-in all common organic solvents including pyridine: nated bis-ligated Schiff base complexes of Co (II)their magnetic moments range from 3·12 to 3·42 have been reported" to show slightly lower than nor-B. M. But the Ni(II) complexes (class B complexes) mal magnetic moment values.with ligands containing the CH3 group in 2 (ligandIII) or 2' (ligand I) or in both the positions (Iiga~d References ~..>II) are highly soluble in polar and non-polar organic '1-: MAJUMDAR, A. K., N-Benzoylphenylhydroxylamine and itssolvents. Analytical, cryoscopic, magnetic moment /- analogues (Pergamon Press, London), 1972.and electronic spectral data (Table 1) indicate that ,~. GUPTA, V. K. & TANDON, S. G., Analyt. cbim, Acta, 661 It·: t 1 d al (1973), 39.the crass B com> exes are n~erlc oc a?e r. 1. MAZUMDAR, A. K. & DAS, GAYATRI, Anulyt, chim, Acta,compoundss-" structurally resembling t.he tnme~ic v 36 (1966), 454.bis(acetylacetonato) complex of nickel'. The ,to MITRA, B. K., PAL, B. K. & CHATTOPADHYAYA, S., Talanta, {ib d for the transtion 3A ---+3T (P) is obscured / 22 (1975), 431.an 2g 19 d d 5. FIG GIS, B. N. in Moder« coordination chemistry, edited byby the strong charge-tr~nsfer band observe ~rou~ J. Lewis & R. G. Wilkins (Irrterscience, New York), 1960. ~400 nm. The absorption spectra of the. tnmer:c J. DRAGO, R. S., Physical methods in inorganic chemistry ::/class B complexes in pyridine show two isosbestic (Reinhold, New York), 1965.oints near 720 and 830 nm indicatinc the coordi- 7. FACKLER, (Jr), J. P. & COTTON, F. A., J. Am. chem, Soc.,p . f ·d·::' t N·(II) 82 (1960). 5005.nation of two molecules 0 pyn me 0 1 I &< YAMADA, S., OHNO, E., KUGE, Y., TAKEUCHI, A., YAMA-maintaining, however, their octahedral configura- v NOUCHI, K. & IWASAKI, K., Coord. chem: Reu., 3 R--~tion. (1968), 247.355

Steric Effect in Ni(II) & Co(II) Complexes of Methyl Substituted N-Benzoyl-N-phenylhydroxylamines (N-phenylbenzohydroxamic Acids)

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Steric Effect in Ni(II) & Co(II) Complexes of Methyl Substituted N-Benzoyl-N-phenylhydroxylamines (N-phenylbenzohydroxamic Acids)

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