Cobalt bis(oxalato)nickelate pentahydrate, Co[Ni(C2O4)2]×5H2O and cadmium bis(oxalato)nickelate

tetrahydrate, Cd[Ni(C2O4)2]×4H2O have been synthesized and characterized by elemental analysis,

reflectance and IR spectral studies. Thermal decomposition studies (TG, DTG and DTA ) in air

showed that both the compound of cobalt and cadmium produced the oxide, MNiOx (x=3 for M=Co;

x=2 for M=Cd ) at 325 and 360°C respectively. DSC studies in nitrogen attributed only the mixture

of both the metal at the end

BARUAH , S D

DASS , N N

DEB , N

IR@NEIST - North East Institute of Science and Technology (CSIR)

Journal of Thermal Analysis and Calorimetry, Vol. 59 (2000) 791797SYNTHESIS, CHARACTERIZATION AND THERMALDECOMPOSITION OF M1[M2(C2O4)2]× xH2O(x=5 FOR M1=Co AND x=4 FOR M1=Cd; M2=Ni)N. Deb1, S. D. Baruah2 and N. N. Dass31Department of Chemistry, North Eastern Regional Institute of Science and Technology, Nirjuli791109 Arunachal Pradesh2Regional Research Laboratory, Jorhat 785006, Assam3Department of Chemistry, Dibrugarh University, Dibrugarh 786004, Assam, India(Received November 16, 1998; in revised form March 5, 1999)AbstractCobalt bis(oxalato)nickelate pentahydrate, Co[Ni(C2O4)2]× 5H2O and cadmium bis(oxalato)nickelatetetrahydrate, Cd[Ni(C2O4)2]× 4H2O have been synthesized and characterized by elemental analysis,reflectance and IR spectral studies. Thermal decomposition studies (TG, DTG and DTA ) in airshowed that both the compound of cobalt and cadmium produced the oxide, MNiOx (x=3 for M=Co;x=2 for M=Cd ) at 325 and 360°C respectively. DSC studies in nitrogen attributed only the mixtureof both the metal at the end.Keywords: IR, oxalato complexes, thermal decompositionIntroductionCation defícient one-dimensional (I-D) metallic complexes for platinum with oxalate asligand i.e. Rbl.67[Pt(C2O4)2]× 1.5H2O and a series of divalent CD bis(oxalato) platinumsalts, M0.8[Pt(C2O4)2]× 6H2O (where M=Mg2+, Mn2+, Co2+, Ni2+ and Zn2+) which are foundto be isostructural at room temperature had been reviewed [1] some time back.Verdaguer et al. [2] synthesized, NiCu(C2O4)2× 4H2O, which was the simplest one-dimen-sional ordered bimetallic system with different electronic spins. The structure and mag-netic properties of the system were also investigated. The thermal decomposition ofLnCo(C2O4)3× xH2O (where Ln=La, Pr, Nd) led to [3] the rare earth cobaltites, LnCoO3;while a mixture of CeO2 and Co3O4 was formed from CeCo(C2O4)3× 8H2O. While study-ing [4] the same compounds later on, the cobaltites were found to be influenced by sur-rounding gas atmosphere. Thermal decomposition of coprecipitated zinc-copper oxalatesin nitrogen was reported [5] a long time ago. The study indicated the formation of aninterpenetrating structure or mixed crystals during coprecipitation and the end productwas mixed oxide and copper metal. We have studied [68] the compounds of the typeM[M(C2O4)2]× xH2O (where M=same metal) with Co, Ni and Cd, and found the different14182874/2000/ $ 5.00' 2000 AkadØmiai Kiadó, BudapestAkadØmiai Kiadó, BudapestKluwer Academic Publishers, Dordrechtintermediates and end products in different atmospheres. Although there have been quitea few reports on the mixed two metal oxalates, so far oxalates of cobalt and nickel, andcadmium and nickel have not been reported. Keeping in view of the possibility of forma-tion of mixed metal oxides as end product, we report here the synthesis, characterizationand thermal decomposition of Co[Ni(C2O4)2]× 5H2O and Cd[Ni(C2O4)2]× 4H2O. We havefollowed similar method of preparation adopted earlier for M[M(C2O4)2]× xH2O [68].ExperimentalAll the reagents used were AR grade. The chloride free nickel hydroxide preparedfrom nickel chloride was dissolved in glacial acetic acid and heated on a steam bath.A light pink precipitate was separated by adding cobaltous chloride followed bydropwise addition of saturated solution of oxalic acid. The precipitate was washedseveral times with distilled water and dried over calcium chloride. Similarly, afteradding cadmium chloride the respective powder compound of light blue colour wasisolated. The water content of the compounds were determined gravimetrically. Themetal content were estimated using standard methods. A Carlo Erba 1108 elementalanalyser was used to determine the carbon and hydrogen contents. Analysis as calcu-lated for Co[Ni(C2O4)2]× 5H2O: Co, 15.35%; Ni, 15.29%; C, 12.51%; H, 2.63%; H2O,23.46%; found: Co, 14.97%; Ni, 14.93%; C, 12.62%; H, 2.61%; H2O, 23.52%; calc.for Cd[Ni(C2O4)2]× 4H2O: Cd, 26.80%; Ni, 13.99%; C,11.46%; H, 1.92%; H2O,17.18%; found: Cd, 26.63%; Ni,14.12%; C, 11.24%; H, 1.89%; H2O, 17.08%.IR spectra (4000200 cm1) were recorded as nujol mulls using a Perkin Elmer IR883 spectrophotometer. Diffuse reflectance spectra were recorded with a ShimadzuUV-240 spectrophotometer. TG, DTG and DTA upto 1000°C were carried out in air at10°C min1 using a Shimadzu DT 30B instrument. DSC was carried out in dynamic ni-trogen using a Perkin Elmer PC series DSC 7 at a heating rate of 5 and 10°C min1. X-raypowder diffraction were obtained using a Rigaku X-ray diffractometer system D/Max.IIIC.Results and discussionThe light pink compound, Co[Ni(C2O4)2]× 5H2O and blue compound, Cd[Ni(C2O4)2]×4H2O were insoluble in water and common organic solvents. However, they decom-posed in the presence of strong acid or alkali. The analytical and microanalytical re-sults supports the proposed formula of the compounds. The XRD pattern (Table 1) ofthe compounds differed from each other which suggests they are not isomorphous.The IR peaks were assigned (Table 2) on the basis of earlier studies [68, 10, 11] andreported data [9]. These suggests the presence of coordinated oxalato group. How-ever, the possibility of the association of some of the water molecules with coordi-nated oxalato groups through hydrogen bonding cannot be ruled out as shown by thepresence of a broad band between 28003800 cm1.J. Therm. Anal. Cal., 59, 2000792 DEB et al.: OXALATO COMPLEXESTable 1 Prominent lines in the X-ray powder diffraction pattern of Co[Ni(C2O4)2]× 5H2O andpyrolysed product at 400°C, Cd[Ni(C2O4)2]× 4H2O and product from TG at 500°CCo[Ni(C2O4)2]× 5H2OPyrolysed product ofCo[Ni(C2O4)2]× 5H2Oat 400oCCd[Ni(C2O4)2]× 4H2OProduct ofCd[Ni(C2O4)2]× 4H2Ofrom TG at 500oCD(¯) I(REL) D(¯) I(REL) D(¯) I(REL) D(¯) I(REL)14.98 16.26 8.53 100.00 19.21 18.07 1.78 85.65.58 100.00 8.03 87.65 14.03 17.81 1.73 95.45.11 75.38 7.31 83.50 10.28 30.26 1.66 91.44.41 80.63 6.24 64.86 7.84 38.11 1.59 90.54.37 75.44 5.28 31.13 6.42 46.85 1.57 87.34.11 71.85 4.79 26.70 5.55 100.00 1.53 100.03.62 62.25 4.42 24.29 4.86 53.23 1.48 76.93.59 62.67 4.04 14.37 4.46 68.56 1.44 77.43.33 62.64 3.83 17.15 4.07 53.91 1.43 70.62.74 49.38 3.39 14.08 3.52 37.39 1.42 63.12.48 4.68 3.26 15.61 3.20 52.93 1.36 76.32.30 37.73 3.06 13.61 2.84 33.45 1.34 75.42.19 37.01 2.93 12.73 2.85 35.71 1.32 64.22.00 35.44 2.76 12.74 2.62 23.60 1.29 71.32.01 33.94 2.75 12.98 2.25 22.21 1.26 60.41.97 30.93 2.19 9.70 2.15 19.96 1.24 61.62.33 11.82 2.11 19.41 1.22 74.22.21 1.21 1.99 23.31 1.19 64.72.11 8.16 1.90 19.08 1.18 87.32.04 11.84 1.15 72.21.95 8.77 1.13 56.11.92 8.03 1.14 56.61.86 9.35 1.09 53.31.83 7.43 1.07 63.81.78 10.54 1.06 53.61.71 9.18 1.05 52.41.69 8.61 1.02 57.61.66 8.45 1.01 58.8The removal of water molecule at high temperature further indicates this type ofassociation. The electronic spectrum of the solid sample of Co[Ni(C2O4)2]× 5H2Odisplayed a complex multicomponent band centered around 20,000 (16,890,22,200, 32,670 cm1). The complexity could be due to severe distortion from idealJ. Therm. Anal. Cal., 59, 2000DEB et al.: OXALATO COMPLEXES 793geometry for octahedral/tetrahedral or square planar geometries around cobaltand nickel atoms. The multicomponent bands, 16,890, 20,000, 27,170 and30,770 cm1 showed in reflectance spectrum of Cd[Ni(C2O4)2]× 4H2O also suggeststhe distorted geometries of nickel environment. The distorted structure of oxa-lates of the type M[M(C2O4)2]× xH2O with cobalt and nickel had been concluded[6, 7] earlier. The band around 45,450 cm1 in the UV region of both compoundswere due [7, 10] to intraligand pfip * transition.Table 2 Selected bands in the IR spectra of Co[Ni(C2O4)2]× 5H2O and Cd[Ni(C2O4)2]× 4H2OIR bands/cm1AssignmentsCo[Ni(C2O4)2]× 5H2O Cd[Ni(C2O4)2]× 4H2O28403800 b 28003800 b n sy(OH)+n asy(OH) orhydrogen bonding1640 S 1660 S d sy(HOH)15001800 b 15001800 b n asy(C=O)1360 S 1370 S n sy(CO) and/or n (CC)1320 S 1320 S n sy(CO) and/or d (OC=O)825 m 830 m, 780 m d (OC=O) and/or n (MO)or coordinated water605 s 620 s crystal water530 w  n (MO) and/or n (CC)455 mS 460 mS n (MO) and/or ringdeformation310 s 320 m p (out-of-plane bending)s  small; m  medium; S  strong; b  broad; w  weakThe TG profile (Fig. l) of Co[Ni(C2O4)2]× 5H2O, shows the removal of the first watermolecule at 160°C, followed by an inclined slope upto 235°C (mass loss, found 20% ;calc., 18.79%) indicating the removal of four molecules of water. Complete deaquatedcompound is produced at 307°C with 23% mass loss (calc., 23.47%). An endotherm be-tween 165250°C (D Tmin=215°C) in DTA and a change in DTG between 148257°Ccorresponds to the dehydration step. The breakdown of the deaquated compound takesplace within a very short temperature range (307325°C) as shown by a steep slope inTG upto 325°C with a mass loss of 57.4%. The mass loss apparently suggests that theproduct is CoNiO3( calc., 56.83%). XRD pattern (Table 1) of the black product obtainedafter independent pyrolysis upto 400°C indicates [12] the contamination with traces ofoxides and carbides of cobalt and nickel as well as carbon along with the main product.The XRD pattern does not attribute the formation of CoNiO2 at 400°C. The carbonformed due to disproportionation of CO(g) which inturn converted to carbides. Thoughthe simple oxalates of cobalt and nickel, MC2O4× H2O produce [13] their respective ox-ides in air at 305 and 352°C, in this study the formation of mixed metal oxides is noticedJ. Therm. Anal. Cal., 59, 2000794 DEB et al.: OXALATO COMPLEXESat intermediate temperature of 325°C. In DTA an exothermic peak between 290340°C( maxD T =310°C ) and a sharp change in the range of 285330°C in DTG are for the de-composition step. The product formed at 325°C is stable upto 765°C in TG followed by aslight mass loss upto 1000°C (through a break at 890°C) with 60.5% mass loss might bedue to change to CoNiO2 (calc. 61%). A small downward hump in DTA around 830°Cand a break in TG at 890°C are apparently due to change of phase at high temperature.The DSC profile in N2 (Fig. 2) at 5°C min1 shows two changes. By changing the heatflow axis the endotherm between 180.7227.6°C for dehydration clearly separates fromthe change 345394°C for decomposition. While the scanning is done at 10°C min1(Fig. 3) the endotherm records between 173.6251.7°C; the range of decomposition splitinto two. The first peak is between 353.9366.5°C and the second between 369.6382.2°C. This suggests that the proper heat flow distinctly separate the phases during de-composition. The product formed in DSC study at 430°C with mass loss of 67.09% isstable in N2, indicated by no further change of DSC profile. The intimate mixture ofmetal cobalt and nickel could be assumed as an end product (calc. mass loss, 69.35%).Nagase et al. [14] reported the respective metal of Co and Ni formed in N2 from the sim-J. Therm. Anal. Cal., 59, 2000DEB et al.: OXALATO COMPLEXES 795Fig. 1 TG, DTG and DTA curves of Co[Ni(C2O4)2]× 5H2O in airFig. 2 DSC curve of Co[Ni(C2O4)2]× 5H2O at 5°C min1 in nitrogenJ. Therm. Anal. Cal., 59, 2000796 DEB et al.: OXALATO COMPLEXESFig. 3 DSC curve of Co[Ni(C2O4)2]× 5H2O at 10°C min1 in nitrogenFig. 4 TG, DTG and DTA curves of Cd[Ni(C2O4)2]× 4H2O in airFig. 5 DSC curve of Cd[Ni(C2O4)2]× 4H2O at 10°C min1 in nitrogenple oxalate, MC2O4× 2H2O; however, initial mass loss temperature of decomposition ofcobalt and nickel oxalates were 338 and 310°C respectively.In the TG curve (Fig. 4) the compound, Cd[Ni(C2O4)2]× 4H2O, loses first mole-cule of water at 105°C. The inclined nature of the curve upto 226°C (mass loss found,17.4% ; calc., 17.19%) indicates the formation of anhydrous compound. Two distinctchanges in the range 50240°C in DTG as well as two clear endotherm in DTA be-tween 80112°C ( D Tmin=100°C ) and 160250°C (D Tmin=205°C) are for the stepwiseremoval of water molecules. The anhydrous compound loses mass of 2.6% in therange 226332°C due to partial breaking of C O2 42- group; subsequently a steep slopeupto 360°C apparently indicates the formation of grey coloured CdNiO2 (mass lossfound, 51.50%; calc., 51.55%). However, XRD pattern of the residue (Table 1) iso-lated at 500°C in TG confirms the presence of trace of CdCO3, CdO and NiO alongwith main product. An exothermic peak between 323380°C (D Tmin= 350°C) in DTAand the change in DTG (315375°C) are accounted for this decomposition. The prod-uct loses mass very slowly in a wide range of temperature in TG and finally at1000°C with a mass loss of 56.2% indicates the product might be CdNiOx (x<1). TheDSC profile (Fig. 5) in N2 shows three distinct steps for the decomposition. The firststep ranges between 85.9119.4°C is for dehydration, followed by two decomposi-tion steps in the ranges 173.8241.3 and 341.9383°C. After 445°C the profile doesnot show any change, indicated by a straight DSC profile, which suggests no furtherchange of the product formed at 445°C. The mass loss of 67.49% after scanning upto600°C indicates that the product might be a mixture of both the metal only. The for-mation of respective metals were reported [13] in N2 from their oxalates.References1 A. E. Underhill and D. M. Watkins, Chem. Soc. Rev., 9 (1980) 429.2 M. Verdaguer, M. Julve, A. Michalowicz and O. Khan, Inorg. Chem., 22 (1983) 2624.3 K. Nag and Ajoy Roy, Thermochim. Acta, 17 (1976) 247.4 M. G. Usha, M. Subba Rao and T. R. Narayanan Kutty, Thermochim. Acta, 43 (1981) 35.5 B. D. Dalvi and A. M. Chavan, J. Thermal Anal., 14 (1978) 331.6 N. Deb, P. K. Gogoi and N. N. Dass, J. Thermal Anal., 35 (1989) 27.7 N. Deb, P. K. Gogoi and N. N. Dass, J. Thermal Anal., 36 (1990) 465.8 N. Deb, P. K. Gogoi and N. N. Dass, J. Instn. Chemists (India), 61 (1989) 185.9 K. Nakamoto, Infrared Spectra of Inorganic and Coordination Compounds, 2nd ed., Wiley, NewYork 1969, pp. 83, 89, 219, 245.10 N. Deb, S. D. Baruah and N. N. Dass, J. Therm. Anal., 45 (1995) 457.11 N. Deb, S. D. Baruah and N. N. Dass, Thermochim. Acta, 285 (1996) 301.12 Joint Committee on Powder Diffraction Standards, Inorganic Index to the Powder DiffractionFile, 1971, 1601, Parklane, Pennsylvania.13 D. Dollimore, D. L. Griffiths and D. Nicholson, J. Chem. Soc., (1963) 2617.14 K. Nagase, K. Sato and N. Tanaka, Bull. Chem. Soc. Jpn., 48 (1975) 439.J. Therm. Anal. Cal., 59, 2000DEB et al.: OXALATO COMPLEXES 797

Synthesis, characterization and thermal decomposition of M1[M2(C2O4)2].xH2O (x=5 for M1=Co and x=4 for M1=Cd;M2=Ni

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Synthesis, characterization and thermal decomposition of M1[M2(C2O4)2].xH2O (x=5 for M1=Co and x=4 for M1=Cd;M2=Ni

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