Indian Journal of ChemistryVol. 23A, December 1984, pp. 1044-1045

Characterization of the ReactionProducts of Hydrazine & Phenylhydrazine

with Coba1t(II), Nickel(II) & Zinc(II)Acetylacetonates

R C AGGARWAL" & D S SURYA NARAYANADepartment of Chemistry,

Banaras Hindu University, Yaranasi 221005.

Received 16 March 1984; revised and accepted 25 June 1984

Complexes of the types M(AcHzh and M(acach(PHzh [M=Co(ll), Ni(ll) or Zn(II); AcHzH =acetylacetone monohydrazone;acacH = acetylacetone and PHz =phenylhydrazine] have beenprepared by the reactions of hydrazine and phenylhydrazinerespectively with metal(II) acetylacetonates. The complexes havebeen characterised by elemental analyses, molar conductivity,magnetic susceptibility, electronic and IR spectral studies. Themagnetic moment and electronic spectral data suggest octahedralstereochemistry for Co(II) and Ni(II) complexes. IR spectra indicatebridging bidentate and monodentate behaviours ofN - N moiety inM(AcHzh and M(acach(PHzh type of complexes respectively.

Although literature is replete with examples oftransition metal complexes of bis(acetylacetone)di-amine ligands!" 5, relatively few complexes have beenreported with ligands derived from the condensation ofacetylacetone wth only one end of the diamine":", Thereactions of transition metal(II) acetylacetonates withdifferent chelating ligands containing at least one NH2group have also been studied":". Recently, Datta andcoworkers!" have shown that the reactions ofVO(acach with benzoylhydrazine .and related ligandsyield two types of schilT base complexes: one involvingthe condensation ofvanadyl oxygen and the other thatof the carbonyl oxygen of the acetylacetonate ring. Nowork appears to have been done on the reactions ofhydrazine and phenylhydrazine with metal(II)acetylacetonates. A study of the reactions of the abovehydrazines with Co(ll), Ni(II) and Zn(ll) acetylaceto-nates was therefore undertaken and the resultsobtained are discussed in this note.

All the chemicals used in the present work wereBDH reagents or of equivalent grade. Hydrazinehydrate and phenylhydrazine were distilled twicebefore use. Hydrated metal(l I) acetylacetonates wereprepared as described in literature I I. Ex perimentaldetails pertaining to elemental analyses, molarconductivity, magnetic susceptibility, electronic and IRspectral studies were similar to those described in ourearlier paper 12

AcHzH was prepared from the ice-cold ethanolicsolutions of hydrazine hydrate and acetylacetone

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following the procedure given by Domnin et al.13[m.p.60° (lit. m.p. 59.5-60SC]. Acetylacetonemono-hydrazone schilT base complexes of Co(lI), Ni(II) andZn(II) were prepared as follows: About 0.4 ml ofhydrazine hydrate in 10 ml of methanol was addeddropwise with constant stirring to a suspension of 1.5 gof the hydrated metal(II) acetylacetonate in 30 ml ofmethanol and heated slowly on a water-bath upto40°C until the suspension was completely dissolved.The complexes, which precipitated on vigorous stirringfor further 15 min, were suction-filtered, washed withwarm methanol and dried in vacuo. The phei:ylhydra-zine complexes were prepared by mixing and stirringthe methanolic solutions of phenylhydrazine and themetal(II) acetylacetonate in ~ 2: 1 molar ratio. Thecomplexes, which precipitated almost immediately,were suction-filtered, washed with methanol and driedin vacuo over cone. H2S04, Prolonged heating orrefluxing of the reaction mixtures containing hydrazineor phenylhydrazine resulted in the formation ofcompounds of indefinite compositions.

The analytical data of the schilT base complexes(Table 1) suggest that two molecules of hydrazine reactwith one molecules of metal(ll) acetylacetonate. Theanalytical data also show the formation of 1: 2 additioncomplexes with phenylhydrazine. While AcHzcomplexes ofCo(II), Ni(II) and ZnOI) melt at 166',205and 189'C respectively and are soluble in non-polarsolvents like methanol, ethanol etc., all thephenylhydrazine complexes melt with decompositionabove 250C and are insoluble in the above solvents.However, all the complexes are freely soluble in polarsolvents like DMF or DMSO. The molar conductancevalues of the complexes in DMF (10-3 M solutions)fall in the range 3.76-8.42 mhos em? mol- I suggestingthe non-ionic nature of all the complexes underdiscussion". The Il", values of CoOl) and Ni(I1)complexes (4.98-5.02 and 3.04-3.10 B.M. respectively)are consistent with spin-free octahedral geometryaround these metal ions I 5.

An intense band in the region 31,250-31,746 ern I ofthe UV spectra of M(AcHzh type complexes and aband in the region 31,545-32,895 cm - I of the spectra ofM(acach(PHzh type complexes is attributed to a 1[-1[*

transition due to the pscudoaromaticity of cnamineand acetylacetonate ring respectively present inthem'2.'6

The electronic spectra of Co(ll) complexes arcconsistent with an octahedral stereochemistry as theyshow two J-J bands at 8.772-9,346 and 18,519-20,408cm I which can be assigned to 4T2y

NOTES

Table I-Analytical, Magnetic and Electronic Spectral Data of the ComplexesColour Found (Calc.), % Ileff. Dq B IJ pc LFSE

(B.M.) (em -I) (cm-I) ( '/~) (kJmol-l)Metal N

Pink 20.45 19.46 4.98 995.4 854.5 0.879 12.1 95.26(20.68) (19.65)

Pinkish 12.21 11.58 5.02 1043.9 684.4 0.704 29.6 99.9brown (12.46) (11.84)Blue 20.21 19.43 3.10 985.2 932.8 0.896 10.4 141.42

(20.62) (19.67)Greenish 12.33 11.63 3.04 995.0 806.1 0.774 22.6 142.83blue (12.42) (11.85)Greenish 22.04 18.98white (22.44) (19.22)Light 13.18 11.39yellow (13.64) (11.68)

Compound

Co(AcHzh

Cotacac), (PHzh

Ni(AcHzh

Ni(acach(PHzh

Zn(AcHzh

Zn(acach(PHzh

.-4TI9(F)(vl) and 4T1g(P).-4T1g(F)(h) transitionsrespectively!" The spectra of Ni(II) complexes yieldthree d-d bands at 9,852-9,950, 15,980-16,130 and22,270-23,510 cm - 1 assignable to the transitionsarising from 3Azg ground state to 3Tzg(v1), 3TI9(F)(vz)and 3 T1g(P)(V3) excited states respectively. Thepositions and assignments of the ban lis indicateoctahedral environment around the nickel(II)I? Thep0 values of Co(ll) and Ni(II) complexes (Table1)indicate maximum covalency of 12.1 and 29.6 percentin M(AcHz}z and phenylhydrazine complexesrespectively.

The nujol mull spectrum of acetylacetonemono-hydrazone gives a broad band in the region 3500-3000 em - 1 probably due to the presence of inter- andintra-molecular hydrogen bonding between the OHand NHjNHz groups of the ligand. Replacement ofthis broad band by two well-defined bands in theregions 3320-3310 and 3185-3180 ern - 1 in the spectraof its complexes suggests the presence of NHz groupand absence of OH group in the complexes. The v(N- N) band observed at 888 cm - 1 in the' spectrum ofacetylacetone monohydrazone is shifted to the region980-958 em - 1 in the spectra of M(AcHzh complexes. A'positive shift of 70-92 ern - 1 in the above modeprovides a strong evidence for the bridging bidentatenature of the N - N moiety of the ligand 1 B.

Phenylhydrazine gives a broad band in the region34()()-3250 cm - I and a weak band at 3090 cm - 1 due toNH/NHz groups and these bands are shifted to lowerfrequencies (3390, 3195 and 3040 cm - I) in thecomplexes. indicating the coordination of phenyl-hydrazinel'l. A positive shift of 40-49cm-1 in the \'(N- N) band in the complexes as compared to its position(Xn cm - I) in the ligand supports the un identatecoordination of the (N - N) moiety of phenyl-hydrazine/". The bands observed in the regions 1590-1560 and 1515-14XOcm-1 in the spectra of all the

complexes are assigned to perturbed carbonyl and (C..:...:..:.C)/(C..:...:..:.N)stretching vibrations respectively 16.1 9. Thenon-ligand bands obtained in the regions 430-410 and310-268 em -I in the spectra of M(AcHz}z andM(acac)z(PHz}z type complexes respectively areassigned to v(M - 0) mode while those obtained in theregion 258-227 cm - 1 in the spectra of all the complexesunder discussion are assigned to v(M - N) modezo.zl.References

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