Studies on lron(lll), Cobalyll), Nickel(ll) and Coppefll) Complexes of N-Benzoyl-N'-(4-antipyrylmethylidene) . hyd razine

Transcription

1 Studies on lron(lll), Cobalyll), Nickel(ll) and Coppefll) Complexes of N-Benzoyl-N'-(4-antipyrylmethylidene). hyd razine

2 This chapter deals with the synthesis and characterisation of nineteen complexes of ir(3n(j), cobalt(), nickel(l1) and copper(1) with the Schiff base N-Benzoyl-N'-(4-antipyrylmethy1idene)hydre (BAMH). Fig N-Benzoyl-N1..(4-antipyrylmethylidene)hydrine (BAMH) The ligand BAhH would be expected to behave as a neutral tridentate ligand coordinating through both the carbonyl oxygens and the azomethine nitrogen forming two chelate rings (one six membered and the other five membered) incorporating the metal ion. But the possibility of non-participation of any one of the donor sites cannot be ruled out. Experimental 'The details of the preparation of the ligand and metal salts were described in chapter 2.

3 4.1 Preparation of the Complexes ron(1) Complexes Perchlorate, Thiocyanate Chloride and Bromide Complexes A quantity of one mmol of Fe(C104),. 6H20, Fe(SCN)3.6H20, FeC13. 6H20 or FeBr3. 6H20 in ethyl acetate (10 ml) was added to a boiling suspension of 2.2 mmol of BAMH in ethyl acetate (100 ml). The mixture was refluxed for about 3 h on a stearnbath. The resulting solution was concentrated and cooled. The complexes, which precipitated on cooling, were filtered and washed several times with hot benzene to remove the excess ligand. These were recrystallised from methanol and dried under vacuum over phosphoms(v)oxide. Nitrate Complex A quantity of one mrnol of Fe(N03),. 6H20 in methanol (10 ml) was added to a boiling suspension of 2.2 mmol of BAMH in ethyl acetate (100 ml). The mixture was refluxed for about 2 h on a steambath. The resulting solution was concentrated and cooled. The complex, which precipitated on cooling, was filtered and washed several times with hot benzene to remove the excess ligand. t was recrystallised from acetonitrile and dried under vacuum over phosphoms(v)oxide. Cobat(1) Complexes Perchlorate, Bromide and odide Complexes A quantity of one mmol of Co(C104)2.6H20, CoBr2. 6H20 or Co2. 6H20 in ethyl acetate (10 ml) was added to a boiling suspension of 2.2 mmol of BAMH in ethyl acetate (100 ml). The mixture was

4 -4.-,.j;q"-. --_'% -',,,, 'j).!;. '.-.i,,..-'. --., 1./. '... Z.--.,,JPd> - -,- #-., ;. 4 ; refluxed for aboul3 h on a steam bath. The complexes, w & k i./." on cooling, were filtered and washed several times with hoi be-%& remove the excess ligand. These were recrystallised from methanol and dried under vacuum over phosphorus(v)oxide. Nitrate Complex A quantity of one rnrnol of Co(N03k. 6H20 in methanol (10 ml) was added to a boiling suspension of 2.2 mmol of BAMH in ethyl acetate (100 ml). The mixture was refluxed for about 3 h on a stearnbath. The resulting solution was concentrated and cooled. The complex, which precipitated on cooling, was filtered and washed several times with hot benzene to remove the excess ligand. t was recrystallised 60m acetonitrile and dried under vacuum over phosphorus(v)oxide. Chloride Complex A quantity of one mmol of CoC12.6H20 in acetone (10 ml) was added to a boiling suspension of 2.2 mmol of BAMH in acetone (100 ml). The mixture was refluxed for about 3 h. The complex, which precipitated on cooling, was filtered and washed several times with hot benzene to remove the excess ligand. t was recrystallised from methanol and dried under vacuum over phosphoms(v)oxide. Nickel(1) Complexes Perchlorate and odide Complexes A quantity of one mmol of Ni(C104)>.6H20 or Ni2.6H20 in ethyl acetate was added to a boiling suspension of 2.2 mmol BAMH in ethyl acetate (100 ml). The mixture was refluxed for about 4 h on a steambath. \..:,

5 The complexes, which precipitated on cooling, were filtered and washed several times with hot benzene to remove the excess ligand. These were recrystallised from methanol and dried under vacuum over phosphoms(v)oxide. Chloride Complex A quantity of one mmol of NiC12. 6H20 in methanol (10 ml) was added to a boiling suspension of 2.2 mmol of BAMH in ethyl acetate (100 ml). The mixture was refluxed for about 3 h on a steambath. The complex, which precipitated on cooling, was filtered and washed several times with hot benzene to remove the excess ligand. t was recrystallised from acetonitrile and dried under vacuum over phosphorus(v)oxide. Bromide and Nitrate Complexes A quantity of one mmol of NiBr2. 6H2O or Ni(NO&. 6H2O in acetone (10 ml) was added to a boiling suspension of 2.2 mmol BAMH in acetone (100 ml). The mixture was refluxed for about 3 h on a steam bath. The resulting solution was concentrated and cooled. The complexes, which precipitated on cooling, were filtered and washed several times with hot benzene to remove the excess ligand. t was recrystallised from methanol and dried under vacuum over phosphorus(v)oxide. Copper(1) Complexes Perchlorate Complex A quantity of one mmol of C~(C104)~. 6H2O in ethyl acetate (1 0 ml) was added to a boiling suspension of 2.2 mmol of BAMH in

6 ethyl acetate (100 ml). 'The mixture was reflwed for about 2 h on a steambath. 'The complex, which precipitated on cooling, was filtered and washed several times with hot benzene to remove the excess ligand. t was recrystallised from methanol and dried under vacuum over phosphorus(v)oxide. Nitrate and Chloride (2omplexes A quantity of one mmol of Cu@O,)L. 3Hz0 or CuC12. 2Hz0 in acetone (10 ml) was added to a boiling suspension of 2.2 mmol of BAMH in acetone (100 ml) for copper nitrate or 1.1 mmol of BAMH in acetone (100 ml) for copper chloride. The mixture was refluxed for about 2 h on a steambath. The precipitated complexes were tiltered and washed several tirnes with hot benzene to remove the excess ligand. These were recrystallised from methanol and dried under vacuum over phosphorus(\~)oxide. Bromide Complex A quantity of ont: nimol of CuBr?. 4H20 in acetonitrile (10 ml) was added to a boilingsolution of 2.2 mmol of BAMH in acetonitrile. The mixture was refluxed ior about 2 h on a steambath. The complex, which precipitated on cooling, was filtered and washed several times with hot benzene to remove the excess ligand. t was recrystallised ti-om methanol and dried under vacuum over phosphorus(v)oxide. Analyses and Physicochemical Studies of the Complexes The procedural details of the analyses and physicochemical studies of the complexes are given in Chapter 2.

7 4.2 Results and Discussion Appearance and Solubility of the Complexes The iron(1) complexes are brown non-hygroscopic solids. These are soluble in DMF, ethanol, methanol, and nitrobenzene but insoluble in benzene, chloroform, ethyl acetate and toluene. The cobalt(1) complexes are yellowish brown in colour except the chloride complex which is rose red in colour. All of these are non-hygroscopic and soluble in acetonitrile, DMF, ethanol, methanol and nitrobenzene but insoluble in benzene, chloroform, ethyl acetate and toluene. The nickel(1) complexes are light green in colour and are non-hygroscopic solids. These are soluble in acetonitrile, DMF, ethanol, methanol and nitrobenzene but insoluble in benzene, chloroform, ethyl acetate and toluene. The copper(rr) complexes are light yellow in colour except the bromide complex which is brown in colour. These are non-hygroscopic and are soluble in DMF, ethanol, methanol and nitrobenzene but insoluble in benzene, chloroform, ethyl acetate and toluene Elemental Analyses The 19 newly prepared complexes were subjected to elemental analyses. The results obtained are given in Tables 4.1 to 4.4.

8 The analytical data suggest that the complexes may be formulated as follows. t Fe(BAMH)2 Xj Co(BAMH)z X2 Ni(BAMH)2 X2 L A X = Clod, NO3, C, Br or - X = Clod, NO,, SCN, C, or Br X = Clod, NO,, C1, Br or Electrical Conductance The molar conductance data of iron(), cobalt(), nickel(l1) and copper(l1) complexe:j of BAMH in a set of three different non-aqueous solvents from among acetonitrile, DMF, methanol and nitrobenzene are given in Tables 4.5 to,4.8. ron(1) Complexes The molar conductance values of the perchlorate and nitrate complexes of BAMH (10"hl solutions) in DMF, methanol and nitrobenzene fall in the range expected for 1 :2 electrolytes, while for the chloride, bromide and thiocyanate complexes 1:1 electrolytic behaviour is obse~ved.'~ Thus the complexes may 1x formulated as [Fe(BAMH)2(C104)](C104)2, [Fe(BAMH)z(NO,)](N0;)2, and [Fe(BAMHhX2]X C or Br) (where X = SCN,

9 Cobalt(1) Complexes The molar conductance values of the cobalt(1) complexes of BAMH (10.'~ solution) in acetonitrile, DMF and nitrobenzene fall in the range expected for 1:2 electrolytes.144 Thus the complexes may be formulated as [Co(BAMH)2]X2 (where X = C104, N03, C1, Br or ). Nickel(1) Complexes The molar conductance values of the nickel(l1) complexes of BAMH (10"~ solution) in acetonitrile, DMF and nitrobenzene are in the range suggested for non-electrolytes1" except for the perchlorate and nitrate complexes which show 1: 1 electrolytic beha~iour.'~~ Copper(1) Complexes The molar conductance values of the copper(1) complexes of BAMH (10"~ solution) in DMF, methanol and nitrobenzene fall in the range expected for 1 :2 electrolytes except the chloride and bromide complexes which show non-electrolytic behaviour.'" Thus the complexes may be formulated as [Cu(BAMH)Z]Xl (where X = C104 or NO,), [Cu(BAMH)C12] and [Cu(BAMH),Br2] nfrared Spectra The important infrared spectral data of BAMH and their complexes together with the tentative assignments are presented in Tables 4.9 to The infkred spectrum of the he ligand BAMH shows bands at 3270, 1674, 1630, 1571 and 998 cm". 711e band at 3270 cm" is attributed to N-H stretching vibrations.'*' The bands at 1674 and 1630 cm-' are attributed to the

10 stretching vibmtions of the tarbony1 groups of the pymmlone ring and benzoyl nl~iet~'~~.'~ respectively. :The smng band at 1571 cm.' and a weak band at 998 cm"' are due to C=N and N-N stretching vibrations respectively ron(1) Complexes The infrared spectral bands at 1674 cm- characteristic of v(c=o) of the pyrazolone ring of BAMH is shifted to the region cm- in the complexes indicating the coordination of carbonyl oxygen.188 The band corresponding to v(c=o) of bermyl moiety remain practically unaltered in all the complexes at about 1628 cm" indicating the non-coordination of benzoyl oxygen.lw The strong band observed at 1571cm.l in BAMH attributed to C=N stretching vibration is shifted to the range cm.' indicating the coordination of the azomethine nitrogen in the c~rn~lexes.'~~.~~~ The shift of v(n-n) band at 998 cm- of BAMH to higher frequencies ( cm-') in the complexes further supports coordination through the azomethine mtrogen.lx' The triply split hand with maxima observed at around 1144, and cm- due to the va, v6 and vl vibrations respectively of the perchlorate ion of Cz, symmetry indicate that the perchlorate ion may he coordinated in a bidentate fashion But the band at 1090 cnl-' is attributed to the v; vibration of the uncoordinated perchlorate of Td symmetry. Thus the presence of both uncoordinated and bidentately coordinated perchlorate ions is observed in the perchlorate complex. The band observed around 940 and 632 cm-' corresponding to the

11 v2 and vj vibrations respectively of the coordinated perchlorate ((22") ion and the band at 624 cm-' due to the v4 vibration of the uncoordinated perchlorate (Td), which are not present in the spectrum of the free ligand, also support the coexistence of both uncoordinated and bidentately coordinated perchlorate ions in the complex. 156,158 n the nitrate complex, a very strong band observed at 1383 cm-' due to the v3 vibration of the Dl,, symmetry indicates the presence of uncoordinated nitrate ion. 143, This is supported by the presence of another band of medium intensity at 821 cm'l due to the v2 vibration of the uncoordinated nitrate ion.192 The presence of coordinated nitrate ion with C2, symmetry is indicated by the bands observed at around 1440 and 1244 cm-' due to v4 and vl vibrations respectively.'73 A medium intensity band observed around 1052 cm" due to v2 vibration of the nitrate (Cz,) ion stands as an additional evidence for the coordination of nitrate ion.6' Since the difference between the two frequencies, (v4-vl) is 196 cm- the coordinated nitrate ion is bidentate.'" n the thiocyanate complex, a sharp band at 2054 cm- is attributable to N-coordinated thiocyanate ion. The presence of bands at 854 and 472 cm-' stands as an additional evidence for N-coordinated thiocyanate ion n the far infrared spectra of chloride and bromide complexes, Fe-C and Fe-Br stretching vibrations are observed at 310 and 285 cm-, respectively'57 which are not present in the spectrum of the free ligand. Further v(fe-0) and v(fe-n) stretching vibrations are observed at about

12 550 and 455 cml respectively in all these complexes.'05 These results which are in agreement with the conductance data, indicate that one of the perchlorate and nitrate ions as well as two of the thiocyanate, chloride and bromide ions. are coordinated to the metal ion in these complexes. Cobalt(1) Complexes The ingared spectral bands at 1674 cm-' characteristic of v(c=o) of the pyrazolone ring are shifted to the region cm'l in the complexes indicating rhe coordination of carbonyl oxygen.'" The band at 1630 cm- corresponding to v(c=o) of benzoyl moiety is sh~fted to the region cm-' ~ndicating the coordination of benzoyl oxygen in these complexes.'88 The sbong band observed at 1571 cm-' in the ligand amibuted to C=N stretching vibration is shifted to cm-' indicating the coordination of the azomethine nitrogen in the complexes.'88 The v(n-n) band at 998 cm-' in the ligand which is shifted to higher frequencies ( cm-) in the complexes further supports the coordination through the azomethine nitrogen."' n the perchlorate complex, the band observed at 1089 cm" is assigned to v3 vibration of uncoordinated perchlorate ion of Td This is further supported by the presence of another strong band at 624 cm" due to "4 vibration of the perchlorate ionlix of Td symmetry. n the nitrate complex, the strong band observed at 1384 cm-' is attributed to the v3 vibration of uncoordinated nitrate ion of D3h

13 symmetry.'73 This is further supported by the presence of another medium intensity band at 825 cm- due to the vz vibration of nitrate ion of D3h symmetry.173 Further Co-0 and Co-N stretching vibrations are observed at about 555 and 450 cm-' respectively in all of these complexes.'05 The above spectral observations along with the conductance data indicate that the perchlorate, nitrate and halide ions remain as uncoordinated in all the complexes. Nickel(1) Complexes The infiared spectral band at 1674 cm' characteristic of v(c=o) of the pyramlone ring which is shifted to the region cm-' in the complexes indicate that the carbonyl oxygen is co~rdinated.'~~ The band corresponding to v(c=o) of benzoyl moiety remain practically unaltered in all the complexes at about 1625 cm-', indicating the non- coordination of benzoyl oxygen in these complexes.190 The strong band observed at 1571 cm- in the ligand attributed to C=N stretching vibration is shifted to cm-' in the complexes, indicating the coordination of azomethine nitrogen.s8 The v(n-n) band in the ligand at 998 cm'l shifted to higher frequencies ( cm-') in the complexes further supports the coordination through the azomethine nitrogen.''' n the perchlorate complex the triply split band with maxima observed at 1142, 1110 and 1020 cm-' are due to Vs, V6 and V vibrations respectively of the perchlorate ion of C2" symmetry, indicating the coordination of perchlorate ion in a bidentate fashion. 156,SR

14 But the band observed at 1089 cm- is assigned to the v3 vibration of uncoordinated perchlorate ion of Td n addition, the vibrational frequencies observed at 940 and 636 cm-' corresponding to v2 and v3 vibrations of the perchlorate ion of C ~V symmetry and the band at 625 cm- due to the v,i vibration of the perchlorate ion of Td symmetry also support the coexistence of both bidentately coordinated and uncoordinated perchlorate ions in this complex. n the nitrate:complex characteristic vibrational frequencies of both ionic and coordinated nitrate ions are observed. A very strong band observed at 1384 cm- due to the v3 vibration of the nitrate ion of Djh symmetry indicates the presence of uncoordinated nitrate ion."3 This is supported by another band of medium intensity observed at 830 cm-'. 'The presence of coordinated nitrate ion is indicated by the bands observed around 1440 and 1247 cm- due to the v4 and v, vibration respectively of the nitrate of C2" symmetry.'73 A medium intensity band observed around 1052 cm- due to the v2 vibration of the nitrate ion (C2") stands as an additional evidence for the presence of coordinated nitrate ion. The difference between the two highest frequency bands, (v4-vl j, of the nitrate ion of Czv symmetry is 193 cm.' which indicates that the (coordinated nitrate ion is bidentate.'" n the far infrared spectrum of the chloride, bromide and iodide complexes, Ni-C1, Ni-Br and Ni- stretching vibrations occur at 240, 165 and 125 cm'l respectively which are not present in the spectrum of the free ligand.15'

15 Further v(ni-0) and v(ni-n) stretching vibrations are observed at about 550 and 450 cm'l respectively in all the complexes. 105,157 ~ h, above results along with the conductance data confirm that one of the perchlorate and nitrate ions as well as two of the chloride, bromide and iodide ions are coordinated to the metal ion in these complexes. Copper(1) Complexes The infrared spectral band at 674 cm-' characteristic of v(c=o) of the pyrazolone ring shifted to the region cm-' in the complexes indicate that the carbonyl oxygen is c~ordinated.'~~ The band corresponding to v(c=o) of benzoyl moiety remain practically unaltered in all the complexes at about 1630 cm-' indicating the non-coordination of benzoyl oxygen in these complexes.'97 The strong band observed at 1571 cm-' in the ligand attributed to C=N stretching vibration is shifted to cm" region indicating the coordination of azomethine nitrogen in the complexes.188 The v(n-n) band at 998 cm- in the ligand, shifted to higher frequency ( cm'l) in the complexes, further supports the coordination through the azomethine nitrogen.lg7 n the perchlorate complex, the band observed at 1086 cm-' is assigned to the v3 vibration of uncoordinated perchlorate ion of Td symmetry.'s8 This is also supported by the presence of a medium intensity band at 624 cm-' due to the v4 vibration of perchlorate ion of Td symmetry.ls8 n the nitrate complex a strong band at 1378 cm- is assigned to v3 vibration of uncoordinated nitrate ion of D3h symmetry.'73 This is

16 fwther supported by the presence of a medium intensity band at 821 cm-' due to vz vibration of nitrate'73 ion of Djh symmetry. n the far infrad spectrum of the chloride and bromide complexes Cu-C1 and Cu-Br stretching vibrations occur at 310 and 292 cm-' respectively'57 but these are not present in the spectrum of the ligand. Further v(cu-0) and v(cu-n) stretching vibrations are observed at about 550 and 460 cm-' respectively in all these complexes. 105,157 The above observations along with the conductance data confirm that the perchlorate and nitrate ions remain as uncoordinated in these cornplexes while the chloride and bromide ions are coordinated to the metal ion Electronic Spectral Studies The electronic!spectrum of BAMH shows two bands with maxima at 23,866 and 41,153 cm-' corresponding to n -+ n* and n + n* transitions respectively. But in the spectra of the complexes, these transitions are found to be slightly shifted. The important electronic spectral data of the cornplexes of BAMH with tentative assignments are presented in Tables 4.13 to ron(1) Complexes n iron(1) complexes n -t n* bands are found to be blue-shifted to the region ,630 cm" while n -+ T* bands are red-shifted to the regon 39,370-40,983 m respectively when compared to that of BAMH. The spectra of a:ll the complexes exhibit a band in the region 19,230-20,080 cm-' corresponding to 6 ~ g -+ 4 ~ 1 g transition consistent

17 with octahedral iron(1) complexes. A strong band observed in the region 33,112-33,783 cm-' may be due to a charge transfer process. Cobalt(1) Complexes n cobalt(1) complexes n -t n* bands are found to be blue-shifted to the region 25,062-25,641 cm- while n + n* bands are red-shifted to the region 40,485-40,816 cm-' respectively when compared to that of BAMH. The band observed in the regions 19,607-20,833 cm" and 13,774-15,873cm- may be attributed to 4 ~ (F) ~ -+ g?lg (P) and 91, (F) -+ 4~2g (F) transitions respectively supportingoctahedml geometry around the metal ion in these A low energy band observed in the region 9,2169,523cm.' may be attributed to 9, (F)-+ 92, (F) transition consistent with octahedral configuration in all these complexes.s0~162 The strong band observed in the 33,333-33,557 cm-' region may be due to a charge transfer process. Nickel(1) Complexes n nickel(1) complexes n -+ n* bands are found to be blue-shifted to the region 24,510-25,839 cm-' while n + n* bands are found to be red-shifted to the region 40, ,052 cm-' respectively when compared to that of BAMH. The band observed in the regions 21,551-21,978 cm-' and 15,527-16,891 cm-' are attributed to 'A~,(F) -+ 3~~g(~) and 3 A2,(F) -t 3 ~~g(~) transitions respectively consistent with octahedral geometry around nickel(1) in these complexes. 50,201 n addition to this a low energy band in the region 9,191-9,541 cm-' attributable to 3~2,(~)-+3~2,(~) transition further support octahedral geometry around

18 nickel(l1) in these ~om~lexes.~~.~~~ An intense absorption band in the region 32,573-33,898 cm-' may be due to a charge transfer process. Copper(1) Complexes n copper(1) complexes n -+ rr* and n 4 rr* bands are found to be red-shifted to the regions 22,123-22,471 cm-' and 39,68240,816 cm" respectively when compared to that of BAMH. The band observed in 2 the region 13,477-13,820 cm- is attributed to *B, + Alg transition consistent with square planar196 geometry around the copper(1) in all the complexes except the bromide complex. The broad band at 19,608 cm-' in the bromide complex: indicates tetragonal configuration around the copper(1) ion. 186,197 The electronic spectra of all the complexes exhibit an intense absorption band in the region 33,222-33,444 cm- which may be due to a charge transfer process Magnetic Behaviour The magnetic susceptibility measurements were done as described in Chapter 2. complexes are presented in Tables 4.13 to ron(1) Complexes The effective magnetic moments of the The magnetic moments of the iron(1) complexes of BAMH are found to be in the range 5.61 to 6.05 BM. This suggests a high spin octahedral configuration around the metal ion Cobalt(1) Complexes The observed magnetic moment values of the complexes are in the range BM. n an octahedral field, the ground state is

19 triply degenerate which would cause an orbital angular momentum contribution to the magnetic moment. The moments therefore would lie between the limits of 3.88 and 5.20 BM depending upon the extent of orbital angular momentum contribution. The magnetic moments of the present complexes are very close to those expected for a high spin octahedral geometry.19* Nickel(1) Complexes The magnetic moments of the complexes are in the range BM. The typical octahedral nickel(1) complexes have magnetic moments between BM depending on the magnitude of the orbital contributi~n.~~ The results indicate that these complexes probably have octahedral geometry.'99 Copper(1) Complexes The magnetic moments of copper(1) complexes vary in the range BM. This clearly indicates that the complexes except the chloride complex are monomeric in nature and any metal-metal interaction is absent.g6 The magnetic moment of the chloride complex is slightly lower than that expected which may be due to metal-metal interaction EPR Spectra The X-band EPR spectra of the copper(1) complexes were recorded in 1:1 methanol-toluene mixture at liquid nitrogen temperature using DPPH free radical as the 'g' marker (Fig. 4.2). All the complexes have a well-resolved g, and a broadened g, region. n

20 all the spectra no superhyperfine splitting from the ligand part is observed H (Gauss) Fig. 4.2 EPR Spectra of copper(1) complexes of BAMH The various spin Hamiitonian parameters computed are presented in Table The trend gl>g,> indicates that the unpaired electron is most likely in the d, orbital.'83 The covalency parameter KL-Y a2 is found to be in the range 0.75 to 0.76 indicating the fairly covalent nature in the metal-ligand bonding.'86 Further the shape of the EPR spectra indicates that the geometry around the copper(1) ion is square planar in the perchlorate. nitrate and cf~lo~ide cc~mplexes and an elongated octahedron in

21 the bromide complex as is evident from the less intense low field side and high intense high field side.20' 4.3 Summary and Conclusion The iron(), cobalt(), nickel(1) and copper(1) complexes of N-Benzoyl-N'-(4-antipy1ymethylidene)hydrazine have been synthesised and characterised by elemental analyses, molar conductance, infrared and electronic spectra as well as magnetic susceptibility measurements. The copper(1) complexes were also characterised by EPR spectral analyses. ron(1) Complexes According to elemental analyses and molar conductance data, the iron(1) complexes may be formulated as [Fe(BAMH)2X]X2 (X = Clod or NO,) and [Fe(BAMH)2X2]X (X = SCN, C1 or Br). The infrared spectra reveals that BAMH acts as a neutral bidentate ligand coordinating through the carbonyl oxygen of antipyrine ring and the azomethine nitrogen in all the complexes. The molar conductance data and infrared spectra indicate that one of the perchlorate and nitrate ions is coordinated bidentately leaving the other two as counter anions while in the thiocyanate, chloride and bromide complexes two of the anions are coordinated. The electronic spectra and magnetic moment data suggest a high spin octahedral geometry around the iron(1) ion in all these complexes. Thus a coordination number of six is assigned to the metal ion in these complexes.

22 The tentative struchlres of the complexes are presented in Fig H5 o=c \/ - 1 H C6H~ N-H C=O C6H5 C6H5 O==C 0 1 H H--N N 7sH5 \ /\ N=C, H C6Hs N-H C=O C6H~ CH3 J

23 - - ph5 O=C H N-H c6h5 C=O C6H5 - - (X = SCN, C1, or Br) Fig. 4.3 Tentative structures of iron(1) complexes of BAMH X Cobalt(1) Complexes According to the elemental analyses and molar conductance data, cobalt(1) complexes may be represented by the general formula [CO(BAMH)~]X~ (X=C104, NO3, Cl, Br or ). The infrared spectral data suggests that BAMH acts as a neutmi tridentate ligand coordinating through the carbonyl oxygens of the antipyrine ring and the benzoyl group as well as the azomethine nitrogen in all these complexes. The molar conductance data and the infrared spectra indicate that both the anions remain as counter anions in all these complexes. The electronic spectra and magnetic moment data suggest an octahedral geometry around the cobalt(1) ion in these complexes. Thus a cmrd'mation number of six is assigned to the metal ion in these complexes. The tentative structures of the complexes are presented in Fig. 4.4.

24 (X = '2104, NO,, C1, Br or ) Fig. 4.4 Tentative structure of cobalt(1) complexes of BAMH J Nickel(11) Complexes n accordance with the elemental analyses and molar conductance data, the nickel(l1) complexes of BAMH may be formulated as [Ni(BAlylf)2(C104)1(C104), [Ni(BAMH)2(NO,)](NO,) or [Ni(BAMH)2X2] (Xz=C, Br or ). The infrared spectra reveal that BAMH acts as a neut;ral bidentate ligand coordinating through the carbonyl oxygen of the antipyrine ring and the azomethine nitrogen. The molar conductance data and infrared spectra indicate that one of the perchlorate and nitrate ions is coordinated bidentately leaving the other as counter anion. 0'0th of the chloride, bromide or iodide ions are: coordinated to the metal.

25 122-4 The tentative structures of the complexes are presented in Fig H5 o=c (c104) - C6H5 N-H C=O C6H5 H H5 O=C 0 (NO31! csh5 N-H C=O C 6H5 H -

26 N-H (X = C, Br or ) Fig. 4.5 Tentative structures of nickel(1) complexes of BAMH Copper(1) Complexes The elemental ;malyses and molar conductance data of the copper(1) complexes of B.4MH indicate that these complexes have the general formulae [CU(BPLMH)]X~, (X = C104 or NO?), [Cu(BAMH)>Br2] or [Cu(BAMH)C12]. The infrared spectral data indicate that BAMH acts as a neutral bidentat': ligand coordinating through the carbonyl oxygen of antipyrine ring and the azomethine nitrogen in all these complexes. The molar conductance data and the infrared spectra reveal that both the perchlorate and nitrate ions remain as counter anions while both the chloride and bromide ions are coordinated to the metal ion in these complexes. From the electronic spectra, a square planar geometry is assigned to the copper(1) ion in the perchlorate,

27 nitrate and chloride complexes while an octahedral geometry is suggested for the bromide complex. The tentative structures of the complexes are presented in the Fig c=o. ' H N-H C6H5! : C=O C6H5'' (X = '2104 Or NO,) - - ' '76H5 C=O - x2 c6h5 N-H c=o C6H5 -

28 H \ 7sH5 C=O N-H - L C6H5 Fig. 4.6 Tentative structures of copper(1) complexes of BAMH