摘要:

122 J. CHEM. RESEARCH (S) 1997 Synthesis and Characterization of the Homobimetallic [Bis(2-hydroxy-1-naphthaldehyde) oxaloyldihydrazonato]- bisdioxomolybdenum(VI) Tetrahydrate Complex and its Reactivity towards Proton and Electron Donor Reagents Ram A. Lal,* Syamal Adhikari Asim Pal Alakananda N. Siva and Arvind Kumar Department of Chemistry Tripura University Agartala-799004 Tripura India 4) and then characterized. temperature and of both the complexes at LNT are identical and can be interpreted assuming axial symmetry. The electronic spectra of all the complexes are dominated by the strong band in the 400–600 nm region which are assigned to ligand-to-metal charge-transfer transitions masking any d–d bands occurring in this region for 4 and 5. I The IR and 1H NMR spectra of the ligand suggest that it primarily exists in the keto form.23 The absence of a signal in the dH 10–14 region of 1 and the absence of a very strong amide I band in the 1700–1640 cmµ1 region and the appearance of strong to very strong bands in the 1615–1590 cmµ1 region in the IR spectra of 1 4 and 5 confirm the coordination of the dihydrazine to the metal centre through phenolic and enolized carbonyl oxygen atoms in the enol form.The shift of the vC�O and vNH bands to a higher wavenumber in the IR spectra and the shift of the dNH signal upfield in the 1H NMR spectra as compared to those in free dihydrazone eliminate the possibility of coordination of the ligand to the metal centre through I C�O and I NH groups in 2 and 3.The average downfield shift of dH CH�N by 0.26–0.17 ppm in 1–3 and the average shift of the vC�N band to a lower frequency by ca. 7 cmµ1 in all complexes suggest coordination of the azomethine nitrogen atom to the metal centre. The two to three very strong bands in the 947–907 cmµ1 region in 2 and 3 are characteristic of a cis-MoO2+ 2 . The absence of any band characteristic of I C�O and NH2 groups in the 1660–1630 cmµ1 region along with the absence of vMo�O bands and the appearance of medium-intensity bands at 1506 I sylshH3 (1:6) I [Mo2(napoxlh)(sylsh)2]•5H2O 4 [Mo2(napoxlh)(inh)2(H2O)2]•3H2O 5 The homobimetallic molybdenum(VI) complexes [(MoO2)2(napoxlh)] .4H2O 1 [{(m2-O)MoO2}MoO2(napoxlhH2)] .2L.4H2O [L=pyridine (py) 2 3-pic 3] and the molybdenum(V) complexes [MoO2(napoxlh)(sylsh)2] .5H2O 4 and [Mo2(napoxlh)(inh)2(H2O)2] .3H2O 5 (3-pic=3-picoline sylshH3=salicyloylhydrazine and inhH3=isonicotinoylhydrazine) are synthesized from bis(2-hydroxy-1-naphthaldehyde) oxaloyldihydrazone (napoxlhH Polyfunctional dihydrazones possessing amide azomethine and phenol functions in duplicate have recently attracted the attention of researchers11,12 because they have potential to yield homo- and hetero-polynuclear complexes which are of interest in areas such as multimetallic enzymes and homogeneous and heterogeneous catalysis.Molybdenum is a trace element that occurs in the redox active sites of over a dozen molybdoenzymes and its heterobimetallic complexes are important in homogeneous and heterogeneous catalysis.1 All these observations have kindled renewed interest in the coordination chemistry of molybdenum.To the best of our knowledge a study on molybdenum–dihydrazone complexes has not been reported. Here we report the synthesis and characterization of molybdenum(VI) and molybdenum(V) complexes derived from the polyfunctional dihydrazone ligand bis(2-hydroxy-1-naphthaldehyde) oxaloyldihydrazone. The complexes isolated in the present study are suggested to have the compositions [(MoO2)2(napoxlh)] .4H2O 1 [{(m2-O)MoO2}Mo2(napoxlhH2)] .2L.4H2O (where L=py 2 3-pic 3) and [Mo2(napoxlh)-(sylsh)3].5H2O 4 and [Mo2 (napoxlh)(inh)2(H2O)2] .3H2O 5. These are respectively intensely orange red yellowish brown brownish yellow reddish orange and dark red.The complexes are air stable and decompose above 300 °C. The experimental values of the molecular weights in DMSO suggested that 1–4 are dimeric while 5 is monomeric. The complexes are non-electrolytes in DMSO. The complexes were isolated by the procedures shown in Scheme 1. MoO2(acac)2+napoxlhH4 ethanol 3:1 reflux 2 h py or 3-pic [(MoO2)2(napoxlh)]•4H2O [{(m2-O)MoO2}MoO2(napoxlhH2)]2L•4H2O (1:8) ethanol reflux 1 h t ethanol reflux 4 h InhH3 (1:6) ethanol reflux 4 h 1 Scheme 1 Complexes 1–3 have zero mB values and are EPR silent. Complexes 4 and 5 have mB values of 3.02 and 3.16 respectively suggesting the presence of two molybdenum(V) centres in the same molecule without any significant metal– metal interactions.Complex 5 shows a characteristic powder spectrum at room temperature with g=2.079 and a hyperfine splitting (coupling constant) of ca. 52 G to the molybdenum nucleus. On the other hand the powder spectra of 4 at room and 1484 cmµ1 characteristic of vN�N 27 in 4 and 5 suggests the condensation of the NH2 group of the salicyloylhydrazine and of isonicotinoylhydrazine with a Mo�O group. The presence of downfield signals in the dH 9.12–7.38 region in 2 and 3 as compared to those for 1 at dH 8.39–7.04 the absence of any signal in the downfield region assignable to the pyridine or the 3-picolinium proton and the absence of any band in the 300–260 cmµ1 region in the low frequency IR spectra assignable to pyridyl or 3-picolyl nitrogen–metal bond dismiss the possibility of coordination of pyridine or 3-picoline to the metal centre or the presence of pyridinium or 3-pico- 2 L = py 3 L = 3-pic *To receive any correspondence.J. Chem. Research (S) 1997 122–123 J. Chem. Research (M) 1997 0749–0772 HC HN N C O H O O H C N O NH CH Fig. 1 Ligand anti-cis-configuration linium ions. A new band at 703 cmµ1 in 5 is attributed to rocking vibrations of coordinated water molecules. The splitting of the dH CH�N signal of 1 and 3 and the vC�N band in the IR spectra of all the complexes into doublets suggests that the ligand coordinates to the metal centre in an anti-cis-configuration14 (Fig. 1). On the basis of the various physicochemical and spectral data presented and discussed all the complexes are suggested to have octahedral stereochemistry around the molybdenum centre with an anti-cis-configuration of the coordinated dihydrazone.We thank RSIC NEHU Shillong for recording IR and 1H NMR spectra RSIC CDRI Lucknow for C H N analyses J. CHEM. RESEARCH (S) 1997 123 and RSIC IIT Madras for recording electronic and EPR spectra. One of us (S. A.) thanks the Council of Scientific and Industrial Research (New Delhi) for awarding a SRF. Techniques used IR 1H and 13C NMR elemental analysis EPR References 28 Figures 2 Received 16th October 1995; Accepted 23rd December 1996 Paper E/5/96810J References 1 C. D. Garner and J. M. Charnock in Comprehensive Coordination Chemistry ed.G. Wilkinson R. D. Gillard and J. A. McCleverty Pergamon Oxford 1987 vol. 3 p. 1329. 11 R. L. Dutta and Md. M. Hossain J. Sci. Ind. Res. 1985 44 645. Solinas and M. A. Zoroddu J. Chem. Soc. Daltons Trans. 1993 12 A. Bacchi L. P. Battaglia M. Carcelli C. Pelizzi G. Pelizzi C. 775. 14 R. A. Lal A. N. Sieva L. M. Mukherjee R. K. Thapa K. K. Narang and M. K. Singh Spectrochim. Acta Part A 1994 50 1005. 23 A. Yaccouta-Nour M. M. Mostafa and A. K. T. Maki Transition Met. Chem. 1990 15 34; Spectrochim. Acta Part A 19088 44 1291. 27 H. Kang S. Liu S. N. Shaikh T. Nicholson and J. Zubieta Inorg. Chem. 1989 28 920. MoO2(acac)2+napoxlhH4 [(MoO2)2(napoxlh)]•4H2O [{(m2-O)MoO2}MoO2(napoxlhH2)]2L•4H2O 2 L = py 3 L = 3-pic 1 [Mo2(napoxlh)(sylsh)2]•5H2O 4 [Mo2(napoxlh)(inh)2(H2O)2]•3H2O 5 ethanol reflux 2 h 3:1 (1:8) ethanol reflux 1 h py or 3-pic ethanol reflux 4 h ethanol reflux 4 h InhH3 (1:6) sylshH3 (1:6) 122 J.CHEM. RESEARCH (S) 1997 J. Chem. Research (S) 1997 122–123 J. Chem. Research (M) 1997 0749–0772 Synthesis and Characterization of the Homobimetallic [Bis(2-hydroxy-1-naphthaldehyde)o]- bisdioxomolybdenum(VI) Tetrahydrate Complex and its Reactivity towards Proton and Electron Donor Reagents Ram A. Lal,* Syamal Adhikari Asim Pal Alakananda N. Siva and Arvind Kumar Department of Chemistry Tripura University Agartala-799004 Tripura India The homobimetallic molybdenum(VI) complexes [(MoO2)2(napoxlh)] .4H2O 1 [{(m2-O)MoO2}MoO2(napoxlhH2)] .2L.4H2O [L=pyridine (py) 2 3-pic 3] and the molybdenum(V) complexes [MoO2(napoxlh)(sylsh)2] .5H2O 4 and [Mo2(napoxlh)(inh)2(H2O)2] .3H2O 5 (3-pic=3-picoline sylshH3=salicyloylhydrazine and inhH3=isonicotinoylhydrazine) are synthesized from bis(2-hydroxy-1-naphthaldehyde) oxaloyldihydrazone (napoxlhH4) and then characterized.Polyfunctional dihydrazones possessing amide azomethine and phenol functions in duplicate have recently attracted the attention of researchers11,12 because they have potential to yield homo- and hetero-polynuclear complexes which are of interest in areas such as multimetallic enzymes and homogeneous and heterogeneous catalysis. Molybdenum is a trace element that occurs in the redox active sites of over a dozen molybdoenzymes and its heterobimetallic complexes are important in homogeneous and heterogeneous catalysis.1 All these observations have kindled renewed interest in the coordination chemistry of molybdenum.To the best of our knowledge a study on molybdenum–dihydrazone complexes has not been reported. Here we report the synthesis and characterization of molybdenum(VI) and molybdenum(V) complexes derived from the polyfunctional dihydrazone ligand bis(2-hydroxy-1-naphthaldehyde) oxaloyldihydrazone. The complexes isolated in the present study are suggested to have the compositions [(MoO2)2(napoxlh)] .4H2O 1 [{(m2-O)MoO2}Mo2(napoxlhH2)] .2L.4H2O (where L=py 2 3-pic 3) and [Mo2(napoxlh)-(sylsh)3].5H2O 4 and [Mo2 (napoxlh)(inh)2(H2O)2] .3H2O 5. These are respectively intensely orange red yellowish brown brownish yellow reddish orange and dark red. The complexes are air stable and decompose above 300 °C.The experimental values of the molecular weights in DMSO suggested that 1–4 are dimeric while 5 is monomeric. The complexes are non-electrolytes in DMSO. The complexes were isolated by the procedures shown in Scheme 1. Complexes 1–3 have zero mB values and are EPR silent. Complexes 4 and 5 have mB values of 3.02 and 3.16 respectively suggesting the presence of two molybdenum(V) centres in the same molecule without any significant metal– metal interactions. Complex 5 shows a characteristic powder spectrum at room temperature with g=2.079 and a hyperfine splitting (coupling constant) of ca. 52 G to the molybdenum nucleus. On the other hand the powder spectra of 4 at room temperature and of both the complexes at LNT are identical and can be interpreted assuming axial symmetry.The electronic spectra of all the complexes are dominated by the strong band in the 400–600 nm region which are assigned to ligand-to-metal charge-transfer transitions masking any d–d bands occurring in this region for 4 and 5. The IR and 1H NMR spectra of the ligand suggest that it primarily exists in the keto form.23 The absence of a signal in the dH 10–14 region of 1 and the absence of a very strong amide I band in the 1700–1640 cmµ1 region and the appearance of strong to very strong bands in the 1615–1590 cmµ1 region in the IR spectra of 1 4 and 5 confirm the coordination of the dihydrazine to the metal centre through phenolic and enolized carbonyl oxygen atoms in the enol form. The shift of the vC�O and vNH bands to a higher wavenumber in the IR spectra and the shift of the dNH signal upfield in the 1H NMR spectra as compared to those in free dihydrazone eliminate the possibility of coordination of the ligand to the metal centre through I I C�O and I I NH groups in 2 and 3.The average downfield shift of dH CH�N by 0.26–0.17 ppm in 1–3 and the average shift of the vC�N band to a lower frequency by ca. 7 cmµ1 in all complexes suggest coordination of the azomethine nitrogen atom to the metal centre. The two to three very strong bands in the 947–907 cmµ1 region in 2 and 3 are characteristic of a cis-MoO2+ 2 . The absence of any band characteristic of I I C�O and NH2 groups in the 1660–1630 cmµ1 region along with the absence of vMo�Ot bands and the appearance of medium-intensity bands at 1506 and 1484 cmµ1 characteristic of vN�N 27 in 4 and 5 suggests the condensation of the NH2 group of the salicyloylhydrazine and of isonicotinoylhydrazine with a Mo�O group.The presence of downfield signals in the dH 9.12–7.38 region in 2 and 3 as compared to those for 1 at dH 8.39–7.04 the absence of any signal in the downfield region assignable to the pyridine or the 3-picolinium proton and the absence of any band in the 300–260 cmµ1 region in the low frequency IR spectra assignable to pyridyl or 3-picolyl nitrogen–metal bond dismiss the possibility of coordination of pyridine or 3-picoline to the metal centre or the presence of pyridinium or 3-pico- *To receive any correspondence. Scheme 1 HC N H O HN C O CH N H O NH C O J. CHEM. RESEARCH (S) 1997 123 linium ions. A new band at 703 cmµ1 in 5 is attributed to rocking vibrations of coordinated water molecules.The splitting of the dH CH�N signal of 1 and 3 and the vC�N band in the IR spectra of all the complexes into doublets suggests that the ligand coordinates to the metal centre in an anti-cis-configuration14 (Fig. 1). On the basis of the various physicochemical and spectral data presented and discussed all the complexes are suggested to have octahedral stereochemistry around the molybdenum centre with an anti-cis-configuration of the coordinated dihydrazone. We thank RSIC NEHU Shillong for recording IR and 1H NMR spectra RSIC CDRI Lucknow for C H N analyses and RSIC IIT Madras for recording electronic and EPR spectra. One of us (S. A.) thanks the Council of Scientific and Industrial Research (New Delhi) for awarding a SRF. Techniques used IR 1H and 13C NMR elemental analysis EPR References 28 Figures 2 Received 16th October 1995; Accepted 23rd December 1996 Paper E/5/96810J References 1 C. D. Garner and J. M. Charnock in Comprehensive Coordination Chemistry ed. G. Wilkinson R. D. Gillard and J. A. McCleverty Pergamon Oxford 1987 vol. 3 p. 1329. 11 R. L. Dutta and Md. M. Hossain J. Sci. Ind. Res. 1985 44 645. 12 A. Bacchi L. P. Battaglia M. Carcelli C. Pelizzi G. Pelizzi C. Solinas and M. A. Zoroddu J. Chem. Soc. Daltons Trans. 1993 775. 14 R. A. Lal A. N. Sieva L. M. Mukherjee R. K. Thapa K. K. Narang and M. K. Singh Spectrochim. Acta Part A 1994 50 1005. 23 A. Yaccouta-Nour M. M. Mostafa and A. K. T. Maki Transition Met. Chem. 1990 15 34; Spectrochim. Acta Part A 19088 44 1291. 27 H. Kang S. Liu S. N. Shaikh T. Nicholson and J. Zubieta Inorg. Chem. 1989 28 920. Fig. 1 Ligand an

ISSN:0308-2342    

DOI:10.1039/a506810j

出版商:RSC    

年代:1997

数据来源: RSC