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Shape selective solvent inclusion within the lattice of bis(N1,N1,N5,N5-tetrabenzyl-2,4-dithiobiureto)nickel(II)
www.elsevier.nl/locate/inoche Inorganic Chemistry Communications 2 (1999) 527–529
Shape selective solvent inclusion within the lattice of bis(N1,N1,N5,N5-tetrabenzyl-2,4-dithiobiureto)nickel(II) Timothy S. Billson a, Jonathan D. Crane a,*, Ekkehard Sinn a, Simon J. Teat b, Eleanor Wheeler a, Nigel A. Young a a
Department of Chemistry, The University of Hull, Cottingham Road, Kingston-upon-Hull, HU6 7RX, UK b CCLRC, Daresbury Laboratory, Daresbury, Warrington, Cheshire, WA4 4AD, UK Received 30 August 1999
Abstract The crystal structure of the stable toluene solvate of bis(N1,N1,N5,N5-tetrabenzyl-2,4-dithiobiureto)nickel(II) shows that the solvent molecules are held within lattice cavities of well-defined size and shape. Recrystallisation from a mixture of xylenes was found to yield selectively the p-xylene solvate. q1999 Elsevier Science S.A. All rights reserved. Keywords: Nickel complexes; Bidentate ligands; Dithiobiuret complexes; Solvent inclusion; Crystal structures
1. Introduction
2. Experimental
2,4-Dithiobiuret and its derivatives are well known as neutral and monoanionic S,S-bidentate ligands [1–3]. Although a variety of simple N1,N1,N5,N5-tetrasubstituted-2,4-dithiobiurets (I) have been prepared [4] only the coordination chemistry of the tetramethyl derivative has been investigated in any detail [5–7], despite the potential for incorporating a wide range of functional groups into these ligands. In particular, the ease of synthesis of stable, diamagnetic, square planar, d8 complexes allows the facile preparation of ‘octopus’ molecules, with eight ‘tentacles’ radiating from the central core. Such polypodal molecules have long been of interest for selective solvent inclusion [8] and are of increasing importance as building blocks for new molecular materials; either as cores for dendrimers or as central tethering points for polyfunctional molecular assemblies [9]. We herein describe the synthesis and crystal structure of the octabenzyl derivative of the nickel(II) complex as a low molecular weight representative of this family of compounds, and its selective formation of a p-xylene solvate.
* Corresponding author. Tel.: q44 1482 465 457; fax: q44 1482 466 410; e-mail: [email protected]
2.1. Synthesis of bis(N1,N1,N5,N5-tetrabenzyl2,4-dithiobiureto)nickel(II) toluene solvate, (NiL2PC7H8) Dimethylthiocarbamoyl chloride (1.24 g, 10 mmol) and potassium thiocyanate (0.98 g, 10 mmol) in dry acetonitrile (50 cm3) were heated at reflux for 1 h. Excess dibenzylamine (7.89 g, 40 mmol) was added to the cooled, yellow reaction mixture and the solvent removed under reduced pressure. The residue was suspended in xylene (50 cm3) and heated at reflux under nitrogen for a further 30 min, after which time the evolution of dimethylamine gas from the reaction mixture had ceased. The reaction mixture was cooled, the solvent removed under reduced pressure and the residue suspended in acetonitrile (50 cm3). With vigorous stirring nickel(II) acetate tetrahydrate (1.25 g, 5 mmol) was added, followed by water (150 cm3). The crude product was filtered off as a brown powder, washed with methanol, air dried and recrystallised from toluene to yield brown crystals suitable for a single crystal X-ray structure determination; yield 1.74 g (31%). Anal. Calc. for C67H64N6NiS4 (MWs1140.21): C, 70.58; H, 5.66; N, 7.37; S, 11.25. Found: C, 70.72; H, 5.73; N, 7.05; S, 11.31%. 1H NMR (270 MHz, CDCl3): d 7.37– 7.13 (37H, m, Ph), 6.96 (8H, m, Ph), 5.10 (8H, s, PhCH2), 4.54 (8H, s, PhCH2), 2.35 (3H, s, PhCH3).
1387-7003/99/$ - see front matter q1999 Elsevier Science S.A. All rights reserved. PII S 1 3 8 7 - 7 0 0 3 ( 9 9 ) 0 0 1 4 6 - X
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StyleTag -- Journal: INOCHE (Inorganic Chemistry Communications)
Article: 284
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T.S. Billson et al. / Inorganic Chemistry Communications 2 (1999) 527–529
˚ and angles Fig. 1. ORTEP [17] view of the structure of the NiL2 molecule in NiL2PC7H8 with thermal ellipsiods shown at 50%. Selected bond lengths (A) (8): Ni(1)–S(1), 2.1752(6); Ni(1)–S(2), 2.1782(7); S(1)–C(1), 1.752(2); S(2)–C(2), 1.738(2); C(1)–N(1), 1.347(3); C(1)–N(2), 1.331(3); C(2)– N(2), 1.327(3); C(2)–N(3), 1.358(3); S(1)–Ni(1)–S(2), 95.71(3); S(1)–Ni(1)–S(2a), 84.29(3); Ni(1)–S(1)–C(1), 108.25(7); Ni(1)–S(2)–C(2), 114.31(8); S(1)–C(1)–N(2), 127.0(2); S(2)–C(2)–N(2), 127.7(2); C(1)–N(2)–C(2), 126.4(2). Symmetry transformation: a: 1yx, 1yy, 1yz.
2.2. Preparation of bis(N1,N1,N5,N5-tetrabenzyl2,4-dithiobiureto)nickel(II) p-xylene solvate, (NiL2PC8H10) Recrystallisation of the toluene solvate NiL2PC7H8 (1.14 g, 1 mmol) from mixed xylenes (25 cm3; o:m:p ratio 3:5:2) yielded the p-xylene solvate NiL2PC8H10 as brown crystals, yield 0.72 g (62%). Anal. Calc. for C68H66N6NiS4 (MWs1154.24): C, 70.76; H, 5.76; N, 7.28; S, 11.11. Found: C, 70.96; H, 6.00; N, 7.40; S, 11.53%. 1H NMR (270 MHz, CDCl3): d 7.35–7.20 (20H, m, Ph), 7.15 (12H, m, Ph), 7.06 (4H, s, C6H4Me2), 6.93 (8H, m, Ph), 5.10 (8H, s, PhCH2), 4.55 (8H, s, PhCH2), 2.30 (6H, s, ArCH3). 13C NMR (67.8 MHz, CDCl3): d 176.8, 136.6, 136.4, 134.7 (pxylene), 128.9 (p-xylene), 128.6, 128.5, 128.0, 127.5, 127.0, 126.9, 53.8, 51.7, 21.0 (p-xylene).
The crystal structure 1 of NiL2PC7H8 reveals that the toluene molecules occupy the cavities in the lattice of NiL2 molecules [10,11]. The nickel atom lies on a crystallographic centre of inversion with Ni–S bond distances of 2.175 and ˚ (Fig. 1). These distances are slightly longer than for 2.178 A all other bis-dithiobiureto-nickel(II) structures and the ligand backbone also displays a significant twist away from planarity, both presumably due to the steric effects of the eight benzyl groups 2 [12–16]. The toluene molecule also lies on a crystallographic inversion centre and hence is disordered over two orientations (Fig. 2); the NiL2∆toluene intermolecular interactions are all weak and the closest intermolecular contact is an aromatic T-stacking interaction between the hydrogen atom attached to C(6) and C(101)/C(102). It is probable that the lattice structure is dictated by the many weak interactions between the large NiL2 molecules and the 1
3. Results and discussion The symmetrical S,S-bidentate ligand N1,N1,N5,N5-tetrabenzyl-2,4-dithiobiuret (HL) was prepared by the reaction of excess dibenzylamine with in situ generated dimethylthiocarbamylthiocyanate in xylene at reflux. HL was directly complexed with nickel(II) acetate to yield the diamagnetic, square planar complex NiL2, which was recrystallised from toluene to yield crystals of the stable toluene solvate NiL2PC7H8. The composition was confirmed by 1H NMR spectroscopy and, moreover, no significant loss of toluene was observed from the crystals upon drying in air at room temperature for three days.
Thursday Oct 28 10:45 AM
Crystal data: NiL2PC7H8, C67H64N6NiS4, Mrs1140.21, triclinic, space ˚, group P1# (No. 2), as11.301(3), bs11.713(3), cs12.047(3) A ˚ 3, Zs1, as96.630(6), bs113.891(5), gs98.828(7)8, Us1412.6(6) A Dcs1.339 g cmy3, ms0.540 mmy1, F(000)s599. Crystal dimensions 0.20=0.14=0.02 mm. Data for 1PC7H8 were collected at 150(2) K employ˚ , on a Bruker AXS SMART CCD area detector ing a wavelength of 0.6890 A diffractometer with a silicon(111) crystal monochromator and a palladium coated focusing mirror on the single crystal diffraction station (no. 9.8) at Daresbury Laboratory Synchrotron Radiation Source. Coverage of a hemisphere of reciprocal space was achieved by 0.28 increments in v, with umins1.968 and umaxs29.038 (index ranges: y10FhF15, y15FkF16, y16FlF12). Corrections were applied to account for incident beam decay. A solution was provided via direct methods and refined by full-matrix leastsquares on F2. 9593 reflections were measured, producing 7084 unique data with Rints0.0238, and 5052 unique data [I)2s(I)]. 358 parameters refined to R1s0.0512 and wR2s0.1036 [I)2s(I)] with Ss1.013 and residual ˚ y3. electron density extremes of 0.676 and y0.502 e A 2 For bis(2,4-dithiobiureto)nickel(II) complexes the average Ni–S dis˚. tance is typically 2.15–2.17 A
StyleTag -- Journal: INOCHE (Inorganic Chemistry Communications)
Article: 284
T.S. Billson et al. / Inorganic Chemistry Communications 2 (1999) 527–529
529
Acknowledgements We thank the EPSRC and the University of Hull for their support.
References
Fig. 2. ORTEP [17] view of the packing for NiL2PC7H8. The disordered toluene molecule lies in a cavity defined by four NiL2 molecules. Shortest ˚ S(1)∆C(103a), 3.811(3); S(2)∆C(104a), non-bonded contacts (A): 3.743(6); C(6)∆C(101), 3.565(3); C(6)∆C(102), 3.638(3); C(6)∆C(103a), 3.720(3). Symmetry transformation: a: 1yx, y1yy, yz.
resulting lattice cavities are of an appropriate size and shape to host the toluene molecules. The solid state structure of NiL2PC7H8 indicates that pxylene should also readily form a stable solvate with NiL2. Indeed, the recrystallisation of NiL2PC7H8 from a mixture of xylenes (o:m:p ratio 3:5:2) was found by 1H and 13C NMR spectroscopy to yield almost exclusively ()95%) the pxylene solvate NiL2PC8H10. Thus the NiL2 host lattice is sufficiently rigid and the cavities are of a sufficiently welldefined size and shape to select the minor component from this mixture of xylene isomers. 4. Supplementary material Supplementary data for NiL2PC7H8 are available from the CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK, quoting the deposition number: CCDC 133309.
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[1] G. Wilkinson, R.D. Gillard, J.A. McCleverty (Eds.), Comprehensive Coordination Chemistry, vol. 2, Pergamon, Oxford, 1987, p. 639. [2] J.E. McGrady, D.M.P. Mingos, J. Chem. Soc., Perkin Trans. 2 (1996) 355. [3] Y.Y. Kharitonov, L.N. Ambroladze, Zh. Neorg. Khim. 32 (1987) 1381. [4] J.E. Oliver, S.C. Chang, R.T. Brown, A.B. Borkovec, J. Med. Chem. 14 (1971) 772. [5] I. Shibuya, H. Nakanishi, Bull. Chem. Soc. Jpn. 60 (1987) 2686. [6] A.W. Gal, J.W. Gosselink, F.A. Vollenbroek, Inorg. Chim. Acta 32 (1979) 235. [7] A.W. Gal, J.W. Gosselink, F.A. Vollenbroek, J. Organomet. Chem. 142 (1977) 357. ¨ [8] J.L. Atwood, J.E.D. Davies, D.D. MacNicol, F. Vogtle (Eds.), Comprehensive Supramolecular Chemistry, vol. 6, Pergamon, Oxford, 1996, p. 399. ¨ [9] J.L. Atwood, J.E.D. Davies, D.D. MacNicol, F. Vogtle (Eds.), Comprehensive Supramolecular Chemistry, vol. 10, Pergamon, Oxford, 1996, p. 777. [10] R.J. Cernik, W. Clegg, C.R.A. Catlow, G. Bushnell-Wye, J.V. Flaherty, G.N. Greaves, I.D. Burrows, D.J. Taylor, S.J. Teat, M. Hamichi, J. Synchrotron Rad. 4 (1997) 279. [11] W. Clegg, M.R.J. Elsegood, S.J. Teat, C. Redshaw, V.C. Gibson, J. Chem. Soc., Dalton Trans. (1998) 3037. [12] A. Houlton, D.M.P. Mingos, D.J. Williams, J. Chem. Soc., Chem. Commun. (1994) 503. [13] A. Houlton, D.M.P. Mingos, D.J. Williams, Transition Metal Chemistry (London) 19 (1994) 653. [14] T. Uechi, I. Ueda, N. Matsumoto, S. Kida, Inorg. Chim. Acta 33 (1979) 87. [15] A. Pignedoli, G. Peyronel, L. Antolini, Gazz. Chim. Acta 102 (1972) 679. [16] D.A. Fletcher, R.F. McMeeking, D. Parkin, The United Kingdom Chemical Database Service, J. Chem. Inf. Comput. Sci. 36 (1996) 746. [17] L.J. Farrugia, ORTEP-3 for Windows, J. Appl. Crystallogr. 30 (1997) 565.
StyleTag -- Journal: INOCHE (Inorganic Chemistry Communications)
Article: 284
Shape selective solvent inclusion within the lattice of bis(N1,N1,N5,N5-tetrabenzyl-2,4-dithiobiureto)nickel(II) Timothy S. Billson a, Jonathan D. Crane a,*, Ekkehard Sinn a, Simon J. Teat b, Eleanor Wheeler a, Nigel A. Young a a
Department of Chemistry, The University of Hull, Cottingham Road, Kingston-upon-Hull, HU6 7RX, UK b CCLRC, Daresbury Laboratory, Daresbury, Warrington, Cheshire, WA4 4AD, UK Received 30 August 1999
Abstract The crystal structure of the stable toluene solvate of bis(N1,N1,N5,N5-tetrabenzyl-2,4-dithiobiureto)nickel(II) shows that the solvent molecules are held within lattice cavities of well-defined size and shape. Recrystallisation from a mixture of xylenes was found to yield selectively the p-xylene solvate. q1999 Elsevier Science S.A. All rights reserved. Keywords: Nickel complexes; Bidentate ligands; Dithiobiuret complexes; Solvent inclusion; Crystal structures
1. Introduction
2. Experimental
2,4-Dithiobiuret and its derivatives are well known as neutral and monoanionic S,S-bidentate ligands [1–3]. Although a variety of simple N1,N1,N5,N5-tetrasubstituted-2,4-dithiobiurets (I) have been prepared [4] only the coordination chemistry of the tetramethyl derivative has been investigated in any detail [5–7], despite the potential for incorporating a wide range of functional groups into these ligands. In particular, the ease of synthesis of stable, diamagnetic, square planar, d8 complexes allows the facile preparation of ‘octopus’ molecules, with eight ‘tentacles’ radiating from the central core. Such polypodal molecules have long been of interest for selective solvent inclusion [8] and are of increasing importance as building blocks for new molecular materials; either as cores for dendrimers or as central tethering points for polyfunctional molecular assemblies [9]. We herein describe the synthesis and crystal structure of the octabenzyl derivative of the nickel(II) complex as a low molecular weight representative of this family of compounds, and its selective formation of a p-xylene solvate.
* Corresponding author. Tel.: q44 1482 465 457; fax: q44 1482 466 410; e-mail: [email protected]
2.1. Synthesis of bis(N1,N1,N5,N5-tetrabenzyl2,4-dithiobiureto)nickel(II) toluene solvate, (NiL2PC7H8) Dimethylthiocarbamoyl chloride (1.24 g, 10 mmol) and potassium thiocyanate (0.98 g, 10 mmol) in dry acetonitrile (50 cm3) were heated at reflux for 1 h. Excess dibenzylamine (7.89 g, 40 mmol) was added to the cooled, yellow reaction mixture and the solvent removed under reduced pressure. The residue was suspended in xylene (50 cm3) and heated at reflux under nitrogen for a further 30 min, after which time the evolution of dimethylamine gas from the reaction mixture had ceased. The reaction mixture was cooled, the solvent removed under reduced pressure and the residue suspended in acetonitrile (50 cm3). With vigorous stirring nickel(II) acetate tetrahydrate (1.25 g, 5 mmol) was added, followed by water (150 cm3). The crude product was filtered off as a brown powder, washed with methanol, air dried and recrystallised from toluene to yield brown crystals suitable for a single crystal X-ray structure determination; yield 1.74 g (31%). Anal. Calc. for C67H64N6NiS4 (MWs1140.21): C, 70.58; H, 5.66; N, 7.37; S, 11.25. Found: C, 70.72; H, 5.73; N, 7.05; S, 11.31%. 1H NMR (270 MHz, CDCl3): d 7.37– 7.13 (37H, m, Ph), 6.96 (8H, m, Ph), 5.10 (8H, s, PhCH2), 4.54 (8H, s, PhCH2), 2.35 (3H, s, PhCH3).
1387-7003/99/$ - see front matter q1999 Elsevier Science S.A. All rights reserved. PII S 1 3 8 7 - 7 0 0 3 ( 9 9 ) 0 0 1 4 6 - X
Thursday Oct 28 10:45 AM
StyleTag -- Journal: INOCHE (Inorganic Chemistry Communications)
Article: 284
528
T.S. Billson et al. / Inorganic Chemistry Communications 2 (1999) 527–529
˚ and angles Fig. 1. ORTEP [17] view of the structure of the NiL2 molecule in NiL2PC7H8 with thermal ellipsiods shown at 50%. Selected bond lengths (A) (8): Ni(1)–S(1), 2.1752(6); Ni(1)–S(2), 2.1782(7); S(1)–C(1), 1.752(2); S(2)–C(2), 1.738(2); C(1)–N(1), 1.347(3); C(1)–N(2), 1.331(3); C(2)– N(2), 1.327(3); C(2)–N(3), 1.358(3); S(1)–Ni(1)–S(2), 95.71(3); S(1)–Ni(1)–S(2a), 84.29(3); Ni(1)–S(1)–C(1), 108.25(7); Ni(1)–S(2)–C(2), 114.31(8); S(1)–C(1)–N(2), 127.0(2); S(2)–C(2)–N(2), 127.7(2); C(1)–N(2)–C(2), 126.4(2). Symmetry transformation: a: 1yx, 1yy, 1yz.
2.2. Preparation of bis(N1,N1,N5,N5-tetrabenzyl2,4-dithiobiureto)nickel(II) p-xylene solvate, (NiL2PC8H10) Recrystallisation of the toluene solvate NiL2PC7H8 (1.14 g, 1 mmol) from mixed xylenes (25 cm3; o:m:p ratio 3:5:2) yielded the p-xylene solvate NiL2PC8H10 as brown crystals, yield 0.72 g (62%). Anal. Calc. for C68H66N6NiS4 (MWs1154.24): C, 70.76; H, 5.76; N, 7.28; S, 11.11. Found: C, 70.96; H, 6.00; N, 7.40; S, 11.53%. 1H NMR (270 MHz, CDCl3): d 7.35–7.20 (20H, m, Ph), 7.15 (12H, m, Ph), 7.06 (4H, s, C6H4Me2), 6.93 (8H, m, Ph), 5.10 (8H, s, PhCH2), 4.55 (8H, s, PhCH2), 2.30 (6H, s, ArCH3). 13C NMR (67.8 MHz, CDCl3): d 176.8, 136.6, 136.4, 134.7 (pxylene), 128.9 (p-xylene), 128.6, 128.5, 128.0, 127.5, 127.0, 126.9, 53.8, 51.7, 21.0 (p-xylene).
The crystal structure 1 of NiL2PC7H8 reveals that the toluene molecules occupy the cavities in the lattice of NiL2 molecules [10,11]. The nickel atom lies on a crystallographic centre of inversion with Ni–S bond distances of 2.175 and ˚ (Fig. 1). These distances are slightly longer than for 2.178 A all other bis-dithiobiureto-nickel(II) structures and the ligand backbone also displays a significant twist away from planarity, both presumably due to the steric effects of the eight benzyl groups 2 [12–16]. The toluene molecule also lies on a crystallographic inversion centre and hence is disordered over two orientations (Fig. 2); the NiL2∆toluene intermolecular interactions are all weak and the closest intermolecular contact is an aromatic T-stacking interaction between the hydrogen atom attached to C(6) and C(101)/C(102). It is probable that the lattice structure is dictated by the many weak interactions between the large NiL2 molecules and the 1
3. Results and discussion The symmetrical S,S-bidentate ligand N1,N1,N5,N5-tetrabenzyl-2,4-dithiobiuret (HL) was prepared by the reaction of excess dibenzylamine with in situ generated dimethylthiocarbamylthiocyanate in xylene at reflux. HL was directly complexed with nickel(II) acetate to yield the diamagnetic, square planar complex NiL2, which was recrystallised from toluene to yield crystals of the stable toluene solvate NiL2PC7H8. The composition was confirmed by 1H NMR spectroscopy and, moreover, no significant loss of toluene was observed from the crystals upon drying in air at room temperature for three days.
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Crystal data: NiL2PC7H8, C67H64N6NiS4, Mrs1140.21, triclinic, space ˚, group P1# (No. 2), as11.301(3), bs11.713(3), cs12.047(3) A ˚ 3, Zs1, as96.630(6), bs113.891(5), gs98.828(7)8, Us1412.6(6) A Dcs1.339 g cmy3, ms0.540 mmy1, F(000)s599. Crystal dimensions 0.20=0.14=0.02 mm. Data for 1PC7H8 were collected at 150(2) K employ˚ , on a Bruker AXS SMART CCD area detector ing a wavelength of 0.6890 A diffractometer with a silicon(111) crystal monochromator and a palladium coated focusing mirror on the single crystal diffraction station (no. 9.8) at Daresbury Laboratory Synchrotron Radiation Source. Coverage of a hemisphere of reciprocal space was achieved by 0.28 increments in v, with umins1.968 and umaxs29.038 (index ranges: y10FhF15, y15FkF16, y16FlF12). Corrections were applied to account for incident beam decay. A solution was provided via direct methods and refined by full-matrix leastsquares on F2. 9593 reflections were measured, producing 7084 unique data with Rints0.0238, and 5052 unique data [I)2s(I)]. 358 parameters refined to R1s0.0512 and wR2s0.1036 [I)2s(I)] with Ss1.013 and residual ˚ y3. electron density extremes of 0.676 and y0.502 e A 2 For bis(2,4-dithiobiureto)nickel(II) complexes the average Ni–S dis˚. tance is typically 2.15–2.17 A
StyleTag -- Journal: INOCHE (Inorganic Chemistry Communications)
Article: 284
T.S. Billson et al. / Inorganic Chemistry Communications 2 (1999) 527–529
529
Acknowledgements We thank the EPSRC and the University of Hull for their support.
References
Fig. 2. ORTEP [17] view of the packing for NiL2PC7H8. The disordered toluene molecule lies in a cavity defined by four NiL2 molecules. Shortest ˚ S(1)∆C(103a), 3.811(3); S(2)∆C(104a), non-bonded contacts (A): 3.743(6); C(6)∆C(101), 3.565(3); C(6)∆C(102), 3.638(3); C(6)∆C(103a), 3.720(3). Symmetry transformation: a: 1yx, y1yy, yz.
resulting lattice cavities are of an appropriate size and shape to host the toluene molecules. The solid state structure of NiL2PC7H8 indicates that pxylene should also readily form a stable solvate with NiL2. Indeed, the recrystallisation of NiL2PC7H8 from a mixture of xylenes (o:m:p ratio 3:5:2) was found by 1H and 13C NMR spectroscopy to yield almost exclusively ()95%) the pxylene solvate NiL2PC8H10. Thus the NiL2 host lattice is sufficiently rigid and the cavities are of a sufficiently welldefined size and shape to select the minor component from this mixture of xylene isomers. 4. Supplementary material Supplementary data for NiL2PC7H8 are available from the CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK, quoting the deposition number: CCDC 133309.
Thursday Oct 28 10:45 AM
[1] G. Wilkinson, R.D. Gillard, J.A. McCleverty (Eds.), Comprehensive Coordination Chemistry, vol. 2, Pergamon, Oxford, 1987, p. 639. [2] J.E. McGrady, D.M.P. Mingos, J. Chem. Soc., Perkin Trans. 2 (1996) 355. [3] Y.Y. Kharitonov, L.N. Ambroladze, Zh. Neorg. Khim. 32 (1987) 1381. [4] J.E. Oliver, S.C. Chang, R.T. Brown, A.B. Borkovec, J. Med. Chem. 14 (1971) 772. [5] I. Shibuya, H. Nakanishi, Bull. Chem. Soc. Jpn. 60 (1987) 2686. [6] A.W. Gal, J.W. Gosselink, F.A. Vollenbroek, Inorg. Chim. Acta 32 (1979) 235. [7] A.W. Gal, J.W. Gosselink, F.A. Vollenbroek, J. Organomet. Chem. 142 (1977) 357. ¨ [8] J.L. Atwood, J.E.D. Davies, D.D. MacNicol, F. Vogtle (Eds.), Comprehensive Supramolecular Chemistry, vol. 6, Pergamon, Oxford, 1996, p. 399. ¨ [9] J.L. Atwood, J.E.D. Davies, D.D. MacNicol, F. Vogtle (Eds.), Comprehensive Supramolecular Chemistry, vol. 10, Pergamon, Oxford, 1996, p. 777. [10] R.J. Cernik, W. Clegg, C.R.A. Catlow, G. Bushnell-Wye, J.V. Flaherty, G.N. Greaves, I.D. Burrows, D.J. Taylor, S.J. Teat, M. Hamichi, J. Synchrotron Rad. 4 (1997) 279. [11] W. Clegg, M.R.J. Elsegood, S.J. Teat, C. Redshaw, V.C. Gibson, J. Chem. Soc., Dalton Trans. (1998) 3037. [12] A. Houlton, D.M.P. Mingos, D.J. Williams, J. Chem. Soc., Chem. Commun. (1994) 503. [13] A. Houlton, D.M.P. Mingos, D.J. Williams, Transition Metal Chemistry (London) 19 (1994) 653. [14] T. Uechi, I. Ueda, N. Matsumoto, S. Kida, Inorg. Chim. Acta 33 (1979) 87. [15] A. Pignedoli, G. Peyronel, L. Antolini, Gazz. Chim. Acta 102 (1972) 679. [16] D.A. Fletcher, R.F. McMeeking, D. Parkin, The United Kingdom Chemical Database Service, J. Chem. Inf. Comput. Sci. 36 (1996) 746. [17] L.J. Farrugia, ORTEP-3 for Windows, J. Appl. Crystallogr. 30 (1997) 565.
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Article: 284