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DOI: 10.1039/A903487K (Paper) Reference Section for: J. Chem. Soc., Dalton Trans., 1999, 2987-2997

Syntheses, structures and magnetism of α-Mn(dca)2, [Mn(dca)2(H2O)2]·H2O, [Mn(dca)2(C2H5OH)2]·(CH3)2CO, [Fe(dca)2(CH3OH)2] and [Mn(dca)2(L)2], where L = pyridine, CH3OH or DMF and dca– = dicyanamide, N(CN)2–[hair space]†

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Stuart R. Batten, Paul Jensen, Cameron J. Kepert, Mohamedally Kurmoo, Boujemaa Moubaraki, Keith S. Murray and David J. Price

Abstract

The dicyanamide anion has been observed to adopt two bridging co-ordination modes (µ and µ3) in α-Mn(dca)2, [Mn(dca)2(H2O)2]·H2O, [Mn(dca)2(C2H5OH)2]·(CH3)2CO, [Fe(dca)2(CH3OH)2] and [Mn(dca)2(L)2] [L = py, CH3OH or DMF; dca = dycanamide N(CN)2–], and generates weak ligand fields thus stabilising high spin configurations. The N- or O-bonded ligands L play an important role in the stabilisation of both the molecular structures and the three dimensional structure, via hydrogen bonding. The unsolvated α-Mn(dca)2 adopts a rutile-like single network structure, based on the near orthogonal packing of ‘ribbons’ of . . . Mn(N[triple bond, length half m-dash]C–N–C[triple bond, length half m-dash]N)2Mn . . ., similar to that found for the isomorphous analogues of Co, Ni, Fe and Cu. Magnetisation measurements confirmed a high spin manganese d5 system displaying antiferromagnetic coupling (θ = –25 K) above 25 K and undergoing long range magnetic ordering (TN = 16 K) to a spin-canted antiferromagnet (weak ferromagnet). Magnetisation and heat capacity measurements on some samples of α-Mn(dca)2 indicated a possible second transition at ≈6 K, the nature of which is under investigation. From the hysteresis data at 2 K (remnant magnetisation of 29 cm3 Oe mol–1 and coercive field of 406 Oe) a canting angle of 0.05° is estimated for this soft magnet. Other samples gave a higher value for the coercive field. The α-M(dca)2 series has a diverse range of ground states; CuII (d9) is a paramagnet, NiII (d8) and CoII (d7) are ferromagnets and FeII (d6) and MnII (d5) are canted antiferromagnets. Reasons for this diversity are given on the basis of the nature of exchange coupling pathways within the rutile structure and a mechanism for the long range magnetic ordering is proposed. A range of 1-D chain complexes of type [Mn(dca)2(L)2], containing ‘ribbons’ of doubly bridged Mn(N[triple bond, length half m-dash]C–N–C[triple bond, length half m-dash]N)2Mn have been structurally characterised. The complex [Fe(dca)2(CH3OH)2] is isostructural with the manganese analogue. 2-D Square grids are found in crystals of [Mn(dca)2(C2H5OH)2]·(CH3)2CO and in [Mn(dca)2(H2O)2]·H2O, the latter displaying, in addition, penetration of ribbons of trans-Mn(dca)2(H2O)2 through the grids. Dehydration or desolvation results in formation of the α-Mn(dca)2 phase. The Lewis-base adducts all display very weak antiferromagnetic coupling (J ≈ –0.12 cm–1) and no magnetic long-range order. Dissolution of the compounds in protic solvents leads to complete dissociation of the dicyanamide, and the axially co-ordinated ligands, L, can readily be exchanged by reaction or recrystallisation in different co-ordinating solvents.

References

  1. S. R. Batten, P. Jensen, B. Moubaraki, K. S. Murray and R. Robson, Chem. Commun., 1998, 439 RSC .
  2. M. Kurmoo and C. J. Kepert, New J. Chem., 1998, 22, 1515 RSC ; Mol. Cryst. Liq. Cryst., 1999, in the press Search PubMed .
  3. O. Kahn, Adv. Inorg. Chem., 1995, 43, 179 CrossRef CAS .
  4. W. R. Entley and G. S. Girolami, Science, 1995, 268, 397 CrossRef CAS .
  5. T. Mallah, S. Thiebaut, M. Verdaguer and P. Veillet, Science, 1993, 262, 1554 CrossRef CAS .
  6. M. Kurmoo, Th. Jestädt, S. J. Blundell, C. J. Kepert, A. Lappas, K. Prassides, W. Hayes, B. W. Lovett and F. L. Pratt, unpublished work .
  7. J. L. Manson, C. R. Kmety, Q.-Z. Huang, J. W. Lynn, G. M. Bendele, S. Pagola, P. W. Stephens, L. M. Liable-Sands, A. L. Rheingold, A. J. Epstein and J. S. Miller, Chem. Mater., 1998, 10, 2552 CrossRef CAS .
  8. P. Jensen, S. R. Batten, G. D. Fallon, D. C. R. Hockless, B. Moubaraki, K. S. Murray and R. Robson, J. Solid State Chem., 1999, 145, 387 CrossRef CAS .
  9. M. Kurmoo, K. Lattaud, S. Vilminot, A. De Cian and C. J. Kepert, unpublished work .
  10. F. D. M. Haldane, Phys. Rev. Lett., 1983, 50, 1153 CrossRef ; G. E. Granroth, M. W. Meisel, M. Chaparala, Th. Jolicoeur, B. H. Ward and D. R. Talham, Phys. Rev. Lett., 1996, 77, 1616 CrossRef CAS .
  11. D. J. Price, B. Sc. Honours Thesis, Chemistry Department, Monash University, November 1998 .
  12. K. S. Murray, S. R. Batten, B. Moubaraki, D. J. Price and R. Robson, Mol. Cryst. Liq. Cryst., 1999, in the press Search PubMed .
  13. J. Mroziński, M. Hvastijová and J. Kohout, Polyhedron, 1992, 11, 2867 CrossRef CAS ; M. Hvastijová, J. Kohout, J. Mroziński and L. Jäger, Pol. J. Chem., 1995, 69, 852 CAS ; M. Hvastijová, Collect. Czech. Chem. Commun., 1994, 59, 2611 CrossRef CAS ; H. Köhler, A. Kolbe and G. Lux, Z. Anorg. Allg. Chem., 1977, 428, 103 CrossRef .
  14. H. Köhler, Z. Anorg. Allg. Chem., 1964, 331, 237 CrossRef .
  15. Z. Otwinowski and W. Minor, Methods in Enzymol., 1996 Search PubMed .
  16. G. M. Sheldrick, SHELX 97, Program for crystal structure refinement, University of Göttingen, 1997 .
  17. G. M. Sheldrick, SHELXS-86, Program for crystal structure determination, in Crystallographic Computing 3, eds. G. M. Sheldrick, C. Kruger and R. Goddard, Oxford University Press, Oxford, 1985, 175 Search PubMed .
  18. G. M. Sheldrick, SHELXL 93, Program for the refinement of crystal structures using single crystal diffraction data, University of Göttingen, 1993 .
  19. E. Dubler, A. Reller and H. R. Oswald, Z. Kristallogr., 1982, 161, 265 CAS .
  20. J. L. Manson, A. M. Arif and J. S. Miller, J. Mater. Chem., 1999, 9, 979 RSC .
  21. R. E. Marsh, Acta Crystallogr., Sect. B, 1995, 51, 897 CrossRef .
  22. G. C. DeFotis, E. D. Remy and C. W. Scherrer, Phys. Rev. B, 1990, 41, 9074 CrossRef CAS ; J. N. McElearney, L. L. Balagot, J. A. Muir and R. D. Spence, Phys. Rev. B, 1979, 19, 306 CrossRef CAS .
  23. M. G. F. Vaz, L. M. M. Pinheiro, H. O. Stumpf, A. F. C. Alcântara, S. Golhen, L. Ouahab, O. Cador, C. Mathoniere and O. Kahn, Chem. Eur. J., 1999, 5, 1486 CrossRef CAS .
  24. I. Dzyaloshinsky, J. Phys. Chem. Solids, 1958, 4, 241 CrossRef ; T. Moriya, Phys. Rev., 1960, 120, 91 CrossRef .
  25. S. G. Carling, P. Day, D. Visser and R. E. Kremer, J. Solid State Chem., 1993, 106, 111 CrossRef CAS .
  26. P. Jensen, S. R. Batten, G. D. Fallon, B. Moubaraki, K. S. Murray and D. J. Price, Chem. Commun., 1999, 177 RSC .
  27. J. B. Goodenough, Magnetism and the Chemical Bond, Wiley, New York, 1963 Search PubMed .
  28. M. E. Fisher, Am. J. Phys., 1964, 32, 343 .
  29. T. Smith and S. A. Friedberg, Phys. Rev., 1968, 176, 660 Search PubMed .
  30. G. S. Rushbrooke and P. J. Wood, Mol. Phys., 1963, 6, 409 ; M. E. Lines, J. Phys. Chem. Solids, 1970, 31, 101 CrossRef CAS .
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