Bent vs. linear imido ligation at the octahedral molybdenum(VI) dithiocarbamate stabilised centre

Abstract

Molybdenum(VI) bis(imido) complexes [Mo(NR)₂(S₂CNEt₂)₂] 3a–3p have been prepared via two synthetic routes and their structures investigated. Thermolysis of [MoO₂(S₂CNEt₂)₂] 1 with 2,6-disubstituted aryl isocyanates affords air-stable bis(imido) complexes 3i–3m in high yields after column chromatography, a route which fails for sterically less demanding isocyanates. A more general preparation involves room temperature addition of two equivalents of [S₂CNEt₂]^– to the labile bis(imido) complexes [Mo(NR)₂Cl₂(dme)] 2a–2p (dme = 1,2-dimethoxyethane) to afford 3a–3p in high yields. In this manner related complexes [Mo(NR)₂(S₂CNMe₂)₂] 4 (R = Ph or Bu^t) and [Mo(NPh)₂(S₂PPh₂)₂] 5a have also been prepared. Structural and spectroscopic studies have been carried out in order to determine the degree of bending of the imido ligands. Six complexes have been characterised by X-ray crystallography. In all cases one of the imido ligands is linear (Mo–N–C ≥ 160°), while the angle at the second is dependent upon the nature of R and ranges from 180 to 139°. Solid-state ¹³C CPMAS spectroscopy reveals that the difference in bond angles at the two nitrogen centres (Δ°) correlates closely with the difference in chemical shifts of the ipso-carbon atoms (Δδ). This then has been used to probe the relative bond angles at nitrogen for non-crystallographically characterised complexes. In solution even at low temperatures both imido ligands are equivalent indicating a rapid interconversion between linear and bent bonding modes.

References

1. P. J. Walsh, A. M. Baranger and R. G. Bergman, J. Am. Chem. Soc., 1992, 114, 1708; D. Mansuy, J.-P. Mahy, A. Dureault, G. Bedi and P. Battioni, J. Chem. Soc., Chem. Commun., 1984, 1161; J. T. Groves and T. Takahashi, J. Am. Chem. Soc., 1983, 105, 2073.
2. R. R. Schrock, J. S. Murdzek, G. C. Bazan, J. Robbins, M. DiMare and M. B. O'Regen, J. Am. Chem. Soc., 1990, 112, 3875; J. Robbins, G. C. Bazan, J. S. Murdzek, M. B. O'Regen and R. R. Schrock, Organometallics, 1991, 10, 2902; R. Schrock, R. T. DePue, J. Feldman, C. J. Schaverien, J. C. Dewan and A. H. Liu, J. Am. Chem. Soc., 1988, 110, 1423; R. Schrock, R. T. DePue, J. Feldman, K. B. Yap, D. C. Yang, W. M. Davis, L. Y. Park, M. DiMare, M. Schofield, J. Anhaus, E. Walborsky, E. Evitt, C. Kruger and P. Betz, Organometallics, 1990, 9, 2262.
3. D. E. Wigley, Prog. Inorg. Chem., 1994, 42, 239; W. A. Nugent and B. L. Haymore, Coord. Chem. Rev., 1980, 31, 123; W. A. Nugent and J. M. Mayer, Metal–Ligand Multiple Bonds, Wiley, New York, 1988.
4. G. Parkin, A. van Asselt, D. J. Leahy, L. R. Whinnery, N. G. Hua, R. W. Quan, L. M. Henling, W. P. Schaefer, B. D. Santarsiero and J. E. Bercaw, Inorg. Chem., 1992, 31, 82.
5. A. Bell, W. Clegg, P. W. Dyer, M. R. Elsegood, V. C. Gibson and E. L. Marshall, J. Chem. Soc., Chem. Commun., 1994, 2247.
6. W. A. Nugent, R. L. Harlow and R. J. McKinney, J. Am. Chem. Soc., 1979, 101, 7265.
7. D. W. H. Rankin, H. E. Robertson, A. A. Danopoulos, P. D. Lyne, D. M. P. Mingos and G. Wilkinson, J. Chem. Soc., Dalton Trans., 1994, 1563.
8. G. V. Goeden and B. L. Haymore, Inorg. Chem., 1983, 22, 157.
9. W. A. Nugent and R. L. Harlow, J. Chem. Soc., Chem. Commun., 1979, 1105.
10. G. K. Lahiri, S. Goswami, L. R. Favello and A. Chakraworty, Inorg. Chem., 1987, 26, 3365.
11. R. C. B. Copley, P. W. Dyer, V. C. Gibson, J. A. K. Howard, E. L. Marshall, W. Wang and B. Whittle, Polyhedron, 1996, 15, 3001.
12. V. C. Gibson, C. Redshaw, W. Clegg, M. R. Elsegood, U. Siemeling and T. Türk, J. Chem. Soc., Dalton Trans., 1996, 4513.
13. A. F. Clifford and C. S. Kobayashi, Inorg. Synth., 1960, 6, 204; N. A. Milas and I. M. Iliopulos, J. Am. Chem. Soc., 1959, 81, 6089.
14. B. L. Haymore, E. A. Maatta and R. A. D. Wentworth, J. Am. Chem. Soc., 1979, 101, 2063; E. A. Maatta and R. A. D. Wentworth, Inorg. Chem., 1978, 18, 2409.
15. V. C. Gibson, E. L. Marshall, C. Redshaw, W. Clegg and M. R. Elsegood, J. Chem. Soc., Dalton Trans., 1996, 4197.
16. A. A. Danopoulos, G. Wilkinson and D. J. Williams, J. Chem. Soc., Chem. Commun., 1991, 181.
17. A. A. Danopoulos, G. Wilkinson, T. K. N. Sweet and M. B. Hursthouse, J. Chem. Soc., Chem. Commun., 1993, 495; J. Chem. Soc., Dalton Trans., 1994, 1037; 1995, 205; 937.
18. T. I. Gountchev and T. D. Tilley, J. Am. Chem. Soc., 1997, 119, 12831.
19. M. Minelli, R. L. Kuhlman, S. J. Shaffer and M. Y. Chiang, Inorg. Chem., 1992, 31, 3891.
20. M. Minelli, M. R. Carson, D. W. Whisenhunt, Jr., W. Imhof and G. Huttner, Inorg. Chem., 1990, 29, 4801.
21. K. J. Weller, S. D. Gray, P. M. Briggs and D. E. Wigley, Organometallics, 1995, 14, 5588.
22. S. Cai, R. R. Schrock, R. R. Kempe and W. M. Davis, Polyhedron, 1998, 17, 747.
23. O. D. Sloan and P. Thornton, Polyhedron, 1988, 7, 329.
24. R. R. Schrock, S. W. Seidel, N. C. Mosch-Zanetti, D. A. Dobbs, K. Y. Shih and W. M. Davis, Organometallics, 1997, 16, 5195.
25. B. A. Arndtsen, H. F. Sleiman, A. K. Chang and L. McElwee-White, J. Am. Chem. Soc., 1991, 113, 4871.
26. A. Saravanamuthu, D. M. Ho, M. E. Kerr, C. Fitzgerald, M. R. M. Bruce and A. E. Bruce, Inorg. Chem., 1993, 32, 2202.
27. Z. Li, R. W. Quan and E. N. Jacobsen, J. Am. Chem. Soc., 1995, 117, 5889.
28. R. H. Holm, Chem. Rev., 1987, 87, 1401.
29. A. M. Bond and R. L. Martin, Coord. Chem. Rev., 1984, 54, 23; D. Coucouvanis, Prog. Inorg. Chem., 1970, 11, 233.
30. T. A. Coffey, G. D. Forster, G. Hogarth and A. Sella, Polyhedron, 1993, 12, 2741.
31. I. S. Kolomnikov, Yu. D. Koreshkov, T. S. Lobeeva and M. E. Volpin, J. Chem. Soc., Chem. Commun., 1970, 1432; E. A. Maatta, Inorg. Chem., 1984, 23, 2650; A. J. Nielson, Inorg. Synth., 1986, 24, 194; M. L. H. Green, G. Hogarth, P. C. Konidaris and P. Mountford, J. Chem. Soc., Dalton Trans., 1990, 3781.
32. T. A. Coffey, G. D. Forster and G. Hogarth, J. Chem. Soc., Dalton Trans., 1996, 183; J. Chem. Soc., Chem. Commun. 19931524.
33. T. A. Coffey, G. D. Forster and G. Hogarth, J. Chem. Soc., Dalton Trans., 1995, 2337.
34. F. W. Moore and M. L. Larson, Inorg. Chem., 1967, 6, 998.
35. D. D. Devore and E. A. Maatta, Inorg. Chem., 1985, 24, 2846.
36. H. H. Fox, K. B. Yap, J. Robbins, S. Cai and R. R. Schrock, Inorg. Chem., 1992, 31, 2287.
37. K. Dehnicke and J. Strahle, Angew. Chem., Int. Ed. Engl., 1981, 20, 413; W. P. Griffith, A. J. Nielson and M. J. Taylor, J. Chem. Soc., Dalton Trans., 1988, 647.
38. D. C. Bradley, S. R. Hodge, J. D. Runnacles, M. Hughes, J. Mason and R. L. Richards, J. Chem. Soc., Dalton Trans., 1992, 1663.
39. A. V. Ivanov, T. Rodyna and O. N. Antzutkin, Polyhedron, 1998, 17, 3101.
40. N. Kaltsoyannis and W.-S. Kim, unpublished results.
41. G. M. Sheldrick, SHELXTL, University of Göttingen, 1985.
42. G. M. Sheldrick, SHELXTL PLUS, Program package for structure solution and refinement, version 4.2, Siemens Analytical Instruments Inc., Madison, WI, 1990.