Tris(pyrrolyl)phosphine-Substituted Acetylene-Dicobaltcarbonyl Complexes: Syntheses, Structural Characterization, and Reactivity Studies Jaume Castro, † Albert Moyano,* ,† Miquel A. Perica `s, † Antoni Riera, † Miguel Angel Maestro, ‡ and Jose ´ Mahı ´a ‡ Unitat de Recerca en Sı ´ntesi Asime ` trica (URSA), Departament de Quı ´mica Orga ` nica, Facultat de Quı ´mica, Universitat de Barcelona, Martı ´ i Franque ` s 1-11, 08028 Barcelona, Spain, and Servicios Xerais de Apoio a ´ Investigacio ´ n, Campus da Zapateira, s/n, Universidade da Corun ˜ a, 15071 A Corun ˜ a, Spain Received November 22, 1999 The first tris(pyrrolyl)phosphine-substituted alkyne-dicobaltcarbonyl complexes have been prepared by reaction of the corresponding dicobalthexacarbonyl complexes with tris(pyrrolyl)- phosphine, and their solid-state structures have been studied by X-ray diffraction. In accordance with the strong π-acceptor character of the tris(pyrrolyl)phosphine ligand, these complexes present a Pauson-Khand reactivity very similar to that of the parent, unsub- stituted ones. On the other hand, the cobalt-stabilized propargyl cations derived from tris- (pyrrolyl)phosphine-substituted (2-propynol)dicobaltcarbonyl complexes undergo an unprec- edented intramolecular Nicholas reaction in which one of the pyrrole rings acts as an internal nucleophile, and that gives rise to a new structural type of chelated alkyne-dicobaltcarbonyl complexes. Introduction Trivalent phosphorus derivatives (phosphines or phos- phites) find wide application in coordination chemistry, organometallic chemistry, and homogeneous catalysis. 1 Smooth variation of the steric or electronic character- istics of the phosphorus substituents allows the modula- tion of the character (σ-donor, π-acceptor) of these ligands; this fact has stimulated research in this area toward the preparation of new ligands with designed properties. Phosphine-substituted alkyne-dicobaltcarbonyl com- plexes 2 have been studied in connection with two important synthetic processes: the Pauson-Khand 3 and Nicholas 4 reactions. Both achiral 5 and chiral 6 phos- phines have been investigated, the latter in the context of the development of enantioselective versions of these reactions. However, the substitution of a carbon monoxide by a phosphine ligand is usually accompanied by a loss of reactivity of the corresponding complexes. Billington and Pauson 7 have employed a variety of substituted alkyne-dicobaltcarbonyl complexes in Pauson-Khand reactions using 2,5-dihydrofuran as a † Universitat de Barcelona. ‡ Universidade da Corun ˜ a. (1) See the following and references therein: (a) Wilson, M. R.; Woska, D. C.; Prock, A.; Giering, W. P. Organometallics 1993, 12, 1742-1752. (b) Corbridge, D. E. C. Phosphorus. An Outline of its Chemistry, Biochemistry and Techology, 4th ed.; Elsevier: New York, 1990. (c) Levason, W. The Chemistry of Organophosphorus Compounds; Hartley, R. F., Ed.; Wiley: New York, 1990; Vol. 1, Chapter 15. (d) McCauliffe, C. A. Comprehensive Coordination Chemistry; Wilkinson, G., Gillard, R. D., McCleverty, J. A., Eds.; Pergamon: Oxford, 1987; Vol. 2, p 989. (e) Collman, J. P.; Hegedus, L. S.; Norton, J. R.; Finke, R. G. Principles and Applications of Organotransition Metal Chemistry; University Science Books: Mill Valley, CA, 1987; p 66. (f) Homogeneous Catalysis with Metal Phosphine Complexes; Pignolet, L. H., Ed.; Plenum: New York, 1983. (2) For the use of (µ-η 2 , η 2 -alkyne)Co2(CO)6 systems in synthesis, see: (a) Dickson, R. S.; Fraser, P. J. Adv. Organomet. Chem., 1974, 12, 323-377. (b) Schore, N. E. Chem. Rev. 1988, 88, 1081-1119. Protection of triple bonds: (c) Nicholas, K. M.; Pettit, R. Tetrahedron Lett. 1971, 3475-3478. (d) Seyferth, D.; Nestle, M. O.; Wehman, A. T. J. Am. Chem. Soc. 1975, 97, 7417-7426. As reagents in a variety of carbon-carbon and carbon-heteroatom bond formation processes: (e) Schore, N. E.; Najdi, S. D. J. Org. Chem. 1987, 52, 5296-5298. (f) Nagasawa, T.; Taya, K.; Kitamura, M.; Suzuki, K. J. Am. Chem. Soc. 1996, 118, 8949-8950. (g) Dare, S.; Ducroix, B.; Bernard, S.; Nicholas, K. M. Tetrahedron Lett. 1996, 37, 4341-4344. (3) Reviews on the Pauson-Khand reaction: (a) Pauson, P. L. In Organometallics in Organic Synthesis. Aspects of a Modern Interdis- ciplinary Field; de Meijere, A.; tom Dieck, H., Eds.; Springer: Berlin, 1988; pp 233-246. (b) Harrington, P. J. Transition Metals in Total Synthesis; Wiley: New York, 1990; pp 259-301. (c) Schore, N. E. Organic Reactions 1991, 40,1-90. (d) Schore, N. E. In Comprehensive Organic Synthesis; Trost, B. M., Ed.; Pergamon Press: Oxford, 1991; Vol. 5, pp 1037-1064. (4) Nicholas reaction: (a) Nicholas, K. M. Acc. Chem. Res. 1987, 20, 207-214. (b) Caffyn, A. J. M.; Nicholas, K. M. In Comprehensive Organometallic Chemistry-II; Hegedus, L. S., Ed.; Pergamon: Oxford, 1995; Vol. 12, p 685. (c) Mukai. C.; Hanaoka, M. Synlett 1996, 11-17. (5) Monodentate phosphines: (a) Jeffery, J. C.; Pereira, R. M. S.; Vargas, M. D.; Went, M. J. J. Chem. Soc., Dalton Trans. 1995, 1805- 1811. (b) Bradley, D. H.; Khan, M. A.; Nicholas, K. M. Organometallics 1992, 11, 2598-2607. (c) Hughes, R. P.; Doig, S. J.; Hemond, R. C.; Smith, W. L.; Davis, R. E.; Gadol, S. M.; Holland, K. D. Organometallics 1990, 9, 2745-2753. (d) Bonnet, J.-J.; Mathieu, R. Inorg. Chem. 1978, 17, 1973-1976. (e) Bird, P. H.; Fraser, A. R.; Hall, D. N. Inorg. Chem. 1977, 16, 1923-1931. (f) Anderson, J. C.; Taylor, B. F.; Viney, C.; Wilson, G. J. J. Organomet. Chem. 1996, 519, 103-106. Bidentate phosphines: (g) Gelling, A.; Wend, M. J. J. Organomet. Chem. 1993, 455, 203-210. (h) Yang, K.; Bott, S. G.; Richmond, M. G. J. Organomet. Chem. 1996, 516, 65-80. (i) Gelling, A.; Jeffery, J. C.; Povey, D. C.; Went, M. J. J. Chem. Soc., Chem. Commun. 1991, 349-351. (j) Mirza, H. A.; Vittal, J. J.; Puddephatt, R. J.; Frampton, C. S.; Manojlovic- Muir, L.; Xia, W.; Hill, R. H. Organometallics 1993, 12, 2767-2776. (6) (a) Bladon, P.; Pauson, P. L.; Brunner, H.; Eder, R. J. Organomet. Chem. 1988, 355, 449-454. (b) Brunner, H.; Niedernhuber, A. Tetra- hedron: Asymmetry 1990, 1, 711-714. (c) Hay, A. M.; Kerr, W. J.; Kirk, G. G.; Middlemiss, D. Organometallics 1995, 14, 4986-4988. (d) Castro, J.; Moyano, A.; Perica ´ s, M. A.; Riera, A.; Alvarez-Larena, A.; Piniella, J. F. J. Organomet. Chem. 1999, 585, 53-58. (e) Derdau, V.; Laschat, S.; Dix, I.; Jones, P. G. Organometallics 1999, 18, 3859-3864. (7) Billington, D. C.; Helps, I. M.; Pauson, P. L.; Thomson, W.; Willison, D. J. Organomet. Chem. 1988, 354, 233-242. 1704 Organometallics 2000, 19, 1704-1712 10.1021/om990914y CCC: $19.00 © 2000 American Chemical Society Publication on Web 04/06/2000