Oxygen vs. carbon co-ordination of α-keto-stabilized phosphorus ylides Ph₃P=C(H)COR (R = Me, Ph or OMe) to palladium(II) cationic complexes

Abstract

The reactivity of several C,N-cyclometallated palladium(II) complexes [Pd(C₆H₄CH₂NMe₂-2)L(L ′)]ClO₄ and [Pd{R-C₆H₄CH(Me)NMe₂-2 }L(L′)]ClO₄ [L = PPh₃ or pyridine (py), L′ = NCMe or thf (tetrahydrofuran); L = L′ = NCMe] towards α-keto-stabilized phosphorus ylides Ph₃P=C(H)COR (R = Me, Ph or OMe) has been studied. When L = PPh₃, L′ = thf the ylide co-ordinates invariably through the carbonyl oxygen atom, and trans to the orthometallated C₆H₄ group, a rather unusual mode for the soft palladium(II) centre. When L = py, L′ = thf the co-ordination mode of the ylide and its site varies as a function of the nucleophilic character of the ylidic carbon atom. Thus, Ph₃P=C(H)COMe (where the ylidic carbon is a poor nucleophile) co-ordinates through the carbonyl oxygen atom (trans to the C₆H₄ group), while the better nucleophile Ph₃P=C(H)CO₂Me co-ordinates through the ylidic carbon and trans to the NMe₂ group. When L = L′ = NCMe the less nucleophilic ylides Ph₃=C(H)COR (R = Me or Ph), give products in which a mixture of both O- and C-co-ordination modes are found, while Ph₃P=C(H)CO₂Me gives exclusively C-co-ordination trans to the NMe₂ group. Infrared and NMR spectroscopies allow the unambiguous characterization of these products, and the crystal structure of [Pd(C₆H₄CH₂NMe₂-2)(py) {C(H)(CO₂Me)PPh₃}]ClO₄ has also been determined.

References

1. A. W. Johnson, W. C. Kaska, K. A. O. Starzewski and D. A. Dixon, Ylides and Imines of Phosphorus, Wiley, New York, 1993, ch. 14 and refs. therein.
2. M. E. Jung and S. A. Abrecht, J. Org. Chem., 1988, 53, 423.
3. (a) J. Buckle, P. G. Harrison, T. J. King and J. A. Richards, J. Chem. Soc., Chem. Commun., 1972, 1104; (b) J. Buckle and P. G. Harrison, J. Organomet. Chem., 1973, 49, C17; (c) I. Kawafune and G. Matsubayashi, Inorg. Chim. Acta, 1983, 70, 1; (d) R. Usón, J. Forniés, R. Navarro, P. Espinet and C. Mendivil, J. Organomet. Chem., 1985, 290, 125; (e) J. A. Albanese, D. A. Staley, A. L. Rheingold and J. L. Burmeister, Inorg. Chem., 1990, 29, 2209.
4. (a) H. Nishiyama, K. Itoh and Y. Ishii, J. Organomet. Chem., 1975, 87, 129; (b) E. T. Weleski, J. L. Silver, M. D. Jansson and J. L. Burmeister, J. Organomet. Chem., 1975, 102, 365; (c) P. Bravo, G. Fronza and T. Ticozzi, J. Organomet. Chem., 1976, 111, 361; (d) H. Koezuka, G. Matsubayashi and T. Tanaka, Inorg. Chem., 1976, 15, 417; (e) G. Fronza, P. Bravo and C. Ticozzi, J. Organomet. Chem., 1978, 157, 299; (f) M. Onishi, Y. Ohama, K. Hiraki and H. Shintani, Polyhedron, 1982, 1, 539; (g) G. Facchin, R. Bertani, M. Calligaris, G. Nardin and M. Mari, J. Chem. Soc., Dalton Trans., 1987, 1381; (h) J. A. Albanese, A. L. Rheingold and J. L. Burmeister, Inorg. Chim. Acta, 1988, 150, 213; (i) J. Vicente, M. T. Chicote and J. Fernández-Baeza, J. Organomet. Chem., 1989, 364, 407; (j) G. Facchin, R. Bertani, L. Zanotto, M. Calligaris and G. Nardin, J. Organomet. Chem., 1989, 366, 409; (k) J. Vicente, M. T. Chicote, M. C. Lagunas and P. G. Jones, J. Chem. Soc., Dalton Trans., 1991, 2579; (l) M. Kalyanasundari, K. Panchanatheswaran, W. T. Robinson and H. Wen, J. Organomet. Chem., 1995, 491, 103.
5. L. R. Falvello, S. Fernández, R. Navarro and E. P. Urriolabeitia, Inorg. Chem., 1996, 35, 3064.
6. F. I. Randall and A. W. Johnson, Tetrahedron Lett., 1968, 24, 2841.
7. H. J. Bestmann and J. P. Snyder, J. Am. Chem. Soc., 1967, 89, 3936.
8. A. J. Speziale and K. W. Ratts, J. Am. Chem. Soc., 1963, 85, 2790.
9. M. Kalyanasundari, K. Panchanatheswaran, V. Parthasarathi, W. T. Robinson and H. Wen, Acta Crystallogr., Sect. C, 1994, 50, 1738.
10. P. Braunstein, D. Matt, Y. Dusausoy, J. Fischer, A. Mitschler and L. Ricard, J. Am. Chem. Soc., 1981, 103, 5115.
11. (a) J. Spencer, M. Pfeffer, N. Kyritsakas and J. Fischer, Organometallics, 1995, 14, 2214; (b) M. Pfeffer, N. Sutter-Beydoun, A. De Cian and J. Fischer, J. Organomet. Chem., 1993, 453, 139.
12. A. J. Canty, in Comprehensive Organometallic Chemistry II, eds. G. Wilkinson, F. G. A. Stone and E. W. Abel, Pergamon, Oxford, 1995, vol. 9, p. 271 and refs. therein.
13. R. S. Cahn, C. Ingold and V. Prelog, Angew. Chem., Int. Ed. Engl., 1966, 5, 385.
14. A. J. Deeming, I. P. Rothwell, M. B. Hursthouse and L. New, J. Chem. Soc., Dalton Trans., 1978, 1490.
15. (a) A. D. Ryabov, G. M. Kazankov, A. K. Yatsimirsky, L. G. Kuz'mina, D. Y. Burtseva, N. V. Dvortsova and V. A. Polyakov, Inorg. Chem., 1992, 31, 3083; (b) F. Maassarani, M. Pfeffer, G. Le Borgne and D. Grandjean, Organometallics, 1986, 5, 1511.
16. (a) R. G. Pearson, Inorg. Chem., 1973, 12, 712; (b) M. Pfeffer, D. Grandjean and G. Le Borgne, Inorg. Chem., 1981, 20, 4426.
17. J. A. Davies and F. R. Hartley, Chem. Rev., 1981, 81, 79.
18. J. Dehand, J. Jordanov, M. Pfeffer and M. Zinsius, C. R. Hebd. Seances Acad. Sci., Ser. C, 1975, 281, 651.
19. L. R. Falvello, S. Fernández, R. Navarro and E. P. Urriolabeitia, New. J. Chem., in the press.
20. S. Y. M. Chooi, M. K. Tan, P. H. Leung and K. F. Mok, Inorg. Chem., 1994, 33, 3096.
21. W. C. Wolsey, J. Chem. Educ., 1973, 50, A335.
22. J. Forniés, R. Navarro and V. Sicilia, Polyhedron, 1988, 7, 2659.
23. F. Ramírez and S. Dershowitz, J. Org. Chem., 1957, 22, 41.
24. O. Isler, H. Gutmann, M. Montavon, R. Ruegg, G. Ryser and P. Zeller, Helv. Chim. Acta, 1957, 40, 1242.
25. G. M. Sheldrick, SHELXS 86, Acta Crystallogr., Sect. A, 1990, 46, 467.
26. G. M. Sheldrick, SHELXL 93; FORTRAN program for the refinement of crystal structure from diffraction data, University of Göttingen, 1993.
27. K. Harms, personal communication, 1995.
28. SHELXTL PLUS, Release 4-21/V, Siemens Analytical X-Ray Instruments, Madison, WI, 1990.