NMR Studies of Chiral P,S-Chelate Platinum, Rhodium, and Iridium Complexes and the X-ray Structure of a Palladium(II) Allyl Derivative Alberto Albinati, † Ju ¨ rgen Eckert, ‡ Paul Pregosin,* ,§ Heinz Ru ¨ egger, § Renzo Salzmann, § and Corinna Sto ¨ssel § Laboratory of Inorganic Chemistry, ETH-Zentrum, CH-8092 Zu ¨ rich, Switzerland, Institute of Pharmaceutical Chemistry, University of Milan, I-20131 Italy, and Los Alamos National Laboratory, Los Alamos, New Mexico Received September 25, 1996 X Several Rh(I), Ir(III), and Pt(II) complexes of the chiral P,S-bidentate ligand 2 have been prepared and characterized. Detailed two-dimensional NMR studies show that (i) the boat- type chelate ring and the stereogenic sulfur center can invert rapidly at ambient temperature and (ii) the sulfur donor may dissociate, essentially destroying the chiral pocket. The solid- state structure of [Pt(η 3 -C 3 H 5 )(2)]PF 6 (3) has been determined and the sulfur substituent shown to have an axial orientation. The six-membered chelate ring takes up a boatlike conformation. As shown by an X-ray diffraction study for 3, and via incoherent inelastic neutron scattering (IINS) measurements for the Pd analog, 4, the OH group is remote from the metal atom. Introduction Chiral chelating ligands are now widely employed in enantioselective homogeneous catalysis. 1 Initially, diphosphine ligands predominated; 2 however, in recent studies mixed donor ligands have been shown to be advantageous. 3-7 Specifically, the development of P,O- and P,N-donor ligands has led to high observed enan- tiomeric excesses in allylic alkylation and Heck chem- istry. 8 We have recently shown 9 that a P,S combination, in which the S-donor arises from a thioglucose, e.g. 1, can have some utility. We have also studied ligand 2 in connection with the Pd-catalyzed allylic alkylation reaction. 1 Ligand 2 was potentially interesting in that (i) its chirality is not associated with the phosphine backbone, (ii) it is a mixed-donor bidentate species, and (iii) there might be some interesting secondary chemistry associated with the OH function. Unfortunately, in the allylation reac- tion, the observed enantiomeric excesses were disap- pointing. 10 Since the successful design of future cata- lysts depends on avoiding auxiliaries prone to “err”, it seemed important to trace the problems in the chem- istry of this ligand. We report here on some Pt(II), Rh- (I), and Ir(III) complexes of 2 and suggest that the lack of selectivity associated with 2 arises from the presence † University of Milan. ‡ Los Alamos National Laboratory. § ETH Zu ¨ rich. X Abstract published in Advance ACS Abstracts, February 1, 1997. (1) Trost, B. M.; van Vranken, D. L. Chem. Rev. 1996, 96, 395. Togni, A.; Venanzi, L. M. Angew. Chem. 1994, 33, 497. Tanner, D. Angew. Chem., Int. Ed. Engl. 1994, 106, 625. Hayashi, T. In Catalytic Asymmetry Synthesis; Ojima, I., Ed.; VCH: Deerfield Beach, FL, 1993; p 325. (2) Mackenzie, P. B.; Whelan, J.; Bosnich, B. J. Am. Chem. Soc. 1985, 107, 2046. Auburn, P. R.; Mackenzie, P. B.; Bosnich, B. J. Am. Chem. Soc. 1985, 107, 2033. Trost, B. M.; Breit, B.; Peukert, S.; Zambrano, J.; Ziller, J. W. Angew. Chem. 1995, 107, 2577. Hayashi, T.; Yamamoto, A. Tetrahedron Lett. 1988, 29, 669. Hayashi, T.; Yamamoto, A.; Ito, Y.; Nishioka, E.; Miura, H.; Yanagi, K. J. Am. Chem. Soc. 1989, 111, 6301. Togni, A.; Breutel, C.; Soares, M.; Zanetti, N.; Gerfin, T.; Gramlich, V.; Spindler, F.; Rihs, G. Inorg. Chim. Acta 1994, 222, 213. Togni, A.; Breutel, C.; Schnyder, A.; Spindler, F.; Landert, H.; Tijani, A. J. Am. Chem. Soc. 1994, 116, 4062. Togni, A.; Barbaro, P. Organometallics 1995, 14, 3570. (3) Brown, J. M.; Hulmes, D. I.; Guiry, P. J. Tetrahedron 1994, 50, 4493. Brown, J. M.; Lloyd-Jones, G. C. J. Am. Chem. Soc. 1994, 116, 866. (4) Rieck, H.; Helmchen, G. Angew. Chem. 1995, 107, 2881. Knu ¨ hl, G.; Sennhenn, P.; Helmchen, G. J. Chem. Soc., Chem. Commun. 1995, 1845. Sprinz, J.; Kiefer, M.; Helmchen, G.; Reggelein, M.; Huttner, G.; Zsolnai, I. Tetrahedron Lett. 1994, 35, 1523. Sprinz, J.; Helmchen, G. Tetrahedron Lett. 1993, 1769. (5) Lloyd-Jones, G. C.; Pfaltz, A. Angew. Chem. 1996, 107, 534. Pfaltz, A. Acc. Chem. Res. 1993, 26, 339. von Matt, P.; Pfaltz, A. Angew. Chem., Int. Ed. Engl. 1993, 32, 566. Leutenegger, U.; Umbricht, C.; Fahrni, P.; von Matt, P.; Pfaltz, A. Tetrahedron 1992, 48, 2143. Mueller, D.; Umbricht, B.; Weber, A.; Pfaltz, A. Helv. Chim. Acta 1991, 74, 232. (6) Frost, C. G.; Williams, M. J. Synlett 1994, 551. Dawson, G.; Frost, C. G.; Williams, J. M. J. Tetrahedron Lett. 1993, 34, 3149. (7) Togni, A.; Burckhardt, U.; Gramlich, V.; Pregosin, P.; Salzmann, R. J. Am. Chem. Soc. 1996, 118, 1031. Burckhardt, U.; Hintermann, L.; Schnyder, A.; Togni, A. Organometallics 1995, 14, 5415. Abbenhuis, H. C. L.; Burckhardt, U.; Gramlich, V.; Togni, A.; Albinati, A.; Mueller, B. Organometallics 1994, 13, 4481. (8) Loiseleur, O.; Meier, P.; Pfaltz, A. Angew. Chem. 1996, 108, 218. (9) Albinati, A.; Pregosin, P. S.; Wick, K. Organometallics 1996, 15, 2419. (10) Herrmann, J.; Pregosin, P. S.; Salzmann, R.; Albinati, A. Organometallics 1995, 14, 3311. 579 Organometallics 1997, 16, 579-590 S0276-7333(96)00823-0 CCC: $14.00 © 1997 American Chemical Society