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Notes Concise Synthesis of Enantiopure (S)-(+)-2,2′-Bis(tert-butyldimethylsilyl)-1,1′-diphosphaferrocene: Anion-Dependence of Its Coordination to Palladium(II) Centers Yves Cabon, Duncan Carmichael,* and Xavier-Fre´de´ric Le Goff Laboratoire “He´te´roe´le´ments et Coordination” Ecole Polytechnique, CNRS, 91128 Palaiseau Cedex, France ReceiVed January 4, 2008 Summary: A conVenient synthesis of enantiopure (S)-(+)-2,2′bis(tert-butyldimethylsilyl)-3,3′,4,4′-tetramethyl-1,1′-diphosphaferrocene is described. The compound shows unusual coordination properties with respect to Otsuka’s Pd(II) dimer di-(S)-chloro-[1-[1-(dimethylamino)ethyl]-2-naphthyl-C,N]palladium(II)].
Introduction The now-extensive chemistry of enantiopure C2-symmetrical phosphines can be traced to Kagan and Dang’s seminal studies of the tartrate-derived DiOP.1 The ubiquitousness of backbonechiral ligands of this sort reflects their well-documented synthetic and conformational2 simplicity as well as the very easy access to a wide range of many enantiopure C2-symmetric precursors that is provided by the chiral pool.3-6 Other classes of enantiopure C2-symmetric ligands (e.g., P-7-9 or axially10,11 chiral) frequently deliver equivalent or superior enantioselectivity; their lesser prevalence can be explained, at least in part, by the effort required to develop simple and efficient routes to the requisite enantiopure building blocks.
* Corresponding author. E-mail:
[email protected]. Fax: intl + 33 1 69334440. Tel: intl + 33 1 69334415. (1) Kagan, H. B.; Dang, T. P. J. Am. Chem. Soc. 1972, 94, 6429. (2) Inasmuch as, for example, a square-planar complex containing a C2symmetric ligand and a prochiral substrate will have only two isomers, while a C1-symmetric phosphine will generate four. See for example: Ramsden, J. A.; Claridge, T. D. W.; Brown, J. M. J. Chem. Soc., Chem. Commun. 1995, 2469. (3) Dieguez, M.; Claver, C.; Pamies, O. Eur. J. Org. Chem. 2007, 462, 1–4634. (4) Dieguez, M.; Pamies, O. P.; Claver, C. Chem. ReV. 2004, 104, 3189– 3215. (5) Dieguez, M.; Pamies, O.; Ruiz, A.; Diaz, Y.; Castillon, S.; Claver, C. Coord. Chem. ReV. 2004, 248, 2165–2192. (6) Blaser, H. U. Chem. ReV. 1992, 92, 935–952. (7) Crepy, K. V. L.; Imamoto, T. AdV. Synth. Catal. 2003, 345, 79– 101. (8) Johansson, M. J.; Kann, N. C. Mini-ReV. Org. Chem. 2004, 1, 233– 247. (9) Grabulosa, A.; Granell, J.; Muller, G. Coord. Chem. ReV. 2007, 251, 25–90. (10) Berthod, M.; Mignani, G.; Woodward, G.; Lemaire, M. Chem. ReV. 2005, 105, 1801–1836. (11) Shimizu, H.; Nagasaki, I.; Saito, T. Tetrahedron 2005, 61, 5405– 5432.
Metallocene-based phosphines12-15 offer exceptional potential because of their easily varied ligand bite angles16 and high modularity17 but, because convenient large-scale routes to simple enantiopureplanar-chiralC2-symmetricalderivativesarescarce,18-23 enantiopure phosphorus-containing metallocenes generally show C1-24,25 orC2-symmetrycombiningplanarandcentralchiralities.26-29 In principle, since the influence of the planar chirality should be expressed particularly favorably if the donor atom is embedded within the metallocene skeleton, we were interested to devise a semimacroscopic route to enantiopure C2-symmetrical planar-chiral phosphaferrocenes; this discrete class was hitherto represented only by 1, which was obtained on a small (12) Arrayas, R. G.; Adrio, J.; Carretero, J. C. Angew. Chem., Int. Ed. 2006, 45, 7674–7715. (13) Barbaro, P.; Bianchini, C.; Giambastiani, G.; Parisel, S. L. Coord. Chem. ReV. 2004, 248, 2131–2150. (14) Atkinson, R. C. J.; Gibson, V. C.; Long, N. J. Chem. Soc. ReV. 2004, 33, 313–328. (15) Colacot, T. J. Chem. ReV. 2003, 103, 3101–3118. (16) Brown, J. M.; Guiry, P. J. Inorg. Chim. Acta 1994, 220, 249–259. (17) Blaser, H. U.; Brieden, W.; Pugin, B.; Spindler, F.; Studer, M.; Togni, A. Top. Catal. 2002, 19, 3–16. (18) Zhang, W. B.; Kida, T.; Nakatsuji, Y.; Ikeda, I. Tetrahedron Lett. 1996, 37, 7995–7998. (19) Reetz, M. T.; Beuttenmuller, E. W.; Goddard, R.; Pasto, M. Tetrahedron Lett. 1999, 40, 4977–4980. (20) Zhang, W. B.; Shimanuki, T.; Kida, T.; Nakatsuji, Y.; Ikeda, I. J. Org. Chem. 1999, 64, 6247–6251. (21) Laufer, R.; Veith, U.; Taylor, N. J.; Snieckus, V. Can. J. Chem. 2006, 84, 356–369. (22) Wang, Y. P.; Weissensteiner, W.; Spindler, F.; Arion, V. B.; Mereiter, K. Organometallics 2007, 26, 3530–3540. (23) Zhang, H. L.; Hou, X. L.; Dai, L. X.; Luo, Z. B. Tetrahedron: Asymmetry 2007, 18, 224–228. For further selected examples see also: Voituriez, A.; Panossian, A.; Fleury-Bregeot, N.; Retailleau, P.; Marinetti, A. J. Am. Chem. Soc. 2008, 130, 14030–14031. Pickett, T. E.; Francesc, X.; Roca, F. X.; Richards, C. J. J. Org. Chem. 2003, 68, 2592–2599. (24) Stepnika, P., Ed. Ferrocenes: Ligands, Materials and Biomolecules; John Wiley: Chichester, 2008. (25) Ferber, B.; Kagan, H. B. AdV. Synth. Catal. 2007, 349, 493–507. (26) Many of these are derived from the Ugi amine: Marquarding, D.; Klusacek, H.; Gokel, G.; Hoffmann, P.; Ugi, I. J. Am. Chem. Soc. 1970, 92, 5389–5393. See for example: Josiphos: Blaser, H. U.; Brieden, W.; Pugin, B.; Spindler, F.; Studer, M.; Togni, A. Top. Catal. 2002, 19, 3– 16. Walphos: Sturm, T.; Xiao, L.; Weissensteiner, W. Chimia 2001, 55, 688–693. (27) Liu, D.; Li, W.; Zhang, X. M. Org. Lett. 2002, 4, 4471–4474. (28) Berens, U.; Burk, M. J.; Gerlach, A.; Hems, W. Angew Chem., Int. Ed. 2000, 39, 1981–1984. Marinetti, A.; Labrue, F.; Genet, J. P. Synlett 1999, 1975–1977. (29) Hayashi, T.; Yamamoto, A.; Hojo, M.; Kishi, K.; Ito, Y.; Nishioka, E.; Miura, H.; Yanagi, K. J. Organomet. Chem. 1989, 370, 129–139.
10.1021/om800009e CCC: $40.75 2009 American Chemical Society Publication on Web 12/15/2008
Notes
Figure 1. Molecular structure (50% probability ellipsoids) of rac1,1′-diphosphaferrocene 6. Selected bond lengths (Å) and angles (deg): P1-C1 1.792(3), C1-C2 1.429(4), C2-C3 1.430(5), C3-C4 1.398(5), P1-Fe 2.273(1), C1-Fe 2.079(3), C2-Fe 2.075(3), C3-Fe 2.091(3), C4-Fe 2.092(3); C4-P1-C1 89.83(2), P1-C1-C2 111.2(2), C1-C2-C3 112.90, C2-C3-C4 111.9(3), C3-C4-P1 114.1(2), P1-Centroid-Centroid-P2 8.3.
scale by chiral HPLC.30 These compounds present the unusual electronic characteristics of the sp2-hybridized phosphorus atom31 and the possibility of very facile installation and variation of substituents in the 2-position through well-established [1,5] sigmatropic shift chemistry.32-34 The silyl-substituted phospholide required for the study was prepared in a one-pot synthesis from 1-phenyl-3,4-dimethylphosphole 235 through an amended version of our previously described methodology32 which furnishes 4 conveniently in 82% yield on ca. 20 g scales. The colorless, air-sensitive phospholide reacts cleanly with anhydrous FeCl2 to provide mixed (ca. 1:1) diastereomers of the requisite phosphaferrocenes, which were separated from refluxing ether; the desired rac-complex 6 crystallized preferentially upon cooling in a nonoptimized yield of 17% (Figure 1).36 The bright red phosphaferrocene products proved air-stable as solids and were found to be quite convenient to handle. Resolving phosphines that contain no organic functional groups is often tedious and, on the laboratory scale, palladiumbased reagents are frequently employed.9,37,38 Obvious constraints mean that such protocols are rarely employed on larger batches but the well-documented39-45 poor compatibility of relatively “hard” palladium(II) centers with “soft” 1,1′-diphosphaferrocene donors of the type implicated here allows a straightforward and economical resolution.46 Otsuka’s naphthyl1-ethylamine-derived complex 1037,38,47 is unreactive toward phosphaferrocenes 6 in donor solvents; however, it shows weak coordination in dichloromethane that can be driven to completion by the addition of silver tetrafluoroborate.48 The product diastereomers, which show an Fe:Pd stoichiometry of 1:2, are quite easily separated by washing with ethylacetate and the less (30) Qiao, S.; Hoic, D. A.; Fu, G. C. Organometallics 1998, 17, 773– 774. (31) Le Floch, P. Coord. Chem. ReV. 2006, 250, 627–681. (32) Carmichael, D.; Mathey, F.; Ricard, L.; Seeboth, N. Chem. Commun. 2002, 2976–2977. (33) Mathey, F. Acc. Chem. Res. 2004, 37, 954–960. (34) Holand, S.; Jeanjean, M.; Mathey, F. Angew. Chem., Int. Ed. 1997, 36, 98–100.
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soluble complex 8 was obtained in monocrystalline form, suitable for a diffraction study, through vapor diffusion of pentane into its dichloromethane solution (Figure 2). The unusual49 monocationic dimer contains an (S)-configured phosphametallocene and a chloride anion bridging the two (S)configured Pd components. The requirement for the silver salt implies a fragility of complex 8 in the presence of halide and, consistently, addition of iodide in polar solvents releases the phosphametallocene and regenerates palladium dimer.50 The two components can be separated by rinsing with pentane, thus allowing the (rather costly) enantiopure palladium fragment to be recovered conveniently and recycled. The approach presented here opens up a straightforward and concise route, which does not require the intervention of preparative chiral HPLC, to the hitherto relatively inaccessible enantiopure planar-chiral C2-symmetrical phosphametallocene structure. The product, 9, can be made to associate or dissociate from enantiopure Pd(II) centers through variation of halide concentration and this provides an unusual and very simple means of recycling the resolving agent. The generality of these procedures and the potential of ligands such as 9 to provoke further unusual coordination chemistry are under investigation. We thank CNRS, Ecole Polytechnique, and the Fondation de l’Ecole Polytechnique (“Gaspard Monge” grant to Y.C.) for support and Dr. J. M. Brown, FRS (Oxford), for acces to the MicroTOF spectrometer.
Experimental Section All operations were performed either using cannula techniques on Schlenk lines under an atmosphere of dry nitrogen or in a Braun Labmaster 130 drybox under dry purified argon. 1-Phenyl-3,4dimethylphosphole 235 and Otsuka’s complex 1038 were obtained as described previously. Solvents were distilled under dry nitrogen, THF and ether from sodium-benzophenone ketyl, pentane from sodium-benzophenone ketyl-tetraglyme, methanol from sodium methoxide, and dichloromethane from P4O10. Deuterobenzene was used as received from Aldrich, while deuterochloroform was deacidified through neutral alumina prior to use. Other solvents were also used as received. NMR measurements were made on a Bruker Avance 300 spectrometer and are referenced to internal C6D5H or CHCl3 and external H3PO4 as appropriate. Mass spectra were obtained from dichloromethane solutions on a Bruker electrospray MicroTOF spectrometer. Melting points were measured between glass slides in air. Compound 4. 1-Phenyl-3,4-dimethylphosphole, 2 (14.6 g, 78 mmol) and freshly beaten lithium strips (2.4 g, 1% sodium, 344 mmol) were stirred in THF for 2.5 h. The excess lithium was removed and, after addition of t-BuCl (15 mL, 137 mmol), the mixture was stirred overnight. The pale solution was evaporated to dryness, treated with toluene, again evaporated to dryness, and extracted with pentane (50 mL). The pentane extracts were separated and discarded; the residue was then resuspended in THF, treated with a single portion of freshly sublimed TBSCl (10.2 g, 68.0 mmol) at ice-bath temperature, evaporated to dryness in Vacuo at e20 °C, extracted with pentane (2 × 75 mL), filtered through Celite, and pumped down (e20 °C) to give a pale oil. Resuspension in icecold THF (200 mL), addition of KOtBu (7.6 g, 68.0 mmol), and stirring for 20 min was followed by concentration of the solution under reduced pressure to give a pale red oil. Addition of pentane, followed by vigorous stirring, gave a white precipitate of the solvent-free potassium 2-tert-butyldimethylsilyl-3,4-dimethylphospholide, 4, which was collected, washed with pentane (2 × 20 mL), and dried (14.7 g, 56 mmol, 72%). (35) Holand, S.; Jeanjean, M.; Mathey, F. Angew. Chem., Int. Ed. 1997, 36, 98–100.
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Notes
Figure 2. Molecular structure (50% probability ellipsoids) of 8 (dichloromethane of solvation and BF4- counterion removed for clarity). Selected bond lengths (Å) and angles (deg): Pd(1)-C(25) 2.007(4); Pd(1)-P(1) 2.227(1); Pd(1)-N(1)2.121(3); Pd(1)-Cl(1) 2.415(1); Pd(2)-C(39) 2.024(4); Pd(2)-N(2)2.127(3); Pd(2)-P(2) 2.224(1); Pd(2)-Cl(1) 2.400(1); Pd(2)-Cl(1)-Pd(1) 137.8(1). 31
P (THF-d8): δ 110.5. 1H (THF-d8): δ 6.91 (d, 1H, P-CH, 2JH-P ) 39 Hz), 2.35 (s, 3H, CH3), 2.28 (s, 3H, CH3), 1.02 (s, 9H, (36) The preparation and separation of meso- and rac-diastereomers of 2,2′-bis(trimethylsilyl)-3,3′,4,4′-tetramethyl-1,1′-diphosphaferrocene, through a much longer synthetic route, has been reported previously by Deschamps and Mathey. No attempt to separate enantiomers was described. See: Deschamps, B.; Mathey, F. Bull. Soc. Chim. Fr. 1996, 133, 541–545. (37) Wild, S. B. Coord. Chem. ReV. 1997, 166, 291–311. (38) Tani, K.; Brown, L. D.; Ahmed, J.; Ibers, J. A.; Yokota, M.; Nakamura, A.; Otsuka, S. J. Am. Chem. Soc. 1977, 99, 7876–7886. (39) Sava, X.; Ricard, L.; Mathey, F.; Le Floch, P. Organometallics 2000, 19, 4899–4903. (40) Ogasawara, M.; Yoshida, K.; Hayashi, T. Organometallics 2001, 20, 3913–3917. (41) Ganter, C.; Kaulen, C.; Englert, U. Organometallics 1999, 18, 5444– 5446. (42) Hayashi, Ogasawara, et al have prepared enantiopure 1,1′-phosphametallocenes (M ) Fe, Ru) without recourse to resolution by using phospholyl ligands that are 2,5-disubsituted with C-chiral (either biaryl or menthyl) groups. These provide good precedence for enantioselection. See: Ogasawara, M.; Ito, A.; Yoshida, K.; Hayashi, T. Organometallics 2006, 25, 2715–2718. Ogasawara, M.; Yoshida, K.; Hayashi, T. Organometallics 2001, 20, 3913. (43) Melaimi, M.; Ricard, L.; Mathey, F.; Le Floch, P. J. Organomet. Chem. 2003, 684, 189–193. (44) Melaimi, M.; Mathey, F.; Le Floch, P. J. Organomet. Chem. 2001, 640, 197–199. (45) Sava, X.; Ricard, L.; Mathey, F.; Le Floch, P. Chem.-Eur. J. 2001, 7, 3159–3166. (46) Dunina, V. V.; Razmyslova, E. D.; Gorunova, O. N.; Livantsov, M. V.; Grishin, Y. K. Tetrahedron: Asymmetry 2005, 16, 817–826. (47) Alcock, N. W.; Hulmes, D. I.; Brown, J. M. J. Chem. Soc., Chem. Commun. 1995, 395–397. (48) The corresponding phenylethylamine derivative reacts with the phosphaferrocene complexes in the absence of Ag+, but separation of the product diastereomers is difficult. (49) A analogue, containing a bridging biquinoline ligand, has been characterized crystallographically. See:Dai, L. X.; Zhou, Z. H.; Zhang, Y. Z.; Ni, C. Z.; Zhang, Z. M.; Zhou, Y. F. J. Chem. Soc., Chem. Commun. 1987, 1760–1762. (50) As noted by a referee, the parallel ring orientation observed in the phosphaferrocene inhibits a chelating coordination mode at the palladium(II) center, which might otherwise be observed with compounds such as 1,1′diphosphazirconocene dichlorides: Nief, F.; Mathey, F.; Ricard, L. J. Organomet. Chem. 1990, 384, 271–278. The latter compounds are faceinverting, so different methods of resolution are likely to be preferable in these cases. For an elegant approach, see: Hollis, T. K.; Wang, L. S.; Tham, F. J. Am. Chem. Soc. 2000, 122, 11737–11738. Freeman, W. P.; Ahn, Y. J.; Hollis, T. K.; Whitaker, J. A.; Vargas, V. C.; Rubio, R. J.; Alingog, K. D.; Bauer, E. B.; Tham, F. S. J. Organomet. Chem. 2008, 693, 2415–2423. (51) The palladium reagent is recovered as the corresponding iodobridged dimer (identified by comparison of the 1H NMR spectrum with an authentic sample). Stirring in acetone with a silver salt and subsequent addition of chloride allows the dichloro-bridged complex 10 to be recovered conveniently.
C(CH3)3), -0.54 (s, 6H, Si(CH3)2). 13C (THF-d8): δ 134.1 (d, P-CH, 1 JC-P ) 45 Hz), 131.6 (s, P-CH-CMe), 129.6 (d, P-C(TBS)-CMe, 1 JC-P ) 62 Hz), 129.3 (s, P-C(TBS)CMe), 26.5 (d, C(CH3)3, 4JC-P ) 2 Hz), 16.7 (s, CH3), 15.8 (s, CH3), 7.3 (s, -C(CH3)3), -3.1 (d, -Si(CH3)2tBu, 3JC-P ) 10 Hz) ppm. Compound 6. FeCl2 (240 mg, 1.89 mmol) was added in one portion to a THF (20 mL) solution of potassium 2-TBS-3,4dimethylphospholide, 4 (1.00 g, 3.78 mmol). The red solution was stirred for 2 h and the solvent was then removed under reduced pressure. The resulting solids were extracted into pentane (20 mL), which was filtered through Celite and removed under reduced pressure. The crude red ca. 1:1 mixture of rac- and mesodiastereoisomers 5 and 6 (899 mg, 1.78 mmol, 94%) was taken up in ether (5 mL) and crystallized at -40 °C. The mother liquor was removed while still cold, giving a solid showing a de of ca. 65%. Two further analogous recrystallizations from ether at -40 °C gave the orange-red diastereopure rac-complex 6 (163 mg, 0.32 mmol, 17%). Material suitable for the X-ray diffraction study was obtained by slow cooling of a saturated refluxing methanol solution. 31P NMR (C6D6): δ -44.2 (AA′XX′, 2JP-H)35.1 Hz, JP-P′ ) 10.5 Hz, JP-H′ ) 0.6 Hz). 1H NMR (C6D6): δ 3.43 (AA′XX, 2H, CH-, 2JH-P ) 35.1 Hz, JH-P′ ) 0.6 Hz, JH-H′ ) 0 Hz), 1.81 (s, 6H, CH-C(CH3)-), 1.77 (s, 6H, C(TBS)-C(CH3)), 0.94 (s, 18H, C(CH3)3), 0.68 (s, 6H, SiMetBu(CH3)), 0.20 (s, 6H, SiMetBu(CH3)). 13C NMR (C6D6): δ 104.0 (s, CH-CMe-), 98.9 (s, C(TBS)-CMe-), 87.0 (d, CH, 1JC-P ) 69.3 Hz), 83.8 (d, P-C(TBS)-, 1JC-P ) 79.7 Hz), 27.34 (s, C(CH3)3), 18.5 (s, CMe3), 17.7 (s, C(TBS)-C(CH3)-), 16.0 (s, CHC(CH3)), 0.0 (s, SiMetBu(CH3)), -1.0 (s, SiMetBu(CH3)) ppm. HRMS: found 506.1804, requires 506.1806. Anal. Calcd for C24H44FeP2Si2: C, 56.90; H, 8.76. Found: C, 56.93; H, 8.71. Mp ) 172-172.5 °C. Compound 8. A dichloromethane solution (5 mL) of rac-2,2′bis(TBS)-3,3′,4,4′-tetramethyl-1,1′-diphosphaferrocene, 6 (100 mg, 0.20 mmol), was treated with equimolar palladium dimer 10 (134.3 mg, 0.20 mmol) and silver tetrafluoroborate (38.9 mg, 0.20 mmol). After stirring for 10 min, the deep yellow solution was filtered through Celite and the solvent was removed under reduced pressure. The yellow mixture of diastereomers was triturated in ethylacetate (5 mL) and centrifuged, and the mother liquor was removed. The process was repeated three times. The residue was recovered and dried under reduced pressure, yielding the diastereopure yellow powder 8. Single crystals suitable for the diffraction study were obtained by vapor diffusion of pentane into a solution of the compound in dichloromethane (104 mg, 0.08mmol, 42%). 31P NMR (DCM-d2): δ 61.4 (d, 2JP-H ) 32 Hz). 1H NMR (DCM-d2): δ 7.80 (d, 2H, H4 and H7, 3JH-H ) 9.1 Hz), 7.51 (m, 2H, H5 and H6), 7.36
Notes
Organometallics, Vol. 28, No. 1, 2009 373 Scheme 1a
a Reaction scheme: (i) Li (excess), THF, 0 °C, 3 h; then tBuCl (excess), THF, 20 °C, 12 h; then TBSCl (1 equiv), THF, 0 °C, 10 min. (ii) KOtBu, (1 equiv), 0 °C, 2h; i+ii: 72%. (iii) FeCl2, (1 equiv), 20 °C, 2 h; then crystallisation from Et2O; for 6: 17%. (iV) 10 (1 equiv), AgBF4 (1 equiv), CH2Cl2, 20 °C, 30 min; then trituration with EtOAc; for 8: 42%. (V) NaI (2 equiv), THF, 20 °C, 1 h, 90%.
(d, H9, J ) 9.3 Hz), 7.08 (dd, H2, J ) 9.1 and 6.0 Hz), 4.59 (qq, 1H, N-CH, 3JH-H ) 7.1 Hz, 4JH-H ) 5.4 Hz), 3.55 (d, P-CH, 2JH-P ) 32 Hz), 3.12 (3H, NMe(CH3), 4JH-H ) 5.4 Hz), 3.02 (s, 3H, N(CH3)Me), 2.29 (s, 3H, P-CH-C(CH3)), 2.12 (s, 3H, P-C(TBS)C(CH3)), 1.92 (s, 3H, NMe2-CH(CH3)), 0.97 (s, 9H, C(CH3)3), 0.60 (s, 3H, Si(CH3)Me(tBu)), 0.11 (s, 3H, SiMe(CH3)(tBu)). 13C NMR (DCM-d2): δ 149.2 (s, C1), 146.0 (s, C10), 137.6 (d, C2, J ) 21.4 Hz), 131.2 (s, C3), 128.8 (s, C4), 128.3 (s, C8), 126.3 (s, C5), 125.8 (d, C9, J ) 7.1 Hz), 125.1 (s, C6), 123.4 (s, C7), 103.3 (d, -PCH-CMe, 2JC-P ) 6.4 Hz), 100.6 (s, P-C(TBS)-CMe), 73.3 (s, NMe2-CHMe), 69.5 (d, P-C(TBS), 1JC-P ) 61.0 Hz), 66.7 (d, P-CH, 1 JC-P ) 40.8 Hz), 53.2 (s, NMe(CH3)), 49.7 (s, N(CH3)Me), 26.4 (s, C(CH3)3), 23.6 (s, NMe2-CH(CH3)), 18.3 (s, CMe3), 13.9 (d, P-CH-C(CH3), 3JC-P ) 6 Hz), 13.4 (d, P-C(TBS)-C(CH3), 3JC-P ) 7 Hz), 0.0 (s, -Si(CH3)Me(tBu)), -2.9 (s, -SiMe(CH3)(tBu)). Anal. Calcd for C105H154B2Cl4F8Fe2N4P4Pd4Si4 (8 · 1/2CH2Cl2): C, 49.24; H, 6.06. Found: C, 49.14; H, 6.14. Mp ) 224-225 °C (dec). The mother liquors were combined and shown to have a de of ca. 80% in favor of 7. Compound 9. A THF (3 mL) solution of the diastereopure palladium complex 8 (100 mg, 0.08 mmol) was treated with sodium iodide (24.0 mg, 0.16 mmol). The solution was stirred for 30 min, and the THF was removed under reduced pressure. The solids were extracted with pentane (10 mL), and the extract was filtered through Celite. Removal of solvent under reduced pressure gave deep red, air-stable crystals of 9 (36.9 mg, 0.07 mmol, 90%). [R]D25 +55 (c 0.5, CH2Cl2). Anal. Calcd for C24H44FeP2Si2: C, 56.90; H, 8.76. Found: C, 56.77; H, 8.71. Mp: 165-167 °C. Other data as for 6. Crystallographic data: 6: C24H44FeP2Si2, M ) 506.56, monoclinic, space group P21/c, a ) 7.462(1) Å, b ) 23.903(1) Å, c ) 16.032(1) Å, β ) 108.35(1)°, V ) 2714.1(4) Å3, Z ) 4, Dc ) 1.240 g cm-3, F(000) ) 1088. Graphite-monochromated Mo KR radiation, λ ) 0.71069 Å, µ ) 0.77 cm-1, T ) 150(1) K. Of 6216 independent reflections collected on a Kappa CCD diffractometer from a red needle of dimensions 0.20 × 0.20 × 0.04 mm over h ) -9 to 6, k ) -31 to 28, l ) -17 to 20, 4911 having I > 2σ(I) were refined on F2 using direct methods in SHELXL. wR2 ) 0.146, R1 ) 0.055, GoF ) 1.062. For 8 · 1/2CH2Cl2: C105H154B2Cl4F8Fe2N4P4Pd4Si4, M ) 2561.4, tetragonal, space group P41212, a ) 21.022(1) Å, b ) 21.022(1) Å, c ) 30.883(1) Å, V ) 13648.0(1) Å3, Z ) 4, Dc ) 1.288 g cm-3, F(000) ) 5424. Graphite-monochromated Mo KR radiation, λ ) 0.71069 Å, µ ) 0.973 cm-1, T ) 150.0(10) K. Of 15 613 independent reflections from an orange needle of 0.40 × 0.16 × 0.12 mm collected as above over h ) -27 to 26; k ) -22 to 25; l ) -28 to 40, 14 179 having I > 2σ(I) were refined on F2 using direct methods in SHELXL. wR2 ) 0.128, R1 ) 0.045, GoF ) 1.072, Flack’s parameter ) -0.015(17). Full data are provided as Supporting Information. Supporting Information Available: CIF files and full crystallographic tables for complexes 6 and 8. This material is available free of charge via the Internet at http://pubs.acs.org. OM800009E
