Platinum-catalyzed asymmetric hydrophosphination of activated olefins using the catalyst precursor Pt(R,R-Me-Duphos)(trans-stilbene) (1) gives chiral phosphines with control of stereochemistry at phosphorus or carbon centers. Stoichiometric reactions of 1 allow observation of P-H oxidative addition, diastereoselective olefin insertion, and reductive elimination steps, which make up the proposed catalytic cycle.Chiral phosphines, valuable ligands for metal-catalyzed asymmetric reactions, 1 are usually prepared either by resolution or by using a stoichiometric amount of a chiral auxiliary. 2 Surprisingly little work has been reported on metal-catalyzed asymmetric syntheses. 3 We report here that Pt-catalyzed asymmetric hydrophosphination of activated olefins 4 can be used to prepare chiral phosphines with control of stereochemistry at phosphorus or carbon. Although the enantiomeric excesses (ee's) available thus far are low, mechanistic understanding may allow further development of these new reactions.Scheme 1 shows a mechanism for Pt-catalyzed hydrophosphination, proposed on the basis of our previous studies. 5 After P-H oxidative addition, P-C bond formation occurs by selective insertion of the olefin into the Pt-P bond. Reductive elimination forms the product and regenerates Pt(0). Since the insertion step can be diastereoselective, 5,6 use of a chiral Pt catalyst could lead to enantio-enriched product. For example, a disubstituted olefin could give a phosphine (Scheme 2) with controlled stereochemistry at either of the alkene carAn important recent exception is Burk's synthesis of Duphos ligands, which relies on Ru-Binap-catalyzed asymmetric hydrogenation of -keto esters (Burk, M. J.; Feaster, J. E.; Nugent, W. A.; Harlow, R. L. J. Am. Chem. Soc. 1993, 115, 10125-10138).(4) Pringle and co-workers have shown that Pt-catalyzed hydrophosphination can be used to prepare functionalized phosphines. (a) Costa, E.; Pringle, P. G.; Worboys, K. Chem. Commun. 1998, 49-50. (b) Costa, E.; Pringle, P. G.; Smith, M. B.; Worboys, K. Nolan, S. P.; Porchia, M.; Sishta, C.; Marks, T. J. In Energetics of Organometallic Species; Martinho Simoes, J. A., Ed.; Kluwer: Dordrecht, 1992; pp 35-51. (5) (a) Wicht, D. K.; Kourkine, I. V.; Lew, B. M.; Nthenge, J. M.; Glueck, D. S. J. Am. Chem. Soc. 1997, 119, 5039-5040. (b) Wicht, D. K.; Kourkine, I. V.; Kovacik, I.; Glueck, D. S.; Concolino, T. E.; Yap, G. P. A.; Incarvito, C. D.; Rheingold, A. L. Organometallics 1999, 18, 5381-5394.Scheme 1. Proposed Mechanism for Pt-Catalyzed Hydrophosphination a a [Pt] ) Pt(diphosphine), X ) CN, CO2R, or other electronwithdrawing group. Scheme 2. Proposed Mechanism for Pt-Catalyzed Asymmetric Hydrophosphination of Disubstituted Alkenes a a [Pt] ) Pt(chiral diphosphine), X ) CN, CO2R, or other electron-withdrawing group. 950Organometallics 2000, 19,[950][951][952][953] 10.

The structures of three ortho-lithiated phenyloxazolines, the parent (1), the para-tert-butyl analogue (2), and the para-chloro analogue (3), were studied in solution. All three compounds are mixtures of monomers and dimers in THF/ether mixed solvents, with 2 the most aggregated and 3 the least. They are converted to monomers with HMPA and PMDTA. In the PMDTA complexes, the lithium appears to still be chelated to the oxazoline ring. Single-crystal X-ray structures were obtained for 1 and 2. Both are centrosymmetric dimers of B-type (each lithium coordinated to one oxazoline ring).

Attempts to prepare fluoroalkyl(hydrido) complexes of iridium by reactions of [Ir(C5Me5)(PMe3)(RF)I] {RF = CF2CF2CF3, CF(CF3)2} with either NaBH4 or LiAlH4 afford (inter alia) iridium hydrides [Ir(C5Me5)(PMe3)(CHCFCF3)H] or [Ir(C5Me5)(PMe3)(C{CF3}CF2)H], in which the fluoroalkyl groups are converted to unsaturated ligands via apparent α-CF activation and elimination of HF. A clean and selective route to desired saturated fluoroalkyl(hydrido) complexes [Ir(C5Me5)(PMe3)(RF)H] {RF = CF2CF2CF3, CF2CF3, CF(CF3)2} is afforded by treatment of the aqua cations [Ir(C5Me5)(PMe3)(RF)(H2O)]BF4 with 1,8-bis(dimethylamino)naphthalene (“Proton Sponge”). The reaction also affords the corresponding rhodium analogue [Rh(C5Me5)(PMe3)(CF2CF2CF3)H] from the corresponding aqua precursor. The source of the hydride is unambiguously defined as an N−CH3 group by using the perdeuteromethylated analogue of Proton Sponge, which provides clean routes to the corresponding fluoroalkyl(deutero) complexes of iridium. Triethylamine or cobaltocene also effect this reaction, though not as cleanly as Proton Sponge. The mechanism of this novel transformation is discussed. The fluoroalkyl(hydrido) complexes are thermally robust, but do react with chlorinated solvents to give the corresponding chlorides. Single-crystal X-ray diffraction studies of the structures of [Ir(C5Me5)(PMe3)(CF2CF2CF3)H], [Rh(C5Me5)(PMe3)(CF2CF2CF3)H], and [Rh(C5Me5)(PMe3)(CF2CF2CF3)Cl] are reported and compared.

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