Synthesis of novel (P,S) ligands based on chiral nonracemic episulfides. Use in asymmetric hydrogenation

Article abstract of DOI:10.1021/om990023q

A strategy for the synthesis of new chiral (P,S) ligands is described. It is based on the opening of chiral nonracemic episulfides using phosphorus nucleophiles. Chiral episulfides, CH₂CH(R)S, 4, are derived either from the reaction of thiourea with the corresponding epoxide (4a, R = CH₃) or from the stepwise conversion of chiral diols to the episulfide via the thiocarbonate (4b, R = cyclohexyl). The reaction of lithium salts of phosphines, R₂′PLi (R = Ph, cyclohexyl), with episulfides is regioselective and gives the ring-opened products 5-8, PR₂CH₂CH(R′)SLi. Upon treatment with electrophiles, R″Cl (R″ = -CH₂Ph, -CH₂-(C₅(CH₃)₅), -CH₂(C¹⁴H₉), -CH(C₁₄H¹²)), they give novel chiral (P,S) ligands, PR′₂CH²CH-(R′)SR″, 9-17 in 31-93% yield. Reactions of PCy₂CH₂CH(CH³)SCH₂(C ₆(CH₃)₅), 11, with LMCl₂ (LM = (DME)Ni, (COD)Pd, and (NBD)Pt; DME = dimethoxyethane, COD - 1,5-cyclooctadiene, NBD = 2,5-norbornadiene) yields the corresponding metal complexes, (11)-MCl₂, 18. Variable-temperature ¹H NMR spectroscopy indicates that in these complexes sulfur inversion occurs on the NMR time scale. Compound 18b (M = Pd) was characterized by single-crystal X-ray analysis. Reaction of PCy₂CH₂CH(CH₃)SCH(C₁₄H ₁₂), 13, with (COD)-PdCl₂ results in C-S bond cleavage and produces a dinuclear thiolato-bridged complex, dichlorobis{μ-[2-(dicyclohexylphosphino)1-(methyl)ethanethiolato]-P,μ-S}- dipalladium(II), 19. Complex 19 was characterized by single-crystal X-ray analysis. Reactions of ligands 9-17 with Rh(COD)₂⁺OTf^- (COD = cyclooctadiene, OTf^- = CF₃SO₃^-) yields rhodium complexes that have been tested in the asymmetric hydrogenation of α-enamide methyl esters, providing enantioselectivities of up to 51%. The rhodium complex obtained with ligand 11, (11)Rh-(COD)OTf, 22, was characterized by single-crystal X-ray analysis.

Full text of DOI:10.1021/om990023q

Organometallics 1999, 18, 2061-2073
2061
Articles
Syn th esis of Novel (P ,S) Liga n d s Ba sed on Ch ir a l
Non r a cem ic Ep isu lfid es. Use in Asym m etr ic
Hyd r ogen a tion
Elisabeth Hauptman,* Paul J . Fagan, and William Marshall
Central Research and Development Department, Biochemical Science and Engineering,
The DuPont Company, Experimental Station, Wilmington, Delaware 19880-0328
Received J anuary 19, 1999
A strategy for the synthesis of new chiral (P,S) ligands is described. It is based on the
opening of chiral nonracemic episulfides using phosphorus nucleophiles. Chiral episulfides,
CH2CH(R)S, 4, are derived either from the reaction of thiourea with the corresponding
epoxide (4a , R ) CH3) or from the stepwise conversion of chiral diols to the episulfide via
the thiocarbonate (4b, R ) cyclohexyl). The reaction of lithium salts of phosphines, R2′PLi
(R ) Ph, cyclohexyl), with episulfides is regioselective and gives the ring-opened products
5-8, PR2CH2CH(R′)SLi. Upon treatment with electrophiles, R′′Cl (R′′ ) -CH2Ph, -CH2-
(C5(CH3)5), -CH2(C14H9), -CH(C14H12)), they give novel chiral (P,S) ligands, PR′2CH2CH-
(R′)SR′′, 9-17 in 31-93% yield. Reactions of PCy2CH2CH(CH3)SCH2(C6(CH3)5), 11, with
LMCl2 (LM ) (DME)Ni, (COD)Pd, and (NBD)Pt; DME ) dimethoxyethane, COD ) 1,5-
cyclooctadiene, NBD ) 2,5-norbornadiene) yields the corresponding metal complexes, (11)-
1
MCl2, 18. Variable-temperature H NMR spectroscopy indicates that in these complexes
sulfur inversion occurs on the NMR time scale. Compound 18b (M ) Pd) was characterized
by single-crystal X-ray analysis. Reaction of PCy2CH2CH(CH3)SCH(C14H12), 13, with (COD)-
PdCl2 results in C-S bond cleavage and produces a dinuclear thiolato-bridged complex,
dichlorobis{µ-[2-(dicyclohexylphosphino)-1-(methyl)ethanethiolato]-P,µ-S}-dipalladium(II), 19.
Complex 19 was characterized by single-crystal X-ray analysis. Reactions of ligands 9-17
+
with Rh(COD)2 OTf- (COD ) cyclooctadiene, OTf- ) CF3SO3-) yields rhodium complexes
that have been tested in the asymmetric hydrogenation of R-enamide methyl esters, providing
enantioselectivities of up to 51%. The rhodium complex obtained with ligand 11, (11)Rh-
(COD)OTf, 22, was characterized by single-crystal X-ray analysis.
In tr od u ction
as (P,O),5 (P,N),6 and (P,S)7 ligands. Reports on catalytic
reactions using the latter class are scarce partially
owing to fear of metal poisoning by sulfur. The use of
these ligands has been reported for the carbonylation
Chiral bidentate ligands have been used extensively
to perform asymmetric transformations.1 The most
commonly employed are bidentate phosphines;2-4 how-
ever, promising catalytic allylic alkylations and Heck
reactions have appeared using mixed-donor ligands such
(4) (a) Knowles, W. S.; Sabacky, M. J .; Vineyard, B. D. J . Chem.
Soc., Chem. Commun. 1972, 10. (b) Vineyard, B. D.; Knowles, W. S.;
Sabacky, M. J .; Bachman, G. L.; Weinkauff, D. J . J . Am. Chem. Soc.
1977, 99, 5946. (c) Kagan, H. B.; Dang, T.-P. J . Am. Chem. Soc. 1972,
94, 6429. (d) Fryzuk, M. D.; Bosnich, B. J . Am. Chem. Soc. 1977, 99,
6262. (e) Miyashita, A.; Yasuda, A.; Takaya, H.; Toriumi, K.; Ito, T.;
Souchi, T.; Noyori, R. J . Am. Chem. Soc. 1980, 102, 7932. (f) Miyashita,
A.; Takaya, H.; Souchi, T.; Noyori, R. Tetrahedron 1984, 40, 1245. (g)
Takaya, H.; Akutagawa, S.; Noyori, R. Org. Synth. 1988, 67, 20. (h)
Takaya, H.; Mashima, K.; Koyano, K.; Yagi, M.; Kumobayashi, H.;
Takemomi, T.; Akutagawa, S.; Noyori, R. J . Org. Chem. 1986, 51, 629.
(i) Burk, M. J .; Feaster, J . E.; Harlow, R. L. Organometallics 1990, 9,
2653. (j) Burk, M. J . J . Am. Chem. Soc. 1991, 113, 8518. (k) Burk, M.
J .; Feaster, J . E.; Nugent, W. A.; Harlow, R. L. J . Am. Chem. Soc. 1993,
115, 10125. (l) Burk, M. J .; Lee, J . R.; Martinez, J . P. J . Am. Chem.
Soc. 1994, 116, 10847. (m) Longmire, J . M.; Zhu, G.; Zhang, X.
Tetrahedron Lett. 1997, 38, 375-378. (n) Longmire, J . M.; Zhang, X.
Tetrahedron Lett. 1997, 38, 1725-1728. (o) Zhu, G.; Cao, P.; J iang,
Q.; Zhang, X. J . Am. Chem. Soc. 1997, 119, 1799-1800. (p) Chan, A.
S. C.; Hu, W.; Pai, C.-C.; Lau, C.-P. J . Am. Chem. Soc. 1997, 119, 9570-
9571.
(1) (a) Bosnich, B. In Asymmetric Catalysis; Bosnich, B., Ed.;
Martinus Nijhoff: Dordrecht, The Netherlands, 1986. (b) Brunner, H.
Synthesis 1988, 645. (c) Collins, A. N.; Sheldrake, G. N.; Crosby, J .
Chirality in Industry II; J ohn Wiley & Sons: New York, 1997. (d)
Morrison, J . D. In Asymmetric Synthesis; Morrison, J . D., Ed.; Academic
Press: New York, 1985; Vol 5. (e) Noyori R. In Asymmetric Catalysis
in Organic Synthesis; Noyori, R., Ed.; J ohn Wiley & Sons: New York,
1994. (f) Nugent, W. A.; Rajanbabu, T. V.; Burk, M. J . Science 1993,
259, 479. (g) Ojima I. In Catalytic Asymmetric Synthesis; Ojima, I.,
Ed.; VCH: New York, 1993. (h) Schmid, R.; Broger, E. A.; Cereghetti,
M.; Crameri, Y.; Foricher, J .; Lalonde, M.; Muller, R. K.; Scalone, M.;
Schoettel, G.; Zutter, U. Pure Appl. Chem. 1996, 68, 131-138. (i)
Seyden-Penne, J . In Chiral Auxiliaries & Ligands in Asymmetric
Synthesis; Seyden-Penne, J ., Ed.; J ohn Wiley & Sons: New York, 1995.
(2) Knowles, W. S. Acc. Chem. Res. 1983, 16, 106.
(3) (a) Noyori, R.; Takaya, H. Acc. Chem. Res. 1990, 23, 345. (b)
Noyori, R. Science 1990, 248, 1194.
10.1021/om990023q CCC: $18.00 © 1999 American Chemical Society
Publication on Web 05/06/1999

2062 Organometallics, Vol. 18, No. 11, 1999
Hauptman et al.
of methanol,7m the reduction of ketones by hydrogen
transfer (ee up to 20%),7i,l and the hydroformylation of
styrene.7i Pregosin has synthesized and structurally
characterized a number of metal complexes bearing
chiral P,S-donor ligands. In particular, palladium com-
plexes with ligands such as 1 and 2 were shown to carry
out asymmetric allylic alkylation.7a,c,d
in asymmetric hydrosilylation of ketones (ee up to
57%).7p In these ligand systems it is difficult to tune
electronic and steric effects. Here, we report a simple
and versatile route to chiral (P,S) ligands amenable to
“combinatorial” screening8 and some preliminary stud-
ies of their use in asymmetric hydrogenation.
Resu lts a n d Discu ssion
The opening of episulfides by phosphorus nucleophiles
has been reported and in the case of terminal episulfides
proceeds regioselectively to the less hindered site.9
Subsequent quenching with electrophiles leads to the
corresponding (P,S) ligand (eq 1).
The approach shown in eq 1 contains two nearly
quantitative steps and allows the introduction of three
2
degrees of molecular diversity represented by 1R, R,
Ligand 1 gives 88% ee for the classic test substrate
PhCHdCHCH(OAc)Ph, and 2 gives much smaller ee’s
in the 20-30% range. For chiral hydroformylation of
styrene, a maximum of ca. 14% ee was achieved. Most
recently, Achiwa has reported the use of (P,S) ligands
3
and R. Thus, this strategy seemed adequate for auto-
mated synthesis and screening (the first step is byprod-
uct free while the second step generates inert LiCl).
Coordination of these ligands to a metal center would
place the element of chirality, sulfur, directly next to
the metal where the key enantioselective steps occur.
In addition, with large groups on phosphorus, one side
of the (P, S, metal) plane would be blocked. This in
combination with bulky groups both on the backbone
and sulfur would cause R2 and R3 to be trans to each
other upon ligand coordination, thereby limiting the
number of coordination modes of alkene substrate.
Finally, the electronic dissimilarity of sulfur and phos-
phorus might lead to electronic effects that have been
found to be important in some cases for obtaining
favorable ee’s.10 All of the above arguments encouraged
us to prepare these ligands.
(5) (a) Knuhl, G.; Sennhenn, P.; Helmchen, G. J . Chem. Soc., Chem.
Commun. 1995, 1845. (b) Kadyrov, R.; Heinicke, J .; Kindermann, M.
K.; Heller, D.; Fischer, C.; Selke, R.; Fischer, A. K.; J ones, P. G. Chem.
Ber./ Recl. 1997, 130, 1663-1670. (c) Heinicke, J .; Kadyrov, R.;
Kindermann, M. K.; Koesling, M.; J ones, P. G. Chem. Ber. 1996, 129,
1547-1560. (d) Heinicke, J .; J ux, U.; Kadyrov, R.; He, M. Heteroatom.
Chem. 1997, 8, 383-396. (e) Heinicke, J .; Kadyrov, R.; Kindermann,
M. K.; Koesling, M.; J ones, P. G. Chem. Ber./ Recl. 1997, 130, 431. (f)
Dunbar, K.; Sun, J .-S.; Quillevere, A. Inorg. Chem. 1994, 33, 3598. (g)
Lindner, E.; Andres, B. Chem. Ber. 1987, 120, 761-767.
(6) (a) Sprinz, J .; Kiefer, M.; Helmchen, G.; Reggelein, M.; Huttner,
G.; Zsolnai, L. Tetrahedron Lett. 1994, 35, 1523. (b) Knoebel, A. K. H.;
Escher, I. H.; Pfaltz, A. Synlett 1997, 12, 1429-1431. (c) Wehman, P.;
van Donge, H. M. A.; Hagos, A.; Kamer, P. C.; van Leeuwen, P. W. N.
M. J . Organomet. Chem. 1997, 529, 387-393. (d) Nagel, U.; Nedden,
H. G. Chem. Ber./ Recl. 1997, 130, 535-542. (e) Schnyder, A.; Togni,
A.; Wiesli, U. Organometallics 1997, 16, 255-260. (f) Blochl, P. E.;
Togni, A. Organometallics 1996, 15, 4125. (g) Kubota, H.; Koga, K.
Heterocycles 1996, 42, 543-547. (h) Valk, J .-M.; Whitlock, G. A.;
Layzell, T. P.; Brown, J . M. Tetrahedron: Asymmetry 1995, 6, 2593-
2596. (i) Grazia, C.; Nicolo, F.; Drommi, D.; Bruno, G.; Faraone, F. J .
Chem. Soc., Chem. Commun. 1994, 19, 2251-2252. (j) Katti, K. V.;
Cavell, R. G. Comments Inorg. Chem. 1990, 10, 53-73.
(7) (a) Barbaro, P.; Currao, A.; Herrmann, J .; Nesper, R.; Pregosin,
P.; Salzmann, R. Organometallics 1996, 15, 1879-1888. (b) Leung, P.-
H.; Loh, S.-K.; Mok, K. F.; White, A. J . P.; Williams, D. J . J . Chem.
Soc., Dalton Trans. 1996, 4443-4448. (c) Tschoerner, M.; Trabesinger,
g.; Albinati, A.; Pregosin, P. Organometallics 1997, 16, 3447-3453.
(d) Albinati, A.; Eckert, J .; Pregosin, P.; Ruegger, H.; Salzmann, R.;
Stossel, C. Organometallics 1997, 16, 579-590. (e) Albinati, A.;
Pregosin, P. S.; Wick, K. Organometallics 1996, 15, 2419-2421. (f)
Borwitzky, A.; Schareina, T.; Paetzold, E.; Oehme, G. Phosphorus,
Sulfur, and Silicon 1996, 114, 115-121. (g) Spencer, J .; Gramlich, V.;
Hausel R.; Togni, A. Tetrahedron: Asymmetry 1996, 7, 41-44. (h)
Herrmann, J .; Pregosin, P. S.; Salzmann, R.; Albinati, A. Organome-
tallics 1995, 14, 3311-3318. (i) Gladiali, S.; Dore, A.; Fabbri, D.
Tetrahedron: Asymmetry 1994, 5, 1143-1146. (j) Leung, P.-H.; Willis,
A. C.; Wild, S. B. Inorg. Chem. 1992, 31, 1406-1410. (k) Bressan, M.;
Morandini, F.; Morvillo, A., Rigo, P. J . Organomet. Chem. 1985, 280,
139-146. (l) Bressan, M.; Bonuzzi, C.; Morandini, F.; Morvillo, A. Inorg.
Chim. Acta 1991, 182, 153-156. (m) Dilworth, J . R.; Miller, J . R.;
Wheatley, N.; Baker, M. J .; Sunley, J . G. J . Chem. Soc., Chem.
Commun. 1995, 1579. (n) Rigo, P.; Bressan, M.; Basato, M. Inorg.
Chem. 1979, 18, 860-863. (o) Bressan, M.; Morandini, F.; Rigo, P. J .
Organomet. Chem. 1983, 247, C8-C10. (p) Hiraoka, M.; Nishikawa,
A.; Morimoto, T.; Achiwa, K. Chem. Pharm. Bull. 1998, 46, 704. (q)
Albinati, A.; Herrman, J .; Pregosin, P. S. Inorg. Chim. Acta 1997, 264,
33.
(8) For recent examples of catalysts discovered by combinatorial
methods, see: (a) Reddington, E.; Sapienza, A.; Gurau, B.; Viswanathan,
R.; Sarangapani, S.; Smotkin, E. S.; Mallouk, T. E. Science 1998, 280,
1735. (b) Gennari, C.; Nestler, H. P.; Piarulli, U.; Salom, B. Liebigs
Ann./ Recueil 1997, 637. (c) Menger, F. M.; Eliseev, A. V.; Migulin, V.
A. J . Org. Chem. 1995, 60, 6666. (d) Liu, G.; Ellman, J . A. J . Org.
Chem. 1995, 60, 7712. (e) Gilbertson, S. R.; Wang, X. Tetrahedron Lett.
1996, 37, 6475. (f) Burgess, K.; Lim, H.-J ., Porte, A. M., Sulikowski,
G. A. Angew. Chem., Int. Ed Engl. 1996, 35, 220. (g) Cole, B. M.;
Shimizu, K. D.; Krueger, C. A.; Harrity, J . P. A.; Snapper, M. L.;
Hoveyda, A. H. Angew. Chem., Int. Ed. Engl. 1996, 35, 1668. (h)
Shimizu, K. D.; Cole, B. M.; Krueger, C. A.; Kuntz, K. W.; Snapper,
M. L.; Hoveyda, A. H. Angew. Chem., Int. Ed. Engl. 1997, 36, 1704. (i)
Sigman, M. S.; J acobsen, E. N. J . Am. Chem. Soc. 1998, 120, 4901.
(9) (a) Issleib Von K.; Franze, Kl.-D. J . Prakt. Chem. 1973, 315, 471.
(b) Chatt, J .; Dilworth, J . R.; Schmutz, J . A.; Zubieta, J . A. J . Chem.
Soc., Dalton Trans. 1979, 1595. (c) Wieber, M.; Clarius, T. Z. Anorg.
Allg. Chem. 1995, 621, 1288.
(10) (a) Casalnuovo, A. L.; Rajanbabu, T. V.; Ayers, T. A.; Warren,
T. H. J . Am. Chem. Soc. 1994, 116, 9869. (b) Rajanbabu, T. V.; Ayers,
T. A.; Casalnuovo, A. L. J . Am. Chem. Soc. 1994, 116, 4101. (c)
Rajanbabu, T. V.; Casalnuovo, A. L. Pure Appl. Chem. 1994, 66, 1535.

Synthesis of Novel (P,S) Ligands
Organometallics, Vol. 18, No. 11, 1999 2063
Syn th esis of Ch ir a l Ep isu lfid es. Literature prece-
dents for the synthesis of chiral nonracemic thiiranes
are rare.11 Episulfides are most commonly synthesized
from epoxides using thiourea or potassium thiocyan-
ate.12 On chiral epoxides, these reactions proceed with
inversion of configuration. We synthesized chiral pro-
pylene sulfide from commercially available (S)-(-)-
propylene oxide using thiourea in tetraethylene glycol/
water. This procedure was modeled after that reported
by Bouda et al.13 The reaction proceeds smoothly over
12 h at ambient temperature, and the product can be
isolated by vacuum transfer from the reaction mixture
(eq 2). The enantiomeric purity of chiral propylene
sulfide was determined by derivatization of the phos-
phido ring-opened product (vide infra) with (-)-cam-
phanic chloride and found to be ca. 88%.
prevent further oligomerization reactions. Lithium salts
5-8 are obtained as white solids (pure by 31P NMR
spectroscopy) and were used without further purifica-
tion. The salts were then reacted with electrophiles (eq
4). Benzyl halide derivatives were the most reactive
Using a procedure of Sharpless et al.,14 we found that
the synthesis of monosubstituted chiral episulfides is
more versatile starting from chiral diols. We have
synthesized the chiral diol from reduction of enantio-
merically pure hexahydromandelic acid, but many more
diols should be readily available through the Sharpless
dihydroxylation reaction.15 Reaction of the diol with
thiocarbonyldiimidazole yields the corresponding thio-
carbonate.16 Subsequent reaction with a catalytic amount
of bromide promotes isomerization to the sulfur-bound
carbonate, which upon reaction with hydroxide extrudes
carbonate and produces the episulfide with net inver-
sion. All the steps are quantitative except the last one,
which occurs in ca. 55% yield.17 The enantiomeric purity
of the episulfide was determined by derivatization with
(S)-(+)-methoxymethylpyrrolidine and found to be g95%.
Syn th esis of P ,S Liga n d s. Propylene sulfide or the
thiirane of vinyl cyclohexane can be ring-opened using
lithium salts of phosphines, LiPR2 (R ) Cy, Ph). This
reaction takes places at -78 °C and is regiospecific; the
opening occurs exclusively at the least hindered carbon.
A stoichiometric amount of episulfide is necessary to
electrophiles as expected for nucleophilic substitution.
All these ligands were obtained in good yields (50-93%)
and gave satisfactory elemental analyses and spectro-
(11) (a) J ohnson, C. R., Tanaka, K. Synthesis 1976, 413. (b) Soai,
K.; Mukaiyama, T. Bull. Chem. Soc. J pn. 1979, 52, 3371 (c) Iranpoor,
N.; Kazemi, F. Tetrahedron 1997, 53, 11377 and references therein.
(12) (a) Zoller, U. In Small Ring Heterocycles; Hassner, A. Ed.; J ohn
Wiley & Sons: New York, 1983; Vol. 42, Part 1, p 333. (b) Sander, M.
Chem. Rev. 1966, 66, 297. (c) Vedejs, E.; Krafft, G. A. Tetrahedron
1982, 38, 2857. (c) Gao, Y.; Sharpless, K. B. J . Org. Chem. 1988, 53,
4114. Alternative routes for the synthesis of thiiranes have recently
been reported. (d) From cyclic sulfates of vic-diols, see: Calvo-Flores,
F. G.; Garcia-Mendoza, P.; Hernandez-Mateo, F.; Isac-Garcia, J .;
Santoyo-Gonzales, F. J . Org. Chem. 1997, 62, 3944 and references
therein. (e) From S-(â-oxoalkyl)thiophosphate, see: Dybowski, P.;
Skowronska, A. Synthesis 1997, 1134. (f) For an unusual episulfidation,
see also: Waldemar, A.; Frohling, B.; Peters, K.; Weinkotz, S. J . Am.
Chem. Soc. 1998, 120, 8914.
1
scopic data. The most notable features in the H NMR
spectra were the protons R to the sulfur, which were
found in the range 3.0-2.5 ppm as complex multiplets
resulting from 1H-1H coupling as well as 1H-31P
coupling. In the case of benzyl-like sulfur substituents,
the methylene protons R to the sulfur are diastereotopic,
coupled to each other, and appear in the 4.0-3.5 ppm
region as an AB quartet.
Syn th esis of Meta l Com p lexes. Owing to the novel
nature of these ligands, we first set out to establish their
bidentate nature by making various square planar
metal complexes of nickel, palladium, and platinum.
Their synthesis is outlined in eq 5.
While in the nickel case DME (DME ) 1,2-dimethoxy-
ethane) was easily displaced (within minutes), the
formation of both the palladium and platinum com-
plexes occurred more slowly over several hours. Spec-
troscopic data as well as the crystal structure of the
(13) Bouda, H.; Borredon, M. E.; Delmas, M.; Gaset, A. Synth.
Commun. 1989, 19, 491.
(14) Richardson, P.; Sharpless, K. B. Personal communication.
(15) (a) Beller, M.; Sharpless, K. B. In Appl. Homogeneous Catal.
Organomet. Compd.; Cornils, B., Herrmann, W. A., Eds.; VCH:
Weinheim, Germany, 1996; Vol. 2, pp 1009-1024. (b) Kolb, H. C.;
VanNieuwenhze, M. S.; Sharpless, K. B. Chem. Rev. 1994, 94, 2483.
(c) J ohnson, R. A.; Sharpless, K. B. In Catalytic Asymmetric Synthesis;
Ojima, I., Ed.; VCH: New York, 1993; pp 227-22.
(16) For a recent report of this reaction, see: De Angelis, F.; Marzi,
M.; Minetti, P.; Misiti, D.; Muck, S. J . Org. Chem. 1997, 62, 4159.
(17) The yield was not optimized; polymerization of the episulfide
is a very likely side reaction under these conditions.

2064 Organometallics, Vol. 18, No. 11, 1999
Hauptman et al.
palladium complex established the structure shown
above. Upon complexation, a shift of the 31P NMR signal
was observed going, for example, from -7.6 to +74.2
ppm for complex 18b. Complex 18c shows a typical 31P-
Pt coupling of 3408 Hz.
A noteworthy feature of the Pd and Ni complexes was
the broadening of the diastereotopic hydrogens adjacent
to sulfur (AB spin system). It is likely that this dynamic
process is associated with sulfur inversion. This is a
well-known process at metal centers and for this par-
ticular system seems to occur on the NMR time scale
(see eq 6).18 To gain more insight into this process, a
F igu r e 1. ORTEP drawing of (PCy2CH2CH(CH3)SCH2C5-
(CH3)5)PdCl2, 18b. The hydrogen atoms have been omitted.
Ta ble 1. Cr ysta llogr a p h ic Da ta , Collection
P a r a m eter s, a n d Refin em en t P a r a m eter s for 18b,
19, a n d 22
18b
19
22
mol formula
fw
cryst dimens
(mm)
space grp
cell param
a (Å)
b (Å)
c (Å)
PdCl2SPC27H45 Pd2Cl2S2P2C30H56 RhS3PF3OC35H60
610.00
0.25 × 0.10 × 0.18 × 0.14 ×
0.28 0.25
P21/n C2/c
826.56
783.94
0.44 × 0.29 ×
0.39
P21/n
1
8.547(1)
24.226(4)
14.700(3)
103.97(1)
2953.8
4
29.125(1)
13.340(1)
19.740(1)
113.71(1)
7022.1
8
10.451(2)
18.584(3)
19.733(4)
104.62(1)
3708.5
low-temperature H NMR study was carried out on the
Ni complex where the line broadening was the most
noticeable. Since the line broadening was somewhat
anomalous (the “A” line was broader than the “B” line),
we carried out magnetization transfer experiments at
temperatures where the spectra appeared static (-50
to -90 °C). Instead of observing an expected decrease
in intensity for B upon irradiating A we noticed a small
increase in intensity that could simply be explained by
a nuclear Overhauser effect (proximity of the two spins).
This indicates that the CH2 protons are not exchanging
with each other. The difference in line width could be
associated with different T2 relaxation at each site or
different long-range H-P couplings for the A and B sites
â (deg)
V (Å3)
Z
4
Dc (g/mL)
temp (°C)
radiation
(wavelength,
Å)
1.372
1.564
1.404
-45
-112
-100
Mo KR
Mo KR
Mo KR
(0.709 30)
(0.709 30)
(0.709 30)
monochromator graphite
linear abs. coeff 9.37
graphite
13.89
graphite
6.98
(cm-1
)
scan mode
2θ limits (deg) 1.7 e 2θ e 52.0 3.1 e 2θ e 48.2
octants collcd
total no. unique 6179
reflns
data with
I g xσ(I)
R
Rw
GoF
no. params
max ∆/σ
largest res
dens (e/Å3)
4.0 e 2θ e 50.0
++-, -+-
6963
+++, -++
NA
18069
4
(for example, J P-H). We propose that exchange occurs
2770 (x ) 3)
4755 (x ) 3)
4375 (x ) 3)
with another isomer present at very low concentration.19
If we assume similar shifts and coupling constants for
the AB quartet for the Ni, Pd, and Pt complexes, the
rate of sulfur inversion appears to increase in the
0.044
0.037
1.07
289
0.00
0.80
0.038
0.042
2.16
343
0.01
0.57
0.05
0.048
1.63
415
0.20
1.31
(18) (a) Abel, E. W.; Long, N. J .; Orrell, K. G.; Osborne, A. G.; Sik,
V. J . Organomet. Chem. 1990, 394, 455. (b) Abel, E. W.; Booth, M.;
Orrell, K. G.; Pring, G. M. J . Chem Soc., Dalton Trans. 1981, 1944
and references therein. (c) Cross, R. J .; Smith, G. J .; Wardle, R. Inorg.
Nucl. Chem. Lett. 1971, 7, 191. (d) Orrell, K. G.; Sik, V.; Brubaker, C.
H.; McCulloch, B. J . Organomet. Chem. 1984, 276, 267. (e) Yamazaki,
S.; Ama, T. Bull. Chem. Soc. J pn. 1989, 62, 931. (f) Ascenso, J . R.;
Carvalho, M.; Dias, A. R.; Romao, C. C.; Calhorda, M. J .; Veiros, L. F.
J . Organomet. Chem. 1994, 470, 147. (g) Benson, I. B.; Knox, S. A. R.;
Naish, P. J .; Welch, A. J . J . Chem Soc., Dalton Trans. 1981, 2235. (h)
Abel, E. W.; Shamsuddin, A. K. A.; Farrow, G. W.; Orrell, K. G. J .
Chem. Soc., Dalton Trans. 1977, 47. (i) Gladiali, S.; Fabbri, D.; Kolla`r,
L.; Claver, C.; Ruiz, N.; Alvarez-Larena, A.; Piniella, J . F. Eur. J . Inorg.
Chem. 1998, 113.
following order: Pt < Pd < Ni, a trend observed
previously for Pd and Pt.18h The mechanism of sulfur
inversion is still controversial, but experimental evi-
dence seems to favor a planar intermediate as opposed
to a dissociation-recombination mechanism.18 These
observations were made during the study of metals
bound to chelating dithioether ligands, and the proposed
“in place” mechanism might not be favored for chelating
(P,S) ligands. This inversion at sulfur coupled with the
high conformational flexibility of the ligands may be
responsible for the moderate enantioselectivities ob-
served in the asymmetric hydrogenations (see below).
(19) Under static conditions, we would expect two sets of AB
quartets (two diastereomeric complexes); however, the second isomer
could not be detected by 1H NMR spectroscopy. This prevents us from
accurately determining the rate at which they interconvert using the
slow exchange conditions.

Synthesis of Novel (P,S) Ligands
Organometallics, Vol. 18, No. 11, 1999 2065
Ta ble 2. Selected In ter a tom ic Dista n ces (Å) for
(P Cy2CH2CH(CH3)SCH2C5(CH3)5)P d Cl2, 18ba
Ta ble 4. Selected In ter a tom ic Dista n ces (Å) for
[(P Cy2CH2CH(CH3)SP d Cl]2, 19a
Pd(1)-Cl(1)
Pd(1)-Cl(2)
Pd(1)-S(1)
Pd(1)-P(1)
S(1)-C(3)
2.377(2)
2.309(2)
2.271(2)
2.221(2)
1.842(6)
1.833(6)
P(1)-C(2)
P(1)-C(21)
P(1)-C(31)
C(2)-C(3)
C(3)-C(4)
1.828(6)
1.826(7)
1.834(6)
1.513(8)
1.534(9)
Pd(1)-Pd(2)
Pd(1)-Cl(1)
Pd(2)-Cl(2)
Pd(1)-S(1)
Pd(1)-S(2)
Pd(2)-S(1)
Pd(2)-S(2)
Pd(1)-P(1)
Pd(2)-P(2)
S(1)-C(3)
2.9893(6)
2.342(1)
2.327(1)
2.278(1)
2.415(1)
2.3877(10)
2.276(1)
2.249(1)
2.240(1)
1.854(4)
1.842(4)
P(1)-C(2)
P(1)-C(21)
P(1)-C(31)
P(2)-C(5)
P(2)-C(41)
P(2)-C(51)
C(2)-C(3)
C(3)-C(4)
C(5)-C(6)
C(6)-C(11)
1.839(4)
1.838(4)
1.842(4)
1.830(4)
1.845(4)
1.519(6)
1.512(6)
1.525(6)
1.514(6)
S(1)-C(5)
a
Numbers in parentheses are the estimated standard devia-
tions.
Ta ble 3. Selected Bon d An gles (d eg) for
(P Cy2CH2CH(CH3)SCH2C5(CH3)5)P d Cl2, 18ba
S(2)-C(6)
a
Numbers in parentheses are the estimated standard devia-
C(3)-S(1)-C(5)
Pd(1)-P(1)-C(2)
Pd(1)-P(1)-C(21)
Pd(1)-P(1)-C(31)
C(2)-P(1)-C(21)
C(2)-P(1)-C(31)
S(1)-C(3)-C(2)
S(1)-C(3)-C(4)
102.3(3)
106.5(2)
113.6(2)
115.9(2)
105.3(3)
106.9(3)
107.7(4)
110.5(5)
S(1)-C(5)-C(10)
P(1)-C(2)-C(3)
114.1(4)
114.0(5)
114.0(5)
111.2(5)
111.4(5)
113.3(5)
111.7(6)
107.8(3)
tions.
P(1)-C(21)-C(22)
P(1)-C(21)-C(26)
P(1)-C(31)-C(32)
P(1)-C(31)-C(36)
C(2)-C(3)-C(4)
C(21)-P(1)-C(31)
in P,S chelate complexes there is a tendency for pseudo-
axial substituents on sulfur.7c,d
All attempts to synthesize and recrystallize (13)PdCl2
failed and resulted instead in the cleavage of the S-C
bond and the formation of the dimeric complex 19 (see
eq 7).
a
Numbers in parentheses are the estimated standard devia-
tions.
F igu r e 2. ORTEP drawing of [(PCy2CH2CH(CH3)SPdCl]2,
19. The hydrogen atoms have been omitted.
The structure of complex 19 was confirmed by X-ray
crystallography, and an ORTEP diagram is reported in
Figure 2. Single crystals of complex 19 were obtained
by recrystallization from CH2Cl2/hexane over a period
of a few days at ambient temperature. Crystallographic
data and collection and refinement parameters are
listed in Table 1; selected interatomic distances and
angles are summarized in Tables 4 and 5, respectively.
The geometry around each palladium is distorted square
planar. As observed in other thiolate-bridged complexes
of d8 transition metals, the molecules are folded along
the S-S axis leading to a butterfly core structure. This
folding brings the two palladium atoms close together
(2.9893(6) Å). The chelate bite angles, S-Pd-P, 86.85-
(4)° and 87.51(4)°, are in the normal range7q,22a,23 and
close to that of the mononuclear complex 18b (87.84-
(7)°). The S-Pd-S angles (80.95(4)° and 81.59(4)°) are
The structure of complex 18b was verified by an X-ray
structural determination from crystals grown by slow
evaporation of a CH2Cl2 solution. An ORTEP diagram
is shown in Figure 1. Crystallographic data, collection
parameters, and refinement parameters are listed in
Table 1; selected interatomic distances and angles are
summarized in Tables 2 and 3, respectively. The coor-
dination geometry around the metal center is a slightly
distorted square-plane with a P-Pd-S angle of 87.84-
(7)°. This angle is typical of neutral Pd(II) complexes7b,20
and smaller than that of cationic (P,S)Pd(II) allyl
complexes described by Togni and Pregosin (94.6-
96.9°).7a,e,g,h Both the Pd-S and Pd-P bond lengths at
2.271(2) and 2.221(2) Å are typical,7,20 but the two Pd-
Cl distances, 2.309(2) Å and 2.377(2) Å, differ signifi-
cantly. The latter effect is attributed to the larger trans
influence of phosphorus versus sulfur. The methyl
substituent on the metallacycle is in a pseudoequatorial
position trans to the sulfur substituent.21 This structure
is also in accordance with Pregosin’s observation that
(22) (a) Roundhill, D. M.; Roundhill, S. G. N.; Beaulieu, W. B.;
Bagchi, U. Inorg. Chem. 1980, 19, 3365. (b) Eller, P. G.; Riker, J . M.;
Meek, D. W. J . Am. Chem. Soc. 1973, 95, 3540. (c) Lockyer, T. N. Aust.
J . Chem. 1974, 27, 259. (d) Marty, W.; Schwarzenbach, G. Chimia
1970, 24, 431. (e) Kim, J . S.; Reibenspies, J . H.; Darensbourg, M. Y. J .
Am. Chem. Soc. 1996, 118, 4115. (f) Aurivillius, K.; Bertinsson, G.-I
Acta Crystallogr. 1982, B38, 1295. (g) Chooi, S. Y. M.; Leung, P.-H
Bull. Sing. Natl. Inst. Chem. 1991, 19, 69. For a study of electron-
transfer induced C-S bond cleavage, see: Mullen, G. E. D.; Went, M.
J .; Wocadlo, S.; Powell, A. K.; Blower, P. J . Angew. Chem., Int. Ed.
Engl. 1997, 36, 1205.
(20) Clark, G. R.; Orbell, J . D. J . Organomet. Chem. 1981, 215, 121.
(21) The structures reported by Pregosin and Togni are all six-
membered ring metallacycles, and the methyl substituents in these
tend to be equatorial in most cases.

2066 Organometallics, Vol. 18, No. 11, 1999
Hauptman et al.
Ta ble 5. Selected Bon d An gles (d eg) for
[(P Cy2CH2CH(CH3)SP d Cl]2, 19a
Ta ble 6. Selected In ter a tom ic Dista n ces (Å) for
(P Cy2CH2CH(CH3)SCH2C5(CH3)5)Rh (COD)+, 22a
Pd(2)-Pd(1)-Cl(1) 125.85(3) Pd(1)-S(2)-C(6)
Pd(1)-Pd(2)-Cl(2) 123.68(3) Pd(2)-S(2)-C(6)
108.8(1)
102.8(1)
107.6(1)
Rh(1)-S(1)
Rh(1)-P(1)
Rh(1)-C(11)
Rh(1)-C(12)
Rh(1)-C(15)
Rh(1)-C(16)
S(1)-C(1)
2.339(1)
2.304(1)
2.195(5)
2.159(5)
2.246(5)
2.240(5)
1.819(7)
1.861(7)
1.833(6)
1.840(5)
1.857(5)
C(1)-C(2)
1.446(9)
1.541(8)
1.528(8)
1.388(8)
1.496(7)
1.518(9)
1.515(10)
1.505(8)
1.358(9)
1.497(8)
1.524(8)
C(1)-C(3)
Pd(2)-Pd(1)-S(1)
Pd(2)-Pd(1)-S(2)
Pd(1)-Pd(2)-S(2)
Pd(2)-Pd(1)-P(1)
Pd(1)-Pd(2)-P(2)
Cl(1)-Pd(1)-S(1)
Cl(1)-Pd(1)-S(2)
Cl(2)-Pd(2)-S(1)
Cl(2)-Pd(2)-S(2)
Cl(1)-Pd(1)-P(1)
Cl(2)-Pd(2)-P(2)
S(1)-Pd(1)-S(2)
S(1)-Pd(2)-S(2)
S(1)-Pd(1)-P(1)
S(2)-Pd(1)-P(1)
S(1)-Pd(2)-P(2)
S(2)-Pd(2)-P(2)
Pd(1)-S(1)-Pd(2)
Pd(1)-S(2)-Pd(2)
Pd(1)-S(1)-C(3)
Pd(2)-S(1)-C(3)
51.79(3) Pd(1)-P(1)-C(2)
C(5)-C(20)
C(11)-C(12)
C(11)-C(18)
C(12)-C(13)
C(13)-C(14)
C(14)-C(15)
C(15)-C(16)
C(16)-C(17)
C(17)-C(18)
48.39(3) Pd(1)-P(1)-C(21) 111.8(1)
52.49(3) Pd(1)-P(1)-C(31) 116.9(1)
117.92(3) Pd(2)-P(2)-C(5)
107.2(1)
121.49(3) Pd(2)-P(2)-C(41) 115.3(1)
177.6(1)
Pd(2)-P(2)-C(51) 114.0(1)
S(1)-C(5)
97.42(1) C(2)-P(1)-C(21)
97.59(4) C(2)-P(1)-C(31)
108.4(2)
104.4(2)
P(1)-C(2)
P(1)-C(31)
P(1)-C(41)
175.26(4) C(21)-P(1)-C(31) 107.1(2)
94.55(6) C(5)-P(2)-C(41)
93.02(4) C(5)-P(2)-C(51)
106.7(2)
106.4(2)
a
Number in parentheses are the estimated standard devia-
tions.
80.95(4) C(41)-P(2)-C(51) 106.7(2)
81.59(4) S(1)-C(3)-C(2)
86.85(4) S(1)-C(3)-C(4)
165.88(4) S(2)-C(6)-C(5)
168.69(4) S(2)-C(6)-C(11)
87.51(4) P(1)-C(2)-C(3)
79.64(3) P(2)-C(5)-C(6)
79.12(3) C(2)-C(3)-C(4)
107.8(3)
108.5(3)
108.6(3)
108.7(3)
111.9(3)
111.1(3)
114.3(4)
111.9(3)
48.57(3)
Ta ble 7. Selected Bon d An gles (d eg) for
(P Cy2CH2CH(CH3)SCH2C5(CH3)5)Rh (COD)+, 22a
S(1)-Rh(1)-P(1)
85.67(6) Rh(1)-S(1)-C(1)
105.5(2)
111.8(2)
105.4(3)
107.4(2)
116.8(2)
117.1(2)
104.2(3)
103.4(3)
106.5(2)
70.0(3)
S(1)-Rh(1)-C(11)
S(1)-Rh(1)-C(12)
S(1)-Rh(1)-C(15)
S(1)-Rh(1)-C(16)
P(1)-Rh(1)-C(11)
P(1)-Rh(1)-C(12)
P(1)-Rh(1)-C(15)
P(1)-Rh(1)-C(16)
C(11)-Rh(1)-C(12)
C(11)-Rh(1)-C(15)
C(11)-Rh(1)-C(16)
C(12)-Rh(1)-C(15)
C(12)-Rh(1)-C(16)
C(15)-Rh(1)-C(16)
163.4(1)
158.9(2)
93.3(1)
90.6(1)
97.4(2)
96.9(2)
170.5(2)
154.1(2)
37.2(2)
86.4(2)
79.5(2)
80.8(2)
95.7(2)
35.2(2)
Rh(1)-S(1)-C(5)
C(1)-S(1)-C(5)
Rh(1)-P(1)-C(2)
Rh(1)-P(1)-C(31)
Rh(1)-P(1)-C(41)
C(2)-P(1)-C(31)
C(2)-P(1)-C(41)
C(31)-P(1)-C(41)
Rh(1)-C(11)-C(12)
104.5(1)
107.5(1)
C(5)-C(6)-C(11)
Pd(1)-Pd(2)-S(1)
a
Numbers in parentheses are the estimated standard devia-
tions.
Rh(1)-C(16)-C(17) 106.9(4)
S(1)-C(1)-C(2)
S(1)-C(1)-C(3)
S(1)-C(5)-C(20)
P(1)-C(2)-C(1)
113.7(5)
111.7(5)
110.6(4)
114.0(5)
a
Numbers in parentheses are the estimated standard devia-
tions.
ligands 9-17 results in rapid displacement of one
cyclooctadiene and formation of LRh(COD)+TfO-. The
1H NMR spectra of all these complexes show broad
signals corresponding to the coordinated cyclooctadiene.
Once again, this fluxional process is probably associated
with sulfur inversion and potentially contributes to the
moderate enantioselectivities reported below in the
asymmetric hydrogenation reactions.
F igu r e 3. ORTEP drawing of (PCy2CH2CH(CH3)SCH2C5-
(CH3)5)Rh(COD)+, 22. The counterion TfO- as well as
hydrogen atoms have been omitted.
typical, but the Pd-S-Pd angles (79.64(3)° and 79.12-
(3)°) are about 15° smaller than similar complexes.7q,22a,23
This latter feature might be due to the fact that most
of the structures reported are dicationic,23 which would
widen this angle because of strong electrostatic repul-
sions. However, in another neutral palladium structure
most closely related to this work, [PdCl(L)]2 (L ) (R)-
1-[(S)-diphenylphosphino)ferrocenyl]ethyl mercaptan),7q
a Pd-S-Pd angle of 92.61(7)° was observed. The Pd-
Cl bonds (2.342(1) and 2.327(1) Å) are typical, and again
owing to the strong trans influence of the phosphine,
the Pd-S distances trans to P are longer (2.415(1) and
2.3877(10) Å) than those trans to Cl (2.278(1) and 2.276-
(1) Å). The Pd-P distances (2.249(1) and 2.240(1) Å) are
typical and close to those of the mononuclear complex
18b (2.221(2) Å). The cleaveage of C-S bonds has been
reported for complexes of this type and may be very
relevant to the stability of metal catalysts bearing these
ligands.7q,22
Complex (11)Rh(COD)+OTf-, 22, was recrystallized
from THF/hexane at -30 °C and characterized by X-ray
crystallography. An ORTEP diagram is shown in Figure
3. Crystallographic data and collection and refinement
Syn th esis of LRh (COD)+TfO- a n d Th eir Use a s
+
Hyd r ogen a tion Ca ta lysts. Treatment of Rh(COD)2
-
(23) Capdevila, M.; Clegg, W.; Gonzales-Duarte, P.; Harris, B.; Mira,
I.; Sola, J .; Taylor, I. C. J . Chem. Soc., Dalton Trans. 1992, 2817.
OTf- (COD ) 1,5-cyclooctadiene, OTf- ) CF3SO3-) with

Synthesis of Novel (P,S) Ligands
Organometallics, Vol. 18, No. 11, 1999 2067
Ta ble 8. Rh -Ca ta lyzed Asym m etr ic Hyd r ogen a tion
Ta ble 9. Rh -Ca ta lyzed Asym m etr ic Hyd r ogen a tion
of r-En a m id e Ester s (R ) P h )a
of r-En a m id e Ester s Usin g Ca ta lyst 26a
catalyst
% conversion
% eeb (confign)c
R
% eeb (confign)c
20
21
22
23
24
25
26
27
28
100
100
100
100
37
100
100
44
26.6 (S)
50.1 (S)
18.3 (S)
26.1 (S)
27.7 (S)
29.9 (R)
38.8 (R)
5.1 (S)
CH3
Ph
4-F-(C6H5)
19.0 (R)
38.6 (R)
41.3 (R)d
26.3 (R)
17.6 (R)d
14.8 (R)d
4.9 (R)d
3-F-(C6H5)
3-Br-(C6H5)
3,5-F2-(C6H4)
3,5-(CF3)2-(C6H4)
2-naphthalene
3-OMe-(C6H5)
3-thienyl
25.2 (R)d
35.8 (R)d
27.7 (R)
50.9 (R)
74
100
24.7 (R)
98.0 (S)
(R,R)-MeDUPHOS
2-thienyl
a
Reactions were conducted at ambient temperature and a
pressure of H2 of 80 psi using 0.39 M methanol solutions of
substrate and the catalyst precursors 2 mol %. Reaction time was
a
Reactions were conducted at ambient temperature and a
pressure of H2 of 80 psi using 0.39 M methanol solutions of
substrate and the catalyst precursor 2 mol %. Reaction time was
16 h. Enantiomeric excesses were determined by chiral capillary
GC using Chrompack’s Chirasil-L-Val column (25 m). Absolute
configurations for the products were confirmed by comparing with
b
16 h. Enantiomeric excesses were determined by chiral capillary
b
GC using Chrompack’s Chirasil-L-Val column (25m). Absolute
configurations for the products were confirmed by comparing with
that of the product obtained with (R,R)-MeDUPHOS.
d
that of the product obtained with (R,R)-MeDUPHOS. THF had
to be added to get most of the substrates in solution.
parameters are listed in Table 1; selected interatomic
distances and angles are summarized in Tables 6 and
7, respectively.
inherent electronic asymmetry generated by the use of
two different heteroatoms on the bidentate ligand could
possibly compensate for the flexibility of the present
ligand systems, generating hope that an appropriate
combination of substituents and substrates can be found
to obtain higher ee’s in the future. We are currently
exploring the use of these and related ligands for other
asymmetric transformations.
The (P,S) ligand forms a puckered five-membered
chelate ring with the Rh whose geometry is essentially
square planar. The bite angle is 85.67(6)°, a typical
value for five-membered ring chelates. Both the Rh-S
and Rh-P bond lengths at 2.339(1) and 2.304(1) Å are
typical,24 but the Rh-(C1,C2) and Rh-(C3,C4) differ
significantly again due to the stronger trans influence
of the phosphorus versus sulfur. Similar to complex 18b,
the methyl substituent on the metallacycle is in a
pseudoequatorial position trans to the sulfur substitu-
ent, which is in a pseudoaxial position leaving the
heteroatom in a very open area.7c,d
Exp er im en ta l Section
Gen er a l In for m a t ion . All complexes were manipulated
under an atmosphere of dry, oxygen-free nitrogen within a
Vacuum Atmospheres drybox, on a high-vacuum line, or on a
standard Schlenk line. Methylene chloride was distilled in an
N2 atmosphere from phosphorus pentoxide prior to use.
Tetrahydrofuran (THF), toluene, diethyl ether, and hexane
were distilled in an N2 atmosphere from sodium benzophenone
ketyl. Methanol was distilled from Mg(OMe)2. Hydrogen
(99.9995%) gas was purchased from Matheson and used as
received. The compounds (S)-(+)-hexahydromandelic acid,
thiocarbonyldiimidazole, n-butyllithium (1.6 M in hexanes),
(S)-(-)-propylene oxide, arylbenzyl chlorides, and bis(1,5-
cyclooctadiene)rhodium(I) trifluoromethanesulfonate ((COD)2-
Rh+OTf-) were purchased from Aldrich Chemical Co. The
complexes (DME)NiCl2 (DME ) 1,2-dimethoxyethane) and
(COD)PdCl2 (COD ) 1,5-cyclooctadiene) were obtained from
Strem Chemicals Inc. (NBD)PtCl2 (NBD ) norbornadiene) was
prepared following a published procedure.25 The compounds
Cy2PLi and Ph2PLi were prepared as white solids by depro-
tonation of the corresponding phosphines with n-butyllithium
in hexane. All R-(acylamino)acrylate substrates were prepared
either by standard Erlenmeyer procedures26 or by the method
of Schmidt et al.27 Procedures below are given for the prepara-
tion of the racemic phosphorus-sulfur ligands, and these same
procedures were used to prepare the corresponding S and/or
R enantiomers. All preparative chromatography was done
using columns prepared with silica gel. 1H NMR, 13C NMR,
and 31P NMR spectra were recorded on either a General
Electric 300, Bruker 500, or Varian 500 spectrometer. Chemi-
Complexes 20-28 are active catalysts for the enan-
tioselective hydrogenation R-enamide esters (eq 9).
Specific results are displayed in Tables 8 and 9.
The results presented in Table 8 do not show obvious
trends based on ligand steric or electronic arguments.
The ee’s obtained are low to moderate, ranging from
5.1% to 50.1%. The results in Table 9 seem to indicate
that higher ee’s are obtained with more electron-poor
substrates. The unusually high ee obtained for (2-
thienyl)-CHC(CO2Me)(NHAc), 51%, could be explained
by an additional point of attachment of the substrate
via sulfur.
Con clu sion
The lack of correlations of the enantioselectivity with
phosphorus-sulfur ligand structure and electronics in
this study is most likely associated with the possible
hemilabile nature of this type of ligand and/or the sulfur
inversion processes discussed above. One might expect
from previous studies by others that stronger ligand
binding and backbone rigidity would yield higher ee’s.
The apparent flexibility discovered for the ligands in this
study is an apparent drawback. On the other hand, the
1
cal shifts for H NMR and 13C NMR are reported by reference
to protonated or 13C signals of the solvent in ppm downfield
from (CH3)4Si. 31P NMR chemical shifts are positive downfield
(and negative upfield) from external 85% H3PO4. Elemental
(25) Drew, D.; Doyle, J . R. Inorg. Synth. 1972, 13, 47.
(26) Schmidt, U.; Lieberknecht, A.; Wild, J . Synthesis 1988, 159.
(27) Schmidt, U.; Griesser, H.; Leitenberger, V.; Lieberknecht, A.;
Mangold, R.; Meyer, R.; Riedl, B. Synthesis 1992, 487.
(24) Dick, D. G.; Stephan, D. W. Can. J . Chem. 1986, 64, 1870.

2068 Organometallics, Vol. 18, No. 11, 1999
Hauptman et al.
analyses were performed by Oneida Research Services, Inc.
Gas chromatographic analyses were performed using a Hewlett-
Packard Model HP 5890 GC. A 25 m × 0.25 mm Chiralsil-L-
Val (chiral fused silica, Chrompack) was used to determine
enantiomeric excesses in the asymmetric hydrogenation of
R-(acylamino)acrylates.
32.7 (t, J C-H ) 137 Hz), 26.3 (t, J C-H ) 134 Hz), 26.0 (t, J C-H
) 124 Hz), 25.9 (t, J C-H ) 124 Hz), 24.5 (t, J C-H ) 170 Hz).
HREIMS: m/z ) 142.0825 (C8H14S, ∆ +0.9 mmu).
Deter m in a tion of th e En a n tiom er ic Excess of th e
Th iir a n es Der ived fr om Com m er cia l Ch ir a l (R)-Hexa h y-
d r om a n d elic Acid . A small vial was charged with 110 mg
(0.77 mmol) of chiral 2-cyclohexylthiirane (R or S) and 93 mg
(0.81 mmol) of (S)-(+)-(methoxymethyl)pyrrolidine (neat). The
mixture was heated to 110 °C and kept there for 6.5 h. 1H
NMR analysis indicates that the reaction was complete and
for each case (R or S) generated a single diastereoisomer
indicating an enantiomeric excess of >95%. Key 1H NMR
signals for the single diastereomer are the diastereotopic
protons R to oxygen and nitrogen (two AB quartets centered
at 2.42 and 3.29 ppm) and the methoxy methyl (s, 3.10 ppm).
A 50/50 mixture of both diastereoisomers was obtained by
carrying out the above reaction with racemic 2-cyclohexylthi-
irane. The key 1H NMR signals for the other diastereoisomers
are as follows: two AB quartets at 2.46 and 3.38 ppm and a
methoxy signal at 3.13 ppm.
Syn th esis of (R)-P r op ylen esu lfid e (4a ). A glass reaction
tube sealable with a Teflon stopcock was charged with 3.68 g
(48.3 mmol) of thiourea, 24.2 mL of tetraethylene glycol, and
4.79 mL of water. This was placed on a high vacuum line and
was freeze-thaw degassed. Into this tube was vacuum trans-
ferred 3.03 mL (43.2 mmol) of (S)-(-)-propylene oxide. The tube
was sealed by closing the stopcock, and the contents were
mixed by mechanical rotation of the tube for 12 h. The reaction
tube was then placed back onto the high vacuum line, and the
product was vacuum transferred out of the reaction mixture
into another vessel cooled to -78 °C containing anhydrous
sodium sulfate to adsorb water. The propylene sulfide was then
vacuum transferred into another vessel containing anhydrous
sodium sulfate for further drying. It was then vacuum trans-
ferred into a clean vessel for storage and used without further
purification or drying. Each of the vacuum transfers was
conducted as quickly as possible over a period of time to
minimize the amount of water transferred from one vessel to
the next. Yield: 2.19 g (68%). NMR data were identical to that
of commercially available racemic propylene sulfide.
Syn th esis of Cy2P CH2CH(CH3)SLi (5). Ch ir a l Ver sion
(95% Yield ). A 100-mL Schlenk flask was charged with 1.282
g (6.28 mmol) of Cy2PLi dissolved in 20 mL of THF. The flask
was cooled to -78 °C, and 4a (520 mg, 7.01 mmol) was vacuum
transferred into the lithium salt solution. It was kept at -78
°C for 45 min, after which time the dry ice/acetone bath was
removed and the yellowish solution allowed to reach ambient
temperature. After an additional 20 min, the solvent was
removed in vacuo. The solid was washed three times with 30
mL of hexane and dried in vacuo. Yield: 1.37 g (78%). The
Syn th esis of (S)-CyCHOC(S)OCH2. The chiral diol ob-
tained from the lithium aluminum hydride reduction of (S)-
(+)-hexahydromandelic acid (5.0 g, 31.6 mmol)28 was dissolved
in CH2Cl2, and thiocarbonyldiimidazole (8.0 g, 44.9 mmol) was
added. It was stirred at ambient temperature for 24 h, after
which time the solvent was removed in vacuo. Chromatogra-
phy of the oily residue (4:1, hexane/ethyl acetate) yielded 4.38
g (74%) of a white crystalline solid after removal of solvent.
1H NMR (CDCl3, 300 MHz, 23 °C): δ 4.66 (m, 2 H, CH2O),
4.64 (m, 1 H, CHO), 1.78 (m, 6 H), 1.23 (m, 4 H). 13C NMR
(CDCl3, 75 MHz, 23 °C): δ 192.0 (s, C(S)), 86.1 (d, J ) 154
Hz, CHO), 71.6 (t, J C-H ) 153 Hz, CH2O), 40.9 (d, J C-H ) 129
1
lithium salt was used without further purification. H NMR
(THF-d8, 300 MHz, 23 °C): δ 2.80 (m, 1 H, CH), 1.31 (d, J )
6 Hz, 3 H, CH3), 2.0-1.0 (m, 24 H). 13C NMR (THF-d8, 125
MHz, 23 °C): δ 40.1 (brs, CH(CH3)), 34.9 (d, J P-C ) 20 Hz),
34.6 (d, J P-C ) 11 Hz, CH of Cy), 34.3 (d, J P-C ) 12 Hz, CH of
Cy), 31.5 (d, J P-C ) 14 Hz, CH2 of Cy), 31.2 (d, J P-C ) 13 Hz,
CH2 of Cy), 30.2 (d, J P-C ) 8 Hz, CH2 of Cy), 28.6 (m), 27.8 (s).
31P{H} NMR (THF-d8, 121 MHz, 23 °C): δ -7.6.
Deter m in a tion of th e En a n tiom er ic Excess of th e
Liga n d s Der ived fr om 4a . An NMR tube was charged with
33 mg (0.12 mmol) of Cy2PCH2CH(CH3)SLi (5) and (1S)-(-)-
camphanic chloride (26 mg, 0.12 mmol). The mixture of solids
was dissolved in ca. 0.6 mL of THF-d8. The 31P NMR shows
two distincts signals corresponding to two diastereoisomers
(-7.3, s, minor, -6.9, s, major). Integration of these signals
allows the determination of the enantiomeric excess: 88%. A
50/50 mixture of the diastereoisomers was obtained using
racemic propylene sulfide.
Hz, ipso CH), 27.6, 27.3, 25.8, 25.3, 25.1 all triplets, J C-H
)
140 Hz). C, H Anal. Found (Calcd): C, 58.20 (58.03); H, 7.62
(7.58).
Syn th esis of (S)-CyCHOC(O)SCH. A 500-mL round-
bottomed flask was charged with 4.0 g (21.5 mmol) of (S)-
CyCHOC(S)OCH2 dissolved in 200 mL of THF. Tetrabutylam-
monium bromide (1.5 g, 4.7 mmol) was added. It was brought
to reflux and kept there overnight. The solvent was then
removed in vacuo and the residue chromatographed (4:1
1
hexane/ethyl acetate). Yield: 3.88 g (97%). H NMR (CDCl3,
Syn th esis of Cy2P CH2CH(Cy)SLi (6). A 100-mL Schlenk
flask was charged with 509 mg (2.49 mmol) of Cy2PLi dissolved
in 15 mL of THF. The flask was cooled to -78 °C and
300 MHz, 23 °C): δ 4.38 (m, 1 H, CHO), 3.37 (m, 1 H, CH2S),
2.2-0.8 (m, 11 H, Cy). 13C NMR (CDCl3, 75 MHz, 23 °C): δ
172.7 (s, C(O)), 85.5 (d, J C-H ) 150 Hz, CHO), 41.7 (d, J C-H
)
135 Hz, ipso CH), 34.5 (t, J ) 143 Hz, CH2S), 29.0, 27.9, 26.0,
25.6, 25.4, all triplets, J C-H ) 136 Hz). C, H Anal. (Calcd): C,
57.52 (58.03); H, 7.39 (7.58).
Syn th esis of (R)-2-Cycloh exylth iir a n e (4b). A 50-mL
round-bottomed flask was charged with 1.316 g (7.06 mmol)
CyCH2SCH (390 mg, 2.74 mmol), 4b, in 3 mL of THF was
added dropwise. It was kept at -78 °C for 5-10 min, after
which time the dry ice/acetone bath was removed and the
colorless solution allowed to reach ambient temperature. After
an additional 30 min, the solvent was removed in vacuo.
Yield: 0.765 g (89%). The lithium salt was used without
further purification. 1H NMR (THF-d8, 300 MHz, 23 °C): δ
2.6 (brm, 1 H), 2.1-1.0 (brm, 35 H). 13C{H} NMR (THF-d8,
125 MHz, 23 °C): δ 49.3 (brs, CH(Cy)), 45.4 (d, J P-C ) 17 Hz,
CH of Cy), 33.9 (d, J P-C ) 9 Hz, CH of Cy), 33.7 (d, J P-C ) 7
Hz, CH of Cy), 32.0-24.0 (overlapping multiplets correspond-
ing to CH2’s). 31P{H} (THF-d8, 121 MHz, 23 °C) NMR: δ -7.2.
Syn th esis of P h 2P CH2CH(CH3)SLi (7). A Schlenk flask
was charged with 2.76 g (14.4 mmol) of Ph2PLi dissolved in
40 mL of THF. The flask was cooled to -78 °C, and 4a (1.12
g, 15.1 mmol) dissolved in ca. 10 mL THF was added dropwise
via syringe. The reaction mixture was kept at -78 °C for 30
min, after which time the dry ice/acetone bath was removed
and the colorless solution allowed to reach ambient temper-
of (S)-CyCHOC(O)SCH dissolved in 15 mL of MeOH. The flask
was cooled to 0 °C, and 5.65 mL of a 2 N solution of NaOH
was added dropwise. A white precipitate formed immediately.
After 2 h most of the solvent was removed in vacuo. The
residue was then neutralized with 5% HCl, and the product
was extracted with 2 × 30 mL of CH2Cl2. Methylene chloride
was removed on a rotary evaporator, and the residue was
1
distilled under vacuum (10-2 Torr). Yield: 0.550 g (55%). H
NMR (CDCl3, 300 MHz, 23 °C): δ 2.69 (m, 1 H, CH), 2.67 (d,
1 H, J ) 6 Hz, CHH), 2.46 (d, 1 H, J ) 6 Hz, CHH), 2.0-0.5
(m, 11 H, Cy). 13C NMR (CDCl3, 75 MHz, 23 °C): δ 44.8 (d, J
) 132 Hz), 41.9 (t, J C-H ) 163 Hz), 32.9 (t, J C-H ) 137 Hz),
(28) Nugent, W. A.; Harlow, R. L. J . Am. Chem. Soc. 1994, 116, 6142.

Synthesis of Novel (P,S) Ligands
Organometallics, Vol. 18, No. 11, 1999 2069
ature. After an additional 25 min, the solvent was removed in
vacuo. Yield: 3.55 g. Accounting for 15 mol % of THF in the
salt, this corresponds to 3.37 g (88% yield). The lithium salt
(C6D6, 121 MHz, 23 °C): δ -9.8. MS: M + 1 at m/e ) 363.39.
C, H Anal. (Calcd): C, 73.05 (72.88); H, 9.68 (9.73).
Syn th esis of Cy2P CH2CH(CH3)SCH2(C6(CH3)5) (11). A
vial was charged with 355 mg (1.28 mmol) of Cy2PCH2CH-
(CH3)SLi dissolved in ca. 5 mL of THF. Pentamethylbenzyl
chloride (239 mg, 1.21 mmol) dissolved in ca. 5 mL THF was
then added dropwise. After the solution was stirred at ambient
temperature for 45 min, the solvent was removed in vacuo.
The product was extracted with hexane (3 × 30 mL) and
filtered and the solvent removed in vacuo from the filtrate.
Yield: 416 mg (79%). 1H NMR (C6D6, 300 MHz, 23 °C): δ 3.57
(AB quartet, 2H, CH2(C6(CH3)5), 2.99 (m, 1 H, CH), 2.42 (s,
6H, 2 CH3’s), 2.05 (s, 3 H, 1 CH3), 2.06 (s, 6 H, 2 CH3’s), 1.60
(d, J ) 7 Hz, 3 H, CH3), 2.3-0.5 (m, 24 H). 13C{H} NMR (C6D6,
125 MHz, 23 °C): δ 133.7 (s), 132.8 (s), 132.6 (s), 131.6 (s),
41.7 (d, J C-P ) 25 Hz, CH(S)), 34.5 (d, J C-P ) 15 Hz, P
cyclohexyl CR), 33.8 (d, J C-P ) 15 Hz, P cyclohexyl CR), 32.5
(s, SCH2arene), several multiplets due to the cyclohexyl H’s
were observed in the range 25.0-35.0 ppm, 22.8 (d, J C-P ) 9
Hz, CH(CH3)(S)), 17.0 (s, CH3), 16.9 (s, CH3), 16.7 (s, CH3).
31P{H} NMR (C6D6, 121 MHz, 23 °C): δ -7.6. C, H Anal.
(Calcd): C, 74.78 (74.95); H, 10.50 (10.48).
Syn th esis of Cy2P CH2CH(CH3)SCH2(a n th r a cen e) (12).
A 250-mL round-bottomed flask was charged with 1.00 g (3.59
mmol) of 5 dissolved in ca. 50 mL of THF. To this was added
9-chloromethylanthracene (810 mg, 3.57 mmol) in small por-
tions. After the solution was stirred at ambient temperature
for 5 h (the reaction was complete within an hour), the solvent
was removed in vacuo. The product was extracted with toluene
(100 mL) and filtered, and the solvent was removed in vacuo
from the filtrate. Yield: 1.16 g (70%). 1H NMR (C6D6, 300 MHz,
23 °C): δ 8.49 (dd, J ) 9, 0.8 Hz, 2 H), 8.11 (s, 1 H), 7.78 (ddd,
J ) 9, 0.6, 0.6 Hz, 2 H), 7.31 (m, 4H), 4.71 (s, 2 H, SCH2), 3.06
(m, 1 H, CH), 1.62 (d, J ) 7 Hz, 3 H, CH3), 2.0-0.5 (m, 24 H).
13C{H} NMR (C6D6, 125 MHz, 23 °C): δ 132.1 (s), 130.6 (s),
130.2 (s), 129.5 (s), 127.6 (s), 126.3 (s), 125.2 (s), 125.0 (s), 41.8
(d, J P-C ) 25 Hz, CH(CH3)), 34.2 (d, J P-C ) 15 Hz, CH of Cy),
33.6 (d, J P-C ) 15 Hz, CH of Cy), 31.3 (d, J P-C ) 23 Hz, CH2
of Cy), 30.7-26.0 (overlapping multiplets corresponding to
CH2’s of Cy), 23.1 (d, J P-C ) 10 Hz, CH3). 31P{H} NMR (C6D6,
121 MHz, 23 °C): δ -8.2. C, H Anal. (Calcd): C, 77.30 (77.88);
H, 8.14 (8.50). MS: M + 1 at m/e ) 463.51.
Syn th esis of Cy2P CH2CH(CH3)SCH(su ber a n e) (13). A
250-mL round-bottomed flask was charged with 1.183 g (4.25
mmol) of Cy2PCH2CH(CH3)SLi 5 dissolved in ca. 30 mL of
THF. To this was added 5-chlorodibenzosuberane (970 mg,
4.24 mmol) dissolved in ca. 30 mL of THF dropwise. After the
solution was stirred at ambient temperature for 1 h, the
solvent was removed in vacuo. The product was extracted with
hexane and small amounts of diethyl ether. The combined
extracts were filtered, and solvent was removed in vacuo from
the filtrate. Yield: 1.431 g (73%). 1H NMR (C6D6, 300 MHz,
23 °C): δ 7.5-6.5 (m, 8H, aromatic signals), 5.35 (s, 1 H), 4.12
(m, 1 H), 3.65 (m, 1 H), 2.76 (m, 4 H), 1.62 (d, J ) 6.5 Hz),
2.0-1.0 (m, 24 H). 13C{H} NMR (C6D6, 125 MHz, 23 °C): δ
141.5 (s), 140.9 (s), 138.7 (s), 138.2 (s), 131.5 (s), 131.2 (s), 130.7
(s), 130.6 (s), 126.2 (s), 125.9 (s), 56.4 (s), 40.7 (d, J P-C ) 23
Hz, CH(CH3)), 34.2 (d, J P-C ) 15 Hz, CH of Cy), 34.0-25.0
(overlapping multiplets corresponding to CH2’s and a CH of
Cy), 23.0 (d, J P-C ) 10 Hz, CH3). 31P{H} NMR (C6D6, 121 MHz,
23 °C): δ -8.6. MS: M + 1 at m/e ) 465.52. C, H Anal.
(Calcd): C, 77.72 (77.54); H, 8.86 (8.89).
1
was used without further purification. H NMR (THF-d8, 300
MHz, 23 °C): δ 8-7 (m, 10 H, arene), 2.85 (m, 1 H, CH), 2.46
(ddd, J ) 13, 6, 2.3 Hz, 1 H), 2.25 (dd, J ) 13, 8 Hz, 1 H), 1.38
(d, J ) 6 Hz, 3 H, CH3). 13C NMR (THF-d8, 125 MHz, 23 °C):
δ 141.5 (d, J P-C ) 7 Hz, quaternary C Ph), 141.4 (d, J P-C ) 7
Hz, quaternary C Ph), 134.0 (dd, J P-C ) 13 Hz, J C-H ) 142
Hz, CH Ph), 133.8 (dd, J P-C ) 13 Hz, J C-H ) 142 Hz, CHPh),
128.90 (dd, J C-P ) 6 Hz, J C-H ) 160 Hz, CHPh), 128.88 (d,
J C-P ) 6 Hz, J C-H ) 160 Hz, CHPh), 128.7 (dd, J C-P ) 15 Hz,
J C-H ) 160 Hz, 2 CH Ph), 46.9 (dt, J C-P ) 10 Hz, J C-H ) 128
Hz, CH2PPh2), 33.1 (dd, J P-C ) 16 Hz, J C-H ) 137 Hz, CH-
(CH3)), 31.4 (dq, J P-C ) 8 Hz, J C-H ) 126 Hz, CH(CH3)). 31P-
{H} NMR (THF-d8, 121 MHz, 23 °C): δ -17.6.
Syn th esis of P h 2P CH2CH(Cy)SLi (8). A 50-mL Schlenk
flask was charged with 650 mg (3.38 mmol) of Ph2PLi dissolved
in 10 mL of THF. The flask was cooled to -78 °C, and 4b (505
mg, 3.55 mmol) in 5 mL of THF was added dropwise. It was
kept at -78 °C for 30 min, after which time the dry ice/acetone
bath was removed and the colorless solution allowed to reach
ambient temperature. After an additional 30 min, the solvent
was removed in vacuo. Yield: 1.0 g (88%). The lithium salt
1
was used without further purification. H NMR (THF-d8, 300
MHz, 23 °C): δ 7.6-7.4 (m, 4 H, arene), 7.4-7.3 (m, 6 H,
arene), 2.62 (m, 1 H, CHCy), 2.54 (ddd, J ) 14, 6, 2 Hz, 1 H,
CHHPPh2), 2.30 (ddd, J ) 14 Hz, J ) 9 Hz, J ) 2 Hz,
CHHPPh2), 1.9-1.0 (m, 11 H, Cy). 13C{H} NMR (THF-d8, 125
MHz, 23 °C): δ 140.4 (d, J P-C ) 14 Hz, quaternary C Ph), 139.6
(d, J P-C ) 15 Hz, quaternary C Ph), 134.2 (d, J P-C ) 20 Hz,
CH Ph), 133.5 (d, J P-C ) 19 Hz, CH Ph), 130.0-129.0
(overlapping multiplets accounting for C-H of Ph), 45.1 (d,
J C-P ) 7 Hz, CH), 44.8 (d, J P-C ) 16 Hz, CH), 38.0 (d, J P-C
)
14 Hz, CH2PPh2), 31.8 (s, CH2 of Cy), 28.7 (s, CH2 of Cy), 27.52
(s, CH2 of Cy), 27.48 (s, CH2 of Cy), 27.3 (s, CH2 of Cy). 31P{H}
NMR (THF-d8, 121 MHz, 23 °C): δ -16.8.
Syn th esis of Cy2P CH2CH(CH3)SCH3 (9). A vial was
charged with 462 mg (1.66 mmol) of 5 dissolved in ca. 10 mL
of THF. Methyl iodide (127 µL, 2.04 mmol) was then added
dropwise. After being stirred at ambient temperature for 15
min, the solvent was removed in vacuo. The product was
extracted with hexane (20 mL) followed by toluene (25 mL)
and filtered, and the solvent was removed in vacuo from the
filtrate. The compound was further purified by oil sublimation
1
in vacuo. Yield: 444 mg (93%). H NMR (C6D6, 300 MHz, 23
°C): δ 2.77 (m, 1 H, CH), 1.90 (s, 3 H, SCH3), 1-2 (m, 24 H),
1.45 (d, J ) 7 Hz, 3 H, CH3). 13C{H} NMR (C6D6, 125 MHz, 23
°C): δ 41.5 (d, J P-C ) 25 Hz, CH(CH3)), 34.3 (d, J P-C ) 14 Hz,
CH of Cy), 33.6 (d, J P-C ) 14 Hz, CH of Cy), 32.0-25.0
(overlapping multiplets corresponding to CH2’s), 21.8 (d, J P-C
) 10 Hz, SCH3), 13.8 (s, CH3). 31P{H} NMR (THF-d8, 121 MHz,
23 °C): δ -9.3. C, H Anal. (Calcd): C, 67.40 (67.09); H, 10.84
(10.91).
Syn th esis of Cy2P CH2CH(CH3)SCH2P h (10). A 100 mL
round-bottomed flask was charged with 0.841 g (3.02 mmol)
of 5 dissolved in ca. 30 mL of THF. Benzyl bromide (490 mg,
2.87 mmol) was then added dropwise. The initial slurry turned
into a clear yellow solution. After the solution was stirred at
ambient temperature for 1 h, the solvent was removed in
vacuo. The product was extracted with hexane (100 mL) and
filtered, and the solvent was removed in vacuo from the
filtrate. Yield: 742 mg (71%). 1H NMR (C6D6, 300 MHz, 23
°C): δ 7.5-6.8 (m, 5 H, Ph), 3.57 (AB quartet, 2 H, CH2Ph),
2.70 (m, 1 H, CH), 1.43 (d, J ) 7 Hz, 3 H, CH3), 2.0-0.5 (m,
24 H). 13C{H} NMR (C6D6, 125 MHz, 23 °C): δ 139.0 (s), 128.9
(s), 128.6 (s), 126.9 (s), 39.0 (d, J P-C ) 24 Hz, CH(CH3)), 35.6
Syn th esis of Cy2P CH2CH(Cy)SCH3 (14). A vial was
charged with 217 mg (0.63 mmol) of 6 dissolved in ca. 10 mL
of THF. Then methyl iodide (43 µL, 0.69 mmol) was added.
After the solution was stirred at ambient temperature for 30
min, the solvent was removed in vacuo. The product was
extracted with hexane and filtered, and the solvent was
1
(s, CH2Ph), 34.4 (d, J P-C ) 16 Hz, CH of Cy), 33.5 (d, J P-C
)
removed in vacuo from the filtrate. Yield: 110 mg (50%). H
15 Hz, CH of Cy), 32.0-26.0 (overlapping multiplets corre-
NMR (C6D6, 300 MHz, 23 °C): δ 2.58 (m, 1 H), 2.02 (s, 3 H,
sponding to CH2’s), 22.1 (d, J P-C ) 10 Hz, SCH3). 31P{H} NMR
SCH3), 2.0-1.0 (brm, 35 H). 13C{H} NMR (C6D6, 125 MHz, 23

2070 Organometallics, Vol. 18, No. 11, 1999
Hauptman et al.
°C): δ 55.1 (d, J P-C ) 22 Hz, CH(Cy)), 42.9 (d, J P-C ) 9 Hz,
CH of Cy), 34.4 (d, J P-C ) 16 Hz, CH of Cy), 34.2 (d, J P-C ) 16
Hz, CH of Cy), 32.0-26.0 (overlapping multiplets correspond-
ing to CH2’s), 16.2 (d, J P-C ) 3 Hz, SCH3). 31P{H} NMR (C6D6,
121 MHz, 23 °C): δ -8.8. We were not able to obtain a
satisfactory elemental analysis for this compound. When we
submitted this compound for high-resolution mass spectro-
scopy we observed a molecular ion at 354.2510 (M+ - CH3).
Syn th esis of Cy2P CH2CH(Cy)SCH2(C6(CH3)5) (15). A
vial was charged with 252 mg (0.73 mmol) of 6 dissolved in
ca. 3 mL of THF. Pentamethylbenzyl chloride (136 mg, 0.69
mmol) dissolved in ca. 7 mL of THF was then added dropwise.
After the solution was stirred at ambient temperature for 1
h, the solvent was removed in vacuo. The product was
extracted with hexane and filtered, and the solvent was
Syn t h esis of (Cy2P CH2CH (CH3)SCH2(C5(CH3)5)NiCl2
(18a ). A vial was charged with 50 mg (0.23 mmol) of (DME)-
NiCl2. Then 99 mg (0.23 mmol) of 11 dissolved in ca. 3 mL of
CH2Cl2 was added. A red-purple solution resulted. After the
solution was stirred at ambient temperature for 30 min, the
solvent was removed. The resulting sticky oil was triturated
with hexane until a purple solid was obtained. The solid was
collected by filtration, washed with hexane, and dried in vacuo.
1
Yield: 103 mg (69%). H NMR (CD2Cl2, 23 °C, 300 MHz): δ
5.14 (brm, 1 H, CHH(C5(CH3)5)), 4.86 (brm, 1 H, CHH
(C5(CH3)5)), 3.0-2.5 (m, 2 H), 2.34 (s, 6 H, 2CH3’s), 2.21 (s, 3
H, CH3), 2.20 (s, 6 H, 2 CH3’s), 2.0-1.0 (brm, 23 H), 0.61 (brd,
J ) 6 Hz, 3 H, CH(CH3)). 13C NMR (CD2Cl2, 23 °C, 75 MHz):
δ 136.2 (s), 133.9 (s), 133.5 (s), 127.7 (s), 47.4 (d, J C-H ) 146
Hz, CH(CH3)), 40.8 (t, J C-H ) 145 Hz, CH2(C5(CH3)5)), 38.0-
26.0 (overlapping broad and sharp multiplets), 21.8 (brq, J C-H
1
removed in vacuo from the filtrate. Yield: 306 mg (88%). H
) 125 Hz, CH3), 18.0 (q, J C-H ) 126 Hz, CH3), 17.3 (q, J C-H
)
NMR (C6D6, 300 MHz, 23 °C): δ 4.08 (AB quartet, 2 H, CH2-
(C6(CH3)5), 2.78 (m, 1 H, CH), 2.52 (s, 3 H, CH3), 2.07 (s, 6 H,
2 CH3’s), 2.2-1.0 (brm, 35 H). 13C{H} NMR (C6D6, 125 MHz,
23 °C): δ 133.6 (s), 132.8 (s), 132.5 (s), 132.0 (s), 54.9 (d, J P-C
) 22 Hz, CH(Cy)), 44.0 (d, J P-C ) 8 Hz, CH of Cy), 35.6 (d,
J P-C ) 4 Hz, SCH2), 34.4 (dd, J P-C ) 15 Hz CH of Cy), 34.3 (d,
J P-C ) 15 Hz, CH of Cy), 32.0-26.0 (overlapping multiplets
corresponding to CH2’s), 16.93 (s, CH3), 16.88 (s, 2 CH3), 16.80
(s, 2 CH3). 31P{H} NMR (C6D6, 121 MHz, 23 °C): δ -7.4. C, H
Anal. (Calcd): C, 76.35 (76.75); H, 10.70 (10.67).
Syn th esis of P h 2P CH2CH(CH3)SCH3 (16). A vial was
charged with 450 mg (1.69 mmol) of 7 dissolved in ca. 10 mL
of THF. Methyl iodide (127 µL, 2.04 mmol) was then added
dropwise. After the solution was stirred at ambient temper-
ature for 15 min, the solvent was removed in vacuo. The
product was extracted with hexane (20 mL) followed by toluene
(25 mL) and filtered, and the solvent was removed in vacuo
from the filtrate. Yield: 279 mg (60%). 1H NMR (C6D6, 300
MHz, 23 °C): δ 7.3-7.5 (m, 4 H, Ph), 7.15 (m, 6 H, Ph), 2.62
(m, 1 H, CH), 2.51 (ddd, J ) 14 Hz, J ) 5 Hz, J ) 1.5 Hz, 1
H), 2.11 (ddd, J ) 14 Hz, J ) 10 Hz, J ) 2.5 Hz), 1.69 (s, 3 H,
SCH3), 1.35 (d, J ) 7 Hz, 3 H, CH3). 13C{H} NMR (THF-d8,
125 MHz, 23 °C): δ 139.8 (d, J P-C ) 15 Hz, quaternary C Ph),
139.1 (d, J P-C ) 15 Hz, quaternary C Ph), 133.4 (d, J P-C ) 20
Hz, CH Ph), 133.0 (d, J P-C ) 19 Hz, CH Ph), 129.0-128.0
(overlapping multiplets accounting for C-H of Ph), 39.1 (d,
J C-P ) 17 Hz, CH), 37.3 (d, J P-C ) 16 Hz, CH2), 21.9 (d, J P-C
) 9 Hz, CH3), 13.2 (s, CH3). 31P{H} NMR (C6D6, 121 MHz, 23
°C): δ -20.9. C, H Anal. (Calcd): C, 70.05 (70.04); H, 6.74
(6.98).
126 Hz, CH3), 17.0 (q, J C-H ) 126 Hz, CH3). 31P{H} NMR (CD2-
Cl2, 23 °C, 121 MHz): 50-100 very broad signal. C, H Anal.
(Calcd): C, 57.53 (57.67); H, 7.87 (8.07).
Syn th esis of (Cy2P CH2CH(CH3)SCH2(C5(CH3)5)P d Cl2
(18b). A vial was charged with 102 mg (0.36 mmol) of (COD)-
PdCl2, and this was suspended in 10 mL of diethyl ether. Then
162 mg (0.37 mmol) of 11 dissolved in ca. 5 mL of diethyl ether
was added. As the reaction proceeded, a very lightly colored
yellow solid precipitated. After the solution was stirred at
ambient temperature overnight, the solid was collected by
filtration, washed with diethyl ether, and dried in vacuo.
Yield: 152 mg (70%). A single crystal was obtained by
recrystallization from CH2Cl2/hexane at -30 °C. 1H NMR (CD2-
Cl2, 23 °C, 300 MHz): δ 5.32 (br AB quartet, 2 H, CH2S,
broadening was due to inversion at S; see text for details), 3.59
(m, 1 H, CH(CH3)), 2.68 (s, 6 H, 2 CH3’s), 2.55 (s, 3 H, CH3),
2.53 (s, 6 H, 2CH3’s), 2.9-1.4 (brm, 24 H), 1.15 (d, J ) 7 Hz,
3H, CH(CH3)). 13C{H} NMR (CD2Cl2, 23 °C, 75 MHz): δ 136.3
(s), 133.9 (s), 133.4 (s), 127.4 (s), 48.7 (s, CH(CH3)), 42.6 (s),
37.1 (d, J P-C ) 26 Hz), 35.1 (d, J P-C ) 29 Hz), 34.1 (d, J P-C
)
26 Hz), 30.0-25.0 (overlapping multiplets), 21.4 (d, J P-C ) 16
Hz), 18.0 (s, CH3), 17.3 (s, CH3), 17.0 (s, CH3). 31P{H} NMR
(CD2Cl2, 23 °C, 121 MHz): 74.2. C, H Anal. (Calcd): C, 53.11
(53.16); H, 6.94 (7.44).
X-r a y Str u ctu r a l An a lysis of 18b. A single colorless
crystal of (Cy2PCH2CH(CH3)SCH2(C5(CH3)5)PdCl2 (wedge, 0.25
× 0.10 × 0.28 mm3) was grown by slow evaporation of a CD2-
Cl2 solution at ambient temperature. The crystal was mono-
clinic (P21/n, No. 14) with the following cell dimensions
determined from 25 reflections (µ(Mo) ) 9.37 cm-1): a ) 8.547-
(1) Å, b ) 24.226(4) Å, c ) 14.700(3) Å; â ) 103.97(1)°; V )
2953.8 Å3; Z ) 4; FW ) 610.00 (PdCl2SPC27H45); density (calcd)
) 1.372 g/cm3. Data were collected at -45 °C on an Enraf-
Nonius CAD4 diffractometer with a graphite monochromator
using Mo KR radiation (λ ) 0.7107 Å). A total of 6179 data
were collected (1.7° e 2θ e 52.0°; maximum h, k, l ) 10, 29,
18; data octants +++, -++; ω scan method; typical half-height
peak width ) 0.16°ω; scan speed ) 1.70-5.00 deg/min). Two
standards were collected 28 times (1% fluctuation). There were
2770 unique reflections with I g 3.0σ(I). The structure was
solved by direct methods (SHELXS). The structure was refined
by full-matrix least squares on F with scattering factors from
the International Tables for X-ray Crystallography (Kinoch
Press: Birmingham, England, 1974; Vol. 4) including anoma-
Syn th esis of P h 2P CH2CH(CH3)SCH2(C6(CH3)5) (17). A
vial was charged with 330 mg (1.24 mmol) of 7 dissolved in
ca. 5 mL of THF. Pentamethylbenzyl chloride (240 mg, 1.22
mmol) dissolved in ca. 5 mL of THF was then added dropwise.
After being stirred at ambient temperature for 1.5 h, the
solvent was removed. The product was extracted with hexane/
toluene (5 mL/10 mL) and filtered and the solvent removed in
vacuo from the filtrate. The oily residue was triturated with
small amounts of hexane until a solid was obtained; the white
solid was collected by filtration and dried. Yield: 157 mg (31%).
1H NMR (C6D6, 300 MHz, 23 °C): δ 7.44 (m, 4 H, arene), 7.06
(m, 6 H, arene), 3.73 (AB quartet, 2 H, CH2(C6(CH3)5), 2.86
(m, 1 H, CH), 2.61 (dd, J ) 14 Hz, J ) 5 Hz, 1 H, CHHPPh2),
2.34 (s, 6 H, 2CH3’s), 2.23 (ddd, J ) 14 Hz, J ) 9 Hz, J ) 2
Hz, 1 H, CHHPPh2), 2.05 (s, 3 H, CH3), 2.04 (s, 6 H, 2 CH3’s),
1.48 (d, J ) 7 Hz, 3 H, CH3). 13C{H} NMR (THF-d8, 125 MHz,
23 °C): δ 139.7 (d, J P-C ) 15 Hz, quaternary C Ph), 139.4 (d,
lous terms for Pd, Cl, S, and P (biweight‚[σ2(I) + 0.0009I2]-1/2
)
(excluded 5). All non-hydrogen atoms were refined anisotro-
pically; H atoms were refined isotropically. There were 289
parameters, and the data-to-parameter ratio was 9.57; final
R ) 0.044 (Rw ) 0.037). The error of fit was 1.07 with a
maximum ∆/σ of 0.00. Because the refinement for a few of the
methyl hydrogens gave thermal parameters larger than
desired (12.2), all of the hydrogens were idealized close to their
previously refined positions. The largest residual density )
0.80 e/Å3.
J P-C ) 15 Hz, quaternary C Ph), 133.7 (s), 133.24 (d, J P-C
)
19 Hz, CH Ph), 133.16 (d, J P-C ) 19 Hz, CH Ph), 132.7 (s),
132.5 (s), 131.2 (s), 129.0-128.0 (overlapping multiplets ac-
counting for C-H of Ph), 39.3 (d, J C-P ) 17 Hz, CH), 37.9 (d,
J P-C ) 16 Hz, CH2PPh2), 31.9 (d, J ) 1.5 Hz, SCH2), 22.9 (d,
J P-C ) 8 Hz, CHCH3), 16.9 (s, CH3), 16.8 (s, CH3), 16.5 (s, CH3).
31P{H} NMR (C6D6, 121 MHz, 23 °C): δ -19.8. C, H Anal.
(Calcd): C, 76.38 (77.10); H, 7.50 (7.91).

Synthesis of Novel (P,S) Ligands
Organometallics, Vol. 18, No. 11, 1999 2071
Syn th esis of (Cy2P CH2CH(CH3)SCH2(C6(CH3)5))P tCl2
(18c). A vial was charged with 43 mg (0.12 mmol) of (NBD)-
PtCl2. Then 51 mg (0.12 mmol) of 11 dissolved in ca. 5 mL of
CH2Cl2 was added. After the solution was stirred overnight
at ambient temperature, the solvent was removed. The product
was washed with hexane. The crystalline complex has 0.5
equiv of CH2Cl2 of solvation. The elemental analysis reflects
a somewhat lower content of dichloromethane possibly owing
to loss of solvent during transport of the sample. Yield: 57
ature for 30 min, the solvent was removed in vacuo. The
resulting oily solid was washed with hexane (2 × 10 mL) and
dried in vacuo. The yield of the orange solid was 186 mg (53%).
1H NMR (CD2Cl2, 23 °C, 300 MHz): δ 7.50 (m, 2 H, arene),
7.41 (m, 3 H, arene), 5.07 (brs, 2 H, COD), 4.93 (brs, 1 H, COD),
4.73 (brs, 1 H, COD), AB quartet centered at 4.08 ppm (2 H,
CH2Ph), 2.98 (m, 1 H, CH(CH3), 2. 7-1.0 (brm, 24 H), 1.54 (d,
J ) 6 Hz, 3 H, CH3). 13C{H} NMR (CD2Cl2, 23 °C, 125 MHz):
δ 133.4 (s, quaternary C, arene), 129.7 (s, 2 CH, arene), 129.6
(s, 2 CH, arene), 129.3 (s, CH, arene), 102.0 (dd, J ) 16, 7 Hz,
COD olefinic carbon), 100.7 (dd, J ) 8, 8 Hz, COD olefinic
carbon), 85.9 (d, J ) 11 Hz, COD olefinic carbon), 85.1 (d, J )
11 Hz, COD olefinic carbon), 46.6 (d, J ) 6 Hz, CH(CH3)), 39.0
(s, CH2Ph), 37.1 (d, J ) 21 Hz, CH of Cy), 34.6 (d, J ) 23 Hz,
CH of Cy), 34.0-25.0 (overlapping multiplets accounting for
CH2’s), 20.4 (d, J ) 14 Hz, CH(CH3)). 31P{H} NMR (CD2Cl2,
23 °C, 121 MHz): 53.3 (d, J Rh-P) 139 Hz). C, H Anal. (Calcd):
C, 51.48 (51.52); H, 6.47 (6.56).
1
mg (ca. 64%). H NMR (CD2Cl2, 23 °C, 300 MHz): δ 4.96 (AB
quartet, 2 H, CH2S), 3.14 (m, 1 H, CH(CH3)), 2.36 (s, 6 H, 2
CH3’s), 2.23 (s, 3 H, CH3), 2.22 (s, 6H, 2 CH3’s), 2.1-1.1 (brm,
24 H), 0.89 (brd, J ) 6 Hz, 3 H, CH(CH3)). 13C{H} NMR (CD2-
Cl2, 23 °C, 75 MHz): δ 137.2 (s), 134.0 (brs), 133.4 (brs), 127.4
(s), 49.6 (s, CH(CH3)), 42.8 (s, CH2 arene), 35.4 (d, J P-C ) 34
Hz, CH of Cy), 32.9 (d, J P-C ) 34 Hz, PCH2), 32.7 (d, J P-C
)
36 Hz, CH of Cy), 30.0-26.0 (overlapping multiplets), 20.2 (d,
J P-C ) 13 Hz), 18.0 (s, CH3), 17.3 (s, CH3), 17.0 (s, CH3). 31P{H}
NMR (CD2Cl2, 23 °C, 121 MHz): 47.3 (t, J Pt-P ) 3408 Hz). C,
H Anal. (Calcd): C, 45.36 (44.57); H, 6.06 (6.26).
Syn t h esis of (Cy2P CH2CH (CH3)SCH2(C6(CH3)5))R h -
(COD)+OTf- (22). A vial was charged with 112 mg (0.24
mmol) of Rh(COD)2+OTf- dissolved in ca. 5 mL of THF. Then
104 mg (0.24 mmol) of 11 dissolved in ca. 5 mL of THF was
added dropwise. As the addition occurred, the solution turned
from red to orange. After the solution was stirred at ambient
temperature for 30 min, the solvent was removed in vacuo.
The resulting oily solid was washed with hexane and dried in
vacuo. Yield: 182 mg (96%). 1H NMR (CD2Cl2, 23 °C, 300
MHz): δ 5.0-4.5 (brm, 3 H, COD), 4.22 (brs, 1 H, COD), 4.15
(d of AB quartet, 1 H, CHH), 4.08 (d of AB quartet, 1 H, CHH),
3.15 (m, 1 H, CH(CH3)), 2.44 (s, 6 H, C5(CH3)5), 2.24 (s, 9 H,
C5(CH3)5), 1.54 (d, J ) 7 Hz, 3 H, CH3), 2.5-1.0 (brm, 24 H).
13C{H} NMR (CD2Cl2, 23 °C, 125 MHz): δ 136.8 (s, arene),
134.0 (s, arene), 133.5 (s, arene), 126.3 (s, arene), 103.3 (brs,
COD olefinic carbon), 99.9 (brs, COD olefinic carbon), 86.4 (brs,
COD olefinic carbon), 85.3 (brs, COD olefinic carbon), 47.7 (d,
J ) 7 Hz, CH(CH3)), 36.9 (d, J ) 21 Hz, CH of Cy), 36.5 (s,
CH2 arene), 34.7 (d, J ) 23 Hz, CH of Cy), 34.0-25.0
(overlapping multiplets accounting for CH2’s), 20.1 (d, J ) 13
Hz, CH(CH3)), 17.9 (brs, CH3), 17.4 (s, CH3), 17.1 (s, CH3).
31P{H} NMR (CD2Cl2, 23 °C, 121 MHz): 51.8 (d, J Rh-P ) 139
Hz). C, H Anal. (Calcd): C, 54.46 (54.54); H, 7.26 (7.25).
X-r a y Str u ctu r a l An a lysis of 19. A single gold crystal of
[Cy2PCH2CH(CH3)SPdCl]2 (irregular block, 0.18 × 0.14 × 0.25
mm3) was grown by slow evaporation of a hexane/dichlo-
romethane solution at ambient temperature. The crystal was
monoclinic (C2/c, No. 15) with the following cell dimensions
(µ(Mo)) 13.89 cm-1): a ) 29.125(1) Å, b ) 13.340(1) Å, c )
19.740(1) Å; â ) 113.71(1)°; V ) 7022.1 Å3; Z ) 8; FW ) 826.56
(Pd2Cl2S2P2C30H56); density (calcd) ) 1.564 g/cm3. One hemi-
sphere of data were collected at -112 °C on a Rigaku RU300,
R-AXIS image plate area detector using Mo KR radiation (λ )
0.7107 Å). A total of 18 069 data were collected (3.1° e 2θ e
48.2°; maximum h, k, l ) 33, 15, 22). There were 4755 unique
reflections with I g 3.0σ(I). The structure was solved by direct
methods (SHELXS) and refined by full-matrix least squares
on F with scattering factors from the International Tables for
X-ray Crystallography (Kinoch Press: Birmingham, England,
1974; Vol. 4) including anomalous terms for Pd, Cl, S, and P
(biweight‚[σ2(I) + 0.0009I2]-1/2) (excluded 9). All non-hydrogen
atoms were refined anisotropically; H atoms were refined
isotropically. There were 343 parameters, and the data-to-
parameter ratio was 13.84; final R ) 0.038 (Rw ) 0.042). The
error of fit was 2.16 with a maximum ∆/σ of 0.01. Because the
refinement for a few of the cyclohexyl hydrogens gave thermal
parameters larger than desired, all of the hydrogens were
idealized close to their previously refined positions. The largest
residual density ) 0.57 e/Å3.
X-r a y Str u ctu r a l An a lysis of 22. A single orange crystal
of (Cy2PCH2CH(CH3)SCH2(C6(CH3)5))Rh(COD)+OTf- (irregu-
lar block, 0.44 × 0.29 × 0.39 mm3) was grown from tetrahy-
drofuran/hexane at -30 °C. The crystal was monoclinic (P21/
n, No. 14) with the following cell dimensions determined from
50 reflections (µ(Mo) ) 6.98 cm-1): a ) 10.451(2) Å, b )
18.584(3) Å, c ) 19.733(4) Å; â ) 104.62(1)°; V ) 3708.5 Å3; Z
) 4; FW ) 783.94 (RhS3PF3OC35H60); density (calcd) ) 1.404
g/cm3. Data were collected at -100 °C on a Syntex R3
diffractometer with a graphite monochromator using Mo KR
radiation (λ ) 0.7107 Å). A total of 6963 data were collected
(4.0° e 2θ e 50.0°; maximum h, k, l ) 12, 22, 23; data octants
++-, -+-; ω scan method; typical half-height peak width )
0.31°ω; scan speed ) 3.90-14.60 deg/min). Two standards
were collected 73 times, and adjustments were made for a 3%
decrease in intensity. There were 4375 unique reflections with
I g 3.0σ(I). The structure was solved by direct methods
(MULTAN) and was refined by full-matrix least squares on F
with scattering factors from the International Tables for X-ray
Crystallography (Kinoch Press: Birmingham, England, 1974;
Vol. 4) including anomalous terms for Rh, S, and P (biweight‚
[σ2(I) + 0.0009I2]-1/2) (excluded 4). All non-hydrogen atoms
were refined anisotropically; H atoms were refined isotropi-
cally. There were 415 parameters, and the data-to-parameter
ratio was 10.53; final R ) 0.050 (Rw ) 0.048). The error of fit
was 1.63 with a maximum ∆/σ of 0.20. Because the refinement
for a few of the methyl hydrogens gave thermal parameters
larger than desired (14.8), all of the hydrogens have been
idealized close to their previously refined positions. The largest
residual density ) 1.31 e/Å3.
Syn th esis of (Cy2P CH2CH(CH3)SCH3)Rh (COD)+OTf-
(20). A vial was charged with 252 mg (0.54 mmol) of
Rh(COD)2+OTf-, and this was suspended in ca. 5 mL of THF.
Then 154 mg (0.54 mmol) of 9 dissolved in ca. 5 mL of THF
was added dropwise. After the solution was stirred at ambient
temperature for 30 min, the solvent was removed in vacuo.
The resulting oily solid was washed with hexane and dried in
vacuo. The yield of the orange solid was 323 mg (93%). 1H NMR
(CD2Cl2, 23 °C, 300 MHz): δ 5.5-4.5 (brs, 4 H, COD), 3.11
(m, 1 H, CH(CH3)), 2.40 (s, 3 H, SCH3), 1.60 (d, J ) 6 Hz, 3 H,
CH3), 2.5-1.0 (brm, 24 H). 13C{H} NMR (CD2Cl2, 23 °C, 125
MHz): δ 103.4 (s, COD olefinic carbon), 98.8 (s, COD olefinic
carbon), 86.0 (d, J ) 11 Hz, COD olefinic carbon), 84.4 (d, J )
10 Hz, COD olefinic carbon), 49.3 (d, J ) 6 Hz, CH(CH3)), 36.9
(d, J ) 21 Hz, CH of Cy), 34.7 (d, J ) 23 Hz, CH of Cy), 34.0-
25.0 (overlapping multiplets accounting for CH2’s), 19.6 (d, J
) 15 Hz, CH(CH3)), 17.3 (s, SCH3). 31P{H} NMR (CD2Cl2, 23
°C, 121 MHz): 51.4 (d, J Rh-P ) 139 Hz). C, H Anal. (Calcd):
C, 44.84 (46.44); H, 6.54 (6.70).
Syn th esis of (Cy2P CH2CH(CH3)SCH2P h )Rh (COD)+OTf-
(21). A 100-mL round-bottomed flask was charged with 229
mg (0.49 mmol) of Rh(COD)2+OTf-, and THF was added until
a clear solution was obtained. Then 177 mg (0.49 mmol) of
Cy2PCH2CH(CH3)SCH2Ph, 10, dissolved in ca. 10 mL of THF
was added. After the solution was stirred at ambient temper-

2072 Organometallics, Vol. 18, No. 11, 1999
Hauptman et al.
Syn th esis of (Cy2P CH2CH(CH3)SCH2(a n th r a cen e))Rh -
(COD)+OTf- (23). A vial was charged with 157 mg (0.34
mmol) of Rh(COD)2+OTf-, and this was suspended in ca. 2 mL
of THF. Then 155 mg (0.34 mmol) of 12 dissolved in ca. 8 mL
of THF was added dropwise. During addition, the suspension
turned into a clear orange solution. After the solution was
stirred at ambient temperature for 30 min, the solvent was
removed in vacuo. The resulting oily solid was washed with
hexane and dried in vacuo. The complex crystallized with two
of THF. Then 182 mg (0.36 mmol) of 15 dissolved in ca. 15
mL of THF was added dropwise. During addition the solution
turned from red to orange. After the solution was stirred at
ambient temperature for 45 min, the solvent was removed in
vacuo. The resulting oily solid was washed with hexane and
dried in vacuo. The solid contained traces of THF as isolated.
Yield: 317 mg (ca. 100%). 1H NMR (CD2Cl2, 23 °C, 300 MHz):
δ 5.0-4.5 (brm, 3 H, COD), 4.34 (d of AB quartet, 1 H, CHH),
4.23 (brs, 1 H, COD), 4.01 (d of AB quartet), 2.41 (s, 6 H, C5-
(CH3)5), 2.25 (s, 3 H, C5(CH3)5), 2.24 (s, 6 H, C5(CH3)5), 3.0-
0.5 (m, 36 H). 13C{H} NMR (CD2Cl2, 23 °C, 125 MHz): δ 136.9
(s), 134.1 (s), 133.4 (s), 126.7 (s), 104.0 (dd, J ) 7, 7 Hz, COD
olefinic carbon), 100.6 (dd, J ) 6, 6 Hz, COD olefinic carbon),
86.1 (d, J ) 10 Hz, COD olefinic carbon), 84.4 (d, J ) 10 Hz,
COD olefinic carbon), 68.2 (s, SCH2), 58.0 (s, CHCy), 40.6 (d,
J ) 11 Hz, CH of Cy), 37.0 (d, J ) 20 Hz, CH of Cy), 35.0 (d,
J ) 22 Hz, CH of Cy), 35.0-20.0 (overlapping multiplets
accounting for CH2’s), 17.9 (brs, CH3), 17.4 (s, CH3), 17.1 (s,
CH3). 31P{H} NMR (CD2Cl2, 23 °C, 121 MHz): δ 52.1 (d, J P-Rh
) 140 Hz). C, H Anal. (Calcd): C, 57.74 (57.20); H, 7.77 (7.61).
Syn t h esis of (P h 2P CH2CH(CH 3)SCH 3)R h (COD)+OTf-
(27). A vial was charged with 152 mg (0.32 mmol) of
Rh(COD)2+OTf-, and this was suspended in ca. 5 mL of THF.
Then 89 mg (0.32 mmol) of 16 dissolved in ca. 5 mL of THF
was added dropwise. During addition, the slurry turned into
a clear orange solution. After the solution was stirred at
ambient temperature for 30 min, the solvent was removed.
The resulting oily solid was washed with hexane (ca. 10 mL)
and dried in vacuo. Yield: 204 mg (99%). 1H NMR (CD2Cl2,
23 °C, 300 MHz): δ 8.0-7.3 (m, 10 H, arene), 5.43 (brs, 2 H,
COD), 4.39 (brs, 1 H, COD), 3.85 (brs, 1 H, COD), 2.51 (s, 3 H,
SCH3), 1.60 (d, J ) 6 Hz, CH(CH3), 2.8-1.9 (brm, 11 H). 13C
NMR (THF-d8, 125 MHz, 23 °C): δ 135.0 (d, J ) 13 Hz), 133.1
(s), 131.8 (d, J ) 2.5 Hz), 131.5 (d, J ) 10 Hz), 130.2 (d, J )
11 Hz), 129.8 (d, J ) 11 Hz), 106.3 (dd, J ) 7, 7 Hz, COD
olefinic carbon), 102.7 (dd, J ) 9, 9 Hz, COD olefinic carbon),
90.1 (d, J ) 11 Hz, COD olefinic carbon), 84.4 (d, J ) 10 Hz,
COD olefinic carbon), 45.5 (d, J ) 9 Hz, CH), 37.9 (d, J ) 30
Hz, CH2), 33.1 (d, J ) 3 Hz, CH2), 30.5 (s, CH2 of COD), 30.2
(s, CH2 of COD), 28.7 (s, CH2 of COD), 19.6 (s, CH3), 19.1 (d,
J ) 17 Hz, CH3). 31P{H} NMR (CD2Cl2, 23 °C, 121 MHz): δ
46.2 (d, J P-Rh ) 146 Hz). C, H Anal. (Calcd): C, 47.87 (47.32);
H, 4.80 (4.92).
1
molecules of THF. Yield: 285 mg (88%). H NMR (CD2Cl2, 23
°C, 300 MHz): δ 8.58 (s, 1 H, arene), 8.28 (d, J ) 9 Hz, 2 H,
arene), 8.11 (d, J ) 8 Hz, 2 H, arene), 7.69 (ddd, J ) 7, 7, 1
Hz, 2 H, arene), 7.59 (dd, J ) 8, 8 Hz, 2H, arene), 5.09 (AB
quartet, 2 H, CH2(anthracene)), 4.81 (brs, 1 H, COD), 4.77 (brs,
1 H, COD), 4.52 (brs, 1 H, COD), 3.68 (m, THF), 3.30 (m, 1 H,
CHCy), 1.49 (d, J ) 6 Hz, CHCH3), 2.5-1.0 (brm, 32 H). 13C-
{H} NMR (C6D6, 125 MHz, 23 °C): δ 131.8 (s), 130.9 (s), 130.2
(s), 130.1 (s), 127.8 (s), 126.0 (s), 123.7 (s), 123.3 (s), 103.2 (dd,
J ) 8, 8 Hz, COD olefinic carbon), 99.0 (brs, COD olefinic
carbon), 87.2 (d, J ) 11 Hz, COD olefinic carbon), 85.4 (d, J )
10 Hz, COD olefinic carbon), 48.2 (d, J P-C ) 7 Hz, CH(CH3)),
37.0 (d, J P-C ) 21 Hz, CH of Cy), 34.7 (d, J P-C ) 23 Hz, CH of
Cy), 33.0-25 (overlapping multiplets corresponding to CH2’s
of Cy), 20.4 (d, J P-C ) 13 Hz, CH3). 31P{H} NMR (CD2Cl2, 23
°C, 121 MHz): δ 53.2 (d, J P-Rh ) 139 Hz). C, H Anal. (Calcd):
C, 58.30 (58.38); H, 6.98 (6.45).
Syn t h esis of (Cy2P CH2CH (CH3)SCH2(su b er a n e))R h -
(COD)+OTf- (24). A vial was charged with 87 mg (0.19 mmol)
of Rh(COD)2+OTf- and 87 mg (0.19 mmol) of 13. THF (ca. 10
mL) was then added. After the orange solution was stirred at
ambient temperature for 15 min, the solvent was removed in
vacuo. The resulting oily solid was washed with hexane and
1
dried in vacuo. Yield: 117 mg (76%). H NMR (CD2Cl2, 23 °C,
300 MHz): δ 7.5-7.0 (m, 8 H, aromatic), 5.32 (s, 1 H), 5.22
(brs, 1 H, COD), 5.11 (brs, 1 H, COD), 4.63 (brs, 1 H, COD),
3.84 (m, 2 H), 3.45 (brs, 1 H, COD), 3.00 (m, 3 H), 1.12 (d, J )
7 Hz, 3 H), 2.5-1.0 (brm, 32 H). 13C{H} NMR (C6D6, 125 MHz,
23 °C): δ 141.4 (s, quaternary C), 141.3 (s, quaternary C),
134.4 (s, quaternary C), 134.3 (s, quaternary C), 132.3 (s), 132.0
(s), 131.5 (s), 131.0 (s), 130.5 (s), 130.3 (s), 127.24 (s), 127.17
(s), 104.0 (dd, J ) 7, 7 Hz, COD olefinic carbon), 100.4 (dd, J
) 10, 6 Hz, COD olefinic carbon), 86.3 (d, J ) 11 Hz, COD
olefinic carbon), 86.2 (d, J ) 11 Hz, COD olefinic carbon), 64.2
(s, CH), 47.1 (d, J P-C ) 7 Hz, CH(CH3)), 37.6 (d, J P-C ) 21 Hz,
CH of Cy), 35.0 (d, J P-C ) 21 Hz, CH of Cy), 34.0-25.0
(overlapping multiplets corresponding to CH2’s of Cy and
suberane), 22.4 (d, J P-C ) 7 Hz, CH3). 31P{H} NMR (CD2Cl2,
23 °C, 121 MHz): δ 60.0 (d, J P-Rh ) 140 Hz). C, H Anal.
(Calcd): C, 55.92 (56.79); H, 6.10 (6.48).
Syn th esis of (Cy2P CH2CH(Cy)SCH3)Rh (COD)+OTf- (25).
A vial was charged with 213 mg (0.45 mmol) of Rh(COD)2+OTf-,
and this was suspended in ca. 5 mL of THF. Then 161 mg
(0.45 mmol) of 14 dissolved in ca. 5 mL of THF was added
dropwise. During addition, the solution turned from red to
orange. After stirring at ambient temperature for 30 min the
solvent was removed in vacuo. The resulting oily solid was
washed with hexane and dried in vacuo. Yield: 297 mg (91%).
1H NMR (CD2Cl2, 23 °C, 300 MHz): δ 5.21 (brs, 2 H, COD),
4.87 (brs, 2 H, COD), 2.89 (m, 1 H, CHCy), 2.43 (s, 3 H, SCH3),
2.6-1.0 (brm, 35 H). 13C{H} NMR (CD2Cl2, 23 °C, 125 MHz):
δ 104.0 (dd, J ) 8, 8 Hz, COD olefinic carbon), 99.4 (dd, J )
7, 7 Hz, COD olefinic carbon), 86.0 (d, J ) 11 Hz, COD olefinic
carbon), 84.5 (d, J ) 10 Hz, COD olefinic carbon), 59.2 (s,
CHCy), 39.4 (d, J ) 12 Hz, CH of Cy), 37.0 (d, J ) 21 Hz, CH
of Cy), 34.9 (d, J ) 23 Hz, CH of Cy), 35.0-22.0 (overlapping
multiplets accounting for CH2’s), 17.7 (s, SCH3). 31P{H} NMR
(CD2Cl2, 23 °C, 125 MHz): δ 51.3 (d, J P-Rh ) 140 Hz). C, H
Anal. (Calcd): C, 47.21 (50.41); H, 6.74 (7.19).
Syn t h esis of (P h 2P CH2CH (CH3)SCH2(C6(CH3)5)R h -
(COD)+OTf- (28). A vial was charged with 86 mg (0.18 mmol)
of Rh(COD)2+OTf-, and this was suspended in ca. 5 mL of
THF. Then 77 mg (0.18 mmol) of 17 dissolved in ca. 5 mL of
THF was added dropwise. During addition, the red slurry
turned into a clear orange-yellow solution. After the solution
was stirred at ambient temperature for 30 min, the solvent
was removed. The resulting oily solid was washed with hexane
(ca. 10 mL) and dried in vacuo. Yield: 117 mg (82%). 1H NMR
(CD2Cl2, 23 °C, 300 MHz): δ 7.95 (m, 2 H, Ph), 7.8-7.4 (m, 6
H, arene), 7.35 (m, 2 H, Ph), 5.55 (brs, 1 H, COD), 4.93 (brs,
1 H, COD), 4.67 (brs, 1 H, COD), 4.40 (brs, 1 H, COD), 4.39
(d, J ) 12 Hz, CHH(C6(CH3)5), 4.03 (d, J ) 12 Hz, CHH(C6-
(CH3)5), 3.82 (brs, 1 H, CH(CH3)), 2.23 (s, 3 H, CH3), 2.22 (s, 6
H, 2CH3’s), 2.8-1.9 (brm, 10 H), 1.43 (d, J ) 6 Hz, 3 H, CH-
(CH3)). 13C{H} NMR (THF-d8, 125 MHz, 23 °C): δ 136.9 (s),
134.9 (d, J ) 12 Hz), 134.0 (s), 133.5 (s), 133.2 (s), 131.9 (s),
131.6 (d, J ) 10 Hz), 130.3 (d, J ) 10 Hz), 129.8 (d, J ) 10
Hz), 129.0 (s), 126.4 (s), 105.7 (brm, COD olefinic carbon), 104.9
(brm, COD olefinic carbon), 89.9 (d, J ) 11 Hz, COD olefinic
carbon), 85.1 (d, J ) 11 Hz, COD olefinic carbon), 44.4 (d, J C-P
) 9 Hz, CH), 39.7 (s, SCH2 arene), 38.4 (d, J P-C ) 32 Hz, CH2-
PPh2), 33.1 (s, CH2 of COD), 30.6 (s, CH2 of COD), 30.2 (s,
CH2 of COD), 28.8 (s, CH2 of COD), 20.4 (d, J P-C ) 15 Hz,
CHCH3), 17.5 (s, CH3), 17.4 (s, CH3), 17.0 (s, CH3). 31P{H}
NMR (CD2Cl2, 23 °C, 121 MHz): δ 47.9 (d, J P-Rh ) 145 Hz).
Syn t h esis of (Cy2P CH2CH (Cy)SCH2(C6(CH3)5))R h -
(COD)+OTf- (26). A vial was charged with 170 mg (0.36
mmol) of Rh(COD)2+OTf-, and this was suspended in ca. 5 mL

Synthesis of Novel (P,S) Ligands
Organometallics, Vol. 18, No. 11, 1999 2073
Typ ica l P r oced u r e for th e Hyd r ogen a tion Ru n s
thank Professor Barry Sharpless and Dr. Paul Rich-
ardson for providing us with experimental procedures
to make chiral episulfides from diols and giving permis-
sion to publish the procedures reported here in advance
of their work.
Hydrogenation reactions were carried out using 2 mol
% catalyst (MeOH solution) and a 0.39 M solution of
substrate, RC(H)C(CO2Me)(NHAc), in MeOH. The reac-
tion vessel was placed at 80 psi H2 and kept stirring at
ambient temperature for 16 h. Conversion analysis was
1
Su p p or tin g In for m a tion Ava ila ble: X-ray data for 18b,
19 and 22, including tables of fractional coordinates and
isotropic thermal parameters, anisotropic thermal parameters,
interatomic distances, intramolecular angles, intramolecular
nonbonding distances, and intermolecular distances and ORTEP
diagrams of 18b, 19 and 22. This material is available free of
charge via the Internet at http://pubs.acs.org.
achieved by H NMR spectroscopy, and analysis of the
enantiomeric excess was done by GC (Chirasil-L-Val).
Results can be found in Tables 8 and 9.
Ack n ow led gm en t. We thank Gary A. Halliday and
Ronald J . Davis for technical assistance and Chris
Roefor assistance in the interpretation of the variable-
temperature 1H NMR spectra of complexes 18. We
OM990023Q