Diastereoselectivity in chiral ruthenium complexes of bidentate bisphosphine monoxide ligands: Controlling epimerization in aldehyde complexes and 16-electron intermediates

Article abstract of DOI:10.1021/om981053g

Heterobidentate and hemilabile ligands involving P,O-donor chelates produce chiral metal centers when hound to arene-ruthenium complexes. This chirality in cymene complexes produces diastereotopic methyl groups in the isopropyl ligand which serve as a detector of the chirality at the metal. [CyRu(η²-chelate-P,O)Cl]⁺ cations are precursors to strong 16-electron dicationic Lewis acids which have potential use in asymmetric catalysis. Sixteen-electron complexes of this type, however, provide a pathway with a low barrier to racemization or epimerization of the metal center in intermediates, such as [CyRu(η²-chelate-P,O)(PhCHO)]²⁺. Substitution of the central carbon in diphenylphosphinomethane monoxide (dppmO) forces the ligand to adopt a configuration with the substituent in an endo position, thus forcing the 16-electron intermediate to return diastereoselectively to its original configuration and prevents epimerization. Thus, an X-ray structure shows that (R*_RuR*_C)-[CyRu(η²- Ph₂PCHR)Ph₂PO-P,O)Cl]⁺ is the preferred diastereomeric pair. In the parent, [CyRu(η²-dppmO-P,O)(ligand)]²⁺, racemization occurs at the metal center, since there is nothing driving the preferential formation of either the R or S ruthenium center. When the ligands are chiral, however, the metal center epimerizes to minimize steric interactions in the two diastereomers. The equilibrium between [(R_Ru)-CyRu(η²-dppmO-P,O)(R_C-ligand)] ²⁺ and [(S_Ru)-CyRu(η²-dppmO-P,O)(R_C-ligand)] ²⁺ reflects a 37% de for (1R)-(-)-myrtenal. Since a substituent on the central carbon prevents epimerization at the metal center, this diastereoselectivity is reflected in a preference for binding of (R_C)-ligand by either [(R_RuR_C)-CyRu(η²-Ph ₂PCHPr)Ph₂PO-P,O)]²⁺ or [(S_RuS_C)-CyRu(η²-Ph ₂PCHPr)Ph₂PO-P,O)]²⁺. An X-ray structure of rac-[(R_Ru*,R_C*)-CyRu(η²-Ph ₂PCHPr)Ph₂PO-P,O)(PhCHO]²⁺ shows that the aldehyde assumes an orientation that would suggest one stereoface of the aldehyde may be more susceptible to attack.

Full text of DOI:10.1021/om981053g

3096
Organometallics 1999, 18, 3096-3104
Dia ster eoselectivity in Ch ir a l Ru th en iu m Com p lexes of
Bid en ta te Bisp h osp h in e Mon oxid e Liga n d s: Con tr ollin g
Ep im er iza tion in Ald eh yd e Com p lexes a n d 16-Electr on
In ter m ed ia tes
J . W. Faller,* Ben P. Patel, Mauricio A. Albrizzio, and Michael Curtis
Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520
Received December 29, 1998
Heterobidentate and hemilabile ligands involving P,O-donor chelates produce chiral metal
centers when bound to arene-ruthenium complexes. This chirality in cymene complexes
produces diastereotopic methyl groups in the isopropyl ligand which serve as a detector of
the chirality at the metal. [CyRu(η2-chelate-P,O)Cl]+ cations are precursors to strong 16-
electron dicationic Lewis acids which have potential use in asymmetric catalysis. Sixteen-
electron complexes of this type, however, provide a pathway with a low barrier to
racemization or epimerization of the metal center in intermediates, such as [CyRu(η2-chelate-
P,O)(PhCHO)]2+. Substitution of the central carbon in diphenylphosphinomethane monoxide
(dppmO) forces the ligand to adopt a configuration with the substituent in an endo position,
thus forcing the 16-electron intermediate to return diastereoselectively to its original
configuration and prevents epimerization. Thus, an X-ray structure shows that (R*Ru,R*C)-
[CyRu(η2- Ph2PCHR)Ph2PO-P,O)Cl]+ is the preferred diastereomeric pair. In the parent,
[CyRu(η2-dppmO-P,O)(ligand)]2+, racemization occurs at the metal center, since there is
nothing driving the preferential formation of either the R or S ruthenium center. When the
ligands are chiral, however, the metal center epimerizes to minimize steric interactions in
the two diastereomers. The equilibrium between [(RRu)-CyRu(η2-dppmO-P,O)(RC-ligand)]2+
and [(SRu)-CyRu(η2-dppmO-P,O)(RC-ligand)]2+ reflects a 37% de for (1R)-(-)-myrtenal. Since
a substituent on the central carbon prevents epimerization at the metal center, this
diastereoselectivity is reflected in a preference for binding of (RC)-ligand by either [(RRu,RC)-
CyRu(η2-Ph2PCHPr)Ph2PO-P,O)]2+ or [(SRu,SC)-CyRu(η2-Ph2PCHPr)Ph2PO-P,O)]2+. An X-ray
structure of rac-[(RRu*,RC*)-CyRu(η2-Ph2PCHPr)Ph2PO-P,O)(PhCHO]2+ shows that the
aldehyde assumes an orientation that would suggest one stereoface of the aldehyde may be
more susceptible to attack.
In tr od u ction
alcohols, phosphinosulfoxides, or bisphosphine monox-
ides. We are currently focusing on phosphinosulfoxides
and bisphosphine monoxide ligand systems in our
development of chiral ruthenium Lewis acids.6 These
studies are particularly relevant to maintaining the
chirality at a metal center, which might otherwise
undergo rapid racemization or epimerization via a free
Lewis acid.
Herein, we describe the synthesis and characteriza-
tion of a new series of ruthenium Lewis acid precursors
containing chiral bisphosphine monoxide ligands based
on the 1,1′-bis(diphenylphosphino)methane monoxide
(dppmO, 1a ) skeleton. Although a number of metal
complexes of 1a are known, only a few are known that
contain substitution on the backbone,7,8 and the work
reported here represents the first example that inves-
tigates the stereochemistry of complexes with the chiral
derivatives Ph2PCH(R)P(O)Ph2 (R ) CH3, 1b; Ph,
Owing in part to their mixed donor properties, het-
erobidentate phosphines have found wide use in cataly-
sis as hemilabile ligands capable of generating open
coordination sites for substrate binding. An equally
important, yet less exploited, feature of these ligands
is that they are unsymmetrical and upon chelation
generate chirality and electronic asymmetry at the
metal center in certain complexes. Of the following
known motifs, η2-P/N,1 η2-P/S,2 η2-P/Se,3 η2-P/C,4 and
η2-P/O,5 we have recently become interested in the
latter, which can be obtained via ether phosphines,
â-ketophosphines, phosphinocarboxylates, phosphino
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10.1021/om981053g CCC: $18.00 © 1999 American Chemical Society
Publication on Web 07/10/1999

Diastereoselectivity in Chiral Ru Complexes
Organometallics, Vol. 18, No. 16, 1999 3097
Sch em e 1. P r ep a r a tive Str a tegies for th e Syn th eses of Liga n d s 1a -1d : (a ) Dieth yl Eth er , -78 °C; (b) THF ,
-78 °C
Sch em e 2. F or m a tion of η1 Com p lexes 2-5
1c;C3H7, 1d ). The results described below suggest that
the presence of the substituent and the chiral center in
the backbone of 1b-1d can influence their binding mode
upon chelation, leading to high diastereoselectivity in
the formation of the metal complexes.
readily oxidized to the bisphosphine oxides, which often
led to problems with isolation of pure ligand. We have
adapted the procedures (Scheme 1) for preparation of
the ligands in situ, but avoid the oxidation problem by
complexation of the phosphine prior to isolation. One
published procedure favors treatment of Ph3PO with an
alkyllithium, which serves to displace a phenyl as LiPh,
which in turn lithiates the activated alkyl and provides
a Ph2PCHRLi intermediate, as shown for the butyl
derivative, 1d . In our hands, starting with the diphe-
nylalkylphosphine oxide produced cleaner products,
particularly with ligands other than 1d .
Resu lts
Liga n d Syn th esis. Procedures for the preparation
of the bisphosphine monoxide ligands 1a -1d are avail-
able in the literature (Scheme 1).8-10 Except for the
parent 1a , the ligands were hygroscopic and were
Syn th esis of [(η6-Cy)Ru Cl2(η1-P h 2P CH(R)P (O)-
P h 2)] Com p lexes. The ligands 1a and 1b readily
cleaved the ruthenium dimer [(η6-Cy)RuCl2]2 (Cy )
cymene) in dichloromethane to yield [(η6-Cy)RuCl2(η1-
Ph2PCH2P(O)Ph2)] (2) and [(η6-Cy)RuCl2(η1-Ph2PCH-
(CH3)P(O)Ph2)] (3), in which the phosphorus atom of the
chelate was bound to the metal center (Scheme 2). In
the 31P{1H} NMR spectrum this mode of coordination
was marked by a large downfield shift in the P(III)
(7) (a) Coyle, R. J .; Slovokhotov, Y. L.; Antipin, M. Y.; Grushin, V.
V. Polyhedron 1998, 17, 3059-3070. (b) Brassat, I.; Englert, U.; Keim,
W.; Keitel, D. P.; Killat, S.; Suranna, G. P.; Wang, R. M. Inorg. Chim.
Acta 1998, 280, 150-162. (c) Blagborough, T. C.; Davis, R.; Ivison, P.
J . Organomet. Chem. 1994, 467, 85-94. (d) Shih, K.-Y.; Fanwick, P.
E.; Walton, R. A. Inorg. Chim. Acta 1993, 212, 23-29. (e) Rossi, R.;
Marchi, A.; Marvelli, L.; Magon, L.; Peruzzini, M.; Castellato, U.;
Graziani, R. Inorg. Chim. Acta 1993, 204, 63-71. (f) Katti, K. V.;
Barnes, C. L. Inorg. Chem. 1992, 31, 4231-4235. (g) Fontaine, X. L.
R.; Fowles, E. H.; Layzell, T. P.; Shaw, B. L.; Thorton-Pett, M. J . Chem.
Soc., Dalton Trans. 1991, 1519-1524. (h) Carriedo, G. A.; Rodriguez,
M. L.; Garcia-Granda, S.; Aguirre, A. Inorg. Chim. Acta 1990, 178,
101-106. (i) Darensbourg, D. J .; Zalewski, D. J .; Plepys, C.; Campana,
C. Inorg. Chem. 1987, 26, 3727-3732. (j) Berry, D. E.; Browning, J .;
Dixon, K. R.; Hilts, R. W. Can. J . Chem. 1988, 66, 1272-1282. (k)
Wegman, R. W.; Abatjoglu, A. G.; Harrison, A. M. J . Chem. Soc., Chem.
Commun. 1987, 1891-1892. (l) Bao, Q.-B.; Landon, S. J .; Rheingold,
A. L.; Haller, T. M.; Brill, T. B. Inorg. Chem. 1985, 24, 900-908. (m)
Grim, S. O.; Walton, E. D. Inorg. Chem. 1980, 19, 1982-1987.
(8) (a) Higgins, S. J .; Taylor, R.; Shaw, B. L. J . Organomet. Chem.
1987, 325, 285-292. (b) Grim, S. O.; Satek, L. C.; Tolman, C. A.; J esson,
J . P. Inorg. Chem. 1975, 14, 656-660. (c) Bennett, M. A.; Matheson,
T. W.; Robertson, G. B.; Smith, A. K.; Tucker, P. A. Inorg. Chem. 1980,
19 (4), 1014-1020. (d) Nelson, S. M.; Parks, M.; Walker, B. J . J . Chem.
Soc., Perkin Trans. 1 1976, 1205-1209 (for 1c).
2
resonance and a significant reduction in the J PP
coupling constant. In the cases of 1c and 1d , these
ligands also cleaved the ruthenium dimer in dichlo-
romethane to initially yield [(η6-Cy)RuCl2(η1-Ph2PCH-
(Ph)P(O)Ph2)] (4) and [(η6-Cy)RuCl2(η1-Ph2PCH(C3H7)P-
(O)Ph2)] (5) in situ, but then reacted further by displacing
a chloride ligand and chelating the metal center to
produce their respective η2- isomers, [(η6-Cy)RuCl(η2-
Ph2PCH(Ph)P(O)Ph2)][Cl] (4′) and [(η6-Cy)RuCl(η2-Ph2-
PCH(C3H7)P(O)Ph2)][Cl] (5′). As a consequence, the η1
compounds 4 and 5 were not isolable.
(9) Some useful modifications of preparations are given by: (a)
Visseaux, M.; Dormond, A.; Baudry, D. Bull. Soc. Chim. Fr. 1993, 130,
173-184. (b) Brock, S. L.; Mayer, J . M. Inorg. Chem. 1991, 30, 2138-
2143.
Coor d in a tion Isom er ism in Com p lexes 2-5. We
found that in moderately polar solvents (CH2Cl2 and
CHCl3) the η1 complexes 3-5 readily form an equilib-
rium with their respective η2 coordination isomers, [(η6-
Cy)RuCl(η2-Ph2PCH(R)P(O)Ph2)][Cl] (R ) CH3, 3′; Ph,
(10) 31P{1H} NMR (293 K, δ): 1a (THF) 29.4 (d, 2J PP ) 53 Hz, P(V)),
-27.9 (d, 2J PP ) 53 Hz, P(III)); 1b (CHCl3) 36.1 (d, 2J PP ) 65 Hz, P(V)),
-12.6 (d, 2J PP ) 65 Hz, P(III)); 1c (CHCl3), 30.0 (d, 2J PP ) 56 Hz, P(V)),
-6.8 (d, 2J PP ) 56 Hz, P(III)); 1d (CHCl3), 35.7 (d, 2J PP ) 69 Hz, P(V));
2
-9.7 (d, J PP ) 69 Hz, P(III)).

3098 Organometallics, Vol. 18, No. 16, 1999
Faller et al.
Sch em e 3. Coor d in a tion Isom er ism in Com p lexes
As shown in Figure 2, chelation of the ligand produces
a chiral metal center. Consequently 6 is isolated and
crystallized as a racemate. Upon chelation, in addition
to the chiral environment at the metal centers in
compounds 7-9, the bridging carbon provides a second
chiral center; thus diastereomeric complexes could form.
Given that these ligands are capable of chelating the
metal in two possible modes and therefore producing
two distinct diastereomers in compounds 7-9, we were
pleased to note that only one set of resonances was
observed in each of the 31P{1H} NMR spectra, indicating
that only one diastereomer was present in solution in
significant concentration. This suggests that there is a
preferred mode of ligand chelation, which presumably
arises from steric interactions of the R group in the
ligand backbone with other ligands.
Th e P r efer r ed Dia ster eom er of [(η6-Cy)Ru Cl(η2-
P h 2P CH(C3H7)P (O)P h 2)][SbF 6] (9). Diffraction qual-
ity crystals of {9[O(C2H5)2]}were grown from a dichlo-
romethane/diethyl ether solution, and the structure was
determined by the X-ray diffraction as shown in Figure
3. In support of the solution data, only the enantiomers
of one diastereomer of 9 were observed in the solid state
with the configurations of (RRu, RC) and (SRu, SC) or
relative configurations of (RRu*, RC*). The propyl chain
in the backbone of the ligand was found to be oriented
away from the chloride ligand, most likely as a result
of steric effects. It follows that the same configuration
would exist in all three η2 compounds, 7-9; thus the
relative configuration of the metal center and carbon
center of the single diastereomers observed in solution
for 7 and 8 can be assigned by analogy to 9. The
presence of the chiral center in the backbone of these
ligands gives rise to high diastereoselectivity in the
formation of chelated complexes.
3-5
4′; C3H7, 5′) (Scheme 3). In the case of 3/3′, an ∼1:1
equilibrium was ultimately established at room tem-
perature (t1/2 - 30 min) in CH2Cl2. The rate of inter-
conversion in ethyl acetate is considerably slower. The
difference in charge between these two coordination
isomers allowed for facile separation by column chro-
matography on silica gel and isolation of pure 3. If pure
3 was redissolved in CD2Cl2, the equilibrium distribu-
tion was established over several hours. In contrast,
under conditions similar to those described above, the
η1 coordination isomers of 4 and 5 converted quantita-
tively (t1/2 of several minutes) in CH2Cl2 and CHCl3 to
4′ and 5′, respectively, and remained as the chelated η2
isomers independent of solvent choice. As a result,
compounds 4 and 5 could only be isolated as the η2
coordination isomers 4′ and 5′. Surprisingly this equi-
librium was not observed for the parent compound [(η6-
Cy)RuCl2(η1-Ph2PCH2P(O)Ph2)] (2), even after several
days in dichloromethane. This suggests that the steric
bulk in the ligand backbones of complexes 5 might be
driving the chelation, in a rough analogy with the
Thorpe-Ingold effect.11 In most cases we converted
-
the chloride salts to the SbF6 salts to allow purifica-
Ald eh yd e a n d Su lfoxid e Com p lexes [(η6-Cy)Ru -
(L)(η2-P h 2P CH(R)P (O)P h 2)][SbF 6]2. A series of alde-
hyde derivatives of complexes 7-9 were prepared in
situ, and their 31P{1H} NMR data are summarized in
Table 2. Complexes 7-9 were first treated with AgSbF6,
in dichloromethane, to produce complexes that we
indicate as the free acid [(η6-Cy)Ru(η2-Ph2PCH(R)P(O)-
Ph2)][SbF6]2, but may either be solvates or aqua com-
plexes or contain coordinated SbF6. These precursors
were then treated with excess quantities of the ap-
propriate aldehyde. The critical observation in the 31P-
{1H} NMR spectra for the achiral aldehyde derivatives
is the presence of only an AX pattern indicative of a
tion and preparation of crystals suitable for X-ray
diffraction.
Syn th esis of [(η6-Cy)Ru Cl2(η2-P h 2P CH(R)P (O)-
P h 2)][SbF 6] Com p lexes. The η2 complexes [(η6-Cy)-
RuCl(η2-Ph2PCH2P(O)Ph2)][SbF6] (6) and [(η6-Cy)RuCl-
(η2-Ph2PCH(CH3)P(O)Ph2)][SbF6] (7) were prepared by
reaction of the respective η1 complexes, 2 and 3, with 1
equiv of AgSbF6 in dichloromethane at room tempera-
ture. The η2 complexes [(η6-Cy)RuCl2(η2-Ph2PCH(Ph)P-
(O)Ph2)][SbF6] (8) and [(η6-Cy)RuCl2(η2-Ph2PCH(C3H7)P-
(O)Ph2)][SbF6] (9) were prepared under similar conditions
except starting from the η2 isomers, 4′ and 5′. In all four
complexes both phosphorus resonances in the 31P{1H}
NMR spectra were shifted downfield, and we have
tentatively assigned the resonance furthest downfield
to the P(V) phosphorus.
1
single diastereomer. In the H NMR spectra the arene
protons and the isopropyl methyl protons are diaste-
reotopic and free aldehyde is observed, which indicates
that the complexes are not undergoing rapid equilibra-
tion. There is only a very small coordination shift of the
CHO proton (0.02 ppm) so that 31P spectra allow better
characterization of binding. These spectra are similar
to the spectra of the chloride complexes 7-9, where only
one diastereomer was observed in solution. In these
aldehyde complexes, a single diastereomer with the
substituent oriented away from the aldehyde is ex-
pected. The crystal structure data for [(η6-Cy)Ru(Ph-
CHO)(η2-Ph2PCH(C3H7)P(O)Ph2)][SbF6]2, 10, is given in
Table 1. The endo propyl group of 10 is shown in Figure
4 and further illustrates this point. This structure also
demonstrates that the carbonyl is σ-bonded rather than
X-r a y Diffr a ction Stu d y of Som e Key Com p lexes.
-
The structures of compound 3 and the SbF6 salts
derived from 3′ and 5′, 6 and 9 were determined by
X-ray diffraction methods, and the data are summarized
in are Table 1. The structure of an aldehyde complex,
10, which is discussed later, is also included in the
table. Figure 1 shows the structure of a typical η1
complex, 3.
(11) (a) Sternbach, D. D.; Rossana, D. M.; Onan, K. D. Tetrahedron
Lett. 1985, 26, 591-594. (b)Eliel, E. L.; Wilen, S. H. Ease of Ring
Closure as a Function of the Ring Atoms and Substituents. The Thorpe-
Ingold Effect. Stereochemistry of Organic Compounds; J ohn Wiley &
Sons: New York, 1994; pp 682-684.

Diastereoselectivity in Chiral Ru Complexes
Organometallics, Vol. 18, No. 16, 1999 3099
Ta ble 1. Cr ysta llogr a p h ic Da ta for [(η6-Cy)Ru Cl2(η-P h 2P CH(CH3)P (O)P h 2)] (3),
[(η6-Cy)Ru Cl(η2-P h 2P CH2P (O)P h 2)][SbF 6] (6), [(η6-Cy)Ru Cl(η2-P h 2P CH(C3H7)P (O)P h 2)][SbF 6] (9),
a n d [(η6-Cy)Ru (P h CHO)(η2-P h 2P CH(C3H7)P (O)P h 2)][SbF 6] (10)
3
6
9
10
formula
fw
a, Å
b, Å
c, Å
â (deg)
V, Å3
Z
RuCl2P2OC36H39
721.63
SbRuClP2F6OC35H36
906.88
SbRuClP2F6OC38H42
948.96
18.5995(4)
14.2399(3)
14.7627(2)
90
Sb2RuClP12F2OC45H48
1255.37
22.2276(4)
10.7706(2)
19.9741(3)
90
31.82(4)
9.686(5)
21.511(7)
98.56(5)
6555(7)
8
11.2691(7)
19.190(2)
16.958(1)
96.316(4)
3644.9(4)
4
3910.0(2)
4
4781.9(1)
4
space group
C2/c (No. 15)
1.462
7.67
-103
0.71069
0.035
P21/ n (No. 14)
1.652
13.73
24
0.71069
0.048
Pna21 (No. 33)
1.612
12.84
-90
0.71069
0.037
Pna21 (No. 33)
1.708
15.50
-90
0.71069
0.019
F
calcd, g cm-3
µ (Mo KR), cm-1
temp, °C
λ (Å)
R(Fo)
Rw(Fo)
0.037
0.047
0.040
0.023
GOF
1.65
1.73
1.63
1.06
F igu r e 3. ORTEP representation of [(η6-Cy)RuCl(η2-Ph2-
PCH(C3H7)P(O)Ph2)][SbF6] (9′′), with 30% probability el-
lipsoids. There is an unresolved disorder in the isopropyl
group and orientation of the cymene ring.
F igu r e 1. ORTEP representation of [(η6-Cy)RuCl2(η-Ph2-
PCH(CH3)P(O)Ph2)] (3), with 50% probability ellipsoids.
and this has been observed in other systems12 and
interpreted theoretically.21 This suggests that the sys-
tem should give good selectivity in reactions on the
(12) (a) Schilling, B. E. R.; Hoffmann, R.; Faller, J . W. J . Am. Chem.
Soc. 1979, 101, 592-598. (b) Faller, J . W.; Ma, Y.; Smart, C. J .; Diverdi,
M. J . J . Organomet. Chem. 1991, 420, 237-252. (c) Garner, C. M.;
Mendez, N. Q.; Kowalczyk, J . J .; Fernancez, J . M.; Emerson, K.; Larsen,
R. D.; Gladysz, J . A. J . Am. Chem. Soc. 1990, 112, 5146-5160. (d)
Huang, Y. H.; Gladysz, J . A. J . Chem. Educ. 1988, 65, 298-303.
(13) (a) Hofmann, P. Angew. Chem., Int. Ed. Engl. 1977, 16, 536-
537. (b) Ward, T. R.; Schafer, O.; Daul, C.; Hofmann, P. Organome-
tallics 1997, 16, 3207-3215. (c) J ohnson, T. J .; Folting, K.; Streib, W.
E.; Martin, J . D.; Huffman, J . C.; J ackson, S. A.; Eisenstein, O.;
Caulton, K. G. Inorg. Chem. 1995, 34, 488-499.
(14) (a) Dewey, M. A.; Stark, G. A.; Gladysz, J . A. Organometallics
1996, 15, 4798-4807. (b) Fernandez, J . M.; Gladysz, J . A. Organome-
tallics 1989, 8, 207-219.
(15) Faller, J . W.; Chase, K. J .; Mazzieri, M. R. Inorg. Chim. Acta
1995, 229, 39-45.
F igu r e 2. ORTEP representation of [(η6-Cy)RuCl(η2-Ph2-
PCH2P(O)Ph2)][SbF6] (6), with 30% probability ellipsoids.
(16) (a) Cesarotti, E.; Angoletta, M.; Walker, N. P. C.; Hursthouse,
M. B.; Vefghi, R.; Schofield, P. A.; White, C. J . Organomet. Chem. 1985,
286, 343-360. (b) Cesarotti, E.; Chiesa, A.; Ciani, G. F.; Sironi, A.;
Vefghi, R.; White, C. J . Chem. Soc., Dalton Trans. 1984, 653-661.
(17) Faller, J . W.; Ma, Y. Organometallics 1992, 11, 2726-2729.
(18) Campion, B. K.; Heyn, R. H.; Tilley, T. D. J . Chem. Soc., Chem.
Commun. 1988, 278-280. See also amine analogues: (a) Mauthner,
K.; Slugovc, C.; Mereiter, K.; Schmid, R.; Kirchner, K. Organometallics
1997, 16, 1956-1961. (b) Gemel, C.; Mereiter, K.; Schmid, R.; Kirchner,
K. Organometallics 1997, 16, 5601-5603.
π-bonded owing to the harder strong acid character of
the dicationic Lewis acid. There is also a pronounced
tilt of the aldehyde to allow preferential interaction of
the π orbitals of the aldehyde carbonyl with specific d
orbitals owing to a differential electronic effect of the P
and O donors. The torsion angles are φ(P1-Ru1-O2-
C39) ) 153.4(2)° and φ(O1-Ru1-O2-C39) ) 70.7(2)°,

3100 Organometallics, Vol. 18, No. 16, 1999
Faller et al.
Ta ble 2. 31P {1H} NMRa Da ta of
[CyRu L(η2-P h 2P CH(R)P (O)P h 2)][SbF 6]2 Com p lexes
L
P(III) P(V) 2J PP (Hz) ∆P(III) ∆P(V)
R ) CH3
solventob
50.0
49.0
53.8
53.6
55.7
55.8
71.2
66.5
70.9
70.0
72.3
72.3
30
27
26
25
24
25
Clc
-4.6
0.2
-3.5
0.9
cinnamaldehyde
crotonaldehyde
methacrolein
benzaldehyde
0.0
0.0
2.1
2.3
2.2
2.3
R ) C3H7
72.3
68.2
74.2
74.1
solventob
50.9
50.1
54.8
54.5
57.6
58.0
34
28
27
28
28
28
Clc
-4.1
0.3
-5.9
0.1
cinnamaldehyde
crotonaldehyde
methacrolein
benzaldehyde
0.0
0.0
76.2
76.5
3.1
2.0
3.5
2.4
R ) Ph
65.3
60.3
65.0
64.9
solventob
58.4
57.1
59.3
59.3
61.4
61.3
34
30
30
33
32
31
F igu r e 4. ORTEP representation of [(η6-Cy)Ru(PhCHO)-
(η2-Ph2PCH(C3H7)P(O)Ph2)][SbF6]2 (10), with 50% prob-
ability ellipsoids.
Clc
-2.2
0.0
0.0
2.1
2.0
-3.6
0.1
0.0
-1.5
-0.5
cinnamaldehyde
crotonaldehyde
methacrolein
benzaldehyde
63.5
64.4
Ta ble 3. Com p a r ison of Selected Bon d Len gth s (Å)
a n d An gles (d eg)
a
Spectra of solutions in CH2Cl2 were recorded on a GE-Omega
300 MHz spectrometer (121 MHz for 31P) and chemical shifts are
reported in δ relative to an 85% H3PO4 (aq) external standard.
3
6
9
10
Ru-Cl(1)
Ru-P(1)
Ru-O(1)
P(2)-O(1)
2.403(1)
2.374(1)
2.148(4)
1.484(3)
2.403(1)
2.353(2)
2.154(3)
1.517(4)
2.397(1)
2.329(1)
2.109(2)
1.528(3)
b
2.360(1)
1.520(2)
The methylene chloride solvate is assumed, but coordinated
-
SbF6 could be a ligand. c Complexes with chloro ligands have a
charge of +1.
P(1)-Ru-O(1)
Ru-O(1)-P(2)
Ru-P(1)-C(11)
P(1)-C(11)-P(2)
O(1)-P(2)-C(11)
80.8(1)
81.2(1)
82.11(5)
125.2(1)
105.7(1)
105.1(2)
108.4(2)
coordinated aldehyde, as has been observed with other
chiral systems of this type having bound aldehydes.12
A comparison of selected bond lengths and angles is
given in Table 3. One might note that there is an
increase in all ligand angles involved in the five-
membered chelate ring relative to the monodentate
ligand. The bite angle is also rather small. Thus there
is some strain introduced in forming the chelate, and
factors that reduce it may account for the greater
tendency to form chelates in some complexes.
122.2(2)
114.8(1)
119.6(2)
115.4(2)
125.2(2)
103.5(2)
108.6(3)
109.2(2)
106.9(1)
107.5(1)
110.0(1)
withdrawing group appears to be required for chiral
stability, and this has been rationalized theoretically.13
The 18-electron CpRu(CO)(PPh3)X system does not
racemize, a feature also noted earlier using the neo-
menthyl-substituted cyclopentadienyl ligand.16 How-
ever, when a chiral sulfoxide replaces the halide,
epimerization can occur at the metal center, presumably
via the 16-electron intermediate.17 In our CyRu(P,O-
ligand)2+ intermediate, the unsymmetrical “two-legged
piano stool” might be expected to have a low barrier to
conversion to a form of the CyRuPO moiety having a
plane of symmetry. In fact some 16-electron CpRuLX
complexes have been characterized crystallographically
and found to have a “planar” Ru.18 Hence, moderately
rapid epimerization or racemization might be antici-
pated when weak bonding of a ligand is involved.
Scheme 4 depicts two possible mechanisms by which the
diastereomers in either the solvento or aldehyde com-
plexes could interconvert.
The cymene ligand is particularly diagnostic of rapid
racemization. The methyl groups of the isopropyl and
the aromatic cymene protons are diastereotopic when
the Ru chiral center is maintained on the NMR time
scale. For example, if [(η6-Cy)RuCl(η2-Ph2PCH2P(O)-
Ph2)][SbF6], 6, racemized rapidly, a single isopropyl
methyl doublet would be observed, rather than the two
actually observed at δ 1.19 and δ 1.04.19 The benzalde-
hyde complex also shows two isopropyl resonances at δ
1.32 and δ 1.13. The solvento complex also shows two
isopropyl resonances at δ 1.42 and δ 1.23. Thus, even
for more weakly bound ligands, the racemization rate
is slow on the NMR time scale (t1/2 > 1 s). The dimethyl
sulfoxide complex derived from 6 also shows diaste-
Discu ssion
The 16-electron Lewis acid formed by abstraction of
halide or the dissociation of an aldehyde might not be
expected to be stable to racemization or epimerization.13
Nevertheless, there are cases where racemization does
not occur, such as with CpRe(NO)(PPh3)X14 or the
intermediate in CpMo(NO)(allyl)X when halides are
exchanged.15 Empirically, the presence of a strong
(19) Although racemization of the complex, involving a rapid inter-
conversion of RRu and SRu, would average the methyls in 6, the presence
of the stereogenic centers in the Me-, Ph-, and Bu-substituted ligands
would not allow averaging of the environments and the isopropyl
methyls and cymene aromatics would remain diastereotopic. As shown
in 3, the methyl substituent in the backbone favors twisting of the
phenyls, which creates a chiral environment close to the metal, even
though the chiral center is remote. This results in cymene aromatic
shifts ranging over 1.6 ppm and diastereotopic isopropyl methyls
differing by 0.35 ppm. An unusual downfield shift of ∼1 ppm of one
pair of phenyl protons to δ 8.86 is also indicative of the differential
interaction of the nonequivalent phenyls.
(20) At this time, it is not known which atom of the sulfoxides acts
as the donor; however it is clear from 31P NMR that coordination occurs
preferentially to one or the other because only diastereomers of one
complex were formed. Sulfur binding is preferred in cyclopentadienyl-
ruthenium cation analogues;17 however, the higher acidity in the arene
complexes may well promote O binding.
(21) (a)Faller, J . W.; Liu, X. Tetrahedron Lett. 1996, 37, 3449-3452.
(b) Faller, J . W.; Sams, D. W. I.; Liu, X. J . Am. Chem. Soc. 1996, 118,
1217-1218. (c) Faller, J . W.; Parr, J . J . Am. Chem. Soc. 1993, 115,
804-805.

Diastereoselectivity in Chiral Ru Complexes
Organometallics, Vol. 18, No. 16, 1999 3101
substituent with halide or ligand. As shown in Figure
5, the exo methylene hydrogen in 6 is 2.88 Å from the
Cl (assuming a 1.09 Å C-H length) at approximately
the sum of the van der Waals radii (∼2.90 Å). This H- - -
Cl distance decreases to 2.67 Å in 9 owing to steric
interactions in the ring upon introduction of the propyl
group. If the exo methylene H were replaced by a methyl
group and the conformation of the ring remained the
same, then the H- - - Cl distance would decrease to 1.46
Å, which would create a severe repulsion problem.
The complexes with a substituent on the backbone
have the potential of selectively returning to a specific
metal chirality after forming a 16-electron intermediate,
but those based on the dppmO ligand would racemize
with an achiral aldehyde or solvent. One can then assess
the potential for epimerization at the metal center by
observing the effects with chiral aldehydes.
F igu r e 5. Comparison of ring conformations in 6 and 9.
Only the ipso carbons of the phenyls are shown.
Syn th esis of [CyRu L(η2-P h 2P CH(R)P (O)P h 2)]-
[SbF 6]2 Com p lexes Wh er e L ) (1R)-(-)-m yr ten a l,
t-Bu S(O)Me, Me2SO, (R)-(+)-(p-C6H4Me)S(O)Me. The
generation of an open coordination site on the complexes
[CyRuCl(η2-Ph2PCH(R)P(O)Ph2)][Cl] and CyRuCl2(η1-
Ph2PCH2P(O)Ph2) was accomplished by removal of
chloride via AgCl formation upon the addition of Ag-
SbF6. We will refer to the intermediate formed as the
16-electron Lewis acid, [CyRu(η2-Ph2PCH(R)P(O)Ph2)]-
[SbF6]2; however, it is more likely to be a solvento
complex or involve coordinated SbF6.
The potential problem of displacing the phosphine
oxide portion of the chelate with sulfoxides was inves-
tigated by adding a large excess of Me2SO to [CyRu-
(Me2SO)(η2-Ph2PCH2P(O)Ph2)][SbF6]2; the η1 complex
was not detected. The 31P NMR data for the sulfoxide
and myrtenal complexes are presented in Table 4.
The addition of (1R)-(-)-myrtenal to [CyRuL(η2-Ph2-
PCH2P(O)Ph2)]2+ yields two diastereomers (Scheme 5).
Since there is no substituent on the bridging carbon to
constrain epimerization at the metal center, epimeriza-
reotopic methyls indicative of slow exchange and slow
racemization.20
The methylene protons in the ligand in 6 also are
nonequivalent, which further indicates that racemiza-
tion is slow. An interesting feature here is that the 31P-
1H couplings to the nonequivalent protons are substan-
tially different: J H-P ) 10.2 and 17.3 Hz for the
resonance at δ 3.71 and J H-P ) 0.9 and 12.8 Hz for the
proton resonance at δ 3.23. Since the methyl-substituted
analogue (7) shows a single methylene proton with J H-P
) 12.1 and 21.1 Hz, this suggests that the exo proton
has the larger couplings, and the assignments would
be δ 3.71 for Hexo and δ 3.23 for Hendo in 6. The couplings
are a sensitive function of angle and vary substantially
for ligands other than chloride.
A comparison of chelated ligands 1a and 1d as found
in 6 and 9 is shown in Figure 5. The chelate ring is
slightly puckered with the methylene backbone away
from the cymene ring. This provides virtually no steric
interaction of the endo methylene substituent with the
cymene ring, but a potential interaction of the exo
Sch em e 4. Tw o P ossible Mech a n ism s for th e In ter con ver sion of Dia ster eom er s in th e Ald eh yd e
Der iva tives of Com p lexes 7-9: (a ) Dissocia tion of L, F ollow ed by In ver sion of Ch ela te a n d Recoor d in a tion
of L; (b) Hem id issocia tion of Ch ela te P (O) Moiety, F ollow ed by Rota tion a bou t Ru -P Bon d a n d
Rech ela tion of Liga n d

3102 Organometallics, Vol. 18, No. 16, 1999
Ta ble 4. 31P {1H} NMRa Da ta of [CyRu L(η2-P h 2P CH(R)P (O)P h 2)][SbF 6]2 Com p lexes
Faller et al.
major diastereomer
minor diastereomer
P(V)
P(III)
P(V)
2 J PP (Hz)
P(III)
2 J PP (Hz)
de
R ) H
20
20
22
18
(1R)-(-)-myrtenal
(R)-(+)-(p-tol)S(O)Me
rac-t-BuS(O)Me
Me2SO
48.1
48.9
44.8
45.6
73.4
72.0
72.0
70.8
47.7
45.3
44.6
74.3
70.4
72.1
22
18
23
37b
<2b
20b
R ) CH3
(1R)-(-)-myrtenal
(R)-(+)-(p-tol)S(O)Me
rac-t-BuS(O)Me
Me2SO
56.3
52.4
51.4
51.4
71.8
69.4
70.8
69.8
25
26
28
26
57.3
55.1
51.7
72.2
71.9
69.6
28
27
29
40c
<4c
25c
a
Spectra were recorded at 121 MHz for 31P, and chemical shifts are reported in ppm downfield from an 85% H3PO4 (aq) external
standard. Diastereomeric excess values do vary significantly with Ru:L ratio. c Diastereomeric excess values vary with Ru:L ratio and
b
were interpolated for 5:1 Ru:L.
Sch em e 5. Dia ster eom er s of th e Com p lex of (1R)-Myr ten a l w ith [CyRu (η2-d p p m O-P ,O)]2+
tion at the metal occurs to yield a 37% de with a t1/2
1 min. The addition of t-BuS(O)Me also produces a
modest de of 20%.
<
We are currently exploring the use of these ligands for
use in asymmetric Lewis acid catalysis. In addition, we
are developing the use of these racemic bisphosphine
monoxides in chiral poisoning/acceleration strategies.21
When R ) Me, there are three chiral centers in the
complex with a chiral aldehyde. One would not expect
a significant difference in the preference for having the
methyl oriented away from L, and thus the metal
chirality could not adapt to steric interactions with a
chiral ligand in the same way as found for [CyRuL(η2-
Ph2PCH2P(O)Ph2)]2+. Hence, one would expect the di-
astereoselectivity to be expressed for the enantiomers
of a chiral ligand. As observed with the achiral alde-
hydes, the backbone substituent forces a particular
configuration at the metal. The selectivity for the chiral
ligands, i.e., aldehydes or sulfoxides, is that due to the
difference in Keq’s for (R)-ligand and the [RRu, RC] or
[SRu, SC] Lewis acid. The relative amounts of the two
Exp er im en ta l Section
Gen er a l. All synthetic manipulations were carried out
using standard Schlenk techniques under inert atmosphere.
Reagent grade diethyl ether and dichloromethane were dried
over benzophenone ketyl and CaH2, respectively, and thor-
oughly degassed by pump/thaw techniques prior to use to
prevent oxidation of the ligands. Absolute methanol and ethyl
acetate, and Silica-60 (EM Separation Technologies) used for
chromatography, were reagent grade and used without further
purification. The ligands 1a -1d and the ruthenium dimer
[CyRuCl2]2 were prepared according to published procedures.8
The solution of 1.6 M n-BuLi in hexanes was used as received.
trans-Cinnamaldehyde, 99+% (Aldrich), crotonaldehyde, 99+%
(Aldrich), methacrolein, 95% (Aldrich), (1R)-(-)-myrtenal (Al-
drich), (R)-(+)-(p-tol)S(O)Me (Aldrich), dimethyl sulfoxide, and
AgSbF6 were used without further purification. The racemate
of t-BuS(O)Me was prepared according to a published proce-
dure.22 1H and 31P{1H} NMR spectra were recorded on a
Bruker 500 MHz or a GE Omega 300 MHz (operating at 121
MHz for 31P) spectrometer, and chemical shifts are reported
in ppm relative to residual solvent peaks (1H) or an 85% H3-
PO4 (aq) external standard (31P). Elemental analyses were
carried out by Robertson Microlit Labs, Patterson, NJ , or
Atlantic Microlabs.
complexes will vary with the concentration of free [RRu
,
RC] or [SRu, SC] Lewis acid that is available, and thus
the de varies with relative concentration. The highest
selectivity is observed when the [Ru]total . [L]total ratio
is high; that is, when [RRu, RC]:[SRu, SC] for the free acid
is ∼1:1. As [Ru]total approaches [L]total, the de decreases
as both enantiomers of the Lewis acid effectively become
ligated. To provide a standard reference point, the de
given for R ) Me was interpolated for the ratio of 5:1
for Ru:L. (We are currently investigating more quanti-
tative determinations of the equilibrium constants.) The
data in Table 4 demonstrate that there is a significant
selectivity in the binding of the chiral aldehyde.
P r ep a r a tion of [(η6-Cy)Ru Cl2(η1-P h 2P CH2P (O)P h 2)] (2).
Ligand 1a (157 mg, 0.39 mmol) was dissolved in 10 mL of dry
degassed dichloromethane. An equivalent of the [CyRuCl2]2
dimer (120 mg, 0.196 mmol) was added, and the mixture was
stirred for 2 h. The solvent was removed, and the red solid
residue was recrystallized from a dichloromethane/diethyl
Con clu sion
We have shown that the chirality of a metal center
can be retained by appropriate substitution of backbone
in the ligand, even if there is the potential for epimer-
ization via the formation of a 16-electron intermediate.
1
ether solution in nearly quantitative yield. H NMR (CDCl3,
(22) Henbest, H. B.; Reid, J . A. W.; Stirling, C. J . M. J . Chem. Soc.
1964, 1220-1223.

Diastereoselectivity in Chiral Ru Complexes
Organometallics, Vol. 18, No. 16, 1999 3103
293 K, δ): 7.98 (m, 4 H, Ph), 7.37 (m, 4 H, Ph), 7.26 (m, 8 H,
Ph), 7.18 (m, 4 H, Ph), 5.25 (d, 2 H, J ) 6.3 Hz, Cy CH), 5.11
(d, 2 H, J ) 6.3 Hz, Cy CH), 3.87 (apparent t ) dd, 2 H, J H-P
) 9.9, 9.9 Hz, P-CH2-P), 2.48 (spt, 1H, J ) 6.8 Hz, Cy
CH(CH3)2), 1.82 (s, 3 H, Cy CH3), 0.80 (d, 6 H, J ) 6.8 Hz, Cy
(CH3)2CH). 31P{1H} NMR: 23.6 (d, J P-P )33.0 Hz, P(III)), 25.7
(d, J P-P )33.0 Hz, P(V)). Anal. Calcd for C35H36Cl2OP2Ru: C,
59.49; H, 5.14. Found: C, 59.33; H, 5.26.
H, d, J ) 6.9 Hz, Cy CH3CH2-CH3). 31P{1H} NMR: 49.0 (d,
2
2J PP ) 28 Hz), 66.5 (d, J PP ) 27 Hz). Anal. Calcd for [C36H38
-
ClOP2Ru][SbF6]: C, 46.95; H, 4.16. Found: C, 46.53; H, 4.31.
P r ep a r a tion of [(η6-Cy)Ru Cl(η2-P h 2P CH(P h )P (O)P h 2)]-
[SbF 6] (8). Ligand 1c (930 mg, 1.95 mmol) was dissolved in
10 mL of dry degassed CH2Cl2, and 1 equiv of the [(η6-Cy)-
RuCl2]2 dimer (600 mg, 0.98 mmol) was added. The resulting
deep red solution was stirred at room temperature under
nitrogen for 30 min. Removal of the solvent under vacuum
typically produced a red-orange oil, which was transferred to
a silica gel chromatography column (2 × 5 cm) and eluted with
ethyl acetate under nitrogen pressure. Typically after 100 mL
of ethyl acetate a deep red-orange band remained on top of
the column and could only be eluted using absolute methanol.
This band contained the η2 coordination isomer [CyRuCl(η2-
Ph2PCH(CH3)P(O)Ph2)][Cl] (4′), which was isolated as an
orange, air-stable solid after removing the methanol under
vacuum, but not further purified. Compound 8 was prepared
by reaction of 4′ (200 mg, 0.26 mmol) with 1 equiv of AgSbF6
(88 mg) in dichloromethane at room temperature. The pre-
cipitated AgCl, which formed immediately, was filtered from
the solution, and the solvent was removed under vacuum. The
product was recrystallized from dichloromethane and diethyl
ether in 80-90% yield. 1H NMR (CDCl3, 293 K, δ):7.8-6.8 (25
H, m, Ph), 6.03 (2 H, overlapped doublets, J ) 5.8 Hz, Cy CH)
5.91 (1 H, d, J ) 5.8 Hz, Cy CH), 5.62 (1 H, d, J ) 5.8 Hz, Cy
CH), 5.47 (1 H, dd, 2J P-H ) 5.8 Hz; P-(HC)Ph-P; 2J P-H ) 11.6
Hz,), 2.82 (1 H, spt, J ) 6.9 Hz, Cy CH(CH3)2), 1.96 (3 H, s,
Cy CH3), 1.26 (3 H, d, J ) 6.9 Hz, Cy CH3-CHCH3), 1.17 (3
P r ep a r a t ion of [(η6-Cy)R u Cl2(η1-P h 2P CH (CH3)P (O)-
P h 2)] (3). One equivalent of the ligand 1b (680 mg, 1.6 mmol)
was dissolved in 10 mL of dry degassed dichloromethane, along
with a stoichiometric amount of the [CyRuCl2]2 dimer (500 mg,
0.8 mmol). The resulting deep red solution was stirred at room
temperature under nitrogen for 30 min. Removal of the solvent
under vacuum typically produced a red-orange oil, which was
transferred to a silica gel chromatography column (2 × 5 cm)
and eluted with ethyl acetate under nitrogen pressure. The
second fraction typically eluted a deep red-orange band,
followed by several colorless to pale yellow fractions. A deep
red-orange band remained on top of the column and could only
be eluted using absolute methanol. The early colored band
contained the η1 coordination isomer of 3; when this fraction
was left to stand overnight in air, large red crystals of 3 formed
(∼40% yield). The deep red band which was eluted with
methanol contained the η2 coordination isomer [CyRuCl(η2-
Ph2PCH(CH3)P(O)Ph2)][Cl] (3′), which was isolated as an red-
orange air-stable solid after removing the methanol under
vacuum (typically ∼40% yield). 1H NMR (CDCl3, 293 K, δ) for
3: 8.86 (2 H, m, Ph), 7.8-7.1 (18H, m, Ph), 5.63 (1 H, d, J )
5.9 Hz, Cy CH), 4.98 (1 H, d, J ) 6.1 Hz, Cy CH), 4.96 (1 H,
qdd obscured, P2CH-CH3), 4.92 (1 H, d, J ) 5.9 Hz, Cy CH),
4.04 (1 H, d, J ) 6.1 Hz, Cy CH), 3.04 (1 H, spt, J ) 6.9 Hz,
Cy CH(CH3)2), 1.53 (3 H, s, Cy CH3), 1.38 (3 H, d, J ) 6.9 Hz,
Cy CH3-CHCH3), 1.23 (3 H, d, J ) 6.9 Hz, Cy CH3CH-CH3),
H, d, J ) 6.9 Hz, Cy CH3CH2-CH3). 31P{1H} NMR: 57.1 (d,
2
2J PP ) 30 Hz), 60.3 (d, J PP ) 30 Hz). Anal. Calcd for [C41H40
-
ClOP2Ru][SbF6]‚CH2Cl2: C, 47.24; H, 3.96. Found: C, 47.74;
H, 3.87.
P r ep a r a tion of [CyRu Cl(η2-P h 2P CH(C3H7)P (O)P h 2)]-
2
2
0.88 (3 H, ddd, J ) 7.5 Hz; J P-H ) 16.4 Hz; J P-H ) 16.8 Hz
P2C-CH3). 31P{1H} NMR for 3: 32.8 (d, 29 Hz), 33.8 (d, 29
Hz). Anal. Calcd for C36H38Cl2OP2Ru: C, 60.00; H, 5.31.
Found: C, 59.89; H, 5.10.
[SbF 6] (9). The same procedure was used as described for 8
1
except 1d was used. H NMR (CDCl3, 293K, δ): 7.8-7.3 (20
H, Ph), 5.98 (1 H, d, 5.7 Hz, Cy CH), 5.71 (2 H, d, 5.7 Hz, Cy
CH), 5.62 (1 H, d, 5.7 Hz, Cy CH), 4.35 (1 H, m, P-prCH-P),
2.36 (1 H, spt, 6.9 Hz, Cy CH3CHCH3), 2.08 (3 H, s,Cy CH3),
1.6-1.1 (4 H, br m CH2CH2CH3), 0.99 (3 H, d, 6.9 Hz CH3-
CHCH3), 0.74 (3 H, d, 6.9 Hz, CH3-CHCH3), 0.65 (3 H, t, 7.1
Hz, CH2CH2CH3). 31P{1H}: 50.1 (d, 2J PP ) 29 Hz), 68.2 (d, 2J PP
) 28 Hz). The compound was ground finely and kept under
vacuum overnight before analysis to remove ether. Anal. Calcd
for [C38H42ClOP2Ru][SbF6]: C, 48.10; H, 4.46. Found: C, 48.31;
H, 4.24.
P r ep a r a tion of [(η6-Cy)Ru Cl(η2-P h 2P CH2P (O)P h 2)]-
[SbF 6] (6). Silver hexafluoroantimonate (49 mg, 0.14 mmol)
was added to 2 (100 mg, 0.14 mmol) in 6 mL of dichlo-
romethane. The solution was stirred for 20 min in the dark
and filtered through Celite to remove the precipitated silver
chloride. The solvent was removed, and the product was
recrystallized from a dichloromethane/diethyl ether solution,
88% yield. 1H NMR (CD2Cl2, 293K, δ): 7.10-7.73 (20 H m,
Ph), 5.83 (1 H, d, J ) 6.0 Hz, Cy CH), 5.56 (1 H, d, 6.0 Hz, Cy
CH), 5.54 (s, 2 H, Cy CH, Cy CH), 3.71 (1 H, ddd, J ) 14.6 Hz,
2J H-P )10.2 Hz, 17.3 Hz, P-(HC)H-P), 3.23 (1H, ddd, J )
14.6 Hz, 2J H-P )12.8 (CHexo)-P, 2J H-P ) 0.9 (CHendo)-P), 2.56
(1 H, spt, J ) 7.0 Hz, Cy CH(CH3)2), 1.94 (3 H, s, Cy CH3),
1.19 (3 H, d, J ) 7.0 Hz, Cy CH3-CHCH3)), 1.04 (3 H, d, J )
7.0 Hz, Cy CH3-CH-CH3). 31P{1H} NMR: 44.8 (d, J P-P )15.8
Hz, P(III)), 68.5 (d, J P-P )15.8 Hz, P(V)). Anal. Calcd for
[C35H36ClOP2Ru][SbF6]: C, 46.36; H, 4.00. Found: C, 46.13;
H, 3.95.
Gen er a l P r oced u r e for th e in Situ Obser va tion of
Ald eh yd e a n d Su lfoxid e Com p lexes, [CyRu (η2-P h 2P CH-
(R)P (O)P h 2)(L)][SbF 6]2. These experiments were carried out
in air for all systems. A 10 mL round-bottom flask was charged
with 200 mg of an η2-[SbF6]- complex (either 7, 8, or 9) and 5
mL of freshly distilled dichloromethane in air. To the orange
solutions were added 1.1 equiv of AgSbF6, which caused the
immediate precipitation of AgCl as a fluffy white solid; stirring
was continued for 1 h before the AgCl was filtered. The bright
orange solution was divided into portions. Each portion was
treated with a ligand in several additions so that the reso-
nances of the product and starting acid could be identified by
31P{1H} NMR. Ultimately10 equiv of the appropriate aldehyde
was added. When necessary, anhydrous MgSO4 was added to
remove water from the solvent. Phosphorus NMR are given
in Table 2. Proton NMR for some representative complexes
are given below.
P r epar ation of [(η6-Cy)Ru Cl(η2-P h 2P CH(CH3)P (O)P h 2)]-
[SbF 6] (7). Compound 7 was prepared as the SbF6 salt by
reaction of 3 (100 mg, 0.14 mmol) with 1 equiv of AgSbF6 in
dichloromethane at room temperature. The reaction was
complete within minutes, and the precipitated AgCl was
filtered before the solvent was removed under vacuum. The
product was recrystallized from dichloromethane and diethyl
ether (80-90% yield). 1H NMR (CDCl3, 293 K, δ): 7.8-7.3
(20H, m, Ph), 5.91 (1 H, d, J ) 6.1 Hz, Cy CH), 5.72 (1 H, d,
J ) 5.7 Hz, Cy CH), 5.67 (1 H, d, J ) 6.1 Hz, Cy CH), 5.51 (1
H, d, J ) 5.7 Hz, Cy CH), 4.42 (1 H, qdd, q, J ) 7.4 Hz, d,
[CyRu (η2-P h 2P CH(H)P (O)P h 2)(solven t)][SbF6]2. 1H NMR
(CD2Cl2, 293 K, δ) 7.9-7.1 (20 H, m, Ph), 6.23 (1 H, d, J ) 6.0
Hz, Cy CH) 5.78 (1 H, d, J ) 5.7 Hz, Cy CH), 5.61 (1 H, d, J
) 6.0 Hz, Cy CH), 5.49 (1 H, d, J ) 5.7 Hz, Cy CH), 3.56 (1 H,
2
2J P-H ) 12.1 Hz; d, J P-H ) 21.1 Hz, P2CH-CH3), 2.47 (1 H,
2
2
spt, J ) 6.9 Hz, Cy CH(CH3)2), 2.08 (3H, s, Cy CH3), 1.50 (1H,
ddd, J ) 15.7 Hz, P-(HC)H-P; J P-H ) 5.6 Hz; J P-H ) 13.0
2
2
2
ddd, d, J ) 7.4 Hz; d, J P-H ) 11.4 Hz; d, J P-H ) 18.3 Hz
P2C-CH3), 1.02 (3 H, d, J ) 6.9 Hz, Cy CH3-CHCH3), 0.91 (3
Hz), 3.40 (1 H, ddd, J ) 15.7 Hz, P-(HC)H-P; J P-H ) 9.5
Hz; 2J P-H ) 11.1 Hz), 2.81 (1 H, spt, J ) 6.9 Hz, Cy CH(CH3)2),

3104 Organometallics, Vol. 18, No. 16, 1999
Faller et al.
2.07 (3 H, s, Cy CH3), 1.42 (3 H, d, J ) 6.9 Hz, Cy CH3-
CHCH3), 1.23 (3 H, d, J ) 6.9 Hz, Cy CH3CH2-CH3).
X-r a y Cr ysta llogr a p h y. Crystallographic data are listed
in Table 1. The structure of 3 was determined at -103 °C from
data collected with a serial diffractometer (Rigaku AFC5S),
whereas data for 6 were collected on a Nonius KappaCCD at
room temperature. Data for 9′′ and 10 were collected on a
Nonius KappaCCD at -90 °C. The CCD data were collected
with one æ scan, followed by at least one ω scan to get a data
set as nearly complete as possible (less than 10 reflections
remaining to fill the Ewald sphere). The structures were solved
by direct methods (SIR92) using the teXan crystal structure
analysis package, and the function minimized was ∑w(|Fo| -
|Fc|)2 in all cases. Hydrogen atoms were placed at calculated
positions before each refinement and were included in the
refinement, but were not refined. An empirical absorption
correction (DIFABS) was applied for 3, and SORTAV was
applied to the CCD data. Large thermal parameters for
portions of the cymene ring and the isopropyl groups were
observed in several structures, indicating disorder in orienta-
tion of the isopropyl group and to some extent the arene ring.
Satisfactory disorder models could not be found, but the
disorders were minor and did not appear to affect the impor-
tant features of the structure involving other ligands as judged
from thermal parameters. Structures 9 and 10 are in polar
space groups (Pna21)and were also refined with the coordinates
inverted to establish the polarity. The number of observations
with I > 3σ(I), the number of variables, and the reflection/
parameter ratios were as follows: 3 4434, 379, 11.7; 6 4477,
424, 10.6; 9′′, 5009, 450, 11.1; 10, 7126, 576, 12.4.
[CyRu (η2-P h 2P CH(H)P (O)P h 2)(P h CHO)][SbF6]2. 1H NMR
(CD2Cl2, 293 K, δ) 9.95 (1 H, s, PhC(O)H), 7.9-7.1 (25 H, m,
Ph), 6.23 (1 H, d, J ) 6.5 Hz, Cy CH) 5.88 (1 H, d, J ) 6.5 Hz,
Cy CH), 5.64 (1 H, d, J ) 7.0 Hz, Cy CH), 5.63 (1 H, d, J ) 6.5
2
Hz, Cy CH), 3.67 (1 H, ddd, J ) 16.0 Hz, P-(HC)H-P; J P-H
2
) 8.8 Hz; J P-H ) 12.7 Hz), 3.49 (1 H, ddd, J ) 16.0 Hz,
P-(HC)H-P; 2J P-H ) 9.8 Hz; 2J P-H ) 11.1 Hz), 2.70 (1 H, spt,
J ) 6.9 Hz, Cy CH(CH3)2), 2.07 (3 H, s, Cy CH3), 1.32 (3 H, d,
J ) 6.9 Hz, Cy CH3-CHCH3), 1.13 (3 H, d, J ) 6.9 Hz, Cy
CH3CH2-CH3).
[CyRu (η2-P h 2P CH(H)P (O)P h 2)(DMSO)][SbF6]2. 1H NMR
(CD2Cl2, 293 K, δ 8.1-7.0 (20 H, m, Ph), 6.32 (1 H, d, J ) 5.7
Hz, Cy CH) 5.79 (1 H, d, J ) 6.0 Hz, Cy CH), 5.58 (1 H, d, J
) 5.7 Hz, Cy CH), 5.41 (1 H, d, J ) 6.0 Hz, Cy CH), 3.47-3.44
(2H, overlapped ddd, P-(HC)H-P), 2.86 (1 H, spt, J ) 6.9 Hz,
Cy CH(CH3)2), 2.35 (3 H, s, CH3S(O)CH3), 2.21 (3 H, s, CH3S-
(O)CH3), 2.07 (3 H, s, Cy CH3), 1.36 (3 H, d, J ) 6.9 Hz, Cy
CH3-CHCH3), 1.12 (3 H, d, J ) 6.9 Hz, Cy CH3CH2-CH3).
[CyR u (η2-P h 2P CH (CH 3)P (O)P h 2)(DMSO)][Sb F 6]2. 1H
NMR (CD2Cl2, 293 K, δ 7.9-7.1 (20 H, m, Ph), 6.07 (1 H, d, J
) 5.7 Hz, Cy CH) 6.05 (1 H, d, J ) 6.0 Hz, Cy CH), 5.71 (1 H,
d, J ) 6.0 Hz, Cy CH), 5.41 (1 H, d, J ) 5.7 Hz, Cy CH), 3.91
(1 H, qdd: q, 7.4 Hz, CHCH3; d, 2J P-H ) 12.1 Hz; 2J P-H ) 19.7
Hz), 2.62 (1 H, spt, J ) 7.0 Hz, Cy CH(CH3)2), 2.57 (3 H, s,
CH3S(O)CH3), 2.21 (3 H, s, CH3S(O)CH3), 2.06 (3 H, s, Cy CH3),
1.21 (3 H, d, J ) 7.0 Hz, Cy CH3-CHCH3), 1.13 (3 H, ddd, J
) 7.4 Hz, CHCH3, J P-H ) 12.2 Hz, J P-H ) 17.3), 0.83 (3 H, d,
J ) 7.0 Hz, Cy CH3CH2-CH3).
Ack n ow led gm en t . This research was supported
by grants from the National Science Foundation (CHE-
9726423) and the Petroleum Research Fund adminis-
tered by the American Chemical Society.
Cr ysta lliza tion of [(η6-Cy)Ru Cl2(η1-P h 2P CH(CH3)P (O)-
P h 2)], 6. Crystals for X-ray diffraction were grown by slow
evaporation of solvent from a solution of the complex in ethyl
acetate at room temperature.
Cr ysta lliza tion of [(η6-Cy)Ru Cl2(η1-P h 2P CH2P (O)P h 2)],
3, {[CyRu Cl(η2-P h 2P CH(C3H7)P (O)P h 2)][SbF6]‚[O(C2H5)2]},
9′′, an d [CyRu (P h CHO)(η2-P h 2P CH(C3H7)P (O)P h 2)][SbF6]2,
10. Crystals for X-ray diffraction were grown at room temper-
ature by slow vapor diffusion of diethyl ether into a dichlo-
romethane solution of the compound in a closed concentric vial
system. An ether molecule crystallized with compound 9 to
yield 9′′.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data, structure solution and refinement, atomic coordinates,
anisotropic thermal parameters, interatomic distances and
angles, and hydrogen atom coordinates for 3, 6, 9, and 10. This
material is available free of charge via the Internet at
http://pubs.acs.org.
OM981053G