Mechanistic studies on the formation of η2-diphosphine (η6-p-cymene)ruthenium(II) compounds

Article abstract of DOI:10.1021/om060752n

A new range of pendent diphosphine (η⁶-p-cymene) ruthenium(II) complexes, [RuCl(PPh₃)(η¹-(P-P))- (η⁶-p-cymene)]PF₆ (P-P -dppm, cis-PPh ₂CHCHPPh₂ (dppv), dppe, dppp, dppf), have been prepared by substitution of the labile acetonitrile ligand in [RuCl(CH₃CN) (PPh₃)(η⁶-p-cymene)]PF₆. The formation of chelate complexes, [RuCl(η²-(P-P))(η⁶-p-cymene)] ⁺, from these pendent phosphine complexes and from the related neutral complexes, [RuCl₂(η¹-(P-P))(η⁶- p-cymene)] (P-P = dppm, dppv), has been investigated, including determination of activation enthalpies (ΔH?) and entropies (ΔS?). A concerted substitution mechanism is proposed for the latter complexes, in which methanol plays an important role in the ring-closing process by formation of hydrogen bonds with the chloride ligands. This proposal is supported by volumes of activation (ΔV?) determined by variable-pressure UV-visible spectroscopy. In contrast, a dissociative mechanism is proposed for the series of cationic pendent phosphine complexes, which generally require higher temperatures to effect ring closure. Secondary reaction pathways can be observed in some cases and are discussed in terms of differences between the phosphine complexes and supplemented by investigations using electrospray ionization mass spectrometry (ESI-MS). The X-ray structures of [RuCl(PPh₃) (η¹-(P-P))(η⁶-p-cymene)]PF₆ (P-P = dppm, dppv, dppp) and [RuCl(η²-dppv)-(η⁶-p-cymene) ]PF₆ are also reported.

Full text of DOI:10.1021/om060752n

586
Organometallics 2007, 26, 586-593
Mechanistic Studies on the Formation of η2-Diphosphine
(η6-p-cymene)ruthenium(II) Compounds
Adrian B. Chaplin, Ce´line Fellay, Ga´bor Laurenczy, and Paul J. Dyson*
Institut des Sciences et Inge´nierie Chimiques, Ecole Polytechnique Fe´de´rale de Lausanne (EPFL),
CH-1015 Lausanne, Switzerland
ReceiVed August 21, 2006
A new range of pendent diphosphine (η6-p-cymene)ruthenium(II) complexes, [RuCl(PPh3)(η1-(P-P))-
(η6-p-cymene)]PF6 (P-P ) dppm, cis-PPh2CHCHPPh2 (dppv), dppe, dppp, dppf), have been prepared
by substitution of the labile acetonitrile ligand in [RuCl(CH3CN)(PPh3)(η6-p-cymene)]PF6. The formation
of chelate complexes, [RuCl(η2-(P-P))(η6-p-cymene)]+, from these pendent phosphine complexes and
from the related neutral complexes, [RuCl2(η1-(P-P))(η6-p-cymene)] (P-P ) dppm, dppv), has been
investigated, including determination of activation enthalpies (∆Hq) and entropies (∆Sq). A concerted
substitution mechanism is proposed for the latter complexes, in which methanol plays an important role
in the ring-closing process by formation of hydrogen bonds with the chloride ligands. This proposal is
supported by volumes of activation (∆Vq) determined by variable-pressure UV-visible spectroscopy. In
contrast, a dissociative mechanism is proposed for the series of cationic pendent phosphine complexes,
which generally require higher temperatures to effect ring closure. Secondary reaction pathways can be
observed in some cases and are discussed in terms of differences between the phosphine complexes and
supplemented by investigations using electrospray ionization mass spectrometry (ESI-MS). The X-ray
structures of [RuCl(PPh3)(η1-(P-P))(η6-p-cymene)]PF6 (P-P ) dppm, dppv, dppp) and [RuCl(η2-dppv)-
(η6-p-cymene)]PF6 are also reported.
phosphine ligands represent an important subgroup3 and, as well
as finding various applications in catalysis, show considerable
potential as catalysts in biphasic hydrogenation reactions.4
While the use of bidentate phosphine ligands is prevalent in
the coordination chemistry of the transition metals, it is
interesting to note that the actual process of forming these
complexes has received relatively little attention. The chelation
reactions for a variety of bidentate phosphine ligands on metal
carbonyl complexes of group VI (eq 1)5 and recently in those
of ruthenium (eq 2)6 have previously been investigated and
found to proceed with varying degrees of bond breaking and
making. For ruthenium, entropies of activation range from 63
to -13 J mol-l K-1 and were taken to imply a mechanism with
predominately dissociative to significantly associative character
Introduction
Half-sandwich ruthenium(II)-η6-arene complexes are an
important and widely used class of organometallic compound,
which exhibit a diverse range of coordination chemistry and
show considerable potential as precursors for catalytic organic
transformations.1-4 In particular, complexes of this nature
bearing chelating ligands, [RuX(η6-arene)(L-L′)]+, have well-
demonstrated catalytic utility and are of current interest for a
variety of asymmetric reactions.2,3 Complexes bearing bidentate
* Corresponding author. E-mail: paul.dyson@epfl.ch.
(1) For examples see: (a) Rigby, J. H.; Kondratenko, M. A. Top.
Organomet. Chem. 2004, 7, 181-204. (b) Bennett, M. A. Coord. Chem.
ReV. 1997, 166, 225-254. (c) Bennett, M. A. ComprehensiVe Organo-
metallic Chemistry II; Abel, E. W., Stone, F. G. A., Wilkinson, G., Eds.;
Elsevier: Oxford, 1995, Vol. 7, pp 549-602. (d) Le Bozec, H.; Touchard,
D.; Dixneuf, P. H. AdV. Organomet. Chem. 1989, 29, 163-247. (e) Naota,
T.; Takaya, H.; Murahashi, S.-I. Chem. ReV. 1998, 98, 2599-2660. (f)
Bustelo, E.; Dixneuf, P. H. AdV. Synth. Catal. 2005, 347, 393-397. (g)
Castarlenas, R.; Dixneuf, P. H. Angew. Chem., Int. Ed. 2003, 42, 4524-
4527, and references therein. (h) Farrington, E. J.; Brown, J. M.; Barnard,
C. F. J.; Rowsell, E. Angew. Chem., Int. Ed. 2002, 41, 169-171. (i)
Akiyama, R.; Kobayashi, S. Angew. Chem., Int. Ed. 2002, 41, 2602-2604.
(j) Simal, F.; Demonceau, A.; Noels, A. F. Angew. Chem., Int. Ed. 1999,
38, 538-540.
along the series PPh2(o-C6H4)PPh2 < Cy2P(CH2)2PCy2
<
Me2P(CH2)2PMe2 < dppp e dppm ≈ dppb ≈ dppe ,
PPh2(NMe)PPh2.7 The reaction between monodentate phosphine
ligands and the widely used ruthenium(II) precursor [RuCl2-
(η6-p-cymene)]2, a well-established route to complexes of the
type [RuCl2(PR3)(η6-p-cymene)] (eq 3), has been investigated
in detail by Serron and Nolan.8 They measured the enthalpy of
(2) For illustrative examples see: (a) Noyori, R.; Hashiguchi, S. Acc.
Chem. Res. 1997, 30, 97-102. (b) Hannedouche, J.; Clarkson, G. J.; Wills,
M. J. Am. Chem. Soc. 2004, 126, 986-987. (c) Geldbach, T. J.; Dyson, P.
J. J. Am. Chem. Soc. 2004, 126, 8114-8115. (d) Zhou, Y.-G.; Tang, W.;
Wangm, W.-B.; Li, L.; Zhang, X. J Am. Chem. Soc. 2002, 124, 4952-
4953.
(3) (a) Qiu, L.; Kwong, Y.; Wu, J.; Lam, W. H.; Chan, S. Yu, W.-Y.;
Li, Y.-M.; Guo, R.; Zhou, Z.; Chan, A. S. C. J. Am. Chem. Soc. 2006, 128,
5955-5965. (b) Mashima, K.; Kusano, K.-H.; Sato, N.; Matsumura, Y.-I.;
Nozaki, K.; Kumobayashi, H.; Sayo, N.; Hori, Y.; Ishizaki, T.; Akutagawa,
S.; Takaya, H. J. Org. Chem. 1994, 59, 3064-3076. (c) Mashima, K.;
Matsumura, Y.-I.; Kusano, K.-H.; Kumobayashi, H.; Sayo, N.; Hori, Y.;
Ishizaki, T.; Akutagawa, S.; Takaya, H. J. Chem. Soc., Chem. Commun.
1991, 609-610. (d) Mashima, K.; Kusano, K.-H.; Ohta, T.; Noyori, R.;
Takaya, H. J. Chem. Soc., Chem. Commun. 1989, 1208-1210.
(4) (a) Daguenet, C.; Scopelliti, R.; Dyson, P. J. Organometallics 2004,
23, 4849-4857. (b) Daguenet, C.; Dyson, P. J. Organometallics 2004, 23,
6080-6083. (c) Ghebreyessus, K. Y.; Nelson, J. H. J. Organomet. Chem.
2003, 669, 48-56. (d) Daguenet, C.; Dyson, P. J. Catal. Commun. 2003,
4, 153-157.
(5) (a) Connor, J. A.; Day, J. P.; Jones, E. M.; McEwen, G. K. J. Chem.
Soc., Dalton Trans. 1973, 347-354. (b) Connor, J. A.; Riley, P. I. J.
Organomet. Chem. 1975, 94, 55-60.
(6) Bunten, K. A.; Farrar, D. H.; Poe¨, A. J.; Lough, A. J. Organometallics
2000, 19, 3674-3682.
(7) Abbreviations used for diphosphines and related ligands: PPh2CH2-
PPh2 (dppm), cis-PPh2CHCHPPh2 (dppv), PPh2(CH2)2PPh2 (dppe), PPh2-
(CH2)3PPh2 (dppp), 1,1′-bis(diphenylphosphino)ferrocene (dppf), [(S)-2-
(dimethylamino)-3-phenylpropyl]diphenylphosphine (S-phephos).
(8) Serron, S. A.; Nolan, S. P. Organometallics 1995, 14, 4611-4616.
10.1021/om060752n CCC: $37.00 © 2007 American Chemical Society
Publication on Web 12/15/2006

η2-Diphosphine (η6-p-cymene)ruthenium(II) Compounds
Organometallics, Vol. 26, No. 3, 2007 587
1
Table 1. Selected H, 13C, and 31P NMR Data for Complexes 1 and [2a-e]PF6 (CDCl3, 293 K)a
1
[2a]PF6
[2b]PF6
[2c]PF6
[2d]PF6
[2e]PF6
ligand
H7
CH3CN
1.75
3.05
dppm
0.93
2.78
0.06
98.7
132
23.0
22.0
52
dppv
0.99
2.58
0.19
100.6
130
25.8
7.4
55
dppe
0.84
2.76
0.07
98.8
132
dppp
0.85
2.76
0.05
99
dppf
1.10
2.67
0.19
99
H8
∆[H9, H10]
C1
0.02
103.6
116.6
35.5
C4
132
132
PPh3
Ru-PPh2
23.2b
23.0b
52b
23.2
18.4
52
23.3
19.7
52
c
2JPP
pend-PPh2
JPP
-28.8
44
-33.2
15
-13.0
26
-18.1
-19.4
d
b
a Labels as in Scheme 1. From simulation analysis. c 2J(PPh3, η1-(P-P)). d J(η1-(P-P), η1-(P-P)).
reaction for these reactions by solution calorimetry and found
significant dependence on both steric and electronic factors.
[M(CO)5(η1-(P-P))] f [M(CO)4(η2-(P-P))] + CO (1)
[Ru(CO)4(η1-(P-P))] f [Ru(CO)3(η2-(P-P))] + CO
(2)
[RuCl2(η6-p-cymene)]2 + 2PR3 f
2[RuCl2(PR3)(η6-p-cymene)] (3)
With a view to further enhance understanding of the formation
of bidentate phosphine ruthenium(II)-η6-arene complexes, we
have prepared a range of pendent phosphine complexes of the
type [RuCl(PPh3)(η1-(P-P))(η6-p-cymene)]PF6 (P-P ) dppm,
dppv, dppe, dppp, dppf) and studied the formation of chelate
complexes from these cationic precursors and those of the
neutral pendent phosphine complexes [RuCl2(η1-(P-P))(η6-p-
cymene)] (P-P ) dppm,9 dppv10), for comparison purposes.
Figure 1. ORTEP representation of [2b]PF6; thermal ellipsoids
are drawn at the 50% probability level. Counterion is omitted for
clarity. Relevant bond parameters are given in Table 2.
Table 2. Key Bond Lengths (Å) and Angles (deg) for
[2a]PF6, [2b]PF6, and [2d]PF6
Results and Discussion
[2a]PF6
[2b]PF6
[2d]PF6
1. Synthesis and Characterization. Substitution of the labile
acetonitrile ligand in [RuCl(CH3CN)(PPh3)(η6-p-cymene)]PF6,
1, with diphosphine in CH2Cl2 at room temperature affords the
pendent phosphine complexes [RuCl(PPh3)(η1-(P-P))(η6-p-
cymene)]PF6, [2]PF6 (P-P ) dppm, a; dppv, b; dppe, c; dppp,
d; dppf, e), in high yield, with the exception of [2e]PF6, which
is obtained in only moderate yield following recrystallization
(ca. 35%), owing to chelation occurring during the course of
the reaction and workup (Scheme 1). Small amounts of dimeric
species, where the diphosphine bridges two metal centers, can
also be observed by ESI-MS and 31P NMR spectroscopy during
the preparation of [2d]PF6. This impurity is readily removed
by recrystallization, and such dimeric species are not observed
for the other reactions, presumably owing to the reluctance of
the phosphine to bridge two charged centers, in marked contrast
to similar reactions of diphosphines with [RuCl2(η6-p-cymene)]2.10
The pendent coordination mode of the diphosphine is clearly
evidenced by 31P NMR spectroscopy, where, typically, three
distinct resonances are observed, with large 2JPP couplings (ca.
50 Hz) between the coordinated phosphorus centers.11 The
resonance corresponding to the pendent center is in each case
Ru1-Cl1
2.394(2)
2.393(2)
2.373(2)
2.281(7)
2.333(6)
2.27(4)
87.95(6)
85.69(5)
94.28(6)
2.3907(9)
2.3756 (11)
2.3811(9)
2.328(3)
2.345(3)
2.28(5)
86.49(4)
87.73(3)
93.77(4)
2.401(2)
2.393(2)
2.359(2)
2.293(6)
2.342(5)
2.28(4)
88.29(6)
88.04(5)
93.97(5)
Ru1-P1
Ru1-P3
Ru1-C1
Ru1-C4
Ru1-Cavg
Cl1-Ru1-P1
Cl1-Ru1-P3
P1-Ru1-P3
located at lower frequency, and for [2a-c]PF6, JPP couplings
are observed between the diphosphine centers. The 1H and 13
NMR spectra also corroborate the structures well; relevant NMR
data for 1 and [2a-e]PF6 are compiled in Table 1.
The X-ray structures of [2a]PF6 (Figure S2), [2b]PF6 (Figure
1), and [2d]PF6 (Figure S3) exhibit the typical “piano-stool”
geometry around the ruthenium and have generally comparable
structural parameters to the related complex [RuCl(PPh3)2(η6-
p-cymene)]BF4 (3),12 although the P-Ru-P angles are signifi-
cantly reduced in comparison, i.e., [2a]PF6 94.28(6)°, [2b]PF6
93.77(4)°, [2d]PF6 93.97(5)°, 3 97.97(2)°. In each case, the Ru-
C4 distances are elongated, in comparison to the other arene
C
Scheme 1
(9) Coleman, A. W.; Jones, D. F.; Dixneuf, P. H.; Brisson, C.; Bonnet,
J.-J.; Lavigne, G. Inorg. Chem. 1984, 23, 952-956.
(10) Chaplin, A. B.; Scopelliti, R.; Dyson, P. J. Eur. J. Inorg. Chem.
2005, 4762-4774.
(11) For [2c]PF6, the coordinated phosphorus resonances are non-first-
order and are instead observed as a multiplet between 22.0 and 23.7 ppm;
see Figure S1.
(12) Lalremputa, R.; Carroll, P. J.; Kollipara, M. R. J. Coord. Chem.
2003, 56, 1499-1504.

588 Organometallics, Vol. 26, No. 3, 2007
Chaplin et al.
Figure 3. Effect of MeOH concentration on the chelation of
complexes 4a and 4b in 1,2-dichlorethane at 298 K (data for the
chelation of 4b at [MeOH] ) 0 is extrapolated from higher
temperature data).
investigate the stability of complexes [2a-e]+, to supplement
the discussion of the chelation kinetics (see below), selective
fragmentation of the parent peak was carried out (ESI-MS2),
Figure 2. Loss of PPh3 is found to be the primary fragmentation
path for these complexes and occurs to approximately the same
extent for each complex with the exception of [2e]+, where it
occurs much more readily, suggesting that it is more weakly
coordinated in this complex. Additionally, loss of the arene
occurs for [2a]+ and [2b]+, notably more for the dppm complex,
but to a significantly lower extent than PPh3 loss. Some
diphosphine loss can be detected for [2b]+, but it is a
comparably minor fragmentation pathway.
Figure 2. ESI-MS2 of complexes [2a-e]PF6 (CH2Cl2, 50 °C, 19%
normalized collision energy).
Scheme 2. Chelation of Complexes 4a and 4b
2. Chelation Kinetics. The neutral pendent phosphine
complexes [RuCl2(η1-(P-P))(η6-p-cymene)] (P-P ) dppm, 4a;
dppv, 4b) readily form ionic chelate complexes via ring closure
of the pendent phosphine moiety in 1,2-dichloroethane (or
CH2Cl2)-MeOH solutions; see Scheme 2. In the absence of
MeOH, this process is almost suppressed for complex 4a (4a:
[5a]+ ≈ 1:0.05 after 7 days in CH2ClCH2Cl at 293 K), while
greatly reduced for 4b. To quantify these observations, a kinetic
study of the influence of the MeOH concentration on the rate
of chelation was carried out in 1,2-dichloroethane by following
the changes in the 31P NMR spectra over time. The results from
these experiments, depicted in Figure 3, confirm the large
influence of methanol on the ring-closure process (related data
are also listed in Table 3). Arena and co-workers observed a
similar trend for the chelation reactions of complexes of formula
[RuCl2(η6-arene)(P-N*)] (P-N* ) P-bound enantiomerically
pure (â-aminoalkyl)phosphine) in chloroform, with the observed
rate and MeOH concentration linearly correlated.14 This cor-
relation was ascribed to a bimolecular solvolysis involving initial
substitution of one Cl- ligand by a MeOH molecule followed
by ring closure. Accordingly, decreases in the reaction rate were
observed on the addition of excess chloride. In contrast, the
addition of excess [NMe4]Cl (20 equiv) does not inhibit the
observed rate of chelation for 4a and 4b and there is no
significant linear correlation between the observed rate and the
MeOH concentration. Furthermore, no decreases are found if
the reactions are carried out with a large excess of CH3CN, a
more strongly coordinating solvent. Together, these results
suggest that the ring-closing process for complexes 4a and 4b
does not occur via dissociative substitution. The significant role
atoms, consistent with the solution 13C NMR data.13 The Ru-
C1 distance is also elongated in the dppv complex, [2b]PF6,
suggesting more constrained bonding, and this hypothesis is
supported by reduced intramolecular contacts between the two
phosphines [P3‚‚‚C11 ) 4.038(7) Å in [2a]PF6; 3.865(3) Å in
[2b]PF6; 4.021(7) Å in [2d]PF6].
The ESI-MS of 1 and [2a-e]PF6 display the desired parent
ions, together with peaks of lower relative intensity resulting
from loss of either CH3CN or phosphine ligand, respectively.
Of these, the peak resulting from loss of CH3CN is the most
significant, with a relative intensity of 55%, consistent with the
labile nature of this ligand, whereas those resulting from loss
of PPh3 have relative intensities of ca. 20%. In the spectra of
[2b]+ and [2e]+, loss of the diphosphine is also observed, with
relative intensities of 15% and 11%, respectively. To further
(13) Considerable shifts to higher frequency are observed for the C4
resonance (see Scheme 1 for labeling) on substitution of the CH3CN,
indicative of weaker coordination of C4 to the metal center due to increased
steric bulk in the coordination sphere. The increase in steric bulk is also
apparent from changes in the p-cymene H7 and H8 resonances and the H9
and H10 resonances, which become distinctly diastereotopic for [2a-e]PF6,
particularly for [2b]PF6 and [2e]PF6. In the case of [2e]PF6, the observation
of a NOE interaction between H6 and H12 (Experimental Section, Figure
6), indicating that the dppf ligand adopts a conformation with the ferrocene
moiety approaching the plane of the coordinated arene, may help explain
the origin of these shifts.
(14) Arena, C. G.; Calamia, S.; Farone, F.; Graiff, C.; Tiripicchio, A. J.
Chem. Soc., Dalton Trans. 2000, 3149-3157.

η2-Diphosphine (η6-p-cymene)ruthenium(II) Compounds
Organometallics, Vol. 26, No. 3, 2007 589
Table 3. Rate of Chelation for 4a and 4b in Different Solvent Mixtures at 298 K
ligand
dppm
solvent (v/v)
104kobs/s-1 (298 K)a
t
1/2 (298 K)b
4a f [5a]Cl
4b f [5b]Cl
2:1 MeOH-CH2ClCH2Cl
0.25
0.14
0.097
0.11
0.026
0.15
0.99
0.64
0.41
0.002d
0.43
0.11
0.82
47 min
80 min
120 min
100 min
440 min
77 min
12 min
18 min
28 min
4 daysd
27 min
100 min
14 min
1:1 MeOH-CH2ClCH2Cl
1:2 MeOH-CH2ClCH2Cl
1:1:1 MeOH-CH2ClCH2Cl-CH3CN
1:1:1 MeOH-CH2ClCH2Cl-DMSO
1:1 MeOH-CH2ClCH2Cl + [NMe4]Clc
2:1 MeOH-CH2ClCH2Cl
dppv
1:1 MeOH-CH2ClCH2Cl
1:2 MeOH-CH2ClCH2Cl
CH2ClCH2Cl
1:1:1 MeOH-CH2ClCH2Cl-CH3CN
1:1:1 MeOH-CH2ClCH2Cl-DMSO
1:1 MeOH-CH2ClCH2Cl + [NMe4]Clc
b
c
d
a Errors were typically (5%. t1/2 (ln(2)/kobs) values included for ease of comparison. 20 equiv per complex. Extrapolated from higher temperature data.
Table 4. Activation Parameters for the Chelation of Complexes 4a and 4b
ligand
solvent
∆Hq/kJ mol-1
∆Sq/J mol-1K-1
∆Vq/cm3 mol-1 (298 K)
4a f [5a]Cl
4b f [5b]Cl
4b f [5b]Cl
dppm
dppv
dppv
1:1 MeOH-CH2ClCH2Cl
1:1 MeOH-CH2ClCH2Cl
CH2ClCH2Cl
92.7 ( 1.0
79 ( 2
97 ( 2
-7 ( 3
-41 ( 5
-29 ( 7
+2.7 ( 0.3
-4.0 ( 0.5
of the MeOH in this process may be attributed to the formation
of hydrogen bonds with the chloride ligands, which serve to
stabilize the loss of chloride, consistent with the observation
that the addition of DMSO, a good H-bond acceptor,15 signifi-
cantly decreases the rate of chelation for both complexes 4a
and 4b. In all cases the chelation proceeded smoothly and no
side products or intermediates were observed by 31P NMR
spectroscopy.
The chelation of 4b can also be effected in 1,2-dichloroethane
at elevated temperatures, although accompanied by the formation
of significant amounts of trans-[RuCl2(η2-dppv)2], identified by
a resonance at 53.6 ppm in 31P NMR spectra.16 Another minor
product is also observed with a resonance at 84.4 ppm and
possibly corresponds to a higher nuclearity, chloride-bridged,
species owing to the similarity of the chemical shift with related
1,2-bis(diphenylphosphino)benzene complexes, prepared from
η2-diphosphine ruthenium-arene complexes.17 Under compa-
rable conditions, an authentic sample of [5b]Cl showed no
significant decomposition, indicating that these two side products
are likely to originate from arene loss, rather than chloride loss,
during the ring-closing reaction. This alternative reaction
pathway seems to be dominant in 1,2-dichloroethane for 4a, as
heating does not result in the formation of [5a]+, but primarily
in trans-[RuCl2(η2-dppm)2]18 and [RuCl2(η6-p-cymene)]2(µ-
dppm).19 Such a difference is consistent with the observed
fragmentation patterns of [2a]+ and [2b]+ (Figure 2), with the
dppm complex showing a larger tendency for arene loss.
Activation enthalpies and entropies for the chelation reactions
of 4a and 4b in 1:1 MeOH-1,2-dichloroethane (by following
the consumption of 4a or 4b) and 4b in 1,2-dichloroethane (by
following the formation of [5b]+) have been determined by 31
P
NMR spectroscopy, and additionally, the volumes of activation
for the former have been determined using variable-pressure
UV-visible spectroscopy; the results of these studies are
compiled in Table 4, with the pressure dependence depicted in
Figure 4. Together these activation parameter values are
consistent with a concerted substitution of chloride during the
ring-closure process. Complex 4a seems to react with a more
dissociative character owing to the more positive ∆Sq value and
positive ∆Vq value, whereas 4b reacts with a higher degree of
associative character.20 This difference in reactivity is also
implied by the large difference in the chelate bite angles in these
complexes [[5a]BF4, 71.29(6)°;4 [5b]PF6, 83.46(3)°, 83.39(3)°],
with the larger bite angle of the dppv ligand more closely
resembling that of the nonchelating bite angle of 97.7° in 3.12
The activation parameters determined for 4b are comparable
(15) Abraham, M. H. Chem. Soc. ReV. 1993, 73-83.
(16) Batista, A. A.; Cordeiro, L. A. C.; Olvia, G.; Nascimento, O. R.
Inorg. Chim. Acta 1997, 258, 131-137.
(17) (a) Mashima, K.; Komura. N.; Yamagata, T.; Tani, K.; Haga, M.-
A. Inorg. Chem. 1997, 36, 2908-2912. (b) Mashima, K.; Nakamura, T.;
Matsuo, Y.; Tani, K. J. Organomet. Chem. 2000, 607, 51-56.
(18) Jung, C. W.; Garrou, P. E.; Hoffman, P. R.; Caulton, K. G. Inorg.
Chem. 1984, 23, 726-729.
(19) Estevan, F.; Lahuerta, P.; Latorre, J.; Sanchez, A.; Sieiro, C.
Polyhedron 1987, 6, 473-478.
(20) The overall volume of activation is comprised of both intrinsic and
solvational contributions (∆Vqobs ) ∆Vqintr + ∆Vqsolv). Because the chelation
of 4a and 4b involves the creation of charged species ([5a]+Cl-, [5b]+Cl-,
respectively), the overall volume of activation value will include a negative
contribution from changes in the solvation during this process (electro-
striction), making the precise interpretation of the overall volume of
activation less straightforward [van Eldik, R.; Hubbard, C. D. High Pressure
Chemistry; van Eldik, R., Kla¨rner, F.-G., Eds.; Wiley-VCH: Weinhein,
2002]. However, owing to the similarity of these two complexes, contribu-
tions from electrostriction are likely to be similar. In addition to the volumes
of activation, similar arguments apply to the interpretation of the activation
entropies for the chelation of 4a and 4b. The electrostriction is likely to be
negilable in the chelation of [2a-e]PF6, as there is no change in charge,
and furthermore 1,2-dichloroethane is an apolar solvent (electrostriction
during the chelation of 4b in 1,2-dichloroethane could also be expected to
be small).
Figure 4. Pressure dependence for the chelation of complexes 4a
(R2 ) 0.971) and 4b (R2 ) 0.933) in 1:1 MeOH-CH2ClCH2Cl at
298 K determined by high-pressure UV-visible spectroscopy.

590 Organometallics, Vol. 26, No. 3, 2007
Table 5. Activation Parameters for the Chelation of Complexes [2a-e]PF6 in 1,2-Dichloroethane
Chaplin et al.
104kobs/s-1
t1/2 (353 K),b
ligand
∆Hq/kJ mol-1
∆Sq/J mol-1 K-1
(353 K)a
min
c
[2a]PF6 f [5a]PF6
dppm
dppv
dppe
dppp
dppf
118 ( 3
119 ( 3
136 ( 5
132 ( 2
126 ( 4
23 ( 8
3.8
3.8
4.1
5.2
160
30
30
28
22
1
d
[2b]PF6 f [5b]PF6
[2c]PF6 f [5c]PF6
25 ( 10
74 ( 15
66 ( 5
[2d]PF6 f [5d]PF6
e
[2e]PF6 f [5e]PF6
77 ( 12
b
c
a Calculated from fit to Eyring equation. t1/2 (ln(2)/kobs) values included for ease of comparison. Side products: [RuCl2(PPh3)(dppm)2], [RuCl(PPh3)2(η6-
p-cymene)]+. Side products: [RuCl2(dppv)2], [RuCl(PPh3)2(η6-p-cymene)]+. Side product: [RuCl(PPh3)2(η6-p-cymene)]+.
d
e
Scheme 3. Preparation of 5b
Scheme 4. Chelation of Complexes [2a-e]PF6
to those reported for the chelation of [RuCl2(η6-p-cymene)(S-
phephos)]7 in CHCl3-MeOH (∆Hq ) 75.66 kJ mol-1, ∆Sq )
-48.07 J mol-1 K-1).14
(6:[5a]+ ≈ 1:41; 6:[5b]+ ≈ 1:4; 6:[5e]+ ≈ 1:13 at 333 K near
reaction completion).13 Additionally, arene loss is observed
during the reactions of [2a]PF6 and [2b]PF6, as indicated by a
distinctive ABX pattern, which may be assigned to [RuCl2-
(PPh3)(η2-dppm)] (7),21 and signals corresponding presence of
cis- and trans-[RuCl2(η2-dppv)2] (8)16 in the 31P NMR spectra,
respectively. This pathway is significantly more favored for the
dppm complex than that of the dppv complex (7:[5a]+ ≈ 1:3;
8:[5b]+ ≈ 1:5 at 333 K near reaction completion), matching
the previous trend observed for the corresponding reactions of
4a and 4b in 1,2-dichloroethane and the ESI-MS data, shown
in Figure 2. Complexes [2c]PF6 and [2d]PF6 react smoothly to
form the corresponding chelate complexes, [5c]PF6 and [5d]PF6,
with high selectivity.
Activation parameters for the chelation of [2a-e]PF6 in 1,2-
dichloroethane have been determined by following the formation
of complexes [5a-e]+ by 31P NMR spectroscopy and are
summarized in Table 5. A precise comparison to those of the
chelation reactions of 4a and 4b is not possible owing to
electrostriction of the solvent during these reactions, originating
from the creation of charged species in solution,20 although the
large positive ∆Sq values characteristic of the chelation reactions
of [2a-e]PF6 are clearly indicative of a large degree of
dissociation during this process in comparison to the concerted
process proposed for the neutral compounds.22 The magnitude
of the activation enthalpies is also consistent with a rate-limiting
step involving dissociation of PPh3.23 The ∆Sq values for the
reactions of complexes [2a]PF6 and [2b]PF6 are lower in
magnitude than the other cationic complexes, perhaps indicating
a more concerted chelation process. The formation of the chelate
complex of dppf, [5e]PF6, is much more rapid than the other
cationic phosphine complexes studied in this investigation,
showing an appreciable rate at room temperature (t1/2 ) 1.6
days at 298 K, extrapolated). The origin of this marked
difference may stem from the bulky nature of the dppf ligand,
weakening the Ru-PPh3 bond. ESI-MS2 of [2e]+ is consistent
Following the investigation of the chelation process, a one-
pot, high-yielding synthesis of [5b]Cl was developed and is
shown in Scheme 3. Via this method, the pendent phosphine
complex 4b is prepared from the reaction between [RuCl2(η6-
p-cymene)]2 and dppv in CH2Cl2 and the ring closure effected
by the addition of MeOH, giving [5b]Cl in 99% yield. The
corresponding PF6 salt is readily obtained by metathesis in
MeOH using [NH4]PF6, and its solid-state structure determined
by X-ray diffraction is depicted in Figure 5.
Complexes [2a-e]PF6 also undergo ring-closing reactions
on heating in 1,2-dichloroethane, with the loss of PPh3, leading
to the formation of chelating compounds [5a-e]PF6; see
Scheme 4. In each case, this process is the primary reaction
pathway for the complexes and concurs with the ESI-MS data,
which indicated that PPh3 is the most labile ligand in these
complexes. Formation of [RuCl(PPh3)2(η6-p-cymene)]+, 6,12 is
observed during the reactions of [2a]PF6, [2e]PF6, and, most
significantly, [2b]PF6, most probably owing to a large degree
of steric pressure in the coordination sphere of these complexes
(21) 31P{1H} NMR (CH2ClCH2Cl, internal D2O reference): δ 38.8 (t,
2JPP ) 34, 1P, PPh3), 5.6 (dd, 2JPP ) 69, 2JPP ) 34, 1P, PPh2), 4.7 (dd, 2JPP
Figure 5. ORTEP representation of [5b]PF6, one of the two
molecular units in the asymmetric cell. Thermal ellipsoids are drawn
at the 50% probability level. Counterion and solvent molecule are
omitted for clarity. Key bond lengths (Å) and angles (deg),
equivalent parameters from the other unit in brackets: Ru1-Cl1,
2.3978(7) {2.3936(7)}; Ru1-P1, 2.3172(8) {2.3205(8)}; Ru1-P2,
2.3240(7) {2.3133(8)}; Ru1-C1, 2.284(3) {2.276(2)}; Ru1-C4,
2.312(3) {2.308(2)}; Ru1-Cav, 2.27(3) {2.27(3)}; Cl1-Ru1-P1,
84.68(3) {84.70(3)}; Cl1-Ru1-P2, 82.92(3) {82.99(3)}; P1-
Ru1-P2, 83.46(3) {83.39(3)}.
2
) 69, JPP ) 34, 1P, P′Ph2). The analogous compounds [RuCl2(PPh3)(η2-
(P-P))] (P-P ) dppp, dppb) have been reported and exhibit similar 31P
NMR spectra, although with larger J(P-P)(P-P) coupling constants [ref 18].
(22) Since electrostriction effects are likely to be minimal in 1,2-
dichloroethane, a comparison between the chelation reactions of the charged,
[2b]PF6, and neutral, 4b, pendant complexes is likely to be reliable. Hence,
the large difference in magnitude and different sign of the ∆Sq values for
these complexes supports the mechanistic hypotheses.
(23) Dias, P. B.; Minas de Piedade, M. E.; Simo˜es, J. A. M. Coord.
Chem. ReV. 1994, 135-136, 737-807.

η2-Diphosphine (η6-p-cymene)ruthenium(II) Compounds
Organometallics, Vol. 26, No. 3, 2007 591
Scheme 5. Schematic Representation of Proposed
Transition States for the Chelation Reactions
1 (labels for the carbon atoms of ligands increase from the
coordinated atom, excluding the Ph groups) and Figure 6.
Preparation of [RuCl(CH3CN)(PPh3)(η6-p-cymene)]PF6. A
suspension of [RuCl2(PPh3)(η6-p-cymene)] (1.30 g, 2.29 mmol) and
[NH4]PF6 (0.49 g, 2.98 mmol) in CH3CN (70 mL) was heated at
reflux for 10 min. The solvent was then removed and the residue
extracted with CH2Cl2 through Celite. The product was precipitated
as an oil by the addition of pentane, the supernatant removed by
decantation, and then sonicated twice in pentane and then diethyl
ether. Yield: 1.43 g (87%) as a yellow powder. 1H NMR
with this hypothesis, showing the facile loss of PPh3 in
comparison to [2a-d]+. Both ∆Hq and ∆Sq values for the
chelation reactions of the dppm, dppe, and dppp complexes are
significantly larger than those of the corresponding complexes
involving substitution of CO: [Ru(CO)4(η1-(P-P))] (P-P [∆Hq/
kJ mol-1, ∆Sq/J mol-1 K-1] ) dppm [105 ( 3, 13 ( 5], dppe
[107.5 ( 1.3, 13 ( 6], dppp [109.2 ( 1.3, 21 ( 4]).6
3
(CDCl3): δ 7.45-7.70 (m, 15H, PPh3), 6.13 (d, JHH ) 5.6, 1H,
3
3
H5), 5.94 (d, JHH ) 5.6, 1H, H3), 5.41 (d, JHH ) 5.6, 1H, H2),
4.66 (d, 3JHH ) 5.5, 1H, H6), 3.05 (sept, 3JHH ) 6.7, 1H, H8), 1.95
(s, 3H, H12), 1.75 (s, 3H, H7), 1.38 (d, 3JHH ) 7, 3H, H9), 1.36 (d,
3JHH ) 7, 3H, H10). 13C{1H} NMR (CDCl3): δ 134.5 (d, JPC
)
2
4
1
10, PPh3), 131.4 (d, JPC ) 3, PPh3), 130.0 (d, JPC ) 49, PPh3),
128.6 (d, 3JPC ) 11, PPh3), 127.4 (s, C11), 116.6 (d, 2JPC ) 8, C4),
103.6 (s, C1), 95.6 (d, JPC ) 6, C3), 89.7 (s, C6), 89.2 (br, C5),
2
Conclusions
85.0 (br, C2), 31.2 (s, C8), 23.6 (s, C10), 21.2 (s, C9), 18.3 (s, C7),
The chelation kinetics of a series of ruthenium(II)-η6-p-
cymene phosphine complexes have been studied. Neutral
complexes of general formula [RuCl2(η1-(P-P))(η6-p-cymene)]
(P-P ) dppm, 4a; dppv, 4b) readily form chelate complexes,
[RuCl(η2-(P-P))(η6-p-cymene)]Cl, in the presence of MeOH,
which assists the ring-closing process by formation of hydrogen
bonds with the chloride ligands, thereby facilitating their
activation. In the absence of such interactions the process is
much slower, requiring elevated temperatures, and arene loss
becomes increasingly dominant. On the basis of entropies,
enthalpies, and volumes of activation, a concerted chloride
substitution mechanism is proposed, as illustrated in Scheme
5. Related cationic complexes of formula [RuCl(PPh3)(η1-(P-
P))(η6-p-cymene)]PF6, 2 (P-P ) dppm, a; dppv, b; dppe, c;
dppp, d; dppf, e) also form chelate complexes, [RuCl(η2-(P-
P))(η6-p-cymene)]PF6, via a dissociative mechanism involving
loss of PPh3. However, elevated temperatures are generally
required and a number of alternative reaction pathways can be
observed for complexes [2a]PF6, [2b]PF6, and [2e]PF6, albeit
of secondary importance. Notably, ESI-MS of complexes [2a-
e]PF6 has provided not only useful structural information but
also a number of insights in the reactivity, supplementing the
kinetic investigations well.
3.2 (s, C12). 31P{1H} NMR (CDCl3): δ 35.5 (s, 1P, RuPPh3),
1
-144.1 (sept, JPF ) 713, 1P, PF6). ESI-MS (CH2Cl2) positive
ion: m/z, 533 (55%) [M - CH3CN]+, 574 [M]+; negative ion: m/z,
145 [PF6]-. Anal. Calcd for C30H32ClF6NP2Ru (719.05 g mol-1):
C, 50.11; H, 4.49; N, 1.95. Found: C, 50.32; H, 4.55; N, 1.95.
Preparation of [RuCl(PPh3)(η1-P-P)(η6-p-cymene)]PF6: Gen-
eral Procedure. A solution of [RuCl(CH3CN)(PPh3)(η6-p-cymene)]-
PF6 (0.50 g, 0.70 mmol) and diphosphine (3 equiv, 2.1 mmol) in
CH2Cl2 (20 mL) was stirred at RT for 1-2 h. The product was
then precipitated by the addition of excess diethyl ether (100 mL),
washed with ether (3 × 50 mL), and dried in vacuo. Further
purification, if necessary, was achieved by recrystallization from
CH2Cl2-pentane.
[RuCl(PPh3)(η1-dppm)(η6-p-cymene)]PF6. Yield: 0.67 g (90%)
as a microcrystalline yellow-orange solid. Orange crystals suitable
for X-ray diffraction were obtained by recrystallization from
1
CH2Cl2-pentane. H NMR (CDCl3): δ 6.9-7.9 (m, 35H, PPh),
3
3
3
5.93 (dd, JHH ) 6.2, JPH ) 4, 1H, H6), 5.66 (d, JHH ) 6.1, 1H,
H3), 5.25 (dd, JHH ) 6.4, JPH ) 4, 1H, H2), 4.95 (d, JHH ) 6.0,
3
3
3
1H, H5), 3.68 (ddd, JHH ) 16.1, JPH ) 6.5, JPH ) 2, 1H, H11),
2
2
2
2.78 (sept, 3JHH ) 6.9, 1H, H8), 1.31 (d, 3JHH ) 6.9, 3H, H9), 1.25
(d, JHH ) 6.9, 3H, H10), 0.95 (obscured, 1H, H11′), 0.93 (s, 3H,
3
H7). 13C{1H} NMR (CDCl3): δ 127.5-134.5 (m, PPh), 132 (C4),
99.3 (d, 2JPC ) 3, C2), 98.7 (s, C1), 95.6 (d, 2JPC ) 3, C6), 90.1 (d,
2JPC ) 10, C5), 87.2 (d, 2JPC ) 10, C3), 31.7 (s, C8), 21.5 (s, C9/10),
Experimental Section
21.3 (s, C10/9), 18.9 (dd, JPC ) 33,1JPC ) 26, C11), 15.1 (s, C7).
1
31P{1H} NMR (CDCl3): δ 23.0 (d, 2JPP ) 52, 1P, Ru-PPh3), 22.0
All organometallic manipulations were carried out under a
nitrogen atmosphere using standard Schlenk techniques. CH2Cl2
was dried catalytically under dinitrogen using a solvent purification
system, manufactured by Innovative Technology Inc. 1,2-Dichloro-
ethane was distilled from P2O5 under dinitrogen. All other solvents
were p.a. quality. [RuCl2(η6-p-cymene)]2,24 [RuCl2(PPh3)(η6-p-
cymene)],25 [RuCl2(η1-dppm)(η6-p-cymene)],4d and [RuCl2(η1-
dppv)(η6-p-cymene)]10 were prepared as described elsewhere. All
other chemicals are commercial products and were used as received.
NMR spectra were recorded with a Bruker Avance 400 spectrometer
at room temperature, unless otherwise stated. Chemical shifts are
given in ppm and coupling constants (J) in Hz. Simulation analysis
of the 31P NMR spectra of [2c]PF6 was carried out using g-NMR.26
ESI-MS were recorded on a Thermo Finnigan LCQ DECA XPPlus,
using a literature protocol,27 and microanalyses performed at the
EPFL. Labeling schemes for the NMR data are indicated in Scheme
2
2
2
(dd, JPP ) 52, JPP ) 44, 1P, Ru-PPh2), -28.8 (d, JPP ) 43.7,
1
1P, pend-PPh2), -144.4 (sept, JPF ) 713, 1P, PF6). ESI-MS
(CH2Cl2) positive ion: m/z, 655 (18%) [M - PPh3]+, 917 [M]+;
negative ion: m/z, 145 [PF6]-. Anal. Calcd for C53H51ClF6P4Ru
(1062.40 g mol-1)‚3/4CH2Cl2: C, 57.33; H, 4.70. Found: C, 57.13;
H, 4.53.
[RuCl(PPh3)(η1-dppv)(η6-p-cymene)]PF6. Yield: 0.53 g (71%)
as a yellow powder. Orange crystals suitable for X-ray diffraction
were obtained by slow diffusion of diethyl ether into a CH2Cl2
solution of the compound at RT. 1H NMR (CDCl3): δ 7.91-8.03
(m, 2H, RuPPh2), 7.00-7.71 (m, 29H, PPh), 6.93-7.00 (m, 2H,
pend-PPh2), 6.84 (ddd, 2JPH ) 38, 3JHH ) 13.7, 3JPH ) 4, 1H, H11),
6.53 (ddd, 2JPH ) 30, 2JPH ) 29, 3JHH ) 13.6, 1H, H12), 6.45-6.51
(m, 2H, pend-PPh2), 6.11 (dd, 3JHH ) 6.1, 3JPH ) 5, 1H, H6), 5.76
3
3
3
(d, JHH ) 6.2, 1H, H3), 5.21 (dd, JHH ) 6.4, JPH ) 5, 1H, H2),
4.66 (d, 3JHH ) 6.1, 1H, H5), 2.58 (sept, 3JHH ) 6.9, 1H, H8), 1.30
(d, 3JHH ) 7.0, 3H, H9), 1.11 (d, 3JHH ) 6.9, 3H, H10), 0.99 (s, 3H,
(24) Bennett, M. A.; Huang, T. N.; Matheson, T. W.; Smith, A. K. Inorg.
Synth. 1982, 21, 74-78.
H7). 13C{1H} NMR (CDCl3): δ 149.2 (dd, JPC ) 21, JPC ) 8,
1
2
(25) Bennett, M. A.; Smith, A. K. J. Chem. Soc., Dalton Trans. 1974,
233-241.
C11), 135.0 (dd, JPC ) 45, JPC ) 21, C12), 127-139 (m, PPh),
1
2
130 (C4), 100.6 (s, C1), 98.8 (d, JPC ) 5, C2), 94.0 (d, JPC ) 2,
2
2
(26) Budzelaar, P. H. M. g-NMR v4.0; IvorySoft, 1997.
(27) Dyson, P. J.; McIndoe, J. S. Inorg. Chim. Acta 2003, 354, 69-74.
C6), 91.2 (d, JPC ) 9, C5), 88.7 (d, JPC ) 10), 31.4 (s, C8), 21.9
2
2

592 Organometallics, Vol. 26, No. 3, 2007
Chaplin et al.
(s, C9), 21.2 (s, C10), 15.5 (s, C7). 31P{1H} NMR (CDCl3): δ 25.8
2
2
3
(d, JPP ) 55, 1P, Ru-PPh3), 7.4 (dd, JPP ) 54, JPP ) 15, 1P,
Ru-PPh2), -33.2 (d, 3JPP ) 15, 1P, pend-PPh2), -144.2 (sept, 1JPF
) 713, 1P, PF6). ESI-MS (CH2Cl2) positive ion: m/z, 533 (15%)
[M - dppv]+, 667 (21%) [M - PPh3]+, 929 [M]+; negative ion:
m/z, 145 [PF6]-. Anal. Calcd for C54H51ClF6P4Ru (1074.41 g
mol-1)‚1/2CH2Cl2: C, 58.61; H, 4.69. Found: C, 58.54; H, 4.65.
[RuCl(PPh3)(η1-dppe)(η6-p-cymene)]PF6. Yield: 0.53 g (71%)
as a yellow powder. 1H NMR (CDCl3): δ 7.1-7.89 (m, 31H, PPh),
6.89-7.1 (m, 4H, pend-PPh2), 6.07 (dd, 3JHH ) 6.2, 3JPH ) 4, 1H,
H6), 5.69 (d, JHH ) 6.2, 1H, H3), 5.23 (dd, JHH ) 6.2, JPH ) 5,
1H, H2), 4.83 (d, 3JHH ) 6.1, 1H, H5), 2.76 (sept, 3JHH ) 7.0, 1H,
H8), 2.60-2.7 (m, 1H, H12/11), 1.38-1.52 (m, 1H, H11/12), 1.30 (d,
3JHH ) 7.0, 3H, H9), 1.23 (d, 3JHH ) 6.9, 3H, H10), 0.96-1.09 (m,
1H, H11′/12′), 0.84 (s, 3H, H7), 0.70-0.9 (m, 1H, H12′/11′). 13C{1H}
NMR (CDCl3): δ 128-138 (m, PPh), 132 (C4), 99.2 (br, C2), 98.8
(s, C1), 95.5 (br, C6), 89.9 (d, 2JPC ) 9, C5), 87.0 (d, 2JPC ) 9, C3),
31.6 (s, C8), 22 (C11/12), 21.8 (s, C9), 21.0 (s, C10), 17 (C12/11), 14.9
(s, C7). 31P{1H} NMR (CDCl3): δ 22.0-23.7 (m, 2P, RuPPh),
-13.0 (dd, 3JPP ) 27, 5JPP ) 6, 1P, pend-PPh2), -144.3 (sept, 1JPF
) 713, 1P, PF6). ESI-MS (CH2Cl2) positive ion: m/z, 669 (24%)
[M - PPh3]+, 931 [M]+; negative ion: m/z, 145 [PF6]-. Anal. Calcd
for C54H53ClF6P4Ru (1076.42 g mol-1): C, 60.25; H, 4.96. Found:
C, 60.65; H, 5.09.
3
3
3
Figure 6. NMR labeling scheme for [2e]PF6 and the observed
NOE interaction.
stirred for an additional 150 min, during which time the solution
became yellow. The solution was concentrated to ca. 5 mL and
diethyl ether (50 mL) added. The product was then filtered, washed
with diethyl ether (3 × 20 mL) and pentane (2 × 10 mL), and
dried in vacuo. Yield: 0.45 g (99%). The hexafluorophosphate
analogue was prepared by metathesis using [NH4]PF6 (1.2 equiv)
in methanol, with a yield of 91%. NMR data are in agreement with
the literature.28 Yellow crystals of [RuCl-(η2-dppv)(η6-p-cymene)]-
PF6 suitable for X-ray diffraction were obtained by slow diffusion
of diethyl ether into a CH2Cl2 solution of the compound at RT.
Kinetics. Chelation kinetics were monitored using 31P NMR
spectroscopy, integrating relative to an internal standard in sealed
capillary tubes; PPh3 in toluene for 4a f [5a]Cl and 4b f [5b]Cl
and PO(OEt)3 in toluene for [2a-e]PF6 f [5a-e]PF6. Peaks from
the resulting chelate complexes were in agreement with the literature
data.28 Integrations were preformed using NMRICMA, an iterative
fitting application for MatLab.29 Samples of [2a-e]PF6 were
prepared under dinitrogen in screw cap NMR tubes. Concentrations
were typically ∼20 mM. The reaction temperature was determined
before and after each measurement using an external temperature
probe and generally showed good agreement ((0.2 K). Additional
data are listed in Tables S1 and S3.
Variable-pressure UV-visible spectrophotometric measurements
for the chelation of 4a f [5a]Cl and 4b f [5b]Cl were performed
on a Perkin-Elmer Lambda 5 spectrophotometer. A “Le Noble”
piston-type cell with an optical path length of about 2 cm was used
and immersed in the pressure-transmitting fluid (1:1 MeOH-
CH2ClCH2Cl mixture) inside a pressurizable and thermostatable
pressure vessel.30 The temperature was controlled by circulation
of water from a thermostat bath and measured using a Pt-resistance
thermometer. Concentrations were 0.5 mM. The temperature was
fixed at 298 K and the pressure varied between 1 and 1500 bar,
with the rate monitored by the decrease in absorbance at 375 nm.
Full data are listed in Table S2.
[RuCl(PPh3)(η1-dppp)(η6-p-cymene)]PF6. Yield: 0.25 g (76%)
as a yellow powder. Orange crystals suitable for X-ray diffraction
were obtained by recrystallization from CH2Cl2-pentane at 4 °C.
3
1H NMR (CDCl3): δ 6.9-7.8 (m, 35H, PPh), 6.03 (dd, JHH
)
6.1, 3JPH ) 5, 1H, H6), 5.67 (d, 3JHH ) 6.1, 1H, H3), 5.25 (dd, 3JHH
) 6.0, 3JPH ) 5, 1H, H2), 4.89 (d, 3JHH ) 6.0, 1H, H5), 2.76 (sept,
3JHH ) 6.8, 1H, H8), 2.55-2.69 (m, 1H, H11), 1.5-1.66 (m, 1H,
H13), 1.39-1.51 (m, 1H, H11′), 1.30 (d, JHH ) 6.9, 3H, H9), 1.25
3
(d, 3JHH ) 6.8, 3H, H10), 0.8-0.98 (m, 1H, H12), 0.85 (s, 3H, H7),
0.59-0.73 (m, 1H, H13′), 0.36-0.56 (m, 1H, H12′). 13C{1H} NMR
(CDCl3): δ 128-135 (m, PPh), 132 (C4), 99 (C1), 99 (C2), 95.3
(d, 2JPC ) 3, C6), 89.6 (d, JPC ) 10, C5), 87.3 (d, JPC ) 10, C3),
2
2
31.6 (s, C8), 29.1 (dd,1JPC ≈ JPC ) 12, C13), 21.8 (dd,1JPC ) 26,
3
3JPC ) 12, C11), 21.8 (s, C9), 21.0 (s, C10), 19.7 (dd, JPC ) 19,
2
2JPC ) 9, C12, 14.9 (s, C7). 31P{1H} NMR (CDCl3): δ 23.2 (d, 2JPP
2
) 52, 1P, Ru-PPh3), 18.4 (d, JPP ) 52, 1P, Ru-PPh2), -18.1 (s,
1P, pend-PPh2), -144.3 (sept,1JPF ) 713, 1P, PF6). ESI-MS
(CH2Cl2) positive ion: m/z, 683 (21%) [M - PPh3]+, 945 [M]+;
negative ion: m/z, 145 [PF6]-. Anal. Calcd for C55H55ClF6P4Ru
(1090.45 g mol-1): C, 60.58; H, 5.08. Found: C, 60.58; H, 5.07.
[RuCl(PPh3)(η1-dppf)(η6-p-cymene)]PF6. Yield: 0.30 g (35%)
as an orange powder following recrystallization from CH2Cl2-
pentane at -20 °C. 1H NMR (CDCl3): δ 6.9-7.8 (m, 35H, PPh),
5.61-5.70 (m, 2H, H2 + H3), 5.47 (dd, 3JHH ) 6.1, 3JPH ) 5, 1H,
H6), 4.98 (br, 1H, H15), 4.48 (br, 1H, H14), 4.26 (br, 1H, H13), 4.19
(d, 1H, H5), 3.94 (br, 1H, H17/20), 3.92 (br, 1H, H18/19), 3.88 (br,
1H, H12), 3.83 (br, 1H, H19/18), 3.74 (br, 1H, H20/17), 2.67 (sept,
Kinetic measurements were made by following the reaction over,
typically, three or more half-lives, and all data gave good fits to
single-exponential first-order behavior (e.g., Figures S4 and S6).
Errors quoted for the rate constants are the standard errors calculated
from the exponential fitting. The rates of the reaction for 4a f
[5a]Cl and 4b f [5b]Cl in 1:1 MeOH-CH2ClCH2Cl were within
the experimental error for three different concentrations of 4b and
two of 4a, as were duplicate measurements of each. The temperature
dependence of the chelation reactions, when determined, all showed
excellent Eyring behavior; see Figures S5 and S7-S11, and the
quoted errors originate from the standard errors from linear fits of
ln(kobs/t) vs 1/T (i.e. σ(∆Hq) ) R[σ(slope)], σ(∆Sq) ) R[σ(intercept)]).
3JHH ) 6.9, 1H, H8), 1.35 (d, 3JHH ) 6.9, 3H, H9), 1.16 (d, 3JHH
)
7.0, 3H, H10), 1.10 (s, 3H, H7). 13C{1H} NMR (CDCl3, selected
peaks only): δ 132 (C4), 99 (C1), 99 (C2), 96 (C6), 89 (C5), 88
(C11), 87 (C3), 79 (C16), 75 (C20/17), 74 (C14), 74 (C12), 74 (C17/20),
74 (C18/19), 74 (C19/18), 73 (C15), 71 (C13), 31 (C8), 22 (C10), 21
2
(C9), 15 (C7). 31P{1H} NMR (CDCl3): δ 23.3 (d, JPP ) 52, 1P,
2
Ru-PPh3), 19.7 (d, JPP ) 52, 1P, Ru-PPh2), -19.4 (s, 1P, pend-
PPh2), -144.4 (sept,1JPF ) 713, 1P, PF6). ESI-MS (CH2Cl2) positive
ion: m/z, 533 (11%) [M - dppf]+, 825 (23%) [M - PPh3]+, 1087
[M]+; negative ion: m/z, 145 [PF6]-. Anal. Calcd for C62H57ClF6-
FeP4Ru (1232.39 g mol-1): C, 60.43; H, 4.66. Found: C, 60.38;
H, 4.67.
(28) Jensen, S. B.; Rodger, S. J.; Spicer, M. D. J. Organomet. Chem.
1998, 556, 151-158.
Preparation of [RuCl(η2-dppv)(η6-p-cymene)]Cl. A solution
of [RuCl2(η6-p-cymene)]2 (0.20 g, 0.33 mmol) and cis-
PPh2CHCHPPh2 (0.31 g, 0.78 mmol) in CH2Cl2 (5 mL) was stirred
at RT for 30 min. MeOH (10 mL) was added and the solution was
(29) Helm, L.; Borel, A.; Yerly, F. NMRICMA 3.0 for Matlab; Institut
des Sciences et Inge´nierie Chimiques, EPFL Lausanne, 2004.
(30) (a) Le Noble, E. J.; Schlott, R. ReV. Sci. Instrum. 1976, 47, 770-
771. (b) Richens, D. T.; Ducommun, Y.; Merbach, A. E. J. Am. Chem.
Soc. 1987, 109, 603-604.

η2-Diphosphine (η6-p-cymene)ruthenium(II) Compounds
Organometallics, Vol. 26, No. 3, 2007 593
Table 6. Crystal Data and Details of the Structure Determinations
[2a]PF6
[2b]PF6
[2d]PF6
[5b]PF6
formula
M
C53H51ClF6P4Ru‚CH2Cl2
1147.26
C54H51ClF6P4Ru
1074.35
C55H55ClF6P4Ru‚2CH2Cl2
1260.24
C36H36ClF6P3Ru‚CH2Cl2
897.00
T [K]
140(2)
100(2)
100(2)
100(2)
cryst syst
space group
a [Å]
b [Å]
c [Å]
monoclinic
P2(1)/n
13.9506(7)
18.7248(11)
21.1365(13)
triclinic
P1h
9.7360(19)
11.657(2)
21.649(4)
100.32(3)
99.40(3)
98.34(3)
2346.1(8)
2
1.521
0.590
3.05 e θ e 25.03
46 107
8278 [Rint ) 0.0482]
8278/0/598
0.0326, 0.0652
1.110
monoclinic
P2(1)/c
16.067(3)
16.140(3)
21.951(4)
monoclinic
P2(1)
11.162(2)
30.243(6)
11.176(2)
R [deg]
â [deg]
δ [deg]
V [Å3]
Z
107.004(5)
100.06(3)
91.33(3)
5280.0(5)
4
1.443
0.627
3.05 e θ e 25.03
30 281
9226 [Rint ) 0.0497]
9226/38/673
0.0733, 0.2201
1.061
5604.7(19)
4
1.494
0.690
2.91 e θ e 25.03
43 673
9474 [Rint ) 0.0451]
9474/28/747
0.0624, 0.1471
1.119
3771.6(13)
4
1.580
0.813
3.25 e θ e 25.03
70 101
13 289 [Rint ) 0.0442]
13 289/1/907
0.0211, 0.0465
1.119
density [g cm-3
]
µ [mm-1
]
θ range [deg]
no. of measd reflns
no. of unique reflns
no. data/restr/params
R1, wR2 [I > 2σ(I)]a
GoFb
Flack x
0.014(11)
2
2
b
2
a R1 ) ∑||Fo| - |Fc||/∑|Fo|, wR2 ) {∑[w(Fo2 - Fc )2]/∑[w(Fo )2]}1/2. GoF ) {∑[w(Fo2 - Fc )2]/(n - p)}1/2 where n is the number of data and p is the
number of parameters refined.
Numerical analysis was carried out using Origin 7.0 or OriginPro
7.5.31
sites. The [PF6]- counterion in [2d]PF6 is disordered over two sites.
Some of the solvent molecules in the structures of [2a]PF6 and
[2d]PF6 were constrained or split over multiple sites. It was also
necessary to restrain the atomic displacement parameters of some
of the solvent atoms in both [2a]PF6 and [2d]PF6 and two atoms
in a phenyl group of [2d]PF6. Graphical representations of the
structures were made with ORTEP3.37
Crystallography. Relevant details about the structure refinements
are given in Table 6, and selected geometrical parameters are found
in Table 2. Data collection for the X-ray structure determinations
were performed on a KUMA CCD diffractometer system ([2a]PF6)
and Bruker APEX II CCD diffractometer system ([2b]PF6, [2d]PF6,
[5b]PF6) using graphite-monochromated Mo KR radiation (0.71073
Å) and a low-tempetature device. Data reduction was performed
using CrysAlis RED32 ([2a]PF6) and EvalCCD33,34 ([2b]PF6,
[2d]PF6, [5b]PF6). Structures were solved using SIR9735 and
refined (full-matrix least-squares on F2) using SHELXTL.33,36 An
absorption correction (SADABS) was applied to the data sets of
[2b]PF6, [2d]PF6, and [5b]PF6.33 All non-hydrogen atoms were
refined anisotropically, with hydrogen atoms placed in calculated
positions using the riding model with the exception of those on C8
in [2a]PF6, which were located on the Fourier difference map and
then constrained. Disorder in the p-cymene ring of [2a]PF6 was
satisfactorily modeled by splitting the isopropyl moiety over two
Acknowledgment. We are grateful to Dr. R. Scopelliti for
assistance with crystallography. We also thank the New Zealand
Foundation for Research, Science and Technology for a Top
Achiever Doctoral Fellowship (A.B.C.) and the EPFL and the
Swiss National Science Foundation for financial support.
Note Added after ASAP Publication. In the version of this
paper that appeared on the Web December 15, 2006, incorrect
values appeared in Tables 4 and 5. In addition, two minor text
changes were needed. The version of this paper that now appears
is correct.
Supporting Information Available: Crystallographic informa-
tion for [2a]PF6, [2b]PF6, [2d]PF6, and [5b]PF6 in CIF format,
Figures S1-S11, and Tables S1-S3. This material is available free
of charge via the Internet at http://pubs.acs.org.
(31) Origin 7.0 or OriginPro 7.5; OriginLab Corporation: Northampton,
MA, 2002.
(32) CrysAlis RED; Oxford Diffraction Ltd.: Abingdon, Oxfordshire,
U.K., 2003.
(33) Bruker AXS, Inc.: Madison, WI, 1997.
(34) Duisenberg, A. J. M.; Kroon-Batenburg, L. M. J.; Schreurs, A. M.
M. J. Appl. Crystallogr. 2003, 36, 220.
OM060752N
(35) Altomare A.; Burla, M. C.; Camalli, M.; Cascarano, G. L.;
Giacovazzo, C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Spagna,
R. J. Appl. Crystallogr. 1999, 32, 115-119.
(36) Sheldrick, G. M. SHELXTL; University of Go¨ttingen: Germany,
1997.
(37) Farrugia, L. J. J. Appl. Crystallogr. 1997, 30, 565.