Neutral and cationic complexes with P-bonded 2-pyridylphosphines as N-donor ligands toward rhodium. Electrical charge vs steric hindrance on the conformational control

Article abstract of DOI:10.1021/ic0600477

Bimetallic palladium(II)-rhodium(I) and gold(I)-rhodium(I) complexes of the type [(4,4′-Me₂-bipy)(C₆F₅)Pd(μ- PPh_3-n-Py_n)Rh(diene)](BF₄)₂ and [(C₆F₅)Au(μ-PPh_3-nPy_n)Rh(diene)] (BF₄) (n = 2, 3; Py = 2-pyridyl) have been synthesized. The P donor atom of the bridging ligands (μ-PPh_3-nPy_n) is coordinated to the Pd or to the Au center. The resulting complexes react with [Rh(diolefin)(solv)₂]⁺ (solv = acetone) in a way similar to pyrazolylborates, affording square-planar or pentacoordinated rhodium complexes with two or the three N-donor ends chelating the Rh atom. The metallacycles formed upon chelation can adopt one of two conformations in the square-planar Rh(I) complexes, either bringing the other metal close to the Rh center or bringing it to a remote position. The first conformation is preferred for the gold P-coordinated complexes and the second for the palladium complexes. The X-ray structures of [(4,4′-Me₂-bipy)](C₆F ₅)Pd(μ-PPhPy₂)Rh(COD)](BF₄)₂ (COD = 1,5 cyclooctadiene) and [Au(C₆F₅)(μ-PPhPy ₂)Rh-(TFB)](BF₄) (TFB = 5,6,7,8-tetrafuoro-1,4-dihydro-1, 4-etenonaphthalene) are reported.

Full text of DOI:10.1021/ic0600477

Inorg. Chem. 2006, 45, 6628−6636
Neutral and Cationic Complexes with P-Bonded 2-Pyridylphosphines as
N-Donor Ligands toward Rhodium. Electrical Charge vs Steric
Hindrance on the Conformational Control
Juan A. Casares, Pablo Espinet,* Jose´ M. Mart´ın-AÄ lvarez, and Vero´nica Santos
Qu´ımica Inorga´nica, Facultad de Ciencias, UniVersidad de Valladolid, E-47071 Valladolid, Spain
Received January 10, 2006
Bimetallic palladium(II)
Pyn)Rh(diene)](BF4)2 and [(C6F5)Au(
The P donor atom of the bridging ligands (
complexes react with [Rh(diolefin)(solv)2]+ (solv
−
rhodium(I) and gold(I)
−
rhodium(I) complexes of the type [(4,4
2, 3; Py 2-pyridyl) have been synthesized.
-PPh3 nPyn) is coordinated to the Pd or to the Au center. The resulting
′-Me2-bipy)(C6F5)Pd(µ-PPh3 -
-n
µ
-PPh3 nPyn)Rh(diene)](BF4) (n
)
)
-
µ
-
)
acetone) in a way similar to pyrazolylborates, affording square-
planar or pentacoordinated rhodium complexes with two or the three N-donor ends chelating the Rh atom. The
metallacycles formed upon chelation can adopt one of two conformations in the square-planar Rh(I) complexes,
either bringing the other metal close to the Rh center or bringing it to a remote position. The first conformation is
preferred for the gold P-coordinated complexes and the second for the palladium complexes. The X-ray structures
of [(4,4
′
-Me2-bipy)](C6F5)Pd(
µ-PPhPy2)Rh(COD)](BF4)2 (COD ) 1,5 cyclooctadiene) and [Au(C6F5)(µ-PPhPy2)Rh-
(TFB)](BF4) (TFB
)
5,6,7,8-tetrafuoro-1,4-dihydro-1,4-etenonaphthalene) are reported.
Introduction
ligand in molecules with both hard and soft metal centers.
The coordination chemistry of the related (PPhPy2) and
tetradentate (PPy3) ligands has been much less studied, but
there are a few reports on their catalytic application as
amphiphilic water-soluble ligands and as proton carriers.4-6
As a part of our ongoing research on complexes with
pyridylphosphines and their derivatives,4,7 we have studied
before heterobimetallic complexes with PPhPy2 and PPy3 as
The coordination chemistry of the 2-pyridylphosphines is
currently a topic of great interest that has been extensively
reviewed.1 Most studies have been concerned with PPh2Py
(Py ) 2-pyridyl), which is a useful building block for the
synthesis of homo- or hetero-bimetallic compounds because
the rigidity induced by the small bite angle of the ligand
favors the formation of M-M bonds. The synthetic relevance
of this strategy was early recognized by Balch and co-
workers, and it continues to be a useful synthetic tool.2,3 On
the other hand, the different electronic properties for P and
N donor atoms facilitate chemoselective bonding of the
(4) (a) Pruchnik, F. P.; Smolenski, P.; Wajda-Hermanowicz, K. J.
Organomet. Chem. 1998, 570, 63-69. (b) Buhling, A.; Kamer, P. C.
J.; van Leeuwen, P. W. N. M.; Elgersma, J. W. J. Mol. Catal. A:
Chem. 1997, 116, 297-308. (c) Baird, I. R.; Smith, M. B.; James, B.
R. Inorg. Chim. Acta 1995, 235, 291-297. (d) Buhling, A.; Kamer,
P. C. J.; van Leeuwen, P. W. N. M. J. Mol. Catal. A: Chem. 1995,
98, 69-80 (e) Drent, E.; Arnoldy, P.; Budzelaar, P. H. M. J.
Organomet. Chem. 1993, 455, 247 (f) Xie, Y.; Lee, C.-L.; Yang, Y.;
Rettig, S. J.; James, B. R. Can. J. Chem. 1992, 70, 751-756.
(5) (a) Schutte, R. P.; Rettig, S. J.; Joshi, A. J.; James, R. J. Inorg. Chem.
1997, 36, 5809-5817. (b) Wajda-Hermanowicz, K.; Pruchnik, F.;
Zuber, M. J. Organomet. Chem. 1996, 508, 75-81.
(6) (a) Espinet, P.; Hernando, R.; Iturbe, G.; Villafan˜e, F.; Orpen, A. G.;
Pascual, I. Eur. J. Inorg. Chem. 2000, 5, 1031-1038. (b) Casares, J.
A.; Espinet, P.; Hernando, R.; Iturbe, G.; Villafan˜e, F. Inorg. Chem.
1997, 36, 44-49.(c) Espinet, P.; Go´mez-Elipe, P.; Villafan˜e, F. J.
Organomet. Chem. 1993, 450, 145-150.
* To whom correspondence should be addressed. E-mail: espinet@
qi.uva.es.
(1) (a) Espinet, P.; Soulantica, K. Coord. Chem. ReV. 1999, 499-556.
(b) Zhang, Z. Z.; Cheng, H. Coord. Chem. ReV. 1996, 147, 1-39. (c)
Newkome, G. R. Chem. ReV. 1993, 93, 2067-2089.
(2) See for instance: (a) Olmstead, M. M.; Maisonnet, A.; Farr, J. P.;
Balch, A. L. Inorg. Chem. 1981, 20, 4060. (b) Farr, J. P.; Olmstead,
M. M.; Balch, A. L. Inorg. Chem. 1983, 22, 1229. (c) Zang, Z.-Z.;
Wang, H.-K.; Wang, H.-G. J. Organomet. Chem. 1986, 314, 357. (d)
Farr, J. P.; Olmstead, M. M.; Wood, F. D.; Balch, A. L. J. Am. Chem.
Soc. 1983, 105, 792.
(3) For recent reports on the use of pyridylphosphines as bridging ligands
see: (a) Zhang, T. L.; Chen, C. G.; Qin, Y.; Meng, X. G. Inorg. Chem.
Commun. 2006, 9 (1), 72-74. (b) Zhang, T. L.; Qin, Y.; Wu, D. Y.;
Liu, C. L. J. Coord. Chem. 2005, 58, 1485-1491. (c) Li, Q. S.; Xu,
F. B.; Cui, D. J.; Yu, K.; Zeng, X. S.; Leng, X. B.; Song, H. B.;
Zang, Z. Z. Dalton Trans. 2003, 8, 1551-1557. (d) Driess, M.; Franke,
F.; Merz, K. Eur. J. Inorg. Chem. 2001, 10, 2661-2668.
(7) (a) Alonso, M. A.; Casares, J. A.; Espinet, P.; Mart´ınez-Ilarduya, J.
M.; Pe´rez-Briso, C. Eur. J. Inorg. Chem. 1998, 1745-1753. (b)
Casares, J. A.; Espinet, P.; Mart´ınez de Ilarduya, J. M.; Lin, Y.-S.
Organometallics 1997, 16, 770-779. (c) Casares, J. C.; Coco, S.;
Espinet, P.; Lin, Y.-S. Organometallics 1995, 14, 3058-3067. (d)
Casares, J. A.; Espinet, P.; Mart´ın-Alvarez, J. M.; Espino, G.; Pe´rez-
Manrique, M.; Vattier, F. Eur. J. Inorg. Chem. 2001, 289-296.
6628 Inorganic Chemistry, Vol. 45, No. 17, 2006
10.1021/ic0600477 CCC: $33.50
© 2006 American Chemical Society
Published on Web 07/27/2006

2-Pyridylphosphine Rhodium Complexes
Chart 1
Scheme 1
bridging ligands.4,8,9 In complexes where the pyridyl groups
coordinate a “[Rh(diolefin)]+” fragment (once the P func-
tionality has been blocked by oxidation or by coordination
to a soft metal to form a metaloligand), the conformational
behavior of the resulting chelated ligand can be compared
to that of pyrazolylborate ligands (Chart 1). Complexes
Tp′ML2 (M ) Rh(I), Ir(I)) display κ2 or κ3 coordination
modes depending on the nature of the Tp′ ligand, the metal,
and the coligands. While κ3 coordination yields 18-electron
trigonal bipyramidal structures (complexes C in Chart 1),
κ2 binding results in 16-electron square-planar species. In
the latter, the different substituents at the boron can be
oriented in pseudoequatorial or pseudoaxial positions in the
boat defined by the chelate, giving rise to different conform-
ers (A or B in Chart 1). These aspects, well studied in
pyrazolylborate chemistry,10,11 have been also examined before
for complexes with the metaloligands [Pt(C6F5)3(PPh3-nPyn)]-
(n ) 2, 3), where other features not present in the Tp′
systems, such as the charge on the metals and the remarkable
bulk of [Pt(C6F5)3(PPyn)]-, are involved.9 Structures D and
E, similar to A and B in the Tp′ system, were found. In this
work, we examine the behavior of complexes [M](µ-PPh3-n
-
Pyn)Rh(diolefin) (n ) 2, 3; diolefin ) norbornadiene,
tetrafluorobenzobarrelene (TFB, 5,6,7,8-tetrafuoro-1,4-dihy-
dro-1,4-etenonaphthalene)) in which the metal fragment
participating in the metaloligand, [M], is neutral Au(C6F5)
or cationic [Pd(C6F5)(4,4′-Me2-bipy)]+ instead of anionic
[Pt(C6F5)3]-.
Results and Discussion
Synthesis of the Complexes. Complexes [Pd(C6F5)(4,4′-
Me2-bipy)(PPhPy2)](BF4) (2) and [Pd(C6F5)(4,4′-Me2-bipy)-
(PPy3)](BF4) (3) were prepared by substitution of bromide
by PPhPy2 or PPy3 in the precursor [Pd(C6F5)Br(4,4′-Me2-
bipy)] (1). These cationic complexes were used as N-donor
ligands toward [Rh(diolefin)(solv)2]+ (solv ) solvent), which
were prepared in situ, affording the dicationic Pd/Rh
complexes 4-7 (Scheme 1). In a similar way the neutral
gold(I) complexes [Au(C6F5)(PPhPy2)] (8) and [Au(C6F5)-
(PPy3)] (9) were used to prepare the monocationic Au/Rh
complexes 10-13 (Scheme 2).
(8) (a) Alonso, M. A.; Casares, J. A.; Espinet, P.; Soulantica, K.; Charmant,
A. G.; Orpen, A. G. Inorg. Chem. 2000, 39, 705-711. (b) Casares, J.
A.; Espinet, P.; Soulantica, K.; Pascual, I.; Orpen, A. G. Inorg. Chem.
1997, 36, 5251..
As discussed below, all complexes 4-7 have a type E
structure (Chart 1) in the solid state and in solution, keeping
the two cationic metal centers separated, while all complexes
10-12 prefer a type D structure. Only 13 shows in solution
a mixture of two isomers with structures F (major) and D
(minor). The X-ray structures of 4 and 11 were studied.
Solid-State Structures. [(4,4′-Me2-bipy)(C6F5)Pd(µ-
PPhPy2)Rh(COD)](BF4)2 (4). The solid-state structure of
(9) Casares, J. A.; Espinet, P.; Mart´ın-AÄ lvarez, J. M.; Santos, V. Inorg.
Chem. 2004, 43, 189-197.
(10) (a) Trofimenko, S. Chem. ReV. 1993, 93, 943-980. (b) Kitajima, N.;
Tolman, W. B. Prog. Inorg. Chem. 1995, 43, 419-531. (c) Slugovc,
C.; Padilla-Mart´ınez, I.; Sirol, S.; Carmona, E. Coord. Chem. ReV.
2001, 213, 129-157.
(11) (a) Bucher, U. E.; Currao, A.; Nesper, R.; Ru¨eger, H.; Venanzi, L.
M.; Younger, E. Inorg. Chem. 1995, 34, 66-74. (b) Sanz, D.; Santa-
Mar´ıa, M. D.; Claramunt, R. M.; Cano, M.; Heras, J. V.; Campo, J.
A.; Ru´ız, F. A.; Pinilla, E.; Monge, A. J. Organomet. Chem. 1996,
526, 341-350.
Inorganic Chemistry, Vol. 45, No. 17, 2006 6629

Casares et al.
Figure 1. Left, ORTEP representation of the cation of complex 4. Right, space-filling representation showing how one bipy ring is forced inside the cleft
between the two coordinated Py groups.
Table 1. Selected Distances [Å] and Angles [deg] of the Cation of
corresponding centroids. The proximity between these two
aromatic rings can be expected to hinder their rotation about
Complex 4, [(4,4′-Me2Bipy)(C6F5)Pd(µ-PPhPy2)Rh(COD)]2+a
Pd(1)-C(21)
Pd(1)-N(2)
Pd(1)-N(1)
Pd(1)-P(1)
N(3)-Rh(1)
N(4)-Rh(1)
Rh(1)-M(1)
Rh(1)-M(2)
Rh(1)-P(1)
Rh(1)-Pd(1)
1.999(5)
2.083(4)
2.104(3)
2.2526(14)
2.110(4)
2.093(4)
2.013(6)
2.014(6)
3.375(5)
5.570(4)
C(21)-Pd(1)-N(2)
C(21)-Pd(1)-N(1)
N(2)-Pd(1)-N(1)
C(21)-Pd(1)-P(1)
N(2)-Pd(1)-P(1)
N(1)-Pd(1)-P(1)
N(4)-Rh(1)-N(3)
KPy(1)-KPy(2)
94.22(16)
172.96(17)
78.82(14)
88.04(14)
175.00(12)
98.98(11)
87.50(15)
61.93(12)
the C-P and C-Pd bonds, but due to the symmetry expected
for 4 in solution (where the Pd coordination plane should
become a symmetry plane), this hindrance cannot be
confirmed nor disproved by NMR spectroscopy. However,
the hindrance to rotation about the P-C bond has been
confirmed for the sterically equivalent 6 (see below).
The chelate formed by the two Py groups coordinated to
rhodium shows a boatlike conformation of type E (Chart 1)
with the [Pd(C6F5)(4,4′-Me2-bipy)]+ fragment occupying the
pseudoequatorial position and the phenyl group in the
pseudoaxial one. This conformation forces the P-pyridyl
groups to adopt a bite angle slightly smaller than 90°, as
often found in other complexes with these ligands.4a,7 On
the other hand, the angle between the two 2-pyridyl rings
(61.93(12)°) is forced here to be larger than usual because
of the steric requirement of one pyridyl ring of the 4,4′-
Me2-bipy group, which is sandwiched between them. For
comparison, the angle found in the zwitterionic complex [Pt-
(C6F5)3(µ-PPhPy2)Rh(COD)], without any fragment slotted
in the space between the 2-pyridyl rings, is 51.59(11)°.9
[Au(C6F5)(µ-PPhPy2)Rh(TFB)](BF4) (11). The structure
of the cation of complex 11 is shown in Figure 2 and the
selected bond distances and angles are given in Table 2.
The rhodium atom is in a square-planar coordination
environment, while the gold atom has a distorted linear
coordination with a C-Au-P angle of 167.8(3)° due to the
clash between the C6F5 ring and the TFB ligand of a
neighboring cation, as can be seen in Figure 3. The chelate
formed by the two Py groups coordinated to rhodium
a M1 and M2 are C61-C62 and C65-C66 centroids. KPy(1)-KPy(2)
are the planes where the pyridyl groups are located.
Scheme 2
the cation of complex 4 is shown in Figure 1, and selected
bond distances and angles are given in Table 1.
The metallic centers, palladium and rhodium, are located
in square-planar coordination environments, with bond
distances and angles within the range of normal values.15
The two coordination planes are almost perpendicular
(82.89(5)°). The ligand 4,4′-Me2-bipy is on the palladium
coordination plane and shows a small bite angle (78.82(14)°).
The C6F5 ring is almost perpendicular to the palladium
coordination plane, as usually found, and almost parallel to
the P-Ph ring, with a distance of 3.695(8) Å between the
(13) Proposals of dissociation of a nonolefinic ligand can be found in: (a)
Yoshida, T.; Tani, K.; Yamagata, T.; Tatsuno, Y.; Saito, T. J. Chem.
Soc. Chem. Commun. 1990, 292-294. (b) Berger, H.; Nesper, R.;
Pregosin, P. S.; Ru¨egger, H.; Wo¨rle, M. HelV. Chim. Acta 1993, 76,
1520. (c) Yang, H.; Lugan, N.; Mathieu, R. Organometallics 1997,
16, 2089. (d) Valentini, M.; Selvakumar, K.; Wo¨rle, M.; Pregosin, P.
S. J. Organomet. Chem. 1999, 587, 244-251. (e) Selvakumar, K.;
Valentini, M.; Pregosin, P. S. Organometallics 2000, 19, 1299.
(14) The dissociation of one olefin has also been proposed: (a) Crociani,
B.; Antonaroli, S.; Di Vona, M. L.; Licoccia, L. J. Organomet. Chem.
2001, 631, 117-124.
(12) See, for instance: (a) Alonso, M. A.; Casares, J. A.; Espinet, P.;
Soulantica, K.; Orpen, G.; Phetmung, H. Inorg. Chem. 2003, 42,
3856-3864. (b) Haarman, H. F.; Ernsting, J. M.; Kranenburg, M.;
Kooijman, H.; Veldamn, N.; Spek, A. L.; van Leeuwen, P. W. N. M.
Organometallics 1997, 16, 887. (c) Heitner, H. I.; Lippard, S. J. Inorg.
Chem. 1972, 11, 1447. (d) Vrieze, K.; van Leeuwen, P. W. N. M.
Prog. Inorg. Chem. 1971, 14, 1. (e) Heitner, H. I.; Lippard, S. J. Am.
Chem. Soc. 1970, 92, 3486.
(15) Line shape analysis was carried out using the standard gNMR
program: Budzelaar, P. H. M. gNMR; Cherwell Scientific Publishing
Ltd.: Oxford, U.K.
6630 Inorganic Chemistry, Vol. 45, No. 17, 2006

2-Pyridylphosphine Rhodium Complexes
in solution the conformation found in the solid state
(conformation E in Chart 1). No other conformers are
detected. Accordingly, only one signal is observed in their
31P NMR spectra. Interestingly, in the related compounds
[(C6F5)3Pt(µ-PPhPy2)Rh(L)2] (L2 ) (CO)2, COD, or TFB),
only one isomer (D) was observed for L2 ) (CO)2, whereas
two isomers (D and E) were seen for L2 ) COD or TFB.9
The size of the ancillary ligand on Rh had a clear influence
on the stability of the two isomers and, for the smallest
ligand, CO, the preference was clearly for isomer D, which
allowed for a closer approach of the anionic Pt center to the
cationic Rh center. Since the cationic [Pd(C6F5)(4,4′-Me2-
bipy)]+ fragment is not expected to be bulkier than the
anionic [(C6F5)3Pt]- fragment (rather, it is probably smaller,
taking into account the restrictions to rotation of the
pentafluorophenyl rings already studied in ref 9), it seems
that the attractive anion-cation forces in [(C6F5)3Pt(µ-
PPhPy2)Rh(L)2] and the repulsive cation-cation forces in
[Pd(C6F5)(4,4′-Me2-bipy)(µ-PPy3)Rh(diolefin)](BF4)2 may
have some influence in the exclusive preference for confor-
mation E found for the latter.
Figure 2. ORTEP representation of the cation 11.
In the 19F NMR spectra the complexes with PPhPy2 as
bridging ligand (4 and 5) show three 2:2:1 signals corre-
sponding to a spin system A2M2XZ (where Z is the 31P
nucleus), showing that in solution the coordination plane of
the palladium moiety is also a symmetry plane of the whole
dication. The symmetry observed on the C6F5 group confirms
that the structure of the cation in solution is that of an E
conformer, since the same 19F spectral pattern was found
before in the E conformers of the zwitterionic complexes
[(C6F5)3Pt(µ-PPhPy2)Rh(L)2] (L2 ) (CO)2, COD, or TFB),
whereas all the 19F nuclei of each C6F5 were non-equivalent
Figure 3. Representation of the packing of two neighboring cations of
complex 11.
1
in conformers D.9 Moreover, four of the five H nuclei of
the phenyl ring are equivalent by pairs in complexes 4 and
Table 2. Selected Distances [Å] and Angles [deg] of the Cation of
Complex 11, [(C6F5)Au(µ-PPhPy2)Rh(TFB)]+a
1
5, and only three cross-peaks are obtained in the H-13C
1
HMQC experiment on the aromatic region. The H olefin
Rh(1)-N(2)
Rh(1)-N(1)
Rh(1)-M(1)
Rh(1)-M(2)
Rh(1)-P(1)
Au(1)-P(1)
Au(1)-C(51)
Au(1)-Rh(1)
2.096(6)
2.116(6)
2.002(5)
2.020(5)
3.214(5)
2.2684(18)
2.060(8)
3.736(5)
N(2)-Rh(1)-N(1)
C(51)-Au(1)-P(1)
KPy(1)-KPy(2)
89.0(2)
167.8(3)
63.2(3)
signals appear broadened in the spectrum of 4 at 25 °C in
deuterated acetone due to the apparent rotation of the
cyclooctadiene. This process is very often observed in
diolefin rhodium(I) complexes, and it has been attributed to
solvent coordination followed by Berry pseudorotation in the
pentacoordinated intermediate but also to the dissociation
of one ligand followed by a rearrangement in the tricoordi-
nated intermediate.12-14 In the complex with TFB as diolefin
a M1 and M2 are C1-C2 and C3-C4 centroids. KPy(1)-KPy(2) are
the planes where the pyridines are located.
-
describes a boatlike conformation of type D (Chart 1) with
the Au(C6F5) group in the axial position. The phenyl group
is in the equatorial position and is contained in the plane bi-
secting the dihedral angle between the two Py groups, per-
pendicular to the rhodium coordination plane. The line con-
necting the gold and rhodium atoms (which are at a nonin-
teraction distance of 3.736(5) Å) is almost perpendicular to
the rhodium coordination plane. The orientation of the C6F5
ring, almost perpendicular to the rhodium coordination plane,
is due to packing forces, not to intramolecular interactions.
Solution Behavior. Dicationic Complexes with the [Pd-
(C6F5)(4,4′-Me2-bipy)]+ Fragment, 4-7. Table 3 sum-
marizes the most relevant spectroscopic data of complexes
4-13 in solution. The dicationic complexes 4-7 maintain
and BF4 as counteranion (5a) this exchange is faster and
1
only one H olefin signal is observed at 25 °C. Also in the
19F NMR spectrum, the 19F nuclei of TFB appear equivalent
by pairs at room temperature. Although the tetrafluoroborate
dicationic complexes are insoluble in most organic solvents,
after exchanging the anion by BAF (BAF ) tetrakis[3,5-
1
bis(trifluoromethyl)phenyl]borate), the H NMR in CD2Cl2
of complex 5b could be registered, showing two olefinic
signals for the TFB ligand, meaning that the olefin rotation
in this solvent is slow. The rotation rate was measured by
spin saturation transfer at 0 °C affording krot ) 1.8 s-1 in
pure CD2Cl2, and krot ) 3.9 s-1 in a 9:1 mixture of CD2Cl2/
acetone-d6. Further increase in the ratio of acetone in the
solvent mixture makes the exchange rate too fast to be
Inorganic Chemistry, Vol. 45, No. 17, 2006 6631

Casares et al.
Table 3. Spectroscopic Data
compound
(isomer, %)
δ31P (ppm)
δ
13Ca (ppm)
156.5
δ
13Cb (ppm)
δ 1Hc (ppm)
IRd (cm-1
)
[Pd(C6F5)(4,4′-Me2-bipy)(µ-PPhPy2)Rh(COD)](BF4)2 (4)
1622
1586
1564
1559(sh)
1618
1587
1622
1588
1572
(E, 100%)
49.61
90.5
85.7
9.92
[Pd(C6F5)(4,4′-Me2-bipy)(µ-PPhPy2)Rh(TFB)](BF4)2
(5a or 5b)
[Pd(C6F5)(4,4′-Me2-bipy)(µ-PPy3) Rh(COD)](BF4)2 (6)
(E, 100%)
(E, 100%)
47.68
47.92
154.4f
64.6
65.5f
92.2
84.9
89.8
87.3
65.8
67.0f
9.73
156.6
156.1
152.2
9.93
9.78
8.11
[(C6F5)(4,4′-Me2-bipy)Pd(µ-PPy3) Rh(TFB)](BF4)2
(7a or 7b)
(E, 100%)
154.4f
152.1f
9.70
7.92
1622
1590
1574
1564
1587
46.70
[(C6F5)Au(µ-PPhPy2)Rh(COD)](BF4) (10)
[(C6F5)Au(µ-PPhPy2)Rh(TFB)](BF4) (11)
[(C6F5)Au(µ-PPy3)Rh(COD)](BF4) (12)
[(C6F5)Au(µ-PPy3)Rh(TFB)](BF4) (13)
(D, 100%)
(D, 100%)
(D, 100%)
(D, 27%)
(F, 73%)
34.66
35.81
29.94
31.91
45.70
154.2
155.3
92.4
87.8
69.9
66.0
92.6
87.8
7.33
7.65
1588
154.6
153.0
7.24
8.90
7.64
8.97
8.97
1589
1575
1583
e
e
-
-
156.6
47.6
a Chemical shift of the C6 from the 2-pyridyl group in PPhPy2 ligand. b Chemical shift of olefinic carbons. c Chemical shift of the H3 from the 2-pyridyl
group in PPhnPy3-n ligand. d Nujol mull. e No data available due to low solubility. f In CD2Cl2 after exchanging the anion by BAF (that is, for 5b or 7b).
Scheme 3. Lowering of Symmetry by the Noncoordinated Py in
Complex 6 (Left) and Hindrance to Coordination of the Third Py Group
measured by this technique since extensive saturation transfer
occurs during the selective excitation pulse. Line shape
analysis in pure acetone as solvent afforded krot ) 55 s-1
for 5b, and krot ) 200 s-1 for 5a.15 The observed dependence
of the rotation rate with the solvent supports a major
contribution of an associative mechanism involving coordi-
nation of acetone to give a pentacoordinated rhodium
intermediate in which a isomerization process (such as Berry
pseudorotation or turnstile) occurs. The small but non-
negligible rotation rate value obtained in pure CD2Cl2 for
5b suggests that, since BAF has a very low coordinating
ability, a non-associative mechanism is simultaneously
operating, possibly through the dissociation of a coordinated
olefin. The contribution of traces of water or Cl- to an
associative mechanism in dichloromethane cannot be ex-
cluded, since these impurities are not easily removed. The
effect of the counteranion is extremely difficult to foresee,
since in dichloromethane the ions are expected to form ion
pairs and the counteranion effect depends largely on the
relative position of the anion and the cation.16,17
In complexes with PPy3 as bridging ligand (6 and 7), the
palladium coordination plane of Pd is not a symmetry plane
due to the noncoordinated pyridyl group (Scheme 3, left).
In the 1H NMR spectra of [Pd(C6F5)(4,4′Me2-bipy)(µ-PPy3)-
Rh(COD)](BF4)2 (6), at room temperature separate signals
are obtained for the coordinated and noncoordinated P-Py
groups, showing that the possible coordinated/noncoordinated
Py exchange is a very slow process. At the same temperature,
the cyclooctadiene signals coalesce due to olefin rotation.
Finally, in the 19F NMR spectrum at room temperature, the
Fortho atoms (F atoms ortho to the Pd-C bond) of the C6F5
(Right)
group give two broad signals due to the slowness of Py rota-
tion about the P-Py bond, which are well resolved in the
spectrum at -10 °C. The slowness of P-Py rotation and Py
exchange in 6 are in sharp contrast with the ease observed
for the same processes in the same conformer E of [Pt(C6F5)3-
(µ-PPy3)Rh(COD)],9 which needs to be cooled below 203 K
to stop the substitution and concurrent P-Py rotation. This
difference can be understood considering the steric hindrance
to coordination of the third P-Py group in complex 6. This
hindrance arises from the restriction to rotation of the
pentafluorophenyl, imposed by the bipy ligand on Pd, which
in turn is locked in the slot between the two coordinated
P-Py groups (Scheme 3; this hindrance is very obvious for
the analogous complex 4 in the space-filling representation
in Figure 1, right). In the analogous complex [Pt(C6F5)3(µ-
PPy3)Rh(COD)], the Pt(C6F5)3 frame rotates freely about the
P-Pt bond, and this make possible the P-Py rotation and
its coordination to rhodium.
Complex [Pd(C6F5)(4,4′-Me2-bipy)(µ-PPy3)Rh(TFB)](BF4)2
(7) behaves similarly, but some processes are faster than for
6. At 25 °C, there is no observable exchange between
coordinated and noncoordinated P-Py groups, which give
separate signals in the H NMR spectrum. The rotation of
the noncoordinated pyridyl about the P-Py bond is notice-
(16) Loupy, A.; Tchoubar, B. Salt Effects in Organic and Organometallic
Chemistry; VCH: New York, 1995.
(17) Aullo´n, G.; Esquius, G.; Lledo´s, A.; Maseras, F.; Pons, J.; Ros, J.
Organometallics 2004, 23, 5530-5539.
1
6632 Inorganic Chemistry, Vol. 45, No. 17, 2006

2-Pyridylphosphine Rhodium Complexes
Chart 2
ably faster than for 6, making equivalent the two coordinated
P-Py groups at room temperature. In fact, this process has
very low activation energy, and in order to slow the rotation
and achieve the non-equivalence of the signals of the
coordinated pyridyl groups, it is necessary to cool the sample
to 186 K. Rotation of the diolefin is also observed, making
equivalent the upper and lower halves of the TFB and is
also faster than in complex 6. This rotation, combined with
the pyridine rotation, renders equivalent the four olefinic
1
protons at room temperature. In the H NMR at 187 K, the
Scheme 4. Equilibrium between Isomers D and F of Complex 13
TFB protons give separate signals, and at higher tempera-
tures, the signals coalesce, first due to the pyridine rotation
(leading to left-right equivalence of the olefinic protons)
and then due to the TFB rotation in the rhodium complex
(leading to up-down equivalence of the nuclei on olefinic
and on bridging carbons). The same two processes are
observed more easily in the 19F NMR spectra due to the
larger chemical shift separations of the non-equivalent nuclei
under slow exchange conditions. Above 223 K, the rotation
of the noncoordinated Py renders equivalent the two Fortho
atoms of the C6F5 attached to palladium, while the pair of
fluorine atoms of the TFB ligand coordinated to rhodium
remain non-equivalent. The exchange rates have been
measured by line shape analysis at 232.2 K.15 At this
temperature, the P-Py rotation rate is k ) 2.4 × 103 s-1
(∆Gq232 ) 41.3 kJ mol-1), and the TFB rotation rate is k )
135 s-1 (∆Gq232 ) 46.8 kJ mol-1). The change of the anion
[(C6F5)Au(µ-PPy3)Rh(COD)](BF4) (12) show only confor-
mation D (Chart 2).
In 10 and 11, the phenyl group undergoes some restriction
to rotation due to interactions with the two coordinated
pyridyl groups, giving rise to broadening of the phenyl
signals in their 1H NMR spectra in CDCl3 below 260 K due
to the restricted rotation about the P-C bond. However, the
phenyl signals were not resolved in the low-temperature limit
for this solvent.
Complexes 10-12 do not undergo rotation of the diolefin
coordinated to rhodium in CDCl3, but in acetone-d6, the
rotation equilibrates the up and down halves of the diolefins
at room temperature.
Complex 12 does not show exchange between the coor-
dinated and noncoordinated pyridines in their spectra at 298
K. This is to be expected, as the substitution pathway requires
change from D to E conformation and this, as observed in
complex 13 (see below) and also in [(C6F5)3Pt(µ-PPy3)Rh-
(diolefin)], has high activation energy.9
-
BF4 for BAF yields a complex of the same cation but
soluble in CD2Cl2. Their NMR spectra show that the cation
[Pd(C6F5)(4,4′-Me2-bipy)(µ-PPy3)Rh(TFB)]+ has very similar
Py rotation rates in CD2Cl2 and in acetone-d6: Also, the
olefin rotation rate is very similar in the two solvents. In
other words, contrary to the behavior observed for 5, the
dynamic processes are little influenced by the solvent or the
anion. Then, this difference should be related to the existence
of the third Py group. The olefin rotation can be satisfactorily
explained assuming the coordination of the third Py group
to give a pentacoordinate intermediate on which this rotation
occurs. It is interesting to note that one might expect that
this mechanism should produce also the equivalence of the
three Py groups, as observed in closely related systems.18
However, this is a special case where both the rotation of
the third Py group around the Py-P bond and the rotation
of the Pd coordination plane around the Pd-P bond are
severely hindred by clash of the third Py group with the C6F5
group and the coordinated 4,4′-Me2-bipy group with the two
coordinated Py groups flanking it, respectively (see Scheme
3 and Figure 1, right)). For this reason, the third Py group
never exchanges with the other two in the time scale of our
experiments. This hindrance to rotation is comparable to that
found for triptycene rotors, which have usually a very high
activation energy, about 100 kJ mol-1.19
The only compound in which two isomers are present in
solution is [(C6F5)Au(µ-PPy3)Rh(TFB)](BF4) (13). The equi-
1
librium is slow in CDCl3 at 293 K and the 31P, 19F, and H
NMR spectra show signals from two isomers in a ratio D/F
) 1:2.7 (Scheme 4). It is known for Tp′Rh-olefin complexes
that κ3-Tp′ compounds display the olefinic carbon signal at
higher field than their κ2-Tp′ analogues.11b,20 A similar effect
is found here, and the olefinic carbon signals of the major
isomer of 13 (F) are shielded almost 20 ppm relative to the
same signals of the square planar analogue with PPhPy2, 11
(Table 3). The carbon signals from the minor isomer were
too weak to be detected.
In the 1H NMR spectra in acetone-d6, the olefinic signals
of 13 are in coalescence. While the major isomer (F) gives
(18) Fast interconversion is observed, for example, in complexes 7 and 8
in ref 9 (please note a mistake in the discussion on Py exchange in
that paper, where complex 7E is labeled as 6E).
(19) (a) Kelly, T. R.; Tellitu, I.; Pe´rez Sestelo, J. Angew. Chem., Int. Ed.
Engl. 1997, 36, 1866-1867. (b) Davis, A. P. Angew. Chem., Int. Ed.
1998, 37, 909-910. (c) Kelly, T. R.; Silva, R. A.; De Silva, H.; Jasmin,
S.; Zhao, Y. J. Am. Chem. Soc. 2000, 122, 6935-6949.
(20) Del Ministro, E.; Renn, O.; Ru¨egger, H.; Venanzi, L. M.; Burckhardt,
U.; Gramlich, V. Inorg. Chim. Acta 1995, 240, 631.
The difference between complexes with TFB and COD
toward the olefin rotation has also been observed in
complexes [Pt(C6F5)3(µ-PPy3)Rh(diolefin)].9
Monocationic Complexes with the Fragment [Au-
(C6F5)], 10-13. Complexes [(C6F5)Au(µ-PPhPy2)Rh(diolefin)]-
(BF4) 10 (diolefin ) COD), 11 (diolefin ) TFB), and
Inorganic Chemistry, Vol. 45, No. 17, 2006 6633

Casares et al.
[Pd2(µ-Br)2Br2(C6F5)2],28 [Au(C6F5)(PPhPy2)], and [Au(C6F5)-
(PPy3)]6b were prepared by published methods. Combustion CHN
analyses were made on a Perkin-Elmer 2400 CHN microanalyzer.
IR spectra were recorded on a Perkin-Elmer FT 1720 X spectro-
photometer.
just one olefinic and one alkyl signal in all the temperature
range, the minor one (D) shows two olefinic and two alkyl
proton signals at 243 K. In the aromatic zone, the signals of
the three pyridyl groups of isomer F are equivalent, while
for the minor D isomer, the coordinated and noncoordinated
pyridines give different signals. We have found that the
chemical shift of the H3 proton of the coordinated pyridines
is very sensitive to the conformation of the chelate ring,
appearing in the range δ ) 6.7-7.7 ppm for D complexes,
and δ > 9.5 ppm for E complexes. The lower chemical shift
for complexes D is probably due to the contribution of the
diamagnetic effect of the noncoordinated aryl group located
between the two H3 protons. The effect is quite general and
has been also observed in complexes [(C6F5)3Pt(µ-PPhn-
Py3-n)RhL2].9 For the minor isomer of complex 13, the H3
protons of the coordinated pyridines appear at 7.6 ppm (Table
3), supporting a D structure. The EXSY (exchange spec-
troscopy) spectrum registered at 243 K with a mixing time
of 0.4 s shows no cross-peaks due to pyridine substitution
in D or exchange between isomers D and F; there are only
cross-peaks correlating the olefinic signals of the D isomer
due to olefin rotation. However, the same experiment at 273
K with mixing time of 0.6 s (the same T1 measured by spin
recovery) gave cross-peaks correlating signals of both
isomers: the pyridyl groups of F exchange with both pyridyls
of D (coordinated and noncoordinated). Considering the
limited precision of this experiment, only the order of
magnitude of the rate constant can be estimated, which is
1/T1 ≈ 1-10 at this temperature.21
NMR Spectra. 1H NMR (300.16 MHz), 19F NMR (282.4 MHz),
31P NMR (121.4 MHz), and 13C{1H} (75.47 MHz) spectra were
recorded on Bruker ARX 300 and AC 300 instruments equipped
with a VT-100 variable-temperature probe. Chemical shifts are
reported in ppm from SiMe4 (1H), CCl3F (19F), H3PO4 (85%) (31P),
or K2[PtCl4] (1 M, D2O) (195Pt), with positive shifts downfield, at
ambient probe temperature unless otherwise stated. J values are
given in Hz. 13C NMR were registered as 1H-13C correlation
experiments, which were made with a HMQC sequence with BIRD
selection and GARP decoupling during acquisition. Chemical shifts
of quaternary carbons are not listed in the experimental data. The
EXSY experiments were carried out with a standard NOESY
program operating in phase sensitive mode, with a 5% random
variation of the evolution time to avoid COSY cross-peaks. The
saturation transfer experiments were carried out by using a 180°
Gaussian-shaped soft pulse for the selective excitation of the desired
signal, followed by a variable delay (10 values were used between
10-5 and 8 s) and a 90° nonselective pulse. The data analysis was
carried out as described in the literature.29
Synthesis of the Complexes. [Pd(C6F5)(Br)(4,4′-Me2-bipy)] (1).
To a stirred solution of [Pd(µ-Br)(Br)(C6F5)]2(NBu4)2 (2.0 g, 1.48
mmol) in CH2Cl2 (15 mL) was added solid 4,4′-dimethyl-2,2′-
bipyridine (546 mg, 2.96 mmol). After 30 min, the product was
precipitated by the addition of ethanol (80 mL) to give a yellow
solid that was filtered, washed with ethanol and diethyl ether, and
vacuum-dried. After being isolated, the product is almost insoluble
in common solvents, precluding its characterization by NMR
spectroscopy. Yield 1.56 g (98%). Anal. Calcd for C18H12BrF5N2-
Pd: C, 40.21; H, 2.25; N, 5.21. Found: C, 39.96; H, 2.32; N, 5.08.
IR (Nujol mull, cm-1): 1618 m, ν(CN).
[Pd(C6F5)(4,4′-Me2-bipy)(PPhPy2)]BF4 (2). To a suspension of
[Pd(C6F5)(Br)(4,4′-Me-bipy)] (250.0 mg, 0.465 mmol) in acetone
(80 mL) was added AgBF4 (90.5 mg, 0.465 mmol) and PPhPy2
(135.2 mg, 0.512 mmol). The solution was stirred for 24 h, protected
from the light, and filtered through Celite. The solvent was
evaporated and the residue was washed with 2-propanol, giving a
white solid that was filtered and vacuum-dried. Yield 206.9 mg
(55%). Anal. Calcd for C34H25N4BF9PPd: C, 50.49; H, 3.12; N,
6.93. Found: C, 50.45, H, 3.12 N, 6.50.31P NMR (293 K, CDCl3):
δ 31.69. 1H NMR (293 K, CDCl3): δ 8.61 (m, 4H); 8.33 (m, 2H);
7.98 (m, 2H); 7.88 (m, 3H); 7.71 (m, 2H); 7.61 (m, 1H); 7.59 (m,
2H); 7.52 (d, 2H); 7.20 (d, 1H); 2.60 (s, 3H); 2.50 (s, 3H). 19F
NMR (293 K, CDCl3): δ -161.83 (m, 2F); -159.40 (t, 1F);
-150.44 (s, 4F, BF4); -116.47 (m, 2F). IR (Nujol mull, cm-1):
1619 (1627 shoulder) m, ν(CN); 1576 m, ν(CN).
Conclusions
When there is no charge interaction, as in the (neutral
gold)-rhodium bimetallic complexes, the preferred confor-
mation directs the bulkiest P substituent toward the N-
coordinated metal (rhodium), in a behavior comparable to
that observed before for κ2-Tp′ ligands.8 An additional
stabilization energy to give another conformation comes from
the chelation of the third pyridine ring in complexes with
PPy3, as found in 13, but this seems to depend largely on
the electronic requirements of the rhodium center, since the
pentacoordinate geometry is not found in complex 12.
For complexes where the two metal centers are cationic,
the electrical repulsion between them forces the metals to
be as separate as possible. This has consequences on the
conformation preferred (type E). The fact that there are no
type F dicationic complexes seems to be the result of the
particular geometry of the palladium frame chosen, which
hinders the coordination of the third pyridine to the rhodium.
[Pd(C6F5)(4,4′-Me2-bipy)(PPy3)](BF4) (3). Prepared as described
for 2 but using PPy3 (135.6 mg, 0.511 mmol) instead of PPhPy2.
Yield 450.1 mg (60%). Anal. Calcd for C33H24N5BF9PPd: C, 48.95;
H, 2.99; N, 8.65. Found: C, 48.87; H, 3.04; N; 8.38. 31P NMR
Experimental Section
General Methods. All reactions were carried out under N2.
Solvents were distilled using standard methods. The compounds
[Rh2(µ-Cl)2(1,5-COD)2],22 [Rh2(µ-Cl)2(TFB)2],23 PPhPy2,24 PPy3,25
[AuCl(tht)],26 [Au(C6F5)(tht)],26 (NBu4)2[Pd2(µ-Br)2(C6F5)4],27 (NBu4)2-
1
(293 K, CDCl3): δ 30.10. H NMR (293 K, CDCl3): 8.64 (m,
(25) Kurtev, K.; Ribola, D.; Jones, R. A.; Cole-Hamilton, D. J.; Wilkinson,
G. J. C. S. Dalton. 1980, 55-58.
(26) Uso´n, R.; Laguna, A.; Laguna, M. Inorg. Synth. 1988, 26, 85.
(27) Uso´n, R.; Fornie´s, J.; Mart´ınez, F.; Toma´s, M. J. Chem. Soc., Dalton
Trans. 1980, 888.
(28) Uso´n, R.; Fornie´s, J.; Nalda, J. A.; Lozano, M. J.; Espinet, P.; Albe´niz,
A. C. Inorg. Chim. Acta 1989, 156, 251.
(29) Green, M. L. H.; Sella, A.; Wong, L.-L. Organometallics 1992, 11,
2650.
(21) Perrin, C.; Dwyer, T. J. Chem. ReV. 1990, 90, 935-937.
(22) Giordano, G.; Crabtree, R. H. Inorg. Synth. 1990, 28, 88.
(23) Roe, D. M.; Massey, A. G. J. Organomet. Chem. 1971, 28, 273.
(24) Newcome, G.; Hagen, D. C. J. Org. Chem. 1978, 43, 947-949. Xie,
Y.; Lee, C.; Yang, Y.; Rettig, S. J.; James, B. R. Can. J. Chem. 1992,
70, 751.
6634 Inorganic Chemistry, Vol. 45, No. 17, 2006

2-Pyridylphosphine Rhodium Complexes
3H); 8.60 (s, 1H); 8.55 (s, 1H); 7.97 (m, 3H); 7.78 (m, 3H); 7.52
(m, 1H); 7.45 (m, 1H); 7.42 (m, 3H); 7.21 (d, 1H); 6.90 (d, 1H);
2.61 (s, 3H); 2.52 (s, 3H). 19F NMR (293 K, CDCl3): δ -162.02
(m, 2F); -159.40 (t, 1F-); -150.37 (s, 4F-BF4); -116.43 (m, 2F).
IR (Nujol mull, cm-1): 1618 (1642sh) m, ν(CN); 1569 m, ν(CN).
[(4,4′-Me2-bipy)(C6F5)Pd(µ-PPhPy2)Rh(COD)](BF4)2 (4). To
a stirred solution of [Rh2(µ-Cl)2(COD)2] (45.9 mg, 0.093 mmol)
in acetone (20 mL) was added AgBF4 (36.2 mg, 0.186 mmol). After
30 min, the AgCl formed was filtered through Celite, and solid
[Pd(C6F5)(4,4′-Me-bipy)(PPhPy2)](BF4) (150.0 mg, 0.186 mmol)
was added to the yellow solution. The mixture was stirred for 20
min more, the solvent evaporated to dryness, and the residue stirred
with 5 mL of thf (thf ) tetrahydrofuran) affording a yellow solid
that was filtered and vacuum-dried. The solid was recrystallized
from CH2Cl2/ethanol. Yield 164.9 mg (80%). Anal. Calcd for
C42H37N4B2F13PPdRh: C, 45.58; H, 3.37; N, 5.06. Found: C, 45.79;
H, 3.24; N, 4.94. 31P NMR (293 K, (CD3)2CO): δ 49.61. 1H NMR
(293 K, (CD3)2CO): δ 9.84 (m, 2H); 9.40 (d, 2H); 8.67 (s, 1H);
8.58 (s, 1H); 8.29 (m, 2H); 7.96 (m, 2H); 7.88 (m, 1H); 7.75 (m,
1H); 7.62 (m, 4H); 7.53 (d, 1H); 6.93 (d, 1H); 6.72 (d, 1H); 2.61
(s, 3H); 2.43 (s, 3H). 19F NMR (293 K, (CD3)2CO): δ -117.38
(m, 2F); -150.33 (s, 4F-BF4); -158.45 (t, 1F); -160.10 (m, 2F).
IR (Nujol mull, cm-1): 1622 m, ν(CN); 1586 m, ν(CN); 1564 m,
ν(CN); 1559, ν(CN).
[(4,4′-Me2-bipy)(C6F5)Pd(µ-PPhPy2)Rh(TFB)](BF4)2 (5a). Pre-
pared as described for 4 but using [Rh2(µ-Cl)2(TFB)2] (67.8 mg,
0.093 mmol) instead of [Rh2(µ-Cl)2(COD)2]. Yield 166.5 mg (73%).
Anal. Calcd for C46H31N4B2F17PPdRh: C, 45.12; H, 2.55; N, 4.57.
Found: C, 45.20; H, 2.80; N, 4.39. 31P NMR (293 K, (CD3)2CO):
δ 47.68. 1H NMR (293 K, (CD3)2CO): δ 9.73 (t, 2H, H-3-Pycoord);
9.12 (d, 2H, H-6-Pycoord); 8.70 (s, 1H, 4,4′-Me2-bipy); 8.63 (s, 1H,
4,4′-Me2-bipy); 8.29 (m, 2H, H-4-Pycoord); 7.99 (m, 1H, Ph); 7.91
(m, 3H, H-5-Pycoord); 7.91 (m, 1H, 4,4′-Me2-bipy); 7.76 (m, 2H,
Ph); 7.48 (m, 4H, Ph); 7.48 (m, 4H, 4,4′-Me2-bipy); 7.03 (d, 1H,
4,4′-Me2-bipy); 5.13 (m, broad, 2H-TFB); 4.00 (s, broad, 4H-TFB);
2.61 (s, 3H, 4,4′-Me2-bipy); 2.47 (s, 3H, 4,4′-Me2-bipy). 19F NMR
(293 K, (CD3)2CO): δ -160.11 (m, 2F); -160.11 (m, 2F); -117.53
(d, 2F); -158.12 (m, 1F); -150.46 (s, 4F-BF4); -147.11 (d, 2F).
IR (Nujol mull, cm-1): 1618 ν(CN); 1587 ν(CN).
instead of [Rh2(µ-Cl)2(COD)2] and [Pd(C6F5)(4,4′-Me-bipy)(PPy3)]-
(BF4) (150.0 mg, 0.185 mmol) instead of [Pd(C6F5)(4,4′-Me2-bipy)-
(PPhPy2)](BF4). Yield: 125.4 mg (55%). Anal. Calcd for C45H30N5B2-
F17PPdRh: C, 44.10; H, 2.47; N, 5.71. Found: C, 43.93; H, 2.64;
N, 5.60. 31P NMR (293 K, (CD3)2CO): δ 46.70. 1H NMR (293 K,
(CD3)2CO): δ 9.70 (t, 2H, H-3-Pycoord); 9.08 (d, 2H, H-6-Pycoord);
8.86 (d, 1H, H-6-Pynoncoord); 8.72 (s, 1H, 4,4′-Me2-bipy); 8.63 (s,
1H, 4,4′-Me2-bipy); 8.30 (t, 3H, H-4-Pycoord); 8.30 (t, 3H, H-3-
Pynoncoord); 8.06 (m, 1H, H-4-Pynoncoord); 7.92 (m, 1H, 4,4′-Me2-
bipy); 7.92 (m, 3H, H-5-Pycoord); 7.83 (m, 1H, H-5-Pynoncoord); 7.56
(d, 2H, 4,4′-Me2-bipy); 7.05 (d, 1H, 4,4′-Me2-bipy); 5.22 (m, broad,
TFB); 4.05 (m, broad, 4H-TFB); 2.60 (s, 3H, 4,4′-Me2-bipy); 2.50
(s, 3H, 4,4′-Me2-bipy); 1.30 (m, broad, 2H-TFB). 19F NMR (293
K, (CD3)2CO): δ -160.48 (m, 2F); -160.03 (m, 2F-TFB);
-157.83 (m, 1F); -150.43 (s, 4F-BF4); -146.95 (d, 2F-TFB);
-116.77 (d, 2F). 31P NMR (310K, (CD3)2CO): δ 50.89. IR (Nujol
mull, cm-1): 1622 ν(CN); 1590 ν(CN); 1574 ν(CN); 1564 ν(CN).
To register NMR spectra in CD2Cl2, the anion BF4 was exchanged
with BAF following the same procedure described above for 5.
[(C6F5)Au(µ-PPhPy2)Rh(COD)](BF4) (10). To a stirred solution
of [Rh2(µ-Cl)2(COD)2] (115.0 mg, 0.233 mmol) in 15 mL of acetone
was added solid TlBF4 (135.9 mg, 0.466 mmol). After 30 min,
[Au(C6F5)(PPhPy2)] (293.0 mg, 0.466 mmol) was added to the
solution. The mixture was stirred for 30 min more, the TlCl formed
was filtered through Celite, and the solvent was evaporated to 5
mL. The addition of ethanol (20 mL) and further evaporation of the
remaining acetone gave the product as a yellow crystalline solid that
was filtered and vacuum-dried. Yield 334.0 mg (77%). Anal. Calcd
for C30H25N2AuBF9PRh: C, 38.91; H, 2.72; N, 3.02. Found: C,
1
38.67; H, 2.75, N, 2.96. 31P NMR (293 K CDCl3) δ : 34.55. H
NMR (293 K CDCl3): δ 4.50 (m, 2H-olefin); 4.27 (m, 2H-olefin);
2.98 (m, 2H); 2.51 (m, 2H); 2.18 (m, 2H); 1.90 (m, 2H). 19F NMR
(293 K CDCl3): δ -164.5 (tdt, 2F); -160.42 (t, 1F); -156.92 (s,
4F); -119.52 (d, 2F). IR (Nujol mull, cm-1): 1587 ν(CN).
[(C6F5)Au(µ-PPhPy2)Rh(TFB)](BF4) (11). Prepared as 10 but
using [Rh2(µ-Cl)2(TFB)2] (173.0 mg, 0.234 mmol) instead of [Rh2-
(µ-Cl)2(COD)2]. Yield 370.0 mg (74%). Anal. Calcd for C34H19N2-
AuBF13PRh: C, 39.11; H, 1.82; N, 2.68. Found: C, 38.96; H, 1.88;
1
N, 2.77. 31P NMR (293 K (CD3)2CO): δ 36.39. H NMR (293 K
(CD3)2CO): δ 9.12 (d, 2H); 8.45 (m, 2H); 8.10 (m, 3H); 7.99 (m,
2H); 7.76 (m, 2H); 7.65 (m, 2H); 6.31 (broad, 1H); 5.63 (broad,
1H); 4.87 (broad, 2H); 4.57 (broad, 2H). IR (Nujol mull, cm-1):
1588 ν(CN).
Preparation of a Solution of [(4,4′-Me2-bipy)(C6F5)Pd(µ-
PPhPy2)Rh(TFB)] [B(3,5-C6H3(CF3)2)4]2 (5b). To a solution of
5 (15 mg, 0.012 mmol) in acetone was added NaBAF (24 mg, 0.027
mmol); the resulting solution was filtered to remove NaBF4, and
the solvent was evaporated. The residue was dissolved in ether,
filtered again, and evaporated to dryness, giving a residue that was
insoluble in CDCl3 but quite soluble in CD2Cl2.
[(4,4′-Me2-bipy)(C6F5)Pd(µ-PPy3)Rh(COD)](BF4)2 (6). Pre-
pared as described for 4 but using [Pd(C6F5)(4,4′-Me2-bipy)(PPy3)]-
(BF4) (150.0 mg, 0.185 mmol) instead of [Pd(C6F5)(4,4′-Me-
bipy)(PPhPy2)](BF4). Yield 147.1 mg (72%). Anal. Calcd for
C41H36N5B2F13PPdRh: C, 44.46; H, 3.28; N, 6.32. Found: C, 44.12;
H, 3.17; N, 6.10. 31P NMR (293 K, (CD3)2CO): δ 47.92. 1H NMR
(293 K, (CD3)2CO): δ 9.78 (broad, 2H); 9.34 (d, 2H); 8.74 (d,
1H); 8.66 (s, 4,4′-Me2-bipy, 1H); 8.57 (s, 4,4′-Me2-bipy, 2H); 8.26
(m, 2H); 8.07 (m, 2H); 7.95 (m, 2H); 7.82 (m, 4,4′-Me2-bipy, 1H);
7.69 (m, 1H); 7.51 (d, 4,4′-Me2-bipy, 1H); 6.92 (d, 4,4′-Me2-bipy,
1H); 6.78 (m, 4,4′-Me2-bipy, 1H); 2.59 (s, 4,4′-Me2-bipy, 3H); 2.41
(s, 4,4′-Me2-bipy, 3H). 19F NMR (293 K, (CD3)2CO): δ -160.56
(m, 2F); -158.14 (m, 1F); -150.26(s, 4F-TFB); -117.42 (broad,
1F); -115.83 (broad, 1F). IR (Nujol mull, cm-1): 1622 ν(CN);
1588 ν(CN); 1572 ν(CN).
[(C6F5)Au(µ-PPy3)Rh(COD)](BF4) (12). Prepared as 10 but
using [Rh2(µ-Cl)2(COD)2] (117.6 mg, 0.238 mmol), TlBF4 (139.0
mg, 0.477 mmol), and [Au(C6F5)(PPy3)] (300.0 mg, 0.477 mmol)
instead of [Au(C6F5)(PPhPy2)]. Yield 295.0 mg (67%). Anal. Calcd
for C29H24N3AuBF9PRh: C, 37.57; H, 2.60; N, 4.53. Found: C,
1
37.38; H, 2.83; N, 4.33. 31P NMR (293 K CDCl3): δ 29.94. H
NMR (293 K CDCl3): δ 9.09 (d, 2H, H-6-Pycoord); 9.00 (d, 1H,
H-6-Pynoncoord); 8.90 (t, 1H, H-3-Pynoncoord); 8.20 (m, 1H, H-4-
Pynoncoord); 7.84 (m, 2H, H-4-Pycoord); 7.80 (m, 1H, H-5-Pynoncoord);
7.64 (t, 2H, H-5-Pycoord); 7.24 (m, 2H, H-3-Pycoord); 4.58 (m, 2H-
olefin); 4.32 (m, 2H-olefin); 3.02 (m, 2H); 2.52 (m, 2H); 2.14 (m,
2H); 1.90 (m, 2H). 19F NMR (293 K CDCl3): δ -165.40 (t, 2F);
-159.95 (t, 1F); -156.36 (s, 4F, BF4); -119.48 ppm (d, 2F). 13
C
NMR (293 K CDCl3): δ 154.6 (C-6-Pycoord); 153.0 (C-6-Pynoncoord);
138.8 (C-4-Pycoord); 138.3 (C-4-Pynoncoord); 137.6 (C-3-Pynoncoord);
130.8 (C-3-Pycoord); 128.5 (C-5-Pynoncoord); 127.7 (C-5-Pycoord); 92.6
(C-olefin); 87.9 (C-olefin); 32.1 (COD); 29.8 (COD). IR (Nujol
mull, cm-1): 1589 ν(CN); 1575 ν(CN).
[(4,4′-Me2-bipy)(C6F5)Pd(µ-PPy3)Rh(TFB)](BF4)2 (7). Pre-
pared as 4 but using [Rh2(µ-Cl)2(TFB)2] (67.1 mg, 0.092 mmol)
[(C6F5)Au(µ-PPy3)Rh(TFB)](BF4) (13). Prepared as 12 but
using [Rh2(µ-Cl)2(TFB)2] (174.0 mg, 0.240 mmol) instead of [Rh2-
Inorganic Chemistry, Vol. 45, No. 17, 2006 6635

Casares et al.
Table 4. Data of the X-ray Diffraction Studies
compound
4‚Me2CO
11
Crystal Data
C45H43B2F13N4OPPdRh
1164.73
empirical formula
fw
C34H19AuBF13N2PRh
1044.17
cryst syst
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
monoclinic
P21/c
10.9644(14)
22.662(3)
19.628(3)
90
103.981(3)
90
3830.4(18)
4
1.635
0.853
2328
0.25 × 0.08 × 0.08
Data Collection
298(2)
triclinic
P1h
10.2401(11)
10.2403(11)
16.5327(18)
93.909(2)
106.585(2)
92.388(2)
1654.3(3)
2
Z
D
calc (g cm-3
)
2.096
5.080
996
0.24 × 0.06 × 0.06
absorption coefficient (mm-1
F(000)
)
cryst size (mm3)
temp (K)
300(2)
θ range for data collection
wavelength (Å)
index ranges
1.40-23.27°
0.71073 (Mo KR)
-12 e h e 11
0 e k e 25
1.57-23.27°
0.71073 (Mo KR)
-11 e h e 10
-11 e k e 11
0 e l e 18
0 e l e 21
reflns collected
17 484
7737
independent reflns
completeness to θ
6724 (Rint ) 0.0506)
23.27° (98.8%)
4742 (Rint ) 0.0284)
23.28° (99.4%)
Refinement
SADABS
1.000000 and 0.777393
6724/0/682
absorption correction
max. and min. transmission
data/restraints/params
GOF on F2
SADABS
1.000000 and 0.582875
4742/0/478
0.993
1.029
final R indices [I > 2σ(I)]
R1 ) 0.0375, wR2 ) 0.0552
R1 ) 0.0766, wR2 ) 0.0613
0.451 and -0.482
R1 ) 0.0374, wR2 ) 0.0945
R1 ) 0.0471, wR2 ) 0.1058
1.033 and -1.341
R indices (all data)
largest diff. peak and hole (e Å-3
)
(µ-Cl)2(COD)2]. Yield 330.0 mg (66%). Anal. Calcd for C33H18N3-
AuBF13PRh: C, 37.91; H, 1.72; N, 4.02. Found: C, 37.53; H, 1.80;
N, 3.90. 31P NMR (293 K (CD3)2CO): δ 46.47 (major isomer,
73%); 32.03 (minor isomer 27%). 1H NMR (293 K (CD3)2CO): δ
9.63 (d, 3H); 9.08 (d, 3H); 8.96 (m, 4H); 8.43 (m, 4H); 8.09 (broad,
3H); 7.94 (broad, 3H); 7.68 (d, 4H); 6.29 (s, broad, 1H); 5.96 (s,
2H); 5.60 (s, broad, 1H); 4.87 (s, broad, 2H); 4.58 (s, broad, 2H);
3.91 (s, 4H. 19F NMR (293 K (CD3)2CO): δ -162.31 (2F-major);
-161.75 (2F-minor); -160.46 (2F- major); -159.96 (2F- minor);
-157.76 (1F- major and 1F- minor); -150.41 (4F- major and
4F- minor); -148.33 (1F- minor); -147.33 (2F- major);
-147.00 (broad, 1F- minor); -115.27 (2F- major); -114.49
(2F- minor). IR (Nujol mull, cm-1): 1583 m, ν(CN). IR (CH2Cl2
solution, cm-1): 1587 and 1572, ν(CN).
Experimental Procedure for X-ray Crystallography. Suitable
single crystals were mounted on glass fibers, and diffraction
measurements were made using a Bruker SMART CCD area-
detector diffractometer with Mo KR radiation (λ ) 0.71073 Å).30
Intensities were integrated from several series of exposures, each
exposure covering 0.3° in ω, the total data set being a hemisphere.31
Absorption corrections were applied, based on multiple and
symmetry-equivalent measurements.32 The structure was solved by
direct methods and refined by least squares on weighted F2 values
for all reflections (see Table 4).33 All non-hydrogen atoms were
assigned anisotropic displacement parameters and refined without
positional constraints. Hydrogen atoms were taken into account at
calculated positions, and their positional parameters were refined.
Both BF4 counteranions in compound 4‚Me2CO were disordered.
Refinement proceeded smoothly to give R1 ) 0.0375 for 4‚Me2-
CO and R1 ) 0.0374 for 11 based on the reflections with I >
2σ(I). Complex neutral-atom scattering factors were used.34 Crystal-
lographic data (excluding structure factors) for the structures 4‚
Me2CO and 11 reported in this paper have been deposited with the
Cambridge Crystallographic Data Centre as Supplementary publica-
tion nos. CCDC-293670 and CCDC-293671. Copies of the data
can be obtained free of charge on application to the CCDC, 12
Union Road, Cambridge CB2 1EZ, U.K. [Fax: (internat.) + 44-
1223/336-033; Email: deposit@ccdc.cam.ac.uk].
Acknowledgment. Financial support by the Ministerio
de Educacio´n y Ciencia (Project No. CTQ2004-07667/BQU)
and the Junta de Castilla y Leo´n (Project No. VA 060/04) is
very gratefully acknowledged.
Supporting Information Available: Additional NMR data and
selected NMR spectra. This material is available free of charge
via the Internet at http://pubs.acs.org.
(30) SMART, v 5.051; Bruker Analytical X-ray Instruments, Inc.: Madison,
WI, 1998.
IC0600477
(31) SAINT, v 6.02; Bruker Analytical X-ray Instruments, Inc.: Madison,
WI, 1999.
(32) Sheldrick, G. M. SADABS: A Program for Absorption Correction with
the Siemens SMART System; University of Go¨ttingen: Go¨ttingen,
Germany, 1996.
(33) SHELXTL program system Version 5.1; Bruker Analytical X-ray
Instruments, Inc.: Madison, WI, 1998.
(34) International Tables for Crystallography; Kluwer: Dordrecht, 1992;
Vol. C.
6636 Inorganic Chemistry, Vol. 45, No. 17, 2006