Solid-state and solution structures of a series of [(HBPz3Me2)Rh(CO)(PR3)] and [(HBPz3Me2,4Cl)Rh(CO)(PR3)] complexes

Article abstract of DOI:10.1002/1099-0682(200109)2001:10<2689::aid-ejic2689>3.0.co;2-u

Addition of 1 equiv. of a phosphane or phosphite ligand to the κ³-bonded [Tp^Me2Rh(CO)₂] and [Tp^Me2,4ClRh(CO)₂] dicarbonyl precursors gives the monosubstituted complexes [TpRh(CO)L]. The X-ray crystal

Full text of DOI:10.1002/1099-0682(200109)2001:10<2689::aid-ejic2689>3.0.co;2-u

FULL PAPER
Solid-State and Solution Structures of a Series of [(HBPz3Me2)Rh(CO)(PR3)]
and [(HBPz3Me2,4Cl)Rh(CO)(PR3)] Complexes
[a]
Francois Malbosc,[a] Valerie Chauby,
Carole Serra-Le Berre,[a] Michel Etienne,[b]
´
¸
Jean-Claude Daran,[b] and Philippe Kalck*[a]
Keywords: Pyrazolylborato ligands / Rhodium / IR spectroscopy / Square-planar complexes / Fluxional behavior
Addition of 1 equiv. of a phosphane or phosphite ligand to
the κ3-bonded [TpMe2Rh(CO)2] and [TpMe2,4ClRh(CO)2] dicar- phosphite complexes [TpMe2,4ClRh(CO){P(OPh)3}] and
bonyl precursors gives the monosubstituted complexes pentacoordinated
[TpMe2,4ClRh(CO){P(OMe)3}] adopt
as in the solid state. According to infrared analyses, the
a
[TpRh(CO)L]. The X-ray crystal structures show that the geometry both in the solid state and in solution. However,
three complexes [TpMe2Rh(CO)(PMe3)], [TpMe2Rh(CO)-
(PMePh2)], and [TpMe2,4ClRh(CO)(PMePh2)] adopt square-
planar geometries. The X-ray crystal structure of
the infrared data for [TpMe2Rh(CO){P(OPh)3}] and
[TpMe2Rh(CO){P(OMe)3}] indicate that the TpMe2 ligand is in
a κ3 coordination mode in the solid state, as already evid-
[TpMe2Rh(CO){P(OPh)3}] is consistent with an interaction be- enced by the X-ray crystal structure, but in a κ2 mode in solu-
tween the dangling pyrazolyl group and the rhodium centre,
the Rh−N distance being 2.762(3) A. Analysis of ν(BH) and dangling and coordinated pyrazolyl groups, as studied by
tion. We also describe an exchange phenomenon between
˚
ν(CO) stretching frequencies shows that all the phosphane-
NMR.
containing complexes are square planar in solution as well
Introduction
Since the first report of pyrazolylborato ligands by Trofi-
menko in 1966,[1] hydrotris(pyrazolyl)borates have been
extensively used as σ donor ligands in a wide variety of
transition metal complexes.[2] They can provide stable com-
plexes, e.g. by replacing the isoelectronic cyclopentadienyl
and pentamethylcyclopentadienyl ligands, and offer greater
flexibility. Indeed, these ligands can adopt various modes
of coordination ranging from the ubiquitous κ3 and κ2
forms to the less common κ1 coordination mode.[3,4] Even
rarer is their recently recognized ability to act as coun-
terions (i.e., a κ0 form)[5] in transition metal salts. Venanzi
and co-workers have studied the geometry adopted in solu-
tion by complexes of the type [{HB(3R,4RЈ,5R"-
pyrazolyl)3}Ir(η4-C8H12)], or, using the nomenclature of
Trofimenko,[2] of the type [Tp3R,4RЈ,5RЈЈIr(COD)].[6] In its κ2
coordination mode, the ligand can have the non-coordin-
ated pyrazolyl group either far from the iridium centre or
dangling in such a position that the κ3 mode can readily be
achieved, as depicted in Scheme 1.
Scheme 1. The three coordination modes of Tp (adapted from
ref.[3]
)
rance between an R substituent in the 3-position and the
hydrogen atoms of the two double bonds of the cyclo-
octadiene ligand in [Tp3R,4RЈ,5RЈЈIr(C8H12)] plays an import-
ant role.[6] Venanzi and co-workers,[6] as well as Akita,
Moro-oka et al. for related [TpiPrRh(diene)] complexes,[7]
have used the wavenumber of the ν(BH) stretching vibration
to assign a κ2 or a κ3 bonding mode for the Tp ligand.
When ν(BH) is near to 2470 cmϪ1, a square-planar complex
in a κ2 mode is observed, whereas a ν(BH) band at around
2540 cmϪ1 is indicative of a trigonal-bipyramidal structure
with a κ3 coordination mode.[7]
Electronic and steric effects of each pyrazolyl group play
an important role in determining the equilibrium between
the three different forms κ2-e (the pyrazolyl in a pseudo-
equatorial position), κ2-s (scorpionate[6]), and κ3. The na-
ture of the substituent in the 3-position, i.e. adjacent to the
potentially coordinating nitrogen atom, exerts a strong in-
fluence on this equilibrium. More specifically, steric hind-
This class of complexes has become of particular interest
since
Ghosh
and
Graham
demonstrated
that
[TpMe2Rh(CO)2] photochemically activates one CϪH bond
of benzene or cyclohexane to afford the corresponding
hydrido phenyl or cyclohexyl rhodium complexes.[8] This
latter complex reacts with methane to afford
[a]
`
Laboratoire de Catalyse, Chimie Fine et Polymeres, ENSCT,
118 route de Narbonne, 31077 Toulouse Cedex, France
Laboratoire de Chimie de Coordination du CNRS,
205 route de Narbonne, 31062 Toulouse Cedex, France
[b]
Eur. J. Inorg. Chem. 2001, 2689Ϫ2697
WILEY-VCH Verlag GmbH, 69451 Weinheim, 2001
1434Ϫ1948/01/1010Ϫ2689 $ 17.50ϩ.50/0
2689

F. Malbosc, V. Chauby, C. Serra-Le Berre, M. Etienne, J.-C. Daran, P. Kalck
FULL PAPER
[TpMe2Rh(CO)(H)(CH3)]. The mechanism of this photo- 85%). In the case of complex 11, PMe2Ph in dichlorome-
chemically induced CϪH bond activation has been studied thane has to be added slowly at room temperature to avoid
by Purwoko and Lees,[9] as well as by Bergman and co- formation
of
the
disubstituted
complex
[κ1-
workers.[10] The process is believed to involve a sequence of TpMe2,4ClRh(CO)(PMe2Ph)2].[4] 11 can then be recrystal-
elimination of a CO ligand, coordination of the CϪH bond lized at low temperature, leaving 2 and the bis-adduct in
in an η2 mode, a change from κ3 to κ2 bonding of the TpMe2 solution. All the complexes have been fully characterized by
1
ligand to the rhodium, and finally oxidative addition of infrared, H, and 31P NMR, and in some cases by 13C and
the alkane.[7] The observation of the intermediate [(κ2- 103Rh NMR. The solid-state structures of 3, 5, 8, and 12
TpMe2)Rh(CO)(η2-RH)] has prompted us to report the pre- have been confirmed by X-ray analyses.
paration of a series of [TpЈRh(CO)(PR3)] complexes, which
were designed to have a more nucleophilic centre with a
view to enhancing their CϪH activating ability. The present
Molecular Structures of the Complexes 3, 5, 8, and 12
paper deals with the preparation and characterization of
[TpMe2Rh(CO)L] and [TpMe2,4ClRh(CO)L] (L ϭ phos-
X-ray crystal structures have been obtained for four com-
phane, phosphite) complexes. We have performed a detailed
plexes, two of which (3 and 12) have been described in brief
study of their solid-state and solution structures, as probed
by infrared and NMR spectroscopies, and by X-ray crystal
in previous reports.[4,11] Salient data are presented in
Table 1.
structure determinations. While this project was in pro-
gress,[11] the synthesis of [TpMe2Rh(CO)(PPh3)] was pub-
lished.[12] Several [TpMe2Rh(CO)(PR3)] complexes have
been described in the Ph.D. thesis of C. K. Ghosh.[13]
˚
Table 1. Salient distances [A] and angles [°] (SP ϭ square plane) in
complexes with PR3: 3, 5, 8, and 12
PMe3: 3
1.797(4)
2.2447(9)
2.113(3)
2.101(3)
3.632(3)
P(OPh)3: 8 PMePh2: 5 PMePh2: 12
RhϪC1
RhϪP1
RhϪN1
RhϪN3
RhϪN5
1.802(4)
2.1794(9)
2.110(3)
2.097(3)
2.762(3)
78.91
1.818(4)
2.2503(9)
2.097(3)
2.095(3)
3.661(4)
52.12
1.810(2)
2.258(5)
2.0923(15)
2.0911(16)
3.800(2)
48.05
Results and Discussion
Preparation of [TpMe2Rh(CO)(PR3)] and [TpMe2,4ClRh-
(CO)(PR3)] Complexes
Pz3ϪSP angle 55.05
N6ϪB1ϪH1 109.9
111.7(20)
115.5(22)
113.3(14)
Addition of one equivalent of a phosphane or a
phosphite ligand PR3 to [TpMe2Rh(CO)2] (1) or
[TpMe2,4ClRh(CO)2] (2) at room temperature results in the
substitution of one CO ligand to afford the corresponding
[TpRh(CO)(PR3)] complexes as shown in Equations (1)
and (2).
We first focus on the structures of 5 and 12, which have
the same PMePh2 phosphane ligand. Both complexes show
the same square-planar environment (see Figure 1 for 5 and
Figure 2 for 12), with two pyrazolyl groups bonded to the
rhodium metal centre and the third one in a dangling posi-
˚
tion. The RhϪN5 distances of 3.661(4) and 3.800(2) A in
5 and 12, respectively, preclude any bonding interaction be-
tween these atoms. The difference between these distances
is due to the rotation of the free pyrazolyl group, since the
angle between the pyrazolyl and the square plane varies
from 52.12° to 48.05°. The RhϪN1, RhϪN3, and RhϪP1
distances can be considered as being the same in these com-
plexes. Within each complex, the RhϪN distances to the
coordinated pyrazolyl groups, RhϪN1 and RhϪN3, are
equal, irrespective of the ligand in the trans position (i.e.
The rate of this reaction is determined by the nature of CO or PMePh2). As usual, the ν(CO) stretching frequencies
the ligand. The more basic but sterically hindered tricy- are more sensitive to the electronic modifications of the
clohexylphosphane PCy3 reacts with 2 within about 1 h to metal centre than the RhϪC, CϪO, and RhϪO distances
give 9. The ligands PMe3, PMe2Ph, PMePh2, and even for the CO ligands. Indeed, the four RhϪO1 bond lengths
P(OMe)3 react within a few minutes, as monitored by for 3, 5, 8, and 12 are 2.949 [ν(CO) ϭ 1961 cmϪ1], 2.954
infrared spectroscopy. The syntheses of 8, 15, and 16, con- (1984 cmϪ1), 3.099 (1975 cmϪ1), and 2.910 A (1996 cmϪ1),
˚
taining the less basic ligands P(OPh)3 and P(OiPr)3, require respectively. A square-planar environment is also found for
several hours. According to infrared data, these substitution 3 (Figure 3), and the RhϪN1 and RhϪN3 bond lengths
reactions are quantitative and isolated yields are high (Ͼ are identical within experimental error.
2690
Eur. J. Inorg. Chem. 2001, 2689Ϫ2697

Structures of a Series of [(HBPz3Me2)Rh(CO)(PR3)] and [(HBPz3Me2,4Cl)Rh(CO)(PR3)] Complexes
FULL PAPER
Figure 1. Molecular view of complex 5; ellipsoids are drawn at a
30% probability level
Figure 3. Molecular view of complex 3; ellipsoids are drawn at a
30% probability level
Figure 2. Molecular view of complex 12; ellipsoids are drawn at a
30% probability level
Figure 4. Molecular view of complex 8; ellipsoids are drawn at a
30% probability level
a κ2 coordination mode.[12] One-electron oxidation results
in the formation of [TpMe2Rh(CO)(PPh3)]ϩ, X-ray analysis
of which showed it to contain a κ3-TpMe2. The rhodium(II)
centre is then in a square-pyramidal environment, with the
Complex [TpMe2Rh(CO){P(OPh)3}], 8, has also been
analysed by X-ray crystallography, in view of its unexpected
infrared spectra (vide infra). The geometry about the rhod-
ium is again square-planar (Figure 4). The most notable
˚
axial RhϪN5 bond length being 2.224(2) A as opposed to
˚
feature is an RhϪP1 distance of 2.1794(9) A, which is signi-
˚
˚
2.091(2)
A
and 2.093(2)
A
for the two other
ficantly shorter than the RhϪP1 distances observed with
rhodiumϪnitrogen distances. Thus, the P(OPh)3-containing
˚
˚
PMe3 in 3 (2.245 A) or with PMePh2 in 5 and 12 (2.250 A
˚
complex 8 shows a lengthening of ca. 0.5 A when compared
˚
and 2.258 A, respectively). This is consistent with the better
to the rhodium(II) complex. Overall, we conclude that a κ3
coordination mode is favoured by a decrease in the electron
density at the metal centre.
π-accepting properties of a phosphite as compared to a
phosphane. A further feature deserves comment. The
˚
RhϪN5 distance is 2.762(3) A, longer than that of a true
˚
coordination bond (ca. 2.1 A), but shorter than the sum of
Infrared Study of Complexes 3؊15
˚
the van der Waals radii (3.3 A). Such a distance is thus
consistent with an RhϪN5 interaction. Recently, Connelly
Previous studies have shown that the ν(BH) stretching fre-
et al. reported the X-ray structure of [TpMe2Rh(CO)(PPh3)], quency offers a reliable means of ascertaining the coordina-
which has a square-planar geometry with TpMe2 adopting tion mode of tris(pyrazolyl)borato ligands.[6,7] Particularly
Eur. J. Inorg. Chem. 2001, 2689Ϫ2697
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F. Malbosc, V. Chauby, C. Serra-Le Berre, M. Etienne, J.-C. Daran, P. Kalck
FULL PAPER
interesting are the absolute values of the ν(BH) frequencies electron density at the metal centre. Thus, complexes 3؊6
determined by Moro-oka et al., which are ca. 2470 cmϪ1 and 9؊13 consistently show square-planar geometries, with
for κ2 coordination and 2540 cmϪ1 for κ3 coordination.[7] TpMe2 and TpMe2,4Cl adopting the κ2 coordination mode.
The measured ν(BH) values for all the complexes are pre- The diagnostic criterion of Moro-oka et al., as established
sented in Tables 2 and 3. Spectra were obtained from for [TpMe2Rh(diene)], is also valid here.
samples in both KBr and CH2Cl2. For the complexes bear-
The situation is slightly more subtle when the less basic
ing more basic phosphanes, i.e. those with PR3 ϭ PMe3, phosphite ligands are considered. For complexes 14 and 15,
PMe2Ph, PMePh2, and PPh3 (3؊6 and 9؊13), the ν(BH) the ν(BH) values (Table 3 and Figure 5) suggest that the
values are near to 2480 cmϪ1 and 2485 cmϪ1 in the solid coordination mode of the TpMe2,4Cl ligand is κ3. Hence, al-
state and in solution, respectively, irrespective of the TpЈ though we have been unable to obtain X-ray quality crystals
ligand. Figure 5 shows a plot of ν(BH) in CH2Cl2 as a func- to confirm the proposal, complexes 14 and 15 would seem
tion of the basicity of the phosphorus ligand on the De- to exhibit a pentacoordinated geometry. Interestingly, for
[14]
ν(BH) is seen to be independent of the the TpMe2-based complexes 7 and 8, which contain the
´
rencsenyi scale;
phosphane basicity, i.e. it is only weakly sensitive to the same P(OMe)3 and P(OPh)3 phosphite ligands, the ν(BH)
frequencies are only consistent with a κ2 coordination mode
in CH2Cl2 solution (2477 and 2479 cmϪ1, respectively). In
Table 2. ν(BH) and ν(CO) stretching frequencies for the complexes
contrast, data obtained in KBr suggest that a κ3 mode is
preferred in the solid state (2508 and 2518 cmϪ1 for 7 and 8,
respectively). This is reminiscent of the weaker interaction
between the third pyrazolyl group and the rhodium centre
revealed by the X-ray crystal structure of 8 (vide supra).
Consequently, the TpMe2 ligand is not in a genuine κ3 coor-
dination mode in 8, but the position of the third pyrazolyl
substituent induces a geometry around the boron atom that
[TpMe2Rh(CO)(PR3)] in KBr dispersions and in CH2Cl2 solutions
ν(BH) [cmϪ1
]
ν(CO) [cmϪ1
]
[TpMe2Rh(CO)(PR3)]
CH2Cl2
KBr
CH2Cl2
KBr
P(OPh)3
P(OMe)3
PPh3
PMePh2
PMe2Ph
PMe3
2479
2477
2472
2476
2473
2470
2518
2508
2468
2463
2464
2443
2009
1996
1978
1979
1973
1969
1984
1963
1965
1975
1968
1961
results in a ν(BH) band at around 2510 cmϪ1
.
As a further representative of the phosphite family in the
[TpMe2,4ClRh(CO)(PR3)] complexes, we have introduced
P(OiPr)3, the basicity of which is intermediate between
those of P(OMe)3 and PPh3. Table 3 and Figure 5 unam-
biguously show that the environment in complex 16 is
square-planar, from which we conclude that the steric hind-
rance induced by the phosphite ligand is sufficiently strong
to compensate the decrease in electron density at the metal
centre that would favour the approach of the third pyrazo-
lyl group.
The ν(CO) stretching frequencies were measured both in
solution and in the solid state for all the complexes (Tables 2
and 3). Figure 6 shows a plot of ν(CO) as a function of the
basicity of the PR3 ligand (CH2Cl2 solution). The points rep-
resenting those complexes having a κ2-bonded TpMe2 ligand
lie on a straight line with a correlation coefficient of 0.98. As
usual, the ν(CO) frequencies reliably reflect the electron den-
sity at Rh as the basicity of the ligand is varied.
Table 3. ν(BH) and ν(CO) stretching frequencies for the complexes
[TpMe2,4ClRh(CO)(PR3)] in KBr dispersions and in CH2Cl2 solu-
tions
ν(BH) [cmϪ1
]
ν(CO) [cmϪ1
]
[TpMe2,4ClRh(CO)(PR3)]
CH2Cl2
KBr
CH2Cl2
KBr
P(OPh)3
P(OiPr)3
P(OMe)3
PPh3
PMePh2
PMe2Ph
PMe3
2554
2483
2553
2482
2486
2485
2484
2483
2542
2469
2536
2477
2477
2482
2477
2483
2010
1995
2002
1984
1985
1981
1973
1973
2004
1996
1998
1988
1996
1978
1963
1977
PCy3
For complexes 9؊16, the situation is less straightforward.
A straight line can clearly be seen in Figure 6 for complexes
9؊13 and 16, which exhibit a κ2 coordination mode in solu-
tion. This is in agreement with the conclusions drawn from
the analysis of the ν(BH) frequencies. However, the ν(CO)
values for complexes 14 and 15 lie at higher frequencies.
The corresponding points in the plot do not fall on the
previous straight line, but the line plotted between these two
points is parallel to the first one. Thus, Figure 6 shows the
monotonous variations in the electron density in [κ2-
TpMe2,4ClRh(CO)(PR3)]
(lower
line)
and
[κ3-
TpMe2,4ClRh(CO){P(OR)3}] (upper line). It is important to
note that we might have expected a decrease in the ν(CO)
stretching frequency due to the coordination of the third
pyrazolyl group, i.e. a line in the plot lower than the κ2
Figure 5. The ν(BH) values for complexes 3؊16 in CH2Cl2 solution
´
plotted as a function of phosphane basicity on the Derencsenyi
scale
2692
Eur. J. Inorg. Chem. 2001, 2689Ϫ2697

Structures of a Series of [(HBPz3Me2)Rh(CO)(PR3)] and [(HBPz3Me2,4Cl)Rh(CO)(PR3)] Complexes
FULL PAPER
protons is broader, two methyl groups of a pyrazolyl group
give rise to signals at δ ϭ 2.32 and 2.75, while the four
remaining TpMe2 methyls give rise to two signals at δ ϭ
1.88 (broad) and 2.05. Thus, the NMR spectra show a non-
rigidity for this complex, although the slow-exchange limit
was not reached.
In order to assign the signals in a situation in which the
stereochemical non-rigidity of the complex would be
avoided, we protonated 4 with 1 equiv. of HBF4, a reaction
yielding [{κ2-HB(PzMe2)2(HPzMe2)}Rh(CO)(PMe2Ph)][BF4]
(4H؉).[15] The infrared spectrum of 4H؉ in KBr shows
ν(CO) and ν(BH) bands at 1987 and 2502 cmϪ1, respect-
ively, close to those of 4 (1968 and 2464 cmϪ1). Direct pro-
tonation at the rhodium centre would have led to a shift in
the position of the ν(CO) band of between 50 and 100
cmϪ1. No ν(RhϪH) band was observed. These data are
consistent with a square-planar environment for the rhod-
ium atom and a κ2 coordination mode for the TpMe2 ligand.
No spectroscopic evidence for a hydrido ligand was found,
Figure 6. The ν(CO) frequencies for complexes 3؊16 in CH2Cl2
solution plotted as a function of phosphane basicity on the De-
´
rencsenyi scale
straight line. In fact, this coordination leads to a pentacoor-
dinated geometry, in which the CO force constant is no
longer comparable to that for a square-planar geometry.
1
but a H NMR signal at δ ϭ 11.84 is consistent with the
presence of an NH group. Thus, protonation of 4 occurs on
NMR Studies; Fluxionality of Complexes 3؊15
Most of the complexes have been studied by 1H, 13C, 31P,
and 103Rh NMR, and in some cases at variable temperature
as they are fluxional. We were particularly interested in the
PMe2Ph-containing complex 4 since, in its square-planar
environment and with the third pyrazolyl group in a dang-
ling position, as a result of which the plane of symmetry is
lost, two diastereotopic methyl groups are to be expected.
However, the 1H NMR spectrum recorded at room temper-
ature (Figure 7) features a doublet due to the Me groups of
the PMe2Ph ligand (JPH ϭ 9 Hz) and two singlets at δ ϭ
2.15 and 2.21 due to the TpMe2 methyl substituents. At
183 K (Figure 8), the signal due to the phosphane methyl
the free pyrazolyl arm as expected. The methyl region of
1
the H NMR spectrum shown in Figure 9 confirms the ab-
sence of a symmetry plane in 4H؉. The two methyls of
PMe2Ph are diastereotopic and six TpMe2 methyl signals are
observed. An RhϪH coupling (1.6 Hz) is apparent from
the higher field doublet. With the aid of {1H,1H}, {1H,13C}
HMQC, and HMBC measurements and {1H,1H} NOESY
1
experiments, all the H NMR signals have been assigned,
as shown in Figure 10. It is worth noting that the two lower
field methyl peaks at δ ϭ 2.38 and 2.48 are attributable to
the 3-Me and 5-Me groups of the pyrazolyl group trans to
the CO ligand, respectively. Moreover, there is no exchange
between the two pyrazolyl groups bonded to rhodium.
1
Figure 9. H NMR spectrum of complex 4H؉; *peaks attributable
to the starting material 4
1
Figure 7. H NMR spectrum of complex 4 at 293 K
1
1
Figure 8. H NMR spectrum of complex 4 at 183 K
Figure 10. H NMR signal assignments for complex 4H؉
Eur. J. Inorg. Chem. 2001, 2689Ϫ2697
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F. Malbosc, V. Chauby, C. Serra-Le Berre, M. Etienne, J.-C. Daran, P. Kalck
FULL PAPER
Study of the Exchange Phenomenon in 4
equivalent of the appropriate phosphane ligand to
[TpMe2Rh(CO)2] and [TpMe2,4ClRh(CO)2], respectively. As
For complex 4 at 183 K (Figure 8), the two methyl proton
signals observed at δ ϭ 2.32 and 2.75 are assigned to the
pyrazolyl trans to the CO ligand, these chemical shifts being
very close to those of the pyrazolyl ligand trans to CO in
4H؉. Hence, the methyl signal at δ ϭ 1.88 is attributable to
the dangling pyrazolyl, while that at δ ϭ 2.05 is due to the
pyrazolyl trans to the phosphane. The exchange rate for the
former is slightly higher than the rate corresponding to the
coalescence temperature. At low temperature, the latter pyr-
azolyl methyl groups undergo exchange with a low activa-
tion energy. Since the pyrazolyl trans to CO is not involved
in the exchange phenomenon, we propose a square-pyram-
idal transition state, as shown in Figure 11. In a trigonal-
bipyramidal transition state, the apical pyrazolyl group
would exchange at the same rate with either of the two
equatorial groups. When the temperature is raised, the third
pyrazolyl trans to CO is also exchanged, so that the fast-
exchange limit is reached at room temperature.
shown by the X-ray crystal structures of four complexes
and by an infrared study in the solid state and in solution,
these complexes adopt a square-planar structure. In the
case of a phosphite ligand, the dangling pyrazolyl group
resides near the rhodium. The bonding mode is then inter-
mediate between κ2 and κ3. NMR studies have shown a
fluxional behaviour for all the [TpЈRh(CO)(PR3)] com-
plexes indicating that the more stable geometries are
square-planar and that the transition state is close to
square-pyramidal. Similar complexes have been prepared
by Jones et al. with isocyanide ligands, while Carmona et al.
have prepared iridium complexes with the general formula
[TpЈIr(C2H4)(L)].[16,17]
Experimental Section
General Remarks: All experiments were carried out under argon.
Reactions were performed using standard Schlenk techniques.
Solvents were HPLC quality and were distilled under dinitrogen,
toluene from sodium/benzophenone and dichloromethane from
CaSO4. They were frozen and degassed in vacuo, and were stored
over molecular sieves under argon. Pentane was purified according
to the method of Perrin and Armarego,[18] distilled from CaH2 un-
der argon, frozen, and degassed in vacuo. Commercial phosphites
and phosphanes were used without purification. Ϫ NMR spectra
were recorded with Bruker AC 200, WM 250, or AMX 400 spectro-
meters. Ϫ A PerkinϪElmer 1710 FT-IR spectrometer was used to
record the infrared spectra. Solid samples were analysed in KBr
and liquid samples were analysed between CaF2 windows (vs: very
strong, s: strong, m: medium, w: weak, vw: very weak, sh: shoul-
der). Ϫ X-ray analyses were performed with Enraf-Nonius CAD 4
or STOE IPDS diffractometers.
Figure 11. Proposed transition-state geometry for the exchange
phenomenon between two square-planar isomers of 4
HPzMe2,4Cl: This material[19] was prepared by the slow addition of
hydrazine hydrate (20 mL, 412 mmol) to 3-chloro-2,4-pentanedione
(49 mL, 411 mmol) in ethanol (600 mL) at 80 °C. The mixture was
stirred for 3 h at 80 °C. After evaporation of the ethanol, the prod-
uct was dissolved in CH2Cl2. The resulting solution was stirred
with a small amount of MgSO4 for 2 h and then filtered through
Celite. The solvent was evaporated until crystallization commenced
and then hexane (300 mL) was added. The solution was kept at 0
°C, whereupon white crystals were deposited. The crystals were
washed with hexane (3 ϫ 20 mL) at 0 °C and were then sublimed
This study shows that in a square-planar complex the
pendant pyrazolyl group readily coordinates. Decoordina-
tion of the pyrazolyl trans to PMe2Ph then provides the
free pyrazolyl, as indicated in Figure 11. This phenomenon
places the free pyrazolyl group either above or below the
plane, such that the magnetic environments of the two
methyl groups of PMe2Ph become identical on the NMR
time scale.[10]
The same exchange phenomenon has been observed
for [TpMe2Rh(CO)(PMe3)],[11] [TpMe2,4ClRh(CO)(PMePh2)],
and [TpMe2Rh(CO)(PMePh2)]. For [TpMe2Rh(CO)-
{P(OPh)3}], however, the three pyrazolyl groups are still in
fast exchange at 183 K. This is reminiscent of the results of
the X-ray diffraction analysis, where the pendant pyrazolyl
group and the rhodium centre were found to be in close
proximity, and is consistent with the proposed geometry of
the transition state and a low activation energy for the ex-
change between the square-planar isomers.
at 110 °C to yield 48.2 g (90%) of HPzMe2,4Cl. Ϫ 1H NMR (CDCl3,
Ϫ1
˜
25 °C): δ ϭ 2.24 (s, 6 H, CH3). Ϫ IR (KBr): ν ϭ 1588 cm
[ν(CϭN)].
KHBPz3Me2,4Cl: This ligand[20] was prepared by the addition of 3,5-
dimethyl-4-chloropyrazole (40.0 g, 307.2 mmol) to potassium tetra-
hydroborate (3.686 g, 68 mmol). The mixture was slowly heated to
120 °C. When the evolution of hydrogen had subsided, the temper-
ature was raised to 220 °C. The reaction was seen to be complete
when hydrogen evolution had ceased. Then, toluene (20 mL) was
quickly added to avoid agglomeration of the product. The solution
was concentrated to three-quarters of its original volume and then
hexane (50 mL) was added. The resulting solution was kept at 0
°C. White crystals were deposited, which were washed with hexane
(3 ϫ 30 mL) at 0 °C. The crystals were freed of excess HPzMe2,4Cl
by sublimation to yield 27.11 g (90%) of KHBPz3Me2,4Cl. Ϫ 1H
Conclusion
The complexes [TpMe2Rh(CO)(PR3)] and [TpMe2,4ClRh-
(CO)(PR3)] can readily be prepared by addition of one NMR (CDCl3, 25 °C): δ ϭ 2.00 [s, 9 H, CH3(PzMe2,4Cl)], 2.14 [s, 9
2694
Eur. J. Inorg. Chem. 2001, 2689Ϫ2697

Structures of a Series of [(HBPz3Me2)Rh(CO)(PR3)] and [(HBPz3Me2,4Cl)Rh(CO)(PR3)] Complexes
FULL PAPER
H, CH3(PzMe2,4Cl)]. Ϫ IR (KBr): ν˜ ϭ 2468 cmϪ1 [ν(BH)], 1541
cmϪ1 [ν(CϭN)].
ate, as shown by a ν(CO) band at 1973 cmϪ1 in the IR spectrum.
The solvent was evaporated and the product was washed at 45 °C
for 6 h, yielding 0.21 g (80%) of 4. Ϫ 1H NMR (C6D6, 25 °C): δ ϭ
1.43 (d, 6 H, PMe2, 2JPϪH ϭ 9 Hz), 2.15 [s, 9 H, CH3(PzMe2)], 2.21
[s, 9 H, CH3(PzMe2)], 5.83 [s, 3 H, CH(pz)], 7.82 (m, 5 H, PPh). Ϫ
31P NMR (C6D6, 25 °C): δ ϭ 20.13 (d, 1 P, 1JRhϪP ϭ 151 Hz). Ϫ IR
(KBr): ν˜ ϭ 2464 [ν(BH)], 1968 cmϪ1 [ν(CO)]. Ϫ C24H33BN6OPRh
(566.3): calcd. C 50.91, H 5.87, N 14.84; found C 50.31, H 5.96,
N 14.62.
KHBPz3Me2: This ligand[21] was prepared by the addition of 3,5-
dimethylpyrazole (15.0 g, 117.2 mmol) to potassium tetrahydrobor-
ate (1.405 g, 28 mmol). The mixture was slowly heated to 110 °C.
When the evolution of hydrogen had subsided, the temperature was
increased to 190 °C. The reaction was seen to be complete when the
hydrogen evolution had ceased. Then, toluene (20 mL) was quickly
added to avoid agglomeration of the product. The solution was
concentrated to three-quarters of its original volume and then hex-
ane (50 mL) was added. The resulting solution was kept at 0 °C.
White crystals were deposited, which were washed with hexane
(3 ϫ 30 mL) at 0 °C. The crystals were freed of excess HPzMe2 by
sublimation to yield 8.47 g (85%) of KHBPz3Me2. Ϫ 1H NMR
[TpMe2Rh(CO)(PMePh2)] (5): Complex 5 was prepared by adding
PMePh2 (89.7 µL, 0.48 mmol) to a solution of [TpMe2Rh(CO)2]
(0.20 g, 0.44 mmol) in CH2Cl2 (20 mL). The reaction was complete
within 15 min, as shown by IR [ν(CO) ϭ 1979 cmϪ1]. The solution
was filtered and the filtrate was concentrated to dryness. Crystal-
lization of the residue from toluene/heptane at Ϫ18 °C yielded
0.23 g (85%) of yellow crystals of 5. Ϫ 1H NMR (C6D6, 25 °C):
(CDCl3, 25 °C): δ ϭ 2.00 [s, 9 H, CH3(PzMe2)], 2.14 [s, 9 H,
Ϫ1
CH3(PzMe2)]. Ϫ IR (KBr): ν ϭ 2438 cm [ν(BH)], 1538 cmϪ1
˜
2
3
δ ϭ 1.60 (dd, 3 H, PMePh2, JPϪH ϭ 10, JRhϪH ϭ 1 Hz), 2.05 [s,
[ν(CϭN)].
9 H, CH3(PzMe2)], 2.32 [s, 9 H, CH3(PzMe2)], 5.71 [s, 3 H,
CH(PzMe2)], 7.42 (m, 10 H, PPh2). Ϫ 31P NMR (C6D6, 25 °C): δ ϭ
[Rh(µ-Cl)(CO)2]2: This complex was prepared by bubbling CO
through a solution of RhCl3·3H2O (3.0 g, 11.4 mmol) in methanol
(100 mL) at 65 °C for 20 h. The methanol was then slowly evapor-
ated by passing nitrogen through the solution. Red crystals were
obtained, which were sublimed in vacuo at 50 °C to yield 4.21 g
1
˜
30.60 (d, 1 P, JRhϪP ϭ 155 Hz). Ϫ IR (KBr): ν ϭ 2463 [ν(BH)],
1975 cmϪ1 [ν(CO)]. Ϫ UV/Vis (pentane): λmax ϭ 357 nm. Ϫ
C29H35BN6OPRh (628.3): calcd. C 55.44, H 5.61, N 13.37; found
C 52.40, H 5.16, N 12.34.
˜
(95%) of the product. Ϫ IR (KBr): ν ϭ 2102 m, 2082 s, 2020 s
[TpMe2Rh(CO)(PPh3)] (6): Complex 6 was prepared by adding solid
PPh3 (0.16 g, 0.48 mmol) to a solution of [TpMe2Rh(CO)2] (0.20 g,
0.44 mmol) in CH2Cl2 (15 mL). The reaction was monitored by IR
and was seen to be complete after 2 h [ν(CO) ϭ 1978 cmϪ1]. The
solution was then filtered and the filtrate was concentrated to dry-
ness. Crystallization of the residue from toluene/heptane at Ϫ18 °C
yielded 0.24 g (80%) of yellow crystals of 6. Ϫ 1H NMR (C6D6,
25 °C): δ ϭ 1.75 [s, 9 H, CH3(PzMe2)], 2.15 [s, 9 H, CH3(PzMe2)],
5.70 [s, 3 H, CH(PzMe2)], 7.3 (m, 15 H, PPh3). Ϫ 31P NMR (C6D6,
cmϪ1 [ν(CO)].
[TpMe2Rh(CO)2] (1): Compound
1 was prepared by adding
Me2
KHBPz3
(1.89 g, 4.15 mmol) to a solution of [Rh(µ-Cl)(CO)2]2
(1.0 g, 2.57 mmol) in CH2Cl2 (60 mL). The mixture was stirred for
4 h, in the course of which it turned from yellow-orange to brown.
The reaction was monitored by infrared spectroscopy. KCl formed
during the reaction was filtered off and washed with CH2Cl2. The
combined filtrate and washings were concentrated in vacuo,
yielding 1.9 g (90%) of 1 as a yellow-orange solid. Ϫ 1H NMR
(C6D6, 25 °C): δ ϭ 2.31, 2.37 [s, 6 H, CH3(PzMe2)], 5.77 [s, 3 H,
CH(PzMe2)]. Ϫ IR (KBr): ν˜ ϭ 2512 [ν(BH)], 2054 s, 1973 s cmϪ1
[ν(CO)]. Ϫ UV/Vis (pentane): λmax ϭ 355 nm.
25 °C): δ ϭ 42.86 (d, 1 P, 1JRhϪP ϭ 161 Hz). Ϫ IR (KBr): ν ϭ 2468
˜
[ν(BH)], 1965 cmϪ1 [ν(CO)]. Ϫ C34H37BN6OPRh (690.4): calcd. C
59.15, H 5.40, N 12.17; found C 59.48, H 5.47, N 11.90.
[TpMe2Rh(CO){P(OMe)3}] (7): Complex 7 was prepared by adding
P(OMe)3 (52 µL, 0.44 mmol) to a solution of [TpMe2Rh(CO)2]
(0.20 g, 0.44 mmol) in CH2Cl2 (15 mL). The reaction was immedi-
ate, as shown by IR [ν(CO) ϭ 1996 cmϪ1]. The solvent was evapor-
ated and the residue was washed with hexane at 0 °C and dried in
[TpMe2,4ClRh(CO)2] (2): Addition of solid KHBPz3
(2.26 g,
Me2,4Cl
5.15 mmol) to
a yellow-orange solution of [Rh(µ-Cl)(CO)2]2
(1.00 g, 2.57 mmol) in CH2Cl2 (60 mL) yielded a brown slurry after
4 h. The progress of the reaction was monitored by IR. The solu-
tion was then filtered and the removed solid was washed with
CH2Cl2. The combined filtrate and washings were concentrated in
vacuo, yielding 1.3 g (90%) of 2 as a yellow-orange solid. Ϫ 1H
NMR (C6D6, 25 °C): δ ϭ 2.12, 2.41 [s, 6 H, CH3(PzMe2,4Cl)]. Ϫ IR
(KBr): ν˜ ϭ 2544 [ν(BH)], 2088 w, 2059 s, 2020 w, 1984 s cmϪ1
[ν(CO)]. Ϫ UV/Vis (pentane): λmax ϭ 361 nm.
1
vacuo to yield 0.19 g (85%) of 7. Ϫ H NMR (C6D6, 25 °C): δ ϭ
1.92 [s, 9 H, CH3(OMe3)], 1.75 [s, 9 H, CH3(PzMe2)], 2.15 [s, 9 H,
CH3(PzMe2)]. Ϫ 31P NMR (C6D6, 25 °C): δ ϭ 142.8 (d, 1 P,
1
Ϫ1
˜
JRhϪP ϭ 266 Hz). Ϫ IR (KBr): ν ϭ 2508 [ν(BH)], 1963 cm
[ν(CO)].
[TpMe2Rh(CO){P(OPh)3}] (8): Complex 8 was prepared by adding
P(OPh)3 (253 µL, 0.96 mmol) to a solution of [TpMe2Rh(CO)2]
(0.40 g, 0.87 mmol) in CH2Cl2 (20 mL). The reaction was complete
within 2 h, as shown by IR [ν(CO) ϭ 2009 cmϪ1]. The solvent was
then evaporated and the residue was washed with hexane at 0 °C
and dried in vacuo at 45 °C for 6 h to yield 0.21 g (80%) of 8. Ϫ
1H NMR (C6D6, 25 °C): δ ϭ 2.23 [s, 9 H, CH3(PzMe2)], 2.28 [s, 9
H, CH3(PzMe2)], 5.70 [s, 3 H, CH(PzMe2)], 7.20 [m, 15 H, P(OPh)3].
[TpMe2Rh(CO)(PMe3)] (3): Complex 3 was prepared by adding
PMe3 (0.96 mL, 0.96 mmol, 1  in toluene) to a solution of
[TpMe2Rh(CO)2] (0.4 g, 0.88 mmol) in CH2Cl2 (20 mL). The reac-
tion was immediate, as indicated by a ν(CO) band at 1969 cmϪ1 in
the IR spectrum. The solvent was then evaporated and the residue
was washed with hexane at 0 °C and dried in vacuo at 40 °C for
6 h to yield 0.36 g (85%) of 3. Ϫ 1H NMR (C6D6, 25 °C): δ ϭ 0.91
2
(d, 9 H, PMe3, JPϪH ϭ 3 Hz), 1.75 [s, 9 H, CH3(PzMe2)], 2.15 [s,
Ϫ
31P NMR (C6D6, 25 °C): δ ϭ 126.40 (d, 1 P, 1JRhϪP ϭ 279 Hz).
9 H, CH3(PzMe2)]. Ϫ 31P NMR (C6D6, 25 °C): δ ϭ 5.02 (d, 1 P,
Ϫ
IR (KBr):
2518 [ν(BH)], 1984 cmϪ1 [ν(CO)].
˜
ν ϭ Ϫ
1
Ϫ1
˜
JRhϪP ϭ 145 Hz). Ϫ IR (KBr): ν ϭ 2443 [ν(BH)], 1961 cm
[ν(CO)].
C34H37BN6O4PRh (738.4): calcd. C 55.91, H 5.05, N 10.05; found
C 55.30, H 5.04, N 11.38.
[TpMe2Rh(CO)(PMe2Ph)] (4): Complex 4 was prepared by adding
[TpMe2,4ClRh(CO)(PCy3)] (9): Complex 9 was prepared by adding
PMe2Ph (62.4 µL, 0.44 mmol) to a solution of [TpMe2Rh(CO)2] solid PCy3 (0.16 g, 0.58 mmol) to a solution of [TpMe2,4ClRh(CO)2]
(0.20 g, 0.44 mmol) in CH2Cl2 (15 mL). The reaction was immedi-
(0.30 g, 0.54 mmol) in toluene (30 mL). The mixture was stirred for
2695
Eur. J. Inorg. Chem. 2001, 2689Ϫ2697

F. Malbosc, V. Chauby, C. Serra-Le Berre, M. Etienne, J.-C. Daran, P. Kalck
4 h. The solvent was then evaporated in vacuo and the yellow res- 2494 [ν(BH)], 2007 cmϪ1 [ν(CO)]. Ϫ UV/Vis (pentane): λmax
FULL PAPER
ϭ
idue was washed three times with hexane at 0 °C and dried in vacuo
to yield 0.39 g of 9. Ϫ 1H NMR (C6D6, 25 °C): δ ϭ 1.75 (m, 33 H,
PCy3), 2.15 [s, 9 H, CH3(PzMe2,4Cl)], 2.30 [s, 9 H, CH3(PzMe2,4Cl)]. Ϫ
345 nm
[TpMe2,4ClRh(CO){P(OiPr)3}] (16): Complex 16 was prepared by
adding P(OiPr)3 (0.145 mL, 0.59 mmol) to solution of
2
31P NMR (C6D6, 25 °C): δ ϭ 47.70 (d, JRhϪP ϭ 152 Hz). Ϫ IR
a
[TpMe2,4ClRh(CO)2] (0.30 g, 0.54 mmol) in CH2Cl2 (30 mL). The
volatiles were evaporated to leave a yellow powder, which was
washed three times with hexane at 0 °C and dried in vacuo yielding
0.36 g of 16. Ϫ 1H NMR (C6D6, 25 °C): δ ϭ 1.10 [d, 6 H,
(KBr): ν ϭ 2477 [ν(BH)], 1963 cmϪ1 [ν(CO)]. Ϫ UV/Vis (pentane):
˜
λmax ϭ 350 nm.
[TpMe2,4ClRh(CO)(PMe3)] (10): Complex 10 was prepared by add-
ing PMe3 (0.4 mmol, 0.4 mL of a 1  solution in toluene) to a
solution of [TpMe2,4ClRh(CO)2] (0.20 g, 0.37 mmol) in pentane
(30 mL). The orange solution immediately turned yellow. The pent-
ane was evaporated in vacuo to leave 0.20 g of 10 as a yellow solid.
Ϫ 1H NMR (C6D6, 25 °C): δ ϭ 0.87 (d, 9 H, PMe3, 2JPϪH ϭ 3 Hz),
2.09 [s, 9 H, CH3(PzMe2,4Cl)], 2.21 [s, 9 H, CH3(PzMe2,4Cl)]. Ϫ 31P
NMR (C6D6, 25 °C): δ ϭ Ϫ9.66 (d, 1JPϪH ϭ 116 Hz). Ϫ IR (KBr):
ν˜ ϭ 2477 [ν(BH)], 1963 cmϪ1 [ν(CO)]. Ϫ UV/Vis (pentane): λmax ϭ
350 nm.
OCH(CH3)2, JHϪH ϭ 6 Hz], 2.09 [s, 9 H, CH3(PzMe2,4Cl)], 2.37 [s,
3
9 H, CH3(PzMe2,4Cl)], 4.51 [m, 1 H, OCH(CH3)2]. Ϫ 31P NMR
(C6D6, 25 °C): δ ϭ 126.53 (d, 1 P, 1JRhϪP ϭ 243 Hz). Ϫ IR (KBr):
Ϫ1
˜
ν ϭ 2469 [ν(BH)], 1996 cm [ν(CO)].
[{κ2-HB(PzMe2)2(HPzMe2)}Rh(CO)(PMe2Ph)]؉[BF4]؊
(4H؉):
Complex 4H؉ was prepared by adding HBF4 (25 µL, 54% in di-
ethyl ether) to a solution of [TpMe2Rh(CO)(PMe2Ph)] (0.10 g,
0.18 mmol) in diethyl ether (10 mL) at Ϫ78 °C. The solution was
stirred for 15 min at this temperature and was then allowed to
slowly warm to 25 °C, whereupon a white product precipitated.
This solid was collected by filtration, washed with diethyl ether,
[TpMe2,4ClRh(CO)(PMePh2)] (12): Complex 12 was prepared by
adding PMePh2 (74 µL, 0.40 mmol) to
a
solution of
and dried in vacuo yielding 0.08 g of 4H؉. Ϫ H NMR (C6D6, 25
1
[TpMe2,4ClRh(CO)2] (0.20 g, 0.36 mmol) in pentane (30 mL) at 0 °C.
A yellow solid was immediately precipitated, which was collected
by filtration and dried in vacuo to afford a yellow powder. This
powder was washed three times with hexane at 0 °C and dried in
°C): δ ϭ 1.41 [dd, 3 H, JPϪH ϭ 9, JRhϪH ϭ 1.6 Hz, (PMe2Ph)],
1.47 (dd, 3 H, JPϪH ϭ 9, JRhϪH ϭ 0.5 Hz, PMe2Ph), 1.83, 2.02,
2.38, 2.43, 2.45, 2.48 [s, 3 H, Me(PzMe2)], 7.50 (m, 5 H, PPh). Ϫ
31P NMR (C6D6, 25 °C): δ ϭ 15.86 (d, JRhϪP ϭ 151 Hz). Ϫ IR
(KBr): ν˜ ϭ 2502 [ν(BH)], 1987 cmϪ1 [ν(CO)].
1
vacuo yielding 0.25 g of 12. Ϫ H NMR (C6D6, 25 °C): δ ϭ 1.56
2
3
(dd, 3 H, PMePh2, JPϪH ϭ 9, JRhϪH ϭ 1 Hz), 2.09 [s, 9 H,
CH3(PzMe2,4Cl)], 2.12 [s, 9 H, CH3(PzMe2,4Cl)], 7.08 (m, 10 H,
PMePh2). Ϫ 31P NMR (C6D6, 25 °C): δ ϭ 27.38 (d, 1 P, 1JRhϪP ϭ
157 Hz). Ϫ IR (KBr): ν˜ ϭ 2477 [ν(BH)], 1996 cmϪ1 [ν(CO)]. Ϫ
UV/Vis (pentane): λmax ϭ 352 nm.
X-ray Crystal Structure Determinations: For compound 5, data
were collected at room temperature with a STOE IPDS diffracto-
meter equipped with a graphite-oriented monochromator using
˚
Mo-Kα radiation (λ ϭ 0.71073 A). The final unit cell parameters
[TpMe2,4ClRh(CO)(PPh3)] (13): Complex 13 was prepared by adding
solid PPh3 (0.95 g, 0.36 mmol) to a solution of [TpMe2,4ClRh(CO)2]
(0.20 g, 0.36 mmol) in toluene (25 mL). The reaction was complete
within 2 h. The solvent was then evaporated in vacuo yielding
were obtained by the least-squares refinement of 5000 reflections.
An Enraf-Nonius CAD4F diffractometer was used for the data col-
lection of compound 8. For both compounds, only statistical fluc-
tuations were observed in the intensities of standard reflections
monitored throughout the course of the data collections. The struc-
tures were solved by direct methods (SIR-97)[22] and refined by
least-squares methods on F. All H atoms attached to carbon were
1
0.25 g of a yellow solid. Ϫ H NMR (C6D6, 25 °C): δ ϭ 1.75 [s, 9
H, CH3(PzMe2,4Cl)], 2.15 [s, 9 H, CH3(PzMe2,4Cl)], 7.3 (m, 15 H,
1
PPh3). Ϫ 31P NMR (C6D6, 25 °C): δ ϭ 42.86 (d, 1 P, JRhϪP
ϭ
˚
161 Hz). Ϫ 13C{1H} NMR (C6D6, 25 °C): δ ϭ 9.86, 11.81 [s,
CH3(PzMe2,4Cl)], 107.52 [s, CH(PzMe2,4Cl)], 129.66 [s, C(PzMe2,4Cl)],
127.60 (d, JPϪC ϭ 10 Hz, PPh3), 133.6 (d, JPC ϭ 12 Hz, PPh). Ϫ
IR (KBr): ν˜ ϭ 2477 [ν(BH)], 1988 cmϪ1 [ν(CO)].
introduced in calculated positions [d(CH) ϭ 0.96 A] and their
atomic coordinates were recalculated after each cycle. They were
given isotropic thermal parameters 20% higher than those of the
carbon to which they were attached. H atoms attached to boron
were located by difference Fourier syntheses and their atomic and
isotropic thermal parameters were refined. The absolute configura-
tion of 5 was determined by careful examination of the sensitive
reflections and refinement of Flack’s enantiopole parameter.[23] Le-
ast-squares refinements were carried out by minimizing the func-
tion Σw(|Fo| Ϫ |Fc|), where Fo and Fc are the observed and calcu-
lated structure factors. The weighting scheme used in the final re-
finement cycles was w ϭ wЈ[1 Ϫ {∆F/6σ(Fo)}2]2; here, wЈ ϭ 1/
ΣХ1nArTr(x) with three coefficients Ar for the Chebyshev polyno-
mial ArTr(x), where x ϭ Fc/Fc(max).[24] Models reached conver-
gence with R ϭ Σ(||Fo| Ϫ |Fc||)/Σ(|Fo|) and Rw ϭ [Σw(|Fo| Ϫ |Fc|)2/
Σw(Fo)2]1/2, giving the values listed in Table 4. The calculations were
[TpMe2,4ClRh(CO){P(OMe)3}] (14): Complex 14 was prepared by
adding P(OMe)3 (0.077 mL, 0.03 mmol) to
a solution of
[TpMe2,4ClRh(CO)2] (0.15 g, 0.27 mmol) in CH2Cl2 (20 mL). The
reaction was complete within 1 h (IR monitoring). The solvent was
then evaporated to leave a yellow powder, which was washed three
times with hexane at 0 °C and dried in vacuo to yield 0.16 g of 14.
1
Ϫ H NMR (C6D6, 25 °C): δ ϭ 1.80 [s, 9 H, (OCH3)3], 2.05 [s, 9
H, CH3(PzMe2,4Cl)], 2.41 [s, 9 H, CH3(PzMe2,4Cl)]. Ϫ 31P NMR
(C6D6, 25 °C): δ ϭ 142.24 (d, 1 P, 1JRhϪP ϭ 262 Hz). Ϫ IR (KBr):
Ϫ1
˜
ν ϭ 2536 [ν(BH)], 1998 cm [ν(CO)].
[TpMe2,4ClRh(CO){P(OPh)3}] (15): Complex 15 was prepared by carried out with the CRYSTALS program package[25] run on a PC.
adding P(OPh)3 (0.155 g, 0.591 mmol) to solution of
Graphical representations were generated using ORTEP.[26] Crys-
[TpMe2,4ClRh(CO)2] (0.30 g, 0.54 mmol) in CH2Cl2 (30 mL). The tallographic data (excluding structure factors) for the structures re-
a
reaction mixture was stirred for 4 h. The CH2Cl2 was then evapor-
ated to leave a yellow powder, which was washed three times with
ported in this paper have been deposited with the Cambridge Crys-
tallographic Data Centre as supplementary publication nos.
hexane at 0 °C and dried in vacuo yielding 0.39 g of 15. Ϫ 1H CCDC-149636 (5) and -149637 (8). Copies of the data can be ob-
NMR (C6D6, 25 °C): δ ϭ 2.06 [s, 9 H, CH3(PzMe2,4Cl)], 2.37 [s, 9
tained free of charge on application to the CCDC, 12 Union Road,
H, CH3(PzMe2,4Cl)], 7.04 [m, 15 H, P(OPh)3]. Ϫ 31P NMR (C6D6, Cambridge CB2 1EZ, U.K. [Fax: (internat.) ϩ 44-1223/336-033;
1
˜
25 °C): δ ϭ 123.05 (d, 1 P, JRhϪP ϭ 279 Hz). Ϫ IR (KBr): ν ϭ E-mail: deposit@ccdc.cam.ac.uk].
2696
Eur. J. Inorg. Chem. 2001, 2689Ϫ2697

Structures of a Series of [(HBPz3Me2)Rh(CO)(PR3)] and [(HBPz3Me2,4Cl)Rh(CO)(PR3)] Complexes
FULL PAPER
Table 4. Crystal data
5
8
empirical formula
formula mass
crystal system
space group
C29H35BN6OPRhCH2Cl2
713.26
orthorhombic
P21ca
14.222(3)
14.673(2)
15.991(7)
90.0
90.0
90.0
3337(2)
4
1.420
3 Ͻ 2θ Ͻ 50
6134
5868 (0.020)
4659 [I Ͼ 2σ(I)]
0.0271, 0.0319
1.043
C34H37BN6O4PRh
738.40
triclinic
¯
P1
˚
a, A
10.673(1)
12.239(2)
13.805(2)
87.43(1)
87.44(1)
77.57(1)
1758.1(4)
2
1.395
2.9 Ͻ 2θ Ͻ 48.4
13956
5189 (0.038)
4152 [I Ͼ 2σ(I)]
0.0355, 0.0423
1.064
˚
b, A
˚
c, A
α, °
β, °
γ, °
3
˚
V, A
Z
ρ (calcd.) g·cmϪ3
2θ range, °
no. of reflns. collected
no. of unique reflns. (Rint
reflections used
R, Rw
)
GoF
Flack’s parameter
Variable parameters
0.01(2)
385
429
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Acknowledgments
We thank the group Electrochimie de la Direction des Etudes et
´
Recherches of Electricite de France for financial support of part of
this study and for a fellowship to V. C. We gratefully acknowledge
Engelhardt-Comptoir-Lyon-Alemand-Louyot for a loan of rhod-
ium. G. Commenges, F. Lacassin, and Y. Coppel are thanked for
carrying out NMR experiments with the 400-MHz NMR spectro-
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