Rhodium complexes of 3,4-di(β-naphthyl)-2,5-diarylcyclopentadienone: Indirect detection of slowed naphthyl rotation

Article abstract of DOI:10.1016/S0022-328X(02)01624-8

In the solid state, (4a, aryl = phenyl, 4b, aryl = m-xylyl) exist as head-to-tail dimers in which each rhodium is bonded to the γ-carbon of the acetylacetonate ligand in the other half of the molecule. These dimers are also favoured in solution at low temperature, and restricted naphthyl rotation results in the formation of numerous comformers whereby the naphthyls can adopt either proximal or distal orientations. These rotamers can be detected by observation of the ¹H- and ¹³C-NMR methyl resonances in the acetylacetonate moiety. Triphenylphosphine cleaves the dimers (4a and 4b) to give the corresponding monomers, (C₄Ar₂(naphthyl)₂C=O)Rh(acac)PPh₃ (5a and 5b), and the crystal structure of 5a exhibits a proximal/distal disorder of one naphthyl substituent. The rotamers of 5a and 5b are also present in solution, and the variable-temperature ³¹P-NMR spectra yield activation enthalpies of 8.2±0.5 kcal mol^-1 for naphthyl rotation in each compound.

Full text of DOI:10.1016/S0022-328X(02)01624-8

Journal of Organometallic Chemistry 656 (2002) 243ꢂ257
/
www.elsevier.com/locate/jorganchem
Rhodium complexes of 3,4-di(b-naphthyl)-2,5-
diarylcyclopentadienone: indirect detection of slowed naphthyl
rotation
Laura E. Harrington a, James F. Britten a, Donald W. Hughes a, Alex D. Bain a,
Jean-Yves The´pot b, Michael J. McGlinchey a,*
a Department of Chemistry, McMaster University, 1280 Main Street West, Hamilton, Ont., Canada L8S 4M1
b Laboratoire de Chimie des Complexes de Metaux de Transition et Synthe`se Organique, URA CNRS 415, Universite´ de Rennes I, Campus de Beaulieu,
35042 Rennes, France
Received 9 April 2002; received in revised form 27 May 2002; accepted 27 May 2002
Abstract
In the solid state, [(acetylacetonate)-3,4-di(b-naphthyl)-2,5-diarylcyclopentadienone]rhodium(I) (4a, arylꢀ
/
phenyl, 4b, arylꢀm-
/
xylyl) exist as head-to-tail dimers in which each rhodium is bonded to the g-carbon of the acetylacetonate ligand in the other half of
the molecule. These dimers are also favoured in solution at low temperature, and restricted naphthyl rotation results in the
formation of numerous conformers whereby the naphthyls can adopt either proximal or distal orientations. These rotamers can be
detected by observation of the 1H- and 13C-NMR methyl resonances in the acetylacetonate moiety. Triphenylphosphine cleaves the
dimers (4a and 4b) to give the corresponding monomers, (C4Ar2(naphthyl)2CÄ
structure of 5a exhibits a proximal/distal disorder of one naphthyl substituent. The rotamers of 5a and 5b are also present in
solution, and the variable-temperature 31P-NMR spectra yield activation enthalpies of 8.290.5 kcal molꢁ1 for naphthyl rotation in
each compound. # 2002 Elsevier Science B.V. All rights reserved.
/
O)Rh(acac)PPh3 (5a and 5b), and the crystal
/
Keywords: Rhodiumꢂacetylacetonate dimers; Hindered naphthyl rotation; Variable-temperature NMR; X-ray crystallography
/
1. Introduction
In earlier work, we and others have shown that in
(C6Et6)ML3 systems, such as [(C6Et6)Cr(CO)(CS)
(NO)]ꢃ, the barriers to ethyl rotation (11.5 kcal
molꢁ1) and to tripodal rotation (9.5 kcal molꢁ1) are
clearly different, indicating that these fluxional pro-
cesses are not correlated [9,10]. It has also been
Recent reports from this laboratory have described
the syntheses, structures and molecular dynamics of a
number of propeller systems of the type (CnArn)z9 or
(CnArn)MLx, where nꢀ
/
5, 6, 7 and Ar is phenyl or
demonstrated
that,
in
the
series
(C5Ph5)
ferrocenyl [1ꢂ6]. The goal is to build molecules in which
/
Fe(CO)(CHO)PR3 [1], (C6Ph6)Cr(CO)3 [2], C6Ph5Fc
[3], [C7Ph7]ꢃ [5] and C7Ph6FcH [3], enlarging the central
ring (which, of course, decreases the angle between the
substituents) leads to an increase in the dihedral angle
between the peripheral and central ring planes: C5Ph5
rotations of the peripheral aryl groups and of the MLx
moiety are correlated in a fashion analogous to a bevel
gear [7]. As explicated by Mislow [8], molecules that
resemble a larger object in form only may be described
as iconic models, whereas an analogic model ‘may
resemble its object in behavior as well as form’.
Â
/
508 [11], C6Ph6 Â
/
658 [12], C7Ph7 Â808 [5]. However,
/
in the heptaphenyltropylium cation, it also results in a
loss of planarity such that the seven-membered ring
adopts a shallow boat-like structure so as to minimize
unfavorable steric interactions between ipso carbons [5].
Returning to the (C5Ph5)ML3 series, it is relatively
straightforward to derive a barrier for tripodal rotation
* Corresponding author. Tel.: ꢃ
905-522-2509
E-mail address: mcglinc@mcmaster.ca (M.J. McGlinchey).
/
1-905-525-9140x27318; fax: ꢃ1-
/
0022-328X/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 3 2 8 X ( 0 2 ) 0 1 6 2 4 - 8

244
L.E. Harrington et al. / Journal of Organometallic Chemistry 656 (2002) 243ꢂ257
/
since, when this process becomes slow on the NMR
time-scale, the degeneracy of the ring carbons is broken,
and gives rise to five individual 13C resonances [1]. It is,
however, more challenging to measure the barrier to
peripheral ring rotation since, even on a high-field
spectrometer, there is considerable peak overlap that
renders spectral simulation a non-trivial task.
good to low yields (81 and 8%, respectively), where R is
an a- or b-naphthyl substituent; one complex was
structurally characterized, but no dynamic studies were
performed [23]. We now describe the syntheses, struc-
tures and fluxional behaviour of rhodium-acetylaceto-
nate derivatives of 3,4-di(b-naphthyl)-2,5-diarylcyclo-
pentadienone (arylꢀphenyl, m-xylyl).
/
The greatly enhanced chemical shift range exhibited
by 19F nuclei, relative to that normally encountered in
1H-NMR, prompted us to consider incorporation of a
pentafluorophenyl ring that might provide a suitable
label with which to monitor peripheral ring rotation.
Consequently, we chose to synthesize C5(C6H5)4
2. Results and discussion
As depicted in Scheme 1, the cyanide-catalyzed
dimerization of b-naphthaldehyde to the corresponding
naphthoin (1), subsequent oxidation with CuSO4 in
pyridine to yield b-naphthil (2), and reaction with 1,3-
diphenylpropanone or 1,3-bis(m-xylyl)propanone [17]
gives the required 3,4-di-(b-naphthyl)-2,5-diarylcyclo-
pentadienones (3a and 3b).
(C6F5)OH*
/a
potential precursor to C5(C6H5)4-
(C6F5)Br, and thence to [h5-C5(C6H5)4(C6F5)]-
Fe(CO)2Br. Although 1,2,3,4-tetraphenyl-5-pentafluor-
ophenylcyclopentadienol has now been prepared and
characterized by X-ray crystallography, the yield is
unacceptably low, and the major product arises from
1,6-addition of C6F5Li to tetraphenylcyclopentadienone
(tetracyclone) [13]. In related work, Deck [14,15] has
demonstrated the viability of using a C6F5 group to
probe the barrier to peripheral ring rotation in com-
2.1. X-ray crystallographic results
Treatment of 3a and 3b with (acetylacetonato)bis
(ethylene)rhodium(I) gave the desired complexes (4a and
4b), whose structures are shown in Fig. 1. Both
molecules adopt a head-to-tail dimeric arrangement in
which the rhodium is bonded to the g-carbon of the
acetylacetonate ligand, as previously found for the
plexes of the type [C5(C6F5)nH5ꢁn]MLx, where nꢀ2, 3
/
or 4, and a corresponding penta-aryl derivative has
recently appeared in a patent [16]. Very recently, The´pot
and Lapinte have reported a convenient route to penta-
arylcyclopentadienols containing either ortho- or meta-
difluorophenyl rings [17]; these ligands hold promise of
providing useful probes for the dynamics of
(C5Ar5)MLn systems.
analogous (C4Ph4CÄ/O)Rh(acac) complex (5) and simi-
In an attempt to increase the steric demand of the
peripheral rings, we chose to incorporate naphthyl
substituents, which effectively serve as phenyl groups
with a ‘labeled edge’, allowing for the distinction
between syn and anti isomers. A few studies have been
aimed towards the development of naphthyl substituents
for use as controls over structure and reactivity, as well
as peripheral substituents in propeller structures [18ꢂ
/
28]. In addition, several a- and b-naphthyl substituted
benzenes have been synthesized, and, in some cases,
barriers to naphthyl rotation have been reported [24ꢂ
/
27]. A notable application of the steric hindrance offered
by a naphthyl group is the chiral cyclopentadienyl
ligand proposed by Baker et al. [28] in which the
constrained motion of an a-naphthyl substituent would
restrict the site of metal coordination and generate a
chiral cyclopentadienyl metal complex with the potential
for use in asymmetric synthesis.
While numerous metal complexes of tetracyclone
have been described [29], we are aware of only one
naphthyl analogue, even though the syntheses of several
potential ligands are known from cursory early reports
[30]. A number of years ago, Rausch et al. reported the
synthesis of a series of (h5-C5H5)Co(h4-C4Ph2R2) and
Scheme 1. Synthesis of aryl-substituted cyclopentadienone complexes
of Rh(acac)(PPh3), where aryl is phenyl, m-xylyl or b-naphthyl.
(h5-C5H5)Co(h4-C5Ph2R2CÄ
/O) complexes produced in

L.E. Harrington et al. / Journal of Organometallic Chemistry 656 (2002) 243ꢂ
/257
245
Fig. 1. Molecular structures of the dimers [(C4Ar2(b-naphthyl)2Cꢀ
/
O) Rh(acac)]2, Arꢀphenyl, m-xylyl, (4a, 4b; 30% thermal ellipsoids), with
/
hydrogen atoms omitted for clarity.
lar compounds [29a,31ꢂ
rhodium in one monomer to the g-carbon of the
acetylacetonate ligand of the other monomer is
/
36]. The bond distance from the
corresponding interplanar angle between the plane of
the pentamethylcyclopentadienyl ring and that contain-
ing O(1)Ã
/
RuÃO(2) in the [Cp*Ru(acac)]2 system is 588
/
˚
2.353(9) in 4a and 2.389(6) A in 4b, values comparable
[31,32].
˚
to the 2.39(1) A found in the tetracyclone analogue, 4c
[29a]. These may also be compared with the increased
˚
bond length of 2.408 A displayed in the [Cp*Ru(acac)]
Interestingly, in 4a, the two naphthyl ligands on the
cyclopentadienone ring of one monomeric moiety are
arranged distal with respect to dimeric core, whereas the
naphthyl rings in the other half of the molecule adopt
proximal orientations, which precludes the presence of a
C2 axis in the dimer. In addition, 4a contains open
channels between the dimeric units, which are partially
occupied by dichloromethane solvent molecules. The
solvent is structurally essential, as the crystals rapidly
collapse to powder if the solvent is allowed to evaporate.
In 4b, there is one naphthyl group distal and one
proximal in each monomer, and the molecule possesses
an inversion center. Crystals of 4b do not have the same
structural dependence on the presence of solvent;
however, disordered, partially occupied solvent mole-
cules are present in the structure.
In continuation of our investigation of the chemistry
of these electrophilic species, 4a and 4b were allowed to
react with two equivalents of triphenylphosphine at
room temperature to give 5a and 5b, respectively, in
which the dimers have been cleaved upon addition of the
phosphine ligand. The crystal structures of these mono-
mers appear as Fig. 2, and as before, the aryl groups in
the a-positions of the cyclopentadienone rings exhibit a
‘cup-shaped’ orientation.
˚
dimer [31,32], and the decreased 2.287(6) A found in the
dication [{Cp*Rh(acac)}2]2ꢃ synthesized by Maitlis and
coworkers [35]. The aryl substituents in the a-positions
of the cyclopentadienone rings of 4a and 4b are arranged
in a ‘cup-shaped’ geometry around the metal, the latter
being in a square pyramidal environment in which the
centers of the two cyclopentadienone double bonds and
the acetylacetonate oxygens form a square plane capped
by the g-carbon of the other monomer.
The RhÃ
carbons C(2)Ã
in the dimers; however, the Rh(1)Ã
longer, 2.412(12) [2.412(7) A] for 4a (4b), in agreement
with previous studies [29a]. The carbonyl carbon is bent
away from the plane of the cyclopentadienone ring by
19.5(1) [16.0(3)8], similar to that found for the tetra-
/
C bond distances to the cyclopentadienone
˚
/
C(5) range from 2.116(10) to 2.155(6) A
/
C(1) distance is much
˚
cyclone analogue (178). The Rhꢂacac ring forms an
/
angle of 68.9(4) [69.8(3)8] with the plane of the
cyclopentadienone ring carbons, closely approximating
the 658 found in the tetracyclone derivative, but
significantly deviating from the near orthogonal ar-
rangement found in the 3-ferrocenyl-2,4,5-triphenylcy-
clopentadienone analogue (888) [29a]. The latter
complex is monomeric, presumably as a response to
the steric requirements of the ferrocenyl substituent. The
As before, the rhodium is in a square-based pyramidal
environment, and the distances from rhodium to C(2)
through C(5) in the cyclopentadienone ring range from

246
L.E. Harrington et al. / Journal of Organometallic Chemistry 656 (2002) 243ꢂ257
/
Fig. 3. Bird’s eye view of 5a, showing one disordered b-naphthyl
substituent.
is disordered and exhibits both distal and proximal
orientations in a 55:45 ratio, respectively. Similar
behaviour has been reported in a molybdenum complex
containing the 1-(2,5-dimethoxyphenyl)-2,3,4,5-tetra-
phenylcyclopentadienyl ligand, (8) [38,39]. In the di-
meric species 9, the dimethoxyphenyl groups are
apparently rigid, and no barrier to rotation was
determined, while in complex 10, this aryl rotation
barrier was reported to be 16.3 kcal molꢁ1. The solid
state structure of 10 revealed a disorder in which one of
the dimethoxyphenyl groups was found in two con-
formations with occupancies of 0.24 and 0.76 (Scheme
2). In 5b, both naphthyl groups are oriented distal to the
metal.
It is interesting to note the presence of several
combinations of naphthyl orientations in the four
crystal structures: in 4a, one monomer has both
naphthyls distal, the other monomer has both proximal;
in 4b, both monomers contain one distal and one
proximal naphthyl. In the monomer 5a, one naphthyl
Fig. 2. Molecular structures of (C4Ar2(b-naphthyl)2CÄ
/
O) Rh
(acac)(PPh3), (a) Arꢀphenyl, (b) Arꢀm-xylyl, (5a, 5b; 30% thermal
/
/
ellipsoids), with hydrogen atoms omitted for clarity.
˚
2.141(11) to 2.177(3) A; the RhÃ
/
C(1) distance is 2.450(3)
˚
[2.448(13) A] in 5a (5b). The carbonyl group is bent
away from the rest of the molecule by 21.0(3) [22(1)8],
slightly greater than in the dimer. The RhÃ
/
P distance is
˚
2.3861(10) [2.402(4) A], somewhat longer than the
conventional range of literature values (2.201ꢂ
/
2.303
P distance
˚
A) [37], and significantly longer than the RuÃ
/
˚
(2.245 A) found in Koelle’s Cp*Ru(acac)(P(OMe)3)
system [31]. In contrast to 4a, 4b and other dimeric
structures, the plane of the acac ring in 5a (5b) makes a
much smaller angle of 37.3(2) [37.8(6)8] with the C(2)Ã
/
C(5) plane of the cyclopentadienone ring, presumably as
a result of the steric bulk of the added phosphine. This
observation parallels the behaviour of Cp*Ru(a-
cac)(P(OMe)3) which also forms a corresponding inter-
planar angle of 378 [31].
A particularly interesting feature of the crystal
structure of 5a (Fig. 3) is that one of the naphthyl rings
Scheme 2. Molecules 9 and 10.

L.E. Harrington et al. / Journal of Organometallic Chemistry 656 (2002) 243ꢂ
/257
247
is distal and one is disordered proximal/distal, while 5b
contains two distal naphthyl groups. The various
naphthyl conformations observed in the solid state
illustrate the ability of these complexes to accommodate
the bulk of the naphthyl groups, and support the
contention that many of these rotamers are present in
solution at low temperature, at the limits of restricted
naphthyl rotation, in the absence of crystal packing
forces.
2.2. Variable temperature NMR results
1
The H- and 13C-NMR spectra of 4a and 4b at room
temperature each showed a single methyl signal for the
acac ligand, and the expected, well-resolved resonances
readily assignable to the b-naphthyl and phenyl, or m-
xylyl, substituents. However, in both systems, cooling
the sample from 303 to 263 K resulted in the broadening
1
and dispersion of the H and 13C aromatic resonances.
Fig. 4. Variable-temperature 500 MHz 1H-NMR spectrum of 4b in the region of the m-xylyl-methyl and acac-methyl protons. (b): Variable-
temperature 125 MHz 13C-NMR spectrum of 4b in the region of the m-xylyl-methyl and acac-methyl carbons.

248
L.E. Harrington et al. / Journal of Organometallic Chemistry 656 (2002) 243ꢂ257
/
Moreover, as the temperature was reduced, the initially
sharp 1H peaks at 2.13 and 2.16 ppm for the acacꢂ
not anticipate the presence of detectable quantities of
other rotamers, since the ‘pseudo-tripod’ cannot adopt
conformers of comparable energy. This leaves restricted
naphthyl rotation as the only viable explanation for the
/
methyl protons in 4a and 4b respectively, broadened
and gradually moved to markedly lower frequency.
Furthermore, in both molecules, as shown in Fig. 4a
for 4b, further cooling induced the splitting of the broad
peak for the acac methyl protons and, at 173 K, several
peaks centered around 1.35 ppm began to emerge.
plethora of acacꢂmethyl resonances.
/
If the dimer of 4b shown in Fig. 1 were the only
isomer present in solution, then two methyl signals
would be anticipated, as the molecule would have
effective Ci symmetry. The observation of multiple
methyl resonances indicates not only that rotation of
the naphthyls is hindered, but also that several con-
formations can co-exist at low temperature. Table 1 and
Plate 1 list the seven possible isomers of the dimers (each
Similar splitting behaviour is also observed in the 13
C
regime, whereby the resonance of the acac methyl
carbon at 27.7 ppm (for 4b) clearly splits into several
peaks (Fig. 4(b)). The anticipated observation of a RhÃ
C coupling for the dimer is prevented by the monomerꢂ
dimer exchange process. Thus, a JRhÃC of ca. 10 Hz, as
seen in RhÃCp* systems [35], would not be discernible,
even at slow monomerꢂdimer exchange rates.
/
/
of which bears four acacꢂmethyl groups) that may be
/
/
present as a result of restricted naphthyl rotation. If all
rotamers were equally probable, thus giving rise to a
statistical distribution, there would be sixteen equally
intense methyl singlets. At 173 K, the 1H- and 13C-NMR
/
It is apparent that the methyl groups of the acetyl-
acetonate ligand serve as a probe for the observation of
the fluxional behaviour of the naphthyl groups. In order
for the protons and carbons of the acac methyl groups
to split, they must be in different magnetic environments
at low temperature. Thus, assuming that 4a and 4b
spectra of 4a and 4b exhibit several acacꢂmethyl
/
environments, and we suggest that the numerous peaks
originate from the presence of the more energetically
favourable rotamers, with intensities governed by the
relative fraction of each isomer present. This interpreta-
exhibit rapid monomerꢂdimer equilibria at room tem-
/
1
perature (analogous to the behavior of Koelle’s
Cp*Ru(acac) system) [36], then time-averaged NMR
spectra would be expected in which there is only one
tion is supported by the variable-temperature H-NMR
behaviour of (tetracyclone)Rh(acac), 4c, whose acacꢂ
/
methyl signal likewise exhibits a gradual shielding
upon cooling (d 2.09 ppm at 303 K and 1.12 at 163
K) which never loses its singlet character. The complex-
ity of the spectra of 4a and 4b preclude the determina-
tion of activation parameters, since the assignment of
each line to its respective rotamer and the determination
of the relative population of the isomers is not viable
[40].
peak for the acacꢂmethyl protons and carbons, and all
/
the naphthyl environments should also be equivalent.
However, at lower temperatures, as the dimer concen-
tration increases, restricted rotation of the naphthyl
1
groups becomes evident. One obvious effect on the H-
NMR spectra is the gradual shift to lower frequency of
the acacꢂmethyl resonances as the temperature is
/
reduced; this phenomenon is readily explained in terms
of the increasing fraction of dimer in the sample,
whereby the methyl protons lie in the aromatic shielding
region of the aryl substituents in the other half of the
molecule.
With the goal of determining a barrier for naphthyl
rotation, variable-temperature NMR data were also
acquired for 5a and 5b. In the spectra of both
complexes, the peaks for the acacꢂmethyl protons and
/
carbons do not split, even at 163 K. However, as
illustrated in Fig. 5, the 31P-NMR spectrum of 5a (5b)
yields a doublet with JRhÃP of 165.6 (167.3 Hz) at room
temperature, which decoalesces into two doublets at 163
K.
There are several possible explanations for the origin
of the 31P splitting at low temperature, (a consequence
of the use of an indirect method of observation): (i)
hindered rotation of the metal tripod, (ii) restricted
Although a barrier to Rh(acac) rotation relative to a
tetra-substituted cyclopentadienone ring has been re-
ported [29a], this involved the replacement of a periph-
eral phenyl group in tetracyclone by a bulky ferrocenyl
substituent. This not only prevents dimer formation but
also provides the asymmetrical substitution required for
the examination of the fluxional behaviour of the
acetylacetonate group. In that case, two methyl signals
1
were observed at low temperature in the H- and 13C-
rotation about the PÃ/Cipso bonds of the triphenylpho-
NMR, yielding a barrier to acac rotation of 12.5 kcal
molꢁ1. We note, however, that the fluxional process
merely interconverts isoenergetic rotamers. In both 4a
and 4b, and for the tetracyclone analogue, 4c, the solid
state structures are such that the ketonic unit eclipses the
sphine propeller, and (iii) restricted naphthyl rotation.
Molecular modeling studies suggest that there is no
significant steric barrier to tripodal rotation attributable
to the presence of the naphthyl groups, which might
have been expected to interfere with the bulky triphe-
nylphosphine ligand during rotation. Moreover, a vari-
able-temperature study of the (tetracyclone)Rh-
(acac)(PPh3) analogue, 5c, shows no splitting in either
the proton or phosphorus NMR spectra at low tem-
Rh(1)Ã/C(7A) bond. EHMO calculations reveal that this
rotamer is favoured because of better overlap between
the frontier orbitals of the Rh(acac) and the p system of
the cyclopentadienone. As a result of this, one would

L.E. Harrington et al. / Journal of Organometallic Chemistry 656 (2002) 243ꢂ
/257
249
Table 1
Possible isomers of 4a and 4b
Isomer
Point
group
Naphthyl orientation
Number of identical isomers,
or enantiomers
Number of methyl
resonances
Predicted intensities of
methyl peaks
A
B
C
C2h
C2h
Cs
All distal
All proximal
1
1
2
1
1
2
4
4
4,4
Upper half, both distal; lower half,
both proximal; or vice versa
3 distal, 1 proximal
D
E
C1
C1
C2
Ci
4
4
2
2
4
4
2
2
4,4,4,4
4,4,4,4
4,4
3 proximal, 1 distal
F
1 distal, 1 proximal on each ring
1 distal, 1 proximal on each ring,
with an inversion center
G
4,4
Plate 1. Possible isomers of 4; P and D represent Proximal and Distal b-naphthyl substituents, respectively, R is a phenyl or m-xylyl substituent.
Only one enantiomer of the chiral compounds is shown.
perature. This observation supports the view that the
fluxional behavior is attributable to restricted rotation
of the naphthyl groups, rather than slowed rotation of
the Rh(acac)(PPh3) unit with respect to the cyclopenta-
dienone ring. The substitution of two phenyl groups by
two naphthyl substituents (which effectively act as meta-
substituted phenyl rings) is not likely to create enough
steric strain to drastically increase the barrier to tripodal

250
L.E. Harrington et al. / Journal of Organometallic Chemistry 656 (2002) 243ꢂ
/257
Table 2
Crystallographic collection and refinement parameters for 4a, 4b, 5a and 5b
4a 4b
5a
5b
Empirical formula
Molecular weight
Description
C
84H62O6Rh2×(CH2Cl2)2.54 C46H39O3Rh×(CH2Cl2)0.70 C60H46O3PRh×CH2Cl2
C64H54O3PRh×C6H14
1589.13
red needle
0.1ꢄ0.22ꢄ0.5
173(2)
802.13
1033.77
yellow needle
0.20ꢄ0.06ꢄ0.03
173(2)
1005.01
orange plate
0.21ꢄ0.09ꢄ0.03
173(2)
red plate
0.10ꢄ0.10ꢄ0.08
173(2)
Size (mm3)
Temperature (K)
Crystal system
Space group
tetragonal
I41/a
monoclinic
P21/c
Monoclinic
P21/n
Monoclinic
P21/n
˚
a (A)
26.633(7)
26.633(7)
43.698(16)
90
15.698(7)
21.468(12)
12.646(7)
90
10.084(3)
21.330(6)
23.082(6)
90
12.300(5)
20.625(8)
22.487(9)
90
˚
b (A)
˚
c (A)
a (8)
b (8)
g (8)
90
90
108.228(15)
90
96.795(4)
90
102.156(6)
90
3
˚
V (A )
Z
Calculated density
30 995(16)
16
1.362
4047(4)
4
1.316
4930(2)
4
1.393
5577(4)
4
1.300
(g cmꢁ3
Scan mode
)
f- and v-scans
12 973
0.654
f- and v-scans
1654
0.553
f- and v-scans
2128
0.534
f- and v-scans
2288
0.383
F(000)
Absorption coefficient
(mmꢁ1
)
u range (8)
Index ranges
1.43ꢂ
/
25.00
1.37ꢂ
/
27.64
1.30ꢂ
/
27.50
1.35ꢂ20.80
ꢁ135h 513, ꢁ225k 522,
ꢁ245l 524
/
ꢁ335h 534,
ꢁ325k 534,
ꢁ565l 556
11 4275
ꢁ205h 520,
ꢁ275k 525,
ꢁ155l 516
35 434
ꢁ135h 513,
ꢁ245k 527,
ꢁ295l 527
46 593
Reflections collected
Independent reflections
Data/restraints/params
Goodness of fit on F2
(all)
27 351
5818
13 652
12 531/0/930
1.385
9296
9294/0/484
1.060
11 274
11 274/28/817
1.011
5643/0/327
0.940
Final R (I ꢀ2s(I))
R indices (all data)
Transmission (ratio of
max to min)
R1ꢀ0.0969, wR2ꢀ0.2646 R1ꢀ0.0782, wR2ꢀ0.1969 R1ꢀ0.0423, wR2ꢀ0.0930 R1ꢀ0.0711, wR2ꢀ0.1571
R1ꢀ0.1808, wR2ꢀ0.3897 R1ꢀ0.1685, wR2ꢀ0.2339 R1ꢀ0.0788, wR2ꢀ0.1044 R1ꢀ0.1916, wR2ꢀ0.2400
0.871372
0.764648
0.529629
0.876043
Largest difference peak
and hole
4.223 and ꢁ1.215
1.190 and ꢁ0.831
0.456 and ꢁ0.484
0.678 and ꢁ0.551
ꢁ3
˚
(e A
)
Fig. 5. Variable-temperature 202 MHz 31P-NMR spectra of 5a and 5b, respectively.

L.E. Harrington et al. / Journal of Organometallic Chemistry 656 (2002) 243ꢂ
/257
251
rotation, especially if the naphthyl groups can rotate
and move to accommodate the bulk of the triphenylpho-
sphine. However, EHMO calculations suggest that there
is a significant electronic barrier to tripodal rotation in
rotation in order for the different environments of the
phosphorus atoms to be distinguishable. Similarly,
restricted RhÃ
/
P rotation alone would not result in
decoalescence of the phosphorus spectrum.
the PPh3 systems (Â
/
12 kcal molꢁ1). This is a con-
Consequently, we assert that the observation of the
second 31P-NMR doublet is consistent only with the
slowed interconversion of the naphthyl groups between
their two favoured conformations (distal/distal and
distal/proximal). The presence of the two rotamers
would place the phosphorus nuclei in different environ-
ments, thus influencing the appearance of the 31P-NMR
spectrum. Activation enthalpies for the naphthyl rota-
tion processes in 5a and 5b were derived from Eyring
plots prepared by lineshape analysis of the 31P spectra,
sequence of the less favourable overlap of the frontier
orbitals on the cyclopentadienone ring with those of the
Rh(acac)(PPh3) unit when the tripod is rotated through
1808 from that observed crystallographically. Slowed
tripodal rotation would merely result in the formation
of a single rotamer, with essentially no detectable
concentration of any other, and only one peak would
be expected in the 31P-NMR spectrum. Thus, restricted
tripodal rotation is not the origin of the fluxional
behaviour in these systems.
yielding barriers of 8.29
This may be compared with the reported barriers of
8ꢂ
10 kcal molꢁ1 for pentafluorophenyl rotation in
[1,2,4-(C6F5)3C5H2]2Fe and [1,2,4-(C6F5)3C5H2]Re-
(CO)3 [14] and 99
1 kcal molꢁ1 for hindered phenyl
/
0.5 kcal molꢁ1 (Fig. 6).
There is precedence in the literature for the observa-
tion of restricted rotation about the PÃ
/
Cipso bonds of
/
the triphenylphosphine ligand [41ꢂ54]. In the solid state
/
[41] and in solution [42], PPh3 adopts a chiral, propeller
conformation in which the helix can be oriented in a
clockwise or anti-clockwise orientation, resulting in a
pair of enantiomers. Conformational analyses of the
dynamic behaviour of triphenylphosphine have been
performed by Mislow [43] and Kurland [44], and the
/
rotation in [C5(C6H5)4H]2Fe [55]. Restricted aryl rota-
tion in other substituted cyclopentadienones has been
reported; for instance, 1H- and 13C-NMR at 233 K were
used to determine barriers of Â
/
15 and Â
20 kcal molꢁ1
/
for the rotation of the a- and b-substituents, respec-
tively, in tetra-o-tolylcyclopentadienone [40]. Hay-
interconversion of enantiomers or full rotation about PÃ
/
Cipso bonds have been determined to involve cooperative
motion of the phenyl substituents [41,45]. The use of
PR3 as a probe to monitor dynamic behaviour in other
woodꢂFarmer and Battiste observed two signals in the
/
methyl region of the room temperature 1H-NMR of 2,4-
diphenyl-3,5-bis(o-tolyl)cyclopentadienone, and deter-
regions of a molecule has also been established [1,47ꢂ
/
mined a barrier of 21.89
0.4 kcal molꢁ1 for o-tolyl
rotation [56]. In 1979, Rausch et al. observed six methyl
/
54], and we have previously suggested that the ligand
may not serve as an innocent probe, but may also give
rise to different conformers at low-temperature [1].
Barriers to rotation of tri-substituted phosphines in
many organometallic derivatives have been established
1
peaks in the H-NMR of cyclopentadienyl cobalt 3,5-
diphenyl-2,4-bis(mesityl)cyclopentadienone, however,
no variable-temperature studies were performed to
determine a barrier to mesityl rotation [57]. It has
been established that substitution in the ortho position
of the peripheral groups in these sterically encumbered
molecules dramatically increases barriers to rotation,
and that meta-substitution merely reflects the buttres-
sing effects of the ortho-protons [6,58]. A b-naphthyl
group acts effectively as a meta-substituted phenyl
group, thus the barrier to rotation would be expected
to be much lower than in these ortho-substituted
cyclopentadienones. However, a-naphthyl substituents
would be expected to offer significantly greater steric
hindrance and rigidity, and studies of the extension of
this chemistry to these bulky groups are ongoing.
[45ꢂ48], and several studies have shown that steric,
/
rather than electronic, factors are dominant in determin-
ing their magnitude [49]. Examples include an upper
barrier of 7.6 kcal molꢁ1 for PÃ
/Cipso rotation in
(C5H5)Fe(CO)(CN)(PPh3) estimated by Faller, et al.
[48] and 10.3 kcal molꢁ1 determined by Davies, et al.
[45] for (C5H5)Fe(CO)(COCH3)(PPh3).
In 5a and 5b, cessation of PÃ
/
Cipso rotation would
result in the formation of enantiomers, as expected,
however, these would not be differentiable by NMR
without the presence of another source of chirality in the
molecule, that is, the creation of diastereomers. As
described by Willem [40], the ‘fundamental inability of
NMR spectroscopy to distinguish enantiomers or en-
antiotopic sites in an achiral environment’ prevents the
observation of this behaviour without another chiral
center in the molecule. This necessarily involves the
restricted rotation of the naphthyl substituents, which
would result in the formation of diastereomers and
allow for the differentiation of phosphorus environ-
Finally, there is another interesting feature of the 31P-
NMR spectra of 5aꢂc that merits comment; the spectral
/
lineshapes exhibited a significant temperature and
magnetic field dependence (Fig. 7). At room tempera-
ture, the 202 MHz 31P spectra exhibited low intensity,
broad, asymmetrical peaks, however, as the temperature
was decreased, the peaks became sharper and more
symmetrical. The 31P spectra were also run on a lower
field instrument (81 MHz), and the peaks were notice-
ably sharper.
ments by NMR. Thus, even if PÃ
/
Cipso rotation is
slowed, the naphthyl groups must also exhibit restricted

252
L.E. Harrington et al. / Journal of Organometallic Chemistry 656 (2002) 243ꢂ257
/
3. Conclusions
The incorporation of naphthyl substituents into
cyclopentadienoneꢂrhodium complexes results in the
/
formation of mixtures of rotamers in which the
naphthyls can adopt either proximal or distal orienta-
tions. In the dimers 4a and 4b, slowed naphthyl rotation
can be detected by observation of the acetylacetonate
1H-NMR methyl resonances. In the phosphine com-
plexes 5a and 5b, the variable-temperature 31P-NMR
spectra yield enthalpies of activation for naphthyl
Fig. 6. Example of simulated lineshape spectra using the MEXICO
program for 5a.
rotation of 8.29
0.5 kcal molꢁ1. Efforts are continuing
/
to synthesize poly-arylated ligands in which all the
peripheral substituents are naphthyls, and these will be
the subject of future reports.
4. Experimental
4.1. General methods
All reactions involving organometallic reagents were
carried out under an atmosphere of dry nitrogen
employing conventional benchtop and glovebag techni-
ques. Tetrahydrofuran solvent was dried according to
standard procedures before use [61]. Silica gel (particle
Fig. 7. Field strength and temperature dependence of the 31P-NMR
lineshape for 5a.
size 20ꢂ45 mm) was employed for flash column chro-
/
1
matography. H- and 13C-NMR spectra were obtained
on a Bruker Avance DRX-500 spectrometer at 500.13
and 125.76 MHz, respectively, and were referenced to
the residual proton signal, or 13C signal, of the solvent.
The exact cause of this behaviour has not been
established, but the data suggest that it is the result of
the influence of the chemical shift anisotropy (CSA)
relaxation mechanism. The shape of the 31P lines
improves at lower field, which could be attributable
Assignments were based on standard 1HÃ
/
1H and
1HÃ13C two-dimensional techniques. 31P-NMR spectra
/
were acquired at 202.46 MHz and were externally
referenced to the 31P signal of 85% H3PO4 in D2O. As
a result of the poor resolution and asymmetry of the 31
P
either to the decreased spinꢂspin (T2) relaxation due to
/
peaks at room temperature (r.t.) (as discussed above),
the spectral data quoted below were collected at 243 and
163 K, which allowed for accurate peak assignment and
coupling constant determination in both 5a and 5b.
Mass spectra were measured on a Finnigan 4500
spectrometer by direct electron impact (DEI) or direct
chemical ionization (DCI) with NH3, as well as electro-
spray (ESI). Infrared spectra were recorded on a Bio-
Rad FTS-40 spectrometer. Melting points (m.p.) (un-
the CSA of the phosphorus, or to reduced scalar
relaxation from the CSA-induced T1 of the rhodium.
CSA relaxation is also implied by the asymmetry of the
doublet, which is characteristic of a relaxation cross-
term between dipolar coupling and CSA. This is a well-
established effect [59] that has recently become impor-
tant as the basis for the TROSY experiment in the
structure determination of large biological macromole-
cules [60]. The unusual effect of the sharpening of the
phosphorus lines at lower temperatures suggests that the
rhodium T1 may be below its temperature minimum,
and may be getting longer with a reduction in both
temperature and motion. Direct NMR measurements of
the rhodium would be necessary to establish this
proposition. This effect is not present at low tempera-
ture, thus does not impede the observation of splitting
behaviour.
corrected) were determined on a FisherꢂJohns melting
/
point apparatus. Elemental analyses were performed by
Guelph Chemical Laboratories, Guelph, Ont., Canada.
The reagents b-naphthaldehyde and 1,3-diphenylpro-
panone were used as received from commercial sources.
(Acetylacetonato)bis(ethylene)rhodium(I) [62], (acetyl-
acetonato)(2,3,4,5-tetra-phenylcyclopentadienone) rho-
dium(I) (4c) [29a] and 1,3-bis(m-xylyl)propanone [17]
were prepared according to literature procedures.

L.E. Harrington et al. / Journal of Organometallic Chemistry 656 (2002) 243ꢂ
/257
253
4.2. 1,2-Di-(b-naphthyl)-2-hydroxyethanone, b-
naphthoin (1)
15], 190 (17), 172 (C11H8O2, 52), 155 (C10H7CO, 100),
144 (C10H8O, 19), 80 (40).
In an adaptation of the literature procedure for the
synthesis of benzoin [63], b-naphthaldehyde (10.12,
0.06) and NaCN (1.92 g, 0.04 mmol) were dissolved in
20 ml H2O and 40 ml ethanol, then stirred under reflux
for ca. 30 min, resulting in the formation of a thick,
yellow precipitate, which was filtered by suction and
dried to give 1 (8.23 g, 0.03 mol; 88%) as a pale yellow
4.4. 3,4-Di-(b-naphthyl)-2,5-di-phenylcyclopentadienone
(3a)
Analogous to the synthesis of tetracyclone [66], b-
naphthil (2) (4.73 g, 0.02 mol) and 1,3-diphenylpropa-
none (3.51 g, 0.02 mol) were dissolved in 125 ml of hot
ethanol with stirring. Once the reaction mixture began
to reflux, KOH (0.85 g, 0.02 mol) dissolved in ca. 10 ml
hot ethanol, was added dropwise through the top of the
condenser to the stirring mixture. The solution darkened
immediately from yellow to deep red, eventually turning
powder, m.p. 124ꢂ
/
126 8C (lit. [64] 125ꢂ126 8C).
/
Further concentration of the reaction mixture gave an
additional 0.77 g of product, resulting in an overall yield
1
of 96%. H-NMR (200 MHz, CD2Cl2): d 8.53 (s, 1H,
naphthyl-H1), 8.03ꢂ
/
7.44 (m, 13H, naphthyl rings), 6.31
very dark redꢂpurple. The solution was stirred for ca. 30
min, then cooled and the solvent was removed under
vacuum to leave 3a (4.42 g, 9.13 mmol; 61%) as a dark
/
(s, 1H, CH), 4.68 (br, 1H, OH). 13C-NMR (50 MHz,
CD2Cl2): d 199.3 (CO), 137.2, 136.1, 133.8, 133.5, 132.6,
131.3 (naphthyl C’s), 131.6, 130.0, 129.4, 128.9, 128.3,
128.0, 127.7, 127.3, 126.9, 125.2, 124.5 (naphthyl CH’s),
purple powder, m.p. 227ꢂ
/
230 8C (lit. [30c] 227ꢂ
/
229 8C). Calc. for C37H24O×
/
H2O: C, 88.41; H, 5.22.
Found: C, 88.21; H, 4.68%. IR (CH2Cl2): nmax (cmꢁ1) at
76.7 (CHÃ
(C10H7CO, 99), 127 (C10H7, 100), 101 (C8H5, 13), 77
(C6H5, 24). MS (DCI; m/z (%)): 330 (MꢃHꢃNH3,
1%), 313 (Mꢃ OH, 100),
H, 37), 312 [Mꢃ, 22], 295 (MÃ
/
OH). MS (DEI; m/z (%)): 312 [Mꢃ, 2%], 155
1
1710 (CO). H-NMR (500 MHz, CD2Cl2): [assignments
/
/
are quoted with respect to the normal labeling for a b-
naphthyl substituent] d 7.76 (d, 2H, J(HH) 7.9 Hz,
naphthyl-H5), 7.62 (d, 2H, J(HH) 8.3 Hz, naphthyl-H4),
7.49 (d, 2H, J(HH) 8.8 Hz, naphthyl-H8), 7.48 (s, 2H,
naphthyl-H1), 7.46 (dd, 2H, J(HH) 7.5 Hz, 7.5 Hz,
naphthyl-H6), 7.37 (dd, 2H, J(HH) 7.2 Hz, 7.2 Hz,
naphthyl-H7), 7.30 (s, 6H, phenyl-H2,4,6), 7.25 (s, 4H,
phenyl-H3,5), 7.11 (d, 2H, J(HH) 8.2 Hz, naphthyl-H3).
13C-NMR (125 MHz, CD2Cl2): d 200.9 (CO), 155.2
(naphthyl-C2, cyclopentadienone-C3), 133.6 (naphthyl-
C4a), 133.4 (naphthyl-C8a), 131.7 (phenyl-C1), 131.5
(cyclopentadienone-C2), 130.9 (phenyl-C2,6), 129.7
(naphthyl-C1), 128.8 (naphthyl-C8), 128.6 (phenyl-
/
/
267 (C21H15, 4), 201 (C16H9, 15), 155 (C10H7CO, 26),
128 (C10H8, 4), 77 (C6H5, 1).
4.3. 1,2-Di-(b-naphthyl)ethan-1,2-dione, b-naphthil (2)
The literature procedure for the synthesis of benzil
[65] was modified for the preparation of 2. Thus, CuSO4
(8.76 g, 0.05 mol) was added to 13 ml pyridine and 25 ml
H2O in a 250 ml round-bottom flask. When all the
CuSO4 was dissolved, 1,2-di-(b-naphthyl)-2-hydro-
xyethanone (1) (8.23 g, 0.03 mol) was added and the
reaction mixture was stirred under reflux for ca. 2 h,
then left to cool overnight. The blue aqueous layer was
decanted, leaving a yellow solid that was washed with
water, then with hot HCl (10%). The product was
filtered, then dissolved in CH2Cl2, dried over MgSO4,
filtered and the solvent was removed under vacuum to
give 2 (7.53 g, 0.02 mol; 93%) as a yellow powder, m.p.
C
3,4,5), 128.3 (naphthyl-C5), 128.1 (naphthyl-C4), 127.4
(naphthyl-C6,3), 126.9 (naphthyl-C7); (assignments for
naphthyl-H,C5 and H,C8, naphthyl-H,C6 and H,C7 and
naphthyl-C4a and C8a may be interchanged). MS (DEI;
m/z (%)): 484 [Mꢃ, 2%], 280 (C10H7CHCHC10H7, 10),
228 (C10H7CÅ
85 (62), 84 (100). MS (DCI; m/z (%)): 485 (Mꢃ
228 (C10H7CÅCC6H5, 2), 136 (14), 125 (100).
/
CC6H5, 4), 140 (C10H7CH, 12), 125 (15),
/
H, 17%),
/
157ꢂ
/
160 8C (lit. [64] 158ꢂ
159 8C). 1H-NMR (200
/
MHz, CD2Cl2): [assignments are quoted with respect
to the normal labeling for a b-naphthyl substituent] d
8.47 (s, 1H, naphthyl-H1), 8.15 (dd, 1H, J(HH) 8.6 Hz,
4.5. 3,4-Di-(b-naphthyl)-2,5-di(m-xylyl)cyclopenta-
dienone (3b)
1.52 Hz, naphthyl-H4), 8.04ꢂ
H
/
7.92 (m, 3H, naphthyl-
3,5,8), 7.67 (dt, 1H, J(HH) 5.9 Hz, 1.2 Hz, naphthyl-
As with 3a, b-naphthil (2) (0.76 g, 2.0 mmol) and 1,3-
bis(3,5-dimethylphenyl)propanone (1.047 g, 3.8 mmol)
were dissolved in 125 ml of hot ethanol with stirring.
While the mixture was refluxing, KOH (0.3 g, 5.4 mmol)
dissolved in 10 ml hot ethanol was added dropwise
through the top of the condenser, and the solution
H6), 7.58 (dt, 1H, J(HH) 7.65 Hz, 1.2 Hz, naphthyl-H7);
(assignments for naphthyl-H6 and H7 may be inter-
changed). 13C-NMR (50 MHz, CD2Cl2): d 195.2 (CO),
136.8, 132.7, 130.8 (naphthyl C’s), 133.9, 130.2, 129.9,
129.5, 128.3, 127.6, 123.9 (naphthyl CH’s). MS (DEI; m/
z (%)): 310 [Mꢃ, 6%], 155 (C10H7CO, 100), 127 (C10H7,
97), 101 (C8H5, 10), 77 (C6H5, 19). MS (DCI; m/z (%)):
darkened to a redꢂpurple colour. The solution was
/
stirred for ca. 30 min, then cooled, resulting in the
formation of a dark purple solid which was collected by
vacuum filtration to give 3b (0.88 g, 1.6 mmol; 82%),
328 (Mꢃ
/
NH3ꢃ
/
H, 37%), 311 (Mꢃ
H, 69), 310 [Mꢃ,
/

254
L.E. Harrington et al. / Journal of Organometallic Chemistry 656 (2002) 243ꢂ257
/
m.p. 285ꢂ
/
288 8C. Calc. for C42H32O: C, 91.08; H, 5.97.
thyl-C8,3), 128.4 (phenyl-C3,4,5), 128.3 (naphthyl-C5),
128.1 (naphthyl-C4), 127.3 (naphthyl-C6), 127.0 (naph-
thyl-C7), 99.5 (acac-gC), 95.5 (cyclopentadienone-C3),
95.4 (naphthyl-C2), 76.1 (cyclopentadienone-C2), 76.1
(phenyl-C1), 27.7 (acac-CH3); (assignments for naph-
thyl-H,C5 and H,C8, naphthyl-H,C6 and H,C7 and
naphthyl-C4a and C8a may be interchanged). MS (ESI;
Found: C, 90.65; H, 6.09%. IR (CH2Cl2): nmax (cmꢁ1) at
1
1708 (CO). H-NMR (500 MHz, CD2Cl2): [assignments
are quoted with respect to the normal labeling for a b-
naphthyl substituent] d 7.75 (dd, 2H, J(HH) 8.1 Hz, 1.2
Hz, naphthyl-H5), 7.60 (d, 2H, J(HH) 8.4 Hz, naphthyl-
H4), 7.48 (d, 2H, J(HH) 8.1 Hz, naphthyl-H8), 7.44 (s,
2H, naphthyl-H1), 7.43 (ddd, 2H, J(HH) 7.5 Hz, 6.9 Hz,
1.3 Hz, naphthyl-H6), 7.35 (ddd, 2H, J(HH) 8.1 Hz, 6.9
Hz, 1.2 Hz, naphthyl-H7), 7.10 (dd, 2H, J(HH) 8.5 Hz,
1.7 Hz, naphthyl-H3), 6.88 (s, 6H, xylyl-H2,4,6), 2.16 (s,
12H, xylyl-CH3). 13C-NMR (50 MHz, CD2Cl2): d 201.2
m/z (%)) 687 [Mꢃ, 4%], 669 (MÃ
/H2O, 100).
4.7. (Acetylacetonato)[3,4-di-(b-naphthyl)-2,5-di(m-
xylyl)cyclopentadienone]rhodium(I), (4b)
(CÄ
/
O), 154.8 (naphthyl-C2), 138.1 (xylyl-C3,5), 133.6
As with 4a, (acetylacetonato)bis(ethylene)rhodium(I)
(0.41 g, 1.6 mmol) and 3b (0.82 g, 1.5 mmol) were
dissolved in 30 ml dry THF and stirred under gentle
reflux for ca. 2 h. The volume of the solution was
reduced under vacuum to ca. 15 ml, then 10 ml of
hexanes was added dropwise, resulting in the formation
of a precipitate of 4b (1.00 g, 1.4 mmol; 90%) as a red
powder which was collected by vacuum filtration, m.p.
(naphthyl-C4a), 133.3 (naphthyl-C8a), 131.7 (cyclopenta-
dienone-C2), 131.5 (cyclopentadienone-C3), 129.9 (xylyl-
C4), 129.6 (naphthyl-C1), 128.7 (naphthyl-C8), 128.5
(xylyl-C2,6), 128.2 (naphthyl-C5), 127.9 (naphthyl-C4),
127.5 (naphthyl-C3), 127.2 (naphthyl-C6), 127.0 (xylyl-
C1), 126.7 (naphthyl-C7), 21.6 (xylyl-CH3); (assignments
for naphthyl-H,C5 and H,C8, naphthyl-H,C6 and H,C7
and naphthyl-C4a and C8a may be interchanged). MS
244ꢂ247 8C. Calc for C46H39O3Rh: C, 74.39; H, 5.29.
/
(DEI; m/z (%)): 540 [Mꢃ, 27%], 512 (MÃ
(C10H7CÅCC10H7, 11), 256 (C10H7CÅCC6(CH3)2H3,
25), 239 (6), 128 (C10H8, 4), 84 (100). MS (DCI; m/z
(%)): 557 (MꢃNH3, 8%), 541 (MꢃH, 100), 279
(C10H7CÅCC10H7ꢃH, 8), 396 (MÃC10H7ÃOH, 8), 256
(C10H7CÅCC6(CH3)2H3, 17), 86 (24).
/
CO, 4), 278
Found: C, 73.85; H, 5.70%. IR (CH2Cl2): nmax (cmꢁ1) at
1
1638 (CO). H-NMR (500 MHz, CD2Cl2): [assignments
/
/
are quoted with respect to the normal labeling for a b-
naphthyl substituent] d 7.99 (s, 2H, naphthyl-H3), 7.73
(d, 2H, J(HH) 8.1 Hz, naphthyl-H8), 7.58 (s, 2H,
naphthyl-H1), 7.58 (d, 2H, J(HH) 7.8 Hz, naphthyl-
H5), 7.54 (s, 2H, naphthyl-H4), 7.52 (s, 4H, xylyl-H2,6),
7.44 (dd, 2H, J(HH) 7.0 Hz, 7.0 Hz, naphthyl-H7), 7.37
(dd, 2H, J(HH) 7.2 Hz, 7.2 Hz, naphthyl-H6), 6.97 (s,
2H, xylyl-H4), 5.53 (s, 1H, acac-gH), 2.24 (s, 12H, xylyl-
CH3), 2.16 (s, 6H, acac-CH3). 13C-NMR (125 MHz,
/
/
/
/
/
/
/
4.6. (Acetylacetonato)(3,4-di-(b-naphthyl)-2,5-
diphenylcyclopentadienone)rhodium(I), (4a)
(Acetylacetonato)bis(ethylene)rhodium(I) (0.22 g,
0.87 mmol) and 3a (0.26 g, 0.54 mmol) were dissolved
in 30 ml dry THF and stirred under gentle reflux for ca.
2 h. The volume of the solution was reduced to half
under vacuum, and 10 ml of hexanes was added,
resulting in the formation of a red precipitate, which
was collected by vacuum filtration to give 4a (0.29 g,
0.42 mmol; 78%) as a red powder, m.p. 267 8C (dec).
Calc. for C42H31O3Rh: C, 73.47; H, 4.55. Found: C,
73.95; H, 4.34%. IR (CH2Cl2): nmax (cmꢁ1) at 1640
CD2Cl2): d 188.0 (acac-CO), 164.0 (CÄ
/
O), 133.4 (naph-
thyl-C4a), 133.3 (naphthyl-C8a), 131.2 (naphthyl-C3),
130.0 (xylyl-C4), 129.6 (xylyl-C3,5), 129.1 (xylyl-C2,6),
128.5 (naphthyl-C4), 128.5 (naphthyl-C1), 128.3 (naph-
thyl-C8), 127.9 (naphthyl-C5), 127.2 (naphthyl-C7),
126.9 (naphthyl-C6), 99.5 (acac-gC), 95.6 (cyclopenta-
dienone-C3), 95.5 (naphthyl-C2), 76.8 (cyclopentadie-
none-C2), 76.7 (xylyl-C1), 27.7 (acac-CH3), 21.5 (xylyl-
CH3); (assignments for naphthyl-H,C5 and H,C8, naph-
thyl-H,C6 and H,C7 and naphthyl-C4a and C8a may be
interchanged). MS (ESI; m/z (%)) 743 [Mꢃ, 2%], 725
1
(CO). H-NMR (500 MHz, CD2Cl2): [assignments are
quoted with respect to the normal labeling for a b-
naphthyl substituent] d 7.95 (s, 2H, naphthyl-H1), 7.83
(dd, 4H, J(HH) 7.2 Hz, 1.3 Hz, phenyl-H2,6), 7.73 (dd,
2H, J(HH) 8.1 Hz, 1.3 Hz, naphthyl-H5), 7.59 (d, 2H,
J(HH) 8.5 Hz, naphthyl-H4;), 7.56 (d, 2H, J(HH) 8.2
Hz, naphthyl-H8), 7.50 (dd, 2H, J(HH) 8.5 Hz, 1.2 Hz,
naphthyl-H3), 7.45 (ddd, 2H, J(HH) 8.1 Hz, 6.9 Hz, 1.3
Hz, naphthyl-H6), 7.38 (ddd, 2H, J(HH) 8.1 Hz, 6.9 Hz,
1.3 Hz, naphthyl-H7), 7.33 (tt, 2H, J(HH) 7.2 Hz, 1.3
Hz, phenyl-H4), 7.26 (dd, 4H, J(HH) 7.8 Hz, 7.2 Hz,
phenyl-H3,5), 5.50 (s, 1H, acac-gH), 2.13 (s, 6H, acac-
CH3). 13C-NMR (125 MHz, CD2Cl2): d 188.1 (acac-
(MÃ
/
H2O, 100), 684 (MÃ
/
COÃ
/
2CH3Ã
/
H, 11).
4.8. (Acetylacetonato)(3,4-di-(b-naphthyl)-2,5-
diphenylcyclopentadienone)(triphenylphosphine)
rhodium(I), (5a)
Triphenylphosphine (0.06 g, 0.23 mmol) was dissolved
in 10 ml dry THF and added by syringe to a stirring
solution of 4a (0.13 g, 0.20 mmol) in 30 ml dry THF.
The mixture was stirred under reflux for 1 hour, and the
solvent was reduced to half under vacuum. Hexanes (10
ml) was added, resulting in the formation of a yellow
precipitate, which was collected by vacuum filtration to
CO), 163.6 (CÄO), 133.5 (naphthyl-C4a), 133.3 (naph-
thyl-C8a), 131.3 (phenyl-C2,6, naphthyl-C1), 128.5 (naph-
/

L.E. Harrington et al. / Journal of Organometallic Chemistry 656 (2002) 243ꢂ
/257
255
give 5a (0.19 g, 0.19 mmol; 98%) as a yellow powder,
m.p. 185ꢂ188 8C. Calc. for C60H46O3PRh×CH2Cl2: C,
70.92; H, 4.69. Found: C, 70.60; H, 4.15%. IR (CH2Cl2):
nmax (cmꢁ1) at 1635 (CO). 1H-NMR (500 MHz,
CD2Cl2): [assignments are quoted with respect to the
normal labeling for a b-naphthyl substituent] d 8.03 (s,
2H, naphthyl-H1), 7.70 (d, 4H, J(HH) 7.5 Hz, phenyl-
(d, 4H, J(HH) 7 Hz, naphthyl-H5,8), 7.51 (d, 2H, J(HH)
8.5 Hz, naphthyl-H4), 7.41 (s, 4H, xylyl-H2,6), 7.39 (d,
2H, J(HH) 6.8 Hz, naphthyl-H6), 7.38 (d, 2H, J(HH) 7
Hz, naphthyl-H7), 7.37 (d, 2H, J(HH) 8.9 Hz, naphthyl-
/
/
H3), 7.31 (dd, 6H, J(HH) 8.6 Hz, 8.6 Hz, PPh3Ã
2,6), 7.27 (t, 3H, J(HH) 7.3 Hz, PPh3Ãphenyl-H4), 7.05
(dd, 6H, J(HH) 6.7 Hz, 6.9 Hz, PPh3Ãphenyl-H3,5), 6.87
/
phenyl-
H
/
/
H
2,6), 7.64 (dd, 2H, J(HH) 7.0 Hz, 1.6 Hz, naphthyl-
(s, 2H, xylyl-H4), 5.20 (s, 1H, acac-gH), 2.15 (s, 12H,
xylyl-CH3), 1.85 (s, 6H, acac-CH3), (couplings for
naphthyl-H5,7,8 were not well resolved due to overlap).
13C-NMR (125 MHz, CD2Cl2): d 188.1 (acac-CO),
H5), 7.62 (dd, 2H, J(HH) 7.1 Hz, 1.8 Hz, naphthyl-H8),
7.45 (d, 2H, J(HH) 8.6 Hz, naphthyl-H4), 7.37 (dd, 2H,
J(HH) 7.9 Hz, 6.9 Hz, naphthyl-H6), 7.36 (dd, 2H,
J(HH) 7.9 Hz, 1.8 Hz, naphthyl-H7), 7.27 (d, 2H,
J(HH) 8.5 Hz, naphthyl-H3), 7.21 (d, 6H, J(HH) 8
170.2 (CÄ
Hz, PPh3Ã
(naphthyl-C8a), 131.6 (naphthyl-C1), 131.5 (d, J(CP)
43.2 Hz, PPh3Ãphenyl-C1), 130.0 (naphthyl-C7), 129.7
(PPh3Ãphenyl-C4), 129.2 (xylyl-C2), 128.3 (xylyl-C4),
128.2 (naphthyl-C5), 128.1 (naphthyl-C8), 127.9 (d,
J(CCCP) 9.2 Hz, PPh3Ãphenyl-C3,5), 127.0 (naphthyl-
/
O), 137.1 (xylyl-C3,5), 134.7 (d, J(CCP) 17.6
/phenyl-C2,6), 133.2 (naphthyl-C4a), 133.0
Hz, PPh3Ã
/
phenyl-H2,6), 7.21 (t, 3H, J(HH) 8 Hz, PPh3Ã
/
phenyl-H4), 7.17 (t, 2H, J(HH) 7.4 Hz, phenyl-H4), 7.02
/
(dd, 4H, J(HH) 7.7 Hz, 7.7 Hz, phenyl-H3,5), 6.97 (dd,
/
6H, J(HH) 6.5 Hz, 6.9 Hz, PPh3Ã
1H, acac-gH), 1.80 (s, 6H, acac-CH3). 13C-NMR (125
MHz, CD2Cl2): d 188.4 (acac-CO), 170.2 (CÄO), 134.6
(d, J(CCP) 10.6 Hz, PPh3Ãphenyl-C2), 133.2 (naphthyl-
C4a), 133.0 (naphthyl-C8a), 131.6 (naphthyl-C1), 131.3
(d, J(CP) 50.7 Hz, PPh3Ãphenyl-C1), 131.0 (phenyl-
2,6), 129.8 (PPh3Ãphenyl-C4), 128.8 (naphthyl-C3),
128.5 (naphthyl-C5), 128.1 (naphthyl-C8), 128.0 (d,
J(CCCP) 12.9 Hz, PPh3Ãphenyl-C3,5), 127.9 (phenyl-
3,5), 127.8 (naphthyl-C6), 127.1 (naphthyl-C4), 126.8
/phenyl-H3,5), 5.13 (s,
/
/
C4), 126.7 (naphthyl-C3), 126.5 (naphthyl-C6), 104.4
(naphthyl-C2, cyclopentadienone-C3), 101.4 (acac-gC),
64.3 (xylyl-C1, cyclopentadienone-C2), 28.8 (acac-CH3),
21.5 (xylyl-CH3); (assignments for naphthyl-H,C5 and
H,C8, naphthyl-H,C6 and H,C7 and naphthyl-C4a and
C8a may be interchanged). 31P-NMR (202 MHz,
/
/
C
/
/
CD2Cl2, 243 K): d 23.4 (d, J(RhP) 167.3 Hz, RhÃ
PPh3); (202 MHz, CD2Cl2, 163 K): d 23.5 (d, J(RhP)
164.2 Hz, RhÃPPh3), 23.2 (d, J(RhP) 158.4 Hz, RhÃ
PPh3). MS (ESI; m/z (%)): 1005 [Mꢃ, 7], 946 (MÃ
COÃ
2CH3ÃH, 38), 905 (MÃHacac, 18), 743 (MÃPPh3, 11),
725 (MÃPPh3ÃH2O, 100), 684 (MÃPPh3ÃCOÃ2CH3,
9), 631 (13).
/
C
(naphthyl-C7), 126.6 (phenyl-C4), 104.7 (naphthyl-C2,
cyclopentadienone-C3), 101.7 (acac-gC), 64.2 (phenyl-
C1, cyclopentadienone-C2), 28.7 (acac-CH3); (assign-
ments for naphthyl-H,C5 and H,C8, naphthyl-H,C6
and H,C7 and naphthyl-C4a and C8a may be inter-
changed). 31P-NMR (202 MHz, CD2Cl2, 243 K): d 22.5
/
/
/
/
/
/
/
/
/
/
/
/
(d, J(RhP) 165.6 Hz, RhÃ
163 K): d 23.5 (d, J(RhP) 159.8 Hz, RhÃ
J(RhP) 156.8 Hz, RhÃPPh3). MS (ESI; m/z (%)): 949
[Mꢃ, 3%], 890 (MÃ
COÃ2CH3ÃH, 7), 849 (MꢃH-acac,
83), 557 (C4(C6H5)2(C10H7)2RhÃH, 9), 277 (C10H7CÅ
CC10H6, 100).
/
PPh3); (202 MHz, CD2Cl2,
4.10. (Acetylacetonato)(2,3,4,5-tetraphenyl-
cyclopentadienone)(triphenylphosphine) rhodium(I),
(5c)
/PPh3), 22.9 (d,
/
/
/
/
/
/
/
As with 5a, triphenylphosphine (0.22 g, 0.84 mmol)
was dissolved in 10 ml dry THF and added dropwise by
syringe to a stirring solution of 4c (0.25 g, 0.42 mmol) in
30 mL dry THF. After refluxing for 1 h, the solvent was
removed under vacuum to give 5c (0.13 g, 0.15 mmol,
4.9. (Acetylacetonato)(3,4-di-(b-naphthyl)-2,5-di-m-
xylylcyclopentadienone)(triphenylphosphine)
rhodium(I), (5b)
36%) as a yellowꢂorange powder, m.p. 136 8C (dec).
/
Calc. for C52H42O3PRh×
/
CH2Cl2: C, 68.23; H, 4.76.
Found: C, 68.10; H, 5.06%. IR (CH2Cl2): nmax (cmꢁ1
Triphenylphosphine (0.29 g, 1.1 mmol) was dissolved
in 10 ml dry THF and added by syringe to a stirring
solution of 4b (0.80 g, 1.1 mmol) in 30 ml dry THF. The
mixture was stirred under reflux for 1 h, and the solvent
was reduced to half under vacuum. Ca. 10 ml of hexanes
)
1
at 1627 (CO). H-NMR (500 MHz, CD2Cl2): d 7.65,
7.29 (d, 8H, J(HH) 7.6 Hz, phenyl-H2,6), 5.94 (m, 9H,
PPh3), 7.14 (t, 4H, J(HH) 7.0 Hz, phenyl-H4), 7.08, 7.05
(dd, 8H, J(HH) 7.40 Hz, 8.5 Hz, phenyl-H3,5), 6.97 (s,
6H, PPh3), 4.98 (s, 1H, acac-gH), 1.75 (s, 6H, acac-
CH3). 13C-NMR (125 MHz, CD2Cl2): d 188.1 (acac-
was added, creating a yellowꢂ
(0.93 g, 0.92 mmol; 84%), which was collected by
vacuum filtration, m.p. 188ꢂ191 8C. Calc. for
/orange precipitate of 5b,
/
CO), 170.0 (CÄ
/
O), 135.5, 134.6, 134.5, 132.7, 131.6,
C64H54O3PRh×
/
2H2O: C, 73.84; H, 5.62. Found: C,
73.44; H 6.45%. IR (CH2Cl2): nmax (cmꢁ1) at 1626
131.0, 129.7, 128.0, 127.9, 127.8, 126.5 (aromatic rings),
101.6 (acac-gC), 28.8 (acac-CH3). 31P-NMR (81 MHz,
1
(CO). H-NMR (500 MHz, CD2Cl2): [assignments are
CD2Cl2): d 21.1 (d, J(RhP) 162.5 Hz, RhÃ
/
PPh3). MS
COÃ2CH3ÃH,
Hacac, 100), 279 (C4(C6H5)3, 6).
quoted with respect to the normal labeling for a b-
naphthyl substituent] d 8.14 (s, 2H, naphthyl-H1), 7.68
(ESI; m/z (%)): 849 [Mꢃ, 0.7%], 790 (MÃ
9), 749 (MÃ
/
/
/
/

256
L.E. Harrington et al. / Journal of Organometallic Chemistry 656 (2002) 243ꢂ257
/
4.11. Lineshape analysis
5. Supplementary material
NMR simulations were carried out using the program
MEXICO [67] (available from Alex Bain). This program
does an iterative least-squares fit of the calculated
lineshape to the experimental data, and is capable of
varying all the parameters: shifts, couplings and rates.
This was a standard, non-mutual (non-degenerate)
exchange problem. In this analysis, the chemical shift
difference and rate were varied (using a simplex algo-
rithm) to obtain the best fit. The calculation of errors in
a multi-parameter fit is a difficult problem. For this
case, they were estimated by changing the parameters
and visually monitoring the fit to the experimental data.
The errors quoted correspond to a clear and obvious
mismatch between calculated and observed. Full details
can be found in [68].
Supporting Information Available: Crystallographic
data for the structural analysis have been deposited at
the Cambridge Crystallographic Data Center, CCDC
numbers 175627 (4a), 175628 (4b), 175629 (5a) and
175630 (5b). Copies of this information may be obtained
free of charge from The Director, CCDC, 12 Union
Road, Cambridge CB2 1EZ, UK (Fax: ꢃ44-1223-
/
336033; e-mail: deposit@ccdc.cam.ac.uk or www:
http://www.ccdc.cam.ac.uk). Fully labeled thermal ellip-
soid plots are also available (four pages).
Acknowledgements
Financial support from the Natural Sciences and
Engineering Research Council of Canada (NSERC) is
gratefully acknowledged. L.E.H. thanks NSERC for a
Graduate Scholarship, and McMaster University for a
Centennial Scholarship. We also thank Stacey Brydges
for helpful discussions.
4.12. Crystallographic data for 4a, 4b, 5a and 5b
X-ray crystallographic data for 4a, 4b, 5a and 5b
(Table 2) were collected from a suitable sample mounted
with epoxy on the end of a thin glass fiber. For 4a, the
rapid lattice solvent evaporation was minimized by the
mounting of a suitable crystal in an atmosphere
saturated with solvent, and quickly freezing it to 173
K on the diffractometer. Data were collected on a P4
Bruker diffractometer equipped with a Bruker SMART
References
[1] L. Li, A. Decken, B.G. Sayer, M.J. McGlinchey, P. Bre´gaint, J-Y.
The´pot, L. Toupet, J-R. Hamon, C. Lapinte, Organometallics 13
(1994) 682.
[2] B. Mailvaganam, B.G. Sayer, M.J. McGlinchey, J. Organomet.
Chem. 395 (1990) 177.
1K CCD area detector (employing the program SMART)
[69] and a rotating anode utilizing graphite-monochro-
[3] H.K. Gupta, S. Brydges, M.J. McGlinchey, Organometallics 18
(1999) 115.
˚
0.710.73 A). Data proces-
mated Moꢂ
/
Ka radiation (lꢀ
/
[4] L.C.F. Chao, H.K. Gupta, D.W. Hughes, J.F. Britten, S.S.
Rigby, A.D. Bain, M.J. McGlinchey, Organometallics 14 (1995)
1139.
sing was carried out by use of the program SAINT [70],
while the program SADABS [71] was utilized for the
scaling of diffraction data, the application of a decay
correction and an empirical absorption correction based
on redundant reflections. Structures were solved by
using the direct-methods procedure in the Bruker
SHELXL [72] program library and refined by full-matrix
least-squares methods on F2. All non-hydrogen atoms
were refined using anisotropic thermal parameters, with
the exception of 5b, in which the crystal did not diffract
[5] S. Brydges, J.F. Britten, L.C.F. Chao, H.K. Gupta, M.J.
McGlinchey, D.L. Pole, Chem. Eur. J. 4 (1998) 1201.
[6] S. Brydges, L.E. Harrington, M.J. McGlinchey, Coord. Chem.
Rev. in press, 2002.
[7] H. Iwamura, K. Mislow, Acc. Chem. Res. 21 (1988) 175.
[8] K. Mislow, Chemtracts: Org. Chem. 2 (1989) 151.
[9] B. Mailvaganam, C.S. Frampton, S. Top, B.G. Sayer, M.J.
McGlinchey, J. Am. Chem. Soc. 113 (1991) 1177.
[10] M.J. McGlinchey, Adv. Organomet. Chem. 34 (1992) 285 (and
references therein).
˚
beyond 1 A, creating difficulties in refining anisotropi-
[11] H. Schumann, A. Lentz, R. Weimann, J. Pickardt, Angew. Chem.
Int. Ed. Engl. 33 (1994) 1731.
cally on the carbon atoms. Hydrogen atoms were added
as fixed contributors at calculated positions, with
isotropic thermal parameters based on the carbon
atom to which they are bonded. In the course of the
refinement process for 4a and 4b, several dichloro-
methane solvent molecules were located in the asym-
metric unit, and a satisfactory refinement of the solvate
atomic positions was not attained, though the diffrac-
tion data allowed for complete anisotropic refinement of
the target molecules. As a result, the values for the
residual electron density in the region of the solvent
molecules and the refinement statistics associated with
the structures are high.
[12] (a) J.C.J. Bart, Acta Crystallogr. Sect. B 24 (1968) 1277;
(b) E.M. Larson, R.B. Von Dreele, P. Hanson, J.D. Gust, Acta
Crystallogr. Sect. C 46 (1990) 784.
[13] H.K. Gupta, M. Stradiotto, D.W. Hughes, M.J. McGlinchey, J.
Org. Chem. 65 (2000) 3652.
[14] M.P. Thornberry, C. Slebodnick, P.A. Deck, F.R. Fronczek,
Organometallics 19 (2000) 5352.
[15] M.P. Thornberry, C. Slebodnick, P.A. Deck, F.R. Fronczek,
Organometallics 20 (2001) 920.
[16] S. Becke, U. Denninger, S. Kahlert, W. Obrecht, C. Schmid, H.
Windisch, PCT Int. Appl. WO 0212154 (2002).
[17] J-Y. The´pot, C. Lapinte, J. Organomet. Chem. 627 (2001) 179.
[18] (a) W. Clegg, J.C. Lockhart, M.B. McDonnell, J. Chem. Soc.
Perkin Trans. I (1985) 1019;

L.E. Harrington et al. / Journal of Organometallic Chemistry 656 (2002) 243ꢂ
/257
257
(b) J.C. Lockhart, M.B. McDonnell, W. Clegg, M.N.S. Hill, J.
Chem. Soc. Perkin Trans. II (1987) 639.
[43] (a) K. Mislow, Acc. Chem. Res. 9 (1976) 26;
(b) K. Mislow, D. Gust, R.J. Finnocchiaro, R.J. Boettcher, Top.
Curr. Chem. 47 (1974) 1;
[19] R. Glaser, J.F. Blount, K. Mislow, J. Am. Chem. Soc. 102 (1980)
2777.
(c) K. Mislow, Pure Appl. Chem. 25 (1971) 549.
[44] R.J. Kurland, I.I. Schuster, A.K. Colter, J. Am. Chem. Soc. 87
(1965) 2279.
[20] (a) S. Ito, M. Fujita, N. Morita and T. Asao, Chem. Lett. (1995)
475.;
(b) S. Ito, M. Fujita, N. Morita, T. Asao, Bull. Chem. Soc. Jpn. 68
(1995) 3611.
[45] S.G. Davies, A.E. Derome, J.P. McNally, J. Am. Chem. Soc. 113
(1991) 2854 (and references therein).
[21] J. Clayden, J.H. Pink, Angew. Chem. Int. Ed. Engl. 37 (1998)
1937.
[46] G. Hunter, R.L. MacKay, P. Kremminger, W. Weissensteiner, J.
Chem. Soc. Dalton Trans. (1991) 3349.
[22] C. Kiefl, Eur. J. Org. Chem. (2000) 3279.
[23] M.D. Rausch, E.F. Tokas, E.A. Mintz, A. Clearfield, M.
Mangion, I. Bernal, J. Organomet. Chem. 172 (1979) 109.
[24] (a) Z. Marcinow, P.W. Rabideau, J. Organomet. Chem. 55 (1990)
3812;
[47] J.A.S. Howell, M.G. Palin, P. McArdle, D. Cunningham, Z.
Goldschmidt, H.E. Gottlieb, D. Hezroni-Langerman, Organome-
tallics 12 (1993) 1694.
[48] J.W. Faller, B.V. Johnson, J. Organomet. Chem. 96 (1975) 99.
[49] G. Hunter, T.J.R. Weakley, W. Weissensteiner, J. Chem. Soc.
Dalton Trans. (1987) 1545.
(b) M.V. Alfimov, Y.B. Scheck, N.P. Kovalenko, Chem. Phys.
Lett. 43 (1976) 154;
[50] J.A. Chudek, G. Hunter, R.L. MacKay, P. Kremminger, K.
(c) Y.B. Scheck, N.P. Kovalenko, M.V. Alfimov, J. Lumin. 15
(1977) 157;
Schlogl, W. Weissensteiner, J. Chem. Soc. Dalton Trans. (1990)
¨
2001.
(d) J.H. Magill, A.R. Ubbelohde, Trans. Faraday Soc. 54 (1958)
1811;
[51] J.A. Chudek, G. Hunter, R.L. MacKay, P. Kremminger, W.
Weissensteiner, J. Chem. Soc. Dalton Trans. (1991) 3337.
[52] L.D. Field, B.A. Messerle, L. Soler, I.E. Buys, T.W. Hambley, J.
Chem. Soc. Dalton Trans. (2001) 1959.
(e) D.J. Plazek, J.H. Magill, J. Chem. Phys. 45 (1966) 3038;
(f) S.R. Samanta, A.K. Mukherjee, A.J. Bhattacharyya, Curr. Sci.
57 (1988) 926.
[53] G. Hunter, J.F. Blount, J.R. Damewood, Jr., D.J. Iverson, K.
Mislow, Organometallics 1 (1982) 448.
[25] C.M. Whitaker, R.J. McMahon, J. Phys. Chem. 100 (1996) 1081.
[26] H.E. Katz, J. Organomet. Chem. 52 (1987) 3932.
[27] P.N. Riley, M.G. Thorn, J.S. Vilardo, M.A. Lockwood, P.E.
Fanwick, I.P. Rothwell, Organometallics 18 (1999) 3016.
[28] R.W. Baker, M.A. Foulkes, J.A. Taylor, J. Chem. Soc. Perkin
Trans. I (1998) 1047.
[54] H. Adams, N.A. Bailey, A.F. Browning, J.A. Ramsden, C. White,
J. Organomet. Chem. 387 (1990) 305.
[55] M.P. Castellani, J.M. Wright, S.J. Geib, A.L. Rheingold, W.C.
Trogler, Organometallics 5 (1986) 1116.
[56] J. Haywood-Farmer, M.A. Battiste, Chem. Ind. (1971) 1232.
[57] M.D. Rausch, G.F. Westover, E. Mintz, G.M. Reisner, I. Bernal,
A. Clearfield, J.M. Troup, Inorg. Chem. 18 (1979) 2605.
[58] (a) D. Gust, J. Am. Chem. Soc. 99 (1977) 6980;
(b) A. Patton, J.W. Dirks, D. Gust, J. Organomet. Chem. 44
(1979) 4749.
[29] (a) H.K. Gupta, N. Rampersad, M. Stradiotto, M.J. McGlinchey,
Organometallics 19 (2000) 184 (and references therein);
(b) H. Adams, N.A. Bailey, P.D. Hempstead, M.J. Morris, S.
Riley, R.L. Beddoes, E.S. Cook, J. Chem. Soc. Dalton Trans.
(1993) 91.
[30] (a) C.F.H. Allen, Chem. Rev. 62 (1962) 653;
(b) M.A. Ogliaruso, M.G. Romanelli, E.I. Becker, Chem. Rev. 65
(1965) 261;
[59] (a) H. Shimizu, J. Chem. Phys. 40 (1964) 3357;
(b) E.L. Mackor, C. MacLean, Prog. Nucl. Magn. Reson.
Spectrosc. 3 (1967) 129.
(c) B.A. Arbusov, J.A. Akmed-Zade, Z. Obshch. Khim. 12 (1942)
1928.
[60] K. Pervushin, R. Reik, G. Wider, K. Wuthrich, Proc. Natl. Acad.
¨
Sci. USA 94 (1997) 12366.
[31] U. Koelle, J. Kossakowski, G. Raabe, Angew. Chem. Int. Ed.
Engl. 29 (1990) 773.
[61] D.D. Perrin, W.L.F. Armarego, D.R. Perrin, Purification of
Laboratory Chemicals, second ed., Pergamon Press, New York,
1980.
[32] M.E. Smith, F.J. Hollander, R. Anderson, Angew. Chem. Int. Ed.
Engl. 32 (1993) 1294.
[62] R. Cramer, Inorg. Synth. 15 (1974) 14.
[33] R.N. Hargreaves, M.R. Truter, J. Chem. Soc. A (1969) 2282.
[34] K. Kite, A.F. Psaila, J. Organomet. Chem. 441 (1992) 159.
[35] W. Rigby, H-B. Lee, P.M. Bailey, J.A. McCleverty, P.M. Maitlis,
J. Chem. Soc. Dalton Trans. (1979) 387.
[63] R. Adams, C.S. Marvel, Org. Synth. Coll. I (1932) 94.
[64] J.D. Fulton, R. Robinson, J. Chem. Soc. (1939) 200.
[65] H.T. Clarke, E.E. Dreger, Org. Synth. Coll. I (1932) 87.
[66] J.R. Johnson, O. Grummitt, Org. Synth. Coll. III (1955) 806.
[67] A.D. Bain, G.J. Duns, Can. J. Chem. 74 (1996) 819.
[68] A.D. Bain, D.M. Rex, R.N. Smith, Magn. Reson. Chem. 39
(2001) 122.
[36] U. Koelle, C. Rietmann, G. Raabe, Organometallics 16 (1997)
3273.
[37] A.R. Siedle, in: G. Wilkinson (Ed.), Comprehensive Coordination
Chemistry, 1987, p. 365.
[69] G.M. Sheldrick, SMART, Release 4.05; Siemens Energy and
Automation Inc., Madison, WI, 53719, 1996.
[70] G.M. Sheldrick, SAINT, Release 4.05; Siemens Energy and
[38] W.M. Harrison, C. Saadeh, S.B. Colbran, D.C. Craig, J. Chem.
Soc. Dalton Trans. (1997) 3785.
[39] C. Saadeh, S.B. Colbran, D.C. Craig, A.D. Rae, Organometallics
12 (1993) 133.
Automation Inc., Madison, WI, 53719, 1996.
[71] G.M. Sheldrick, SADABS (Siemens Area Detector Absorption
Corrections); Siemens Energy and Automation Inc., Madison,
WI, 53719, 1996.
[40] R. Willem, H. Pepermans, C. Hoogzand, K. Hallenga, M. Gielen,
J. Am. Chem. Soc. 103 (1981) 2297.
[41] C.P. Brock, J.A. Ibers, Acta Crystallogr. Sect. B 29 (1973) 2426.
[42] E.E. Wille, D.S. Stephenson, P. Capriel, G. Binsch, J. Am. Chem.
Soc. 104 (1982) 405.
[72] G.M. Sheldrick, SHELXTL, Version 5.03; Siemens Crystallo-
graphic Research Systems, Madison, WI, 1994.