Syntheses, structures, and reactivity of new pentamethylcyclopentadienyl- rhodium(III) and -iridium(III) 4-acyl-5-pyrazolonate complexes

Article abstract of DOI:10.1021/ic050985r

New [Cp*M(Q)Cl] complexes (M = Rh or Ir, Cp* = pentamethylcyclopentadienyl, HQ = 1-phenyl-3-methyl-4R(C=O)-pyrazol-5-one in general, in detail HQ^Me, R = CH₃; HQ^Et, R = CH₂CH₃; HQ^Piv, R = CH₂-C(CH ₃)₃; HQ^Bn, R = CH₂-(C ₆H₅); HQ^S, R = CH-(C₆H ₅)₂) have been synthesized from the reaction of [Cp*MCl₂]₂ with the sodium salt, NaQ, of the appropriate HQ proligand. Crystal structure determinations for a representative selection of these [Cp*M(Q)Cl] compounds show a pseudo-octahedral metal environment with the Q ligand bonded in the O,O′-chelating form. In each case, two enantiomers (S_M) and (R_M) arise, differing only in the metal chirality. The reaction of [Cp*Rh(Q^Bn)Cl] with MgCH₃Br produces only halide exchange with the formation of [Cp*Rh(Q^Bn)Br]. The [Cp*Rh(Q)Cl] complexes react with PPh₃ in dichloromethane yielding the adducts Cp*Rh(Q)Cl/ PPh₃ (1:1) which exist in solution in two different isomeric forms. The interaction of [Cp*Rh(Q^Me)Cl] with AgNO₃ in MeCN allows generation of [Cp*Rh(Q^Me)(MeCN)]NO₃· 3H₂O, whereas the reaction of [Cp*Rh(Q^Me)Cl] with AgClO₄ in the same solvent yields both [Cp*Rh(Q ^Me)(H₂O)]ClO₄ and [Cp*Rh(Cl)(H ₂O)₂]ClO₄; the H₂O molecules derive from the notrigorously anhydrous solvents or silver salts.

Full text of DOI:10.1021/ic050985r

Inorg. Chem. 2005, 44, 7933−7942
Syntheses, Structures, and Reactivity of New
Pentamethylcyclopentadienyl-Rhodium(III) and -iridium(III)
4-Acyl-5-Pyrazolonate Complexes
Claudio Pettinari,*,§ Riccardo Pettinari,§ Mauro Fianchini,§ Fabio Marchetti,§ Brian W. Skelton,‡ and
Allan H. White‡
Department of Chemical Sciences, UniVersity of Camerino, Via S. Agostino 1, 62032 Camerino,
Italy, and Chemistry M313, School of Biomolecular, Biomedical and Chemical Sciences,
UniVersity of Western Australia, Crawley, Western Australia, 6009, Australia
Received June 16, 2005
New [Cp*M(Q)Cl] complexes (M
4R(C
O)-pyrazol-5-one in general, in detail HQMe, R
HQBn, R (C6H5); HQS, R
CH2 CH (C6H5)2) have been synthesized from the reaction of [Cp*MCl2]2 with the
)
Rh or Ir, Cp*
)
pentamethylcyclopentadienyl, HQ
)
1-phenyl-3-methyl-
d
)
CH3; HQEt, R CH2CH3; HQPiv, R
)
)
CH2 C(CH3)3;
−
)
−
)
−
sodium salt, NaQ, of the appropriate HQ proligand. Crystal structure determinations for a representative selection of
these [Cp*M(Q)Cl] compounds show a pseudo-octahedral metal environment with the Q ligand bonded in the
O,O′-chelating form. In each case, two enantiomers (SM) and (RM) arise, differing only in the metal chirality. The
reaction of [Cp*Rh(QBn)Cl] with MgCH3Br produces only halide exchange with the formation of [Cp*Rh(QBn)Br]. The
[Cp*Rh(Q)Cl] complexes react with PPh3 in dichloromethane yielding the adducts Cp*Rh(Q)Cl/PPh3 (1:1) which
exist in solution in two different isomeric forms. The interaction of [Cp*Rh(QMe)Cl] with AgNO3 in MeCN allows
generation of [Cp*Rh(QMe)(MeCN)]NO3 3H2O, whereas the reaction of [Cp*Rh(QMe)Cl] with AgClO4 in the same
‚
solvent yields both [Cp*Rh(QMe)(H2O)]ClO4 and [Cp*Rh(Cl)(H2O)2]ClO4; the H2O molecules derive from the not-
rigorously anhydrous solvents or silver salts.
Introduction
and of these, only the dinuclear cationic compound [Rh2(η5-
Cp*)2(acac)2][BF4]2 has been structurally characterized.5
Optically active half-sandwich metallocene complexes of
rhodium(III) and iridium(III) have recently attracted con-
siderable attention because of their ability to act as
active stereospecific catalysts.6 Other Cp*M compounds,
such as the cationic iridium complex, [Cp*IrMe(PMe3)-
(ClCH2Cl)]+[BAr4]- (Ar ) aryl), exhibit highly interesting
reactivity in the C-H activation reactions of various func-
tionalized substrates at ambient temperature.7 A number of
complexes containing N∧N8 and N∧O9 bidentate ligands
have been described and employed for enantioselective
hydrogen transfer reactions.10 Most of the organometallic
chiral-at-metal compounds are half-sandwich complexes
containing a Cp*, a halide ligand, and an unsymmetrical
The chemistry of Rh(I) â-diketonates has been extensively
investigated and a number of complexes of the form [Rh(â-
diketonate)(L)2] (where L ) alkene, CO, P(aryl)3, and
P(alkyl)3) have found applications in a variety of reactions
including, for example, alkene hydroboration,1 CO hydro-
genation,2 and hydroformylation.3 [Rh(acac)(CO)2] is a
known catalytic system in the presence of tertiary phosphines
for hydroformylation, hydrogenation, and isomerization
reactions of olefins.4 By contrast, only a limited number of
Rh(III) â-diketonate complexes, containing the penta-
methylcyclopentadienyl ligand (Cp*), have been synthesized,
* To whom correspondence should be addressed. Fax: 0039 0737
637345. E-mail: claudio.pettinari@unicam.it.
§ University of Camerino.
‡ University of Western Australia.
(1) (a) Westcott, S. A.; Blom, H. P.; Marder, T. B.; Baker, R. T. J. Am.
Chem. Soc. 1992, 114, 8863-8869. (b) Westcott, S. A.; Marder, T.
B.; Baker, R. T. Organometallics 1993, 12, 975-979.
(2) Baker, R. T.; Nguyen, P.; Marder, T. B.; Westcott, S. A. Angew. Chem.,
Int. Ed. Engl. 1995, 34, 1336-1338.
(3) Angermund, K.; Baumann, W.; Donius, E.; Fornika, R.; Go¨rls, H.;
Kessler, M.; Kru¨ger, C.; Leitner, W.; Lutz, F. Chem.sEur. J. 1997,
3, 755-764.
(4) (a) Moasser, B.; Gladfelter, W. L.; Roe, D. C. Organometallics 1995,
14, 3832-3838. (b) Trzeciak, A. M.; Glowiak, T.; Grzybek, R.;
Ziolkowski, J. J. J. Chem. Soc., Dalton Trans. 1997, 11, 1831-1837.
(5) Rigby, W.; Lee, H. B.; Bailey, P. M.; McCleverty, J.; Maitlis, P. M.
J. Chem. Soc., Dalton Trans. 1979, 387-394.
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(7) Arndtsen, B. A.; Bergman, R. G. Science 1995, 20, 1970-1973.
10.1021/ic050985r CCC: $30.25
Published on Web 09/27/2005
© 2005 American Chemical Society
Inorganic Chemistry, Vol. 44, No. 22, 2005 7933

Pettinari et al.
light petroleum (40-60 °C) were dried by refluxing over freshly
cut sodium. Methanol was dried over CaO. Dichloromethane was
freshly distilled from CaH2. Other solvents were dried and purified
by standard procedures. The samples were dried in vacuo to constant
weight (20 °C, ∼ 0.1 Torr). Elemental analyses were carried out
in-house with a Fisons Instruments 1108 CHNSO-elemental
analyzer. IR spectra in the range of 4000-150 cm-1 were recorded
with a Perkin-Elmer System 2000 FT-IR instrument. 1H, 13C{1H},
and 31P{1H} NMR spectra were recorded on a VXR-300 Varian
Figure 1. 4-Acyl-5-pyrazolone (HQ) pro-ligands employed in this work.
anionic chelate ligand with a chiral carbon atom. This type
of system has been thoroughly investigated and has been
reported to yield two diastereomers differing in the metal
configuration. As the configuration at the metal is often
labile, epimerization processes have been observed in solu-
tion.11 Analogous chemistry with related O,O-donors has
received less attention, one reason being that Rh-O and
Ir-O linkages are considered to be characteristically weak
because of a mismatch of the hard basic ligands with the
soft late-transition-metal centers.
1
Spectrometer (300 MHz for H, 75 MHz for 13C, and 121.4 MHz
for 31P). Melting points are uncorrected and were measured on an
SMP3 Stuart scientific instrument and on a capillary apparatus.
Positive and negative electrospray mass spectra were obtained with
a Series 1100 MSI detector HP spectrometer, using an acetonitrile
mobile phase. Solutions (3 mg/mL) for electrospray-ionization mass
spectrometry (ESI-MS) were prepared using reagent-grade acetone
or acetonitrile. For the ESI-MS data, masses and intensities were
compared to those calculated using the IsoPro Isotopic Abundance
Simulator Version 2.1.15
Syntheses of Complexes. [Chloro(pentamethylcyclopenta-
dienyl)(1-phenyl-3-methyl-4-acetylpyrazolon-5-ato)rhodium(III)],
[Cp*Rh(QMe)Cl] (1). A toluene solution (10 mL) containing
[Cp*RhCl2]2 (0.200 g, 0.32 mmol) and NaQMe (0.157 g, 0.64 mmol)
was stirred overnight under N2 at room temperature to give a red-
orange precipitate, which was filtered off and washed with 5 mL
of toluene. The orange-brown residue was recrystallized from 1:1
CH2Cl2/light petroleum (40-60 °C) and shown to be compound 1
(0.190 g, 0.38 mmol, 60% yield). mp: 255-258 °C. Anal. Calcd
for C22H26ClN2O2Rh: C, 54.06; H, 5.36; N, 5.73. Found: C, 53.73;
H, 5.45; N, 5.45. IR (Nujol, cm-1): 1606s, 1590s, 1575s, 1539s,
ν(C-C, C-N), 514m, 456s, 445sh, 398m, 301w, 259s ν(Rh-
Cl).1H NMR (CDCl3, 293 K): δ 1.67 (s, 15H, CH3Cp*), 2.35 (s,
3H, 3-CH3), 2.44 (s, 3H, COCH3), 7.15-7.40m, 7.97d (5H,
N-C6H5). 13C NMR (CDCl3, 293 K): δ 8.96 (s, CH3Cp*), 17.65
(s, 3-CH3), 28.22 (COCH3), 92.30, 92.49 (d, CCp*, J(103Rh-13C) )
9.5 Hz), 105.80 (s, C4), 120.88, 124.94, 128.59, 139.18 (s, N-C6H5
of Q), 148.90 (s, C3), 162.57 (s, C5), 190.26 (s, CO).
[Chloro(pentamethylcyclopentadienyl)(1-phenyl-3-methyl-4-
acetylpyrazolon-5-ato)iridium(III)], [Cp*Ir(QMe)Cl] (2). A tolu-
ene solution (10 mL) containing [Cp*IrCl2]2 (0.201 g, 0.25 mmol)
and NaQMe (0.132 g, 0.55 mmol) was stirred overnight under N2
at room temperature to give an orange precipitate, which was filtered
off and washed with 5 mL of toluene. The residue was recrystallized
from 1:1 CH2Cl2/light petroleum (40-60 °C) and shown to be
compound 2 (0.161 g, 0.28 mmol, 55% yield). mp: 278-280 °C.
Anal. Calcd for C22H26ClIrN2O2: C, 45.71; H, 4.53; N, 4.85.
Found: C, 45.24; H, 4.85; N, 4.83. IR (Nujol, cm-1): 1602s, 1590s,
1575s, 1539s, ν(C-C, C-N), 513w, 466m, 455w, 270s ν(Ir-
Cl).1H NMR (CDCl3, 293 K): δ 1.64 (s, 15H, CH3Cp*), 2.37 (s,
3H, 3-CH3), 2.41 (s, 3H, COCH3), 7.17-7.43m, 7.85d, 7.95d (5H,
N-C6H5). 13C NMR (CDCl3, 293 K): δ 9.13 (s, CH3Cp*), 17.47
(s, 3-CH3), 27.68 (COCH3), 83.57 (s, CCp*), 106.61 (s, C4), 120.90,
125.19, 128.67, 138.98 (s, N-C6H5), 148.94 (s, C3), 161. 16 (s,
C5), 189.22 (s, CO).
4-Acyl-5-pyrazolones (HQ) (Figure 1) have often been
described as analogues of â-diketone ligands and employed
in their anionic chelating σ-donor forms in complexes of
different metal acceptors.12 They can be easily functionalized
in the acyl fragment, and their complexes are generally more
stable than the corresponding â-diketonates.
We have previously reported that the acylpyrazolonates
are suitable ligands for the synthesis of stable Rh(I) metal
complexes, which have been widely investigated by X-ray
crystallography and NMR spectroscopy.13 As an extension
of the previous investigations on compounds that contain
the {(η5-Cp*)M} fragments (M ) Rh, Ir),14 we report, here,
a systematic study of the reactions of [{(η5-Cp*)MCl}2(µ-
Cl)2] (M ) Rh, Ir) compounds with HQ ligands (Figure 1).
The reactivities of some of these derivatives toward Grignard
reagents, PPh3 and AgX (X ) NO3 or ClO4) are also
included.
Experimental Section
Materials and Methods. All chemicals and reagents were of
reagent grade quality and were used as received without further
purification. All solvents were distilled prior to use. Toluene and
(8) (a) Murata, K.; Ikariya, T.; Noyori, R. J. Org. Chem. 1999, 64, 2186-
2187. (b) Carmona, D.; Lahoz, F. J.; Felipe, S.; Oro, L.; Lamata, M.
P.; Viguri, F.; Mir, C.; Cativiela, C.; Lopez-ram de Viu, M. P.
Organometallics 1998, 17, 2986-2995.
(9) (a) Carmona, D.; Vega, C.; Lahoz, F. J.; Atencio, R.; Oro, L. A.;
Lamata, M. P.; Viguri, F.; San Jose`, E. Organometallics 2000, 19,
2273-2280. (b) Carmona, D.; Vega, C.; Lahoz, F. J.; Atencio, R.;
Oro, L. A.; Lamata, M. P.; Viguri, F.; San Jose`, E.; Vega, C.; Reyes,
J.; Joo`, F.; Katho, A. Chem.sEur. J. 1999, 5, 1544-1564.
(10) Carmona, D.; Lamata, M. P.; Oro, L. A. Eur. J. Inorg. Chem. 2002,
2239-2251.
(11) Brunner, H.; Kollnberger, A.; Zabel, M. Polyhedron, 2003, 22, 2639-
2646.
(12) (a) Marchetti, F.; Pettinari, C.; Cingolani, A.; Leonesi, D.; Drozdov,
A.; Troyanov, S. I. J. Chem. Soc., Dalton Trans. 1998, 3325-3334.
(b) Caruso, F.; Rossi, M.; Tanski, J.; Sartori, R.; Sariego, R.; Moya,
S.; Diez, S.; Navarrete, E.; Cingolani, A.; Marchetti, F.; Pettinari, C.
J. Med. Chem. 2000, 43, 3665-3670. (c) Cingolani, A.; Effendy;
Marchetti, F.; Pettinari, C.; Pettinari, R.; Skelton, B. W.; White, A.
H. Inorg. Chem. 2002, 41, 1151-1161.
(13) (a) Pettinari, C.; Accorroni, F.; Cingolani, A.; Marchetti, F.; Cassetta,
A.; Barba, L. J. Organomet. Chem. 1998, 566, 187-201. (b) Pettinari,
C.; Marchetti, F.; Pettinari, R.; Pizzabiocca, A.; Drozdov, A.;
Troyanov, S. I.; Vertlib, V. J. Organomet. Chem. 2003, 688, 216-
226.
[Chloro(pentamethylcyclopentadienyl)(1-phenyl-3-methyl-4-
propionylpyrazolon-5-ato)rhodium(III)], [Cp*Rh(QEt)Cl] (3).
Orange compound 3 (0.090 g, 0.17 mmol, 64% yield) was prepared
following a procedure similar to that reported for 1 using
(14) Carmona, E.; Cingolani, A.; Marchetti, F.; Pettinari, C.; Pettinari, R.;
Skelton, B. W.; White, A. H. Organometallics 2003, 22, 2820-2826.
(15) Senko, M. W. IsoPro Isotopic Abundance Simulator, version 2.1;
National High Magnetic Field Laboratory, Los Alamos National
Laboratory: Los Alamos, NM.
7934 Inorganic Chemistry, Vol. 44, No. 22, 2005

Rhodium(III) Cyclopentadienyl â-diketonate Complexes
[Cp*RhCl2]2 and NaQEt and was recrystallized from 1:1 CH2Cl2/
light petroleum (40-60 °C). mp 217-219 °C. Anal. Calcd for
C23H28ClN2O2Rh: C, 54.94; H, 5.61; N, 5.57. Found: C, 54.90;
H, 5.84; N, 5.20. IR (Nujol, cm-1): 1605s, 1589s, 1576s, 1534s,
ν(C-C, C-N), 461m, 270s ν(Rh-Cl).1H NMR (CDCl3, 293K):
δ 1.24 (t, 3H, CH2CH3), 1.67 (s, 15H, CH3Cp*), 2.35 (s, 3H, 3-CH3),
2.59 (dd, 2J(A-X) ) 7.32 Hz, ∆δV/J ) 2.04), 2.66 (dd, 2J(A-X)
NMR (CDCl3, 293 K): δ 8.65 (s, CH3Cp*), 17.74 (s, 3-CH3), 44.86
(s, CH2C6H5), 92.25, 92.44 (d, CCp*, J(103Rh-13C) ) 9.5 Hz),
120.86, 124.98, 126.80, 128.54, 128.58, 129.83, 136.38, 139.14 (s,
N-C6H5 and COCH2C6H5), 148.34 (s, C3), 189.98 (s, CO), C4 and
C5 not observed.
[Chloro(pentamethylcyclopentadienyl)(1-phenyl-3-methyl-4-
(2-phenylacetyl)pyrazolon-5-ato)iridium(III)], [Cp*Ir(QBn)Cl]
(7). Dark-yellow compound 7 (0.075 g, 0.15 mmol, 55% yield)
was prepared following a procedure similar to that reported for 3
using [Cp*IrCl2]2 and NaQBn and was recrystallized from 1:1 CH2-
Cl2/light petroleum (40-60 °C). mp: 180-185 °C. Anal. Calcd
for C28H30ClIrN2O2: C, 51.41; H, 4.62; N, 4.28. Found: C, 51.20;
H, 4.70; N, 4.10. IR (Nujol, cm-1): 1605s, 1590m, 1577s, 1532m
2
) 7.32 Hz, ∆δV/J ) 1.93), 2.80 (dd, J(A-X) ) 7.32 Hz, ∆δV/J
2
) 2.00), 2.88 (dd, J(A-X) ) 7.32 Hz, ∆δV/J ) 2.00), 7.12-
7.20m, 7.32-7.40m, 7.95d (5H, N-C6H5). 13C NMR (CDCl3, 293
K): δ 8.92 (s, CH3Cp*), 9.84 (s, CH2CH3), 17.76 (s, 3-CH3), 32.14
(s, CH2CH3), 92.19, 92.38 (d, CCp*, J(103Rh-13C) ) 9.4 Hz), 105.80
(s, C4), 120.88, 124.86, 128.56, 139.26 (s, N-C6H5), 148.44 (s,
C3), 162.80 (s, C5), 193.80 (s, CO).
1
ν(C-C, C-N), 512m, 462w, 273s ν(Ir-Cl). H NMR (CDCl3,
293 K): δ 1.47 (s, 15H, CH3Cp*), 2.44 (s, 3H, 3-CH3), 3.77, 3.84,
[Chloro(pentamethylcyclopentadienyl)(1-phenyl-3-methyl-4-
(3,3-dimethylbutanoyl)pyrazolon-5-ato)rhodium(III)], [Cp*Rh-
(QPiv)Cl] (4). Dark yellow compound 4 (0.092 g, 0.17 mmol, 63%
yield) was prepared following a procedure similar to that reported
for 1 using [Cp*RhCl2]2 and NaQPiv and was recrystallized from
1:1 CH2Cl2/light petroleum (40-60 °C). mp: 235-238 °C. Anal.
Calcd for C26H34ClN2O2Rh: C, 57.31; H, 6.29; N, 5.14. Found:
C, 56.93; H, 6.31; N, 5.03. IR (Nujol, cm-1): 1606s, 1591s, 1578s,
1537s ν(C-C, C-N), 510m, 472s, 266s ν(Rh-Cl). 1H NMR
(CDCl3, 293 K): δ 1.12 (s, 9H, CH2C(CH3)3), 1.71 (s, 15H,
2
4.22, 4.30 (q, 2Hgem, COCH2C6H5, J(A-X) ) 15.20 Hz, ∆δV/J
) 6.02), 7.18-7.41m, 7.93d (10H, N-C6H5 and COCH2C6H5). 13
C
NMR (CDCl3, 293 K): δ 8.88 (s, CH3Cp*), 17.58 (s, 3-CH3), 44.57
(s, CH2(Ph)), 83.56 (s, CCp*), 106.66 (s, C4), 120.86, 125.23,
126.89, 128.60, 128.67, 129.67, 135.85, 138.91 (s, N-C6H5 and
COCH2C6H5), 148.41 (s, C3), 161.61 (s, C5), 188.83 (s, CO).
[Chloro(pentamethylcyclopentadienyl)(1-phenyl-3-methyl-4-
(2,2-diphenylacetyl)pyrazolon-5-ato)rhodium(III)], [Cp*Rh-
(QS)Cl] (8). Orange compound 8 (0.101 g, 0.16 mmol, 57% yield)
was prepared following a procedure similar to that reported for 1
using [Cp*RhCl2]2 and NaQS and was recrystallized from 1:1
CH2Cl2/light petroleum (40-60 °C). mp: 226-228 °C. Anal. Calcd
for C34H34ClN2O2Rh: C, 63.71; H, 5.35; N, 4.37. Found: C, 63.90;
H, 5.45; N, 4.20. IR (Nujol, cm-1): 1607s, 1591s, 1579s, 1531m,
ν(C-C, C-N), 459m, 278s ν(Rh-Cl).1H NMR (CDCl3, 293 K):
δ 1.43 (s, 15H, CH3Cp*), 2.29 (s, 3H, 3-CH3), 5.72 (s, 1H,
CH(C6H5)2), 7.10-7.41m, 7.93d (15H, N-C6H5 and CH2(C6H5)2).
13C NMR (CDCl3, 293 K): δ 8.62 (s, CH3Cp*), 17.57 (s, 3-CH3),
58.26 (s, CH(C6H5)2), 92.30 (d, CCp*, J(103Rh-13C) ) 9.4 Hz),
120.93, 124.98, 126.8, 127.17, 128.22, 128.56, 129.40, 129.60,
130.12, 138.87 (s, N-C6H5 and CH2(C6H5)2), 148.39 (s, C3), 161.80
(s, C5), 189.85 (s, CO), C4 not observed.
[Chloro(pentamethylcyclopentadienyl)(1-phenyl-3-methyl-
4-(2,2-diphenylacetyl)pyrazolon-5-ato)iridium(III)], [Cp*Ir-
(QS)Cl] (9). Orange compound 9 (0.120 g, 0.16 mmol, 55% yield)
was prepared following a procedure similar to that reported for 3
using [IrCp*Cl2]2 and NaQCH-Ph2 and was recrystallized from 1:1
CH2Cl2/light petroleum (40-60 °C). mp: 151-154 °C. Anal. Calcd
for C34H34ClIrN2O2: C, 55.92; H, 4.69; N, 3.84. Found: C, 55.88;
H, 4.84; N, 3.83. IR (Nujol, cm-1): 1605s, 1591s, 1578s, 1532m,
ν(C-C, C-N), 509w, 465w, 280s ν(Ir-Cl).1H NMR (CDCl3, 293
K): δ 1.39 (s, 15H, CH3Cp*), 2.31 (s, 3H, 3-CH3), 5.73 (s, 1H,
CH(C6H5)2), 7.10-7.55m, 7.95d (15H, N-C6H5 and CH2(C6H5)2).
13C NMR (CDCl3, 293 K): δ 8.81 (s, CH3Cp*), 17.42 (s, 3-CH3),
57.92 (s, CH(Ph)2), 83.60 (s, CCp*), 120.92, 125.21, 126.94, 127.26,
127.68, 128.26, 128.64, 129.07, 129.64, 130.12, 138.46, 141.23 (s,
N-C6H5 and CH2(C6H5)2), 148.08 (s, C3), 189.32 (s, CO), C4 not
observed.
CH3Cp*), 2.39 (s, 3H, 3-CH3), 2.49, 2.55, 2.68, 2.74 (q, 2Hgem
,
CH2C(CH3)3, 2J(A-X) ) 13.18 Hz, ∆δV/J ) 2.88), 7.16-7.41m,
7.95d (5H, N-C6H5). 13C NMR (CDCl3, 293 K): δ 8.90 (s,
CH3Cp*), 18.25 (s, 3-CH3), 30.43 (s, CH2C(CH3)3), 32.55 (s,
CH2C(CH3)3), 50.09 (s, CH2C(CH3)3), 91.99, 92.13 (d, CCp*
,
J(103Rh-13C) ) 9.2 Hz), 120.73, 124.66, 128.28, 138.99 (s,
N-C6H5), 148.19 (s, C3), 192.84 (s, CO), C4 and C5 not observed.
[Chloro(pentamethylcyclopentadienyl)(1-phenyl-3-methyl-4-
(3,3-dimethylbutanoyl)pyrazolon-5-ato)iridium(III)], [Cp*Ir-
(QPiv)Cl] (5). Yellow compound 5 (0.105 g, 0.16 mmol, 58% yield)
was prepared following a procedure similar to that reported for 3
using [IrCp*Cl2]2 and NaQPiv and was recrystallized from 1:1
CH2Cl2/light petroleum (40-60 °C). mp: 160-162 °C. Anal. Calcd
for C26H34ClIrN2O2: C, 49.24; H, 5.40; N, 4.42. Found: C, 49.07;
H, 5.35; N, 4.20. IR (Nujol, cm-1): 1603s, 1591s, 1578s, 1537m
1
ν(C-C, C-N), 510w, 476w, 279s ν(Ir-Cl). H NMR (CDCl3,
293 K): δ 1.11 (s, 9H, CH2C(CH3)3), 1.66 (s, 15H, CH3Cp*), 2.41
(s, 3H, 3-CH3), 2.46, 2.53, 2.67, 2.74 (q, 2Hgem, CH2C(CH3)3, 2J(A-
X) ) 13.19 Hz, ∆δV/J ) 3.20), 7.15-7.41m, 7.91d (5H, N-C6H5).
13C NMR (CDCl3, 293 K): δ 9.32 (s, CH3Cp*), 18.33 (s, 3-CH3),
30.63 (s, CH2C(CH3)3), 32.65 (s, CH2C(CH3)3), 49.96 (s, CH2C-
(CH3)3), 83.48 (s, CCp*), 108.13 (s, C4), 120.94, 125.14, 128.62,
138.04 (s, N-C6H5). 148.52 (s, C3), 161. 86 (s, C5), 192.24 (s,
CO).
[Chloro(pentamethylcyclopentadienyl)(1-phenyl-3-methyl-4-
(2-phenylacetyl)pyrazolon-5-ato)rhodium(III)], [Cp*Rh(QBn)-
Cl] (6). Brown-red compound 6 (0.110 g, 0.19 mmol, 59% yield)
was prepared following a procedure similar to that reported for 1
using [Cp*RhCl2]2 and NaQBn and was recrystallized from 1:1 CH2-
Cl2/light petroleum (40-60 °C). mp: 230-233 °C. Anal. Calcd
for C28H30ClN2O2Rh: C, 59.53; H, 5.35; N, 4.96. Found: C, 59.53;
H, 5.61; N, 4.95. IR (Nujol, cm-1): 1607s, 1590s, 1577s, 1531s
[(Pentamethylcyclopentadienyl)(1-phenyl-3-methyl-4-
acetylpyrazolon-5-ato)(acetonitrile)rhodium(III)]nitrate Tri-
hydrate, [Cp*Rh(QMe)(MeCN)]NO3‚3H2O (10). A CH3CN solu-
tion (10 mL) containing [Cp*Rh(QMe)Cl] (0.120 g, 0.24 mmol) and
AgNO3 (0.048 g, 0.28 mmol) under N2 at room temperature was
stirred overnight. After 48 h, a colorless precipitate formed, which
was filtered of and shown to be AgCl. The clear yellow solution
obtained was evaporated under vacuum; the yellow residue was
washed with light petroleum (40-60 °C) and was identified as 10.
mp: 200-201 °C. Anal. Calcd for C24H35N4O8Rh: C, 47.22; H,
1
ν(C-C, C-N), 512w, 456s, 264s ν(Rh-Cl). H NMR (CDCl3,
293K): δ 1.48 (s, 15H, CH3Cp*), 2.43 (s, 3H, 3-CH3), 3.79, 3.87,
2
4.23, 4.31 (q, 2Hgem, COCH2C6H5, J(A-X) ) 15.40 Hz, ∆δV/J
1
) 5.81), 7.12-7.40, 7.94-7.99 (m, 10H, Ph). H NMR (CDCl3,
318 K): δ 1.48 (s, 15H, CH3Cp*), 2.41 (s, 3H, 3-CH3), 3.81, 3.86,
2
4.22, 4.26 (q, 2Hgem, CH2C6H5, J(A-X) ) 14.90 Hz, ∆δV/J )
8.18), 7.12-7.40m, 7.96d (10H, N-C6H5 and COCH2C6H5). 13C
Inorganic Chemistry, Vol. 44, No. 22, 2005 7935

Pettinari et al.
4
5.78; N, 9.18. Found: C, 46.90; H, 5.81; N, 9.22. IR (Nujol, cm-1):
1604s, 1589s, 1574s, 1519s, ν(C-C, C-N), 1450sh, 1277sbr ν-
(NO3), 514m, 456m.1H NMR (CDCl3, 293 K): δ 1.6 (s br, 21H,
CH3Cp* + H2O), 2.0 (s br, 3H, MeCN), 2.32 (s, 3H, 3-CH3), 2.41
(s, 3H, COCH3), 7.10-7.40, 7.92-7.96 (m, 5H, N-Ph). 13C NMR
(CDCl3, 293 K): δ 8.83 (s, CH3Cp*), 17.48 (s, 3-CH3), 27.83
(COCH3), 92.47, 92.61 (d, CCp*, J(103Rh-13C) ) 10.5 Hz), 120.77
(s, C2 and C6Ph-Q), 125.19 (s, C4Ph-Q), 128.69 (s, C3 and C5Ph-Q),
138.92 (s, C1Ph-Q), 148.84 (s, C5Py).
15H, CH3Cp*, J(31P-1H) ) 3.66 Hz), 2.08 (d, 3H, 3-CH3), 2.38
(d, 3H, COCH3), 7.15-7.82m, 8.08m (5H, N-C6H5, 15H, P(C6H5)3).
13C NMR (CDCl3, 293 K): δ 8.96 (d, J(103Rh-13C) ) 4.55 Hz,
2
CH3Cp*), 9.01 (d, 2J(103Rh-13C) ) 4.46 Hz, CH3Cp*), 16.90, 17.22
(s, 3-CH3), 27.72, 28.24 (COCH3), 99.34 (d, 1J(103Rh-13C) ) 6.7
Hz, CCp*), 99.38 (d, 1J(103Rh-13C) ) 6.8 Hz, CCp*), 106.12, 104.30
(s, C4), 118.93, 120.45, 126.10, 127.14, 129.55, 129.71, 138.17,
138.82 (s, N-C6H5 of Q), 128.86 (d, 3J(31P-13C) ) 11.06 Hz, m-C),
129.42 (d, 3J(31P-13C) ) 10.90 Hz, m-C), 129.75 (d, 4J(31P-13C)
) 3.82 Hz, p-C), 131.32 (sbr, p-C), 132.71 (d, 1J(31P-13C) ) 15.64
[(Pentamethylcyclopentadienyl)(1-phenyl-3-methyl-4-
acetylpyrazolon-5-ato)(aqua)rhodium(III)]perchlorate, [Cp*Rh-
(QMe)(H2O)]ClO4 (11). Compound 11 was prepared following a
procedure similar to that reported for 10 using [Cp*Rh(QMe)Cl]
and AgClO4. After 48 h, a pale-yellow precipitate formed, which
was removed by filtration and shown to be AgCl and AgQ. The
clear red-yellow solution obtained was evaporated under vacuum;
the red-yellow residue was washed with light petroleum (40-60
°C) and was identified as a mixture of 11 and [Cp*Rh(Cl)(H2O)2]-
ClO4. Recrystallization from CH3CN/Et2O yields microcrystalline
11 (0.200 g, 0.35 mmol, 70% yield). mp: 230-233 °C. Anal. Calcd
for C22H28ClN2O7Rh: C, 46.29; H, 4.94; N, 4.91. Found: C, 45.87;
H, 5.10; N, 4.85. IR (Nujol, cm-1): 3400 br, 1606s, 1589sh, 1577s,
1530m, ν(C-C, C-N), 1080sbr ν(ClO4), 509w, 463m.1H NMR
((CD3)2CO), 293K): δ 1.73(s, 15H, CH3Cp*), 2.18 (s, 2H, H2O),
2.37 (s, 3H, 3-CH3), 2.56 (s, 3H, COCH3), 7.20-7.37m, 7.42-
7.58m, 7.98d (5H, N-Ph). 13C NMR (CDCl3, 293 K): δ 8.39 (s,
Hz, i-C), 132.77 (d, J(31P-13C) ) 16.78 Hz, i-C), 134.74, (d,
1
2J(31P-13C) ) 10.30 Hz, o-C), 135.68 (d, 2J(31P-13C) ) 9.54 Hz,
o-C), 148.69, 149.82 (s, C3), 161.95, 163.84 (s, C5), 191.71, 193.02
(s, CO).31P NMR (CDCl3, 293 K): 30.71, (d, 1J(31P-Rh) ) 147.7
1
Hz), 30.44 (d, J(31P-Rh) ) 143.9 Hz).
[(Pentamethylcyclopentadienyl)(1-phenyl-3-methyl-4-(3,3-
dimethylbutanoyl)pyrazolon-5-ato)(triphenylphosphine)rho-
dium(III)]chloride, [Cp*Rh(QPiv)(PPh3)]Cl (14). Red compound
14 (0.167 g, 0.20 mmol, 76% yield) was prepared following a
procedure similar to that reported for 13 using [Cp*Rh(QPiv)Cl]
and PPh3. mp: 100 °C (dec). Anal. Calcd for C44H49ClN2O2PRh:
C, 65.47; H, 6.12; N, 3.47. Found: C, 65.51; H, 6.28; N, 3.42. IR
(Nujol, cm-1): 1621m, 1589m, 1566s, 1522w ν(C-C, C-N),
1
523s, 510m, 497m, 394sbr. H NMR (CDCl3, 293 K): δ 0.90 (s,
9H, CH2C(CH3)3), 1.06 (s, 9H, CH2C(CH3)3), 1.10 (d, 15H, CH3Cp*
,
4J(31P-1H) ) 2.60 Hz), 1.36 (d, 15H, CH3Cp*, 4J(31P-1H) ) 2.66
Hz), 2.23 (s, 3H, 3-CH3), 2.36 (m, 3H, 3-CH3), 7.30-7.50, 7.70-
7.85, 8.05 (m, 5H, N-Ph). 2.08 (d, 3H, 3-CH3), 2.38 (d, 3H,
COCH3), 7.15-7.82m, 8.08m (5H, N-C6H5, 15H, P(C6H5)3).13C
NMR (CDCl3, 293 K): δ 9.02 (d, 2J(103Rh-13C) ) 2.87 Hz,
CH3Cp*), 9.12 (d, 2J(103Rh-13C) ) 2.65 Hz, CH3Cp*), 17.92, 18.40
(s, 3-CH3), 29.85, 30.41 (s, CH2C(CH3)3), 49.87, 50.12 (s, CH2C-
(CH3)3), 99.70 (d, 1J(103Rh-13C) ) 6.1 Hz, CCp*), 99.95 (d,
1J(103Rh-13C) ) 5.7 Hz, CCp*), 120.45, 121.10, 126.02, 126.74,
CH3Cp*), 16.92 (s, 3-CH3), 27.67 (COCH3), 94.43, 94.57(d, CCp*
,
J(103Rh-13C) ) 10.5 Hz), 105.47 (s, C4), 120.98, 125.93, 129.08,
138.79 (s, N-C6H5 of Q), 149.59 (s, C5Py), 162.35 (s, C5), 192.34
(s, CO).
[Bromo(pentamethylcyclopentadienyl)(1-phenyl-3-methyl-4-
(2-phenylacetyl)pyrazolon-5-ato)rhodium(III)], [RhCp*(QBn)-
Br] (12). [Cp*RhCl2]2 (0.140 g, 0.22 mmol) was dissolved in 10
mL of THF, and 0.45 mL of Grignard reagent (MgCH3Br solution,
1.0 M in hexane) was added. The red solution was stirred for 48 h
under N2 at room temperature, evaporated under vacuum, and
treated with CH2Cl2. A colorless precipitate formed, which was
filtered off and shown to be MgCl2. The filtrate was dried under
vacuum; then 10 mL of toluene was added to give a red solution,
and finally NaQBn was added. The mixture was stirred overnight
under N2 at room temperature to give a red-orange precipitate, which
was filtered off, washed with 5 mL of toluene, and then recrystal-
lized from 1:1 CH2Cl2/light petroleum (40-60 °C); it has been
identified as 12. Anal. Calcd for C28H30BrN2O2Rh: C, 55.19; H,
4.96; N, 4.60. Found: C, 54.98; H, 5.10; N, 4.30. IR (Nujol, cm-1):
127.92, 128.62, 137.50, 138.17 (s, N-C6H5), 127.82 (d, J(31P-
3
13C) ) 14.55 Hz, m-C), 128.91 (d, 3J(31P-13C) ) 18.22 Hz, m-C),
128.30 (d, 4J(31P-13C) ) 4.27 Hz, p-C), 130.76 (sbr, p-C), 133.10
(d, 1J(31P-13C) ) 19.42 Hz, i-C), 133.27 (d, 1J(31P-13C) ) 23.10
Hz, i-C), 134.47, (d, J(31P-13C) ) 10.35 Hz, o-C), 134.93 (d,
2
2J(31P-13C) ) 9.67 Hz, o-C), 147.14, 148.42 (s, C3), 160.67, 162.18
(s, C5), 190.80, 192.62 (s, CO). 31P NMR (CDCl3, 293 K): δ 30.04
(d, J(31P-Rh) ) 149.8 Hz), 30.43 (d, J(31P-Rh) ) 144.1 Hz).
[(Pentamethylcyclopentadienyl)(1-phenyl-3-methyl-4-(2,2-
diphenylacetyl)pyrazolon-5-ato)(triphenylphosphine)rho-
dium(III)]chloride, [RhCp*(QS)(PPh3)]Cl (15). Orange compound
15 (0.150 g, 0.16 mmol, 75% yield) was prepared following a
procedure similar to that reported for 13 using RhCp*(QS)Cl and
PPh3. Anal. Calcd for C52H49ClN2O2PRh: C, 69.14; H, 5.47; N,
1
1
1
1609s, 1591s, 1581s, 1528m ν(C-C, C-N), 512w, 450w. H
NMR (CDCl3, 293 K): δ 1.52 (s, 15H, CH3Cp*), 2.42 (s, 3H,
2
3-CH3), 3.79, 3.87, 4.21, 4.29 (q, 2Hgem, COCH2C6H5, J(A-X)
1
) 15.40 Hz, ∆δV/J ) 5.57), 7.12-7.40m, 7.94d (10H, N-C6H5
and COCH2C6H5).
3.10. Found: C, 68.80; H, 5.28; N, 3.02. H NMR (CDCl3, 293
K): δ 0.84 (d, 15H, CH3Cp*, 4J(31P-1H) ) 3.20 Hz), 1.37 (d, 15H,
CH3Cp*, 4J(31P-1H) ) 3.78 Hz), 2.01 (s, 3H, 3-CH3), 2.34 (s, 3H,
3-CH3), 5.22 (s, 1H, CH(C6H5)2), 5.35 (s, 1H, CH(C6H5)2), 7.00-
8.01 (m, 5H, N-C6H5, 15H, P(C6H5)3). 31P NMR (CDCl3, 293 K):
δ 28.97 (d, 1J(31P-Rh) ) 149.6 Hz), 30.44 (d, 1J(31P-Rh) ) 144.1
Hz). Compound 15 has been also obtained when the reaction was
carried out at -80 °C for 5 min.
[(Pentamethylcyclopentadienyl)(1-phenyl-3-methyl-4-
acetylpyrazolon-5-ato)(triphenylphosphine)rhodium(III)]-
chloride, [Cp*Rh(QMe)(PPh3)]Cl (13). A dichloromethane solution
(10 mL) containing RhCp*(QMe)Cl (0.085 g, 0.17 mmol) and PPh3
(0.044 g, 0.17 mmol) was stirred for 72 h under N2 at room
temperature. The orange solution was dried in a vacuum and
recrystallized from 1:1 CH2Cl2/light petroleum (40-60 °C), and
the crystals were shown to be compound 13 (0.102 g, 0.136 mmol,
80% yield). mp: 100 °C (dec). Anal. Calcd for C40H41ClN2O2PRh,
C, 63.96; H, 5.50; N, 3.73. Found: C, 64.12; H, 5.68; N, 3.57. IR
(Nujol, cm-1): 3180w ν(Ph), 1610sh, 1592m, 1570s, ν(C-C,
C-N), 1096s, 1021s, 521s, 511s, 499msh, 396vs. 1H NMR (CDCl3,
293 K): δ 1.15 (d, 15H, CH3Cp*, 4J(31P-1H) ) 3.36 Hz), 1.34 (d,
X-ray Diffraction Studies. Full spheres of CCD area-detector
diffractometer data were measured at ca. 153 K (Bruker AXS
instrument, ω-scans; monochromatic Mo KR radiation, λ ) 0.71073
Å) yielding Nt(otal) reflections; those merging to N unique (Rint
quoted) after “empirical”/multiscan absorption correction (propri-
etary software), No with F > 4σ(F) considered “observed”, were
used in the full-matrix least-squares refinement, refining anisotropic
7936 Inorganic Chemistry, Vol. 44, No. 22, 2005

Rhodium(III) Cyclopentadienyl â-diketonate Complexes
Table 1. Crystal and Refinement Data
1a
2
4b
6
formula
Mr
C22H26ClN2O2Rh
488.8
C22H26ClIrN2O2
578.1
C26H34N2O2Rh
544.9
C28H30ClN2O2Rh
564.9
cryst syst
space group
a (Å)
b (Å)
c (Å)
monoclinic
P21/n (No. 14)
8.540(1)
17.163(3)
13.769(2)
monoclinic
P21/n (No. 14)
8.6997(6)
17.049(1)
13.9360(9)
monoclinic
P21/n (No. 14)
16.059(5)
19.606(7)
8.081(3)
monoclinic
P21/c (No. 14)
7.582(2)
21.345(6)
15.458(5)
R (deg)
â (deg)
γ (deg)
V (Å3)
97.287(4)
96.470(2)
92.177(7)
102.037(7)
2002
1.622
2054
1.869
2542
1.424
2447
1.533
Dc (g cm-3
)
Z
4
1.01
4
6.7
4
0.80
4
0.84
µ (mm-1
)
specimen (mm)
′T′min/max
2θmax (deg)
Nt
N (Rint
No
0.44× 0.22 × 0.15
0.12× 0.08 × 0.06
0.19× 0.14 × 0.02
0.19× 0.14 × 0.08
0.84
0.73
0.58
0.90
75
75
50
55
42157
10628 (0.039)
8115
42837
10806 (0.045)
7799
20656
4564 (0.16)
1685
25402
5542 (0.062)
4294
)
R
Rw
0.044
0.050
0.035
0.040
0.079
0.103
0.043
0.067
7
8
12
formula
Mr
C28H30ClIrN2O2
654.2
C34H34ClN2O2Rh
641.0
C28H30BrN2O2Rh
609.4
cryst syst
space group
a (Å)
b (Å)
c (Å)
Monoclinic
P21/c (#14)
7.5905(7)
21.337(2)
15.560(2)
Monoclinic
P1h(#2)
Monoclinic
P21/c (#14)
7.618(1)
21.329(4)
15.605(3)
8.2875(6)
13.778(1)
14.610(1)
109.429(2)
95.937(2)
106.875(2)
1468
R (deg)
â (deg)
γ (deg)
V (Å3)
101.893(2)
101.784(3)
2466
1.762
2482
1.630
Dc (g cm-3
)
1.450
Z
4
5.6
2
0.71
4
2.3
µ (mm-1
)
specimen (mm)
′T′min/max
2θmax (deg)
Nt
N (Rint
No
0.18× 0.10 × 0.08
0.15× 0.09 × 0.06
0.15× 0.09 × 0.07
0.65
0.92
0.84
75
75
27373
15079 (0.025)
11973
50
51205
12742 (0.048)
9804
17150
4512 (0.054)
3482
)
R
Rw
0.037
0.049
0.043
0.044
0.038
0.043
a (x,y,z,Uiso
)
H
refined. b Weak and limited data would support meaningful anisotropic displacement parameter refinement for Rh, Cl only.
displacement parameter forms for the non-hydrogen atoms,
(x,y,z,Uiso)H constrained at estimated values. Conventional residuals
to produce [Cp*M(Q)Cl] derivatives 1-9 (eq 1)
R and Rw on |F| at convergence (weights ) (σ2(F) + 0.0004F2)-1
)
[MCp*Cl}2(µ-Cl)2] + 2QNa f [Cp*M(Q)Cl] + 2NaCl
1-9
are quoted. Neutral atom complex form factors were employed
within the Xtal 3.7 program system.16 Pertinent results are given
below and in Tables 1 and 3 and the figures, the latter showing
50% probability amplitude displacement envelopes for the non-
hydrogen atoms; the hydrogen atoms have an arbitrary radii of
0.1 Å.
(1)
1: M ) Rh, Q ) QMe
3: M ) Rh, Q ) QEt
5: M ) Ir, Q ) QPiv
7: M ) Ir, Q ) QBn
9: M ) Ir, Q ) QS
2: M ) Ir, Q ) QMe
4: M ) Rh, Q ) QPiv
6: M ) Rh, Q ) QBn
8: M ) Rh, Q ) QS
Results and Discussion
The [{(η5-C5Me5)MCl}2(µ-Cl)2] (M)Rh, Ir)17 compounds
were reacted at room temperature with stoichiometric
amounts of the sodium salt of acylpyrazolone NaQ in toluene
Slow diffusion of petroleum ether into toluene or dichloro-
methane solutions of [Cp*M(Q)Cl] compounds produced,
in a number of cases, single crystals suitable for X-ray
structure analyses. Complexes 1-9 are air-stable and soluble
in chlorinated and other common solvents such as toluene,
(16) Hall, S. R., du Boulay, D. J., Olthof-Hazekamp, R., Eds. The Xtal 3.7
System; University of Western Australia: Crawley, Australia, 2001.
(17) White, C.; Yates, A.; Maitlis, P. M.; Heinekey, D. M. Inorg Synth.
1992, 29, 228-234.
Inorganic Chemistry, Vol. 44, No. 22, 2005 7937

Pettinari et al.
Table 2. Selected Geometries, [Cp*MQX]a
1
2
4
6
7
8
12
M/X/Q
Rh/Cl/QMe
Ir/Cl/QMe
Rh/Cl/QPiv
Rh/Cl/QBn
Ir/Cl/QBn
Rh/Cl/QS
Rh/Br/QBn
distances (Å)
M-X
2.3996(6)
2.100(2)
2.093(2)
2.106(2)
-2.128(2)
2.119(9)
1.740
2.4065(9)
2.111(3)
2.108(2)
2.127(3)
-2.144(3)
2.136(6)
1.752
2.378(5)
2.13(1)
2.11(1)
2.01(2)
-2.17(2)
2.10(6)
1.74
2.414(1)
2.111(3)
2.095(3)
2.113(4)
-2.144(4)
2.131(12)
1.752
2.4058(9)
2.113(3)
2.107(3)
2.124(3)
-2.140(4)
2.134(6)
1.750
2.4208(5)
2.126(1)
2.122(2)
2.125(2)
-2.139(2)
2.132(6)
1.750
2.5457(6)
2.103(3)
2.104(3)
2.120(4)
-2.148(4)
2.125(13)
1.752
M-O(41)
M-O(5)
M-C(Cp*)
<M-C(Cp*)>
M-C(0)
angles (deg)
C(0)-M-X
127.8
124.3
128.0
88.73(4)
86.54(4)
88.62(6)
129.0(1)
122.1(1)
129.4
125.3
129.2
86.09(7)
84.24(7)
88.2(1)
129.4(2)
122.5(2)
127.5
126.8
128.5
87.8(4)
86.0(3)
86.2(5)
130(1)
122(1)
127.4
126.6
126.4
86.29(7)
89.34(7)
87.8(1)
128.7(3)
121.9(3)
128.6
127.6
127.8
84.31(7)
86.76(7)
87.05(11)
130.0(3)
123.0(2)
126.6
126.7
127.1
86.94(4)
89.38(4)
87.09(5)
126.0(1)
117.2(1)
126.4
126.5
126.7
86.91(8)
89.95(8)
87.6(1)
129.1(3)
121.9(3)
C(0)-M-O(41)
C(0)-M-O(5)
X-M-O(41)
X-M-O(5)
O(41)-M-O(5)
M-O(41)-C(41)
M-O(5)-C(5)
interplanar dihedral angles (deg)
N2C3/C6
N2C3/C5
4.64(8)
49.60(9)
6.0(1)
51.7(1)
4.4(7)
55.4(9)
5.7(1)
68.9(2)
5.5(1)
68.7(1)
24.04(8)
89.47(8)
5.3(2)
70.1(2)
out-of-plane deviations (Å)
δM/C3N2
δM/C5
0.143(4)
1.737(1)
0.163(7)
1.747(1)
0.22(4)
1.737(2)
0.322(8)
1.750(1)
0.260(7)
1.747(1)
0.882(4)
1.746(1)
0.330(9)
1.750(1)
a C(0) is the centroid of Cp*.
Table 3. Selected Ligand Geometriesa
distances (Å)
1
2
6
7
8
12
N(1)-N(2)
N(1)-C(5)
N(1)-C(11)
N(2)-C(3)
C(3)-C(4)
C(4)-C(41)
C(4)-C(5)
C(41)-O(41)
C(5)-O(5)
O(41)‚‚‚O(5)
1.390(3)
1.362(3)
1.405(3)
1.305(3)
1.426(3)
1.403(3)
1.418(3)
1.253(3)
1.261(3)
2.929(2)
1.401(4)
1.362(4)
1.431(4)
1.315(5)
1.430(5)
1.404(5)
1.429(5)
1.267(4)
1.267(4)
2.934(6)
1.403(4)
1.379(5)
1.422(5)
1.310(5)
1.431(5)
1.417(5)
1.428(5)
1.254(5)
1.265(5)
2.916(4)
1.400(4)
1.364(5)
1.425(5)
1.311(5)
1.440(5)
1.411(5)
1.424(5)
1.262(4)
1.275(4)
2.906(4)
1.396(2)
1.368(3)
1.416(3)
1.317(3)
1.430(2)
1.415(3)
1.429(2)
1.265(2)
1.272(2)
2.927(2)
1.402(5)
1.371(6)
1.423(6)
1.308(6)
1.441(6)
1.408(5)
1.430(6)
1.263(5)
1.267(5)
2.912(5)
angles (degrees)
1
2
6
7
8
12
N(2)-N(1)-C(5)
N(2)-N(1)-C(11)
C(5)-N(1)-C(11)
N(1)-N(2)-C(3)
N(2)-C(3)-C(4)
N(2)-C(3)-C(31)
C(4)-C(3)-C(31)
C(3)-C(4)-C(5)
C(3)-C(4)-C(41)
C(5)-C(4)-C(41)
C(4)-C(41)-O(41)
C(4)-C(41)-C(42)
O(41)-C(41)-C(42)
N(1)-C(5)-C(4)
N(1)-C(5)-O(5)
111.9(2)
118.5(2)
129.6(2)
105.9(2)
111.7(2)
118.4(2)
129.9(2)
105.0(2)
130.5(2)
124.6(2)
123.6(2)
121.3(2)
115.1(2)
105.5(2)
122.9(2)
112.5(3)
117.8(3)
129.7(3)
105.2(3)
112.0(3)
118.3(3)
129.6(3)
104.9(3)
130.8(3)
124.3(3)
123.7(3)
121.8(3)
114.5(3)
105.3(3)
123.1(3)
111.5(3)
111.0(3)
111.9(2)
118.0(2)
129.6(1)
105.8(2)
111.6(1)
118.3(2)
129.5(2)
105.0(2)
131.5(1)
123.1(1)
123.0(2)
120.1(1)
116.8(2)
105.4(1)
123.5(2)
111.9(4)
118.1(3)
129.8(3)
105.9(3)
112.0(4)
117.9(4)
130.1(4)
104.6(3)
132.2(4)
122.8(4)
124.2(4)
122.2(4)
113.6(4)
105.6(4)
123.0(4)
119.0(3)
129.4(3)
106.3(3)
111.4(3)
117.5(3)
131.0(4)
105.6(3)
132.2(3)
121.9(3)
124.9(3)
121.4(3)
113.6(3)
105.0(3)
122.7(3)
118.6(3)
130.4(3)
106.4(3)
111.2(3)
118.0(3)
130.3(4)
104.1(3)
132.2(2)
123.4(3)
123.7(1)
122.6(3)
113.7(3)
106.8(3)
122.4(3)
a 4 is less precise and is, therefore, omitted.
acetonitrile, or acetone. The moderate yields (55-63%) are
often the result of the large solubility of 1-9 in the solvents
employed during the workup. No evidence of a cyclometa-
lation reaction has been found in the case of the Ir(Cp*)
derivatives. The IR spectra of 1-9 show the absence of broad
absorptions in the range of 2300-2800 cm-1, ascribed to
intramolecular ν(O-H‚‚‚O) in the neutral free HQ pro-
ligands. In addition, the shift to lower frequencies of the
ν(CdO) band (at ca. 1600 cm-1) is in accordance with the
deprotonation of HQ and the subsequent coordination of the
heterocycle to the metal in the anionic form. In the far-IR
region, several absorptions have been detected in the 480-
7938 Inorganic Chemistry, Vol. 44, No. 22, 2005

Rhodium(III) Cyclopentadienyl â-diketonate Complexes
Figure 3. Proposed ionic structure for compounds 10 and 11.
room temperature. Coalescence studies (also in different
solvents) were not possible in the case of the Ir complexes
5 and 7 because decomposition commences at temperatures
above 40 °C. Decomposition is also observed in nitromethane
or benzene solutions.
The reactions of [Cp*Rh(QMe)Cl] 1 with AgX in not-
anhydrous MeCN yielded derivatives 10 and 11.
[Cp*Rh(QMe)Cl] + AgX Solv8 [Cp*Rh(QMe)(Solv)]X + AgCl
(2)
10: X ) NO3; Solv ) MeCN
11: X ) ClO4; Solv ) H2O
They are salt-like, both in solution and in the solid state.
The latter assumption is confirmed from their IR spectra,
which exhibit bands from noncoordinated nitrate (10) and
perchlorate groups (11). In both cases, the halide exchange
is accompanied by coordination of a solvent molecule,
consistent with the low tendency of Rh to coordinate NO3
and ClO4 groups. A byproduct in the synthesis of compound
11 is [Cp*Rh(Cl)(H2O)2]ClO4, which we have always found
in the mother liquor or in the precipitate, independent of the
amount of silver salt employed. The 1H and 13C NMR spectra
of 10 and 11 exhibit the same pattern found in the spectrum
of 1, suggesting O2-chelating bidentate coordination for Q
and η5-coordination for Cp*, in accordance with the structure
proposed in Figure 3.
Attempts to alkylate compounds 1-9 led only to halide
exchange, as revealed for example by the reaction of 6 with
CH3MgBr. This produces the complex [Cp*Rh(QBn)Br], 12,
where a chloride ligand has been displaced by bromide in
the rhodium coordination sphere. It is worth noting that
halogen-exchange reactions often require a 10-fold excess
of NaX (X ) Br or I) and that, after a short time, the reaction
mixture reaches equilibrium. In the present case, the reaction
is fast, and the chloride displacement by bromide is complete
within about 2 min. The spectroscopic features of 12 are
similar to those found for the parent compound 6, the only
difference being the expected displacement of the band,
because of Rh-X, from 260 cm-1 in 6 to 240 cm-1 in 12.
Chloride dissociation is also observed in the interactions of
derivatives 2, 4, and 6 with PPh3 yielding complexes
[Cp*Rh(Q)(PPh3)]Cl, 13-15. The displacement of the Cl
from the Rh-coordination sphere and the formation of an
ionic compound has been confirmed by the disappearance
of the IR band for ν(Rh-Cl). In no case was the coordination
of two PPh3 groups observed, nor when the reaction was
carried out in a large excess of the P donor. In contrast to
Figure 2. Two enantiomers of complexes 1-9.
440 and 290-260 cm-1 ranges. These may be assigned to
ν(M-O) and ν(M-Cl), respectively.18 The 1H NMR spectra
of compounds 1-9, recorded in CDCl3, agree well with the
formulas proposed. Thus, the presence of an η5-Cp* group
is inferred from the observation of a unique signal from the
methyl protons that invariably appears in the proximity of
1.65 ppm. Moreover, the Cp* ring-carbon nuclei resonate
at 92 ppm in the 13C{1H} NMR spectrum, exhibiting a
coupling of ca. 9 Hz with the 103Rh nucleus. Resonances
from the Q ligand are analogous to those found for other
rhodium acylpyrazolonates previously reported, consistent
with O,O′-chelation to the metal (see the X-ray single-crystal
studies below).13 These organometallic compounds are chiral-
at-metal, and they can exist as a couple of two enantiomers
(Figure 2a). In addition, the geminal methylene protons of
the Q-acyl substituent in complexes 3-7 are diastereotopic
and produce the expected AB quartets (see Experimental
section). For this reason, we have explored the use of the
diasterotopic CH2 protons of bonded QEt, QPiv, and QBn as a
probe in coalescence experiments carried out to understand
the stability of metal configuration in solution (Figure 2b).
We performed some VT NMR experiments by warming
the solution of derivatives 3, 4, and 6, and no change was
observed in the CDCl3 spectra up to 55 °C; the AB quartets
were always present. On the other hand, complexes 3, 4,
and 6 immediately dissociate in the strongly coordinating
deuterated solvents DMSO and CD3CN which can displace
the Q ligand from the metal coordination sphere, totally, or
at least partially, upon rupture of one diketonate arm. In fact,
in these solvents, quartets are not present both at low and
(18) Nakamura, Y.; Isobe, K.; Morita, H.; Yamazaki, S.; Kawaguchi, S.
Inorg. Chem. 1972, 11, 1573-1578.
Inorganic Chemistry, Vol. 44, No. 22, 2005 7939

Pettinari et al.
Figure 4. Three possible isomers for compounds 13-15.
Table 4. Selected ESI-MS Data (CH3CN)
compound
or mixture
[Cp*M(Q)]+ {[Cp*M(Q)]2Cl}+ {[Cp*M(Br)]2Cl}+ (Cp*)2M2Br3
[Cp*M(PPh3)(Q)]+ [Cp*MCl(MeCN)]+ (Cp*)2M2Cl3
+
+
1a
453 (100)
453 (55)
543 (100)
543 (10)
605 (100)
695 (100)
941 (10)
1 + RBr
670 (25)
849 (23)
715 (100)
893 (100)
2b
1121 (10)
404 (70)
404 (70)
2 + RBr
8c
1245 (8)
1425 (5)
9d
11e
314 (100)
580 (20)
580 (40)
11 + RBr
670 (75)
715 (10)
13f
453 (5)
453 (5)
715 (100)
715 (100)
771 (100)
13 + RBr
14g
a [Cp*Rh(QMe)Cl]. b [Cp*Ir (QMe)Cl]. c [Cp*Rh(QS)Cl]. d [Cp*Ir(QS)Cl]. e [Cp*Rh(QMe)H2O]ClO4. The most abundant peak in the positive spectrum of
11 is m/z 627 (100) {[Cp*Rh(Cl)]2Br}+. In the negative spectrum of 11, the most abundant peaks are m/z 99 (100) [ClO4]- and m/z 534 (20) [Rh(Cp)(ClO4)3]-.
f [Cp*Rh(QMe)(PPh3)]Cl. g [Cp*Rh(QPiv)(PPh3)]Cl.
the situation described above for complexes 1-9, the 1H and
31P NMR spectra of compounds 13-15 exhibit signals from
the two possible isomers (for instance, doublets δ 30.71 and
30.44, with a 1J(P-Rh) value of ca. 145 Hz can be detected
in the 31P{1H} NMR of 13). In CDCl3 solution at room
temperature, the equilibrium concentration of isomers is
approximately 4:1 for all compounds 13-15. We hypothesize
that in solution the breaking of one of the Rh-Odiketonate bonds
(likely to be dependent on the steric hindrance of the P donor)
and the coordination of solvent molecules or of the same
chloride ions, occurs with the formation of two different
species, for example, two of those reported in Figure 4. This
seems to be supported by the IR spectra of 13-15 in which
the CdO stretching frequencies have different values from
those reported for the corresponding [Cp*Rh(Q)(Cl] contain-
ing a bidentate Q ligand. However, we cannot exclude the
possibility of a complete dissociation of 13-15 in solution
and formation, for example, of [Cp*Rh(PPh3)(Solv)(Cl]
species.
Table 4 summarizes the ESI MS data for selected
derivatives 1, 2, 8, 9, 11, 13, and 14 and also for mixtures
containing derivative 1 or 8 and AgClO4, PR3, benzyl-
bromide, or Grignard reagents. The m/z values of prominent
peaks corresponding to rhodium or iridium cations are given
together with formula assignments. It is to point out that, in
the case of the halide derivatives 1, 2, 8, and 9, the most
abundant signal is that from the [Cp*M(Q)]+ cation. In the
ESI spectra of 1, 2, 8, and 9, a signal ascribed to a dinuclear
species generated by the loss of one halide group wherein
two cyclopentadienyl-metal moieties are likely bridged by
an halide or a pyrazolonate ligand is also present. When an
equimolar quantity or an excess of benzyl bromide or
Grignard reagent, RMgX (R ) Et, Bun; X ) Br), was added
to a MeCN solution of 1 or 8, signals corresponding to the
[(Cp*)2Rh2Br3]+ and [(Cp*)2Rh2Br2Cl]+ species were im-
mediately identified. In the case of PR3 derivatives 13-14,
the signals from the ionic species [Cp*Rh(PR3)(Q)]+ were
always the most abundant. No change was observed in the
ESI spectra when benzyl bromide was added to a solution
containing derivative 13, suggesting a high stability for these
species in solution.
A different behavior has been found in the positive
spectrum of derivative 11, the most abundant species detected
in solution being [Cp*Rh(Cl)]+, [(Cp*)2Rh2(Cl)3]+, and
[(Cp*)2Rh2(Cl)2(ClO4)]+. The anionic ligand Q- is present,
unassociated, in the negative spectrum together with signals
from the ClO4- and [Cp*Rh(ClO4)3]- anions. This suggests
a high instability of compound 11 in MeCN solution where
it immediately dissociates yielding a plethora of species,
which also contain coordinated perchlorate groups, and
confirming the possibility of displacing anionic ligands, such
as the pyrazolonate donors, from the metal coordination
sphere with solvent molecules, such as MeCN or H2O.
Finally, when benzyl bromide was added to a solution of
11 in MeCN, the ESI-MS spectrum exhibits, in the positive
mode, a number of peaks from dinuclear species containing
bridging-halide groups: [(Cp*)2Rh2(Cl)3]+, [(Cp*)2Rh2(Cl)-
Br3]+, [(Cp*)2Rh2(Cl)2Br]+, and [(Cp*)2Rh2(Br)3]+. In the
positive spectra, no signals containing the â-diketonate donor,
the most abundant species found in the negative ESI spectra,
have been detected.
The result of the “low-temperature” single-crystal X-ray
structure determinations are consistent with the above
formulations in terms of stoichiometry and connectivity; in
all cases, the species take the form [Cp*M(Q)X] with one
mononuclear neutral molecule, devoid of crystallographic
symmetry and no intrinsic molecular symmetry, comprising
the asymmetric unit of each structure (Figure 5); all
7940 Inorganic Chemistry, Vol. 44, No. 22, 2005

Rhodium(III) Cyclopentadienyl â-diketonate Complexes
Figure 5. Projections of individual molecules of 1, 4, 6, and 8 (as representative) normal to their ligand planes.
although the M-O-C angles differ between O(41 and 51).
Some differences are evident for 8, most notably in the N2C3/
C5 interplanar dihedral angle, perhaps dependent on some
steric effect derivative of the bulk of the ligand substituent,
but also in respect of the angle, at O(5), where the effect
may be electronic, contingent on both the substituent and
the change in torsion of the nearly phenyl group. An
inspection of the distances and angles within the conjugated
section of the aromatic ligand across the series shows
remarkable insensitivity in this dimension (Table 3). Not
surprisingly, crystal packings appear to be primarily deter-
mined by inversion-related parallel dispositions of the planar
components.
Figure 6. Racemic mixture found in the crystals of 1, 2, 6, 7, 8, and 12.
compounds crystallize in centrosymmetric space groups (i.e.,
the specimens were racemic) (Figure 6).19 Isomorphous
arrays are found for M ) Rh, Ir; X ) Cl (1, 2, 6, and 7) and
M ) Rh, X ) Br (12) permitting the comparison of different
metal atoms in similar other-atom environments and of
different halides in otherwise similar systems. In all such
systems, except 12, where X ) Br, and 4, where the precision
is limited, the metal-donor atom distances are remarkably
invariant (Table 2); the angles are slightly more diverse, but
not so much as to suggest the presence of any unusual or
unexpected trends, and although the oxygen donors are of
two rather different types, their M-O distances are similar,
Conclusions
Rh(III) diketonate complexes of formula [Cp*M(Q)Cl] (M
) Rh or Ir, Cp* ) pentamethylcyclopentadienyl, HQ )
1-phenyl-3-methyl-4R(CdO)-pyrazol-5-one) can be easily
synthesized by reaction of [Cp*MCl2]2 with the adequate
sodium salt NaQ. [Cp*M(Q)Cl] complexes exist as enanti-
omers, both in the solid state and in solution, the metal being
a center of chirality. It is noteworthy that [Cp*M(Q)Cl]
complexes are stable in the solid state and in the atmosphere
(19) Consiglio, G.; Morandini, F. Chem. ReV. 1987, 87, 761-778.
Inorganic Chemistry, Vol. 44, No. 22, 2005 7941

Pettinari et al.
for a long time, and they are also stable in weak polar
solvents (such as CHCl3) and up to 55 °C. No signal from
the coalescence of the geminal methylene-proton quartets
in derivatives 3-7 has been found. This is a probe of the
lack of interconversion and of the stability of both conforma-
tions in solution. These compounds are resistant to carban-
ionic attack by RMgX or RX species. Br- is however able
to displace the Cl- from the Rh center. The Cl- can be also
displaced by solvent molecules, as in the exchange reaction
of [Cp*M(Q)Cl] with AgX (X ) NO3, ClO4), in which ionic
species [Cp*M(Q)(MeCN)]X or [Cp*M(Q)(H2O)]X are
obtained. Finally P donors, such as PPh3, are able to
coordinate [Cp*Rh(Q)Cl], easily displacing Cl- from the
metal coordination sphere and yielding ionic chiral-at-metal
complexes [Cp*Rh(Q)(PPh3)]Cl. Also, the acylpyrazolonate
ligand, Q, can be expelled from the metal coordination
sphere, as demonstrated by ESI-MS studies and by the
formation of byproducts such as [Cp*Rh(Cl)(H2O)2]ClO4 in
the reaction of [Cp*Rh(Q)Cl] with an excess AgClO4.
Acknowledgment. We would like to thank Ernesto
Carmona for helpful discussion and the University of
Camerino INTAS Project 00469, Cooperlink, and
Fondazione CARIMA.
Supporting Information Available: Full crystallographic data
in CIF format. This material is available free of charge via the
Internet at http://pubs.acs.org.
IC050985R
7942 Inorganic Chemistry, Vol. 44, No. 22, 2005