Ferrocene bis(phosphonite)s: Synthesis and characterization of a novel class of sterically congested ligands

Article abstract of DOI:10.1021/ic010750p

The synthesis and crystallographic characterization of the ferrocene bis(phosphonite) 6 as well as the corresponding Rh(I) complex 7 containing the sterically congested dibenzo[d.f] [1,3,2]dioxaphosphepin ring system is reported. The high yields of products obtained in three different transition-metal catalyzed reactions suggest that 6 is a robust ligand useful in variety of reactions.

Full text of DOI:10.1021/ic010750p

Inorg. Chem. 2002, 41, 127−131
Ferrocene Bis(phosphonite)s: Synthesis and Characterization of a
Novel Class of Sterically Congested Ligands1
Sai P. Shum, Stephen D. Pastor,* and Grety Rihs†
Ciba Specialty Chemicals Corporation, 540 White Plains Road, P.O. Box 2005,
Tarrytown, New York 10591
Received July 13, 2001
Phosphorus-based ligands continue to play a pivotal role
in the development of stereoselective transition-metal-
catalyzed reactions. Although phosphine-based ligands have
been extensively used in the optimization of catalytic proc-
esses, the use of readily modifiable phosphite or phosphonite
ligands offers an attractive alternative to phosphine-based
ligands. Recently, sterically hindered bis(phosphite) ligands
incorporating the seven-membered dibenzo[d,f][1,3,2]dioxa-
Figure 1. Chemical Abstracts numbering system for the dibenzo[d,f][1,3,2]-
dioxaphosphepin ring system.
phosphepin ring system were reported to be an effective ligand
for rhodium-catalyzed hydroformylation reactions (Figure
1).2 Van Leeuwen et al. suggested that the large natural bite
angle in ligands such as 1 increases the stereoselectivity of
ligands to meet the electronic requirements for high stereo-
selectivity in a particular reaction.
the rhodium(I)-catalyzed hydroformylation reaction.3
A
relationship between the ratio of normal to iso olefin hydro-
formylation as a function of ligand bite angle has been
established.4 Gladfelter et al. made the important observation
that the geometric inclination of the bis(phosphite)ruthenium
carbonyl complex (P-Ru-P bond angle of 118.98°) pre-
pared from 2 is due to steric rather than electronic factors.5
Nevertheless, the ratio of iso to normal olefin hydroformyl-
ation has been shown in an elegant study by Casey to be
subject to electronic effects.6 In principle, the facile prepara-
tion of aryl phosphites or phosphonites with electron-
accepting or -donating groups allows for the tailoring of
* To whom correspondence should be addressed. E-mail: steve.pastor@
cibasc.com.
† Present address: Physics Department, Novartis Services AG, Postfach,
CH-4002, Basel, Switzerland.
(1) Presented in part at the 217th ACS National Meeting, Anaheim, CA,
March 21-25, 1999; Abstract INOR 194.
(2) (a) Billig, E.; Abatjoglou, A. G.; Bryant, D. R. U.S. Patent 4,748,261,
1988; Chem. Abstr. 1987, 107, 7392. See also: (b) Babin, J. E.;
Whiteker, G. T. U.S. Patent 5,360,938, 1994; Chem. Abstr. 1995, 122,
186609.
(3) (a) Buisman, G. J. H.; van der Veen, L. A.; Klootwijk, A.; de Lange,
W. G. J.; Kamer, P. C. J.; van Leeuwen, P. W. N. M.; Vogt, D.
Organometallics 1997, 16, 2929 and references therein. (b) For recent
work, see: van der Veen, L. A.; Keeven, P. H.; Shoemaker, G. C.;
Reek, J. N. H.; Kamer, P. C. J.; van Leeuwen, P. W. N. M.; Lutz, M.;
Spek, A. L. Organometallics 2000, 19, 872.
(4) van Leeuwen, P. W. N. M.; Kamer, P. C. J.; Reek, J. N. H.; Dierkes,
P. Chem. ReV. 2000, 100, 2741.
(5) Moasser, B.; Gross, C.; Gladfelter, W. L. J. Organomet. Chem. 1994,
471, 201.
(6) Casey, C. P.; Paulsen, E. L.; Beuttenmueller, E. W.; Proft, B. R.;
Matter, B. A.; Powell, D. R. J. Am. Chem. Soc. 1999, 121, 63.
Ferrocene provides a versatile backbone for the synthesis
of chelating ligands.7 During the course of our work,8 Reetz9
and Nifant’ev10 reported the synthesis of chiral ferrocene
diphosphonite ligands that were highly efficient in rhodium-
catalyzed hydrogenation and hydrosilation reactions, respec-
tively. Our current interest in seven- and eight-membered
cyclic phosphite ligands11 led to the current investigation of
(7) Ferrocenes; Togni, A., Hayashi, T., Eds.; VCH: Weinheim, Germany,
1995.
(8) Pastor, S. D.; Shum, S. P. U.S. Patent No. 5,817,850; Chem. Abstr.
1998, 129, 290222.
(9) (a) Reetz, M. T.; Gosberg, A.; Goddard, R.; Kyung, S.-H. J. Chem.
Soc., Chem. Commun. 1998, 2077. (b) See also: Reetz, M. T.;
Neugebauer. Angew. Chem., Int. Ed. Engl. 1999, 38, 179.
(10) Nifant’ev, I. EÄ .; Manzhukova, L. F.; Antipin, M. Yu.; Struchkov, Yu.
T.; Nifant’ev, EÄ . E. Russ. J. Gen. Chem. 1995, 65, 682.
10.1021/ic010750p CCC: $22.00 © 2002 American Chemical Society
Published on Web 12/07/2001
Inorganic Chemistry, Vol. 41, No. 1, 2002 127

NOTE
added dropwise 67 mL (107 mmol) of a 1.6 M solution of
n-butyllithium in hexane at ambient temperature. The reaction
mixture was stirred for 20 min, and then to the resultant red
suspension was added 12.0 g (103 mmol) of N,N,N′,N′-tetramethyl-
ethylenediamine (exothermic). The reaction mixture was heated at
reflux for 2 h during which time an orange suspension formed.
The reaction mixture was allowed to cool to ambient temperature,
and 100 mL of tetrahydrofuran (THF) was added to the reaction
mixture. To the resultant reaction mixture cooled to -40 °C was
added dropwise a solution of 51.8 g (109 mmol) of 4 in 100 mL of
THF. The reaction mixture was allowed to warm slowly to ambient
temperature, and then it was heated at reflux for 6 h. The reaction
mixture was allowed to cool to ambient temperature, and any
insoluble precipitate was removed by filtration. The volatiles were
removed in vacuo, and the residue was triturated with 150 mL of
hexane. The resultant solid was recrystallized from a mixture of
acetonitrile and THF to give 25 g (47.7%) of a light brown solid,
mp 356 °C (under nitrogen). 31P{1H} NMR (benzene-d6): δ 193.2.
1H NMR (benzene-d6; 80 °C): δ 1.28 (s, 36 H), 1.43 (s, 36 H),
4.42 (unresolved m, 4 H), 4.50 (m, 4 H), 7.26 (d, 4 H), 7.46 (d, 4
H). 13C{1H} NMR (benzene-d6): δ 31.3 (s), 31.4 (s), 34.3 (s), 35.4
(s), 71.5 (d, J ) 4 Hz), 72.4 (d, J ) 21 Hz), 80.0 (d, J ) 40 Hz),
124.1 (s), 126.7 (s), 134.5 (d, J ) 4 Hz), 140.1 (d, J ) 1 Hz),
146.2 (s), 147.8 (d, J ) 6 Hz). MS: m/z 1064 (M+•). Anal. Calcd
for C66H88FeO4P2: C, 74.56; H, 8.34; P, 5.83. Found: C, 74.13; H,
8.04; P, 5.83.
sterically congested bis(phosphonite) ligands based upon the
ferrocene motif.
Experimental Section
1H NMR (300.08 MHz and 499.84, respectively) spectra were
taken on Varian model Gemini-300 or Unity-500 spectrometers.
All 1H chemical shifts are reported in ppm relative to tetramethyl-
silane, where a positive sign is downfield from the standard. 31P
NMR spectra (121.47 and 202.33 MHz, respectively) were obtained
on a Varian model Gemini-300, or Unity-500 spectrometers. All
31P chemical shifts are reported in ppm relative to 85% phosphoric
acid (external), where a positive sign is downfield from the standard.
19F NMR spectra (282.33 MHz) were obtained on a Varian model
1
Gemini-300 spectrometer. Significant H NMR data are tabulated
in the following order: multiplicity; atom assignments; coupling
constant in hertz; number of protons. MALDI TOF MS obtained
on a PerSeptive Biosysteme Voyager-DE STR spectrometer. Merck
silica gel 60 (200-400 mesh) was used for flash and column
chromatography. ICN Silica TSC (60 Å) was used for dry-column
chromatography. Merck precoated (0.25 mm) silica gel F-254 plates
were used for TLC. Reagents were purchased from commercial
laboratory supply houses. Solvents were dried prior to use when
necessary with appropriate drying agents. Reactions were carried
out in dried apparatus under a dry inert atmosphere of either nitrogen
or argon. The Analytical Research Department, Ciba Specialty
Chemicals Corp., performed elemental analyses. Detailed proce-
dures for the catalytic reactions carried out in this study are included
in the Supporting Information.
X-ray Structural Analysis. Crystals suitable for X-ray crystal-
lographic analysis were grown by slow evaporation of a THF
solution of 6. Crystal data: C66H88FeO4P2‚4C4H8O; formula weight
) 1351.15; monoclinic system; crystal size ) 0.54 × 0.54 × 0.13
mm; cell parameters a ) 33.419(6) Å, b ) 10.678(1) Å, c )
22.684(6) Å, â ) 102.08(2)°; V ) 7916(3) Å3; space group )
C2/c; dcalc ) 1.135 Mg‚m-3; Z ) 4; θ range from data collection
) 2.7-74.2°; intensity variation ) (2%; µ ) 2.250 mm-1; Nonius
CAD4 diffractometer; Cu KR radiation; graphite crystal mono-
chromator; number of variables 330; number of reflections measured
8297; number of reflections in least squares 6660; R ) 0.081; largest
difference peak/hole 1.425/-0.367; structure solution solved by
direct methods (Siemens SHELXS) and parameters refined by full-
matrix least-squares calculations (SHELXS) with anisotropic
displacement parameters for all non-H atoms. The difference Fourier
map showed 30 of 44 hydrogen atoms, with the positions of the
remaining ones calculated by assuming normal geometry (H atom
parameters idealized and not refined). The Fourier map showed
four disordered THF molecules/ferrocene ligand. The parameters
of the THF atoms could not be refined.
3,3′,5,5′-Tetrakis(1,1-dimethylethyl)-2,2′-dihydroxy-1,1′-bi-
phenyl (3). To a stirred mixture of 2,4-di-tert-butylphenol (20.6 g,
0.1 mole) and potassium hydroxide (44.0 g, 0.8 mol) in 250 mL of
distilled water at 85-90 °C was added dropwise over 1 h a 30%
aqueous solution of hydrogen peroxide (30 mL, 0.27 mol). The
reaction mixture was slowly cooled to room temperature, and then
the aqueous phase was decanted. The precipitate was collected by
filtration, and the filter cake was washed sequentially with water
(1 L), 3 M hydrochloric acid (300 mL), and water (300 mL). The
wet filter cake was partitioned between a mixture of diethyl ether
(100 mL), toluene (50 mL), and water (50 mL). The organic phase
was extracted sequentially with 6 M hydrochloric acid (4 × 30
mL), 5% sodium bicarbonate (50 mL), and water (50 mL). The
organic phase was dried over anhydrous sodium sulfate, and the
solvent was removed in vacuo. The product was purified by
tritration with acetonitrile (50 mL) to give 12.8 g (63%) of a white
1
solid, mp 197 °C (lit.12 mp 195-196.5 °C). H NMR (CDCl3): δ
1.34 (s, 18 H), 1.47 (s, 18 H), 5.22 (exchangeable s, OH, 2 H),
[(6)RhIAcAc] (7). Synthesis. To a stirred solution of 2.1 g (1.9
mmol) of 6 in 5 mL of benzene-d6 was added portionwise 0.5 g
(1.9 mmol) of (acetylacetonato)dicarbonylrhodium(I). (Caution!
Vigorous eVolution of carbon monoxide is obserVed after each
addition.) The reaction mixture was allowed to stir until gas
evolution was complete (2 h). Upon standing for 72 h, the resultant
precipitate was collected by filtration to give 1.27 g (53%) of a
yellow crystalline solid, mp 240-245 °C. 31P{1H} NMR (benzene-
4
4
7.12 (d, J ) 2.5 Hz, 2 H), 7.41 (d, J ) 2.5 Hz, 2 H). MS: m/z
410 (molecular ion). Anal. Calcd for C28H42O2: C, 81.90; H, 10.31.
Found: C, 82.08; H, 10.34.
1,1′-Bis[2,4,8,10-tetrakis(1,1-dimethylethyl)dibenzo[d,f][1,3,2]-
dioxaphosphepin-6-yl]ferrocene (6). Synthesis. To a stirred
solution of 9.5 g (50 mmol) of ferrocene in 250 mL of hexane was
(11) (a) Pastor, S. D.; Shum, S. P.; Rodebaugh, R. K.; DeBellis, A. D.;
Clarke, F. H. HelV. Chim. Acta 1993, 76, 900. (b) Malen, A. H.;
NabiRahni, M. A.; Pastor, S. D.; Stevens, E. D.; Snyder, J. A.
Phosphorus, Sulfur, Silicon 1993, 82, 1. (c) Pastor, S. D.; Richardson,
C. F.; NabiRahni, M. A. Phosphorus, Sulfur, Silcon Relat. Elem. 1994,
90, 95. (d) Pastor, S. D.; Shum, S. P.; DeBellis, A. D.; Burke, L. P.;
Rodebaugh, R. K.; Clarke, F. H.; Rihs, G. Inorg. Chem. 1996, 35,
949. (e) Pastor, S. D.; Rogers, J. S.; NabiRahni, M. A. Inorg. Chem.
1996, 35, 2157. (f) Pastor, S. D.; Shum, S. P. Tetrahedron: Asymmetry
1998, 9, 543. (g) DeBellis, A. D.; Pastor, S. D.; Rihs, G.; Rodebaugh,
R. K.; Smith, A. R. Inorg. Chem. 2001, 40, 2156.
1
1
d6): δ 178.4 (d, JPRh ) 266.8 Hz). H NMR (benzene-d6) (300
MHz): δ 1.26 (s, 36 H), 1.88 (s, 36 H), 1.59 (s, CH3, 6 H), 3.84
(unresolved m, 4 H), 4.81 (m, 4 H), 5.24 (, 1 H), 7.27 (d, 4J ) 2.5,
4
4 H), 7.47 (d, J ) 2.5, 4 H). Matrix-assisted laser desorption
ionization (MALDI) time-of-flight MS [2-(2H-benzotriazol2-yl)-
4-methylphenol matrix]: m/z 1264. The MS spectrum displays the
isotope pattern consistent with that expected for the presence of
iron and rhodium. Anal. Calcd for C71H95FeO6P2Rh: C, 67.40; H,
7.57. Found: C, 66.91; H, 7.45.
(12) Kushioka, K. J. Org. Chem. 1983, 48, 4948.
128 Inorganic Chemistry, Vol. 41, No. 1, 2002

NOTE
X-ray Structural Analysis. Crystals suitable for X-ray crystal-
lographic analysis were grown from a saturated solution of 7 in a
mixture of benzene and dichloromethane. Crystal data: C71H95FeRh-
O6P2‚4(C6H6)(CH2Cl2); formula weight ) 1548.42; monoclinic
system; crystal size ) 0.63 × 0.54 × 0.08 mm; cell parameters
a ) 19.462(2) Å, b ) 36.482(4) Å, c ) 12.124(1) Å, â ) 93.07(1)°;
V ) 8596(2) Å3; space group ) P21/c; dcalc ) 1.224 Mg‚m-3; Z )
4; θ range from data collection ) 3.7-54.5°; intensity decay )
(22%; µ ) 4.213 mm-1; Philips PW1100 automatic diffractometer;
Mo KR radiation; graphite crystal monochromator; number of
variables 919; number of reflections measured 11 197; number of
reflections in least squares 9532; R ) 0.057; largest difference peak/
hole 0.826/-0.642; structure solution solved by direct methods
(Siemens SHELXS) and parameters refined by full-matrix least-
squares calculations (SHELXS) with anisotropic displacement
parameters for all non-H atoms. Hydrogen atom positions were
calculated and not refined.
Figure 2. Molecular structure of 6 showing the crystallographic numbering
scheme.
Results and Discussion
Upon standing, crystals of the rhodium(I) complex 7
separated from solution. In the 31P{1H} NMR spectrum
(benzene-d6) of 7, a doublet was observed at δ 178.4, which
was assigned to the two equivalent phosphorus atoms of the
dibenzo[d,f][1,3,2]dioxaphosphepinyl substituents bonded to
Synthesis. The bisphenol 3 was prepared by the oxidative
coupling of 2,4-di-tert-butylphenol with hydrogen peroxide
under alkaline conditions. The phosphorochloridite 4 was
prepared by the reaction of the bisphenol 3 with phosphorus-
(III) chloride as reported in the literature.11a The ferrocenyl-
bis(phosphonite) 6 was prepared by the reaction of 1,1′-di-
lithioferrocene, which was prepared in situ from ferrocene
(5) and n-butyllithium/N,N,N′,N′-tetramethylethylenediamine,
with 2 equiv of 4 (48% recrystallized).
1
rhodium with JPRh ) 266.8 Hz. As in the free ligand, the
observation of only one phosphorus signal in the 31P{1H}
NMR spectrum is consistent with rapid ring inversion of the
dibenzo[d,f][1,3,2]dioxaphosphepinyl rings on the NMR time
scale.
X-ray Crystallography. Crystals of 6 were obtained by
slow evaporation of a tetrahydrofuran solution. In the solid
state, the molecule of 6 has C2 symmetry with the 2-fold
axis running through the iron atom (see Figure 2). All of
the bond lengths are within the expected ranges.15 The Fe-C
bond distances are between 2.030 and 2.046 Å, which is in
the range found in ferrocene.16 The planes defined by the
two cyclopentadienyl rings are parallel to each other. The
C(5)-C(10)-C(11)-C(16) dihedral angle about the single
In the 31P{1H} NMR spectrum (benzene-d6) of 6 a singlet
was observed at δ 193.2, which was assigned to the two
equivalent phosphorus atoms of the dibenzo[d,f][1,3,2]-
dioxaphosphepinyl substituents. This observation is consistent
with rapid ring inversion of the dibenzo[d,f][1,3,2]dioxa-
phosphepinyl rings (atropisomerization about the C-C bond
connecting the two aryl rings) on the NMR time scale. If
ring inversion was slow on the NMR time scale, two
atropisomers with nonequivalent phosphorus atoms would
be expected to be observable with relative absolute configu-
rations of (R*, R*) and (R*, S*), which refers throughout
this paper to the relative absolute configurations the two
stereoaxes.13,14
(13) The examination of a Drieding molecular model suggests that the
alternate explanation of a planar ring conformation is highly unlikely.
The formation of a single diastereoisomer cannot be rigourously
excluded; albiet, in this case the four tert-butyl substituents of the
dibenzo[d,f][1,3,2]dioxaphosphepinyl ring are nonequivalent. For
examples, see ref 11.
(14) For a discussion on topicity and anisochrony in NMR, see: Eliel,
E. L.; Wilen, S. H.; Mander, L. N. Stereochemistry of Organic
Compounds; Wiley-Interscience: New York, 1994; pp 465-508.
(15) Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpan, A.
G. J. Chem. Soc., Perkin Trans. 2 1987, Supplement S1-S19.
(16) Seiler, P.; Dunitz, J. D. Acta Crystallogr., Sect. B 1979, 35, 1068.
The rhodium(I) complex 7 was prepared by the reaction
of 6 with (acetylacetonato)dicarbonylrhodium(I) in benzene.
Inorganic Chemistry, Vol. 41, No. 1, 2002 129

NOTE
Given the posit that pyramidal geometry is achieved when
the sum of the requisite bond angles about phosphorus is
270° (for “pure” p character), the two phosphorus atoms (sum
of the angles about P(3) ) 304.9°; P(4) ) 302.4°) are
midway between pyramidal and tetrahedral geometry. The
coordination geometry about the rhodium atom in 7 is square
planar within 0.08 Å of the best-calculated plane through
the Rh, P(3), P(4), O(5), and O(6) atoms. The acetylacetonate
chelate ring [Rh, O(5), C(11), C(12), C(13), and O(6)] is
planar and is tilted 0.4° to the rhodium coordination plane.
Catalytic Reactions. The ferrocene bis(phosphonite) 6
was screened as a ligand for transition-metal-catalyzed
hydrosilation,11f,21 hydrogenation, and cross-coupling (C-C
bond formation) reactions (Suzuki reaction).22 The hydro-
silation of acetophenone with diphenylsilane catalyzed by
the Rh(I) complex 7 followed by hydrolysis of the silyl ether
gave phenethyl alcohol in 93% isolated yield (eq 1). How-
ever, the actual catalytic species may be different from 7
and be formed in situ under the reaction conditions. The
hydrosilation of acetophenone with diphenylsilane using the
Rh(I) complex formed in situ from 6 and chloro(1,5-cyclo-
octadiene)rhodium(I) dimer23 followed by hydrolysis of the
silyl ether gave phenethyl alcohol in 90% isolated yield.
Hydrogenation of the R,â-unsaturated C-C double bond
of dimethyl itaconate with a cationic Rh complex prepared
from 6 and bis(bicyclo[2.2.1]hepta-2,5-diene)rhodium(I) per-
chlorate gave the saturated succinate ester in 99% isolated
yield (eq 2). The ferrocenylbis(phosphonite) 6 was evaluated
as a ligand for C-C bond formation (Suzuki reaction)
following the experimental protocol of Buchwald.24,25 3-Tri-
fluoromethyl-1,1′-biphenyl26 was formed in 90% isolated
Figure 3. Molecular structure of 7 showing the crystallographic numbering
scheme.
bond connecting the two aryl rings of the dibenzo[d,f][1,3,2]-
dioxaphosphepin ring is 54.2(8)°, which is in the range found
for other sterically hindered dibenzo[d,f][1,3,2]dioxaphosphepin
rings.11a,11b,17,18 Given the posit that pyramidal geometry is
achieved when the sum of the requisite bond angles about
phosphorus is 270° (for “pure” p character), the two
equivalent phosphorus atoms (301.8°) are midway between
pyramidal and tetrahedral geometry.
Crystals of 7 suitable for X-ray crystallography were
prepared by crystallization from a mixture of benzene and
dichloromethane (see Figure 3). In the solid state, all of the
bond lengths are within the expected ranges.15 The Fe-C
bond distances are between 2.006 and 2.071 Å, which is in
the range found in ferrocene.16 The planes defined by the
two cyclopentadienyl rings are tilted 5.2° relative to each
other. The geometry about Rh(I) in 7 is square planar. The
Rh-P bond lengths (2.161 and 2.177 Å) and Rh-O bond
lengths (2.060 and 2.069 Å) are similar to those found in
other Rh(I) acetylacetonate complexes.19 The C(16)-C(21)-
C(22)-C(23) and C(49)-C(54)-C(55)-C(56) dihedral angles
about the single bonds connecting the two aryl rings of
the dibenzo[d,f][1,3,2]dioxaphosphepin rings are -52.83
(0.91) and -55.68 (0.89)°, which is in the range found for
other sterically hindered dibenzo[d,f][1,3,2]dioxaphosphepin
rings.11a,11b,17,18 The solid-state conformation of 7 is that of
the (R*, R*) atropisomer. However, caution should be
exercised in the comparison of solution with solid-state
conformations determined by X-ray structural analysis. Anet
and Yavari warned that lattice energy, along with the
resultant crystal-packing effects in the solid state, could
render the solid-state conformation different from that
observed in solution.20
(20) Anet, F. A. L.; Yavari, I. J. Am. Chem. Soc. 1977, 99, 6986. (b) For
an example where solution and solid-state conformation is different
in an eight-membered ring, see: Burke, L. P.; DeBellis, A. D.; Fuhrer,
H.; Meier, H.; Pastor, S. D.; Rihs, G.; Rist, G.; Rodebaugh, R. K.;
Shum. S. P. J. Am. Chem. Soc. 1997, 119, 8313.
(21) For recent work on catalytic hydrosilation reactions, see: (b) Dinh,
L. V.; Gladysz, J. A. Tetrahedron Lett. 1999, 40, 8995. (c) Heldmann,
D. K.; Seebach, D. HelV. Chim. Acta 1999, 82, 1096. (d) Moreau, C.;
Frost, C. G.; Murrer, B. Tetrahedron Lett. 1999, 40, 5617. (e) Bideau,
F. L.; Henique, J.; Samuel, E.; Elschenbroich, C. Chem. Commun.
(Cambridge) 1999, 1397. (f) Yun, J.; Buchwald, S. L. J. Am. Chem.
Soc. 1999, 121, 5640. (g) Tsuruta, H.; Imamoto, T. Tetrahedron:
Asymmetry 1999, 10, 877. (h) Kuwano, R.; Uemura, T.; Saitoh, M.;
Ito, Y. Tetrahedron Lett. 1999, 40, 1327. (i) Nagashima, H.; Suzuki,
A.; Iura, T.; Ryu, K.; Matsubara, K. Organometallics 2000, 19, 3579.
(j) Son, S. U.; Paik, S. J.; Chung, Y. K. J. Mol. Catal. A: Chem.
2000, 151, 87. (k) Kuwano, R.; Sawamura, M.; Shirai, J.; Takahashi,
M.; Ito, Y. Bull. Chem. Soc. Jpn. 2000, 73, 485.
(22) For the first reported use of a triaryl phosphite in biaryl coupling
reactions, see: (a) Albisson, D. A.; Bedford, R. B.; Lawrence, S. E.;
Scully, P. N. J. Chem. Soc., Chem. Commun. 1998, 2095. (b) Zaph,
A.; Beller, M. Chem. Eur. J. 2000, 6, 1830.
(23) The 31P{1H} NMR spectrum of the complex formed in solution is
consistent with a symmetrical dimeric species [31P{1H} NMR (benzene-
d6) δ 169.2 (d, 1JPRh ) 272.6 Hz)]. Consistent with this interpretation,
addition of pyridine leads to formation of a monomeric complex with
nonequivalent phosphorus atoms [31P{1H} NMR (benzene-d6) (121.47
(17) Holmes, R. R.; Prakasha, T. K.; Pastor, S. D. Phosphorus-31 NMR
Spectral Properties in Compound Characterization and Structural
Analysis; Quin, L. D., Verkade, J. G., Eds; VCH: Weinheim,
Germany, 1994; pp 27-39 and references therein.
(18) DeBellis, A. D.; Pastor, S. D.; Rihs, G.; Rodebaugh, R. K.; Smith, A.
R. Inorg. Chem. 2001, 40, 2156.
(19) (a) Lamprecht, G. J.; Leiopoldt, J. G.; van Zyl, G. J. Inorg. Chim.
Acta 1995, 97, 31. (b) Meetsma, A.; Jongsma, T.; Challa, G.; van
Leeuwen, P. W. N. M. Acta Crystallogr., Sect. C 1993, 49, 1160. (c)
van Rooy, A.; Kamer, P. C.; van Leeuwen, P. W. N. M.; Goubitz, K.;
Fraanje, J.; Veldman, N.; Spek, A. L. Organometallics 1996, 15, 835.
(d) Esteruelas, M. A.; Lahoz, F. J.; On˜ate, E.; Oro, L. A.; Rodr´ıguez,
L.; Steinert, P.; Werner, H. Organometallics 1996, 15, 3436.
1
2
MHz) δ 169.0 (dd, JPRh ) 267.2 Hz, JPRhP ) 54.8 Hz), 179.0 (dd,
2
1JPRh ) 236.9 Hz, JPRhP ) 54.8 Hz)].
(24) Wolf, J. P.; Singer, R. A.; Yang, B. H.; Buchwald, S. L. J. Am. Chem.
Soc. 1999, 121, 9550.
(25) For a general review of the Suzuki reaction, see: Suzuki, A. In Metal-
Catalyzed Cross-Coupling Reactions; Diederich, F., Stang, J. P., Eds.;
Wiley-VCH: Weinheim, Germany, 1998; Chapter 2.
(26) For previous synthesis, see (a) Trost, B. M.; Arndt, H. C. J. Am. Chem.
Soc. 1973, 95, 5288. (b) Aubert, C.; Be´gue´, J.-P.; Bonnet-Delphon,
D. Chem. Lett. 1989, 1835.
130 Inorganic Chemistry, Vol. 41, No. 1, 2002

NOTE
yield by reaction of 3-(trifluoromethyl)phenylboronic acid
with bromobenzene using the catalyst formed in situ from 6
and palladium(II) acetate (eq 3).
In summary, the synthesis and characterization of the first
ferrocenylbis(phosphonite) 6 and Rh(I) complex 7 containing
a sterically congested tetralkyl-substituted dibenzo[d,f][1,3,2]-
dioxaphosphepin ring system is reported. The high yields
of products obtained in three different transition-metal-
catalyzed reactions suggest that 6 is a robust ligand useful
in a wide variety of reactions.
Acknowledgment. The authors wish to thank Ciba
Specialty Chemicals Corp. for support and permission to
publish this work. The authors thank Mr. Bogden Piatek for
obtaining MALDI mass spectra.
Supporting Information Available: Two X-ray crystallo-
graphic files, in CIF format, and detailed experimental procedures
for the catalytic reactions. This material is available free of charge
via the Internet at http://pubs.acs.org.
IC010750P
Inorganic Chemistry, Vol. 41, No. 1, 2002 131