Reactions of a hydroxy phosphonite ligand in the coordination sphere of rhodium(I)

Article abstract of DOI:10.1021/om0204686

The complexation behavior of 6-(3,3′-di-tert-butyl-5,5′-dimethoxy-2-hydroxy-2′-oxybiphenyl) -6H-[c,e]-1,2-oxaphosphorine, which generates an active and n-regioselective rhodium(I) catalyst for the isomerizing hydroformylation of internal octenes, was studied. Investigations in the absence of CO/H₂ revealed that coordination of the phenolate moiety of the hydroxy phosphonite on the rhodium center is possible. Interestingly, under conditions related to the hydroformylation (syngas, higher temperature and P:Rh ratios) the ligand suffers two transformations. The first is based on a transesterification reaction involving 2 equiv of the hydroxy phosphonite, giving rise to a substituted biphenol and a symmetric bidentate phosphorus ligand of a heretofore uncertain structure. The second transformation is concerned with a selective Rh(I)-catalyzed P-C bond cleavage of the initial phosphonite structure under the formation of a phosphite. X-ray structural analyses will illustrate the structures of rhodium(I) complexes bearing the original hydroxy phosphonite ligand, a phenoxy phosphonite chelate, and a phosphite formed by selective P-C bond cleavage, respectively.

Full text of DOI:10.1021/om0204686

Organometallics 2003, 22, 4265-4271
4265
Rea ction s of a Hyd r oxy P h osp h on ite Liga n d in th e
Coor d in a tion Sp h er e of Rh od iu m (I)
Detlef Selent,*,† Wolfgang Baumann,† Rhett Kempe,‡ Anke Spannenberg,†
Dirk Ro¨ttger,§ Klaus-Diether Wiese,§ and Armin Bo¨rner*,†,|
Leibniz-Institut fu¨r Organische Katalyse an der Universita¨t Rostock e. V.,
18055 Rostock, Germany, Fachbereich Chemie, Carl von Ossietzky Universita¨t,
26129 Oldenburg, Germany, Oxeno C4-Chemie, 45772 Marl, Germany,
and Fachbereich Chemie der Universita¨t Rostock, 18059 Rostock, Germany
Received J une 13, 2002
The complexation behavior of 6-(3,3′-di-tert-butyl-5,5′-dimethoxy-2-hydroxy-2′-oxybiphenyl)-
6H-[c,e]-1,2-oxaphosphorine, which generates an active and n-regioselective rhodium(I)
catalyst for the isomerizing hydroformylation of internal octenes, was studied. Investigations
in the absence of CO/H2 revealed that coordination of the phenolate moiety of the hydroxy
phosphonite on the rhodium center is possible. Interestingly, under conditions related to
the hydroformylation (syngas, higher temperature and P:Rh ratios) the ligand suffers two
transformations. The first is based on a transesterification reaction involving 2 equiv of the
hydroxy phosphonite, giving rise to a substituted biphenol and a symmetric bidentate
phosphorus ligand of a heretofore uncertain structure. The second transformation is
concerned with a selective Rh(I)-catalyzed P-C bond cleavage of the initial phosphonite
structure under the formation of a phosphite. X-ray structural analyses will illustrate the
structures of rhodium(I) complexes bearing the original hydroxy phosphonite ligand, a
phenoxy phosphonite chelate, and a phosphite formed by selective P-C bond cleavage,
respectively.
In tr od u ction
class of trivalent P compounds hitherto fully underes-
timated as ligands for homogeneous catalysis give very
active rhodium catalysts for the hydroformylation of
internal octenes under mild conditions.11 Of particular
interest was our finding that the catalyst formed with
the hydroxy phosphonite 1 was superior with respect
to n-regioselectivity in comparison to the methyl ether
analogue and other related monodentate phosphonites.
Rhodium(I) complexes bearing trivalent phosphorus
compounds as ancillary ligands play a pivotal role as
efficient homogeneous catalysts in the hydroformylation
of alkenes, representing a process of crucial economic
importance.1-3 Current academic and industrial re-
search is focused on the identification of ligands which
allow the highly regioselective production of terminal
aldehydes from 1-olefins.4 As an alternative, the forma-
tion of n-aldehydes by isomerization/hydroformylation
of internal olefins has attracted increasing attention.5-13
Recently, we reported that phosphonites belonging to a
* To whom correspondence should be addressed. E-mail: D.S.,
detlef.selent@ifok.uni-rostock.de; A.B., armin.boerner@ifok.uni-ros-
tock.de.
† Leibniz-Institut fu¨r Organische Katalyse an der Universita¨t Ros-
tock e. V.
‡ Carl von Ossietzky Universita¨t.
We speculated that the unique catalytic properties
found for the hydroxy ligand could be attributed to the
effect of the phenolic OH group: e.g., hemilabile coor-
dination to the metal center.14 To find rationalizations,
the coordination behavior and the stability of 1 were
investigated in detail. Herein, we will give proof that
§ Oxeno C4-Chemie.
| Fachbereich Chemie der Universita¨t Rostock.
(1) Frohning, C. D.; Kohlpaintner, C. W. In Applied Homogeneous
Catalysis with Organometallic Compounds; Cornils, B., Herrmann, W.
A., Eds.; VCH-Wiley: Weinheim, Germany, 1996; Vol. 1, pp 3-25.
(2) Herrmann, W. A.; Cornils, B. Angew. Chem., Int. Ed. Engl. 1997,
36, 1047.
(3) Beller, M.; Cornils, B.; Frohning, C. D.; Kohlpaintner, C. W. J .
Mol. Catal. A 1995, 104, 17.
(4) van Leeuwen, P. W. N. M., Claver, C., Eds. Rhodium Catalyzed
Hydroformylation; Kluwer: Dordrecht, The Netherlands, 2000.
(5) van Leeuwen, P. W. N. M.; Roobeek, C. F. Brit. Patent 2,068,-
377, 1980 (to Shell).
(6) van Leeuwen, P. W. N. M.; Roobeek, C. F. J . Organomet. Chem.
1983, 258, 343.
(9) van der Veen, L. A.; Kamer, P. C. J .; van Leeuwen, P. W. N. M.
Angew. Chem., Int. Ed. 1999, 111, 336.
(10) van der Veen, L. A.; Kamer, P. C. J .; van Leeuwen, P. W. N.
M. Organometallics 1999, 18, 4765.
(11) Selent, D.; Ro¨ttger, D.; Wiese, K.-D.; Bo¨rner, A. Angew. Chem.,
Int. Ed. 2000, 39, 1639.
(7) Billig, E.; Abatjoglou, A. G.; Bryant, D. R.; Murray, R. E.; Maher,
J . M. U.S. Patent 4,717,775, 1988 (to Union Carbide Corporation).
(8) Burke, P. M.; Garner, J . M.; Kreutzer, K. A.; Teunissen, A. J . J .
M.; Snuder, C. S.; Hansen, C. B. WO 97/33854, 1997 (to DSM/DuPont).
(12) Selent, D.; Hess, D.; Wiese, K.-D.; Ro¨ttger, D.; Kunze, C.;
Bo¨rner, A. Angew. Chem., Int. Ed. 2001, 40, 1696.
(13) Klein, H.; J ackstell, R.; Wiese, K.-D.; Borgmann, C.; Beller, M.
Angew. Chem., Int. Ed. 2001, 40, 3408.
10.1021/om0204686 CCC: $25.00 © 2003 American Chemical Society
Publication on Web 09/19/2003

4266 Organometallics, Vol. 22, No. 21, 2003
Selent et al.
Sch em e 1. Coor d in a tion a n d P h en ola te Ch ela te
F or m a tion a t Rh (I) of P h osp h on ite 1
F igu r e 1. Crystal structure of 2. Hydrogen atoms are
omitted for clarity. The thermal ellipsoids correspond to
30% probability. The torsion angle between phenylic planes
defined by C21, C22, C31, C30, C40, C33 (mean deviation
from the best plane 0.0161 Å) and C23, C24, C25, C26, C27,
C28 (mean deviation from the best plane 0.0086 Å) is 58.3°.
The mean deviation from the best plane defined by X1a,
X1b, Rh1, P1, Cl1 is 0.0687 Å (X1a, X1b: midpoints of
cyclooctadiene double bonds). Selected bond lengths and
angles are given in Table 1. For details of the X-ray
structural analysis see Table 4.
the hydroxy phosphonite is not inert as a ligand
but subject to two different transformation reactions
which take place under conditions related to hydro-
formylation.
Resu lts a n d Discu ssion
Com p lex F or m a tion of th e Hyd r oxy P h osp h o-
n ite w ith Rh od iu m (I). Since each interpretation of the
influence of ligands used in homogeneous catalysis is
based on the assumption of ligand stability, first we
confirmed that the hydroxy phosphonite 1 showed
sufficient thermal stability at the temperature of hy-
droformylation in the absence of rhodium(I).15 Thus,
compound 1 was treated in a sealed tube in p-xylene at
140 °C for several hours. The 31P NMR spectrum showed
no tendency to decompose.
Ta ble 1. Selected Bon d Len gth s a n d An gles in 2
Bond Lengths (Å)
Rh(1)-P(1)
Rh(1)-Cl(1)
Rh(1)-C(1)
Rh(1)-C(8)
Rh(1)-C(4)
Rh(1)-C(5)
C(1)-C(8)
C(4)-C(5)
P(1)-O(1)
2.233(2)
2.371(2)
2.289(6)
2.264(6)
2.120(7)
2.165(7)
1.365(10)
1.379(10)
1.619(4)
P(1)-O(2)
1.630(4)
1.409(7)
1.792(7)
1.437(8)
1.453(10)
1.374(9)
1.412(7)
1.491(9)
1.390(8)
O(2)-C(16)
P(1)-C(9)
C(9)-C(14)
C(14)-C(15)
C(15)-C(16)
O(1)-C(21)
C(22)-C(23)
C(30)-O(5)
Subsequent treatment of 2 equiv of 1 with electroni-
cally unsaturated [ClRh(COD)]2 (COD ) cyclooctadiene-
1.5) in thf at room temperature afforded a yellow
solution. In the 31P NMR spectrum resonances of two
1
Bond Angles (deg)
diastereoisomers at δ 123.1 (d, J (P-Rh) ) 230.3 Hz)
O(1)-P(1)-O(2)
O(1)-P(1)-C(9)
O(2)-P(1)-C(9)
O(1)-P(1)-Rh(1)
O(2)-P(1)-Rh(1)
97.2(2)
106.0(3)
99.9(3)
123.3(2)
112.7(2)
C(9)-P(1)-Rh(1)
C(4)-Rh(1)-C(5)
C(8)-Rh(1)-C(1)
P(1)-Rh(1)-Cl(1)
C(21)-O(1)-P(1)
114.1(2)
37.5(3)
34.9(3)
93.47(7)
130.9(3)
1
and δ 131.8 (d, J (P-Rh) ) 220.5 Hz) were observed,
formed in a 1:5.9 ratio. These diastereomers are due to
the hindered rotation of the biphenol unit and the
stereogenic phosphorus atom. Obviously small confor-
mational changes of the nearly planar oxaphosphorine
are not restricted at room temperature. Therefore, no
additional diastereomers were detected in the NMR
spectra. An orange solid crystallized, which was identi-
fied to be the major complex 2 (Scheme 1). The X-ray
structural analysis of this complex showed that the
hydroxy phosphonite coordinates in a monodentate
fashion (Figure 1; selected bond lengths and angles are
given in Table 1). The coordination geometry around the
rhodium center is nearly ideally planar, as expected for
a 16e Rh(I) complex. Nearly planar geometry is also
observed for the dibenzo fused oxaphosphorine ring.
Though there is no direct coordination of the OH group
at the rhodium center, the crystal structure gives
evidence for hydrogen bonding involving the coordinated
chloride anion (Cl(1)‚‚‚H(-O(3)) distance 2.342 Å). The
biphenyl unit exhibits a torsion angle of 58.3° due to
the steric demand of the bulky ortho-substituted tert-
butyl substituents. The Rh-P distance is 2.233(2) Å,
which is significantly longer compared to the respective
distances of 2.156 and 2.174 Å found for the only two
other examples of rhodium phosphonite complexes that,
to the best of our knowledge, have been characterized
structurally so far.16,17
To prove the possibility of hemilabile oxygen coordi-
nation, we studied the reaction of the lithium phenolate
derived from 1 with [ClRh(COD)]2. Interestingly, all
attempts to react the free hydroxy phosphonite in the
absence of rhodium(I) with butyllithium or KC7H7,
respectively, in thf at -20 °C did not give the expected
(14) The hemilabile behavior of phosphino ethers has been found
to be valuable for transition-metal-catalyzed carbonylation reactions:
Bader, A.; Lindner, E. Coord. Chem. Rev. 1991, 108, 27. Remote
hydroxy groups present in rhodium catalysts used for asymmetric
hydrogenation of prochiral olefins are used for the control of the
reactivity of the metal: Bo¨rner, A. Eur. J . Inorg. Chem. 2001, 327.
(15) A 0.1 M solution of hydroxy phosphonite 1 was used for this
experiment.
(16) Bondoux, D.; Tkatchenko, I.; Houalla, D.; Wolf, R.; Pradat, C.;
Riess, J . G.; Mentzen, B. F. J . Chem. Soc., Chem. Commun. 1978, 1022.
(17) Kumar, R.; Puddephatt, R. J .; Fronczek, F. R. Inorg. Chem.
1990, 29, 4850.

Reactions of a Hydroxy Phosphonite Ligand
Organometallics, Vol. 22, No. 21, 2003 4267
Ta ble 2. Selected Bon d Len gth s a n d An gles in 3
(for On e of th e Sym m etr y-In d ep en d en t Molecu les)
Bond Lengths (Å)
Rh(2)-P(2)
Rh(2)-O(23)
Rh(2)-C(9)
Rh(2)-C(10)
Rh(2)-C(13)
Rh(2)-C(14)
C(9)-C(10)
C(13)-C(14)
2.240(1)
2.013(3)
2.136(5)
2.141(5)
2.266(5)
2.289(5)
1.375(7)
1.373(8)
P(2)-O(21)
P(2)-O(22)
P(2)-C(17)
O(21)-C(20)
O(22)-C(37)
O(23)-C(53)
O(24)-C(56)
C(54)-C(69)
1.630(3)
1.617(3)
1.799(5)
1.415(5)
1.423(5)
1.337(5)
1.390(6)
1.495(7)
Bond Angles (deg)
98.6(1) Rh(2)-O(23)-C(53) 132.8(3)
P(2)-Rh(2)-O(23)
Rh(2)-P(2)-O(21) 111.0(1) C(9)-Rh(2)-C(10)
Rh(2)-P(2)-O(22) 116.5(1) C(13)-Rh(2)-C(14)
Rh(2)-P(2)-C(17) 123.1(2) O(21)-P(2)-C(17)
37.5(2)
35.1(2)
98.7(2)
Sch em e 2. P r op osed Resu lt of Ca ta lyst
P r efor m a tion w ith [Rh ]/1
F igu r e 2. Crystal structure of one of the two symmetry-
independent molecules of 3. Hydrogen atoms are omitted
for clarity. The thermal ellipsoids correspond to 30%
probability. The torsion angle between phenylic rings
defined by C53, C54, C55, C56, C57, C58 (mean deviation
from the best plane 0.0151 Å) and C37, C38, C65, C64, C70,
C69 (mean deviation from the best plane 0.0162 Å) is 91.2°.
The mean deviation from the best plane defined by X1a,
X1b, Rh2, P2, O23 is 0.0303 Å (X1a, X1b: midpoints of
cyclooctadiene double bonds). Selected bond lengths and
angles are given in Table 2. For details of the X-ray
structural analysis see Table 4.
phenolate salt but led to immediate unselective forma-
tion of a mixture of phosphorus-containing products. In
contrast, a clean reaction took place when a base such
as n-butyllithium was added to the Rh-coordinated
phosphonite. Under these conditions elimination of HCl
occurred and a single diastereomer of the phenolate-
phosphonite chelate complex 3 crystallized in 60% yield
(Scheme 1).18 The new complex was characterized in 31P
NMR spectroscopy by a resonance at δ 135.9 (1J (31P-
103Rh) ) 241.4 Hz).
An X-ray structure analysis was performed showing
two symmetry-independent molecules in the asym-
metric unit. The structure analysis confirmed the
formation of a mononuclear eight-membered rhodacyclic
complex (see Figure 2; selected bond lengths and angles
are given in Table 2). The chelate-like coordination at
the rhodium center is facilitated after a pronounced
rotation around the biphenyl axis. Torsion angles of 91.2
and 82.1°, respectively, were determined. These features
give evidence that there is no hindrance which prevents
the aryloxy group from coordinating; therefore, the
sterically demanding phosphonite phenolate ligand can
achieve a relatively stable chelate coordination at
rhodium, similar to the case for o-phosphino pheno-
lates.19
Tr a n sfor m a tion of Hyd r oxy P h osp h on ite 1 u n -
d er CO/H2. Subsequently, hydroxy phosphonite 1 was
added to complex 3 under syngas in toluene, corre-
sponding to a P/Rh ratio of 2 (Scheme 2).20 The mixture
was heated to 80 °C for 4 h at 20 bar and then cooled
and depressurized to give a light brown solution. 1H
NMR spectra of the solution revealed the formation of
a mixture of several hydrido rhodium complexes, which
were characterized by a set of overlapping hydride shifts
at approximately δ -10.1. The 31P{1H} NMR spectrum
showed doublet resonances between δ 171.3 and 172.4,
1
all exhibiting coupling constants J (P-Rh) in the range
of 197-205 Hz. The unusually large ligand 31P down-
field shift of approximately 35 ppm relative to the free
phosphonite matches the complexation shift usually
observed for diphosphite ligands coordinated to a hy-
1
drido rhodium core.21 A H,31P HMQC NMR spectrum
verified that all phosphorus resonances give correlation
signals to the hydride part of the proton spectrum.
Coupling constants J (H-P) between 13.5 and 15.4 Hz
were measured. The signals observed clearly correspond
to a set of complexes with a HRhP2 core possessing
chemically equivalent phosphorus atoms. Storage of the
reaction solution at low temperature afforded the crys-
(18) Complex 3 gave a powerful hydroformylation catalyst for a
mixture of internal octenes, provided an excess of 1 was present
(conditions: 140 °C/20 bar of CO/H2 (1:1), toluene, [3] ) 0.1078 M,
olefin:Rh ratio of 15 700). Catalysis in the presence of 9 equiv of the
hydroxy phosphonite resulted in 50% yield of aldehyde with a linearity
of ca. 48%. Obviously the same catalyst is generated from 3 as it is
from the acetyl acetonate precursor.11
(19) Kadyrov, R.; Heinicke, J .; Kindermann, M. K.; Heller, D.;
Fischer, C.; Selke, R.; Fischer, A. K.; J ones, P. G. Chem. Ber./ Recl.
1997, 130, 1663. Trzeciak, A. M.; Zio´lkowski, J . J .; Lis, T.; Choukroun,
R. J . Organomet. Chem. 1999, 575, 87.
(20) As was proved by 31P NMR spectroscopy, the mixture of
phenolate rhodium complex 3 and ligand 1a in toluene did behave
inertly at room temperature, as long as an argon atmosphere was
present.
(21) van Rooy, A.; Kamer, P. C. J .; van Leeuwen, P. W. N. M.;
Goubitz, K.; Fraanje, J .; Veldman, N.; Spek, A. L. Organometallics
1996, 15, 835.

4268 Organometallics, Vol. 22, No. 21, 2003
Selent et al.
tallization of colorless needles, which were identified to
be 3,3′-di-tert-butyl-5,5′-dimethoxybiphenyl-2,2′-diol.22
Workup of the filtrate gave a brown residue, showing
fragments in FAB MS at m/e 915 (M+, 10%) and 859
(M+ - 2CO, 62%). Obviously, in the presence of rhodium
and syngas 2 equiv of 1 reacts under transesterification,
thus forming the parent dihydroxy biphenyl and dia-
stereomeric HRhP2(CO)2 type complexes. The coordi-
nated bidentate ligand is likely a symmetric diphospho-
nite with a 3,3′-di-tert-butyl-5,5′-dimethoxybiphenyl-
2,2′-diolate backbone, phosphorylated with two of the
oxaphosphorine moieties as present in 1.23
P -C Bon d Activa tion of 1. Next, complex 3 was
treated in toluene under ambient temperature with an
excess of the ligand (overall ratio Rh:P ) 1:20). Then
the temperature was raised while the syngas pressure
was maintained constant at 20 bar. After cooling and
depressurization, 31P and 1H NMR spectra were re-
corded for every batch. Spectra recorded after an initial
treatment at 80 °C/30 min showed signals identical with
those of the hydride complexes described above together
with resonances of the free ligand at δ 134.8 and 135.2.
Integration verified a ratio of coordinated to uncoordi-
nated phosphorus of 1:9; therefore, further evidence was
provided that 2 equiv of 1 are consumed for complex
formation. Heating of the reaction mixture under 20 bar
of CO/H2 to 100 °C/4 h led to the appearance of a new
singlet at δ 139.2. This signal gained 11% of the relative
intensity of the uncoordinated ligand part of the 31P
NMR spectrum when the solution was kept at 120 °C
for 4 h; simultaneously, the signals of 1 lost intensity.
At 140 °C the reaction was more pronounced, giving a
67% fraction of the new compound within 4 h and
resulting in the complete transformation of the free
F igu r e 3. Crystal structure of 5. Hydrogen atoms are
omitted for clarity. The thermal ellipsoids correspond to
30% probability. The mean deviation from the best plane
defined by X1a, X1b, Rh1, P1, Cl1 is 0.0881 Å (X1a, X1b:
midpoints of cyclooctadiene double bonds). Selected bond
lengths and angles are given in Table 3. For details of the
X-ray structural analysis see Table 4.
1
hydroxy phosphonite after 8 h. The H NMR spectrum
Sch em e 3. Hyd r oxy P h osp h on ite to P h osp h ite
Tr a n sfor m a tion a n d P r od u ct Tr a p p in g
indicated the formation of a compound with chemically
equivalent tert-butyl and methoxy substituents, respec-
tively, characterized by singlets at δ 1.34 and 3.83. No
crystallization of the new compound was achieved;
therefore, the reaction solution was treated with an
appropriate amount of [ClRh(COD)]2 at room temper-
ature. As a result, the phosphite rhodium complex
[ClRh(COD)(4)] (5) was obtained in analytically pure
form after workup and recrystallization from toluene/
hexane (Scheme 3, Figure 3; selected bond lengths and
angles are given in Table 3). Complex 5 crystallized as
fine, needlelike yellow crystals which could be handled
in air for a short time. Structural features of the complex
such as Rh-P and Rh-Cl bond lengths as well as the
distances from the rhodium center to the vinylic carbon
atoms of coordinated cyclooctadiene do not markedly
differ from those obtained for the chloro phosphonite
complex 2.
found when the hydroxy phosphonite was heated in the
absence of rhodium. This means that a catalytic reaction
of the coordinated ligand must take place which pre-
sumably involves nucleophilic attack of the phenolic
hydroxy group at phosphorus.24 Formally, the P-C bond
breakage observed can be considered as the reverse
reaction of Lewis-acid-catalyzed formation of 6-chloro-
(6H)-dibenzo-(c,e)(1,2)-oxaphosphorine, which was used
Obviously, the hydroxy phosphonite when used in
excess suffers selective P-C bond activation, giving a
phosphite. It should be noted that no phosphite was
(22) The bis(phenol) was identified by comparison with an sample
synthesized independently by the procedure described in: Moasser,
B.; Gross, C.; Gladfelter, W. L. J . Organomet. Chem. 1994, 471, 201.
(23) Unfortunately, all attempts failed to synthesize this compound
according to a protocol described by: Maas, H.; Paciello, R.; Ro¨per,
M.; Fischer, J .; Siegel, W. German Pat. DE 198 10 794 A 1, 1998 (to
BASF AG). These attempts failed even after variation of the reaction
temperature between -40 and 60 °C or by application of n-butyllithium
or potassium benzyl in thf/hexane mixtures as well as with a large
excess of triethylamine as a base in toluene.
(24) The outcome of the reaction observed matches earlier results
on transition-metal-mediated P-C bond cleavage by nucleophilic attack
of alkoxide ligands; see, for example: van Leeuwen, P. W. N. M.;
Roobeek, C. F.; Orpen, A. G. Organometallics 1990, 9, 2179 and
references therein.

Reactions of a Hydroxy Phosphonite Ligand
Organometallics, Vol. 22, No. 21, 2003 4269
Ta ble 3. Selected Bon d Len gth s a n d An gles in 5
Ta ble 4. Cr ysta llogr a p h ic Da ta for 2, 3, a n d 5
Bond Lengths (Å)
2
3
5
Rh(1)-P(1)
Rh(1)-Cl(1)
Rh(1)-C(1)
Rh(1)-C(2)
Rh(1)-C(5)
Rh(1)-C(6)
C(1)-C(2)
2.223(1)
2.358(1)
2.120(5)
2.144(5)
2.247(6)
2.291(5)
1.390(7)
1.358(8)
P(1)-O(1)
P(1)-O(2)
P(1)-O(4)
O(1)-C(9)
O(2)-C(17)
O(4)-C(24)
C(29)-C(30)
C(10)-C(22)
1.605(3)
1.608(4)
1.602(4)
1.406(5)
1.422(6)
1.428(6)
1.496(8)
1.500(7)
formula
C
42H49ClO5-
PRh
C
42H48O5-
PRh
C
42H49ClO5-
PRh
fw
803.14
180
0.710 73
monoclinic
P21/n
14.023(3)
12.684(3)
22.639(5)
90
104.63(3)
90
3896.2(15)
4
1.369
0.591
1672
766.68
200
0.710 73
triclinic
P1h
12.562(2)
17.480(3)
18.107(3)
68.860(10)
82.430(10)
89.39(2)
3673.2(11)
4
803.14
200
0.710 73
tetragonal
P41
10.831(2)
10.831(2)
31.904(6)
90
temp, K
wavelength, Å
cryst syst
space group
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
C(5)-C(6)
Bond Angles (deg)
89.45(5)
105.2(1)
125.6(1)
115.0(1)
104.6(2)
P(1)-Rh(1)-Cl(1)
Rh(1)-P(1)-O(1)
Rh(1)-P(1)-O(2)
Rh(1)-P(1)-O(4)
O(1)-P(1)-O(2)
O(1)-P(1)-O(4)
O(2)-P(1)-O(4)
C(1)-Rh(1)-C(2)
C(5)-Rh(1)-C(6)
P(1)-O(4)-C(24)
108.5(2)
96.9(2)
38.1(2)
34.8(2)
131.8(3)
90
90
3742.7(12)
4
1.452
0.615
1672
Z
d
calcd, g cm-3
1.386
0.553
1600
as a starting material for 1a synthesis,11 from o-
phenylphenol and phosphorus trichloride.25
µ, mm-1
F(000)
cryst dimens, mm 0.3 × 0.3 × 0.2 1.0 × 0.3 × 0.1 0.3 × 0.2 × 0.1
To confirm the structure of 4 by an independent
synthetic pathway, 3,3′-di-tert-butyl-5,5′-dimethoxy-1,1′-
biphenyl-2,2′-diylphosphorochloridite26 was reacted with
o-phenylphenol in the presence of triethylamine to give
the desired 6,6′-di-tert-butyl-4,4′-dimethoxy-2,2′-bisphe-
noxyphosphinooxy(2-phenyl)phenyl. This phosphite is a
new member of a series of compounds which belong to
the parent 2,2′-bisphenoxyphosphinooxyphenyl.27 Upon
coordination to rhodium(I) the relevant 31P NMR spec-
trum was characterized by a remarkable upfield shift
of 19 ppm, leading to a resonance at δ 119.1. The
complex prepared from such a phosphite sample with
[ClRh(COD)]2 showed the same analytical properties as
5.
θ range, deg
no. of rflns
collected
1.86-24.29
1.90-24.22
1.88-20.96
11 182
10 923
8011
no. of indep rflns 6116
10 923
6080
3930
3630
no. of obsd rflns
3309
(I > 2σ(I))
no. of params
R1 (I > 2σ(I))
wR2 (all data)
452
883
0.039
0.071
451
0.029
0.064
0.060
0.143
benzophenone prior to use. Chemicals were purchased from
Aldrich Chemical Co. Phosphonite 1a was prepared according
to the literature procedure.11 NMR spectra were obtained on
a Bruker ARX 400 spectrometer (400.1 MHz for 1H NMR,
100.6 MHz for 13C NMR, and 162.0 MHz for 31P NMR at a
magnetic field strength of 9.4 T); all shifts are given relative
to TMS (1H, 13C) or 85% H3PO4 (31P). Mass spectra were
measured on a Intectra AMD 402/3 instrument. Elemental
analysis data were measured on a Leco CHNS-932 apparatus.
IR spectra were recorded on a Nicolet Magna-IR 550 spec-
trometer.
P r essu r e Rea ction s. A 200 mL Buddeberg autoclave
equipped with a gas stirrer, a thermocouple, a storage vessel
allowing the addition of reactants under pressure applied, a
sampling device, a Bronkhorst Hitec pressure controller, and
a Bronkhorst gas flow meter was used. The autoclave allowed
us to add and remove any media and reagents with the strict
exclusion of air. A high-grade pure syngas (99.997%; CO/H2
1:1) was purchased from Linde AG. The hydroformylation
experiments of internal octenes using complex 3 as a catalyst
precursor were carried out by using the methodology and
substrate described in detail in ref 11.
X-r a y Str u ctu r a l An a lyses. Suitable crystals of com-
pounds 2, 3, and 5 were obtained from toluene/hexane solu-
tions. X-ray data were collected on a STOE-IPDS diffracto-
meter using graphite-monochromated Mo KR radiation. The
structures were solved by direct methods (SHELXS-86)29 and
refined by full-matrix least-squares techniques against F2
(SHELXL-93).30 XP (Siemens Analytical X-ray Instruments,
Inc.) was used for structure representations. Crystallographic
data are given in Table 4.
P r ep a r a tion of [ClRh (COD-1.5)(1)] (2). A solution of
[ClRh(COD-1.5)]2 (0.862 g, 1.75 mmol) in thf (60 mL) was
treated dropwise with a 0.0915 M stock solution of 1a in thf
(38.2 mL, 3.5 mmol) at room temperature. After it was stirred
for an additional 2 h, the solution was concentrated to 15 mL
in vacuo and stored at 5 °C for 3 days. The orange crystals
that formed were filtered off, washed with cold hexane (2 × 5
mL), and dried in vacuo.
Con clu sion s
The results may be summarized as follows: the
observed coordination modes of 1 found in complexes 2
and 3 in the absence of syngas at room temperature may
be important only at early stages of the catalyst forma-
tion. Under conditions more related to hydroformylation
the reactive phenolic OH group present in 1 is respon-
sible for two modes of ligand transformation. In addition
to transesterification, also P-C bond activation and
cleavage take place. As a result, new trivalent P
compounds arise with the ability to coordinate on the
metal. Catalytic investigations are in progress to assess
the individual contribution of each newly formed orga-
nometallic compound to the overall result of the isomer-
izing hydroformylation of internal olefins.28
Exp er im en ta l Section
Gen er a l Con sid er a tion s. All reactions were carried out
using standard Schlenk techniques under an atmosphere of
argon (Linde AG). Solvents were distilled from sodium/
(25) Kleiner, H.-J . EP 0582957 A1, 1994 (to BASF AG).
(26) Arena, C. G.; Nicolo, F.; Drommi, D.; Bruno, G.; Faraone, F. J .
Chem. Soc., Dalton Trans. 1996, 23, 4357.
(27) Arbuzov, B. A.; Kadyrov, R. A.; Arshinova, R. P.; Mukmeneva,
N. A. Bull. Acad. Sci. USSR, Div. Chem. Sci. (Engl. Transl.) 1981, 30,
567.
(28) To prove the properties of pure phosphite 4 as a catalyst
modifier, hydroformylation of internal octenes was carried out at 140
°C/20 bar (CO:H2 ) 1:1). With different Rh:P ratios applied (1:10, 1:20),
relatively low regioselectivities of 34.8 and 34.4% were obtained.
Aldehyde yields were 83.1 and 89.4%, respectively. These results match
the data earlier obtained with the ether phosphonite 1b. In our opinion
it is reasonable to suggest that the newly formed phosphite 4 supports
the isomerization activity and stability of the catalyst, respectively,
rather than regioselective olefin hydroformylation.
(29) Sheldrick, G. M. Acta Crystallogr., Sect. A 1990, 46, 467.
(30) Sheldrick, G. M. SHELXL-93; University of Go¨ttingen, Go¨ttin-
gen, Germany, 1993.

4270 Organometallics, Vol. 22, No. 21, 2003
Selent et al.
A second crop of crystals was obtained after concentration
of the mother liquor to 5 mL. Overall yield: 2.585 g (92%).
Anal. Calcd for C42H49O5PClRh: C, 62.81; H, 6.15; P, 3.86; Rh,
12.81. Found: C, 62.79; H, 6.13; P, 3.61; Rh, 12.41. FAB-MS:
m/e 802 (3%, M+), 767 (53%, M+ - Cl), 694 (100%, M+ - COD).
Spectroscopic data (major diastereoisomer): 31P{1H} NMR
(CD2Cl2) δ 131.8 (d, 1J PRh ) 220.5 Hz); 13C{1H} NMR (CD2Cl2)
δ 28.1 (s, C(CH3)3), 29.6 (s, C(CH3)3), 30.4 (s, C(CH3)3), 32.4
) 3.5 Hz), H(1); -10.13 (dt, J HP ) 15.4 Hz, J HRh ) 3.9 Hz),
H(2); -10.13 (dt, J HP ) 15.4 Hz, J HRh ) 3.9 Hz), H(3); -10.13
(dt, J HP ) 15.4 Hz, J HRh ) 3.4 Hz), H(4); -10.14 (dt, J HP
)
13.5 Hz, J HRh ) 3.7 Hz), H(5). IR (toluene, 0.2 mm CaF2): ν-
(CO) 1942.6 (s), 2009.4 (s), ν(Rh-H) 1955.4 (m, sh) cm-1. FAB
MS: m/e 915 (M+, 10%) 875 (50%), 859 (M+ - 2CO, 62%), 687
(M+ - CO - H - phosphorine, 100%), 659 (M+ - 2 CO - H -
phosphorine, 73%), 602 (50%).
2
(d, J CRh) 2.8 Hz, CH2 cyclooctadiene), 32.6 (s, C(CH3)3), 34.7
P -C Activa tion of Hyd r oxy P h osp h on ite 1 a n d F or -
m a tion of Com p lex 5. A solution containing [acacRh(COD-
1.5)] (28.9 mg, 0.093 mmol) and phosphonite 1 (1.036 g, 1.861
mmol) in toluene (35 mL) was transferred into the autoclave
via cannula. Syngas was applied (33 bar) and the reactor
heated with stirring to 140 °C. Then the pressure was adjusted
to 50 bar. After 8 h of reaction time, the autoclave was cooled
and depressurized and the reaction solution transferred to a
Schlenk tube. Evaporation of the solvent in vacuo afforded a
brown oily residue, which was treated with 10 mL of hexane
to give an amorphous brown precipitate. After filtration, 5 mL
of hexane added to the filtrate gave a second fraction of
precipitate, which was removed also. 31P NMR showed the
filtrate to contain only one phosphorus compound with a signal
at δ 139.2 ppm (toluene-d8, chemical shift in CD2Cl2 138.3
ppm). Evaporation of the solvent gave 0.783 g (1.407 mmol,
76%) of phosphite 4. For details of analyses see the indepen-
dent phosphite synthesis described in the next paragraph. The
phosphite obtained (0.783 g, 1.407 mmol) was dissolved in thf
(20 mL) and added at room temperature to a solution of [ClRh-
(COD-1.5)]2 (0.347 g, 0.703 mmol) in thf (20 mL). After the
mixture was stirred overnight, the solvent was removed in
vacuo to form a yellow-brown solid, which was washed with
cold hexane (3 × 5 mL) and recrystallized from toluene/hexane.
Yield: 0.751 g (66%) of [ClRh(COD-1.5)(4)]. Anal. Calcd for
2
(d, J CRh) 1.9 Hz, CH2 cyclooctadiene), 55.4 (s, OCH3), 56.1
1
1
(s, OCH3), 73.1 (d, J CRh ) 13.4 Hz), 73.3 (d, J CRh ) 13.4 Hz,
both dCH- cyclooctadiene), phenylic carbons at 113.2, 114.1,
114.5, 114.9 (all s), 120.7 (d, J CP ) 3.8 Hz), 123.5 (d, J CP ) 4.8
Hz), 125.0, 125.7 (both s), 129.1 (d, J CP ) 17.2 Hz), 130.2, 132.3,
134.1, 134.4 (all s); 1H NMR (CD2Cl2) δ 1.26 (s, 9H, C(CH3)3),
1.51 (s, 9H, C(CH3)3), 1.81, 1.94, 2.18, 2.30 (all m, 2H, CH2
cyclooctadiene), 3.04 (br, 1H, dCH- cyclooctadiene), 3.04, 3.50
(both s, 3H, OCH3), 3.86, 5.33, 5.59 (all br, 1H, dCH-
cyclooctadiene), 5.59 (s, 1H, OH), phenylic protons at: 6.11
(d, 1H), 6.27 (d, 1H), 6.35 (s, 1H), 6.66 (d, 1H), 6.95, 7.05, 7.12,
7.23,7.25, 7.52, 7.73, 7.99 (all dd, 1H).
P r ep a r a tion of [Rh (COD-1.5)(1-p h en ola te)] (3). A solu-
tion of 2 (1.596 g, 1.99 mmol) in thf (75 mL) was treated with
a 0.1 M solution of n-butyllithium in hexane (19.9 mL, 1.99
mmol) at room temperature. After the mixture was stirred for
2 h, the solvent was evaporated in vacuo. The residue was
washed with cold hexane (65 mL), filtered off, and then
extracted with boiling diethyl ether (80 mL). After storage at
5 °C overnight the ethereal solution was cold filtered and the
precipitate was washed with cold ethyl ether (6 mL) and then
dried in vacuo at 50 °C for 3 h. Yield: 0.921 g of yellow
microcrystalline material (60%). Anal. Calcd for C42H48O5-
PRh: C, 65.79; H, 6.31; P, 4.04; Rh, 13.42. Found: C, 65.52;
H, 6.21; P, 3.81; Rh, 13.18. FAB-MS: m/e 767 (58%, M+), 659
(100%, M+ - COD). 31P{1H} NMR (CD2Cl2): δ 135.95 (d, 1J PRh
) 241.4 Hz). 13C{1H} NMR (CD2Cl2): δ 27.2 (s, C(CH3)3), 29.3
(s, C(CH3)3), 29.9 (s, C(CH3)3), 31.4 (s, C(CH3)3), 32.6, 36.0 (both
C
42H49O5PClRh: C, 62.81; H, 6.15. Found: C, 63.01; H, 6.32.
FAB-MS: m/e 802 (7%, M+), 767 (38%, M+ - Cl), 694 (89%,
M+ - COD), 659 (100%, M+ - COD - Cl). 31P{1H} NMR (CD2-
Cl2): δ 119.1 (d, J PRh ) 273.3 Hz), 13C{1H} NMR (CD2Cl2): δ
28.4 (s, CH2 cyclooctadiene), 31.6 (s, C(CH3)3), 33.4 (s, CH2
cyclooctadiene), 35.9 (s, C(CH3)3), 56.0 (s, OCH3), 71.0 (d, J CRh
) 13.4 Hz, dCH- cyclooctadiene), phenylic carbons at 113.4
(d, J CP ) 16.2 Hz), 113.8, 115.2 (both s), 121.9 (d, J CP ) 5.7
Hz), 124.3, 127.4, 127.7, 128.1, 131.5, 132.1 (all s), 133.0 (d,
J CP ) 5.7 Hz), 135.7, 137.9 (all s), 141.8 (d, J CP ) 11.5 Hz),
2
d, J CRh ) 1.9 Hz, CH2 cyclooctadiene), 56.4 (s, OCH3), 57.0
1
1
(both s, OCH3), 66.6 (d, J CRh ) 13.4 Hz), 68.5 (d, J CRh ) 12.4
Hz, both dCH- cyclooctadiene), phenylic carbons at 112.9 (dd),
113.6 (dd), 113.9 (dd), 115.2 (s), 121.4 (d), 123.9 (dd), 124.8
(s), 125.3 (s), 127.9 (d), 130.2 (s), 132.3 (s), 132.9 (s), 133.3 (s).
1H NMR (CD2Cl2): δ 1.54 (s, 9H, C(CH3)3), 1.83 (s, 9H,
C(CH3)3), 2.21 (2H), 2.30 (4H), 2.47 (2H; all m, CH2 cyclooc-
tadiene), 3.65 (s, 3H, OCH3) 3.69, 3.93 (both br, 1H, dCH-
cyclooctadiene), 4.00 (s, 3H, OCH3), 5.85 (br, 2H, dCH-
cyclooctadiene), phenylic protons at 6.12 (d, 1H), 6.70 (d, 1H),
6.98 (d, 1H), 7.21 (ddd, 1H), 7.23 (d, 1H), 7.31 (ddd, 1H), 7.33
(d, 1H), 7.47 (ddd, 1H), 7.61 (ddd, 1H), 7.74 (ddd, 1H), 8.05
(dd, 1H), 8.20 (dd, 1H).
1
142.3 (d, J CP ) 3.9 Hz), 149.4 (d, J CP ) 8.6 Hz), 156.0 (s). H
NMR (CD2Cl2): δ 1.37 (s, 18H, C(CH3)3), 1.98 (br m, 4H, CH2
cyclooctadiene), 2.19, (br m, 4H, CH2 cyclooctadiene), 3.58 (br,
2H, dCH- cyclooctadiene), 3.71 (s, 6H, OCH3), 5.45 (br, 2H,
dCH- cyclooctadiene), phenylic protons at 6.60 (d, 2H), 6.88
(d, 2H), 7.02 (m, 2H), 7.14 (m, 1H), 7.20 (m, 3H), 7.30 (m, 1
H), 7.45 (m, 2H).
Rea ction of Com p lex 3 w ith Hyd r oxy P h osp h on ite 1
u n d er Syn ga s. A solution of complex 3 (406 mg, 0.529 mmol)
in toluene (30 mL) was treated with the hydroxy phosphonite
(294.7 mg, 0.529 mmol) at room temperature. After the
mixture was stirred for 1 h, a sample of the reaction solution
(2 mL) was evaporated to dryness. A 31P NMR spectrum
measured in toluene-d8 showed no signals other than those of
the starting compounds. The reaction solution was transferred
to the autoclave and stirred under syngas (20 bar) at 80 °C
for 4 h. The autoclave was cooled and depressurized and the
solution transferred to a Schlenk tube. The reaction solution
was concentrated to half its original volume in vacuo and
stored at -23 °C for 2 weeks. The colorless crystals that formed
were filtered off, washed with hexane, and dried in vacuo.
Yield: 93 mg (49%) of 3,3′-di-tert-butyl-5,5′-dimethoxybiphe-
nyl-2,2′-diol (mp 228 °C). The filtrate was evaporated to
dryness in vacuo, giving a brown solid, consisting of five HRh-
(CO)2P2 complexes. 31P{1H} NMR: δ 171.3 (d), J PRh ) 201.1
In d ep en d en t Syn th esis of P h osp h ite 4. A solution of
3,3′-di-tert-butyl-5,5′-dimethoxy-1,1′-biphenyl-2,2′-diylphospho-
rochloridite26 (1.303 g, 3.08 mmol) in diethyl ether (15 mL)
was slowly treated with a mixture of 2-phenylphenol (0.524
g, 3.03 mmol) and triethylamine (0.533 g, 5.27 mmol) in diethyl
ether (10 mL) at room temperature. After it was stirred for 4
h, the reaction mixture was filtered and the solvent removed
in vacuo. The residue obtained was dried in vacuo at 80 °C
for 3 h to give the product as an colorless oil. Yield: 1.657 g
(97%). Anal. Calcd for C34H37O5P: C, 73.36; H, 6.70. Found:
C, 73.10; H, 6.73. EIMS (70 eV): m/e 556 (95%, M+), 387 (100%,
M+ - o-(C6H5)C6H4O). 31P{1H} NMR (CD2Cl2): δ 138.3. 13C-
{1H} NMR (CD2Cl2): δ 30.9 (s, C(CH3)3), 35.6 (s, C(CH3)3), 55.9
(s, OCH3), phenylic carbons at 113.2 (s), 114.8 (s), 121.5 (d,
J CP ) 12.4 Hz), 124.6, 127.4, 128.4, 128.8, 130.0, 131.7 (all s),
134.0 (d, J CP ) 3.8 Hz), 134.2, 138.2 (both s), 141.7 (d, J CP
)
1
5.7 Hz), 143.0, 149.1, 156.3 (all s). H NMR (CD2Cl2): δ 1.34
(s, 18H, C(CH3)3), 3.83 (s, 6H, OCH3), phenylic protons at 6.75
(m, 2H), 6.99 (m, 2H), 7.18 (m, 2H), 7.29 (m, 4H), 7.39 (m,
1H), 7.45 (m, 2H).
Hz, P(1); 171.5 (dd), J PRh ) 198.3 Hz, P(2); 171.7 (dd), J PRh
)
198.3 Hz, P(3); 171.9 (d), J PRh ) 197.0 Hz, P(4); 172.4 (d), J PRh
1
) 201.1 Hz, P(5). H NMR: δ -10.07 (dt, J HP ) 14.6 Hz, J HRh

Reactions of a Hydroxy Phosphonite Ligand
Organometallics, Vol. 22, No. 21, 2003 4271
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data and structure refinement details, atomic coordinates,
bond lengths and angles, anisotropic displacement parameters,
and hydrogen coordinates for 2, 3 and 5. This material is
available free of charge via the Internet at http://pubs.acs.org.
Ack n ow led gm en t. We thank Mrs. Marianne Gei-
sendorf for reliable and skilled technical assistance.
Financial support from OXENO C4-Chemie, Marl,
Germany, and the Fonds der Chemischen Industrie is
gratefully acknowledged. We acknowledge a generous
gift of rhodium salts by OMG Ag & Co. KG, dmc2
division (Hanau, Germany).
OM0204686