Novel rhodium(I) complexes with (2-hydroxyphenyl)diphenylphosphine ligand: Catalytic properties and X-ray structures of Rh(OC6H4PPh2)(CO)(PPh3) and Rh(OC6H4PPh2){P(OPh)3</su

Article abstract of DOI:10.1016/S0022-328X(98)00981-4

The novel rhodium complexes with the bidentate PO ligand (PO=OC₆H₄PPh₂^-) of the form Rh(PO)(CO)L (L^a=POH=HOC₆H₄PPh₂ (1), PPh₃ (2), P(NC₄H₄

Full text of DOI:10.1016/S0022-328X(98)00981-4

Journal of Organometallic Chemistry 575 (1999) 87–97
Novel rhodium(I) complexes with (2-hydroxyphenyl)diphenylphosphine
ligand: catalytic properties and X-ray structures of
Rh(OC6H4PPh2)(CO)(PPh3) and Rh(OC6H4PPh2){P(OPh)3}2 · 0.5C6H6
a
a,
a
b
*
Anna M. Trzeciak , Jo´zef J. Zio´lkowski *, Tadeusz Lis , Robert Choukroun
a
*
*
Faculty of Chemistry, Uni6ersity of Wroclaw, 14 F. Joliot-Curie Str., 50-383 Wroclaw, Poland
b Laboratoire de Chimie de Coordination du CNRS, 205 route de Narbonne, 31077 Toulouse Cedex, France
Received 15 July 1998
Abstract
The novel rhodium complexes with the bidentate PO ligand (PO=OC6H4PPh2−) of the form Rh(PO)(CO)L (La=POH=
HOC6H4PPh2 (1), PPh3 (2), P(NC4H4)3 (4), PPh2(NC4H4) (6)) and Rh(PO)L2 (Lb=P(OPh)3 (3), P(NC4H4)3 (5)) were obtained by
ligand exchange in Rh(b-diketone)(CO)2, Rh(b-diketone)(CO)L and Rh(b-diketone)L2 complexes. All complexes of the
Rh(PO)(CO)La type exist in solution as isomers with both phosphorus atoms in the trans position as was shown by
31P{1H}-NMR. The trans influence of the phosphorus atom of a bidentate PO ligand is stronger than that of oxygen atom, which
˚
is manifested by the differences of Rh–P bonds in (2) (2.283(1) and 2.327(1) A) and of Rh–P (phosphite) bonds in (3) (2.233(2)
˚
and 2.139(2) A). The complexes (1) and (2) used alone or with an excess of free phosphine (POH, PPh3, P(NC4H4)3) are not active
in hexen-1-e hydroformylation at 1 MPa CO/H2=1 and at 353 K. The lack of catalytic activity is explained by the extremely high
stability of the chelate (PO) ring which does not allow the formation of the active form of the catalyst. In contrast, the complex
(3) used alone as the catalyst precursor produces 54 and 72.9% of aldehydes when used with a six-fold excess of P(OPh)3. Complex
(1) modified with P(OPh)3 catalyses hexen-1-e hydroformylation with a 73.6–84.6% yield of aldehydes. Under hydroformylation
reaction conditions, the PO ligand is removed from the coordination sphere of (1) and complexes of the form
HRh(CO){P(OPh)3}3 and HRh{P(OPh)3}4 are formed. © 1999 Elsevier Science S.A. All rights reserved.
Keywords: Rhodium complexes; Phosphines; Catalysis; X-ray structure
1. Introduction
P–O ligand can be substituted easily by the substrate
molecule, which facilitates its activation. Therefore,
metal complexes with hemilabile ligands are usually
activating small molecules, such as CO, CO2, H2 [6–8].
Hydroxyphenyl phosphines, which contain hard oxy-
gen and soft phosphorus belong to bifunctional ligands
which may coordinate to the metal as bidentate (form
A) or monodentate (form B).
The oxo-phosphorus ligands, which belongs to the
group of hemilabile ligands, have recently been applied
frequently in such metal complex catalysed processes as
hydrogenation, carbonylation, hydroformylation or de-
hydrogenation [1–5]. The presence of two coordination
sites in a P–O ligand, a labile and an inert one in
respect to the substitution reaction, make these ligands
very attractive.
In catalytic reaction conditions the labile site of the
* Corresponding author. Tel.: +48-71-3286325; fax: +48-71-
3282348.
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(98)00981-4

88
A.M. Trzeciak et al. / Journal of Organometallic Chemistry 575 (1999) 87–97
Scheme 1.
The examples of both modes of coordination have
ca. 80% of hexen-2-e (hexen-1-e isomerization reac-
tion product) are obtained [13]. However, the intro-
duction of PPh3 to the system increases the yield of
aldehydes to 80–90% [13,14].
Initial studies of hexen-1-e hydroformylation with
the catalytic system containing Rh(acac)(CO)2 and
POH (at 1 MPa H2/CO and 353 K) pointed to a
quite different effect of POH ligand on the reaction.
Even at a small concentration of POH a significant
decrease of the yield of both products, aldehyde and
hexen-2-e, was observed as compared with the respec-
been found for ruthenium [9], nickel, palladium, plat-
inum, cobalt [10] and rhenium [11] coordination com-
pounds but till now not for rhodium(I). Some
polynuclear rhodium(II) complexes with tris(2,4,6-
trimethoxyphenyl)phosphine in which demethylated
phosphine coordinates as PO ligand bridging two
rhodium(II) ions have been obtained [12].
In this paper we present results of structural as
well as reactivity studies of rhodium(I) complexes
with (2-hydroxyphenyl)diphenylphosphine (POH).
The main goal of our studies was to investigate the
properties of POH phosphine as a modifying ligand
in respect of its application in catalytic systems used
for olefin hydroformylation. It is well known that the
proper selection of ligands coordinated to the metal
in homogeneous catalysts is a main factor determin-
ing their catalytic activity demonstrated by the high
yield and selectivity of the given reaction.
Although triphenylphosphine is a classical example
of such effective modifying ligand, we found interest-
ing to study how the presence of OH group in the
ortho position of the phenyl ring of POH will change
its modifying properties. It was expected that struc-
tural investigations of the new Rh(I) complexes as
well as detailed studies of its preparation may provide
some new information about the coordination proper-
ties and specificity of both the potential donor atoms
in the POH ligand.
Such properties determine the pathway and the
mechanism of the ligand substitution reaction in
rhodium(I) complexes as catalyst precursors and
therefore are important for preparation of the new,
catalytically active species.
tive yield in
a
reaction catalyzed by an
Rh(acac)(CO)2+PPh3 system. When [POH]:[Rh]=0.5
only 79.2% of hexen-2-e was found after 2 h and
when [POH]:[Rh]=2 or 3 no reaction products were
found.
From these simple experiments one may conclude
that the POH ligand not only does not create a cata-
lytically active form of rhodium(I) complex, but even
deactivates Rh(acac)(CO)2 as a catalyst precursor. To
explain the rather inhibiting effect of the POH ligand
on the hydroformylation reaction, the properties of
specially prepared complexes with PO have been
studied.
2.1. Synthesis of Rh(PO)(CO)La and Rh(PO)L2b
complexes
In syntheses of metal complexes with POH de-
scribed up to now, chloride complexes were usually
used as the substrates: K2PtCl4 [10], {Ru(h-
C5Me5)Cl}4 [9], [ReOCl4]−, [ReOCl3(PPh3)2] [11].
Chlorides were removed as HCl or NaCl (when
sodium acetate was added) usually under reflux con-
dition.
We have found, that b-diketonate ligands are sub-
stituted easily by PO according to the Scheme 1. In
the following Rh(I) complexes: Rh(acac)(CO)2,
Rh(acac)(CO)(PPh3), Rh(acac)(CO)(P(NC4H4)3), Rh(a-
cac)(CO)(PPh2(NC4H4)), Rh(acac){P(OPh)3}2, Rh(bt-
a){P(OPh)3}2 and Rh(acac){P(NC4H4)3}2 (acac=ace-
tyloacetonate, bta=benzoyloacetonate) total substi-
2. Results and discussion
On the basis of our earlier papers we concluded
that with Rh(acac)(CO)2 as a hexen-1-e hydroformy-
lation catalyst precursor only 20% of aldehydes and

A.M. Trzeciak et al. / Journal of Organometallic Chemistry 575 (1999) 87–97
89
Scheme 2.
tution of b-diketonate ligand by POH undergoes at
room temperature within a few minutes.
2.1.1. Reaction of Rh(acac)(CO)2 with
(2-methoxyphenyl)diphenylphosphine (POCH3)
The replacement of a proton in POH by the methyl
group changes tremendously the reactivity of the ligand
(POCH3) towards Rh(acac)(CO)2. Regardless of the
ratio of [POCH3]:[Rh] only a complex of the form
Rh(acac)(CO)(POCH3), (7), is formed (Scheme 2), just
as in the reaction with PPh3. Its spectroscopic parame-
ters (1H-, 31P{1H}-NMR) are very close to those of
Rh(acac)(CO)(PPh3).
Different rhodium(I) complexes with b-diketonates
can be used as starting complexes for syntheses and in
some cases the same products may be obtained, i.e.
reaction of Rh(bta){P(OPh)3}2 and Rh(acac){P-
(OPh)3}2 with POH produce the same complex (3) of
the form Rh(PO){P(OPh)3}2. From the observation of
the reaction of rhodium(I) b-diketonates with POH
phosphine one may conclude that POH always acts first
as proton donor and cannot be regarded as normal
phosphine with only nucleophilic properties. A good
illustration of the properties of POH ligand is provided
by its reaction with Rh(acac)(CO)2, which is not typical
as compared with other phosphines. Generally, phos-
phines depending on their s-donor and/or p-acceptor
properties substitute one or two CO ligands in
Rh(acac)(CO)2. Therefore, stronger s-donor phos-
phines L (L=PPh3, PPh2(NC4H4)) produce Rh(acac)
(CO)L complexes as the substitution reaction products
whereas stronger p-acceptor phosphorus ligands, L,
(L=P(OPh)3, P(NC4H4)3) give Rh(acac)L2 complexes
[15,16]. Regardless of the kind of phosphorus ligands
used, an acetylacetonato ligand always remains in the
coordination sphere. However, when POH phosphine
reacts with Rh(acac)(CO)2, complex (1) is formed as a
product of the substitution of one CO group by a
neutral POH ligand and the simultaneous substitution
of acac by an anionic chelating form of phosphine, PO.
Complex (1) (Rh(PO)(CO)(POH)) is the only iden-
tified product of the reaction of Rh(acac)(CO)2 with
POH, regardless of the concentration of phosphine
used.
At the ratio [POH]:[Rh]=1:1, the substitution of CO
in Rh(acac)(CO)2 was not complete, which was proved
by IR (wCO observed at 2020 and 2070 cm−1), confirm-
ing the presence of unreacted Rh(acac)(CO)2. When
POH phosphine was applied in excess, unreacted POH
remained in the reaction mixture. The highest yield of
complex (1) (87%) was obtained at the ratio of
[POH]:[Rh]=2:1.
Apart from the reaction of Rh(acac)(CO)2 with POH
(in which acac and CO are substituted by PO and POH,
respectively), in all other reactions under studies mainly
acac is substituted by PO. In the reaction of POH with
Rh(acac)L2 (L=P(OPh)3, P(NC4H4)3), only one
product of the general formula Rh(PO)L2 was found.
2.2. Spectroscopic characterization of Rh(PO)(CO)(La)
and Rh(PO)Lb2 complexes
2.2.1. 31P{1H}-NMR spectra
The 31P{1H}-NMR spectrum of complex (1) was
recorded for a reaction mixture containing Rh(acac)-
(CO)2+1.5 POH in a C6D6 solution as well as for an
isolated compound (1) dissolved in CDCl3. Both spec-
tra are identical and characteristic for a structure in
which phosphorus atoms are located in the trans posi-
tion. This is manifested by the relatively high value of
the coupling constant 2J(P–P)=304 Hz. Similar results
were obtained for trans-RhCl(CO)[cp2ZrCl(PCH2Ph2)2]
(363.2 Hz) [17] and trans-[Rh{Ph2PCH···C(···O)-
2
Ph}(CO)(PPh3)] (301 Hz) [5] complexes. The J(P–P)
value equal to 307 Hz for complex (2) points to the
trans position of P-atoms in that complex in solution.
31P{1H}-NMR measurements made it possible to dis-
tinguish different coordination modes of hydroxyphos-
phine POH. When POH forms a chelate ring the
phosphorus signal switches down-field up to l=ca. 45
ppm, whereas in the case of the coordination of a
neutral POH molecule, the 31P{1H}-NMR signal is
observed at about 25 ppm. The assignment of the
31P{1H}-NMR band at ca. 45 ppm to chelating coordi-
nation of PO was clear after comparison with 31P{1H}-
NMR spectra of complexes (1), (2), (3) (Fig. 1) and (5)
(Table 1).
Complexes with pyrrolyl phosphines ((4) and (6))
show dynamic properties in solution at room tempera-
ture, which is demonstrated by the lack of P–P as well
as Rh–P (pyrrolylphosphine) couplings (Fig. 2).
In the 31P{1H}-NMR spectra of (4) and (6) measured
at 293 K the doublets from the PO ligand at 46.9 and
47.0 ppm, respectively, are observed as well as singlets
from N-pyrrolylphosphines at 91.0 and 69.7 ppm. The

90
A.M. Trzeciak et al. / Journal of Organometallic Chemistry 575 (1999) 87–97
Fig. 1. 31P-NMR spectrum of Rh(OC6H4PPh2){P(OPh)3}2 (3).
posed of two double doublets, which undoubtedly
lack of
a
coupling between rhodium and N-
confirms that both phosphorus ligands PO and
PPh2(NC4H4) are located in the trans position (Fig.
2). Similar temperature changes of the spectrum of
the
pyrrolylphosphine phosphorus indicates the dissocia-
tion of coordinated N-pyrrolylphosphine and
dynamic equilibrium of 16 and 14 electron complexes
(Scheme 3).
The lowering of temperature to 223 K allowed us
to get a well resolved spectrum of complex (4) com-
a
[Rh{Ph2PCH···C(···O)Ph}(CO)(PPh3)]
complex
in
which triphenylphosphine dissociates have been ob-
served by other authors [5].
In the case of complex (6) the decrease of tempera-
ture to 223 K is not sufficient to obtain conditions of
slow exchange. The lines assigned to complex (6) are
broadened and resolved badly, which allowed us only
to estimate the parameters of the spectra (Table 1).
Table 1
31P-NMR data of Rh(PO) complexes (1)–(6) in C6D6
Complex
(1)
(2)
(4)a
(6)a
(3)
45.8
137.8
118.1
248
(5)
42.3
141.3
96.7
210
106.5
238
407
39
l1
47.4
132
25.5
46.3
134
26.3
44
129
89
43.9
132
68
J(Rh–P1)
l2
2.2.2. The exchange of phosphines in complexes of the
Rh(PO)(CO)La type
J(Rh–P2)
l3
136
138
203
153
It was expected that phosphines with p-acceptor
properties stronger than POH would be able to sub-
stitute the POH ligand in (1) or the PPh3 ligand in
(2). However, the analysis of 31P{1H}-NMR spectra
of a solution containing complex (1) and a two-fold
excess of P(NC4H4)3 showed after 3 h as well as after
12 h unchanged substrates, which excludes the substi-
tution of CO or POH by P(NC4H4)3.
130.9
274
J(Rh–P3)
J(P1–P2)
J(P1–P3)
J(P2–P3)
304
308
407
332
480
38
79
64
a CDCl3, 223 K.
On the other hand, both complexes (1) and (2)
react with P(OPh)3 producing complex (3), which was
proved by 31P{1H}-NMR spectra measured in situ as
well as for the isolated reaction product (Scheme 4).

A.M. Trzeciak et al. / Journal of Organometallic Chemistry 575 (1999) 87–97
91
Fig. 2. 31P-NMR spectra of Rh(OC6H4PPh2)(CO)[PPh2(NC4H4)] (4) at 293 and 223 K. *Rh(PO)(CO)(POH).
2.2.3. Trans influence in Rh(PO)(CO)(La) complexes
than the oxygen atom, which is manifested in different
bond lengths proved by X-ray analysis for complexes
(2) and (3). In complex (2), the Rh–P bond length of
chelating PO and terminal PPh3 phosphines are differ-
ent (Scheme 5). The length of the Rh–P(phosphite)
bond in complex (3) in the trans position to the phos-
All
synthesized
complexes
of
the
form
Rh(PO)(CO)(La), (1), (2), (4) and (6), exist in solution
as only one isomer with both phosphorus atoms in the
trans position. The phosphorus atom of the bidentate
POH phosphine results in a stronger trans influence

92
A.M. Trzeciak et al. / Journal of Organometallic Chemistry 575 (1999) 87–97
Scheme 3.
Scheme 5.
phorus atom of the chelating PO ligand is longer than
that of the Rh–P bond in the trans position to oxygen
of the PO ligand (Scheme 5) (Tables 2 and 3).
Both complexes, (2) and (3), have a square planar
structure (Figs. 3 and 4) with a small deviation
˚
(0.024(2) A) of rhodium atom out of the plane formed
by the four atoms coordinated to rhodium in complex
(2). A five-membered chelate ring formed by the PO
ligand coordinating to rhodium is similar in both com-
plexes (2) and (3) with the Rh–O bonding equal to
1
2.2.4. H-NMR spectra
1H-NMR spectra of complexes (1)–(6) demonstrate
multiplets in the region of 6–8 ppm, typical for phenyl
protons (see Section 4). In complex (1) the signal of the
OH group proton is shifted down-field to 12.9 ppm. A
similar position of OH resonance was observed in the
1H-NMR spectrum of a ruthenium complex in which
the hydrogen bond between the OH group of a
monodentate POH ligand and the oxygen atom of a
chelating PO ligand was found by X-ray [9]. It is
reasonable to propose the presence of a hydrogen bond
also in complex (1).
˚
2.042(3) and 2.058(3) A and the Rh–P bonds equal to
˚
2.283(1) and 2.305(2) A, respectively. The P(1)–Rh–
O(6) angle is 83.2(1)° in (2) and 83.1(1)° in (3). The
corresponding angle in the ruthenium complex Ru(h-
C5Me5)(PO)(POH) is 80.49(7)°, whereas in rhenium(V)
complexes it is between 76.1(2) and 80.9(3)° [11].
The Rh–C(7) distance in complex (2) equal to
˚
1.795(5) A is comparable with Rh–C distances in other
rhodium–carbonyl complexes [18–20].
The Rh–P(2) bond in complex (2), 2.327(1) A, is
˚
elongated in comparison with the Rh–P bonds in
Rh(b-diketone)(CO)(PPh3) type complexes [18–20].
Such a bond elongation could be explained by a
stronger trans influence of the phosphorus of a PO
ligand than that of the oxygen of a b-diketone. In
˚
complex (3), where the Rh–P(2) bond is 2.139(2) A,
trans influence is more distinct, whereas the Rh–P(3)
bond is much longer and equals 2.233(2) A. In the
2.2.5. IR spectra
˚
The coordination of POH phosphine to rhodium(I)
as a PO chelating ligand causes significant changes in
the IR spectrum—a shift of frequencies in the region of
850 and 1250 cm−1 as well as band splitting at ca. 1460
and 1580 cm−1 (Table 4). In rhenium complexes with
POH major changes in IR caused by coordination were
observed only in the region of 580–900 cm−1 [11].
Rh(acac){P(OPh)3}2 complex Rh–P bonds are 2.147(2)
˚
and 2.156(2) A, very close to the Rh–P(2) bond dis-
tance in complex (3) [21].
The chelate coordination of the PO ligand causes the
shift of electron density in the oxophenyl ring, slightly
different in complexes (2) and (3). In both complexes,
(2) and (3), the delocalization of electron density in
fragment C(1)–C(6)–C(5) and the elongation of C(1)–
C(6) and C(5)–C(6) bonds are observed. The other
C–C bond distances in the oxophenyl ring of (3) are
similar to those in the remaining phenyl rings of phos-
2.3. Molecular structure of (2) and (3) complexes
Selected bond distances and angles in complexes (2)
and (3) are given in Table 2 and Table 3, respectively.
Scheme 4.

A.M. Trzeciak et al. / Journal of Organometallic Chemistry 575 (1999) 87–97
93
Table 2
Selected
Rh(OC6H4PPh2)(CO)(PPh3) (2)
cantly increases the yield of aldehydes [27], in further
experiments an excess of different phosphines, like
POH, PPh3 or P(NC4H4)3 was applied; however in all
experiments only trace amounts (1.5%) of hexen-2-e or
hexen-3-e, the isomerization products of hexen-1-e,
were found. The IR spectra of post-reaction mixtures
showed unchanged complexes (1) or (2). It seems to be
clear that the high stability of the PO chelate ring in
both complexes makes difficult their transformation to
the active form of the catalysts. Similarly POH phos-
phine added to Rh(acac)(CO)2 as a catalyst precursor
completely blocks catalytic activity. Contrary to the
above mentioned phosphine modifying ligands, phos-
phite P(OPh)3 is able to transform complex (1) to the
active form. A three-fold excess of P(OPh)3 per
rhodium is already enough to obtain 73.6% of alde-
hydes (Table 5).
˚
bond
lengths
(A)
and
angles
(°)
in
˚
Bond lengths (A)
Rh–P(1)
Rh–P(2)
Rh–O(6)
Rh–C(7)
P(1)–C(11)
C(1)–C(2)
C(3)–C(4)
C(5)–C(6)
2.283(1)
2.327(1)
2.042(3)
1.795(5)
1.816(5)
1.409(6)
1.406(7)
1.413(6)
C(7)–O(7)
P(1)–C(1)
O(6)–C(6)
C(1)–C(6)
P(1)–C(21)
C(2)–C(3)
C(4)–C(5)
1.160(5)
1.803(5)
1.321(5)
1.400(6)
1.818(4)
1.361(6)
1.364(6)
Bond angles (°)
P(1)–Rh–P(2)
C(7)–Rh–O(6)
C(7)–Rh–P(1)
C(7)–Rh–P(2)
168.4(1)
178.0(2)
95.3(2)
95.9(2)
P(2)–Rh–O(6)
P(1)–Rh–O(6)
Rh–P(1)–C(1)
Rh–O(6)–C(6)
85.8(1)
83.2(1)
100.2(2)
120.3(3)
To identify the catalytically active form of the cata-
lyst in the reaction under consideration, the solution of
complex (1) with an excess of P(OPh)3 heated (353 K)
under 1 MPa of CO/H2 during 1 h was analysed by
31P{1H}-NMR technique. The spectrum showed the
origin of the doublets of hydrido phosphito complexes
of the form HRh{P(OPh)3}4 (l 130 ppm, J(Rh–P) 233
Hz) and HRh(CO){P(OPh)3}3 (l 140.5 ppm, J(Rh–P)
240 Hz) [22]. It means that under hydroformylation
reaction conditions, conducted at the excess of free
P(OPh)3, (2-hydroxyphenyl)-diphenylphosphine (POH)
was removed from the rhodium coordination sphere
and the catalytic system became like Rh(acac)(CO)2+
P(OPh)3, which had been studied previously [23].
It is worth noting that complex (3) alone used as a
catalyst for hexen-1-e hydroformylation produces ca.
54% of aldehydes and ca. 43% of hexen-2-e. Spectro-
phine. In the oxophenyl ring of complex (2), C(2)–C(3)
and C(4)–C(5) bonds of 1.36 A are in agreement with
˚
the double-bond character and the other bonds are
longer. The different distribution of electrons in the
oxophenyl rings of (2) and (3) can be explained by the
influence of the remaining ligands coordinated to
rhodium. In complex (3) two p-acceptor P(OPh)3 lig-
ands interact equally on the chelate ring. In complex (2)
the p-acceptor character of CO and the s-donor char-
acter of PPh3 cause the unsymmetrical distribution of
electrons in the chelating fragment.
2.4. Catalytic acti6ity
The catalytic activity of rhodium(I) complexes with a
POH ligand were tested in the hydroformylation reac-
tion of hexen-1-e, under 1 MPa of CO/H2=1 at 353 K.
When complexes (1) or (2) were used alone, after 2 h
only ca. 1.5% of hexen-2-e was obtained whereas in a
similar reaction catalyzed by Rh(acac)(CO)2 66.5% of
hexen-2-e and 14.2% of aldehydes were produced. Since
usually the addition of free phosphorus ligands signifi-
1
scopic analysis based on IR, H-NMR and 31P-NMR
measurements showed that in the presence of a H2/CO
mixture, complex (3) undergoes total transformation
into HRh(CO){P(OPh)3}3 and Rh6(CO)16 within 1 h
(Scheme 6). The observed catalytic activity is the joint
effect of the parallel action of HRh(CO){P(OPh)3}3
responsible for hydroformylation and the Rh6(CO)16
cluster, which catalyses the isomerization of olefin. The
yield of aldehydes is increased up to 72.9% after the
introduction of free P(OPh)3 to the reaction medium.
The opposite effect is brought about by POH phos-
phine, which strongly inhibits the catalytic activity of
complex (3) and/or retards its action as a homogeneous
catalyst (Table 5).
Table 3
Selected
˚
bond
lengths
(A)
and
angles
(°)
in
Rh(OC6H4PPh2){P(OPh)3}2 · 0.5C6H6 (3)
˚
Bond lengths (A)
Rh–P(1)
Rh–P(2)
Rh–P(3)
Rh–O(6)
P(1)–C(21)
C(2)–C(3)
C(4)–C(5)
2.305(2)
2.139(2)
2.233(2)
2.058(3)
1.821(4)
1.390(5)
1.384(6)
P(1)–C(1)
C(1)–C(6)
O(6)–C(6)
P(1)–C(11)
C(1)–C(2)
C(3)–C(4)
C(5)–C(6)
1.804(4)
1.413(6)
1.311(4)
1.823(4)
1.393(5)
1.380(6)
1.412(5)
3. Summary
Bond angles (°)
P(1)–Rh–P(2)
P(1)–Rh–P(3)
P(1)–Rh–O(6)
P(2)–Rh–O(6)
95.2(1)
171.5(1)
83.1(1)
P(2)–Rh–P(3)
P(3)–Rh–O(6)
Rh–P(1)–C(1)
Rh–O(6)–C(6)
93.4(1)
88.4(1)
100.2(2)
120.3(3)
(a) The investigations of the catalytic activity of the
complexes under consideration warrant the conclusion
that the stability of the chelate ring formed by PO
coordinating to rhodium is extremely high, even under
178.2(1)

94
A.M. Trzeciak et al. / Journal of Organometallic Chemistry 575 (1999) 87–97
Table 4
IR data (in KBr) of POH ligand and Rh(PO) complexes (cm−1
)
POH/complex
(1)
697
(2)
697
(4)
697
(6)
697
(5)
692
696
753
750
750
750
750
761
807
880
1240
861
1238
1261
1280
850
840
1235
1260
850
1238
1260
854
1265
1266
1285
1290
1431
1462
1311
1439
1450
1480
1550
1582
1310
1430
1450
1470
1540
1570
1301
1430
1451
1480
1530
1575
1313
1442
1455
1482
1551
1582
1431
1458
1480
1550
1582
1579
wCO
1966
1963
1986
1966
N-pyrrolylphosphine, P(NC4H4)3, of similar electronic
and steric properties.
conditions of the hydroformylation reaction (353 K and
1 MPa of H2/CO=1). That fact practically excludes
the application of systems containing rhodium com-
plexes and POH for hydroformylation. It is worth
noting that almost all other rhodium complexes, irre-
spective of their structure, are activated under H2/CO
pressure and can be used as catalyst precursors.
(b) In the investigated group of complexes with PO
ligands only the phosphito complex (3) exhibits cata-
lytic properties, even in the absence of a phosphorus
ligand excess.
(d) In contrast to POH, the use of POCH3 phosphine
for the modification of a Rh(acac)(CO)2 catalyst pre-
cursor showed a similar effect to that of PPh3. At a
five-fold excess of POCH3 the yield of aldehydes in-
creased to 82.3% and that of hexen-2-e 16.5%. The
relatively low value of the n/iso ratio (ca. 1.7) may be
caused by the higher steric hindrance of POCH3 phos-
phine as compared with PPh3 (Table 6).
(c) Only P(OPh)3 is able to convert inactive com-
plexes (1) or (2) into catalytically active rhodium hy-
dride species. Such properties were not found for
Fig. 3. Molecular structure of Rh(OC6H4PPh2)(CO)(PPh3) (2).
Fig. 4. Molecular structure of Rh(OC6H4PPh2){P(OPh)3}2 (3).

A.M. Trzeciak et al. / Journal of Organometallic Chemistry 575 (1999) 87–97
95
Table 5
Products of hexen-1-e hydroformylation with the complex (3) only and with the catalytic systems (3)/P(OPh)3, (3)/POH and (1)/P(OPh)3 at 1 MPa
CO/H2 (1:1), 353 K, after 2 ha
Catalytic system
[P]:[Rh]
Hexen-1-e
Hexen-2-e
Aldehydes
n/iso
(3) only
(3)/P(OPh)3
(3)/POH
(1)/P(OPh)3
(1)/P(OPh)3
(1)/P(OPh)3
–
6
3
3
6
9
2
–
44
22.3
–
25.9
14.8
18.2
54
72.9
–
73.6
84.6
80.3
2.7
7.5
–
3.6
4.8
4.6
100
0.4
0.6
0.4
a [(3)]=8×10−6 mol, [(1)]=9×10−6 mol, [hexen-1-e]=6.5×10−3 mol (0.8 cm3), toluene 1.5 cm3.
(6): Yield: 82%. Anal. Calc. for C35H28NO2P2Rh: C,
63.75; H, 4.28; N, 2.12; Found: C, 63.80; H, 4.43; N,
1.98. 1H-NMR(C6D6)/l: 6.47 t, 6.67 t, 7.1 s, 7.3 m, 7.53
m, 7.76 m, 7.92 m.
4. Experimental
Rhodium complexes Rh(acac)(CO)2 [24], Rh(acac)
(CO)(PPh3) [25], Rh(acac)(CO)(P(NC4H4)3) [16],
Rh(acac)(CO)(PPh2(NC4H4)) [16], Rh(acac){P(OPh)3}2
[26], Rh(bta){P(OPh)3}2 [17], Rh(acac){P(NC4H4)3)2
[16], HRh{P(OPh)3}4 [28], HRh(CO)(PPh3)3 [29] and
POH [30] were prepared according to the literature.
PPh2(CH3OC6H4) was purchased from Aldrich
Chemical. The solvents were purified using typical pro-
cedures. Syntheses were carried out under N2 atmo-
sphere by using Schlenk technique.
4.3. Rh(PO){P(OPh)3}2 (3)
To 0.26 g (3.2×10−4 mol) of Rh(acac){P(OPh)3}2 in
3 cm3 of benzene 0.1 g (3.6×10−4 mol) POH was
added. The solution was stirred for 1 h and then
evaporated under vacuum, washed with heptane and
dried. Yield: 0.26 g (81%). Anal. Calc. for C54H44-
O7P3Rh: C, 64.79; H, 4.43; Found: C, 64.20; H, 4.15.
1H-NMR(C6D6)/l: 6.5 m, 6.9 m, 7.1 m, 7.2 d, 7.5 d, 7.8
m. The crystals for X-ray analysis have been obtained
from a benzene–heptane solution. Recrystallization
from a benzene–ethanol solution gave the compound
with ethanol in the crystal.
Complex (5) was obtained in a similar procedure,
using Rh(acac){P(NC4H4)3}3 as a substrate.
(5): Yield: 80%. Anal. Calc. for C42H38N6OP3Rh: C,
60.13; H, 4.57; N, 10.02; Found: C, 60.00; H, 4.31, N,
9.82. 1H-NMR(C6D6)/l: 5.99, 6.23, 6.35 t, 6.78, 7.03 m,
7.09 s, 7.59 m.
4.1. Rh(PO)(CO)(POH) (1)
To the solution of Rh(acac)(CO)2 (0.052 g, 2×10−4
mol) in 3 cm3 of benzene 0.11 g (4×10−4 mol) of POH
was added and stirred for ca. 1 h, then vacuum evapo-
rated to ca. 50% of the initial volume. Addition of
heptane (ca. 2 cm3) accelerates precipitation. The
product was filtrated and washed with heptane. Yield:
0.12 g (87%). Anal. Calc. for C37H29O3P2Rh: C, 64.74;
1
H, 4.26; Found: C, 64.25; H, 4.19. H-NMR(C6D6)/l:
6.69 m (PO), 7.1 m (PO), 7.27 m, 7.88 m, 12.9 (OH).
4.4. Rh(acac)(CO)(POCH3) (7)
1H-NMR (C6D6)/l: 1.41 (CH3 acac), 1.85 (CH3
acac), 3.06 (CH3), 5.21 (CH acac), 6.35 m, 6.55 t, 6.97
m, 7.1 m, 7.88 m. 31P{1H}-NMR (C6D6)/l: 39.6,
J(Rh–P) 180 Hz.
4.2. Rh(PO)(CO)(PPh3) (2)
This compound was prepared like (1) using 0.11 g
(2.2×10−4 mol) of Rh(acac)(CO)(PPh3) and 0.065 g
(2.3×10−4 mol) POH. Yield: 0.125 g (85%). Anal.
Calc. for C37H29O2P2Rh: C, 66.28; H, 4.36; Found: C,
1
66.00; H, 4.21. H-NMR(C6D6)/l: 6.6 m (PO), 7.22 m
5. Hydroformylation experiments
(PO), 7.42 m, 7.79 m.
Complexes (4) and (6) were obtained in a similar
procedure using as substrates Rh(acac)(CO)(P(NC4-
H4)3) and Rh(acac)(CO)(PPh2(NC4H4)) complexes, re-
spectively.
Hydroformylation reactions were performed in a
steel autoclave (40 cm3) under 1 MPa of H2/CO (1: 1)
starting pressure. The catalyst precursor (e.g.
Rh(acac)(CO)2 or (2) or (3), 8×10−6–1×10−5 mol)
and an appropriate amount of phosphine were
weighted in small teflon vessels and introduced to the
autoclave under a dinitrogen atmosphere. Toluene (1.5
cm3) and hexen-1-e (0.8 cm3, 6.5×10−3 mol) were
(4): Yield: 81%. Anal. Calc. for C31H26N3O2P2Rh: C,
58.39; H, 4.11; N, 6.59; Found: C, 58.76; H, 4.60; N,
1
6.10. H-NMR(C6D6)/l: 6.31 s, 6.7 m, 7.07 m, 7.23 m,
7.84 s.

96
A.M. Trzeciak et al. / Journal of Organometallic Chemistry 575 (1999) 87–97
Scheme 6.
˚
added. The autoclave was closed, purged with dihydro-
gen and filled with 5 atm. of H2 and 5 atm. of CO. The
autoclave was heated to 353 K and reaction mixture
was stirred magnetically. After 2 h the autoclave was
cooled and opened. The products were separated from
the catalyst by the vacuum distillation and analysed by
GC (or GC–MS).
13.506(6), c=18.850(8) A, h=80.10(4), i=79.04(4),
3
˚
k=76.06(4)°, U=2427.8(18) A , Z=2, Dcalc. =1.422 g
cm−3, F(000)=1070, T=120(2) K, v(Mo–Ka)=
0.505 mm−1, u(Mo–Ka)=0.71073 A.
˚
7.3. Data collection and processing
For both crystals the intensities were collected with a
KUMA KM4 four-circle diffractometer in the ꢀ−2q
mode (with crystals of dimensions 0.25×0.2×0.14 mm
for 2 and 0.6×0.05×0.15 mm for (3) and Mo–Ka
radiation; 5221 (2BqB25°) of which 4549 unique
(Rint=0.043) and 8991 (2BqB26°) of which 8217
unique (Rint=0.068) reflections were measured, respec-
tively. For both crystals analytical absorption correc-
tions were applied; Tmin=0.842 and Tmax=0.907 and
6. Instruments
The following instruments were used: IR spectra:
FT-IR Nicolet Impact 400; GC–MS: Hewlett-Packard
5890II; NMR: Bruker 300 MHz (121.5 MHz for
31P{1H}-NMR). TMS was used as an internal standard
in 1H measurements and 85% H3PO4 as an external
standard in 31P{1H} measurements.
T
min=0.768 and Tmax=0.956 for 2 and 3, respectively.
The structures were solved by the Patterson method
and refined by full-matrix least-squares calculations
using SHELXL93 [31]. Atomic scattering factors and
anomalous dispersion terms used in the refinement were
taken from Ref. [32]. The carbon-bonded hydrogen
atoms were included in geometrically calculated posi-
7. Crystallography
7.1. Crystal data for complex 2
Yellow crystals, C37H29O2P2Rh, M=670.45, mono-
˚
tions with d(C–H)=0.95 A and with Uiso(H)=1.2
clinic, space group, P21/n, a=9.871(3), b=14.688(4),
Ueq(C). Final R1=S(ꢀꢀFoꢀ−ꢀFcꢀꢀ)/S ꢀFoꢀ=0.0322 [for
3
˚
˚
I\2|(I)], wR(F2)={S [w(Fo2 −Fc2)2]/S w(Fo2)2]}1/2
=
c=20.768(7) A, i=95.61(3)°, U=2996.6(16) A , Z=
4, Dcalc. =1.486 g cm−3, F(000)=1368, T=120(2) K,
0.0867, S=1.054 (for all data) for 2 and R1=S (ꢀꢀFoꢀ−
v(Mo–Ka)=0.71 mm−1, u(Mo–Ka)=0.71073 A.
˚
ꢀFcꢀꢀ)/S ꢀFoꢀ=0.0334
[for
I\2|(I)],
wR(F2)=
{S [w(Fo2 −Fc2)2]/S w(F2o)2]}1/2=0.0886, S=1.021 (for
all data) for 3.
7.2. Crystal data for complex 3
Yellowish needles, C54H44O7P3Rh · 0.5C6H6, M=
1039.77, triclinic, space group, P1, a=10.097(4), b=
Acknowledgements
Table 6
The authors wish to thank Mr Maurycy Chruszcz for
the performing of the catalytic reactions.
Products of hexen-1-e hydroformylation with the catalytic system
Rh(acac)(CO)2/POCH3 at 1 MPa CO/H2 (1:1), 353 K, after 2 ha
[POCH3]:[Rh]
Hexen-1-e
Hexen-2-e
Aldehydes n/iso
References
0.5
2.0
3.0
5.0
19.2
39.4
10.7
0.8
80.8
48.3
63.2
16.5
–
12.1
25.9
82.3
B1
1.2
1.7
[1] W. Keim, Angew. Chem. 102 (1990) 251.
[2] C.A. Willoughby, R.R. Duff, W.M. Davis, S.L. Buchwald,
Organometallics 15 (1996) 472.
[3] J. Heinicke, R. Kadyrov, M.K. Kindermann, M. Koesling, P.G.
Jones, Chem. Ber. 129 (1996) 1547.
a [Rh]=1 x 10-5 mol, [hexen-1-e]=6.5 x 10-3 mol (0.8 cm3), toluene
1.5 cm3.

A.M. Trzeciak et al. / Journal of Organometallic Chemistry 575 (1999) 87–97
97
[4] A. Bader, E. Lindner, Coord. Chem. Rev. 108 (1997) 27.
[5] P. Braunstein, Y. Chauvin, J. Nahring, A. DeCian, J. Fischer, A.
Tiripicchio, F. Ugozzoli, Organometallics 15 (1996) 5551.
[6] E. Lindner, B. Keppeler, P. Wegner, Inorg. Chim. Acta 258
(1997) 97.
[18] T.G. Leipoldt, L.D.C. Bok, J.S. van Vollenhoven, A.I. Pieterse,
J. Inorg. Nucl. Chem. 40 (1978) 61.
[19] J.G. Leipoldt, S.S. Basson, J.T. Nel, Inorg. Chim. Acta 74 (1983)
85.
[20] J.G. Leipoldt, S.S. Basson, L.D.C. Bok, T.I.A. Gerber, Inorg.
Chim. Acta 26 (1978) 35.
[21] J.G. Leipoldt, G.J. Lamprecht, G.J. van Zyl, Inorg. Chim. Acta
[7] E. Lindner, K. Gierling, B. Keppeler, H.A. Mayer,
Organometallics 16 (1997) 3531.
[8] E.T. Singewald, X. Shi, Ch.A. Mirkin, S.J. Shofer, C.L. Stern,
Organometallics 15 (1996) 3062.
96 (1985) 31.
*
[22] A.M. Trzeciak, J.J. Zio´lkowski, S. Aygen, R. van Eldik, J. Mol.
[9] M. Canestrari, B. Chaudret, F. Dahan, Yong-Sheng Huang, R.
Poilblanc, Tang-Chong Kim, M. Sanchez, J. Chem. Soc. Dalton
Trans. (1990) 1179.
[10] H.D. Empsall, B.L. Shaw, B.L. Turtle, J. Chem. Soc. Dalton
Trans. (1976) 1500.
Catal. 34 (1986) 337.
[23] A.M. Trzeciak, J.J. Zio´lkowski, J. Mol. Catal. 34 (1986) 213.
[24] Yu. Varshavsky, T.G. Tcherkasova, Zh. Neorg. Khim. 12 (1967)
1709.
[25] F. Bonati, G. Wilkinson, J. Chem. Soc. (1964) 3156.
*
*
[11] C. Bolzati, F. Tisaro, F. Refosco, G. Bandoli, A. Dolmella,
Inorg. Chem. 35 (1996) 6221.
[26] A.M. Trzeciak, J.J. Zio´lkowski, Inorg. Chim. Acta 64 (1982)
267.
*
[12] K.R. Dunbar, J.M. Matonic, V.P. Saharan, Inorg. Chem. 33
(1994) 25.
[27] H. Janecko, A.M. Trzeciak, J.J. Zio´lkowski, J. Mol. Catal. 26
(1984) 355.
*
*
[13] E. Mieczyn´ska, A.M. Trzeciak, J.J. Zio´lkowski, J. Mol. Catal. 73
[28] A.M. Trzeciak, J.J. Zio´lkowski, Trans. Met. Chem. 12 (1987)
(1992) 1.
408.
*
[14] E. Mieczyn´ska, A.M. Trzeciak, J.J. Zio´lkowski, J. Mol. Catal. 80
[29] D. Evans, G. Yagupsky, G. Wilkinson, J. Chem. Soc. A (1968)
2660.
(1993) 189.
*
*
[15] A.M. Trzeciak, J.J. Zio´lkowski, Inorg. Chim. Acta 96 (1985) 15.
[30] H.D. Empsall, J. Chem. Soc. Dalton. Trans. (1976) 1500.
[31] G.M. Sheldrick, SHELXL93, Program for the refinement of crys-
tal structures, University of Go¨ttingen, 1993.
[32] International Tables for X-Ray Crystallography, vol. 4, Kynoch
Press, Birmingham, 1974.
*
[16] A.M. Trzeciak, T. Glowiak, R. Grzybek, J.J. Zio´lkowski, J.
Chem. Soc. Dalton Trans. (1997) 1831.
[17] R. Choukroun, D. Gervais, J. Chem. Soc. Chem. Commun.
(1982) 1300.
.