New insight into role of ortho-metallation in rhodium triphenylphosphite complexes. Hydrogen mobility in hydrogenation and isomerization of unsaturated substrates

Article abstract of DOI:10.1016/S0022-328X(99)00594-X

The hydrogen transfer from two rhodium(I) hydrido complexes HRh{P(OPh)₃}₄ and HRh(CO){P(OPh)₃}₃ to methyl acrylate and/or allylbenzene leads to the formation of ortho-metallated complexes Rh{P(OC₆H₄)(OPh)₂}{P(OPh)₃} ₃ (I) and Rh{P(OC₆H₄)(OPh)₂}(CO){P(OPh)₃} ₂ (II), respectively. During these reactions unsaturated substrates, methyl acrylate or allylbenzene undergo stoichiometric hydrogenation. A similar reaction was also observed for HRh{P(OR)₃}₄ complexes (R=3-CH₃C₆H₄, 4-CH₃C₆H₄). The complex HRh{P(OPh)₃}₄ catalyses the isomerization of hex-1-ene to hex-2-ene in the absence of H₂; however at 1 atm of H₂ the formation of hexane is observed. Hydrido complexes of the type HRh{P(OR)₃}₄ in D₂ atmosphere undergo H/D exchange at the ortho position of coordinated triarylphosphite. Deuteration of the ortho protons in complexes with R=Ph, 3,5-(CH₃)₂C₆H₃ and 4-CH₃C₆H₄ is total, whereas only one ortho hydrogen is replaced in the case of R=3-CH₃C₆H₄. The formation of an ortho-metallated chelating ring causes a downfield shift in the ¹H-NMR signal of one proton from the phenyl ring to δ ca. 8 ppm.

Full text of DOI:10.1016/S0022-328X(99)00594-X

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 597 (2000) 69–76
New insight into role of ortho-metallation in rhodium
triphenylphosphite complexes. Hydrogen mobility in hydrogenation
and isomerization of unsaturated substrates
Anna M. Trzeciak *, Jo´zef J. Zio´*lkowski
Faculty of Chemistry, Uni6ersity of Wroc*law, 14 F. Joliot–Curie str., PL-50–383 Wroc*law, Poland
Received 3 August 1999; received in revised form 24 September 1999
Dedicated to Professor Stanis*law Pasynkiewicz on the occasion of his 70th birthday.
Abstract
The hydrogen transfer from two rhodium(I) hydrido complexes HRh{P(OPh)3}4 and HRh(CO){P(OPh)3}3 to methyl acrylate
and/or allylbenzene leads to the formation of ortho-metallated complexes Rh{P(OC6H4)(OPh)2}{P(OPh)3}3 (I) and
Rh{P(OC6H4)(OPh)2}(CO){P(OPh)3}2 (II), respectively. During these reactions unsaturated substrates, methyl acrylate or
allylbenzene undergo stoichiometric hydrogenation. A similar reaction was also observed for HRh{P(OR)3}4 complexes (R=3-
CH3C6H4, 4-CH3C6H4). The complex HRh{P(OPh)3}4 catalyses the isomerization of hex-1-ene to hex-2-ene in the absence of H2;
however at 1 atm of H2 the formation of hexane is observed. Hydrido complexes of the type HRh{P(OR)3}4 in D2 atmosphere
undergo H/D exchange at the ortho position of coordinated triarylphosphite. Deuteration of the ortho protons in complexes with
R=Ph, 3,5-(CH3)2C6H3 and 4-CH3C6H4 is total, whereas only one ortho hydrogen is replaced in the case of R=3-CH3C6H4. The
formation of an ortho-metallated chelating ring causes a downfield shift in the 1H-NMR signal of one proton from the phenyl ring
to l ca. 8 ppm. © 2000 Elsevier Science S.A. All rights reserved.
Keywords: Rhodium complexes; ortho-Metallation; Triarylphosphite; Hydrogenation; Isomerization
1. Introduction
“ Rh{P(OC6H4)(OPh)2}{P(OPh)3}2 (Ia) obtained in
the reaction of RhCl{P(OPh)3}3 with PhMgCl [9]
and rhodium(III) complex of formula [(C5Me5)-
Rh{P(OC6H4)(OPh)2}{P(OPh)3}]PF6 [10].
Recently van Leeuwen and co-workers repeated the
synthesis of I and Ia and on the basis on 31P{1H}-NMR
spectral analysis postulated that both complexes are
identical [5].
The formation of ortho-metallated bonding by a
triarylphosphite ligand coordinated to the metal is one
of the most typical reactions of transition metals with
that ligand. Formation of the five-membered metallacy-
cle favours stabilization of the ortho-metallated com-
plex. A number of well-characterized (with spectro-
scopic and/or diffractometric methods) ortho-metal-
lated complexes are known for iridium [1–4]. In the
case of rhodium, until now only three monomeric or-
tho-metallated complexes are described in the literature:
“ Rh{P(OC6H4)(OPh)2}{P(OPh)3}3 (I) of trigonal
bipyramidal structure [5] obtained by heating of
HRh{P(OPh)3}4 in n-alkanes [6–8];
Several ortho-metallated complexes with tri-phenyl-
phosphine, mainly dimeric rhodium(II) complexes, are
also known [11].
The ortho-metallated structure is strongly supported
by H/D exchange at the ortho positions of phenyl ring
of triphenylphosphite coordinated to rhodium [6,9,12].
In this paper we present a new synthetic route to
ortho-metallated complexes based on hydrogen trans-
fer from hydrido complexes of rhodium(I), HRh{P-
(OPh)3}4 and HRh(CO){P(OPh)3}3, to the olefins. The
studies of the above-mentioned hydrogen-transfer reac-
* Corresponding author: Fax: +48-71-328-2348.
E-mail address: ania@wchuwr.chem.uni.wroc.pl (A.M. Trzeciak)
0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00594-X

70
A.M. Trzeciak, J.J. Zio´*lkowski / Journal of Organometallic Chemistry 597 (2000) 69–76
the dihydrido complex showed a resonance at l −9.5
ppm, split into two multiplets as a result of PꢀH coupling
characteristic for the cis arrangement of two hydrido
ligands in the [(H)2Rh{P(OPh)3}4]BPh4 complex.
Two new complexes, Ib and Ic, the analogs of I, have
been obtained applying a similar procedure (boiling
heptane) to HRh{P(O-3-CH3C6H4)3}4 and HRh{P(O-4-
CH3C6H4)3}4, respectively. All three compounds (I, Ib
and Ic), although with slightly different phosphito lig-
ands, have almost identical 31P{1H}-NMR spectral
parameters according to a computer simulation (Table 1).
The typical downfield resonances at l ca. 150 ppm of the
phosphorus atom involved in the metallacycle [17] are
detected in all spectra.
In further studies we found that complex I is also
formed in boiling benzene or toluene solution of
[Rh{P(OPh)3}4]BPh4 complex. However, dihydrogen is
not produced and the formation of the ortho-metallated
complex can be explained by ortho-proton abstraction
and HBPh4 formation:
Scheme 1.
tion is important for understanding the reactivity of
HRh{P(OPh)3}4 and HRh(CO){P(OPh)3}3 complexes,
known as active catalysts of hydrogenation and hydro-
formylation [5,13–16].
2. Results and discussion
2.1. Preparation of ortho-metallated complexes
D
[Rh{P(OPh)3}4]BPh4“
Complex I may be easily obtained by heating of a
HRh{P(OPh)3}4 suspension in boiling heptane [6] as well
as in benzene or toluene. We have found that dihydrogen
evolved in this reaction passed through the benzene
solution of [Rh{P(OPh)3}4]BPh4 formed [(H)2Rh-
{P(OPh)3}4]BPh4 (Scheme 1). The 1H-NMR spectrum of
Rh{P(OC6H4)(OPh)2}{P(OPh)3}3+HBPh4
I
(1)
The new ortho-metallated compound of formula
Rh{P(OC6H4)(OPh)2}(CO){P(OPh)3}2 (II) was obtained
when hydrido–carbonyl complex, HRh(CO){P(OPh)3}3,
was heated in benzene solution or as a suspension in
heptane.
Table 1
31P{1H}-NMR data (C6D6, l/ppm (J(RhꢀP)/Hz) of complexes I, Ib,
Ic and Ie
D
HRh(CO){P(OPh)3}3“
Rh{P(OC6H4)(OPh)2}(CO){P(OPh)3}2+H2
[I]
(2)
Similar complexes IIb and IIc with P(O-3-CH3C6H4)3
and P(O-4-CH3C6H4)3 ligands, respectively, have been
synthesized applying an identical procedure. In the
31P{1H}-NMR spectra of complexes II, IIb and IIc, the
multiplet found at l 160 ppm was assigned to the
phosphorus of the ortho-metallated five-membered ring
(Table 2). Two other triphenylphosphites are equivalent
and display a doublet of doublets at l 128 ppm (Fig. 1).
The analysis of 31P{1H}-NMR spectra allows one to
propose for those complexes a trigonal bipyramidal
structure with CO and the ortho carbon atom of the
phenyl ring occupying apical positions. It is interesting
to note that all coupling constants are positive, whereas
J(PAꢀPC) in the 31P{1H}-NMR spectrum of I (and Ib, Ic)
is negative.
a
I
Ib b
Ic c
Ie d
lA
151.6
(236)
78
123.6
(159)
71
115.3
(236)
−314
154.5
(242)
72
127.2
(158)
71
117.6
(242)
−314
151.1
(241)
83
129.1
(166)
73
118.4
(241)
−308
146.5
(249)
56
41.5
(98)
J(PAꢀPB)
lB
J(PBꢀPC)
lC
50
115.9
(250)
−336
J(PAꢀPC)
a I, PB,C=P(OPh)3, PA=P(OC6H4)(OPh)2 [5].
b Ib,
P
B,C=P(O-3-CH3C6H4)3,
PA=P(O-3-CH3C6H3)(O-3-
Reaction of II with P(OPh)3 produces I, whereas the
reverse reaction occurs when a solution of I is saturated
with CO. Both transformations are observed in 31P{1H}-
NMR experiments within a few minutes (Scheme 2).
CH3C6H4)2.
c Ic,
PB,C=P(O-4-CH3C6H4)3,
PA=P(O-4-CH3C6H3)(O-4-
CH3C6H4)2.
d Ie, PA=P(OC6H4)(OPh)2, PC=P(OPh)3, PB=PPh3.

A.M. Trzeciak, J.J. Zio´*lkowski / Journal of Organometallic Chemistry 597 (2000) 69–76
71
Table 2
31P{1H}-NMR data (C6D6, l/ppm (J(RhꢀP)/Hz) of complexes II, IIb, IIc, III and IIIa
a
II
IIb b
IIc c
III d
IIIa e
lA
161.3 (231)
295
127.8 (234)
161.3 (231)
295
127.8 (234)
161.6 (233)
292
128.9 (233)
153.1 (221)
84
116.9 (227)
28
21.7 (73)
28
152.2 (228)
36
38.1 (130)
17
−7.1 (74)
36
J(PAꢀPB)
lB
J(PBꢀPC)
lC
J(PAꢀPC)
a II, PB=P(OPh)3, PA=P(OC6H4)(OPh)2.
b IIb, PB=P(O-3-CH3C6H4)3, PA=P(O-3-CH3C6H3)(O-3-CH3C6H4)2.
c IIc, PB=P(O-4-CH3C6H4)3, PA=P(O-4-CH3C6H3)(O-4-CH3C6H4)2.
d III, PA=P(OC6H4)(OPh)2, PB=P(OPh)3, PC=PPh3.
e IIIa, PA=P(OC6H4)(OPh)2, PB,C=dppb.
The complexes I and II, respectively, are slowly
formed in benzene solutions of HRh{P(OPh)3}4 or
HRh(CO){P(OPh)3}3 left under nitrogen at room tem-
evolved dihydrogen is removed from the reaction
medium.
3l
perature. According to P{1H}-NMR up to 10% of the
2.2. Reactions of HRh{P(OPh)3}4 or
ortho-metallated complexes were obtained in 2 h. Both
ortho-metallated complexes, I and II, react quickly with
H2 forming the corresponding hydrido complexes
(Scheme 2). This explains why heating HRh{P(OPh)3}4
or HRh(CO){P(OPh)3}3 in closed vessels always gives a
lower yield of I or II if compared with reactions carried
out in open vessels with simultaneous removal of dihy-
drogen from the solution. For example, the benzene
solution of HRh(CO){P(OPh)3}3 heated for ca. 20 min
in a closed vessel produced ca. 50% of II (according to
31P-NMR), whereas 10 min of heating is enough for
100% conversion of HRh{P(OPh)3}4 into I when
HRh(CO){P(OPh)3}3 with unsaturated substrates:
methyl acrylate, allylbenzene, styrene and hex-l-ene
We have found that in the absence of free H2 both
rhodium hydrido complexes, HRh{P(OPh)3}4 and
HRh(CO){P(OPh)3}3, react with equimolar amounts of
unsaturated substrates as stoichiometric hydrogenating
reagents (each mole of the rhodium complex donates
one mole of dihydrogen). Stoichiometric hydrogenation
is observed when methyl acrylate, styrene or allylben-
zene are used as substrates and methyl propionate,
ethylbenzene and propylbenzene are formed, respec-
Fig. 1. 31P{1H}-NMR spectrum of complex II in C6D6.
Scheme 2.

72
A.M. Trzeciak, J.J. Zio´*lkowski / Journal of Organometallic Chemistry 597 (2000) 69–76
When a ca. ten-fold excess of CH2ꢁCHC(O)OCH3 was
added to the solution of HRh(CO){P(OPh)3}3 after 2 h
only complex II was found. In this reaction traces of
aldehyde were also detected as a result of CO transfer
from HRh(CO){P(OPh)3}3 to methyl acrylate.
The above reaction was monitored by IR spec-
troscopy and the wCO region of the spectrum is shown in
Fig. 2. The intensity of the wCO band at 2056 cm−1
,
characteristic for the starting complex (HRh-
(CO){P(OPh)3}3), decreased over time and a new band
at 2032 cm−1 (II) appeared. The presence of an isos-
bestic point (at 2042 cm−1) may suggest a quantitative
transformation of the starting complex HRh(CO)-
{P(OPh)3}3 into II.
Scheme 3.
The addition of free triphenylphosphite caused a
decrease in the rates of hydrogen transfer as well as in
the transformation of HRh{P(OPh)3}4 into I. In addi-
tion, in the reaction mixture the other rhodium complex
[18] with a characteristic 31P{1H}-NMR spectrum
showing signals at ca. 80 ppm was found (Fig. 3(b)).
Fig. 2. IR spectra in the region 1950–2150 cm−1 measured during
the reaction of HRh(CO){P(OPh)3}3+CH2ꢁCHC(O)OCH3. Reac-
tion time: 1, 3 min; 9, 85 min.
tively. Allylbenzene additionally undergoes catalytic
isomerization to methylstyrene, whereas hex-1-ene is
only isomerized to hex-2-ene (Scheme 3).
Hydrogenation (deuteration) of methyl acrylate was
demonstrated in the reaction with DRh{P(O-2,6-
D2C6H3)3}4 (Reaction (3)) and reaction product
CH2DꢀCHDꢀC(O)OCH3 was identified by MS.
DRh{P(O-2,6-D2C6H3)3}4+CH2=CHC(O)OCH3
“Rh{P(O-2-DC6H3)(O-2,6-D2C6H3}{P(O-2,6-
D2C6H3)3}3+CDH2-CDH-C(O)OCH3
(3)
During stoichiometric hydrogenation of unsaturated
substrates the hydrido complexes HRh{P(OPh)3}4 and
HRh(CO){P(OPh)3}3 are transformed into I and II,
respectively. In the reaction of HRh{P(OPh)3}4 with
allylbenzene leading to propylbenzene (hydrogenation
product) and methylstyrene (isomerization product),
the existence of both rhodium complexes — the start-
ing hydrido complex (in higher concentration) and
complex I — were detected in the reaction mixture.
During isomerization of hex-1-ene only HRh-
{P(OPh)3}4 was found in solution.
Fig. 3. 31P{1H}-NMR spectra in C6D6 in the region 75–125 ppm for
the systems (a) HRh{P(OPh)3}4+CH2ꢁCHC(O)OCH3 and (b)
HRh{P(OPh)3}4+3 P(OPh)3+CH2ꢁCHC(O)OCH3.
The rate of the hydrogen-transfer reaction increases
with increasing unsaturated substrate concentration.

A.M. Trzeciak, J.J. Zio´*lkowski / Journal of Organometallic Chemistry 597 (2000) 69–76
73
Table 3
NMR spectrum of complex III exclude a mutual trans
position for the two phosphorus atoms in the molecule.
The J(P(PPh )ꢀP(P(OPh) ) coupling constants were found
Products of hydrogenation/isomerization of hex-1-ene with rhodi-
um(I) catalysts at 40°C, 1 atm H2 after 2 h
3
3
to be close to 400 Hz in octahedral complexes of Os [19],
Ru [20] and square planar complexes of Rh [21] with
phosphine coordinated trans to phosphite. According to
this criterion, the complex of formula Rh{P(OC6H4)-
(OPh)2}(dppb) (IIIa) is not a square planar structure
(Table 2).
Rh(I) catalyst
Reaction yield (%)
Hexane
Hex-2-ene
[Rh{P(OPh)3}4]ClO4
15
18
24
18
8
6
[Rh{P(OPh)3}4]ClO4+N(iPr)3
[Rh{P(OPh)3}4]ClO4+NEt3
HRh(P(OPh)3}4
71
72
81
92 a
The interesting process of ligand exchange between I
‚
HRh(CO){P(OPh)3}3
and Rh(P O)(CO)(POH) (POH=PPh2C6H4OH) pro-
‚
duces complex II and Rh(P O){P(OPh)3}2 (Reaction
a 20% of hex-3-ene.
(4)):
‚
‚
I+Rh(P O)(CO)(POH)“II+Rh(P O){P(OPh)3}2
(4)
It must be noted that all the stoichiometric hydrogena-
tion reactions described above proceed with the
HRh{P(OR)3}4 and HRh(CO){P(OR)3}3 types of com-
plex only. The hydrogenation of methyl acrylate did not
occur with in situ prepared [(H)2Rh{P(OPh)3}4]-
(BPh4) as well as with [Rh{P(OPh)3}4](BPh4), although
the latter forms ortho-metallated complex I when heated
(Reaction (1)).
The rhodium triphenylphosphito complexes exhibit
different reactivity in reactions with hex-1-ene under 1
atm of H2 (Table 3). The conversion of hex-1-ene to
hex-2-ene with HRh{P(OPh)3}4 as well as with
HRh(CO){P(OPh)3}3 is complete. In the case of
HRh(CO){P(OPh)3}3 some amounts (20%) of hex-3-ene
were also found. In comparable conditions [Rh{P-
(OPh)3}4]ClO4 is much less active; however in the pres-
ence of amines its activity increases and may compete
with that of HRh{P(OPh)3}4. The addition of amine
facilitates heterolytic splitting of H2 and the formation
of HRh{P(OPh)3}4 [9].
It was surprising that the ortho-metallated fragment
remained unchanged during ca. 3 h in the presence of a
weak proton donor like coordinated (2-hydroxyphenyl)-
diphenylphosphine. However in a similar reaction of II
‚
with Rh(P O)(CO)(POH) the ortho-metallated ring was
‚
protonated and the mixture of Rh(P O)(CO){P(OPh)3}
‚
and Rh(P O){P(OPh)3}2 was identified by 31P{1H}-
NMR (Reaction (5)):
‚
II+Rh(P O)(CO)(POH)
‚
‚
“Rh(P O)(CO){P(OPh)3}+Rh(P O){P(OPh)3}2
(5)
Complex I reacts easily with stronger proton donors
like HClO4 or HCl producing well-known Rh(I) com-
plexes: [Rh{P(OPh)3}4]ClO4 and Rh{P(OPh)3}3Cl, re-
spectively. In the reaction of I with formic acid a mixture
of Rh{P(OPh)3}4(HCO2) and Rh{P(OPh)3}3(HCO2) was
obtained.
2.3. Ligand exchange in complexes I and II
2.4. H/D exchange in Rh-phosphito complexes
Triphenylphosphito ligands coordinated to rhodi-
um(I) in complexes I and II can be partially substituted
by PPh3 or diphenylphosphinobutane (dppb); however
the ortho-metallated fragment remains unchanged.
A new complex with an identical trigonal bipyramidal
structure of formula Rh{P(OC6H4)(OPh)2}{P(OPh)3}2-
(PPh3) (Ie) is formed in reaction of I with PPh3. The
31P{1H}-NMR spectrum parameters of Ie are very sim-
ilar to those of I and according to them (Table 1)
triphenylphosphine is coordinated in a trans position to
the carbon atom of the ortho-metallated ring. Applica-
tion of a large excess of PPh3 in the reaction with I
([PPh3]: I=5) leads to the formation of some amounts
of a tetracoordinated complex Rh{P(OC6H4)(OPh)2}-
{P(OPh)3}(PPh3) (III), which is the only product of the
reaction of II with PPh3 ([PPh3]: II=2). It is worth noting
that complex III is not square planar although such
Reaction of I with D2 (1 atm) at room temperature
leads to the formation of DRh{P(O-2,6-D2C6H3)3
(100%) in 5 h, which is in agreement with literature data
[6,9]. Similarly the complex HRh(CO){P(OPh)3}3 reacts
with D2 giving an analogous H/D exchange product.
Unexpectedly H/D exchange in HRh{P(O-3-CH3-
C6H4)3}4 is not complete since the proton neighbouring
the methyl group is not exchanged. This was concluded
from 1H-NMR spectrum measured during H/D ex-
change, in which the singlet assigned to the ortho proton
at 7.18 ppm (H4) remained, whereas the doublet of (H1)
at 7.28 ppm disappeared (Fig. 4). It is interesting to note
that in the HRh{P-(O-3,5-(CH3)2C6H3)3}4 complex the
total deuteration of the ortho protons is realized in 2 h.
In reaction of [Rh{P(OPh)3}4]ClO4 with D2 (1 atm at
room temperature) only [(D)2Rh{P(OPh)3}4]ClO4 was
obtained but H/D exchange in phenyl rings was not
observed.
.
symmetry was expected, since CꢀMꢀP [2] in the metalla-
cycle is ca. 80°. Low values of J(PꢀP) in the 31P{1H}-

74
A.M. Trzeciak, J.J. Zio´*lkowski / Journal of Organometallic Chemistry 597 (2000) 69–76
2.5. 1H-NMR spectra of ortho-metallated complexes I and
II
Both ortho-metallated complexes, I and II, have rather
complicated 1H-NMR spectra in the phenyl proton
region, which is caused by the unequivalency of coordi-
nated triphenylphosphites. The most obvious character-
istic seems to be the appearance of downfield-shifted
resonances (at 8.1 ppm for I and 8.6 ppm II if compared
with the spectra of parent hydrido complexes (HRh-
{P(OPh)3}4 and HRh(CO)(P(OPh)3}3}, respectively)
(Fig. 5).
1
A similar signal was also observed in the H-NMR
spectrum of the cobalt(I) analog, Co{P(OC6H4)(OPh)2}-
{P(OPh)3}3 [22].
Applying COSY and homodecoupling, we have found
that the doublets at 7.61, 7.42 and 7.24 ppm are a result
of the ortho protons of phosphite ligands A, B and C of
complex I, respectively (Fig. 5). This interpretation was
1
confirmed by analysis of the H-NMR spectrum of the
ortho-metallated complex obtained by heating of
DRh{P(O-2,6-D2C6H3)}4 in heptane (Reaction (6)). In
1
Fig. 5. H-NMR spectra of Rh{P(OC6H4)(OPh)2}{P(OPh)3}3 (I), (A)
and Rh{P(O-2-DC6H3)(O-2,6-D2C6H3)2}{P(O-2,6-D2C6H3)3}3 (B) in
C6D6 in the phenyl proton region (* traces of C6H6 in C6D6).
that spectrum the multiplet at 8.1 ppm was found, but
doublets in the region 7.6–7.2 ppm were not observed
(Fig. 5).
DRh{P(O-2,6-D2C6H3)3}4
D
“Rh{P(O-2-DC6H3)(O-2,6-D2C6H3}-
{P(O-2,6-D2C6H3)3}3
(6)
The downfield resonances were observed in all ortho-
metallated complexes investigated by us, which may
suggest their assignment to meta protons; however the
final interpretation needs additional study. In fact we
were not able to prepare the ortho-metallated complex
by heating of HRh{P(O-3,5-(CH3)2C6H3)3}4 as well as by
its reaction with methyl acrylate.
3. Experimental
Fig. 4. 1H-NMR spectra of HRh{P(O-3-CH3C6H4)3}4 (A) and
DRh{P(O-2-D, 3-CH3C6H3)3}4 (B) in C6D6 in the phenyl proton
region (* traces of C6H6 in C6D6).
All reactions were carried out in inert atmosphere
using the standard Schlenk technique.

A.M. Trzeciak, J.J. Zio´*lkowski / Journal of Organometallic Chemistry 597 (2000) 69–76
75
Rhodium complexes were prepared according to lit-
erature methods: HRh{P(OPh)3}4 [23], HRh(CO)-
{P(OPh)3}3 [24], Rh(acac)(CO)2 [25], [Rh{P(OPh)3}4]-
BPh4 [26], [Rh{P(O-3,5-(CH3)2C6H3)3}4]BPh4 [26]
reaction. Small samples after solvent evaporation were
analysed by IR spectroscopy using KBr disks. The
average reaction time was 3 h, the longest time for H/D
exchange was 12 h. After that time the solvent was
evaporated and the isolated complex analysed by IR
spectroscopy and/or 1H-NMR. In some experiments
the reaction course was monitored with H-NMR di-
rectly in C6D6 solution without isolation of the
complex.
‚
Rh(P O)(CO)(POH) [21].
HRh{P(O-3-CH3C6H4)3}4 and HRh{P(O-4-CH3C6-
H4)3}4 complexes have been prepared by the method
described for HRh{P(OPh)3}4 [23], in the reaction of
Rh(acac)(CO)2 with P(OR)3 under 1 atm of H2. Com-
1
1
plexes have been characterized with H-NMR.
3.6. Monitoring of H/D exchange with IR
3.1. HRh{P(O-3-CH3C6H4)3}4
It was found that H/D exchange can be easily ob-
1H-NMR data (C6D6), l/ppm: −10.2 (q of d;
served in the IR spectra in the region 1400–1600 cm−1
.
1
1J(RhꢀH) 7 Hz, J(PꢀH) 45 Hz; RhꢀH); 2.12 (s, CH3);
The following changes in the IR spectra are detected
during deuteration:
HRh{P(OPh)3}4: the intensity of the band at 1490
cm−1 decreases and a new band at 1440 cm−1
appears.
6.83 (d, 1J(HꢀH) 6.8 Hz; p-H); 7.09 (t, 1J(HꢀH) 7.9 Hz;
1
m-H); 7.14 (s, o-H); 7.24 (d, J(HꢀH) 7.9 Hz; o-H).
3.2. HRh{P(O-4-CH3C6H4)3}4
HRh(CO){P(OPh)3}3: the intensity of the band at
1H-NMR data (C6D6),l/ppm: −10.6 (q of d;
1490 cm−1 decreases and a new band at 1443 cm−1
1
1J(RhꢀH) 6 Hz, J(PꢀH) 41 H z; RhꢀH); 2.13 (s, CH3);
appears; wCO 2030.5; 2039 cm−1
.
1
1
6.91 (d, J(HꢀH) 8.1 Hz; m-H); 7.24 (d, J(HꢀH) 8.0
Hz; o-H).
HRh{P(O-3-CH3C6H4)3}4: the intensity of the band
at 1480 cm−1 decreases and the new band at 1400
cm−1 appears.
HRh{P(O-4-CH3C6H4)3}4: the intensity of the band
at 1510 cm−1 decreases and a new band at 1460
cm−1 appears.
HRh{P(O-3,5-(CH3)2C6H3)3}4: the intensity of the
band at 1450 cm−1 decreases and a new band at
1400 cm−1 appears;
3.3. HRh{P(O-3,5-(CH3)2C6H3)3}4
To
a suspension of 0.11 g of [Rh{P(O-3,5-
(CH3)2C6H3)3}4]BPh4 in 3 cm3 of ethanol 0.5 cm3 of
ethanol containing 0.003 g NaBH4 was added. During
stirring the colour changed from yellow to white. The
white precipitate was filtrated and washed with ethanol.
1H-NMR data (C6D6), l/ppm: −10.05 (q of d;
3.7. Identification of rhodium complexes formed in
reactions
1J(RhꢀH) 6 Hz, J(PꢀH) 45 Hz; RhꢀH); 2.1 (s, CH3);
6.67 (s, p-H); 7.1 (s, o-H).
1
3.7.1. Rh{P(OPh)3}3(HCO2)
3.4. Hydrogen-transfer reactions
31P{1H}-NMR l1: 118.1 ppm, dt, J(RhꢀP)=277 Hz;
l2 106.7 ppm, dd, J(RhꢀP)=230 Hz, J(PꢀP)=64 Hz.
The reactions were carried out at room temperature
(r.t.) in Schlenk or in NMR tubes. The typical reaction
solution contained 4.1−4.6×10−5 mol of HRh-
{P(OPh)3}4 or HRh(CO){P(OPh)3}3 and 1×10−4 mol
of unsaturated substrate like styrene or hex-1-ene or
2.6×10−4 mol of methyl acrylate in 0.5 cm3 of C6H6
3.7.2. [Rh{P(OPh)3}4](HCO2)
31P{1H}-NMR l: 108.6 ppm, d, J(RhꢀP)=214 Hz.
3.7.3. [(H)2Rh{P(OPh)3}4](BPh4)
1
or C6D6. The reaction was monitored with H-NMR
31P{1H}-NMR l1: 118.7 ppm, dt, J(RhꢀP)=169 Hz;
J(PꢀP)=48 Hz, l2 110.5 ppm, dt, J(RhꢀP)=145.0 Hz.
1H-NMR: l:−9.5 ppm, d of m, J(PꢀHtrans) 230 Hz.
(or/and 31P-NMR) and final organic products were
analysed with GC–MS after separation from the
rhodium complexes by vacuum transfer.
3.7.4. RhCl[P(OPh)3]3
3.5. H/D exchange
31P{1H}-NMR: l1 117 ppm, dt, J(RhꢀP)=279 Hz,
J(PꢀP)=54 Hz; l2 109 ppm, dd, J(RhꢀP)=223.1 Hz.
The reactions were carried out at r.t. in Schlenk tubes
under 1 atm of D2. Typically, a solution of 0.02 g of
rhodium complex in 1 cm3 of C6H6 or C6D6 was
prepared under dinitrogen, the tube was evacuated and
D2 was introduced. The mixture was stirred during the
‚
3.7.5. Rh(P O)(CO){P(OPh)3}
31P{1H}-NMR: l1 121.6 ppm, dd, J(RhꢀP)=236 Hz,
J(PꢀP)=476 Hz; l2 41.6 ppm, dd, J(RhꢀP)=130 Hz.

76
A.M. Trzeciak, J.J. Zio´*lkowski / Journal of Organometallic Chemistry 597 (2000) 69–76
[7] M. Preece, S.D. Robinson, J.N. Wingfield, J. Chem. Soc. Dalton
Trans. (1976) 613.
[8] S.D. Robinson, J. Chem. Soc. Chem. Commun. (1968) 521.
[9] E.K. Barefield, G.W. Parshall, Inorg. Chem. 11 (1972) 964.
[10] S.J. Thompson, C. White, P.M. Maitlis, J. Organomet. Chem.
136 (1977) 87.
3.7.6. Deuterium transfer from DRh{P(O-2,6-
D2ꢀC6H3)3}4 to CH2ꢁCHC(O)OCH3
MS data of CDH2ꢀCDHꢀC(O)OCH3: 90 [3, M+],
89(17), 88(17), 59(35), 58(46), 57(46) CH3ꢀCH2ꢀC(O)O-
CH3: 86 [2, M+], 85(10), 58(15), 56(10), 55(47).
[11] F.P. Pruchnik, R. Starosta, P. Smolen´ski, E. Shestakova,
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[12] B.C. Whitmore, R. Eisenberg, J. Am. Chem. Soc. 106 (1984)
3225.
4. Instruments
The following instruments were used: IR spectra:
FT-IR Nicolet Impact 400; GC–MS, Hewlett–Packard
5890 II; NMR, Bruker 300 MHz (121.5 MHz for
31P{lH}-NMR). TMS was used as an internal standard
in 1H and 85% H3PO4 as an external standard in
3lP{1H}-NMR measurements.
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.