31P-NMR and X-ray studies of new rhodium(I) β-ketoiminato complexes Rh(R1C(O)CHC(NH)R2)(CO)(PZ3) where PZ3=PPh3, PCy3, P(OPh)3 or P(NC4H4)3<

Article abstract of DOI:10.1016/S0022-328X(01)00805-1

The substitution of the CO ligand in rhodium(I) β-ketoiminato complexes Rh(R₁{O,N}R₂)(CO)₂ ({O,N}=R₁C(O)CHC(NH)R₂; R₁, R₂=CF₃, Me, CMe₃ in several combinati

Full text of DOI:10.1016/S0022-328X(01)00805-1

Journal of Organometallic Chemistry 628 (2001) 195–210
www.elsevier.nl/locate/jorganchem
31P-NMR and X-ray studies of new rhodium(I) b-ketoiminato
complexes Rh(R1C(O)CHC(NH)R2)(CO)(PZ3) where PZ3=PPh3,
PCy3, P(OPh)3 or P(NC4H4)3
Yuri S. Varshavsky a, Margarita R. Galding a, Tatiana G. Cherkasova a,
Ivan S. Podkorytov a, Alexey B. Nikol’skii a, Anna M. Trzeciak b, Zofia Olejnik b,
Tadeusz Lis b, Jo´zef J. Zio´łkowski b,*
a Institute of Chemistry, St. Petersburg State Uni6ersity, Petrod6orets, Uni6ersitetskii pr., 2, 198904 St. Petersburg, Russia
b Faculty of Chemistry, Uni6ersity of Wroclaw, 14 F. Joliot-Curie St., 50383 Wroclaw, Poland
Received 30 January 2001; accepted 9 March 2001
Abstract
The substitution of the CO ligand in rhodium(I) b-ketoiminato complexes Rh(R1{O,N}R2)(CO)2 ({O,N}=
R1C(O)CHC(NH)R2; R1, R2=CF3, Me, CMe3 in several combinations) by phosphorus ligands PZ3 (PZ3=PCy3, PPh3, P(OPh)3,
P(NC4H4)3) leads to Rh(R1{O,N}R2)(CO)(PZ3) complexes characterised by 31P{1H}-NMR and X-ray methods. The stronger
s-donor PZ3 ligands (PZ3=PCy3, PPh3) substitute almost exclusively the CO group trans to N, forming P-trans-to-N isomers.
The complexes Rh(CF3{O,N}Me)(CO)(PCy3) (II), Rh(CF3{O,N}CMe3)(CO)(PCy3) (III), Rh(CF3{O,N}Me)(CO)(PPh3) (IV) and
Rh(CF3{O,N}CMe)(CO)(PPh3) (V) are of a square-planar geometry with a slight tetrahedral distortion around the rhodium atom
in II, III and V. The RhꢀP(PCy3) bonds are slightly longer than the RhꢀP(PPh3) bonds. The reaction of stoichiometric amounts
of the less basic P(OPh)3 or P(NC4H4)3 ligands leads to the formation of both isomers of the Rh(R1{O,N}R2)(CO)(P(OPh)3) or
,
Rh(R1{O,N}R2)(CO)(P(NC4H4)3) complex in comparable yields. The RhꢀP(P(OPh)3) distance (2.195(2) A) in the isomer of
,
Rh(CF3{O,N}CMe3)(CO)(P(OPh)3) with P(OPh)3 coordinated trans to N (VI) is ca. 0.04 A longer than in the isomer of that
complex with P(OPh)3 coordinated trans to O (VII). The CO substitution in Rh(R1{O,N}R2)(CO)2 by PZ3 ligands (PPh3, PCy3,
,
P(OPh)3) causes the shortening of the RhꢀC(CO) bond by ca. 0.04 A compared to Rh(CF3{O,N}Me)(CO)2 (I), making difficult
the coordination of another PZ3 ligand, especially one with stronger s-donor properties. The more p-acceptor P(OPh)3 ligands
form bis-phosphito complexes and Rh(CF3{O,N}CMe3){P(OPh)3}2 (VIII) exhibits inequivalence of the two P(OPh)3 ligands in
solution (31P-NMR) as well as in solid form (X-ray). © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Rhodium(I) complexes; b-Ketoiminato complexes; X-ray; Substitution reaction
studies of the key stages of catalytic cycles. Dicarbonyl
complexes of the Rh(LL)(CO)2-type react with phos-
1. Introduction
phorus ligands forming Rh(LL)(CO)(PZ3) complexes
Rhodium(I) dicarbonyl complexes of the formula
Rh(LL)(CO)2 with chelating monoanionic ligands LL−
coordinated to rhodium via {O,O}, {O,N} or {O,S}
donor atoms represent a group of compounds that has
been recently intensively studied [1–7] as catalyst pre-
cursors in hydroformylation, isomerisation and hydro-
genation of olefins as well as model compounds in
[8]. Furthermore, stronger p-acceptor ligands like
P(OPh)3 or P(NC4H4)3 substitute both the CO groups,
forming Rh(LL)(PZ3)2 complexes [9–13]. Kinetic stud-
ies have shown that the s-donor/p-acceptor properties
of PZ3 ligand determine the CO substitution rate, which
increases as the p-acceptor properties of PZ3 increase
[14]. The values of the first oxidation potential of
Rh(acac)(CO)(PZ3) complexes increase with the in-
crease of the net electron donor properties of PZ3
estimated electrochemically [15]. The typical coordina-
* Corresponding author. Tel.: +48-713-204253; fax: +48-71-
3282348.
E-mail address: jjz@wchuwr.chem.uni.wroc.pl (J.J. Zio´łkowski).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)00805-1

196
Y.S. Varsha6sky et al. / Journal of Organometallic Chemistry 628 (2001) 195–210
tion number for these complexes is four, but some
examples of pentacoordinate complexes, Rh(LL)(CO)-
(PZ3)2, are also reported [1,16,17].
All the dicarbonyl complexes selected for the studies
in this paper belong to a family of compounds de-
scribed in the early 1990s [35–37]. Among phosphorus
donor ligands only triphenylphosphine was involved in
previous NMR studies that confirmed its preferable
trans coordination to N [38–41].
The reaction of triphenylphosphine with dicarbonyl
complexes containing unsymmetrical b-diketonate lig-
ands leads to the formation of two isomers of an
Rh(LL)(CO)(PPh3)-type complex, but in most cases
only one isomer was isolated in the solid form [18–22].
The only example of both isomers structurally charac-
terised has been reported for Rh[CH3C(O)CHC-
(O)C6H5](CO)(PPh3) [23]. It was concluded from X-ray
studies that the main factor determining the isomer
formation is the trans influence of the donor atoms in
the chelating ligand (LL), and the carbonyl group trans
to the donor atom with the stronger trans influence is
substituted [18,24–26]. In some complexes the opposite
substitution reaction has also been observed and this
was explained by the steric hindrance of a bulky sub-
stituent, e.g. CMe3 in the b-diketonato group [20].
Contrary to the X-ray studies of solids, the analyses of
complexes in solution confirmed the presence of com-
parable amounts of both isomeric forms of
Rh{O,O}(CO)(PPh3) [9,27–30]. The preferable coordi-
nation of PPh3-trans-to-N has been NMR- and X-ray-
confirmed for some rhodium(I) complexes, e.g.
Rh(oxine)(CO)(PPh3) [31,32], Rh(oxine)(CO)(P(OPh)3)
[14,33] and Rh(Me{O,N}Me)(CO)(PPh3) [34].
2. Results and discussion
2.1. Rh(R1{O,N}R2)(CO)2-type complexes
The IR spectra of Rh(R1{O,N}R2)(CO)2 complexes
showed that the position of the different substituents R1
and R2 has practically no influence on the values of the
w(CO) frequencies, whether in solid form or in solution
(Table 1). The w(CO) frequencies of the complexes
under study are located in between the values observed
previously for their analogues with R1=R2=Me
(2074, 2002 cm−1) and R1=R2=CF3 (2092, 2026
cm−1) in hexane solution [38]. In the analogous series
of
Rh(I)
b-diketonato
complexes
of
the
Rh(R1{O,O}R2)(CO)2-type, the corresponding changes
in the w(CO) frequencies caused by the presence of
electronegative CF3 substituents in the chelating ligand
also span a range of about 20 cm−1 [42].
The inequivalence of the two CO groups in those
complexes is consistent with the different values of
1J(RhC), (ca. 65 Hz for the C trans to N and ca. 72 Hz
for the C trans to O, respectively; Table 1) and is in
agreement with the generally accepted Fermi contact
model of spin–spin coupling [43]. In the 13C-NMR
spectra of all the dicarbonyl complexes the 1J(RhC)
value for the carbon trans to O is higher than that for
the carbon trans to N by ca. 6–8 Hz. The inequivalence
of the carbonyl groups in Rh(CF3{O,N}Me)(CO)2 (I),
has also been characterised by the difference in the CꢀO
The main goal of the studies presented in this paper
was to elucidate the isomer formation during the substi-
tution of CO with a variety of phosphorus ligands PZ3
(PZ3=PCy3, PPh3, P(OPh)3, P(NC4H4)3) in Rh(R1-
{O,N}R2)(CO)2 complexes, where R1{O,N}R2 is a b-
ketoiminato ligand, R1C(O)CHC(NH)R2.
Table 1
The w(CO) band position in the IR spectra and 13C-NMR parameters a of Rh(R1{O,N}R2)(CO)2 complexes
R1
R2
w(CO) (cm−1
(KBr)
)
w(CO), (cm−1
(hexane)
)
l (ppm); 1J(RhC) (Hz)
(C-trans-to-O)
l (ppm); 1J(RhC) (Hz)
(C-trans-to-N)
2J(CC) (Hz)
3J(CH) (Hz)
CF3
CF3
Me
2005.4
2078.8
2016
2086
185.2; 72.3
185.4; 72.1
184.1; 65.2
184.1; 66.2
8.7
9.3
2.7
2.5
CMe3 1996.0
2004.4
2014
2085
2072.3
2082.8
CMe3 CF3
Me CF3
2005.2
2075.8
2016
2084
185.6; 71.8
185.3; 71.7
184.4; 65.5
184.2; 65.6
9.1
8.5
2.5
2.4
2006.0
2075.5
2015
2082
a In chloroform solutions.

Y.S. Varsha6sky et al. / Journal of Organometallic Chemistry 628 (2001) 195–210
197
stretching force constant values, 17.24 and 16.66×102
N m−1 [35], with the lower value assumed to corre-
spond to the CO group trans to O.
In the spectrum of Rh(CF3{O,N}CMe3)(CO)-
(P(OPh)3), the frequency at 1992 cm−1 has been tenta-
tively assigned to the isomer with the carbonyl group
trans to O (complex VI) and the one at 2009 cm−1 to
VII.
It is pertinent to note that in the 13C-NMR spectra of
Rh(R1{O,N}R2)(CO)2 with R1=Me, R2=CF3 and
R1=CF3, R2=Me the resonances of the carbonyl
carbons cis to N are split due to coupling to the NH
The parameters of the 31P{1H}-NMR spectra of the
Rh(R1{O,N}R2)(CO)(PZ3) complexes obtained in solu-
tion by treating a dicarbonyl complex Rh(R1{O,N}R2)-
(CO)2 with one equivalent of the corresponding phos-
phorus ligand are collected in Table 2. For those cases
in which the reaction product was a mixture of both
isomers, the NMR parameters were assigned according
3
proton, with J(CH)$2.5 Hz [40] (Table 1).
2.2. CO substitution in Rh(R1{O,N}R2)(CO)2
complexes by PZ3 ligands
1
to the finding that J(RhꢀP) correlates with the trans
The reactions of Rh(R1{O,N}R2)(CO)2 complexes
with stoichiometric amounts of a phosphorus ligand
PZ3 were carried out in benzene and/or acetone solu-
tions, and in all cases monocarbonyl complexes,
Rh(R1{O,N}R2)(CO)(PZ3), were formed:
influence of the group located trans to P [39,44]. Conse-
quently, the higher values of the 1J(RhꢀP) coupling
constants were assigned to phosphorus ligands coordi-
nated trans to oxygen [9]. The lower values of the
1J(RhꢀP) coupling constants were assigned to phospho-
rus atoms bound trans to nitrogen. In the series of
Rh(R1{O,N}R2)(CO)2+PZ3
1
complexes under study the J(RhꢀP) values for isomers
containing the PZ3 ligand coordinated trans to N de-
crease in the order PCy3BPPh3BP(NC4H4)3B
P(OPh)3, in line with the increase of the p-acceptor
properties of the phosphorus ligands.
“Rh(R1{O,N}R2)(CO)(PZ3)+CO
PZ3=PCy3,PPh3,P(OPh)3,P(NC4H4)3
(1)
If higher concentrations of PZ3 ([PZ3]:[Rh]\1) are
applied, the next carbonyl ligand may be substituted,
and Rh(R1{O,N}R2)(PZ3)2 complexes are formed for
PZ3=P(OPh)3 and P(NC4H4)3, but not for PPh3 or
PCy3:
The data collected in Table 2 corroborate the conclu-
sion that the formation of isomers is dependent on the
s-donor/p-acceptor properties of the phosphorus lig-
and. Stronger s-donors like PCy3 or PPh3 replace
almost exclusively the CO ligand in the position trans
to nitrogen. The reaction products, Rh(R1{O,N}R2)-
(CO)(PCy3)-type complexes, exist in solution as only
one isomer, with the PCy3 ligand trans to nitrogen,
regardless of temperature changes (from +40 to −
40°C) or kind of solvent used (acetone, benzene, tolu-
ene). Solutions of Rh(R1{O,N}R2)(CO)(PPh3)-type
complexes contain small amounts (ca. 10%) of isomers
with PPh3 coordinated to rhodium in the position trans
to oxygen (P-trans-to-O) and ca. 90% of isomers in
which PPh3 coordinates to rhodium in the position
trans to nitrogen (P-trans-to-N) (Scheme 1). A domina-
tion of isomers with P-trans-to-N was observed earlier
for Rh(R1{O,N}R2)(CO)(PPh3) complexes in chloro-
form [39].
Rh(R1{O,N}R2)(CO)2+PZ3
“Rh(R1{O,N}R2)(PZ3)+2CO
PZ3=P(OPh)3, P(NC4H4)3
(2)
One of the products of reaction (2), Rh(CF3{O,N}-
CMe3){P(OPh)3}2 (VIII), was also characterised by X-
ray studies (Fig. 7, Table 10).
Phosphorus ligands selected for these studies demon-
strate different s-donor/p-acceptor properties that af-
fect the w(CO) band position in the IR spectra of the
Rh(R1{O,N}R2)(CO)(PZ3) complexes. For Rh(CF3-
{O,N}Me)(CO)(PZ3) complexes, the w(CO) frequencies
(cm−1) change in the following order of increasing
p-acceptor properties of the PZ3 ligand:
A completely different course of CO substitution was
found for stronger p-acceptor ligands like P(OPh)3 or
P(NC4H4)3, and neither of the isomers is preferred in
these cases (Table 2, Scheme 1). The ratio of the
isomers depends, however, on the solvent used.
PCy3 PPh3
1946 B1973 B2001
P(OPh)3 P(NC4H4)3
B2006
w(CO)
(cm−1
)
The complex Rh(Me{O,N}CF3)(CO)(P(OPh)3) ob-
tained in C6D6 solution in the reaction of the respective
dicarbonyl complex with P(OPh)3 exists as a mixture of
two isomers, with domination of P trans to O isomer,
(ca. 62%). After complete evaporation of C6D6 and
dissolution of the residue in (CD3)2CO, a new mixture
of the isomers was obtained containing 33% of the one
with P-trans-to-O and 67% of that with P-trans-to-N.
When acetone (0.2 cm3) was added to the benzene
A similar relation was obtained for the w(CO) fre-
quencies of the form
(cm−1)complexes
Rh(CF3{O,N}CMe3)(CO)(PZ3):
PCy3 PPh3
P(OPh)3
P(NC4H4)3
w(CO)
(cm−1
1956 B1971 B1992,
B2002
)
2009

198
Y.S. Varsha6sky et al. / Journal of Organometallic Chemistry 628 (2001) 195–210
Table 2
31P{1H}-NMR parameters for Rh(R1{O,N}R2)(CO)(PZ3) complexes a
R1
R2
Solvent
l
31P (ppm) [1J(RhP) (Hz)] isomer content (%) b
Isomer
PCy3
PPh3
P(OPh)3
P(NC4H4)3
c
CF3
Me
T
P-trans-to-N
55.8 [143.7] 100 complex 45.6 [150.7] 90
126.8 [253.0] 76
II
complex IV
d
c
P-trans-to-O
P-trans-to-N
60.5 [175.3] 10
129.5 [291.0] 24
123.5 [251.3] 62
c
A
51.4 [141.2] 100 complex
100.3 [217.4] 90
II
d
c
P-trans-to-O
P-trans-to-N
125.0 [290.8] 38
107.5 [247.7] 10
CF3
CMe3
T
56.0 [145.2] 100 complex 47.5 [151.0] 90
126.4 [255.0] 50 complex 104.4 [218.8] e 62
III
complex V
59.0 [174.2] 10
VI
d
P-trans-to-O
P-trans-to-N
P-trans-to-O
129.9 [290.0] 50 complex 112.9 [250.3] e 38
VII
c
A
51.5 [144.9] 100 complex
122.3 [251.3] 33 complex 100.1 [217.4] 77
VI
125.2 [287.2] 67 complex 108.8 [244.1] 23
III
d
c
VII
CMe3 CF3
T
P-trans-to-N
P-trans-to-O
P-trans-to-N
P-trans-to-O
54.9 [147.1] 100
46.6 [153.9] 80
125.7 [257.0] f 39
130.0 [291.0] f 61
121.9 [253.1] 79
125.9 [287.2] 21
105.6 [219.9] e 66
112.9 [250.3] e 34
101.4 [217.4] 82
108.7 [247.8] 18
d
59.9 [172.8] 20
c
A
50.6 [145.0] 100
d
c
Me
CF3
B
P-trans-to-N
P-trans-to-O
P-trans-to-N
P-trans-to-O
50.3 [143.6] 100
47.7 [153.0] 100
126.2 [255.6] 37
130.6 [289.9] 63
122.1 [254.9] 67
125.8 [287.2] 33
105.4 [222.0] 58
112.9 [248.0] 42
d
d
c
c
c
c
A
101.1 [219.0] 100
d
a A, acetone; B, benzene; T, toluene.
b Calculated from 31P-NMR spectra.
c Insoluble.
d Not detectable.
e In benzene solution.
f 40°C.
Scheme 1.
solution of the same complex (0.5 cm3), the content of
the P-trans-to-O isomer, VII, decreased from 62 to
50%.
Stronger s-donors like PCy3 and PPh3 replaced
P(OPh)3 in the Rh(CF3{O,N}CMe3)(CO)(P(OPh)3)
complexes (VI and VII) despite the fact that the RhꢀP
bond in a Rh–phosphito complex is remarkably shorter
than in complexes with PPh3 or with PCy3. It is impor-
tant to note that the starting complex, existing in
solution as a mixture of two isomers, in reaction with
PPh3 (or PCy3) produced only one isomer of the mono-
carbonyl complex, nearly 100% of the P-trans-to-N
isomer of Rh(CF3{O,N}CMe3)(CO)(PCy3) (III) or
2.3. Exchange of phosphorus ligands in
Rh(R1{O,N}R2)(CO)(PZ3) complexes
Our observations regarding the exchange of phos-
phorus ligands in Rh(CF3{O,N}CMe3)(CO)(PZ3)-type
of complexes for equimolar amounts of the entering
PZ3 ligand and the starting complex are summarised in
Table 3.
Rh(CF3{O,N}CMe3)(CO)(PPh3)
(Table 3, (i) and (ii)).
(V),
respectively

Y.S. Varsha6sky et al. / Journal of Organometallic Chemistry 628 (2001) 195–210
199
The analogous isomer (P-trans-to-N) was also ob-
tained in the reactions of Rh(CF3{O,N}Me)(CO)-
(P(OPh)3) with PPh3. In both the reactions with PPh3 as
the entering ligand, another product, Rh(R1{O,N}R2)-
(P(OPh)3)2, was also found, independent of the PPh3
excess used.
The substitution of coordinated PCy3 by P(OPh)3
produced only 5% of Rh(CF3{O,N}CMe3)(P(OPh)3)2
(VIII), (Table 3, (iii)). In contrast, Rh(CF3{O,N}-
CMe3)(CO)(PPh3) (V), reacted with P(OPh)3 more ef-
fectively, and ca. 50% conversion of the starting com-
plex to Rh(CF3{O,N}CMe3)(P(OPh)3)2 (VIII), was
observed.
We propose to explain the reactions presented in
Table 3 by means of Eqs. (3) and (4). In each case
((i)–(iv)), a combination of the reversible exchange of
phosphorus ligands (Eq. (3)) and the subsequent irre-
versible replacement of CO by P(OPh)3 in the car-
bonylphosphite complex (Eq. (4)) takes place:
phite) complex is not detected. If PZ% =PPh3, (ii), the
3
equilibrium concentration of the carbonylphosphite
complex is much greater, and a bis(phosphite) complex
is formed in ca. 50%.
In cases (iii) and (iv) triphenylphosphite (PZ%) re-
3
places CO from the resulting carbonylphosphite com-
plex according to the same Eq. (4). This complex is
present in the equilibrium reaction mixture in a small
amount in case (iii) (PZ3=PCy3), when the equilibrium
(3) is almost completely shifted to the left, and in a
relatively large quantity (ꢀ50%) in case (iv) (PZ3=
PPh3).
In case (v) one more reaction product was detected, a
mixed complex containing two different phosphorus
ligands, Rh(CF3{O,N}CMe3)(P(NC4H4)3)(PPh3), whose
analogues were surprisingly not observed in any other
reaction. The formation of this product may be de-
scribed by Eq. (7). Eqs. (5) and (6) are essentially
similar to Eqs. (3) and (4), respectively:
Rh(R1{O,N}R2)(CO)(PPh3)+P(NC4H4)3
Rh(R1{O,N}R2)(CO)(PZ3)+PZ%
3
lRh(R1{O,N}R2)(CO)(P(NC4H4)3)+PPh3
Rh(R1{O,N}R2)(CO)(P(NC4H4)3)+P(NC4H4)3
“Rh(R1{O,N}R2)(P(NC4H4)3)2+CO
(5)
(6)
lRh(R1{O,N}R2)(CO)(PZ%)+PZ3
(3)
(4)
3
Rh(R1{O,N}R2)(CO)(P(OPh)3)+P(OPh)3
lRh(R1{O,N}R2)(P(OPh)3)2+CO
Rh(R1{O,N}R2)(P(NC4H4)3)2+PPh3
The liberated P(OPh)3 molecule in cases (i) and (ii)
replaces the CO ligand in the starting carbonylphos-
phite complex, which is present in the reaction mixture
in an amount depending on the position of equilibrium
“Rh(R1{O,N}R2)(P(NC4H4)3)(PPh3)+P(NC4H4)3
(7)
(3). If PZ% =PCy3, (i), the equilibrium (3) is almost
completely shifted to the right, and hence a bis(phos-
Mixed complexes containing two different phospho-
rus ligands can be easily obtained by displacing
3
Table 3
The results of phosphorus ligands exchange reactions in complexes Rh(CF3{O,N}CMe3)(CO)(PZ3), according to Eqs. (3) and (4) determined by
31P-NMR
Starting complex
Entering ligand
PCy3
Complexes in the resulting reaction mixture
(i)
Rh(CF3{O,N}CMe3)(CO)(P(OPh)3)
62% P-trans-to-N
Rh(CF3{O,N}CMe3)(CO)(PCy3)
100% P-trans-to-N
100%
50%
38% P-trans-to-O
(ii)
(iii)
Rh(CF3{O,N}CMe3)(CO)(P(OPh)3
62% P-trans-to-N
38% P-trans-to-O
PPh3
Rh(CF3{O,N}CMe3)(CO)(PPh3)
100% P-trans-to-N
Rh(CF3{O,N}CMe3)(P(OPh)3)2
50%
95%
Rh(CF3{O,N}CMe3)(CO)(PCy3)
100% P-trans-to-N
P(OPh)3
Rh(CF3{O,N}CMe3)(CO)(PCy3)
100% P-trans-to-N
(starting complex)
Rh(CF3{O,N}CMe3)(P(OPh)3)2
5%
(iv)
(v)
Rh(CF3{O,N}CMe3)(CO)(PPh3)
100% P-trans-to-N
P(OPh)3
Rh(CF3{O,N}CMe3)(CO)(PPh3)
ꢀ100% P-trans-to-N
(starting complex)
50%
Rh(CF3{O,N}CMe3)(P(OPh)3)2
50%
Rh(CF3{O,N}CMe3)(CO)(PPh3)
100% P-trans-to-N
P(NC4H4)3
Rh(CF3{O,N}CMe3)(CO)(PPh3)
ꢀ100% P-trans-to-N
(starting complex)
Rh(CF3{O,N}CMe3)(P(NC4H4)3)(PPh3)
Rh(CF3{O,N}CMe3)(P(NC4H4)3)2
comparable amounts

200
Y.S. Varsha6sky et al. / Journal of Organometallic Chemistry 628 (2001) 195–210
The above-mentioned mixed complex was identified
as the only isomer (PPh3-trans-to-N) on the basis of the
31P{1H}NMR spectra. The 1J(RhꢀP(PPh3)) coupling
constant is 153.2 Hz, almost identical to Rh(CF3-
{O,N}CMe3)(CO)(PPh3) (V), in which PPh3 is coordi-
nated trans to nitrogen. The second value of the
1J(RhꢀP(P(OPh)3) coupling constant is 318.3 Hz and is
very close to the 1J(RhꢀP) coupling constant in the
P-trans-to-O isomer of the Rh(CF3{O,N}CMe3)(CO)-
(P(OPh)3) complex (VI) (Table 2). Thus, in terms of the
substitution reactions the ketoiminato bis(phosphite)
complex is quite similar to the dicarbonyl one. In both
cases only one ligand (P(OPh)3 or CO, respectively),
coordinated trans to nitrogen, is substituted by
triphenylphosphine. The substitution of P(OPh)3 lo-
cated trans to N in VIII can be related to the RhꢀP
,
distance being longer by ca. 0.04 A compared with that
trans to O.
Fig. 1. The packing fragment of I with 50% ellipsoids. The short
It is interesting to note that PCy3 easily substitutes
triphenylphosphite in the Rh(CF3{O,N}CMe3)(CO)-
(P(OPh)3) complex (VI and VII) but not in
Rh(CF3{O,N}CMe3)(P(OPh)3)2 (VIII).
,
Rh···Rh distances of ca. 3.4 A are marked by dotted lines. Symmetry
codes: % −x+1, −y, −z; %% −x+1, −y+1, −z+1.
Table 4
Any replacement of the carbonyl group located cis to
a strong s-donor ligand, like PCy3 or PPh3, was not
observed (an effect described earlier as cis-symbiosis of
carbonyl groups with strong s-donor/weak p-acceptor
ligands [45]).
,
Selected geometric parameters (A, °) for [Rh(CF3{O,N}CH3)(CO)2]
(I) a
Molecule 1
Molecule 2
Rh(1)ꢀC(2)
Rh(1)ꢀC(1)
Rh(1)ꢀN(1)
Rh(1)ꢀO(11)
C(1)ꢀO(1)
1.838(3)
1.869(3)
2.030(3)
2.033(2)
1.129(4)
1.134(3)
1.306(3)
1.286(3)
3.419(2)
3.402(3)
Rh(2)ꢀC(4)
Rh(2)ꢀC(3)
Rh(2)ꢀN(2)
Rh(2)ꢀO(21)
C(3)ꢀO(3)
1.847(3)
1.877(3)
2.038(3)
2.046(2)
1.131(3)
1.134(4)
1.295(4)
1.289(3)
3.395(2)
2.4. X-ray studies
2.4.1. Structure of [Rh(CF3{O,N}Me)(CO)2] (I)
C(2)ꢀO(2)
C(4)ꢀO(4)
The rhodium(I) dicarbonyl complex I crystallises
with two independent molecules of very similar geome-
try in an asymmetric unit. These molecules are related
by an approximate centre of symmetry. The most char-
acteristic feature of the crystal packing is that the
molecules are stacked in the [001] direction forming
one-dimensional chains characterised by three different
N(1)ꢀC(11)
O(11)ꢀC(13)
Rh(1)ꢀRh(1)c1
Rh(1)ꢀRh(2)
N(2)ꢀC(21)
O(21)ꢀC(23)
Rh(2)ꢀRh(2)c2
C(2)ꢀRh(1)ꢀC(1)
C(2)ꢀRh(1)ꢀN(1)
87.85(14)
93.35(12)
C(4)ꢀRh(2)ꢀC(3)
C(4)ꢀRh(2)ꢀN(2)
C(3)ꢀRh(2)ꢀN(2)
C(4)ꢀRh(2)ꢀO(21)
C(3)ꢀRh(2)ꢀO(21)
N(2)ꢀRh(2)ꢀO(21)
O(3)ꢀC(3)ꢀRh(2)
O(4)ꢀC(4)ꢀRh(2)
88.75(13)
91.78(12)
178.55(10)
178.08(9)
89.96(11)
89.54(10)
177.8(3)
C(1)ꢀRh(1)ꢀN(1) 177.74(10)
C(2)ꢀRh(1)ꢀO(11) 176.02(10)
C(1)ꢀRh(1)ꢀO(11) 89.42(12)
N(1)ꢀRh(1)ꢀO(11) 89.47(10)
O(1)ꢀC(1)ꢀRh(1) 177.7(3)
O(2)ꢀC(2)ꢀRh(1) 176.9(3)
,
Rh···Rh distances (all being about 3.4 A), which are
comparable to those found for other rhodium dicar-
bonyl complexes [46–48]. A fragment of the chain with
the atom labelling scheme is shown in Fig. 1 and
selected geometric parameters are given in Table 4.
The rhodium coordination geometry is essentially
square-planar with small deviations of donor atoms
178.5(3)
a Symmetry transformations codes: c1−x+1, −y, −z; c2 −
x+1, −y+1, −z+1.
,
from the mean plane (ca. 0.04 and 0.03 A for molecules
P(OPh)3 in Rh(CF3{O,N}CMe3)(P(OPh)3)2 (VIII) with
1 and 2, respectively). However, analysis of the bond
lengths shows that those in the coordination sphere of
Rh(1) are about 3| shorter than those in the coordina-
tion sphere of Rh(2). The RhꢀO and the RhꢀC dis-
tances trans to O in each molecule are comparable to
those in [Rh(acac)(CO)2] [47]. In contrast, the RhꢀC
triphenylphosphine. In
a
reaction of equimolar
amounts of PPh3 and Rh(CF3{O,N}CMe3)(P(OPh)3)2
(VIII) the 30% conversion of the starting rhodium
complex to Rh(CF3{O,N}CMe3)(P(OPh)3)(PPh3) was
observed:
,
distances trans to N are ca. 0.030(3) A longer than the
RhꢀC distances trans to O, indicating a stronger trans
influence exerted by nitrogen compared with oxygen. It
seems that the observed trans influence of nitrogen is

Y.S. Varsha6sky et al. / Journal of Organometallic Chemistry 628 (2001) 195–210
201
enhanced by the presence of the CF3 substituent in the
chelate ligand, because the corresponding difference of
the bond lengths in [Rh(Ph{O,N}Ph)(CO)2] is equal to
,
only 0.015(5) A [49]. The bond lengths in the chelate
ring of I are close to the average values for different
metal complexes with Schiff bases derived from b-dike-
tones [50].
2.4.2. Structure of Rh(R1{O,N}R2)(CO)(PZ3)
complexes II–VII
Crystals of phosphine- or phosphite-containing com-
plexes II–VII comprise discrete molecules held together
mainly by van der Waals forces. Close intermolecular
contacts indicating weak interactions of the NꢀH···O
and (or) CꢀH···O types (Table 8) were found in the
Fig. 4. Molecular structure of V with 50% ellipsoids.
structures of II, III, V and VI. Besides, (C)ꢀH···p
,
interactions (H···p 2.9–3.1 A) between the p-cloud of
the chelate ring and the hydrogen atoms of the cyclo-
hexyl ring (III), the phenyl ring (IV, V, VI) or the
tert-butyl group (VII) were detected. They result in a
nearly orthogonal arrangement of the phenyl and
chelate rings, observed for IV, V and VI. The inter-
molecular interactions, although weak, determine the
crystal packing, which is different for each of the six
monocarbonyl compounds presented.
Views of the monocarbonyl compounds are pre-
sented in Figs. 2–6, and selected interatomic distances
and angles in Tables 5–7. Due to a significant similarity
between the molecular structures of II and III, only a
view of III is presented in Fig. 2, with the numbering
scheme for both the compounds. As can be seen from
the figures, complexes II–V display a trans to N dispo-
sition of the phosphorous ligand. The Rh(CF3{O,N}-
CMe3)(CO)(P(OPh)3) complex formed two isomers,
complex VI containing a P(OPh)3 ligand trans to N and
complex VII having the same ligand trans to O. All the
six complexes, II–VII, with expected square-planar co-
ordination of the Rh atom, have the chelate ring, the
carbonyl ligand and the P atom (from phosphorus
ligand) approximately in the same plane. The most
striking differences between these complexes lie in the
spatial arrangements of the phosphorus ligands. The
bulky PCy3 ligand adopts almost the same spatial ar-
rangement with respect to the flat fragment of the
molecule in the two compounds II and III in spite of
the different packing interactions. The significant
spread in the values of the CꢀPꢀC and the RhꢀPꢀC
angles observed in the complexes II and III (Table 5)
results from the steric interaction between the cyclo-
hexyl rings and between the cyclohexyl rings and the
Fig. 2. Molecular structure of III with 50% ellipsoids.
Fig. 3. Molecular structure of IV with 50% ellipsoids.

202
Y.S. Varsha6sky et al. / Journal of Organometallic Chemistry 628 (2001) 195–210
Table 5
carbonyl ligand. This indicates that the size of the PCy3
ligand exceeds the coordination site. In contrast, the
smaller but also rather compact PPh3 ligand has signifi-
cantly different orientations about the RhꢀP and PꢀC
bonds in the two compounds IV and V as can be seen
from a comparison of Figs. 3 and 4. However, in this
case the spread in the angles about the P atom is small,
which may imply no significant steric strains, and the
spatial arrangement of the ligand depends mainly on
intermolecular interactions. Also, the P(OPh)3 ligand
,
Selected geometric parameters (A, °) for [Rh(CF3{O,N}Me)(CO)-
(PCy3)] (II) and [Rh(CF3{O,N}CMe3)(CO) (PCy3)] (III)
II
III
RhꢀC(6)
RhꢀO(1)
RhꢀN
1.791(3)
2.048(2)
2.058(2)
2.290(2)
1.150(3)
1.294(3)
1.289(3)
1.849(2)
1.785(3)
2.042(2)
2.052(2)
2.2822(13)
1.162(3)
1.298(3)
1.283(3)
1.852(3)
RhꢀP
C(6)ꢀO(2)
NꢀC(1)
O(1)ꢀC(3)
PꢀCav
C(6)ꢀRhꢀO(1)
C(6)ꢀRhꢀN
O(1)ꢀRhꢀN
C(6)ꢀRhꢀP
177.63(9)
93.08(9)
88.29(8)
89.26(7)
89.44(5)
178.44(9)
93.17(9)
87.80(7)
90.13(7)
88.98(5)
O(1)ꢀRhꢀP
NꢀRhꢀP
177.01(6)
103.68(11)
112.11(12)
103.08(10)
111.33(8)
111.32(9)
114.49(8)
177.4(2)
175.07(6)
103.36(10)
111.39(11)
103.97(10)
110.47(8)
110.32(8)
116.34(7)
178.1(2)
C(31)ꢀPꢀC(21)
C(31)ꢀPꢀC(11)
C(21)ꢀPꢀC(11)
C(31)ꢀPꢀRh
C(21)ꢀPꢀRh
C(11)ꢀPꢀRh
O(2)ꢀC(6)ꢀRh
Table 6
,
Selected geometric parameters (A, °) for [Rh(CF3{O,N}Me)-
(CO)(PPh3)] (IV) and [Rh(CF3{O,N}CMe3)(CO)(PPh3)] (V)
IV
V
RhꢀC(6)
RhꢀO(1)
RhꢀN
1.804(3)
2.045(2)
2.045(2)
2.2811(11)
1.148(3)
1.297(3)
1.288(3)
1.828(5)
1.803(7)
2.036(4)
2.062(5)
2.277(2)
1.151(8)
1.304(8)
1.284(7)
1.827(7)
RhꢀP
Fig. 5. Molecular structure of VI with 50% ellipsoids.
C(6)ꢀO(2)
NꢀC(1)
O(1)ꢀC(3)
PꢀCav
C(6)ꢀRhꢀO(1)
C(6)ꢀRhꢀN
O(1)ꢀRhꢀN
C(6)ꢀRhꢀP
O(1)ꢀRhꢀP
NꢀRhꢀP
O(2)ꢀC(6)ꢀRh
C(11)ꢀPꢀC(21)
C(11)ꢀPꢀC(31)
C(21)ꢀPꢀC(31)
C(11)ꢀPꢀRh
C(21)ꢀPꢀRh
C(31)ꢀPꢀRh
178.68(11)
92.65(11)
87.94(9)
89.49(9)
89.91(6)
177.4(2)
94.7(3)
87.9(2)
88.6(2)
88.82(13)
176.17(16)
179.4(7)
102.8(3)
105.9(3)
104.3(3)
115.3(3)
114.1(2)
113.3(2)
177.82(7)
177.8(2)
103.52(12)
103.28(12)
103.82(12)
116.45(9)
113.75(9)
114.48(9)
has different orientations with respect to the flat frag-
ment of the molecules in two isomers, VI and VII,
which indicates some rotational freedom around the
RhꢀP bond, similar to that observed in the case of the
PPh3 complexes. Consideration of the angles about the
Fig. 6. Molecular structure of VII with 50% ellipsoids. The NꢀH···O
hydrogen bonds are marked by a dashed line.

Y.S. Varsha6sky et al. / Journal of Organometallic Chemistry 628 (2001) 195–210
203
Table 7
This may suggest that a binding site cis to the N atom
is more sterically hindered. It also seems that in-
tramolecular hydrogen interactions of the CꢀH···O-type
(in VI) and the NꢀH···O-type (in VII), both of which
involve the phosphite ligand (Table 8), affect to a large
degree the conformations observed for the P(OPh)3
ligand. Furthermore, because hydrogen interactions
may be expected to occur in a transition state involved
in the substitution reactions, one might expect that the
formation of NꢀH···O intramolecular bonding would
enhance the stability of the isomer with the P(OPh)3
ligand cis to N, while in the case of the PPh3 or PCy3
ligands the potentially attractive CꢀH···O interaction
would enhance the stability of the isomer with the P
ligand trans to N.
Despite the different distortions discussed above, the
bond distances in the phosphorous ligands are normal
and the average of the three C(O)ꢀPꢀC(O) angles regu-
larly decreases in the order PCy3\PPh3\P(OPh)3 (ca.
106.3, 104.0 and 101.2°, respectively), while the average
of the three RhꢀPꢀC(O) angles (112.4, 114.6 and
116.9°) increases in the order PCy3BPPh3BP(OPh)3.
It is interesting that the different steric properties of
the phosphorus ligands have almost no effect on the
coordination geometry around rhodium and the ge-
ometries of the b-ketoiminate ligands. The distances
and angles of the two ketoiminate ligands in all the
complexes are very similar to each other and to the
parameters found for the dicarbonyl complex I. A
slight distortion of the coordination geometry about the
Rh atom in II, III and V can be seen from the trans
NꢀRhꢀP and OꢀRhꢀC angles, some of which are devi-
,
Selected geometric parameters (A, °) for two isomers (VI and VII) of
[Rh(CF3{O,N}CMe3)(CO){P(OPh)3}]
VI
VII
RhꢀC(6)
RhꢀO(1)
RhꢀN
1.809(3)
2.035(2)
2.056(3)
2.195(2)
1.154(4)
1.294(4)
1.295(3)
1.605(4)
1.408(6)
1.849(3)
2.051(2)
2.034(2)
2.1535(9)
1.131(4)
1.305(4)
1.291(3)
1.607(3)
1.408(3)
RhꢀP
C(6)ꢀO(2)
NꢀC(1)
O(1)ꢀC(3)
PꢀOav
OꢀC(Ph)av
C(6)ꢀRhꢀO(1)
C(6)ꢀRhꢀN
O(1)ꢀRhꢀN
C(6)ꢀRhꢀP
O(1)ꢀRhꢀP
NꢀRhꢀP
C(1)ꢀNꢀRh
O(31)ꢀPꢀO(21)
O(31)ꢀPꢀO(11)
O(21)ꢀPꢀO(11)
O(31)ꢀPꢀRh
O(21)ꢀPꢀRh
O(11)ꢀPꢀRh
C(11)ꢀO(11)ꢀP
C(21)ꢀO(21)ꢀP
C(31)ꢀO(31)ꢀP
176.71(10)
95.04(13)
88.21(11)
88.64(11)
88.11(8)
89.45(10)
177.67(11)
88.33(9)
88.84(9)
178.28(6)
93.37(7)
176.30(7)
130.8(2)
130.3(2)
101.90(11)
99.16(10)
104.48(11)
117.16(8)
114.44(10)
117.35(9))
122.0(2)
104.02(11)
105.70(10)
92.26(10)
110.79(8)
121.97(8)
119.50(8)
120.7(2)
121.9(2)
126.1(2)
123.2(2)
128.4(2)
P atom (Table 7) reveals that the variation of these
angles in VI is comparable to that in the PPh3 com-
plexes (IV, V), while in VII these angles are distorted
even more than those in the PCy3 complexes (II, III).
Table 8
Intra- and intermolecular hydrogen-like bonds a,b
,
,
,
Compound
DꢀH···O
d(DꢀH) (A)
d(H···A) (A)
d(D···A) (A)
Ú(DHA) (°)
II
NꢀH(1)···O(2)c1
0.91(3)
1.00
0.95(3)
1.00
0.95
0.95
2.30(3)
2.51
2.52(3)
2.42
2.63
2.46
3.172(3)
3.022(3)
3.369(4)
3.038(3)
3.503(4)
3.144(3)
3.271(4)
3.217(10)
3.187(4)
3.464(4)
3.365(4)
2.909(3)
2.982(6)
3.038(6)
3.317(8)
3.354(8)
3.255(7)
3.307(8)
162(2)
112
148(2)
119
153
129
C(31)ꢀH(31)···O(1)
C(42)ꢀH(44)···O(2)c2
C(31)ꢀH(31)···O(1)
C(35)ꢀH(35)···O(2)c3
C(36)ꢀH(36)···O(1)
C(26)ꢀH(26)···O(1)
C(41)ꢀH(41)···O(2)c4
NꢀH(1)···O(2)c5
III
IV
0.95
2.54
133
V
VI
1.02(8)
0.77(3)
0.95
2.70(7)
2.64(3)
2.61
112(5)
130(3)
150
C(25)ꢀH(25)···O(2)c6
C(36)ꢀH(36)···O(1)
NꢀH(1)···O(31)
N(1)ꢀH(1)···O(11)
N(2)ꢀH(2)···O(31)
C(412)ꢀH(412)···O(3)
C(412)ꢀH(412)···O(42)
C(212)ꢀH(212)···O(1)
C(212)ꢀH(212)···O(22)
0.95
2.52
148
VII
VIII
0.82(3)
0.91(7)
1.07(6)
0.95
0.95
0.95
2.32(3)
2.23(7)
2.36(6)
2.78
2.77
2.63
130(3)
139(6)
120(4)
117
121
124
0.95
2.70
122
a Symmetry codes: c1−x, −y, −z; c2 −x+3/2, y−1/2, −z+3/2; c3 x+1/2, −y, z; c4 2−x, 1/2+y, −z; c5 −x+1, −y+1, −z+1;
c6 2−x, 2−y, −z.
b D, donor atom (N or C, respectively).

204
Y.S. Varsha6sky et al. / Journal of Organometallic Chemistry 628 (2001) 195–210
,
mean value of 1.842(8) A found for the two indepen-
dent carbonyl groups (trans to O) in the dicarbonyl
complex I. The shortening of the RhꢀC distance after
the substitution of one carbonyl group with the phos-
phorus ligand enhances carbonyl p-back bonding as
expected, taking into account the higher p-acceptor
character of the CO compared with phosphines and
phosphites.
The RhꢀO and RhꢀN distances show no significant
variations within the series of monosubstituted com-
plexes, but their average values, 2.042(5) and 2.053(7)
,
A, respectively, indicate that the RhꢀN distance tends
to be longer than the RhꢀO distance within this series
,
and is longer than the RhꢀN distances (av. 2.034(6) A)
in I. It is pertinent to note that these bond distances
may be affected by intra- and intermolecular hydrogen
interactions. However, it should also be noted that the
RhꢀN distances trans to P found in other similar com-
plexes with N,O-bidentate ligands, e.g. [Rh(oxine)-
(CO)(PZ3)] (Z=Ph [32], OPh [14]) and [Rh(LL)-
(CO)(PPh3)] where LL is 2-picolinate [52], are within
Fig. 7. Superposition of the two independent molecules of VIII with
the numbering scheme for one molecule. The NꢀH···O hydrogen
bonds are marked by dotted lines.
,
the 2.088(6)–2.098(2) A range.
The most striking differences of Rhꢀligand distances
were found in two isomeric phosphite complexes VI
and VII. Both RhꢀP distances and RhꢀC distances are
ated from linearity by at least 5°. Another major distor-
tion is the NꢀRhꢀC6 angle in II–VI and the NꢀRhꢀP
angle in VII, in each case greater than 90°, which
indicates a weak steric interaction between the hydro-
gen bonded to N and the adjacent ligand. It appears
that this repulsing interaction, together with the steric
hindrances of each specific phosphorus ligand, can af-
fect the process of isomer formation and can be respon-
sible for the behaviour of the monocarbonyl complexes,
studied here, during the substitution reactions.
Some trends can be noted if one focuses on the
lengths of the bonds formed by rhodium (Table 9).
A comparison of the RhꢀP bonds in the series of
monocarbonyl complexes with the phosphorus ligand
positioned trans to N shows that only the RhꢀP bond
in complex VI differs significantly from those in phos-
,
ca. 0.04 A longer when they are trans to N than when
they are trans to O. Also, the RhꢀO and RhꢀN dis-
tances differ in these two isomeric complexes, in each
case the bonds trans to the P(OPh)3 ligand being ca.
,
0.02 A longer than those trans to the carbonyl. The
correlation between the RhꢀP and RhꢀC bonds and the
s-donor/p-acceptor properties of the donor atom trans
to PPh3 has been shown previously for [Rh(LL)(CO)-
(PPh3)] complexes, where LL denotes different biden-
tate ligands [14,24,53].
2.4.3. Structure of [Rh(CF3{O,N}CMe3){P(OPh)3}2]
(VIII)
The unit cell of the diphosphite complex VIII con-
tains two independent molecules, different slightly in
their molecular conformation (see Fig. 7). The bond
distances and angles are given in Table 10. Generally,
the two P(OPh)3 ligands exhibit the same features as the
corresponding groups in VI and VII; the average
OꢀPꢀO and RhꢀPꢀO angles for each of the four phos-
phite ligands in VIII (ca. 99.6 and 117°, respectively)
are similar to those in VI and VII; the spread of these
angle values is significantly greater for P(OPh)3 ligands
trans to O than for those trans to N; the NꢀH···O
hydrogen bonding involves one of the phosphite oxy-
gens in each molecule. It is worth noticing that the cone
angles, calculated for the P(OPh)3 ligand from the
molecular structures of VI,VII and VIII, are all ca.
145°, which value is significantly greater than Tolman’s
minimised value of 128° [51]. In VIII, the steric hin-
drance of two phosphite ligands, cis to each other,
,
phine complexes (II–V), being ca. 0.1 A shorter. Varia-
,
tions on the order of 0.01 A found in the RhꢀP
distances for the five phosphine complexes presented in
Table 9 are only slightly greater (4–6|) than experi-
mental error; nevertheless, the RhꢀP distance tends to
be greater for the PCy3 than for the PPh3 complexes.
The RhꢀP bonding distances are consistent with the
decreasing order of the p-acceptor properties of the
phosphorus ligands: P(OPh)3\PPh3\PCy3. In addi-
tion, the fact that the RhꢀP distance is similar in the
PCy3 and the PPh3 complexes suggests domination of
electronic rather than steric properties of ligands.
The RhꢀC distances show only slight variations for
complexes in which the carbonyl group is trans to O,
,
and the mean value of 1.799(8) A is the same as that
found for the analogous PPh3 complexes with O,O-
chelate ligands [24] but is significantly shorter than the

Y.S. Varsha6sky et al. / Journal of Organometallic Chemistry 628 (2001) 195–210
205
results in obtuse PꢀRhꢀP angles and in distortions of
the coordination spheres greater than in VI or VII.
Slight variations occur in the bond distances in the two
molecules of VIII, the most significant being that the
RhꢀP distance trans to O in one molecule is shorter by
,
0.012(2) A than that in the other one. However, the
RhꢀP distances in each independent molecule differ
,
considerably (by ca. 0.04–0.05 A), once more evidenc-
ing a stronger trans influence exerted by the nitrogen
atom than by the oxygen atom. At the same time, the
RhꢀO and RhꢀN distances are practically equal to each
other for the two molecules, but both are ca. 0.02–0.03
,
A longer than those (trans to CO) in I, the difference
being similar to that observed for the two isomeric
complexes VI and VII. A comparison of the RhꢀP
distances in VIII with the corresponding distances in VI
and VII shows that a substitution of the carbonyl
ligand in the latter by the phosphite ligand results in the
,
shortening of these bonds by ca. 0.017–0.019 A. This
may be rationalised by a gain of electron density on the
metal d(p) orbitals, owing to the replacement of the CO
ligand by the weaker p-acceptor P(OPh)3 ligand.
3. Experimental
[Rh(CO)2Cl]2 was synthesised as described in the
literature [54].
Dicarbonyl complexes, Rh(R1{O,N}R2)(CO)2, were
obtained according to the procedures previously de-
scribed, either by a reaction of H(b-ketim) with
[Rh(CO)2Cl]2 in the presence of BaCO3 [8] or by ex-
change reactions between [Rh(CO)2Cl]2 and copper(II)
b-ketoiminates [36]. 13C-enriched samples of [Rh-
(CO)2Cl]2 were obtained by bubbling 13CO (ꢀ85% 13C)
through a suspension of [Rh(C2H4)2Cl]2 [55] in C6H6.
Free b-ketoamines are not stable enough due to
isomerisation and hydrolysis [56,57] and therefore were
recrystallised before use. Copper(II) b-ketoiminate
complexes are much more stable.
3.1. Rh[CF3C(O)CHC(NH)Me](CO)2 (I) [35,36]
Solid Cu[CF3C(O)CHC(NH)Me]2 (0.24 g, 0.65
mmol) was added to a solution of [Rh(CO)2Cl]2 (0.194
g, 0.5 mmol) in hexane (20 ml). The suspension was
stirred for 2 h at 40°C and then cooled to r.t. The
reddish-brown precipitate contained copper(II) chlo-
ride; it was filtered off, and the solvent was removed
under reduced pressure. The residue was dissolved in
CHCl3 and purified by column chromatography (silica
gel, CHCl3). The eluate was evaporated to dryness.
Recrystallisation of the orange product from hexane
followed by drying under vacuum yielded orange crys-
tals (0.24 g, 77%). Anal. Found: C, 27.17; H, 1.52; N,
5.21; Rh, 33.08. Calc. for C7H5F3NO3Rh: C, 27.03; H,

206
Y.S. Varsha6sky et al. / Journal of Organometallic Chemistry 628 (2001) 195–210
1
1.62; N, 4.5; Rh, 33.15%; H-NMR (l ppm): 2.28 (s,
CH3), 5.73 (d, J=1.5 Hz, CH), 8.1 (NH); 19F-NMR (l
ppm): −69.93 (s, CF3).
3.4. Rh[CMe3C(O)CHC(NH)CF3](CO)2
Dark red crystals with green dichroism were obtained
as above using C(CH3)3C(O)CHC(NH2)CF3. Yield:
0.38 g, 83%. Anal. Found: C, 34.13; H, 3.00; N, 3.25;
Rh, 29.07. Calc. for C10H11NO3F3Rh: C, 34.02; H,
3.2. Rh[MeC(O)CHC(NH)CF3](CO)2 [36]
1
Orange crystals were obtained as above using
Cu[MeC(O)CHC(NH)CF3]2. Yield: 0.23 g, 74%. Anal.
Found: C, 27.60; H, 1.62; N, 4.76; Rh, 33.09. Calc. for
C7H5F3NO3Rh): C, 27.03; H, 1.62; N, 4.50; Rh,
33.15%; 1H-NMR (l ppm): 2.21 (s, CH3), 5.64 (d,
J=2.0 Hz, CH), 7.35 (NH); 19F-NMR (l ppm): −
67.77 (s, CF3).
3.14; N,3.97; Rh, 29.14%; H-NMR (l ppm): 1.21 (s,
CH3), 5.81 (CH), 7.8 (NH); 19F-NMR (l ppm): −
67.71 (s, CF3).
3.5. Rh(R1{O,N}R2)(CO)(PPh3) and
Rh(R1{O,N}R2)(CO)(PCy3)
These complexes were obtained in reactions of
equimolar amounts of Rh(R1{O,N}R2)(CO)2 and PPh3
or PCy3, respectively, in C6H5CH3 or C6H6 (0.5 cm3).
After addition of ca. 0.2 cm3 of hexane the solution was
left to crystallise in a refrigerator. Crystals suitable for
X-ray analysis were obtained from these solutions. All
complexes of that type were also obtained as orange-
yellow microcrystalline powders in reactions of equimo-
lar amounts of the reactants in acetone or hexane with
yields of 85–95%.
3.3. Rh[CF3C(O)CHC(NH)CMe3](CO)2
Solid CF3C(O)CHC(NH2)CMe3 (0.26 g, 1.33 mmol)
and excess BaCO3 (0.8 g) were added to a solution of
[Rh(CO)2Cl]2 (0.25 g, 0.64 mmol) in CHCl3 (10 ml).
The reaction mixture was stirred for 4 h at r.t., filtered,
and evaporated to dryness under reduced pressure.
Recrystallisation of crude product from hexane fol-
lowed by drying under vacuum yielded dark red crys-
tals with green dichroism (0.36 g, 79%). Anal. Found:
C, 34.08; H, 3.15; N, 3.55; Rh, 29.20. Calc. for
C10H11F3NO3Rh: C, 34.02; H, 3.14; N, 3.97; Rh,
29.14%; 1H-NMR (l ppm): 1.26 (s, CH3), 5.92 (d,
Jꢀ2.0 Hz, CH), 8.3 (NH); 19F-NMR (l ppm): −69.73
(s, CF3).
The analytical and NMR data presented below for
the triphenylphosphine complexes are related to mix-
tures of both isomers. Owing to the low intensity of the
NMR signals of the P-trans-to-O isomer, the corre-
sponding values of the imino proton chemical shift and
4
the J(HH) coupling constants of NH and CH protons
(ca. 2 Hz) are not reported. Proton resonances of the
phenyl and cyclohexyl groups are omitted. In the 13C-
NMR spectra the resonances of carbonyl carbons are
split due to coupling with 103Rh (ca. 75 Hz), 31P (ca. 22
1
Table 10
Hz) and imino H (ca. 1.5 Hz) nuclei.
,
Selected geometric parameters (A, °) for [Rh(CF3{O,N}CMe3)-
{P(OPh)3}2] (VIII)
3.6. Rh(CF3{O,N}Me)(CO)(PPh3)
Molecule 1
Molecule 2
Anal. Found: C, 52.91; H, 3.76; N, 2.60; Rh, 18.77.
Calc. for C24H20F3NO2RhP: C, 52.86; H, 3.70; N, 2.57;
Rh, 18.87%. P-trans-to-N isomer (IV): 1H-NMR (l
ppm): 2.22 (s, CH3), 5.56 (d, J=1.9 Hz, CH), 8.45
(NH); 19F-NMR (l ppm): −70.26 (s, CF3); 13C-NMR
(l ppm): 190.3 (ddd, J=76.4 Hz, J=22.0 Hz, J=1.6
Rh(1)ꢀO(1)
Rh(1)ꢀN(1)
Rh(1)ꢀP(1)
Rh(1)ꢀP(2)
C(1)ꢀN(1)
O(1)ꢀC(3)
PꢀOav
2.052(4)
2.056(5)
2.140(2)
2.179(2)
1.288(8)
1.298(7)
1.613(11)
1.401(10)
Rh(2)ꢀO(3)
Rh(2)ꢀN(2)
Rh(2)ꢀP(3)
Rh(2)ꢀP(4)
C(10)ꢀN(2)
O(3)ꢀC(30)
PꢀOav
2.064(4)
2.069(5)
2.128(2)
2.178(2)
1.310(7)
1.283(7)
1.613(13
1.407(11)
1
Hz, CO). P-trans-to-O isomer: H-NMR: 1.68 (s, CH3),
5.74 (d, CH); 19F-NMR: −69.66 (s, CF3); 13C-NMR (l
ppm): 189.4(dd, J=67.9 Hz, J=22.6 Hz, CO).
OꢀC(Ph)av
OꢀC(Ph)av
O(1)ꢀRh(1)ꢀN(1)
O(1)ꢀRh(1)ꢀP(1)
N(1)ꢀRh(1)ꢀP(1)
O(1)ꢀRh(1)ꢀP(2)
N(1)ꢀRh(1)ꢀP(2)
P(1)ꢀRh(1)ꢀP(2)
O(13)ꢀP(1)ꢀO(12) 104.5(2)
O(13)ꢀP(1)ꢀO(11) 103.1(2)
O(12)ꢀP(1)ꢀO(11)
87.6(2)
176.45(12)
89.07(15)
88.98(12)
175.7(2)
94.42(6)
O(3)ꢀRh(2)ꢀN(2)
O(3)ꢀRh(2)ꢀP(3)
N(2)ꢀRh(2)ꢀP(3)
O(3)ꢀRh(2)ꢀP(4)
N(2)ꢀRh(2)ꢀP(4)
P(3)ꢀRh(2)ꢀP(4)
O(33)ꢀP(3)ꢀO(32) 104.7(2)
O(33)ꢀP(3)ꢀO(31) 103.4(2)
O(31)ꢀP(3)ꢀO(32)
88.1(2)
176.39(12)
88.43(15)
90.55(12)
178.21(14)
92.85(6)
3.7. Rh(Me{O,N}CF3)(CO)(PPh3)
Anal. Found: C, 52.78; H, 3.56; N, 2.40; Rh, 18.72.
Calc. for C24H20F3NO2RhP: C, 52.86; H, 3.70; N, 2.57;
1
Rh, 18.87%. P-trans-to-N isomer: H-NMR (l ppm):
90.7(2)
92.1(2)
1.73 (s, CH3), 5.42 (d, J=1.7 Hz, CH), 8.27 (NH);
19F-NMR (l ppm): −67.86 (s, CF3); 13C-NMR (l
ppm): 190.4 (ddd, J=74.6 Hz, J=22.6 Hz, J=1.5 Hz,
CO). P-trans-to-O isomer: 1H-NMR: 2.24 (s, CH3),
O(23)ꢀP(2)ꢀO(22) 102.7(2)
O(23)ꢀP(2)ꢀO(21)
O(22)ꢀP(2)ꢀO(21)
O(43)ꢀP(4)ꢀO(42) 102.1(2)
O(43)ꢀP(4)ꢀO(41) 100.0(2)
O(42)ꢀP(4)ꢀO(41)
99.1(2)
96.4(2)
96.8(2)

Y.S. Varsha6sky et al. / Journal of Organometallic Chemistry 628 (2001) 195–210
207
5.65 (d, CH); 19F-NMR: −68.56 (s, CF3); 13C-NMR (l
ppm): 189.5 (dd, J=68.5 Hz, J=22.9 Hz, CO).
Rh(R1{O,N}R2)(CO)(P(OPh)3) and Rh(R1{O,N}R2)-
(CO)(P(NC4H4)3) complexes have not been isolated
from the solutions prepared for 31P{1H}-NMR mea-
surements by use of equimolar amounts of
Rh(R1{O,N}R2)(CO)2 and P(OPh)3 or P(NC4H4)3.
Small samples for IR measurements have been obtained
by solvent evaporation in vacuo. Crystals of VI and VII
have been obtained by slow evaporation of CDCl3–
MeOH solutions in a refrigerator.
3.8. Rh(CF3{O,N}CMe3)(CO)(PPh3)
Anal. Found: C, 55.61; H, 4.20; N, 2.30; Rh, 17.24.
Calc. for C27H26F3NO2RhP: C, 55.19; H, 4.46; N, 2.39;
Rh, 17.52%. P-trans-to-N isomer (V): 1H-NMR (l
ppm): 1.26 (s, CH3), 5.77 (d, J=2.0 Hz, CH), 8.8
(NH); 19F-NMR (l ppm): −70.00 (s, CF3); 13C-NMR
(l ppm): 190.6 (ddd, J=75.1 Hz, J=22.1 Hz, J=1.6
Rh(R1{O,N}R2)(P(OPh)3)2 complexes have been ob-
tained as yellow powders in reactions of Rh(R1{O,N}-
R2)(CO)2 with three- to fivefold excesses of P(OPh)3 in
hexane. The complete CO substitution was confirmed
by the absence of w(CO) bands in the IR spectra and
the presence of two resonances of inequivalent P(OPh)3
ligands in 31P{1H}-NMR. Complex VIII have been
obtained by recrystallisation of the crude product from
MeOH.
1
Hz, CO). P-trans-to-O isomer: H-NMR: 0.74 (s, CH3),
5.61 (d, CH); 19F-NMR: −69.36 (s, CF3); 13C-NMR (l
ppm): 189.8 (dd, J=68.5 Hz, J=22.2 Hz, CO).
3.9. Rh(CMe3{O,N}CF3)(CO)(PPh3)
31P{1H}-NMR data in CDCl3, l(ppm) [1J(RhꢀP)]
Anal. Found: C, 55.77; H, 4.64; N, 2.16; Rh, 17.30.
Calc. for C27H26F3NO2RhP: C, 55.19; H, 4.46; N, 2.39;
2
(Hz); J(PꢀP) (Hz) are the following:
1
Rh, 17.30%. P-trans-to-N isomer: H-NMR (l ppm):
Rh(CF3{O,N}CMe3)(P(OPh)3)2 (VIII): 126.6 [300],
122.8 [262]; 104.
0.72 (s, CH3), 5.60 (d, J=2.2 Hz, CH), 8.25 (NH);
19F-NMR: (l ppm): −67.70 (s, CF3); 13C-NMR (l
ppm): 190.4 (ddd, J=75.2 Hz, J=22.0 Hz, J=1.7 Hz,
CO). P-trans-to-O isomer: 1H-NMR: 1.25 (s, CH3),
5.72 (d, CH); 19F-NMR: −68.28 (s, CF3); 13C-NMR (l
ppm): 189.4 (dd, J=68.3 Hz, J=23.0 Hz, CO).
Rh(CMe3{O,N}CF3)(P(OPh)3)2: 124.5 [303], 121.3
[264]; 102.
Rh(Me{O,N}CF3))(P(OPh)3)2: 125.6 [301], 121.7 [267];
103.
The spectral (IR and NMR) parameters of the com-
pounds under consideration were partially published
previously [35,36,38,41]. IR spectra were recorded on
Specord IR 75 or Nicolet Impact 400 instruments.
NMR spectra (in CDCl3) were recorded on a Bruker
AM-500 instrument in a pulse mode at the following
3.10. Rh(CF3{O,N}Me)(CO)(PCy3) (II)
Anal. Found: C, 51.42; H, 6.80; N, 2.59. Calc. for
C24H38F3NO2RhP: C, 51.16; H, 6.80; N, 2.50%. 1H-
NMR (l ppm): 2.17 (s, CH3), 5.51 (d, J=1.7 Hz, CH),
8.4 (NH); 19F-NMR: (l ppm): −70.09 (s, CF3).
1
frequencies: H, 500.14 MHz; 13C, 125.76 MHz; 19F,
470.56 MHz. The solvent CDCl3 resonances served as
internal standards for the 1H and 13C spectra (l1H
from residual protons 7.25 ppm and l13C 77.04 ppm).
The 19F chemical shifts were determined with hex-
afluorobenzene (l19F −162.9 ppm) as an external
standard. 31P{1H}-NMR spectra have been measured
on a Bruker 300 (121.5 MHz for 31P) with 85% H3PO4
as an external standard. The amounts of complexes
have been calculated from the signals’ intensities
(integration).
3.11. Rh(Me{O,N}CF3)(CO)(PCy3)
Anal. Found: C, 51.00; H, 6.13; N, 2.75. Calc. for
C24H38NO2F3RhP: C, 51.42; H, 6.30; N, 2.50%. 1H-
NMR (l ppm): 1.99 (s, CH3), 5.38 (d, J=2.2 Hz, CH),
8.2 (NH); 19F-NMR: (l ppm): −68.10 (s, CF3).
3.12. Rh(CF3{O,N}CMe3)(CO)(PCy3) (III)
3.14. X-ray measurements
Anal. Found: C, 53.61; H, 6.21; N, 2.31. Calc. for
C27H44F3NO2RhP: C, 53.80; H, 6.86; N,2.33%. 1H-
NMR (l ppm): 1.24 (s, CH3), 5.68 (d, J=2.2 Hz, CH),
8.7 (NH); 19F-NMR: (l ppm): −69.84 (s, CF3).
Diffraction data for crystals I–VII were collected on
a Kuma KM4 k-geometry diffractometer (ꢀ–2q scan)
and for VIII on a Kuma KM4CCD area detector
difractometer (ꢀ scan) [58], with graphite monochro-
,
3.13. Rh(CMe3{O,N}CF3)(CO)(PCy3)
mated Mo–Ka radiation (u=0.71073 A). The empiri-
cal correction [59] for absorption was applied for II,
III, VI and VII, while no corrections were needed for I,
IV, V and VII. For VIII, 6952 overlapping reflections,
which occur owing to the large c lattice parameter, had
been removed during data reduction. The structure IV
Anal. Found: C, 53.08; H, 7.00; N, 2.29. Calc. for
C27H44F3NO2RhP: C, 53.80; H, 6.86; N, 2.33%. 1H-
NMR (l ppm): 1.14 (s, CH3), 5.57 (d, J=2.2 Hz, CH),
8.7 (NH); 19F-NMR: (l ppm): −67.92 (s, CF3).

208
Y.S. Varsha6sky et al. / Journal of Organometallic Chemistry 628 (2001) 195–210
Table 11
Crystal data and structure refinement for I–VIII
Compound
I
II
III
IV
V
VI
VII
VIII
Empirical
formula
Formula
weight
C7H5F3NO3Rh C24H38F3NO2 C27H44F3NO2- C24H20F3NO2- C27H26F3NO2- C27H26F3NO5- C27H26F3NO5- C44H41F3NO7-
PRh
PRh
PRh
PRh
PRh
PRh
P2Rh
311.03
563.43
605.51
545.29
587.37
635.37
635.37
917.63
Temperature 120(2)
(K)
120(2)
120(2)
120(2)
120(2)
120(2)
120(2)
100(2)
Crystal
system
Space group
Triclinic
Monoclinic
Monoclinic
Orthorhombic Monoclinic
Triclinic
Monoclinic
Monoclinic
(
(
P1
P21/n
Yellow
P21/n
Yellow
Pca21
P21
P1
P21/c
Pink-blue
Cc
Yellow
Crystal colour Yellow–
Pale yellow
Pale yellow
Yellow
brown
Crystal habit Parallelepiped Block
Plate
0.60×0.20
×0.15
Block
0.40×0.40
×0.40
Plate
0.25×0.15
×0.15
Block
0.70×0.35
×0.35
Plate
0.25×0.06
×0.37
Parallelepiped
0.4 (sphere)
Crystal size
(mm)
0.13×0.13
×0.08
0.75×0.40
×0.40
Unit cell
dimensions
,
a (A)
7.957(5)
11.174(6)
12.086(6)
109.05(5)
107.07(5)
92.78(5)
958.5(9)
4
8.027(6)
21.128(12)
15.224(10)
12.348(6)
16.643(7)
14.487(6)
16.681(8)
8.400(4)
16.172(8)
11.387(9)
8.177(8)
13.792(13)
9.632(6)
10.348(6)
14.687(8)
99.86(5)
96.14(5)
107.57(6)
1355.2(14)
2
9.388(3)
26.043(8)
11.351(4)
18.599(4)
11.463(3)
39.371(6)
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
V (A )
100.26(6)
105.84(4)
99.87(8)
107.29(3)
101.23(3)
3
,
2541(3)
4
2864(2)
4
2266(2)
4
1265(2)
2
2649.8(15)
4
8233(3)
8
Z
v(Mo–Ka)
1.813
0.778
0.695
0.870
0.785
0.747
0.764
0.558
(mm−1
)
Max 2q
56
50
52
56
50
46
54
57
Reflections
collected
7534
4466
5664
5500
3976
3453
5847
25 434
Reflections
observed
Completeness 0.96
2806
3648
4194
4614
2679
3080
3926
11 162
0.908
0.964
0.963
1.00
0.998
0.910
0.97
to qmax
Data/
parameters
4440/311
4466/309
0.0233
0.0667
1.061
5664/360
0.0242
0.0678
1.042
5488/309
0.0236
0.0642
1.046
3866/349
0.0307
0.0882
1.041
3453/387
0.0226
0.0661
1.060
5730/355
0.0269
0.0813
1.034
12 351/1058
0.0456
0.0962
1.085
a
R
(F,
0.0222
0.0647
F2\2|)
Rw (F2, all
b
data)
Goodness-of- 0.987
fit on F2
Weights a/b
Flack
c
0.0347/0.114
–
0.0354/1.459
–
0.0343/0.766
–
0.0407/0.000
−0.03(2)
0.0494/0.000
−0.02(4)
0.0448/0.602
–
0.0434/1.326
–
0.0136/52.29
0.00(2)
parameter
a R=ꢀ(ꢁꢁFoꢁ−ꢁFcꢁꢁ)/ꢀꢁFoꢁ.
b Rw=[ꢀw(Fo2−Fc2)2/ꢀw(Fo2)]1/2
.
c w=1/[|2(Fo2)+(aP)2+bP] where P=[max(0 or Fo2)+2F2c]/3.
is isomorphous to that found [34] for the similar com-
pound, Rh(Me{O,N}Me)(CO)(PPh3). The other struc-
tures were solved using direct methods with SHELXS97
[60] and refined by the full-matrix least-squares method
on all the F2 data using SHELXL97 [60]. The hydrogen
atoms of the phosphorus ligands were included in the
geometrical positions and refined as the riding model.
The hydrogen atoms of the chelate ligands were found
from difference Fourier maps and refined. The non-hy-
drogen atoms were refined with anisotropic thermal
parameters. All hydrogen atoms were given isotropic
thermal parameters equivalent to 1.2 times those of the
atom to which they are attached. Crystal and refine-
ment data for all the crystals are compiled in Table 11.

Y.S. Varsha6sky et al. / Journal of Organometallic Chemistry 628 (2001) 195–210
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Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC nos. 154496–154503 for I–VIII.
Copies of this information may be obtained free of
charge from The Director, CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK (Fax: +44-1223-336033;
e-mail: deposit@ccdc.cam.ac.uk or www: http://
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The authors from St. Petersburg State University are
grateful to the Education Ministry of Russian Federa-
tion for financial support (grant 98-8-4.1-14). A.M.T.
and J.J.Z. thank the State Committee for Research
(KBN) for financial support; project PBZ-KBN 15/09/
T09/99/01d. Free b-ketoamines and their copper(II)
complexes, Cu(b-ketim)2, were kindly furnished by K.I.
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of Science, Ekaterinburg), whose contribution is grate-
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