First examples of [Rh(Bident)(CO)(L)] complexes where L is N-donor ligand: Molecular structure of [Rh(8-Oxiquinolinato)(CO)(NH3)]

Article abstract of DOI:10.1016/j.jorganchem.2007.09.022

Selective oxidation of one (trans to N) carbonyl group in [Rh(8-Oxiquinolinato)(CO)₂] with stoichiometric amount of Me₃NO in MeCN produces a solution containing [Rh(Oxq)(CO)(Me₃N)] and [Rh(Oxq)(CO)(MeCN)]. The ammonia complex, [Rh(Oxq)(CO)(NH₃)], has been prepared by action of NH₃ gas on this solution and characterized by IR, ¹H and ¹³C NMR, and X-ray data. Spectral parameters, ν(CO), δ ¹³C, and ¹J(CRh), were measured in situ for a series of complexes [Rh(Oxq)(CO)(L)] (L = NAlk₃, Py, PBu₃, PPh₃, P(OPh)₃, C₈H₁₄) formed upon action of L on [Rh(Oxq)(CO)(NH₃)] in THF. A new ν(CO) and δ ¹³C based scale of σ-donor/π-acceptor properties of ligands L is proposed including NH₃ and CO as the natural endpoints.

Full text of DOI:10.1016/j.jorganchem.2007.09.022

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Journal of Organometallic Chemistry 692 (2007) 5788–5794
www.elsevier.com/locate/jorganchem
First examples of [Rh(Bident)(CO)(L)] complexes where L
is N-donor ligand: Molecular structure
of [Rh(8-Oxiquinolinato)(CO)(NH3)]
a,
a
a
a
b
Yu.S. Varshavsky *, M.R. Galding , T.G. Cherkasova , S.N. Smirnov , V.N. Khrustalev
a
Institute of Chemistry, St. Petersburg State University, Petrodvorets, Universitetskii pr., 26, 198504 St. Petersburg, Russia
b
Nesmeyanov Institute of Organoelement Compounds, Vavilova Street, 28, 117813 Moscow, Russia
Received 5 July 2007; received in revised form 26 August 2007; accepted 24 September 2007
Available online 29 September 2007
Abstract
Selective oxidation of one (trans to N) carbonyl group in [Rh(8-Oxiquinolinato)(CO)2] with stoichiometric amount of Me3NO in
MeCN produces a solution containing [Rh(Oxq)(CO)(Me3N)] and [Rh(Oxq)(CO)(MeCN)]. The ammonia complex, [Rh(Oxq)-
1
(CO)(NH3)], has been prepared by action of NH3 gas on this solution and characterized by IR, H and 13C NMR, and X-ray data.
1
Spectral parameters, m(CO), d 13C, and J(CRh), were measured in situ for a series of complexes [Rh(Oxq)(CO)(L)] (L = NAlk3, Py,
PBu3, PPh3, P(OPh)3, C8H14) formed upon action of L on [Rh(Oxq)(CO)(NH3)] in THF. A new m(CO) and d 13C based scale of
r-donor/p-acceptor properties of ligands L is proposed including NH3 and CO as the natural endpoints.
Ó 2007 Elsevier B.V. All rights reserved.
Keywords: Rhodium(I) complexes; Carbonyl frequencies; 13C chemical shifts; N-donors; Electronic parameters; Crystal structure
1. Introduction
the spectral and structural characterization of the first
[Rh(Bident)(CO)(L)] complex with N-donor ligand L in
the cis to CO position, namely [Rh(Oxq)(CO)(NH3)]
(HOxq is 8-hydroxyquinoline), and present the spectral
characteristics of some of its analogs, [Rh(Oxq)(CO)(A-
mine)] (without isolation). To obtain these complexes, we
used an ordinary technique of indirect replacement of CO
ligand from transition metal carbonyl complexes, stoichi-
ometric oxidation of carbonyl group by one equivalent of
trimethylamine oxide with subsequent action of ligand L
[1–9].
Dozens (or perhaps hundreds) of complexes of general
formula [Rh(Bident)(CO)L], where Bident is a monoanion-
ic bidentate ligand and L is a neutral monodentate ligand,
were synthesized and widely studied during the last five
decades. Remarkably, all these complexes contained
ligands L with more or less pronounced p-acceptor proper-
ties, such as phosphines, phosphites, arsines, olefins, or car-
bonyl group (soft bases, in other words). To our knowledge
no complexes of this type with N-donor ligands L (or other
hard bases) were described up to date. Contrary to phos-
phines which readily replace one carbonyl group from
dicarbonyl complexes, [Rh(Bident)(CO)2], N-donors are
not capable of such a reaction, and this fact prevents the
direct synthesis of title compounds. We report here on
2. Results and discussion
2.1. Preparation of parent monocarbonyl moieties
Addition of trimethylamine oxide, Me3NO, (1 mole per
Rh) to the suspension of partially solved [Rh(Oxq)(CO)2]
in acetonitrile, MeCN, (with carbonyl stretching maxima
at 2080 and 2006 cmÀ1) gives brownish-yellow solution.
*
Corresponding author. Tel.: +7 812 428 4710; fax: +7 812 2743445.
E-mail address: yurel@peterlink.ru (Yu.S. Varshavsky).
0022-328X/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.09.022

Yu.S. Varshavsky et al. / Journal of Organometallic Chemistry 692 (2007) 5788–5794
5789
In its IR spectrum two strong carbonyl bands of compara-
ble intensity are present, at 1972 and 1948 cmÀ1, the second
of them being slightly more intense. Removal of solvent
yields black solid with a kind of metallic lustre. In the IR
spectrum of acetonitrile solution of this solid, the position
of the absorption bands remained unchanged, but the max-
imum at 1972 cmÀ1 showed an increase in relative intensity.
Upon addition of Me3N to this solution, or to the primary
reaction mixture, the 1948 cmÀ1 band increased in its inten-
sity at the expense of the 1972 cmÀ1 band. At the large
excess of Me3N only one maximum (1948 cmÀ1) remained
in the spectrum. We assign these bands to the monocarbon-
yl complexes, [Rh(Oxq)(CO)(MeCN)] (1972 cmÀ1) and
[Rh(Oxq)(CO)(Me3N)] (1948 cmÀ1), originated from the
coordinatively unsaturated moiety, [Rh(Oxq)(CO)], pri-
mary product of the carbonyl ligand oxidation. The
changes in the relative intensity of observed bands are obvi-
ously due to competition between Me3N originated from
amine oxide and solvent MeCN for the vacant coordina-
tion position in [Rh(Oxq)(CO)].
group and concurrent formation of two monocarbonyl
derivatives, [Rh(Acac)(CO)(MeCN)] and [Rh(Acac)(CO)-
(Me3N)].
2.2. Synthesis and characterization of
[Rh(Oxq)(CO)(NH3)]
On bubbling ammonia gas through a reaction mixture
prepared as described in Section 2.1, a light-yellow crystal-
line solid precipitates. The product is soluble in acetone,
ethanol, chloroform, but the intensity of carbonyl band is
markedly diminished at storage of these solutions. The
solution in tetrahydrofurane is more stable under inert
atmosphere and thus was used for spectral measurements.
The intense IR band of CO stretching vibrations has a
maximum at 1942 cmÀ1, a broad band with complicated
shape at 3320–3170 cmÀ1 is due to NH stretching vibra-
tions of ammonia ligand. 13C NMR spectrum of complex
1
contains one doublet at 192.4 ppm, J(CRh) 75.8 Hz. As
1
mentioned above, the high value of J(CRh) is indicative
13C NMR spectrum of the reaction mixture (13C
enriched preparation of starting dicarbonyl complex, sol-
vent MeCN-d3) showed two doublets from carbonyl car-
bons, d 13C 189.8 ppm, 1J(CRh) 72.4 Hz and d 13C
192.2 ppm, 1J(CRh) 80.0 Hz. Comparison of relative
intensity variations of the doublets with variations in
the IR band intensities allowed us to assign these dou-
blets to [Rh(Oxq)(CO)(MeCN)] and [Rh(Oxq)(CO)-
(Me3N)], respectively. Substitution of MeCN and Me3N
ligands for other nitrogen donors transforms these parent
moieties into desired monocarbonyl complexes. For
instance, addition of pyridine to the reaction mixture
results in the appearance of new strong 13C doublet, d
13C 192.2 ppm, 1J(CRh) 78.2 Hz, and severe decrease
or almost complete disappearance of both original dou-
blets. On the action of aliphatic tertiary amines, even
in excess, incomplete Me3N replacement was observed.
The high values of the spin–spin coupling constants,
1J(CRh) > 70 Hz, for observed doublets indicate that in
both parent moieties, [Rh(Oxq)(CO)(MeCN)] and
[Rh(Oxq)(CO)(Me3N)], carbonyl ligand is located in the
trans position to the oxygen atom of the oxiquinolinato
ligand [10,11]. Thus, we can conclude that carbonyl
ligand in the starting dicarbonyl complex is oxidized
selectively in the trans to N position.
of trans to O position of carbonyl group, which is in con-
formity with our conclusion on the structure of the parent
1
monocarbonyl moiety. H spectrum of complex contains a
group of signals from aromatic oxiquinolinato protons in
the region 6.5–8.5 ppm (6H) and a broadened singlet from
ammonia protons at 3.1 ppm (3H). On the basis of elemen-
tal analysis, IR, and NMR data, we formulate this complex
as [Rh(Oxq)(CO)(NH3)] containing NH3 ligand in the trans
position to the nitrogen atom of oxiquinolinato ligand.
The molecular structure of ammonia complex is shown
in Fig. 1. The selected bond lengths and angles are pre-
sented in Table 1.
Selected bond lengths in [Rh(Oxq)(CO)(L)], L = NH3,
PPh3, and P(OPh)3, with the corresponding carbonyl group
frequencies are given in Table 2.
+
Me3NO
MeCN
x
1- )
(
+ CO2
x
+
N
N
N
O
Rh
OC
O
O
Rh
Rh
CO
OC
OC
MeCN
Me3N
According to our preliminary observations the action of
Me3NO on [Rh(Acac)(CO)2] in acetonitrile solution
proceeds in like manner. Addition of one mol of Me3NO
per rhodium results in the oxidation of one carbonyl
Fig. 1. The structure of [Rh(Oxq)(CO)(NH3)] (50% probability
ellipsoids).

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Yu.S. Varshavsky et al. / Journal of Organometallic Chemistry 692 (2007) 5788–5794
Table 1
Table 3
˚
Selected bond lengths (A) and angles (°) for the complex [Rh(Oxq)-
(CO)(NH3)] with estimated standard deviations in parentheses
Spectral parameters of carbonyl groups in [Rh(8-Oxiquinolinato)(CO)(L)]
complexes in THF (*MeCN) solutions
m(CO) (cmÀ1
)
d
13C (ppm)
1J(CRh); 2J(CRhP) (Hz)
˚
Bond lengths (A)
Bond angles (°)
L
Rh(1)–C(1)
Rh(1)–N(1)
Rh(1)–O(1)
Rh(1)–N(2)
C(1)–O(2)
1.786(4)
2.024(3)
2.058(2)
2.080(3)
1.163(4)
C(1)–Rh(1)–N(1)
N(1)–Rh(1)–O(1)
C(1)–Rh(1)–N(2)
O(1)–Rh(1)–N(2)
N(1)–Rh(1)–N(2)
C(1)–Rh(1)–O(1)
O(2)–C(1)–Rh(1)
97.30(14)
81.88(11)
91.72(13)
89.04(10)
170.67(11)
178.34(14)
179.2(3)
NH3
1942
1944
1948
1942
1942
1950
1952
1966
1972
1972
1990
2078, 2004
192.4
192.5
192.2
191.9
192.0
192.2
192.4
192.1
189.8
189.4
189.6
186.5
187.3
75.8
80.5
80.0
79.8
80.0
78.2
72.2; 22.4
70.9; 21.8
72.4
NMe3
NMe*3
NEt3
NBu3
Py
PBu3
PPh3
MeCN*
C8H14
P(OPh)3
CO
73.8
68.7; 29.9
71.8
It is seen that increase of p-acceptor ability of ligand L
when passing from NH3 to P(OPh)3 leads to substantial
decrease of the carbonyl C–O bond length and parallel
increase of the m(CO) frequency. Also it might be noticed
that the phosphite complex has the longest Rh–CO bond.
The lengths of bonds formed by rhodium centre with two
donor atoms of oxiquinolinato ligand vary in the opposite
directions: Rh–N (trans to L) is longest one, whereas Rh–O
(cis to L) is shortest one for L = P(OPh)3. Noteworthy is
the considerable difference between two Rh–N bond
65.8
Within the N-donor part of the series, ligands are ranked
in the expected order, NH3, NR3 < Py < MeCN. The order
of the P-donor ligands, PBu3 < PPh3 < P(OPh)3, is also
quite ordinary. In the middle part of the series, these two
ranges of ligands are intermixed. The relative positions of
ligands in the whole series, NH3, NR3 < Py, PBu3 < PPh3 <
MeCN, C8H14 < P(OPh)3 < CO, apparently are governed
by what can be called their ‘‘net donating ability’’ [16]
resulted from the interplay of their r-donor and p-acceptor
properties. With reference to 13C chemical shifts, the gen-
eral trend is near to opposite: ammonia, amines, PBu3
and PPh3 comprise a group with high d 13C values,
192.5–192.1 ppm, whereas strongest p-acceptors, MeCN,
C8H14, P(OPh)3 and CO, show markedly lower d 13C val-
ues, 189.8–186.5 ppm. As would be expected, the position
of the olefin ligand, C8H14, is close to the week r-donor/
strong p-acceptor ends of both, m(CO) and d 13C, series.
The endpoints of the whole series of studied ligands
correspond to the ligands of antipodal p-acceptor proper-
ties: ammonia, ligand with no p-acceptor ability, and
carbonyl group, the strongest one among the p-acceptor
ligands. It should be remarked that the 1J(CRh) values
for complexes of NH3 and aliphatic amines are considerably
higher as compared with complexes of more p-acceptor
ligands.
3
˚
˚
lengths in the ammonia complex: 2.080(3) A for the sp
hybridized ammonia nitrogen and 2.024(3) A for the sp
2
hybridized oxiquinolinato nitrogen which is capable to p
dative interaction with rhodium centre. DFT calculation
made by Sizova [15] demonstrated the different order of
these bonds in terms of Wiberg bond indexes: 0.333 for
Rh–N(ammonia) against 0.397 for Rh–N(oxiquinolinato);
the calculated bond lengths were both overestimated,
˚
2.151 and 2.088 A, respectively, but with remainder
˚
˚
(0.063 A) close to the experimental value (0.056 A).
2.3. Carbonyl group frequencies and 13C chemical shifts in
the series of [Rh(Oxq)(CO)(L)] complexes
Ammonia ligand in [Rh(Oxq)(CO)(NH3)] is more or less
easily replaced by other N-donors and cyclooctene in THF
solutions; P-donors replace it readily. We used these reac-
tions to measure IR and 13C NMR spectra of the
[Rh(Oxq)(CO)(L)] complexes in situ, without isolation of
reaction products. The data so obtained are given in Table
3; spectral parameters of parent dicarbonyl complex
(L = CO) are included as well.
The segmental examples of rhodium(I) complexes con-
taining carbonyl ligand in the cis position to two mutually
trans N-donors were mentioned in the literature. The spec-
tral characteristics we report here for some complexes of
this structural type agree well with the data published pre-
It can be seen from these data that m(CO) frequencies
increase markedly in order of increasing p-acceptor and
decreasing r-donor ability of ligand L from NH3 to CO.
Table 2
Selected bond lengths in the crystalline [Rh(Oxq)(CO)(L)] complexes and related carbonyl stretching frequencies (THF solutions)
m(CO) (cmÀ1) (this work)
r(C–O) (A)
r(Rh–C) (A)
r(Rh–N) (A)
r(Rh–O) (A)
Reference
˚
˚
˚
˚
L
NH3
PPha3
P(OPh)3
a
1942
1966
1992
1.163(4)
1.155(11)
1.146
1.786(4)
1.786(9)
1.813(3)
2.024(3)b
2.098(9)
2.097(2)
2.058(2)
2.042(5)
2.022(2)
This work
[13]
[14]
There are two X-ray studies of [Rh(Oxq)(CO)(PPh3)], published in 1971 [12] and 1981 [13]. We present here the data from the latest one.
8-Oxiquinolinato nitrogen.
b

Yu.S. Varshavsky et al. / Journal of Organometallic Chemistry 692 (2007) 5788–5794
5791
viously [17–19]. Notice also the parallel trends of the spec-
tral parameters in two closely related pairs of complexes,
[Rh(Oxq)(CO)2] vs. [Rh(Oxq)(CO)(Py)] (see Table 3) and
[Rh(Py)Cl(CO)2] vs. [Rh(Py)2Cl(CO)] [18].
of Rh(Acac)(CO)2 in benzene. IR spectra were recorded on
a Specord 75 IR instrument (CaF2 windows). NMR spec-
1
tra (300.1 MHz H, 121.5 MHz 31P {1H}, and 75.5 MHz
13C {1H}) were measured on a Bruker DPX-300 spectrom-
eter in MeCN-d3 and THF-d8 as solvents. The 1H chemical
shifts were measured with solvent residual protons as inter-
nal standard, d 1H 1.93 ppm for MeCN; d 1H 1.72 ppm for
THF. The 13C chemical shifts were measured using 13CO
enriched samples with solvent 13C as internal standard (d
13C 118.10 ppm for MeCN; d 13C 25.26 ppm for THF).
The 31P chemical shifts were measured with 85% phospho-
ric acid as external standard, d 31P = 0.0 ppm. Elemental
analyses were performed with Hewlett–Packard 185
microanalyzer.
3. Concluding remarks
The use of the carbonyl ligand as a spectral probe
responding to variations in the electronic situation at
the metal centre under the effect of its ligand surrounding,
oxidation state, etc. has a long history. Both the CO
stretching frequencies and carbonyl 13C chemical shifts
were employed to build experimental scales of r-donor/
p-acceptor ability (or net donating ability) of ligands.
These scales of ligand electronic parameters, from the first
ones proposed in 1960–70s, e.g. [20] and including latest
one advanced in a new century [21], are reviewed and
analyzed in the comprehensive analytical review [16].
Here, we put forward one more scale based on the spec-
tral parameters of a series of rhodium(I) complexes of
the general formula [Rh(Oxq)(CO)(L)]. We believe this
scale attractive because:
4.1. Synthesis of [Rh(Oxq)(CO)2]
To the solution of [Rh(Acac)(CO)2] (0.516 g, 2.0 mmol)
in benzene (20 ml) the solution of 8-hydroxyquinoline
(0.304 g, 2.1 mmol) in benzene (5 ml) was added. The dark
brown crystals with violet lustre appeared immediately. In
30 min the crystals were collected by filtration, washed with
hexane and dried under reduced pressure. Yield: 0.576 g
(95%). The product was identified by IR and 13C NMR
as [Rh(Oxq)(CO)2]. IR (CHCl3): 2084 and 2010 cmÀ1
[25,26]. The 13C-enriched complex was prepared by the
same way using [Rh(Acac)(13CO)2]. 13C NMR (CDCl3):
184.5 ppm, 1J(CRh) 71.4 Hz and 186.0 ppm, 1J(CRh)
(i) It combines ligands of different classes, like N- and P-
donors, olefins, CO, and seems to be prospective with
regard to other ligands as well, which are incapable to
replace carbonyl group directly from [Rh(Bi-
dent)(CO)2] complexes, but can be introduced into
the [Rh(Bident)(CO)(L)] complexes by the indirect
method we described here.
(ii) Spanning a wide range of r-donor/p-acceptor prop-
erties of ligands L, the scale includes ammonia ligand,
which seems to provide a natural zero point on the
scale of p-acceptor ability.
67.6 Hz [27]. In THF m(CO) 2078 and 2004 cmÀ1 13C
;
NMR (THF-d8): 186.5 ppm, 1J(CRh) 71.8 Hz and
1
187.3 ppm, J(CRh) 65.8 Hz.
4.2. The interaction of [Rh(Oxq)(CO)2] with Me3NO
(iii) Like the scale [21], it is based on monocarbonyl com-
plexes and thus makes it possible to use immediately
the experimentally measured m(CO) values without
more or less approximate calculations of force con-
stants. Notice that the proposed scale is based on
the series of compounds, which differ from each other
in a sole ligand L, not in a pair of mutually trans dis-
posed ligands. This may be of some importance tak-
ing into account possible effect of changes in the L
trans to L interaction.
To a suspension of [Rh(Oxq)(CO)2] (0.303 g, 1.0 mmol)
in acetonitrile (10 ml) a fresh prepared solution of
Me3NO Æ 2H2O (0.111 g, 1.0 mmol) in acetonitrile (18 ml)
was added dropwise on stirring at 0 °C. The dark suspen-
sion gradually turned into brownish-yellow solution,
which was then stirred throughout 1 h at room tempera-
ture. IR of the reaction mixture thus obtained (solution
I) in the carbonyl stretching area: m(CO) 1972 and
1948 cmÀ1; the last band is more intense. The intensity
of carbonyl bands in the spectrum of solution I remained
unchanged for one to two days. Removal of solvent from
a part of solution I (5 ml) yielded black solid with metallic
lustre; this product, being freshly prepared, is soluble in
MeCN and THF. In the IR spectrum of its solution in
MeCN, the band at 1972 cmÀ1 is more intense, and the
band at 1948 cmÀ1 is less intense then in solution I. IR
spectrum of this product in THF shows only one m(CO)
band at 1944 cmÀ1. The 13C enriched sample of reaction
mixture (solution II) was prepared in a similar man-
ner from 13C enriched [Rh(Oxq)(13CO)2]. 13C NMR:
(MeCN-d3) 189.8 ppm, 1J(CRh) 72.4 Hz and 192.2
ppm, 1J(CRh) 80.0 Hz; (THF-d8) 192.5 ppm, 1J(CRh)
80.5 Hz.
4. Experimental
All operations were carried out in atmosphere of dry
argon using classical Schlenk techniques. All solvents were
purified according to standard procedures [22]. Deuterated
solvents were stored over Al2O3 and distilled prior to use.
Gaseous NH3 was prepared by standard method [23].
Me3NO Æ 2H2O was used as purchased from ‘‘Avocado
Research Chemicals Ltd’’. [Rh(Acac)(CO)2] was prepared
by published procedure [24]. The 13C-enriched complex
was prepared by action of 50% enriched 13CO on a solution

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Yu.S. Varshavsky et al. / Journal of Organometallic Chemistry 692 (2007) 5788–5794
4.3. Substitution reactions
m(CO) 1972 cmÀ1 (THF). The analogous operation was
performed with a portion of the solution II (molar ratio
1
4.3.1. Interaction with NMe3
C8H14:Rh ꢀ 3). 13C NMR (THF-d8): 189.4 ppm, J(CRh)
To a portion (4 ml, 0.14 mmol Rh) of the solution I (see
Section 4.2) the solution of NMe3 (0.017 g, 0.29 mmol) in
MeCN (0.2 ml) was added at 0 °C (molar ratio
NMe3:Rh ꢀ 2). In resulting reaction mixture the m(CO)
band at 1948 cmÀ1 increased in relative intensity as com-
pared to the spectrum of solution I. When the large excess
of NMe3 was added (molar ratio NMe3:Rh ꢀ 10), only the
strong band at 1948 cmÀ1 remained. Upon replacement of
solvent by THF, m(CO) band at 1944 cmÀ1 appeared. Upon
action of the large excess of NMe3 on solution II (molar
ratio NMe3:Rh ꢀ 10), 13C NMR (MeCN-d3): 192.2 ppm,
73.8 Hz. At the molar ratio C8H14:Rh = 1, 189.4 ppm,
1J(CRh) 73.8 Hz and 192.5 ppm, J(CRh) 80.5 Hz.
1
4.4. [Rh(Oxq)(CO)(NH3)]
Through the reaction mixture obtained like the solution
I from [Rh(Oxq)(CO)2] (0.727 g, 2.4 mmol) in MeCN
(15 ml) and Me3NO Æ 2H2O (0.266 g, 2.4 mmol) in MeCN
(42 ml) a stream of ammonia gas was passed at 0 °C during
0.5 h. A light-yellow crystalline solid precipitated gradu-
ally. The reaction mixture was left to stand for 1 h, and
then the precipitate was collected by filtration under argon,
washed with MeCN and dried under reduced pressure.
Yield: 0.396 g (56%). After concentration of mother liquid
to 5 ml, 0.050 g of product was filtered more; total yield
0.446 g (64%). Anal. Calc. for C10H9N2O2Rh: C, 41.12;
H, 3.08; N, 9.59; Rh, 35.24. Found: C, 41.10; H, 3.31; N,
9.72; Rh, 35.84%. The crystalline complex is stable on
keeping under argon atmosphere. The complex is soluble
in acetone, ethanol, chloroform, THF, but only THF solu-
tion is sufficiently stable (under inert atmosphere). IR
(THF): m(CO) 1942 cmÀ1, m(NH) 3320–3170 cmÀ1 (broad).
1J(CRh) 80.0 Hz; (THF-d8) 192.5 ppm, J(CRh) 80.5 Hz.
1
4.3.2. Interaction with NBu3
To a portion of the solution I (4 ml, 0.14 mmol Rh)
NBu3 (0.263 g, 1.42 mmol) was added (molar ratio
NBu3:Rh = 10). Yellowish-brown solution was obtained.
After 18 h IR (MeCN): m(CO) 1972 cmÀ1 (weak) and
1948 cmÀ1 (strong). On removal of solvent under reduced
pressure yellowish-brown residue was obtained and then
dissolved in THF (3 ml). IR: m(CO) 1942 cmÀ1 (strong).
The analogous operation was performed with a portion
of the solution II (molar ratio NBu3:Rh = 10). 13C NMR
(THF-d8): 192.5 ppm, 1J(CRh) 80.5 Hz (weak) and
1H NMR (THF-d8): a group of signals in the region d H
1
6.5–8.5 ppm (oxiquinolinato protons, 6H), a broadened
singlet at d 1H 3.1 ppm (NH3, 3H). For 13C NMR measure-
ment was used the sample prepared by the same way from
13C enriched [Rh(Oxq)(CO)2]. 13C NMR (THF-d8):
1
192.0 ppm, J(CRh) 80.0 Hz.
4.3.3. Interaction with pyridine
1
To a portion of the solution I (4 ml, 0.14 mmol Rh) pyr-
idine (0.023 g, 0.21 mmol) was added (molar ratio
Py:Rh = 1.5). After 1 h MeCN was removed under reduced
pressure. Yellowish-brown residue was obtained and then
dissolved in MeCN or THF. IR: m(CO) 1954 cmÀ1
(MeCN); 1950 cmÀ1 (THF). The analogous operation
was performed with a portion of the solution II (molar
ratio Py:Rh = 1.5). 13C NMR (MeCN-d3): 191.8 ppm,
192.4 ppm, J(CRh) 75.8 Hz.
4.5. Ammonia ligand replacement from
[Rh(Oxq)(CO)(NH3)]
4.5.1. Interaction with NEt3
To the solution of [Rh(Oxq)(CO)(NH3)] (0.015 g,
0.05 mmol) in THF (2 ml) NEt3 (0.010 g, 0.1 mmol) was
added (molar ratio NEt3:Rh = 2). After 1 h IR: m(CO)
1J(CRh) 78.8 Hz; (THF-d8) 192.2 ppm, J(CRh) 78.2 Hz.
1
1942 cmÀ1
.
13C NMR (THF-d8): 191.9 ppm, 1J(CRh)
4.3.4. Interaction with PBu3
79.8 Hz (very weak) and 192.4 ppm, 1J(CRh) 75.8 Hz
To a portion of the solution I (4 ml, 0.14 mmol Rh) PBu3
(0.028 g, 0.14 mmol) was added (molar ratio PBu3:Rh = 1).
After 1 h MeCN was removed under reduced pressure, and
yellowish-brown residue was dissolved in MeCN or THF.
IR: m(CO) 1954 cmÀ1 (MeCN); m(CO) 1952 cmÀ1 (THF).
The analogous operation was performed with a portion of
the solution II. At the molar ratio PBu3:Rh = 0.75, 13C
(starting complex).
4.5.2. Interaction with NBu3
To the solution of [Rh(Oxq)(CO)(NH3)] (0.015 g,
0.05 mmol) in THF (2 ml) NBu3 (0.018 g, 0.1 mmol) was
added (molar ratio NBu3:Rh = 2). After 1 h IR: m(CO)
1942 cmÀ1. The analogous operation was performed with
the solution of 13C enriched [Rh(Oxq)(CO)(NH3)] (molar
ratio NBu3:Rh = 10). 13C NMR (THF-d8): 192.0 ppm,
1
2
NMR (THF-d8): 192.4 ppm, J(CRh) 72.2 Hz, J(CRhP)
1
22.4 Hz and weak signal 192.5 ppm, J(CRh) 80.5 Hz.
1J(CRh) 80.0 Hz (week) and 192.4 ppm, J(CRh) 75.8 Hz
1
4.3.5. Interaction with cyclooctene
(starting complex).
To a portion of the solution I (4 ml, 0.14 mmol Rh)
C8H14 (0.046 g, 0.4 mmol) was added (molar ratio
C8H14:Rh ꢀ 3). After 1 h solvent was removed under
reduced pressure, and yellowish-brown residue was dis-
solved in MeCN or THF. IR: m(CO) 1974 cmÀ1 (MeCN);
4.5.3. Interaction with pyridine
To the solution of [Rh(Oxq)(CO)(NH3)] (0.015 g,
0.05 mmol) in THF (2 ml) pyridine (0.006 g, 0.076 mmol)
was added (molar ratio Py:Rh = 1.5). After removal of

Yu.S. Varshavsky et al. / Journal of Organometallic Chemistry 692 (2007) 5788–5794
5793
the solvent under reduced pressure, the residue was dis-
1972 and 1942 cmÀ1
.
13C NMR (THF-d8): 189.4 ppm,
1
solved in THF. IR: m(CO) 1950 cmÀ1
.
13C NMR (THF-
1J(CRh) 73.8 Hz (week) and 192.4 ppm, J(CRh) 75.8 Hz
(starting complex). At the molar ratio C8H14:Rh = 3. After
1 h IR: m(CO) 1972 cmÀ1. In 13C NMR spectrum the same
doublets, but of close relative intensities, were observed. At
the molar ratio C8H14:Rh ꢀ 10, 13C NMR (THF-d8):
189.4 ppm, 1J(CRh) 73.8 Hz. Spectral data agree with
reported early for [Rh(Oxq)(CO)(C8H14)] [29].
1
d8): 192.2 ppm, J(CRh) 78.2 Hz.
4.5.3.1. Direct action of pyridine on [Rh(Oxq)
(CO)2]. To the suspension of [Rh(Oxq)(CO)2] (0.013 g,
0.043 mmol) in toluene (5 ml) pyridine (0.004 g, 0.05 mmol)
(molar ratio Py:Rh ꢀ 1.2) was added. After about 3 h at
25 °C in the IR spectrum of reaction mixture only m(CO)
bands of starting [Rh(Oxq)(CO)2] (2078, 2002 cmÀ1) were
observed. After heating (1 h at 80 °C), in the IR spectrum
of reaction mixture along with m(CO) bands of
[Rh(Oxq)(CO)2] a new band at 1950 cmÀ1 appeared. At fur-
ther heating all carbonyl bands became weak. At heating
[Rh(Oxq)(CO)2] with excess pyridine (molar ratio:
Py:Rh = 3) intensities of all m(CO) bands decreased
rapidly.
4.6. X-ray crystal structure determination
Crystal of [Rh(Oxq)(CO)(NH3)] (C10H9N2O2Rh,
M = 292.10) orthorhombic, space group P212121, at T =
˚
˚
˚
100 K: a = 4.4251(8) A, b = 13.774(2) A, c = 15.956(3) A,
3
V = 972.5(3) A , Z = 4, F(000) = 576, dcalc = 1.995 g/cm3,
˚
l = 1.734 mmÀ1. Data were collected on a Bruker three-
circle diffractometer equipped with a SMART 1K CCD
detector (k(Mo Ka)-radiation, graphite monochromator,
u and x scan mode, hmax = 27.6°) and corrected for Lor-
entz and polarization effects and for absorption [30]. The
structure was determined by direct methods and refined
by a full-matrix least-squares technique on F2 with aniso-
tropic displacement parameters for all non-hydrogen
atoms. The absolute structure was objectively determined
by the refinement of Flack parameter which has become
equal to 0.04(4). The hydrogen atoms were placed in calcu-
lated positions and refined in riding mode with fixed ther-
mal parameters. The final R-factors are R1 = 0.0265 for
2029 independent reflections with I > 2r(I) and
wR2 = 0.0465 for all 2229 independent reflections. All cal-
culations were carried out using the SHELXTL-PLUS program
(PC Version 5.10) [31].
4.5.4. Interaction with PBu3
To the solution of [Rh(Oxq)(CO)(NH3)] (0.015 g,
0.05 mmol) in THF (2 ml) PBu3 (0.008 g, 0.04 mmol) was
added; molar ratio PBu3:Rh = 0.8. IR: m(CO) 1952 cmÀ1
.
31P NMR (THF-d8): 34.1 ppm, 1J(PRh) 156.0 Hz. 13C
NMR (THF-d8): 192.4 ppm, 1J(CRh) 72.2, 2J(CRhP)
1
22.4 Hz and 192.4 ppm, J(CRh) 75.8 Hz (week, starting
complex). Spectral data agree with 13C NMR parameters
of [Rh(Oxq)(CO)(PBu3)] obtained by action of PBu3 on
1
[Rh(Oxq)(CO)2]. 13C NMR (CDCl3): 190.9 ppm, J(CRh)
2
72.4, J(CRhP) 22.6 Hz.
4.5.5. Interaction with PPh3
To the solution of [Rh(Oxq)(CO)(NH3)] (0.015 g,
0.05 mmol) in THF (2 ml) PPh3 (0.0104 g, 0.04 mmol) in
THF (0.5 ml) was added (molar ratio PPh3:Rh = 0.8). IR:
Acknowledgement
1
m(CO) 1966 cmÀ1
.
31P NMR (THF-d8): 42.4 ppm, J(PRh)
166.3 Hz. 13C NMR (THF-d8): 192.1 ppm, 1J(CRh)
71.3 Hz, 2J(CRhP) 21.8 Hz and 192.4 ppm, 1J(CRh)
75.8 Hz (week, starting complex). Spectral data agree with
reported early for [Rh(Oxq)(CO)(PPh3)] [27a,28].
Financial support from the Russian Foundation for Ba-
sic Research (Project No. 05-03-32463) is gratefully
acknowledged.
Appendix A. Supplementary material
4.5.6. Interaction with P(OPh)3
To the solution of [Rh(Oxq)(CO)(NH3)] (0.015 g,
0.05 mmol) in THF (2 ml) P(OPh)3 (0.0124 g, 0.04 mmol)
was added (molar ratio P(OPh)3:Rh = 0.8). IR: m(CO)
CCDC 651127 contains the supplementary crystallo-
graphic data for [Rh(Oxq)(CO)(NH3)]. These data can be
obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_re-
quest/cif. Supplementary data associated with this article
can be found, in the online version, at doi:10.1016/
j.jorganchem.2007.09.022.
1990 cmÀ1
.
31P NMR (THF-d8): 126.2 ppm, 1J(PRh)
282.2 Hz. 13C NMR (THF-d8): 189.4 ppm, 1J(CRh)
69.0 Hz, 2J(CRhP) 29.9 Hz and.192.4 ppm, 1J(CRh)
75.8 Hz (week, starting complex). Spectral data agree with
31P NMR [14] and with 13C NMR (CDCl3) for [Rh(Oxq)(-
CO)(P(OPh)3)] obtained by action of P(OPh)3 on
[Rh(Oxq)(CO)2]: 188.0 ppm, 1J(CRh) 70.0 Hz, 2J(CRhP)
29.4 Hz.
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