A facile route to carbonylhalogenometal complexes (M = Rh, Ir, Ru, Pt) by dimethylformamide decarbonylation

Article abstract of DOI:10.1002/1099-0682(200109)2001:9<2327::AID-EJIC2327>3.0.CO;2-D

Dimethyl formamide (DMF) can be a convenient source of the carbonyl ligand in the coordination chemistry of rhodium, ruthenium, iridium, and platinum. We have undertaken a thorough study concerning the course of this reaction. In a first step, DMF-containing complexes are produced, which is usually accompanied by chloride redistribution. Then, upon refluxing, carbonyl species in the same oxidation state are obtained, presumably as a result of HCl-mediated DMF decomposition. Provided that water levels are kept low, reduction can occur to provide the complexes [NH₂(CH₃)₂][RhCl₂(CO) ₂], [NH₂(CH₃)₂][RuCl₃(CO) ₂(DMF)], [RuCl₂(CO)₂(DMF)₂], and [NH₂(CH₃)₂][IrCl₂(CO) ₂]. In the case of platinum, reduction is not effective and [NH₂(CH₃)₂][PtCl₃(CO)] is obtained. No carbonylpalladium species can be synthesized in this way, the reaction producing copious amounts of colloidal metal. Adding phosphanes to these chlorocarbonyl-containing solutions allows easy, one-step syntheses of a variety of complexes.

Full text of DOI:10.1002/1099-0682(200109)2001:9<2327::AID-EJIC2327>3.0.CO;2-D

FULL PAPER
A Facile Route to Carbonylhalogenometal Complexes (M ؍ Rh, Ir, Ru, Pt) by
Dimethylformamide Decarbonylation
Philippe Serp,[a] Marc Hernandez,[b] Brigitte Richard,[a] and Philippe Kalck*[a]
Keywords: Amides / Carbonylations / Carbonyl complexes / Rhodium
Dimethyl formamide (DMF) can be a convenient source of
the carbonyl ligand in the coordination chemistry of rhodium,
ruthenium, iridium, and platinum. We have undertaken a
tion can occur to provide the complexes [NH2(CH3)2]-
[RhCl2(CO)2], [NH2(CH3)2][RuCl3(CO)2(DMF)], [RuCl2(CO)2-
(DMF)2], and [NH2(CH3)2][IrCl2(CO)2]. In the case of plat-
thorough study concerning the course of this reaction. In a inum, reduction is not effective and [NH2(CH3)2][PtCl3(CO)]
first step, DMF-containing complexes are produced, which is
usually accompanied by chloride redistribution. Then, upon
refluxing, carbonyl species in the same oxidation state are
is obtained. No carbonylpalladium species can be synthe-
sized in this way, the reaction producing copious amounts of
colloidal metal. Adding phosphanes to these chlorocarbonyl-
obtained, presumably as a result of HCl-mediated DMF de- containing solutions allows easy, one-step syntheses of a
composition. Provided that water levels are kept low, reduc-
variety of complexes.
ordination by the solvent could affect the catalyst reactivity.
Recently, DMF has been shown to be a ligand of palladium
and copper in the course of the oxidation of an alkene to
the corresponding ketone.[4] Finally, Mitsudo et al. have de-
veloped the direct hydroamidation of alkenes by formam-
ides using ruthenium catalysts.[5] A CϪH formyl activation
step is invoked in the catalytic cycle.
Introduction
Because of its properties (stable, aprotic, polar, and high
boiling point), DMF has been employed as a solvent in a
wide variety of catalytic reactions including hydrogenations,
hydroformylations,
carbonylations,
and
syn-gas
reactions.[1Ϫ17] Nevertheless, in some cases, its implication
as a reactant has been observed and solvent effects that do
not seem to be directly linked with its polarity have been
noticed, particularly when the catalytic reaction involves
carbon monoxide or further reactions with carbonyl com-
pounds. Thus, in the course of an investigation of the ruth-
enium-catalyzed hydroesterification of ethylene, the results
of which have been reported previously,[1,2] a strong solvent
effect was noted. In this reaction, the solvent could be in-
volved in the formation of the active species; in particular,
the complex [PPN][RuCl3(CO)2(DMF)] has been isolated
after reaction of the precatalyst [PPN][RuCl3(CO)3] with
boiling DMF.[1] In the hydroformylation of formaldehyde
In the transfer hydrogenation of -glucose carried out in
DMF with [RuCl2(PPh3)3] as a catalyst, a deactivation of
the catalyst has been observed.[6,7] At 123 °C, the starting
complex was transformed into the catalytically inactive spe-
cies [RuCl2(CO)(DMF)(PPh3)2], for which the authors as-
sumed that a decarbonylation of the solvent had occurred
to generate the carbonyl ligand. In the case of ethylene
hydroesterification starting from RuCl3·xH2O, Petit et al.[8]
proposed a partial decomposition of DMF to explain the
production of [NMe4]I, which involves iodomethane, used
to promote the reaction, and dimethylamine produced by
DMF decomposition. For the decarbonylation of alkyl
formates in the presence of chloride salts of osmium,[9]
a
using
a
rhodium catalyst of the general formula
positive effect of the solvent has also been noticed. In this
case, a catalytic decomposition of DMF to give CO and
dimethylamine was proposed; the production of the amine,
which can catalyze the decarbonylation of alkyl formates,
would seem to provide a good explanation of this effect
since formates are usually decomposed in basic media. In
this latter study, no information was given regarding the
osmium species present at the end of the reaction.
Apart from the aforementioned catalytic reactions, a
careful examination of the literature shows that the use of
DMF as a carbonylating agent for the synthesis of organo-
metallic compounds has not yet been systematically exam-
ined. Even though it has long been known that transition
metal salts can give well-characterized carbonyl complexes,
[RhCl(CO)L2] (L: tertiary phosphane ligand), a dramatic
effect has been noticed when using DMF as the solvent.[3]
This represents an unusual solvent dependence, particularly
as the hydroformylation of alkenes can normally be carried
out in almost any solvent. The authors postulated that co-
[a]
`
Laboratoire de Catalyse, Chimie Fine et Polymeres, Ecole
´
´
Nationale Superieure d’Ingenieurs en Arts Chimiques et
Technologiques,
118, route de Narbonne, 31077 Toulouse Cedex, France
Fax: (internat.) ϩ 33-5/62885600
E-mail: pkalck@ensct.fr
[b]
Department of Chemistry, University of Victoria,
P. O. Box 3065, Victoria, B.C. V8W 36V, Canada
Eur. J. Inorg. Chem. 2001, 2327Ϫ2336
WILEY-VCH Verlag GmbH, 69451 Weinheim, 2001
1434Ϫ1948/01/0909Ϫ2327 $ 17.50ϩ.50/0
2327

P. Serp, M. Hernandez, B. Richard, P. Kalck
FULL PAPER
or in some cases carbonylhydrido complexes, upon treat-
ment with alcohols, acyl halides, aldehydes, or formic acid,
little is known about the decarbonylation of DMF. Rusina
Results and Discussion
A. Reaction of RhCl3·3H2O with DMF
and Vlcek were the first to report such a reaction,[18] study-
´
ing the formation of carbonyl complexes of the platinum
group metals and using DMF as the CO source. Thus, the
complex [RhCl(CO)(PPh3)2] was prepared by refluxing a
solution of RhCl3 in DMF in the presence of triphenyl-
Infrared Monitoring of the Reduction and Identification of
Several Intermediate Species
When RhCl3·3H2O is refluxed in commercially available
phosphane. Later, Varshavskii and Cherkasova[19] prepared N,N-dimethylformamide, the color of the solution changes
the acetylacetonato complex [Rh(acac)(CO)2] by two differ- from dark red to orange within 30 min. If the heating is
ent routes. The first was similar to that employed by Rusina continued, some metallic rhodium begins to precipitate, in-
´
and Vlcek, involving a one-pot reaction of the salt and dicating a complete reduction of the salt. IR monitoring of
acetylacetone in boiling DMF (procedure A). The second the reaction shows that, after 2 min, the dark-red solution
route (procedure B) required the prior formation of car- contains a carbonyl species at low concentration since a
bonyl-containing rhodium intermediates obtained by heat- weak carbonyl band is detected at 2092 cmϪ1. After 5 min,
ing RhCl3 in DMF, which were then treated with acetylacet- as the solution lightens, two new bands with the same in-
one to give [Rh(acac)(CO)2]. The same group has proposed tensity appear beside the band at 2092 cmϪ1, one at
that in the case of RhCl3·3H2O and H2PtCl6, the 2063 cmϪ1 and the other at 1984 cmϪ1. After 15 min, the
[RhCl2(CO)2]Ϫ and [PtCl3(CO)]Ϫ anions, respectively, are band at 2092 cmϪ1 has disappeared and only the two strong
produced by DMF decarbonylation.[20] Nevertheless, no ex- bands at 2063 and 1984 cmϪ1, characteristic of the
planation was given concerning the course of the reaction.
Since these first synthetic results, other β-diketonato constant after 30 min of reaction.
[RhCl2(CO)2]Ϫ anion, are present; their intensity remains
complexes of rhodium have been prepared according to
Direct evaporation of the solvent from the final orange
procedure A.[21Ϫ24] Vaska’s compound [IrCl(CO)(PPh3)2] solution leads to the deposition of large amounts of black
has also been prepared by this procedure.[25] The same insoluble rhodium species along with the complex
method was used to prepare other carbonylphosphane-con- [NH2(CH3)2][RhCl2(CO)2] and the salt [NH2(CH3)2]Cl. Al-
taining iridium complexes.[26,27] Decarbonylation of DMF ternatively, addition of one molar equivalent of [AsPh4]Cl
has also been used for the preparation of ruthenium species affords [AsPh4][RhCl2(CO)2] in 70% yield after recrystal-
containing bipyridyl ligands of the general formula lization of the crude product from dichloromethane/n-hept-
[Ru(CO)L(bipy)2]nϩ starting from RuCl3·3H2O.[28Ϫ33] In ane (see Table 1).
most of these cases, procedure A is employed and very long
In order to identify the first carbonyl intermediate species
reaction times are required. Recently, Forster et al.[34] have giving a νCO band at 2092 cmϪ1, several experiments were
reported
a
1-h
synthesis
of
the
complex performed that showed this compound to be
[RuCl(CO)(LϪLЈ)2]ϩ (LϪLЈ: pyridyltriazole) using proced- [RhCl4(CO)(DMF)]Ϫ, as detailed below. A precedent for
ure B. The 2-methylimidazole-containing complex trans- this anion is the related complex [RhCl4(CO)(CH3OH)]Ϫ,
[Ru(CO)(DMF)(2-MeIm)4][CF3SO3]3 was synthesized from which gives a νCO band at 2103 cm .
Ϫ1 [39] This rhodium(III)
[Ru(DMF)6][CF3SO3]3 by a reaction involving abstraction intermediate is depicted in Scheme 1, together with all the
of CO from DMF,[35] the required dimethylamine co-prod- isolated intermediates that can be proposed as being in-
uct having been detected. The decarbonylation of DMF has volved in the formation of [RhCl2(CO)2]Ϫ from
also been investigated with the molybdenum complex trans- RhCl3·3H2O through DMF decarbonylation.
[Mo(N2)2(dppe)2] [dppe: bis(diphenylphosphanyl)ethane] in
In the first of the aforementioned experiments, direct
refluxing benzene.[36] The products of this reaction are the FABϪ mass-spectrometric analysis of the dark-red DMF
complex [Mo(CO)(DMF)(dppe)2] and dimethylamine, solution obtained after 2 min revealed only the presence of
which was detected by GLC. The authors proposed a mech- two main fragments, one at m/z ϭ 245 corresponding to
anism that is exactly the reverse process of the carbonyl- [RhCl4]Ϫ and the other at m/z ϭ 210 due to [RhCl3]Ϫ. To
ation of amines by noble metals. The complex [Mo- intercept this first intermediate, 1 mol-equiv. of [AsPh4]Cl
(CO)(HCONEt2)(dppe)2] has been similarly prepared start- was added to this solution, the solvent was evaporated, and
ing from diethylformamide. Carbon monoxide and di- the product was precipitated by adding acetone/n-heptane.
methylamine have also been found as the sole products of A reddish powder was obtained, which did not show any
the decomposition of DMF photocatalyzed by a ruthenium carbonylϪrhodium band in its IR spectrum, but rather a
compound containing a porphyrin ligand.[37]
broad CO band at 1641 cmϪ1 characteristic of coordinated
In the course of our investigations on noble metal cata- DMF (free DMF: 1673 cmϪ1). As mass-spectrometric ana-
lyzed carbonylation reactions, we have undertaken a com- lysis suggested that chloro-rich species were produced at an
prehensive study of the reactions of RhCl3·3H2O, early stage of the reaction and that direct isolation of the
IrCl3·3H2O, RuCl3·3H2O, K2PtCl4, PdCl2, and Na2PdCl6 first carbonyl compound was not possible, probably due to
with DMF and other amides. Preliminary results of our in- its low concentration and the lability of the CO ligand un-
vestigations of the reactions of RhCl3·3H2O and der our experimental conditions, we investigated the effect
IrCl3·3H2O with DMF have already been reported.[38]
of an excess of chloride with regard to the stabilization of
2328
Eur. J. Inorg. Chem. 2001, 2327Ϫ2336

A Facile Route to Carbonylhalogenometal Complexes
FULL PAPER
ing cationic complexes, which should presumably have a
lower chlorine content. After treating RhCl3·3H2O with
DMF at room temperature for 16 h, we isolated a cationic
species that could clearly be formulated as [RhCl2-
(DMF)4]Cl. This complex shows one νCO band at 1639
cmϪ1 (m, broad) in its IR spectrum, which is consistent
with a D4h group symmetry, the four coordinated DMF
ligands lying in the equatorial plane.
A second cationic complex was isolated as a blue by-
product from the RhCl3·3H2O solution in DMF after heat-
ing with an excess of KCl. After 15 min,
[NH2(CH3)2]2[RhCl5(DMF)] precipitated; after this had
been filtered off, the blue species was obtained by slow crys-
tallization from the filtrate. Positive-mode electrospray MS
data of the blue material showed that no chloro ligands
were present, although the assignment of the more intense
peaks at m/z ϭ 280.9, 340.8, 415.0, and 502.8 remains un-
certain due to rather facile loss of the coordinated DMF.
The presence of one νCO band at 1655 cmϪ1 in the IR spec-
trum due to the DMF ligands, and of peaks corresponding
to coordinated DMF {in D2O solution: δ ϭ 7.80 [s, 1 H,
Scheme 1. General reaction pathway for the generation of HCON(CH3)2], 2.88 and 2.73 [s, 3 H, HCON(CH3)2]} in
[RhCl2(CO)2]Ϫ from RhCl3·3H2O and DMF
the 1H NMR spectrum, leads us to propose an
[Rh(DMF)6]3ϩ structure for this complex. The analogous
ruthenium complex [Ru(DMF)6]nϩ (n ϭ 2, 3) has recently
intermediate species. In the presence of 5Ϫ10 mol-equiv. of been characterized.[41] This [Rh(DMF)6]3ϩ complex, for
KCl, rapid precipitation of the violet complex which the counterions are light, as shown by FAB-MS
[NH2(CH3)2]2[RhCl5(DMF)] was observed upon refluxing (negative mode), can be formulated as [Rh(DMF)6]Cl3 and
RhCl3·3H2O solutions in DMF. Further heating of the re- can be expected to react with an excess of ClϪ anions to
action mixture led to the quick re-dissolution of this spe- afford the anionic species [RhCl5(DMF)]2Ϫ. The various in-
cies, and pure [AsPh4][RhCl2(CO)2] was obtained from the termediate cationic rhodium species that have been isolated
orange solution by adding [AsPh4]Cl after 25 min of reac- are reported in Table 1.
tion. Therefore, the presence of excess of ClϪ in the medium
does not change the outcome of the reaction but allows
trapping of [NH2(CH3)2]2[RhCl5(DMF)]. The correspond-
ing aqua anion [RhCl5(H2O)]2Ϫ has been reported to be the
predominant chlororhodium(III) complex present in hydro-
chloric acid solutions of RhCl3·3H2O.[26]
It can be concluded from IR monitoring of the reaction
and from the isolation or trapping of some of the interme-
diate species, that the reaction of DMF with the starting
rhodium(III) salt involves a complex series of equilibria.
The presence of ClϪ ions strongly affects the balance be-
tween the identified anionic and cationic species. Both the
CO ligand and the [NH2(CH3)2]ϩ cation arising from DMF
have been identified, but no evidence of DMF activation at
the metal centre can be given.
In
a separate experiment, we carbonylated [NH2-
(CH3)2]2[RhCl5(DMF)] by bubbling CO through a solution
in DMF for 15 min at 50 °C. After the addition of
[AsPh4]Cl and evaporation of the solvent, an orange pow-
der was recovered, which analyzed as [AsPh4]2[RhCl5(CO)]
and gave a νCO band at 2081 cmϪ1 (see Table 1). The
[RhCl5(CO)]2Ϫ anion has previously been reported by Col-
ton et al. as an intermediate species when RhCl3·3H2O is
treated with hydrochloric and formic acid mixtures to pro-
duce [RhCl2(CO)2]Ϫ.[40] Thus, upon monitoring of the reac-
tion in the absence of CO bubbling, [RhCl5(CO)]2Ϫ is not
detected.
We have discovered that reaction of [AsPh4]2[RhCl5(CO)]
with 5 equiv. of DMF in boiling chloroform allows isolation
of the reddish complex [AsPh4][RhCl4(CO)(DMF)] in good
yields. This compound shows a νCO band at 2092 cmϪ1 in
DMF.
Water- and/or HCl-Assisted DMF Activation
A further series of experiments was carried out in order
to gain better insight into the parameters that affect the
course of the reaction, in particular the role of ClϪ ions.
Firstly, the use of commercial DMF, containing around
0.1% of water, produced [RhCl2(CO)2]Ϫ in 30 min as an
orange solution containing a small amount of black rhod-
ium (Table 2, Figure 1). In each experiment, [AsPh4]Cl was
added and the yield of isolated [AsPh4][RhCl2(CO)2] was
determined. In run 1 of Table 2, the yield achieved was
70%.
The addition of chloride (KCl) to the reaction medium
As these latter anionic species contain more chlorine (five stabilizes the system, as shown by the absence of any metal-
and four Cl ligands, respectively) than the starting rhodium lic rhodium, but no significant promoting effect on the re-
salt, further attempts were made to identify the correspond- duction was observed (runs 2 and 3 in Table 2). Such an
Eur. J. Inorg. Chem. 2001, 2327Ϫ2336
2329

P. Serp, M. Hernandez, B. Richard, P. Kalck
FULL PAPER
Table 1. Isolated intermediate rhodium species
Product
Color
IR (νCO [cmϪ1])
MS[a][b] (m/z)
DMF[c]
KBr pellets
[Rh(DMF)6]Cl3
[RhCl2(DMF)4]Cl
[NH2(CH3)2]2[RhCl5(DMF)]
[AsPh4]2[RhCl5(CO)]
[AsPh4][RhCl4(CO)(DMF)]
[AsPh4][RhCl2(CO)2]
blue
red
violet
orange
reddish
yellow
Ϫ
Ϫ
Ϫ
2081
2092
2063, 1984
1655
1639
1641
2075
2085, 1637
2054, 1975
502.8[a]: not assigned
465[a]: [RhCl2(DMF)4]ϩ
326[a]: [RhCl5(NH2(CH3)2)]Ϫ
662.8[b]: [AsPh4RhCl5]Ϫ
273[a]: [RhCl4(CO)]Ϫ
229[a]: [RhCl2(CO)2]Ϫ
[a]
[b]
[c]
FAB. Ϫ Electrospray. Ϫ Free DMF: 1675 cmϪ1
.
Table 2. Influence of the addition of chloride and/or water on the reaction
(Run number) Formulation[a]
Isolated products (yield), reaction time
Solution colour and comments
(1) RhCl3·3H2O/DMF
(2) RhCl3·3H2O/5 KCl/DMF
[AsPh4][RhCl2(CO)2] (70%); 30 min
[NH2(CH3)2]2[RhCl5(DMF)]; 5 min
[AsPh4][RhCl2(CO)2] (72%); 25 min
[AsPh4][RhCl2(CO)2] (65%); 45 min
Reaction incomplete after 45 min
[AsPh4][RhCl2(CO)2] (88%); 12 min
Ϫ
Orange Ϫ small amount of black rhodium
Orange Ϫ no black rhodium
Orange Ϫ no black rhodium
Orange Ϫ some black rhodium
Ϫ
Lemon-yellow Ϫ no black rhodium
Ϫ
Lemon-yellow Ϫ no black rhodium
(3) RhCl3·3H2O/10 KCl/DMF
(4) RhCl3·3H2O/5 HCl/dioxane/DMF
(5) RhCl3·3H2O/10 HCl/dioxane/DMF
(6) RhCl3·3H2O/5 HCl/water/DMF
(7) RhCl3·3H2O/10 HCl/water/DMF
(8) RhCl3·3H2O/5 H2O/DMF
[AsPh4][RhCl2(CO)2] (85%); 12 min
[a]
RhCl3·3H2O: 0.2 g (0.75 mmol); DMF: 5 mL; T ϭ 160 °C; subsequent addition of [AsPh4]Cl for product isolation.
Figure 2. Intensity of the νCO band of [RhCl4(CO)DMF]Ϫ at 2092
cmϪ1 during the reaction of RhCl3·3H2O with: (
᭺
) DMF; (
ᮀ
) DMF
Figure 1. Intensity of the νCO band of [RhCl2(CO)2]Ϫ at 1984 cmϪ1
ϩ 10 mol-equiv. of dry HCl per RhCl3·3H2O; (
᭛) DMF ϩ 5 molar
during the reaction of RhCl3·3H2O with: (
᭺
) DMF; (
ᮀ) DMF ϩ
equivalents of H2O per RhCl3·3H2O
10 mol-equiv. of dry HCl per RhCl3·3H2O; (
equiv. of H2O per RhCl3·3H2O
᭝) DMF ϩ 5 mol-
compared to run 1, suggesting that larger quantities of CO
excess of chloride improved the precipitation of [NH2- were provided by the acid-catalyzed DMF decomposition.
(CH3)2]2[RhCl5(DMF)].
As the yield of [RhCl2(CO)2]Ϫ was lower when the concen-
The addition of 5Ϫ10 equiv. of dry HCl (5  HCl in tration of [RhCl4(CO)(DMF)]Ϫ was significant, we suggest
diethyl ether or dioxane) to the RhCl3·3H2O/DMF mixture that anhydrous HCl is rapidly neutralized by NH(CH3)2
was found to have a different and pronounced effect (runs arising from the DMF. Thus, no more carbon monoxide
4 and 5 in Table 2). With 10 equiv., even after reaction for can be generated in the medium to maintain the reaction
45 min, the solution remained dark-orange with precipita- and more particularly the reduction. This experiment fur-
tion of black rhodium. Moreover, the carbonyl band at ther shows that rhodium is unlikely to directly promote the
2092 cmϪ1 persisted in the IR spectrum (Figures 1 and 2), DMF decomposition.
beside the two bands due to [RhCl2(CO)2]Ϫ, indicating
On the contrary, when aqueous solutions of HCl were
that the reaction was incomplete. Precipitation of used (37% in water), another phenomenon was observed;
[NH2(CH3)2]Cl, arising from DMF decomposition, was with 5Ϫ10 equiv. of acid (runs 6 and 7 in Table 2), the reac-
also noted. In this case, it is clear from Figure 2 that the tion was complete within 12 min and the solution became
production of [RhCl4(CO)(DMF)]Ϫ was greatly enhanced lemon-yellow, giving the highest yield achieved in this study
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Eur. J. Inorg. Chem. 2001, 2327Ϫ2336

A Facile Route to Carbonylhalogenometal Complexes
FULL PAPER
(88%). The change in color, i.e. from orange for runs 1 to 5 210 °C), the νCO bands of [NH4][RhCl2(CO)2] were detected
to lemon-yellow for runs 6 and 7, might be taken to indicate at 2079 and 2005 cmϪ1 above 100 °C, but the solution was
a more complete reaction, as evidenced by the higher yields dark and large quantities of black material were deposited.
of the isolated product achieved in the latter cases.
Using
diethylformamide
at
160
°C
produced
Finally, the role of water itself was examined. We have [H2NEt2][RhCl2(CO)2] (νCO ϭ 2060, 1981 cmϪ1) in 30 min
observed that by adding 5 equiv. of water per mol of rhod- without any metallic precipitate. Although this reaction ap-
ium, the reduction can be achieved within 12 min (Table 2, peared to be quantitative on the basis of IR measurements,
Figure 1 and Figure 2) and the yield of [RhCl2(CO)2]Ϫ re- on a small preparative scale the yield of isolated product,
aches 85% with no black rhodium formation. We propose usually [AsPh4][RhCl2(CO)2], was ca. 70%. Yields of
that the presence of water assists the reduction step from around 85% were achieved when small quantities of water
[RhCl4(CO)(DMF)]Ϫ to [RhCl2(CO)2]Ϫ and that the addi- were introduced to promote the reductive carbonylation.
tion of HCl accelerates the production of CO from DMF, Finally, using N-methylacetamide (CH3CONHCH3; m.p.
as evidenced by the significant amounts of ammonium 28 °C) at 180 °C, a black solution with copious precipita-
chloride detected in the medium. Formally, COCl2 is elimin- tion of a black material was obtained in less than 5 min,
ated in the reduction step and is rapidly hydrolyzed, but and no CO stretching band could be detected in the IR
we prefer to consider the water-gas shift reaction, which spectrum of the solution.
produces CO2 and H2 from CO and H2O. The reduction
step is, in fact, the reductive elimination of HCl from the Direct Preparation of Several Rhodium Complexes
coordination sphere of the rhodium(III) species. Equa-
Starting from DMF solutions containing the
tion (1) shows the overall stoichiometry of several reactions.
[NH2(CH3)2][RhCl2(CO)2] complex, we added various li-
The complex [RhI2(CO)2]Ϫ has previously been shown to
gands at room temperature to produce the corresponding
be a good catalyst of the water-gas shift reaction.[42]
rhodium(I) complexes (procedure B). Direct addition of 2
equiv. of PPh3, as reported by Varshavskii et al.,[19]
[RhCl4(CO)(DMF)]Ϫ ϩ 2 CO ϩ H2O Ǟ
P(OPh)3, or tris(m-sulfonatophenyl)phosphane (TPPTS)
furnished the corresponding [RhCl(CO)L2] square-planar
(1)
[RhCl2(CO)2]Ϫ ϩ 2 HCl ϩ CO2 ϩ DMF
complexes in high yields. Addition of 3 mol of P(OPh)3 re-
sulted in the generation of [RhCl{P(OPh)3}3]. The use of
bis(diphenylphosphanyl)propane gave [Rh(CO)(dppp)2]Cl
in 75% yield.
To sum up this section on the rhodium activity, we have
shown that DMF coordinates to the rhodium salt to give
[RhCl2(DMF)4]Cl, disproportionation of which affords
[RhCl5(DMF)2]2Ϫ and [Rh(DMF)6]3ϩ. The latter species
gives the former dianionic one in the presence of chloro
ligands. Isolation of [RhCl5(DMF)]2Ϫ with [NH2(CH3)2]ϩ
as the counterion shows that, at this stage of the rhodiu-
m(III) chemistry, significant amounts of DMF have been
decomposed, thus indicating the presence of an acidic me-
dium. As commercial RhCl3·3H2O is obtained by evapora-
tion of acidic aqueous solutions of rhodium trichloride,
traces of HCl can be present at the beginning of the reac-
tion. However, as no carbonyl species have been detected in
the early stages, we conclude that the formation of
[RhCl2(CO)2]Ϫ resembles an autocatalytic process, which
does not involve the activation of DMF at the rhodium
center.
Substitution of the chloro ligand can also be performed.
As in the case of [Rh(acac)(CO)2],[19] addition of 1,1-di-
methylethanethiol afforded the corresponding bridged di-
nuclear complex [Rh2(µ-StBu)2(CO)4] in 80Ϫ85% yield.
After stirring for 5 min, IR monitoring showed that the
tetracarbonyl complex had been formed, and the sub-
sequent addition of 2 equiv. of PPh3 or TPPTS resulted
in the formation of [Rh2(µ-StBu)2(CO)2(PPh3)2] or [Rh2(µ-
StBu)2(CO)2(TPPTS)2], respectively.
We have observed that for phosphane ligands, procedure
A, in which all the reactants are introduced at the begin-
ning, gives the same results but with much longer reaction
times (2Ϫ5 h). However, no clean reaction could be
achieved by adding HStBu according to procedure A.
Hence, the present method allows the high-yielding pre-
paration in a one-pot procedure of various carbonylrhod-
ium complexes without the use of carbon monoxide gas.
Use of Other Amides
In order to test the generality of the reaction, we investig-
ated the behavior of various formamides in this reductive
carbonylation. At 180 °C, N-methylformamide gave yellow
solutions containing a small amount of black material in
B. Reaction of IrCl3·3H2O with DMF
An identical study has been carried out on IrCl3·3H2O
around 1 min. In their IR spectra, such solutions showed in DMF. It is known from the literature[43] that
only the two νCO bands of [RhCl2(CO)2]Ϫ at 2073 and 1997 [IrCl2(CO)2]Ϫ can be generated using carbon monoxide by
cmϪ1. The yield of [AsPh4][RhCl2(CO)2] was 72%. When refluxing in a high boiling point alcohol such as 2-methoxy-
the same reaction was performed at 140 °C, the expected ethanol. This is presumably due to the higher stability or
product was obtained in less than 10 min without any pre- inertness of iridium(III) compared to rhodium(III).
cipitation of metallic rhodium. When a solution of
In the present case, refluxing of a solution of IrCl3·3H2O
RhCl3·3H2O in formamide was gently heated from room in DMF resulted in a beige precipitate after 5 min, which
temperature to 120 °C (i.e., well below its boiling point of rapidly redissolved on further heating. This species was isol-
Eur. J. Inorg. Chem. 2001, 2327Ϫ2336
2331

P. Serp, M. Hernandez, B. Richard, P. Kalck
FULL PAPER
ated by stopping the reaction and, after cooling, analyzed
as [NH2(CH3)2]2[IrCl5(DMF)]. As for rhodium, the forma-
tion of this species was favored in the presence of an excess
of ClϪ ions, for instance in aqueous HCl. After reaction for
10 min, the IR spectrum of the solution showed a νCO band
at 2048 cmϪ1. The intensity of this band increased, while
the color of the solution became progressively more orange.
After 30 min, addition of [AsPh4]Cl to trap this inter-
mediate species resulted in the production of [AsPh4]-
[IrCl4(CO)(DMF)], which was isolated as an orange precip-
itate in 69% yield following the addition of water. On fur-
ther heating of the initial solution, the two νCO bands at
2045 and 1965 cmϪ1 intensified, which was accompanied
by a concomitant decrease in the band at 2048 cmϪ1. Heat-
ing for 15 h was required to completely transform the start-
ing complex into [IrCl2(CO)2]Ϫ, albeit with a large amount
of black metal. Addition of [AsPh4]Cl allowed the isolation
of [AsPh4][IrCl2(CO)2] in 10% yield.
Scheme 2. General reaction pathway for the generation of
[RuCl3(CO)2(DMF)]Ϫ
and
[RuCl2(CO)2(DMF)2]
from
RuCl3·3H2O and DMF
In order to improve the reduction step from
[IrCl4(CO)(DMF)]Ϫ to [IrCl2(CO)2]Ϫ, 5 equiv. of water
were added. The reaction indeed became faster, but large
amounts of the black precipitate were still present. Addition
of 5 equiv. of aqueous HCl (37% in water) and heating for
60 min resulted in the clean production of [IrCl2(CO)2]Ϫ in
70% yield. Anhydrous HCl or larger amounts of aqueous
HCl were found to have a negative effect.
This reaction was thus slower than that for rhodium. The
direct isolation of [IrCl5(DMF)]2Ϫ and [IrCl4(CO)(DMF)]Ϫ
indicates that the same mechanism should be operative for
both metals. As for rhodium, both the CO ligand and the
[NH2(CH3)2]ϩ cation arising from DMF decomposition
could be identified, but again no evidence was found for
DMF activation at the metal center.
[PPN]2[RuCl4(CO)(DMF)], showing νCO bands at 1929
cmϪ1 and 1638 cmϪ1 due to coordinated DMF.
We found that by adding 2.5 equiv. of dry HCl to a solu-
tion of RuCl3·3H2O in DMF, a single complex showing two
νCO bands at 2041 and 1963 cmϪ1 was obtained after reac-
tion for 60 min. In the course of the reaction, the two inter-
mediates giving rise to the bands at 2020 and 1929 cmϪ1
(here shifted to 1919 cmϪ1 due to medium effect) were also
transiently observed, but disappeared more quickly. The
two final νCO bands at 2041 and 1963 cmϪ1 are attributable
to [RuCl3(CO)2(DMF)]Ϫ,[1] which was isolated as the PPN
salt in 65% yield. Addition of larger amounts of dry HCl
resulted in the production of small amounts of
[RuCl3(CO)3]Ϫ (νCO bands at 2124, 2008 cmϪ1), together
with [RuCl3(CO)2(DMF)]Ϫ; this can be attributed to a
higher concentration of CO in the solution.
A second complex, showing νCO bands at 2054 and 1975
cmϪ1, was isolated following the addition of [PPN]Cl to the
yellow solution exhibiting the four νCO bands at 2054, 2041,
1975, and 1963 cmϪ1 (after refluxing a solution of
RuCl3·3H2O in DMF for 2 h). The products were isolated
by precipitation with water. The yellow precipitate was
found to contain [PPN][RuCl3(CO)2(DMF)] and the un-
known complex. Column chromatographic separation on
silica allowed isolation of the latter species as pure
[RuCl2(CO)2(DMF)2]. Scheme 2 summarizes the reaction
pathway for the reductive carbonylation of RuCl3·3H2O; it
does not involve any DMF activation at the metal center.
As for rhodium and iridium, the solution containing the
carbonylchloro species could be used to prepare various
complexes. The complex cis,cis,trans-[RuCl2(CO)2(PPh3)2]
could be selectively obtained by adding PPh3 to the solution
containing the [RuCl3(CO)2(DMF)]Ϫ anion (obtained from
a DMF/dry HCl mixture) at 140 °C.
Addition of 2 equiv. of PPh3 to the solution containing
[IrCl2(CO)2]Ϫ was found to result in the immediate forma-
tion of [IrCl(CO)(PPh3)2]. Thus, it appears that procedure
B, which involves addition of the ligand after generation of
the carbonylchloro anion, is faster than procedure A for
generating the desired compound.
C. Reaction of RuCl3·3H2O with DMF
In the case of ruthenium, the reaction was found to be
slower and more complex than that for rhodium. Scheme 2
depicts the various complexes detected during this study.
On heating a solution of RuCl3·3H2O in DMF, a νCO
band was seen at 2020 cmϪ1 in the IR spectrum after
15 min,
corresponding
to
the
red
species
[PPN]2[RuCl5(CO)], which was isolated following the addi-
tion of [PPN]Cl. After further heating for 25 min, five more
νCO bands appeared at 2054, 2041, 1975, 1963, and 1929
cmϪ1. The band at 2020 cmϪ1 rapidly disappeared, whereas
that at 1929 cmϪ1 persisted for up to 2 h. The other four
bands showed no evolution on heating for longer times. No
ruthenium black was observed in the course of the reaction.
In a separate experiment, reaction of RuCl3·3H2O with
DMF in the presence of 5 equiv. of aqueous HCl allowed
D. Reactions of K2PtCl4, PdCl2, and Na2PdCl6 with DMF
The reactivities of palladium and platinum salts were
isolation
of
the
green
ruthenium(II)
product found to differ markedly from those of rhodium, iridium,
2332
Eur. J. Inorg. Chem. 2001, 2327Ϫ2336

A Facile Route to Carbonylhalogenometal Complexes
FULL PAPER
ide and the other reagents were used as received (Aldrich). Ϫ Ele-
mental analyses were performed with a Carlo Erba EA-1110 instru-
ment. Ϫ Infrared spectra were recorded with a PerkinϪElmer 225
spectrophotometer using a 0.1-mm cell equipped with CaF2 win-
dows. Ϫ NMR spectra were recorded with a Bruker AC 200 MHz
instrument (1H, 31P, and 13C). 1H and 13C NMR spectroscopic data
were referenced to the solvent peaks, while 31P NMR spectra were
referenced to 85% H3PO4 as an external standard. Chemical shifts
are expressed in ppm and coupling constants in Hz. Ϫ Mass spec-
trometry (FAB, Xe 100 eV, NBA matrix) was performed with a
and ruthenium. Indeed, on refluxing PdCl2 or Na2PdCl6 in
DMF, the rapid formation of colloidal palladium suspen-
sions was observed within 10 min. Attempts to stabilize
possible carbonyl species by adding anhydrous or aqueous
HCl, KCl, or even [PPN]Cl, were unsuccessful. Heating a
solution of PdCl2 in DMF at 100 °C for 2 h resulted in the
formation of a dark solid, which was identified as
[PdCl2(DMF)2]. This compound has already been pre-
pared[44] by treating PdCl2 with DMF at room temperature.
However, upon dissolution in another solvent, this complex Nermag R10-10 apparatus. Ϫ Procedure B was used for all the syn-
theses.
dissociates with loss of its two DMF ligands. Thus, we did
not succeed in finding conditions under which a carbonyl-
palladium complex could be directly produced from a palla-
dium salt through DMF decarbonylation.
As regards platinum, the refluxing of K2PtCl4 in DMF
produced copious amounts of black metal. Neither HCl
(anhydrous or aqueous) nor KCl prevented this precipita-
tion. Nevertheless, the IR spectrum of the solution showed
the presence of a weak νCO band at 2087 cmϪ1. Thus, we
added 1 equiv. of [PPN]Cl at the beginning of the reaction.
Under these conditions, the carbonylplatinum(II) complex
[PPN][PtCl3(CO)] could be cleanly obtained without any
black precipitate, albeit in a yield of just 52%.
Rhodium Complexes
[NH2(CH3)2]2[RhCl5(DMF)]: The complex was prepared from
RhCl3·3H2O (1.0 g, 3.8 mmol) and KCl (1.41 g, 19 mmol) in DMF
(15 mL). On heating the solution under reflux (160 °C) for 15 min,
it turned progressively from deep-red to dark-orange and the prod-
uct precipitated as a violet powder. After cooling to room temper-
ature, the product was collected by filtration using a Büchner fun-
nel, washed with acetone, and dried in vacuo to give 0.255 g (15%
based on RhCl3·3H2O). Ϫ IR (KBr pellets): νCO ϭ 1636 cmϪ1 (co-
ordinated DMF).
Ϫ δ ϭ 7.81 [s, 1 H,
1H NMR (D2O):
HCON(CH3)2], 2.88 and 2.73 [2 s, 2 ϫ 3 H, HCON(CH3)2], 2.60
[s, 6 H, NH2(CH3)2]. Ϫ 13C{1H} NMR (D2O): δ ϭ 165.2 [d,
HCON(CH3)2, JRhϪC ϭ 17 Hz], 31.4 and 36.9 [s, HCON(CH3)2],
34.6 [s, NH2(CH3)2]. Ϫ MS (FABϪ, H2O): m/z (%) ϭ 418 (100)
[{NH2(CH3)2}2{RhCl5[HN(CH3)2]}]Ϫ, 383 (19) [{NH2(CH3)2}2-
{RhCl4[HN(CH3)2]}]Ϫ, 326 (26) [RhCl5{HN(CH3)2}]Ϫ, 244 (31)
[RhCl4]Ϫ. Ϫ C7H23Cl5N3ORh (445.45): calcd. C 18.87, H 5.20, N
9.43, O 3.59; found C 18.53, H 5.20, N 9.39, O 3.32.
Conclusion
Dimethylformamide, as well as diethylformamide and
methylformamide, can act as convenient sources of carbon
monoxide. This study has shown that, mainly for rhodium,
iridium, and ruthenium, it is possible to produce carbonyl-
halo complexes in high yields. The presence of small
amounts of water clearly assists the reduction of the com-
mercial salts into rhodium(I), [RhCl2(CO)2]Ϫ, iridium(I)
[AsPh4][RhCl4(CO)(DMF)]: The complex was prepared from
[AsPh4]2[RhCl5(CO)] (0.18 g, 0.179 mmol) and DMF (0.065 g,
0.895 mmol) in CHCl3 (10 mL). The solution was heated under
reflux for 15 min, allowed to cool, filtered, and the product was
precipitated by adding n-heptane. It was collected by filtration us-
ing a Büchner funnel, washed with n-heptane, and dried in vacuo
to give 0.11 g {88% based on [AsPh4]2[RhCl5(CO)]}. Ϫ IR (KBr
[IrCl2(CO)2]Ϫ, and ruthenium(II) [RuCl4(CO)(DMF)]2Ϫ
.
pellets): νCO ϭ 2085, 1637 cmϪ1 (coordinated DMF). Ϫ H NMR
1
Presumably, the reduction proceeds through the water-gas
shift reaction. As no evidence has been found for DMF
activation at the metal center, an HCl-mediated decomposi-
tion of the solvent is proposed to explain the formation of
CO and [NH2(CH3)2]ϩ.
(CDCl3): δ ϭ 7.88 [s, 1 H, HCON(CH3)2], 2.89 and 2.75 [2 s, 2 ϫ
3 H, HCON(CH3)2]. Ϫ MS (FABϪ, CH3CN): m/z (%) ϭ 362 (10)
[RhCl4(DMF)]Ϫ, 289 (100) [RhCl4]Ϫ.
Ϫ C28H27AsCl4NO2Rh
(729.17): calcd. C 46.12, H 3.73, N 1.92, O 4.39; found C 45.53, H
3.40, N 1.79, O 4.32.
The good yields obtained for these carbonyl complexes
show that the methodology used in this work is either an
attractive one-step route for preparation of the complexes,
or a means of directly obtaining the catalytic precursors in
DMF solution. Such a procedure is not applicable in the
case of palladium, since it leads only to deposition of the
black metal, and appears to be limited for platinum, for
which [PtCl3(CO)]Ϫ is obtained in modest yield. Finally, by
the direct addition of various ligands to the carbonylhalo-
containing DMF solutions, as described here with a few
examples, the corresponding classical complexes may be ob-
tained in high yields according to a simplified procedure.
[RhCl2(DMF)4]Cl: The complex was prepared from RhCl3·3H2O
(0.5 g, 1.9 mmol) in DMF (15 mL). The solution was stirred at
room temperature for 48 h, then filtered, and the solvent was evap-
orated in vacuo at 50 °C. The resulting oil was treated at room
temperature with acetone to yield a brown precipitate. The final
product was washed several times with acetone and dried in vacuo
to give 0.105 g (11% based on RhCl3·3H2O). Ϫ IR (KBr pellets):
νCO ϭ 1639 cmϪ1 (coordinated DMF). Ϫ 1H NMR (D2O): δ ϭ
8.04 [s, 1 H, HCON(CH3)2], 2.96 and 2.78 [2 s, 2 ϫ 3 H,
HCON(CH3)2].
Ϫ δ ϭ 168.8 [d,
13C{1H} NMR (D2O):
HCON(CH3)2, JRhϪC ϭ 19 Hz], 41.4 and 36.1 [s, HCON(CH3)2].
Ϫ MS (FABϩ, H2O): m/z (%) ϭ 465 (6) [RhCl2(DMF)4]ϩ, 392 (5)
[RhCl2(DMF)3]ϩ, 356 (11.8) [RhCl(DMF)3]ϩ, 319 (3)
[RhCl2(DMF)2]ϩ,
248
(100)
[RhCl2(DMF)]ϩ.
Ϫ
C12H28Cl3N4O4Rh (501.64): calcd. C 28.73, H 5.63, N 11.17, O
12.76; found C 28.43, H 5.29, N 10.39, O 11.32.
Experimental Section
General Remarks: All synthetic manipulations were carried out un-
der nitrogen using standard Schlenk techniques. Dimethylformam-
[AsPh4][RhCl2(CO)2]: The complex was prepared from
RhCl3·3H2O (1.0 g, 3.8 mmol) and H2O (0.35 mL, 19.5 mmol) in
Eur. J. Inorg. Chem. 2001, 2327Ϫ2336
2333

P. Serp, M. Hernandez, B. Richard, P. Kalck
FULL PAPER
DMF (15 mL). On heating the solution under reflux (160 °C), it
2.28 mmol) to the aforementioned [NH2(CH3)2][RhCl2(CO)2] solu-
turned progressively from deep-red to yellow. IR monitoring tion [prepared from RhCl3·3H2O (0.3 g, 1.14 mmol) and H2O
indicated the formation of the carbonylchloro anion. After 15 min, (0.35 mL, 19.5 mmol) in DMF (15 mL)] at room temperature. The
[AsPh4]Cl (1.58 g, 3.8 mmol) was added and the mixture was con- reaction was immediate, giving a significant evolution of CO. The
centrated to a volume of 3 mL in vacuo at 100 °C. It was then
allowed to cool to room temperature and ca. 6  aq. HCl (20 mL)
was added dropwise to precipitate the complex as a yellow powder.
The product was collected by filtration using a Büchner funnel,
washed with ca. 6  aq. HCl (100 mL), and dried in vacuo to give
complex was precipitated by adding cold water (50 mL). Collection
of the product by filtration using a Büchner funnel and washing
with water (150 mL) afforded a clean product in yields of around
70%. Ϫ IR (KBr pellets): νCO ϭ 1930 cmϪ1. Ϫ 31P{1H} NMR
(CDCl3): δ ϭ Ϫ11.8 (td, Peq, JRhϪPeq ϭ 122 Hz, JPeqϪPax ϭ 30 Hz),
16.1 (td, Pax, JRhϪPax ϭ 85 Hz, JPeqϪPax ϭ 30 Hz) [A2B2X]. Ϫ 31P-
1.98 g (85% based on RhCl3·3H2O). Ϫ IR (KBr pellets): νCO
ϭ
2054, 1975 cmϪ1. Ϫ MS (FABϪ, CH3CN): m/z (%) ϭ 229 (8) 103Rh COSY (CDCl3): δRh ϭ 1255. Ϫ C55H52ClOP4Rh (991.27):
[RhCl2(CO)2]Ϫ, 201 (16) [RhCl2(CO)]Ϫ, 173 (100) [RhCl2]Ϫ. Ϫ
C26H20AsCl2O2Rh (613.18): calcd. C 50.93, H 3.29; found C 50.62,
H 3.27.
calcd. C 66.64, H 5.29, O 1.61; found C 66.42, H 4.87, O 1.84.
[Rh2(µ-StBu)2(CO)4]: This compound was prepared by adding 10
equiv. of 1,1-dimethylethanethiol (900 µL, 11 mmol) to the afore-
mentioned [NH2(CH3)2][RhCl2(CO)2] solution [prepared from
[RhCl(CO)L2] Complexes [L ؍ PPh3, P(OPh)3, or TPPTS]: These
three compounds were prepared from RhCl3·3H2O (0.3 g, RhCl3·3H2O (0.3 g, 1.14 mmol) and H2O (0.35 mL, 19.5 mmol) in
1.14 mmol) and H2O (0.11 mmL, 6.11 mmol) in DMF (10 mL) in
a closed Schlenk tube without any reflux condenser system. On
DMF (15 mL)] at room temperature. After 5 min, the IR spectrum
of the solution showed four νCO bands at 2062, 2050, 1999, and
heating the solution under reflux, it turned progressively from deep- 1984 cmϪ1. The complex was precipitated by the dropwise addition
red to yellow. IR monitoring of the reaction indicated the forma-
of cold water (50 mL). Collection of the product by filtration using
tion of the carbonylchloro anion [RhCl2(CO)2]Ϫ. After 15 min, the a Büchner funnel and washing with water (150 mL) afforded a
mixture was cooled to room temperature and 1.95 equiv. of the clean product in 80Ϫ85% yield. Ϫ IR (KBr pellets): νCO ϭ 2060,
appropriate phosphane was added [0.58 g of PPh3, 0.69 g of
P(OPh)3 or 1.45 mg of TPPTS]. The reaction was immediate, giving 29.05, H 3.66, O 12.92, S 12.90; found C 28.87, H 3.77, O 12.45,
2044, 2003, 1990, 1983 cmϪ1. Ϫ C12H18O4Rh2S2 (496.22): calcd. C
a significant evolution of CO. An IR spectrum of the solution
showed a single νCO band at 1977 cmϪ1 (PPh3 complex), 2012 cmϪ1
[P(OPh)3 complex], or 1982 cmϪ1 (TPPTS complex). The yellow
complexes were precipitated by the addition of cold water (50 mL)
[PPh3 and P(OPh)3 complexes] or ethanol (50 mL) (TPPTS com-
plex). Collection of the products by filtration using a Büchner fun-
nel and washing with water (150 mL) [PPh3 and P(OPh)3 com-
plexes] or ethanol (150 mL) (TPPTS complex) afforded clean prod-
ucts in reproducible yields of around 80%.
S 12.56.
[Rh2(µ-StBu)2(CO)2L2] Complexes (L ؍ PPh3 or TPPTS): To the
aforementioned solution of [Rh2(µ-StBu)2(CO)4] in DMF (see pre-
vious synthesis), which exhibited four νCO bands at 2062, 2050,
1999, and 1984 cmϪ1, 1 equiv. of the appropriate phosphane per
mol of rhodium was added (0.3 g of PPh3 or 0.73 g of TPPTS).
An immediate evolution of CO was noticed and the reaction was
complete within 5 min. The IR spectrum of the solution showed a
νCO band at 1977 cmϪ1 (PPh3 complex) or 1982 cmϪ1 (TPPTS
[RhCl(CO)(PPh3)2]: IR (KBr pellets): νCO ϭ 1960 cmϪ1 (vs). Ϫ complex). The complex was precipitated by adding cold water
31P{1H} NMR (CDCl3): δ ϭ 32.5 (d, JRhϪP ϭ 125 Hz). Ϫ (50 mL) (PPh3 complex) or ethanol (50 mL) (TPPTS complex).
C37H30ClOP2Rh (690.95): calcd. C 64.32, H 4.38, O 2.32; found C Collection of the product by filtration using a Büchner funnel and
64.36, H 4.57, O 3.08.
washing with water (150 mL) (PPh3 complex) or ethanol (150 mL)
(TPPTS complex) afforded clean products in reproducible yields of
around 80%.
[RhCl(CO){P(OPh)3}2]: IR (KBr pellets): νCO ϭ 1998 cmϪ1 (vs).
Ϫ
31P{1H} NMR (CDCl3): δ ϭ 113.6 (d, JRhϪP ϭ 214 Hz). Ϫ
C37H30ClO7P2Rh (786.95): calcd. C 56.47, H 3.84, O 14.23; found [Rh2(µ-StBu)2(CO)2(PPh3)2]: IR (KBr pellets): νCO ϭ 1964, 1948
C 56.24, H 4.07, O 14.34.
cmϪ1. Ϫ 31P{1H} NMR (CDCl3): δ ϭ 37.5 (d, JRhϪP ϭ 151 Hz).
Ϫ C26H20O2P2Rh2S2 (964): calcd. C 56.91, H 5.57, O 3.30, S 6.60;
found C 56.81, H 5.51, O 3.20, S 6.38.
[RhCl(CO)(TPPTS)2]: IR (KBr pellets): νCO ϭ 1968 cmϪ1 (vs). Ϫ
31P{1H} NMR (CDCl3): δ ϭ 34.2 (d, JRhϪP ϭ 126 Hz). Ϫ
C37H36ClNa6O25P2S6Rh (1411.32): calcd. C 31.49, H 2.57, O 28.34; [Rh2(µ-StBu)2(CO)2(TPPTS·3H2O)2]: IR (KBr pellets): νCO
found C 32.12, H 2.63, O 29.68.
ϭ
1967 cmϪ1. Ϫ 31P{1H} NMR (D2O): δ ϭ 39.7 (d, JRhϪP ϭ 152 Hz).
Ϫ C46H54O26Na6P2Rh2S8 (1685.14): calcd. C 32.79, H 3.23, O
24.69; found C 33.24, H 3.25, O 25.41.
[RhCl{P(OPh)3}3]: This compound was prepared by adding 3
equiv. of P(OPh)3 (1.05 g, 3.42 mmol) to the aforementioned
[NH2(CH3)2][RhCl2(CO)2] solution [prepared from RhCl3·3H2O Iridium Complexes
(0.3 g, 1.14 mmol) and H2O (0.35 mL, 19.5 mmol) in DMF
[NH2(CH3)2]2[IrCl5(DMF)]: The complex was prepared from
(15 mL)] at room temperature. The reaction was immediate, giving
a significant evolution of CO. The complex was precipitated by
adding cold water (50 mL). Collection of the product by filtration
using a Büchner funnel and washing with water (150 mL) afforded
a clean product in reproducible yields of around 80%. Ϫ 31P{1H}
NMR (CDCl3): δ ϭ 112.5 (dd, JRhϪPA ϭ 222 Hz, JPAϪPB ϭ 55 Hz),
118.9 (td, JRhϪPB ϭ 281 Hz, JPAϪPB ϭ 55 Hz). Ϫ C54H45ClO9P3Rh
(1069.23): calcd. C 60.66, H 4.24, O 13.47; found C 60.29, H 4.43,
O 13.08.
IrCl3·3H2O (0.5 g, 1.42 mmol) and aqueous HCl (37%, 250 µL) in
DMF (5 mL). On heating the solution under reflux (160 °C), it
turned progressively from deep-red to dark-orange and the product
precipitated as a beige powder. After 6 min, the mixture was al-
lowed to cool to room temperature and the product was collected
by filtration using a Büchner funnel, washed with acetone, and
dried in vacuo to give 0.155 g (20% based on IrCl3·3H2O). Ϫ IR
1
(KBr pellets): νCO ϭ 1645 cmϪ1 (coordinated DMF). Ϫ H NMR
(D2O): δ ϭ 7.99 [s, 1 H, HCON(CH3)2], 3.07 and 2.98 [2 s, 2 ϫ 3
[Rh(CO)(dppp)2]Cl (dppp ؍ 1,3-diphenylphosphanylpropane): This H, HCON(CH3)2], 2.63 [s, 6 H, NH2(CH3)2]. Ϫ 13C{1H} NMR
compound was prepared by adding 2 equiv. of dppp (0.94 g,
(D2O): δ ϭ 174.4 [d, HCON(CH3)2, JRhϪC ϭ 16 Hz], 35.8 and 40.8
Eur. J. Inorg. Chem. 2001, 2327Ϫ2336
2334

A Facile Route to Carbonylhalogenometal Complexes
[s, HCON(CH3)2], 37.4 [s, NH2(CH3)2]. C7H23Cl5IrN3O
FULL PAPER
Ϫ
DMF (8 mL) in a closed Schlenk tube without any reflux con-
(534.76): calcd. C 15.72, H 4.34, N 7.86, O 2.99; found C 15.77, H denser system. On heating the solution under reflux (160 °C), it
4.23, N 7.63, O 3.60.
turned progressively from deep-red to dark-green. After 30 min, the
heating was stopped and [PPN]Cl (0.4 g, 0.7 mmol) was added. The
green complex was precipitated by adding cold water (25 mL),
washed with further water (50 mL), and dried in vacuo to give
[AsPh4][IrCl4(CO)(DMF)]: The complex was prepared from
IrCl3·3H2O (0.5 g, 1.42 mmol) in DMF (5 mL). On heating the so-
lution under reflux (160 °C), it turned progressively from deep-red
to orange. After 30 min, the heating was stopped and [AsPh4]Cl
(0.6 g, 1.43 mmol) was added. The mixture was concentrated to a
volume of 2 mL and the pale-yellow complex was precipitated by
the addition of cold water (25 mL), washed with water (50 mL),
and dried in vacuo to give 302 mg (26% based on IrCl3·3H2O). Ϫ
IR (KBr pellets): νCO ϭ 2060, 1645 cmϪ1 (coordinated DMF). Ϫ
1H NMR (CDCl3): δ ϭ 8.53 [s, 1 H, HCON(CH3)2], 3.02 and 2.98
[2 s, 2 ϫ 3 H, HCON(CH3)2]. Ϫ MS (FABϪ, CH3CN): m/z (%) ϭ
405 (100) [IrCl4(DMF)]Ϫ, 362 (12) [IrCl4(CO)]Ϫ, 337 (25) [IrCl4]Ϫ.
Ϫ C28H27AsCl4IrNO2 (818.48): calcd. C 41.09, H 3.32, N 1.71, O
3.91; found C 40.86, H 3.33, N 1.78, O 2.75.
0.138 g (26% based on RuCl3·3H2O). Ϫ IR (KBr pellets): νCO
ϭ
1918, 1644 cmϪ1 (coordinated DMF). Ϫ H NMR (CD2Cl2): δ ϭ
8.61 [s, 1 H, HCON(CH3)2], 2.98 and 2.95 [2 s, 2 ϫ 3 H,
HCON(CH3)2]. Ϫ C76H67Cl4N3O2P4Ru (1421.16): calcd. C 64.23,
H 4.75, N 2.96, O 2.25; found C 64.32, H 4.52, N 2.38, O 1.86.
1
[PPN][RuCl3(CO)2(DMF)]: The complex was prepared from
RuCl3·3H2O (0.4 g, 1.53 mmol) and anhydrous 4  HCl in dioxane
(1 mL, 4 mmol) in DMF (15 mL) in a closed Schlenk tube without
any reflux condenser system. On refluxing the solution, it turned
progressively from red to orange. IR monitoring indicated the
formation of the carbonylchloro anion (νCO
ϭ 2042 and
1964 cmϪ1). After 1 h, the solution was allowed to cool and
[PPN]Cl (0.88 g, 1.53 mmol) was added. After concentration of the
mixture in vacuo at 100 °C to a volume of 5 mL, cold water
(10 mL) was added dropwise to precipitate the complex as a yellow
powder. The product was collected by filtration using a Büchner
funnel, washed with water (100 mL), dried in vacuo, and recrystal-
lized from acetone/heptane to give 0.85 g of yellow crystals (64%
based on RuCl3·3H2O). Ϫ IR (KBr pellets): νCO ϭ 2045, 1970,
[AsPh4][IrCl2(CO)2]: The complex was prepared from IrCl3·3H2O
(0.3 g, 0.85 mmol) and HCl (0.15 mL, 37% in water) in DMF
(10 mL). On heating the solution under reflux, it turned from red
to orange. After 50 min, HCl (0.10 mL, 37% in water) was added
and refluxing was maintained for a further 10 min. Thereafter, the
solution was allowed to cool to room temperature and [AsPh4]Cl
(0.355 g, 0.85 mmol) was added. After evaporation of the solvent,
the complex was washed with acetone/diethyl ether (1:9) to furnish
0.42 g of yellow crystals (71% based on IrCl3·3H2O). Ϫ IR (KBr
pellets): νCO ϭ 2036, 1967 cmϪ1. Ϫ MS (FABϪ, CH3CN): m/z
(%) ϭ 319 (19) [IrCl2(CO)2]Ϫ, 291 (100) [IrCl2(CO)]Ϫ. Ϫ C26H20As-
Cl2IrO2 (702.49): calcd. C 44.45, H 2.87, O 4.56; found C 44.62, H
2.98, O 4.34.
1
1636 cmϪ1 (coordinated DMF). Ϫ H NMR (CDCl3): δ ϭ 8.52 [s,
1 H, HCON(CH3)2], 2.91 [s, 6 H, HCON(CH3)2]. Ϫ MS (FABϪ,
CH3CN): m/z (%) ϭ 300 (100) [RuCl3(CO)(DMF)]Ϫ, 280.5 (19)
[RuCl3(DMF)]Ϫ, 264.8 (7) [RuCl3(CO)2]Ϫ, 208 (31) [RuCl3]Ϫ. Ϫ
C41H37Cl3N2O3P2Ru (875.13): calcd. C 56.27, H 4.26, N 3.20, O
5.48; found C 56.62, H 4.27, N 3.05, O 5.34.
[IrCl(CO)(PPh3)2]: The complex was prepared by adding 2 equiv.
[RuCl2(CO)2(DMF)2]: The complex was prepared from
RuCl3·3H2O (0.4 g, 1.53 mmol) in DMF (15 mL) in a closed
Schlenk tube without any reflux condenser system. On refluxing
the solution, it turned progressively from red to orange. After 2 h,
it was allowed to cool and [PPN]Cl (0.88 g, 1.53 mmol) was added.
After concentration of the mixture in vacuo at 100 °C to a volume
of 5 mL, cold water (10 mL) was added dropwise to precipitate a
yellow powder. The product was collected by filtration using a
Büchner funnel, washed with water (100 mL), and dried in vacuo.
Chromatographic separation on a column of silica [Degussa Siper-
nat 22; eluent: acetone/2-propanol (20:80, v/v)] furnished the pure
complex in the first fraction; yield 0.17 g (30% based on
RuCl3·3H2O). Ϫ IR (CHCl3): νCO ϭ 2073, 2009, 1652, 1645 cmϪ1
(coordinated DMF). Ϫ 1H NMR (CDCl3): δ ϭ 8.28 [s, 1 H,
of
PPh3
(0.89 g,
3.4 mmol)
to
the
aforementioned
[NH2(CH3)2][IrCl2(CO)2] solution in DMF [prepared from
IrCl3·3H2O (0.6 g, 3.8 mmol) and HCl (0.35 mL, 37% in water) in
DMF (15 mL)] at room temperature. The reaction was immediate
and the IR spectrum of the solution showed a single νCO band at
1965 cmϪ1. The lemon-yellow complex was then precipitated by
adding cold water (100 mL), collected by filtration using a Büchner
funnel, and washed with cold methanol (100 mL). After drying in
vacuo, 1.59 g of [IrCl(CO)(PPh3)2] was collected (60% based on
IrCl3·3H2O). Ϫ IR (KBr pellets): νCO ϭ 1957 cmϪ1. Ϫ 31P{1H}
NMR (CDCl3): δ ϭ 24.1 (s). Ϫ C37H30ClIrOP2 (780.27): calcd. C
56.96, H 3.88, O 2.05; found C 56.62, H 4.27, O 3.34.
Ruthenium Complexes
HCON(CH3)2], 8.37 [s,
HCON(CH3)2], 3.16 [s,
1
3
H, HCON(CH3)2], 3.18 [s, 3 H,
H, HCON(CH3)2], 3.06 [s, 3 H,
[PPN]2[RuCl5(CO)]: The complex was prepared from RuCl3·3H2O
(0.4 g, 1.53 mmol) in DMF (15 mL) in a closed Schlenk tube with-
out any reflux condenser system. The solution was heated under
reflux and IR monitoring of the reaction showed the formation of
the carbonylchloro anion (νCO ϭ 2020 cmϪ1). After 10 min, the
solution was allowed to cool and [PPN]Cl (0.88 g, 1.53 mmol) was
added. After concentration of the solution in vacuo at 100 °C to a
volume of 5 mL, cold water (10 mL) was added dropwise to precip-
itate the complex as a dark-red powder. After collection of the
product by filtration using a Büchner funnel and washing with
water (100 mL), the product was dried in vacuo to give 0.15 g (7%
based on RuCl3·3H2O). Ϫ IR (KBr pellets): νCO ϭ 2008 cmϪ1. Ϫ
C73H60Cl5N2OP4Ru (1383.52): calcd. C 63.37, H 4.37, N 2.02, O
1.16; found C 63.22, H 4.33, N 2.18, O 1.55.
HCON(CH3)2], 3.00 [s, 3 H, HCON(CH3)2]. Ϫ C8H14Cl2N2O4Ru
(374.19): calcd. C 25.68, H 3.77, N 7.49, O 17.10; found C 25.58,
H 3.11, N 6.92, O 16.45.
cis,cis,trans-[RuCl2(CO)2(PPh3)2]: The complex was prepared by
adding 2 equiv. of PPh3 (0.8 g, 3.05 mmol) to the aforementioned
[NH2(CH3)2][RuCl3(CO)2(DMF)] solution in DMF [prepared from
RuCl3·3H2O (0.4 g, 1.53 mmol) and anhydrous HCl (1 mL,
4 mmol, 4  in dioxane) in DMF (15 mL)] at 140 °C. The solution
was maintained at this temperature until its IR spectrum showed
the νCO bands at 2058 and 1994 cmϪ1 characteristic of cis,cis,trans-
[RuCl2(CO)2(PPh3)2] (1 h). The yellow solution was then allowed
to cool to room temperature, and the pale-yellow complex was pre-
cipitated by adding cold water. It was collected by filtration using
[PPN]2[RuCl4(CO)(DMF)]: The complex was prepared from a Büchner funnel, washed with water (100 mL), and dried in vacuo
RuCl3·3H2O (0.3 g, 1.15 mmol) and HCl (250 µL, 37% in water) in
to give 0.7 g of the title compound (64% based on RuCl3·3H2O).
Eur. J. Inorg. Chem. 2001, 2327Ϫ2336
2335

P. Serp, M. Hernandez, B. Richard, P. Kalck
FULL PAPER
Ϫ IR (KBr pellets): νCO ϭ 2054, 1992 cmϪ1. Ϫ 31P{1H} NMR
(CDCl3): δ ϭ 17.2 (s). Ϫ C38H30Cl2O2P2Ru (752.58): calcd. C
60.65, H 4.02, O 4.25; found C 60.85, H 4.15, O 4.94.
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Palladium and Platinum Complexes
[PdCl2(DMF)2]: The complex was prepared from PdCl2 (0.2 g,
1.13 mmol) in DMF (15 mL). The solution was heated for 120 min
at 100 °C and then concentrated to dryness in vacuo at 50 °C. The
complex (0.091 g, 25% based on PdCl2) was recovered as a black
powder. Ϫ IR (KBr pellets): νCO ϭ 1656 cmϪ1 (coordinated DMF).
Ϫ C6H14Cl2N2O2Pd (323.52): calcd. C 22.28, H 4.36, N 8.66; found
C 22.50, H 3.91, N 7.90.
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[PPN][PtCl3(CO)]: The complex was prepared from K2PtCl4 (0.4 g,
0.96 mmol) and [PPN]Cl (0.554 g, 0.97 mmol) in DMF (15 mL).
The solution was refluxed for 120 min and then allowed to cool to
room temperature. The complex (0.438 g, 53% based on K2PtCl4)
was recovered by precipitation with cold water and washed with
further water (100 mL). Ϫ IR (KBr pellets): νCO ϭ 2072 cmϪ1. Ϫ
13C{1H} NMR (CDCl3): δ ϭ 150.2 (s). Ϫ C37H30Cl3NOP2Pt
(868.04): calcd. C 51.20, H 3.48, N 1.61; found C 51.89, H 3.77,
N 2.14.
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Acknowledgments
The authors are grateful to Engelhard CLAL for a generous loan
of rhodium and palladium salts.
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´
[I01040]
2336
Eur. J. Inorg. Chem. 2001, 2327Ϫ2336