Square-planar carbonylchlororhodium(I) complexes containing trans-spanning diphosphine ligands as catalysts for the carbonylation of methanol

Article abstract of DOI:10.1002/hlca.200590032

The rhodium(I) complexes trans-[Rh(diphos)(CO)Cl] 7 (diphos = pbpb), 8 (diphos = nbpb), and 9 (diphos = cbpb) were synthesized (Scheme 4) and used as catalysts for the carbonylation of MeOH to AcOH (Scheme 1). The trans coordination imposed by the rigid C-spacer framework of the diphos ligands pbpb, nbpb, and cbpb, demonstrated by ³¹P-NMR and IR spectroscopy of 7-9 and unambiguously confirmed by single-crystal X-ray structure analysis of 7, improved the thermal stability of the rhodium(I) system under carbonylation conditions and, hence, the catalytic performance of the complexes. For the catalytic carbonylation of MeOH, the active catalyst could be prepared in situ from the mixture of [Rh(CO)₂Cl]₂ and the corresponding diphos ligand pbpb, nbpb, or cbpb, giving the same results as carbonylation in the presence of the isolated complexes 7, 8 or 9 (see Table). The highest activity was observed for complex 7 (or the mixture [Rh(CO)₂Cl] ₂/ pbpb, the catalytic turnover number (TON) being 950 after 15 min (170°, 22 bar).

Full text of DOI:10.1002/hlca.200590032

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Helvetica Chimica Acta ± Vol. 88 (2005)
Square-Planar Carbonylchlororhodium(I) Complexes Containing trans-
Spanning Diphosphine Ligands as Catalysts for the Carbonylation of
Methanol
by Sylvain Burger, Bruno Therrien, and Georg Süss-Fink*
Â
Ã
Ã
Institut de Chimie, Universite de Neuchatel, Avenue de Bellevaux 51, CH-2007 Neuchatel
(fax: ‡ 41-32/7182511; e-mail: georg.suess-fink@unine.ch)
Â
Dedicated to Professor Andre Merbach on the occasion of this 65th birthday
The rhodium(I) complexes trans-[Rh(diphos)(CO)Cl] 7 (diphos ˆ pbpb), 8 (diphos ˆ nbpb), and 9
(diphos ˆ cbpb) were synthesized (Scheme 4) and used as catalysts for the carbonylation of MeOH to AcOH
(Scheme 1). The trans coordination imposed by the rigid C-spacer framework of the diphos ligands pbpb, nbpb,
and cbpb, demonstrated by 31P-NMR and IR spectroscopy of 7 ± 9 and unambiguously confirmed by single-
crystal X-ray structure analysis of 7, improved the thermal stability of the rhodium(I) system under
carbonylation conditions and, hence, the catalytic performance of the complexes. For the catalytic carbonylation
of MeOH, the active catalyst could be prepared in situ from the mixture of [Rh(CO)2Cl]2 and the corresponding
diphos ligand pbpb, nbpb, or cbpb, giving the same results as carbonylation in the presence of the isolated
complexes 7, 8 or 9 (see Table). The highest activity was observed for complex 7 (or the mixture [Rh(CO)2Cl]2/
pbpb, the catalytic turnover number (TON) being 950after 15 min (170 8, 22 bar).
Introduction. ± The carbonylation of MeOH to generate AcOH is one of the most
important homogeneously catalyzed industrial processes [1] (Scheme 1). The produc-
tion of AcOH by the Monsanto process is based on soluble Rh-catalysts and operates at
pressures of 30to 60bar and temperatures of 150to 20
8. The process gives
selectivities of over 99% based on MeOH [2]. The reaction requires the presence of
iodide, which converts MeOH prior to carbonylation into the actual substrate MeI [2].
The anion cis-[Rh(CO)2I2]À was found to be the initial catalytically active species [3].
As the rate-determining step of the catalytic cycle is the oxidative addition of MeI to
cis-[Rh(CO)2I2]À [4], electron enrichment at the metal center is expected to facilitate
this step and to improve the rate of AcOH formation. Consequently, square-planar
rhodium(I) complexes with ligands that increase the electron density at the Rh-atom
have been developed and studied as catalysts; they give better or at least comparable
activities than the original Monsanto catalyst [5 ± 8].
Scheme 1. Production of Acetic Acid by Carbonylation of Methanol
Cole-Hamilton and co-workers have investigated the use of strong electron-
donating ligands (trialkylphosphines) as promoters for Rh-based carbonylation
catalysts [9]. Complexes of the type trans-[Rh(PEt3)2(CO)X] (X ˆ Cl, Br, or I) have
a CO absorption centered around 1960cm À1, as compared to 1988 and 2059 cmÀ1 for
ꢀ 2005 Verlag Helvetica Chimica Acta AG, Zürich

Helvetica Chimica Acta ± Vol. 88 (2005)
479
cis-[Rh(CO)2I2]À, suggesting a more electron-rich metal center in the triethylphos-
phine complexes. Indeed, trans-[Rh(PEt3)2(CO)Cl] turned out to be a very active
catalyst precursor for AcOH production [9].
Complexes containing P,P-linked bis[phosphine] ligands have also been studied as
catalysts for the carbonylation of MeOH [10][11], they are in general more stable than
their complexes containing unlinked bis(monophosphine) analogues. However, since
complexes containing P,P-linked bis[phosphines] are usually cis-configured, they are
less active than the trans-configured bis(monophosphine) complexes [11]. The stability
of such Rh-complexes employed as catalysts under the harsh carbonylation conditions
is a crucial point. Therefore, we decided to develop trans-spanning P,P-linked
bis[phosphine] (diphos) ligands that, in combination with RhI complexes, might
combine the activity of complexes such as trans-[Rh(PEt3)2(CO)Cl] [9] with the
stability of complexes such as cis-[Rh(Ph2PCH2CH2PAr2)(CO)Cl] [11].
The diphos ligand 2-{[2-(diphenylphosphino)benzoyl]phenylamino}ethyl 2-(diphen-
ylphosphino)benzoate (pbpbz) reacts with [Rh(CO)2Cl]2 to give trans-
[Rh(pbpbz)(CO)Cl] (1), imposing trans coordination at the Rh-center [12]
(Scheme 2). Indeed, this complex turned out to be very robust and highly active for
MeOH carbonylation: it converts MeOH into AcOH at 1708 and a CO pressure of
22 bar within 15 min with a turnover number (TON) of 800 mol product per mol
catalyst (as compared to 380for cis-[Rh(CO)2I2]À). Moreover, 1 can be reused after a
catalytic run showing almost the same activity [12].
Scheme 2. trans-Coordination of the diphos Ligand pbpbz Generating Square-Planar Rhodium(I) Centers
Based on the fundamental mechanistic work of Forster [3][13] and Maitlis and co-
workers [14][15] on the catalytic cycle involving cis-[Rh(CO)2I2]À, we have proposed
the mechanism shown in Scheme 3 when trans-[Rh(pbpbz)(CO)Cl] (1) is used as a
catalyst precursor [12]: after generation of the catalytically active iodo derivative 2, the
oxidative addition of MeI generates complex 3, which rearranges to give complex 4.
Uptake of CO converts 4 into 5, which reductively eliminates AcI to regenerate 2. From
the catalytic mixture, we have isolated the dinuclear complexes 6a and 6b, which arise
from the mononuclear complex 4 by loss of a bis[phosphine] ligand; 6a and 6b may be
considered a resting state of the key species 4 [12].

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Scheme 3. Proposed Mechanism of the Carbonylation of Methanol to Acetic Acid Catalyzed by 1 as the Catalyst
Precursor [12]
As shown by their single-crystal X-ray structure analyses, the isomeric 6a and 6b
differ in the orientation of the two acetyl ligands and the coordination sites of the
bridging diphos ligand [12]. The formation of these two isomers is presumably due to
the rotational freedom of the CÀO (acyl) bond with respect to the more restricted
rotation of the CÀN (amide) bond of pbpbz in 1, which can be explained by an
increased steric angle of the N-atom carrying an additional substituent.
For this reason, we decided to develop more-rigid diphos ligands imposing trans
geometry by using linkers containing two amide functions. We, therefore, synthesized
the diphos ligands N,N'-(1,2-phenylene)bis[2-(diphenylphosphino)benzamide] (pbpb)

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481
[16] and N,N'-naphthalene-1,8-diylbis[2-(diphenylphosphino)benzamide] (nbpb) [17]
as well as the well known trans-configurated racemic ligand N,N'-[(1RS,2RS)-cyclo-
hexane-1,2-diyl]bis[2-(diphenylphosphino)benzamide] (cbpb), which was first synthe-
sized by Trost and co-workers [18] (see Fig. 1).
Fig. 1. The rigid diphos ligands N,N'-(1,2-phenylene)(pbpb), N,N'-naphthalene-1,8-diyl(nbpb), and N,N'-
[(1RS,2RS)-cyclohexane-1,2-diyl]bis[2-(diphenylphosphino)benzamide](cbpd)
In this paper, we report the coordination of these diphos ligands to RhI to give the
trans-configured square-planar complexes trans-[Rh(pbpb)(CO)Cl] (7), trans-
[Rh(nbpb)(CO)Cl] (8), and trans-[Rh(cbpb)(CO)Cl] (9), the molecular structure of
7, and the catalytic potential of these complexes for the carbonylation of MeOH.
Results and Discussion. ± The 2-(diphenylphosphino)benzoic acid, easily available
by Wurtz coupling from sodium 2-chlorobenzoate and sodium diphenylphosphide [19],
is an attractive building block for the synthesis of P,P-linked bis [phosphine] ligands by
condensation of the acid function with diols, diamines, or amino alcohols [20]. Peptidic
coupling between benzene 1,2-diamine, naphthalene-1,8-diamine, or racemic trans-
cyclohexane-1,2-diamine and 2-(diphenylphosphino)benzoic acid afforded the diphos
ligands pbpb [16], nbpb [17], and cbpb [18] in good yields (see Fig. 1). These diphos
ligands are expected to form trans-coordinated square-planar complexes comprising a
13- or 14- membered metallacycle due to their rigid C-framework. Accordingly, the PdII
complex trans-[Pd(pbpb)Cl2] has been synthesized and structurally characterized [16].
Di-m-chlorotetracarbonyldirhodium, [Rh(CO)2Cl]2, reacted with 2 equiv. of pbpb,
nbpb, and cbpb to give the RhI complexes 7, 8, and 9, respectively (Scheme 4). These
compounds were isolated after chromatographic purification as air-stable yellow solids.
The symmetrical complexes 7 and 8 showed only one resonance in the 31P-NMR
spectrum, while 9 gave rise to two signals. All complexes displayed a characteristic s in
the 1H-NMR spectrum (CDCl3) at d ca. 8.5 for the amide protons and a strong nÄ(CO)
absorption around 1950cm À1 in the IR spectrum, comparable with the nÄ(CO) reported
for other trans-[Rh(PR3)2(CO)X] complexes [7][23] but significantly lower than that
of cis-[Rh(dppe)(CO)I] (dppe ˆ ethane-1,2-diylbis[diphenylphosphine] [11]. A me-
dium-to-strong absorption at ca. 3370cm À1 is indicative of the amide function in each
complex. The trans-coordination of the diphos ligands in complexes 7 ± 9, deduced from
IR and NMR data, was unequivocally confirmed by the single-crystal X-ray structure
analysis of 7 (Fig. 2).
In the crystal structure of 7, the Rh-atom is in a square-planar geometry,
surrounded by a Cl-, a C-, and two P-atoms. The chelating diphos ligand pbpb adopts a

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Scheme 4. Synthesis of trans-[Rh(diphos)(CO)Cl] Complexes 7 ± 9 from [Rh(CO)2Cl]2 and the diphos Ligands
pbpb, nbpb, and cbpb
Fig. 2. ORTEP [24] View of complex 7. Displacement ellipsoids are drawn at the 50% probability level, H-
atoms and CHCl3 molecules are omitted for clarity. Selected bond lengths [Š] and angles [0]: P(1) ± Rh(1)
2.318(2), P(2) ± Rh(1) 2.343(2), Cl(1) ± Rh(1) 2.373(2), C(50) ± Rh(1) 1.818(10), C(50) ± O(3) 1.147(11);
C(50) ± Rh(1)-Cl(1) 179.2(3), Cl(1) ± Rh(1) ± P(1) 91.47(8), Cl(1) ± Rh(1) ± P(2) 89.13(8), C(50) ± Rh(1) ± P(2)
91.2(3), C(50) ± Rh(1)-P(1) 88.3(3), P(1) ± Rh(1) ± P(2) 173.44(9), O(3) ± C(50) ± Rh(1) 177.9(9).
trans coordination geometry. The CÀRhÀCl and the PÀRhÀP axes are almost linear,
the corresponding angles being 179.2(3) and 173.44(9)8, respectively. The RhÀCO
distance is comparable to those observed in other trans-[Rh(PR3)2(CO)Cl] complexes

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[24 ± 30]. In the crystal structure of 7, an intramolecular H-bond is observed between
the NH of an amine function and the RhÀCl moiety (NÀCl 3.355(7) Š, NÀH ´´´ Cl
161.78). The N ´´´ Cl distance is slightly longer than the one observed in the analogous
complex [Rh(Ph2PÀCH(o-ClC6H4)ÀNHPh)2(CO)Cl] (3.116(3) Š) [31]. Intermolec-
ular interactions also take place: the five CHCl3 molecules present in the crystal
interact weakly with complex 7.
The bis[phosphine] ligands pbpb, nbpb, and cbpb were studied in combination with
[Rh(CO)2Cl2] for the catalytic carbonylation of MeOH to give AcOH in the presence
of MeI and H2O. The reaction was carried out at 1708 under a CO pressure of 22 bar,
the catalyst/substrate ratio being 1:2000. After 15 min of stirring at 1708, the reaction
was stopped and the mixture analyzed by 1H-NMR and GC to determine the quantities
of products formed. In all cases, 1H-NMR and GC gave substantially the same results.
As a control experiment, the catalytic reaction was also carried out with the Monsanto
catalyst [Rh(CO)2I2]À, which was formed in situ from [Rh(CO)2Cl]2 under the reaction
conditions (Table, Entry 1) and also with the asymmetric bis[phosphine] ligand
Ph2PC6H4C(O)N(Ph)(CH2)2OC(O)C6H4PPh2 (pbpbz), which we reported previously
(Table, Entry 3) [12]. After each experiment, all volatiles were removed under reduced
pressure, and the residue was used for a second catalytic run. The same quantities of
MeOH, MeI, and H2O were used for each test. The results of the catalytic runs are
summarized in the Table.
Table. Methanol Carbonylation Dataa)
Entry
Catalyst precursor
TONb)
1
2
3
4
5
6
7
8
[Rh(CO)2Cl]2
380 Æ 10
200 Æ 10
80 Æ 10
800 Æ 10
950 Æ 10
750 Æ 10
970 Æ 10
740 Æ 10
600 Æ 10
500 Æ 10
630 Æ 10
520 Æ 10
800 Æ 10
600 Æ 10
820 Æ 10
590 Æ 10
Residue of Entry 1
[Rh(CO)2Cl]2/pbpbzc)
Residue of Entry 3
0
[Rh(CO)2Cl]2/pbpb
Residue of Entry 5
trans-[Rh(pbpb)(CO)Cl] (7)
Residue of Entry 7
[Rh(CO)2Cl]2/nbpb
Residue of Entry 9
trans-[Rh(nbpb)(CO)Cl] (8)
Residue of Entry 11
[Rh(CO)2Cl]2/cbpb
Residue of Entry 13
trans-[Rh(cbpb)(CO)Cl] (9)
Residue of Entry 15
9
10
11
12
13
14
15
16
a) Catalytic conditions: [Rh(CO)2Cl]2 (57 mmol), ligand (0.12 mmol, 2 equiv.), MeOH (110.2 mmol), MeI
(11.4 mmol), H2O (81.9 mmol), 1708, 22 bar, 900 rpm, reaction time 15 min. b) Turnover numberˆ mol MeOH
converted into AcOH per mol catalyst precursor. c) For pbpbz, see Scheme 2.
The MeOH carbonylation data (Table) clearly showed an increase in the catalytic
activity in the presence rigid bis[phosphine] ligands imposing trans geometry at the Rh-
center: with respect to the classical Monsanto catalyst, which gave a turnover number
of 380within 15 min under standard conditions ( Entry 1), higher turnover numbers
(600 ± 950) were observed in the presence of these diphos ligands (Entries 3, 5, 9, and

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13), the highest activity being observed for the combination [Rh(CO)2Cl]2/pbpb (TON
950, Entry 5). The lower activity of the system [Rh(CO)2Cl]2/nbpb (TON 600, Entry 9)
is presumably due to the lower solubility of nbpb in the reaction medium. The isolated
complexes trans-[Rh(pbpb)(CO)Cl] (7), trans-[Rh(nbpb)(CO)Cl] (8), and trans-
[Rh(cbpb)(CO)Cl] (9) exhibited the same catalytic activities (Entries 7, 11, and 15) as
the mixtures of [Rh(CO)2Cl]2 and the corresponding diphos ligand (Entries 5, 9 and
13). Also, the stability of the catalytic system was increased with these diphos ligands:
Whereas the catalytic activity of the classical Monsanto catalyst [Rh(CO)2Cl]2
decreased from TON 380to 200for the second catalytic run ( Entries 1 and 2), the
activity loss was considerably lower with the diphos ligands (TON 950 vs. 750for pbpb,
TON 600 vs. 500 for nbpb, and TON 800 vs. 600 for cbpb), however without reaching
the stability of the [Rh(CO)2Cl]2/pbpbz system (Entries 3 and 4) [12].
Conclusions. ± The bis[phosphine] ligands pbpb, nbpb, and cbpb containing rigid
spacers reacted with [Rh(CO)2Cl]2 to give the trans-configured Rh-complexes trans-
[Rh(pbpb)(CO)Cl] (7), trans-[Rh(nbpb)(CO)Cl] (8), and trans-[Rh(cbpb)(CO)Cl]
(9). The catalytic activities of these complexes in the carbonylation of MeOH to give
AcOH was studied. Complexes 7 ± 9 turned out to be more active and more stable than
the classical Monsanto catalyst. The same catalytic activity as for 7 ± 9 was also obtained
by in situ formation of these complexes from the precursor mixtures [Rh(CO)2Cl]2/
diphos (diphos ˆ pbpb, nbpb, or cbpb).
This work is supported by the Swiss National Science Foundation (Grant No. 20-61227-00). We thank
Professor H. Stoeckli-Evans for helpful discussions.
Experimental Part
General. The ligands pbpb, nbpb, and cbpb were synthesized according to [16 ± 18]. Solvents were dried and
distilled under N2 prior to use. All reactions were carried out under N2 by using standard Schlenk techniques. All
other reagents were purchased (Fluka) and used as received. CC ˆ Column chromatography. IR Spectra:
Perkin-Elmer 1720X FTIR spectrometer; nÄ in cmÀ1. NMR Spectra: Varian Gemini-200-BB instrument; d in ppm
referenced to the signals of the residual protons of the deuterated solvents, J in Hz. MS: in m/z. Microanalyses
were carried out in the Laboratory of Pharmaceutical Chemistry, University of Geneva, Switzerland.
Catalytic Runs. In a typical experiment, [Rh(CO)2Cl]2 (24 mg, 0.06 mmol) and the ligand (0.12 mmol) (or
directly the complex) were dissolved in MeOH (4.46 ml). The soln. was placed in a 100-ml stainless-steel
autoclave, and MeI (11 mmol) and H2O (200 mmol) were added. After purging with CO (3Â), the autoclave
was pressurized with CO (22 bar) and placed into an oil bath preheated to 1708. The mixture was magnetically
stirred at 900 rpm. After 35 min, the autoclave was cooled to r.t., and the pressure was released. The soln. was
filtered and analyzed by NMR and GLC (Dani-86.10 gas chromatograph, split-mode capillary injection system,
flame-ionization detector, Cp-wax-52-CB capillary column (25 m  0.32 mm).
1(SP-4-1)-Carbonylchloro[N,N'-(1,2-phenylene)bis[2-(diphenylphosphino-kP)benzamide]]rhodium (7). A
soln. of [Rh(CO)2Cl]2 (50 mg, 0.13 mmol) and pbpb (95 mg, 0.14 mmol) in CH2Cl2 (20ml) was stirred at r.t. for
2 h. The solvent was evaporated, the residue dissolved in acetone (10ml), the soln. filtered and then evaporated,
and the resulting yellow solid washed with hexane (3 Â 10ml), dried in vacuo, and subjected to CC (silica gel,
CH2Cl2/EtOH (9 :1): 67 mg (56%) of 7. IR (KBr): 3390m, 3029w, 2975m, 2854m, 1976vs, 1650m, 1586m, 1493m,
1450s, 1269m, 1100m, 760m, 70 1s. 1 H-NMR (CDCl3): 8.63 (s, 2 NH); 7.60± 6.80( m, 32 arom. H); 13C{1H}-NMR
(CDCl3). 168.75 (CˆO), 141.75, 136.34, 135.06, 135.00, 131.43, 131.05, 130.91, 130.48, 129.55, 129.18, 128.92,
‡
128.88, 125.91, 125.15 (arom. C). 31P-NMR (CDCl3): 37.12 (J(P,Rh) ˆ 130). ESI-MS: 816 ([M À Cl] ). Anal.
calc. for C45H34ClN2O3P2Rh (851.07): C 63.5, H 4.0, N 3.3; found: C 63.2, H 4.1, N 3.1.
(SP-4-1)-Carbonylchloro[N,N'-naphthalene-1,8-diylbis[2-(diphenylphsophino-kAbenzamide]]rhodium
(8). As described for 7, with [Rh(CO)2Cl]2 (50 mg, 0.13 mmol), pbpb (95 mg, 0.14 mmol), and CH2Cl2 (20ml).

Helvetica Chimica Acta ± Vol. 88 (2005)
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CC (silical gel, CH2Cl2/EtOH 20:1) gave 50mg (40%) of 8. IR (KBr): 3378m, 3019w, 2956m, 2875m, 1964vs,
1648m, 1599m, 1490m, 1478m, 1438s, 1266m, 1098m, 747m, 698s. 1 H-NMR (CDCl3): 8.63 (s, 2 NH); 7.70± 6.80
(m, 34 arom. H). 13C{1H}-NMR (CDCl3). 168.42 (CˆO); 141.65, 136.40, 136.29, 135.67, 135.21, 135.01, 132.02,
131.43, 131.09, 130.78, 129.99, 129.54, 128.91, 128.84, 126.76, 125.33 (arom. C). 31P-NMR (CDCl3): 35.47
‡
(J(P,Rh) ˆ 135). ESI-MS: 865 ([M À Cl] ). Anal. calc. for C49H36ClN2O3P2Rh (901.13): C 65.3, H 4.0, N 3.1;
found: C 65.1, H 4.3, N 3.2.
(SP-4-1)-Carbonylchloro{N,N'-[(1RS,2RS)-cyclohexane-1,2-diyl]bis[2-(diphenylphosphino-KP)benzamide]}-
rhodium (9). As described for 7, with [Rh(CO)2Cl]2 (50 mg, 0.13 mmol), cbpb (95 mg, 0.14 mmol), and CH2Cl2
(20ml). CC (silica gel, acetone/hexane 1 :2) yielded 73 mg (61%) of 9. IR (KBr): 3364m, 3026w, 2955m, 2933m,
2869m, 1965s, 1650s, 1602m, 1583m, 1478m, 1316m, 1300m, 1255s, 1219m, 1190s, 1156m, 1095m, 1044m, 977m,
865w, 738m, 673w, 624w, 599w. 1H-NMR (CDCl3): 8.66 (s, 2 NH): 7.70± 6.80 ( m, 28 arom. H); 3.48 (m,
2 NHCH); 1.0± 2.0( m, 8 H (chx). 13C{1H}-NMR (CDCl3): 179.63, 179.30(C ˆO); 141.62, 138.11, 137.21, 136.39,
136.03, 135.79, 135.48, 135.17, 134.86, 134.35, 133.98, 133.59, 133.24, 132.69, 131.96, 131.54, 131.13, 130.55, 130.36,
130.22, 129.40, 129.13, 129.01, 128.58, 128.14, 127.76 (arom. C); 49.38 (NHCH); 31P-NMR (CDCl3): 35.68 (d,
‡
J(P,Rh) ˆ 130); 35.54 (d, J(P,Rh) ˆ 130). ESI-MS: 821 ([M À Cl] ). Anal. calc. for C45H40ClN2O3P2Rh (857.12):
C 63.6, H 4.7, N 3.3; found: C 63.9, H 4.4, N 3.2.
X-Ray Crystallographic Study. Crystal data for 7 ´ (CHCl3)5: C50H39Cl16N2O3P2Rh, M 1447.88; triclinic, space
group P-1; cell parameters a ˆ 12.700(1), b ˆ 14.785(1), c ˆ 17.058(2) Š, a ˆ 70.49(1), b ˆ 80.42(1), g ˆ
89.36(1)8, Vˆ 2973.4(5) Š3, T 153(2) K, Z ˆ 2, Dc ˆ 1.617 g cmÀ3, m ˆ 1.103 mmÀ1; 23385 reflections measured,
10742 unique (Rint ˆ 0.1514), which were used in all calculations. Crystals of 7 were obtained by slow
evaporation of a CHCl3 soln. A crystal (yellow plate, 0.48 Â 0.38 Â 0.07 mm) was mounted on a Stoe Image-
Plate-Diffraction system equipped with a f circle goniometer; Mo-Ka graphite monochromated radiation (l
0
0.71073 Š); f range 0± 200 , increment of 1.48; exposure time 10min per frame, 2 q range from 2.0± 26 0; Dmax
±
Dmin ˆ 12.45 ± 0.81 Š. The structure was solved by direct methods by using the program SHELXS-97 [33]. The
refinement and all further calculations were carried out with SHELXL-97 [34]. The H-atoms were included in
calculated positions and treated as riding atoms with the SHELXL default parameters. The non-H-atoms were
refined anisotropically by using weighted full-matrix least-square on F2 with 667 parameters. R1 ˆ 0.0855 (I >
À3
2s(I)) and wR2 ˆ 0.2029; g.o.f. ˆ 0.882; max./min. residual density 1.759/ À 1.194 eŠ
.
CCDC-249715 (7 ´ (CHCl3)5) contains the supplementary crystallographic data for this paper. These data
can be obtained free of charge at www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cambridge
Crystallographic Data Centre, 12, Union Road, Cambridge CB2 1EZ, UK; fax: ‡ 441223336033; E-mail:
deposit@ccdc.cam.ac.uk).
REFERENCES
[1] K. Weisermel, H.-J. Arpe, ꢁIndustrial Organic Chemistryꢂ, 3rd edn., VCH, Weinheim, 1997.
[2] G. W. Parshall, S. D. Ittel, ꢁ Homogeneous Catalysisꢂ, 2nd edn., Wiley-Interscience, New York, 1992, p. 96.
[3] D. Forster, J. Am. Chem. Soc. 1976, 98, 846.
[4] S. J. Dossett, A. Gillon, A. G. Orpen, J. S. Fleming, P. G. Pringle, D. F. Wass, M. D. Jones, Chem. Commun.
2001, 699.
[5] T. Ghaffar, H. Adams, P. M. Maitlis, A. Haynes, G. J. Sunley, M. J. Baker, Chem. Commun. 1998, 1023.
[6] J. Rankin, A. D. Poole, A. C. Benyei, D. J. Cole-Hamilton, Chem. Commun. 1997, 1835.
[7] K. V. Katti, B. D. Santarsiero, A. A. Pinkerton, R. G. Cavell, Inorg. Chem. 1993, 32, 5919.
[8] M. J. Baker, M. F. Giles, A. G. Orpen, M. J. Taylor, R. J. Watt, Chem. Commun. 1995, 197; L. Gonzalvi, H.
Adams, G. J. Sunley, E. Ditzel, A. Haynes, J. Am. Chem. Soc. 1999, 121, 11233.
[9] J. Rankin, A. D. Poole, A. C. Benyei, D. J. Cole-Hamilton, Chem. Commun. 1997, 1835.
[10] K. G. Moloy, R. W. Wegman, Organometallics 1989, 8, 2883.
[11] C.-A. Carraz, E. J. Ditzel, A. G. Orpen, D. D. Ellis, P. G. Pringle, G. J. Sunley, Chem. Commun. 2000, 1277.
[12] C. M. Thomas, R. Mafua, B. Therrien, E. Rusanov, H. Stoeckli-Evans, G. Süss-Fink, Chem.±Eur. J. 2002, 8,
3343.
[13] D. Forster, Adv. Organomet. Chem. 1979, 17, 255.
[14] A. Haynes, B. E. Mann, D. J. Gulliver, G. E. Morris, P. M. Maitlis, J. Am. Chem. Soc. 1991, 113, 8567.
[15] P. M. Maitlis, A. Haynes, G. J. Sunley, M. J. Howard, J. Chem. Soc., Dalton Trans. 1996, 2187.
[16] S. Burger, B. Therrien, G. Süss-Fink, Eur. J. Inorg. Chem. 2003, 8, 3099.
[17] S. Burger, B. Therrien, G. Süss-Fink, Inorg. Chim. Acta. 2004, 4, 1213.

486
Helvetica Chimica Acta ± Vol. 88 (2005)
[18] B. M. Trost, D. L. Van Vranken, C. Bingel, J. Am. Chem. Soc. 1992, 114, 9327.
[19] J. E. Hoots, T. B. Rauchfuss, D. A. Wrobleski, Inorg. Synth. 1982, 21, 178.
[20] B. M. Trost, D. L. Van Vranken, Angew. Chem. 1992, 104, 194; Angew. Chem., Int. Ed. 1992, 31, 228; A.
Hassner, L. Krepski, V. Alexanian, Tetrahedron 1978, 34, 2069; A. Hassner, V. Alexanian, Tetrahedron Lett.
1978, 19, 4475; E. F. V. Scriven, Chem. Soc. Rev. 1983, 12, 129; C. M. Thomas, A. Neels, H. Stoeckli-Evans,
G. Süss-Fink, Eur. J. Inorg. Chem. 2001, 12, 3005.
[21] W. E. Hill, D. M. A. Minahan, J. G. Taylor, C. A. McAuliffe, J. Am. Chem. Soc. 1982, 104, 60 0 1.
[22] S. Burger, B. Therrien, G. Süss-Fink, Acta Crystallogr., Sect. E 2004, 60, m1163.
[23] J. Rankin, A. C. Benyei, A. D. Poole, D. J. Cole-Hamilton, J. Chem. Soc., Dalton Trans. 1999, 3771.
Â
[24] A. Monge, E. Gutierrez-Puebla, J. V. Heras, E. Pinilla, Acta Crystallogr., Sect. C 1983, 39, 446.
[25] B. D. Murray, H. Hope, J. Hvoslef, P. P. Power, Organometallics 1984, 3, 657.
[26] L. J. Farrugia, J. Appl. Crystallogr. 1997, 30, 565.
[27] Y. J. Chen, J. C. Wang, Y. Wang, Acta Crystallogr., Sect. C 1991, 47, 2441.
[28] J. M. Kessler, J. H. Nelson, J. S. Frye, A. DeCian, J. Fischer, Inorg. Chem. 1993, 32, 1048.
[29] C. Corcoran, J. Fawcett, S. Friedrichs, J. H. Holloway, E. G. Hope, D. R. Russell, G. C. Saunders, A. M.
Stuart, J. Chem. Soc., Dalton Trans. 2000, 161.
[30] A. Muller, A. Roodt, S. Otto, Š. Oskarsson, S. Yong, Acta Crystallogr., Sect. E 2002, 58, m715.
[31] M. R. Wilson, A. Prock, W. P. Giering, A. L. Fernandez, C. M. Haar, S. P. Nolan, B. M. Foxman,
Organometallics 2002, 21, 2758.
[32] J. M. Camus, J. Andrieu, R. Poli, P. Richard, C. Baldoli, S. Maiorana, Inorg. Chem. 2003, 42, 2384.
[33] G. M. Sheldrick, J. Andrieu, R. Poli, P. Richard, C. Baldoli, S. Maiorana, Acta Crystallogr., Sect. A 1990, 46,
467.
[34] G. M. Sheldrick, ꢂSHELXL-97ꢂ, Univ. of Göttingen, Göttingen, Germany, 1999.
Received October 16, 2004