Evaluation of Triflate Displacement by Water in CH2Cl2 Solution: Comparison of trans-[Rh(CO)(PPh3)2(OSO2CF3)] and the Crystalline Salt trans-[Rh(CO)(PPh3)2(OH2)][OTf]

Full text of DOI:10.1021/ic951287h

Inorg. Chem. 1996, 35, 3073-3076
3073
Evaluation of Triflate Displacement by Water in
CH2Cl2 Solution: Comparison of
trans-[Rh(CO)(PPh3)2(OSO2CF3)] and the
Crystalline Salt trans-[Rh(CO)(PPh3)2(OH2)][OTf]
Anna Svetlanova-Larsen and John L. Hubbard*
Department of Chemistry and Biochemistry,
Utah State University, Logan, Utah 84322-0300
ReceiVed October 5, 1995
Introduction
During the course of our studies of the organometallic
chemistry of the electrophilic [Cp*Ru(NO)]2+ fragment, we have
determined that dissociation of OTf- from Cp*Ru(NO)(OTf)2
to give the corresponding solventocations is somewhat exo-
thermic but entropically costly due to the solvent reorganization
required for the formation of the product ion pairs (Cp* )
η-C5(CH3)5; OTf ) OSO2CF3-).1 Thus, we find that in a
homogeneous H2O-saturated CH2Cl2 solution of Cp*Ru(NO)-
(OTf)2, the major species in solution is the neutral ditriflate
complex with only small amounts of [Cp*Ru(NO)(OTf)(OH2)]+
and [Cp*Ru(NO)(OH2)2]2+ being present. In H2O solution,
OTf- solvolysis is promoted by the considerable Lewis acidity
of the [Cp*Ru(NO)]2+ fragment, leading to H3O+ and dinuclear
µ-hydroxy complexes.1b,2
The nature of weakly coordinating ions is important in the
discussion of coordination unsaturation and catalytic reactivity.3,4
We continue to be interested in the equilibria of OTf-
displacement by coordinating solvents and weak ligands. In
concert with our work on Cp*Ru(NO)(OTf)2, some previous
work has shown OTf- to be a “moderately strong” ligand.5 For
example, a kinetic study of the M(CO)5(OTf) complexes (M )
Mn, Re) showed substitution of OTf- by oxygen donor solvents
in CH2Cl2 to occur for M ) Mn but not for M ) Re.6 If one
considers OTf- to be a fairly good ligand, the report that trans-
[Rh(CO)(PPh3)2(OH2)][OTf] persists in solution with no detect-
able traces of the parent complex trans-[Rh(CO)(PPh3)2(OTf)]
Figure 1. Molecular structure of trans-[Rh(PPh3)2(CO)(OH2)][OTf].
Selected bond distances (Å): Rh-P(1), 2.333(4); Rh-C(1), 1.70(1);
Rh-O(1), 2.00(1); P(1)-C(21), 1.81(2); P(1)-C(31), 1.84(1); P(1)-
C(41), 1.81(2); C(1)-O(1), 1.05(1). Selected bond angles (deg): C(1)-
Rh-P(1), 90(3); O(2)-Rh-P(1), 87.4(7); Rh-C(1)-O(1), 177(3).
would be counterintuitive7 even though the dissociation of OTf-
in the “basic” d8 Rh complexes might be expected to be more
favorable than in electrophilic d6 complexes like Cp*Ru(NO)-
(OTf)2.7,8 Prompted by the rather sketchy analytical details
reported for trans-[Rh(CO)(PPh3)2(OH2)][OTf]‚H2O9 and the
importance of square planar rhodium complexes in catalytic
reactions,10 we embarked on a reinvestigation of this case to
see if H2O actually displaces the OTf- ligand in CH2Cl2. The
results of this study show that OTf- is a better ligand than H2O
in CH2Cl2.
Results
Characterization of trans-[Rh(CO)(PPh3)2(OH2)][OTf].
The combustion analysis for the crystalline material isolated
from the reaction of trans-[Rh(CO)(PPh3)2(Cl)] with AgOTf in
benzene agrees with the formula “[Rh(CO)(PPh3)2(OTf)]‚H2O”.
The use of more than 1 equiv of AgOTf in the reaction leads to
significant contamination of the product with AgOTf.11 The
presence of unreacted AgOTf in the product is easily detected
by a broadening of the 19F NMR signal, the depression of the
melting point from 178 °C, and the reduction of the carbon
content as determined by combustion analysis.
The single-crystal structure determination for crystals of
“[Rh(CO)(PPh3)2(OTf)]‚H2O” shows consistency with the ana-
lytical formulation. The calculated crystal density of 1.57 g/cm3
is the same as the density determined by flotation in CCl4/
hexane. The molecular structure of the complex unambiguously
shows a trans-arrangement of the PPh3 ligands (Figure 1).
(1) (a) Burns, R. M.; Hubbard, J. L. J. Am. Chem. Soc. 1994, 116, 9514.
(b) Svetlanova-Larsen, A.; Zoch, C. R.; Hubbard, J. L. Organome-
tallics, in press.
(2) Lewis acidic metal ions like Al3+ are noted for their reactivity in water
to give acidic solutions containing polynuclear µ-OH complexes;
see: Burgess, J. Metal Ions in Solution; John Wiley & Sons: New
York, 1978.
(3) (a) Lawrance, G. A. Chem. ReV. 1986, 86, 17 and references therein.
(b) Beck, W.; Su¨nkel, K.; Chem. ReV. 1988, 88, 1405 and references
therein. (c) Blosser, P. W.; Gallucci, J. C.; Wojcicki, A. Inorg. Chem.
1992, 31, 2376.
(4) Humphrey, R. B.; Lamanna, W. M.; Brookhart, M.; Husk, G. R. Inorg.
Chem. 1983, 22, 3355.
(5) (a) Hollis, T. K.; Robinson, N. P.; Bosnich, B. Organometallics 1992,
11, 2645. (b) Hollis, T. K.; Robinson, N. P.; Bosnich, B. J. Am. Chem.
Soc. 1992, 114, 5464. (c) Bonnesen, P. V.; Puckett, C. L.; Honeychuck,
R. V.; Hersh, W. H. J. Am. Chem. Soc. 1989, 111, 6070. (d)
Honeychuck, R. V.; Bonnesen, P. V.; Farahi, J.; Hersh, W. H. J. Org.
Chem. 1987, 52, 5293. (e) Odenkirk, W.; Rheingold, A. L.; Bosnich,
B. J. Am. Chem. Soc. 1992, 114, 6392. (f) Haggin, J. Aqueous Media
Offer Promises And Problems In Organometallic Catalysis. Chem. Eng.
News Oct. 10, 28-33. (g) Wang, L.; Flood, T. C. J. Am. Chem. Soc.
1992, 114, 3169; (h) Wang, C.; Ziller, J. W.; Flood, T. C. J. Am.
Chem. Soc. 1995, 117, 1647. (i) Wang, L.; Lu, R. S.; Bau, R.; Flood,
T. C. J. Am. Chem. Soc. 1993, 115, 6999. (j) Darensbourg, D. J.;
Stafford, N. W.; Joo, F.; Reibenspies, J. H. J. Organomet. Chem. 1995,
488, 99. (k) McGrath, D. V.; Grubbs, R. H. Organometallics 1994,
13, 224.
(7) Branan, N. M.; Hoffman, N. W.; McElroy, E. A.; Prokopuk, N.;
Salazar, A. B.; Robbins, M. J.; Hill, W. E.; Webb, T. R. Inorg. Chem.
1991, 30, 1200.
(8) (a) Werner, H. Pure Appl. Chem. 1982, 54, 177. (b) Werner, H. Angew.
Chem., Int. Ed. Engl. 1983, 22, 927.
(9) Neither the work in ref 3 nor that in references therein reported the
combustion analysis, mp, and solid-state IR νCO data for the Rh-OTf
complex: Branan, D. M.; Hoffman, N. W.; McElroy, E. A.; Ramage,
D. L.; Robbins, M. J; Eyler, J. R.; Watson, C. H.; deFur, P.; Leary, J.
A. Inorg. Chem. 1990, 29, 1915.
(10) Collman, J. P.; Hegedus, L. S.; Norton, J. R.; Finke, R. G. Principals
of Organotransition Metal Chemistry; University Science Books: Mill
Valley, CA, 1987; chapters 10-12 and references therein.
(11) This reaction can be successfully performed in fluorobenzene with 1
equiv of AgOTf according to the published procedure for the synthesis
of (PPh3)2Ir(CO)(OTf): Liston, D. J.; Lee, Y. J.; Scheidt, W. R.; Reed,
C. A. J. Am. Chem. Soc. 1989, 111, 6643.
(6) (a) Nitschke, J.; Schmidt, S. P.; Trogler, W. C. Inorg. Chem. 1985,
24, 1972. (b) Trogler, W. C. J. Am. Chem. Soc. 1979, 101, 6459.
S0020-1669(95)01287-0 CCC: $12.00 © 1996 American Chemical Society

3074 Inorganic Chemistry, Vol. 35, No. 10, 1996
Notes
Despite disorder of the CO and H2O ligands, the molecular
structure clearly shows the presence of an outersphere OTf-
ion (see Experimental Section). Henceforth, we will refer to
this material as trans-[Rh(CO)(PPh3)2(OH2)][OTf].
Discussion
In contrast to an earlier report,7 the results of our study show
that trans-[Rh(CO)(PPh3)2(OTf)] does not undergo OTf- sub-
stitution by H2O in CH2Cl2. The 20 cm-1 difference in the
νCO absorptions for analytically pure trans-[Rh(CO)(PPh3)2-
(OH2)][OTf] and trans-[Rh(CO)(PPh3)2(OTf)] clearly illustrates
the difference between cationic trans-[Rh(CO)(PPh3)2(OH2)]+
and neutral trans-[Rh(CO)(PPh3)2(OTf)] in the solid-state.
However, the presence of a single carbonyl-containing species
in CH2Cl2 in solutions prepared from either trans-[Rh(CO)-
(PPh3)2(OH2)][OTf] or trans-[Rh(CO)(PPh3)2(OTf)] is compel-
ling evidence that trans-[Rh(CO)(PPh3)2(OTf)] is the only
detectable complex in solution. The H2O is easily removed by
azeotropic distillation in benzene. The 31P NMR signals of
trans-[Rh(CO)(PPh3)2(OTf)] in CH2Cl2 shift to ca. 3 ppm to
lower field upon the addition of pyridine, and identical 31P NMR
signals are generated when pyridine is added to trans-[Rh(CO)-
(PPh3)2(OH2)][BF4]. This shows that pyridine displaces both
H2O and OTf-, giving the trans-[Rh(CO)(PPh3)2(py)]+ ion from
two different starting points. The similarity of the 31P NMR
signals of trans-[Rh(CO)(PPh3)2(OTf)] and trans-[Rh(CO)-
(PPh3)2(Cl)] is consistent with these complexes being neutral
species in solution. The similarity of the downfield 31P NMR
signals from CH2Cl2 solutions of trans-[Rh(CO)(PPh3)2(OH2)]-
[BF4] and trans-[Rh(CO)(PPh3)2(py)][OTf] is consistent with
the presence of the trans-[Rh(CO)(PPh3)2(OH2)]+ and trans-
[Rh(CO)(PPh3)2(py)]+ cations in solution. The conductivity
measurements lead to the same conclusion as the 31P NMR data.
The low electrolytic character of trans-[Rh(CO)(PPh3)2(OTf)]
and trans-[Rh(CO)(PPh3)2(Cl)] suggests they dissolve in CH2-
Cl2 as neutral complexes whereas the significantly higher molar
conductivity of trans-[Rh(CO)(PPh3)2(OH2)][BF4] shows the
presence of the trans-[Rh(CO)(PPh3)2(OH2)]+ and [BF4]- ions
in the CH2Cl2 solution.
The IR spectrum of trans-[Rh(CO)(PPh3)2(OH2)][OTf] in a
Nujol mull shows a strong νCO absorption at 2008 cm-1. A
CH2Cl2 solution of trans-[Rh(CO)(PPh3)2(OH2)][OTf] shows a
νCO absorption at 1996 cm-1. The 19F NMR spectrum of this
CH2Cl2 solution shows a single sharp resonance at δ -78.5
and the 31P NMR spectrum shows a doublet at δ 28.2 (J ) 125
Hz). The presence of water in the homogeneous CH2Cl2
solutions does not alter the IR spectrum or the 19F, 31P, and 1H
NMR spectra. The molar conductivity of a 0.02 M solution of
trans-[Rh(CO)(PPh3)2(OH2)][OTf] in CH2Cl2 is 2.0 (1) Ω-1
cm-1 mol-1. For comparison, the molar conductivity of a 0.01
M solution of trans-[Rh(CO)(PPh3)2(Cl)] in CH2Cl2 is 1.5 (1)
Ω-1 cm-1 mol-1
.
Isolation of trans-[Rh(CO)(PPh3)2(OTf)]. Analytically pure
trans-[Rh(CO)(PPh3)2(OTf)] is obtained by the azeotropic
removal of water from a benzene solution prepared with trans-
[Rh(CO)(PPh3)2(OH2)][OTf] or by freeze-drying the benzene
solution under high vacuum. The IR spectrum of micro-
crystalline trans-[Rh(CO)(PPh3)2(OTf)] in Nujol shows a νCO
absorption at 1988 cm-1, and the νCO absorption appears at 1996
cm-1 when the complex is dissolved both in rigorously dry CH2-
1
Cl2 and in H2O-saturated CH2Cl2. The H, 19F, and 31P NMR
signals of trans-[Rh(CO)(PPh3)2(OTf)] in rigorously dry CH2-
Cl2 are identical to those observed for trans-[Rh(CO)(PPh3)2-
(OH2)][OTf] and do not change upon the addition of H2O. The
solid residue remaining after removal of the H2O-saturated CH2-
Cl2 shows a νCO absorption at 2008 cm-1 in Nujol.
Reactivity of trans-[Rh(CO)(PPh3)2(OH2)][OTf]. Addition
of [Ph3PNPPh3]Cl to a CH2Cl2 solution of trans-[Rh(CO)-
(PPh3)2(OH2)][OTf] causes an immediate shift of the 19F NMR
resonance from δ -78.52 to δ -78.60. The appearance of a
While 19F NMR spectroscopy is especially important in the
study of the Cp*Ru(NO)(OTf)2,1 the small chemical shift
difference between bound and free OTf- precludes the applica-
tion of 19F NMR spectroscopy as a quantitative probe of the
equilibria in the Rh cases.14 Nevertheless, a measurable shift
of the 19F NMR signal occurs when Cl- or pyridine is added to
solutions of trans-[Rh(CO)(PPh3)2(OTf)] in CH2Cl2. Since no
shift in the 19F NMR signal occurs when Cl- is added to trans-
[Rh(CO)(PPh3)2(py)][OTf], this evidence supports OTf- being
bound to Rh when trans-[Rh(CO)(PPh3)2(OH2)][OTf] is dis-
solved in CH2Cl2.
The present study shows the previous assessment of the
equilibria in eq 1 to be incorrect. Our inability to detect the
presence of any cationic trans-[Rh(CO)(PPh3)2(OH2)]+ in CH2-
Cl2 leads to a Keq of at least 102 based on a minimum detection
limit of 1% in the NMR spectra.
ν
CO IR absorption at 1976 cm-1 and a new doublet at δ 26.9 (J
) 127 Hz) in the 31P NMR spectrum of this solution corresponds
to a complete conversion to trans-[Rh(CO)(PPh3)2(Cl)]12 and
free OTf-.
Addition of 1 equiv of pyridine to trans-[Rh(CO)(PPh3)2-
(OH2)][OTf] dissolved in CH2Cl2 causes the initial δ -78.52
19F NMR resonance to shift to δ -78.60. This represents
complete conversion to trans-[Rh(CO)(PPh3)2(py)][OTf] as
indicated by a new doublet in the 31P NMR spectrum at δ 31.8
(J ) 129 Hz) and a single νCO absorption at 2009 cm-1 13
.
Subsequent addition of 1 equiv of [Ph3PNPPh3]Cl to this
solution does not cause any change in 19F NMR spectrum, but
the presence of a mixture of trans-[Rh(CO)(PPh3)2(py)][OTf]
and trans-[Rh(CO)(PPh3)2(Cl)] is indicated by their character-
istic 31P signals and their νCO absorptions at 2009 and 1976
cm-1
.
eq g 102
trans-[Rh(CO)(PPh3)2(OH2)]+ + OTf- a
(1)
Comparative Characteristics of trans-[Rh(CO)(PPh3)2-
(OH2)][BF4]. The CH2Cl2 solutions of trans-[Rh(CO)(PPh3)2-
(OH2)][BF4]7 deteriorate rapidly at ambient temperature, ne-
cessitating their spectral evaluation within 1 h of preparation.
In CH2Cl2, the νCO absorption for trans-[Rh(CO)(PPh3)2(OH2)]-
[BF4] appears at 1999 cm-1 and the 31P NMR spectrum shows
a doublet at δ 31.1 (J ) 128 Hz). Addition of pyridine results
in the shift of the 31P NMR resonance downfield to δ 31.8 (J
) 129 Hz) and the appearance of a single νCO absorption at
2009 cm-1. The molar conductance of 0.01 M solution of trans-
[Rh(CO)(PPh3)2(OH2)][BF4] in CH2Cl2 is 12 (1) Ω-1 cm-1
K
trans-[Rh(CO)(PPh3)2(OTf)] + H2O
It is important to note that the relatively high νCO absorption
energy of trans-[Rh(CO)(PPh3)2(OTf)] in CH2Cl2 might lead
to the incorrect interpretation that a cationic complex is present
(14) Small differences between the 19F NMR signals of bound and free
OTf- occur in related square planar complexes: (a) Stang, P. J.;
Huang, Y. H.; Arif, A. M. Organometallics 1992, 11, 231. (b) Stang,
P. J.; Cao, D. H.; Poulter, G. T.; Arif, A. M. Organometallics 1995,
14, 1110. (c) Bennet, B. L.; Birnbaum, J.; Roddick, D. M. Polyhedron
1995, 14, 187.
mol-1
.
(12) Evans, D.; Osborn, J. A.; Wilkinson, G. Inorg. Synth. 1968, 11, 99.
(13) Reddy, G. K. N.; Ramesh, B. R. J. Organomet. Chem. 1975, 87, 347.

Notes
Inorganic Chemistry, Vol. 35, No. 10, 1996 3075
Table 1. Crystallographic Data for trans-[Rh(CO)(PPh3)2(OH2)][OTf]
chem formula: C38H32O5F3SP2Rh
fw ) 822.6
T ) 173 K
λ ) 0.710 73 Å (Mo KR)
a ) 23.401(8) Å
F(calcd) ) 1.57 g/cm3
b ) 9.122(4) Å
F(obsd) ) 1.57(2) g/cm3
c ) 17.047(6) Å
µ ) 0.70 mm-1
â ) 107.03(3)°
R(F2) [I > 2σ(I)]: R1a ) 0.1057, wR2b ) 0.1740
R(F2) (all data): R1a ) 0.2126, wR2b ) 0.2308
GOFc on F2: 1.108
V ) 3479(2) Å3
Z ) 4
space group: monoclinic, C2/c (No. 15)
2
2
2
a R1 ) ∑||Fo| - |Fc||∑|Fo|. b wR2 ) |∑[w(Fo - Fc2)]2]/∑[w(Fo )2]]1/2
.
c GOF ) [∑[w(Fo - Fc2)2]/(n - p)]1/2 where n ) no. of reflections, p
) no. of parameters refined; w)1/[σ2(Fo )+(0.0326P)2 + 224.2319P] where P ) (Fo + 2Fc2)/3.
2
2
0.20 mmol) in 10 mL of benzene (not rigorously dried) was stirred
in solution. As reported for several other cases, the νNO or νCO
absorptions of OTf- complexes fall at 23-50 cm-1 higher
energy than their Cl- analogues.1,5 For example, the νCO
absorptions for (η-C5(CH3)5)Fe(CO)2OTf are 23 cm-1 higher
than for (η-C5(CH3)5)Fe(CO)2Cl.15 The strongly electron-
withdrawing SO2CF3 moiety on the OTf- donor O-atom likely
reduces the π-donor ability of OTf- compared to Cl-.
In summary, we have shown that solid trans-[Rh(CO)-
(PPh3)2(OH2)][OTf] precipitates preferentially from wet CH2-
Cl2 or benzene solutions rather than anhydrous trans-[Rh(CO)-
(PPh3)2(OTf)]. In CH2Cl2 solution, however, the OTf- ligand
is a substantially better ligand than water, leading to trans-[Rh-
(CO)(PPh3)2(OTf)] as the only detectable species. Triflate
displacement from Rh by H2O does not occur to a significant
extent in CH2Cl2 or benzene. Thus, the OTf- ion in these
vigorously for 12 h. The reaction was deemed complete when the 1976
cm-1 signal of the starting chloride complex was no longer detectable
by IR spectroscopy. The solution was filtered, taken to dryness in Vacuo
and the residue was redissolved in 5 mL of dichloromethane. Addition
of 5 mL of hexane followed by storage at -70 °C for 12 h produced
lemon-yellow crystalline trans-[Rh(CO)(PPh3)2(OH2)][OTf] (120 mg,
0.15 mmol, 79%). IR νCO (CH2Cl2, cm-1): 1996 vs, (Nujol mull, cm-1
)
2008 vs. H NMR (CH2Cl2): δ 7.45 (m, 10 H), δ 7.6 (m, 20 H). 31P
NMR (CDCl3): δ 29.5 (d, J ) 125 Hz), (CH2Cl2): δ 28.2 (J ) 125
Hz). 19F NMR (CH2Cl2): δ -78.52 Anal. Calcd for RhP2C38H30-
O4F3S‚H2O: C, 55.48; H, 3.92. Found: C, 55.43; H, 3.98. Mp: 178-
180 °C.
1
Synthesis of trans-[Rh(CO)(PPh3)2(OTf)]. A Schlenk-distillation
apparatus was filled with a solution prepared from trans-[Rh(CO)-
(PPh3)2(OH2)][OTf] (0.150 g, 0.19 mmol) and 20 mL of rigorously
dried benzene. Distillation resulted in the removal of H2O in the early
cloudy distillate fractions. After the distillate became clear, the
remaining solvent was removed in Vacuo to leave a quantitative yield
of trans-[Rh(CO)(PPh3)2(OTf)] as a yellow powder. IR νCO (Nujol
mull, cm-1): 1988 vs. The IR and NMR spectral properties of Rh-
(CO)(PPh3)2(OTf) in CH2Cl2 solution are identical to those described
above for trans-[Rh(CO)(PPh3)2(OH2)][OTf]. Anal. Calcd for RhP2C38-
H30O4F3S: C, 56.72; H, 3.76. Found: C, 56.54; H, 3.95. Mp: 169-
170 °C.
solvents cannot be classified as a weak ligand in the same
-
category as BF4
.
Experimental Section
General Data. Standard Schlenk techniques were employed for
routine experiments unless otherwise indicated. A Vacuum Atmo-
spheres Dry-Lab glovebox with an N2-atmosphere containing less than
1 ppm H2O and 1 ppm O2 was utilized for the preparation and handling
of anhydrous materials. CH2Cl2 was rigorously dried using PbNa alloy
and transferred in glassware that was dried in a 160 °C oven. The
concentration of H2O in homogeneous H2O-saturated CH2Cl2 was
determined to be 0.198 g/100 mL of CH2Cl2.16 The nitrogen reaction
atmosphere was purified by passing it through scavengers for water
(Aquasorb, Mallinckrodt) and oxygen (Catalyst R3-11, Chemical
Dynamics, So. Plainfield, NJ). Organic solvents were distilled under
nitrogen over appropriate drying agents prior to use.17 All other
chemical reagents were used as received from Aldrich unless stated
otherwise. Infrared spectra were recorded on a Mattson Polaris-Icon
FT-spectrometer. The 31P, 1H, 13C, and 19F NMR spectra were recorded
on a Bruker ARX-400 NMR spectrometer operating at 162 MHz (31P),
400 MHz (1H), and 376.2 MHz (19F). The residual solvent peak of
CDCl3 was used as the internal NMR standard (1H δ 7.24). 19F
chemical shifts were referenced externally to CCl3F (δ 0.0)17 or
internally to 3,5-bis(trifluoromethyl)benzene (δ -63.20 in CDCl3). 1H
NMR spectra in CH2Cl2 were measured using solvent presaturation
techniques and were shimmed and referenced to the signals from CDCl3
sealed inside a 1.5-mm capillary located concentrically inside the 5-mm
NMR tube. The chemical shifts reported for the complexes in CH2Cl2
are identical to those in CD2Cl2. Conductivity measurements were
performed on a YSI Model 31A conductivity bridge. For comparison
purposes, a 0.02 M solution of [Ph3PNPPh3]Cl in CH2Cl2 has a molar
conductance of 50(1) Ω-1 cm-1 mol-1. Melting points were measured
with a Mel-Temp device (Laboratory Devices) in open capillaries and
are uncorrected. Combustion analyses were performed by Atlantic
Microlab, Inc. <Norcross, GA.
An alternative method of preparing trans-[Rh(CO)(PPh3)2(OTf)] was
to freeze-dry the benzene solution of trans-[Rh(CO)(PPh3)2(OH2)][OTf]
under high vacuum using a liquid-nitrogen trap. The residue that
remained had an IR absorption at 1988 cm-1
.
X-ray Structural Analysis of trans-[Rh(CO)(PPh3)2(OH2)][OTf].
A weakly diffracting, but acceptable, crystal was found after the
examination of numerous candidates. The specimen selected was
centered vertically at 173 K on a Siemens P4 Autodiffractometer. The
computer centering of 25 random reflections revealed the monoclinic
lattice with a ) 23.401(8) Å, b ) 9.1222(4) Å, c ) 17.047(6) Å; â )
107.03(3)°, and V ) 3479(2) Å3. Data collection of 0 e h e 26, 0 e
k e 10, -19 e l e 19 for a primitive lattice showed a C-lattice by the
systematic absences h + k * 2n. The presence of a c glide plane was
indicated by the systematic absences h0l, h00, and 00l when h * 2n
and l * 2n. Solution and refinement of the structure was carried out
on an IBM-compatible 486 personal computer using the SHELXS-
8618 and SHELXL-9319 programs from Sheldrick.20 Selection of the
space group C2/c and the use of Patterson methods led to the location
of the Rh atom at the special position (0.5, 0.0, 0.0). The P atom and
the C atoms of the phenyl rings were clearly visible in the first
difference map. The unique PPh3 group showed no sign of disorder.
Three peaks of approximately equal weight were located along a vector
that formed a ca. 90° angle to the Rh-P vector. These peaks were
(18) Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467-473.
(19) Sheldrick, G. M. J. Appl. Crystallogr., manuscript in preparation;
SHELXL-93 scattering factors from: International Tables for X-ray
Crystallography Wilson, A. J. C., Ed.; Kluwer Academic Publishers:
Dordrecht: The Netherlands, 1992; Vol. C, Tables 6.1.1.4 (pp 500-
502, neutral atom scattering factors), 4.2.6.8 (pp 219-222, f ′,f ′′), and
4.2.4.2 (pp 193-199, absorption coefficients).
(20) SHELXL-93 is available from Siemens Analytical X-ray Instruments,
6300 Enterprise Lane, Madison, WI 53719, or directly from G.
Sheldrick, Institu¨t fu¨r Anorganische Chemie der Universita¨t, Tam-
mannstrasse 4, D-37077 Go¨ttingen, Germany: gsheldr@
shelx.uni-ac.gwdg.de.
Synthesis of trans-[Rh(CO)(PPh3)2(OH2)][OTf]. A mixture of
trans-[Rh(CO)(PPh3)2(Cl)] (0.13 g, 0.20 mmol) and AgOTf (0.05 g,
(15) Hubbard, J. L.; McVicar, W. L. J. Organomet. Chem. 1992, 429, 369.
(16) Scheflan, L.; Jacobs, M. The Handbook of SolVents; Van Nostrand:
New York, 1953; p 112.
(17) Gordon, A. J.; Ford, R. A. The Chemist’s Companion; John Wiley &
Sons: New York, 1972; pp 25, 433.

3076 Inorganic Chemistry, Vol. 35, No. 10, 1996
Additions and Corrections
successfully modeled isotropically as a 1:1 disorder of a CO ligand
and an H2O ligand.
the crystals was determined to be 1.57(2) g/cm3 by flotation in a CCl4/
hexane mixture. The calculated density for 4 molecules of trans-[Rh-
(CO)(PPh3)2(OH2)][OTf] per unit cell is 1.57 g/cm3.
After the Rh and P peaks, the next largest peak was located 5.5 Å
from the Rh atom. This peak was situated in the center of three smaller
peaks that formed a ca. 3-fold symmetric trigonal pyramid. Application
of the crystal symmetry operations generated four symmetry-related
peaks that, overall, formed a staggered ethane-like fragment that was
assigned as an end-to-end disordered SO3CF3- moiety. Upon assigning
the large peak as a S atom with a site-occupation factor ) 0.5, the
largest peak in the subsequent difference map was located 0.96 Å from
the S position and just off the vector between S and the position of its
symmetry equivalent S(a). Overall, the pattern appeared to be the
partially resolved superposition of the C atom (from the CF3 group)
and the S atom (of the SO3 group). Therefore, the best approximation
Acknowledgment. The support of the National Science
Foundation (Grant CHE-9215872) to J.L.H. is gratefully
acknowledged. We acknowledge the NSF and the Utah State
University Research Office for jointly funding the purchase of
the USU X-ray diffraction (Grant CHE-9002379) and NMR
(Grant CHE-9311730) facilities.
Supporting Information Available: Tables of crystallographic
data, collection parameters, atomic coordinates, and equivalent isotropic
displacement parameters, complete listing of bond distances and bond
angles, anisotropic displacement parameters, and H-atom coordinates
(5 pages). This material is contained in many libraries on microfiche,
immediately follows this article in the microfilm version of the journal,
and can be ordered from the ACS; see any current masthead page for
ordering information.
-
of the disordered SO3CF3 resulted from a model where both the S
and C(2) atoms where given site-occupation factors of 0.5 and the F(1),
F(2), and F(3) atoms were assigned site-occupation factors of 1.0 each
in order to approximately account for both the superposition of the F
and O atoms.
-
Despite the disorder in the CO, H2O, and SO3CF3 positions,
refinement of the structure to 10.57% was possible. The density of
IC951287H
Ad d ition s a n d Cor r ection s
1995, Volume 34
Anthony F. Lagalante, Brian N. Hansen, Thomas J.
Bruno,* and Robert E. Sievers: Solubilities of Copper(II)
and Chromium(III) â-Diketonates in Supercritical Carbon
Dioxide.
Page 5785. Two sponsors were accidentally omitted from
the Acknowledgment. The following should be added to this
section: R.E.S. and A.F.L. acknowledge NSF Grant ATM-
9115295 and EG&G Rocky Flats Contract ASC222874DB for
providing partial support of this research.
IC960236X