Rhodium cluster complexes containing bridging phenylgermanium ligands

Article abstract of DOI:10.1021/ic050372e

The reaction of Rh₄(CO)₁₂ with Ph₃GeH at 97°C has yielded the first rhodium cluster complexes containing bridging germylene and germylyne ligands: Rh₈(CO)₁₂(μ ₄-GePh)₆, 9, and Rh₃(CO)₅(GePh ₃)(μ-GePh₂)₃(μ₃-GePh)(μ-H), 10. When the reaction is performed under hydrogen, the yield of 9 is increased to 42% and no 10 is formed. Compound 9 contains a cluster of eight rhodium atoms arranged in the form of a distorted cube. There are six μ ₄-GePh groups bridging each face of this distorted cube. Four of the rhodium atoms have two terminal carbonyl ligands, while the remaining four rhodium atoms have only one carbonyl ligand. Compound 10 contains a triangular cluster of three rhodium atoms with one terminal GePh₃ ligand, three bridging GePh₂ ligands, and one triply bridging GePh ligand. There is also one hydrido ligand that is believed to bridge one of the Rh-Ge bonds. Compound 9 reacted with PPhMe₂ at 25°C to give the tetraphosphine derivative Rh₈(CO)₈(PPhMe₂) ₄(μ₄-GePh)₆,11. The structure of 11 is similar to 9 except that a PPhMe₂ ligand has replaced a carbonyl ligand on each the four Rh(CO)₂ groups. Compound 10 reacted with CO at 68°C to give the complex Rh₃(CO)₆(μ-GePh ₂)₃(μ₃-GePh), 12. Compound 12 is formed by the loss of the hydrido ligand and the terminal GePh₃ ligand from 10 and the addition of one carbonyl ligand. All compounds were fully characterized by IR, NMR, elemental, and single-crystal X-ray diffraction analyses.

Full text of DOI:10.1021/ic050372e

Inorg. Chem. 2005, 44, 4276−4281
Rhodium Cluster Complexes Containing Bridging Phenylgermanium
Ligands
Richard D. Adams* and Jack L. Smith, Jr.
Department of Chemistry and Biochemistry, UniVersity of South Carolina,
Columbia, South Carolina 29208
Received March 10, 2005
The reaction of Rh4(CO)12 with Ph3GeH at 97
germylene and germylyne ligands: Rh8(CO)12
When the reaction is performed under hydrogen, the yield of 9 is increased to 42% and no 10 is formed. Compound
9 contains a cluster of eight rhodium atoms arranged in the form of a distorted cube. There are six 4-GePh
°C has yielded the first rhodium cluster complexes containing bridging
(
µ
4-GePh)6, 9, and Rh3(CO)5(GePh3)( -GePh2)3( 3-GePh)( -H), 10.
µ
µ
µ
µ
groups bridging each face of this distorted cube. Four of the rhodium atoms have two terminal carbonyl ligands,
while the remaining four rhodium atoms have only one carbonyl ligand. Compound 10 contains a triangular cluster
of three rhodium atoms with one terminal GePh3 ligand, three bridging GePh2 ligands, and one triply bridging
GePh ligand. There is also one hydrido ligand that is believed to bridge one of the Rh
reacted with PPhMe2 at 25 C to give the tetraphosphine derivative Rh8(CO)8(PPhMe2)4( 4-GePh)6, 11. The structure
of 11 is similar to 9 except that a PPhMe2 ligand has replaced a carbonyl ligand on each the four Rh(CO)2 groups.
Compound 10 reacted with CO at 68 C to give the complex Rh3(CO)6( -GePh2)3( 3-GePh), 12. Compound 12 is
−Ge bonds. Compound 9
°
µ
°
µ
µ
formed by the loss of the hydrido ligand and the terminal GePh3 ligand from 10 and the addition of one carbonyl
ligand. All compounds were fully characterized by IR, NMR, elemental, and single-crystal X-ray diffraction
analyses.
Chart 1
Introduction
In recent studies we have shown that Ph3SnH is an
excellent reagent for the introduction of bridging SnPh2
ligands into polynuclear transition metal cluster complexes
in a process that results in the elimination of benzene.1 For
example, the reaction of Ru5(CO)12(C6H6)(µ5-C) with Ph3-
SnH leads to the formation of two tin-rich compounds, Ru5-
(CO)8(C6H6)(µ-SnPh2)4(µ5-C), 1 (Chart 1), and Ru5(CO)7-
(C6H6)(µ-SnPh2)4(SnPh3)(µ5-C)(µ-H), 2.1 The reaction of
Re2(CO)8[µ-C(H)dC(H)Bun) with Ph3SnH yielded the com-
plex Re2(CO)8(µ-SnPh2)2, 3, with two bridging SnPh2 ligands
across a single Re-Re bond.2 Rhodium and iridium are even
more effective than ruthenium and rhenium in these tin
addition reactions. The reaction of Rh4(CO)12 with Ph3SnH
* Author to whom correspondence should be addressed. E-mail:
Adams@mail.chem.sc.edu.
(1) (a) Adams, R. D.; Captain, B.; Fu, W.; Smith, M. D. Inorg. Chem.
2002, 41, 5593. (b) Adams, R. D.; Captain, B.; Fu, W.; Smith, M. D.
Inorg. Chem. 2002, 41, 2302.
(2) Adams, R. D.; Captain, B.; Johansson, M.; Smith, J. L. J. Am. Chem.
Soc. 2005, 127, 488.
4276 Inorganic Chemistry, Vol. 44, No. 12, 2005
10.1021/ic050372e CCC: $30.25
© 2005 American Chemical Society
Published on Web 05/11/2005

Rh Clusters with Bridging Phenylgermanium Ligands
1
for 11: IR (νCO; cm-1 in hexane) 1967 (vs), 1946 (w); H NMR
has yielded the trirhodium cluster complexes Rh3(CO)6(µ-
SnPh2)3(SnPh3)3, 4, and Rh3(CO)3(SnPh3)3(µ-SnPh2)3(µ3-
SnPh)2, 5, that contain six and eight tin ligands, respectively;
the latter compound contains the first examples of triply
bridging SnPh ligands.3
(CD2Cl2 in ppm) δ ) 7.1-7.5 (m, 50 H, Ph), 1.29 (d, 12 H, Me,
2JP-H ) 9 Hz), 1.30 (d, 12 H, Me, 2JP-H ) 9 Hz); 31P NMR (CD2-
Cl2 in ppm) δ ) -2.30 (d, 4 P, 1JP-Rh ) 158 Hz). Anal. Calcd: C,
35.11; H, 2.95. Found: C, 34.04; H, 2.82.
Synthesis of Rh3(CO)6(µ-GePh2)3(µ3-GePh), 12. Compound 10
(9.7 mg, 0.0061 mmol) was dissolved in hexane and heated to reflux
under a slow purge of CO for 3 h. The solvent was then removed
in vacuo and the product separated using a 2:1 hexane/methylene
chloride solvent mixture to give 7.5 mg (94% yield) of red Rh3-
(CO)6(µ-GePh2)3(µ3-GePh), 12. Spectral data for 12: IR (νCO; cm-1
in hexane) 2055 (m), 2030 (s), 2009 (vs), 1998 (s); 1H NMR (CD2-
Cl2 in ppm) δ ) 6.9-7.8 (m, 35 H, Ph). Anal. Calcd: C, 44.11;
H, 2.69. Found: C, 43.38; H, 2.64.
Crystallographic Analyses. Green crystals of 9 and red crystals
of 10 and 12 were grown by slow evaporation of a CH2Cl2/hexane
solvent mixture at -18 °C. Green crystals 11 were grown from
THF/heptane at room temperature. Each data crystal was glued onto
the end of a thin glass fiber. X-ray intensity data were measured
by using a Bruker SMART APEX CCD-based diffractometer using
Mo KR radiation (λ ) 0.710 73 Å). The raw data frames were
integrated with the SAINT+ program6 by using a narrow-frame
integration algorithm. Corrections for Lorentz and polarization
effects were also applied with SAINT+. An empirical absorption
correction based on the multiple measurement of equivalent
reflections was applied using the program SADABS. All structures
were solved by a combination of direct methods and difference
Fourier syntheses and refined by full-matrix least squares on F2
using the SHELXTL software package.7 For 9, 11, and 12 all non-
hydrogen atoms were refined with anisotropic displacement pa-
rameters. For 10 only the rhodium and germanium atoms were
refined with anisotropic displacement parameters. All hydrogen
atoms were placed in geometrically idealized positions and included
as standard riding atoms during the least-squares refinements.
Crystal data, data collection parameters, and results of the analyses
are listed in Tables 1 and 2.
We have also shown that Ph3GeH can also engage in
multiple addition reactions to ruthenium and iridium cluster
complexes to yield complexes with bridging GePh2 ligands
such as Ru5(CO)11(µ-GePh2)4(µ5-C), 6,4 Ir3(CO)6(µ-GePh2)3-
(GePh3)3, 7,5 and Ir4(CO)4H4(µ-GePh2)4(µ4-GePh)2, 8.5 Com-
pound 8 contains two quadruply bridging GePh ligands.
We have now investigated the reaction of Rh4(CO)12 with
Ph3GeH and have obtained the first examples of rhodium
carbonyl cluster complexes containing bridging GePh2 and
GePh ligands. These results are reported herein.
Experimental Section
General Data. All reactions were performed under a nitrogen
atmosphere. Reagent grade solvents were dried by the standard
procedures and were freshly distilled prior to use. Infrared spectra
were recorded on a Thermo-Nicolet Avatar 360 FT-IR spectro-
1
photometer. H NMR spectra were recorded on a Mercury 300
spectrometer operating at 300.1 MHz. 31P{1H} NMR spectra were
recorded on a Varian Mercury 400 spectrometer operating at 161.9
MHz and were externally referenced against 85% ortho-H3PO4.
Elemental analyses were performed by Desert Analytics (Tucson,
AZ). Product separations were performed by TLC in air on Analtech
0.5 mm silica gel 60 Å F254 glass plates. Rh4(CO)12 was purchased
from Strem Chemicals, Inc. Ph3GeH and PPhMe2 were purchased
from Aldrich and were used without further purification.
Reaction of Rh4(CO)12 with Ph3GeH. Ph3GeH (125 mg, 0.410
mmol) was added to a solution of Rh4(CO)12 (30 mg, 0.040 mmol)
in heptane. The reaction mixture was heated to reflux for 3 h. After
cooling, the solvent was removed in vacuo, and the products were
separated by TLC using a 2:1 hexane/methylene chloride solvent
mixture to yield in order of elution 10.0 mg (12% yield) of green
Rh8(CO)12(µ4-GePh)6, 9, and 11.3 mg (18% yield) of red Rh3(CO)5-
Compounds 9 and 10 crystallized in the monoclinic crystal
system. The space groups P21/c and P21/n, for 9 and 10,
respectively, were identified uniquely on the basis of the systematic
absences in the intensity data. One molecule of hexane cocrystal-
lized with 10 and was located and satisfactorily refined at 50%
occupancy with isotropic displacement parameters. Compounds 11
and 12 crystallized in the triclinic crystal system. The space group
P1h was assumed and confirmed by the successful solution and
refinement of the structures. For 11 there are two independent
formula equivalents and one molecule of THF in the asymmetric
unit.
(GePh3)(µ-GePh2)3(µ3-GePh)(µ-H), 10. Spectral data for 9: IR (νCO
;
cm-1 in hexane) 2031 (s), 2003 (m); 1H NMR (CD2Cl2 in ppm) δ
) 7.4-7.8 (m, 30 H, Ph). Anal. Calcd: C, 28.01; H, 1.47. Found:
C, 28.55; H, 1.68 H. MS (m/z): 2057, M+. Spectral data for 10:
IR (νCO; cm-1 in hexane) 2054 (s), 2034 (s), 2016 (m), 2007 (m),
2001 (m); 1H NMR (CD2Cl2 in ppm) δ ) 6.8-7.6 (m, 50 H, Ph),
1
2
-10.42 (dt, 1 H, µ-H, JRh-H ) 17 Hz, JRh-H ) 2 Hz). Anal.
Calcd: C, 49.29; H, 3.25. Found: C, 48.95; H, 3.36 H.
Improved Route to 9. Ph3GeH (125 mg, 0.410 mmol) was added
to a solution of Rh4(CO)12 (30 mg, 0.040 mmol) in heptane. The
reaction mixture was heated to reflux under a slow purge of H2 for
3 h. After the solvent was removed in vacuo, the product 9 was
separated by TLC by using a 2:1 hexane/methylene chloride solvent
mixture to give 35.2 mg (42% yield).
Synthesis of Rh8(CO)8(PPhMe2)4(µ4-GePh)6, 11. PPhMe2 (4.2
µL, 0.030 mmol) was added to a solution of 9 (15 mg, 0.0073
mmol) in CH2Cl2 and stirred at room temperature for 30 min. The
solvent was then removed in vacuo and the product washed with
acetonitrile and recrystallized from THF/heptane to give 14.7 mg
(80% yield) of Rh8(CO)8(PPhMe2)4(µ4-GePh)6, 11. Spectral data
Results and Discussion
As a result of our successful synthesis of a number of new
iridium carbonyl cluster complexes containing phenylger-
manium ligands from the reaction of Ir4(CO)12 with Ph3GeH,5
we proceeded to investigate the reaction of Rh4(CO)12 with
Ph3GeH. Rh4(CO)12 was found to react with Ph3GeH at 97
°C to yield what are now the first examples of rhodium
carbonyl cluster complexes containing bridging germylyne
and germylene ligands: Rh8(CO)12(µ4-GePh)6, 9, and Rh3-
(CO)5(GePh3)(µ-GePh2)3(µ3-GePh)(µ-H), 10, in 12% and
(3) Adams, R. D.; Captain, B.; Smith, J. L.; Hall, M. B.; Beddie, C. L.;
Webster, C. E. Inorg. Chem. 2004, 43, 7576.
(4) Adams, R. D.; Captain, B.; Fu, W. Inorg. Chem. 2003, 42, 1328.
(5) Adams, R. D.; Captain, B.; Smith, J. L. Inorg. Chem. 2005, 44, 1413.
(6) SAINT+, version 6.2a; Bruker Analytical X-ray Systems, Inc.:
Madison, WI, 2001.
(7) Sheldrick, G. M. SHELXTL, version 6.1; Bruker Analytical X-ray
Systems, Inc.: Madison, WI, 1997.
Inorganic Chemistry, Vol. 44, No. 12, 2005 4277

Adams and Smith
Table 1. Crystallographic Data for Compounds 9 and 10
9
10
empirical formula
fw
Rh8Ge6O12C48H30 Rh3Ge5O5C65H50‚1/2C6H14
2057.54
1625.82
cryst system
lattice params
a (Å)
b (Å)
c (Å)
monoclinic
monoclinic
13.2207(13)
21.769(2)
19.867(2)
90
94.127(3)
90
5703.1(10)
P21/c
4
13.1447(6)
21.6775(10)
23.6975(11)
90
91.5960(10)
90
6749.8(5)
P21/c
4
R (deg)
â (deg)
γ (deg)
V (Å3)
space group
Z
F
calc (g cm-3
)
2.396
5.412
296
1.600
2.954
296
µ(Mo KR) (mm-1
temp (K)
)
2θmax (deg)
50.06
7392
667
0.976
0.001
45.44
5579
397
1.125
no. of observns
no. of params
goodness of fit
max shift in cycle
0.000
residuals:a R, Rw (I > 2σ(I)) 0.0369, 0.0684
0.1162, 0.2330
SADABS
1.000/0.887
0.988
abs corr
max/min
largest peak (e/Å3)
SADABS
0.897/0.613
0.586
Figure 1. ORTEP diagram of the molecular structure of Rh8(CO)12(µ4-
GePh)6, 9, showing 40% thermal ellipsoid probability.
2 1/2
a R ) ∑hkl(||Fo| - |Fc||)/∑hkl|Fo|; Rw ) [∑hklw(|Fo| - |Fc|)2/∑hklwFo ]
;
w ) 1/σ2(Fo); GOF ) [∑hklw(|Fo| - |Fc|)2/(ndata - nvari)]1/2
.
Table 3. Selected Intramolecular Distances and Angles for
Compound 9a
Table 2. Crystallographic Data for Compounds 11 and 12
Bond Distances (Å)
Rh(1)-Rh(2)
Rh(1)-Rh(4)
Rh(1)-Rh(6)
Rh(2)-Rh(3)
Rh(2)-Rh(7)
Rh(3)-Rh(4)
Rh(3)-Rh(8)
Rh(4)-Rh(5)
Rh(5)-Rh(6)
Rh(5)-Rh(8)
Rh(6)-Rh(7)
Rh(7)-Rh(8)
Rh(2)‚‚‚Rh(4)
Rh(2)‚‚‚Rh(6)
Rh(2)‚‚‚Rh(8)
Rh(4)‚‚‚Rh(6)
Rh(4)‚‚‚Rh(8)
Rh(6)‚‚‚Rh(8)
Rh(1)-Ge(1)
Rh(1)-Ge(2)
Rh(1)-Ge(5)
Rh(2)-Ge(1)
2.9234(8)
2.8208(7)
2.9237(8)
2.9274(7)
2.8304(8)
2.8657(8)
2.8258(8)
2.8862(8)
2.8237(7)
2.9331(8)
2.9397(8)
2.8923(7)
3.158(1)
Rh(2)-Ge(2)
Rh(2)-Ge(3)
Rh(3)-Ge(1)
Rh(3)-Ge(3)
Rh(3)-Ge(4)
Rh(4)-Ge(1)
Rh(4)-Ge(4)
Rh(4)-Ge(5)
Rh(5)-Ge(4)
Rh(5)-Ge(5)
Rh(5)-Ge(6)
Rh(6)-Ge(2)
Rh(6)-Ge(5)
Rh(6)-Ge(6)
Rh(7)-Ge(2)
Rh(7)-Ge(3)
Rh(7)-Ge(6)
Rh(8)-Ge(3)
Rh(8)-Ge(4)
Rh(8)-Ge(6)
C-O(av)
2.3928(8)
2.3679(9)
2.7197(9)
2.7102(9)
2.6052(9)
2.3882(9)
2.3580(8)
2.3833(9)
2.6815(9)
2.5704(9)
2.6797(9)
2.3424(9)
2.3787(9)
2.3793(9)
2.6979(9)
2.5490(9)
2.5954(9)
2.3794(9)
2.3529(9)
2.3523(9)
1.14(3)
11
12
empirical formula
fw
cryst system
lattice params
a (Å)
Rh8Ge6P4O8C76H76‚C4H8O Rh3Ge4O6C48H35
2570.16
triclinic
1306.85
triclinic
14.1643(15)
14.4768(15)
24.717(3)
103.590(2)
95.901(2)
104.608(2)
4695.8(9)
P1h
11.5977(10)
12.9543(11)
17.4276(15)
98.147(2)
94.135(2)
113.940(2)
2344.5(3)
P1h
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
space group
Z
3.247(1)
3.189(1)
3.201(1)
3.168(1)
2
2
F
calc (g cm-3
)
1.869
3.373
296
45.98
9257
967
0.987
0.002
1.851
3.605
296
50.06
6457
550
1.032
0.001
µ(Mo KR) (mm-1
temp (K)
)
2θmax (deg)
3.264(1)
no. of observns
no. of params
goodness of fit
max shift in cycle
2.5959(9)
2.6284(9)
2.6340(9)
2.3302(9)
residuals:a R, Rw (I > 2σ(I)) 0.0841, 0.1993
0.0545, 0.1322
SADABS
0.835/0.493
2.157
abs corr
max/min
largest peak (e/Å3)
SADABS
1.000/0.459
2.781
Bond Angles (deg)
50.72(2) Rh(1)-Rh(2)-Rh(3) 107.22(2)
Ge(2)-Rh(1)-Rh(2)
Ge(2)-Rh(1)-Rh(4) 101.81(2) Rh(2)-Rh(1)-Rh(4)
66.669(18)
176(3)
Rh(1)-Ge(1)-Rh(2)
72.58(3) Rh-C-O(av)
2 1/2
a R ) ∑hkl(||Fo| - |Fc||)/∑hkl|Fo|; Rw ) [∑hklw(|Fo| - |Fc|)2/∑hklwFo ]
;
w ) 1/σ2(Fo); GOF ) [∑hklw(|Fo| - |Fc|)2/(ndata - nvari)]1/2
.
a Estimated standard deviations in the least significant figure are given
in parentheses.
18% yields, respectively. Both compounds were character-
ized by a combination of IR, 1H NMR, elemental, and single-
crystal X-ray diffraction analyses. Compound 9 was also
characterized by mass spectral analysis. An ORTEP diagram
of the molecular structure of 9 is shown in Figure 1. Selected
intramolecular bond distances and angles are listed in Table
3. The structure of 9 consists of a distorted cube of eight
rhodium atoms and six GePh groups that quadruply bridge
each face. Quadruply bridging GeR ligands are known and
include compound 8 as well as the nickel compound
Ni9(CO)8(µ4-GeEt)6.8 There are 12 Rh-Rh bonds ranging
from 2.8208(7) to 2.9397(8) Å that link each of the four
Rh(CO)2 groups to three other Rh(CO) groups. In addition,
the four Rh(CO) groups have a tetrahedral arrangement and
contain six longer weak Rh-Rh interactions directly between
themselves that range from 3.158(1) to 3.264(1) Å. An
ORTEP diagram of the Rh8 core of 9 is shown in Figure 2.
The weak Rh-Rh interactions are represented by the open
“bonds” between the metal atoms shown in Figure 2. The
distortion in the Rh8 core is most likely caused by the fact
that four of the rhodium atoms have two carbonyl ligands
(8) Zebrowski, J. P.; Hayashi, R. K.; Bjarnason, A.; Dahl, L. F. J. Am.
Chem. Soc. 1992, 114, 3121.
4278 Inorganic Chemistry, Vol. 44, No. 12, 2005

Rh Clusters with Bridging Phenylgermanium Ligands
Figure 2. ORTEP diagram of the Rh8 core of 9 showing 50% thermal
ellipsoid probability. Open bonds represent the long weak Rh-Rh interac-
tions not shown in Figure 1.
while the other four have only carbonyl ligand. The formation
of the weak Rh-Rh interactions between the four Rh(CO)
groups may be a result of their relative CO ligand deficiency.
Each germanium atom is five coordinate which includes four
Rh-Ge bonds. The Rh-Ge bond distances span a wide
range, 2.3302(9)-2.7197(9) Å, and in general each germa-
nium atom has two short Rh-Ge bonds and two long Rh-
Ge bonds, e.g. Rh(1)-Ge(1) ) 2.5959(9) Å, Rh(2)-Ge(1)
) 2.3302(9) Å, Rh(3)-Ge(1) ) 2.7197(9) Å, and Rh(4)-
Ge(1) ) 2.3882(9) Å; see Table 3. This can be attributed to
the fact that the four rhodium atoms to which they are bonded
are not arranged as a square. There are few examples of
structurally characterized compounds that contain Rh-Ge
bonds to compare with those in 9. One is the compound [Me2-
Si(NtBu)2Ge]4RhCl for which the four independent Rh-Ge
bond distances were reported to be 2.3366(9), 2.3368(7),
2.3711(7), and 2.3756(8) Å.9
The total valence electron count for 9 is 114, which is 6
electrons less than the expected number of 120 for an cubical
arrangement of eight metal atoms.10 There are many ex-
amples of structures of the type M8(µ4-E)6 in the literature;11
however, there is only one previous example of a cluster
that contains an Rh8 core with an electron count of 114
electrons, Rh8(CO)9[µ4-P(C5H9)]6.12 Interestingly, when the
reaction was performed under a hydrogen atmosphere, the
yield of 9 was increased to 42% and no 10 was formed at
all. No hydrogen is incorporated into the cluster. It may
instead serve to assist in the removal of the phenyl groups
from the germane with formation of benzene.1
Figure 3. ORTEP diagram of the molecular structure of Rh3(CO)5(GePh3)-
(µ-GePh2)3(µ3-GePh)(µ-H), 10, showing 30% thermal ellipsoid probability.
The hydrido ligand was not located crystallographically.
Table 4. Selected Intramolecular Distances and Angles for Compounds
10 and 12a
10
12
Bond Distances (Å)
2.824(2)
Rh(1)-Rh(2)
Rh(1)-Rh(3)
Rh(2)-Rh(3)
Rh(1)-Ge(1)
Rh(1)-Ge(3)
Rh(1)-Ge(4)
Rh(2)-Ge(1)
Rh(2)-Ge(2)
Rh(2)-Ge(4)
Rh(3)-Ge(2)
Rh(3)-Ge(3)
Rh(3)-Ge(4)
Rh(3)-Ge(5)
C-O(av)
Rh(1)-Rh(2)
Rh(1)-Rh(3)
Rh(2)-Rh(3)
Rh(1)-Ge(1)
Rh(1)-Ge(3)
Rh(1)-Ge(4)
Rh(2)-Ge(1)
Rh(2)-Ge(2)
Rh(2)-Ge(4)
Rh(3)-Ge(2)
Rh(3)-Ge(3)
Rh(3)-Ge(4)
C-O(av)
2.9101(8)
2.8147(8)
2.8610(8)
2.4815(9)
2.4762(9)
2.4188(8)
2.4783(9)
2.4782(9)
2.4157(9)
2.4782(9)
2.4794(9)
2.4039(9)
1.13(2)
2.891(2)
2.857(2)
2.488(3)
2.522(3)
2.384(3)
2.462(3)
2.501(3)
2.384(3)
2.465(3)
2.476(3)
2.533(3)
2.480(3)
1.18(7)
Bond Angles (deg)
Ge(1)-Rh(1)-Ge(3) 164.32(11) Ge(1)-Rh(1)-Ge(3) 167.68(3)
Ge(4)-Rh(1)-Rh(3) 56.43(8)
Ge(1)-Rh(2)-Rh(3) 116.55(9)
Ge(2)-Rh(2)-Ge(4) 90.04(10)
Rh(1)-Ge(1)-Rh(2) 69.56(8)
Ge(4)-Rh(1)-Rh(3) 54.05(2)
Ge(1)-Rh(2)-Rh(3) 112.09(3)
Ge(2)-Rh(2)-Ge(4) 83.30(3)
Rh(1)-Ge(1)-Rh(2) 71.85(3)
Rh-C-O(av)
176(6)
Rh-C-O(av)
176(2)
a Estimated standard deviations in the least significant figure are given
in parentheses.
phous and isostructural with its iridium homologue, Ir3(CO)5-
(GePh3)(µ-GePh2)3(µ3-GePh)(µ-H), that we recently re-
ported.5 The Rh-Rh bond distances [range 2.824(2)-
2.891(2) Å] are significantly longer than those in Rh4(CO)12
[2.6603(17)-2.7642 Å].13 We have previously shown that
edge-bridging germanium and tin ligands produce lengthen-
ing effects on the M-M bonds that they bridge in related
triangular rhodium and iridium cluster complexes.3,5 Fenske-
Hall calculations on compound 4 have shown that this is
due to very strong Rh-Sn interactions and weak Rh-Rh
interactions. The hydrido ligand in 10 was not located
crystallographically but is believed to bridge the Rh(3)-
Ge(4) bond. The hydrido ligand in the related compound
Ir3(CO)5(GePh3)(µ-GePh2)3(µ3-GePh)(µ-H) was located in a
similar bridging position.5 The Rh(3)-Ge(4) bond [2.533-
An ORTEP diagram of the molecular structure of 10 is
shown in Figure 3. Selected intramolecular bond distances
and angles are listed in Table 4. Compound 10 consists of a
triangular arrangement of three rhodium atoms with one
terminal GePh3 ligand, three bridging GePh2 ligands, and
one triply bridging GePh ligand. This compound is isomor-
(9) Veith, M.; Mu¨ller, A.; Stahl, L.; Notzel, Jarczyk, M.; Huch, V. Inorg.
Chem. 1996, 35, 3848.
(10) (a) Lauher, J. W. J. Am. Chem. Soc. 1978, 100, 5305. (b) Burdett, J.
K.; Miller, G. J. J. Am. Chem. Soc. 1987, 109, 4081.
(11) (a) Lower, L. D.; Dahl, L. F. J. Am. Chem. Soc. 1976, 98, 5046. (b)
Fenske, D.; Merzweiler, J. O. Angew. Chem., Int. Ed. Engl. 1988, 27,
1512. (c) Fenske, D.; Magull, J. Z. Naturforsch., B: Chem. Sci. 1990,
45, 121. (d) Fenske, D.; Krautscheid, M. M. Angew. Chem., Int. Ed.
Engl. 1992, 31, 321. (e) Fenske, D.; Hachgenei, F. R. Angew. Chem.,
Int. Ed. Engl. 1984, 23, 982.
(12) Arif, A. M.; Jones, R. A.; Heaton, D. E.; Nunn, C. M.; Schwab, S. T.
Inorg. Chem. 1988, 27, 254.
(13) Farrugia, L. J. J. Cluster Sci. 2000, 11, 39.
Inorganic Chemistry, Vol. 44, No. 12, 2005 4279

Adams and Smith
Figure 5. ORTEP diagram of the Rh8Ge6P4 core of 11 showing 40%
thermal ellipsoid probability.
Figure 4. ORTEP diagram of the molecular structure of Rh8(CO)8-
(PPhMe2)4(µ4-GePh)6, 11, showing 30% thermal ellipsoid probability. The
atom labeling scheme for the Rh8Ge6 core is similar to that of compound
9 in Figure 1.
Scheme 1
Table 5. Selected Intramolecular Distances and Angles for
Compound 11a
Bond Distances (Å)
Rh(1)-Rh(2)
Rh(1)-Rh(4)
Rh(1)-Rh(6)
Rh(2)-Rh(3)
Rh(2)-Rh(7)
Rh(3)-Rh(4)
Rh(3)-Rh(8)
Rh(4)-Rh(5)
Rh(5)-Rh(6)
Rh(5)-Rh(8)
Rh(6)-Rh(7)
Rh(7)-Rh(8)
Rh(2)‚‚‚Rh(4)
Rh(2)‚‚‚Rh(6)
Rh(2)‚‚‚Rh(8)
Rh(4)‚‚‚Rh(6)
Rh(4)‚‚‚Rh(8)
Rh(6)‚‚‚Rh(8)
Rh(1)-Ge(1)
Rh(1)-Ge(2)
Rh(1)-Ge(5)
Rh(2)-Ge(1)
Rh(2)-Ge(2)
Rh(2)-Ge(3)
2.9423(18)
2.8626(17)
2.9525(18)
2.8660(18)
2.9397(18)
2.9521(19)
2.9561(19)
2.9497(18)
2.9377(17)
2.8780(18)
2.8689(18)
2.9585(18)
3.387(2)
3.288(2)
3.284(2)
3.277(2)
3.266(2)
3.395(2)
2.506(2)
2.611(2)
2.818(2)
Rh(3)-Ge(1)
Rh(3)-Ge(3)
Rh(3)-Ge(4)
Rh(4)-Ge(1)
Rh(4)-Ge(4)
Rh(4)-Ge(5)
Rh(5)-Ge(4)
Rh(5)-Ge(5)
Rh(5)-Ge(6)
Rh(6)-Ge(2)
Rh(6)-Ge(5)
Rh(6)-Ge(6)
Rh(7)-Ge(2)
Rh(7)-Ge(3)
Rh(7)-Ge(6)
Rh(8)-Ge(3)
Rh(8)-Ge(4)
Rh(8)-Ge(6)
Rh(1)-P(1)
Rh(3)-P(2)
Rh(5)-P(3)
Rh(7)-P(4)
C-O(av)
2.512(2)
2.795(2)
2.641(2)
2.424(2)
2.344(2)
2.378(2)
2.826(2)
2.614(2)
2.516(2)
2.374(2)
2.353(2)
2.437(2)
2.812(2)
2.639(2)
2.522(2)
2.349(2)
2.369(2)
2.419(2)
2.301(4)
2.296(5)
2.305(5)
2.289(5)
1.15(6)
and single-crystal X-ray diffraction analyses. The structure
of 11 is similar to 9 except that the four PPhMe2 ligands
have replaced four carbonyl groups, one from each the four
Rh(CO)2 groups. An ORTEP diagram of the Rh8Ge6P4 core
of 11 is shown in Figure 5. If one ignores all phenyl groups,
the molecule possesses an S4 improper rotation axis that
passes through the two atoms Ge(1) and Ge(6). In accord
with this, the 31P NMR spectrum exhibits a single resonance
at -2.30 ppm with appropriate coupling to rhodium, (1JP-Rh
) 158 Hz) which is consistent with the presence of four
1
equivalent PPhMe2 groups. The H NMR spectrum shows
2
two resonances at 1.29 ppm (d, 12 H, Me, JP-H ) 9 Hz)
2
and 1.30 ppm (d, 12 H, Me, JP-H ) 9 Hz) which can be
attributed to the two inequivalent methyl groups on each of
the four phosphorus atoms. The Rh-Rh bond distances in
11, including all distances between the four Rh(CO) groups
[3.277(2)-3.395(2) Å], are generally longer than those
observed in the structure of 9. This can be attributed to the
increase in steric effects introduced by the replacement of
the CO ligands with the bulkier phosphine ligands.
Compound 10 reacted with CO at 68 °C to give the
complex Rh3(CO)6(µ-GePh2)3(µ3-GePh), 12, in 94% yield;
see Scheme 1. An ORTEP diagram of the molecular structure
of 12 is shown in Figure 6. Selected intramolecular bond
distances and angles are listed in Table 4. Compound 12
was fully characterized by IR, NMR, elemental, and single-
crystal X-ray diffraction analyses. Compound 12 was formed
by the loss of the hydrido ligand and the terminal GePh3
ligand from 10 and the addition of one carbonyl ligand. The
Rh-Rh distances in 12, 2.8147(8), 2.8610(8), and 2.9101-
(8) Å, are similar to those in 10. Interestingly, unlike 10 all
three Rh-Ge distances to the triply bridging GePh ligand
in 12 are similar in length, 2.4188(8), 2.4157(9), and 2.4039-
(9) Å.
2.426(2)
2.358(2)
2.381(2)
Bond Angles (deg)
49.81(5) Rh(1)-Rh(2)-Rh(3) 102.66(5)
Ge(2)-Rh(1)-Rh(2)
Ge(2)-Rh(1)-Rh(4) 104.71(6) Rh(2)-Rh(1)-Rh(4)
71.33(5)
177(5)
Rh(1)-Ge(1)-Rh(2)
73.22(7) Rh-C-O(av)
a Estimated standard deviations in the least significant figure are given
in parentheses.
(3) Å] is significantly longer than the Rh(1)-Ge(4) and the
Rh(2)-Ge(4) bonds [2.384(3) and 2.384(3) Å, respectively].
This lengthening effect is most likely due to the presence of
1
the bridging hydrido ligand. The H NMR spectrum of 10
exhibits a single resonance at -10.42 ppm with appropriate
proton-rhodium coupling (1JRh-H ) 17 Hz, 2JRh-H ) 2 Hz)
and is consistent with this assignment.
Compound 9 reacted with PPhMe2 at 25 °C to give the
tetraphosphine derivative Rh8(CO)8(PPhMe2)4(µ4-GePh)6, 11,
in 80% yield. An ORTEP diagram of the molecular structure
of 11 is shown in Figure 4. Selected intramolecular bond
distances and angles are listed in Table 5. Compound 11
was fully characterized by IR, 1H and 31P NMR, elemental,
The reaction of Rh4(CO)12 with Ph3GeH has yielded the
first rhodium carbonyl cluster complexes 9 and 10 that
4280 Inorganic Chemistry, Vol. 44, No. 12, 2005

Rh Clusters with Bridging Phenylgermanium Ligands
reaction of Ir4(CO)12 with Ph3GeH, but no iridium homologue
of 9 has yet been reported. Compound 9 reacts with PPhMe2
to give the CO ligand substitution product 11. It seems likely
that it will be possible to prepare additional rhodium cluster
complexes containing bridging germylene and germylyne
ligands in the future. Germanium has been shown to be a
useful modifier of rhodium for applications in catalysis.14
Perhaps these new rhodium-germanium complexes can be
used as precursors for new rhodium-germanium catalysts.
Acknowledgment. This research was supported by the
Office of Basic Energy Sciences of the U.S. Department of
Energy under Grant No. DE-FG02-00ER14980. We thank
the USC NanoCenter for partial support of this work.
Supporting Information Available: CIF files for the structural
analyses of 9-12. This material is available free of charge via the
Internet at http://pubs.acs.org.
Figure 6. ORTEP diagram of the molecular structure of Rh3(CO)6(µ-
GePh2)3(µ3-GePh), 12, showing 30% thermal ellipsoid probability.
contain bridging germylene and germylyne ligands. Com-
pound 9 is a high-nuclearity, eight metal complex containing
quadruply bridging GePh germylyne ligands. Compound 10
has only three rhodium atoms with three edge bridging GePh2
germylene ligands and one triply bridging GePh germylyne
ligand. A compound similar to 10 was obtained from the
IC050372E
(14) (a) Lafaye, G.; Micheaud-Especel, C.; Montassier, C.; Marecot, P.
Appl. Catal., A 2002, 230, 19. (b) Didillon, B.; Candy, J. P.; Lepepetier,
F.; Ferretti, O. A.; Basset, J. M. Stud. Surf. Sci. Catal. 1993, 78, 147.
(c) Lafaye, G.; Mihut, C.; Especel, C.; Marecot, P.; Amiridis, M. D.
Langmuir 2004, 20, 10612.
Inorganic Chemistry, Vol. 44, No. 12, 2005 4281