Trinuclear Rh2M complexes (M = Ni, Pd) bridged by butyl selenolato and carborane diselenolato ligands

Article abstract of DOI:10.1021/om7004035

Two new half-sandwich trinuclear Rh₂M (M = Ni, Pd) complexes bridged by butyl selenolato and carborane diselenolato ligands, [Cp*R{μ-Se₂C₂(B₁₀H₁₀)}] ₂M[μ-Se(C₄H₉)]₂ [M = Ni (4), Pd (5)], have been prepared by the reactions of the [Cp*Rh{μ-Se ₂C₂(B₁₀H₁₀)}{μ-Se(C ₄H₉)}]^- anion with NiCl₂ and Pd(PhCN)₂Cl₂, respectively. The complexes have been fully characterized by ¹H, ¹³C, and ¹¹B NMR and IR spectroscopy as well as by element analyses. The molecular structures of 4 and S have been determined by single-crystal X-ray diffraction analyses, which show the central MSe₄ moiety in a slightly distorted square-planar coordination geometry for M = Ni, Pd.

Full text of DOI:10.1021/om7004035

5442
Organometallics 2007, 26, 5442-5445
Trinuclear Rh2M Complexes (M ) Ni, Pd) Bridged by Butyl
Selenolato and Carborane Diselenolato Ligands
Shuyi Cai and Guo-Xin Jin*
Shanghai Key Laboratory of Molecular Catalysis and InnoVatiVe Material, Department of Chemistry,
Fudan UniVersity, 200433, Shanghai, People’s Republic of China
ReceiVed April 26, 2007
Summary: Two new half-sandwich trinuclear Rh2M (M ) Ni,
Pd) complexes bridged by butyl selenolato and carborane
diselenolato ligands, [Cp*Rh{µ-Se2C2(B10H10)}]2M[µ-Se(C4H9)]2
[M ) Ni (4), Pd (5)], haVe been prepared by the reactions of
the [Cp*Rh{µ-Se2C2(B10H10)}{µ-Se(C4H9)}]- anion with NiCl2
and Pd(PhCN)2Cl2, respectiVely. The complexes haVe been fully
sandwich complexes of the type [Cp*M{E2C2(B10H10)}] (Cp*
) η5-C5Me5, M ) Co, Rh, Ir; E ) S, Se), which can be used
for further transformations in a controlled way under various
conditions.8-12 Owing to their rigid backbone, our recent studies
have focused on the development of the rational methods to
obtain the metal-chalcogenido cores with desired metal and
chalcogen compositions. In this paper, we report the synthesis
of the [Cp*Rh{µ-Se2C2(B10H10)}{µ-Se(C4H9)}]- anion as the
metallaligand to react with transition metal compounds to afford
the half-sandwich mixed-metal trinuclear complexes bridged by
selenobutyl-diselenolatocarborane ligands.
1
characterized by H, 13C, and 11B NMR and IR spectroscopy
as well as by element analyses. The molecular structures of 4
and 5 haVe been determined by single-crystal X-ray diffraction
analyses, which show the central MSe4 moiety in a slightly
distorted square-planar coordination geometry for M ) Ni, Pd.
Introduction
Results and Discussion
The continuing intense interest in multinuclear transition metal
complexes containing sulfur or selenium donor ligands is
stimulated by their significant relevance to biological processes
and their potential in solid state and catalytic applications.1 This
area of chemistry abounds with complexes of mono- and
bidentate thiolates,2 as well homo- or hetero-polynuclear
complexes containing bridging monothiolates (RS-),3 dithiolate
bridging ligands (-SRS-),4 or tridentate dithiolate-thioether
ligands,5 but heteronuclear complexes containing selenoether-
selenolate ligands are rare.6 On the other hand, the synthesis
and study of organometallic complexes possessing an ancillary
o-carborane dichalcogenolato ligand have continued to receive
attention.7 1,2-Dicarba-closo-dodecaborane-1,2-dichalcogeno-
lates (ortho-carborane dichalcogenolates) can be used as the
voluminous and chemically robust chelate ligands to form half-
Previously, we have reported that treatment of [Cp*Rh(µ-
Cl)Cl]2 with dilithium dichalcogenolato carboranes Li2E2C2-
(B10H10) gave the 16-electron dichalcogenolate complexes
Cp*Rh[E2C2(B10H10)] (E ) S (1a), Se (1b)) and investigated
(4) See for instance the following: (a) Nadasdi, T. T.; Stephan, D. W.
Organometallics 1992, 11, 116, and references therein. (b) Aggarwal, R.
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W. Inorg. Chem. 1994, 33, 1532. (d) Lai, C.-H.; Reibenspies, J. H.;
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S.-Y.; Weng, L.-H. Chin. Sci. Bull. 2003, 48, 1733.
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B. Eur. J. Inorg. Chem. 1999, 873. (b) Bae, J. Y.; Park, Y. I.; Ko, J.; Park,
K. I.; Cho, S. I.; Kang, S. O. Inorg. Chim. Acta 1999, 289, 141.
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Organometallics 2002, 21, 2533. (b) Yu, X.-Y.; Jin, G.-X.; Hu, N.-H.; Weng,
L.-H. Organometallics 2002, 21, 5540.
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M. Angew. Chem., Int. Ed. 2005, 44, 259. (b) Wang, J.-Q.; Hou, X. F.;
Weng, L.-H.; Jin, G.-X. Organometallics 2005, 24, 826. (c) Wang, J.-Q.;
Hou, X. F.; Weng, L.-H.; Jin, G.-X. J. Organomet. Chem. 2005, 690, 249.
(d) Wang, J.-Q.; Cai, S. Y.; Jin, G.-X.; Weng, L.-H.; Herberhold, M.
Chem.-Eur. J. 2005, 11, 7343. (e) Cai, S. Y.; Wang, J.-Q.; Jin, G.-X.
Organometallics 2005, 24, 4226. (f) Cai, S. Y.; Jin, G.-X. Organometallics
2005, 24, 5280. (g) Wang, J.-Q.; Jin, G.-X. Dalton Trans. 2006, 86. (h)
Cai, S. Y.; Lin, Y.-J.; Jin, G.-X. Dalton Trans. 2006, 912. (i) Cai, S. Y.;
Hou, X. F.; Chen, Y. Q.; Jin, G.-X. Dalton Trans. 2006, 3736.
* Corresponding author. E-mail: gxjin@fudan.edu.cn. Tel: +86-21-
65643776. Fax: +86-21-65641740.
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10.1021/om7004035 CCC: $37.00 © 2007 American Chemical Society
Publication on Web 09/28/2007

Notes
Organometallics, Vol. 26, No. 22, 2007 5443
Figure 1. ORTEP drawing of 2‚[Li(THF)2(H2O)2] (30% probability). Hydrogen atoms are omitted for clarity. Selected distances (Å) and
angles (deg): Rh(1)-S(1), 2.375(3); Rh(1)-S(2), 2.357(3); Rh(1)-S(3), 2.380(3); C(1)-S(1), 1.775(9); C(2)-S(2), 1.780(10); C(1)-
C(2), 1.671(13); C(13)-S(3), 1.764(13); S(1)-Rh(1)-S(2), 89.58(9); S(1)-Rh(1)-S(3), 92.02(10); S(2)-Rh(1)-S(3), 82.28(11); Rh(1)-
S(3)-C(13), 112.6(4).
Scheme 1. Synthesis of Complex 2
the addition reactions at the rhodium atom.9 The group 16
chalcogeno ether ligands ER2 (E ) S, Se, or Te) are usually
regarded as modest σ-donors to transition metal centers;7 the
reaction of Cp*Rh[S2C2(B10H10)] (1a) with LiSPh could afford
Figure 2. Molecular structures of 4 and 5 (30% probability).
Hydrogen atoms are omitted for clarity. Selected distances (Å) and
angles (deg) for 4 (M ) Ni): Ni(1)-Se(1), 2.3727(11); Ni(1)-
the lithium salt of Cp*Rh(µ-SPh)[S2C2(B10H10)]- (2) (Scheme
1).13
We attempted to synthesize multinuclear complexes using
1,2-dicarba-closo-dodecaborane-1,2-dithiolato and phenylthi-
olato ligands of complex 2 to hold two metal atoms in close
proximity. The procedures failed when complex 2 was used as
the starting material to react with NiCl2 and Pd(PhCN)2Cl2,
respectively, due to the intramolecular stereoelectronic influence
of the phenylthiolato ligand and the high reactivity of the
derivatives.
Se(3), 2.3119(11); Rh(1)-Se(3), 2.4459(10); Rh(1)-Se(1), 2.4562(9);
Rh(1)-Se(2), 2.4643(11); Se(1)-C(1), 1.968(6); Se(2)-C(2),
1.924(7); Se(3)-C(13), 1.934(7); C(1)-C(2), 1.654(9); Se(3)-
Ni(1)-Se(1), 85.04(3); Se(3)-Rh(1)-Se(1), 80.47(3); Se(3)-
Rh(1)-Se(2), 94.26(3); Ni(1)-Se(1)-Rh(1), 96.10(4); Ni(1)-
Se(3)-Rh(1), 97.99(4). Selected distances (Å) and angles (deg) for
5 (M ) Pd): Pd(1)-Se(3), 2.4102(12); Pd(1)-Se(1), 2.4795(11);
Rh(1)-Se(3), 2.4621(12); Rh(1)-Se(2), 2.4634(12); Rh(1)-Se-
(1), 2.4686(11); Se(1)-C(1), 1.955(7); Se(2)-C(2), 1.957(8); Se-
(3)-C(3), 1.918(8); C(1)-C(2), 1.627(9); Se(3)-Pd(1)-Se(1),
83.68(3); Se(3)-Rh(1)-Se(2), 94.28(4); Se(3)-Rh(1)-Se(1), 82.84-
(4); Se(2)-Rh(1)-Se(1), 91.57(4); Pd(1)-Se(1)-Rh(1), 95.63(4);
Pd(1)-Se(3)-Rh(1), 97.61(5).
Complex 2 can be recrystallized from THF at low temperature
to give well-formed red, single crystals in the triclinic space
group P1h with four molecules in the unit cell. The X-ray
structure analysis of 2 confirms the ionic nature of the complex,
and the molecular structure of [Cp*Rh(µ-SPh){S2C2(B10H10)}]‚
[Li(THF)2(H2O)2] is shown in Figure 1. The anion structure of
2 shows a six-coordinate geometry about the rhodium atom,
assuming that the Cp* ring serves as a three-coordinate ligand.
The Rh-S distance (Rh(1)-S(1) 2.375(3) Å, Rh(1)-S(2)
2.357(3) Å) at the formally 18-electron metal center is signifi-
cantly longer than that of the corresponding 16-electron
complexes Cp′Rh[S2C2(B10H10)] (Cp′ ) Cp*, η5-1,3-tBu2C5H3)
(2.263 Å (av) for Cp*, 2.249 Å (av) for η5-1,3-tBu2C5H3),9,12
which is due to p-orbital donation of the lone pairs from the
sulfur atoms to the electron-deficient metal center. The rhodium
atom environment is transferred from a two-legged piano-stool
geometry in the 16-electron complex to a three-legged version
in the 18-electron complex. The 16-electron pseudoaromatic
metalladichalcogenolene heterocyclic system is destroyed and
bent with a dihedral angle of 159.4° for compound 2, along the
S‚‚‚S vector, which is due to the coordination of the SPh
fragment to the metal center.
In order to gain stable, neutral multinuclear compounds, we
prepared the voluminous substituted lithium salt of Cp*Rh(µ-
SenBu)[Se2C2(B10H10)]- (3), which was obtained from the
reaction of 1b with LiSenBu. Furthermore, the anion complex
3 derived from selenobutyl-selenolatocarborane could be reacted
with nickel or palladium13 complexes to afford hetero-trinuclear
complexes containing the (Rh2M) cores (M ) Ni, Pd) (Scheme
2).
Complexes 4 and 5 are moderately soluble in CH2Cl2 and
THF, but only sparingly soluble in toluene and insoluble in
n-hexane.
The structures of 4 and 5 have been determined by X-ray
analyses using single crystals grown by slow diffusion of hexane
into dichloromethane solution of the corresponding compounds,
after chromatography on silica. Both of them are in the form of
orange prisms in the monoclinic space group C2/c with four
molecules in the unit cell. The molecular structures and selected
bond distances and angles of 4 and 5 are depicted in Figure 2.
(13) Chen, J. C.; Lin, I. J. Organometallics 2000, 19, 5113.

5444 Organometallics, Vol. 26, No. 22, 2007
Notes
Scheme 2. Synthesis of Complexes 4 and 5
Elemental analyses were performed on an Elementar III Vario
EI analyzer. NMR measurements were carried out using Bruker
AC500 spectrometers (chemical shifts are given with respect to
CHCl3/CDCl3 (δ1H ) 7.24; δ13C ) 77.0), external Et2O-BF3 (δ11B
) 0 for ¥(11B) ) 32.08 MHz)). Infrared spectra were obtained on
a Nicolet FT-IR 360 spectrometer (KBr pellet).
The ORTEP diagrams of 4 and 5 (Figure 2) show that the
two complexes have similar structures. The heteronuclear
complexes contain two o-carborane selenolato ligands, two
butyl-selenolato ligands attached to the Cp*Rh fragment, and a
nickel or palladium metal center. The Rh-Se distances are
2.4562(9) and 2.4643(11) Å for compound 4 and 2.4634(12)
and 2.4686(11) Å for compound 5, longer than that of a
“pseudoaromatic” five-membered rhodadithiolene ring in
Cp*Rh[Se2C2(B10H10)] (2.3553 Å (av)).9 The planar pseudoaro-
matic system of the two rhodadiselenene heterocycles 1b is no
longer present in 4 or 5; the dihedral angle at the Se‚‚‚Se vector
in the RhSe2C2 ring is 160.5° for compound 4 and 162.3° for
compound 5. The M-Se(butyl) bond (2.3119(11) Å for 4 and
2.4102(12) Å for 5) is distinctively shorter than the M-Se-
(carborane) bond (2.3727(11) Å for 4 and 2.4795(11) Å for 5);
the cis position of the butyl-selenolato ligand as the stronger
bonded selenium donor is favored due to electronic reasons.
The four-membered metallacycle Rh(1)Se(1)M(1)Se(3) is almost
planar, the dihedral angle along the Se‚‚‚Se vector being 173.5°
for 4 and 174.9° for 5. The dihedral angle of the plane M(1)-
Se(1)Se(3) and the plane M(1)Se(1A)Se(3A) is 171.1° for 4
and 174.0° for 5 and the cis angles at the metal center are in
the range 83.7-100.9°. Thus, the metal center lies perfectly on
the square plane defined by the four donor atoms. The long
Rh(1)‚‚‚M(1) separation (3.592 Å for 4 and 3.666 Å for 5) and
the obtuse angle (M(1)-Se(1)-Rh(1) 96.10(4)° for 4 and
95.63(4)° for 5, M(1)-Se(3)-Rh(1) 97.99(4)° for 4 and
97.61(5)°for 5) indicate that a direct bonding interaction between
the rhodium and metal center (nickel or palladium) is absent.
In summary, two new half-sandwich mixed-metal Rh2M (M
) Ni, Pd) trinuclear complexes bridged by selenobutyl-
selenolatocarborane ligands, [Cp*Rh{µ-Se2C2(B10H10)}]2M[µ-
Se(C4H9)]2 [M ) Ni (4), Pd (5)], have been prepared by
reactions of the [Cp*Rh{µ-Se2C2(B10H10)}{µ-Se(C4H9)}]- anion
with NiCl2 and Pd(PhCN)2Cl2, respectively. The molecular
structures of 4 and 5 have been determined by X-ray crystal-
lography. A detailed investigation on the reaction chemistry of
heteronuclear complexes bridged by mixed alkyl chacogenolato
and carborane chacogenolato ligands is under way.
Preparations of Cp*Rh(µ-SPh)[S2C2(B10H10)]- (2). PhSH (12
mg, 0.11mmol) was dissolved in diethyl ether (15 mL) and lithiated
by the addition of n-butyllithium (39 µL, 0.11 mmol). The mixture
was stirred for 1 h at room temperature. Then a solution of [Cp*Rh-
{S2C2(B10H10)}] (1a) (44 mg, 0.1 mmol) in THF (20 mL) was added
at ambient temperature. The resulting solution was stirred for 16
h, the solvent was then removed under vacuum, and the residue
was purified by recrystallization with THF at -28 °C. 2‚Li(THF)2-
(H2O)2: 65 mg, 88%. Anal. Calcd (%) for C26H50B10LiO4RhS3: C
1
42.15, H 6.80. Found: C 41.83, H 6.73. H NMR (500 MHz,
CDCl3, δ/ppm): 1.56 (s, H2O), 1.80 (s, Cp*), 1.85 (m, CH2 of
THF), 3.76 (m, CH2O of THF), 7.01-7.26 (m, Ph).
Preparation of [Cp*Rh{Se2C2(B10H10)}]2{Ni(SeC4H9)2} (4).
[Cp*Rh{Se2C2(B10H10)}] (1b) (109 mg, 0.2 mmol) was added to
BuSeLi (0.1mmol) in diethyl ether (20 mL), and the mixture was
stirred for 3 h at room temperature. Then a solution of NiCl2 (0.1
mmol) in CH2Cl2 (20 mL) was added at ambient temperature. The
color of the resultant mixture gradually changed from green to red.
After 12 h the solvents were removed under reduced pressure and
the residue was chromatographed on silica gel (2.0 cm × 40.0 cm).
Elution with CH2Cl2/hexane (1:1) gave an orange zone. Evaporation
and crystallization from CH2Cl2/hexane afforded 4 as orange
prismatic crystals (73 mg, 52%). Anal. Calcd (%) for C32H68B20-
1
Se6Rh2Ni: C 27.31, H 4.87. Found: C 27.42, H 4.90. H NMR
(500 MHz, CDCl3, δ/ppm): 0.94 (m, 6H, CH3), 1.41 (m, 4H, CH2),
1.57 (m, 4H, CH2), 1.72 (s, 30H, Cp*), 2.77 (m, 4H, SeCH2). 13C
NMR (500 MHz, CDCl3, δ/ppm): 10.53 (C5Me5), 15.45 (CH3),
23.01 (CH2), 28.05 (CH2), 75.92 (SeCH2), 98.73 (C5Me5, d, J )
5.20). 11B NMR (160 MHz, CDCl3, δ/ppm): -2.09, -7.06,
-11.32, -13.89. IR (KBr disk): ν 2955, 2920, 2845 cm-1 (C-
H), ν ) 2568 cm-1 (B-H).
Preparation of [Cp*Rh{Se2C2(B10H10)}]2{Pd(SeC4H9)2} (5).
[Cp*Rh{Se2C2(B10H10)}] (1b) (109 mg, 0.2 mmol) was added to
BuSeLi (0.1mmol) in diethyl ether (20 mL), and the mixture was
stirred for 3 h at room temperature. Then a solution of Pd-
(PhCN)2Cl2 (28 mg, 0.1 mmol) in CH2Cl2 (20 mL) was added at
ambient temperature. The color of the resultant mixture gradually
changed from green to red. After 12 h the solvents were removed
under reduced pressure and the residue was chromatographed on
silica gel (2.0 cm × 40.0 cm). Elution with CH2Cl2/hexane (1:1)
gave an orange zone. Evaporation and crystallization from CH2-
Cl2/hexane afforded 5 as orange prismatic crystals (95 mg, 65%).
Anal. Calcd (%) for C32H68B20Se6Rh2Pd: C 26.41, H 4.71. Found:
Experimental Section
General Procedure. All manipulations were carried out under
a nitrogen atmosphere using standard Schlenk techniques. All
solvents were dried and deoxygenated before use. The solvents
THF, toluene, and n-hexane were refluxed and distilled over
sodium/benzophenone ketyl under nitrogen prior to use. Silica gel,
Merck 60 (0.06-0.2 mm), was activated at 400 °C and stored under
nitrogen before use in chromatography. The starting materials
1
C 26.21, H 4.65. H NMR (500 MHz, CDCl3, δ/ppm): 0.90 (m,
6H, CH3), 1.26 (m, 4H, CH2), 1.59 (m, 4H, CH2), 1.85 (s, 30H,
Cp*), 2.82 (m, 4H, SeCH2). 13C NMR (500 MHz, CDCl3, δ/ppm):
9.32 (C5Me5), 14.06 (CH3), 22.61 (CH2), 29.66 (CH2), 69.79
13
[Cp*Rh{E2C2(B10H10)}] [E ) S (1a), Se (1b)], and Pd(PhCN)2Cl2
were prepared by literature procedures.

Notes
Organometallics, Vol. 26, No. 22, 2007 5445
(SeCH2), 98.70 (C5Me5, d, J ) 5.10). 11B NMR (160 MHz, CDCl3,
δ/ppm): -2.32, -7.08, -13.43, -14.47. IR (KBr disk): ν 2954,
2922, 2854 cm-1 (C-H), ν ) 2562 cm-1 (B-H).
P1h, a ) 12.094(2) Å, b ) 12.297(2) Å, c ) 14.618(3) Å, R )
88.707(3)°, â ) 73.950(3)°, γ ) 79.967(3)°, V ) 2056.5(7) Å3, Z
) 2, R1 ) 0.0683 for 7178 (I > 2σ(I)), wR2 ) 0.2165 (all data).
Crystal data for 4: fw ) 1492.28, monoclinic, C2/c, a ) 11.488(3)
Å, b ) 21.292(5) Å, c ) 23.703(6) Å, R ) 90°, â ) 100.899(4)°,
γ ) 90°, V ) 5693(2)Å3, Z ) 4, R1 ) 0.0424 for 5575 (I > 2σ(I)),
wR2 ) 0.0923 (all data). Crystal data for 5: fw ) 1539.97,
monoclinic, C2/c, a ) 11.421(3) Å, b ) 21.371(7) Å, c ) 24.034(6)
Å, R ) 90°, â ) 101.274(4)°, γ ) 90°, V ) 5753(3) Å3, Z ) 4,
R1 ) 0.0384 for 5080 (I > 2σ(I)), wR2 ) 0.0665 (all data).
X-ray Crystal Structure Determination of 2, 4, and 5. Crystals
of 2, 4, and 5 were sealed under nitrogen in Lindemann glass
capillaries for X-ray structural analysis. Diffraction data were
collected on a Bruker SMART Apex CCD diffractometer using
graphite-monochromated Mo KR (λ ) 0.71073 Å) radiation. During
the intensity data collection, no significant decay was observed.
The intensities were corrected for Lorentz-polarization effects and
empirical absorption with the SADABS program.14 The structures
were solved by direct methods using the SHELXL-97 program.15
All non-hydrogen atoms were found from the difference Fourier
syntheses. The H atoms were included in calculated positions with
isotropic thermal parameters related to those of the supporting
carbon atoms but were not included in the refinement. All
calculations were performed using the Bruker Smart program.
Crystal data for 2: C26H50B10LiO4Rh2S3, fw ) 740.79, triclinic,
Acknowledgment. Financial support by the National Science
Foundation of China for Distinguished Young Scholars
(20531020, 20421303, 20771028), by the National Basic
Research Program of China (2005CB623800), and by Shanghai
Science and Technology Committee (05JC14003, 06XD14002)
is gratefully acknowledged.
Supporting Information Available: X-ray crystallographic data
for complexes 2, 4, and 5. This material is available free of charge
via the Internet at http://pubs.acs.org.
(14) Sheldrick, G. M. SADABS, A Program for Empirical Absorption
Correction; University of Go¨ttingen: Go¨ttingen, Germany, 1998.
(15) Sheldrick, G. M. SHELXL-97, Program for the Refinement of Crystal
Structures; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
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