Trigonal pyramids: Alternative ground-state structures for sixteen-electron complexes

Article abstract of DOI:10.1002/anie.200601352

(Figure Presented) A structural alternative for sixteen-electron ML ₄ complexes is the trigonal-pyramidal (TP) form. This has been demonstrated by the preparation of TP complexes of rhodium(I) with three equatorial olefin ligands and one axial silyl ligand (see picture: C black, Rh blue, Si orange).

Full text of DOI:10.1002/anie.200601352

Angewandte
Chemie
Rhodium Complexes
DOI: 10.1002/anie.200601352
Trigonal Pyramids: Alternative Ground-State
Structures for Sixteen-Electron Complexes**
Detlev Ostendorf, Clark Landis, and
Hansjörg Grützmacher*
It is widely believed that tetracoordinate complexes of d8
transition metal centers (RhI, IrI, PdII, PtII, etc.) have a planar
structure (P, ideal D4h symmetry) and, indeed, hundreds of
examples are known.[1] However, apart from tetrahedral
structure T, which is observed for high-spin transition metals
from the 4th period,[2] sawhorse (SH, C2v) and trigonal-
pyramidal structures (TP, C3v) are alternatives (Scheme 1).[3]
Scheme 1. Planar (P), tetrahedral (T), sawhorse (SH), and trigonal-
planar (TP) structures.
The highly reactive transient carbonyls [M(CO)4] (M =
Fe, Ru, Os) have SH structures,[4a–c] as do a few recently
isolated Ru0 and RhI complexes, which show remarkable
reactivity.[4d–f]
Even computationally, the TP structure has been rarely
considered. Pidun and Frenking investigated by DFT meth-
=
ods [RhX(CO)3] complexes with X = H, HC O, CH2OH, and
=
OMe. For [Rh(HC O)(CO)3], TP is the (slightly) preferred
ground-state structure, whereas all other complexes have
either a P or an SH form in the global minimum.[5] Within the
complementary spherical electron density (CSED) model,
Mingos identified SH and TP forms as the next best choices to
planar structures for 16-electron complexes of late transition
metals.[6] In computations using the orbital ranked symmetry
analysis method (ORSAM), Bayse and Hall considered d8-
MH4 hydrides with SH and TP forms.[7] Proposals for making
[*] Dr. D. Ostendorf, Prof. Dr. H. Grützmacher
Laboratory of Inorganic Chemistry
Department of Chemistry and Applied Biosciences
ETH Zürich
8093 Zürich (Switzerland)
Fax: (+41)446-331-032
E-mail: gruetzmacher@inorg.chem.ethz.ch
Prof. Dr. C. Landis
Department of Chemistry
University of Wisconsin-Madison
1101 University Ave., Madison, WI 53706 (USA)
E-mail: landis@chem.wisc.edu
[**] This work was supported by the Swiss National Science Foundation
and the ETH Zürich.
Supportinginformation for this article is available on the WWW
under http://www.angewandte.org or from the author.
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5169

Communications
the TP forms the ground-state structures have not been made.
Herein we report the synthesis and isolation of stable
compounds that have such a trigonal pyramidal structure.
What ligand set would make the trigonal pyramid the
ground-state structure for an ML4 complex? We reasoned
that such a structure might be obtained when the resonance
form A contributes strongly to the electronic ground state
with minimal participation of B (Scheme 2).
Scheme 2. Resonance structures A and B contributingto the electronic
ground state of a TP structure.
This case arises when a formally d10-ML3 donor fragment
such as [Rh(C2H4)3]ꢀ, which is known to have a trigonal-
planar structure,[8] is combined with a cation X+, most simply
a proton or a silyl cation SiH3+. Indeed, DFT calculations for
[RhH(C2H4)3] and [Rh(SiH3)(C2H4)3] show that the trigonal-
pyramidal form with H or SiH3 in the apex is significantly
more stable than the planar form (Table 1).[9]
Scheme 3. Syntheses of silane 2 and complexes 3–5.
Table 1: Calculated relative energies of trigonal-pyramidal (TP) and
planar (P) [RhXL3] complexes.[a]
the reaction mixture. When the reaction was performed in
THF, or complex
3
was recrystallized from THF,
X
L
L’
[Rh(trop2SiMe)(C2H4)(thf)] (4) was obtained in 70% yield.
Finally, when 3 was treated with one equivalent of PPh3 in
THF, ethylene evolved and yellow crystals of
[Rh(trop2SiMe)(PPh3)] (5) were isolated in almost quantita-
tive yield.
Single crystals of 3, 4, and 5 were investigated by X-ray
diffraction[12] (Figures 1–3). Clearly, 3 has the predicted
trigonal-pyramidal structure; the calculated and experimental
data agree satisfactorily (see legend to Figure 1). The three
E [kcalmolꢀ1
]
E [kcalmolꢀ1
]
H
SiH3
SiH3
C2H4
C2H4
C2H4
C2H4
C2H4
PH3
ꢀ7.3
ꢀ12.6
ꢀ10.6
0.0
0.0
0.0
[a] B3PW91 functional; 6-31+G* for non-metal atoms, LANL2DZ at Rh.
=
Remarkably, even when one p-acceptor C2H4 ligand is
replaced by a s-donor PH3 ligand, the TP form of [Rh(SiH3)-
(PH3)(C2H4)2] is more stable (by about 11 kcalmolꢀ1) than the
planar cis-[Rh(SiH3)(PH3)(C2H4)2] complex.[10]
coordinated C C units lie in the basal plane and bind in a
trigonal fashion to the Rh atom, which deviates slightly
(0.125 Š) from the plane through ct1–ct3 towards the inside
of the pyramid (Figure 1b). The ct-Rh-Si angles are close to
908. In the crystal lattice, one molecule of chlorobenzene lies
between two molecules of 3, but the absence of contacts
shorter than 3.63 Š rules out any bonding interaction.
The structural parameters of the core of 4 are very similar
to those of 3. The RhI atom deviates by 0.085 Š from the
plane through ct1–ct3 (Figure 2). A THF molecule binds
loosely to the RhI center and completes the trigonal-
bipyramidal coordination sphere typical of an 18-electron
None of the species in Table 1 is likely be isolated, because
ꢀ
ꢀ
insertion of a coordinated C2H4 into the Rh H or Rh Si bond
is expected (RhI complexes are efficient catalysts for hydro-
genation and hydrosilylation). Therefore we synthesized
bis(5H-dibenzo[a,d]cyclohepten-5-yl)methylsilane (trop2Si-
HMe, 2), in which this insertion is unlikely to occur because
of resulting strain energy in the product.[11] Silane 2 is easily
obtained in 85% overall yield from 5-chloro-5H-dibenzo-
[a,d]cycloheptene (tropCl, 1), which was first metalated with
elemental lithium and then coupled in situ with MeHSiCl2
(Scheme 3).
8
I
ꢀ
d -ML5 complex. The very long Rh O distance (2.544 Š)
indicates a very weak interaction.
The crystal lattice of the phosphane silanide complex 5
contains no further solvent molecules, and the complex also
has the predicted trigonal-pyramidal structure: The sum of
the basal bond angles around the rhodium center is 356.68.
Like in 3 and 4, the angles enclosed by the centroids of the
Note that the rigid conformation of 2 will not allow for a
planar structure, but a sawhorse type structure may be
obtainable. Silane 2 was treated with 0.5 equiv of [Rh2(m-
Cl)2(C2H4)4] in chlorobenzene. Ethylene and HCl were
liberated, and yellow crystals of [Rh(trop2SiMe)-
(C2H4)]·C6H5Cl (3) precipitated in about 70% yield from
=
coordinated C C bonds and the apical Si atom are close to
908. The ct-Rh-ct angle (129.68) in 5 is somewhat wider than
5170
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Chemie
those in 3 and 4, while the ct-Rh-P angles are
ꢀ
slightly more acute (111.8, 115.28). The Rh Si
bonds in (2.236(1) and 2.266(2) Š),
(2.243(1) Š), and 5 (2.235(1) Š) are remarkably
3
4
=
short, even shorter than the formal Rh Si bonds
in RhI silylene complexes.[13a] The Rh P distance
ꢀ
ꢀ
of 2.335(1) Š lies within the upper range of Rh P
bond lengths (ca. 2.26–2.34 Š).[14]
All structural features of the core are well
reflected by the computed data for the uncon-
strained model [Rh(SiH3)(PH3)(C2H4)2] (see
legend to Figure 3). Only the experimentally
determined P-Rh-Si angle in 5 (103.4(1)8) is
larger than the calculated one (91.18), certainly
due to steric interactions, which can also be made
responsible for the larger displacement of the Rh
center from the basal plane of 0.220 Š. The acute
C38-P1-Rh1 angle (94.9(1)8), which is signifi-
cantly smaller that the other two C-P-Rh angles
(130.48 and 118.08), is noteworthy. This distortion
may indicate a positive hyperconjugative inter-
Figure 1. a) Structure of 3. Hydrogen atoms are omitted for clarity. Thermal ellipsoids
ꢀ
are drawn at 30% probability. Bond lengths [Š] and angles [8]: Rh Si1 2.236(1),
ꢀ
action of the P C s bond with the empty orbital
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
Rh1A Si1A 2.266(2), Rh C4 2.203(3), Rh C5 2.217(3), Rh C19 2.185(3), Rh C20
at the RhI center pointing outwards from the
basal plane to the missing apical corner of a
trigonal-bipyramidal (TBP) structure. Such dis-
tortions were also observed for complexes with
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
2.217(3), Rh C32 2.222(3), Rh C33 2.231(3), Rh ct1 2.095(3), Rh ct2 2.085(3), Rh
ꢀ
ꢀ
ꢀ
=
ct3 2.117(3), Si1 C16 1.910(3), Si1 C1 1.912(3), Si1 C31 1.874(3), C4 C5trop
=
=
1.405(4), C19 C20trop 1.408(4), C32 C33 1.381(4); ct1-Rh-ct2 125.2(1), ct1-Rh-ct3
115.9(1), ct2-Rh-ct3 117.9(1), ct1-Rh-Si1 91.9(1), ct2-Rh-Si1 91.8(1), ct3-Rh-Si1
96.8(1), C1-Si1-C16 112.6(1), C1-Si1-C31 106.0(1), C31-Si1-C16 105.2(1), C1-Si1-Rh
107.6(1), C16-Si1-Rh 107.9(1), C31-Si1-Rh 117.8(1). ct=centroid of the coordinated
ꢀ
SH-type structure, in which a P C s bond of an
apically bonded PR3 ligand may interact with an
unfilled orbital pointing to the missing equatorial
site of a TBP structure.[4d,e]
=
C C bond. ꢀ(ct-Rh-ct)=359.08; ꢀ(C-Si-C)=323.78. b) Plot of the core of 3.
ꢀ
ꢀ
ꢀ
ꢀ
Computed data for [Rh(SiH3)(C2H4)3]: Rh Si 2.270, Rh ct1 2.103, Rh ct2 2.101, Rh
ꢀ
=
ct3 2.103, Rh C 2.214–2.217, C C 1.397; ct-Rh-ct 119.8, ꢀ(H-Si-H): 320.58; ꢀ(ct-Rh-
ct)=359.38.
The NMR data of 3 and 5 are compatible with
the structures observed in the solid state. In
1
particular, the H NOESY spectrum of 5 shows
intense cross-peaks for the protons of the SiMe
group and the phenyl protons of the PPh3 ligand
indicative of a cis arrangement. Such interactions
are not expected for a compound in which the
PPh3 group is trans to the SiMe group. In the 1H
and 13C NMR spectra of all reported compounds,
the significant shift of the olefinic CH resonances
to lower frequencies (coordination shifts
Ddcoord = dcomplexꢀdligand
:
1H: approx. ꢀ2 ppm,
13C: approx. ꢀ60 ppm)[15] indicates significant
metal-to-ligand backdonation. However, the
inequivalent 1H environments of the coordinated
=
H2C CH2 molecule in 3 lead to a slightly
broadened singlet at room temperature; even at
low temperature (183 K) no sharp distinct signals
were observed, and this indicates a rather low
ꢀ
barrier for rotation around the Rh ct3 axis.
Figure 2. a) Structure of 4. Hydrogen atoms are omitted for clarity. Thermal ellipsoids
The NMR data of 3 in CD2Cl2 and of the THF
complex 4 in [D8]THF are almost identical. We
therefore assume that the equilibrium 3 +
THFÐ4 lies far to left and that the interaction
of the rhodium center with a fifth ligand in the
apical position trans to the Si atom is very weak.
In particular, the 29Si and 103Rh NMR resonances,
which one would expect to respond most sensi-
tively to complexation of an additional fifth
ꢀ
are drawn at 30% probability. Bond lengths [Š] and angles [8]: Rh1 Si1 2.243(1),
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
Rh1 O1 2.544(2), Rh1 C4 2.202(2), Rh1 C5 2.192(2), Rh1 C19 2.213(2), Rh1 C20
ꢀ
ꢀ
ꢀ
ꢀ
2.241(2), Rh1 C32 2.211(2), Rh1 C33 2.211(3), Rh1 ct1 2.080(2), Rh1 ct2 2.113(2),
Rh1 ct3 2.102(3), Si1 C16 1.911(2), Si1 C1 1.917(2), Si1 C31 1.875(2), C4 C5trop
ꢀ
ꢀ
ꢀ
ꢀ
=
=
=
1.410(3), C19 C20trop 1.410(3), C32 C33 1.373(4); ct1-Rh1-ct2 122.9(1), ct1-Rh1-ct3
119.1(1), ct2-Rh1-ct3 117.5(1), ct1-Rh1-Si1 91.8(1), ct2-Rh1-Si1 91.1(1), ct3-Rh1-Si1
94.2(1), ct1-Rh1-O1 81.6(1), ct2-Rh1-O1 92.0(1), ct3-Rh1-O1 89.7(1), C1-Si1-C16
112.7(1), C1-Si1-C31 104.8(1), C31-Si1-C16 103.4(1), C1-Si1-Rh1 107.7(1), C16-Si1-
Rh1 108.5(1), C31-Si1-Rh1 119.9(1). ꢀ(ct-Rh-ct)=359.58; ꢀ(C-Si-C)=320.98. b) Plot
of the core of 4.
Angew. Chem. Int. Ed. 2006, 45, 5169 –5173
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5171

Communications
(olefins) favors the TP form. A deeper investigation of
the electronic structure and factors that stabilize trigonal-
pyramidal molecules as well as their potential use as
Lewis acids with a well-defined rigid structure[16] is
underway.
Experimental Section
All syntheses were performed under an atmosphere of argon by
using standard Schlenk techniques. Details of the syntheses and
a complete listing of spectroscopic data are given in the
Supporting Information.
2: A slight excess of lithium powder (0.310 g, 44.7 mmol) was
added to a solution of 1[17] (5.00 g, 22.1 mmol) in THF (25 mL) at
ꢀ788C. The mixture was stirred for 30 min at 08C and for 2 h at
room temperature. The resulting deep red solution was added to
a solution of dichloromethylsilane (1.26 g, 11.0 mmol) in THF
(20 mL) at 08C. After stirring overnight, all volatile compounds
were evaporated; the residue was taken up in 50 mL of toluene,
the suspension filtered, and 2 was isolated from the filtrate as a
pale yellow solid which was used without further purification.
Yield: 4.07 g (9.5 mmol, 86%). M.p. 588C. 1H NMR (500.2 MHz,
CD2Cl2): d = ꢀ0.27 (d, 3JHH = 3.6 Hz, 3H; CH3), 4.28 (m, 1H;
Figure 3. a) Structure of 5. Hydrogen atoms are omitted for clarity. Thermal
ellipsoids are drawn at 30% probability. Bond lengths [Š] and angles [8]: Rh1 Si1
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
2.235(1), Rh1 C4 2.179(3), Rh1 C5 2.211(3), Rh1 C19 2.182(3), Rh1 C20
ꢀ
ꢀ
ꢀ
ꢀ
2.157(3), Rh1 P1 2.335(1), Rh1 ct1 2.077(3), Rh1 ct2 2.048(3), Si1 C16 1.915(3),
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
Si1 C1 1.906(3), Si1 C31 1.872(3), P1 C32 1.824(3), P1 C38 1.832(3), P1 C44
=
=
1.826(3), C4 C5trop 1.420(4), C19 C20trop 1.432(4); ct1-Rh1-ct2 129.6(1), ct1-Rh1-P1
111.8(1), ct2-Rh1-P1 115.2(1), ct1-Rh1-Si1 93.1(1), ct2-Rh1-Si1 93.0(1), P1-Rh1-Si1
103.4(1), C1-Si1-C16 112.2(1), C1-Si1-C31 103.9(1), C31-Si1-C16 106.6(1), C1-Si1-
Rh1 105.9(1), C16-Si1-Rh1 106.2(1), C31-Si1-Rh1 122.2(1), Rh1-P1-C32 118.0(1),
Rh1-P1-C38 94.9(1), Rh1-P1-C44 130.4(1). ꢀ(ct-Rh-ct)=356.68; ꢀ(C-Si-C)=322.78.
3
3
ꢀ
SiH), 6.65 (d, JHH = 11.9 Hz, 2H; CHolefin), 6.75 ppm (d, JHH =
b) Plot of the core of 5. Computed data for [Rh(SiH3)(PH3)(C2H4)2] (C2v): Rh Si
ꢀ
ꢀ
ꢀ
=
11.9 Hz, 2H; CHolefin). 13C NMR (125.8 MHz, CD2Cl2): d =
ꢀ3.20 (s, 1C; CH3), 132.69 (s, 2C; CHolefin), 133.09 ppm (s, 2C;
CHolefin). 29Si NMR (99.4 MHz, CD2Cl2): d = ꢀ10.44 ppm.
2.279, Rh P 2.342, Rh ct 2.051, Rh C 2.158–2.180, C C 1.410; P-Rh-Si 91.1, H-P-
Rh 2”121.4, H-P-Rh 119.4, ct-Rh-ct 131.0, ct-Rh-P 114.2, ꢀ(ct-Rh-ct)=359.58; ꢀ(H-
Si-H)=319.48.
3: [ Rh(m2-Cl)2(C2H4)4] (46 mg, 0.117 mmol) and 2 (100 mg,
2
0.234 mmol) were dissolved in chlorobenzene (1 mL) at 08C.
After 20 min the color of the reaction mixture had changed from
bright orange to brownish yellow. Over 4 d at ꢀ208C pale yellow
crystals of 3 formed. Yield: 109 mg (0.171 mmol, 70%). M.p. > 1248C
ligand, do not differ much (3: d(29Si) = 100.4, d(103Rh) =
ꢀ712.6; 4: d(29Si) = 97.15, d(103Rh) = ꢀ654.5]. Furthermore,
no cross-peaks between the olefinic protons and a-CH2
protons of the THF molecule were observed. These observa-
tions are in line with predictions made with the CSED model
and the general expectations for the trans influence: The
LUMO of a trigonal-pyramidal d8-ML4 complex is rather high
in energy and “unavailable” for binding of a nucleophile.[6]
Note, however, that planar d8-ML4 complexes are even more
reluctant to interact with nucleophiles when a distortion from
planarity is suppressed. Furthermore, trigonal-bipyramidal
d8-ML5 complexes, conventionally obtained from planar d8-
ML4, have the kinetically labile ligand in an equatorial
position. Those obtained from TP complexes show lability in
the axial position. The remarkable high-frequency shifts of
the 29Si NMR resonances in 3–5 (ca. + 100 ppm vs. ꢀ10.4 ppm
in 2) would be formally in accord with a high weight of
resonance structure A (Scheme 1) but should not be over-
interpreted.
Finally, a cyclic voltammogram of 3 in THF with 0.1m
nBu4NPF6 showed one irreversible oxidation wave at + 0.6 V
and two irreversible reduction waves at ꢀ3.1 and ꢀ3.3 V
versus ferrocenium/ferrocene. This demonstrates the high
thermodynamic stability of the neutral molecule with a
trigonal-pyramidal structure with respect to its cation and
anion, respectively.
Clearly, the trigonal-pyramidal form is a possible ground
state structure for d8-ML4 complexes. Our investigations
indicate that a ligand set composed of at least one very strong
(H, SiR3) and two very weak s-donor but good p-acceptors
1
(decomp.). H NMR (500.2 MHz, CD2Cl2): d = ꢀ0.93 (s, 3H; CH3),
4.72 (d, 3JHH = 10.5 Hz, 2H; CHolefin), 4.94 ppm (d, 3JHH = 10.5 Hz, 2H;
CHolefin). 13C NMR (125.8 MHz, CD2Cl2): d = ꢀ4.78 (s, 1C; CH3),
70.12 (d, 1JRhC = 6.7 Hz, 2C; CHolefin), 71.00 (s, 2C; CHethylene),
73.92 ppm (d, 1JRhC = 8.2 Hz, 2C; CHolefin). 29Si NMR (99.4 MHz,
CD2Cl2): d = 100.35 ppm (d, 1JRhSi = 45.3 Hz). 103Rh NMR (15.8 MHz,
CD2Cl2): d = ꢀ712.58 ppm (s).
4: [ Rh(m2-Cl)2(C2H4)4] (46 mg, 0.117 mmol) and 2 (100 mg,
2
0.234 mmol) were dissolved in THF (1 mL) at room temperature.
Gas evolution (C2H4) was observed and after 5 min the solution was
concentrated to 0.5 mL, shortly warmed to about 408C, and cooled to
room temperature. Pale yellow crystals of 4 began to precipitate, and
the mixture was stored at 78C for 10 d. Yield: 70% (103 mg,
1
0.164 mmol). M.p. > 1788C (decomp). H NMR (500.2 MHz, 263 K,
[D8]THF): d = ꢀ1.07 (s, 3H; CH3), 3.02 (s, 4H; CHethylene), 4.68 (d,
3JHH = 10.4 Hz, 2H; CHolefin), 4.87 ppm (d, 3JHH = 10.4 Hz; 2H,
CHolefin). 13C NMR (125.8 MHz, 263 K, [D8]THF): d = ꢀ6.26 (s, 1C;
1
CH3), 69.46 (d, 1JRhC = 6.7 Hz, 2C; CH2,ethylene), 69.49 (d, JRhC
=
6.7 Hz, 2C; CHolefin), 72.85 ppm (d, 1JRhC = 7.9 Hz, 2C; CHolefin).
29Si NMR (99.4 MHz, [D8]THF): d = 97.15 (d, 1JSiRh = 45.2 Hz).
103Rh NMR (15.8 MHz, [D8]THF): d = ꢀ654.54 ppm.
5: 4 (55 mg, 0.087 mmol) was treated with triphenylphosphane
(23 mg, 0.088 mmol) in THF (1 mL) at room temperature. Ethylene
evolution was observed and after 5 min the solution was layered with
hexane (1 mL) and cooled to ꢀ158C. Yellow crystals of 5 were
isolated by filtration and dried in vacuo (67 mg, 0.085 mmol, 97%).
M.p. > 1618C (decomp). 1H NMR (500.2 MHz, [D8]THF): d = ꢀ0.28
(d, 4JPH = 2.8 Hz, 3H; CH3), 3.86 (m, 2H; CHolefin), 4.29 ppm (m, 2H;
CHolefin). 13C NMR (100.6 MHz, [D8]THF): d = 1.75 (dd, JCP
=
3
10.6 Hz, 2JCRh = 1.5 Hz, 1C; CH3), 65.97 (dd, 1JCRh = 8.6 Hz, JCP
=
2
4.7 Hz, 2C; CHolefin), 70.74 ppm (dd, 1JCRh = 12.6 Hz, 2JCP = 9.0 Hz,
2C; CHolefin). 29Si NMR (79.5 MHz, [D8]THF): d = 103.68 (dd, 1JSiRh
47.6 Hz, 2JSiP = 5.8 Hz). 31P NMR (161.9 MHz, [D8]THF): d =
=
5172
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Angew. Chem. Int. Ed. 2006, 45, 5169 –5173

Angewandte
Chemie
30.90 ppm (d, 1JPRh = 138.6 Hz). 103Rh NMR (12.6 MHz, [D8]THF):
d = ꢀ484.14 ppm (d, JPRh = 139.0 Hz).
1.437 Mgmꢀ3; crystal dimensions 0.36 ” 0.20 ” 0.11 mm; Bruker
1
SMART Apex diffractometer with CCD area detector; MoKa
radiation (l = 0.71073 Š), 200 K, 2Vmax = 56.568; 30672 reflec-
tions, 7483 independent (Rint = 0.0249); direct methods; empiri-
cal absorption correction with SADABS (version 2.03); refine-
ment against full matrix (versus F2) with SHELXTL (version
6.12) and SHELXL-97 (G. M. Sheldrick, Göttingen, 1997); 291
parameters, R1 = 0.0390 and wR2 (all data) = 0.1107, max./min.
residual electron density 0.908/ꢀ0.473 eŠꢀ3. All non-hydrogen
atoms were refined anisotropically. The contribution of the
hydrogen atoms in their calculated positions was included in the
refinement by using a riding model. The chlorobenzene units and
the units of 3 show an alternating alignment. Furthermore, four
percent of the molecules of 3 are disordered about a mirror
Received: April 5, 2006
Published online: July 7, 2006
Keywords: alkene ligands · density functional calculations ·
.
rhodium · Si ligands · silanes
[1] The Cambridge Crystallographic Data Centre (CCDC) cites
more than 1600 RhI complexes with approximately planar
structures.
[2] a) For tetrahedral [CoIXL3], see: S. Deblon, L. Liesum, J.
Harmer, H. Schönberg, A. Schweiger, H. Grützmacher, Chem.
Eur. J. 2002, 8, 601, and references therein; b) for tetrahedral NiII
complexes, see: C. O. Dietrich-Buchecker, J. Guilhem, J.-M.
Kern, C. Pascard, J.-P. Sauvage, Inorg. Chem. 1994, 33, 3498, and
references therein.
ꢀ
ꢀ
plane perpendicular to the Rh Si1 bond (Rh1A Si1A). The
remaining atoms of the disordered molecules overlap with the
ligand atoms of the main structure and could therefore not be
localized. Pale yellow, air-sensitive single crystals of 4 were
obtained from a solution in THF at room temperature. Crystal
data: C37H37OSiRh; orthorhombic; space group P2(1)2(1)2(1);
[3] We refer to trigonal pyramids as structures in which the angles
between the axial and equatorial ligands are equal or close to
908. Alternatively, they may be described as trigonal bipyramids
in which one axial coordination site is vacant. A referee brought
to our attention that MS3(L) fragments (M = V, Mo, Fe) with TP
structures were observed in transition metal sulfide clusters: a) I.
Noda, B. S. Snyder, R. H. Holm, Inorg. Chem. 1986, 25, 3851;
b) E. Nordlander, S. C. Lee, W. C. Cen, Z. Y. Wu, C. R. Natoli,
A. Di Cicco, A. Filipponi, B. Hedman, K. O. Hodgson, R. H.
Holm, J. Am. Chem. Soc. 1993, 115, 5549.
[4] a) M. Poliakoff, J. J. Turner, J. Chem. Soc. Dalton Trans. 1974,
2276; b) M = Ru: P. L. Bogdan, E. Weitz, J. Am. Chem. Soc.
1989, 111, 3163; c) calculations: J. Li, G. Schreckenbach, T.
Ziegler, J. Am. Chem. Soc. 1995, 117, 486. For a general
discussion, see: T. A. Albright, J. K. Burdett, M.-H. Whangbo,
Orbital Interactions in Chemistry, Wiley, 1985, pp. 360, 404; d) P.
Maire, A. Sreekanth, T. Büttner, J. Harmer, I. Gromov, H.
Rüegger, F. Breher, A. Schweiger, H. Grützmacher, Angew.
Chem. 2006, 118, 3343; Angew. Chem. Int. Ed. 2006, 45, 3265;
e) P. Maire, T. Büttner, F. Breher, P. Le Floch, H. Grützmacher,
Angew. Chem. 2005, 117, 6477; Angew. Chem. Int. Ed. 2005, 44,
6318; f) M. Ogasawara, D. Huang, W. E. Streib, J. C. Huffman,
N. Gallego-Planas, F. Maseras, O. Eisenstein, K. G. Caulton, J.
Am. Chem. Soc. 1997, 119, 8642, and references therein.
[5] U. Pidun, G. Frenking, Chem. Eur. J. 1998, 4, 522.
a = 10.9270(5),
b = 12.2839(6),
c = 21.6322(10) Š;
V=
2903.6(2) Š3; Z = 4; 1calcd = 1.438 Mgmꢀ3; crystal dimensions
0.24 ” 0.19 ” 0.15 mm; Bruker SMARTApex diffractometer with
CCD area detector; MoKa radiation (l = 0.71073 Š), 200 K,
2Vmax = 56.628; 30385 reflections, 7220 independent (Rint
=
0.0388); direct methods; refinement against full matrix (versus
F2) with SHELXTL (version 6.12) and SHELXL-97; 362
parameters, R1 = 0.0280 and wR2 (all data) = 0.0626, max./min.
residual electron density 0.930/ꢀ0.378 eŠꢀ3. All non-hydrogen
atoms were refined anisotropically. The contribution of the
hydrogen atoms in their calculated positions was included in the
refinement by using a riding model. Yellow, air-sensitive single
plates of 5 were obtained from a solution in THF layered with n-
hexane at 78C. Crystal data: C49H40SiPRh; monoclinic; space
group P2(1)/c; a = 17.0615(8), b = 10.3224(5), c = 22.1621(11) Š;
V= 3778.5(3) Š3; Z = 4; 1calcd = 1.390 Mgmꢀ3; crystal dimen-
sions 0.30 ” 0.22 ” 0.06 mm; Bruker SMART K1 diffractometer
with CCD area detector; MoKa radiation (l = 0.71073 Š), 200 K,
2Vmax = 52.758; 30210 reflections, 7723 independent (Rint
=
0.0447); direct methods; empirical absorption correction with
SADABS (version 2.03); refinement against full matrix (versus
F2) with SHELXTL (version 6.12) and SHELXL-97; 476
parameters, R1 = 0.0327 and wR2 (all data) = 0.0799, max./min.
residual electron density 0.754/ꢀ0.463 eŠꢀ3. All non-hydrogen
atoms were refined anisotropically. The contribution of the
hydrogen atoms in their calculated positions was included in the
refinement by using a riding model. CCDC-602113 (3), -602114
(4), and -602115 (5) contain the supplementary crystallographic
data for this paper. These data can be obtained free of charge
from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
[6] D. M. P. Mingos, J. Organomet. Chem. 2004, 689, 4420.
[7] C. A. Bayse, M. B. Hall, J. Am. Chem. Soc. 1999, 121, 1348.
[8] [Ag(C2H4)3]+: I. Krossing, A. Reisinger, Angew. Chem. 2003,
115, 5903; Angew. Chem. Int. Ed. 2003, 42, 5725.
[9] All DFT calculations were carried out with the Gaussian03 set
of programs and the B3PW91 functional (for details see
Supporting Information). For [Rh(SiH3)(C2H4)3], the isomer
with the SiH3 group in the basal plane is less stable by
14 kcalmolꢀ1 and corresponds more to an alkyl complex
[Rh(CH2CH2SiH3)(C2H4)2], that is, one ethylene ligand has
ꢀ
[13] To date, 71 compounds with an Rh Si bond are listed in the
I
ꢀ
CCDC data base. For recent examples with Rh Si bonds, see:
a) E. Neumann, A. Pfaltz, Organometallics 2005, 24, 2008; b) R.
Goikhman, M. Aizenberg, Y. Ben-David, L. J. W. Shimon, D.
Milstein, Organometallics 2002, 21, 5060; c) M. Okazaki, S.
Ohshitanai, H. Tobita, H. Ogino, J. Chem. Soc. Dalton Trans.
2002, 2061.
ꢀ
inserted into the Rh Si bond. For [Rh(SiH3)(PH3)(C2H4)2] no
energy minimum for an isomer with a basal SiH3 group was
found.
[10] The isomer with the SiH3 and PH3 groups in trans positions
adopts a SH-type structure which is almost equal in energy to the
planar cis form (DE = ꢀ0.03 kcalmolꢀ1).
[14] F. H. Allen, O. Kennard, D. G. Watson, L. Brammer, A. G.
Orpen, J. Chem. Soc. Perkin Trans. 2 1987, S1.
[15] See for comparison: P. Maire, F. Breher, H. Schönberg, H.
Grützmacher, Organometallics 2005, 24, 3207.
[16] Note that most Lewis acids change their structure on complex-
ation of a nucleophile, for instance, from trigonal planar to
tetrahedral.
[11] The synthesis of the related dibenzophosphasemibullvalene was
recently reported: J. Geier, G. Frison, H. Grützmacher, Angew.
Chem. 2003, 115, 4085; Angew. Chem. Int. Ed. 2003, 42, 3955.
[12] Pale yellow, air-sensitive single crystals of 3 were obtained from
chlorobenzene solution at ꢀ158C. Crystal data: C39H34ClRhSi;
monoclinic; space group P2(1)/c; a = 10.6913(5), b = 11.5133(6),
[17] G. Berti, J. Org. Chem. 1957, 22, 230.
c = 24.6594(12) Š;
V= 3020.2(3) Š3;
Z = 4;
1calcd =
Angew. Chem. Int. Ed. 2006, 45, 5169 –5173
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
5173