Facile synthesis of rhodium(III) porphyrin silyls by silicon-hydrogen bond activation with rhodium(III) porphyrin halides and methyls

Article abstract of DOI:10.1021/om0604472

Rhodium(III) porphyrin silyls were synthesized in high yields conveniently from the reactions of rhodium(III) porphyrin halides and methyls with silanes, via silicon-hydrogen bond activation (SiHA) in solvent-free conditions. Preliminary mechanistic exper

Full text of DOI:10.1021/om0604472

4822
Organometallics 2006, 25, 4822-4829
Facile Synthesis of Rhodium(III) Porphyrin Silyls by
Silicon-Hydrogen Bond Activation with Rhodium(III) Porphyrin
Halides and Methyls
Lirong Zhang and Kin Shing Chan*
Department of Chemistry, The Chinese UniVersity of Hong Kong, Shatin, New Territories, Hong Kong,
People’s Republic of China
ReceiVed May 22, 2006
Rhodium(III) porphyrin silyls were synthesized in high yields conveniently from the reactions of
rhodium(III) porphyrin halides and methyls with silanes, via silicon-hydrogen bond activation (SiHA)
in solvent-free conditions. Preliminary mechanistic experiments suggested that rhodium(III) porphyrin
chlorides initially formed cationic rhodium(III) species, which then underwent heterolysis to give the
products. On the other hand, rhodium(III) porphyrin methyls underwent either oxidative addition or σ-bond
metathesis to form the products.
Introduction
Transition metal silyl chemistry has grown immensely over
the past decades, and research continues to prosper in this area.1
Transition metal silyl complexes have been proposed to be vital
in catalytic processes such as hydrosilylation,2 silane polymer-
ization,3 and silylformylation.4 Late-transition metal silyl com-
plexes are usually electron-rich and display unique structural
and bonding properties5 such as metal silyl dπ back-bonding
interactions.1,6
Our continuing interest in the chemistry of rhodium porphy-
rin,7 in particular easily accessible rhodium porphyrin silyls,8
has prompted us to develop a facile synthesis of rhodium
porphyrin silyls.8 Known synthetic methods for the preparation
of rhodium porphyrin silyls have met with limitations. (1) The
reactions of nucleophilic rhodium(I) porphyrin anions with
trialkylsilyl chlorides require the use of less-friendly sodium
amalgam.8 (2) The one-electron oxidative additions of rhodium-
(II) porphyrins and related macrocycle metal-metal bonded
dimers with Si-H bonds9,10 demand the very inaccessible
rhodium(II) porphyrin dimers. (3) The attempted reactions of
the silyl anion, generated in HMPA, with rhodium porphyrin
halides are not fruitful. The rapid undesirable reaction of the
Me3Si anion with HMPA gives a phosphoryl anion, which
further reacts with cobalt(III) porphyrin chlorides to give cobalt
Figure 1. Structures of rhodium porphyrin complexes.
porphyrin phosphoryls. This approach is likely not amenable
to prepare rhodium porphyrin silyls.
Reactions of hydrosilanes with rhodium porphyrin halides
are in principle applicable to yield rhodium porphyrin silyls.
This method has been applied in various organometallic
complexes successfully1 but not in rhodium porphyrins. We have
adopted this method and discovered that rhodium(III) porphyrin
halides and methyls reacted with silanes to give high yields of
rhodium porphyrin silyls via silicon-hydrogen bond activation
(SiHA) in solvent-free conditions. We now report our results
on the synthesis and properties of rhodium porphyrin silyls as
well as some mechanistic studies of the silicon-hydrogen bond
activation by high-valent Rh(III) porphyrins.12,13
* To whom correspondence should be addressed. E-mail: ksc@cuhk.edu.hk.
(1) Corey, J. Y.; Braddock-Wilking, J. Chem. ReV. 1999, 99, 175-292.
(2) (a) Chatani, N.; Murai, S.; Sonoda, N. J. Am. Chem. Soc. 1993, 105,
1370-1372. (b) Brookhart, M.; Grant, B. E. J. Am. Chem. Soc. 1993, 115,
2151-2156.
Results and Discussion
Optimization. Initially, when Rh(ttp)Cl (1) (Figure 1) was
reacted with HSiEt3 (2a) (100 equiv, 0.6 M) in benzene at 100
°C for 1 day, Rh(ttp)SiEt3 (2b) was obtained with 52% yield
(Table 1, entry 1). When the reaction temperature was increased
to 200 °C, a lower yield of Rh(ttp)SiEt3 (2b) was observed
(Table 1, entry 2). Competitive activation of benzene to form
an unstable intermediate likely occurred, as a rhodium porphyrin
(3) Ojima, I.; Inaba, S. I.; Kogure, T.; Nagai, Y. J. Organomet. Chem.
1973, 55, C7-C8.
(4) Ojima, I.; Donovan, R. J.; Eguchi, M. Tetrahedron 1993, 49, 5431-
5444.
(5) Lin, Z. Y. Chem. Soc. ReV. 2002, 31, 239-245.
(6) Levy, C. J.; Puddephatt, R. J. Organometallics 1995, 14, 5019-5020.
(7) (a) Yeung, S. K.; Chan, K. S. Organometallics 2005, 24, 2561-
2563. (b) Chan, K. S.; Zhang, L.; Fung, C. W. Organometallics 2004, 23,
6097-6098. (c) Mak, K. W.; Yeung, S. K.; Chan, K. S. Organometallics
2002, 21, 2362-2364.
(8) Tse, K.-S.; Wu, B.-M.; Mak, C. W.; Chan, K. S. J. Organomet. Chem.
1998, 568, 257-261.
(9) (a) Feng, M. Q.; Chan, K. S. J. Organomet. Chem. 1999, 584, 235-
239. (b) Feng, M. Q.; Chan, K. S. Organometallics 2002, 21, 2743-2750.
(10) Mizutani, T.; Uesaka, T.; Ogoshi, H. Organometallics 1995, 14,
341-346.
(11) Tse, A. K.-S.; Mak, K. W.; Chan, K. S. Organometallics 1998, 17,
2651-2655.
(12) Activation of aldehdyes with cationic Rh(III) complexes: Corkey,
B. K.; Taw, F. L.; Bergman, R. G.; Brookhart, M. Polyhedron 2004, 23,
2943-2954.
(13) Activation of silanes with cationic iridium complexes via Ir(V)
intemediates: Klei, S. R.; Tilley T. D.; Bergman R. G. J. Am. Chem. Soc.
2000, 122, 1816-1817.
10.1021/om0604472 CCC: $33.50 © 2006 American Chemical Society
Publication on Web 08/22/2006

Facile Synthesis of Rh(III) Porphyrin Silyls
Organometallics, Vol. 25, No. 20, 2006 4823
Table 1. Optimization of the Synthesis of Rh(ttp)SiEt3, 2b
Scheme 1
entry
solvent
equiv of Et3SiH temp (°C) time (h) % 2b
1
2
3
4
benzene
benzene
solvent-free
solvent-free
100
100
250
250
100
200
150
200
24
24
1.5
1.5
52
18
51
81
Table 3. Si-H Activation of Silanes by Rh(por)Me
entry
silane
Rh(por)Me
time
product (% yield)
Table 2. Si-H Activation of Silanes by Rh(por)X
1
2
3
4
5
6
7
8
9
HSiEt3, 2a
Rh(ttp)Me 1d
Rh(tmp)Me, 1e 1 d
Rh(ttp)Me, 1d 1 h
Rh(tmp)Me, 1e 0.5 h Rh(tmp)Si(OEt)3, 4b (68)
Rh(ttp)Me, 1d
Rh(ttp)Me, 1d
1 h
Rh(ttp)SiEt3, 2b (86)
Rh(tmp)SiEt3, 2c (56)
Rh(ttp)Si(OEt)3, 4c (86)
entry
silane
Rh(por)X
time
product (% yield)
HSi(OEt)3, 4a
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
HSiEt3, 2a
Rh(ttp)Cl, 1a
1.5 h Rh(ttp)SiEt3, 2b (81)
Rh(tmp)Cl, 1b 1 d
Rh(tmp)I, 1c 1 d
Rh(tmp)SiEt3, 2c (62)
Rh(tmp)SiEt3, 2c (70)
H2SiPh2, 7a
H2SiPhMe, 9a
HSiBnMe2, 10a Rh(ttp)Me, 1d
HSiPhMe2, 11a Rh(ttp)Me, 1d
HSiPh2Me, 12a Rh(ttp)Me, 1d
0.5 h Rh(ttp)SiPh2H, 7c (67)
3 h
3 h
6 h
Rh(ttp)SiMePhH, 9c (68)
Rh(ttp)SiBnMe2, 10b (68)
Rh(ttp)SiPhMe2, 11b (79)
HSi(OEt)3, 4a
HSiPr3, 5a
Rh(tmp)Cl, 1b 0.5 h Rh(tmp)Si(OEt)3, 4b (62)
Rh(tmp)I, 1c 0.5 h Rh(tmp)Si(OEt)3, 4b (74)
Rh(tmp)Cl, 1b 1 d
Rh(tmp)I, 1c 1 d
Rh(tmp)Cl, 1b 2 d
Rh(tmp)SiPr3, 5b (51)
Rh(tmp)SiPr3, 5b (45)
Rh(tmp)SiiPr3, 6b (16)
Rh(tmp)SiiPr3, 6b (23)
0.5 h Rh(ttp)SiPh2Me, 12c (78)
HSiiPr3, 6a
H2SiPh2, 7a
decreased with the increasing steric hindrance of silanes: HSiEt3
(2a) > HSiiPr3 (6a) > HSitBuMe2 (13a) (Table 2, entries 3, 9,
and 25). Sterically less hindered rhodium porphyrins of ttp
reacted faster and gave higher yields than that of tmp (Table 2,
entries 1 vs 2, 20 vs 21). No significant and systematic
differences of halide effect in rates and yields were observed
for Rh(tmp) X (X ) Cl or I) (e.g., Table 2, entries 2 and 3, 8
and 9, 24 and 25).
For HSiPh2Me (12a) only, the reaction time was important
to achieve high product selectivity. When 12a was reacted with
Rh(ttp)Cl (1a) in 24 h at 200 °C, a nearly 1:1 mixture of Rh-
(ttp)SiPh2Me (12c) (20%) and Rh(ttp)SiMePhH (9c) (18%) was
obtained. Rh(tmp)Cl (1b) also gave 12b (26%) and 9b (28%)
in 24 h. 9b was a consecutive product, as 12b also reacted with
HSiPh2Me to give 9b. However, 9b did not react with HSiPh2-
Me to give 12b at 200 °C in 2 days. Therefore, Rh(tmp)-
SiPhMeH is thermodynamically more stable than Rh(tmp)-
SiPh2Me; presumably the latter is a secondary rather than a
tertiary Rh-silyl complex. 12b remained stable in benzene in
the absence of HSiPh2Me, so a highly reactive intermediate
likely formed from 12b and reacted rapidly with excess HSiPh2-
Me to give 9b. We propose that 12b undergoes a â-hydride
elimination to give Ph2SidCH2 and Rh(tmp)H, which then reacts
with HSiPh2Me to give 9b (Scheme 1).
Rh(tmp)I, 1c
Rh(ttp)Cl, 1a
2 d
0.5 h Rh(ttp)SiPh2H, 7c (72)
Rh(tmp)Cl, 1b 0.5 h Rh(tmp)SiPh2H, 7b (62)
Rh(tmp)I, 1c 0.5 h Rh(tmp)SiPh2H, 7b (56)
Rh(tmp)Cl, 1b 1 h
Rh(tmp)I 1c 1 h
Rh(tmp)Cl, 1b 3 h
H3SiPh, 8a
Rh(tmp)SiPhH2, 8b (82)
Rh(tmp)SiPhH2, 8b (75)
Rh(tmp)SiMePhH, 9b (73)
Rh(tmp)SiMePhH, 9b (66)
Rh(ttp)SiBnMe2, 10b (88)
Rh(tmp)SiBnMe2, 10c (91)
Rh(tmp)SiBnMe2, 11c (77)
Rh(ttp)SiPhMe2, 11b (91)
Rh(tmp)SiPhMe2, 11c (56)
Rh(tmp)SiPhMe2, 11c (48)
H2SiPhMe, 9a
Rh(tmp)I, 1c
HSiBnMe2, 10a Rh(ttp)Cl, 1a
3 h
1 h
Rh(tmp)Cl, 1b 1 h
Rh(tmp)I, 1c
HSiPhMe2, 11a Rh(ttp)Cl, 1a
6 h
1 h
Rh(tmp)Cl, 1b 8 h
Rh(tmp)I, 1c 1 d
HSiPh2Me, 12a Rh(tmp)Cl, 1b 0.5 h Rh(tmp)SiPh2Me, 12b (61)
HSitBuMe2, 13a Rh(tmp)Cl, 1b 1 d
Rh(tmp)I, 1c 1 d
Rh(tmp)SitBuMe2, 13b (10)
Rh(tmp)SitBuMe2, 13b (7)
triflate is known to react with arenes via electrophilic aromatic
substitution at lower temperature14 since no Rh(ttp)Ph was
detected in the reaction mixture. When dichloromethane was
used as the solvent, Rh(ttp)Cl reacted with HSiEt3 (2a) (100
equiv, 0.6 M) at 100 °C for 2 days to give Rh(ttp)SiEt3 (2b)
and Rh(ttp)CH2Cl (3). Both benzene and CH2Cl2 were not
suitable solvents. Therefore, solvent-free conditions were em-
ployed (Table 1, entries 3, 4). Indeed, at 150 °C, 2b was
achieved in a reasonable yield of 51% in just 1.5 h. At 200 °C,
a higher yield of 81% was also observed.
Besides rhodium porphyrin halides, rhodium porphyrin
methyls reacted with silanes successfully to give rhodium
porphryin silyls with comparable yields and rates (eq 3, Table
3). The metathesis reactions appear to be general and applicable
to Rh(tmp)SiEt3. In a silyl exchange reaction, Rh(tmp)SiEt3 (2c)
reacted with H2SiPh2 (7a) at 200 °C in 1 h to give 68% of
Rh(tmp)SiPh2H (7b) and presumably also Et3SiH (eq 4).17
Rh(ttp)Cl + HSiEt3 solvent8 Rh(ttp)SiEt3 + Rh(ttp)CH2Cl
(1)
Synthetic Application. When the optimized solvent-free
conditions at 200 °C were applied to the reactions of a variety
of rhodium porphyrin chlorides and iodides with silanes, good
yields of rhodium porphyrin silyls were generally obtained (eq
2, Table 2). Rh(por)X (X ) Cl or I) dissolved in silanes only
upon heating.
Rh(por)Me + HSiR1R2R3 f Rh(por)SiR1R2R3 (3)
Rh(tmp)SiEt3 + H2SiPh2 200 °C8
1 h
Rh(por)X + HSiR1R2R3 f Rh(por)SiR1R2R3
(2)
Rh(tmp)SiPh H
+ Et3SiH (4)
2
68%
The yields of the products depended on the steric hindrance
of silanes. The cone angles of silanes are identical with the cone
X-ray Structure. The structures of Rh(tmp)SiPh2Me (12b)
and Rh(tmp)SiPhMe2 (11c) were confirmed by single-crystal
X-ray diffraction studies and are shown in Figure 2 (30%
thermal ellipsoids). Crystals were grown from dichloromethane/
methanol solution. Details of data collection and processing
parameters are given in Table 4.
angles of phosphines15 [Et3SiH (132°), Pr3SiH (132°), Pr3SiH
i
(160°), SiH2Ph2 (128°), and HSiMe2Ph (122°)]16 and have been
used as a measure of steric hindrance. In general, more bulky
silanes with larger cone angles reacted with slower rates and
gave lower product yields. For example, the reactivity trend
From Figure 2 and Tables 4 and 5, the coordination sphere
of the rhodium atom of Rh(tmp)SiPh2Me (12b) forms a square
pyramidal geometry with the four porphyrinato nitrogen atoms
(14) Aoyama, Y. Yoshida, T.; Sakurai, K.; Ogoshi, H. Organometallics
1986, 5, 168-173.
(15) Tolman, C. A. Chem. ReV. 1977, 77, 313-348.
(16) (a) Hester, D. M.; Sun, S.; Harper, A. W.; Yang, G. K. J. Am. Chem.
Soc. 1992, 114, 5234-5240. (b) Goikhman, R.; Milstein, D. Chem. Eur. J.
2005, 11, 2983-2988.
(17) Dioumaev, V. K.; Procopio, L. J.; Carroll, P. J.; Berry, D. H. J.
Am. Chem. Soc. 2003, 125, 8043-8058.

4824 Organometallics, Vol. 25, No. 20, 2006
Zhang and Chan
Figure 2. Molecular structure of Rh(tmp)SiPh2Me, 12b.
Figure 3. Molecular structure of Rh(tmp)SiPhMe2, 11c.
occupying the basal sites while the silicon atom of the
diphenylmethyl group resides at the axial site. The mean bond
length of the Rh-N bonds is 2.016 Å, which agrees with the
reported five-coordinated organorhodium(III) porphyrin.18 The
Rh-Si length is 2.329 Å, which is longer than that of Rh(tpp)-
SiMe3 (Rh-Si ) 2.305 Å)8 and Rh(oep)SiEt3 (Rh-Si ) 2.305
Figure 4. Displacement of the atoms of the Rh(tmp)SiPh2Me (12b)
Figure 5. Displacement of the atoms of the Rh(tmp)SiPhMe2 (11c)-
porphyrin core.
porphyrin core.

Facile Synthesis of Rh(III) Porphyrin Silyls
Organometallics, Vol. 25, No. 20, 2006 4825
Table 4. Crystal Data for Rh(tmp)SiPhMe2 (11c) and Rh(tmp)SiPh2Me (12b)
11c
C64H65N4RhSi
12b
C69H65N4RhSi
empirical formula
cryst syst
space group
fw
tetragonal
orthorhombic
I41
Pna21
929.07
1081.25
a (Å)
28.4903(14)
21.854(4)
b (Å)
28.4903(14)
17.372(4)
c (Å)
14.7397(16)
14.901(3)
R (deg)
â (deg)
γ (deg)
Z
90
90
90
8
90
90
90
4
D
calc (g/cm3)
1.152
1.270
absorp coeff
0.347
11964.2(15)
0.369
5657(2)
V (Å3)
F(000)
4352
2264
cryst size (mm)
no. of reflns collected
absorp corr
0.30 × 0.20 × 0.10
0.30 × 0.20 × 0.10
42 238
15 052
SADABS
ABSCOR
max. and min. transmn
refinement method
no. of data/restraints/params
goodness-of-fit on F2
final R indices [I > 2σ(I)]
abs struct param
1.0000 and 0.388594
full-matrix least-squares on F2
7891/0/569
0.9641 and 0.8975
full-matrix least-squares on F2
8771/1/677
0.960
1.105
R1 ) 0.0949, wR2 ) 0.2311
0.29(7)
R1 ) 0.0664, wR2 ) 0.1418
0.56(4)
Table 5. Selected Bond Lengths and Angles of
Rh(tmp)SiPh2Me, 12b
Table 6. Selected Bond Lengths and Angles of
Rh(tmp)SiPhMe2, 11c
Bond Lengths (Å)
Bond Lengths (Å)
Rh(1)-N(1)
Rh(1)-N(3)
Rh(1)-Si(2)
Si (2)-C (71)
2.021 (6)
2.003 (6)
2.329 (3)
1.813 (11)
Rh(1)-N(2)
Rh(1)-N(4)
Si(2)-C(61)
Si(2)-C(81)
2.011 (6)
2.017 (6)
1.855 (10)
1.922 (11)
Rh(1)-N(1)
Rh(1)-N(3)
Rh(1)-Si(1)
Si (1)-C(67)
2.036 (9)
2.009 (9)
2.438 (5)
1.79 (2)
Rh(1)-N(2)
Rh(1)-N(4)
Si(1)-C(61)
Si(1)-C(68)
2.001 (9)
2.027 (9)
1.833 (15)
1.79 (2)
Bond Angles (deg)
Bond Angles (deg)
Si(2)-Rh(1)-N(1)
Si(2)-Rh(1)-N(3)
Rh(1)-Si(2)-C(61) 115.3 (3)
Rh(1)-Si(2)-C(81) 108.3 (4)
C(61)-Si(2)-C(81) 100.9 (6)
99.0 (2)
Si(2)-Rh(1)-N(2)
91.05 (18)
95.05 (18)
Si(1)-Rh(1)-N(1)
Si(1)-Rh(1)-N(3)
90.7 (3)
93.1 (3)
Si(1)-Rh(1)-N(2)
92.2 (3)
91.7 (3)
89.24 (18) Si(2)-Rh(1)-N(4)
Si(1)-Rh(1)-N(4)
Rh(1)-Si(2)-C(71) 115.7 (4)
C(61)-Si(2)-C(71) 112.7 (5)
C(81)-Si(2)-C(71) 101.7 (5)
Rh(1)-Si(1)-C(61) 113.5 (6)
Rh(1)-Si(1)-C(68) 114.7 (8)
Rh(1)-Si(1)-C(67) 111.8 (7)
C(61)-Si(1)-C(67) 106.3 (8)
C(61)-Si(2)-C(68) 102.9 (10) C(67)-Si(1)-C(68) 106.9 (12)
Å),10 owing to the steric hindrance of two phenyl rings. The
porphyrin ring deviates slightly from planarity. The Rh atom is
displaced 0.2417 Å from the mean plane of the porphyrin ring.
The largest deviation relative to the mean plane of four pyrrole
rings is at C12 (0.2371 Å), whereas N2 lies approximately above
the mean plane by about 0.1394 Å. The dihedral angles between
the mesityl plane and the mean porphyrin plane are 86.8°, 80.9°,
75.1°, and 77.7°, respectively. The four mesityl groups are in a
parallel arrangement. The dihedral angles between NC4 pyrroles
and the mean plane are 7.7°, 1.7°, 6.5°, and 3.8°, respectively.
The Rh-Si length of Rh(tmp)SiPhMe2 (11c) is 2.438 Å and
is longer than that of Rh(tpp)SiMe3 (Rh-Si ) 2.305 Å)8 and
Rh(tmp)SiPh2Me (12b). The distances from Si to two methyl
groups are the same (1.79 Å). The porphyrin ring deviates
slightly from planarity. The Rh atom is displaced 0.1013 Å from
the mean plane of the porphyrin ring. The individual NC4 pyrrole
rings are nearly planar. The largest deviation relative to the mean
plane of the four pyrrole rings is at C8 (0.0753 Å), whereas N2
lies approximately above the mean plane by about 0.0456 Å.
The dihedral angles between the mesityl plane and the mean
porphyrin plane are 88.7°, 84.8°, 89.5°, and 79.7° respectively.
The four mesityl groups are in a parallel arrangement. The
dihedral angles between the NC4 pyrroles and the mean plane
are 0.9°, 2.5°, 2.6°, and 1.8° respectively.
tion at high temperature to give a Rh(por) cation, which is then
coordinated by a silane to give a silane complex A.19 Coordina-
tion of the Si-H bond at an electrophilic rhodium center leads
to a Si-H bond weakening. Subsequent activation of a silicon-
hydrogen bond gives a rhodium porphyrin silyl. The detailed
nature of this activation step could be a classical oxidative
addition,12,13 heterolysis,20 or σ-bond metathesis.21
Supporting evidence for the intermediacy of the Rh(por)
cation was obtained in two sets of experiments. First, Rh(ttp)-
Cl reacted with trimethylsilylbenzene at 200 °C for 2 h under
solvent-free conditions in a typical electrophilic aromatic
substitution to give the ipso-substituted Rh(ttp)Ph in 21%. Even
in a nonpolar solvent, ionization of Rh(por)Cl is still possible.
Second, Rh(ttp)OTf 22 (1f) is much more reactive than Rh(ttp)-
Cl toward Et3SiH (Table 7). At 150 °C, Rh(ttp)Cl required 15
h to give Rh(ttp)SiEt3 in 51% yield, while Rh(ttp)OTf only took
15 min to give a much higher yield of Rh(ttp)SiEt3 at 78%
(Table 7, entry 1 vs 3). A less coordinating OTf facilitates the
formation of the Rh(ttp) cation.
We are less clear about the mechanism of the SiHA. Classical
oxidative addition of a high-valent iridium(III) with a silane
(19) For a recent and relevant example: Taw, F. L.; Bergman, R. G.;
Brookhart, M. Organometallics 2004, 23, 886-890.
(20) For base-promoted carbon-hydrogen bond activation in Pt com-
plexes: (a) Harkins, S. B.; Peters, J. C. Organometallics 2002, 21, 1753-
1755. (b) Liang, L. C.; Lin, J.-M. Lee. W.-Y. Chem. Commun. 2005, 2462-
2464.
Mechanism of Si-H Activation by Rh Porphyrin Halides.
Scheme 2 illustrates a possible mechanism for the silicon-
hydrogen bond activation. Rh(por)X initially undergoes ioniza-
(21) Thompson, M. E.; Baxteer, S. M.; Bulls, A. R.; Burger, B. J.; Nolan,
M. C.; Santarsiero, B. D.; Schaefer, W. P.; Bercaw, J. E. J. Am. Chem.
Soc. 1987, 109, 203-219.
(18) Ogoshi, H.; Setsune, J. I.; Yoshida, Z. I. J. Chem. Soc., Perkin Trans.
1 1982, 983-987.
(22) Chan, K. S.; Lau, C. M. Organometallics 2006, 25, 260-265.

4826 Organometallics, Vol. 25, No. 20, 2006
Zhang and Chan
Scheme 2. Mechanism of SiHA of Silane with Rh(ttp)Cl, 1a
Benzonitrile was distilled from anhydrous P2O5. Thin-layer chro-
matography was performed on precoated silica gel 60 F254 plates
for thin-layer analyses for reaction mixtures. For purification of
rhodium complexes, flash column chromatography was used and
carried out in air using silica gel. Samples for microanalyses were
recrystallized from dichloromethane/methanol and were then dried
at 50-60 °C in a vacuum (0.005 mmHg) for 2 days. Rh(ttp)Cl26
(1a) and Rh(tmp)I26 (1c) were prepared according to the literature.
1H NMR spectra were recorded on a Bruker DPX-300 (300
MHz). Chemical shifts were reported with reference to the residual
solvent protons in CDCl3 (δ 7.24 ppm) or with tetramethylsilane
(δ 0.00 ppm) as the internal standard. Chemical shifts (δ) were
reported in parts per million (ppm) in δ scale downfield from TMS.
Coupling constants (J) are reported in hertz (Hz). Mass spectra were
recorded on a Bruker APEX 47e FT-ICR mass spectrometer (FAB-
MS and ESI-MS).
Table 7. Reaction of HSiEt3 with Rh(ttp)X at 150 °C to
Give Rh(ttp)SiEt3, 2b
entry
Rh(ttp)X
time
% Rh(ttp)SiEt3, 2b
1
2
3
4
Rh(ttp)Cl, 1a
Rh(ttp)Cl, 1a
Rh(ttp)(OTf), 1f
Rh(ttp)(OTf), 1f
15 h
5 h
15 min
15 min
51
42a
78
25a
a 10 equiv of 2,6-dimethylpyridine added.
has been convincingly established through the isolation of an
Ir(V) complex, further characterized by X-ray crystallography.13
Rh(V) silyl complexes are known to form from the oxidative
addition reactions of Rh(III) complexes with silanes.23,24 In these
SiHA, we were unable to detect any intermediate that would
be highly unstable. We attempted to find out whether a
heterolysis is operating by the study of base effect, as addition
of a base was expected to facilitate the heterolysis.
Table 7 lists the results of the effect of added 2,6-dimeth-
ylpyridine. For Rh(ttp)Cl, a rate enhancement with a lower
product yield was observed (Table 7, entries 1 and 2). However,
for Rh(ttp)OTf, no rate enhancement and a much poorer product
yield were found. We do not fully understand the difference of
base effect in these complexes. At least for Rh(ttp)Cl, the Si-H
activation was promoted by base.
Mechanism of Si-H Activation by Rh(ttp)R (R ) methyl
and silyl). The mechanism of silane activation with rhodium
porphyrin methyls and silyls is unlikely a heterolysis. A typical
rhodium porphyrin methyl bond falls at about 60 kcal/mol.25
Even at 200 °C, homolysis or heterolysis in a nonpolar solvent
is unlikely. Addition of pyridine in 10 equiv to the reaction
mixture of (EtO)3SiH and Rh(tmp)Me produced little product
even after 3 days, in contrast with 68% of Rh(tmp)Si(OEt)3
formed in 30 min without addition of pyridine (Table 2, entry
4). The coordination of pyridine to Rh(tmp)Me completely shut
down the activation. Unless an intermediate is observed, either
oxidative addition or σ-bond metathesis remains a viable
mechanistic option(s).
Preparation of (5,10,15,20-Tetramesitylporphyrinato)rhodium-
(III) Chloride [Rh(tmp)Cl] (1b).26 H2tmp (120 mg, 0.15 mmol)
and RhCl3‚xH2O (160 mg, 0.61 mmol) were refluxed in PhCN (10
mL) in air for 12 h. After removal of solvent under vacuum, the
mixture was purified by column chromatography using CH2Cl2 as
eluent. A purplish-red solid of 1b (95 mg, 0.10 mmol, 65%) was
obtained after recrystallization from CH2Cl2/MeOH. Rf ) 0.38 (CH2-
1
Cl2). H NMR (300 MHz, CDCl3): δ 1.72 (s, 12 H), 2.03 (s, 12
H), 2.60(s, 12 H), 7.22 (s, 4 H), 7.27 (s, 4 H), 8.60 (s, 8 H). HRMS
(EI): calcd for (C56H52N4ClRh+) m/z 918.2930; found m/z 918.2944.
13C NMR (CDCl3, 100 MHz): δ 21.76, 22.18, 127.44, 128.20,
131.38, 131.82, 137.70, 138.60, 140.47, 142.17.
Reaction between [Rh(ttp)Cl] (1a) and Triethylsilane (2a) in
Benzene. Rh(ttp)Cl26 (10 mg, 0.012 mmol) and trimethylphenyl-
silane (193 µL, 100 equiv) were heated at 100 °C for 1 day under
N2 in the absence of light in benzene (2 mL). Rh(ttp)SiEt3 (2b)
(5.5 mg, 0.0062 mmol, 52%) was obtained after recrystallization
from CH2Cl2/MeOH. Rf ) 0.68 (hexane/CH2Cl2 ) 2:1). 1H NMR
(CDCl3, 300 MHz): δ -3.40 (q, 6 H, J ) 7.8 Hz, 7.2 Hz), -1.35
(t, 9 H, J ) 8.7 Hz), 2.68 (s, 12 H), 7.50 (d, 8 H, J ) 8.1 Hz),
7.97-8.04 (t, 8 H, J ) 7.8 Hz), 8.65 (s, 8 H). 13C NMR (CDCl3,
100 MHz): δ 3.45, 5.87, 22.22, 123.46, 128.03, 128.12, 131.89,
134.21, 134.56, 137.83, 139.95, 144.33. HRMS (FAB): calcd for
(C54H51N4SiRh)+ m/z 886.2933; found m/z 886.2948. Anal. Calcd
for C54H51N4SiRh: C, 73.12; H, 5.80; N, 6.31. Found: C, 73.20;
H, 5.83; N, 6.22.
Reactions of [Rh(tmp)Cl] (1b) with Silanes. General Proce-
dure. The reaction of Rh(tmp)Cl (1b) with triethylsilane (2a) is
described as a typical example. Triethylsilane (0.5 mL) was added
to Rh(tmp)Cl (10 mg, 0.010 mmol), and the mixture was degassed
by the freeze-pump-thaw method (3 cycles). Then the mixture
was heated at 200 °C for 1 day under N2 in the absence of light.
The crude product was purified by chromatography on silica gel
eluting with hexane/CH2Cl2 (10:1) to hexane/CH2Cl2 (5:1). An
orange solid of Rh(tmp)SiEt3 (2c) (6.8 mg, 0.0068 mmol, 62%)
was produced. Rf ) 0.34 (hexane/CH2Cl2 ) 5:1). 1H NMR (CDCl3,
300 MHz): δ -3.19 (q, 6 H, J ) 8.1 Hz), -1.11 (t, 9 H, J ) 7.8
Hz), 1.44 (s, 12 H), 2.33 (s, 12 H), 2.59 (s, 12 H), 6.95 (s, 4 H),
7.31 (s, 4 H), 8.41 (s, 8 H). 13C NMR (CDCl3, 100 MHz): δ 4.79,
7.02, 21.91, 22.08, 23.07, 121.20, 128.50, 128.58, 131.20, 138.10,
138.99, 139.08, 140.60, 143.89. HRMS (FAB): calcd for (C62H67N4-
SiRh)+ m/z 998.4185; found m/z 998.4223. Anal. Calcd for
C62H67N4SiRh: C, 74.53; H, 6.76; N, 5.60. Found: C, 74.31; H,
6.38; N, 5.97.
Conclusion
We have discovered a very facile synthetic approach to
rhodium porphyrin silyl complexes from the reactions of Rh-
(III) porphyrin complexes of halides and methyls with silanes
in solvent-free conditions. Preliminary mechanistic experiments
suggested that rhodium porphyrin halides formed rhodium
prophyrin cations and underwent base-promoted heterolysis in
the silicon-hydrogen bond activation step. On the other hand,
the mechanism of Si-H activation with Rh(ttp)Me likely
operates through oxidative addition or σ-bond metathesis.
Experimental Section
Unless otherwise noted, all chemicals were obtained from
commercial suppliers and used before purification. Hexane for
chromatography was distilled from anhydrous calcium chloride.
Reaction between [Rh(tmp)Cl] (1b) and Triethoxysilane (4a).
Triethoxysilane (0.5 mL) and Rh(tmp)Cl (10 mg, 0.011 mmol) were
heated at 200 °C for 1 h under N2 in the absence of light. An orange
solid of Rh(tmp)Si(OEt)3 (4b) (7.1 mg, 0.0068 mmol, 62%) was
(23) Haynes, A.; Mann, B. E.; Morris, G. E.; Maitlis, P. M. J. Am. Chem.
Soc. 1993, 115, 4093-4100.
(24) Duckett, S. B.; Perutz, R. N. Organometallics 1992, 11, 90-98.
(25) (a) Shilov, A. E.; Shul’pin G. B. Chem. ReV. 1997, 97, 2879-2932.
(b) Labinger, J. A.; Bercaw, J. E. Nature 2002, 507, 507-514. (c) Lersch,
M.; Tilset, M. Chem. ReV. 2005, 105, 2471-2526.
(26) (a) Zhou, X.; Wang, R. J.; Xue, F.; Mak, T. C. W.; Chan, K. S. J.
Organomet. Chem. 1999, 580, 22-24. (b) Zhou, X.; Li, Q.; Mak, T. C.
W.; Chan, K. S. Inorg. Chim. Acta 1998, 270, 551-554.

Facile Synthesis of Rh(III) Porphyrin Silyls
Organometallics, Vol. 25, No. 20, 2006 4827
obtained. Rf ) 0.40 (hexane/CH2Cl2 ) 5:1). 1H NMR (CDCl3, 300
MHz): δ -0.28 (t, 9 H, J ) 6.9 Hz), 0.98 (q, 6 H, J ) 6.9 Hz),
1.57 (s, 12 H), 2.21 (s, 12 H), 2.60 (s, 12 H), 7.17 (s, 4 H), 7.30
(s, 4 H), 8.45 (s, 8 H). 13C NMR (CDCl3, 100 MHz): δ 17.20,
22.10, 22.47, 31.60, 55.63, 120.92, 128.38, 130.99, 137.98, 139.20,
139.53, 140.39, 143.78. HRMS (FAB): calcd for (C62H67N4O3-
SiRh)+ m/z 1046.4032; found m/z 1046.4046. Anal. Calcd for
C62H67N4O3SiRh: C, 71.11; H, 6.45; N, 5.35. Found: C, 71.20;
H, 6.48; N, 5.10.
NMR (CDCl3, 300 MHz): δ -3.36 (d, 3 H, J ) 3.3 Hz), -1.09
(d, 1 H, 2JRh-H ) 3 Hz, JSi-H ) 0.9 Hz), 1.59 (s, 12 H), 1.98 (s, 12
H), 2.59 (s, 12 H), 4.41 (d, 2 H, J ) 6.6 Hz), 6.24 (t, 2 H, J ) 7.6
Hz), 6.58 (t, 1 H, J ) 7.5 Hz), 7.17 (s, 4 H), 7.26 (s, 4 H), 8.43 (s,
8 H). 13C NMR (CDCl3, 100 MHz): δ -3.30, 21.99, 22.10, 22.93,
120.93, 126.96, 128.43, 131.27, 131.96, 137.53, 138.11, 138.92,
139.26, 140.34, 143.47. HRMS (FAB): calcd for (C63H61N4SiRh)+
m/z 1004.3715; found m/z 1004.3677. Anal. Calcd for C63H61N4-
SiRh: C, 75.28; H, 6.12; N, 5.57. Found: C, 74.75; H, 6.05; N,
5.50. IR (KBr, cm-1): νSi-H 2304.
Reaction between [Rh(tmp)Cl] (1b) and Tripropylsilane (5a).
Tripropylsilane (0.5 mL) and Rh(tmp)Cl (10 mg, 0.011 mmol) were
heated at 200 °C for 2 days under N2 in the absence of light. An
orange solid of Rh(tmp)SiPr3 (5b) (5.8 mg, 0.006 mmol, 51%) was
obtained. Rf ) 0.47 (hexane/CH2Cl2 ) 5:1). 1H NMR (CDCl3, 300
MHz): δ -3.15 (dt, 6 H, J ) 3.3, 8.7 Hz), -0.88-0.76 (m, 6 H),
-0.13 (t, 9 H, J ) 9.3 Hz), 1.25 (s, 12 H), 2.39 (s, 12 H), 2.59 (s,
12 H), 7.13 (s, 4 H), 7.32 (s, 4 H), 8.41 (s, 8 H). 13C NMR (CDCl3,
100 MHz): δ 16.86, 18.02, 21.89, 22.08, 23.72, 121.10, 128.52,
131.24, 138.09, 138.88, 139.13, 140.74, 143.95. HRMS (FAB):
calcd for (C65H73N4SiRh)+ m/z 1040.4654; found m/z 1040.4707.
Anal. Calcd for C65H73N4SiRh: C, 74.97; H, 7.07; N, 5.38.
Found: C, 74.56; H, 7.05; N, 5.24.
Reaction between [Rh(tmp)Cl] (1b) and Benzyldimethylsilane
(10a). Benzyldimethylsilane (0.5 mL) and Rh(tmp)Cl (10 mg, 0.011
mmol) were heated at 200 °C for 1 h under N2 in the absence of
light. An orange solid of Rh(tmp)SiBnMe2 (10c) (10.3 mg, 0.010
1
mmol, 91%) was obtained. Rf ) 0.30 (hexane/CH2Cl2 ) 5:1). H
NMR (CDCl3, 300 MHz): δ -3.58 (s, 6 H), -2.04 (s, 2 H), 1.57
(s, 12 H), 2.31 (s, 12 H), 2.62 (s, 12 H), 5.26 (t, 2 H, J ) 6.0 Hz),
6.43 (t, 3 H, J ) 3.0 Hz), 6.97 (d, 1 H, J ) 7.2 Hz), 7.21 (s, 4 H),
7.34 (s, 4 H), 8.50 (s, 8 H). 13C NMR (CDCl3, 100 MHz): δ -2.64,
21.96, 22.101, 23.60, 25.67, 121.19, 123.47, 127.62, 128.57, 131.25,
138.20, 138.96, 140.59, 143.71. HRMS (FAB): calcd for (C65H65N4-
SiRh)+ m/z 1032.4028; found m/z 1032.4022. Anal. Calcd for
C65H65N4SiRh: C, 75.56; H, 6.34; N, 5.42. Found: C, 75.19; H,
6.28; N, 5.37.
Reaction between [Rh(tmp)Cl] (1b) and Triisopropylsilane
(6a). Triisopropylsilane (0.5 mL) and Rh(tmp)Cl (10 mg, 0.011
mmol) were heated at 200 °C for 2 days under N2 in the absence
of light. An orange solid of Rh(tmp)SiiPr3 (6b) (1.8 mg, 0.002
Reaction between [Rh(tmp)Cl] (1b) and Dimethylphenylsilane
(11a). Dimethylphenylsilane (0.5 mL) and Rh(tmp)Cl (10 mg, 0.011
mmol) were heated at 200 °C for 8 h under N2 in the absence of
light. An orange solid of Rh(tmp)SiPhMe2 (11c) (6.2 mg, 0.006
1
mmol, 16%) was obtained. Rf ) 0.50 (hexane/CH2Cl2 ) 5:1). H
NMR (CDCl3, 300 MHz): δ -2.36 (heptet, 3 H, J ) 7.5 Hz),
-1.04 (d, 18 H, J ) 7.5 Hz), 1.56 (s, 12 H), 2.53 (s, 12 H), 2.61
(s, 12 H), 7.06 (s, 4 H), 7.37 (s, 4 H), 8.41 (s, 8 H). 13C NMR
(CDCl3, 100 MHz): δ 14.88, 18.59, 21.66, 22.03, 23.49, 121.47,
128.49, 128.64, 131.73, 138.09, 138.64, 139.05, 140.90, 144.62.
HRMS (FAB): calcd for (C65H73N4SiRh)+ m/z 1041.4732; found
m/z 1041.4786. Anal. Calcd for C65H73N4SiRh: C, 74.97; H, 7.07;
N, 5.38. Found: C, 74.86; H, 6.54; N, 5.13.
1
mmol, 56%) was obtained. Rf ) 0.37 (hexane/CH2Cl2 ) 5:1). H
NMR (CDCl3, 300 MHz): δ -3.22 (s, 6 H), 1.40 (s, 12 H), 2.14
(s, 12 H), 2.61 (s, 12 H), 4.48 (d, 2 H, J ) 6 Hz), 6.30 (t, 2 H, J
) 9.2 Hz), 6.60 (t, 1 H, J ) 9.0 Hz), 7.13 (s, 4 H), 7.29 (s, 4 H),
8.41 (s, 8 H). 13C NMR (CDCl3, 100 MHz): δ -0.68, 21.84, 22.07,
23.32, 121.16, 126.87, 128.03, 128.47, 131.29, 131.50, 138.10,
138.98, 140.70, 143.79. HRMS (FAB): calcd for (C64H63N4SiRh)+
m/z 1018.3872; found m/z 1018.3903. Anal. Calcd for C64H63N4-
SiRh: C, 75.42; H, 6.23; N, 5.49. Found: C, 74.73; H, 6.13; N,
5.28.
Reaction between [Rh(tmp)Cl] (1b) and Diphenylsilane (7a).
Diphenylsilane (0.5 mL) and Rh(tmp)Cl (10 mg, 0.011 mmol) were
heated at 200 °C for 1 h under N2 in the absence of light. An orange
solid of Rh(tmp)SiPh2H (7b) (7.3 mg, 0.0068 mmol, 62%) was
obtained. Rf ) 0.27 (hexane/CH2Cl2 ) 5:1). 1H NMR (CDCl3, 300
MHz): δ -0.73 (s, 1 H), 1.26 (s, 12 H), 1.84 (s, 12 H), 2.58 (s, 12
H), 4.41 (d, 4 H, J ) 7.5 Hz), 6.16 (t, 4 H, J ) 7.5 Hz), 7.14 (s,
4 H), 7.26 (s, 4 H), 8.43 (s, 8 H). 13C NMR (CDCl3, 100 MHz):
δ 21.38, 21.57, 22.15, 120.71, 126.38, 127.85, 130.90, 131.47,
136.18, 137.58, 138.36, 138.72, 139.31, 139.93, 143.21. HRMS
(FAB): calcd for (C68H63N4SiRh)+ m/z 1066.3872; found m/z
1066.3869. Anal. Calcd for C68H63N4SiRh: C, 76.53; H, 5.95; N,
5.25. Found: C, 76.20; H, 5.74; N, 5.10.
Reaction between [Rh(tmp)Cl] (1b) and Diphenylmethylsilane
(12a). Diphenylmethylsilane (0.5 mL) and Rh(tmp)Cl (10 mg, 0.011
mmol) were heated at 200 °C for 15 h under N2 in the absence of
light. An orange solid of Rh(tmp)SiPh2Me (12b) (2.8 mg, 0.003
mmol, 26%) was obtained with Rf ) 0.30 (hexane/CH2Cl2 ) 5:1).
1H NMR (CDCl3, 300 MHz): δ -2.80 (s, 3 H), 1.19 (s, 12 H),
2.08 (s, 12 H), 2.56 (s, 12 H), 4.53 (d, 4 H, J ) 7.6 Hz), 6.26 (t,
4 H, J ) 7.5 Hz), 6.55 (t, 2 H, J ) 7.5 Hz), 7.07 (s, 4 H), 7.28 (s,
4 H), 8.40 (s, 8 H). 13C NMR (CDCl3, 100 MHz): δ -0.83, 21.70,
21.86, 23.15, 31.58, 121.53, 126.63, 127.46, 129.41, 131.29, 131.60,
132.58, 133.58, 138.03, 139.09, 140.63, 144.14. HRMS (FAB):
calcd for (C69H65N4SiRh)+ m/z 1080.4028; found m/z 1080.3979.
Anal. Calcd for C69H65N4SiRh: C, 76.64; H, 6.06; N, 5.18.
Found: C, 76.26; H, 6.02; N, 4.92. Rh(tmp)SiPhMeH (9b) (2.7
mg, 0.003 mmol, 28%) was also produced.
Reactions of [Rh(tmp)I] (1c) with Silanes. General Procedure.
The reaction of Rh(tmp)I27 with triethylsilane (2a) is described as
a typical example. Triethylsilane (0.5 mL) was added to Rh(tmp)I
(10 mg, 0.010 mmol), and the mixture was degassed by the freeze-
pump-thaw method (3 cycles). Then the mixture was heated at
200 °C for 1 day under N2 in the absence of light. The crude product
was purified by chromatography on silica gel eluting with hexane/
CH2Cl2 (10:1) to hexane/CH2Cl2 (5:1). An orange solid of Rh(tmp)-
SiEt3 (2c) (6.0 mg, 0.005 mmol, 70%) was produced.
Reaction between [Rh(tmp)Cl] (1b) and Phenylsilane (8a).
Phenylsilane (0.5 mL) and Rh(tmp)Cl (10 mg, 0.011 mmol) were
heated at 200 °C for 1 h under N2 in the absence of light. An orange
solid of Rh(tmp)SiPhH2 (8b) (8.9 mg, 0.009 mmol, 82%) was
obtained. Rf ) 0.40 (hexane/CH2Cl2 ) 5:1). 1H NMR (CDCl3, 300
MHz): δ -1.20 (s, 2 H), 1.74 (s, 12 H), 1.84 (s, 12 H), 2.59 (s, 12
H), 4.29 (d, 2 H, J ) 7.5 Hz), 6.15 (t, 2 H, J ) 7.5 Hz), 6.53 (t,
1 H, J ) 7.5 Hz), 7.14 (s, 4 H), 7.21 (s, 4 H), 8.45 (s, 8 H). 13C
NMR (CDCl3, 100 MHz): δ 22.08, 22.58, 54.10, 120.83, 126.82,
128.41, 131.30, 132.69, 138.14, 138.87, 139.53, 139.96, 143.39.
HRMS (FAB): calcd for (C62H59N4SiRh)+ m/z 990.3506; found
m/z 990.3559. Anal. Calcd for C62H59N4SiRh: C, 75.13; H, 6.00;
N, 5.65. Found: C, 74.63; H, 6.18; N, 5.17. IR (KBr, cm-1): νSi-H
2304.
Reaction between [Rh(tmp)I] (1c) and Triethoxysilane (4a).
Triethoxysilane (0.5 mL) and Rh(tmp)I (1c) (10 mg, 0.010 mmol)
were heated at 200 °C for 1 h under N2 in the absence of light. An
Reaction between [Rh(tmp)Cl] (1b) and Phenylmethylsilane
(9a). Phenylmethylsilane (0.5 mL) and Rh(tmp)Cl (10 mg, 0.011
mmol) were heated at 200 °C for 3 h under N2 in the absence of
light. An orange solid of Rh(tmp)SiPhMeH (9b) (7.8 mg, 0.008
(27) Wayland, B. B.; Sherry, A. E.; Poszmik, G.: Bunn, A. G. J. Am.
Chem. Soc. 1992, 114, 1673-1681.
1
mmol, 73%) was obtained. Rf ) 0.40 (hexane/CH2Cl2 ) 5:1). H

4828 Organometallics, Vol. 25, No. 20, 2006
Zhang and Chan
orange solid of Rh(tmp)Si(OEt)3 (4b) (7.6 mg, 0.007 mmol, 74%)
was obtained.
H, J ) 9.0 Hz), 8.59 (s, 8 H). 13C NMR (CDCl3, 100 MHz): δ
22.22, 123.34, 126.53, 127.96, 128.02, 128.13, 128.45, 131.72,
131.98, 134.45, 134.55, 135.04, 137.74, 139.83, 143.82. HRMS
(FAB): calcd for (C60H47N4SiRh)+ m/z 954.2620; found m/z
954.2650. Anal. Calcd for C60H47N4SiRh: C, 75.46; H, 4.96; N,
5.86. Found: C, 75.69; H, 5.15; N, 5.56.
Reaction between [Rh(tmp)I] (1c) and Tripropylsilane (5a).
Tripropylsilane (0.5 mL) and Rh(tmp)I (10 mg, 0.010 mmol) were
heated at 200 °C for 2 days under N2 in the absence of light. An
orange solid of Rh(tmp)SiPr3 (5b) (4.6 mg, 0.004 mmol, 45%) was
obtained.
Reaction between [Rh(tmp)I] (1c) and Triisopropylsilane (6a).
Triisopropylsilane (0.5 mL) and Rh(tmp)I (10 mg, 0.010 mmol)
were heated at 200 °C for 2 days under N2 in the absence of light.
An orange solid of Rh(tmp)SiiPr3 (6b) (2.4 mg, 0.002 mmol, 23%)
was obtained.
Reaction between [Rh(tmp)I] (1c) and Diphenylsilane (7a).
Diphenylsilane (0.5 mL) and Rh(tmp)I (10 mg, 0.010 mmol) were
heated at 200 °C for 1 h under N2 in the absence of light. An orange
solid of Rh(tmp)SiPh2H (7b) (6 mg, 0.006 mmol, 56%) was
obtained.
Reaction between [Rh(tmp)I] (1c) and Phenylsilane (8a).
Phenylsilane (0.5 mL) and Rh(tmp)I (10 mg, 0.010 mmol) were
heated at 200 °C for 1 h under N2 in the absence of light. An orange
solid of Rh(tmp)SiPhH2 (8b) (7.3 mg, 0.007 mmol, 75%) was
obtained.
Reaction between [Rh(tmp)I] (1c) and Phenylmethylsilane
(9a). Phenylmethylsilane (0.5 mL) and Rh(tmp)I (10 mg, 0.010
mmol) were heated at 200 °C for 3 h under N2 in the absence of
light. An orange solid of Rh(tmp)SiPhMeH (9b) (6.5 mg, 0.006
mmol, 66%) was obtained.
Reaction between [Rh(tmp)I] (1c) and Benzyldimethylsilane
(10a). Benzyldimethylsilane (0.5 mL) and Rh(tmp)I (10 mg, 0.010
mmol) were heated at 200 °C for 6 h under N2 in the absence of
light. An orange solid of Rh(tmp)SiBnMe2 (10c) (7.8 mg, 0.007
mmol, 77%) was obtained.
Reaction between [Rh(ttp)Cl] (1a) and Benzyldimethylsilane
(10a). Benzyldimethylsilane (0.5 mL) and Rh(ttp)Cl (10 mg, 0.012
mmol) were heated at 200 °C for 1 h under N2 in the absence of
light. An orange solid of Rh(ttp)SiBnMe2 (10b) (10.0 mg, 0.011
1
mmol, 88%) was obtained. Rf ) 0.62 (hexane/CH2Cl2 ) 2:1). H
NMR (CDCl3, 300 MHz): δ -3.94 (s, 6 H), -2.47 (s, 2 H), 2.72
(s, 12 H), 5.30 (d, 2 H, J ) 7.5 Hz), 6.47 (t, 3 H, J ) 6.9 Hz), 7.53
(t, 8 H, J ) 8.4 Hz), 7.80 (d, 4 H, J ) 6.3 Hz), 8.10 (d, 4 H, J )
6.3 Hz), 8.73 (s, 8 H). 13C NMR (CDCl3, 100 MHz): δ -4.45,
22.22, 24.42, 123.60, 127.65, 127.70, 128.06, 128.16, 128.81,
132.03, 134.20, 134.60, 137.93, 139.11, 139.86, 144.19. HRMS
(FAB): calcd for (C57H49N4SiRh)+ m/z 920.2776; found m/z
920.2708. Anal. Calcd for C57H49N4SiRh: C, 74.33; H, 5.36; N,
6.08. Found: C, 73.78; H, 5.36; N, 5.96.
Reaction between [Rh(ttp)Cl] (1a) and Dimethylphenylsilane
(11a). Dimethylphenylsilane (0.5 mL) and Rh(ttp)Cl (10 mg, 0.012
mmol) were heated at 200 °C for 1 h under N2 in the absence of
light. An orange solid of Rh(ttp)SiPhMe2 (11b) (10.2 mg, 0.011
1
mmol, 91%) was obtained. Rf ) 0.58 (hexane/CH2Cl2 ) 5:1). H
NMR (CDCl3, 300 MHz): δ -3.54 (s, 6 H), 2.68 (s, 12 H), 4.22
(d, 2 H, J ) 8.7 Hz), 6.41 (t, 2 H, J ) 6.3 Hz), 6.75 (t, 1 H, J )
6.3 Hz), 7.49 (t, 8 H, J ) 9.0 Hz), 7.92-8.01 (m, 8 H), 8.62 (s, 8
H). 13C NMR (CDCl3, 100 MHz): δ 0.00, 25.96, 35.33, 127.11,
130.09, 131.43, 131.72, 131.83, 134.18, 135.64, 138.24, 141.52,
143.68, 147.76. HRMS(FAB): calcd for (C56H47N4SiRh)+ m/z
906.2620; found m/z 906.2600. Anal. Calcd for C56H47N4SiRh: C,
74.16; H, 5.22; N, 6.17. Found: C, 73.86; H, 5.02; N, 6.13.
Reaction between [Rh(tmp)I] (1c) and Dimethylphenylsilane
(11a). Dimethylphenylsilane (0.5 mL) and Rh(tmp)I (10 mg, 0.010
mmol) were heated at 200 °C for 1 day under N2 in the absence of
light. The suspension slowly became transparent upon heating, and
a red solution was finally formed. An orange solid of Rh(tmp)-
SiPhMe2 (11c) (4.8 mg, 0.005 mmol, 48%) was obtained.
Reaction between [Rh(tmp)SiPh2Me] (12b) and Diphenyl-
methylsilane (12a). Rh(tmp)SiPh2Me (3 mg, 0.003 mmol) and
diphenylmethylsilane (0.5 mL) were heated at 200 °C for 2 days
under N2 in the absence of light. After removing 12a, the reaction
mixture was subjected to NMR, which suggested that 12b had
completely converted to Rh(tmp)SiPhMeH (9b) (100% NMR yield).
Reaction between [Rh(tmp)SiPhMeH] (9b) and Diphenyl-
methylsilane (12a). Rh(tmp)SiPhMeH (9b) (3 mg, 0.003 mmol)
and diphenylmethylsilane (12a) (0.5 mL) were heated at 200 °C
for 3 days under N2 in the absence of light. No Rh(tmp)SiPh2Me
(12b) signals were observed in the NMR spectrum.
Reaction of [Rh(ttp)Cl] (1a) with Triethylsilane (2a). Genaral
Procedure. The reaction between triethylsilane and Rh(ttp)Cl is
described as a typical example. Triethylsilane (0.5 mL) was added
to Rh(ttp)Cl (10 mg, 0.012 mmol), and the mixture was degassed
by the freeze-pump-thaw method (3 cycles). Then the mixture
was heated at 200 °C for 1.5 h under N2 in the absence of light.
The crude product was purified by chromatography on silica gel
eluting with hexane/CH2Cl2 (4:1) to hexane/CH2Cl2 (2:1). An
orange solid of Rh(ttp)SiEt3 (2b) (8.9 mg, 0.010 mmol, 81%) was
obtained.
Reaction between [Rh(ttp)Me] (1d) and Triethylsilane (2a).
Genaral Procedure. The reaction between triethylsilane and Rh-
(ttp)Me26 is described as a typical example. Triethylsilane (0.5 mL)
was added to Rh(ttp)Me (10 mg, 0.013 mmol), and the mixture
was degassed by the freeze-pump-thaw method (3 cycles). Then
the mixture was heated at 200 °C for 1 h under N2 in the absence
of light. The crude product was purified by chromatography on
silica gel eluting with hexane/CH2Cl2 (4:1) to hexane/CH2Cl2 (2:
1). An orange solid of Rh(ttp)SiEt3 (2b) (9.9 mg, 0.011 mmol, 86%)
was obtained.
Reaction between [Rh(ttp)Me] (1d) and Triethoxysilane (4a).
Triethoxysilane (0.5 mL) and Rh(ttp)Me (10 mg, 0.013 mmol) were
heated at 200 °C for 1 h under N2 in the absence of light. An orange
solid of Rh(ttp)Si(OEt)3 (4c) (10.4 mg, 0.011 mmol, 86%) was
obtained. Rf ) 0.52 (hexane/CH2Cl2 ) 2:1). 1H NMR (CDCl3, 300
MHz): δ -0.28 (t, 9 H, J ) 6.9 Hz), 0.77 (q, 6 H, J1 ) 6.9 Hz,
J2 ) 7.2 Hz), 2.64 (s, 12 H), 7.51 (d, 8 H, J ) 6.9 Hz), 7.99 (t, 8
H, J ) 8.7 Hz), 8.70 (s, 8 H). 13C NMR (CDCl3, 100 MHz): δ
3.45, 5.87, 22.22, 123.46, 128.03, 128.12, 131.89, 134.21, 134.56,
137.83, 139.95, 144.33. HRMS (FAB): calcd for (C54H51N4O3-
SiRh)+ m/z 934.2002; found m/z 934.2009. Anal. Calcd for
C54H51N4O3SiRh: C, 69.37; H, 5.50; N, 5.99. Found: C, 69.35;
H, 5.60; N, 5.95.
Reaction between [Rh(ttp)Me] (1d) Diphenylsilane (7a).
Diphenylsilane (0.5 mL) and Rh(ttp)Me (10 mg, 0.013 mmol) were
heated at 200 °C for 0.5 h under N2 in the absence of light. An
orange solid of Rh(ttp)SiPh2H (7c) (8.2 mg, 0.008 mmol, 67%)
was obtained.
Reaction between [Rh(ttp)Cl] (1a) and Diphenylsilane (7a).
Diphenylsilane (0.5 mL) and Rh(ttp)Cl (10 mg, 0.012 mmol) were
heated at 200 °C for 0.5 h under N2 in the absence of light. An
orange solid of Rh(ttp)SiPh2H (7c) (8.5 mg, 0.009 mmol, 72%)
was obtained. Rf ) 0.53 (hexane/CH2Cl2 ) 2:1). 1H NMR (CDCl3,
300 MHz): δ -1.28 (d, 1 H, J ) 2.8 Hz), 2.68 (s, 12 H), 4.31 (d,
4 H, J ) 6.9 Hz), 6.35 (t, 4 H, J ) 8.7 Hz), 6.71 (t, 2 H, J ) 8.7
Hz), 7.48 (t, 8 H, J ) 9.0 Hz), 7.73 (d, 4 H, J ) 9.0 Hz), 7.97 (d,4
Reaction between [Rh(ttp)Me] (1d) and Phenylmethylsilane
(9a). Phenylmethylsilane (0.5 mL) and Rh(ttp)Me (10 mg, 0.013
mmol) were heated at 200 °C for 3 h under N2 in the absence of
light. An orange solid of Rh(ttp)SiPhMeH (9c) (7.7 mg, 0.0086
1
mmol, 68%) was obtained. Rf ) 0.44 (hexane/CH2Cl2 ) 2:1). H
NMR (CDCl3, 300 MHz): δ -3.58 (d, 3 H, J ) 3.3 Hz), -1.58

Facile Synthesis of Rh(III) Porphyrin Silyls
Organometallics, Vol. 25, No. 20, 2006 4829
(d, 1 H, J ) 3.3 Hz), 2.63 (s, 12 H), 4.13 (d, 2 H, J ) 6.9 Hz),
6.36 (t, 2 H, J ) 6.3 Hz), 6.74 (t, 1 H, J ) 7.5 Hz), 7.87 (d, 8 H,
J ) 6.9 Hz), 8.01 (d, 4 H, J ) 6.9 Hz), 8.05 (d, 4 H, J ) 6.9 Hz),
8.63 (s, 8 H). 13C NMR (CDCl3, 100 MHz): δ 0.69, 20.36, 31.59,
123.44, 126.37, 127.69, 128.06, 132.002, 134.37, 137.79, 139.87,
143.97. HRMS (FAB): calcd for (C55H45N4SiRh)+ m/z 892.3718;
found m/z 892.3702. Anal. Calcd for C55H45N4SiRh: C, 73.98; H,
5.08; N, 6.27. Found: C, 73.87; H, 4.99; N, 5.81. IR (KBr, cm-1):
νSi-H 1425.
Reaction between [Rh(ttp)Me] (1d) and Benzyldimethylsilane
(10a). Benzyldimethylsilane (0.5 mL) and Rh(ttp)Me (10 mg, 0.013
mmol) were heated at 200 °C for 0.5 h under N2 in the absence of
light. An orange solid of Rh(ttp)SiBnMe2 (10b) (9.6 mg, 0.010
mmol, 88%) was obtained.
orange solid of Rh(tmp)SiEt3 (2c) (4.9 mg, 0.0056 mmol, 56%)
was produced.
Reaction between [Rh(tmp)Me] (1e) and Triethoxysilane (4a).
Triethoxylsilane (0.5 mL) and Rh(tmp)Me (10 mg, 0.011 mmol)
were heated at 200 °C for 0.5 h under N2 in the absence of light.
An orange solid of Rh(tmp)Si(OEt)3 (4b) (7.9 mg, 0.0075 mmol,
68%) was produced.
Reaction between [Rh(tmp)SiEt3] (2c) and Diphenylsilane
(7a). Rh(tmp)SiEt3 (5 mg, 0.005 mmol) and diphenylsilane (0.5
mL) were heated at 200 °C for 1 h under N2 in the absence of
light, and 2c was consumed completely. After removing 7a, the
mixture was eluted with hexane/CH2Cl2 (5:1) to give an orange
solid of Rh(tmp)SiPh2H (7b) (3.6 mg, 0.0036 mmol, 68%).
Reaction between [Rh(ttp)Cl] (1a) and Trimethylphenylsilane
(14a). Rh(ttp)Cl (10 mg, 0.012 mmol) and trimethylphenylsilane
(0.5 mL) were heated at 200 °C for 1 day under N2 in the absence
of light. An orange solid of Rh(ttp)Ph (14b) (2.0 mg, 0.0024 mmol,
Reaction between [Rh(ttp)Me] (1d) and Dimethylphenylsilane
(11a). Dimethylphenylsilane (0.5 mL) and Rh(ttp)Me (10 mg, 0.013
mmol) were heated at 200 °C for 6 h under N2 in the absence of
light. An orange solid of Rh(ttp)SiPhMe2 (11b) (8.5 mg, 0.009
mmol, 79%) was obtained.
1
18%) was formed. Rf ) 0.50 (hexane/CH2Cl2 ) 2:1). H NMR
(CDCl3, 300 MHz): δ 0.24 (d, 2 H, J ) 8.4 Hz), 2.69 (s, 12 H),
4.73 (t, 2 H, J ) 8.4 Hz), 5.20 (t, 1 H, J ) 6.9 Hz), 7.54 (t, 8 H,
J ) 6.9 Hz), 7.99 (dd, 8 H, J ) 7.5, 7.8 Hz), 8.76 (s, 8 H). HRMS
(FAB): calcd for (C54H41N4Rh)+ m/z 848.2381; found m/z 848.2390.
Reaction between [Rh(ttp)OTf] (1f) and Triethylsilane (2a).
Rh(ttp)OTf22,29 (10 mg, 0.011 mmol) and trimethylphenylsilane (0.5
mL) were heated at 150 °C for 15 min under N2 in the absence of
light. Rh(ttp)SiEt3 (2b) (6.5 mg, 0.006 mmol, 78%) was obtained.
Reaction between [Rh(ttp)Me] (1d) and Diphenylmethylsilane
(12a). Diphenylmethylsilane (0.5 mL) and Rh(ttp)Me (10 mg, 0.013
mmol) were heated at 200 °C for 0.5 h under N2 in the absence of
light. An orange solid of Rh(ttp)SiPh2Me (12c) (9.4 mg, 0.0078
1
mmol, 78%) was obtained. Rf ) 0.56 (hexane/CH2Cl2 ) 2:1). H
NMR (CDCl3, 300 MHz): δ -3.17 (s, 3 H), 2.68 (s, 12 H), 4.46
(d, 4 H, J ) 7.5 Hz), 6.43 (t, 4 H, J ) 7.5 Hz), 6.74 (t, 2 H, J )
7.5 Hz), 7.49 (dd, 8 H, J ) 9 Hz, 7.5 Hz), 7.81 (d, 4 H, J ) 7.5
Hz), 7.91 (d, 4 H, J ) 7.5 Hz), 8.56 (s, 8 H). 13C NMR (CDCl3,
100 MHz): δ -5.40, 22.20, 31.59, 123.44, 126.38, 127.70, 127.96,
128.06, 132.01, 134.38, 134.59, 135.94, 137.73, 139.88, 143.99.
HRMS (FAB): calcd for (C61H49N4SiRh)+ m/z 968.2776; found
m/z 968.2768. Anal. Calcd for C61H49N4SiRh: C, 75.61; H, 5.10;
N, 5.78. Found: C, 75.83; H, 5.18; N, 5.56.
Acknowledgment. We thank the Research Grants Council
of Hong Kong of the SAR of China for financial support (No.
400203).
Supporting Information Available: Text and crystallographic
data for 11c and 12b (pdf and cif).This material is available free
of charge via the Internet at http://pubs.acs.org.
Reactions of [Rh(tmp)Me] (1e) with Silanes. General Proce-
dure. The reaction of Rh(tmp)Me27 (1e) with triethylsilane (2a) is
described as a typical example. Triethylsilane (0.5 mL) was added
to Rh(tmp)Me (10 mg, 0.011 mmol), and the mixture was degassed
by the freeze-pump-thaw method (3 cycles). Then the mixture
was heated at 200 °C for 1 day under N2 in the absence of light.
The crude product was purified by chromatography on silica gel
eluting with hexane/CH2Cl2 (10:1) to hexane/CH2Cl2 (5:1). An
OM0604472
(28) Anderson, J. E.; Yao, C.-L.; Kadish, K. M. Inorg. Chem. 1986, 25,
718-719.
(29) (a) Aoyama, Y.; Tanaka, Y.; Yoshida, T.; Toi, H.; Ogoshi, H. J.
Organomet. Chem. 1987, 329, 251-266. (b) Aoyama, Y. Yoshida, T.;
Sakurai, K.; Ogoshi, H. Organometallics 1986, 5, 168-173.