Stable compounds of composition LGe(II)R (R = OH, PhO, C6F 5O, PhCO2) prepared by nucleophilic addition reactions

Article abstract of DOI:10.1021/om900149k

The stable β-diketiminate germanium(II) compounds LGeR [L = HC(CMeNAr)₂, Ar = 2,6-iPr₂C₆H₃] (R = OTf, OH, PhO, C₆F₅O, PhCO₂) are described. LGeOTf (2) is synthesized by salt metathesis reaction of LGeCl (1) with AgOTf and can be isolated as colorless crystals in 90% yield. Compound L'Ge (3) (L' = CH{(C=CH₂)(CMe)(2,6-iPr₂C₆H₃N) ₂}) was obtained by treatment of LGeOTf (2) with 1 equiv of 1,3di-tert-butylimidazol-2-ylidene (NHC) in toluene. Reaction of 3 with H ₂O, PhOH, C₆F₅OH, and PhCO₂H, respectively, in toluene provided the germanium(II) compounds 4-7 in high yield. Compounds 2-7 were characterized by microanalysis and multinuclear NMR spectroscopy. Furthermore compounds 5, 6, and 7 are confirmed by X-ray structural analysis with the result that compounds 5,6, and 7 are monomeric and the germanium center resides in a trigonal-pyramidal environment.

Full text of DOI:10.1021/om900149k

Organometallics 2009, 28, 3763–3766 3763
DOI: 10.1021/om900149k
Stable Compounds of Composition LGe(II)R (R = OH, PhO,
C6F5O, PhCO2) Prepared by Nucleophilic Addition Reactions
Anukul Jana, Bijan Nekoueishahraki, Herbert W. Roesky,* and Carola Schulzke
::
:: ::
::
Institut fur Anorganische Chemie, Universitat Gottingen, Tammannstrasse 4, 37077 Gottingen, Germany
Received February 24, 2009
The stable β-diketiminate germanium(II) compounds LGeR [L = HC(CMeNAr)2, Ar = 2,6-iPr2C6H3]
(R = OTf, OH, PhO, C6F5O, PhCO2) are described. LGeOTf (2) is synthesized by salt metathesis reaction of
LGeCl (1) with AgOTf and can be isolated as colorless crystals in 90% yield. Compound L0Ge (3) (L0 =
CH{(CdCH2)(CMe)(2,6-iPr2C6H3N)2}) was obtained by treatment of LGeOTf (2) with 1 equiv of 1,3-
di-tert-butylimidazol-2-ylidene (NHC) in toluene. Reaction of 3 with H2O, PhOH, C6F5OH, and PhCO2H,
respectively, in toluene provided the germanium(II) compounds 4-7 in high yield. Compounds 2-7 were
characterized by microanalysis and multinuclear NMR spectroscopy. Furthermore compounds 5, 6, and 7
are confirmed by X-ray structural analysis with the result that compounds 5, 6, and 7 are monomeric and the
germanium center resides in a trigonal-pyramidal environment.
Introduction
we report on the synthesis of different heteroleptic germanium
(II) compounds by the reaction of L0Ge (3) under nucleophilic
addition of RH.
In recent years we have been interested in the synthesis of
compounds with low-valent germanium. We reported on
the preparation and structural characterization of LGeCl,1
LGeF,2 LGeOH,3 LGeH,4 and LGeNH2 (L = CH{(CMe)
Results and Discussion
5
(2,6-iPr2C6H3N)}2) including the reactivity of LGeH.6 These
small molecules are ideal precursors for the preparation of
heterometallic germylenes, which are active catalysts in olefin
polymerization reations.7 All compounds were synthesized
by nucleophilic substitution reactions with the exception of
LGeNH2. The synthesis of LGeNH2 involved the cleavage of
one N-H bond of ammonia by L0Ge (3) (L0 = CH{(CdCH2)-
(CMe)(2,6-iPr2C6H3N)2}). Driess and co-workers indepen-
dently demonstrated that 3 has a dipolar character.8 Herein,
In a previous communication we reported the synthesis of
L0Ge (3)5 from LGeCl (1) and 1,3-di-tert-butylimidazol-2-
ylidene9 (NHC) in a 65% yield. The yield can be improved
when, instead of LGeCl (1), LGeOTf (2) and NHC are used.
The triflate anion ([OSO2CF3]- = OTf-) has served here as an
excellent leaving group, and the conversion is almost quantita-
tive (Scheme 1).
LGeOTf (2) was synthesized under salt metathesis reaction of
LGeCl (1) with AgOTf in toluene and afforded colorless
compound 2 in high yield. LGeOTf (2) was also reported by
Driess and co-workers by the reaction of LGeP(H)SiMe3 with
Me3SiOTf in the presence of Et3N.10 Unlike other β-diketimi-
nate germanium compounds, the1H NMR spectrum of 2 shows
for the iPr substituents at room temperature only one broad
singlet (CH, δ = 3.26 ppm) and one doublet for the methyl
groups. This may be due to the rapid exchange of the triflate
group and the lone pair at the germanium atom. Therefore we
*To whom correspondence should be addressed. Fax: +49-551-
393373. E-mail: hroesky@gwdg.de.
(1) Ding, Y.; Roesky, H. W.; Noltemeyer, M.; Schmidt, H.-G.;
Power, P. P. Organometallics 2001, 20, 1190–1194.
(2) Ding, Y.; Hao, H.; Roesky, H. W.; Noltemeyer, M.; Schmidt,
H.-G. Organometallics 2001, 20, 4806–4811.
(3) (a) Pineda, L. W.; Jancik, V.; Roesky, H. W.; Neculai, D.;
Neculai, A. M. Angew. Chem. 2004, 116, 1443–1445. (b) Angew. Chem.,
Int. Ed. 2004, 43, 1419-1421.
(4) (a) Pineda, L. W.; Jancik, V.; Starke, K.; Oswald, R. B.; Roesky,
H. W. Angew. Chem. 2006, 118, 2664–2667. (b) Angew. Chem., Int. Ed.
2006, 45, 2602-2605.
1
studied the temperature dependence H NMR between +75
and -50 °C. At -50 °C two septets appeared at 3.92 and
2.60 ppm for the CH protons (see Figure 1). However at -50 °C
the exchange of the triflate group and the lone pair is slow on
the NMR time scale compared to that at room temperature.
The calculated exchange rate at different temperatures is the
(5) Jana, A.; Objartel, I.; Roesky, H. W.; Stalke, D. Inorg. Chem.
2009, 48, 798–800.
(6) Jana, A.; Ghoshal, D.; Roesky, H. W.; Objartel, I.; Schwab, G.;
Stalke, D. J. Am. Chem. Soc. 2009, 131, 1288–1293.
(7) (a) Pineda, L. W.; Jancik, V.; Roesky, H. W.; Herbst-Irmer, R.
Inorg. Chem. 2005, 44, 3537–3540. (b) Yang, Y.; Roesky, H. W.; Jones,
P. G.; So, C.-W.; Zhang, Z.; Herbst-Irmer, R.; Ye, H. Inorg. Chem. 2007,
46, 10860–10863.
(9) (a) Arduengo, A. J.; Bock, H.; Chen, C.; Denk, M.; Dixon, D. A.;
Green, J. C.; Herrmann, W. A.; Jones, N. L.; Wagner, M.; West, R. J.
Am. Chem. Soc. 1994, 116, 6641–6649. (b) Scott, N. M.; Dorta, R.;
Stevens, E. D.; Correa, A.; Cavallo, L.; Nolan, S. P. J. Am. Chem. Soc.
2005, 127, 3516–3526.
::
(8) (a) Driess, M.; Yao, S.; Brym, M.; van Wullen, C. Angew. Chem.
2006, 118, 4455 – 4458. (b) Angew. Chem., Int. Ed. 2006, 45, 4349-4352
(c) Yao, S.; van Wullen, C.; Driess, M. Chem. Commun. 2008,
5393–5395.
::
(10) Yao, S.; Brym, M.; Merz, K.; Driess, M. Organometallics 2008,
27, 3601–3607.
r
2009 American Chemical Society
Published on Web 05/15/2009
pubs.acs.org/Organometallics

3764 Organometallics, Vol. 28, No. 13, 2009
Jana et al.
asymmetric unit, respectively (Table 1). Single crystals of both
5 and 6 were obtained from saturated n-hexane solution
at -32 °C after two days. These compounds are stable in the
solid state as well as in solution for a long time without any
decomposition under inert atmosphere. The coordination poly-
hedron around the germanium atom features a distorted
trigonal-pyramidal geometry (Figures 2, 3). The germanium is
attached to two nitrogen atoms from the backbone of the
chelating ligand and the oxygen atom from the OPh and
OC6F5 group, respectively.
The Ge-N bond lengths and N-Ge-N angles are compar-
able with those of related compounds.12 The Ge-O bond
length of 5 (1.860 A) can be compared with that of LGeOH
3
˚
˚
˚
(1.828 A), but in 6 it is a slightly longer Ge-O bond (1.9515 A),
when compared with the latter one.
Subsequently after the successful reaction of L0Ge with H2O,
PhOH, and C6F5OH, respectively, we used a carboxylic acid as
precursor. Treatment of 3 with PhCO2H in toluene at room
temperature after 1 h afforded the corresponding benzoic
acid derivative, germylene benzoate HC(CMeNAr)2GeOC(O)-
Ph (Ar = 2,6-iPr2C6H3) (7), in high yield (85%) (Scheme 1).
Compound 7 is thermally stable. No decomposition was ob-
served at temperatures below the melting point (167 °C) under
an inert atmosphere. Compound 7 is a white solid that is soluble
in benzene, toluene, n-hexane, and THF. 7 was characterized by
1H and 13C NMR spectroscopy, EI mass spectrometry, ele-
Figure 1. 1H NMR spectrum of 2 at various temperatures.
Scheme 1. Preparation of Compounds 2, 3, 4, 5, 6, and 7
1
mental analysis, and X-ray structural analysis. The H NMR
spectrum of compound 7 shows a singlet (δ = 5.16 ppm) for the
γ-CH protons and two septets (δ = 3.61, 3.17 ppm) corre-
sponding to the two different types of CH protons of the iPr
moieties. EI-MS of 7 gave the corresponding monomeric
molecular ion peak M+ at m/z 612.
The molecular structure of 7 has been determined by single-
crystal X-ray diffraction analysis (Figure 4), which demon-
strates that the complex exists as a monomer. Colorless crystals
of 7 were obtained from an n-hexane solution at -30 °C after
one day in a freezer. Compound 7 crystallizes in the monoclinic
space group P21/c, with one monomer in the asymmetric unit.
The coordination polyhedron around the germanium atom
exhibits a distorted trigonal-pyramidal geometry. The sum of
angles around the germanium atom is 268.59°. The Ge-O bond
following: -50 °C, 3.5 s-1; -25 °C, 28 s-1; 0 °C, 250 s-1; +25
°C, 2500 s-1; +50 °C, 26000 s-1
.
In recent years we were interested in the synthesis of hydro-
xides, and we were able to isolate LGeOH, LAl(OH)2, and
LAlMe(OH).11 Therefore we followed the reaction of L0Ge
with H2O, and we expected the formation of the LGeOH by an
alternative route.
˚
distance (1.9462 A) in 7 is quite large when compared with that
˚
of 5 (1.860 A), and it is similar to that of 6 (1.9515 A).
˚
The reaction of L0Ge with H2O in a 1:1 ratio at room
temperature resulted in the formation of LGeOH (4) in almost
quantitative yield (Scheme 1). For a broader feasibility we
extended the reaction of L0Ge with PhOH and C6F5OH and
obtained products 5 and 6, respectively (Scheme 1). 5 and 6 are
colorless solids, which are soluble in n-hexane, n-pentane, THF,
dichloromethane, benzene, and diethyl ether. 5 and 6 were
characterized by 1H and 13C NMR spectroscopy, EI mass
spectrometry, elemental analysis, and X-ray single-crystal
structural analysis. The 1H NMR spectra of 5 and 6 show the
expected pattern for the β-diketiminato ligand.6 The 19F NMR
spectrum of 6 displays three resonances (-158.8, -166.9,
-175.2 ppm) for the ortho, meta, and para fluorine atoms,
respectively. The most intense peak in the EI mass spectra
appeared at m/z = 491 [M - OPh]+ and 673 [M]+ for
compounds 5 and 6, respectively.
Summary and Conclusion
In this contribution, we report the syntheses and character-
ization of three monomeric germanium(II) compounds sup-
ported by the bulky β-diketiminate ligand. The synthetic
strategy takes advantage of the easy access of [CH{(CdCH2)-
(CMe)(Ar)}2Ge] (Ar = 2,6-iPr2C6H3) (3), which is formed by
elimination of CF3SO3H with 1,3-di-tert-butylimidazol-2-yli-
dene. The concept of nucleophilic addition of RH was applied
using H2O, PhOH, C6F5OH, and PhCO2H, respectively, to
afford the monomeric organogermanium(II) compounds 4-7
in high yield. Compounds 5-7 are highly soluble in common
organic solvents.
Experimental Section
Compounds 5 and 6 crystallize in the orthorhombic Pnma
and monoclinic P21/n space groups with one monomer in the
General Considerations. All manipulations were performed in a
dry and oxygen-free atmosphere (N2 or Ar) by using Schlenk-line and
glovebox techniques. Solvents were purified with the M-Braun
(11) Roesky, H. W.; Walawalkar, M. G.; Murugavel, R. Acc. Chem.
Res. 2001, 34, 201-211, and references therein.
(12) Nagendran, S.; Roesky, H. W. Organometallics 2008, 27, 457–492.

Article
Organometallics, Vol. 28, No. 13, 2009 3765
Table 1. Crystallographic Data for the Structural Analyses of Compounds 5, 6, and 7
5
6
7
empirical formula
CCDC No.
T [K]
C35H46GeN2O
715867
133(2)
orthorhombic
Pnma
16.597(3)
20.695(4)
9.2831(19)
C35H41F5GeN2O
715868
133(2)
monoclinic
P21/n
13.162(3)
19.533(4)
13.519(3)
90
103.49(3)
90
3379.8(12)
4
1.323
0.963
1400
C36H46GeN2O2
715869
133(2)
monoclinic
P21/c
18.371(4)
10.627(2)
16.940(3)
90
96.28(3)
90
3287.4(11)
4
1.235
0.965
1296
cryst syst
space group
˚
a [A]
˚
b [A]
˚
c [A]
R [deg]
β [deg]
γ [deg]
90
90
90
3188.5(11)
4
1.215
0.989
1240
3
˚
V [A ]
Z
Dcalcd [g cm-3
]
μ [mm-1
F(000)
]
θ range [deg]
reflns collected
indep reflns
1.97-25.95
11 672
3120
1.87-26.99
30 456
7330
2.22-26.96
31 397
7131
data/restraints/params
reflns collected/unique
R1, wR2 [I > 2σ(I)]a
R1, wR2 (all data) a
GoF
3010/0/192
11 672/3120[R(int) = 0.0839]
0.0747, 0.1429
0.1107, 0.1557
1.062
7330/0/431
30 456/7330[R(int) = 0.0506]
0.0329, 0.0740
0.0482, 0.0784
0.942
7131/0/383
31 397/7131[R(int) = 0.0802]
0.0478, 0.0867
0.0746, 0.0939
1.025
-3
˚
ΔF(max), ΔF(min) [e A
]
2.084, -0.699
0.495, -0.499
0.631, -0.588
P
P
P
P
a R1 = ||Fo| - |Fc||/ |Fo|. wR2 = [ w(F2o - Fc2)2/ w(F2o)2]0.5
.
˚
Figure 2. Molecular structure of 5. Selected bond lengths [A] and
angles [deg]; anisotropic displacement parameters are depicted
at the 50% probability level and all restrained refined
hydrogen atoms are omitted for clarity: Ge1-O1 1.860(4), Ge1-
N1 2.008(3), N1-C17 1.314(5), O1-C1 1.360(7); N1-Ge1-
N1A 88.67(16), N1-Ge1-O1 93.88(12), Ge1-O1-C1 117.5(4).
˚
Figure 3. Molecular structure of 6. Selected bond lengths [A] and
angles [deg]; anisotropic displacement parameters are depicted at
the 50% probability level and all restrained refined hydrogen
atoms are omitted for clarity: Ge1-O1 1.9515(14), Ge1-N1
1.9785(16), N1-C19 1.338(2), O1-C1 1.319(2); N1-Ge1-N2
90.85(6), N1-Ge1-O1 91.11(6), Ge1-O1-C1 129.25(12).
solvent drying system. Compound LGeCl (1) was prepared by a
literature procedure.1 Other chemicals were purchased commercially
and used as received.1H, 13C, and 19F NMR spectra were recorded on
a Bruker 500 MHz instrument and referenced to the deuterated
solvent in the case of the 1H and 13C NMR spectra. 19F NMR spectra
Colorless crystals of 2 were formed after two days. Yield: 0.575 g
(90%); mp 216 °C. 1H NMR (500 MHz, C6D6): δ 7.06-7.15 (m, 6H,
Ar-H), 5.58 (s, 1H, γ-CH), 3.27 (sept, 4H, CH(CH3)2), 1.68 (s, 6H,
CH3), 1.19 (d, 12H, CH(CH3)2), 1.15 (d, 12H, CH(CH3)2) ppm.
13C{1H} NMR (125.75 MHz, C6D6): δ 167.45 (CN), 145.75, 137.91,
125.63 (Ar-C), 120.9 (CF3), 106.39 (γ-C), 25.81 (CHMe2), 24.27
(CHMe2), 23.03 (Me) ppm. 19F{1H} NMR (188.28 MHz, C6D6):
δ -76.5 ppm. EI-MS: m/z (%) 640 (100) [M+]. Anal. Calcd for
were referenced to CFCl3. Elemental analyses were performed by the
::
Analytisches Labor des Instituts fur Anorganische Chemie der
::
::
Universitat Gottingen. Mass spectra were obtained on a Finnigan
Mat 8230 instrument. Melting points were measured in a sealed glass
tube and are not corrected.
C
30H41F3GeN2O3S (640.20): C, 56.36; H, 6.46; N, 4.38; S, 5.02.
Found: C, 56.55; H, 6.93; N, 4.35; S, 5.02.10
Synthesis of [{HC(CMeNAr)2}Ge(II)OSO2CF3] (Ar = 2,6-
iPr2C6H3) (2). A solution of 1 (0.52 g, 1 mmol) in toluene (15 mL)
was added drop by drop to a stirred suspension of AgOSO2CF3
(0.26 g, 1 mmol) in toluene (10 mL) at room remperature. The
solution was stirred for an additional 2 h. After filtration the filtrate
was concentrated to about 10 mL and stored in a -30 °C freezer.
Synthesis of [CH{(CdCH2)(CMe)(Ar)}2Ge] (Ar = 2,6-
iPr2C6H3) (3). 1,3-Di-tert-butylimidazol-2-ylidene (0.360 g, 2.0 mmol)
and 2 (1.280 g, 2.0 mmol) were dissolved in toluene (30 mL) at
room temperature. The reaction mixture was stirred, and the
color of the solution changed from colorless to brown-red. A white

3766 Organometallics, Vol. 28, No. 13, 2009
Jana et al.
CH(CH3)2), 1.10 (d, 6H, CH(CH3)2), 1.06 (d, 6H, CH(CH3)2) ppm.
13C{1H} NMR (125.77 MHz, C6D6): δ 164.23 (CN), 162.34 (CO),
146.64, 143.91, 140.19, 129.34, 125.11, 124.26, 119.94, 118.46 (Ar-C),
98.38 (γ-C), 29.15 (CH(CH3)2), 28.37 (CH(CH3)2), 25.85 (CH-
(CH3)2), 25.29 (CH(CH3)2), 24.64 (CH(CH3)2), 24.59 (CH(CH3)2),
23.26 (CH3) ppm. EI-MS (70 eV): m/z (%) 491 (100) [M - OPh]+
.
Anal. Calcd for C35H46GeN2O (583.39): C, 72.06; H, 7.95; N, 4.80.
Found: C, 71.00; H, 7.53; N, 4.76.
6. C6F5OH (0.190 g, 1 mmol) and 3 (0.490 g, 1 mmol). Yield:
0.540 g (80%); mp 155 °C. 1H NMR (500 MHz, C6D6): δ 6.99-7.10
(m, 6H, Ar-H ), 5.10 (s, 1H, γ-CH), 3.48 (sept, 2H, CH(CH3)2), 3.05
(sept, 2H, CH(CH3)2), 1.55 (s, 6H, CH3), 1.18 (d, 6H, CH(CH3)2),
1.11 (d, 6H, CH(CH3)2), 1.03 (d, 6H, CH(CH3)2), 0.88 (d, 6H, CH-
(CH3)2) ppm. 13C{1H} NMR (125.77 MHz, C6D6): δ 164.69 (CN),
146.15, 143.91, 143.78, 139.89, 137.83, 129.27, 128.50, 125.63, 125.09,
124.33, 123.54 (Ar-C), 100.71 (γ-C), 29.27 (CH(CH3)2), 28.03 (CH-
(CH3)2), 25.49 (CH(CH3)2), 24.79 (CH(CH3)2), 24.44 (CH(CH3)2),
24.09 (CH(CH3)2), 23.38 (CH3) ppm. 19F{1H} NMR (188.31 MHz,
C6D6): δ -158.8 (d, 6F, o-F), -166.9 (t, 6F, m-F), -175.2 (t, 3F, p-F ).
EI-MS (70 eV): m/z (%) 673 (100) [M]+
35H41F5GeN2O (673.34): C, 62.43; H, 6.14; N, 4.16. Found:
C, 62.24; H, 6.05; N, 4.16.
.
Anal. Calcd for
˚
Figure 4. Molecular structure of 7. Selected bond lengths [A] and
angles [deg]; anisotropic displacement parameters are depicted at
the 50% probability level and all restrained refined hydrogen
atoms are omitted for clarity: Ge1-O1 1.9462(19), Ge1-N1
1.978(2), O1-C1 1.311(3), C1-O2 1.216(3); N1-Ge1-N2
90.48(9), N1-Ge1-O1 89.43(8), O1-C1-O2 125.0(3).
C
7. PhCO2H (0.122 g, 1 mmol) and 3 (0.490 g, 1 mmol). Yield:
0.520 g (85%); mp 167 °C. 1H NMR (500 MHz, C6D6): δ 6.99-8.44
(m, 11H, Ar-H ), 5.16 (s, 1H, γ-CH ), 3.61 (sept, 2H, CH(CH3)2), 3.17
(sept, 2H, CH(CH3)2), 1.61 (s, 6H, CH3), 1.21 (d, 6H, CH(CH3)2),
1.13 (d, 6H, CH(CH3)2), 1.07 (d, 6H, CH(CH3)2), 1.05 (d, 6H, CH-
(CH3)2) ppm. 13C{1H} NMR (125.77 MHz, C6D6): δ 165.00 (CN),
161.49 (CCO), 146.45-123.55 (Ar-C), 99.76 (γ-C), 94.24 (CO), 29.35
(CH(CH3)2), 28.60 (CH(CH3)2), 26.52 (CH(CH3)2), 24.67 (CH-
(CH3)2), 24.53 (CH(CH3)2), 24.08 (CH(CH3)2), 23.44 (CH3) ppm.
EI-MS (70 eV): m/z (%) 612 (100) [M]+. Anal. Calcd for C36H46Ge-
N2O2 (611.40): C, 70.72; H, 7.58; N, 4.55. Found: C, 70.11; H, 7.52;
N, 4.55.
precipitate was formed. The reaction mixture was stirred for another
hour, then the white precipitate was separated by filtration and the
remaining red solution was evaporated. The residue was dissolved in n-
hexane (20 mL). Storage of this solution at -30 °C for one day in a
freezer yielded brown-red crystals. Yield: 0.880 g (90%).5,8a
Synthesis of [{HC(CMeNAr)2}Ge(II)OH] (Ar = 2,6-iPr2C6H3)
(4). Water (18 μL, 1 mmol) was added to a red solution of
3 (0.490 g, 1 mmol) in toluene (20 mL) under stirring at room
temperature. The reaction mixture became yellow. Stirring of
the reaction mixture was continued for about 15 min. After that,
the solvent was removed under vacuum and the residue was extracted
with n-hexane (15 mL). The solution was reduced to half of the
volume. Storage of the solution at -30 °C for one day in a freezer
yielded yellow crystals. Yield: 0.480 g (95%).3
Crystallographic Details for Compounds 5, 6, and 7. Suitable
crystals of 5, 6, and 7 were mounted on a glass fiber, and data were
collected on an IPDS II Stoe image-plate diffractometer (graphite-
˚
monochromated Mo KR radiation, λ = 0.71073 A) at 133(2) K. The
data were integrated with X-Area. The structures were solved by
direct methods (SHELXS-97)13 and refined by full-matrix least-
squares methods against F2 (SHELXL-97).13 All non-hydrogen
atoms were refined with anisotropic displacement parameters. Crys-
tallographic data are presented in Table 1.
Synthesis of Compounds 5, 6, and 7. Compounds 5-7 are
prepared in a similar way using different RH precursors.
5. A 10 mL toluene solution of phenol (0.095 g, 1 mmol) was added
to a solution of 3 (0.490 g, 1 mmol) in toluene (20 mL) under stirring at
room temperature, and the color of the solution changed immediately
from red to colorless. After 30 min all the volatiles were removed
under vacuum and the residue was extracted with n-hexane (30 mL)
and concentrated to give colorless crystals of 5 after two days, which
were suitable for X-ray structural analysis. Yield: 0.475 g (82%); mp
203 °C. H NMR (500 MHz, C6D6): δ 6.63-7.13 (m, 11H, Ar-H ),
4.98 (s, 1H, γ-CH ), 3.77 (sept, 2H, CH(CH3)2), 3.27 (sept, 2H, CH-
(CH3)2), 1.60 (s, 6H, CH3), 1.28 (d, 6H, CH(CH3)2), 1.18 (d, 6H,
Acknowledgment. We are thankful to Dr. Michael John
for NMR measurements and the Deutsche Forschungs-
gemeinschaft for financial support.
Supporting Information Available: X-ray data for 5, 6, and 7
(CIF). This material is available free of charge via the Internet at
http://pubs.acs.org.
1
(13) Sheldrick, G. M. Acta Crystallogr., Sect. A 2008, 64, 112–122.