Novel germanium(II) binaphthoxide complexes

Article abstract of DOI:10.1039/b204299a

The germanium(II) bisamide Ge[N(SiMe₃)₂]₂ reacts with the substituted binaphthols (R)-[(HO)₂C₂₀H₁₀(R) ₂-3,3′] (R = SiMe₃, SiMe₂Ph, SiMePh₂, or Si

Full text of DOI:10.1039/b204299a

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Novel germanium(II) binaphthoxide complexes: synthesis and
crystal structure of (R,R)-[Ge{OC H (OSiMe )-2Ј-(SiMe ) -
2
0
10
3
3 2
3
,3Ј} ] and (R)-[Ge{O C H (SiMe Ph) -3,3Ј}{NH }]; catalytic
2
2
20 10
2
2
3
function of Ge[N(SiMe ) ] for the mono-silylation of
3
2 2
3
,3Ј-disubstituted-1,1Ј-bi-2,2Ј-naphthols
Charles S. Weinert,* Phillip E. Fanwick and Ian P. Rothwell*
Department of Chemistry, Purdue University, 1393 Brown Building, West Lafayette, IN,
4
7907-1393, USA. E-mail: rothwell@purdue.edu
Received 3rd May 2002, Accepted 24th June 2002
First published as an Advance Article on the web 11th July 2002
The germanium(II) bisamide Ge[N(SiMe ) ] reacts with
3
2 2
the substituted binaphthols (R)-[(HO) C H (R) -3,3Ј]
2
20 10
2
(
R ؍ SiMe , SiMe Ph, SiMePh , or SiPh ) to yield two
3 2 2 3
novel germanium(II) binaphthoxide complexes; Ge[N-
SiMe ) ] also catalytically silylates one of the hydroxyl
(
3
2 2
groups of (R)-[(HO) C H (SiMe ) -3,3Ј] to yield (R)-
2
20 10
3 2
HOC H -(OSiMe )-2Ј-(SiMe ) -3,3Ј.
20
10
3
3 2
Aryloxide complexes of germanium() are unusual, although
1
many such compounds are known for germanium().
Structurally characterized examples include Ge(OC H Me-4-
6
2
t
2
2
3
Bu -2,6) , and [Fe(CO) {Ge(OC H Bu -2,6-Me-4) }]. We
2
4
6
2
2
2
have begun an investigation into the inorganic and organo-
metallic chemistry that can be supported by resolved
3
,3Ј-disubstituted-1,1Ј-bi-2,2Ј-naphthol as a ligand with metal
4,5
complexes of tantalum. We now wish to report the prepar-
ation and structure of two novel germanium binaphthoxide
complexes, (R,R)-[Ge{OC H (OSiMe )-2Ј-(SiMe ) -3,3Ј} ] (1)
and (R)-[Ge{O C H (SiMe Ph) -3,3Ј}{NH }] (2) and the
catalytic activity of Ge[N(SiMe ) ] for the selective silylation
20
10
3
3
2
2
2
20 10
2
2
3
3
2 2
of one hydroxyl group of (R)-[(HO) C H (R) -3,3Ј] (R =
2
20 10
2
6
SiMe 3; SiMe Ph 4; SiMePh 5; SiPh 6).
3
2
2
3
7
The germanium bisamide Ge[N(SiMe ) ] reacts with two
3
2 2
1
4
equivalents of (R)-[(HO) C H (SiMe ) -3,3Ј] (3) over 12 h in
Fig. 1 ORTEP plot of compound 1. Thermal ellipsoids are drawn at
2
20 10
3 2
the 50% probability level.
benzene to produce complex 1 in 32% overall yield.† Complex 1
readily crystallizes out of solution even at 85 ЊC to produce
crystals suitable for X-ray analysis.‡ An ORTEP plot of 1 is
shown in Fig. 1. The two binaphthoxide ligands are bound to
the germanium metal center though a single oxygen atom. A
trimethylsilyl group has been transferred to the second oxygen
atom. The O–Ge–O angle is 89.4(7)Њ, which is close to the
expected value of 90Њ, and the average Ge–O bond length has a
8
typical value of 1.814(2) Å.
In a separate experiment, reaction of Ge[N(SiMe ) ] with
3
2 2
two equivalents of (R)-[(HO) C H (SiMe Ph) -3,3Ј] (4) led to
2
20 10
2
2
the formation of complex 2 in 20% yield.§ Complex 2 also
readily crystallizes out of solution, and an X-ray structure was
obtained.¶ An ORTEP plot of 2 is shown in Fig. 2. Complex 2
contains only one binaphthoxide ligand chelated to the germ-
anium center in a bidentate fashion through both oxygen atoms
as well as a coordinated ammonia molecule. The NH is the
3
result of the double desilylation of HN(SiMe ) , a conversion
3
2
which has been reported in reactions of HN(SiMe ) with a
3
2
9
silica surface. The environment about the central germanium
atom is distorted trigonal pyramidal, which has also been
found for other three-coordinate divalent germanium species.
The O–Ge–O bond angle in 2 is 97.90(9)Њ, and the O–Ge–N
bond angles have values of 96.2(1) and 81.6(2)Њ. The average
Ge–O bond distance is 1.862(2) Å and the Ge–N bond dis-
tance is 2.093(4) Å, which is similar to distances found in
other three-coordinate germanium species with a neutral
Fig. 2 ORTEP plot of compound 2. Thermal ellipsoids are drawn at
the 50% probability level.
2
948
J. Chem. Soc., Dalton Trans., 2002, 2948–2950
This journal is © The Royal Society of Chemistry 2002
DOI: 10.1039/b204299a

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Scheme 1 Proposed pathway for the silylation of 3 to 7.
1
0–12
N-donor ligand.
Complexes 1 and 2 are the first examples
by reaction of 7 with Ge[N(SiMe ) ] or one of the inter-
3 2 2
of germanium binaphthoxide compounds.
The reaction of a 1 : 1 molar ratio of HN(SiMe ) and 3
in the presence of a catalytic amount of Ge[N(SiMe ) ]
mediate germanium amides which result after all the reactant
HN(SiMe ) has been consumed.
3
2
3 2
Compound 7 can be generated on a preparative scale by this
process.|| Reaction of HN(SiMe ) with 3 in the presence of
3
2 2
(
10 mol%) in C D6 was monitored by NMR spectroscopy.
6
3 2
Compound 3 is catalytically mono-silylated to form (R)-
(HO)C H (OSiMe )-2Ј-(SiMe ) -3,3Ј] (7). A proposed path-
10 mol% Ge[N(SiMe ) ] generated 7 in pure form in 70%
3 2 2
1 13
[
yield. The composition of 7 was confirmed by H and C NMR
spectroscopy and mass spectrometry. Compound 7 is a new
species, and these studies represent the first catalytic silylation
of a binaphthoxide compound using a metal() bisamide.
The reaction of 4 with HN(SiMe ) can also be catalyzed
20
10
3
3 2
way is shown in Scheme 1. After 2 h at 85 ЊC, all of 3 had been
silylated to compound 7, as indicated by three alkylsilyl features
at δ 0.51, 0.48, and Ϫ0.30 ppm as well as a hydroxyl peak at
δ 5.11 ppm. The same features were observed upon exposing
an NMR tube containing 1 to atmospheric moisture, which
results in the hydrolysis of 1 to 7 and an uncharacterized
oxidized germanium species. The catalytic conversion of 3 to
3
2
using Ge[N(SiMe ) ] . An NMR scale reaction shows that 4 is
3
2 2
converted to [(HO)C H (OSiMe )-2Ј-(SiMe Ph) -3,3Ј] (8).
20
10
3
2
2
However, the reaction does not proceed as rapidly. After two
hours at 85 ЊC, 3% of binol 4 remains. Neither heating for an
additional 6 h nor addition of excess HN(SiMe ) drives the
7
is complete at room temperature after 6 hours.
When an excess of HN(SiMe ) was used (3.5 equivalents) all
3
2
3 2
of 3 was silylated to 7 after 2 hours with heating. Addition of 3
reaction to completion. A larger (preparative) scale reaction
was carried out which resulted in only 50% conversion of 4 to 8.
Thus, it is not surprising that complex 2, which contains a
bidentate binaphthoxide ligand, was generated in this reaction
instead of a species similar to 1. The presence of a bulkier
dimethylphenyl group relative to a trimethylsilyl group appears
to have an effect on the progress of the silylation reaction.
To further investigate this postulate, Ge[N(SiMe ) ] was
until the molar ratio with HN(SiMe ) was 1 : 1 led to complete
3
2
conversion to 7 after 4 hours. Further addition of 3 led to a
decrease in activity, and when the molar ratio of 3 to the initial
amount of HN(SiMe ) was 2 : 1, the reaction had stopped.
3
2
Furthermore, the hydroxyl resonance of 7 had broadened and
shifted progressively downfield to a final value of 5.57 ppm.
This is most likely due to hydrogen bonding with the ammonia
generated in the reaction. Complex 1 is likely generated
3
2 2
reacted with the bulkier binol [(HO) C H (SiMePh ) -3,3Ј]
2
20 10
2 2
J. Chem. Soc., Dalton Trans., 2002, 2948–2950
2949

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Ϫ1
(
5). Upon heating a solution of Ge[N(SiMe ) ] and two equiv-
1140.0, λ = 0.71073 Å, T = 150(1) K, µ(Mo-Kα) = 0.673 mm , crystal
3
2 2
dimensions 0.45 × 0.30 × 0.28 mm, 10.00 ≥ 2θ ≤ 54.97Њ; 29283 reflec-
alents of 5 at 85 ЊC for 12 h, a substantial amount of the start-
ing binol 5 remained. Two hydroxyl resonances were observed
at δ 4.70 and 4.85 ppm in a ratio of 96 : 4, indicating only a
small amount of 5 had been silylated. Intense peaks at δ 0.98
tions (12785 independent, R = 0.059), maximum residual electron
int
Ϫ3
2
2
o
density: 0.47 e Å , R = 0.037 (for Fo > 2σ(F )) and wR = 0.082 (all
1
2
2
2
c
2
2 2 1/2
data) with R = Σ||F | Ϫ |F ||/Σ|F | and wR = [Σ w(|F | Ϫ |F |) /Σw|F | ]
.
1
o
c
o
2
o
o
CCDCreferencenumber176939.
§ Preparation of 2: The same procedure for 1 was used for 2, using
.19 g (0.48 mmol) of Ge[N(SiMe ) ] and 0.53 g (0.96 mmol)
and 8.06 ppm also correspond to the SiMePh group and the
2
4
,4Ј-hydrogens of 5, respectively. Weak resonances at δ 8.10 and
Ϫ0.66 ppm were also observed, which also suggests that some
(HO)C H (OSiMe )-2Ј-(SiMePh ) -3,3Ј] had been formed.
0
3
2 2
1
(R)-[H O C H (SiMe Ph) -3,3Ј]. Yield: 0.65 g of 2 (20%). H NMR
2
2
20 10
2
2
3
[
(C D ): δ 8.18 (s, 2 H, 4,4Ј hydrogens), 7.79 (d, J(H,H) = 8.1 Hz, 2 H,
6 6
3
20
10
3
2
2
No new products were observed in the reaction of Ge[N-
SiMe ) ] with (R)-[(HO) C H (SiPh ) -3,3Ј] (6) after heating
6,6Ј hydrogens), 7.58 (m, 4 H, aromatics), 7.35 (d, J(H,H) = 8.4 Hz,
,8Ј hydrogens), 7.14–7.08 (m, 10 H, aromatics), 6.94–6.92 (m, 2 H,
aromatics), 0.75 (s, 6 H, –SiCH Ph), 0.68 (s, 6 H, –SiCH Ph) ppm.
8
(
3
2 2
2
20 10
3 2
for 48 h at 85 ЊC. Thus, the steric bulk of the binol complex
plays a role in the ability of the germanium bisamide to carry
out the silylation reaction.
2
2
¶
Crystal data for 2: C H GeNO Si , M = 642.45, orthorhombic,
36 35 2 2 r
space group P2 2 2 , a = 8.3277(2), b = 10.4652(3), c = 36.0635(8) Å, V =
1
1 1
3
Ϫ3
3
T
143.0(2) Å , Z = 4, ρ = 1.358 g cm , F(000) = 1336.0, λ = 0.71073 Å,
calc
Ϫ1
In order to determine the necessity of the germanium metal
= 150(1) K µ(Mo-Kα) = 1.067 mm , crystal dimensions
center in this process, a 1 : 1 molar ratio of HN(SiMe3)2
0.13 × 0.10 × 0.10 mm, 10.00 ≥ 2θ ≤ 54.99; 20161 reflections (6841
and [(HO) C H (SiMe ) -3,3Ј] was heated in an NMR tube
for 72 hours at 85 ЊC, after which time approximately 30%
of [(HO) C H (SiMe ) -3,3Ј] had been converted to [(HO)-
C H (OSiMe )-2Ј-(SiMe ) -3,3Ј]. Thus, the presence of the
germanium metal center significantly increases the rate of the
silylation reaction. Silylation of other acidic alcohols using
HN(SiMe ) has been reported using ZnCl as the catalyst.
Other metal() bisamides also appear to silylate a hydroxyl
group of 3 with metal-dependant reactivity. Two equivalents
of binol 3 were reacted with both Sn[N(SiMe )2]2 and
Zn[N(SiMe ) ] to give metal binol complexes as evidenced by
NMR spectroscopy. These metal() bisamides also appear to
function as silylation catalysts. Compound 3 is converted to 7
with the zinc compound within 30 minutes at room temperature
and 10 minutes when heated at 85 ЊC. The tin complex converts
independent, R = 0.072), maximum residual electron density: 0.31 e
2
20 10
3
2
int
Ϫ3
Å , R = 0.044 and wR = 0.077. CCDC reference number 176940. See
1
2
http://www.rsc.org/suppdata/dt/b2/b204299a/ for crystallographic data
in CIF or other electronic format.
2
20 10
3 2
20
10
3
3 2
|
| Preparation of 7: To a solution of 0.55 g (1.3 mmol) of (R)-
H O C H (SiMe ) -3,3Ј] in 10 mL of benzene was added HN(SiMe )
3 2
(0.27 mL, 0.21 g, 1.3 mmol) and Ge[N(SiMe ) ] (0.050 g, 0.13 mmol).
[
2
2
20 10
3
2
13
3 2 2
3
2
2
The solution was heated in a sealed flask for 12 h, and the flask was
opened in air after cooling. A white suspension resulted after stirring in
air for 30 min, which was filtered through Celite. The solvent was
removed from the filtrate resulting in a white solid. Yield: 0.4 g (70%).
3
1
3
H NMR (C D ): δ 8.15 (s, 1 H), 8.12 (s, 1 H), 7.74 (d, 1 H, J(H,H) =
3
2 2
6
6
3
9.0 Hz), 7.70 (d, 1 H, J(H,H) = 9.0 Hz), 7.28–6.94 (aromatics, 6 H),
5
.11 (s, –OH ), 0.51 (s, 9 H, –OSiCH ), 0.48 (s, 9 H, –SiCH ), Ϫ0.30 (s, 9
3 3
13
H, –SiCH ) ppm. C NMR (C D ): δ 158.0, 157.0, 139.1, 137.8, 136.0,
3
6
6
1
1
35.8, 130.8, 130.2, 130.0, 129.2, 129.0, 128.9, 127.7, 125.9, 125.8,
25.0, 123.9, 117.6, 115.4, 1.3, 0.5, Ϫ0.3 ppm. HRMS: Calc. for
3
to 7 only after heating for 12 hours. Thus, the identity of the
C H O Si : m/z 502.2180. Found: m/z 502.2180.
2
9
38
2
3
metal appears to play an important role in the rate of the silyl-
ation reaction (Scheme 1). Further studies of the reactivity of
these metal() amides are underway.
1
D. C. Bradley, R. C. Mehrotra, I. P. Rothwell and A. Singh, Alkoxo
and Aryloxo Derivatives of Metals, Academic Press, New York,
2
001 .
P. Cullis, S. Kirkman and R. Wolfenden, J. Am. Chem. Soc., 1980,
02, 2088.
2
3
4
5
Acknowledgements
1
P. B. Hitchcock, M. F. Lappert, S. A. Thomas, A. Thorne, A. J.
Carty and N. J. Taylor, J. Organomet. Chem., 1986, 315, 27.
M. G. Thorn, J. E. Moses, P. E. Fanwick and I. P. Rothwell, J. Chem.
Soc., Dalton Trans., 2000, 2659.
The United States Department of Energy is gratefully
acknowledged.
C. S. Weinert, P. E. Fanwick and I. P. Rothwell, Organometallics,
Notes and references
2
002, 21, 484.
†
in
Preparation of 1: To a solution of Ge[N(SiMe ) ] (0.63 g, 1.6 mmol)
6 G. J. H. Buisman, L. A. van der Veen, A. Klootwijk, W. G. J.
de Lange, P. C. J. Kamer, P. W. N. M. van Leeuwen and D. Vogt,
Organometallics, 1997, 16, 2929.
3
2 2
5 mL of benzene was added 1.37 g (3.18 mmol) of (R)-
[
H O C H (SiMe ) -3,3Ј] in 5 mL benzene dropwise over 5 min. The
2 2 20 10 3 2
mixture was heated at 85 ЊC in a sealed flask for 12 h, after which time
yellow crystals had precipitated. The crystals were isolated by filtration,
washed with benzene (3 × 5 mL) and pentane (3 × 5 mL) and dried
in vacuo. Yield: 0.51 g (32%). Anal. calc. for C H O Si Ge: C, 64.72;
7 D. H. Harris and M. F. Lappert, J. Chem. Soc., Chem. Commun.,
1974, 895.
8 K. M. Baines and W. G. Stibbs, Coord. Chem. Rev., 1995, 145, 157.
9 V. M. Gun’ko, M. S. Vedamuthu, G. L. Henderson and J. P. Blitz,
J. Colloid Interface Sci., 2000, 228, 157.
10 S. Suh and D. M. Hoffman, Inorg. Chem., 1996, 35, 6164.
11 P. Jutzi, S. Keitemeyer, B. Neumann and H. G. Stammler, Organo-
metallics, 1999, 18, 4778.
12 S. Benet, C. J. Cardin, D. J. Cardin, S. P. Constantine, P. Heath, H.
Rashid, S. Teixeira, J. H. Thorpe and A. K. Todd, Organometallics,
1999, 18, 389.
5
8
74
4
6
1
H, 6.93. Found: C, 63.44; H, 6.83%. H NMR (C D ): δ 8.16 (s, 2 H, 4,4Ј
6
6
3
hydrogens), 7.69 (d, 2 H, J(H,H) = 8.1 Hz, 6,6Ј hydrogens), 7.46 (d,
H, J(H,H) = 8.1 Hz, 8,8Ј hydrogens), 7.28–6.83 (aromatics, 14 H),
.68 (s, 9 H, –OSiCH ), 0.24 (s, 18 H, –SiCH ), Ϫ0.28 (s, 18 H, –SiCH )
3
2
0
3
3
3
1
3
ppm. C NMR (C D ): δ 157.3 (C–O–Ge), 138.2 (C–O–SiMe ), 134.9,
6
6
3
1
29.8, 128.9–126.8 (aromatics), 124.3 (C–SiMe ), 123.9 (C–SiMe ), 5.4
3
3
(
OSiCH ), 2.8 (SiCH ), Ϫ0.6 (SiCH ) ppm.
3
3
3
‡
Crystal data for 1: C H GeO Si , M = 1076.34, monoclinic, space
13 H. Firouzabadi and B. Karimi, Synth. Commun., 1993, 23, 1633.
14 M. N. Burnett and C. K. Johnson, ORTEP3, Report ORNL-6895,
Oak Ridge National Laboratory, Oak Ridge, TN, 1996.
5
8
74
4
6
r
group P2 , a = 11.0695(2), b = 21.0832(4), c = 12.8046(3) Å, β =
1
3
Ϫ3
9
9.7148(8), V = 2945.2(2) Å , Z = 2, ρ = 1.214 g cm , F(000) =
calc
2
950
J. Chem. Soc., Dalton Trans., 2002, 2948–2950