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Tetrakis(tri-tert-butylsilyl)-tetrahedro-tetragermane (tBu3Si)4Ge4ЧThe First Molecular Germanium Compound with a Ge4 Tetrahedron.

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P. Selg. H H . Brintringer. R. A. Andersen, I Horvith. Arigeir. C/IPI?I.
1995.
107. 877. An,qeii. Cheni. Int. Ed. Engl. 1995. 34. 791.
Further derails of the crystal structure investigation are available on request
from the F3chinformationszentrum Karlsruhe. D-76344 Eggenstein-Leopoldshafen (Germany). on quoting the depository number CSD-404624.
a ) <i M Sheldrick. SHELXTL-Plus. Rel. 5.03. Siemens Analytical X-ray Instruments Inc.. Madison. Wisconsin. 1995. b) C. K . Johnson. ORTEP 11: a
Fortran Thermal-Ellipsoid Plot Program for Crystal Structure Illustrations.
ORNL-513X. Oak Ridge National Laboratory. Oak Ridge. TN. U S A . March
1976.
After submission of this paper. we learned that Prof. G. Thiele. Universitit
Freiburg. Germany. and his group had obtained complementary crystallographic data on single crystals of solvated (benzene or chloroform) [Pd,CI,,].
grohn ,it room temperature from the corresponding solutions Satisfactory
agreement has heen found between the sets of data obtained independently in
the two laboratories. We thank Prof. G. Thiele for communicating his results
prior t o publication.
Tetrakis(tri-tevt-butylsily1)-tetrahedvotetragermane (tBu,Si),Ge,-The
First Molecular
Germanium Compound with a Ge, Tetrahedron**
Nils Wiberg,* Walter Hochmuth, Heinrich Noth,
Andrea Appel, and Martin Schmidt-Amelunxen
According to a b initio calculations,". 21 the strain energy of
(EH), polyhedra (E = Si, Ge) increases with the number of the
three-membered rings in the framework of the polyhedron, thus
in the order /zc~rahedro-octasilane(-germane) A, triprismo-hexasilane (-germane) B, and tetrn/zedro-tetrasilane (-germane)
In an effort to obtain a molecular germanium compound with
a Ge, tetrahedron by an analogous route, we treated tetrachloro-l,2-bis(supersilyl)digermane fBu,Si-GeC1,-GeC12SitBu, (4). which formed from GeCI, and tBu,SiNa in T H F at
room temperature along with other products (tBu,SiGeCI, ,
(tBu,Si),GeCI,, (tBu,Si), , tBu,SiCI), and was characterized by
X-ray crystallography, with tBu,SiNa in T H F at - 78 'C. This
reaction led to the tetrnhedro-tetragermane 2 in low yield
[Eq. (b)] together with other products containing supersilyl
groups that are also formed in the reaction of GeCI,.C,H,O,
and tBu,SiNa (see below). Compound 4 reacts with sodium in
C,D, at room temperature initially to give the tetrahedrane 2,
which is, however, attacked by sodium; one of the resulting
products, namely rBu,SiNa, reacts as described with unconverted 4.@]rBu,SiNa reacts with GeCl,.C,H,O, in T H F via a series
of-in part isolable-intermediates['l likewise to give 2 and additional products [Eq. (c)].
-4
c&o2
The tetragermane 2 forms intense red crystals, which are hydrolyzed slowly by water, and are rapidly oxidized by air. Compound 2 can be reduced with sodium; among the products of the
reaction is tBu,SiNa, which can be identified by conversion with
Me,SnCI into tBu,Si-SnMe,.
So far we have only been able to obtain crystals suitable for
X-ray diffraction[' 21 from solutions prepared according to
Equation (c) after exchanging T H F by pentane. However, in
addition to 2 these contain superdisilane tBu,Si -SitBu,," 'I
which fills the large holes between the almost spherical molecules of 2 in the crystal, and thereby stabilizes the structure of
the crystal. The monoclinic unit cell of the crystals with the
composition 2(tBu,Si),Ge, '(tBu,Si), (2a) contains four molecules of 2 and-in the cavities-two molecules of rBu,Si-SitBu, (Fig. 1 ) . The building unit 2 in the crystal of 2a contains
almost regular G e tetrahedra (Fig. 2). The Ge- G e (av. 2.44 A)
and Ge-Si (2.38
distances are slightly longer than those in
H,Ge-GeH, (2.41 A[',]) and H,Ge-SiH, (2.36 A['31), respectively; for comparison Si-Si distances in 1 are 2.35 (endo) and
2.37 8, ( e ~ o ) in
, ~H,Si-SiH,
~~
and Me,Si-SiMe, 2.331 and
The fact that tBu,Si-SitBu, in crystals
2.338 A. respecti~ely['~].
1)
Consequently. initially the hexahedranes (ER), (E/R =
Si/SiMe,tB~.[~"l Si/CMe2iPr,[4b1 Si/2,6-C,H,Et,.[4c1 Ge/
CMeEt, ,I4'] Ge/2,6-C,H,Et214c]) and triprismanes (ER),
(E/R = Si/2,6-C,H3iPr, ,[4e1
Ge/CH(SiMe,), ,[4d1
Ge/2,6C,H,iPr,[4e1) were obtained. We synthesized the first molecular
silicon compound I with a Si, t e t r a h e d r ~ n ~by~ .the
~ ] reaction
of tetrabromo-l.2-bis(supersilyl)disilane tBu,Si -SiBr2 - SiBr, SitBu, (3) with supersilylsodium tBu,SiNa in tetrahydrofuran
(THF) [Eq. (a); supersilyl = SitBu,[']].
R
R-EX-
EX2- R
+2RNa
-2RX-2NaX
I
R
3.4
(a) E = Si; X = Br
(b) E = a;
x = C]
R = SitBu3
1, E = S i
2. E = G e
[*] Prof. Dr. N . Wiherg, DipLChem. W. Hochmuth. Prof. Dr. H. Noth.
DiplLChem A. Appel. Dr. M. Schmidt-Amelunxen
lnstitut fur Anorgdnische Chemie der Universitil
Meiserstrass~.I . D-80333 Munchen (Germany)
Fax. Int. code +(89)5902-578
[**I Compounds of Silicon and Its Group Analogues Part 108; Stencally Overlodded Supersilyl Compounds. Part 10. This work was supported by the Deutsche
Forschunpsgemeinschdft. Part 107 and 9: Ref 131.
Fig. 1. Perspective view of the monoclinic unit cell of 2 a along the c axis.
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Fig. 2. Structure o f 2 in the crystal Za (ORTEP plot). Selected bond lengths [A] and
angles ["I: Gel-Ge2 2.447(2), Ge2-Ge3 2.446(2). Ge3-Ge4 2.443(3), Gel-Ge4
2.431(2), Gel-Ge3 2.447(2), Ge2-Ge4 2.435(2), Gel-Sil 2 385(4). Ge2-Si2 2.385(4),
Ge3-Si3 2.378(4), Ge4-Si4 2.383(4), Si-C (av) 1.94; Ge-Ge-Ge 59 62(7)-60.10(7).
Sil-Gel-Ge4 142.3(1). Si2-GeZ-Ge4 141.4(1), Si1-Gel-Ge2 155.8(1). Sil-Gel-Ge3
132.9(1). Si2-Ge2-Ge3 156.7(1). Si2-Ge2-Gel 132.5(1), Si3-Ge3-Ge4 145.6(1). Si4Ge4-Gel 144.9(1). Si3-Ge3-Ge2 131.0(1), Si3-Ge3-Gel 153.7(1), Si4-Ge4-Ge2
146.1(1), Si4-Ge4-Ge3 142.7(1), C-Si-C (av) 112.8
of 2a has a slightly larger Si-Si distance (2.719(8) A) than that
in superdisilane crystals (2.697(2) A['']) is possibly attributed to
van der Waals attractions between supersilane and 2 in 2a (see
below). Although the Ge, tetrahedron suggests a symmetrical
(radial) arrangement of the supersilyl groups, they are slightly
bent; the Si-Ge4-Ge bond angles differ by up to only 3.4", the
Si-Ge2-Ge angles by up to 24.2". The reason for this might be
the proximity of tBu,Si-SitBu,; the center of the Si-Si bond
lies on a crystallographic inversion center.
Experimental Procedure
rBu,SiNa (0.69 mmol) [ l l ] in T H F (1.3 mL) was added dropwise to a solution of
(0.050 g, 0 22 mmol) in T H F (1 mL) at room temperature. After
GeCI;C,H,O,
12 h. the T H F was removed under vacuum from the resulting red-brown suspension, the oily residue was taken up in pentane (2mL), and filtered to remove
insoluble material. Intense red crystals of the composition 2(tBu,Si),Ge;(rBu,Si),
(2a) (0.008 g, 11 % yield) crystallized from the filtrate at - 25 ' C over a long period.
M.p. >360'C (above 280°C slow decomposition). ' H N M R (C,D,, TMS. internal): 6 =1.374 (4 Si/Bu,); "C('H) N M R (C,D,. TMS, internal). 6 = 31.87 (12
CMe,), 26 17(12 CMe,j; 29Si(iH]NMR (C,D,. INEPT. TMS. external): 0 = 59.0
(4 SirBu,); UV (heptane): 1,,, = 501 nm.
Received February 16, 1996 [Z8828IE]
German version: Angeu Chem. 1996, 108. 1437- 1438
Keywords: germanium compounds
tetrahedranes
[1] S. Nagase. Angeii..Chem. 1989, 101. 340: Angun-. Chen?. lnr. Ed. Engl 1989.28,
329; Polyhedron 1991, 10, 1299.
[2] According to calculations (N. MatSUndgd, M S. Gordon, J. Am. Chem. Sor.
1994,l f 6 , 11407) iriprismo-hexasilane and -hexagermane (EH), are considerably more stable than their isomers. hexasila- and hexagermabenzene. rerraherho-Tetrasilane and -tetragermane [l] (EH), are more stable than their isomers,
planar tetrasila- and tetragermacyclobutadiene. but slightly less stable than
(EH), compounds with puckered E, rings. Of course, sterically demanding
substituents contribute to the stabilization of the tetrahedrane structure.
131 N. Wiberg. C . M. M. Finger, H. Auer. K. Polborn. J. Organomer. Chem. 1996,
in press.
[4] Hexahedranes (SIR), and (GeR),: a) H. Matsumoto, K. Higuchi, Y Hoshino.
H. Koike, Y, Naoi, Y. Nagai, J. Chem. Suc Chem. Commun. 1988. 1083; b) H.
Matsumoto, K. Higuchi, S. Kyushin, M. Goto. Angepr. Chem. 1992. 104. 1410;
Angew. Chem. Inr. Ed. Engl. 1992, 31, 1354; c) A. Sekiguchi. T. Yatabe, H.
Kamatani, C . Kabuto, H Sakurai, J Am. Cheni. Sor. 1992, 114, 6260: Triprismanes (SIR), and (GeR),: d) A. Sekiguchi. C. Kabuto. H. Sakurai. Angew.
Chem. 1989. 101.97: Angen.. Cliem. Inr. Ed Engl. 1989.28.55; e) A. Sekiguchi.
T. Yatabe. C . Kabuto, H. Sakurai, J A m . Chcm. Suc. 1993. 115. 5853.
1334
$3 VCH
I~erlrig.~grselIs~liri/r
mhH, 0.69451 Weinherm, 1996
(51 N. Wiberg, C. M. M. Finger. K. Polborn. Angsm. fhcvn. 1993. 105, 1140;
Angeii. Chem. I n ( . Ed. Engl. 1993. 32, 1054.
[6] (SIR),, (SIR),, and (SIR), were first synthesized in 1988 [4a]. 1993 [4e], and
1993 [ 5 ] ,respectively, (GeR),, (GeR),. and (GeR), in 1992 [4c]. 1989 [4d]. and
1996 [this publication].
171 N. Wiberg in Fronriers of' Orfianusilicon Chemistrx (Eds.: A. R. Bassindale.
P. P. Gaspar). Royal Society of Chemistry, Cambridge, 1991, p. 263.
[8] N. Wiberg, W. Hochmuth. K. Polborn. unpublished results.
191 Initially. only ~r.s,rrun.s-l.2.3-trichloro-l,2.3-tris(supersilyl)cyclotrigermane
(rBu,SiGeCI), forms together with (/Bu,3Si),GeCI, as a pale yellow oxidationsensitive. hydrolysis-stable powder (crystals from MeOHirBuOMe 85:'15) 181
(reported in part at the D F G colloquium "Autbau und Funktionalisierung von
Polyedergerusten aus Hauptgruppenelementen" in Kochel. near Munchen.
1995): 'H NMR (C,D,, TMS. internal): 6 =1.386 (s. 2 SirBu,). 1.376 (s.
SirBu,); i3C{1H)N M R (C,D,, TMS. internal): 6 = 31.76131.86 (6 CMe,i3
CMe,). 25.62!21 06 (6 CMe,/3 CMe,): 2 9 S ~N M R (C,D,. TMS. external):
d = 46.33 ( 2 SitBu,), 48.28 (SirBu,). In the further course of the reaction
rBu,SiX (X = H.CI. SitBu,) and a substance. whose NMR shifts resemble
those of a recently described cyclotrigermene [lo], are formed as well as an
unidentifiable compound and the 1~rr.uhedro-tetragermane2.
[lo] A Sekguchi. H. ydmazaki. C. Kabuto. H. Sakurai. J An?. Chsm. Suc. 1995.
I f 7. 8025.
[ I l l N. Wiberg. H. Schuster. A. Simon, K. Peters, Angen.. Clim?. 1986, 9 8 100.
A n p i , . Chrm. In/. E d Engl. 1986, 25. 79.
[12] Crystal structure analysis of 2a: A single crystal (0.4 x 0.3 x 0.25 mm) was
mounted in perfluoroether oil under argon. placed in a Lindemann capillary.
and centered on a Siemens P4 diffractometer at - 70 -C. The data was collected
with a Siemens SMART area detector. the monoclinic unit cell calculated by
using reflections 2 1 0 l / o ( l ) .After reduction of the data. the structure was
solved by direct methods (SHELXTL). Whereas the molecular structure of
(rBu,SiCe), was refined without difficulty. rBu,Si-SirBu, showed rotational
disorder within the rBu, groups. As a result some of the anisotropic temperature parameters of these C atoms are very large and the bond lengths not
meaningful. All non-hydrogen atoms were included in the refinement with
anisotropic temperature parameters. the H atoms in calculated positions with
a riding model. Nevertheless, a comparatively high residual electron density
remains for three atoms (1.816. 1.39. 0 . 9 6 e k ' j in the space between
two (rBu,SiGe), molecules. The following weighting scheme was
applied: i 1 . C ' = o*F: + ( . Y P ) +~ j P with P = (F:+2Ff)i3. Crystallographic
data: C,,H,,,Ge,Si,,
M ,=1027.34. (1 =18.1997(2), h =16.8809(2), c =
25.0074(4)A,/1=97.949(1)-. V = 7 6 0 9 . 1 ( 2 ) A 3 , Z = 8 , p ~ ~ ,=1.124Mgm-3,
',
/ I =1.674mm-'. Data collection: 20 546.6". - 1 8 ~ h 1 1 7 ; - 1 8 1 k 1 1 8 ,
- 1 2 5 1 5 2 7 ; measurement rate: 10 s per setting, 11463 measured relections,
8256 of which symmetry-independent. Refinement with 8248 reflections and
601 variables, weighting scheme: x / j = 0.0753/138.2605. G O F = 1.193, R1
(40) = 0.0927, tvR2 = 0.2676. Further details of the crystal structure investigation may be obtained from the Fachinformationszentrum Karlsruhe, D-76344
Eggenstein-Leopoldshafen (Germany) on quoting the depository number
CSD-405202.
[13] Data from Comprehensive Organometallic Chemistry (Eds.: G. Wilkinson.
F. G. A. Stone. E. W. Abel). Pergamon. Oxford, 1982.
Formation of Macrocyclic Lactones by
Enantioselective Intramolecular Cyclopropanation
of Diazoacetates Catalyzed by Chiral Cu' and
Rh" Compounds"*
Michael P. Doyle,* Chad S. Peterson, and
D a m L. P a r k e r , Jr.
Macrocyclizdtion is an essential synthetic element in the
preparation of large ring compounds, and a variety of transformations have been reported for this process."] Only one, however, the macrocyclization of an o-alkynal in the synthesis of the
[*] Prof M . P. Doyle, Dr. C. S . Peterson, D. L. Parker. Jr.
Department of Chemistry, Trinity University
San Antonio, TX 78212-7200 (USA)
Fax: Int. code +(210)736-7569
e-mail: mdoyle(ir trin1ty.edu
[**I
This work was supported by grants from the Robert A. Welch Foundation and
the National Science Foundation.
0570-0833~96/3512-1334S 15.00 + .2S/O
Angew. Chem. Inr. Ed. EngI. 1996, 35. N o . 12
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