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Hg8 (УMercubaneФ) Clusters in Rb15Hg16.

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The influence of bulky substituents on the course of the
reaction is quite obvious, and Seyferth et a1.16]have reported
that the lithium salt of the trirnethylsilyldiazomethane reacts
with trirnethylsilylchloride giving the bis(trimethylsily1)diazomethane.
The silylated dipolar compound 4 reacts at room temperature, in the presence of a large excess of methyl acrylate,
methyl propiolate and dimethyl fumarate, affording the expected adducts 5-7 in 20 to 30% isolated yield (Table 2).
The facile cleavage of silicon-nitrogen and even siliconcarbon bonds makes this first bis(sily1ated)nitrile-imine 4 a
synthetic equivalent of the parent compound (HCNNH)
which should be a useful tool in organic synthesis. Moreover,
these results demonstrate the wide applicability of the synthetic method used.
Received: April 17. 1989 [Z3296 IE]
German version: Angew. Chem. 101 (1989) 1253
CAS Registry numbers:
3,122093-27-0; 4, 122093-28-1; 5a, 122093-29-2; 5b. 122093-32-7; 6a, 12209330-5; 6b, 122093-33-8; 7, 122093-31-6; 8, 86071-46-7; iPr,SiCI, 13154-24-0;
H,C =CHCO,Me, 96-33-3; HC =CCO,Me, 922-67-8; Me0,CCH =
CHCO,Me, 624-49-7; 29Si, 14304-87-1; dibenzo[l8]crown-6, 14187-32-7.
(71 Yo)
a) R. Huisgen, Angew. Chem. 75 (1963) 604, 742; Angrw. Chem. Inf. Ed.
Engl. 2 (1963) 565, 633.
P. Caramelid, P. Grunanger in A. Padwa (Ed.): 1.3 Dipolar Cycluaddilion
Chemistry, Wiley Interscience, New York 1984.
G. Sicard, A. Baceiredo, G. Bertrand, J. Am. Chem. Soc. 110 (1988) 2663.
4: A solution of triisopropylsilyldiazomethane3 (0.40 g, 2 mmol) and
dibenzo[l8]crown-6 ether (0.80 g, 2 mmol) in TH F (20 mL) was treated
90°C with a stoichiometric amount of BuLi in hexane.
dropwise at
After stirring for 10 minutes at 9 0 ° C triisopropylsilyl chloride (0.39 g.
2 mmol) was added to the mixture. After warming up to room temperature, the solvent was removed by evaporation. The residue was treated
with pentane and after filtration and evaporation of the solvent, 4 (0.56 g.
80% yield) was purified by distillation.
C. Wentrup, S. Fischer, A. Maquestiau, R. Flammang, Angew. Chem. 97
(1985) 74; Angew. Chem. Inf. Ed. Engl. 24 (1985) 56.
D. Seyferth, T. C. Flood, J. Organomef. Chem. 29 (1971) C25.
a) W. Fliege, Disserlalion, Universitat Munchen 1969; b) R. Huisgen, R.
Sustmann, G. Wallbillich, Chem. Ber. 100 (1967) 1786; c) R. Huisgen, W.
Fliege, W. Kolbeck, ihid. 116 (1983) 3027; d) W Fliege, R. Huisgen, J. S.
Clovis, H. Knupfer, ibid. 116 (1983) 3039; e) J. S . Clovis, W. Fliege, R.
Huisgen, ibid. 116 (1983) 3062.
a) K. N. Houk, J. Sims, C. R. Watts, L. J. Luskus, J. Am. Chem. Soc. 95
(1973) 7301; b) K. N. Houk, J. Sims, R. E. Duke, R. W. Strozier, J. K.
George, ibid. 95 (1973) 7287; c) H. Bock, R. Dammel, S. Fischer. C.
Wentrup, Tetrahedron Lerl. 28 (1987) 617.
a) M. Granier, A. Baceiredo, G. Bertrand, Angew. Chem. fOO(1988) 1397;
Angew. Chem. Int. Ed. Engl. 27 (1988) 1350; b) W. Reichen, Helv. Chim.
Acta 59 (1976) 1636; c) A. Padwa, T. Caruso, D. Plache, J. Chem. Sue.
Chem. Commun. 1980. 1229; d) A. Padwa, T. Caruso, S. Nahm, J. Org.
Chem. 45 (1980) 4065; e) C. Wentrup, Helv. Chim. A c f a 61 (1978) 1755: 0
R. Gleiter, W Rettig, C. Wentrup, ibid. 57 (1974) 2111; g) A. Padwa. T.
Caruso, S. Nahm, A. Rodriguez, J Am. Chem. Sue. 104 (1982) 2865.
S. Fischer, C. Wentrup, J. Chem. Soe. Chem. Commun. 1980. 502.
a) C. Wentrup, A. Damerius, W. Reichen, J. Org. Chem. 43 (1978) 2037; b)
C. Wentrup, J. Benedikt, ibid., 45 (1980) 1407; c) L. Garanti, A. Vigevani,
G. Zecchi, TetrahedronLett. 1976,1527; d) L. Garanti, A. Sala, G. Zecchi,
J Org. Chem. 42 (1977) 1389; e) H. Meier, H. Heimgartner, Helv. Chim.
Acfa60 (1977) 3035; fl G. Schmitt, B. Laude, Tetrahedron Lett. 1978,3727.
a) N. H. Toubro, A. Holm, J. Am. Chem. Sue. 102 (1980) 2093; b) W.
Sieber, P. Gilgen, S . Chaloupka, H. J. Hansen, H. Schmid, Helv. Chim.
Aetu 56 (1973) 1679; c) H. Meier, W. Heinzelmann. H. Heimgartner,
Chimia 34 (1 980) 504, 506.
Table2. I3C and 29Si NMR spectroscopic data for the adducts 5-7. The
NMR spectra were recorded at 50.323 MHz (7)and at 75.469 MHz (5,6)
in CDCI,, the "Si NMR spectra at 39.761 MHz in CDCI,.
6( C = N )
6( C m )
-1.02, 8.12
-0.05, 7.40
-0.92, 20.28
1.70, 15.96
0.1 I , 9.39
The low yield of these reactions was probably due to some
decomposition of the products on the silica gel since NMR
analysis of the crude reaction mixtures indicated a nearly
quantitative yield. The non-regioselectivity observed for
non-symmetrical dipolarophiles has already been noted in
the trapping reactions of unstable nitrile iminesL7] and has
been explained using molecular orbital theory.[*]
Depending on the nature of the substituents, nitrile imines
thermally rearrange either by a 1,3 sigmatropic shift to form
diazo compounds,r91a 1,4 shift to form azines,"" or cyclizat i ~ n . ' ~ ~Rearrangement
to a carbodiimide has been detected only at very high temperature (> 500 "C) in the gas
phase"" or photochemically in a matrix along with the
cleavage of the N-N
No thermal rearrangements
have been observed for 4 up to 250 "C in the gas phase, but
irradiation of a pentane solution at 300 or 254 nm for 1 day
quantitatively afforded bis(triisopropylsily1)carbodiimide 8
(Table 1).
f % e
Angew. Chem. Int. Ed. Engl. 28 (1989) N r . 9
Hg, ("Mercubane") Clusters in Rb,&g,,
By Hans-Jorg Deiseroth * and Axel Strunck
RbHg is so far the only compound among the alkali-metal
amalgams of composition MHg (M = alkali metal) whose
conditions of existence are unclear. On attempting to synthesize RbHg by a method that had proven successful in the case
of several other amalgams ['I we have now unexpectedly, but
reproducibly obtained gold-colored, shiny metallic single
crystals of the composition Rb,,Hg,, which are extremely
[*I Prof. Dr. H.-J. Deiseroth, Dr. A. Strunck
Fachbereich 8 - Anorganische Chemie der Universitat-GH
Postfach 101240, D-5900 Siegen (FRG)
VerlugsgesellschafimhH. D-6940 Weinheim. 1989
air-sensitive. The compound contains isolated, almost ideal
cubic-shaped Hg, clusters (“mercubane”) of a type that has
hitherto never been detected in any other amalgam. Rectangular Hg, clusters, as have been found in the amalgams
CsHg, KHg and Na3Hg,,[2-51were also observed.
The tetragonal crystal structure of Rbi,Hg,,,[6, thus far
only observed in this compound, is a defect variant of the
CsCl type. Its structure and its lattice constants[’] can be
interpreted in terms of an ensemble embodying
4 x 4 x 4 = 64 CsCl unit cells (each a E 410 pm, Rb,,Hg,,).
This large cubic cell is somewhat elongated in one direction,
such that it corresponds to the real c-axis of the tetragonal
unit cell of Rb,,Hg,,. The 64 Hg atoms of the idealized unit
cell, arranged in cubic primitive geometry (d(HgHg) = 410 pm) now “relax” to a real structure of a type that
forms eight Hg, squares (32 Hg atoms) and four Hg, cubes
(32 Hg atoms) with Hg-Hg distances of ca. 300 pm (Fig. 1).
Fig. 2. Hg, square (a) and Hg, cube (b) in Rb,,Hg,,:
distance [pm]:
u = 295.6(3), h = 304.2(3), c = 295.5(3), d = 297.9(3), L‘ = 293.9(3); inter-
atomic angles [”] at H g l : 85.66(7), 86.38(7), 86.16(7); Hg2: 94.26(7), 93.44(8),
93.69(7): Hg3: 90.32(7); Hg4: 89.68(8).
According to these calculations the electronic states in the
neighborhood of the Fermi edge are essentially dominated
by Hg(6p) (small proportions of Na(3s) and Na(6s)).
The quasimolecular units Hg, and Hg, in the heavy alkali
metal amalgams belong to a previously unknown class of
mercury clusters. These differ from the already classical linear polycations Hg:@ in that 0, bonds dominate in such
The chemical bonding in the polycations, on the
other hand, has oscharacter. The latter is primarily realized
by removal of electrons from antibonding 6s states, whereas
in the former cases additional electrons (from the alkali metal) are transferred into the 6p states.
A critical interpretation of the phase diagrams determined
from thermal analyses (see, e.g. Ref. [I I]) would indicate the
possibility of further previously unknown alkali-metal amalgams with mercury clusters in the range of composition
around MHg (M = Na, K, Rb, Cs).
Received: May 2, 1989 [Z 3318 IE]
German version: Angew. Chem. 101 (1989) 1286
CAS Registry number:
Rb,,Hg,,, 122469-76-5
Fig. 1. Projection of the crystal structure of Rb,,Hg,, along [OOl]; dotted
Hg-atoms form Hg, cubes, undotted Hg, squares; the numbers indicate the
approximate coordinate of the center of the respective square or cube in 3 . The
R b atoms are shown uncoupled.
The centers of the cubes occupied by rubidium atoms in the
ideal structure are, as a result of the reduced Hg-Hg distance, no longer occupied in the real structure, so that the
composition Hb,,Hg,, = Rb,,Hg,, = RbHg,.,,, approaches RbHg.
The distances within the mercury clusters (d z 300 pm)
and between them (d > 500 pm) are significantly different in
the compound described here. The shortest distances between the clusters (cube-cube, cube- square etc.) are
539.65 pm (Hgl-Hg4); the distances within the clusters are
shown in Figure 2.
The preferred Hg-Hg-Hg angles of ca. 90”, not only in
Rb,,Hg,, but also in KHg, CsHg and Na3Hg,, are a clear
indication of the presence of opbonds (6p) between the Hg
atoms. The bonding electrons necessary for this are provided
by rubidium, which itself is present as Rb@ ion (shortest
Rb-Rb distances in Rb,,Hg,, 378.9 pm, in y-Rb,O 338 pm,
in Rb metal 468 pm). This simplified picture of the chemicaI
bond is also supported by the results of relativistic band
structure calculations for NaHg, another CsCI variant.“]
VerlagsgeselIschofi mbH, 0-6940 Weinhcim. 19x9
[I] H. J. Deiseroth, A. Strunck, W. Bauhofer, Z . Anorg. A&. Chern. i5X (1988)
[2] H. J. Deiseroth, A. Strunck, Angew. Chem. 99 (1987) 701; Angew. Chem.
In/. Ed. Engl. 26 (1987) 687.
[3] H. J. Deiseroth, A. Strunck, W. Bauhofer, Z. Anorg. Allg. Chem., in press.
[4] E. J. Duwell, N. C . Baenziger, Acto Crysrollogr. 8 (1955) 705.
151 J. W. Nielsen, N. C. Baenziger, Acta Crystatlogr. 7 (1954) 277.
[61 Sample preparation : gold colored, shiny metallic, air-sensitive single crystals (diameter a few tenths of a mm) of Rb,,Hg,, were obtained from
samples of the overall composition RbHg (prepared according to [1]) by
tempering at 120 “C in an evacuated Duran glass ampoule ( I % 200 mrn.
0zz 20 mm); m.p. 157 “C (according to DTA investigations).
[7] Crystallographic data for Rb,,Hg,,: space group f4,jo (No. 88), Z = 4,
u = 1665(3), c = 1813(4) pm, p = 627 cm-‘, CAD4 single crystal diffrac= So’, crystal dimensions:
tometer. room temperature. Ma,,, 2 6JmaX
0.30 x 0.28 x 0.51 mm. 2206 observed, unique reflections, 1261 with
f > 3 a(0. Refinement factors R,,,,,= 0.075, R = 0.128 (calculated absorption corrections with the program DIFABS IS]). All structure calculations were carried out with the program system NRCVAX [12]. Further
details of the crystal Structure investigation are available on request from
the Fachinformationszentrum Karlsrube, Gesellschaft fur wissenschaftlich-technische Information mbH, D-7514 EggensteinLeopoldshafen 2 (FRG) on quoting the depository number CSD-54014,
the names of the authors, and the journal citation.
181 H. J. Deiseroth. N. E. Christensen, A. Stupperich, unpublished.
[Y] N . Walker, D. Stuart, A d a CrystaIlogr. A39 (1983) 158.
[lo] N . N. Greenwood, A. Earnshaw: Chc.nistry o/ the E/emenis, Pergamon.
Oxford 1984, p. 1410.
[ l l ] W Biltz, F. Weibke, H. Eggers, Z.Anorg. AIlg. Chem. 219 (1934) 119.
[12] The NRCVAX Crystal Structure System (PC version): E. J. Gabe, F. L.
Lee, Y Le Page in G. M. Sheldrick, C. Kriiger, R. Goddard (Eds.): C r w
tallogruphic Computing 3, Clearendon Press. Oxford 1985, p. 167- 174.
Angew. Chem. In[. Ed. Engl. 28 (19x9) Nr. 9
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