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Dimeric 1 4-Dichloro-2 3 5 6-tetramethyl-1 4-dialumina-2 5-cyclohexadiene a Compound with Aluminum-Olefin -Bonds.

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S. Satge. Phosphorus Sulfur 17 (1983) 22 I ; A. H. Cowley, S. E. Kilduff, N.
C. Norman, M. Pakulski, J. L. Atwood, W. E. Hunter, J. Am. Chem. SOC.
105 (1983) 4845.
[I41 Due to the isolobal behavior of the -P= and -C(H)= fragments, a similar situation is found here as in the compound Me&-CHO: R. J.
Bushby. V. W. Jones, J . Chem. SOC. Chem. Commun. 1979. 688.
of type I to give the dimer 1 (Fig. 1). In contrast, 2 is monomeric; the A1 atoms are coordinatively saturated by TH F,
and the A1,C4 ring is planar.[51
Dimeric 1,4-Dichloro-2,3,5,6-tetrarnethyl1,4-dialumina-2,5-cyclohexadiene,a Compound
with Aluminum-Olefin z-Bonds**
By Hansgeorg Schnockel,* Manfred Leirnkiihler.
Rainer Lotz, and Rainer Mattes
n-Complexes of aluminum with olefins have long been
regarded as intermediates in many reactions of organoaluminum compounds."] Results of IR and N M R spectroscopic investigations on alkenylaluminum compounds provided evidence of intramolecular interactions of the threefold coordinated aluminum with the C = C double bond.['I
We have now been able to prepare, for the first time, a
compound containing the structural unit I and to characterize it by an X-ray structure analysis.
'-'
L
I
II --I-
/
C
\
Fig. I. Molecular structure of 1 in the crystal Hdtched. Al; large circles, CI.
dotted lines, Al-olefin n-bonds. Mean, selected distances [pm] and angles ["I:
AI-CI 210.9, AI-AI 300.5 and 337.0 (see text), AI-C (a)199.0, AI-C (x) 235.5,
C = C 136.7; C-AI-C 115.1, C-AI-CI 114.9, AI-C-CH, 117.7 (standard deviations 0.1-0.3 pm). Further details of the crystal structure investigation are
available o n request from the Fachinformationszentrum Energie, Physik,
Mathematik GmbH, D-7514 Eggenstein-Leopoldshafen2 (FRG), on quoting
the depository number CSD-52 141, the names of the authors, and the full
citation of the journal.
/
'
In 1 , the mean AI-C distance in the n-bonds is 235.4
pm, i.e. approximately 10% greater than the comparable
distance in the Zeise salt K[Pt(C,H,)CI,] (213.1 pm).['] The
Treatment of the active species AICI, generated at eleaverage C = C distance in I is 136.7(3) pm (Zeise salt:
vated temperature, with dimethylacetylene in a low-tem137.5(4) pm) and is thus longer than in an uncoordinated
perature reaction led, upon warming from - 196°C to
C=C
bond. Other than in the Zeise salt, in which the C2H4
room temperature, to formation of dimeric 1,4-dichlorogroup is clearly no longer planar, the highly substituted
2,3,5,6-tetramethyl-l,4-dialumina-2,5-cyclohexadiene
1 .[31
double bonds of 1 are stilt almost planar. The interaction
between the Al atoms and the C=C bonds is not optimal,
4AlCI + 4H3CC-CCH3 --t A14C14Cl,H2, 1
since the AI,C=C vector deviates by 15.5" from the normal
to the C = C group. The pyramidal coordination of the Al
In 1968, Tirnrns prepared 1,4-dibora-2,5-cyclohexadienes
atoms by the C1 atom and the two C atoms clearly indiunder similar conditions by reaction of boron subhalides
cates presence of an aluminum-olefin n-bond.
with alkyne~.[~I
The decomposition of 1 in solution and the
The AI-Cl distance is 21 1 pm, and the length of the AlNMR spectra obtained for such solutions indicate a comC o bonds is 199 pm (C-AI-C and C-AI-CI: 114-116").
plex dynamic behavior.
The distance between two A1 atoms of different six-memThe elemental analysis of 1 (A1 :CI = 1 : l), the detection
bered rings (ca. 300 pm) is relatively small. A closer proxof cis-2-butene as the sole product of hydrolysis, and the
imity of two such atoms, which could lead to a shortening
occurrence of a singlet in the 'H-NMR spectrum at
of the aluminum-olefin n bond, is therefore hindered. In
6=2.08 (90 MHz, C6D6) afforded the first indications of
contrast the distance between the AI atoms within the dithe structure of 1. Surprisingly, the extremely air- and
aluminacyclohexadiene ring is 337 pm (in 2, 347 pm); the
moisture-sensitive compound 1 can be vaporized at ca.
transannular distance between the C C double bonds
140°C, and its mass spectrum shows the expected molecu(334pm) is of the same order of magnitude. The four A1
lar peak with the characteristic fine structure for four chloatoms of 1 form a tetrahedron slightly compressed along
rine atoms. A compound related to the monomer of 1 is
I ,4-diethyl-2,3,5,6-tetraphenyl-1,4-dialumina-2,5-cyclohex- the molecular axis.
adiene.2THF 2 ( T H F = tetrahydrof~ran).'~]
Received: June 16, 1986;
The investigation of the structure of 1 at - 130"C[61gave
revised: July 16, 1986 [ Z 1821 IE]
the following result: Two nonplanar 1,4-dialuminacycloGerman version: Angew. Chem. 98 (1986) 929
hexadiene moieties, twisted through 90" with respect to
each other, are coupled via four aluminum-olefin n-bonds
[*] Priv.-Doz. Dr. H. Schnockel, DipLChem. M. Leimkiihler,
[**I
I>ipl.-Chem. R. Lotz, Prof. Dr. R . Mattes
Anorganisch-chemisches lnstitut der Universitat
Corrensstrasse 36, D-4400 Miinster (FRG)
This work was supported by the Minister fur Wissenschaft und Forschung des Ldndes Nordrhein-Westfalen and by the Fonds der Chemischen Industrie.
Angem Chem. In1 Ed Engl. 25 (1986) No. 10
[I] J . J. Eisch in G. Wilkinson, F. G. A. Stone, E. W. Abel (Eds.): Comprehensive Organometallic Chemistry, Val. 1. Pergamon Press, London 1982,
p. 555.
[ZI T. W. Dolzine, J. P. Oliver, J. Am. Chem. SOC.96 (1974) 1737: for xalkynylaluminum compounds see, for example, G. D. Stucky, A. M.
Mcpherson, W. E. Rhine, J. J. Eisch, J. L. Considine, h i d . 96 (1974)
1941.
I31 Experimental procedure: Equimolar amounts (0.05 mol/h) of dimethylacetylene and AlCl were cocondensed onto a nitrogen-cooled surface
0 V C H Verlagsgesellschaft m b H , 0-6940 Wemheim, 1986
0570-0833/86/1010-0921$ 02.50/0
921
(--4OOO cm’) for 2 h under vacuum conditions. During annealing to room
temperature n-pentane was added. Colorless crystals of 1 separated from
the yellow solution. Apparatus and technical details: H. Schnockel, H.
Kreienkamp, H. R. Lotz, unpublished.
[4] P. L. Timms, J . Am Chem Soc. 90 (1968) 4585: Adu. Inorg. Chem. Radiochem. 14 (1972) I18 In the meantime numerous reactions have been carried out with these boron compounds, which are exclusively monomeric,
six-membered ring complexes; see for example W. Kaim, H. Bock, P.
Hawker, P. L. Timms, J . Chem. Sor. Chem. Commun. 1980, 577; G. E.
Herberich, 9. Hessler, Chem Ber I15 (1982) 3 I 15.
[ S ] H. Hoberg, V. Gotor, A. Milchereit, C. Kruger, J. C. Sekutowski, Angew.
Chem. 89 (1977) 563: Angew. Chem. Inr. Ed. Engl. 16 (1977) 539.
161 1 crystallizes in the space group Pi, a = 1078(2), b = 1451(3),
c = 1560(3) pm, a=97.9(1), /3= 109.4(1), y = 104.2(1)”. Solution of structure by direct methods (SHELX). 8075 reflections with F0>6.01F,,I,
2H,,,,,=54°; 497 parameters, CH3 as rigid group; R=0.035: R,=0.038.
The unit cell contains two independent dimeric molecules. One is slightly
distorted, the other has, to a good approximation, D2*,symmetry.
[7] R. A. Love, T. F. Koetzle, G. J. B. Williams, L. C. Andrews, R. Bau, Inorg.
Chem. 14 (1975) 2653.
Novel Modifications of
Gold, Rhodium, and RutheniumMI, Clusters as Building Blocks of “Superclusters”**
By Giinter Schmid* and Norbert Klein
cores, which constitute the smallest conceivable closedshell clusters. It may be assumed that they are not longlived as isolated particles in solution, there being two
routes open for their stabilization: a) degradation into
small, e.g., tetrahedral particles, which, as predicted by
model calculations could reassemble to form polytetrahedral structures, or b) the assemblage of M I 3 building
blocks to give novel metal structures. It is found that the
latter path is actually followed. If one imagines the M I 3
clusters in their simplest form as being spherically shaped,
such clusters would try to adopt a cubic closest packed
structure,which in the simplest case would be made u p of
thirteen M I 3clusters. Even these (M13)13
clusters could also
aggregate in an organized way to form a second superstructure [(M13)13]nconsisting of closest packed (M13),1
clusters .
This concept of novel metal modifications is confirmed
by the Debye-Scherrer diffraction patterns (CuKn,
A = 1.5418 A) of the powders thus obtained. The metal
atoms originating from the outer shell of the cluster upon
degradation form “normal” metal (M,) which gives rise to
the correspondingly well-known X-ray diffraction pattern.
In addition, reflections are observed which are in very
good agreement with the most important lattice planes to
be expected for the superstructures illustrated below. Thus,
for all metals, one finds three new lattice planes characterizing the superstructures which are integral multiples of
the interplanar spacings of the metals. Rhodium, platinum,
and gold crystallize in the cubic system, as d o also the superstructures. Ruthenium, on the other hand, has a hexagonal structure; nevertheless, the reflections of the three
superstructures observed even in the case of ruthenium are
identical to those found with (the equally large) rhodium,
i.e. ruthenium also forms (Ru 1 3 ) 1 3 superclusters with cubic
structure upon cluster degradation.
The unusual stability of transition-metal clusters with
closed shells (so-called full-shell clusters) has already been
demonstrated on a number of occasions.[’,21They are compounds whose cluster skeleton is stabilized by a ligand
shell. The question of the possibility of existence of closed
shell clusters without protecting ligand peripheries, however, still remains unanswered. According to theoretical
models by Hoard and
closed-shell clusters containing less than ca. 70 metal atoms should be incapatle of
existing; such aggregates form polytetrahedral structures.
We have now succeeded, however, in converting ligandstabilized M55clusters into ligand-free M I 3clusters and in
Table I . hkl values, interplanar spacings d [A]and 28-values of (M,,),,,
identifying these as components of novel “superclusters”.
[(M ,3),3]. and, for comparison, M,-values.
Solutions of [ A U ~ ~ ( P P ~ , ) , , C I , [M5S{P(~B~)3}IZC120],
],~~~
M = Rh,@’ RU,[’~and ~Pt55(As(tBu),)l,C12,]171
in methylene
M
d(M,) hkl Occupation
chloride can be smoothly degraded on platinum electrodes
Rh
1.902 200 8xd(M,)=15.216
15.3
5.8
at 20 V d.c. This type of degradation is not an electrolysis,
0.8725 331 7Xd(M,)= 6.1075 6. I 1 ( d 2 )
14.5
since no discharging takes place. The compounds decom1.0979 222 3 x d ( M , ) = 3.2937 3.24 (d‘)
27.5
pose upon contact with the cathode or anode, and the me15.3
5.8
Ru [a1
tals separate and are deposited on the platinum or are pre6. I 1 (d’)
14.5
3.24 (d‘)
27.5
cipitated in the reaction vessel.[s1 If contact of the clusters
Au
2.039 200 8 x d ( M , ) = 16.312
16.8
5.3
with the electrodes is prevented, e.g. by covering the me0.9358 331 7 x d ( M , ) = 6.5551 6.8(3) (d2)
13.0(5)
thylene chloride solution with a layer of water, electro1.1774 222 3 x d ( M , ) = 3.5322 3 4 3 ) ( d ’ )
14.115)
phoresis is observed, with the clusters migrating to the ca[a] Ru, crystallizes hexagonally: consequently, its structural data are not to
thode. This process is reversible. The degradation of the
be compared with those for ( R U , , ) , ~ .
MSs clusters gives, besides the metal, free phosphane and
arsane and metal halide complexes that are soluble in
CH2C12, in the case of gold [(Ph3P)2AuCI], in the case of
the other metals, complexes of unknown structure.
In Table 1 the new 26-values and lattice planes are colThe cleavage of metal halide and phosphane (or arsane)
lected together with the corresponding values for the norleads to degradation of the whole external shell of 42 metal
mal metals M,, where M = R h , Ru, and Au. Figure 1
atoms of the M,,-cluster, thus leaving naked M,3 cluster
shows a model of the course of the lattice planes observed
in
the first superstructure (MI3)13, while Figure 2 shows a
[*) Prof. Dr. G. Schmid, Dip1.-Chem. N. Klein
model of the second superstructure [(M13)13]n.
All lattice
lnstitut fur Anorganische Chemie der Universitat
planes necessary for characterization of the new metal
Universitatsstrasse 5-7, D-4300 Essen I (FRG)
[**I Large Transitioh-Metal Clusters, Part 5. This work was supported by the
structures are proven. That [(M13)13]n
is composed of cloDeutsche Forschungsgemeinschaft, the Fonds der Chemischen Indussest packed (M13),3clusters is also confirmed by the occurtrie, and Degussa AG. We thank Dr. R. Boese for valuable discussions
rence of lattice planes with a separation of 15.3 and 16.8 A,
and Mrs. G . Schmid for help with the construction of the models.
respectively. The magnitude of n , however, is still unThanks are also due to Dr. H . Srhweder for the SEM photographs and
to Mr. W.Huben for the DMC measurements.-Part 4: [7].
known.
922
0 VCH VerlagsgesellschaJi mbH. 0-6940 Weinheim. 1986
0570-0833/86/1010-0922 $ 02.50/0
Angew. Chem. Inr. Ed. Engl. 25 (1986) No. 10
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