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Association of Bis(trimethylsilyl)amidolithium and Methyl(trimethylsilanolato)beryllium in the Solid State.

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Reactions of the reactive tricarbonyl(hexamethy1borazine)chromium(O), [B3N3(CH3)6]Cr(CO)3[61 ( I ) , with tertiary
phosphines and phosphites in suitable solvents lead rapidly
to good yields of cis-tricarbonyl complexes, provided that
steric factors d o not introduce difficulties [7,81.
We have found that the analogous reaction with PH3, namely:
+ 3 PH3
20 "C
(PH3)3Cr(CO)3 + B3N3(CH3)6
occurs in cyclohexane a t room temperature almost quantitatively within a few minutes. Considering the low solubility
of PH3 in C6H12 at atmospheric pressure, this shows once
more the great tendency of PH3 ligands for complex formation. The identity of the tricarbonyltris@hosphine)chromium(0) (2) produced was proved by total analysis and mass
spectrometry and the I R and 1H-NMR spectra show that it
has exclusively the cis-configuration.
Thus the v c o region of the spectrum shows only two IR
active fundamentals (Al, E), as expected for a molecule of
C3" symmetry, and can be assigned on the basis of a series of
known cis-L3Cr(CO)3 compounds (Table 1). The position of
the A1 band shows that for complex (2),as in PH3 complexes
studied previously, the it-acceptor contribution t o the metalphosphorus bond is greater than in PR3 compounds where
R is alkyl or aryl.
Table 1 . IR spectra (cm-1) of cis-L3Cr(CO)3 complexes (Perkin-Elmer
model 21, LiF optics).
[a] n-Hexane.
[bl Cyclohexane.
The I R spectrum of (2) (KBr pellet, NaCl optics) shows a
band of moderate intensity at 2309 cm-1 in the VPH region
and two strong t o very strong bands at 1027 and 1004 cm-1
and a further strong band at 917 cm-1.
in the 8 p region,
The IH-NMR spectrum (in CD3COCD3) shows two groups
of signals, each containing three broadened bands, symmetrically around T = 6.33, which agrees with the cis-arrangement
of the C O and PH3 ligands[***I. In contrast, the trans-isomer would be expected to show two identical PH3 groups and
one unique PH3 group differently shielded from the other
two. The separations of the mutually symmetrical bands are
338, 308, and 282Hz, and the intensities are in the ratio
1:0.98:0.46, respectively. The bands could not be resolved
into single lines.
The rather complex structure of the proton resonance spectrum is caused by the nuclear-magnetic non-equivalence of
the three PH3 groups: We have here a X3X;X;
spin system. The almost
spectrum of a n AA'A"X3X;X;'
identical chemical shifts of the P H protons in (2) and cis(PH3)2Cr(C0)4 (T = 6.26 in CDC13191) suggest very similar
electronic properties for the Cr-P-H3 bonding. It seems
reasonable to assume that the coupling constants between H
and P in (2) are similar t o those in cis-(PH3)2Cr(C0)4.
Pure (I) (100 mg, 0.33 mole), obtained from (CH3CN)3Cr(C0)3 according to ref. [61, is suspended in cyclohexane
(30 ml) at room temperature and stirred vigorously under
pure PH3 (ca. 800 torr). A color change from orange-yellow
t o pale yellow is complete within 10 min. The product (2) is
formed as a fine, pale-yellow precipitate. If larger amounts
of ( I ) are used, the reaction requires a longer time since the
solid ( I ) reacts slowly owing t o its poor solubility.
For purification, ( 2 ) is collected on a G 4 fritted filter, washed
several times with cold pentane, and finally dried at 0 ° C in
vacuo. The yield of crude product is 88 % (70 mg).
Rapid working is required for complete purification of (2).
This is done by preparation of a saturated solution of the crude
product in hexane at 25OC [ca. 1 2 m g of (2) per 100ml of
hexanel, filtration through filter wool, concentration of the
filtrate to one-third of its volume under water-pump vacuum,
and cooling t o 0 'C. Decantation, washing with cold pentane,
and drying in vacuo affords analytically pure (2), which decomposes at 133-137 "C. Oxygen and moisture must be excluded during these operations.
Compound (2) dissolves only very slightly in aliphatic
saturated hydrocarbons, moderately in ether, and readily in
ethylene glycol dimethyl ether, tetrahydrofuran, o r acetone.
However, it decomposes rapidly in solution, especially if
warmed or exposed to light. It sublimes slowly a t 5O-6O0C
with slight decomposition. Mass spectrometry gave a molecular weight of 238.
Received: February 17, 1969
[ Z 969 IE]
German version: Angew. Chem. 81, 391 (1969)
[*I Prof. Dr. E. 0.Fischer, Dipl.-Chem. E. Louis, and
Dr. C. G. Kreiter
Anorganisch-Chemisches Laboratorium
der Technischen Hochschule
8 Miinchen 2, Arcisstr. 21 (Germany)
[I] Part 5 of Transition Metal-Phosphine Complexes. - Part 4,
see [4].
f2] E. 0. Fischer, E. Louis, and R.J . J . Schneider, Angew. Chem.
80, 122 (1968); Angew. Chem. internat. Edit. 7, 136 (1968).
[3] E. 0. Fischer, E. Louis, W. Bathelt, E. Moser, and J. Miiller,
J. organometallic Chem. 14, 9 (1968); F. Klanberg and E. L.
Muetterties, J. Amer. chem. SOC.90, 3296 (1968); E. Moser and
E. 0.Fischer, J. organometallic Chem. 15, 157 (1968).
141 E. 0.Fischer, E. Louis, W. Bathelt, and J . Miiller, Chem.
Ber., in press.
151 J . M. Campell and F. G. A . Stone, Angew. Chem. 81, 120
(1969); Angew. Chem. internat. Edit. 8, 140 (1969).
[**I Note added inproof (May 5, 1969): Compounds of this type
have meanwhile been prepared by other authors: E. L . Muefterties, personal communication; C. G. Barlow and G. C. Holywell,
J. organometallic Chem. 16, 439 (1969).
[6] R. Prim and H. Werner, Angew. Chem. 79, 63 (1967); Angew. Chem. internat. Edit. 6, 91 (1967).
[7] E. Deckelmann, Diplomarbeit, Technische Hochschule Miinchen 1968.
[S] H. Werner, R. Prinz, and E. Deckelmann, Chem. Ber. 102, 95
[***I Note added in proof (May 5, 1969): X-ray structure determination has been completed and confirms this configuration;
G. Huttner and S. Schelle, to be published.
[9] E. Moser and E. 0. Fischer, J. organometallic Chem. IS, 157
Association of Bis(trimethylsily1)amidolithiumand
Methyl(trimethy1silanolato)beryllium in the
Solid State
By D. Mootz, A . Zinnius, and B. Bottcher [*I
Bis(trimethylsilyl)amidolithium, [(CH3)3Si]zNLi, known since
and today a versatile reagent in preparative inorganic chemistry [21, is dimeric in solution, but, as we found
by X-ray structure analysis, trimeric in the solid state.
Crystals obtained from petroleum ether [31 belong to space
group P2+ with twelve monomer units in the unit cell. The
trimeric unit that is indicated thereby was confirmed by a
complete X-ray structure analysis with more than 3000
photographic data: three crystallographically independent
monomers are associated with formation of a planar sixmembered ring with alternating nitrogen and lithium atoms.
The bonding parameters given in Figure 1 are mean values
Angew. Chem. internat. Edit. J Vol. 8 (1969) No. 5
electron-density function phased therewith showed a tetrameric molecule of formula [(CH3)3SiOBeCH3]4 with a structure analogous t o that of cubane, these facts being confirmed
on refinement. The oxygen and beryllium atoms are situated
at alternatevertices of a n only slightly distorted cube (Figure
2); the 0-Si and Be-C bonds lie o n outward prolongations
of the diagonals of the cube. A symmetry axis of the space
group passes through the middle of the molecule, being
parallel t o the edges of the cube that are shown as approximately vertical in the Figure.
None of the crystallographically independent but chemically
equivalent bonding parameters differs significantly from the
mean values given. The Be-0 distance, 1.73 A. is distinctly
longer than in beryllium oxide"] (1.65 A). This results from
repulsion between the large oxygen atoms, whose distance
from one another in the cube is considerably smaller (2.47 A)
any way than in the more open B e 0 structure (2.70 A).
The structure determined by us is the first certain oxaberyllidcubane, although similar structures have been discussed for
[ROBeCH3]4 where R = benzyl or phenyl [*I.
0 S'
Fig. 1. cyclo-Tris[bis(trimethylsilyl)amidolitbium~ molecule, with bond
lengths and bond angles. Estimated standard deviations are 0.02 to
0.05 8, and 1 to 2".
of chemicaIIy equivalent individual distances and angles,
deviations from the means being small and usually insignificant.
Comparison with the structures recently established for
(X-ray structure analysis [41) and
[(CH3)3Si]zNH (electron diffraction [sl) shows similar values
for the Si-N atomic distances and a distinct minimum of the
SiNSi bond angle for the structure now determined with the
onium configuration of the nitrogen atom:
1.72 8,
1.735 8,
1.731 8,
On treatment of trimethylsilanol with dimethylberyllium a
compound is formed 161 that crystallizes from petroleum
ether in the space group C 2/c. The Patterson function with
cn. 900 data measured o n a single-crystal diffractometer
permitted localization of two independent silicon atoms. A n
Received: February 27, 1969
[ Z 970 IEI
German version: Angew. Chern. 81, 398 (1969)
[*I Prof. Dr. D. Mootz, DipLMin. A. Zinnius, and
Dip1.-Chem. B. Bottcher
Institut fur Anorganische Chemie
der Technischen Universitat
33 Braunschweig, Pockelsstr. 4 (Germany)
and Abteilung fur Rontgenstrukturaoalyse
im Institut fur Molekulare Biologie, Biophysik und Biochemie
3301 Stockheim iiber Braunschweig, Mascheroder Weg 1
[ l ] U. Wannagat and H. Niederprum, Chem. Ber. 94,1540 (1961).
[ 2 ] U . Wannagat, Lecture at the 2nd Int. Sympos. on the Chemistry of Organosilicon Compounds, Bordeaux 1968.
[3] We thank Dr. Burger for crystals of the lithium compound.
[41 D. C. Bradley, M . B. Hursthouse, and P . F. Rodesiler, Chem.
Commun. 1969, 14.
[ 5 ] A. G. Robiette, G . M . Sheldrick, W . S . Sheldrick, B. Beagley,
D. W . J. Cruickshank, J. J . Monaghan, B. J. Aylett, and I. A.
Ellis, Chem. Commun. 1968, 909.
[6] U . Wannagat and B. Buttcher, unpublished.
[7] G. A . Jeffrey, G . S . Parry, and R. L. Morzi, J. chem. Physics
25, 1024 (1956).
[8] N . A. Bell and G. E . Coates, J. chem. SOC.(London) A 1966,
1069; G. E. Coates and M . Tranah, ibid. A 1967, 236.
A New Synthesis of a Linear
Poly(pheny1ene Oxide)
By W. Ried and W. M e r k e l [ * ]
0 Be
Fig. 2. cIoso-Tetrakis[methyl(trimethyls~lanolato)berylliumlmolecule,
with bond lengths and bond angles. Estimated standard deviations are
0.01 to 0.02 8, and 1 ".
Angew. Chem. internat. Edit. [ Vol. 8 (1969) [No. 5
N-Bromosuccinimide and mercury bis(phenylacety1ide) in
benzene afford compound ( I ) as well as 1-bromo-2-phenylacetylene ( 4 ) ; and in T H F the second phenylacetylene group
is also replaced, affording mercury bis(succinimide). However, with 2,4,4,6-tetrabromo-2,5-cyclohexadienone(2) [ * ]
we obtained poly(2,6-dibromo-l,4-phenyleneoxide) (81,
I-bromo-2-phenylacetylene (41, and phenylethynylmercuric
bromide (6j even at room temperature. Like N-bromosuccinimide, the ketone (2) contains a positively activated and
thus very mobile bromine atom.
The polymer is a white amorphous powder, softening in the
region 230-260°C and with the formula ( C 6 H ~ o B r z ) An
osmometric determination [21 in benzene at 36 O C leads to a
mean molecular weight of 13000 -c 650, which corresponds
to a mean chain length of 49-52 units. The I R spectrum
(KBr disk) shows neither a C - 0 nor an 0 - H absorption,
but there is a strong C-0-C band a t about 1190 cm-1.
Since the reaction under nitrogen proceeds in exactly the
same way and here too no diphenoquinone can be detected,
and in consideration of the by-products (41 and (61, the reaction is postulated as occurring by way of (51 and (71. Free
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methyl, trimethylsilyl, solis, associations, trimethylsilanolato, beryllium, amidolithium, state, bis
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