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I t IS surprising that a t-butyl group i n position 5 reinforces
the effcct of a 2-t-butyl g:-oup to such a n extent that no
radical association then takes places. It seems, therefore.
that the steric effect plays a notable role in lbe dissociation
of tetraarylethanes, as it does i n that o f hexaarylclhancs.
By Doz. Dr. Th. Kruck, Prof. W. Hieber, and
DipLChem. W. Lang
Anorganisch-Cheniisches Laboratorium
der Technischen Hochschule Miinchen (Germany)
The ESR spectrum of the radical ( I ) shows a splitting due to
the proton on the central carbon atom into two line groups
with a separation of 15.2 gauss.
Received: November 11th. 1965 [Z t05/9371E]
German version: Angew. Chcm. 76, 207 (1966)
Publication deferred until now at the authors' request
[ l ] J. Coops, U
'. Th. Nnirtn, et a/., Kecueil Trav. chim. Pays-Bas
59, 1109 (1940); 60, 245 (1941).
121 W. Tlieilacker and F. Thater, Angcw. Chem. 69, 328 (1957).
[3] K. H. Fleurke, Dissertation, University of Amsterdam, 1963.
Dedicuted f o Professor Karl Freudeuberg
on the occasiou of his 80th birthday
Cyclopentadienylbis(trifluorophosphine)cobalt (1) is formed
i n 20-30 % yield on treatment of dicyclopentadienylcobalt
with PF3 at 300 atm and 170 "C:
(C~H_cllCo 2 I'F3
+ C~H~CO(PF~
i 1)
As a consequence of the similarity in complex-chemical be-
Ammonothermal Synthesis Qf Magnesium and
Beryllium Amides
By Prof. Dr. R. J u ~ aand DipI.-Chem. H. Jacobs
Institut fur Anorganische Chemie
der Universitat Kiel (Germany)
Dedicated to Profes or Kurl Fi cudenberg
on fhc occurion of his 90th birtlirla,~
The preparation of metal amides from a metal and liquid
ammonia at room temperature or gaseous ammonia at 1 atm
and higher temperatures has its limitations. The reaction is
successful with barium, strontium, and calcium, but with
magnesium no amide is obtained at higher tcmperatures,
and on using liquid ammonia at room temperature we
obtained only small quantities of amorphous (to X-rays)
magnesium amide after 1.5 years i l l . For preparative purposes
we are therefore now using liquid ammonia up to its critical
point (132.5'C, 111.5 atm), and ammonia pressures up to
4000 atm in the supercritical region. We have developed
autoclaves made from "Vacumeit ATS 115" in which the
closures also can be heated. The reagents are placed
in small silver tubes. The pressure in the autoclave is calculated from the specific volume of ammonia.
havior between trifluorophosphine and carbon monoxide [21,
cyclopentadienyl - trifluorophosphine-metal complexes, of
which ( I ) is the first representative, resemble their CO analogues [C5H&o(CO)z 131 in this case] closely in their chemical
and physical properties. Compound (1) is a deep red, oily
liquid, m.p. --8 "C, b.p. 51 "/I3 mm, readily soluble in
organic solvents. Its stability to atmospheric oxygen is poor,
as is to be expected for a trifluorophosphine complex with a
central metal in the (formal) oxidation stage 1. However,
it is stable in a sealed tube up to 195 "C.
hluclear magnetic resonance and infrared spectra confirm a
structure containing a x-bonded, pentagonal, symmetrical
cyclopentadienyl ligand. The IH-NMR signal of the aromatic
ring occurs at --5.02x 10-6 (measured for the pure liquid
versus tetramethylsilane), which is in the range expected for
such a structure; there is no splitting due to coupling of the
nuclear spins of the protons with those of the P and F nuclei.
In the infrared spectrum bands appear at 1112 cni- 1 (C-H deformation) and 325 cm- 1 (metal-ring vibration) with medium
intensity, characteristic of the Ti-bonded cyclopentadienyl ring.
The P-F stretching frequencies are at 905 (vs), 856 (vs), and
842 (vs) cm-1[41. They are thus only slightly shifted from the
positions for trifluorophosphine and it can be concluded that
there is considerable x-bond contribution to the metalphosphorus linkage.
Received: November 19th, 1965 [Z 112/945 IE]
German version: Angew. Chem. 78, 208 (1966)
Mg(NH& was obtained quantitatively at 250 "C and 2500 atni
in 40 hours as a finely crystalline material. On addition of
NaN3 (which forms NaNH2) at 300 to 350°C we obtained
products suitable for X-ray single-crystal investigations.
Be(NM&? which is not formed from BeI,[zJ or from
Be(CH3)2 131 and ammonia at room temperature, was obtained i i i well-crystallized form from the metal at 360 "C and
2500 atni in five days.
[ I ] Part XI11 of Metal-Trifluorophosphine Complexes. -- Part
X11: Th. Kruck and W. Lang, Z . anorg. allg. Chem. (1965), in
[ 2 ] Cf. 771. Kruck and K. Bnur, Chem. Ber. 98, 3070 (1965).
[3] E. 0.Fisrlwr and R. Jira, Z. Naturforsch. lob, 355 (1955);
T. S. Piper, F. A. Cotton, and C. Wilkinson, J. inorg. nucl. Chem.
I , I65 (1955).
We have also obtained iniides and nitrides by this method.
For instance, reaction o f beryllium with ammonia at 400 "C
and 200 atm for about a week gives pure cubic Be3N2,
whereas with a n ammonia stream at 1000 "C this preparation
succeeds only on repeated heating and pulverization.
Adsorption of Methylene Blue on Clays
The study of metal amides is often complicated by the
difficulty that thc materials arc formed only in amorphous
or poorly crystalline form. Such difficulties can often be overcome by use of the procedure described above, which is
patterned on hydrothermal synthesis. For instance, amorphous Zii(NH&, obtained from Zn(CzH5)2 and ammonia,
can be recrystallized without difficulty.
Received: Novcmher 13th, 1965 [ Z 109/942 IE]
German version: Angew. Chem. 78, 208 (1966)
[ I ] Cf. R. Juz(r, Angcw. Chem. 76, 2YG (1964): Angew. Chem.
internat. Edit. 3, 471 (1964).
[ 2 ] R. W. Brrgstrowr, J . Amer. chen:. Soc. 50, 657 (1928).
[3] R. hl~r.t/hofand C'h. C'i?rorh, Z. Chcm. 5 , 142 (1965).
Cliern. iriteinut. Edit.
Vol. 5 (1966) 1 No. 2
[4] vs
very strong.
By Prof. Dr. U. Hofmann, Dip1.-Chem. H. Kottenhahn, and
Dr. S. Morcos
Anorganisch-Chemisches Institut
der Universitat Heidelberg (Germany)
Dedicated to Professor Karl Freudenberg
on the occasion of his 80th birthday
Some time ago we found[ll that adsorption of Methylene
Blue o n charcoal offers a good possibility of determining the
surface area.
Methylene Blue IS a quaternary ammonium chloride,
C16H18N3SC1, so it was expected[zl that it would undergo
cation exchange o n clay earths; the Table shows that this
indeed occurs. The amount of Methylene Blue taken up is
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cobalt, cyclopentadienyl, trifluorophosphine
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