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Novel Boron-Phosphorus Cages with C4B4P4 and C2B4P4 Frameworks.

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Table I. IK hands of 2 and 2a matrix-isolated in argon at 12 K
i.[cm
'I
A + [cm
2
2a
1890 5
I858 vs
1789 s
1629 s
1856 s
1825 vs
1775 s
1619 s
~
'1
34
33
14
10
tronic stabilization is achieved by amino substituents on
the boron atom or if kinetic stabilization is achieved by
bulky substituents on the boron and phosphorus atoms,
then the corresponding phosphinoboranes are monomeric.12b.31Derivatives of the heterocycles 2,Sdihydro- 1H1,2,5-phosphadiborol 1 and 1,2,3,6-tetrahydro- I ,2,3,6-diphosphadiborin 2Is1with amino substituents on boron are
also monomeric. We have now synthesized a derivative of
2 that is dimeric.
The only disappointment in the IR spectrum of 1 (Fig.
1) is the absence of an identifiable triple-bond stretch. It is
probably either hidden under the carbon monoxide bands
(2139, 2149 c m - ' ) or is very weak compared to other
bands in 1 and thus not observed.'"] The other IR bands
of 1 are due to vibrations very similar to those of the hydrocarbon portion of 2. The most striking shifts are those
of the bands at 684 and 643 c m - ' in 2 to 445 and 405
c m - ' in 1.
Received: September 22, 1987 [Z 2437 IE]
German version: Angew. Chem. 100 (1988)402
CAS Registry numbers:
1. 37494.1 1-4;2, 54283-14.6: 2a, 112897-94-6;3, 59129-90-7;4,37490-74-7;
"CO, I64 1-69-6;H?C=CH*, 74-85-1: (CH>)?C=C=C=C(CH,)>, 243 1-31-4.
[I]0.L. Chapman, J. Gano, P. R. West, M. Regitz, G . Maas, J. Am. Chem.
Soc 103 (1981)7033.
[2] M. Suda, S. Masamune, J. Chem. Soc. Chem. Commun. 1974. 504.
[3]The photodecarbonylation of 2 in Ar at 15 K was described by Krebs et
al. Our results clearly show that the spectrum, tentatively assigned to 1
by these authors, has to be reassigned to a n unknown photoproduct: A.
Krebs, W. Cholcha, M. Muller, T. Eicher, H. Pielartzik, H. Schnockel,
Tetrahedron Lett. 25 (1984)5027.
[4]2 . IR (Ar, 12 K): 2976 (s), 2941 (m), 2879 (w), 1890 (s), 1858 (vs), 1842
(m), 1789 (s). 1629 (s), 1463 (w), 1456 (w), 1367 (m), 1205 (m). 1159 (m),
758 (w). 684 (m), 643 (w) c m - ' .
[5]The thermal decomposition of cyclohexyne to give ethylene and butatriene was observed recently: a) J. Tseng, M. L. McKee, P. B. Shevlin, J.
Am. Chem. Soc. I09 (1987)5474; b) A. Runge, W. Sander, unpublished
results.
[6]Tetrdmethylbutatriene: IR (Ar, 12 K): G=2998 (s), 2936 (s), 2914 (vs),
2894 (m). 2873 (m), 2857 (m),2714 (w). 1664 (w), 1452 (s), 1375 (m), 1365
(s), 1705 (w). 1064 (s), 815 (w), 534 (m), 433 (m) c m - ' . For a discussion
of the IR spectrum (gas-phase) see: A. Rogstadt, Spectrochim. Acta A 36
(1980)131.
[7] L. Skattebol, Tetrahedron Leu. 1965. 2175.
[8]a) I>. E. Applequist, P. A. Gebauer, D. E. Gwynn, K. H. O'Connor, J.
Am. Chem. Soc. 94 (1972)4272;b) C.N. Bush, D. E. Applequist, J. Org.
Chem. 42 (1977) 1076.
[9]Photochemical addition of carbon monoxide to 1,2-dehydronaphthalene
has been observed, unpublished observation of F. Diederich and 0. L.
Chapman.
[lo] Y. Tdkehira, F. Toda, Bull. Chem. Soc. Japan 51 (1978) 2441.
[ 1 I ] Recenrly, the triple-bond stretching frequency for unsubstituted cyclohexyne was calculated to be 2003 c m - ' : S. Olivella, M. A. Pericas, A.
Riera. A. Sole, J. Org Chem. 52 (1987)4160.The intensities of the bands
were not calculated and therefore the comparison with the experimental
value\ is difficult. The IR spectrum of 1 shows no IR band in the range
1900 2100 c m . ' (Fig. I).
Novel Boron-Phosphorus Cages with
C4B4P4and CZB4P4Frameworks**
By Matthias Driess, Hans Pritzkow. and Walter Siebert*
In contrast to aminoboranes, phosphinoboranes exist
mainly as cyclic dimers o r trimers.",21 However, if elec-
[*I
[**I
Prof Dr W. Siebert, M. Driess, Dr. H. Pritzkow
Anorganisch-chemisches lnstitut der Universitat
Im Neuenheimer Feld 270, D-6900 Heidelberg (FRG)
This work was supported by the Deutsche Forschungsgemeinschaft, the
Fonds der Chemischen Industrie, and BASF AG.
Angew. Chem. In!. Ed. Engl. 2711988) No 3
2
Reaction of 3 with 1,2-di-tert-butyl-1,2-bis(trimethylsi1yl)diphosphane 4 results in elimination of Me,SiCI and
formation of a dimeric product, which is not the cubanelike compound 5 but, surprisingly, the colorless, constitutionally isomeric compound 6 , having the cuneane cage as
a structural element. Thus, its structure is analogous to that
of S,N, or Hittorf phosphorus. Compound 6 is stable
toward oxygen and moisture u p to ca. 100°C. In contrast
to compounds of types 1 and 2 , compound 6 does not
react with sulfur or selenium in refluxing toluene.
R
4
CI
il
5
The tH(3iP]-NMRspectrum of 6 exhibits two singlets
for the tert-butyl protons and the 3'P(iH)-NMRspectrum
exhibits two triplets at 220 K, which are broadened owing
to 1iB-3'P coupling. The "B-NMR signal at 6=4.2
(b1,2= 170 Hz) is in a region characteristic for tetracoordinated boron. These findings are not in agreement with
structure 5 but rather with structure 6 . This conclusion is
further corroborated by the result of X-ray structure analyses (Fig. l),["' according to which 6 is present in two
modifications, one of which contains two independent
molecules in the unit cell. The structures of the molecules,
however, are not significantly different.
The formation of 6 within twelve hours (at 300 K) can
be followed by 'H-, I'B-, and 3'P-NMR spectroscopy. The
elimination of Me,SiCI was thereby shown to proceed in
two steps via an intermediate that has not yet been characterized. The intermediate, in turn, gives 6 quantitatively
( ' H - N M R spectroscopy).
In order to determine what effect the kind of hydrocarbon bridge has on the cage formation, we incorporated the
methylene group in place of the ethenylene group. The
reaction of CH2(BCI2)?7 with 4 does not result in formation of compound 8, which is analogous to 6 , but rather in
formation of the colorless, constitutionally isomeric compound 9, which is moderately soluble in CH2C12 and
0 V C H Verlagsgesellschaji m h H . 0-6940 Weinheim. 1988
0570-0833/88/0303-0399 $ 02.50/0
399
temperature and stirred for an additional 12 h After removal of all readily
bolatile components under vacuum, an orange powder remained, which was
recrystallized from toluene ( - 3 0 ° C ) . Yield: 2.95 g (560)") 6 , m.p =308"C
(dec.). correct C,H.P elemental a n a l y s i s . ~ ' H ( " P } - N M R
(300 MHz, CDZCII,
300 K): 6 = 1.49 (s, I R H ) , 1.61 (s, IXH), 6.23 (br. s, 4H): .''P('Hl-NMR (80.0
220 K): d = 19.92 (t, 2P, 'J(PP)=87 5 Hz), 14.70(t, 2P): " C NMR (50.3 MHz, CD:CII, 300 K): 6 = 3 2 82 (m, 6 C : C H H , ) , 33.38 (m, 6 C :
CCH.?), 43.18 (m, 2C: CCH2), 43.26 (m, 2C: CCH,), 145.08 (br. s, 4 C : CB):
MS (CI, C H , ) . n?/z 588 (4'%1, Me), 531 (6%. [M-rBu]"). 474 (4"A.
[M-ZIBUI'), 57 (lOO'%, ,Bus).
Fig. I SIereodrawing of the molecular structure of 6 . Important bond
lengths [A] and angles ["I (standard deviations for modification I : 0.0030.015
0.2-0.8": for modification 11: 0.002-0.009
0.1-0.5"; averages for
three molecules): PILP2 2.273, P3-P4 2.254, P1(2)-B 2.02, P3(4)-B 2.000, B-C
1.573, C-C 1.330: B-PI(Z)-B 110.3, B-P3(4)-B 86.7, Pl(2)-P2(1)-B 96.7, P3(4)P4(3)-B 104.9, PI(Z)-B-C 110.2, P3(4)-B-C 100.8, P-B-P 95.0, C-C-B 116.7
A,
A,
CHiCN and whose stability toward oxygen and moisture
is similar to that of 6.
".O"']decane): 4 (5.49 g, 17 mmol) in
CH2Cl2 (100mL) was added slowly at -40°C to 7 (3.03g, 17 mmol) in
CH2ClZ(300 mL). After warming to room temperature, the clear orange reaction solution was concentrated to ca. 80 mL and allowed to stand for 24 h,
resulting in the crystallization of 9, which was further purified by washing
with warm CCI,. Yield: 2.02g (42%) 9, m.p.=218"C (dec.). Correct C,H,P
elemental analysis.-'H("P/~NMR (300 MHz, CDCI?, 300 K): 6 = 1.78 (s,
36H), 1.45 (br. s, 4H): "P{'HJ-NMR (121.5 MHz, CDCI3, 210 K): 6=2.03
(br s); "B-NMR (29.8 MHz, CDCI,, 300 K ) : 6=8.6 (s. h , ? = 130 Hz);
"CI'HJ-NMR (50.3 MHz, CDCI,, 300 K ) : 6=33.45 (m, 12C: CCH3), 43.41
(m, 4C. CCH,), a signal for CB was not observed: MS ( E l , 70 eV): m / z 564
(3%. Ms), 507 (23%. [M-~Bu]"), 451 ( ~ ~ ' ~ ~ . [ M - - I B U - - C ~282
H ~(4%.
] ~ ) ,[ M I
2]@), 57 (100%&,
fBu3)
Received: October 5, 1987 [Z 2458 IE]
German version: Angew Chem. 100 (1988) 410
CAS Registry numbers:
3, 18447-36-4;4, 55793-25-4; 6, 112969-18-3; 7, 40710-68-7: 9, 112969-19.4.
-L
Me,SiCI
7
R = CMe,
&I
[I] J. R. Wasson, Boron-Phosphorut Compounds in: Gmelin, Handbuch der
Anorganischen Chemre. Boruerhindungen Band / 9 / 3 . p. 93.
[2] a) G Fritz, E. Sattler, Z. Anorg. Allg. Chem. 413 (1975) 193; b) R. Koster,
Drorganophosphrnobcrane in: Houhen- We?/-Miiller, Boruerhindungen.
Band 13/36, p. 386.
131 H. Noth, W. Schragle, Z . Narurfbrsrh 8 1 6 (1961) 473.
[4] M. Driess, H . Pritzkow, W. Siebert, Angew. Chem. 99 (1987) 789: Anyew.
Chem Inr. Ed. Eiigl. 26 (1987) 781.
IS] M. Driess, H. Pritzkow, W. Siebert, unpublished results.
161 6 crystallizes in two modifications. I : space group P2,ah, a = 12.703(3),
h= 14.894(7), c = 16.263(4)
V=3077
2 = 4 . Refinement with 2475
reflections ( / 2 0 ( / ) two-circle
,
diffractometer, MoK<,radiation, w scan),
R=0.058 (CI. P, C, B anisotropic, methyl groups as rigid groups) [9].-1::
space group P2,/c. a = 10.236(4), h= lX.I07(7), c=33.239(1 I ) A,
[1=98.66(3)"; Y=6090 A', 2 = 8 . Refinement with 541 1 reflections
( I = 2r7(/), four-circle diffractometer, MoKCt
radiation, w scan), R=0.042
(Cl, P, C, B anisotropic, methyl groups as rigid groups) 191.
[7] We thank Mr. Domnrck, Universitiit Karlsruhe, for the spectra.
[S] 9 : space group C2/m2 a = 13.564(4), h= I1.657(3), c=9.910(3)
/ I = I13.84(3)": Y= 1433 A', Z=2. Refinement with 1584 reflections
(122 0 ( 1 ) , four-circle diffractometer, MoKglradlation, w scan), R =0.034
(CI. P. C, B anisotropic, methyl groups in part as rigid groups) 191.
[9] Further details of the crystal structure investigations may be obtained
from the Fachinformationszentrum Energie, Physik, Mathematik GmbH,
D-75 14 Eggenstein-Leopoldshafen 2 (FRG), on quoting the depository
number CSD-52758, the names of the authors. and the journal citation.
A:
9
The 'H(3'P]-and 3'P('H}-NMR spectra"] of 9 indicate a
highly symmetric arrangement of atoms in the molecule,
which is confirmed by the results of an X-ray structure
analysis (Fig. 2).lXl Compound 9 contains two CBzPz fivemembered rings joined by donor-acceptor bonds, whereas
8 displays two less favorable CBzP four-membered rings.
A',
A,
Synthesis and Properties of
N"-Di-tert-Butoxycarbonyl and
N"-Benzyloxycarbonyl tert-Butoxycarbonyl
Amino Acids""
By Kerstin Gunnarsson, Leif Grehn, and UlfRagnarssonY
Fig. 2. Stereodrawrng of the molecular structure 0 1 9 . Important bond
lengths [A] and angles I"]: P-P 2.242(1), P-B 2.041, 2.036(2), B-C 1.584,
1.587(4); P-P-B 95.0(1), BI-P-B2' 93.9(1), CI-B-P 110.3, I IO.O(l), BI-CILB2
110.3(2).
['I
Experimental Procedure
6 (2,3,8.9-tetra-rert-butyl- l,4,7, IO-tetrachloro-2,3,8,9-tetraphosphoniaI,4,7, I 0-tetraboratapentacyclo[6.4.0.0~~'".0~~7.0~~y]dodeca-5,
1 I -diene): 3 (3.4 g,
178 mmol) was dissolved in CHICll (200 mL) at -20°C. 4 (5.73 g,
17.8 mmol) in C H I C l l (100 mL) was then added to this vigorously stirred SO^
lution. The clear orange-yellow solution was then allowed lo warm to room
400
0 VCH Verlugsyesellsrhaft mhH. 0-6940 Weinheim. I988
Benzyloxycarbonyl"' (Z) and t e r t - b u t o ~ y c a r b o n y l [ ~ ~ ~ ~
(Boc) amino acids are derivatives of fundamental importance in modern peptide synthesis.["] The two groups
[**I
Dr U. Ragnarsson, K. Cunnarsson, B. Sc., Dr. L. Grehn
Institute of Biochemistry, University of Uppsala, BMC
Box 576, S-75123 Uppsala (Sweden)
This work was supported by grants from the Swedish Natural Science
Research Council and the National Swedish Board for Technical Development and by a research scholarship (to K . G.) from the Sven and Liily
Lawski Foundation.
0570-0833/88/0303-04400 $ 02.50/0
Angew. Chem. I n [ . Ed. Engl. 27 11988) N o . 3
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