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The First closo-Diphosphahexaborne P2B4Cl4.

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Experimental Procedure
1 : [Ru"'(Hedta)CI]" was reduced to (Ru"(Hedta)(H20)JB 2 using hydrogen
over platinum black under an atmosphere of hydrogen."" The photocatalyst
CdS/Pt/RuO> was prepared by the published procedure [IS]. Complex 2 exhibits LMCT peaks at 283, 332, and 296 nm. On passing Nz through dilute
M), the peaks corresponding to 2 decrease with the
solutions of 2 ( =
appearance or a new peak at 221 nm, which was taken as a marker peak for
the calculation of the stability constant of 1. The equilibrium constant for the
formation of 1 is given by the following expression:
[ R ~ ( H e d t a ) ( H , o ) ] ~ N,
+ H20
From the solubility of N 2 in water at 25" (7.81 x
mol L-') the equilibrium constant for the formation of 1 at 25" was calculated as
log K , = 2.90_+0.02.
Complex 1 exhibits the v(M-N,) band at 2040 cm-'. Differential pulse polarography (DPP) of l gives a single peak at -0.48 V corresponding to the
redox couple Ru"/Ru'. The cyclic voltammogram of 1 gives reversible peaks
at -0.24 and - 1.0 V for the Ru"'/Ru" and H"/H potentials, respectively.
The peak corresponding to Ru"/Ru' cannot be observed because of the
crossover of the cathodic-potential and anodic-potential curves in this region.
Received: January 7, 1987;
revised: November 27, 1987 and April 7, 1988 [Z 2040 1EJ
German version: Angew. Chem. 100 (1988) 1000
CAS Registry numbers:
NH,, 7664-41-7; N2, 7727-37-9; CdS, 1306-23-6; F't, 7440-06-4; RuO,, 1203610-1 ; [Ru( Hedta)( N2)]'. 76058- 13-4.
[ I ] M. M. Taqui Khan, A. E. Martell: Homogeneous Catalysis by Meral
Complexes. Vol. I , Academic Press, New York 1974.
[2] M. E. Volpin, V. B. Shur: New Trends in the Chemistry ofNtirogen Fixafron. Academic Press, New York 1980.
[3] J. Chatt, J. R. Dilworth, R. L. Richards, Chem. Reu. 78 (1978) 589.
[4] E. E. van Tamelen, Acc. Chem. Res. 3 (1970) 361.
[S] E. E. van Tamelen, B. J. Akermark, J. Am. Chem. SOC.90 (1968) 4492;
N. H. Liu, N. Shanpach, J G. Palmer, G . N. Schrauzer, Inorg. Chem. 23
(1984) 2772.
161 N. T. Denisov, E. M. Burbo, N. 1. Shuvalova, A. E. Shilov, Kinet. Karal.
23 (1982) 874; E. M. Burbo, M. I. Lebedeva, N. T. Denisov, ibid. 27
(1986) 1504.
171 N. T. Denisov, N. I. Shuvalova, A. E. Shilov, Kinet. Katal. 26 (1985)
(81 C. R. Dickson, A. J. Nozik, J. Am. Chem. SOC.I10 (1978) 8007.
[9] C. J. Pickett, J. Talarmin, Nature (London) 317 (1985) 651.
[lo] C. J. Pickett, K. S . Ryder, J. Talarmin, J. Chem. SOC.Dalton Trans. 1986,
[l 11 K. Aika, Angew. Chem. 98 (1986) 556; Angew. Chem. h i . Ed. Engl. 25
(1986) 558.
[I21 G. N. Schrauzer, T. D. Guth, J. Am. Chem. SOC.99 (1977) 7189.
1131 M. Koizumi, H. Yoneyama, H. Tamura, Bull. Chem. SOC.Jpn. 54 (1981)
[I41 M. M . Taqui Khan, R. C. Bhardwaj, C. Bhardwaj, J . Chem. SOC.Chem.
Commun. 1988, 1690.
[IS] M. M. Taqui Khan, G. Ramachandraiah, unpublished.
[I61 K. Kalayanasundaram, E. Borgarello, D. Duonghong, M. Gratzel, Angew. Chem. 93 (1981) 1012: Angew. Chem. Int. Ed. Engl. 20 (1981) 987.
1171 A. A. Diamantis, J. V. Dubrawski, Inorg. Chem. 20 (1981) 1142.
[IS] J.-M. Lehn, J. P. Sauvage, R. Ziessel, K. Hilaire, Isr. J . Chem. 22 (1982)
Tetrahalodiborane(4) molecules BzX4 are transformed
upon heating into trihaloboranes and short-lived BX speciesfZ1or into stable cage molecules B,X, (X = C1, Br;
n = 8- 12).I3]Copyrolysis of halogenated hydrocarbons and
B2X4 results in the formation of perhalogenated carboranes;c41 little is known about the reaction course. The investigation described here was motivated by the question
whether other heteroatoms could be incorporated into halogen-substituted boron clusters.
Pyrolysis of a mixture of B2C14and PCl, at 330°C resulted in the formation of closo-3,4,5,6-tetrachloro-I
,Z-diphosphahexaborane(4) 1 as a hygroscopic, colorless, crystalline solid, in addition to small amounts of side products.
B2Cl, is apparently not only the source of "BCl" units but
acts at the same time as a reducing agent. The idealized
formulation of the reaction is given in Equation (a). In the
mass spectrum of the crude product, additional signals are
observed which have to be assigned to a molecule having
the composition PZB5C15.
7 B2CI.q
+ 2 PC13 * P,B,CI, + 10BCI,
The composition and structure of the phosphaborane 1
are derived from the spectroscopic data (Table 1). Since
the two phosphorus atoms can each contribute three electrons to the framework bonds, a closo-hexaborane is to be
expected according to the Wade rules. Its structure should
be derivable from an octahedron. The structure of the cluster is derived from the values for the chemical shift of the
boron atoms, and the cis arrangement of the phosphorus
atoms from the fact that two "B-NMR signals (1 : 1 ratio)
are observed. The X-ray structure analysis confirms the interpretation of the spectra (Fig.
Table I. Spectroscopic data for 1
"B-NMR (relative to BF3.0Et2, 25.67 MHz, C6D,, room temperature (RT));
61=2.5,62=22.1 (intensity ratio 1 : 1, halfwidth 128 Hz).--"P-NMR(re1ative
t o 85% H3P04, 32.2 MHz, C6D6, RT): 6 = - 187.-MS (70 ev): calculated
and measured pattern of '5C1/37CI/"B/'"B isotope distribution are in agreement): M e (rel. intensity 84%), B,Clf (7), B3CIY (7), [M-BCI,]" (100). Pf
(30), PBzClt (27), P,B2Cla (12), BzCl? (S), BCl? (17)
The First closo-Diphosphahexaborane P,B,CI,**
By Woygang Haubold,* Willi Keller, and Gisela Sawitzki
Dedicated to Professor Heinrich Noth
on the occasion of his 60th birthday
Higher boranes have often been prepared by pyrolysis
of smaller boranes. If appropriate mixtures of boranes and
hydrocarbons are used, carboranes are obtained."' Both
synthetic principles can be extended to haloboranes.
Prof. Dr. W. Haubold, Dr. W. Keller, Dr. G. Sawitzki
lnstitut fur Chemie der Universitat Hohenheim
Garbenstrasse 30, D-7000 Stuttgart 70 (FRG)
This work was supported by the Deutsche Forschungsgerneinschaft and
the Fonds der Chemischen Industrie.
Angew. Chem. Inl. Ed. Engl. 27 (1988) No. 7
Fig. 1. Molecular structure of 1. Selected distances [pm] and angles ["I: P1-P2
222.2(3), B2-B4 167.8(12), other B-B(average) 173, B-P(average) 200, B-Cl(average) 176; Bl-PI-63 76.8(4), BI-P2-B3 77.6(4), PI-P2-B2 81.9(3), P2-Pl-B4
82.3(3), P2-82-84 98.2(5), BI-B2-B3 94.0(6), PI-B4-B2 97.6(5), BI-B4-B3
0 VCH Verlagsgesellschaji mbH. 0-6940 Weinheim. 1988
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The distances and angles reveal the distortion of the octahedron caused by the large phosphorus atoms. The angles at the phosphorus atoms are reduced by displacement
of these atoms from the ideal octahedral positions. Those
at the boron atoms B2 and B4, in trans positions, are increased. The P-P distance corresponds to that of a single
bond. The B2-B4 bond on the opposite side (168 pm) is
shorter than usual for B-B bonds in clusters. The B-P and
the remaining B-B bonds are, as expected for 1, longer
than corresponding two-center bonds. In phosphane-boranes R3P-BR;, the B-P bonds, with one exception, are
shorter than 190 pm; in the diphosphaborirane three-membered ring of (tBuP),BNEt,, the B-P distance is
189.3 pm,['] and in one of the few known clusters containing phosphorus atoms in the framework, the phosphacarborane CHPBloH8C12,it is 202 prn.['l
Experimental Procedure
B,CL (1.5 g, 9.2 mmol) and PCI, (1.0 g, 7.2 mmol) were condensed into a 250mL thick-walled flask equipped with a break seal. After melting and thawing,
the mixture was heated to 330°C for I h and then cooled over ca. 12 h to
room temperature. The volatiles were removed at 0°C and the ocher-colored
residue remaining was extracted several times with ca. 5 mL of BCI,. The
solvent was removed and the colorless solid was sublimed by gentle warming
onto the cooled neck of the flask and then washed with a small amount of
BCI, into another pyrolysis flask. Boron trichloride was removed under
vacuum. After heating for a short time at 240°C and slowly cooling, 50 to
100mg of 1 separated out as colorless, moisture-sensitive needles. In a
sealed, evacuated tube, the compound melts at 74-75°C. Yield: 15-25%
[reaction according to Eq. (a)].
Received: September 30, 1987 [Z 2450 IE]
Publication delayed at authors' request
German version: Angew. Chem. 100 (1988) 958
[ I ] Grnelin Handbuch der Anorganischen Chernie. Erganrungswerk zur 8. Auf
luge. Band 15 (Boruerbindungen 2. Carborane I). Springer, Berlin 1974.
121 R. Weinmann, Dissertation, Universitat Stuttgart 1985.
[3] T. Davan, J. A. Morrison, Inorg. Chem. 25 (1986) 2366.
[4] W. Keller, Disserration, Universitat Stuttgart 1987.
[5] X-ray structure analysis: orthorhombic, space group Pbna (No. 60),
1.941 cm-',
a=600.2(2), b = 1240.1(3), c=2270.6(8) pm, 2 = 8 ; pcalcd=
p = 16.93 c m - ' (Mo,,); T = 170 K; 2471 unique reflections (26<60"),
1825 observed with F > 3 o ( F ) ; R=0.073. Further details of the crystal
structure investigation may be obtained from the Fachinformationszentrum Energie, Physik, Mathematik GmbH, D-7514 Eggenstein-Leopoldshafen 2 (FRG), on quoting the depository number CSD-52767, the names
of the authors, and the journal citation.
161 M. Fehir, R. Frohlich, K.-F. Tebbe, 2. Anorg. Allg. Chem. 474 (1981)
[7] H. S . Wong, W N. Lipscomb, Inorg. Chem. 14 (1975) 1350.
Synthesis and Structure of a
By Albrecht Kramer, Hans Pritzkow, and Walter Siebert'
Dedicated to Professor Heinrich Noth
on the occasion of his 60rh birthday
Dehalogenation of (Z)-1,2-diborylethenes 1 with Na/K
alloy furnishes 1,2- and 1,3-dihydrodiboretes ( l a + 2 ;[la]
l b - 1,3
o r carbaboranes ( IC+(CE~)~(BCI),"'~),
but no eight-membered ring derivatives."] Attempted dimerization of planar 2 to give the diene 3 was also unsuc[*] Prof. Dr. W. Siebert, Dipl.-Chem. A. Kramer, Dr. H. Pritzkow
Anorganisch-chemisches Institut der Universitat
Im Neuenheimer Feld 270, D-6900 Heidelberg 1 (FRG)
This work was supported by the Deutsche Forschungsgemeinschaft, the
Fonds der Chemischen Industrie, and BASF.
0 VCH Verlagsgeseilschafi mbH. 0-6940 Weinheim, 1988
cessful ; instead, an intramolecular rearrangement occurred, giving the puckered 1,3 isomer of 2.1'"1A metaldependent ring formation reaction is observed upon dehalogenation of 12-(bromomethyl)phenyl]chloro(diisopropylamin~)borane;'~
with lithium leads to the formation of I-(diisopropy1amino)dihydrobenzoborete (30%)
and reaction with Na/K alloy to 5,1l-bis(diisopropylamino)tetrahydrodibenzo[bf[l,5]diborocine (9%).
R3 R3
/"=? B
i Pr2N'B,
Ni Pr,
c= c
Ni Pr,
i Pr,N
N i Pr,
Herein we report the synthesis of the 1,2,5,6-tetrahydro1,2,5,6-tetraborocine derivative 3 from 2 in the presence
of hydrogen and Lindlar catalyst. In addition to 3 (27%)
and the starting material 2, Id could be isolated in low
In the dimerization of 2, hydrogen (via PdH2?) serves an
activating function, since no 3 is formed in the presence of
Lindlar catalyst alone. Our initial assumption that Id,
formed by hydrogenation of 2, might be the intermediate
involved in the formation of 3 was not confirmed when we
treated Id with the catalyst. The mechanism of formation
of 3 is still unclear.
The constitution of 3 was established by the NMR and
mass spectra. In the "B-NMR spectrum a signal at
6 = 51.4, which is characteristic of diborane(4) derivatives
with alkenyl and dialkylamino substituents, was
Owing to the BN .n bond, the two iPr groups on each of the
N atoms are nonequivalent [6('H) of 3=1.09 (d, 5=7.0
Hz, 24H), 1.25 (d, 24H), 3.35 (m, 8H), 6.65 (br. s, 4H)]. In
the mass spectrum, the molecular ion peak, with an isotope
distribution characteristic of four boron atoms, appears at
m / z 496 (14.9%).
The X-ray structure analysis shows that 3 is present in
the crystal as a nonplanar eight-membered ring (Fig. l).l5]
The molecule displays a crystallographically determined
twofold axis. Four ring atoms (Bl, C1, C2', B2', and B2,
C2, Cl', Bl') are located in a plane ( f 0 . 0 3 A). The two
planes form an angle of 42" and the bonds B1B2 and
Bl'B2' are nearly perpendicular to each other (82"). The
distances in 3 differ slightly, but significantly, from those
in 2:[Ia1the B-B distance is shorter (1.718 vs. 1.749 A); the
B-N distances (1.412 vs. 1.377 A) and C = C distances
(1.346 vs. 1.312 A) are longer. Better agreement is found
upon comparison with the distances in the I ,2,4,5-tetraborinane ring.I61
Compound 3 is the first organoborane belonging to the
(CR'),(BR2)4 class; three further compounds having this
general formula (R'/R2 = CHJH,"' C2H5/CH3,'*]C2H5/
Cl'"]) exist as carbaboranes owing to their electron deficiency at the boron atoms. In 3, the diisopropylamino
groups satisfy the electron demand of the boron atoms and
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Angew. Chem. Inr. Ed. Engl. 27 (1988) No. 7
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diphosphahexaboran, first, p2b4cl4, closs
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