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Cyclometallaborazines Borazines with Metal Atoms as Ring Building Blocks PhB(MeN)3(TiCl2)2.

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[12] H. Rabaud, J. Clastre, Acta Crystallogr. 1959, 12, 911-915.
[13] C. R. Theocharis, W. Jones, J. Chem. Soc. Faraday Trans. 1 1985, 81,
857 - 874.
[14] It must be checked whether the details about the epitaxy in at least six
orientations of the crystals of dimer 2 a should be reinterpreted, because
this report assumes crystallization solely in the interior of the anthracene
crystal: M. M. Julian, J Chem. SOC.Dalton Trans. 1972, 558-560; D. P.
Craig, J. Rajikan, J Chem. Soc. Faraday Trans. 1978, 74,292-303.
(151 G. Kaupp, Justus Liebigs Ann. Chem. 1973, 844-878; ibid. 1977, 254275; for UVjVIS diradical spectra there is already a review available [M. J.
Johnston in Handbook ofPhotochemistry, Vol. 2 (Ed.: J. C. Scaiano), CRC
Press, Boca Raton, FL, USA 1989, Chap. 21, but it does not even mention
the first 1,4-diradical spectra [G. Kaupp, E. Teufel, H. Hopf, Angew.
Chem. 1979,91,232-234; Angew. Chem. Inr. Ed. Engl. 1979,18,215-2171,
although their resolution is much better than the later spectra of the Scaiano/Johnston group and others.
(161 G. Kaupp, H.-W. Griiter, Angew. Chem. 1979,91,943-944; Angew. Chem.
Int. Ed. Engl. 1979, 18, 881-882; Chem. Ber. 1980, 113, 1458-1471.
material for the synthesis of the target compound and should
react with titanium halides via ring closure to give 2. However, the reaction of l with titanium tetrachloride in the
molar ratio 1 :1 in CHCI, did not afford 2, but led instead to
a red-brown powder 3 and the substituted borazine 4161 in
almost quantitative yields (49 % each) [Eq. (a)].
We obtained deep red crystals of 3 from THF (also soluble
in MeCN) which were suitable for X-ray crystallography.
The results of the structure analysis are shown in Figure
P
Cyclometallaborazines: Borazines
with Metal Atoms as Ring Building Blocks:
PhB(MeN),(TiCl,), * *
By Hans-Joachim Koch, Herbert W! Roesky,*
Rakesh Bohra, Mathias Noltemeyer,
and Hans-Georg Schmidt
Fig. 1. Crystal structure of 3 with two coordinated THF molecules. Selected
distances [pm] and angles ["I: Ti(1)-Ti(2) 273.6(1), Ti(1)-N(1) 188.9(3), Ti(1)N(2) 212.8(3), B-N(2) 145.3(6), B-N(3) 144.7(5), Ti(Z)-N(l) 186.3(3),Ti(2)-N(2)
213.5(3); Ti(l)-N(l)-Ti(2) 93.6(1), Ti(l)-N(2)-Ti(2) 79.9(1), Ti(l)-N(3)-Ti(2)
79.7(1).
Dedicated to Professor Anton Meller
on the occasion of his 60th birthday
Borazine was first reported by A. Stock and E. Pohland in
1926.['] The number of borazines substituted at the ring
framework is legion. However, to our knowledge no derivatives are so far known, which contain transition-metal atoms
as building blocks in the borazine framework. Only quadrinomial boron-containing metallacycles have already been
reported.[' -41
Methyl- bis [ (methyl( trimethylsily1)aminophenyl)boryllamine (l),prepared by Noth et al.,['] served as the starting
Ph,
Me-N\
Ph
1
Me
1
B-N-SiMej
/
/
These confirm that 1 reacts with titanium tetrachloride via
the insertion of two titanium dichloride units to give 3. An
increase in the yield of 3 cannot be achieved by the reaction
of 1 and titanium tetrachloride in the ratio 1:2. Also, a
by-product, which could explain the reaction pathway could
not be isolated. Only a change in solvent from CHCI, to
hexane led to the unstable intermediate 5.
+
Tic$ -
B-N-SiMej
I
Me
1
I
Me
-2CIStMe3
+
la1
Ph
Me
5
Together with 5, compound 4, traces of 3, and a red-brown
TiN-containing polymer were also formed. Compound 5 is
yellow, crystalline, and is obtained in a yield of 17.5 YO.The
crystal structure analysis showed two molecules of 5 in the
asymmetric unit.'']
On the basis of the structures of 3 and 5 (Fig. 2) as well as
the experimental results the following reaction sequence
seems plausible: in the first step, 1 reacts with two equivalents of titanium tetrachloride to give 5. Compound 5 then
decomposes very rapidly via an SNireaction to give 3 and one
equivalent of PhBCI,. The PhBCl, then reacts with a further
equivalent of 5 to give 4, whereby two equivalents of titanium tetrachloride are liberated which themselves then react
aeain with I.
The structure of 3 can be described as a geometric body
whose surface consists of four, bent, irregular squares, or as a
tetrahedron whose apexes are N(2), N(3), Ti(l), and Ti(2),
which On the N(2)-N(3) edge is bridged by a boron atom and
on the Ti(ltTi(2) edge is bridged by a nitrogen atom. The
Y
[*] Prof. Dr. H. W. Roesky, H:J.
Koch, Prof. R. Bohra, Dr. M. Noltemeyer,
H.-G. Schmidt
Institut fur Anorganische Chemie der Universitat
Tammannstrasse 4, D-W-3400 Gottingen (FRG)
f**l
This work was suooorted
- the Deutsche
. _
_. by the Volkswapen-Stiftunr.
Forschungsgemeinschaft, and the Fonds der Chemischen Industrie.
598
0 VCH
Verlagsgesellxhaf! mbH. W-6940 Weinheim. 1992
0570-0833/92j0505-0598 $3.5050+.25/0
Angew. Chem. Int. Ed. Engl. 31 (1992) No. 5
1378vs, 1262s, 1181s, 1111 s, 988s, 702s, 518vs. Correct C, H, N, CI analyses.
"B-NMR (80.21 MHz, C6D6, OEt, . BF,): 6 = 2.2(~). - 'H-NMR
(250.13 MHz, C,D,, TMS ext.): 6 =7.3 (m, Ph, IOH), 3.8 (s, Me, 6H), 2.7 (s,
Me, 3 H).
Received: August 21, 1991 [Z4881 IE]
Publication delayed a t authors' request
German version: Angew. Chem. 1992, 104. 612
Fig. 2. Crystal structure of 5. a) top view, b) side view. Selected distances [pm]
and angles ["I: Ti(l)-Ti(2) 326.4(1), Ti(l)-N(I) 209.6(4), Ti(1)-N(3) 210.8(3),
B(I)-N(l) 145.0(6), B(2)-N(2) 147.2(7), B(2)-N(3) 146.3(6), Ti(2)-N(1) 210.7(3),
Ti(2)-N(3) 212.2(4); Ti(l)-N(l)-Ti(2) 101.9(2), N(l)-Ti(l)-N(3) 75.6(1).
reason for this nonplanar configuration are the strong intramolecular Ti-N interactions [Ti(l)-N(3) 21 3.0(3) and
Ti(2)-N(2) 213.5(3) pm], which, if the THF ligands are considered, lead to a distorted octahedral environment of the
titanium atoms. The lengths of the Ti-N bonds to the threefold coordinated nitrogen atom [Ti(l)-N(I) 188.9(3) and
Ti(2)-N(l) 186.3(3) pm] are similar to that in [($C,H,)TiC1,N(SiMe3),] [187.9(3)~ m ] . [Shorter
~]
Ti-N bonds
are found in the compounds [Ph,P(S)N=TiCl; 3 C,H,N]
[172.0(2) pm]['o] and [(~5-C,Me,)Ti(C1)=NtBu.C,H,N]
I169.8(4) pm].[' The Ti-N bonds to the fourfold coordinated nitrogen atoms are significantly longer [Ti(ltN(2)
212.8(3) and Ti(2)-N(3) 214.1(3) pm].
Compound 5 can best be described as a bicyclo[3.3.l]heptane derivative. The titanium atoms are coordinated differently, whereas Ti(1) is surrounded in a distorted tetragonal
pyramidal manner, Ti(2) is surrounded in a distorted
octahedral manner [intramolecular Ti(2)-N(2) interactions
(244.4 pm)]. The other Ti-N bond lengths (average
210.2 pm) correspond
to those in [Ph,P{p-N(SiMe3)},TiC1,{NPPh,N(SiMe3)~]][1~1
(average 210.3 pm).
Similar Ti-Cl distances to those in 5 (average 222.1 pm)
are present in [(q5-C,H,)TiCI,N(SiMe3)z]L'31
(average
227.1 pm).
The boron-nitrogen framework of 1 is influenced very
little by the titanium atoms in 5, as a comparison of the
structures of 5 and 1[14]
shows; the B-N distances are only
an average of 2.9pm longer in 5. In contrast, the Ti-Ti
distances for 3 and 5 are significantly different [273.6(1) and
326.4(2) pm, respectively]. This may be explained by the
variation of the bridge lengths in 3 (N-B-N) and in 5 (N-BN-B-N). Compound 5 can only be stored for a long period
of time as a crystalline solid under inert conditions. In solution, 5, in contrast to 3, is very unstable and decomposes
within 2-3 minutes to give 3 and 4.
Experimental Procedure
3: To a solution of 1 (2.05 g, 5.0 mmol) in CHCI, (40 mL), TiC1,(0.95 g,
5.0 mmol) in CHCI, (20 mL) was added dropwise at room temperature. The
suspension was refluxed for 4h, then allowed to cool to room temperature and
a red-brown precipitate was filtered off. Finally the powder was extracted
several times in CHCI, and thus compounds 3 (0.99 g, 2.4 mmol, 49 %) and 4
(0.84 g, 2.4 mmol, 49 %) were obtained. 3: m.p. = 135 "C (decomp); IR(nujol/
1461 s, 1377s, 721111. Correct C, H, N, CI
KBr): v'[cm-'] = 2955vs, 2 9 2 5 ~
analyses. "B NMR (80.21 MHz, CD,CN, OEt, BF, ext.): 6 = 24.1 (s). 'H NMR (250.13 MHz, CD,CN, TMS ext.): 6 =7.5 (m. Ph, 5H), 4.5 (s, Me,
3H), 3.6 (s, Me, 6H). - EI-MS: m/z413 ( M ' , 14%).
5: To a suspension of 1 (2.05 g, 5.0 mmol) in hexane (40 mL), TiC1, (1.90 g,
10.0 mmol) in hexane (20 mL) was added dropwise at room temperature. The
reaction mixture was refluxed for 3h and subsequently filtered whilst still hot.
Yellow crystals of 5 together with a red -brown solid, precipitated out from the
filtrate at 25 "C. The crystals were sorted out. Yield 0.50 g (0.88 mmol, 17 %).
m.p. = 105°C (decomp). IR(nujol/KBr): f[cm-'] = 1660m. 1498m, 1456vs,
-
Angew. Chem. I n l . Ed. Engl. 31 (1992) No. 5
0 VCH
[I] A. Stock, E. Pohland, Chem. Eer. 1926, 59, 2215-2223.
[2] D. Fest, C. D. Habben, A. Meller, G. M. Sheldrick, D. Stalke, F. Pauer,
Chem. Ber. 1990, 123, 703-706.
[3] H. Braunschweig, P. Paetzold, R. Boese, Chem. Eer. 1990, !23,485-487.
[4] P. Paetzold, K. Delpy, R. P. Hughes, W. A. Herrmann, Chem. Eer. 1985,
118, 1724- 1725.
[5] H. Noth, M. J. Sprague, J Orgunornet. Chem. 1970, 22, 11-22.
[6] H. Noth, W. Tinhof, Chem. Eer. 1974, 107, 3806-3817.
[7] a) Crystal structure analysis of 3 . 2 TH F Space group P2,/c, a =
1588.9(3), b = 903.1(1), c = 1814.7(4)pm, p = 102.30(1)", V =
2.5442(13) nm3, Z = 4, pea,.a = 1.45 M g t ~ - ~g(MoKm)
,
= 1.06 rnm-',
7440 measured reflections to 20,,, = 45 ', 2776 observed reflections with
IF1 > 3u(IF,I) were used for the structure refinement. R = 0.039
(wR = 0.046, weighting scheme w - ' = u Z ( F ) + 0.0004Fz). b) Further
details of the crystal structure investigation may be obtained from the
Fachinformationszentrum Karlsruhe, Gesellschaft fur wissenschaftlichtechnische Information mbH, D-W-7514 Eggenstein-Leopoldshafen 2
(FRG) on quoting the depository number CSD-55828, the names of the
authors, and the journal citation.
[S] Crystal structure analysis of 5: Space group P2,, a = 879.4(1), b =
2288.0(4), c = 1183.9(1)pm, fi = 91.52(1)", V = 2.3811(5) nm3, Z = 4,
psalrd
= 1.59 Mgrn-,, p(MoK.) = 1.35 m n - ' , 5412 measured reflections
to 20,,, = 45 ",semiempirical absorption correction, 4930 observed reflections with 1 FI > 3uIF,I were used for the structure refinement. R = 0.029
(wR = 0.030, weighting scheme w-' = a Z ( F ) + 0.0004p).[7b]
[9] Y. Bai, H. W. Roesky, M. Noltemeyer, Z . Anorg. Allg. Chem. 1991, S9S,
21 -26.
[lo] H. W. Roesky, H. Voelker, M. Witt, M. Noltemeyer, Angew. Chem. 1990,
102, 712-713; Angew. Chem. let. Ed. Engl. 1990, 29, 669.
[ l l ] Y. Bai, M. Noltemeyer, H. W Roesky, Z. Naturforsch. E , 1991,46, 13571363.
[I21 M. Witt, H. W. Roesky, D. Stalke, F. Pauer, T. Henkel, G. M. Sheldrick,
J. Chem. SOC.Dalton Trans. 1989, 2173-2177.
[13] Y Bai, H. W Roesky, M. Noltemeyer, Z . Anorg. ANg. Chern., in press.
[I41 Crystal structure analysis of 1: Space group P2,/c, a = 1173.2(1),
b = 1360.8(1),c = 3209.0(2) pm, fl = 91.33(2)", V = 5.122(3) nm3, Z = 8,
pcalsd
= 1.06 Mgm-', p(MoKJ = 0.14 mm-', 7967 measured reflections
to 26,,, = 45 empirical absorption correction, 4148 observed reflections
withlFl > 3u(lF,I) were used for the structure refinement. R = 0.077
(wR = 0.074, weighting scheme W - I = a2(FJ + 0.00061+). [7b]
O,
[tBuSiO(ReO,)],, a Model Compound for Metal
Oxides on Silicate Surfaces-Synthesis
from the Stable Trio1 tBuSi(OH), and Re,O,**
By Norbert Winkhofer, Herbert W Roesky,*
Mathias Noltemeyer, and Ward 7: Robinson
Dedicated to Professor Heinz Harnisch
on the occasion of his 65th birthday
Transition metal oxides on silicon dioxide supports find
wide application as catalysts in the petrochemical indusBut to a large extent, the processes taking place on
the catalyst surface are not understood. Their study is hindered by the complicated structure of these silicate surfaces,
making the synthesis of model substances essential. Feher et
al.t3341 succeeded in preparing the heptameric condensation
[*I Prof. Dr. H. W Roesky, N. Wmkhofer, Dr. M Noltemeyer,
Prof. Dr. W. T. Robinson
Institut fur Anorganische Chemie der Universitat
Tammannstrasse 4, D-W-3400 Gottingen (FRG)
[**I T h ~ swork was supported by the Deutsche Forschungsgememschaft and
the Fonds der Chemischen Industrie.
Verlagsgesellschaft mbH, W-6940 Weinheim, 1992
OS70-0833/92/0SOS-OS99$3.50+ ,2510
599
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