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By Nils Wiberg, Sham Kumar Vasisht, and Gerd Fischerf'l
The products (7)-(9)
were characterized by elemental
analysis and NMR, IR, and MS spectra. (9) slowly decomposes at 180°C. Traces of moisture lead to rapid reaction
in accordance with Eq. (b). Compounds (7) and (8) are
also sensitive to hydrolysis and oxidation.
The NMR data of the 3-methylborolan-I-ylamines(7),
(8), and (9) [611B: -59.2, -64.0, and -67.8ppm, resp.;
614N :286,228, and 206 ppm, r e ~ p . ] [ confirm
the coordination
number 3 for the B and N atoms. In spite of the electropositive
character of the boron, the borolanyl group withdraws electron
density from the N atom through BN n interactions, recognizable by the downfield shift of the 14N-NMR signal and by
the 'H-NMR signal of the (CH&Sn group [6'H: -0.16
( 5 ) , -0.26 ( 7 ) , and -0.35ppm (a)].
Because of the low n-electron density on the three boron
atoms and the lability of the B-N bonds, (9) is a powerful
boronating reagentf7].
Tris(3-methylborolan-I -yl)amine (9)
A solution of 1-bromo-3-methylborolane ( 6 ) (5 ml: 6.0g,
37.2 mmol) in toluene (15 ml) is added dropwise at -20°C
to a stirred solution of tris(trimethylstanny1)amine( 5 ) (6.25 g,
12.4mmol) in toluene (20ml). The mixture is allowed to warm
up slowly and then heated under reflux for 7h. Fractional
distillation (10 cm silver-mantle Vigreux column) of the residue
remaining after removal of volatiles affords 8.4 g Me3SnBr
(93 %; b.p. 28-30°C/10-2 torr) and 2.6g (9) (81 %; b.p.
73-74"C/10-2 torr). (9) is a water-clear, viscous liquid which
is very sensitive toward hydrolysis and oxidation.
Analogous reactions of ( 5 ) with (6) in toluene under modified conditions [molar ratios 1 :2 and 1 : 1, resp.; reaction
at 90°C (4 h) and room temperature (2 h), resp.] afford the
trimethylstannyl(3-methylborolan-I-y1)amines(8) (78 %; b. p.
89-91 "C/10-2 torr) and (7) (75%; b.p. 117--119"C/10~1
Received: December 29, 1975 [Z 391 IE]
German version: Angew. Chem. 88, 231 (1976)
CAS Registry numbers:
( 5 ) , 1068-70-8; (6), 22086-42-6; (7). 58485-83-9; ( S ) , 58485-84-0; (9), 5848585-1
Gmelins Handhuch der Anorganischen Chemie. Supplement to 8th Edit.,
Val. 22: Borverbindungen, Part 4 (1975); H. NBth and H. Vahrenkamp,
J. Organometal. Chem. 16, 357 (1969).
'H-NMR data for the reaction products of ( C H 3 p B r and
(CH3)2BN[Si(CH3)3]2 indicate, inter alia, unstable [(CH3)2B]aN; H.
Vahrenkamp, Dissertation, Universitat Munchen 1961.
a) A . D . Buckingham, Proc. Chem. SOC. London 1962, 351; b) R. G .
Geananyel, J. Inorg. Nucl. Chem. 32, 3697 (1970).
a ) M . F. Lapperf and G. Sriuasfaoa, Proc. Chem. Soc. London 1964,
120; h) H. NBth and W Regner, Z. Anorg. Allg. Chem. 352, 1 (1967);
D. Nolle, H . Niirh, and W Wintersrein, ibid. 406, 235 (1974).
R . KBster and D. Iwasaki, Adv. Chem. Ser. 42, 148 (1964): H . N d t h
and W Storch, Chem. Ber. 109, 884 (1976).
Values referred to the external standard BF3.0(C2H,)2 and saturated
aqueous N a N 0 3 solution.
H . NBth and W Storch, unpublished.
Bis(sily1)diimines (azosilanes) corresponding to the bis(a1ky1)diimines(azoalkanes) have been known for several years['].
However, all attempts to synthesize higher homologs of the
type X-N=N-X
(X=GeR3, SnR3, or PbR3) have so far
remained without success[3!
Adaptation of the oxidation of N-lithium tris(trimethylsily1)hydrazidel'l, which affords bis(trimethylsilyl)diimine, to the
preparation of bis(trimethylgermy1)diimine (1 ) was initially
unsuccessful since the germyl hydrazide was not oxidized
to ( I ) but further to nitrogen. However, in hexachloroethane
we have now found an oxidizing agent providing access to
the very easily oxidized azogermane ( 1 ) according to:
( C H&Ge-N -N-G e(C H&
- (CH3)3(XCI
(Preparation of an azostannane-probably even more sensitive to oxidation-accordingly appears extremely difficult.)
The blue diimine derivative (I), which can be sublimed
at -45°C in V ~ C U O( l o F 4 torr), expectedly gives only one
signal in its H-NMR spectrum (6 = - 21.8 Hz, TMS as internal
standard, in C,H,). According to mass spectrometric studies
the energy required for ionization of the highest occupied
n + orbital of the nitrogen lone pairs is only 5.95 0.05 eV 1
it is thus lower than the ionization energy of bis(trimethylsily1)diimine and much lower than that of bis(trimethylmethy1)diimine (cf. Fig. 1). The absorption maximum for the n++J-r*
electronic transition responsible for the color of ( 1 ) on the
other hand lies at 14310cm-' between the corresponding
absorption maxima of the carbon and the silicon compound.
This finding can be rationalized in a simplified manner in
terms of inductive and-especially with regard to the rt*
orbital-mesomeric effects of the substituents attached to
the azo groupr41.
(Me, Sil,N,
(Me, Ge),N,
Fig. 1. Ionization energies ofthe n + orbital and wave numbers of the electronic
transition between the highest occupied n + and the lowest unoccupied n*
orbital of diimines (CH3)3E-N=N-E(CH3)3
(E =C, Si, Ge).
The azogermane ( l ) , which is readily hydrolyzed and extremely sensitive to oxygen[51,has a thermal instability resem- ~ _ _[*] Prof. Dr. N. Wiherg and Dip].-Chem. G. Fischer
lnstitut fur Anorganische Chemie der Universitit
Meiserstrasse 1, SO00 Miinchen 2 (Germany)
Doz. Dr. S. K. Vasisht
Department of Chemistry, Panjab University, E-1/78 Sector-14
Chandigarh-16GO14 (India)
Angew. Chem. Int. Ed. Engl. 1 Vol. 15 (1976) N o . 4
bling that of the corresponding azosilane (thermolysis occurring above ca. - 35 “C).In analogy with (Me,Si)2N2[6”1and
it decomposes at low temperatures almost exclusively ria disproportionation to nitrogen and tetrakis(trimethy1germyl)hydrazine ( 2 ) , which is also accessible by
another route[’’. At higher temperatures, increasing amounts
of (3)-(6) and hexamethyldigermane (7)[81 are also formed.
[7] N. Wiberg and M . Veifh, Chem. Ber. 104, 3176 (1971).
[S] Hexamethylazostannane should therefore already decompose preferentially t o nitrogen and hexamethyldistannane.
Use of the Isoselectivity Principle for Distinguishing
Cationic n- and 6 Complexes[**]
( (:t13)3c;f?\
By Bernd Giese and Joachim Stellmachp]
Use of the kinetic selectivity principle which postulates
a relationship between the competition constants x and the
structures of intermediates X has become subject to increasing
criticism[’]. We were recently able to show that the differences
in activation enthalpies AH: - A H ; determined from the temperature dependence of x provide a much better description
of intermediates[’].
The yields of thermolysis products of ( 1 ) obtained at 80°C
in pentane, e.g., amount to (the values in parentheses refer to
the corresponding compound with Si in place of Ge):
50 (201% (2), 10 (251% (3), 10 (251% ( 4 ) , 1 (101% Is),
20 (201% (6), 10 (01% (7).
A solution of hexachloroethane (6.0 mmol) in ether (50ml)
is added dropwise over 1 h to a stirred solution of N-lithium
(10.0mmol) in ether (100 ml)
at - 70°C. After a reaction time of 1 h the solvent and trimethylgermyl chloride are removed as quickly as possible in the
temperature range - 70 to - 50°C and the product (I ), which
volatilizes between -45 and -35°C at
torr, is condensed
in a cold trap at -60°C (tetrachloroethane is not retained
under these conditions). Repetition of this condensation affords
ca. 2.0mmol of pure ( 1 ) . All operations must be performed
with rigorous exclusion of oxygen and moisture!
Received: December 29, 1975 [Z 392 IE]
German version: Angew. Chem 88.257 (1976)
CAS Registry numbers:
( I ) . 58485-86-2: (2). 34478-38-1 : ( 3 ) . 34478-49-4: ( 4 ) . 13361-68-7:
(5). 41990-70-9: (6). 58485-87-3: ( 7 ) . 993-52-2:
(CH,),CNNC(CH,),. 927-83-3: (CH,),SiNNSi(CH,),. 13436-03-8:
N-lithium tris(trimethylgermyl)hydrazide.58485-88-4:
hexachloroethane. 67-72-1
Part 19 of Diimine and Its Derivatives. This work was supported by
an Alexander von Humboldt Grant to S. K . Y-Part 18: ref. [4]. Also
Part 37 of Compounds of Silicon and Its Group Homo1ogs.-Part 36:
ref. [3c].
N Wihrrg. W-CIi. Joo. and W L‘hlenhrork.Angew. Chem. 80. 661 (1968):
Angew. Chem. Int. Ed. Engl. 7, 640 (1968); N. Wiberg, ibid. 83, 379
(1971) p d 10. 374 (1971), respectively.
Azocompounds ofthetypex-N=N-Y
arealready known:a)X=CR,,
Y =SIR,: U . Wunnugat and C . Kriiger, Z. Anorg. Allg. Chem. 326, 288
(1964); b) X = C R 3 , Y=GeR,: N . Wiberg and M . Vrith, Chem. Ber.
104, 3191 (1971); c) X=SiR3, Y = G e R 3 : N. Wiberg, S. K . Vusisht, G .
Fischer, and E. Weinberg, ibid. 109, 710 (1976).
H. Bock, K . Wiftel, M . Veirh, and N. Wiberg, J. Am. Chem. SOC. 98,
109 (1976). -Thus the absorption of an azostannane is t o be expected
at higher wave numbers than in the case of (I).
Formation of Me3Ge-O-O--CeMe3.
a) N. Wiberg and W Uhlenbrork, J. Organometal. Chem. 70, 239, 249
(1974): b) apart form nitrogen the diimine derivative affords only the
asymmetric hydrazine derivative (Me3Si)2N-N(GeMe3)2.
Angrw. Chnn. Int. Ed. Engl. 1 Vol. I5 (1976) No. 4
As a result of that work we derived the isoselective relationship as a new criterion for distinguishing between intermediatesC21.
The subscripts 1 and 2 stand for the competing trapping
reactions of X leading to the compounds ( I ) and (2). respectively. The symbol 6 indicates that only the changes in the
activation parameters occurring on structural variation of
X are related to each other.
The first application of the isoselectivity principle to radical
halogen abstraction permitted a distinction to be made
between K - and 0 radicals[’! In order to examine the general
significance and scope of equation (a) we have now applied
it to the ionic intermediates occurring on electrophilic additions to olefins. We have recently deduced that addition of
halogens and benzenesulfenyl chloride to dimethyl norbornenedicarboxylate ( 3 ) involves intermediate formation of
the complexes ( 4 ) to ( 6 ) , i.e. bridged ions with electron
deficient bonds, and complexes (7), i. e. bridged onium ions
without electron-deficient bond^[^*^]. Intramolecular endo
attack of the ester groups on the carbon atoms C-6 and
C-5 leads to the lactone esters ( 8 ) to ( 1 5 ). The isomer ratios
of (8)/(12) to (11)/(1.5) correspond to the selectivity values
k6/k5 because the mixtures of isomers are formed in kinetically
controlled reactions[5?
According to equation (b), which is obtained by subtraction
of two Eyring relationships, the temperature dependence of
the selectivity values k6/k5 yields the differences in activation
r] Dr. B. Giese and Dipl.-Chem. J. Stellmach
Chemisches Laboratorium der Universitat
Albertstrasse 21, 7800 Freiburg (Germany)
This work was supported by the Deutsche Forschungsgemeinschaft.
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trimethylgermyl, bis, diimine
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