Preparation, Structure and Reactivity of 2-Chloro-, 2-Fluoro- and 2-Iodo-2,3-dihydro-1H-1,3,2-diazaboroles

Article abstract of DOI:10.1002/(SICI)1099-0682(199808)1998:8<1145::AID-EJIC1145>3.0.CO;2-H

A series of differently substituted 2-chloro-, 2-fluoro- and 2-iodo-2,3-dihydro-1H-1,3,2-diazaboroles have been prepared by various methods. 1,3-Di-tert-butyl-2-fruoro-2,3-dihydro1H-1,3,2-diazaborole (3a), 1,3-di-tert-butyl-2-chloro-2,3-dihydro-1H-1,3,2-diazaborole (5a), 1,3-bis(2,6-dimethyl-phenyl)-2-chloro-2,3-dihydro-1H-1,3,2-diazaborole (5b), 2-chloro-4,5-dimethyl-1,3-dineopentyl-2,3-dihydro-1H-1,3,2-diazaborole (Sc), and 1,3-di-tert-butyl-2-iodo-2,3-dihydro-1H-1,3,2-diazaborole (6a) were formed from the corresponding lithiated Z-1,2-diaminoethenes, by treatment with BF₃·OEt₂, BCl₃, or BI₃ in n-hexane. Compounds 3a, 5a, and 5b are also available by sodium amalgam reduction of the adduct (tBu)(BF₃)N=CH-CH=N(BF₃)(tBu) (2a), and the borolium salts [RN^a=CH-CH=N^b(R)BCl₂]X (N^a-B) (4a: R = tBu, X = BCl₄ and 4b: R = 2,6-Me₂C₆H₂, X = Cl) respectively. The iodo derivative (2,6-Me₂C₆H₂)-N^a-CH=CH-N ^b(2,6-Me₂C₆H₂)BI (N^a-B) (6b) was synthesized in a redox reaction between the 1,4-diazabutadiene 1b and Bl₃. The novel compounds were characterized by ¹H-, ¹¹B- and ¹³C-NMR spectroscopy, as well as by an X-ray structure analysis of 6b.

Full text of DOI:10.1002/(SICI)1099-0682(199808)1998:8<1145::AID-EJIC1145>3.0.CO;2-H

FULL PAPER
Preparation, Structure and Reactivity of 2-Chloro-, 2-Fluoro- and
2-Iodo-2,3-dihydro-1H-1,3,2-diazaborolesȠ
Lothar Weber*a, Eckhard Dobberta, Roland Boeseb, Michael T. Kirchnerb, and Dieter Bläserb
Fakultät für Chemie der Universität Bielefelda,
Universitätsstraße 25, D-33615 Bielefeld, Germany,
Fax: (internat.) ϩ49(0)5201-106-6146
E-mail: lothar.weber@uni-bielefeld.de
Institut für Anorganische Chemie der Universität-Gesamthochschule Essenb,
Universitätsstraße 5Ϫ7, D-45117 Essen, Germany
Received March 3, 1998
Keywords: Boron / Diazaboroles / Halogens / Isocyanides / Heterocycles
A series of differently substituted 2-chloro-, 2-fluoro- and 2-
iodo-2,3-dihydro-1H-1,3,2-diazaboroles have been prepared
with BF3·OEt2, BCl3, or BI3 in n-hexane. Compounds 3a, 5a,
and 5b are also available by sodium amalgam reduction of
by various methods. 1,3-Di-tert-butyl-2-fluoro-2,3-dihydro- the adduct (tBu)(BF3)N=CH–CH=N(BF3)(tBu) (2a), and the
1H-1,3,2-diazaborole (3a), 1,3-di-tert-butyl-2-chloro-2,3-
borolium salts [RNa=CH–CH=Nb(R)BCl2]X (Na–B) (4a: R =
dihydro-1H-1,3,2-diazaborole (5a), 1,3-bis(2,6-dimethyl- tBu, X = BCl4 and 4b: R = 2,6-Me2C6H2, X = Cl) respectively.
phenyl)-2-chloro-2,3-dihydro-1H-1,3,2-diazaborole (5b), 2-
chloro-4,5-dimethyl-1,3-dineopentyl-2,3-dihydro-1H-1,3,2-
diazaborole (5c), and 1,3-di-tert-butyl-2-iodo-2,3-dihydro-
The iodo derivative (2,6-Me2C6H2)–Na–CH=CH–Nb(2,6-
Me2C6H2)BI (Na–B) (6b) was synthesized in a redox reaction
between the 1,4-diazabutadiene 1b and BI3. The novel
1H-1,3,2-diazaborole (6a)
were
formed
from the compounds were characterized by 1H-, 11B- and 13C-NMR
corresponding lithiated Z-1,2-diaminoethenes, by treatment
spectroscopy, as well as by an X-ray structure analysis of 6b.
The formal replacement of a CϭC fragment in pyrrole I imidazol-2-ylidenes. The resulting salts such as V contain
by a BϪN unit affords 2,3-dihydro-1H-1,3,2-diazaboroles the first borylated carbenium ions.[8]
II.
The first reports on heterocycles of the type II date back
to the early 1970s[1][2]. Meanwhile, a series of papers con-
cerned with the synthesis, structure, and bonding of such
molecules has been published.[3][4] Apart from the synthesis
of [Cr(CO)3] complexes with η5-1,3,2-diazaborole li-
gands[5][6] and the cleavage of the NϪSi bond in N-silylated
derivatives by metal amides or alcoholates to yield the cor-
responding alkali metal 1,3,2-diazaborolides,[7] the chemis-
try of heterocycles II has remained largely unexplored. The
lack of functional groups in the 2,3-dihydro-1H-1,3,2-diaza-
boroles examined to date may account for this situation.
Recently we launched a program for the synthesis of 2-
halo-2,3-dihydro-1H-1,3,2-diazaboroles as precursors for a
variety of chemical transformations. In a first account we
described the preparation of 2-bromo-2,3-dihydro-1H-
1,3,2-diazaboroles III and their reactions with water and
The intention of the work described herein is to provide
efficient syntheses for 2-fluoro-, 2-chloro- and 2-iodo-2,3-
dihydro-1H-1,3,2-diazaboroles.
Results and Discussion
For the preparation of 2-bromo-2,3-dihydro-1H-1,3,2-di-
azaboroles, as well as the corresponding fluoro, chloro and
iodo derivatives, two synthetic approaches are generally
available. The first pathway [Scheme 1 (a)], involves the gen-
Supporting information for this article is available on the
WWW under http://www.wiley-vch.de/home/eurjic or from the
author.
Eur. J. Inorg. Chem. 1998, 1145Ϫ1152
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1145

L. Weber, E. Dobbert, R. Boese, M. T. Kirchner, D. Bläser
FULL PAPER
eration of the bis(trifluoroborane) adduct 2a, by the combi- ane (tBu)N(BCl2)ϪCHϭCHϪN(BCl2)(tBu) (A)[10] which
nation of 1,4-diazabutadiene 1a with two molar equivalents subsequently disproportionated into 5a and BCl3 (Scheme
of BF3·Et2O in n-hexane.
2). The synthesis of 5a can also be effected by the reaction
of the lithiated diazabutadiene with BCl3 [Scheme 2 (b)].
Scheme 1
Scheme 2
The adduct was obtained as a yellow amorphous solid in
74% yield. Its 11B{1H}-NMR spectrum in CD3CN shows
only one singlet (at δ ϭ 0.4) for the two chemically and
magnetically equivalent boron atoms. Similarly, only one
resonance was observed in the 19F{1H}-NMR spectrum of
2a (at δ ϭ 73.0) for the six fluorine atoms. The synthesis
of 2-fluoro-1,3,2-diazaborole (3a) was accomplished by the
reduction of 2a with an excess of sodium amalgam in an n-
hexane slurry (Scheme 1). After 36 h, the 11B-NMR spec-
trum only showed the resonance for 3a at δ11B ϭ 20.8. The
crude yellow 3a was purified by fractional condensation at
40°C and 0.01 Torr to give colorless crystals. At tempera-
tures above 40°C the 2-fluoro-1,3,2-diazaborole decom-
posed with liberation of 1a. Compound 3a is soluble in
common aprotic organic solvents. In solution complete de-
composition of the heterocycle occurred within 2 days.
A second approach to 3a [Scheme 1 (b)] made use of the
reduction of 1a by two equivalents of lithium in hexane,
prior to the condensation with BF3·Et2O.
In contrast to the symmetrical adduct 2a, the treatment
of 1a with two molar equivalents of BCl3 in n-hexane at
Ϫ30°C afforded the colorless amorphous borolium tetra-
chloroborate 4a in 71% yield. Accordingly, the 11B-NMR
The reaction of 1,4-diazabutadiene 1b with an equimolar
amount of BCl3 in a hexane/dichloromethane mixture, led
Ϫ
spectrum of the salt gave rise to two singlets for the BCl4
ion[9] and the boron atom of the ring at δ ϭ 1.6 and 7.7 to the violet borolium chloride 4b (38%) and the corre-
respectively. The analogous borolium chloride, described in sponding black tetrachloroborate 4bЈ (7%). The 11B-NMR
the literature, gave a boron resonance at δ ϭ 7.2 (in spectra of the salts displayed signals at δ ϭ 7.2 for 4b, and
CDCl3).[3] The reduction of 4a with sodium amalgam in n- at δ ϭ 7.7 and 1.5 for 4bЈ.
hexane led to the formation of 2-chloro-1,3,2-diazaborole
Reduction of 4b by an excess of sodium amalgam in n-
(5a) as a colorless solid after sublimation (40Ϫ60°C, 0.01 hexane afforded the 2-chloro-1,3,2-diazaborole 5b (55%
Torr, 91%). The course of the reduction was followed by yield). Treatment of 1,4-diazabutadiene 1b with lithium
11B-NMR spectroscopy. After 5 h, the spectrum of the sand and condensation of the lithium derivative with BCl3
supernatant solution showed signals at δ ϭ 32.3 and 21.0 gave 1,3,2-diazaborole 5b (53%) as the final product after 3
in a ratio of 2:1. A small resonance at δ ϭ 47.0 was assigned d. After 1 h, the 11B-NMR spectrum of the yellow solution
to BCl3. After 14 h, the spectrum was dominated by two showed a resonance at δ ϭ 32.5 for an intermediate. Minor
intense singlets at δ ϭ 21.1 and 47.0, in addition to a weak resonances at δ ϭ 22.0 and 47.0 were attributed to 5b and
singlet at δ ϭ 31.8. This observation may be rationalized by BCl3, respectively. After 14 h, a spectrum of the same
the initial formation of the intermediate acyclic aminobor- sample displayed only the singlets of 5b and BCl3. In an
1146
Eur. J. Inorg. Chem. 1998, 1145Ϫ1152

2-Chloro-, 2- Fluoro- and 2-Iodo-2,3-dihydro-1H-1,3,2-diazaboroles
FULL PAPER
additional experiment, the reaction mixture was filtered Scheme 3
after 1 h of stirring at ambient temperature and the concen-
trated hexane solution was stored overnight at Ϫ80°C to
give a tan precipitate. The 11B-NMR spectrum of the tan
precipitate in CDCl3 showed a major resonance at δ ϭ 32.6
and an impurity of 5b at δ ϭ 21.8. The 1H-NMR spectrum
of the tan solid in C6D6 was dominated by singlets at δ ϭ
1.99 (s, 12 H, CH3), 6.40 (s, 2 H, NϭCH), and 6.93 (m, 6
H, aryl-H), in addition to the resonances of 5b. A 2:1 ratio
of the intermediate to 5b was determined. Based on the
spectroscopic data and its good solubility in non-polar sol-
vents, we attributed the formula (Xyl)(Cl2B)NϪCHϭ
CHϪN(BCl2)(Xyl) to this intermediate (Scheme 2).
Lithium reduction of 1,4-diazabutadiene 1c for 10 d in n-
hexane, and the subsequent quenching of the lithium de-
rivative with BCl3 furnished 1,3,2-diazaborole 5c as a dark
brown oil, which slowly solidified to a tan wax (60%).
The synthesis of the 2-iodo-1,3,2-diazaborole (tBu)-
NaϪCHϭCHϪNb(tBu)BI(NaϪB) (6a) was achieved by al-
lowing Li2[(tBu)NCHϭCHN(tBu)] to react with an equim-
olar amount of BI3 to give a colorless, light-sensitive oil
(83%), which completely decomposed within 5 h at room
temperature. In contrast, 2-iodo-1,3,2-diazaborole 6b, ac-
cessible by the redox reaction between 1b and BI3, was sub-
limed at 380°C/0.01 Torr without significant decompo-
sition.
As previously shown, 2-bromo-2,3-dihydro-1H-1,3,2-di- was complete after 5 min (83%). The corresponding iso-
azaborole (7a) can be brought to reaction with imidazolyl- thiocyanato diazaborole 10a, resulted from the reaction of
idenes to give borylated imidazolium salts (eq. 1). In the 5a or 7a with AgSCN under similar conditions. Again, the
light of these data, an analogous synthesis of borylated ni- reactivity of 7a exceeded that of 5a. Derivative 10b was syn-
trilium salts seemed possible, by reaction of compounds thesized from 6b, 5b, or (2,6-Me2C6H3)NaϪCHϭ
5Ϫ7 with organic isocyanides.
CHϪNb(2,6-Me2C6H3)BBr(NaϪB) (7b) (78Ϫ93% yield).
Treatment of 5a, 6a, and 7a with an equimolar amount The reactivity of the 2-halo-1,3,2-diazaboroles was found to
of tert-butyl isocyanide in n-hexane, led to the formation of be: 7b > 5b > 6b.
the 2-cyano-1,3,2-diazaborole (8a). The expected nitrilium
It was not possible to unambiguously identify the BϪX
salt could not be detected spectroscopically. The formation stretching frequencies in the IR-spectra of the 2-halo-1,3,2-
of tert-butylbromide as a byproduct was proven by 1H- diazaboroles 3, 5, 6, and 7. In the IR spectra (KBr) of 8a
˜
NMR spectroscopy (δ ϭ 1.78) and by comparison with an and 8b, weak bands at ν ϭ 2207 and 2218 cmϪ1 are attri-
authentic sample.
buted to the stretching frequency of the CϵN group. In the
The corresponding reaction of 7a with cyclohexyl isocy- IR spectra of MeNaϪCH2ϪCH2ϪNb(Me)BCN(NaϪB)[12]
anide afforded 8a in 38% yield after 5 days. No intermedi- and MeNaϪNbϭNcϪNd(Me)BCN(NaϪB)[13] the ν(CN)
ates were observed spectroscopically. Similarly, 5b and 6b mode was observed as weak bands at 2225 and 2239 cmϪ1
,
were converted into 8b by tert-butyl isocyanide in 70% and respectively. A very intense band in the IR spectrum of 9a
˜
55% yield, respectively (Scheme 3).
at ν ϭ 2317 cmϪ1 was assigned to the asymmetric stretching
No reaction was observed between 2-halo-1,3,2-diaza- frequency of the isocyanato group, which is consistent with
boroles 5Ϫ7 and 2,6-Me2C6H3NϵC. The cyano compound the data for compounds (R2N)2BϪNϭCϭO [νas(NCO) ϭ
8a was also synthesized in high yield by treatment of the 2290 ± 15 cmϪ1],[11c] and the IR spectrum of Me2BϪNϭ
diazaboroles 5a or 7a with a slight excess of silver cyanide CϭO [νas(NCO) ϭ 2285 cmϪ1 vs].[14] These frequencies
in acetonitrile at room temperature. The 2-bromo com- also underline the presence of an isocyanatoborane R2BNϭ
pound was found to be more reactive than the 2-chloro ana- CϭO, and disfavor the isomeric cyanatoborane structure
logue. Similarly, compound 8b was obtained by treatment R2BOCϵN. Similar arguments support an isothiocyanato-
of 6b with AgCN over a period of 2 days (79%).
borane structure in the 1,3,2-diazaboroles 10a and 10b,
In line with the synthetic approach to isocyanatoboranes where very strong bands at 2121 and 2114 cmϪ1, respec-
and isothiocyanatoboranes devised by Lappert et al.,[11] di- tively, are assigned to the νas(NCS) mode. Intense bands
azaborole 5a was converted by silver cyanate in acetonitrile at 871 and 856 cmϪ1 are due to the symmetric stretching
into the isocyanato diazaborole 9a, which was isolated after frequency of the NCS group. The νas(NCS) of a series of
30 min as a colorless thermolabile oil in 78% yield. The isothiocyanatoboranes occurs in the range 2089 ± 31
analogous reaction between 7a and AgOCN to afford 9a cmϪ1 [11]
.
Eur. J. Inorg. Chem. 1998, 1145Ϫ1152
1147

L. Weber, E. Dobbert, R. Boese, M. T. Kirchner, D. Bläser
FULL PAPER
The 11B{1H}-NMR spectra of the halo- and pseudohalo-
diazaboroles display an increased shielding as follows: 3a ഠ
5a (δ ϭ 20.2) > 7a (16.2) > 9a ഠ 10a (14.7) > 8a (12.0) >
6a (6.5). Similarly, the 11B-NMR signals of 5b, 7b, 10b, 8b,
and 6b range from δ ϭ 21.1 to 11.8. The significant high-
field shift of 8a relative to the saturated analogue Me-
NaϪCH2CH2ϪNb(Me)BCN(NaϪB) (δ ϭ 21.0)[12] sustains
the heteroaromatic nature of the rings under discussion.
The ring protons in 3a and 5aϪ10a are observed at δ ϭ
5.99Ϫ6.40, whereas in the dixylyl-substituted derivatives
5bϪ8b and 10b, singlets at δ ϭ 5.71Ϫ5.99 are assigned to
these protons. In the 13C{1H}-NMR spectra of 3a and
5aϪ10a, singlets at δ ϭ 109.9Ϫ114.6 were assigned to the
CϭC group of the rings. The respective 13C-nuclei of
5bϪ8b, and 10b gave rise to resonances at δ ϭ 117.2Ϫ120.0.
Figure 1. Crystal molecular structure of 6b[a]
˚
[a]
Selected bond lengths [A] and bond angles [°]: B(1)ϪI(1)
2.119(5), B(1)ϪN(1) 1.418(4), N(1)ϪC(1) 1.401(4), C(1)ϪC(1Ј)
1.362(8), N(1)ϪC(2) 1.438(4); N(1)ϪB(1)-N(1Ј) 106.9(4),
N(1)ϪB(1)ϪI(1)
B(1)ϪN(1)ϪC(2)
126.6(2),
130.0(3),
B(1)ϪN(1)ϪC(1)
C(1)ϪN(1)ϪC(2)
107.5(3),
122.5(3),
N(1)ϪC(1)ϪC(1Ј) 109.1(2). [B(1), N(1),C(1)ϪC(1Ј)ϪN(1Ј)ϪC(2),
C(3), C(4), C(5), C(6), C(7)] 85.6.
X-ray Structural Analysis of 6b
The molecular structure of 6b (Figure 1) features a planar
1,3,2-diazaborole ring with two nearly orthogonally ori-
ented ortho-xylyl substituents at the nitrogen atoms (in-
terplanar angle between the heterocycle and an arene ring
Figure 2. View of the crystal structure of 6b along the c axis; de-
picted are two adjacent chains with three molecules each
ψ ϭ 85.6°). A C2 axis bisects the molecule along the
˚
˚
B(1)ϪI(1) vector. The bond length B(1)ϪI(1) [2.119(5) A]
is close to the sum of the covalent radii of boron (0.81 A)
˚
and iodine (1.33 A)[15] and compares well with the atomic
distance between the tricoordinate boron and an iodine
atom in the dimer of IBaϪC(Et)ϭC(Et)ϪBb(I)S(BaϪS)
˚
[2.13(2) A][16]. BϪI bond lengths involving sp2-hybridized
˚
˚
[17]
boron atoms range from 2.10(4) A in BI3
to 2.237(6) A
in the triborane [(Me2N)(I)B]2BNMe2[18]. Atomic distances
and valence angles within the diazaborole ring are in good
agreement with the respective data for EtNaϪCHϭ
CHϪNb(Et)BMe(NaϪB).[4] In 6b, the BϪN bond length
˚
[1.418(4) A] indicates multiple-bond character. In a series
of diazaboroles the BϪN bond lengths range from 1.407(3)
˚
˚
to 1.450(2) A. The atomic distance C(1)ϪC(1Ј) [1.362(8) A],
˚
and the NϪC(sp2) bond length [1.401(4) A] also indicate
multiple bonding. For the N(sp2)ϪC(sp2) single bond, the aromatic ring system of the adjacent chain. A chele-
˚
N(1)ϪC(2) bond lenghths of 1.438(4) A were measured. tropic intermolecular interaction of iodine with two hydro-
The endocyclic angles in 6b: N(1)ϪB(1)ϪN(1)Ј [106.9(4)°], gen atoms bonded to sp2-carbon atoms is expected to be
B(1)ϪN(1)ϪC(1) [107.5(3)°], and N(1)ϪC(1)ϪC(1)Ј mostly electrostatic in nature, and seems to dominate the
[109.1(2)°] resemble those in the borylimidazolium cation V molecular packing of 6b. An analysis of specific packing
[107.1(6), 105.9(4), and 110.5(3)°, respectively].[1] This also motifs is possible with the help of a statistical approach
applies to the exocyclic angle N(1)ϪB(1)ϪI(1) [126.6(2)°] in which involves plots of intermolecular distances and angles
6b, and the corresponding angle N(1)ϪB(1)ϪC(6) in V for groups of crystals structures that contain the motif un-
[126.5(3)°].
der investigation (scatter-plots). The more frequent certain
The packing of 6b shows some interesting features. The short contacts with reasonable angles occur, the more likely
molecules are arranged in a pattern with the iodine atoms it is that this represents a “supramolecular synthon”.[19]
pointing to the centers of the carbonϪcarbon double bonds Therefore we performed a search in the CSD,[20] which re-
(distance from the iodine atom to the center of the bond vealed 5703 structures that possess: (1) a cis-1,2-dihydro
˚
3.17 A), such that each iodine atom is in contact with two group, attached to a double or aromatic bond of two car-
˚
hydrogen atoms (distance from iodine to hydrogen 3.093 A, bon atoms, and (2) an uncharged halogen (not fluorine)
˚
with a normalized 1.08 A distance for CϪH). This linkage atom with a single bond. Amongst these, 426 structures and
produces chains of molecules with adjacent chains running 1079 fragments have an intermolecular distance from the
in opposite directions, and with the phenyl groups inter- halogen atom to the hydrogen atoms of less than the sum
˚
˚
locked (Figure 2).
of van der Waals radii plus 1 A (H···Cl 3.95 A; H···Br 4.05
˚
˚
In the layer depicted in Figure 2, one of the methyl A; H···I 4.18 A). A characteristic cheletropic interaction is
groups is oriented so that a hydrogen atom points towards evident from the polar scatter diagrams, given in Figures 3
1148
Eur. J. Inorg. Chem. 1998, 1145Ϫ1152

2-Chloro-, 2- Fluoro- and 2-Iodo-2,3-dihydro-1H-1,3,2-diazaboroles
FULL PAPER
and 4. Figure 3 represents the positions of the halogen albeit not so pronounced, of halogen atoms in the plane of
atoms relative to the aromatic carbonϪcarbon double the carbon and hydrogen atoms (at 0°) again demonstrates
bond, with this bond at the equator, and the cis-oriented the cheletropic character of the interaction in 6b. The angles
hydrogen atoms situated in the northern hemisphere. An used in Figures 3 and 4 were obtained from the *LP2
˚
accumulation of structures at a distance of 4 A from the method in Quest3D[21], where the positions of one hydrogen
center of the aromatic CϭC bond and perpendicular to this atom, the nearest carbon atom, the center of the car-
bond axis demonstrates that the halogen atoms prefer to be bonϪcarbon bond, and the halogen atom were used as the
located in the same manner as we found for 6b. In our case, parameters. The scatter plot was produced by the distance
the intermolecular distance with iodine, and even with bro- between the halogen atom and the center of the car-
mine, is amongst the smallest found for all the given frag- bonϪcarbon double bond. Equivalent scatter plots pro-
ments.
duced for iodine, bromine, and chlorine are available as sup-
porting information on the WWW or from the author.
Figure 3. Polar scatter plot of the distance from the halogen to the
center of the carbonϪcarbon double bond, the angle between the
carbonϪcarbon double bond, and the projection of the intermole-
cular vector to the plane for 1079 fragments in the Cambridge Data
Base that contain the halogen···HCϭCH motif as defined
This work was financially supported by the Fonds der Chemi-
schen Industrie, Frankfurt/Main, and the Deutsche Forschungsge-
meinschaft, Bonn, which are gratefully acknowledged.
Experimental Section
General: All manipulations were performed under dry argon.
Solvents were rigorously dried with an appropriate drying agent
and distilled before use. Ϫ The following compounds were prepared
as described in the literature: tBuNϭCHϪCHϭNtBu (1a),[22] 2,6-
Me2C6H3NϭCHϪCHϭNC6H3Me2-2,6
(1b),[23]
tBuCH2Nϭ
C(Me)ϪC(Me)ϭNCH2tBu (1c),[24] and BI3.[25] Boron trichloride,
boron trifluorideϪdiethyl ether, tBuNC, cyclohexyl isocyanide,
AgCN, AgOCN, and AgSCN were purchased. Ϫ IR spectra:
Bruker FTIR IFS66. Ϫ 1H-, 11B-, 13C-, and 19F-NMR spectra:
Bruker AC 100 (1H, 100.13 MHz; 13C, 25.18 MHz), and Bruker
AM Avance DRX 500 (1H, 500.13 MHz; 11B, 160.46 MHz; 13C,
125.75 MHz; 19F, 470.60 MHz). References: SiMe4 (1H, 13C),
BF3·OEt2 (11B), CFCl3 (19F). Ϫ Mass spectra (EI): VG Autospec
sector-field mass spectrometer (Micromass) 70 eV.
(tBu)(BF3)NϭCHϪCHϭN(tBu)(BF3) (2a):
A solution of
tBuNϭCHϪCHϭNtBu (1a) (10.0 g, 59.0 mmol) in 200 ml of n-
hexane, and an emulsion of BF3·OEt2 (18.6 g, 118.0 mmol) in 200
ml of n-hexane were added separately, dropwise, into a flask filled
with chilled n-hexane (1000 ml, Ϫ10°C). After 24 h of stirring at
room temp., a yellow solid was filtered off and washed with n-
Figure 4. Polar scatter plot of the distance from the halogen to the
center of the carbonϪcarbon double bond and the angle between
the molecular plane and the intermolecular vector (section perpen-
dicular to Figure 3)
hexane (4 ϫ 30 ml). Drying at 0.01 Torr for 2 h gave 2a as a bright
˜
yellow powder (13.2 g, 74%). Ϫ IR (KBr): ν ϭ 3206cmϪ1 w, 3102
w, 2984 vs, 2892 s, 2796 m, 2695 m, 2585 m, 2486 m, 2034 m, 1950
w, 1608 w, 1509 m, 1476 w, 1404 m, 1378 m, 1299 m, 1214 m, 1055
vs, br. [ν(BF)], 534 m, 522 m, 444 m, 419 w. Ϫ 1H NMR (CD3CN):
δ ϭ 1.48 (s, 18 H, tBu), 8.90 (s, 2 H, CH). Ϫ 13C{1H} NMR
(CD3CN): δ ϭ 28.5 [s, C(CH3)3], 66.3 [s, C(CH3)3], 163.2 (s, CH).
Ϫ
11B{1H} NMR (CD3CN): δ ϭ 0.4 (s). Ϫ 19F{1H} NMR
(CD3CN): δ ϭ 73.0 (s). Ϫ C10H20B2F6N2 (303.86): calcd. C 39.52,
H 6.65, N 9.21; found C 39.40, H 6.83, N 9.23.
(tBu)NaϪCHϭCHϪNb(tBu)BF(NaϪB) (3a). Ϫ Path (a): A
slurry of adduct 2a (5.0 g, 16.5 mmol) in n-hexane (100 ml) was
treated at 20°C with sodium amalgam prepared from 3.8 g (165.2
mmol) of sodium and 500 g of mercury. After 36 h of stirring, the
yellow hexane phase was decanted. Solvent and volatile compo-
nents were removed in vacuo (0.1 Torr, 10°C) to give a yellow solid
residue. Purification of crude 3a was achieved by fractional conden-
sation at 40°C and 0.01 Torr (yield 2.38 g, 73%).
The distribution of halogen positions below and above
the one in Figure 3 is shown in Figure 4. Here the equator
of the pole scatter diagram intercepts the center of the
double (aromatic) CϭC bond, with the hydrogen atoms be-
Path (b): 1.4-Diazabutadiene 1a (1.67 g, 10.0 mmol) was re-
duced with lithium sand (0.139 g, 20.0 mmol) in 70 ml of n-hexane
for 7 d at 20°C. The yellow slurry obtained was treated with 1.58
g (10.0 mmol) of BF3·Et2O, and the mixture was stirred for 10 min.
low and above the plane of the diagram. An accumulation, The red solution was filtered, concentrated to ca. 10 ml, and stored
Eur. J. Inorg. Chem. 1998, 1145Ϫ1152 1149

L. Weber, E. Dobbert, R. Boese, M. T. Kirchner, D. Bläser
FULL PAPER
overnight at Ϫ78°C to afford 1.1 g (56%) of colorless crystalline
in 30 ml of n-hexane was added dropwise to the chilled yellow
˜
3a. Ϫ IR (nujol): ν ϭ 1631cmϪ1 w, 1489 sh, 1428 s, 1395 sh, 1366 slurry (Ϫ50°C). The mixture was allowed to warm up to room
s, 1293 m, 1273 w, 1244 s, 1224 m, 1211 m, 1136 s, 1062 w, 1028 temp., and stirring was continued overnight. Filtration and removal
1
w, 951 w, 933 w, 879 w, 822 w, 746 w, 658 w, 623 s. Ϫ H NMR of solvent from the filtrate in vacuo gave 1.74 g (55%) of 5a. Ϫ IR
˜
5
4
(C6D6): δ ϭ 1.26 (d, JFH ϭ 1.1 Hz, 18 H, tBu), 5.99 (d, JFH
ϭ
(CsI, film): ν ϭ 1515 cmϪ1 w, 1464 m, 1399 s, 1367 s, 1347 sh, 1327
2.3 Hz, 2 H, CH). Ϫ 13C{1H} NMR (C6D6): δ ϭ 30.9 [s, C(CH3)3], s, 1285 m, 1237 s, 1209 m, 1136 m, 1030 w, 987 m, 943 w, 893 w,
51.6 [s, C(CH3)3], 109.9 (s, CH). Ϫ 11B{1H} NMR (C6D6): δ ϭ 822 w, 696 w, 662 m. Ϫ H NMR (C6D6): δ ϭ 1.35 (s, 18 H, tBu),
1
20.3 (s). Ϫ 19F{1H} NMR (C6D6): δ ϭ 57.9 (s). Ϫ MS/EI (70 eV);
6.19 (s, 2 H, CH). Ϫ 13C{1H} NMR (C6D6: δ ϭ 30.9 [s, C(CH3)3],
m/z: 199 [Mϩ]. Ϫ C10H20BFN2 (198.09): calcd. C 60.63, H 10.18, 53.2 [s, C(CH3)3], 112.0 (s, CH). Ϫ 11B{1H} NMR (C6D6): δ ϭ
N 14.14; found C 60.44, H 10.59, N 14.17.
20.2 (s). Ϫ MS/EI; m/z (%): 214 (20) [Mϩ], 158 (8.5) [Mϩ Ϫ C4H8],
143 (13) [Mϩ Ϫ C4H8 Ϫ CH3], 102 (100) [Mϩ Ϫ 2 C4H8]. Ϫ
C10H20BClN2 (214.55): calcd. C 55.99, H 9.39, N 13.05; found C
55.11, H 9.42, N 12.85.
[tBuNaϭCHϪCHϭNb(tBu)BCl2]ϩBCl4Ϫ(NaϪB)
(4a):
A
three-necked 2-l flask was filled with 900 ml of n-hexane and cooled
to Ϫ30°C. Solutions of 1a (8.10 g, 48.0 mmol) in 200 ml of n-
hexane and BCl3 (11.30 g, 96.0 mmol) in 200 ml of n-hexane were
added dropwise at a similar rate into the well-stirred n-hexane. The
resulting mixture was stirred overnight. The colorless precipitate
was filtered off and washed with n-hexane (2 ϫ 50 ml) and n-pen-
2,6-Me2C6H3NaϪCHϭCHϪNb(2,6-Me2C6H3)BCl(NaϪB)
(5b). Ϫ Path (a): A slurry of 4.00 g of 4b (10.5 mmol) in 150 ml
of n-hexane was treated with sodium amalgam obtained from 1.38
g of Na (60.0 mmol) and 200 g of mercury. Stirring at ambient
temp. was maintained for 5 d. The solution was decanted from the
tane (2 ϫ 50 ml) before drying in vacuo to give 13.7 g (71%) of 4a.
˜
Ϫ IR (KBr): ν ϭ 2985 cmϪ1 m, 2360 w, 1580 m, 1465 s, br., 1405 metal, and volatile components were removed in vacuo to yield
s, 1385 s, 1232 m, 1191 s, 1119 w, 1071 m, 1036 w, 920 w, 898 m,
821 s, 804 s, 711 m, 657 m, 547 w, 481 w. Ϫ 1H NMR (CD3CN):
δ ϭ 1.70 (s, 18 H, tBu), 8.90 (s, br., 2 H, CH). Ϫ 13C{1H} NMR
(CD3CN): δ ϭ 30.0 [s, C(CH3)3], 67.3 [s, C(CH3)3], 162.7 (s, CH).
1.80 g (55%) of 5b as a colorless solid.
Path (b): A solution of the 1,4-diazabutadiene 1b (4.00 g, 15.0
mmol) in 80 ml of n-hexane was reduced by 0.21 g (30.0 mmol) of
lithium sand during 7 d at 20°C. The resulting brown slurry was
chilled to Ϫ30°C and a solution of 1.76 g (15.0 mmol) of BCl3 in
50 ml of n-hexane was added dropwise. Stirring at room temp. was
continued for 3 d. Filtration was followed by removing volatile
components in vacuo to afford a colorless solid. Recrystallization
Ϫ
11B{1H} NMR (CH3CN): δ ϭ 1.6 (s, BCl4Ϫ), 7.7 (s, N2BCl2). Ϫ
C10H20B2Cl6N2 (402.62): calcd. C 29.83, H 5.01, N 6.96; found C
29.91, H 5.00, N 6.80.
[2,6-Me2C6H3NaϭCHϪCHϭNb(2,6-Me2C6H3)BCl2]ϩClϪ-
(NaϪB) (4b) and [2,6-Me2C6H3NaϭCHϪCHϭNb(2,6-Me2C6H3)-
BCl2]ϩBCl4Ϫ(NaϪB) (4bЈ): A three-necked 2-l flask was charged
with 1200 ml of n-hexane and chilled to Ϫ20°C. As described be-
fore the solutions of BCl3 (5.90 g, 50.0 mmol) in 200 ml of n-hexane
and 1b (13.2 g, 50.0 mmol) in a mixture of n-hexane (150 ml) and
CH2Cl2 (50 ml) were added dropwise into the flask. After warming
up to ambient temp., a violet precipitate was filtered off, washed
with n-hexane (3 ϫ 30 ml) and dried in vacuo to give 7.2 g (38%)
of 4b. The mother liquor was concentrated to ca 500 ml and stored
at 5°C overnight to yield 1.7 g (7%) of black crystalline 4bЈ.
1
from n-hexane gave 2.48 g (53%) of pure 5b. Ϫ H NMR (C6D6):
δ ϭ 2.17 (s, 12 H, CH3), 5.86 (s, 2 H, HCϭN), 6.99 (m, 6 H, aryl-
H). Ϫ 13C{1H} NMR (C6D6): δ ϭ 18.1 (s, CH3), 117.7 (s, HCϭ
N), 127.3 (s, p-C aryl), 135.8 (s, o-C aryl), 139.9 (i-C aryl). Ϫ
11B{1H} NMR (C6D6): δ ϭ 21.1 (s). Ϫ MS/EI; m/z: 310 [Mϩ]. Ϫ
C18H20BClN2 (310.63): calcd. C 69.60, H 6.49, N 9.02; found C
68.78, H 6.45 N 8.87.
(tBuCH2)NaϪC(Me)ϭC(Me)ϪNb(CH2tBu)BCl(NaϪB) (5c):
Lithium sand (0.32 g, 46.8 mmol) was added to a solution of 3.50
g (15.0 mmol) of 1,4-diazabutadiene (1c) in 100 ml of n-hexane.
After stirring the mixture for 10 d at room temp., the resulting
green slurry was chilled to Ϫ30°C, and a solution of 1.76 g (15.0
mmol) of BCl3 in 50 ml of n-hexane was added dropwise. After 2
h of stirring, the slurry was filtered, and the solvent was removed
in vacuo to afford 2.53 g (60%) of 5c as a dark brown oil, which
solidified to a tan wax. Ϫ Due to the lability of the product no
˜
4b: IR (KBr): ν ϭ 2567 cmϪ1 w, 1585 w, 1473 s, br., 1197 m,
1095 w, 884 w, 821 m, 775 m, 656 w, 548 w. Ϫ Due to the poor
solubility and due to decomposition no reliable 1H- and 13C-NMR
spectra were available. Ϫ 11B{1H} NMR (CDCl3): δ ϭ 7.2 (s). Ϫ
C18H20BCl3N2 (381.54): calcd. C 56.66, H 5.28, N 7.34; found C
57.87, H 5.20, N 6.95.
1
reliable IR spectrum was available. Ϫ H NMR (C6D6): δ ϭ 0.89
˜
4bЈ: IR (KBr): ν ϭ 2963 cmϪ1 w, 2922 w, 1608 sh, 1535 sh, 1473
(s, 18 H, tBu), 1.77 (s, 6 H, CH3), 3.21 (s, 4 H, CH2). Ϫ 13C{1H}
NMR (C6D6): δ ϭ 10.9 (s, ϭCϪCH3), 28.4 [s, C(CH3)3], 34.3 (s,
CH2), 53.7 [s, C(CH3)3], 118.9 (s, CϭC). Ϫ 11B{1H} NMR (C6D6):
δ ϭ 22.7 (s). Ϫ MS/EI; m/z: 270 [Mϩ in relation to 11B and 35Cl].
Ϫ C14H28BClN2 (270.65): calcd. C 62.13, H 10.43, N 10.35; found
C 62.02, H 10.56, N 10.31.
s, 1444 s, 1374 s, 1252 sh, 1227 m, 1094 s, 1000 s, 933 m, 908 w,
771 s, 722 w, 668w, 542 w. Ϫ 11B{1H} NMR (CD3CN): δ 7.7 (s,
BN2), 1.5 (s, BCl4Ϫ). Ϫ C18H20B2Cl6N2 (498.71): calcd. C 43.35, H
4.04, N 5.62; found C 38.6, H 4.31, N 4.77. Ϫ Repeated attempts
to purify the crude product by recrystallization failed.
(tBu)NaϪCHϭCHϪNb(tBu)BCl(NaϪB) (5a). Ϫ Path (a): A
sample of 4.46 g (11.0 mmol) of borolium salt 4a was stirred over-
night with 305.2 g of sodium amalgam (96.0 mmol sodium) in 120
ml of hexane. The reaction mixture was protected from light. The
slightly yellow solution was decanted from a yellow precipitate. Fil-
tration and removal of volatile components in vacuo afforded an
orange-yellow oil, which slowly solidified to give orange crystalline
5a. The crude material was sublimed at 40Ϫ60°C (0.01 Torr) to
yield 2.18 g (91%) of colorless product.
(tBu)NaϪCHϭCHϪNb(tBu)BI(NaϪB) (6a): A slurry of 2.50
g (14.8 mmol) of 1,4-diazabutadiene 1a in 100 ml of n-hexane was
allowed to react with lithium sand (0.21 g, 29.6 mmol) for 7 d at
20°C. A solution of 5.83 g (14.9 mmol) of BI3 in 50 ml of n-hexane
was added dropwise to the chilled slurry (Ϫ20°C). Stirring for 2 h
was followed by filtration. The filtrate was liberated from volatile
components in vacuo to afford 3.78 g (83%) of 6a as a colorless
oil. At room temp. the pure compound decomposed completely
within 5 d, whereas in the dark at Ϫ30°C a n-hexane solution of
6a remained unaffected. Ϫ Due to decomposition a reliable IR
spectrum was not available. Ϫ 1H NMR (C6D6): δ ϭ 1.45 (s, 18 H,
tBu), 6.40 (s, 2 H, CH). Ϫ 13C{1H} NMR (C6D6): δ ϭ 31.7 [s,
Path (b): A sample of 1,4-diazabutadiene 1a (2.50 g, 14.8 mmol)
was stirred with lithium sand (0.21 g, 29.6 mmol) in 70 ml of n-
hexane for 7 d at 20°C. A solution of 1.75 g (14.8 mmol) of BCl3
1150
Eur. J. Inorg. Chem. 1998, 1145Ϫ1152

2-Chloro-, 2- Fluoro- and 2-Iodo-2,3-dihydro-1H-1,3,2-diazaboroles
FULL PAPER
C(CH3)3], 54.2 [s, C(CH3)3], 114.6 (s, CϭC). Ϫ 11B{1H} NMR mmol) of 6b was converted into 0.33 g of 8b by treatment with 0.17
(C6D6): δ ϭ 6.5 (s). Ϫ MS /EI; m/z: 306 (27) [Mϩ], 250 (11) [Mϩ Ϫ g (2.0 mmol) of tert-butyl isocyanide.
C4H8], 194 (100) [Mϩ Ϫ 2 C4H8], 178 (3) [Mϩ Ϫ I]. Ϫ C10H20BIN2
From AgCN: A mixture of 6b (0.80 g, 2.0 mmol) and AgCN
(305.99): calcd. C 39.21, H 6.59, N 9.15; found C 39.35, H 6.48,
(0.32 g, 2.4 mmol) was stirred in 50 ml of CH3CN for 2 d at room
N 8.99.
temp. Concentration to dryness, extraction with n-hexane, filtration
(2,6-Me2C6H3)NaϪCHϭCHϪNb(2,6-Me2C6H3)BI(NaϪB) and removal of volatile components from the filtrate yielded 0.47
˜
(6b): A mixture of CH2Cl2 (600 ml) and n-hexane (400 ml) was g (79%) of 8b. Ϫ IR (KBr): ν ϭ 2218 cmϪ1 w [ν(CϵN)], 1949 w,
cooled to Ϫ10°C and two separate solutions of 6.00 g (22.7 mmol)
1868 w, 1791 w, 1647 w, 1594 w, 1541 w, 1479 s, 1441 m, 1399 m,
of 1,4-diazabutadiene 1b in CH2Cl2 (250 ml) and 8.89 g (22.7 1368 w, 1282 m, 1207 m, 1109 m, 915 m, 775 s, 717 m, 658 m, 421
mmol) of BI3 in n-hexane (200 ml) were added dropwise. The reac-
tion was filtered after warming up to room temp. and stirring for
5d. The filtrate was concentrated to dryness. The brown-black resi-
w. Ϫ 1H NMR (C6D6): δ ϭ 2.06 (s, 12 H, CH3), 5.75 (s, 2 H, CH),
6.95 (m, 6 H, H-aryl). Ϫ 13C{1H} NMR (C6D6): δ ϭ 17.8 (s, CH3),
119.4 (s, CϭC), 128.6 (s, pC-aryl). Ϫ 11B{1H} NMR (C6D6): δ ϭ
due was extracted with 150 ml of n-hexane, and the red n-hexane 13.5 (s). Ϫ MS/EI; m/z (%): 301 (100) [Mϩ]. Ϫ C19H20BN3 (301.18):
solution was decanted from insoluble components. Storing the con-
calcd. C 75.70 , H 6.69, N 13.95; found C 75.30, H 7.25, N 13.61.
centrated filtrate (ca 20 ml) at Ϫ4°C for 3 d afforded 2.43 g (26%)
(tBu)NaϪCHϭCHϪNb(tBu)BNCO(NaϪB) (9a): Analogously,
the treatment of 5a (0.43 g, 2.0 mmol) with AgOCN (0.53 g, 2.4
mmol) in 50 ml of CH3CN for 30 min at 20°C afforded 0.35 g
(78%) of 9a as a colorless viscous oil. Complete decomposition of
9a occurred within 2 d. Heterocycle 9a was also prepared from 7a
of colorless crystalline 6b. The compound was purified by subli-
˜
mation at 0.01 Torr and 380°C. Ϫ IR (KBr): ν ϭ 1554 cmϪ1 w,
1551 w, 1475 vs, 1439 m, 1397 s, 1340 m, 1279 s, 1263 s, 1244 m,
1197 m, 1162 w, 1105 s, 1032 w, 908 s, 772 vs, 688 s, 621 s, 569 w,
1
530 w. Ϫ H NMR (C6D6): δ ϭ 2.16 (s, 6 H, CH3), 5.99 (s, 2 H,
and AgOCN in CH3CN (50 ml) for 5 min (83% yield). Ϫ IR (CsI):
HCϭN), 6.98 (m, 6 H, arylH). Ϫ 13C{1H} NMR (C6D6): δ ϭ 18.3
(s, CH3), 120.0 (s, HCϭN), 126.2 (s, p-C-aryl), 135.7 (s, o-C-aryl),
140.7(s, i-C-aryl), Ϫ 11B{1H} NMR (C6D6): δ ϭ 11.8 (s). Ϫ MS/
EI; m/z: 402 (96) [Mϩ], 275 (100) [Mϩ Ϫ I]. Ϫ C18H20BIN2(402.08):
calcd. C 53.72, H 5.01, I 31.56, N 6.97; found C 53.56, H 5.16, I
31.44, N 6.99.
˜
ν ϭ 2972 cmϪ1 s, 2317 vs [νas(NCO)], 1699 m, 1684 m, 1527 w,
1474 m, 1458 m, 1404 s, 1367 s, 1322 s, 1288 w, 1240 s, 1138 m,
1033 w, 1001 w, 822 w, 807 w, 632 m [νsym(NCO)], 596 w. Ϫ 1H
NMR (C6D6): δ ϭ 1.21 (s, 18 H. tBu), 6.04 (s, 2 H, ϭCH). Ϫ
11B{1H} NMR (C6D6): δ ϭ 14.7 (s). Ϫ 13C{1H} NMR (C6D6): δ ϭ
31.0 [s, C(CH3)3], 52.5 [s, C(CH3)3], 111.6 (s, ϭCH), 123.9 (s, br.,
NϭCϭO). Ϫ MS/EI (70 eV); m/z (%): 221 (20) [Mϩ]. Ϫ C11H20
(tBu)NaϪCHϭCHϪNb(tBu)BCN(NaϪB) (8a). Ϫ From Isocy-
anides: A solution of 5a (1.07 g, 5.00 mmol) in 50 ml of n-hexane BN3O (221.12): calcd. C 59.74, H 9.13, N 18.99; found C 59.30, H
was treated at room temp. with 0.43 g (5.0 mmol) of tert-butyl
isocyanide. After 4 h of stirring it was filtered, and the volatile
components removed from the filtrate in vacuo (0.01 Torr) to give
crude 8a as a colorless solid. Purification was achieved either by
recrystallization from n-hexane or by sublimation at 0.03 Torr and
55°C, yield 0.61 g (60%). Similarly, 1.30 g (5.00 mmol) of
(tBu)NaϪCHϭCHϪNb(tBu)BBr(NaϪB) (7a) was converted into
0.66 g (64%) of 8a. Starting from 6a (1.53 g, 5.0 mmol) 0.41 g of
8a (41%) was obtained analogously. The reaction of 0.78 g (3.0
mmol) of 7a with 0.33 g (3.0 mmol) of cyclohexyl isocyanide in 50
ml of n-hexane at 20°C for 5 d also afforded 8a (0.23 g, 38%).
9.33, N 18.63.
(tBu)NaϪCHϭCHϪNb(tBu)BNCS(NaϪB) (10a): Compound
10a was prepared analogously from 5a (0.43 g, 2.0 mmol) and
AgSCN (0.40 g, 2.4 mmol) in CH3CN (50 ml, 20°C, 1 h), yield:
0.42 g (74%). The corresponding reaction of 7a and AgSCN took
place within 10 min to give a 76% yield of 10a. Ϫ IR (CsI): ν ϭ
˜
3133 cmϪ1 w, 2975 s, 2936 sh, 2910 sh, 2875 sh, 2122 vs, br.
[νas(NCS)], 1475 m, 1406 s, 1375 s, 1291 m, 1241 s, 1205 m, 1141
s, 1029 w, 948 w, 871 s [νsym(NCS)], 822 w, 802 m, 683 w, 632 s. Ϫ
1H NMR (C6D6): δ ϭ 1.20 (s, 18 H, tBu), 5.99 (s, 2 H, ϭCH);
(CDCl3): δ ϭ 1.42 (s, 18 H, tBu), 6.16 (s, 2 H, ϭCH). Ϫ 11B{1H}
From AgCN: A mixture of 5a (0.43 g, 2.0 mmol) and silver cyan- NMR (C6D6): δ 14.7 (s). Ϫ 13C{1H} NMR (CDCl3): δ ϭ 31.1 [s,
ide (0.32 g, 2.4 mmol) was stirred in acetonitrile (50 ml) for 1 h at
room temp. After concentration to dryness, the residue was ex-
tracted with n-hexane (3 ϫ 50 ml) and the combined extracts were
filtered. Repeated concentration to dryness gave analytically pure
C(CH3)3], 53.0 [s, C(CH3)3], 111.8 (s, ϭCH), 140.5 (s, NCS),
(C6D6): δ ϭ 31.0 [s, C(CH3)3], 52.9 [s, C(CH3)3], 112.1 (s, ϭCH).
Ϫ MS/EI (70 eV); m/z (%): 237 (70) [Mϩ], 125 (100) [Mϩ Ϫ 2 tBu].
Ϫ C11H20BN3S (237.17): calcd. C 55.71, H 8.50, N 17.72; found C
8a (0.35 g, 84%). The analogous reaction of 7a (0.52 g, 2.0 mmol) 54.89, H 8.78, N 17.24.
with AgCN (0.32 g, 2.4 mmol) in 50 ml of CH3CN for 20 min
(2,6-Me2C6H3)NaϪCHϭCHϪNb(2,6-Me2C6H3)BNCS-
˜
afforded 0.46 (89%) of 8a. Ϫ IR (KBr): ν ϭ 2207 cmϪ1
w
(NaϪB) (10b): A sample of solid AgSCN (0.41 g, 3.0 mmol) was
added to a slurry of 6b (1.00 g, 2.5 mmol) in CH3CN (40 ml) and
stirred for 5 h at 20°C. The slurry was filtered, and the filtrate
concentrated to dryness. The residue was extracted with n-hexane
(3 ϫ 50 ml) and the combined extracts were filtered. The volatile
components were removed from the filtrate to give pure 10b (0.77
g, 93%) as a waxy solid. Analogously, 5b was converted into 10b
[ν(CϵN)], 1501 w, 1467 m, 1405 s, 1368 s, 1344 m, 1295 m, 1261
m, 1234 s, 1207 m, 1147 s, 1100 w, 1032 w, 953 w, 824 s, 804 s, 694
s, 660 sh, 649 s, 500 m. Ϫ 1H NMR (C6D6): δ ϭ 1.29 (s, 18 H,
tBu), 6.14 (s, 2 H, CH). Ϫ 13C{1H} NMR (C6D6): δ ϭ 31.5 [s,
C(CH3)3], 53.7 [s, C(CH3)3], 114.6 (s, CϭC). Ϫ 11B{1H} NMR
(C6D6): δ ϭ 12.0 (s). Ϫ MS/EI; m/z (%): 205 (27) [Mϩ], 149 (10)
[Mϩ Ϫ C4H8], 93 (100) [Mϩ Ϫ 2 C4H8]. Ϫ C11H20BN3 (205.12):
calcd. C 64.40, H 9.85, N 20.48; found C 63.72, H 9.45, N 19.45.
within 3 h in 78% yield. The corresponding bromide gave 10b after
˜
1 h in 87% yield. Ϫ IR (KBr): ν ϭ 2918 cmϪ1 w, 2177 sh, 2114 vs
(2,6-Me2C6H3)NaϪCHϭCHϪNb(2,6-Me2C6H3)BCN(NaϪB) [νas(NCS)], 2038 sh, 1516 w, 1479 s, 1441 s, 1402 s, 1390 s, 1303 w,
(8b). Ϫ From Isocyanides: Equimolar amounts of 5b (0.62 g, 2.0
mmol) and tert-butyl isocyanide (0.17 g, 2.0 mmol) were allowed 768 s, 702 w, 656 w, 643 s. Ϫ H NMR (C6D6): δ ϭ 2.10 (s, 12 H,
to react in 40 ml of n-hexane for 8 h at room temp. The solution
CH3), 5.71 (s, 2 H, ϭCHN), 6.97 (m, 6 H, aryl-H). Ϫ 11B{1H}
was filtered and the colorless filtrate was concentrated to dryness. NMR (C6D6): δ ϭ 14.5 (s). Ϫ13C{1H} NMR (C6D6): δ ϭ 17.9 (s,
The remaining yellow solid was sublimed at 0.001 Torr and ca. CH3), 117.2 (s, ϭCHN), 127.3 (s, p-aryl-C), 128.6 (s, m-aryl-C),
400°C to give 0.42 g (70%) of 8b. Similarly, a sample of 0.80 g (2.0 135.2 (s, o-aryl-C), 139.2 (s, i-aryl-C). Ϫ MS/EI (70 eV); m/z (%):
1285 m, 1201 w, 1111 s, 1032 w, 992 w, 909 m, 856 s [νsym(NCS)],
1
Eur. J. Inorg. Chem. 1998, 1145Ϫ1152
1151

L. Weber, E. Dobbert, R. Boese, M. T. Kirchner, D. Bläser
FULL PAPER
333 (100) [Mϩ]. Ϫ C19H20BN3S (333.15): calcd. C 68.44, H 6.05,
[8]
[9]
L. Weber, E. Dobbert, H.-G. Stammler, B. Neumann, R. Boese,
D. Bläser, Chem. Ber. 1997, 130, 705Ϫ710.
K. M. Harmon, F. E. Cummings, J. Am. Chem. Soc. 1962, 84,
1751.
N 12.61; found C 68.38, H 6.30, N 12.38.
X-ray Structural Analysis of 6b: Colorless single crystals from n-
hexane; 0.42 ϫ 0.37 ϫ 0.32 mm; T ϭ 293 K; Siemens P4 four-circle
diffractometer; Mo-Kα (graphite monochromator, λ ϭ 0.71073 A),
empirical formula C18H20BIN2, monoclinic space group C2/c; unit
In Cl2BNMe2 and Cl2BNEt2 chemical shifts δ11B ϭ 30.8
[10] [10a]
˚
and 30.6 were measured: A. J. Banister, N. N. Greenwood, B.
[10b]
P. Straughan, J. Walker, J. Chem. Soc. 1964, 995Ϫ1000. Ϫ
H. Nöth, H. Vahrenkamp, Chem. Ber. 1966, 99, 1049Ϫ1067.
˚
[11] [11a] M. F. Lappert, H. Pyszora, J. Chem. Soc. 1963, 1744Ϫ1750.
cell dimensions: a ϭ 14.911(2), b ϭ 7.9706(8), c ϭ 16.9105(12) A;
˚
[11b]
β ϭ 114.360(6)°; V ϭ 1830.9(3) A3, dcalcd. ϭ 1.459 g cmϪ3, Z ϭ 4;
µ(Mo-Kα) ϭ 1.747 mmϪ1; range for data collection: 5.3° Յ 2Θ Յ
60.1°; ω-scan, index ranges: Ϫ20 Յ h Յ 0, Ϫ11 Յ k Յ 0, Ϫ21 Յ l
Յ 23; reflections collected 2769 (Rint ϭ 0.017); independent reflec-
tions 2675; parameters 102; absorption correction: empirical φ-
Ϫ
M. F. Lappert, H. Pyszora, M. Rieber, J. Chem. Soc.
[11c]
1965, 4256Ϫ4264. Ϫ
M. F. Lappert, H. Pyszora, J. Chem.
Soc. A 1967, 854Ϫ860.
[12]
[13]
A. Meller, W. Maringgele, U. Sicker, J. Organomet. Chem. 1977,
141, 249Ϫ255.
B. Hessett, J. B. Leach, J. H. Morris, P. G. Perkins, J. Chem.
Soc., Dalton Trans. 1972, 131Ϫ134.
scans, min/max transmission 0.94/0.79 [Rmerg(before/after)
ϭ
[14]
[15]
J. Goubeau, H. Gräbner, Chem. Ber. 1960, 93, 1379Ϫ1387.
Holleman-Wiberg, Lehrbuch der Anorganischen Chemie, vol.
91Ϫ100, de Gruyter, Berlin 1985, p. 133.
F. Zettler, H. Hess, W. Siebert, R. Full, Z. Anorg. Allg. Chem.
1976, 420, 285Ϫ291.
M. A. Ring, J. D. H. Donnay, W. S. Korski, Inorg. Chem. 1962,
1, 109Ϫ111.
G. Linti, D. Loderer, H. Nöth, K. Polborn, W. Rattay, Chem.
Ber. 1994, 127, 1909Ϫ1922.
0.0333/0.0136]. Program used: Siemens SHELXTL Ver. 5.03. Struc-
ture solution: Direct Methods; structure refinement: Full-matrix
least-squares on F2, R1 ϭ 0.042, wR2 ϭ 0.1043 based on 1884
reflections with I > 2σ(I), wR2 (all data) ϭ 0.1189 with w ϭ 1/
[16]
[17]
[18]
[19]
[σ2(Fo2) ϩ (0.0484P)2 ϩ 3.11P], where P ϭ (Fo ϩ 2Fc )/3; GOOF
2
2
˚
(F2) ϭ 1.029, maximum residual electron density 0.922 eAϪ3, hy-
drogen atoms treated as riding groups with the 1.2-fold isotropic U
value of the corresponding C atom and 1.5-fold for methyl
groups.[26]
G. R. Desiraju, Angew. Chem. 1995, 107, 2540Ϫ2558; Angew.
Chem. Int. Ed. Engl. 1995, 34, 2311Ϫ2329.
October 1997 release of CSD with 175093 entries.
F. H. Allen, O. Kennard Chem. Design Automation News 1993,
8, 31Ϫ37.
[20]
[21]
Ƞ
Dedicated to Professor Heinrich Nöth on the occasion of his
[22]
[23]
[24]
[25]
[26]
J. M. Klugman, R. K. Barnes, Tetrahedron 1970, 26,
2555Ϫ2560.
70th birthday.
[1] [1a]
K. Niedenzu, J. S. Merriam, J. Organomet. Chem. 1973, 51,
[1b]
H. tom Dieck, M. Svoboda, T. Greiser, Z. Naturforsch., B 1981,
36, 823Ϫ832.
C1ϪC2. Ϫ
K. Niedenzu, J. S. Merriam, Z. Anorg. Allg.
Chem. 1974, 406, 251Ϫ259.
[2]
M. Svoboda, H. tom Dieck, C. Krüger, Y. H. Tsay, Z. Natur-
forsch., B 1981, 36, 814Ϫ822.
L. Weber, G. Schmid, Angew. Chem. 1974, 86, 519; Angew.
Chem. Int. Ed. Engl. 1974, 13, 467.
[3]
[4]
F. Klanberg, H. W. Kohlschütter, Chem. Ber. 1961, 94,
786Ϫ789.
G. Schmid, J. Schulze, Chem. Ber. 1977, 110, 2744Ϫ2750.
G. Schmid, M. Polk, R. Boese, Inorg. Chem. 1990, 29, 4421-
4429.
Further details of the crystal structure investigation are avail-
able on request from Fachinformationszentrum Karlsruhe,
D-76344 Eggenstein-Leopoldshafen, on quoting the depository
number CSD-408392, the names of the authors, and the jour-
nal citation.
[5]
G. Schmid, J. Schulze, Angew. Chem. 1977, 89, 258-259; Angew.
Chem. Int. Ed. Engl. 1977, 16, 249.
G. Schmid, J. Schulze, Chem. Ber. 1981, 114, 495Ϫ504.
G. Schmid., J. Lehr, M. Polk, R. Boese, Angew. Chem. 1991,
103, 1029Ϫ1031; Angew. Chem. Int. Ed. Engl. 1991, 30, 1015.
[6]
[7]
[98047]
1152
Eur. J. Inorg. Chem. 1998, 1145Ϫ1152