First B-organyloxy-substituted iminoboranes: preparation, stabilization, and reactivity

Article abstract of DOI:10.1021/om0005912

The amino(halo)(organyloxy)boranes ROB(X)N(H)R′ (R = 2,6-^tBu₂C₆H₃) X = Cl, R′ = ^tBu (7), SiMe₃ (8), 2,6-ⁱPr₂C₆H₃ (9), 2,4,6-Me₃C₆H₂ (10), 2,4,6-^tBu₃C₆H₂ (11); R = 2,6-C₆H₅)₂C₆H₃, X = Cl, R′ = ^tBu (12); R = 2,6-^tBu₂C₆H₃) X = F, R′ = ^tBu (13), 2,6-ⁱPr₂C₆H₃ (14); R = ^tBu₃C, X = F, R′ = ⁱPr (15), ^tBu (16), SiMe₃ (17)) were dehydrohalogenated with tert-butyllithium at low temperature.

Full text of DOI:10.1021/om0005912

Organometallics 2000, 19, 5083-5091
5083
F ir st B-Or ga n yloxy-Su bstitu ted Im in obor a n es:
P r ep a r a tion , Sta biliza tion , a n d Rea ctivity
Egbert v. Steuber, Gernot Elter, Mathias Noltemeyer, Hans-Georg Schmidt, and
Anton Meller*
Institut fu¨r Anorganische Chemie der Universita¨t Go¨ttingen, Tammannstrasse 4,
D-37077 Go¨ttingen, Germany
Received J uly 11, 2000
t
The amino(halo)(organyloxy)boranes ROB(X)N(H)R′ (R ) 2,6-tBu2C6H3, X ) Cl, R′ ) Bu
(7), SiMe3 (8), 2,6-iPr2C6H3 (9), 2,4,6-Me3C6H2 (10), 2,4,6-tBu3C6H2 (11); R ) 2,6-C6H5)2C6H3,
X ) Cl, R′ ) tBu (12); R ) 2,6-tBu2C6H3, X ) F, R′ ) tBu (13), 2,6-iPr2C6H3 (14); R ) tBu3C,
i
t
X ) F, R′ ) Pr (15), Bu (16), SiMe3 (17)) were dehydrohalogenated with tert-butyllithium
at low temperature. The reaction involved the intermediate formation of an aryloxy(imino)-
borane in the case of 7, 9, 11, and 12. The diazadiboretidines [ROBdNR′]2 (R ) 2,6-tBu2C6H3,
t
t
i
R′ ) Bu (18), SiMe3 (19), 2,6-iPr2C6H3 (20), 2,4,6-Me3C6H2 (21); R ) Bu3C, R′ ) Pr (22),
SiMe3 (23)) were isolated as the ultimate products of the reactions. The aryloxy(imino)-
borane 2,6-tBu2C6H3-O-BtN-tBu (derived from 7) was reacted with BEt3 and Me3SiN3 to
give the corresponding 1,2-addition products across the (B≡N) triple bond (25 and 26,
respectively). The compounds were characterized by NMR spectroscopy (1H, 11B, 13C, 29Si),
MS (EI and FI), and elemental analyses. X-ray structure determinations are presented for
18, 22, and 26.
In tr od u ction
borylhydroxylamines as precursors for N-oxygen-sub-
stituted iminoboranes.7 Probably oxygen could also be
a suitable neighbor for the boron atom in iminoboranes.
The oxygen atom has two lone electron pairs and can
therefore act as a π-donor toward boron, rather like the
nitrogen atom in amino(imino)boranes. Moreover, the
stability of the B-O bond should facilitate the synthesis
of the starting materials needed. On the other hand,
kinetic stabilization will be more difficult, as there is
only one group on the oxygen atom to produce steric
shielding (but two on the nitrogen atom of amino(imino)-
boranes), and the shielding group is more distant from
the center of unsaturation than in the organyl-substi-
tuted iminoboranes.
Our investigation concentrated on Lewis-base-induced
dehydrohalogenation reactions with amino(halo)(orga-
nyloxy)boranes. Ideally, these reactions could lead to
organyloxy(imino)boranes RO-BtN-R′, a compound
class that has so far been unknown. We also aimed to
establish the influence of the substituents R and R′ on
the stability of any unsaturated product and to describe
the stabilization processes of unstable organyloxy-
(imino)boranes. Finally, we hoped to gain some insight
into the reactivity of the unsaturated target compounds.
In this paper we present the findings of our study of
B-oxygen-substituted iminoboranes.
In the past two decades a large number of new
iminoboranes and amino(imino)boranes were prepared
mainly by two types of elimination reactions with
suitable amino(halo)boranes. Thermally induced elimi-
nation of a halogen(trimethyl)silane in the gas phase
proved an effective method for the synthesis of organyl-
(imino)boranes,1 while many amino(imino)boranes could
more successfully be prepared by dehydrohalogenation
reactions, which can be performed at low temperature
in the presence of strong Lewis bases with bulky
substituents such as tert-butyllithium or lithium bis-
(trimethylsilyl)amide.2 These fundamental studies led
to the conclusion that the stability of iminoboranes
depends on the steric requirements of the substituents
in the immediate vicinity of the (B≡N) triple bond.1,2
Our group has added further details to this field, mainly
by using o-substituted phenyl derivatives to stabilize
such moieties.3-6
In view of the numerous successful syntheses of
iminoboranes and amino(imino)boranes, it seemed prom-
ising to try the preparation of iminoboranes with
elements other than carbon, silicon, or nitrogen attached
to the multiply bonded center. A recent study dealt with
(1) Paetzold, P. Adv. Inorg. Chem. 1987, 31, 123, and literature cited
there.
(2) No¨th, H. Angew. Chem. 1988, 100, 1664, and literature cited
there.
Resu lts a n d Discu ssion
(3) Elter, G.; Meller, A.; Neuhaus, M.; Schmidt-Ba¨se, D. J . Orga-
nomet. Chem. 1990, 381, 299.
(4) Elter, G.; Heine, A.; Luthin, W.; Meller, A.; Sheldrick, G. M.;
Stalke, D. Z. Anorg. Allg. Chem. 1992, 608, 147.
(5) Elter, G.; Geschwentner, M.; Meller, A. Z. Anorg. Allg. Chem.
1993, 619, 1474.
P r ep a r a tion of th e Sta r tin g Ma ter ia ls. The amino
(halo)(organyloxy)boranes which promised to be use-
ful precursors for the synthesis of organyloxy(imino)-
(6) Elter, G.; Gornitzka, H.; Heine, A.; Luthin, W.; Meller, A.;
Stratmann, J .-G. Z. Anorg. Allg. Chem. 1995, 621, 1995.
(7) Albrecht, T.; Elter, G.; Meller, A. Z. Anorg. Allg. Chem. 1999,
625, 1423.
10.1021/om0005912 CCC: $19.00 © 2000 American Chemical Society
Publication on Web 10/27/2000

5084 Organometallics, Vol. 19, No. 24, 2000
Steuber et al.
boranes were prepared in several steps from alcohols
or phenols, respectively, boron trihalides, and a variety
of amines.
In a second step the dihalo(organyloxy)boranes 1-4
were coupled with a number of lithiated or silylated
amines. These reactions, which are summarized in eq
3, led to the amino(halo)(organyloxy)boranes 7-17,
which should allow a dehydrohalogenation reaction as
a final step.
First the sterically hindered phenols 2,6-di-tert-bu-
tylphenol (I) and 2′-hydroxy-m-terphenyl (2,6-diphe-
nylphenol, II) and the alcohol 1,1-di-tert-butyl-2,2-
dimethylpropanol (tri-tert-butylmethanol, III) were
reacted with boron trifluoride and/or boron trichloride
to give organyloxy(dihalo)boranes. The syntheses of the
dichlorophenoxyborane derivatives 18 and 2 required
the initial metalation of the respective phenols, while
the fluorine compounds 3 and 4 could better be prepared
from I and III, respectively, and boron trifluoride diethyl
etherate in the presence of the adduct BF3‚N(iPr)2Et.9
The reactions were carried out at low temperature (eq
1).
We did not succeed in coupling 3 with (Me3Si)2NH
(path (b)) or 4 with lithiated 2,6-diisopropylaniline (path
(a)).
We were unable to isolate compound 4, which decom-
posed when the solvent was removed in vacuo. However,
it was possible to handle this compound in solution after
filtering off the tetrafluoroborate. A characteristic peak
around 40 ppm in the 19F NMR spectrum of the reaction
solution can be assigned to 4 (cf. 19F chemical shift of
3: 41.6 ppm). Our attempts to prepare a chloro-
compound similar to 4 (tri-tert-butylmethoxy(dichloro)-
borane) failed, too. We tried the reaction of boron
trichloride with the alcohol III (in the presence of NEt3)
and with lithium tri-tert-butylmethanolate.
The reaction of the lithium derivatives of I and III
with boron trifluoride diethyl etherate at room temper-
ature led to the fluoro(diorganyloxy)boranes 5 and 6 (eq
2). The monosubstituted compound 3 could be observed
only as a byproduct when the reaction with the phenol
I was carried out at -78 °C.
Rea ction s of th e Am in o(h a lo)(or ga n yloxy)bo-
r a n es 7-17 w ith ter t-Bu tyllith iu m . The elimination
of hydrogen chloride or fluoride, respectively, from the
compounds 7-17 was achieved by treatment with tert-
butyllithium at -78 °C (in hexane). While the reaction
mixtures were allowed to warm to room temperature,
their 11B NMR spectra were continually monitored. We
expected the formation of unsaturated intermediates or
products to be observable in the 11B NMR spectra
because iminoboranes are known to have characteristic
signals in the range 0-15 ppm.1,2 The reactions are
represented in eq 4.
It turned out that the reactions with the fluorine
compounds started only when the temperature rose
above 0 °C, and in some cases (13 and 14) moderate
heating was necessary to initiate the dehydrofluorina-
tion. Under these conditions the intermediate formation
of an organyloxy(imino)borane could not be observed.
Apparently in these cases the organyloxy(imino)borane
species is too short-lived and the corresponding cy-
clodimers are formed almost immediately.
The amino(chloro)(organyloxy)boranes, however, re-
acted with tert-butyllithium at temperatures below 0 °C,
and the dehydrochlorination started at around -20 °C.
With the compounds 7, 9, 11, and 12 an organyloxy-
(imino)borane could be identified as a short-lived inter-
mediate from the 11B NMR spectra of the reaction
solutions. Their NMR signals in the range 5-8 ppm
could be observed for about 2 h but disappeared slowly
(8) Compound 1 has been known for many years: (a) Hunter, D.
H., Steinberg, H. US Pat. 3027397, 1962; Chem. Abstr. 1962, 57, 4595.
(b) Steinberg, H. Organoboron Chemistry. Vol. 1: Boron-Oxygen and
Boron-Sulfur Compounds; Wiley-Interscience: New York, London,
Sydney, 1964; p 515. (c) Armbrecht, M.; Meller, A. Chem. Ber. 1986,
119, 1-8. We listed the compound in the Experimental Section since
spectroscopic data and preparative details for 1 are missing in the
literature.
(9) Harris, J . J .; Rudner, B. Inorg. Chem. 1969, 8, 1258.

First B-Organyloxy-Substituted Iminoboranes
Organometallics, Vol. 19, No. 24, 2000 5085
diazadiboretidine 23 in vacuo, we obtained the related
compound 24 (eq 5). The isobutene was collected in a
cold trap and identified by its 13C NMR spectrum (see
the Experimental Section). X-ray structure determina-
tions were carried out with the compounds 18 and 22
(see below).
Rea ction s w ith Ar yloxy(im in o)bor a n es. Indepen-
dent evidence for the temporary existence of the orga-
nyloxy(imino)boranes in the reactions presented above
can be obtained when the reaction mixtures contain an
additional reactant that offers an alternative reaction
route for the unsaturated intermediate. Under such
conditions, it should be possible to arrive at compounds
other than the cyclodimers that are formed in the
reactions according to eq 4.
A wide variety of reactions have been described both
for iminoboranes and amino(imino)boranes; the extraor-
dinary potential of these compound classes for synthetic
purposes has thus been established.1,2,10-15 However, the
number of reaction types that can possibly be carried
out with our organyloxy(imino)boranes is severely lim-
ited, mainly by the fact that the unsaturated species
can only be handled (for a relatively short period of time)
in the solution in which it was formed. A potential
reaction partner for an organyloxy(imino)borane would
therefore have to meet at least the following require-
ments:
when the reaction mixtures reached temperatures above
0 °C, giving way to the peaks around 25 ppm that can
be associated with the respective cyclodimers. In com-
bination with the 2,6-di-tert-butylphenoxy group the 2,6-
diisopropylphenyl group seems to represent the border-
line case as far as the bulkiness of the imino substituent
is concerned. Less cumbersome substituents such as
mesityl do not even temporarily stabilize the organy-
loxy(imino)borane.
(1) It must not react with the starting materials (tert-
butyllithium and the organyloxy(amino)(halo)borane).
We isolated the diazadiboretidines 18-23 as the
ultimate products of the dehydrohalogenation of the
investigated haloboranes. With their oxygen-substituted
boron atoms they constitute a new type of diazadibore-
tidine. The uniform stabilization pattern observed is in
full agreement with the established behavior of amino-
(imino)boranes. The presence of the oxygen atom does
not alter the way in which the iminoboranes stabilize.
However, it seems to have a strengthening effect on the
boron-halogen bond in the starting compounds, so that
their dehydrohalogenation requires higher tempera-
tures than similar reactions with comparable bis-
(amino)(halo)boranes.4,6
(2) Its reaction with the organyloxy(imino)borane has
to be faster than the cyclodimerization of the iminobo-
rane itself.
Consequently, many reactants are out of question to
start with (e.g., all protic agents such as amines,
alcohols, or thioles and most compounds containing
halogen atoms). Among the remaining options the most
promising reaction types include cycloadditions (with
alkenes, alkynes, azides, dienes, etc.) and insertion
reactions, e.g., with Lewis acids such as trialkylboranes.
We selected the chloroborane 7 as a model compound
for our derivations and investigated the reactivity of its
dehydrochlorinated form toward a range of substances,
including unsaturated hydrocarbons, amino(imino)bo-
ranes, triethylborane, and azides.
No defined product was isolated from the reactions
of the compounds 11, 12, and 16 with tert-butyllithium.
In the case of 11 it is possible that the dehydrochlori-
nation is followed by an intramolecular addition involv-
ing a methyl group of the bulky amino substituent.3
We could not observe cycloaddition reactions with 2,3-
dimethyl-2-butene ([2+2]), 2-butyne ([2+2]), or 2,3-
While the diazadiboretidines with the 2,6-di-tert-
butylphenoxy group could easily be purified by sublima-
tion, the tri-tert-butylmethoxy-substituted compounds
displayed a tendency to split off isobutene when they
were heated, due to the steric pressure that the three
tert-butyl groups exert in the alkoxy substituents. Hence
the compounds 22 and 23 were only obtained by
crystallization. 22 decomposed in an irregular fashion
when it was heated. When we attempted to sublime the
(10) Geisberger, G.; Neukirchinger, K.; No¨th, H. Chem. Ber. 1990,
123, 455.
(11) No¨th, H.; Schu¨bel, J . Chem. Ber. 1991, 124, 1687.
(12) Dreczewski, B.; Englert, U.; Hahnfeld, D.; Pawelec, Z.; Paetzold,
P.; Walz, L.; Wojnowski, W. Chem. Ber. 1992, 125, 1073.
(13) Braunschweig, H.; Paetzold, P.; Spaniol, T. P. Chem. Ber. 1993,
126, 1565.
(14) Loderer, D.; No¨th, H.; Pommerening, H.; Rattay, W.; Schick,
H. Chem. Ber. 1994, 127, 1605.
(15) Costisor, O.; Klo¨fkorn, C.; Paetzold, P.; Schmidt, M.; Spaniol,
T.; Wagner, T.; Chem. Ber. 1995, 128, 1037.

5086 Organometallics, Vol. 19, No. 24, 2000
Steuber et al.
dimethyl-1,3-butadiene (Diels-Alder or [2+2]). In all
these cases the diazadiboretidine 18 was found to be
the only product.
A similar pattern occurred when a cross-dimerization
of our aryloxy(imino)borane with other iminoboranes
was attempted. The relatively stable amino(imino)-
borane (Me3Si)2N-BtN-(2,6-iPr2C6H3)6 was recovered
intact from the reaction mixture alongside the cy-
clodimer 18. The more reactive compound (2,6-iPr2C6H3)-
(SiMe3)N-BtN-(2,6-iPr2C6H3) did not react with the
model aryloxy(imino)borane either; instead it gave the
diazasilaboretidine that has been described as its in-
tramolecular stabilization product.6
These observations made us look for a reaction
partner with a stronger affinity toward the (BtN) triple
bond in the organyloxy(imino)borane, which ought to
be the case with Lewis acids. Accordingly, the reaction
of the aryloxy(imino)borane derived from 7 with an
excess of triethylborane led to the insertion product of
the organyloxy(imino)borane into one of the B-C bonds
25 (eq 6).
similar reaction was tried with phenyl azide, but the
product could not be purified by sublimation because it
decomposed upon heating.
The reactions according to eqs 6 and 7 are again in
full agreement with the established behavior of amino-
(imino)boranes.1,2 The excessive sterical hindrance in
26 prevents a cyclization to give a tetrazaboroline.
Cr ysta l Str u ctu r es. X-ray structure analyses were
performed with the compounds 18, 22, and 26. The
results are depicted in the Figures 1-3, respectively.
Selected atomic distances and angles are summarized
in Table 1, and crystallographic data are compiled in
Table 2. Among the diazadiboretidines it shows that 18
is exactly planar and has a symmetry center in the
center of the ring. In 22 the four-membered ring
deviates somewhat from a planar geometry: the folding
angle is 174.9° and the torsion angle 3.8°. This may be
due to the extreme sterical crowding among the oxygen
atoms. Until now there are five X-ray structure deter-
minations of diazadiboretidines reported in the litera-
ture: those of the B-amino-substituted species [TMPB-
NBu]2 (A)16 (TMP ) 2,2,6,6-tetramethylpiperidine) and
[(Me3Si)2NBNSiMe3]2 (B)17 and those of the B-organyl-
substituted [F5C6BNtBu]2 (C),18 [tBuBNBut]2,19 and
[BuBNtBu]2 (E).20 Of these A, B, C, and E are planar,
D is folded (folding angle 155°, torsion angle 18°). The
mean BN distances in the respective rings are 1.460 Å
in 18, 1.470 Å in 22, 1.468 Å in A, 1.458 Å in B, 1.430
Å in C, 1.486 Å in D, and 1.456 Å in E. The exocyclic
BN bond lengths are 1.465 Å in A and 1.441 Å in B.
The (exocyclic) BO distances are 1.365 Å in 18 and 1.355
Å (mean) in 22. The BO distances are slightly larger
than the exocyclic BO bonds in trihydroxyboroxine
(about 1.349 Å).21 All six diazadiboretidines have slightly
rhomboidal shaped ring systems: the angles about the
ring N atoms vary between (mean) 82.1° in B and 88.0°
in D. It shows that regardless of the type of substituents
As indicated in eq 6, there are two possible routes
leading from 7 to 25. The chloroborane 7 could theoreti-
cally be alkylated by BEt3 prior to any metalation of
the nitrogen atom. We reckoned that in this case it
should be possible to isolate the intermediate amino-
(ethyl)borane. In a separate experiment we therefore
added BEt3 to the chloroborane 7 at -78 °C; the workup
of this reaction mixture gave the starting compound 7
in quantitative yield. This is further evidence for the
intermediate formation of the organyloxy(imino)borane
in the reaction according to eq 6.
The analogous reaction of 7 with trimethylaluminum
did not deliver an amino-alane derivative similar to
25. Instead a mixture of the starting compound 7 and
the corresponding B-methyl-substituted derivative was
recovered and was identified by the mass and NMR
spectra of the distilled product. All our efforts to
separate the two components were foiled by their similar
boiling points. However, this outcome might indicate
that the alkylation represented in eq 6 must indeed be
considered an alternative to the formation of the orga-
nyloxy(imino)borane.
t
bonded to the boron atoms (i.e., RO, C6H5, Bu, and Bu;
there are planar and folded ring systems), only the two
amino-substituted species (A and B) both have planar
rings. This could lead to the assumption that exocyclic
π-bonding might play an important role. However, in
both B-aminodiazadiboretidines (as well as the C6F5
group in C) the substituents are twisted out of the B2N2
plane and cannot overlap to form π-bonds. The longest
BN distance in the ring (1.486 Å) is found in [tBuBNt-
Bu]2 (D), and the shortest in [C6F5BNtBu]2 (C). This all
indicates that exocyclic π-bonding between the boron
atom and its substituent (when it exists) is just one of
(16) No¨th, H.; Schwartz, M.; Weber, S. Chem. Ber. 1985, 118, 4716.
(17) Hess, H. Acta Crystallogr., Sect. B 1969, 25, 2342.
(18) Paetzold, P.; Richter, A.; Thijssen, T.; Wu¨rtenberg, S. Chem.
Ber. 1979, 112, 3811.
(19) Paetzold, P.; von Plotho, C.; Schmid, G.; Boese, R.; Schrader,
B.; Bougeard, D.; Pfeiffer, U.; Gleiter, R.; Scha¨fer, W. Chem. Ber. 1984,
117, 1089.
(20) Paetzold, P.; Schro¨der, E.; Schmid, G.; Boese, R. Chem. Ber.
1985, 118, 3205.
(21) Peters, C. R.; Milberg, M. E. Acta Crystallogr. 1964, 17, 229.
Another successful addition resulted with trimethyl-
silyl azide. According to eq 7 the azide was added across
the (B≡N) bond of our aryloxy(imino)borane, giving the
B-azido derivative 26; the structure of this compound
was determined by an X-ray structure analysis. A

First B-Organyloxy-Substituted Iminoboranes
Organometallics, Vol. 19, No. 24, 2000 5087
refer to the other phenyl group(s), starting with the atom that
is connected to the rest of the molecule.
Sta r tin g Ma ter ia ls. 1,1-Di-tert-butyl-2,2-dimethylpropanol
III22 and phenyl azide23 were prepared according to the
literature. All other starting materials were commercially
available. Concentrations: butyllithium 15% in hexane, tert-
butyllithium 1.5 M in pentane, triethylborane 1 M in hexane,
trimethylaluminum 2 M in heptane.
P r ep a r a tion of th e Dich lor obor a n es 1 a n d 2. A 0.1 mol
sample of 2,6-di-tert-butylphenol I (20.6 g) or 2,6-diphenylphe-
nol II (24.6 g), respectively, was dissolved in 100 mL of hexane.
An equimolar amount of butyllithium was added to this
solution, which was then refluxed for 3 h. After cooling to -78
°C a freshly prepared solution of 0.2 mol boron trichloride (23.2
g) in 100 mL of hexane was added dropwise. The reaction
mixture was stirred for another 2 h at low temperature and
then allowed to warm. The solvent was removed at reduced
pressure and the residue separated from the lithium chloride
by distillation in vacuo. The crude product was purified by a
second distillation.
F igu r e 1. Crystal structure of the diazadiboretidine 18.
2,6-Di-ter t-bu tylp h en oxy(d ich lor o)bor a n e (1): colorless
liquid, bp 84 °C/0.01 Torr. Yield: 22.4 g (78%). Anal. Calcd
for C14H21BCl2O (287.04 g/mol): C, 58.57; H, 7.39. Found: C,
58.49; H, 7.38. MS (EI, 70 eV): m/e (rel intensity) 286 (10)
(C14H2111B35Cl2O) [M+], 271 (60) [M+ - Me], 57 (100) [CMe3+].
1H NMR (CDCl3, 25 °C): δ 7.27 (AB2, 2H, 3/5), 7.06 (AB2, 1H,
4), 1.39 (s, 18H, CMe3). 13C NMR (CDCl3, 25 °C): δ 151.3 (1),
139.8 (2/6), 126.3 (3/5), 124.5 (4), 35.4 (CMe3), 31.7 (CMe3). 11
NMR (CDCl3, 25 °C): δ 31.8.
B
Dich lor o(2,6-diph en ylph en oxy)bor an e (2): colorless solid,
bp 140 °C/0.01 Torr, mp 39 °C. Yield: 22.4 g (58%). Anal. Calcd
for C18H13BCl2O (327.02 g/mol): C, 66.11; H, 4.01. Found: C,
F igu r e 2. Crystal structure of the diazadiboretidine 22.
66.42; H, 4.50. MS (EI, 70 eV): m/e (rel intensity) 326 (C18H13
-
11B35Cl2O) (100) [M+], 290 (85) [M+ - HCl]. H NMR (CDCl3,
25 °C): δ 7.1-7.6 (m, 13H, 3-5 and 8-12). 13C NMR (CDCl3,
25 °C): δ 147.3 (1), 137.0 (2/6 or 7), 133.6 (2/6 or 7), 130.2 (3/5
or 10), 129.4 (8/12 or 9/11), 128.5 (8/12 or 9/11), 127.7 (3/5 or
10), 125.7 (4). 11B NMR (CDCl3, 25 °C): δ 31.3.
1
P r ep a r a tion of th e Diflu or obor a n es 3 a n d 4. At 0 °C a
solution of 0.1 mol ethyldiisopropylamine (12.9 g) in 100 mL
of diethyl ether was added to a solution of 0.2 mol of boron
trifluoride diethyl etherate (28.4 g) in 100 mL of diethyl ether.
The mixture was stirred for 2 h at room temperature and then
cooled to -78 °C. A solution of 0.1 mol of 2,6-di-tert-butylphenol
I (20.6 g) or 1,1-di-tert-butyl-2,2-dimethylpropanol III (20.0 g),
respectively, in 100 mL of diethyl ether was added; the reaction
mixture was stirred for another 4 h at low temperature and
for 12 h at room temperature. Then the solid precipitate was
filtered off. In the case of 4 the clear filtrate was used directly
for further reactions (we assumed the yield to be 70%). For 3
the solvent was removed at reduced pressure, and the residue
was separated from the lithium fluoride by distillation in
vacuo. The crude product was purified by a second distillation.
2,6-Di-ter t-bu tylp h en oxy(d iflu or o)bor a n e (3): colorless
liquid, bp 52 °C/0.01 Torr. Yield: 19.2 g (76%). Anal. Calcd
for C14H21BF2O (254.13 g/mol): C, 66.16; H, 8.35. Found: C,
66.18; H, 8.40. MS (EI, 70 eV): m/e (rel intensity) 254 (15)
[M+], 239 (100) [M+ - Me]. 1H NMR (CDCl3, 25 °C): δ 7.18
(AB2, 2H, 3/5), 6.95 (AB2, 1H, 4), 1.43 (s, 18H, CMe3). 13C NMR
(CDCl3, 25 °C): δ 149.4 (t, 1, 3J CF ) 2.9 Hz), 140.6 (2/6), 125.9
(3/5), 124.4 (4), 35.1 (CMe3), 31.2 (CMe3). 11B NMR (CDCl3, 25
°C): δ 12.4. 19F NMR (CDCl3, 25 °C): δ 41.5.
F igu r e 3. Crystal structure of the azidoborane 26.
several factors that influence the structure of diazadi-
boretidines. Polarization in the σ-system due to the elec-
tronegativity of the substituents andsmost importantlys
packing effects of the overcrowded molecules in the solid
state apparently play an important role.
Exp er im en ta l Section
Gen er a l Rem a r k s. All reactions were carried out under
an atmosphere of dry nitrogen in dry solvents. NMR: Bruker
AM 250, reference SiMe4 internal (1H, 13C, 29Si), BF3‚OEt2
P r ep a r a tion of th e Bis(p h en oxy)bor a n es 5 a n d 6. The
compounds were not intentionally prepared but obtained from
the following procedure: 0.1 mol of 2,6-di-tert-butylphenol I
(20.6 g) or 1,1-di-tert-butyl-2,2-dimethylpropanol III (20.0 g),
1
external (11B), C6F6 internal (19F), 5% solutions for H, 19F, 20%
for 11B, 13C, 29Si. MS: Finnigan MAT 8230. Elemental analyses
(C/H/N) were carried out at the analytical laboratory of the
Institut fu¨r Anorganische Chemie, Universita¨t Go¨ttingen; to
allow a distinction between different phenyl groups, the 1H
and 13C positions of the substituents have been numbered in
the following way: 1-6 refer to the oxygen-bonded phenyl
group, starting with the carbon atom attached to oxygen. 7-12
(22) Anwander, R.; Herrmann, W. A.; Kleine, M.; Scherer, W. Chem.
Ber. 1992, 125, 1971.
(23) Allen, C. F. H.; Lindsay, R. O. Org. Synth. Collect. Vol. 1955,
3, 710.

5088 Organometallics, Vol. 19, No. 24, 2000
Steuber et al.
Ta ble 1. Selected Bon d Len gth s (Å) a n d An gles (d eg) for 18, 22, a n d 26
Compound 18
O(1)-B(1)
1.365(2)
1.399(2)
N(1)-B(1)
1.465(2)
1.948(3)
83.71(12)
N(1A)-B(1)
1.454(2)
N(1)-C(1)
1.475(2)
O(1)-C(11)
B(1)-B(1A)
N(1A)-B(1)-N(1) 96.29(12)
B(1A)-N(1)-B(1)
N(1)-B(1)-O(1)
124.37(14) N(1A)-B(1)-O(1)
139.33(14)
B(1)-O(1)-C(11)
126.33(12) O(1)-C(11)-C(12) 118.33(13) O(1)-C(11)-C(16) 117.92(13) C(16)-C(11)-C(12) 123.61(13)
O(1)-B(1)-B(1A) 172.3(2)
Compound 22
B(1)-N(1)
1.481(2)
1.351(2)
1.465(2)
94.30(13)
137.24(14) C(10)-N(2)-B(1)
140.8(2)
N(1)-B(2)
1.459(2)
B(2)-N(2)
1.474(2)
1.360(2)
1.994(3)
85.82(12)
133.57(14) O(1)-B(1)-N(1)
125.25(15) B(1)-O(1)-C(1)
101.82(12) O(1)-C(1)-C(4)
N(2)-B(1)
O(2)-C(5)
1.455(2)
1.462(2)
B(1)-O(1)
O(1)-C(1)
1.459(2)
1.461(2)
85.42(12)
140.12(14) C(10)-N(2)-B(2)
140.4(2)
B(2)-O(2)
N(1)-C(9)
N(2)-C(10)
B(1)-N(1)-B(2)
B(1)-B(2)
B(1)-N(2)-B(2)
N(1)-B(2)-N(2)
C(9)-N(1)-B(2)
O(1)-B(1)-N(2)
B(2)-O(2)-C(5)
O(1)-B(1)-B(2)
C(9)-N(1)-B(1)
129.90(14)
124.99(15)
146.24(13)
108.28(12)
O(2)-B(2)-N(1)
O(2)-B(2)-N(2)
142.92(13) O(1)-C(1)-C(2)
170.82(14) O(2)-B(2)-B(1)
105.87(12) O(1)-C(1)-C(3)
170.76(14)
Compound 26
B(1)-N(1)
1.416(4)
1.515(4)
114.3(2)
124.3(2)
171.5(3)
B(1)-O(1)
1.376(4)
1.802(3)
125.1(3)
115.1(2)
B(1)-N(2)
1.475(4)
1.220(4)
120.6(2)
120.6(2)
O(1)-C(11)
1.401(3)
1.129(4)
121.3(2)
128.9(3)
N(1)-C(4)
N(1)-Si(1)
N(2)-N(3)
N(3)-N(4)
N(1)-B(1)-N(2)
B(1)-N(1)-C(4)
N(2)-N(3)-N(4)
N(1)-B(1)-O(1)
B(1)-N(1)-Si(1)
N(2)-B(1)-O(1)
Si(1)-N(1)-C(4)
B(1)-O(1)-C(11)
B(1)-N(2)-N(3)
Ta ble 2. Cr ysta llogr a p h ic Da ta for th e Com p ou n d s 18, 22, a n d 26
18
22
26
empirical formula
fw
C
36H60B2N2O2
C32H68B2N2O2
534.50
C21H39BN4OSi
402.46
574.48
temperature (K)
wavelength (Å)
cryst syst
space group
a (Å)
153(2)
203(2)
0.71073
203(2)
0.71073
monoclinic
P21/n
9.040(2)
11.653(2)
16.955(4)
90
99.42(2)
90
1762.0(6)
2
0.71073
monoclinic
P21/c
12.651(6)
11.653(4)
16.858(13)
90
91.11(4)
90
2485(2)
4
monoclinic
P21/c
11.2304(9)
25.997(6)
11.456(2)
90
97.171(11)
90
3318.5(9)
4
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
densitycalcd (Mg m-3
)
1.083
0.065
1.070
0.064
1.076
0.112
abs coeff (mm-1
)
F(000)
632
1200
880
cryst size (mm3)
θ range (deg)
0.70 × 0.60 × 0.40
3.52-25.12
-10 e h e 10
-13 e k e 13
-20 e l e 20
5734
0.80 × 0.70 × 0.40
3.59-25.02
-13 e h e 13
-14 e k e 30
-13 e l e 13
9601
0.90 × 0.80 × 0.80
3.67-25.06
-15 e h e 15
-13 e k e 13
-19 e l e 20
11 136
limiting indices
no. of reflns collected
no of ind reflns
3138
5834
4375
Rint
0.0372
0.0309
0.0715
refinement method
no. of data/restraints/params
goodness-of-fit on F2
final R indices [I>2σ(I)]
full-matrix-least squares on F2
5818/0/365
1.056
3133/0/199
1.037
4369/0/265
1.105
R1)0.0459
wR2)0.1094
R1)0.0622
wR2)0.1236
212/-210
R1)0.0500
wR2)0.1232
R1)0.0644
wR2)0.1420
269/-184
R1)0.0679
wR2)0.1878
R1)0.0761
wR2)0.2089
463/-296
R indices (all data)
largest diff peak/hole [e nm-3
]
respectively, was solved in 100 mL of hexane. An equimolar
amount of butyllithium was added to this solution, which was
then refluxed for 3 h. A solution of 0.1 mol of boron trifluoride
diethyl etherate (14.2 g) in 100 mL of diethyl ether was added
dropwise. The reaction mixture was stirred for another 2 h.
The solvent was removed at reduced pressure, and the residue
was separated from the lithium fluoride by sublimation in
vacuo. The crude product was purified by a second sublimation
in vacuo.
Bis(2,6-d i-ter t-bu tylp h en oxy)(flu or o)bor a n e (5): color-
less solid, sublp 90 °C (bath temperature)/0.01 Torr, mp 151
°C. Yield: 16.7 g (76%, reaction ratio taken into account). Anal.
Calcd for C28H42BFO2 (440.45 g/mol): C, 76.34; H, 9.71.
Found: C, 76.10; H, 9.71. MS (EI, 70 eV): m/e (rel intensity)
440 (45) [M+], 425 (10) [M+ - Me], 219 (100) [M+ - tBu2PhO,
-Me, -H]. 1H NMR (CDCl3, 25 °C): δ 7.27 (AB2, 4H, 3/5), 7.02
(AB2, 2H, 4), 1.45 (s, 36H, CMe3). 13C NMR (CDCl3, 25 °C): δ
3
149.6 (d, 1, J CF ) 2.5 Hz), 141.3 (2/6), 126.2 (3/5), 123.2 (4),
6
35.8 (CMe3), 32.1 (d, CMe3, J CF ) 1.3 Hz). 11B NMR (CDCl3,
25 °C): δ 14.0. 19F NMR (CDCl3, 25 °C): δ 55.4.
Bis(1,1-d i-ter t-b u t yl-2,2-d im et h ylp r op oxy)(flu or o)b o-
r a n e (6): colorless solid, sublp 130 °C (bath temperature)/0.01
Torr, mp 206 °C. Yield: 10.1 g (47%, reaction ratio taken into
account). Anal. Calcd for C26H54BFO2 (428.52 g/mol): C, 72.88;
H, 12.70. Found: C, 72.67; H, 12.80. MS (EI, 70 eV): m/e (rel
intensity) 371 (5) [M+ - CMe3], 57 (100) [CMe3+]. 1H NMR
(CDCl3, 25 °C): δ 1.34 (s, 54H, CMe3). 13C NMR (CDCl3, 25
3
°C): δ 93.7 (d, CCMe3, J CF ) 1.2 Hz), 45.8 (CCMe3), 32.9
(CCMe3). 11B NMR (CDCl3, 25 °C): δ 11.5. 19F NMR (CDCl3,
25 °C): δ 66.1.
P r ep a r a tion of th e Am in o(h a lo)(or ga n yloxy)bor a n es
7 a n d 9-16. A 0.1 mol sample of the relevant amine (7, 12,

First B-Organyloxy-Substituted Iminoboranes
Organometallics, Vol. 19, No. 24, 2000 5089
13, 16: 7.3 g of tert-butylamine; 9, 14: 17.7 g of 2,6-
diisopropylaniline; 10: 13.5 g of 2,4,6-trimethylaniline; 11:
26.1 g of 2,4,6-tri-tert-butylaniline; 15: 5.9 g of isopropylamine)
was solved in 100 mL of hexane. An equimolar amount of
butyllithium was added to these solutions, which were then
refluxed for 3 h. After cooling to -78 °C a solution of 0.1 mol
of the relevant dihalogeno-oxyborane (7, 9-11: 28.7 g of 1;
12: 32.7 g of 2; 13, 14: 25.4 g of 3; 15, 16: 24.8 g of 4) in 100
mL hexane was added dropwise. The reaction mixture was
stirred for another 2 h at low temperature and then allowed
to warm. The solvent was removed at reduced pressure and
the residue separated from the lithium halide by distillation
(7, 10, 12, 13, 15, 16) or sublimation (9, 11) in vacuo. This
process was then repeated to purify the crude product. 10 and
14 crystallized after the distillation.
147.4 (10), 141.4 (2/6), 134.3 (7), 126.1 (3/5), 123.1 (9/11), 122.9
(4), 37.2 (8/12CMe3), 35.9 (2/6CMe3), 34.7 (10CMe3), 32.9 (2/
6CMe3 or 8/12CMe3), 32.4 (2/6CMe3 or 8/12CMe3), 31.4 (10CMe3).
11B NMR (CDCl3, 25 °C): δ 25.6.
(ter t-Bu t yla m in o)(ch lor o)(2,6-d ip h en ylp h en oxy)b o-
r a n e (12): colorless liquid, bp 200 °C (bath temperature)/0.01
Torr. Yield: 23.4 g (64%). Anal. Calcd for C22H23BClNO (363.69
g/mol): C, 72.66; H, 6.37; N, 3.84. Found: C, 72.52; H, 6.21;
N, 3.97. MS (EI, 70 eV): m/e (rel intensity) 363 (5) [M+], 348
(15) [M+ - Me], 246 (100) [(C6H5)2C6H3OH+]. 1H NMR (CDCl3,
25 °C): δ 7.2-7.6 (m, 13H, 3-5 and 8-12), 3.12 (br, 1H, NH),
1.05 (s, 9H, CMe3). 13C NMR (CDCl3, 25 °C): δ 148.7 (1), 138.5
(2/6 or 7), 134.8 (2/6 or 7), 130.0 (3/5 or 10), 129.7 (8/12 or 9/11),
128.0 (8/12 or 9/11), 127.0 (3/5 or 10), 123.8 (4), 49.6 (CMe3),
31.3 (CMe3). 11B NMR (CDCl3, 25 °C): δ 23.5.
(ter t-Bu t yla m in o)(2,6-d i-ter t-b u t ylp h en oxy)(ch lor o)-
bor a n e (7): colorless liquid, bp 110 °C/0.01 Torr. Yield: 18.4
g (57%). Anal. Calcd for C18H31BClNO (323.78 g/mol): C, 66.77;
H, 9.67; N, 4.33. Found: C, 66.67; H, 9.75; N, 4.03. MS (EI,
70 eV): m/e (rel intensity) 323 (10) [M+], 308 (15) [M+ - Me],
57 (100) [CMe3+]. There are two isomers of the compound at
room temperature due to the inhibited rotation around the
B-N bond (ratio 7a /7b ca. 5:4); the rotational barrier is
(ter t-Bu tyla m in o)(2,6-d i-ter t-bu tylp h en oxy)(flu or o)bo-
r a n e (13): colorless liquid, bp 80 °C/0.01 Torr. Yield: 16.2 g
(53%). Anal. Calcd for C18H31BFNO (307.26 g/mol): C, 70.35;
H, 10.19. Found: C, 70.40; H, 9.96. MS (EI, 70 eV): m/e (rel
intensity) 307 (10) [M+], 292 (25) [M+ - Me], 57 (100) [CMe3+].
1H NMR (CDCl3, 25 °C): δ 7.32 (AB2, 2H, 3/5), 7.05 (AB2, 1H,
3
4), 2.64 (d, 1H, NH, J HF ) 17.8 Hz), 1.48 (s, 18H, CCMe3),
1.29 (s, 9H, NCMe3). 13C NMR (CDCl3, 25 °C): δ 150.9 (d, 1,
3J CF ) 5.0 Hz), 141.3 (2/6), 125.7 (3/5), 122.8 (4), 48.3 (d,
1
eliminated at 80 °C. H NMR (C6D6, 25 °C): δ 7.2 (AB2, 2H,
3/5/7a and 7b), 6.9 (AB2, 1H, 4/7a and 7b), 3.24 (br, 1H, NH/
7a ), 3.04 (br, 1H, NH/7b), 1.48 (s, 18H, CCMe3/7a ), 1.46 (s,
18H, CCMe3/7b), 1.20 (s, 9H, NCMe3/7a ), 1.08 (s, 9H, NCMe3/
7b); (C6D6, 80 °C) δ 7.2 (AB2, 2H, 3/5), 6.9 (AB2, 1H, 4), 3.0-
3.2 (br, 1H, NH), 1.45 (s, 18H, CCMe3), 1.16 (br, 9H, NCMe3).
13C NMR (C6D6, 25 °C): δ 153.9 (1/7a ), 151.7 (1/7b), 141.4 (2/
6/7b), 140.9 (2/6/7a ), 126.5 (3/5/7b), 126.1 (3/5/7a ), 123.6 (4/
7b), 123.5 (4/7a ), 50.4 (NCMe3/7a ), 49.2 (NCMe3/7b), 35.7
(CCMe3/7a ), 35.6 (CCMe3/7b), 32.3 (NCMe3/7a ), 31.9 (CCMe3/
7b), 31.8 (CCMe3/7a ), 31.6 (NCMe3/7b). 11B NMR (C6D6, 25
°C): δ 25.1.
3
4
NCMe3, J CF ) 2.4 Hz), 35.2 (CCMe3), 31.9 (d, NCMe3, J CF
)
2.4 Hz), 31.3 (CCMe3). 11B NMR (CDCl3, 25 °C): δ 18.9. 19F
NMR (CDCl3, 25 °C): δ 37.7.
(2,6-Di-ter t-bu tylp h en oxy)(flu or o)(2,6-d iisop r op ylp h e-
n yla m in o)bor a n e (14): colorless solid, bp 160 °C/0.01 Torr,
mp 89 °C. Yield: 34.2 g (83%). Anal. Calcd for C26H39BFNO
(411.41 g/mol): C, 75.89; H, 9.57. Found: C, 76.50; H, 9.84.
MS (EI, 70 eV): m/e (rel intensity) 411 (100) [M+]. 1H NMR
(CDCl3, 25 °C): δ 7.28 (AB2, 2H, 3/5), 7.1 (AB2, 3H, 9-11),
3
7.02 (AB2, 1H, 4), 4.30 (d, 1H, NH, J HF ) 15.4 Hz), 3.50 (sep,
2H, CHMe2, 3J HH ) 6.9 Hz), 1.47 (s, 18H, CMe3), 1.20 (d, 12H,
(2,6-Di-ter t-bu tylp h en oxy)(ch lor o)(2,6-d iisop r op ylp h e-
n yla m in o)bor a n e (9): colorless solid, sublp 175 °C (bath
temperature)/0.01 Torr, mp 114 °C. Yield: 25.2 g (59%). Anal.
Calcd for C26H39BClNO (427.86 g/mol): C, 72.99; H, 9.19; N,
3.27. Found: C, 72.42; H, 9.35; N, 3.40. MS (EI, 70 eV): m/e
(rel intensity) 427 (50) [M+], 57 (100) [CMe3+]. 1H NMR (CDCl3,
25 °C): δ 7.28 (AB2, 2H, 3/5), 7.2 (AB2, 3H, 9-11), 7.02 (AB2,
3
CHMe2, J HH ) 6.9 Hz). 13C NMR (CDCl3, 25 °C): δ 150.6 (d,
1, 3J CF ) 3.7 Hz), 145.0 (8/12), 141.2 (2/6), 133.4 (7), 126.1 (10),
125.8 (3/5), 123.3 (9/11), 123.2 (4), 35.2 (CMe3), 31.3 (CMe3),
28.1 (CHMe2), 23.8 (CHMe2). 11B NMR (CDCl3, 25 °C): δ 18.3.
19F NMR (CDCl3, 25 °C): δ 37.6.
(1,1-Di-ter t-bu tyl-2,2-d im eth ylp r op oxy)(flu or o)(isop r o-
p yla m in o)bor a n e (15): colorless liquid, bp 71 °C/0.01 Torr.
Yield: 16.6 g (58%). Anal. Calcd for C16H35BFNO (287.27
g/mol): C, 66.90; H, 12.28; N, 4.88. Found: C, 67.56; H, 12.18;
3
1H, 4), 4.89 (br, 1H, NH), 3.53 (sep, 2H, CHMe2, J HH ) 6.9
Hz), 1.49 (s, 18H, CMe3), 1.20 (d, 12H, CHMe2, 3J HH ) 6.9 Hz).
13C NMR (CDCl3, 25 °C): δ 151.9 (1), 146.2 (8/12), 141.0 (2/6),
134.0 (7), 127.0 (10), 126.0 (3/5), 123.3 (9/11), 123.2 (4), 35.5
(CMe3), 31.8 (CMe3), 28.2 (CHMe2), 23.7 (CHMe2). 11B NMR
(CDCl3, 25 °C): δ 26.1.
N, 4.92. MS (EI, 70 eV): m/e (rel intensity) 230 (10) [M+
-
CMe3], 174 (70) [M+ - CMe3, -H2CdMe2], 57 (100) [CMe3+].
1H NMR (CDCl3, 25 °C): δ 3.5 (br, 1H, CHMe2), 3.3 (br, 1H,
CHMe2), 2.1 (br, 1H, NH), 1.31 (br, 27H, CMe3), 1.06 (d, 6H,
(2,6-Di-ter t-bu tylp h en oxy)(ch lor o)(2,4,6-tr im eth ylp h e-
n yla m in o)bor a n e (10): colorless solid, bp 190 °C (bath
temperature)/0.01 Torr, mp 113 °C. Yield: 30.7 g (80%). Anal.
Calcd for C23H33BClNO (385.78 g/mol): C, 71.61; H, 8.62; N,
3.63. Found: C, 71.59; H, 8.64; N, 3.62. MS (EI, 70 eV): m/e
(rel intensity) 385 (55) [M+], 57 (100) [CMe3+]. 1H NMR (CDCl3,
25 °C): δ 7.3 (AB2, 2H, 3/5), 7.0-7.1 (AB2, 1H, 4), 6.91 (s, 2H,
9/11), 4.85 (s, 1H, NH), 2.31 (s, 6H, 8/12), 2.28 (s, 3H, 10), 1.50
(s, 18H, CMe3). 13C NMR (CDCl3, 25 °C): δ 151.8 (1), 141.0
(2/6), 135.3 (10), 135.0 (8/12), 134.7 (7), 129.0 (9/11), 125.9 (3/
5), 123.1 (4), 35.5 (CMe3), 31.8 (CMe3), 20.8 (C10Me), 19.4 (C8/
12Me). 11B NMR (CDCl3, 25 °C): δ 25.8.
(2,4,6-Tr i-ter t-bu tylp h en yla m in o)(2,6-d i-ter t-bu tylp h e-
n oxy)(ch lor o)bor a n e (11): yellow solid, sublp 190 °C (bath
temperature)/0.01 Torr, mp 168 °C. Yield: 22.6 g (44%). Anal.
Calcd for C32H51BClNO (512.02 g/mol): C, 75.07; H, 10.04; N,
2.74. Found: C, 74.32; H, 9.85; N, 2.72. MS (EI, 70 eV): m/e
(rel intensity) 510 (60) [C32H5111B35ClNO+-H], 191 (100)
[tBu3C6H3NH2+-Me]; (FI): 511 (100) [C32H5111B35ClNO; M+].
1H NMR (CDCl3, 25 °C): δ 7.38 (s, 2H, 9/11), 7.27 (AB2, 2H,
3/5), 7.00 (AB2, 1H, 4), 5.09 (br, 1H, NH), 1.54 (s, 18H, 2/6CMe3
or 8/12CMe3), 1.50 (s, 18H, 2/6CMe3 or 8/12CMe3), 1.31 (s, 9H,
10CMe3). 13C NMR (CDCl3, 25 °C): δ 151.8 (1), 147.9 (8/12),
3
CHMe2, J HH ) 6.9 Hz); at 60 °C only one peak for CHMe2:
3.4 (br, 2H). 13C NMR (CDCl3, 25 °C): δ 94.2 (CCMe3), 93.6
(CCMe3), 45.8 (CHMe2), 41.5 (br, CCMe3), 32.9 (br, CCMe3),
26.4 (CHMe2); at 60 °C only one peak for CCMe3: 94 (br). 11B
NMR (CDCl3, 25 °C): δ 17.1. 19F NMR (CDCl3, 25 °C): δ 42.6,
44.5; (CDCl3, 60 °C) δ 43.8.
(ter t-Bu t yla m in o)(1,1-d i-ter t-b u t yl-2,2-d im et h ylp r o-
p oxy)(flu or o)bor a n e (16): colorless liquid, bp 68 °C/0.01
Torr. Yield: 21.6 g (72%). Anal. Calcd for C17H37BFNO (301.29
g/mol): C, 67.77; H, 12.38; N, 4.65. Found: C, 67.75; H, 12.32;
N, 5.41. MS (EI, 70 eV): m/e (rel intensity) 244 (2) [M+ -CMe3],
188 (10) [M+ - CMe3, -H2CdCMe2], 57 (100) [CMe3+]. 1H
NMR (CDCl3, 25 °C): δ 2.43 (d, 1H, NH, 3J HF ) 18.0 Hz), 1.29
(s, 27H, CCMe3), 1.19 (d, 9H, NCMe3, 5J HF ) 1.0 Hz). 13C NMR
3
(CDCl3, 25 °C): δ 93.6 (CCMe3), 47.3 (d, NCMe3, J CF ) 2.6
4
Hz), 45.8 (CCMe3), 32.9 (CCMe3), 32.2 (d, NCMe3, J CF ) 2.6
Hz). 11B NMR (CDCl3, 25 °C): δ 17.2. 19F NMR (CDCl3, 25
°C): δ 50.5.
P r ep a r a tion of th e Am in o(ch lor o)(p h en oxy)bor a n e 8.
A 0.1 mol sample of the dichloroborane 1 was mixed at room
temperature with 0.1 mol of 1,1,1,3,3,3-hexamethyldisilazane
(16.1 g) without a solvent. The mixture was refluxed for 2 h.

5090 Organometallics, Vol. 19, No. 24, 2000
Steuber et al.
The chlorosilane formed was removed at reduced pressure, and
the residue was twice distilled in vacuo.
6.98 (AB2, 2H, 4), 1.41 (s, 36H, CMe3), -0.28 (s, 18H, SiMe3).
13C NMR (CDCl3, 25 °C): δ 152.7 (1), 141.3 (2/6), 125.7 (3/5),
123.2 (4), 35.5 (CMe3), 31.2 (CMe3), 1.5 (SiMe3). 11B NMR
(CDCl3, 25 °C): δ 26.3. 29Si NMR (CDCl3, 25 °C): δ -4.0.
(2,6-Di-t er t -b u t ylp h e n oxy)(ch lor o)(t r im e t h ylsilyl-
a m in o)bor a n e (8): colorless liquid, bp 80 °C/0.01 Torr.
Yield: 23.2 g (68%). Anal. Calcd for C17H31BClNOSi (339.79
g/mol): C, 60.09; H, 9.20; N, 4.12. Found: C, 60.55; H, 9.00;
N, 4.65. MS (EI, 70 eV): m/e (rel intensity) 339 (60) [M+], 324
(10) [M+ - Me], 236 (100) [M+ - Me, -NHSiMe3]. 1H NMR
(CDCl3, 25 °C): δ 7.26 (AB2, 2H, 3/5), 7.02 (AB2, 1H, 4), 2.6
(br, 1H, NH), 1.41 (s, 18H, CMe3), 0.20 (s, 9H, SiMe3). 13C NMR
(CDCl3, 25 °C): δ 151.7 (1), 141.1 (2/6), 126.0 (3/5), 123.2 (4),
35.4 (CMe3), 31.6 (CMe3), 1.0 (SiMe3). 11B NMR (CDCl3, 25
°C): δ 27.2. 29Si NMR (CDCl3, 25 °C): δ 7.3.
P r ep a r a tion of th e Am in o(flu or o)(a lk oxy)bor a n e 17.
A 0.1 mol sample of 1,1,1,3,3,3-hexamethyldisilazane (16.1 g,
without a solvent) was added at room temperature to a freshly
prepared solution of 0.1 mol of the difluoroborane 4 in diethyl
ether. The mixture was stirred for 6 h at 25 °C, after which
the ether and the fluorosilane formed were removed at reduced
pressure. The residue was twice distilled in vacuo.
2,4-Bis(2,6-d i-ter t-bu tylp h en oxy)-1,3-bis(2,6-d iisop r o-
p ylp h en yl)-1,3-d ia za -2,4-d ibor etid in e (20): colorless solid,
sublp 250 °C/0.01 Torr, mp 255 °C. Yield: 5.4 g (14%). Anal.
Calcd for C52H76B2N202 (782.80 g/mol): C, 79.79; H, 9.79; N,
3.58. Found: C, 79.19; H, 9.63; N, 3.58. MS (EI, 70 eV): m/e
(rel intensity) 782 (100) [M+], 726 (20) [M+ - CMe3], 57 (100)
[CMe3+]. 1H NMR (CDCl3, 25 °C): δ 7.13 (AB2, 4H, 3/5), 7.0
(AB2, 6H, 9-11), 6.86 (AB2, 2H, 4), 3.25 (sep, 4H, CHMe2, 3J HH
3
) 6.7 Hz), 1.17 (d, 12H, CHMe2, J HH ) 6.7 Hz), 1.16 (s, 36H,
CMe3), 0.65 (d, 12H, CHMe2, 3J HH ) 6.7 Hz). 13C NMR (CDCl3,
25 °C): δ 149.8 (1), 143.9 (8/12), 140.3 (2/6), 135.7 (7), 127.8
(3/5), 124.3 (10), 124.2 (9/11), 123.1 (4), 36.1 (CMe3), 32.1
(CMe3), 28.0 (CHMe2), 25.6 (CHMe2), 24.2 (CHMe2). 11B NMR
(CDCl3, 25 °C): δ 25.0.
2,4-Bis(2,6-d i-ter t-bu tylp h en oxy)-1,3-bis(2,4,6-tr im eth -
ylp h en yl)-1,3-d ia za -2,4-d ibor etid in e (21): colorless solid,
sublp 240 °C/0.01 Torr, mp 200 °C. Yield: 18.5 g (53%). Anal.
Calcd for C46H64B2N2O2 (698.64 g/mol): C, 79.08; H, 9.23; N,
4.01. Found: C, 79.24; H, 9.27; N, 4.07. MS (EI, 70 eV): m/e
(rel intensity) 698.5 (100) [M+], 641.4 (10) [M+ - CMe3]. 1H
NMR (CDCl3, 25 °C): δ 7.1 (AB2, 4H, 3/5), 6.9 (AB2, 2H, 4),
6.62 (s, 4H, 9/11), 2.16 (s, 6H, 10), 1.88 (s, 12H, 8/12), 1.13 (s,
36H, CMe3). 13C NMR (CDCl3, 25 °C): δ 150.4 (1), 141.1 (2/6),
135.5 (10), 133.4 (8/12), 132.4 (7), 128.4 (9/11), 126.0 (3/5), 122.8
(4), 35.6 (CMe3), 31.5 (CMe3), 20.6 (C10Me), 19.4 (C8/12Me).
11B NMR (CDCl3, 25 °C): δ 25.6.
(1,1-Di-ter t-b u t yl-2,2-d im et h ylp r op oxy)(flu or o)(t r im -
eth ylsilyla m in o)bor a n e (17): colorless liquid, bp 75 °C/0.01
Torr. Yield: 12.8 g (40%). Anal. Calcd for C16H37BFNOSi
(317.37 g/mol): C, 60.55; H, 11.75; N, 4.41. Found: C, 60.97;
H, 12.01; N, 4.72. MS (EI, 70 eV): m/e (rel intensity) 260 (10)
[M+ - CMe3], 204 (65) [M+ - CMe3, -H2CdCMe2], 57 (100)
[CMe3+]; (CI, isobutene) 318 (M+ + 1). 1H NMR (CDCl3, 25
°C): δ 1.8 (br, 1H, NH), 1.29 (s, 27H, CMe3), 0.10 (d, 9H, SiMe3,
5J HF ) 0.9 Hz). 13C NMR (CDCl3, 25 °C): δ 94.0 (d, CCMe3,
4
3J CF ) 1.2 Hz), 45.7 (d, CCMe3, J CF ) 0.3 Hz), 32.8 (CCMe3),
1.0 (d, SiMe3, 4J CF ) 1.3 Hz). 11B NMR (CDCl3, 25 °C): δ 18.0.
19F NMR (CDCl3, 25 °C): δ 54.5. 29Si NMR (CDCl3, 25 °C): δ
4.6.
2,4-Bis(1,1-d i-ter t-b u t yl-2,2-d im et h ylp r op oxy)-1,3-d i-
isop r op yl-1,3-d ia za -2,4-d ibor etid in e (22): colorless solid,
mp 158 °C (decomp). Yield: 6.0 g (22%). Anal. Calcd for
P r ep a r a tion of th e Dia za d ibor etid in es 18-23. A 0.1
mol sample of tert-butyllithium (66.7 mL) was added dropwise
to a solution of 0.1 mol of the relevant amino(halo)(organyloxy)-
borane (18: 32.3 g of 7 or 30.7 g of 13; 19: 34.0 g of 8; 20:
42.8 g of 9 or 41.1 g of 14; 21: 38.6 g of 10; 22: 28.7 g of 15;
23: 31.7 g of 17) in 100 mL of hexane at -78 °C. The reaction
mixtures were allowed to warm to room temperature, and
stirring was continued until the temperature reached 0 °C.
When 13 or 14 was used as the starting material, the reaction
mixture was then refluxed for 2 h. The procedure then varied
for the different compounds. 18: After 24 h a layer of colorless
crystals formed on top of the lithium halide. With a sufficiently
large-pored filter the crystals could be separated from the
powdery salt. They were washed twice with hexane, and the
remaining solvent was removed in vacuo. 19-21: The solvent
was removed at reduced pressure, and the residue was
separated from the lithium halide by sublimation in vacuo.
The crude product was purified by a second sublimation. 22,
23: The lithium fluoride was filtered off from the reaction
solution, and the solvent was then removed in vacuo. The
residue was recrystallized from hexane (22) or toluene (23).
1,3-Di-ter t-bu tyl-2,4-bis(2,6-d i-ter t-bu tylp h en oxy)-1,3-
d ia za -2,4-d ibor etid in e (18): colorless solid, mp 290 °C.
Yield: 17.8 g (62%). Anal. Calcd for C36H60B2N2O2 (574.63
g/mol): C, 75.24; H, 10.52; N, 4.88. Found: C, 74.47; H, 10.64;
N, 5.00. MS (EI, 70 eV): m/e (rel intensity) 574 (5) [M+], 559
(100) [M+ - Me]. 1H NMR (CDCl3, 25 °C): δ 7.20 (AB2, 4H,
3/5), 6.93 (AB2, 2H, 4), 1.45 (s, 36H, CCMe3), 0.85 (s, 18H,
NCMe3). 13C NMR (CDCl3, 25 °C): δ 154.2 (1), 140.8 (2/6),
125.4 (3/5), 122.5 (4), 48.7 (NCMe3), 35.6 (CCMe3), 32.6
(NCMe3), 31.2 (CCMe3). 11B NMR (CDCl3, 25 °C): δ 25.0.
1,3-Bis(tr im eth ylsilyl)-2,4-bis(2,6-di-ter t-bu tylph en oxy)-
1,3-d ia za -2,4-d ibor etid in e (19): colorless solid, sublp 190 °C/
0.01 Torr, mp 276 °C. Yield: 7.0 g (23%). Anal. Calcd for
C34H60B2N2O2Si2 (606.65 g/mol): C, 67.32; H, 9.97; N, 4.62.
Found: C, 66.84; H, 9.43; N, 5.16. MS (EI, 70 eV): m/e (rel
C
32H68B2N2O2 (534.52 g/mol): C, 71.91; H, 12.82; N, 5.24.
Found: C, 71.23; H, 12.20; N, 4.74. MS (EI, 70 eV): m/e (rel
intensity) 534 (1) [M+], 421 (10) [M+ - CMe3, -Me2CdCH2],
405 (15) [M+ - 2CMe3, -Me], 57 (100) [CMe3+]; (FI) 534 (30)
[M+], 478 (100) [M+ - Me2CdCH2], 421 (20) [M+ - CMe3,
-Me2CdCH2]. 1H NMR (CDCl3, 25 °C): δ 3.69 (sep, 2H,
3
CHMe2, J HH ) 6.9 Hz), 1.39 (s, 54H, CMe3), 1.14 (d, 12H,
CHMe2, J HH ) 6.9 Hz). 13C NMR (CDCl3, 25 °C): δ 97.7
3
(CCMe3), 45.8(CCMe3), 41.2 (CHMe2), 33.4 (CCMe3), 24.4
(CHMe2). 11B NMR (CDCl3, 25 °C): δ 24.2.
2,4-Bis(1,1-d i-ter t-bu tyl-2,2-d im eth ylp r op oxy)-1,3-bis-
(tr im eth ylsilyl)-1,3-d ia za -2,4-d ibor etid in e (23): colorless
solid, mp 130 °C (decomp). Yield: 26.5 g (90%). Anal. Calcd
for C32H72B2N2O2Si2 (594.72 g/mol): C, 64.63; H, 12.20; N, 4.71.
Found: C, 63.78; H, 11.29; N, 5.94. MS (EI, 70 eV): m/e (rel
intensity) 537 (10) [M+ - CMe3], 57 (100) [CMe3+]; (FI) 594
(100) [M+]. 1H NMR (CDCl3, 25 °C): δ 1.37 (s, 54H, CMe3),
0.15 (s, 18H, SiMe3). 13C NMR (CDCl3, 25 °C): δ 101.4
(CCMe3), 46.3 (CCMe3), 33.8 (CCMe3), 3.4 (SiMe3). 11B NMR
(CDCl3, 25 °C): δ 25.4. 29Si NMR (CDCl3, 25 °C): δ -7.6.
P r ep a r a tion of th e Dia za d ibor etid in e 24. See 22; in-
stead of recrystallization the residue was purified by sublima-
tion in vacuo. The isobutene formed is collected in a cold trap
with 1 mL of CDCl3. The 13C NMR spectrum of this solution
displays two peaks (δ 111, 142 ppm) assigned to the sp2-
hybridized carbon atoms of isobutene.
2,4-Bis(1-ter t-bu tyl-2,2-d im eth ylp r op oxy)-1,3-bis(tr im -
eth ylsilyl)-1,3-d ia za -2,4-d ibor etid in e (24): colorless solid,
sublp 160 °C/0.01 Torr, mp 135 °C. Yield: 8.7 g (36%). Anal.
Calcd for C24H56B2N2O2Si2 (482.51 g/mol): C, 59.74; H, 11.70;
N, 5.81. Found: C, 59.51; H, 11.26; N, 5.78. MS (EI, 70 eV):
m/e (rel intensity) 482 (3) [M+], 425 (10) [M+ - CMe3], 57 (100)
[CMe3+]; (FI) 482 (100) [M+]. H NMR (CDCl3, 25 °C): δ 3.63
1
(s, 2H, OCH), 1.02 (s, 36H, CMe3), 0.14 (s, 18H, SiMe3). 13C
NMR (CDCl3, 25 °C): δ 87.3 (CCMe3), 37.6 (CCMe3), 28.9
(CCMe3), 3.1 (SiMe3). 11B NMR (CDCl3, 25 °C): δ 25.6. 29Si
NMR (CDCl3, 25 °C): δ -5.8.
intensity) 606 (1) [M+], 591 (1) [M+ - Me], 401 (100) [M+
tBu2C6H3O]. 1H NMR (CDCl3, 25 °C): δ 7.24 (AB2, 4H, 3/5),
-

First B-Organyloxy-Substituted Iminoboranes
Organometallics, Vol. 19, No. 24, 2000 5091
P r ep a r a tion of th e Dibor yla m in e 25. A solution of 0.05
mol of 7 (16.2 g) in 50 mL of hexane was cooled to -78 °C; to
this solution was added first 0.1 mol of triethylborane (100
mL) and then 0.05 mol of tert-butyllithium (33.3 mL). The
mixture was then allowed to warm to room temperature while
stirring was continued. The solvent was removed at reduced
pressure, and the residue was separated from the lithium
chloride by distillation in vacuo. The crude product was
purified by a second distillation.
(SiMe3). 11B NMR (CDCl3, 25 °C): δ 21.7. 29Si NMR (CDCl3,
25 °C): δ 7.6. IR (in KBr): νas (N3) 2139 cm-1
.
X-r a y St r u ct u r e Det er m in a t ion s for 18, 22, a n d 26.
Data were collected on a Stoe-Siemens diffractometer with
monochromated Mo KR radiation (λ ) 71.03 pm). The tem-
peratures of the measurements are listed in Table 2. The
structures were solved by direct methods using SHELXS-90.24
All non-hydrogen atoms were refined anisotropically. For the
hydrogen atoms the riding model was used. The structures
were refined against F2 with a weighting scheme of w-1 ) σ2-
ter t-Bu tyl[2,6-d i-ter t-bu tylp h en oxy(eth yl)bor yl](d ieth -
ylbor yl)a m in e (25): yellow liquid, bp 160 °C/0.01 Torr.
Yield: 10.4 g (54%). Anal. Calcd for C24H45B2NO (385.25
g/mol): C, 74.83; H, 11.77; N, 3.64. Found: C, 74.55; H, 11.53;
N, 3.60. MS (EI, 70 eV): m/e (rel intensity) 385 (2) [M+], 370
(Fo2) + (g1P)2 + g2P, with P ) (Fo + 2Fc2)/3 using SHELXL-
2
93.25 The R values are defined as R1 ) ∑||Fo| - |Fc||/∑|Fo| and
wR2 ) [∑w(Fo2 - Fc )2/∑wFo 0.5. Figures 1-3 (hydrogen atoms
]
2
4
omitted) show 50% probability displacement ellipsoids. Crystal
data and structure refinement details are listed in Table 2.
1
(5) [M+ - Me], 356 (15) [M+ - Et], 57 (100) [CMe3+]. H NMR
(CDCl3, 25 °C): δ 7.2 (AB2, 2H, 3/5), 6.9 (AB2, 1H, 4), 1.48 (s,
3
9H, NCMe3), 1.41 (s, 18H, CCMe3), 1.22 (q, 6H, CH2, J HH
Su m m a r y
3
) 7.5 Hz), 0.98 (t, 9H, CH2CH3, J HH ) 7.4 Hz). 13C NMR
(CDCl3, 25 °C): δ 155.3 (1), 140.9 (2/6), 125.2 (3/5), 121.4 (4),
52.1 (NCMe3), 35.8 (CCMe3), 32.6 (NCMe3), 31.7 (CCMe3),
22.2 (B(CH2CH3)2), 11.8 (BCH2CH3), 9.6 (BCH2CH3), 9.0
(B(CH2CH3)2). 11B NMR (CDCl3, 25 °C): δ 74.1 (NBC2), 30.1
(OB(N)C).
P r ep a r a tion of th e Azid obor a n e 26. A solution of 0.05
mol of 7 (16.2 g) in 50 mL of hexane was cooled to -78 °C; to
this solution was added first 0.075 mol of trimethylsilyl azide
(8.6 g) and then 0.055 mol of tert-butyllithium (36.7 mL). The
mixture was then allowed to warm to room temperature while
stirring was continued. The solvent was removed at reduced
pressure, and the residue was separated from the lithium
chloride by sublimation in vacuo. The crude product was
purified by a second sublimation.
The first B-2,6-disubstituted aryloxy(imino)boranes
were detected as intermediates in the dehydrohaloge-
nation of the corresponding amino(aryloxy)chlorobo-
ranes by 11B NMR and addition reactions across the
B≡N triple bond. The as yet undescribed B-organyloxy-
substituted diazadiboretidines are the stable, final
products formed by the dimerization of the organyloxy-
(imino)boranes.
Ack n ow led gm en t. We thank the Fonds der Che-
mischen Industrie, Germany, for financial support.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data, complete fractional coordinates and U values, bond
lengths and angles, and anisotropic displacement parameters,
and fully labeled figures of 50% anisotropic displacement
parameters of the structures 18, 22, and 26. This material is
available free of charge via the Internet at http://pubs.acs.org.
Azid o(2,6-d i-ter t-bu tylp h en oxy)[ter t-bu tyl(tr im eth yl-
silyl)a m in o]bor a n e (26): colorless solid, sublp 90 °C (bath
temperature)/0.01 Torr, mp 93 °C. Yield: 12.7 g (63%). Anal.
Calcd for C21H39BN4OSi (402.46 g/mol): C, 62.67; H, 9.77; N,
13.92. Found: C, 62.82; H, 9.54; N, 13.67. MS (EI, 70 eV): m/e
(rel intensity) 402 (1) [M+], 387 (10) [M+ - Me], 359 (10) [M+
- Me, -N2], 303 (100) [M+ - CMe3, -N3]. 1H NMR (CDCl3,
25 °C): δ 7.23 (AB2, 2H, 3/5), 7.04 (AB2, 1H, 4), 1.52 (s, 9H,
NCMe3), 1.43 (s, 18H, CCMe3), 0.30 (s, 9H, SiMe3). 13C NMR
(CDCl3, 25 °C): δ 152.3 (1), 142.0 (2/6), 125.9 (3/5), 123.8 (4),
54.5 (NCMe3), 35.5 (CCMe3), 34.1 (NCMe3), 31.4 (CCMe3), 6.6
OM0005912
(24) Sheldrick, G. M. Acta Crystallogr. Sect. A 1990, 46, 467.
(25) Sheldrick, G. M. SHELXL-93, program for crystal structure
refinement; University of Go¨ttingen, 1993.