Carbon monoxide and isonitrile insertion into the B-B bond of five-membered cyclic organo-1,2-diboranes

Article abstract of DOI:10.1002/(SICI)1099-0682(199804)1998:4<459::AID-EJIC459>3.0.CO;2-U

The insertion of CO into the B-B bond of 1,2-bis(diisopropylamino)-2,5-dihydro-1H-1,2-diborole (1b) and 1,2-bis(diisopropylamino)-3-methylidene-1,2-diborolane (1c) leads to the dimeric spiro products 1,7,9,14-tetrakis(diisopropylamino)-6,13-dioxa-1,7,9,14-tetraboradispiro[4.2.4. 2]tetradeca-2,10-diene (4b) and 1,7,9,14-tetrakis(diisopropylamino)bismethylidene-6,13-dioxa-1,7,9,14- tetraboradispiro[4.2.4.2]tetradecane (4c). Insertions of CO into the B-B bonds of the cyclic organo-1,2-diborane compounds 5, 6, and 7 are not observed. The reaction of 1b with tert-butyl isocyanide and 2,6-dimethylphenyl isocyanide in THF leads to the formation of the monomeric insertion products 1,3-bis(diisopropylamino)-2-tert-butylimino-1,3-diboracyclohex-4-ene (10b) and 1,3-bis-(diisopropylamino)-2-(2′,6′-dimethylphenylimino)-1,3- diboracyclohex-4-ene (11b). The treatment of 1c with the isonitriles yields 2-tert-butylimino-1,3-bis(diisopropylamino)-4-methylidene-1,3-diboracyclohexane (10c) and 1,3-bis(diisopropylamino)-2-(2′,6′-dimethylphenylimino)-4- methylidene-1,3-diboracyclohexane (11c). The steric requirements of the isonitrile insertion products 10b, c and 11b, c prevent their dimerisation and rearrangement, 11b rearranges to 1-(diisopropylamino)-2-(diisopropylaminohydroxyboryl)-2-(2′,6′- dimethylphenylamino)-1-boracyclopent-3-ene (12b) upon reaction with water from sodium sulfate decahydrate. The compositions of the compounds are derived from the ¹H-, ¹¹B-, ¹³C-NMR data as well as from mass-spectral and C, H, N analyses. In the cases of of 4b and 12b they have been proven by X-ray structure analyses.

Full text of DOI:10.1002/(SICI)1099-0682(199804)1998:4<459::AID-EJIC459>3.0.CO;2-U

FULL PAPER
Carbon Monoxide and Isonitrile Insertion into the B؊B Bond of
Five-Membered Cyclic Organo-1,2-diboranesȠ
Jens Teichmann, Harald Stock, Hans Pritzkow, and Walter Siebert*
Anorganisch-Chemisches Institut der Universität Heidelberg,
Im Neuenheimer Feld 270, D-69120 Heidelberg, Germany
Received October 22, 1997
Keywords: 1,2-Diboraheterocycles / Carbon monoxide insertion / Isonitrile insertion / Dimerisation /
Spiro insertion products
The insertion of CO into the BϪB bond of 1,2-bis(diisopropyl-
amino)-2,5-dihydro-1H-1,2-diborole (1b) and 1,2-bis(diiso-
boracyclohex-4-ene (11b). The treatment of 1c with the isoni-
triles yields 2-tert-butylimino-1,3-bis(diisopropylamino)-4-
propylamino)-3-methylidene-1,2-diborolane (1c) leads to the methylidene-1,3-diboracyclohexane (10c) and 1,3-bis(diiso-
dimeric spiro products 1,7,9,14-tetrakis(diisopropylamino)- propylamino)-2-(2Ј,6Ј-dimethylphenylimino)-4-methylidene-
6,13-dioxa-1,7,9,14-tetraboradispiro[4.2.4.2]tetradeca-2,10- 1,3-diboracyclohexane (11c). The steric requirements of the
diene (4b) and 1,7,9,14-tetrakis(diisopropylamino)bismeth-
ylidene-6,13-dioxa-1,7,9,14-tetraboradispiro[4.2.4.2]tetra-
decane (4c). Insertions of CO into the BϪB bonds of the cyclic
organo-1,2-diborane compounds 5, 6, and 7 are not observed.
The reaction of 1b with tert-butyl isocyanide and 2,6-dime-
thylphenyl isocyanide in THF leads to the formation of the
monomeric insertion products 1,3-bis(diisopropylamino)-2-
tert-butylimino-1,3-diboracyclohex-4-ene (10b) and 1,3-bis-
(diisopropylamino)-2-(2Ј,6Ј-dimethylphenylimino)-1,3-di-
isonitrile insertion products 10b, c and 11b, c prevent their
dimerisation and rearrangement. 11b rearranges to 1-(diiso-
propylamino)-2-(diisopropylaminohydroxyboryl)-2-(2Ј,6Ј-
dimethylphenylamino)-1-boracyclopent-3-ene (12b) upon re-
action with water from sodium sulfate decahydrate. The com-
positions of the compounds are derived from the 1H-, 11B-,
13C-NMR data as well as from mass-spectral and C, H, N
analyses. In the cases of of 4b and 12b they have been proven
by X-ray structure analyses.
The synthesis and structural characterization of the η4- Scheme 1
(4-boryl-1-borabutadiene)-η5-cyclopentadienylcobalt com-
plexes 2a[1] from the 4-methylene-1,2-diborolane 1a,[2] as
well as 2b[3] from the 1H-1,2-diborole 1b[3] and bis(ethene)-
cyclopentadienylcobalt, led to the expectation that related
compounds should be formed with other 14 VE complex
fragments. However, 1b and either Fe(CO)5 or Fe2(CO)9 did
not yield the corresponding η4-(4-boryl-1-borabutadiene)-
tricarbonyliron complex 3b. A few colorless crystals could
be separated from the reaction mixture and mass-spectro-
metric data indicated the presence of a dimer of a reaction
product of carbon monoxide and 1b. Its constitution was
elucidated by an X-ray structure analysis (see below) which
showed the presence of the dimeric spiro compound 4b.[4]
Reactions of CO with organoboranes are long since
known and are well documented.[5] The insertion of CO
into the BϪB bond of three-membered heterocycles was
first observed by Paetzold et al.[6] Tri-tert-butylazadiboriri-
rings NB2CϭNR. With R ϭ Me, Et the primary products
dine [NB2(CMe3)3] and CO yield the tricyclic compound
1,3,4,5,7,8-hexa-tert-butyl-4,9-dioxa-1,7-diaza-2,5,8,10-te-
traboradispiro[2.2.2.2]decane. The proposed mechanism de-
scribes, in the first step, the insertion of CO into the BϪB
bond to give a four-membered NB2CϭO ring, which then
undergoes a [3ϩ3] cyclodimerisation of the BCϭO chain
to yield the corresponding six-membered ring. Sigmatropic
migrations of the amino groups from the boron to the car-
bon atoms result in the final product.
undergo a [3ϩ3] cyclodimerisation of the BCϭN chain to
result in the tricyclic compounds.[7]
In the following we report on our findings concerning
CO and CϭNR insertion into the BϪB bond of five-mem-
bered cyclic organodiboranes.
Results and Discussion
Reactions of Cyclic Organo-1,2-diboranes with Carbon Monoxide
The compound 4b[4] is formed in a good yield when dried
Analogously, isonitriles (RNC) insert into the BϪB bond
of NB2(CMe3)3 to form the corresponding four-membered CO is bubbled into a THF solution of 1b.[3] Due to its weak
Eur. J. Inorg. Chem. 1998, 459Ϫ463
WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1998
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459

J. Teichmann, H. Stock, H. Pritzkow, W. Siebert
Reactions of Organo-1,2-diboranes with Isonitriles
FULL PAPER
solubility 4b precipitates as a solid which is less sensitive to
air and moisture. The reaction between the 3-methylidene-
1,2-diborolane 1c[1] and CO leads to the analogous dimeric
spiro product 1,7,9,14-tetrakis(diisopropylamino)bismethyl-
idene-6,13-dioxa-1,7,9,14-tetraboradispiro[4.2.4.2]tetra-
decane (4c).[4] We assume that, besides 4c, two other iso-
mers have been formed due to various positions of the ex-
ocyclic double bonds. Mass-spectral data and C, H, N
analyses were obtained, but no NMR data could be ob-
tained due to its very low solubility in organic solvents. The
mass spectra of the reaction product of 1c and Fe(CO)5
indicate that the η4-(1-boryl-2-methyl-1-borabutadiene)-
The failure of CO to insert into the BϪB bond of the
compounds 5؊7 is also observed with the isonitriles. The
reaction of the 1,2-diborole 1b with tert-butyl isocyanide
and with 2,6-dimethylphenyl isocyanide at Ϫ30°C in THF
leads to colorless, slightly soluble monomeric products, 2-
tert-butylimino-1,3-diboracyclohex-4-ene (10b) and 2-(2Ј,6Ј-di-
methylphenylimino)-1,3-diboracyclohex-4-ene (11b). As a si-
deproduct in the reaction with 1b its rearrangement to the
known
1,3-bis(diisopropylamino)-2,3-dihydro-1,3-dibor-
1
ole[12][13] was observed. MS and H-, 11B-, and 13C-NMR
data confirmed the composition of the products formed.
tricarbonyliron complex (analogous to 3b) was present[4]
however, it could not be isolated. The reaction of 1a with
,
Scheme 4
Fe(CO)5 also led to traces of the analogous complex.
Scheme 2
In the 1H-NMR spectra all four septuplets of the methine
protons of the isopropyl groups of 10b have different chemi-
cal shifts, whereas the compound 11b shows only one mul-
tiplet and one septuplet for the four groups. This result indi-
cates a rigid structure at room temperature.[10] There is a
high double-bond character between the boron and nitro-
gen atoms.
Because of the quadrupole effect of the boron atoms the
signals of the protons at the vicinal carbon atoms have very
low intensities. The methylene protons can be detected near
δ ϭ 2.2 as a doublet, and the methine protons of the double
bond in the ring are not detected. The signal for the proton
in 4-position is observed at δ ϭ 6.30, and that for the 5-
position at δ ϭ 6.85. In 11b the signal of the proton in the
5-position cannot be observed, because the signals of the
aromatic substituent appear between δ ϭ 6.8 and 7.1.
The reaction between the 3-methylidene-1,2-diborolane
1c and the two isonitriles leads to the 2-tert-butylimino-4-
methylidene-1,3-diboracyclohexane 10c and the 2-(2Ј,6Ј-di-
methylphenylimino)-4-methylidene-1,3-diboracyclohexane
11c.[10]
In addition to 1a؊c, the cyclic organo-1,2-diborane com-
pounds 1,2-bis(diisopropylamino)-1,2-diboret (5)[8], 1,2-
bis(diisopropylamino)-1,2-benzodiboret (6)[9], and 1,2,4-
tris(diisopropylamino)-3,5-dimethyl-1,2,4-triboracyclo-
pentan (7)[10] were treated with dried CO. None of the ex-
pected insertion products were formed and the starting ma-
terials were recovered.
Scheme 3
Scheme 5
It is of interest to note that we did not observe any inser-
tion into the BϪC bonds of the compounds 1a؊c. This is
in contrast to the reaction of CO with the 1,3,4,5-tetraethyl-
2-methyl-2,3-dihydro-1,3-diborole (8), which leads to prod-
uct 9a and 9b.[11] The formation of 9b can be explained by
insertion of CO into the BϪCHMe bond of 8, and ex-
The 11B-NMR shifts of 10c and 11c are δ ϭ 38 and 39,
change of the CHMe group for the oxygen of the inserted which are within the expected region.[14] The 1H-NMR data
CO. The product 9a is formed analogously by insertion of of 11c are comparable to those of 11b. The products are
CO into the BϪCEt bond and exchange of the CHMe soluble only in THF.
group for the oxygen of the inserted CO, which yields the
The steric demand of the five-membered rings 1b and 1c,
BϪOϪB bridge. When 8 is treated with Ni(CO)4,[11] pre- and that of the alkyl substituents of the isonitriles both pre-
sumably 9a is the precursor for the formation of a nickel vent dimerization and rearrangement of the corresponding
complex with two cyclic allyl ligands.
insertion products 10b, c and 11b, c. To induce a rearrange-
460
Eur. J. Inorg. Chem. 1998, 459Ϫ463

Insertion into the BϪB Bond of Five-Membered Cyclic Organo-1,2-diboranes
FULL PAPER
Crystal Structures of 4b and 12b
ment a small dipolar reagent such as water is needed.
Therefore, 10b and sodium sulfate decahydrate were heated
in THF to yield the hydrolysis product 12, which was
characterized by an X-ray structure analysis. 12 can be de-
scribed as one half of a spiro dimer, formed by ring contrac-
tion. The five-membered ring in 12 contains the terminal
carbon atom of the isonitrile and only one boron atom.
The centrosymmetric molecule in 4b is built up by the
central planar 6-membered ring (max. deviation ±0.01 A)
and, almost perpendicular (88.5°) to it, by the outer BC4
rings, which are slightly puckered (±0.05 A). The BϪN
˚
˚
units are planar indicating π interaction. The lengths of the
BϪC and BϪN distances differ, which can be rationalized
in terms of the other atoms connected to the boron atoms.
The BϪN distance at B2, bonded to C1 and C4, is slightly
shorter than that at B1, which is bonded to O1 and C1Ј.
The BϪC distance involving an sp2 carbon atom (B2ϪC4)
is significantly shorter than those with sp3 carbon atoms.
In 12b the same 5-membered ring is present, but instead of
the 6-membered ring two independent groups are attached
to C1, one of which [B(NiPr2)O] is similar to that part of
Scheme 6
The formation of the dimeric insertion and rearrange-
ment products 4a, b, the insertion compounds 10b, c and
11b, c and the product of hydrolysis 12, give evidence for
the reaction path of insertion and rearrangement to the di-
meric molecules. As proposed, the first step is an insertion
of carbon monoxide or isonitrile into the BϪB bond of the
boron heterocycles.[6] The formed products are stable, if the
steric requirements of the isonitriles or the heterocycles are
suitable as in the isonitrile insertion products 10b, c and
11b, c. Rearrangement under ring contraction is the follow-
ing step. This is supported by using water as a dipolar re-
agent to induce rearrangement with formation of 12. In the
case of CO insertion the dimeric spiro compounds 4b, c are
formed. The proposed reaction paths are in agreement with
the mechanistic conclusions of Paetzold et al.[6][7]
Figure 1. Molecular structure of 4b[a]
Scheme 7
[a]
˚
Selected bond lengths [A] and angles [°]: C1ϪB1Ј 1.592(2),
C1ϪO1 1.481(2), C1ϪC2 1.557(2), C1ϪB2 1.624(2),O1ϪB1
1.368(2), B1ϪN1 1.422(2), B2ϪN2 1.397(2), B2ϪC2 1.569(2);
C2ϪC1ϪB2 103.1(1), B1ЈϪC1ϪO1 112.5(1), C1ϪB2ϪC4 105.1(2),
C1ϪB1ЈϪO1Ј 121.2(1), C1ϪO1ϪB1 126.3(1).
Figure 2. Molecular structure of 12b[a]
[a]
˚
Selected bond lengths [A] and angles [°]: C1ϪB1 1.617(2)
C1ϪN3 1.548(2), C1ϪC2 1.556(2), C1ϪB2 1.6 29(2), O1ϪB1
1.376(2), B1ϪN1 1.416(2), B2ϪN2 1.402(2), B2ϪC2 1.562(2);
C2ϪB1ϪB2 102.4(1), B1ϪC1ϪN3 106.0(1), C1ϪB2ϪC4 105.7(1),
C1ϪB1ϪO1 115.9(1).
Eur. J. Inorg. Chem. 1998, 459Ϫ463
461

J. Teichmann, H. Stock, H. Pritzkow, W. Siebert
FULL PAPER
[CH(CH3)2], 28 (100) [CO; C2H4]. Ϫ C34H68O2B4N4 (608.2) calcd.
C 67.15, H 11.27, N 9.21; found C 66.80, H 11.23, N 9.18.
the ring in 4b, while the other [HN(C6H3Me2)] substitutes
for the oxygen in 4b. The distances exhibit the same range
of values as found in 4b and the angles are almost identical,
2-tert-Butylimino-1,3-bis(diisopropylamino)-1,3-diboracyclohex-
apart from those around C1. The 5-membered ring is 4-ene (10b): 415 mg (5 mmol) of tert-butyl isocyanide, dissolved in
20 ml of THF, was added to a solution of 1.30 g (5 mmol) of 1b
in 30 ml of THF at Ϫ30°C. After 15 h at room temp., the solvent
was removed under vacuum. Distillation yielded 600 mg (2.3 mmol,
planar, in contrast to 4b where the steric repulsion of the
diisopropylamino group at B1 pushes the 5-membered ring
towards O1 and causes the distortion of the ring which
adopts a slight envelope form. In 12b this is not possible,
as the dimethylphenyl group at N3 does not allow a tipping
of the ring, which remains planar and lies symmetrically
between the two groups. The angles at C1 in 4b also show
the effect of the distortion. A rotation around the bond
C1ϪN3 would suspend the steric repulsion of the dimeth-
ylphenyl group, but the hydrogen atom at O1 forms an in-
tramolecular hydrogen bond with N3, hindering the ro-
tation around C1ϪN3.
1
46%) of colorless 10b, b.p. 63°C/5·10Ϫ2 Torr. Ϫ H NMR (C6D6,
200 MHz): δ ϭ 0.9Ϫ1.4 [br., 24 H, CH(CH3)2], 1.43 [s, 9 H,
C(CH3)3], 2.21 (d, 2 H, BCH2), 2.95 (m, 1 H, NCH), 3.18 (m, 1 H,
NCH), 3.53 (m, 1 H, NCH), 4.81 (m, 1 H, NCH), 6.25 (d, br., 1
H, BCH), 6.85 (m, br., 1 H, CH2CHCH). Ϫ 11B NMR (C6D6, 64
MHz): δ ϭ 40 (sh), 45.
1,3-Bis(diisopropylamino)-2-(2Ј,6Ј-dimethylphenylimino)-1,3-
diboracyclohex-4-ene (11b): A preparation analogous to 10b, using
660 mg (5 mmol) of 2,6-dimethylphenyl isocyanide and 1.3 g (5
mmol) of 1b, resulted in 900 mg (3.5 mmol, 69%) of colorless 11b,
b.p. 80 °C/5·10Ϫ2 Torr. Ϫ 1H NMR (C6D6, 200 MHz): δ ϭ 0.8Ϫ1.4
[m, 24 H, CH(CH3)2], 2.11 (s, 6 H, H3CAr), 2.21 (d, 2 H,
CHCHCH2), 3.15 [m, 3 H, CH(CH3)2], 4.5 [sept, 1 H, CH(CH3)2],
6.25 (d, 1 H, BCHCH), 6.9 (m, 1 H, CHCHCH2), 6.95 (m, 3 H,
C6H3). Ϫ 11B NMR (C6D6, 64 MHz): δ ϭ 40. Ϫ MS (EI), m/z (%):
394 (36) [Mϩ ϩ 1], 378 [Mϩ Ϫ CH3], 43 (100) [CH(CH3)2].
Support of this work by the Deutsche Forschungsgemeinschaft
(SFB 247), the Fonds der Chemischen Industrie, and the BASF AG
is gratefully acknowledged.
Experimental Section
All reactions and manipulations were performed in dry glassware
under nitrogen by using standard Schlenk techniques. Solvents
were distilled from appropriate drying agents under nitrogen before
use. The commercial carbon monoxide was bubbled through KOH
for drying. Ϫ Et2O·BF3 was used as the external standard for 11B
NMR. Internal standards for 1H and 13C were the signals of the
deuterium-labeled solvents. NMR: CDCl3 and C6D6 solutions,
Jeol-FX-90 and Bruker AC 200. Ϫ MS: Varian MAT CH7 and
Finnigan Mat 8230. Ϫ The following starting materials were pre-
pared by previously described methods: 1,2-bis(diisopropylamino)-
2-tert-Butylimino-1,3-bis(diisopropylamino)-4-methylidene-1,3-
diboracyclohexane (10c): 1.4 g (5 mmol) of 1c was treated with 415
mg (5 mmol) of tert-butyl isocyanide under the same reaction con-
ditions as in the previous experiments to yield 300 mg (0.8 mmol,
16%) of 10c, b.p. 75°C/5·10Ϫ2 Torr. Ϫ 11B NMR (C6D6, 64 MHz)):
δ ϭ 39. Ϫ MS (EI), m/z (%): 360 (87) [Mϩ ϩ 1], 57 (100) [C4H9],
43 (89) [C3H7].
1,3-Bis(diisopropylamino)-2-(2Ј,6Ј-dimethylphenylimino)-4-
methylidene-1,3-diboracyclohexane (11c): The preparation anal-
ogous to 10b using 1.4 g (5 mmol) of 1c and 660 mg (5 mmol) of
2,6-dimethylphenyl isocyanide yielded 800 mg (1.8 mmol, 36%) of
2,5-dihydro-1H-1,2-diborole (1b)[3]
, 1,2-bis(diisopropylamino)-3-
methylidene-1,2-diborolane (1c)[3], 1,2-bis(diisopropylamino)-1,2-
1
11c, b.p. 105°C/5·10Ϫ2 Torr. Ϫ H NMR (C6D6, 200 MHz): δ ϭ
benzodiboret (6)[9]
,
1,2,4-tris(diisopropylamino)-3,5-dimethyl-
1,2,4-triboracyclopentane (7).[10]
0.93 [m, 6 H, CH(CH3)2], 1.2 (m, 2 H, CH2CH2C), 1.45 [m, 18 H,
CH(CH3)2], 2.16 (s, 6 H, H3CAr), 2.75(m, 2 H, BCH2CH2), 3.3 [m,
3 H, CH(CH3)2], 3.95 [m, 1 H, CH(CH3)2], 5.2 (m, 1 H, CϭCH2),
7.00 (m, 1 H, CϭCH2), 7.06 (m, 3 H, C6H3). Ϫ 11B NMR (C6D6,
64 MHz): δ ϭ 38.
1,7,9,14-Tetrakis(diisopropylamino)-6,13-dioxa-1,7,9,14-tetra-
boradispiro[4.2.4.2]tetradeca-2,10-diene (4b): CO was bubbled
through a solution of 950 mg (3.6 mmol) of 1b in 40 ml of THF
at room temp. for 1 h. After 15 min, a colorless solid was formed.
Filtration of the mixture and washing of the residue with THF and
hexane yielded 520 mg (0.9 mmol, 50%) of 4b, m.p. 282°C. The
remaining 1b in the filtrate can be used for further reactions. Ϫ 1H
NMR (CDCl3, 200 MHz): δ ϭ 0.86, 0.88, 0.89, 1.12, 1.15, 1.27 (m,
1-(Diisopropylamino)-2-(diisopropylaminohydroxyboryl)-2-
(2Ј,6Ј-dimethylphenylamino)-1-boracyclopent-3-ene (12): 390 mg (1
mmol) of 11c and 33 mg (0.1 mmol) of Na2SO4·· 10 H2O, dissolved
in 50 ml of THF, were refluxed for 2 h. The hot solution was fil-
tered through a G3 sintered-glass funnel. Crystallisation from a
THF solution at 5°C gave 220 mg (0.5 mmol, 50%) of 12, m.p.
60°C. Ϫ 11B NMR (C6D6, 64 MHz): δ ϭ 38.
3
48 H), 2.75, 2.94, 3.25, 3.75 (sept, 8 H), 7.05 (d, 2 H, JH,H ϭ 7.95
3
3
Hz), 6.19 (d, 2 H, JH,H ϭ 7.95 Hz), 2.33 (d, 2 H, JH,H ϭ 19.0
3
Hz), 2.70 (d, 2 H, JH,H ϭ 19.5 Hz). Ϫ 11B NMR (CDCl3, 29
MHz): δ ϭ 44 (C2BN), 32 (CB(N)O). Ϫ 13C NMR (CDCl3, 50
MHz): δ ϭ 23.0, 23.3, 23.6, 24.9, 25.5, 26.0, 26.4 (CHCH3), 44.6,
45.3, 47.6, 49.3 (NCH), 32.5 (CCH2C), 159.3 (CCHC), (CB not
Crystal-Structure Determinations of 4b and 12b: Crystal data and
details of the structure determinations are listed in Table 1. Unique
sets of intensity data were collected at Ϫ70°C with a four-circle
detected). Ϫ MS (EI), m/z (%): 580 (100) [Mϩ], 453 (85) [Mϩ
Ϫ
˚
diffractometer (Mo-Kα radiation λ ϭ 0.7107 A, graphite mono-
BON(CH(CH3)2)2], 289 (45) [Mϩ/2 Ϫ H], 43 (74) [CH(CH3)2]. Ϫ
C32H64O2B4N4 (580.1) calcd. C 66.25, H 11.12, N 9.66; found C
65.70, H 11.12, N 9.65.
chromator, ω scan). An empirical absorption correction (ψ scans)
was applied. The structures were solved by direct methods
[SHELXS86][15] and refined by least-squares methods based on F2
with all measured reflections [SHELXL97].[16] All non-hydrogen
atoms were refined anisotropically. Hydrogen atoms were included
in calculated positions (CH in 4b), or as part of the rigid group
(CH3 in 4b and 12b). All other hydrogen atoms were located in
difference Fourier maps and refined.
1,7,9,14-Tetrakis(diisopropylamino)bismethylidene-6,13-dioxa-
1,7,9,14-tetraboradispiro [4.2.4.2]tetradecane (4c): 700 mg (2.54
mmol) of 1c were treated with CO as in the previous experiment.
The workup furnished 440 mg (0.72 mmol, 44%) of the colorless
solid 4c, m.p. 289°C (decomp.). The product was almost insoluble
in all organic solvents. Ϫ MS (EI), m/z (%): 608 (45) [Mϩ], 303 (27)
[Mϩ/2 Ϫ H], 481 (36) [Mϩ Ϫ BON(CH(CH3)2)2], 43 (73)
Crystallographic data (excluding structure factors) for the struc-
tures reported in this paper have been deposited with the Cam-
462
Eur. J. Inorg. Chem. 1998, 459Ϫ463

Insertion into the BϪB Bond of Five-Membered Cyclic Organo-1,2-diboranes
FULL PAPER
CB2 1EZ, UK [fax: (internat.)
deposit@ccdc.cam.ac.uk].
ϩ
44(1223)336-003; e-mail:
Table 1. Crystal data and structure refinement for 4b and 12b
4b
12b
Ƞ Dedicated to Professor Hartmut Bärnighausen on the occasion
Empirical formula
Formula weight
Crystal system
C32H64B4NO2
580.11
C24H43B2N3O
411.23
of his 65th birthday.
[1]
G. Gabbert, W. Weinmann, H. Pritzkow, W. Siebert, Angew.
Chem. 1992, 104, 1670; Angew. Chem. Int. Ed. Engl. 1992, 31,
1603.
G. E. Herberich, C.Ganter, L. Wesemann, R. Boese, Angew.
Chem. 1990, 102, 914; Angew. Chem. Int. Ed. Engl. 1990, 29,
912.
G. Gabbert, H. Pritzkow, M. Kaschke, W. Siebert, Chem. Ber.
1994, 127, 1363.
J. Teichmann, Diploma Thesis, Universität Heidelberg, 1995.
A. Pelter, K. Smith, H. C. Brown, Borane Reagents, Academic
Press, London, 1988, 239.
P. Paetzold, B. Redenz-Stormanns, R. Boese, Angew. Chem.
1990, 102, 910; Angew. Chem. Int. Ed. Engl. 1990, 29, 900.
S. Luckert, E. Eversheim, M. Müller, B. Redenz-Stormanns, K.
Englert, P. Paetzold, Chem. Ber. 1995, 128, 1029Ϫ1035.
M. Hildenbrand, H. Pritzkow, W. Siebert, Angew. Chem. 1985,
97, 769; Angew. Chem. Int. Ed. Engl. 1985, 24, 759; M. Hilden-
brand, H. Pritzkow, U. Zenneck, W. Siebert, Angew. Chem.
1984, 96, 371; Angew. Chem. Int. Ed. Engl. 1984, 23, 371.
D. E. Kaufmann, R. Boese, A. Scheer, Chem. Ber. 1994, 127,
2349.
H. Stock, Ph. D. Dissertation, Universität Heidelberg, 1997.
J. Edwin, W. Siebert, C. Krüger, J. Organomet. Chem. 1981,
215, 255Ϫ262.
W. Weinmann, Ph. D. Dissertation, Universität Heidelberg,
1994.
G. Gabbert, Ph. D. Dissertation, Universität Heidelberg, 1993.
H. Nöth, B. Wrackmeyer, Nuclear Magnetic Resonance Spec-
troscopy of Boron Compounds, Springer-Verlag, Berlin, Heidel-
berg, New York, 1978.
monoclinic
P21/c
monoclinic
P21/c
Space group
[2]
[3]
Unit-cell dimensions
˚
a [A]
11.027(6)
10.288(5)
16.804(8)
108.27(2)
1810.2(16)
2
8.147(5)
18.337(13)
17.479(11)
100.80(5)
2565(3)
˚
b [A]
˚
c [A]
β [°]
Volume [A3]
˚
[4]
[5]
Z
4
Calcd. density [g/cm3] 1.064
1.065
Absorp. coeff. [mmϪ1
F(000)
]
0.064
640
0.064
[6]
[7]
[8]
904
Crystal size [mm]
θ range
0.5 ϫ 0.5 ϫ 0.3
1.9Ϫ25.0
0.7 ϫ 0.6 ϫ 0.6
1.6 - 27.0
Ϫ10/10, 0/23, 0/22
Index ranges
No. of reflections
unique
Ϫ13/12, 0/12, 0/19
3180
2355
0.94Ϫ0.99
217
5600
4232
observed [I > 2σ(I)]
Transmission
Parameters
[9]
0.95Ϫ0.99
337
Goodness-of-fit on F2 1.006
Final R indices
1.006
[10]
[11]
R1 [I > 2σ(I)]
wR2 (all data)
0.041
0.103
0.042
[12]
0.108
Largest diff. peak/hole 0.23/Ϫ0.14
0.27/Ϫ0.14
[e AϪ3
]
˚
[13]
[14]
bridge Crystallographic Data Centre as supplementary publication
no. CCDC-100715. Copies of the data can be obtained free
of charge on application to CCDC, 12 Union Road, Cambridge
[15]
[16]
G. M. Sheldrick, SHELXS86, Univ. Göttingen, 1986.
G. M. Sheldrick, SHELXL97, Univ. Göttingen, 1997.
[97242]
Eur. J. Inorg. Chem. 1998, 459Ϫ463
463