Novel [2 + 2] cycloaddition reactions of (dimethylamino)bis(trifluoromethyl)borane, (CF3)2BNMe2, with N-sulfinylsulfonamides, aminoiminophosphines, carbodiimides, and a keteneimine

Article abstract of DOI:10.1021/om970262i

(Dimethylamino)bis(trifluoromethyl)borane, (CF₃)₂BNMe₂ (1), combines with NT-sulfinyl-sulfonamides R-O₂S-N=S=O in a [2 + 2] fashion to form (CF₃)₂B-NMe₂-S(O)-N-SO₂R (R = Me (2a), Et (2b), iPr (2c), Ph (2d), and pTol (2e)). Aminoiminophosphines RN=P-NR₂′ react with 1 analogously to yield the heterocycles (CF₃)₂B-NMe₂-P(NR₂′)-NR (R = SiMe₃, NR₂′ = N(SiMe₃)₂ (3a), TMP (3b); R = tBu, NR₂′ = N(SiMe₃)tBu (3c), NiPr₂ (3d), TMP (3e)). Carbodiimides R-N=C=N-R add to the B=N bond of 1 to give unstable adducts (CF₃)₂B-NMe₂-C(NR)-NR which rearrange at 20 °C to yield the four-membered heterocycles (CF₃)₂B-NR-C(NMe₂)-NR (R = iPr (5a), cC₆H₁₁ (5b)). For carbodiimides with aryl substituents R = pXC₆H₄, this rearrangement competes with an internal electrophilic aromatic substitution reaction and mixtures of the two isomers (CF₃)₂B-NC₆H₄X-C(NMe ₂)-NC₆H₄X (X = H (5c), Me (5d), OMe (5e)) and (CF₃)₂B-CCHCXCHCHC-NH-C(NMe₂)-N-(C ₆H₄X) (X = H (6c), Me (6d), OMe (6e)) are obtained. Ph-N=C=CMe₂ combines with 1 to form the four-membered ring (CF₃)₂B-CMe₂-C(NMe₂)-NPh (8). F₃C-CH₂-N=S=O undergoes an ene-type reaction with 1 by which the dimethylamine borane (F₃C-HC=N-S-(=O))(CF₃)₂B-NHMe₂ (9) is formed. The constitution of the novel boron compounds has been deduced from multinuclear NMR, IR, and mass spectra. The structures of 2a, 3c, 5c, 6d, 6e, and 8 have been investigated by single-crystal X-ray diffraction.

Full text of DOI:10.1021/om970262i

Organometallics 1997, 16, 5321-5330
5321
Novel [2 + 2] Cycloa d d ition Rea ction s of
(Dim eth yla m in o)bis(tr iflu or om eth yl)bor a n e,
(CF 3)2BNMe2, w ith N-Su lfin ylsu lfon a m id es,
Am in oim in op h osp h in es, Ca r bod iim id es, a n d a
Keten eim in e†
David J . Brauer, Silke Buchheim-Spiegel, Hans Bu¨rger,* Ralf Gielen,
Gottfried Pawelke, and J u¨rgen Rothe
Anorganische Chemie, FB 9, Universita¨t-GH, 42097 Wuppertal, Germany
Received March 27, 1997X
(Dimethylamino)bis(trifluoromethyl)borane, (CF3)2BNMe2 (1), combines with N-sulfinyl-
sulfonamides RsO2SsNdSdO in a [2 + 2] fashion to form (CF3)2B-NMe2-S(O)-N-SO2R
(R ) Me (2a ), Et (2b), iPr (2c), Ph (2d ), and pTol (2e)). Aminoiminophosphines RNdPsNR2′
react with 1 analogously to yield the heterocycles (CF3)2B-NMe2-P(NR2′)-NR (R ) SiMe3,
NR2′ ) N(SiMe3)2 (3a ), TMP (3b); R ) tBu, NR2′ ) N(SiMe3)tBu (3c), NiPr2 (3d ), TMP (3e)).
Carbodiimides RsNdCdNsR add to the BdN bond of 1 to give unstable adducts (CF3)2B-
NMe2-C(NR)-NR which rearrange at 20 °C to yield the four-membered heterocycles
(CF3)2B-NR-C(NMe2)-NR (R ) iPr (5a ), cC6H11 (5b)). For carbodiimides with aryl
substituents R ) pXC6H4, this rearrangement competes with an internal electrophilic
aromatic substitution reaction and mixtures of the two isomers (CF3)2B-NC6H4X-C(NMe2)-
NC6H4X (X ) H (5c), Me (5d ), OMe (5e)) and (CF3)2B-CCHCXCHCHC-NH-C(NMe2)-N-
(C6H4X) (X ) H (6c), Me (6d ), OMe (6e)) are obtained. PhsNdCdCMe2 combines with 1 to
form the four-membered ring (CF3)2B-CMe2-C(NMe2)-NPh (8). F3C-CH2-NdSdO
undergoes an ene-type reaction with 1 by which the dimethylamine borane (F3CsHCdNsS-
(dO))(CF3)2B‚NHMe2 (9) is formed. The constitution of the novel boron compounds has been
deduced from multinuclear NMR, IR, and mass spectra. The structures of 2a , 3c, 5c, 6d ,
6e, and 8 have been investigated by single-crystal X-ray diffraction.
In tr od u ction
The remarkable reactivity of the BdN linkage in
(dimethylamino)bis(trifluoromethyl)borane, (CF3)2BNMe2
(1), is exemplified by the facile cycloaddition reactions
which it undergoes with a variety of substrates to form
novel heterocyclic ring systems.1 Of particular interest
are the [2 + 2] cycloaddition reactions of 1 with
isocyanates and isothiocyanates RsNdCdX (X ) O, S).2
At low temperature, these cumulenes add with their
NdC bond to the BdN double bond of 1 to yield four-
extend the reaction in eq 1 to reagents RsNdCdX in
which X is an NR or a CMe2 group.
Resu lts
While MesNdSdO reacts with 1 to form a colorless
product at -30 °C, the product decomposes to reform
the reactants upon warming to room temperature.
However, N-sulfinylsulfonamides RsO2SsNdSdO (R
) Me, Et, iPr, Ph, and pTol) add to 1 in a [2 + 2] fashion
to form the moisture sensitive but thermally stable four-
membered rings 2a -e, eq 2. Despite their bulky
substituents aminoiminophosphines RsNdPsNR2′ com-
bine similarly with 1 to yield the heterocycles 3a -e, eq
3.
membered heterocycles (CF3)2B-NMe2-C(X)-NR ac-
cording to eq 1. Depending on the nature of R and X,
some of these rings rearrange quantitatively to the
isomers (CF3)2B-X-C(NMe2)-NR at ambient temper-
atures. In the present study, we will investigate [2 +
2] cycloaddition reactions of 1 with compounds contain-
ing NdS or NdP double bonds. Furthermore, we will
† Dedicated to Professor M. Weidenbruch on the occasion of his 60th
birthday.
Although carbodiimides RsNdCdNsR bearing tBu
and SiMe3 substituents do not react with 1, derivatives
with R ) iPr and cC6H11 add at 60 and 20 °C,
respectively, across the BdN double bond of 1. In
X Abstract published in Advance ACS Abstracts, October 1, 1997.
(1) Pawelke, G.; Bu¨rger, H. Appl. Organomet. Chem. 1996, 10, 147.
(2) Ansorge, A.; Brauer, D. J .; Bu¨rger, H.; Do¨rrenbach, F.; Hagen,
T.; Pawelke, G.; Weuter, W. J . Organomet. Chem. 1991, 407, 283.
S0276-7333(97)00262-8 CCC: $14.00 © 1997 American Chemical Society

5322 Organometallics, Vol. 16, No. 24, 1997
Brauer et al.
by the more electron rich N-R nitrogen forms the stable
isomers 5a -e. However, when R is a phenyl group, the
phenyl ring in 4′c-e may as well adopt an orientation
which is favorable for an electrophilic aromatic substi-
tution by the tricoordinate boron, eq 7. Electrophilic
contrast to the above-mentioned behavior of the related
isocyanates, the [2 + 2] cycloadducts 4a ,b could not be
isolated as pure materials and we only have NMR
spectroscopic evidence for their existence. These inter-
mediates rearrange under the given reaction conditions
to yield the respective, stable four-membered hetero-
cycles 5a and 5b, eq 4. The reaction products of 1 with
carbodiimides bearing aromatic substituents, R ) pXC6H4
(X ) H, Me, OMe), show a more complex behavior. The
initially formed [2 + 2] cycloadducts 4c-e undergo two
facile rearrangements. While one pathway is the same
as that for 5a ,b and leads to species of type 5, the other
route leads to bicyclic heterocycles of type 6, eq 5. Thus,
attack by boron fuses a six-membered ring, and migra-
tion of a proton leads to the isomers 6c-e.
Keteneimines, RNdCdCR2, possess CdC and polar
NdC linkages, only the latter being expected to enter
into a [2 + 2] cycloaddition reaction with the BdN bond
of 1. We selected PhNdCdCMe2 for a test because it
is easily prepared, bears unobstructive substituents at
carbon, and is relatively stable. However, instead of the
expected [2 + 2] cycloaddition product 8′, only a rear-
ranged species 8 was obtained, eq 8. Its constitution
was elucidated by an X-ray structure investigation.
As mentioned above, electron-withdrawing N-sulfonyl
substituents activate the NdS bond of sulfinylamines
to such an extent that thermally stable [2 + 2] cycload-
dition products with 1 could be isolated. Conceivably,
the NdS bond of F3CsCH2sNdSdO might be activated
analogously. However, its reaction with 1 followed an
ene-type route (eq 9) to deliver the dimethylamine
borane 9sno [2 + 2] cycloaddition product being formed.
P r op er ties a n d Sp ectr a . The derivatives of novel
heterocycles 2a -8 are colorless solids, the melting
points of which are reported in the Experimental
Section. While compounds 3a -e/b and 5a -8 are stable
to air and moisture, the species 2a -d and 9 are
sensitive to hydrolysis and, therefore, have to be handled
in a dry atmosphere. All are soluble in polar organic
solvents.
mixtures of 5c/6c, 5d /6d , and 5e/6e are obtainedsthe
molar ratios determined by NMR being 5:5, 3:7, and 2:8,
respectively. The formation of these isomer pairs can
be explained as follows. The initially formed four-
membered cycloadducts 4a -e are in equilibrium with
acyclic isomers 4′a -e, eq 6. In these isomers, the
position of the NMe2 and N-R groups can interchange
by rotation about an N-C single bond. Ring closure

[2 + 2] Cycloaddition Reactions of (CF3)2BNMe2
Organometallics, Vol. 16, No. 24, 1997 5323
1
The H, 19F, 11B, and 13C NMR spectra of 2a -9 and
the 31P NMR spectra of 3a -e were recorded. The
chemical shifts and 31P coupling constants (Table 1) are
consistent with the proposed structures, and only a few
comments will be necessary.
Compounds 3a -e are sterically overcrowded, and the
substituents attached to the four-membered ring possess
only limited conformational freedom. This is under-
scored by the presence of magnetically nonequivalent
SiMe3 and iPr groups bonded to the exocyclic nitrogen
atoms of 3a and 3d , respectively; that is, no rotation
about the exocyclic P-N bond occurs on the NMR time
F igu r e 1. Perspective drawing of (CF3)2BsNMe2s
S(dO)sNsSO2Me (2a ) with 20% probability thermal el-
lipsoids for the non-hydrogen atoms.
1
scale. Furthermore, 250 MHz H NMR spectra of 3c
Sch em e 1. F r a gm en ta tion of Com p ou n d s 5c/6c-5e/
6e, F or m a tion of th e Ba se P ea k
run between 325 and 225 K reveal that the rotation of
the SiMe3 group is hindered on the NMR time scale too.
Free rotation is observed at 325 K, but at 230 K its
proton resonance splits into three signals at 0.87, 0.43,
and 0.36 ppmsthe coalescence temperature being close
to 300 K. Furthermore, the rather rigid framework of
compounds 3a -e leads to a wide range of element-31P
coupling constants (Table 1) and in the 13C NMR spectra
4
to J (CF) coupling constants (not listed) ranging from
4 to 1.5 Hz.
The IR spectra of 2a -9 were recorded in the 500-
4000 cm-1 region. These are dominated by the very
strong absorptions of the CF3 groups occurring between
1030 and 1120 cm-1. Identification of the isomers 6 is
facilitated by the prominence of their ν(NH) vibration
at 3430 cm-1. All novel species showed the expected
absorptions belonging to their functional groups (ν-
(CdC), ν(CdN), ν(SO2), ν(PN/SiN)). The respective
wavenumbers are given in the Experimental Section
EI mass spectral data for 2a -9 are listed in Table 2.
The peaks of the molecular ions [M]•+ for 2a -9 are weak
if detectable at allsthe ions [M-CF3]+ and [M-C2F5]+
being indicative of the molecular mass. The isomers 5c/
6c, 5d /6d , and 5e/6e show almost identical fragmenta-
tion patterns despite their different molecular frame-
works. This observation does not refute the proposed
structures because fragmentation pathways are con-
ceivable for extracting the same observed ions from each
isomer. For example, the base peaks of these spectra
are assigned to the ion [XC6H4NCN(CH3)2]+ (X ) H, Me,
OMe), and simple fragmentation pathways for the
formation of these ions are suggested in Scheme 1.
Because mass spectra do not distinguish between these
isomers, Table 2 lists only the mass spectral data of the
isomer mixtures 5c/6c-5e/6e.
(7.2(3)°) being much less than that of 3c (27.0(2)°).
While the ring atoms S(1) in 2a and P in 3c exhibit
pyramidal geometries, the 5.0(3)° larger valency angle
sum for the latter may be due to its bulkier exocyclic
substituent. In 3c, the exocyclic N(3) atom lies only
0.050(3) Å from the plane defined by its substituents,
and this plane forms a 71.1(1)° angle with the substitu-
ent plane of the P atom. This orientation minimizes
steric congestion with the other ring substituents and
repulsions between the lone pairs of the N(3) and P
atoms. The steric congestion is underlined by the
gearing of the groups bonded to the N(3) atom, as
evident from Figure 2. While the tricoordinate N(1)
atom of 2a deviates only 0.021(2) Å from the plane
through its substituent atoms, the corresponding devia-
tion of the N(1) atom in 3c is much larger (0.320(3) Å).
Despite these differences, the bond lengths in the two
four-membered rings are surprisingly similar.
Descr ip tion of th e Cr ysta l Str u ctu r es. All of the
crystals studied are composed of discrete monomeric
molecules which form no unusual intermolecular con-
tacts.
Str u ctu r es of 2a a n d 3c. ORTEP drawings of 2a
and 3c are displayed in Figures 1 and 2, and pertinent
bond lengths and angles are listed in Tables 5 and 6.
These compounds contain slightly folded four-membered
ringssthe folding along the N(1)‚‚‚N(2) tieline of 2a
The bonds formed by the three-coordinate N(1) atoms
are shorter than those formed by the four-coordinate
N(2) atoms. On the average, the difference amounts to
0.083(6) Å for the B-N bondssa value which is similar
to that (0.10(1) Å) found for the B-N bonds of (CF3)2B-
NMe2-C(O)-NtBu (10).2 A greater dependency is

5324 Organometallics, Vol. 16, No. 24, 1997
Brauer et al.

[2 + 2] Cycloaddition Reactions of (CF3)2BNMe2
Organometallics, Vol. 16, No. 24, 1997 5325

5326 Organometallics, Vol. 16, No. 24, 1997
Brauer et al.
Ta ble 2. Selected Electr on Im p a ct Ma ss Sp ectr a l Da ta in th e Or d er of Decr ea sin g In ten sity (m /e (r ela tive
in ten sity) [fr a gm en t]+) for 2a -9
2a
2b
79 (100) [CH3SO2]+; 92 (80) [F2BN(dCH2)CH3]+; 44 (39) [N(CH3)2]+; 74 (17) [FBN(CH3)2]+; 124 (7) [CF3BN(CH3)2]+
92 (100) [F2BN(dCH2)CH3]+; 93 (73) [C2H5SO2]+; 74 (36) [FBN(CH3)2]+; 44 (33) [N(CH3)2]+; 124 (27)
[CF3BN(CH3)2]+; 279 (3) [M - CF3]+; 229 (2) [M - C2F5]+; 348 (1) [M]+
2c
2d
44 (100) [N(CH3)2]+; 92 (54) [F2BN(dCH2)CH3]+; 74 (13) [FBN(CH3)2]+; 124 (29) [CF3BN(CH3)2]+; 107 (3) [C3H7SO2]+
77 (100) [C6H5]+; 141 (83) [C6H5SO2]+; 92 (80) [F2BN(dCH2)CH3]+; 44 (19) [N(CH3)2]+; 74 (17)
[FBN(CH3)2]+; 124 (10) [CF3BN(CH3)2]+; 396 (3) [M]+; 277 (3) [M - C2F5]+; 327 (1) [M - CF3]+
91 (100) [C7H7]+; 92 (94) [F2BN(dCH2)CH3]+; 155 (78) [C7H7SO2]+; 74 (15) [FBN(CH3)2]+; 124 (11)
[CF3BN(CH3)2]+; 44 (2) [N(CH3)2]+; 410 (2) [M]+
2e
3a
73 (100) [Si(CH3)3]+; 278 (59) [((CH3)3Si)2NPNSi(CH3)3]+; 118 (48) [(CH3)3SiNP]+; 263 (22) [((CH3)3Si)2NPNSi(CH3)2]+;
74 (18) [FBN(CH3)2]+; 371 (16) [M - C2F4]+; 92 (14) [F2BN(dCH2)CH3]+; 471 (10) [M]+; 94 (9)
[F2BNH(CH3)2]+; 352 (7) [M - C2F5]+; 235 (6) [((CH3)3Si)2NPN(CH3)2]+; 402 (3) [M - CF3]+
118 (100) [(CH3)3SiNP]+; 73 (76) [Si(CH3)3]+; 94 (52) [F2BNH(CH3)2]+; 92 (43) [F2BN(dCH2)CH3]+; 74 (35)
[FBN(CH3)2]+; 243 (27) [C8H15NPNSi(CH3)3]+; 211 (24) [M - C9H18N - C2F4]+; 258 (13)
[C9H18NPNSi(CH3)3]+; 382 (9) [M - CF3]+; 451 (7) [M]+; 332 (5) [M - C2F5]+
3b
3c
57 (100) [C4H9]+; 282 (28) [M - C4H9 - C2F4]+; 368 (24)) [M - C4H9N]+; 73 (14) [Si(CH3)3]+; 439 (11) [M]+;
118 (9) [Si(CH3)3NP]+; 92 (7) [F2BN(dCH2)CH3]+; 74 (5) [FBN(CH3)2]+
3d
57 (100) [C4H9]+; 187 (63) [((CH3)2CH)2NPN(CH3)2]+; 270 (39) [M - C4H8 - CF3]+; 100 (39) [((CH3)2CH)2N]+; 88 (25)
[(CH3)2CHNP]+; 195 (20) [M - ((CH3)2CH)2N - C2F4]+; 395 (15) [M]+; 94 (10) [F2BNH(CH3)2]+; 238 (8) [M - C4H9 - C2F4]+
57 (100) [C4H9]+; 58 (21) [C3H8N]+; 94 (19) [F2BNH(CH3)2]+; 195 (19) [M - C9H18N - C2F4]+; 245 (8) [M - C9H18N - CF2]+;
92 (7) [F2BN(dCH2)CH3]+; 435 (5) [M]+
3e
5a
71 (100) [(H3C)2NCNH]+; 204 (60) [M - CH3 - C2F4]+; 113 (48) [(H3C)2CHNCN(CH3)2]+; 200 (30) [M - C2F5]+; 304 (20)
[M - CH3]+; 119 (17) [F2BNCN(CH3)2]+; 319 (11) [M]+
5b
399 (100) [M]+; 55 (83) [C4H7]+; 71 (82) [(H3C)2NCNH]+; 83 (71) [C6H11]+; 256 (52) [M - C3H7 - C2F4]+; 356 (45) [M - C3H7]+;
153 (44) [C6H11NCN(CH3)2]+; 280 (25) [M - C2F5]+; 119 (21) [F2BNCN(CH3)2]+
5c/6c
5d /6d
5e/6e
8
147 (100) [C6H5NCN(CH3)2]+; 194 (25) [C6H5NCNC6H5]+; 217 (19) [C13H8BN3]+; 387 (18) [M]+; 268 (12) [M - C2F5]+;
287 (9) [M - C2F4]+
161 (100) [H3CC6H4NCN(CH3)2]+; 296 (44) [M - C2F5]+; 222 (39) [H3CC6H4NCNC6H4CH3]+; 415 (28) [M]+; 245 (21)
[C15H12BN3]+; 346 (10) [M - CF3]+; 315 (9) [M - C2F4]+
177 (100) [H3COC6H4NCN(CH3)2]+; 254 (42) [H3COC6H4NCNC6H4OCH3]+; 147 (26) [C6H5NCN(CH3)2]+; 447 (25) [M]+;
277 (15) [C15H12BN3O2]+; 347 (11) [M - C2F4]+; 328 (4) [M - C2F5]+
119 (100) [F2BNCN(CH3)2]+; 98 (87) [(CH3)2NCC(CH3)2]+; 145 (69) [C6H5NCC(CH3)2]+; 238 (62) [M - C2F4]+;
77 (43) [C6H5]+; 228 (22) [M - CF2]+; 338 (11) [M]+
9
94 (100) [F2BNH(CH3)2]+; 92 (22) [F2BN(dCH2)CH3]+; 44 (19) [N(CH3)2]+; 69 (8) [CF3]+; 338(7) [M]+; 74 (5) [FBN(CH3)2]+;
128 (4) [F3CCHdNS]+; 144 (2) [F3CCHdNSO]+; 319 (1) [M - F]+; 269 (1) [M - CF3]+
Ta ble 3. Elem en ta l An a lyses
anal. found: calcd
well, their average values will be quoted in the follow-
ing. These compounds may be formulated as zwitteri-
ons (CF3)2B--X-C+(NMe2)-NPh; X ) NPh (5c), CMe2
(8). The short C(1)-N bond lengths show that the
formal positive charge on the C(1) atom is delocalized
by π bonding to the adjacent nitrogen atoms. This π
interaction explains the essentially planar substitution
of the C(1), N(1), and N(2) atoms, the near (8) or exact
(5c) planarity of the four-membered rings, and the small
dihedral angles between the normals to the ring plane
and the substituent plane of the exocyclic NMe2
groups13.1(2)° (average) and 6.3(1)° in 5c and 8,
respectively. Similar geometric details were observed
compd
formula
C
H
N
2a
2b
2c
2d
2e
3a
3b
3c
3d
3e
5a
5b
5c/6c
5d /6d
5e/6e
8
C5H9BF6N2O3S2
C6H11BF6N2O3S2 20.9; 20.70 3.3; 3.19
C7H13BF6N2O3S2 23.4; 23.22 3.8; 3.62
17.6; 17.98 2.7; 2.72
8.4; 8.39
8.0; 8.05
7.5; 7.74
7.2; 7.07
6.9; 6.83
8.9; 8.91
9.0; 9.31
9.2; 9.57
10.3; 10.63
9.4; 9.65
12.8; 13.17
10.2; 10.53
10.5; 10.85
9.9; 10.12
9.5; 9.40
8.3; 8.29
8.0; 8.29
C
C
C
C
C
C
C
C
C
C
C
C
C
10H11BF6N2O3S2 30.0; 30.32 2.8; 2.80
11H13BF6N2O3S2 31.9; 32.21 3.3; 3.19
13H33BF6N3PSi3 32.8; 33.12 7.0; 7.06
16H33BF6N3PSi
15H33BF6N3PSi
14H29BF6N3P
17H33BF6N3P
11H20BF6N3
17H28BF6N3
17H16BF6N3
19H20BF6N3
19H20BF6N3O2
14H17BF6N2
42.6; 42.58 7.7; 7.37
40.7; 41.01 7.4; 7.57
42.1; 42.55 7.4; 7.40
46.6; 46.91 7.6; 7.64
40.7; 41.40 6.1; 6.32
51.3; 51.15 7.2; 7.07
52.4; 52.74 4.1; 4.17
54.8; 54.97 4.9; 4.86
50.7; 51.03 4.5; 4.51
49.6; 49.73 5.1; 5.07
21.4; 21.32 2.50; 2.39
for (CF3)2B-S-C(NMe2)-NPh (11).2
The B-N distances in 5c, 8, and 11 (average
1.554(3), 1.559(3), and 1.557(9) Å, respectively) may
have been lengthened by C(1)-N π bonding. Thus,
these distances are significantly longer than the average
value (1.500(6) Å) found for the ylid adduct Ph3P-CH2-
(F3C)2B-NMe2 (12),3 but similar to that (1.541(4) Å) of
(F3C)3B-NHCH-NMe2 (13), which unlike 12 has de-
localized C-N π bonding.4
9
C6H8BF9N2OS
found for the differences in the N-S (0.210(3) Å) and
N-P (0.198(4) Å) bond lengths in 2a and 3c, respec-
tively. The large difference might indicate a π compo-
nent to the N(1)-S(1) and N(1)-P bonds similar to that
proposed for the analogous N-C bond of 10, which was
found to be 0.21(1) Å shorter than the other endocyclic
N-C linkage.2
Str u ctu r es of 5c a n d 8. One of the two unique
molecules of 5c is depicted in Figure 3, and the molec-
ular structure of 8 is shown in Figure 4. Selected bond
lengths and angles are listed in Tables 7 and 8 for 5c
and 8, respectively. Crystallographic symmetry is
imposed on the molecules of 5c; that is, the B(I)‚‚‚
C(I1)sN(I2) sequences of the two molecules (I ) 1, 2)
in the asymmetric unit occupy sites of C2 symmetry.
Since the bond lengths and angles of the two crystal-
lographically independent molecules of 5c agree quite
The endocyclic B-C bond distance in 8 (1.662(3) Å)
is significantly longer than the average B-CF3 bond
length (1.610(3) Å) but compares well with the B-CH2-
PPh3 linkage in 12 (average 1.661(6) Å)3 or the endocy-
clic B-C bond (1.655(6) Å) in (14).5
Str u ctu r es of 6d a n d 6e. The structures of 6d and
6e are shown in Figures 5 and 6, and important bond
(3) Brauer, D. J .; Bu¨rger, H.; Dittmar, T.; Pawelke, G.; Rothe, J . J .
Organomet. Chem. 1996, 524, 225.
(4) Ansorge, A.; Brauer, D. J .; Bu¨rger, H.; Krumm, B.; Pawelke, G.
J . Organomet. Chem. 1993, 446, 25.
(5) Ansorge, A.; Brauer, D. J .; Buchheim-Spiegel, S.; Bu¨rger, H.;
Hagen, T.; Pawelke, G. J . Organomet. Chem. 1995, 501, 347.

[2 + 2] Cycloaddition Reactions of (CF3)2BNMe2
Organometallics, Vol. 16, No. 24, 1997 5327
Ta ble 4. Cr ysta l Da ta for 2a , 3c, 5c, 6d , 6e a n d 8
2a
3c
5c
6e
6d
8
formula
Mr
cryst size (mm)
C5H9BF6N2O3S2
334.06
C15H33BF6N3PSi
439.31
C17H16BF6N3
387.13
0.24 × 0.28 ×
0.43
C19H20BF6N3O2
447.19
C19H20BF6N3
415.19
C14H17BF6N2
338.10
0.08 × 0.34 ×
0.35
0.20 × 0.26 ×
0.24 × 0.30 ×
0.09 × 0.22 ×
0.20 × 0.32 ×
0.58
0.40
0.46
0.40
cryst syst
space group
a (Å)
b (Å)
c (Å)
monoclinic
P21/n
orthorhombic
P212121
10.804(2)
13.371(1)
15.760(1)
monoclinic
C2
monoclinic
P21
orthorhombic
Pbca
15.916(1)
14.948(2)
16.639(1)
monoclinic
P21/c
7.395(2)
11.560(2)
14.551(2)
93.59(2)
1241.5(4)
4
19.016(2)
8.9928(7)
11.272(1)
107.555(7)
1837.8(3)
4
7.4031(9)
7.9373(9)
17.659(2)
100.310(9)
1020.9(2)
2
8.4476(9)
16.826(2)
11.3901(9)
92.799(8)
1617.0(3)
4
â (deg)
V (Å3)
Z
2276.7(5)
4
1.282
293
3958.6(6)
8
1.393
298
F (g cm-3
T (K)
)
1.787
299
1.399
295
1.455
293
1.389
296
λ (Å)
2θ range (deg)
index ranges
0.710 73
2-25
1.5405 62
8-150
h, k, l
CAD4
2617
1.541 84
4-138
1.541 84
5-138
1.541 84
9-138
h, k, l
P3
3694
3687
0.116
1.065
0.711-0.815
0.0023(1)
275
1.541 84
9-138
h, (k, (l
AED1
(h, (k, l
P3
(h, (k, l
P3
h, k, (l
P3
diffractometer
no. of reflns measd
no. of unique reflns
R (int)
4740
2193
0.028
0.509
3832
3406
0.031
1.107
0.620-0.836
0.0051(3)
267
0.038
0.103
3665
3308
0.015
1.151
0.733-0.913
0.0134(8)
300
0.036
0.088
3225
3014
0.010
1.149
0.713-0.913
0.0029(4)
217
0.066
0.124
2617
µ (λ) (mm-1
transmission
ext param
)
2.068
0.506-0.653
0.877-0.922
no. of params varied
RF (all)
wRF2 (all)
178
0.053
0.113
266
0.040
0.108
0.074
0.119
Ta ble 5. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for (CF 3)2BsNMe2sS(dO)sNsSO2Me (2a )
B-N(1)
B-N(2)
B-C(1)
B-C(2)
C(3)-N(2)
1.532(3)
1.618(4)
1.623(4)
1.621(4)
1.505(4)
C(4)-N(2)
N(1)-S(1)
N(1)-S(2)
N(2)-S(1)
S(1)-O(1)
1.476(4)
1.684(2)
1.642(2)
1.894(2)
1.434(3)
N(1)-B-N(2)
B-N(1)-S(1)
B-N(1)-S(2)
S(1)-N(1)-S(2)
90.3(2)
102.0(2)
138.5(2)
119.5(1)
B-N(2)-S(1)
90.4(1)
76.9(1)
110.8(2)
108.0(2)
N(1)-S(1)-N(2)
N(1)-S(1)-O(1)
N(2)-S(1)-O(1)
Ta ble 6. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for (CF 3)2BsNMe2sP (N(SiMe3)tBu )sNtBu
(3c)
B-N(1)
1.534(4)
1.613(4)
1.651(5)
1.631(5)
1.495(4)
1.484(4)
C(5)-N(3)
C(12)-N(1)
N(1)-P
1.552(4)
1.486(3)
1.691(2)
1.889(3)
1.683(2)
1.794(3)
B-N(2)
B-C(1)
B-C(2)
C(3)-N(2)
C(4)-N(2)
F igu r e 2. Perspective drawing of (CF3)2B-NMe2-P(N-
N(2)-P
N(3)-P
N(3)-Si
(SiMe3)tBu)-NtBu (3c) with 20% probability thermal el-
lipsoids for the non-hydrogen atoms.
N(1)-B-N(2)
B-N(1)-C(12)
B-N(1)-P
92.2(2)
129.1(2)
96.3(2)
121.5(2)
86.4(2)
108.3(2)
C(5)-N(3)-Si
P-N(3)-Si
N(1)-P-N(2)
N(1)-P-N(3)
N(2)-P-N(3)
118.8(2)
132.6(2)
78.4(1)
113.1(1)
109.2(1)
C(12)-N(1)-P
B-N(2)-P
C(5)-N(3)-P
atom than in 5c or 8sthe dihedral angles being
31.6(2)° and 30.7(1)° in 6d and 6e, respectively. The
greater deviation from coplanarity may be caused in
part by stronger repulsions between the exocyclic sub-
stituents of the N(1) and C(1) atoms in the six-
membered rings as compared to those arising between
substituents of the four-membered rings in 5c and 8.
lengths and angles are tabulated in Tables 9 and 10.
Their major structural features are quite similar. For
example, their heterocyclic six-membered rings are
folded along their B‚‚‚N(2) tielines by 21.4(2)° in 6d and
23.3(1)° in 6e.
The C(1) atoms are the centers of formal positive
charge in these zwitterionic compounds, and the lengths
of the C(1)-N bonds indicate that the positive charge
is delocalized to the three neighboring nitrogen atoms
by π bonding. However, in each compound, the substi-
tution plane of the exocyclic nitrogen atom forms a
larger angle with the coordination plane of the C(1)
Interestingly, the B-N(1) distances in 6d and 6e are
on the average 0.031(6) Å longer than those in 5c and
8. Here, the lengthening may have resulted from the
relatively greater crowding of the CF3 and aryl substit-
uents of the six-membered heterocycles. On the other
hand, the B-C(7) distances in 6d and 6e appear normal.

5328 Organometallics, Vol. 16, No. 24, 1997
Brauer et al.
F igu r e 3. Perspective drawing of one of the two crystal-
lographically independent molecules of (CF3)2BsNPhsC-
F igu r e 5. Perspective drawing of (CF3)2BsCdCHsC-
MedCHsCHdCsNHsC(dNMe2)sN(4-MeC6H4) (6d ) with
(dNMe2)sNPh (5c) with 20% probability thermal ellipsoids
for the non-hydrogen atoms.
20% probability thermal ellipsoids for the non-hydrogen
atomssthe aryl-bonded methyl groups being disordered.
F igu r e 4. Perspective drawing of (CF3)2BsCMe2sC-
F igu r e 6. Perspective drawing of (CF3)2BsCdCHsCO-
MedCHsCHdCsNHsC(dNMe2)sN(4-MeOC6H4) (6e) with
(dNMe2)sNPh (8) with 20% probability thermal ellipsoids
for the non-hydrogen atoms.
20% probability thermal ellipsoids for the non-hydrogen
atoms.
Ta ble 7. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for (CF 3)2BsNP h sC(dNMe2)sNP h (5c)
Ta ble 8. Selected Bon d Len gth s (Å) a n d An gles
B(1)-N(11)
B(1)-C(12)
C(11)-N(11)
C(11)-N(12)
C(13)-N(12)
C(14)-N(11)
1.553(3)
1.604(3)
1.356(2)
1.315(3)
1.456(3)
1.422(2)
B(2)-N(21)
B(2)-C(22)
C(21)-N(21)
C(21)-N(22)
C(23)-N(22)
C(24)-N(21)
1.555(3)
1.603(3)
1.355(2)
1.317(3)
1.454(2)
1.423(2)
(d eg) for (CF 3)2BsCMe2sC(dNMe2)sNP h (8)
B-N(1)
1.559(3)
1.662(3)
1.610(3)
1.611(3)
1.331(2)
1.314(3)
C(1)-C(2)
C(2)-C(5)
C(2)-C(6)
C(3)-N(2)
C(4)-N(2)
C(9)-N(1)
1.523(3)
1.535(3)
1.534(3)
1.460(3)
1.466(3)
1.433(2)
B-C(2)
B-C(7)
B-C(8)
C(1)-N(1)
C(1)-N(2)
N(11)-B(11)-N(11′)a
N(11)-C(11)-N(11′) 100.0(2) N(21)-C(21)-N(21′)
83.9(2) N(21)-B(21)-N(21′)b 83.7(2)
99.9(2)
130.0(1)
88.2(1)
133.3(1)
130.2(2)
121.5(1)
N(11)-C(11)-N(12)
B(1)-N(11)-C(11)
B(1)-N(11)-C(14)
C(11)-N(11)-C(14)
C(11)-N(12)-C(13)
130.0(1) N(21)-C(21)-N(22)
88.1(1) B(2)-N(21)-C(21)
132.6(2) B(2)-N(21)-C(24)
130.6(2) C(21)-N(21)-C(24)
121.8(1) C(21)-N(22)-C(23)
N(1)-B-C(2)
N(1)-C(1)-N(2)
N(1)-C(1)-C(2)
C(2)-C(1)-N(2)
B-C(2)-C(1)
84.7(1)
130.0(2)
98.8(2)
131.1(2)
82.8(1)
B-N(1)-C(1)
93.4(2)
132.5(2)
124.3(2)
121.0(2)
114.6(2)
C(1)-N(1)-C(9)
C(1)-N(2)-C(3)
C(1)-N(2)-C(4)
C(3)-N(2)-C(4)
C(13)-N(12)-C(13′) 116.4(3) C(23)-N(22)-C(23′′) 117.1(2)
B-N(1)-C(1)
133.3(2)
a
b
x′, y′, z′ ) -x + 1, y, -z + 1. x′′, y′′, z′′ ) -x + 1, y, -z.
The reaction of (diethylamino)diphenylborane with
bis(p-tolyl)carbodiimide has already been described by
Lappert et al. in 1966.7 Thus, a direct comparison of
the reactivity of 1 versus that of Ph2BNEt2 is possible.
The latter combines according to eq 10 to yield a
product, 15, with an open-chain structure. This has the
same framework as does 4′d , which is a proposed
intermediate in the formation of 5d and 6d . Appar-
ently, the trifluoromethyl substituents of 4′d make its
Discu ssion
To our knowledge no reaction of aminoboranes with
N-sulfinylsulfonamides and aminoiminophosphines have
been described so far. The observed [2 + 2] cycloaddi-
tion that 1 undergoes with these reactants underscores,
again, its alkene-like behavior. Compounds 2a -e and
3a -e are the first examples with BNSN and BNPN
four-membered rings where both boron and nitrogen are
tetracoordinated. However, related cycloadducts with
tricoordinate boron and nitrogen have been obtained
with aminoiminophosphines and iminoboranes.6
(6) Paetzold, P.; Plotho, C. v.; Niecke E.; Ru¨ger, R. Chem. Ber. 1983,
116, 1678.
(7) J efferson, R.; Lappert, M. F.; Prokai, B.; Tilley, B. P. Soc. A 1966,
1584.

[2 + 2] Cycloaddition Reactions of (CF3)2BNMe2
Organometallics, Vol. 16, No. 24, 1997 5329
Ta ble 9. Selected Bon d Len gth s (Å) a n d An gles
nitrogen atom and decrease the coordination number
of the NMe2 group at the expense of the sterically more
encumbered NR′2 entity. Rearrangement of compounds
2a -e would not only shorten the distance between the
nitrogen substituents but also place a formal positive
charge on the sulfur atom. Perhaps this positive charge
cannot be sufficiently delocalized to the substituents of
the sulfur atom by hyperconjugative N-S and O-S π
bonding.
(d eg) for (CF 3)2BsCdCHsCMedCHsCHdCsN-
HsC(dNMe2)sN(4-MeC6H4) (6d )
B-N(1)
1.590(3)
1.610(3)
1.633(3)
1.620(3)
1.340(3)
1.337(3)
C(1)-N(3)
C(2)-N(2)
C(2)-C(7)
C(11)-N(3)
C(12)-N(3)
C(13)-N(1)
1.346(3)
1.412(3)
1.392(3)
1.456(3)
1.455(3)
1.449(3)
B-C(7)
B-C(9)
B-C(10)
C(1)-N(1)
C(1)-N(2)
N(1)-B-C(7)
108.6(2)
119.9(2)
122.9(2)
117.2(2)
119.4(2)
117.9(2)
119.9(2)
B-N(1)-C(13)
123.5(2)
116.3(2)
125.5(2)
121.3(2)
122.2(2)
115.6(2)
Exp er im en ta l Section
N(1)-C(1)-N(2)
N(1)-C(1)-N(3)
N(2)-C(1)-N(3)
N(2)-C(2)-C(7)
B-C(7)-C(2)
C(1)-N(1)-C(13)
C(1)-N(2)-C(2)
C(1)-N(3)-C(11)
C(1)-N(3)-C(12)
C(11)-N(3)-C(12)
X-r a y Cr ysta l Str u ctu r a l Deter m in a tion s. While crys-
tals of 2a and 3c were mounted in glass capillaries under
argon, those of 5c, 6d , 6e, and 8 were glued to glass fibers.
Cell constants were calculated from the 2θ angles measured
with a Siemens AED1 or Enraf-Nonius CAD4 diffractometer
or from the setting angles determined with a Siemens P3
device. While the Siemens AED1 diffractometer used zirco-
nium-filtered Mo KR radiation, the other instruments em-
ployed graphite monochromators and Cu KR radiation. In-
tensity data were determined by θ-2θ scan techniques and
corrected for absorption. The structures were solved by direct
methods, refined by full-matrix least-squares techniques and
displayed using the SHELXL/PC, version 5, program package
(Sheldrick, G. M. Siemens Industrial Automation, Inc., Madi-
son, WI), which also provided the scattering factors. The
hydrogen atoms of the phenyl and ordered methyl groups were
idealized (C-H 0.95 Å), and the torsional orientations of the
methyl groups about their X-CH3 bonds were refined. While
the hydrogen atoms were varied isotropically, all other atoms
were assigned anisotropic temperature factors. The extinction
B-N(1)-C(1)
Ta ble 10. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for (CF 3)2BsCdCHsCOMedCHsCHdCsN-
HsC(dNMe2)sN(4-MeOC6H4) (6e)
B-N(1)
1.583(3)
1.612(3)
1.633(3)
1.626(3)
1.344(3)
1.340(3)
C(1)-N(3)
C(2)-N(2)
C(2)-C(7)
C(11)-N(3)
C(12)-N(3)
C(13)-N(1)
1.350(3)
1.415(3)
1.382(3)
1.450(3)
1.461(3)
1.449(3)
B-C(7)
B-C(9)
B-C(10)
C(1)-N(1)
C(1)-N(2)
N(1)-B-C(7)
108.2(2)
120.0(2)
122.6(2)
117.3(2)
119.5(2)
118.0(2)
119.8(2)
B-N(1)-C(13)
123.1(2)
116.7(2)
124.9(2)
121.6(2)
121.2(2)
115.9(2)
N(1)-C(1)-N(2)
N(1)-C(1)-N(3)
N(2)-C(1)-N(3)
N(2)-C(2)-C(7)
B-C(7)-C(2)
C(1)-N(1)-C(13)
C(1)-N(2)-C(2)
C(1)-N(3)-C(11)
C(1)-N(3)-C(12)
C(11)-N(3)-C(12)
corrections have the form Fc* ) Fck[1 + 0.001xFc2λ3/sin 2θ]-1/4
Crystal data and refinement details are given in Table 4.
.
B-N(1)-C(1)
Str u ctu r e of 2a . The cell constants were determined from
the Bragg angles of 35 reflections between 10.5° and 14.9°.
No extinction correction was necessary.
Str u ctu r e of 3c. Unit cell dimensions were determined
from the Bragg angles of 25 reflections between 17.2° and
28.6°. No extinction correction was necessary. The absolute
structure parameter,8 -0.05(3), shows that the absolute con-
figuration shown in Figure 2 is correct.
boron much more electrophilic than that of 15. Thus,
4′d rearranges either by attack by boron on the nitrogen
of the carbodiimide or on the ortho carbon of the phenyl
ring. The product distribution mentioned above indi-
cates that the ratio of the two isomers formed depends
on the relative nucleophilicity of the phenyl carbon
atoms.
Str u ctu r e of 5c. Cell constants were determined from 40
reflections with θ between 30.6° and 34.4° and confirmed by
oscillation and Weissenberg photographs made with crystals
mounted along b and c. Of the space groups C2, Cm, and C2/m
which are consistent with the systematic absences, C2 was
chosen on the basis of intensity statistics and confirmed by
the refinement. Following the conventional refinement with
hydrogen atoms, the top 21 peaks in a difference Fourier
synthesis (0.46-0.12 e/Å3) were found to be related to the
atoms of the asymmetric unit by the translation 0 0 1/2. In
order to account for this electron density, the crystal was
assumed to be composed of molecules in the original positions
of occupancy R and molecules translated by c/2 with occupancy
1 - R and otherwise identical parameters. This empirical
twinning model converged rapidly to give R ) 0.950(1). The
absolute structure parameter, 0.1(1), was determined less
precisely.
Str u ctu r e of 6d . The unit cell dimensions were deter-
mined from 40 reflections with θ in the range 30.6-34.4°. The
aryl-bonded methyl groups were found to be disordered, and
the electron density of the hydrogen atoms was fit to hexagons
of six, half-occupancy hydrogen atoms. The other hydrogen
atoms are ordered in the crystalsthe coordinates of H(N2)
being refined.
Lacking N-phenyl groups, compounds 2a -3e could
still possibly rearrange, as indicated in eq 1 to struc-
tures analogous to 5c-e and 8, but indeed, they show
no tendency to do so. The driving force for formation
of the rearranged heterocycles would appear to be the
shift of the formal positive charge from the quaternary
nitrogen to the less electronegative ring carbon atom
with concomitant delocalization of the charge by C-N
π bonding. The latter is best served by a planar four-
membered ring which is coplanar with the valencies of
the exocyclic nitrogen atom. Such coplanarity is pro-
hibited by large substituents on the ring nitrogen atom,
and compounds like 10 were shown not to rearrange.
The corresponding rearrangement of 3a -e seems un-
favorable since it would leave the formal charge on a
Str u ctu r e of 6e. Cell constants were determined using 40
reflections with θ between 27.4° and 34.2°. All of the hydrogen
positions were idealized except for that bonded to N(2), which
(8) Flack, H. D. Acta Crystallogr. 1983, A39, 876.

5330 Organometallics, Vol. 16, No. 24, 1997
Brauer et al.
was refined. The value of the absolute structure parameter,
-0.04(13), shows that the correct polarity was assigned to the
polar axis.
Str u ctu r e of 8. Cell constants were determined from 48
reflections with θ between 30.1° and 33.4°. Since the overall
structure is also consistent with that of its precursor, a
composite atom model (C/N) was used to test the identity of
the C(2) and N(2) atoms. Refinement of this model revealed
no significant disorder (2(2)%); therefore, an ordered structure
was assumed in the final refinement cycles.
2,2-Bis(tr iflu or om eth yl)-4-(d im eth ylim in io)-1,3-d iiso-
p r op yl-1,3-d ia za -2-bor a ta cyclobu ta n e (5a ). (CF3)2BNMe2
(1.93 g, 10 mmol) and diisopropylcarbodiimide (1.62 g, 10
mmol) were sealed in a small ampoule and kept for 2 weeks
at 60 °C. The ampoule was opened, all unreacted material
pumped off, and the residue crystallized from chloroform/
pentane: yield 89%; mp 160 °C. IR (cm-1): 1624 (s, ν(CdN)),
1086, 1050 (vs, ν(CF3)).
2,2-Bis(t r iflu or om et h yl)-1,3-d icycloh exyl-4-(d im et h -
ylim in io)-1,3-d ia za -2-bor a ta cyclobu ta n e (5b), 2,2-Bis(tr i-
flu or om eth yl)-4-(d im eth ylim in io)-1,3-d ip h en yl-1,3-d ia za -
2-b or a t a cyclob u t a n e (5c), 1,1-Bis(t r iflu or om et h yl)-2-
p h e n yl-2,4-d ia za -3-(d im e t h ylim in io)-1-b or a t a -1,2,3,4-
tetr a h yd r on a p h th a len e (6c), 2,2-Bis(tr iflu or om eth yl)-4-
(d im et h ylim in io)-1,3-b is(4-m et h ylp h en yl)-1,3-d ia za -2-
bor a ta cyclobu ta n e (5d ), 1,1-Bis(tr iflu or om eth yl)-2-(4-
m eth ylp h en yl)-7-m eth yl-2,4-d ia za -3-(d im eth ylim in io)-1-
b or a t a -1,2,3,4-t et r a h yd r on a p h t h a len e (6d ), 2,2-Bis-
(t r iflu or om e t h yl)-4-(d im e t h ylim in io)-1,3-b is(4-m e t h -
oxyp h en yl)-1,3-d ia za -2-bor a ta cyclobu ta n e (5e), a n d 1,1-
Bis(t r iflu or om et h yl)-2-(4-m et h oxyp h en yl)-7-m et h oxy-
2,4-d ia za -3-(d im et h ylim in io)-1-b or a t a -1,2,3,4-t et r a h y-
d r on a p h th a len e (6e). General procedure: To a stirred
solution of 10 mmol of the carbodiimide in 10 mL of pentane,
1.93 g (10 mmol) of (CF3)2BNMe2 was added dropwise at -78
°C. The reaction mixture was then allowed to warm to room
temperature as stirring was continued for 3 h. The solvent
and other volatile byproducts were removed in vacuo at 0.1
mbar/20 °C, and 5b, 5c/6c-5e/6e were crystallized from
chloroform/pentane. Thus, separation of the 5/6 mixture of
isomers was achieved only in part. Pure material for spec-
troscopic and structural investigations of 5c, 6d , and 6e was
obtained by manual selection of the differently shaped crystals.
5b: yield 94%; mp 195 °C. IR (cm-1); 1617 (s, ν(CdN), 1096,
1042 (vs, ν(CF3)). 5c/6c: yield 91%; 6c ∼190 °C (dec). IR
(cm-1): 1619 (s, ν(CdN)), 1077, 1051 (vs, ν(CF3)). 5d /6d : yield
86%; 6d ∼206 °C (dec). IR (cm-1): 3425 (s, ν(NH)), 1615 (s,
ν(CdN)), 1087 (vs, ν(CF3)). 5e/6e: yield 65%; 6e ∼200 °C (dec).
IR (cm-1): 3431 (s, ν(NH)), 1600 (s, ν(CdN)), 1080 (vs, ν(CF3)).
P r ep a r a tion of com p ou n d s. 3,3-Bis(tr iflu or om eth yl)-
4,4-d im eth yl-2-(m eth ylsu lfon yl)-1-th ia -2-a za -4-a zon ia -3-
bor a ta cyclobu ta n -1-on e (2a ), 3,3-Bis(tr iflu or om eth yl)-
4,4-d im et h yl-2-(et h ylsu lfon yl)-1-t h ia -2-a za -4-a zon ia -3-
bor a ta cyclobu ta n -1-on e (2b), 3,3-Bis(tr iflu or om eth yl)-
4,4-d im eth yl-2-(isop r op ylsu lfon yl)-1-th ia -2-a za -4-a zon ia -
3-bor a ta cyclobu ta n -1-on e (2c), 3,3-Bis(tr iflu or om eth yl)-
4,4-d im eth yl-2-(p h en ylsu lfon yl)-1-th ia -2-a za -4-a zon ia -3-
bor a ta cyclobu ta n -1-on e (2d ), 3,3-Bis(tr iflu or om eth yl)-
4,4-d im et h yl-2-((4-m et h ylp h en yl)su lfon yl)-1-t h ia -2-a za -
4-a zon ia -3-b or a t a cyclob u t a n -1-on e (2e), a n d 5,5-Bis-
(tr iflu or om eth yl)-1,1,1-tr iflu or o-6-m eth yl-4-th ia -3-a za -6-
a zon ia -5-bor a ta -h ep t-2-en -4-on e (9). To a stirred solution
of 10 mmol of N-sulfinyl reagent in 20 mL of CH2Cl2, 1.93 g
(10 mmol) of (CF3)2BNMe2 was added dropwise at 0 °C. The
reaction mixture was then allowed to warm to room temper-
ature as stirring was continued for 30 min. The solvent and
other volatile byproducts were removed in vacuo at 0.1 mbar/
20 °C. 9 was purified by sublimation at 25 °C/10-2 mbar and
condensed at -25 °C, whereas 2a -e were crystallized from
chloroform. 2a : yield 82%, mp 96 °C. IR (cm-1): 1370 (s,
νas(SO2)), 1153 (s, νs(SO2)), 1109 (vs, ν(CF3)). 2b: yield 78%,
mp 96 °C. IR (cm-1): 1378 (s, νas(SO2)), 1155 (s, νs(SO2)), 1103
vs ν(CF3)). 2c: yield 80%, mp 97 °C. IR (cm-1): 1366 (s,
νas(SO2)), 1147 (s, νs(SO2)), 1110 (vs, ν(CF3)). 2d : yield 88%,
mp 102 °C. IR (cm-1): 1356 (s, νas(SO2)), 1161 (s, νs(SO2)), 1103
(vs, ν(CF3)). 2e: yield 85%, mp 104 °C. IR (cm-1): 1352 (s,
νas(SO2)), 1159 (s, νs(SO2)), 1109 (vs, ν(CF3)). 9: yield 93%,
mp <30 °C. IR (cm-1): 3272 (w, ν(NH)), 1576 (w, ν(CdN)),
1107 (vs, ν(CF3)).
4,4-Bis(tr iflu or om eth yl)-2-(bis(tr im eth ylsilyl)a m in o)-
3,3-dim eth yl-1-(tr im eth ylsilyl)-1-a za -3-a zon ia -2-ph osp h a -
4-b or a t a cyclob u t a n e (3a ), 4,4-Bis(t r iflu or om et h yl)-2-
(2,2,6,6-t e t r a m e t h y lp i p e r i d y l)-3,3-d i m e t h y l-1-(t r i -
m eth ylsilyl)-1-a za -3-a zon ia -2-p h osp h a -4-bor a ta cyclobu -
ta n e (3b), 4,4-Bis(tr iflu or om eth yl)-2-(N-tr im eth ylsilyl-N-
ter t-bu tylam in o)-3,3-dim eth yl-1-ter t-bu tyl-1-aza-3-azon ia-
2-p h osp h a -4-b or a t a cyclob u t a n e (3c), 4,4-Bis(t r iflu or o-
m eth yl)-2-d i(isop r op yla m in o)-3,3-d im eth yl-1-ter t-bu tyl-
1-a za -3-a zon ia -2-p h osp h a -4-bor a ta cyclobu ta n e (3d ), a n d
4,4-Bis(tr iflu or om eth yl)-2-(2,2,6,6-tetr a m eth ylp ip er id yl)-
3,3-d im e t h yl-1-t er t -b u t yl-1-a za -3-a zon ia -2-p h osp h a -4-
bor a ta cyclobu ta n e (3e). To a stirred solution of 10 mmol
of aminoiminophosphine in 20 mL of pentane, 1.93 g (10 mmol)
of (CF3)2BNMe2 was added dropwise at 0 °C. The reaction
mixture was then allowed to warm to room temperature as
stirring was continued for 1 h. The solvent and other volatile
byproducts were removed in vacuo at 0.1 mbar/20 °C, and the
residue was crystallized from chloroform. 3a : yield 91%, mp
65 °C. IR (cm-1): 1110 (vs), 1091 (vs, ν(CF3)), 935 (vs, ν(PN/
SiN)). 3b: yield 90%, mp 70 °C (dec). IR (cm-1): 1104 (vs),
1088 (vs, ν(CF3)), 955 (s), 941 (s, ν(PN/SiN)). 3c: yield 85%,
mp 107 °C. IR (cm-1): 1113 (vs), 1069 (vs, ν(CF3)), 971 (s),
943 (s, 913 s ν(PN/SiN)). 3d : yield 94%, mp 127 °C. IR (cm-1):
1104 (vs), 1079 (vs, ν(CF3)), 954 (vs, ν(PN/SiN)). 3e: yield
89%, mp 98 °C (dec). IR (cm-1): 1106 (vs), 1069 (vs, ν(CF3)),
970 (vs, ν(PN/SiN)).
2,2-Bis(tr iflu or om eth yl)-3,3-d im eth yl-4-(dim eth ylim in -
io)-1-p h en yl-a za -2-bor a ta cyclobu ta n e (8). To a stirred
solution of dimethylketene-N-phenylimine (1.2 g, 8.3 mmol)
in 15 mL of pentane, (CF3)2BNMe2 (1.7 g, 8.8 mmol) was added
dropwise at -78 °C. The reaction mixture was then allowed
to warm to room temperature as stirring was continued for 1
h. The solvent and other volatile byproducts were removed
in vacuo at 0.1 mbar/20 °C, and 8 was crystallized from
ethanol/acetone: yield 78%; mp 130 °C (dec). IR cm-1: 1643
(vs, ν(CdN)), 1592, 1492 (s, ν(CdC)), 1078, 1040 (vs, ν(CF3)).
For elemental analyses see Table 3.
Ack n ow led gm en t. We thank Prof. Dr. C. Kru¨ger
of the Max Plank Institut fu¨r Kohlenforschung, Mu¨l-
heim/Ruhr, for measuring the X-ray data on 3c. Finan-
cial support by the Fonds der Chemischen Industrie is
gratefully acknowledged.
Su p p or tin g In for m a tion Ava ila ble: Tables of atomic
coordinates, hydrogen coordinates, anisotropic displacement
parameters, and bond lengths and angles for 2a , 3c′, 5c, 6d ,
6e, and 8 (22 pages). Ordering information is given on any
current masthead page.
OM970262I