Palladium-catalyzed insertion of alkynes into the Sn-B bond of a 2-stannyl-2,3-dihydro-1H-1,3,2-diazaborole and X-ray structure analyses of 1,3-di-tert-butyl-2[(Z)-2-phenyl-2-trimethylstannylethenyl]-2,3- dihydro-1H-1,3,2-diazaborole and 1,3-di-tert-butyl-2[(Z)-1-ethyl-2- phenyl-2-trimethylstannylethenyl]-2,3-dihydro-1H-1,3,2-diazaborole

Article abstract of DOI:10.1021/om000042w

Reaction of equimolar amounts of 1,3-di-tert-butyl-2-trimethylstannyl-2,3-dihydro-1H-1,3,2-di zaborole (1) with a series of alkynes R¹-C triple bond C-R² (2) (a: R¹ = H, R² = Ph; b: H, 4-ClC₆H₄; c: H, 4-BrC₆H₄; d: Ph, Ph; e: Me, Ph; f: Et, Ph; g: H, n-C₄H₉; h: Et, Et; i: H, n-C₆H₁₃) in the presence of a catalytic amount of [Pd(PPh₃)₄] (2 mol %) regioselectivity afforded high yields of the alkenes as the result of a cis-addition of the BSn bond of 1 to the acetylenic triple bond of 2. Spectroscopic evidence and X-ray structural analyses of 3a and 3f revealed that the bulky borolyl unit was added to the least sterically hindered end of the CC multiple bond.

Full text of DOI:10.1021/om000042w

Organometallics 2000, 19, 2891-2895
2891
P a lla d iu m -Ca ta lyzed In ser tion of Alk yn es in to th e Sn -B
Bon d of a 2-Sta n n yl-2,3-d ih yd r o-1H-1,3,2-d ia za bor ole a n d
X-r a y Str u ctu r e An a lyses of
1,3-Di-ter t-bu tyl-2[(Z)-2-p h en yl-2-tr im eth ylsta n n yleth en yl]-
2,3-d ih yd r o-1H-1,3,2-d ia za bor ole a n d
1,3-Di-ter t-bu tyl-2[(Z)-1-eth yl-2-p h en yl-2-
tr im eth ylsta n n yleth en yl]-2,3-d ih yd r o-1H-1,3,2-d ia za bor ole
Lothar Weber,* Henning B. Wartig, Hans-Georg Stammler, Anja Stammler, and
Beate Neumann
Fakulta¨t fu¨r Chemie der Universita¨t Bielefeld, Postfach 100 131, D-33501 Bielefeld, Germany
Received J anuary 18, 2000
Reaction of equimolar amounts of 1,3-di-tert-butyl-2-trimethylstannyl-2,3-dihydro-1H-1,3,2-
diazaborole (1) with a series of alkynes R1-CtC-R2 (2) (a : R1 ) H, R2 ) Ph; b: H, 4-ClC6H4;
c: H, 4-BrC6H4; d : Ph, Ph; e: Me, Ph; f: Et, Ph; g: H, n-C4H9; h : Et, Et; i: H, n-C6H13) in
the presence of a catalytic amount of [Pd(PPh3)4] (2 mol %) regioselectively afforded high
yields of the alkenes (Z)-R1[B]CdC(R2)SnMe3 (3a -h ) ([B] ) tBuNCHdCHN(tBu)B] as the
result of a cis-addition of the BSn bond of 1 to the acetylenic triple bond of 2. Spectroscopic
evidence and X-ray structural analyses of 3a and 3f revealed that the bulky borolyl unit
was added to the least sterically hindered end of the CC multiple bond.
In tr od u ction
can easily be converted into 2-cyano-, 2-isocyanato-,
2-isothiocyanato,10 2-hydro-, 2-alkyl-, 2-alkynyl-, and
2-stannyl-2,3-dihydro-1H-1,3,2-diazaboroles by halide
replacement with the respective nucleophile.
The synthesis of the first 2,3-dihydro-1H-1,3,2-diaz-
aboroles dates back to the early 1970s,1,2 and since then
a number of papers dedicated to the synthesis, struc-
ture, and bonding of such compounds have been
published.3-6 Besides the preparation of a few tricar-
bonyl chromium complexes7 and the cleavage of an
N-Si bond in some N-SiMe3-substituted 2,3-dihydro-
1H-1,3,2-diazaboroles by sodium amide or potassium
tert-butoxide,8 the chemistry of this ring system is
relatively undeveloped. A thorough investigation of the
chemical reactivity of 2,3-dihydro-1H-1,3,2-diazaboroles
was hampered mainly by the lack of functional substit-
uents in the molecules.
The aim of the work described herein was to provide
an efficient synthesis for 2-alkenyl-2,3-dihydro-1H-1,3,2-
diazaboroles which are highly functionalized at the
organic substituent at the boron center.
Resu lts a n d Discu ssion s
For the synthesis of 2-alkenyl-2,3-dihydro-1H-1,3,2-
diazaboroles III generally two strategies may be envis-
aged. A first approach involves sodium amalgam reduc-
tion of the corresponding borolium salt I, which should
be available by treatment of a 1,4-diazabutadiene with
an alkenylboron dihalide. A second route is based upon
the reaction of a 2-halo-1,3,2-diazaborole II with an
alkenyllithium or an alkenyl Grignard reagent.
A serious limitation of these synthetic pathways is
given in the fact that most functional groups (in the
alkenyl part) are reactive toward a Grignard or an
organolithium reagent.
Recently it was disclosed by J apanese scientists that
this problem to some extent can be circumvented by the
palladium-catalyzed borylsilylation of alkynes and bo-
rylsilylative carbocyclization of diynes, enynes, and
allenes.12-15 Similarly, the borylstannylation of alkynes
Recently we launched a program for the synthesis of
the 2-halo-2,3-dihydro-1H-1,3,2-diazaboroles9,10 as start-
ing materials for further chemical transformations. In
these studies it was demonstrated that these compounds
(1) Merriam, J . S.; Niedenzu, K. J . Organomet. Chem. 1973, 51, C1.
(2) Weber, L.; Schmid, G. Angew. Chem. 1974, 86, 519; Angew.
Chem., Int. Ed. Engl. 1974, 13, 467.
(3) Niedenzu, K.; Merriam, J . S. Z. Anorg. Allg. Chem. 1974, 406,
251.
(4) Kroner, J .; No¨th, H.; Niedenzu, K. J . Organomet. Chem. 1974,
71, 165.
(5) Schmid, G.; Schulze, J . Chem. Ber. 1977, 110, 2744.
(6) Schmid, G.; Polk, M.; Boese, R. Inorg. Chem. 1990, 29, 4421.
(7) (a) Schmid, G.; Schulze, J . Angew. Chem. 1977, 89, 258; Angew.
Chem., Int. Ed. Engl. 1977, 16, 249. (b) Schmid, G.; Schulze, J . Chem.
Ber. 1981, 114, 495.
(8) Schmid, G.; Lehr, J . Polk, M.; Boese, R. Angew. Chem. 1991,
103, 1029; Angew. Chem., Int. Ed. Engl. 1991, 30, 1015.
(9) Weber, L.; Dobbert, E.; Stammler, H.-G.; Neumann, B.; Boese,
R.; Bla¨ser, D. Chem. Ber./ Recl. 1997, 130, 705.
(10) Weber, L.; Dobbert, E.; Boese, R.; Kirchner, M. T.; Bla¨ser, D.
Eur. J . Inorg. Chem. 1998, 1145.
(11) Weber, L.; Dobbert, E.; Stammler, H.-G.; Neumann, B.; Boese,
R.; Bla¨ser, D. Eur. J . Inorg. Chem. 1999, 491, 1.
(12) Onozawa, S.; Hatanaka, Y.; Tanaka, M. Chem. Commun. 1997,
1229.
(13) Onozawa, S.; Hatanaka, Y.; Tanaka, M. Chem. Commun. 1999,
1863.
10.1021/om000042w CCC: $19.00 © 2000 American Chemical Society
Publication on Web 06/24/2000

2892 Organometallics, Vol. 19, No. 15, 2000
Weber et al.
Sch em e 1
Sch em e 2
NMR spectroscopic evidence of the compounds 3a , 3b,
3c, 3e, 3f, 3g, and 3i, however, indicated the selective
formation of a single product. This contrasts to some
extent with Tanaka’s work in which the cis-addition of
and borylstannylative carbocyclization reactions of diynes
and enynes were achieved using boron-tin compounds
such as Me3SnBN(Me)CH2CH2NMe and Me3SnB-
(NEt2)2.15-17
MeNCH2CH2N(Me)BSnMe3 to PhCtCMe (2e) fur-
nished an 85:15 mixture of the regioisomers C and D.16
These reports motivated us to synthesize 2-alkenyl-
2,3-dihydro-1H-diazaboroles via the palladium-assisted
borylstannylation of alkynes using 2-trimethylstannyl-
2,3-dihydro-1H-1,3,2-diazaborole 1. The latter reagent
is easily available in excellent yield from the reaction
of 1,3-di-tert-butyl-2-bromo-2,3-dihydro-1H-diazaborole
with an equimolar amount of in situ-generated LiSnMe3
(eq 1).11
The 119Sn{1H} NMR spectra of the products 3 display
singlet resonances in the region δ -45.6 to -58.0. In
the 11B{1H} NMR spectra of 3a -i the 11B nuclei give
rise to singlets in the narrow range δ 21.1-24.1, which
is typical for 2,3-dihydro-1H-1,3,2-diazaboroles with
organic substituents on the boron atom.1,5,6 The boron
atoms in 3 are markedly shielded when compared with
Tanaka’s borylstannylation products, in which the boron
Reaction of 1 and equimolar amounts of alkynes 2a -i
in the presence of a catalytic amount (2 mol %) of [Pd-
(PPh3)4] in refluxing benzene led to the regio- and
stereoselective formation of alkenes 3a -i. Products
3a -f were obtained as colorless crystals from n-pentane,
whereas 3g-i were isolated as colorless oils by vacuum
distillation (Scheme 2). It is obvious that this addition
reaction proceeds equally well with terminal and inter-
nal alkynes.
However, the attempted borylstannylation of tert-
butylacetylene, phenyl(trimethylsilyl)acetylene, prop-
argylic alcohol, and dimethyl acetylenedicarboxylate
with 1 failed. Basicly, the reaction of unsymmetrically
substituted alkynes such as 2a , 2b, 2c, 2e, 2f, 2g, and
2i could result in formation of regioisomers such as A
and B.
is incorporated in a saturated MeNCH2-CH2N(Me)-B
ring (δ 30.5-30.8).16 The vinylic protons in the 1H NMR
spectra of 3a -c, 3g, and 3i appear as singlets at δ 6.97-
7.28. Coupling with the tin atoms was not detectable.
We therefore assume, in line with Tanaka’s results, that
the 1,3,2-diazaborolyl unit of 1 is attached to the
sterically less hindered end of the alkyne reactant. This
is confirmed by the X-ray analyses of 3a and 3f. The
13C NMR signals of the borylated carbon atoms of the
CdC double bond of 3a -i appear as broad singlets at δ
132.4-147.2 and are slightly shielded with respect to
the stannylated carbon atoms of the alkenes (δ 150.5-
156.3).
The regiochemistry of 3f was unambigiously revealed
by X-ray crystallography, showing that the borolyl unit
was attached to the alkylated carbon of the CdC bond,
and the same obviously holds true for 3e.
(14) Suginome, M.; Matsuda, T.; Nakamura, H.; Ito, Y. Tetrahedron
1999, 55, 8787.
(15) Review: Han, L.-B.; Tanaka, M. Chem. Commun. 1999, 395.
(16) Onozawa, S.; Hatanaka, Y.; Sakakura, T.; Shimada, S.; Tanaka,
M. Organometallics 1996, 15, 5450.

Pd-Catalyzed Insertion of Alkynes
Organometallics, Vol. 19, No. 15, 2000 2893
F igu r e 2. Molecular structure of 3f in the crystal.
Selected bond lengths (Å) and angles (deg): B-N(1)
1.444(3), B-N(2) 1.443(3), C(11)-C(14) 1.349(3), N(1)-C(3)
1.484(3), N(2)-C(7) 1.488(3), Sn(1)-C(14) 2.164(2), N(1)-
C(1) 1.400(3), N(2)-C(2) 1.399(3), C(14)-C(18) 1.495(3),
C(1)-C(2) 1.336(4), B-C(11) 1.577(3), C(11)-C(12)
1.529(3), Sn-C(15) 2.133(3), Sn-C(14) 2.138(3), Sn-C(17)
F igu r e 1. Molecular structure of 3a in the crystal.
Selected bond lengths (Å) and angles (deg): B-N(1)
1.438(3), N(1)-C(11) 1.401(3), N(1)-C(12) 1.491(3), C(11)-
C(11A) 1.341(5), B-C(10) 1.581(5), C(7)-C(10) 1.345(4),
Sn-C(7) 2.179(3), C(6)-C(7) 1.500(4), Sn-C(8) 2.146(3),
Sn-C(9) 2.147(4), N(1)-B-N(1A) 105.9(3), B-N(1)-C(11)
107.1(2), N(1)-C(11)-C(11A) 109.9(1), B-N(1)-C(12)
130.8(2), C(11)-N(1)-C(12) 122.1(2), N(1)-B-C(10)
127.0(1), B-C(10)-C(7) 129.5(3), Sn-C(7)-C(10) 121.7(2),
C(6)-C(7)-C(10) 121.5(3), Sn-C(7)-C(6)116.8(2), C(8)-
Sn-C(8A) 110.1(2), C(8)-Sn-C(9) 105.7(1), C(8)-Sn-C(7)
109.8(1), C(7)-Sn-C(9) 115.6(1).
2.145(2),
N(1)-B-N(2)
105.27(17),
B-N(1)-C(1)
107.32(18), N(1)-C(1)-C(2) 110.0(2), C(1)-C(2)-N(2)
110.03(19), C(2)-N(2)-B 107.33(18), B-N(1)-C(3)
134.71(17), B-N(2)-C(7) 134.42(19), C(2)-N(2)-C(7)
119.92(18), C(1)-N(1)-C(3) 117.92(18), N(1)-B-C(11)
128.08(19), N(2)-B-C(11) 126.64(19), B-C(11)-C(14)
120.78(18), B-C(11)-C(12) 119.37(18), C(12)-C(11)-C(14)
119.84(18), C(11)-C(14)-Sn 126.83(15), Sn-C(14)-C(18)
110.41(14), C(11)-C(14)-C(18) 122.75(18), C(14)-Sn-
C(15) 105.66(10), C(14)-Sn-C(16) 107.13(10), C(14)-Sn-
C(17) 119.24(9), C(15)-Sn-C(16) 108.83(15), C(16)-Sn-
C(17) 106.14(12), C(15)-Sn-C(17) 109.53(13).
X-r a y Str u ctu r a l An a lysis of 3a . No X-ray struc-
tural information on simple borylstannylation products
of monoalkynes has been published to date, although
the molecular structure of the borylstannylative car-
bocyclization product 4 (obtained from 4-MeC6H4S-
nuclear distances and valence angles within the diaz-
aborolyl ring are in good agreement with the respective
data for 1 and merit no further discussion.6,11
(O)2N[CH2-CtCH]2 and MeNCH2CH2N(Me)BSnMe3)
was elucidated by X-ray analysis.17
X-r a y Str u ctu r a l An a lysis of 3f. To unambigiously
determine the regiochemistry of the borylstannylation
product of an unsymmetrical CC triple bond, an X-ray
structural analysis of 3f was performed. Single crystals
were grown from n-pentane at -30 °C. The molecular
structure of 3f (Figure 2) displays a planar 1,3,2-
diazaborole ring which is attached to a (1-ethyl-2-
phenyl-2-trimethylstannyl)ethenyl group via a B-C
single bond of 1.577(3) Å. Again the borolyl group
prefers the lesser congested end of the CC multiple
bond. Bonding parameters within the heterocyclic unit
of 3f are comparable with the situation in 3a . The
difference between the two structures arises from the
orientation of the phenyl rings at the heavily substituted
alkenyl group with respect to the plane of the 1,3,2-
diazaborolyl ring.
In both structures the plane defined by the boron
atom, the tin atom, and the two carbon atoms of the
CC double bond is oriented perpendicularly to the plane
of the heterocycle. In 3a the phenyl ring is included in
the plane of the substituent, whereas in 3f the phenyl
group is orthogonal to the plane with the atoms B(1),
C(11), C(14), and Sn(1) and is parallel to the plane of
the heterocycle (Figure 3). Relevant torsion angles are
N(1)-B(1)-C(11)-C(14) ) 86.7°, N(2)-B(1)-C(11)-
C(14) ) -92.0°, B(1)-C(11)-C(14)-Sn(1) ) -3.5°,
B(1)-C(11)-C(14)-C(18) ) 178.0°, C(11)-C(14)-C(18)-
C(19) ) -86.7°, and C(11)-C(14)-C(18)-C(23) ) 96.7°.
Single crystals of 3a were grown from n-pentane at
-30 °C and were structurally investigated. The molec-
ular structure of 3a (Figure 1) features a planar 1,3,2-
diazaborole ring with a (2-phenyl-2-trimethylstannyl)-
ethenyl substituent which is linked to the boron atom
via a B-C single bond of 1.581(5) Å. The plane defined
by the atoms of the phenyl ring, B, Sn, C(7), C(10), and
C(9) bisects the plane of the heterocycle. Clearly, the
Me3Sn group and the heterocycle are located in a cis-
disposition at the double bond C(7)-C(10) [1.345(4) Å],
whereby the tin atom and the ipso carbon atom of the
phenyl ring are attached to C(7). The bond Sn-C(7) of
2.179(3) Å is elongated when compared with the bond
lengths Sn-C(8) [2.146(3) Å] and Sn-C(9) [2.147(4) Å].
Due to steric congestion, the valence angles B-C(10)-
C(7) [129.5(3)°] and C(7)-Sn-C(9) [115.6(1)°] are mark-
edly opened in comparison to the angles at C(7) [116.8-
(2)-121.7(2)°] and C(8)-Sn-C(9) [105.7(1)°], C(8)-Sn-
C(7) [109.8(1)°], and C(8)-Sn-C(8A) [110.1(2)°]. Inter-
(17) Onozawa, S.; Hatanaka, Y.; Choi, N.; Tanaka, M. Organome-
tallics 1997, 16, 5389.

2894 Organometallics, Vol. 19, No. 15, 2000
Weber et al.
(98) [tBuNCHdCHN(tBu)BH+]. Anal. Calcd for C21H35BN2Sn
(445.04): C, 56.80; H, 7.72; N, 6.31. Found: C, 56.81; H, 7.87;
N, 6.31.
1,3-Di-ter t-b u t yl-2[(Z)-2-p -ch lor op h en yl-2-t r im et h yl-
sta n n yleth en yl]-2,3-d ih yd r o-1H-1,3,2-d ia za bor ole (3b).
1
Yield: 78%, mp 106 °C. H NMR: δ 0.12 [s, 9H, J SnH ) 52.1
Hz, Sn(CH3)3], 1.36 [s, 18H, C(CH3)3], 6.34 (s, 2H, NCH), 7.17
(s, 1H, BCH), 7.24 (m, 4H, Ph). 13C{1H} NMR: δ -8.1 (s, 1J SnC
) 321.4 Hz, SnCH3), 32.3 [s, C(CH3)3], 52.9 [s, C(CH3)3], 112.9
(s, NCH), 127.2 (s, Ph), 128.7 (s, Ph), 131.8 (s, Ph), 146.8 (s,
3
br, BCH), 148.4 (s, J SnC ) 50.6 Hz, iC-Ph), 154.5 (s, SnCd).
11B{1H] NMR: δ 21.1 s. 119Sn{1H} NMR: δ -47.4 s. MS/EI:
m/z (relative intensity) 480 (9) [M+], 180 (100) [tBuNCHd
CHN(tBu)BH+]. Anal. Calcd for C21H34BClN2Sn (479.49): C,
52.60; H, 7.15; N, 5.84. Found: C, 52.79; H, 6.95; N, 5.88.
1,3-Di-ter t-b u t yl-2[(Z)-2-p -b r om op h en yl-2-t r im et h yl-
st a n n ylet h en yl]-2,3-d ih yd r o-1H -1,3,2-d ia za b or ole (3c).
Yield: 52% after 3× recrystallization (crude yield 93%), mp
F igu r e 3. Molecular structure of 3f with a view in the
plane of the 1,3,2-diazaborole ring.
2
123 °C. 1H NMR: δ 0.10 [s, 9H, J SnH ) 52.1 Hz, Sn(CH3)3],
1.31 [s, 18H, C(CH3)3], 6.31 (s, 2H, NCH), 7.05 (d, J HH ) 8.8
Hz, 2H, Ph), 7.17 (s, 1H, BCH), 7.31 (d, J HH ) 8.3 Hz, 2H,
Ph). 13C {1H} NMR: δ -7.9 (s, 1J SnC ) 337.8 Hz, SnCH3), 32.5
[s, C(CH3)3], 53.1 [s, C(CH3)3], 113.2 (s, NCH), 120.1 (s, Ph),
127.8 (s, Ph), 128.3 (s, Ph), 131.9 (s, Ph), 147.2 (s, br, BCH)
149.1 (s, Ph), 154.7 (s, SnCd). 11B{1H} NMR: δ 23.4 s. 119Sn-
{1H} NMR: δ -47.5 s. MS/EI: m/z (relative intensity) 524 (8)
Exp er im en ta l Section
All operations were performed under dry, oxygen-free di-
nitrogen using standard Schlenk techniques. Solvents were
dried by standard methods and freshly distilled under nitrogen
prior to use. 1H, 11B, 13C, and 119Sn NMR spectra were recorded
in C6D6 at 22 °C using Bruker AC 100 (1H, 100.13 MHz, 11B,
32.13 MHz) and Bruker Avance DRX 500 (1H, 500.13 MHz,
11B, 160.46 MHz, 13C, 125.75 MHz, 119Sn, 186.51 MHz)
spectrometers. References: SiMe4 (1H, 13C), BF3‚OEt2 (11B),
[M+], 453 (6) [M+ - Br], 180 (100) [tBuNCHdCHN(tBu)BH+].
Anal. Calcd for C21H34BBrN2Sn (523.94): C, 48.14; H, 6.54;
N, 5.35. Found C, 48.22; H, 6.35; N, 5.31.
1,3-D i -t er t -b u t y l-2[(Z )-1,2-d i p h e n y l-2-t r i m e t h y l-
sta n n yleth en yl]-2,3-d ih yd r o-1H-1,3,2-d ia za bor ole (3d ).
SnMe4 (
119Sn). Elemental analyses were performed at the
Microanalytical Laboratory of the University of Bielefeld.
1
2
Yield: 74%, mp 114 °C. H NMR: δ 0.12 [s, J SnH ) 50.9 Hz,
9H, Sn(CH3)3], 1.40 [s, 18H, C(CH3)3], 6.37 (s, 2H, NCH), 6.94
(m, 4H, Ph), 7.14 (m, 4H, Ph), 7.31 (d, 3J HH ) 7.6 Hz, 6H, Ph).
Compounds tBuNCHdCHN(tBu)BSnMe3 (1),11 p-chlorophen-
ylacetylene,18 and [Pd(PPh3)4]19 were synthesized according to
literature procedures. All other alkynes employed in this work
were purchased from Aldrich.
Gen er a l P r oced u r e for th e Syn th eses of 2-(â-Sta n n yl-
a lk en yl)-1,3,2-d ia za bor oles (3a -i). A sample of the 1,3,2-
1
13C{1H} NMR: δ -7.9 [s, J SnC ) 331.0 Hz, SnCH3], 32.1 [s,
C(CH3)3], 53.9 [s, C(CH3)3], 114.1 (s, NCH), 125.4 (s, Ph), 126.0
(s, Ph), 126.6 (s, Ph), 128.9 (s, Ph), 131.6 (s, Ph), 143.4 (s, BC)),
3
148.2 (s, J SnC ) 57.5 Hz, iC-Ph), 155.2 (s, SnCd). 11B{1H}
NMR: δ 24.1 s. 119Sn{1H} NMR: δ -45.6 s. MS/EI: m/z
diazaborole tBuNCHdCHN(tBu)BSnMe3 (1) (0.450 g, 1.30
mmol) and 2 mol % of the catalyst [Pd(PPh3)4] (0.030 g, 0.026
mmol) were dissolved in benzene (5 mL) at room temperature.
An equimolar amount of the respective alkyne was added, and
the mixture was heated at 80 °C for 2 h. After cooling to
ambient temperature, solvent and volatile components were
removed in vacuo. The residue was dissolved in 20 mL of
n-pentane and filtered. The concentrated filtrate (ca. 5 mL)
was stored at -30 °C to afford the crude products 3a -f as
black crystals. Recrystallization from n-pentane gave analyti-
cally pure materials. In the case of 3g-i the pentane extracts
were freed from solvent and the oily residues were purified
by vacuum distillation to yield 3g-i as colorless oils. The
distillation flask was heated by the air stream (ca. 400 °C) of
a hot air gun.
(relative intensity) 522 (9) [M+], 357 (100) [M+
-
120SnMe3],
178 (69) [tBuNCHdCHN(tBu)BH+]. Anal. Calcd for C27H39N2-
Sn (521.09): C, 62.23; H, 7.54; N, 5.38. Found: C, 62.54; H,
7.55; N, 5.33.
1,3-Di-ter t-bu tyl-2-[(Z)-1-m eth yl-2-p h en yl-2-tr im eth yl-
st a n n ylet h en yl]-2,3-d ih yd r o-1H -1,3,2-d ia za b or ole (3e).
2
Yield: 84%, mp 68 °C. 1H NMR: δ 0.04 [s, J SnH ) 52.1 Hz,
9H, Sn(CH3)3], 1.34 [s, 18H, C(CH3)3], 1.92 (s, 3J SnH ) 63.1 Hz,
3H, C-CH3), 6.29 (s, 2H, NCH), 7.00-7.25 (m, 5H, Ph). 13C-
{1H} NMR: δ -8.8 (s, 1J SnC ) 316.4 Hz, SnCH3), 23.3 (s, 3J SnC
) 69.0 Hz, C-CH3), 32.1 [s, C(CH3)3], 53.5 [s, C(CH3)3], 113.4
(s, NCH), 125.2 (s, Ph), 126.3 (s, Ph), 134.2 (s, Ph), 138.1 (s,
3
br, BC), 147.3 (s, J SnC ) 46.0 Hz, iC-Ph), 152.3 (s, SnCd).
11B{1H} NMR: δ 24.0 s. 119Sn{1H} NMR: δ -51.9 s. MS/EI:
m/z (relative intensity) 460 (9) [M+]. Anal. Calcd for C22H37
-
1,3-Di-ter t-bu tyl-2[(Z)-2-p h en yl-2-tr im eth ylsta n n yleth -
en yl]2,3-d ih yd r o-1H-1,3,2-d ia za bor ole (3a ). Yield: 84%,
BN2Sn (459.07): C, 57.56; H, 8.12; N, 6.10. Found: C, 57.76;
H, 8.38; N, 5.89.
1
mp 79 °C. H NMR: δ 0.15 [s, J SnH ) 52.7 Hz, 9H, Sn(CH3)3],
1.35 [s, 18H, C(CH3)3], 6.32 (s, 2H, NCH), 7.08 (t, J HH ) 7.3
Hz, 1H, Ph), 7.23 (t, J HH ) 7.8 Hz, 2H, Ph), 7.28 (s, 1H, BCH),
7.38 (d, J HH ) 7.5 Hz, 2H, Ph). 13C{1H} NMR: δ -7.7 (s, 1J SnC
) 319.6 Hz, SnCH3), 32.6 [s, C(CH3)3], 53.1 [s, C(CH3)3], 113.1
1,3-Di-ter t-b u t yl-2-[(Z)-1-et h yl-2-p h en yl-2-t r im et h yl-
st a n n ylet h en yl]-2,3-d ih yd r o-1H -1,3,2-d ia za b or ole (3f).
3
Yield: 89%, mp 72 °C. 1H NMR: δ 0.04 [s, J SnH ) 50.7 Hz,
3
Sn(CH3)3], 0.98 (t, J HH ) 7.7 Hz, 3H, CH2CH3), 1.41 [s, 18H,
(s, NCH), 126.2 (s, Ph), 127.8 (s, Ph), 128.8 (s, Ph), 146.1 (s,
3
C(CH3)3], 2.35 (q, J HH ) 7.7 Hz, 2H, CH2CH3), 6.31 (s, 2H,
1
br, BCH), 150.2 (s, J SnC ) 49.4 Hz, iC-Ph), 155.9 (d, J SnC
)
1
NCH), 7.00-7.25 (m, 5H, Ph). 13C{1H} NMR: δ -8.9 (s, J SnC
469.2 Hz, SnCd). 11B{1H} NMR: δ 23.6 s. 119Sn{1H} NMR: δ
-48.9 s. MS/EI: m/z (relative intensity) 446 (100) [M+], 180
3
) 329.9 Hz, SnCH3), 14.3 (s, CH2CH3), 29.4 (s, J SnC ) 66.7
Hz, CH2CH3), 32.2 [s, C(CH3)3], 53.6 [s, C(CH3)3], 113.9 (s,
NCH), 125.1 (s, Ph), 125.9 (s, Ph), 134.2 (s, Ph), 138.0 (s, br,
BCd), 147.7 (s, 3J SnC ) 46.0 Hz, iC-Ph), 151.3 (s, 1J SnC ) 498.6
Hz, SnCd). 11B{1H} NMR: δ 23.4 s. 119Sn{1H} NMR: δ -54.2
s. MS/EI: m/z (relative intensity) 474 (14) [M+], 309 (100) [M+
(18) Vaughn, T. H.; Nieuwland, J . A. J . Am. Chem. Soc. 1934, 56,
1207.
(19) Coulson, D. R. In Inorganic Synthesis; Angelici, R. J ., Ed.; 1990;
Vol. 28 pp 107-109.

Pd-Catalyzed Insertion of Alkynes
Organometallics, Vol. 19, No. 15, 2000 2895
- SnMe3]. Anal. Calcd for C23H39BN2Sn (473.10): C, 58.39;
H, 8.31; N, 5.92. Found: C, 58.47; H, 8.28; N, 6.04.
the approximate dimensions of 1.1 × 1.0 × 0.9 mm3 was
measured on a Siemens P(2)1 diffractometer with Mo KR
radiation (λ ) 0.71073 Å) at 173 K. Crystal data and refine-
ment details (refined from the diffractometer angles of 50
centered reflections): a ) 14.374(5) Å, b ) 12.352(4) Å, c )
25.628(7) Å, V ) 4550(2) Å3, Z ) 8, dcalcd ) 1.299 g cm-3, µ )
1.129 mm-1, space group Cmca, data collection of 3430 unique
intensities (2θmax ) 60°), structure solution by direct methods
and anisotropic refinement with full-matrix least-squares
methods on F2 for all non hydrogen atoms (program used
Siemens SHELXTL plus/SHELXL-97, riding model for hydro-
gen atoms, 134 parameters, maximum residual electron
density 0.9 e/Å3, RF ) 0.031 based on 2940 reflections with
1,3-Di-ter t-bu tyl-2-[(Z)-2-tr im eth ylsta n n ylh ex-1-en yl]-
2,3-d ih yd r o-1H-1,3,2-d ia za bor ole (3g). Yield: 77%, bp ca.
2
350 °C/5‚10-5 bar. 1H NMR: δ 0.12 [s, J SnH ) 50.9 Hz, 9H,
3
Sn(CH3)3], 0.94 (t, J HH ) 7.2 Hz, 3H, CH3CH2), 1.33 [s, 18H,
C(CH3)3], 1.35 (m, 2H, CH2), 1.54 (q, 2H, 3J HH ) 5.0 Hz, CH2),
3
2.46 (t, J HH ) 6.9 Hz, dC-CH2), 6.30 (s, 2H, NCH), 6.95 (s,
1H, BCH). 13C{1H} NMR: δ -8.4 (s, 1J SnC ) 323.2 Hz, SnCH3),
14.2 (s, CH3), 23.1 (s, CH2), 32.5 [s, C(CH3)3], 44.7 (s, CH2),
53.0 [s, C(CH3)3], 112.7 (s, NCH), 143.1 (s, br, BC), 156.3 (s,
SnCd). 11B{1H} NMR: δ 23.6 s. 119Sn{1H} NMR: δ -53.1 s.
MS/EI: m/z (relative intensity) 426 (100) [M+]. Anal. Calcd
for C19H39BN2Sn (425.05): C, 53.69; H, 9.25; N, 6.59. Found:
C, 53.64; H, 9.15; N, 6.53.
2
(I > 2σ(I)), wRF ) 0.079.
X-r a y Str u ctu r a l An a lysis of 3f. Single crystals of 3f were
grown from n-pentane at -30 °C. A colorless crystal with the
approximate dimensions of 0.9 × 0.6 × 0.5 mm3 was measured
on a Siemens P(2)1 diffractometer with Mo KR radiation (λ )
0.71073 Å) at 173 K. Crystal data and refinement details
(refined from the diffractometer angles of 50 centered reflec-
tions): a ) 15.006(6) Å, b ) 10.376(6) Å, c ) 16.364(8) Å, â )
105.68(4)°, V ) 2453(2) Å3, Z ) 4, dcalcd ) 1.281 g cm-3, µ )
1.051 mm-1, space group P21/n, data collection of 7141 unique
intensities (2θmax ) 60°), structure solution by direct methods
and anisotropic refinement with full-matrix least-squares
methods on F2 for all non hydrogen atoms (program used
Siemens SHELXTL plus/SHELXL-97, riding model for hydro-
gen atoms, 266 parameters, maximum residual electron
density 0.812 e/Å3; RF ) 0.0325 based on 6209 reflections with
1,3-Di-ter t-bu tyl-2-[(Z)-2-eth yl-2-tr im eth ylsta n n ylbu t-
1-en yl]-2,3-d ih yd r o-1H-1,3,2-d ia za bor ole (3h ). Yield: 66%,
1
2
bp ca. 350 °C/5‚10-5 bar. H NMR: δ 0.12 [s, J SnH ) 50.9 Hz,
3
9H, Sn(CH3)3], 1.04 (t, J HH ) 7.6 Hz, 3H, CH2CH3), 1.08 (t,
3J HH ) 7.7 Hz, 3H, CH2CH3), 1.31 [s, 18H, C(CH3)3], 2.40 (q,
3J HH ) 7.6 Hz, 2H, CH2CH3), 2.48 (q, 3J HH ) 7.8 Hz, 2H, CH2-
CH3), 6.26 (s, 2H, NCH. 13C{1H} NMR: δ -8.2 (s, 1J SnC ) 316.0
Hz, SnCH3), 12.2 (s, CH3), 14.2 (s CH3), 26.0 (s, CH2), 28.2 (s,
CH2), 32.2 [s, C(CH3)3], 53.4 [s, C(CH3)3], 114.1 (s, NCH), 132.4
(s, BC), 150.5 (s, SnCd). 11B{1H} NMR: δ 23.3 s. 119Sn{1H}
NMR: δ -58.0 s. MS/EI: m/z (relative intensity) 426 (14) [M+].
Anal. Calcd for C19H39BN2Sn (425.05): C, 53.69; H, 9.25; N,
6.59. Found: C, 53.56; H, 9.21; N, 6.24.
1,3-Di-ter t-bu tyl-2-[(Z)-2-tr im eth ylsta n n yloct-1-en yl]-
2,3-d ih yd r o-1H-d ia za bor ole (3i). Yield: 82%, bp ca. 400 °C/
5‚10-5 bar. 1H NMR: δ 0.15 [s, 2J SnH ) 52.1 Hz, 9H, Sn(CH3)3],
2
(I > 2σ(I)), wRF ) 0.0830 for all data. Disorder of tert-butyl
group C(8)-C(10) on three positions (42:32:26).
3
0.91 (t, J HH ) 7.2 Hz, 3H, CH2CH3), 1.32 (m, 6H, CH2), 1.34
3
[s, 18H, C(CH3)3], 1.59 (q, J HH ) 7.1 Hz, 2H, CH2), 2.48 (t,
Ack n ow led gm en t. The present work was finan-
cially supported by the Deutsche Forschungsgemein-
schaft (Bonn, Germany) and the Fonds der Chemischen
Industrie (Frankfurt/M., Germany), which is gratefully
acknowledged.
3J HH ) 7.2 Hz, dC-CH2), 6.30 (s, 2H, NCH), 6.97 (s, 1H, BCH).
1
13C{1H} NMR: δ -8.4 (s, J SnC ) 263.2 Hz, SnCH3), 14.4 (s,
CH3), 23.1 (s, CH2), 23.2 (s, CH2), 29.2 (s, CH2), 29.8 (s, CH2),
32.1 [s, C(CH3)3], 45.0 (s, dC-CH2), 53.0 [s, C(CH3)3], 112.7
(s, NCH), 142.8 (s, br, BC), 156.3 (s, dCSn), 157.5 (s, BCH).
11B{1H} NMR: δ 23.6 s. 119Sn{1H} NMR: δ -53.2 s. MS/EI:
Su p p or tin g In for m a tion Ava ila ble: Table of X-ray data,
atomic coordinates, thermal parameters, and complete bond
distances and angles and thermal ellipsoid plots for compound
3a . This material is available free of charge via the Internet
at http://pubs.acs.org.
m/z (relative intensity) 455 (18) [M+], 180 (100) [tBuNCH2-
CH2N(tBu)BH+]. Anal. Calcd for C21H43BN2Sn (453.10): C,
55.67; H, 9.57; N, 6.18. Found: C, 55.90; H, 9.69; N, 5.99.
X-r a y Str u ctu r a l An a lysis of 3a . Single crystals of 3a
were grown from n-pentane at -30 °C. A colorless crystal with
OM000042W