Abstract:Bei der exothermen Reaktion der 1,2‐Dicarbaundecaborate von Alkalimetallen (I) mit Natriumnitrit und Wasser in Gegenwart von Säuren entstehen neben anderen Produkten die Azacarborane (II) und (III).
“…Isoelectronic with the 11-vertex thiaborane and phosphaborane clusters 1 and 2 are the thia- and phosphadicarbaboranes of the general formula EC 2 B 8 H 10 (E = S, RP). While no previous phosphadicarbaborane has been reported, one thiadicarbaborane, nido -7,9,10-SC 2 B 8 H 10 , has been previously synthesized in a 30% yield from the reaction of aqueous bisulfate with K + C 2 B 9 H 12 - . The structure of this compound has been confirmed by both electron diffraction and ab initio/NMR calculations. , …”
Section: Resultsmentioning
confidence: 89%
“… 4 Comparison of the experimental chemical shifts and assignments for 3 with those DFT/GIAO calculated values for nido -7,10,11-SC 2 B 8 H 10 ( III.a ), nido -7,9,11-SC 2 B 8 H 10 ( III.b ), and nido -7,9,10-SC 2 B 8 H 10 ( III.c ). Experimentally observed 11 B NMR shifts for nido -7,9,10-SC 2 B 8 H 10 : −2.8(B5), −7.4(B2,3), −13.0(B8,11), −13.8(B4,6), −41.5(B1). , …”
A synthetic sequence involving the reaction of a phosphorus or sulfur dihalide with a monoanionic boron cluster
followed by an in situ dehydrohalogenation reaction initiated by proton sponge results in the clean insertion of
the heteroatom into the cage framework. Using this method, a range of nido-11-vertex thia- and phosphaboranes,
thia- and phosphadicarbaboranes, and the first thiaphosphaborane has been produced in high yields. Thus, the
reaction of decaborane with SCl2 or RPCl2 and excess proton sponge gave the known anions, nido-7-SB10H11
-
(1
-) and nido-7-RPB10H11
- [2a
- (R = Me) and 2b
- (R = Ph)], respectively. Acidification of 1
-, 2a
-, and 2b
-
resulted in the isolation of nido-7-SB10H12 (1) and nido-7-RPB10H12 (2a and 2b), respectively, in near-quantitative
yields. Reaction of nido-5,6-C2B8H12 with SCl2 or RPCl2 in the presence of proton sponge produced the new
compounds, nido-7,10,11-SC2B8H10 (3) (77%) and nido-7,10,11-RPC2B8H10 [R = Me (97%) 4a, Ph (83%) 4b],
respectively. Reaction of arachno-6-SB9H11 with PhPCl2 and proton sponge resulted in the formation of the new
mixed heteroatom cage, nido-10-Ph-7,10-SPB9H9 (5), which is the first example of a thiaphosphaborane cluster.
Consistent with their nido skeletal electron counts, all clusters were shown by spectroscopic and DFT/GIAO
computational studies to have similar cage frameworks containing a five-membered open face.
“…Isoelectronic with the 11-vertex thiaborane and phosphaborane clusters 1 and 2 are the thia- and phosphadicarbaboranes of the general formula EC 2 B 8 H 10 (E = S, RP). While no previous phosphadicarbaborane has been reported, one thiadicarbaborane, nido -7,9,10-SC 2 B 8 H 10 , has been previously synthesized in a 30% yield from the reaction of aqueous bisulfate with K + C 2 B 9 H 12 - . The structure of this compound has been confirmed by both electron diffraction and ab initio/NMR calculations. , …”
Section: Resultsmentioning
confidence: 89%
“… 4 Comparison of the experimental chemical shifts and assignments for 3 with those DFT/GIAO calculated values for nido -7,10,11-SC 2 B 8 H 10 ( III.a ), nido -7,9,11-SC 2 B 8 H 10 ( III.b ), and nido -7,9,10-SC 2 B 8 H 10 ( III.c ). Experimentally observed 11 B NMR shifts for nido -7,9,10-SC 2 B 8 H 10 : −2.8(B5), −7.4(B2,3), −13.0(B8,11), −13.8(B4,6), −41.5(B1). , …”
A synthetic sequence involving the reaction of a phosphorus or sulfur dihalide with a monoanionic boron cluster
followed by an in situ dehydrohalogenation reaction initiated by proton sponge results in the clean insertion of
the heteroatom into the cage framework. Using this method, a range of nido-11-vertex thia- and phosphaboranes,
thia- and phosphadicarbaboranes, and the first thiaphosphaborane has been produced in high yields. Thus, the
reaction of decaborane with SCl2 or RPCl2 and excess proton sponge gave the known anions, nido-7-SB10H11
-
(1
-) and nido-7-RPB10H11
- [2a
- (R = Me) and 2b
- (R = Ph)], respectively. Acidification of 1
-, 2a
-, and 2b
-
resulted in the isolation of nido-7-SB10H12 (1) and nido-7-RPB10H12 (2a and 2b), respectively, in near-quantitative
yields. Reaction of nido-5,6-C2B8H12 with SCl2 or RPCl2 in the presence of proton sponge produced the new
compounds, nido-7,10,11-SC2B8H10 (3) (77%) and nido-7,10,11-RPC2B8H10 [R = Me (97%) 4a, Ph (83%) 4b],
respectively. Reaction of arachno-6-SB9H11 with PhPCl2 and proton sponge resulted in the formation of the new
mixed heteroatom cage, nido-10-Ph-7,10-SPB9H9 (5), which is the first example of a thiaphosphaborane cluster.
Consistent with their nido skeletal electron counts, all clusters were shown by spectroscopic and DFT/GIAO
computational studies to have similar cage frameworks containing a five-membered open face.
“…Similar patterns also are found for all isoelectronic compounds of the 11-vertex nido series lacking B-H-B bridges on the open face, such as isomeric nido tetracarbaboranes 7,8,9,10-C 4 B 7 H 11 (compound 6 in Figure 6), 18 2,7,9,10-C 4 B 7 H 11 , 18 and 1,7,8,10-C 4 B 7 H 11 , 18,19 along with dicarbaheteroboranes 7,8,10-C 2 NB 8 H 11 20 and 7,8,10-C 2 SB 8 H 10 . 21,22 The large shielding of the 11 B(1) nucleus is a consequence of high electron density in the open pentagonal face, the area opposite (antipodal) 23 to the B(1)H vertex. Figure 8 shows the excellent correlation of the 11 B chemical shifts among all compounds with the 7,8,10-tricarbollide constitution (structures 3 and 4 -) we have isolated so far (compare also the NMR data of the 7-Me and 7-PhCH 2 substituted 3a derivatives of 4 -).…”
Deamination of
7-(Me3N)-nido-7,8,9-C3B8H10
(1a) leads either to the parent tricarbollide anion
[nido-7,8,9-C3B8H11]-
(2
-
) or to the neutral
tricarbaborane
nido-7,8,9-C3B8H12
(2a), together with a small amount of
8-Me-nido-7,8,9-C3B8H11
(2b). Di- and trisubstituted derivatives of
2a,
7-(Bu
t
MeN)-10-Me-nido-7,8,9-C3B8H10
(2c),
and
7-(Bu
t
MeN)-10,11-Me2-nido-7,8,9-
C3B8H9 (2d) were
obtained as byproducts from the methylation of both
7-(Bu
t
NH2)-nido-7,8,9-C3B8H10
(1b) and
7-(Bu
t
MeNH)-nido-7,8,9-
C3B8H10 (1c) with MeI in
THF under reflux. Heating
of 1a and 2
-
at 350 °C
resulted in the rearrangement of the carbons on the open-face to give
high yields of the
isomeric tricarbollides
10-(Me3N)-nido-7,8,10-C3B8H10
(3a) and
[nido
-7,8,10-C3B8H11]-
(4
-
), respectively.
The
structure of 3a was determined by an X-ray diffraction
analysis, and the geometries of the parent compounds
2
-
, 2a,
and 4
-
were optimized at the
ab initio MP2(fc)/6-31G* level. The structures of
all compounds also were secured
by the excellent agreement between the experimental data and the
IGLO/NMR calculations of the 11B chemical
shifts for the parent compounds at the DZ//6-31G*, DZ//MP2/6-31G*, and
II‘//MP2/6-31G* levels.
“…Of the two possible isomeric arrangements for this, the 7,8,9-configuration has been very recently established for the “tricarbollide” anion [7,8,9-C 3 B 8 H 11 ] - for the neutral tricarbaborane 7,8,9-C 3 B 8 H 12 , and for several of their derivatives, and it has also been proposed for the neutral diarsaheteroboranes 7,8,9-As 2 EB 8 H 8 (where E = S, Se) . The alternative 7,8,10-configuration is adopted by the tricarbollide anion [7,8,10-C 3 B 8 H 11 ] - and its derivatives, 2c-f and by dicarbaheteroboranes of general formulation 10,7,8-EC 2 B 8 H 10 (where E = NH, S, , Se 7 ).…”
Treatment of an acidified solution of the [nido-7,8-C(2)B(9)H(12)](-) anion (1(-)) with NaNO(2) at 0 degrees C in the presence of benzene resulted in the formation of two eleven-vertex azadicarbaboranes, nido-10,7,8-NC(2)B(8)H(11) (2) and arachno-1,8,11-NC(2)B(8)H(13)( )()(3), isolated in yields of 15 and 35%, respectively, together with a small amount (0.9%) of 5-Ph-nido-7,8,10-C(2)NB(8)H(10) (5-Ph-2). Compound 3 was converted in 68% yield into 2 by reaction with PS (PS = "proton sponge"; 1,8-(dimethylamino)naphthalene and acetone. Deprotonation of 2 at the N(10)H vertex gave the [nido-10,7,8-NC(2)B(8)H(10)](-) anion (2(-)), which was easily alkylated with Me(2)SO(4) or PhCH(2)Br to produce the N-alkylated derivatives of 2, 10-R-nido-10,7,8-NC(2)B(8)H(10), where R = Me (10-Me-2, 86%) and PhCH(2) (10-PhCH(2)-2, 69%). The geometries of the parent dicarbazaboranes 2 and 3 were optimized at the MP2(fc)/6-31G level, and the structures of all compounds were thence confirmed by the excellent agreement between experimental data and IGLO/NMR calculations of the (11)B chemical shifts for the parent compounds at the DZ//6-31G, DZ//MP2/6-31G, and II'//MP2/6-31G levels.
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