1,3,2-Dioxaphospholanes with an annelated 1,2-dicarba-closo- dodecaborane(12) unit: Formation and dimerization

Article abstract of DOI:10.1002/ejic.201301219

By using 1,2-hydroxy-1,2-dicarba-closo-dodecaborane(12) and the corresponding dilithium salt [1,2-(LiO)₂-1,2-C₂B ₁₀H₁₀] for the synthesis of 1,3,2-dioxaphospholanes, it was shown that these species are short-liv

Full text of DOI:10.1002/ejic.201301219

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DOI:10.1002/ejic.201301219
1,3,2-Dioxaphospholanes with an Annelated 1,2-Dicarba-
closo-dodecaborane(12) Unit: Formation and Dimerization
Bernd Wrackmeyer,*[a] Elena V. Klimkina,[a] and Wolfgang Milius[b]
Keywords: Carboranes / Dimerization / Heterocycles / NMR spectroscopy / Density functional calculations
By using 1,2-hydroxy-1,2-dicarba-closo-dodecaborane(12)
and the corresponding dilithium salt [1,2-(LiO)2-1,2-
C2B10H10] for the synthesis of 1,3,2-dioxaphospholanes, it
was shown that these species are short-lived with few excep-
311+G(d,p) level of theory], and NMR spectroscopic param-
eters were calculated. One dimer was characterized by X-
ray analysis. All products were found to be sensitive to hy-
drolysis and oxidation. Thus, crystals of 1-[(1,1-dimethyl-
tions. The phosphorus halides undergo disproportionation re- ethyl)hydroxyphosphinyl]oxy-2-hydroxy-1,2-dicarba-closo-
actions towards phosphite derivatives, whereas the P-or- dodecaborane(12) could be isolated and characterized by X-
gano-substituted five-membered rings dimerize to give ten-
membered rings. Even the P-diethylamino and the P-ethoxy
compounds dimerize slowly. Dimerization is the favored pro-
cess when using the dilithium salt together with ether. The
ray analysis, as well as the starting material 1,2-hydroxy-1,2-
dicarba-closo-dodecaborane(12) (with HNEt2/HCl). In all
three solid-state structures, the C–C(carborane) bond lengths
are elongated with respect to all other neutral ortho-carb-
reactions were monitored by multinuclear magnetic reso- orane derivatives bearing second-row substituents at one or
nance spectroscopy (1H, 11B, 13C, 31P NMR). The gas-phase
structures were optimized by DFT methods [B3LYP/6-
both carbon atoms.
Introduction
Vicinal diols play an important role in many fields of
chemistry, and countless variations of the carbon skeleton
are known. However, surprisingly little attention has been
paid to 1,2-dihydroxy-1,2-dicarba-closo-dodecaborane(12)
(1), although the chemistry of the parent “ortho-carborane”
in general is well developed.[1,2] Indeed, the synthesis of 1
was reported only in 2007.[3] Before 1 had been the subject
of theoretical treatment,[4] its solid-state structure is un-
known, and its chemistry has remained almost unexplored
as yet.[5] By contrast, monohydroxy-ortho-carboranes[3,5,6]
and their derivatives[6,7] (including the carborane–phos-
phites[8]) are much better known. We have managed to re-
produce the synthesis of 1 (Scheme 1) by observing care-
fully controlled conditions.
Extending our interest beyond derivatives of the heavy
congeners of 1,[9–12] we have tried to start from 1 to prepare
and study 1,3,2-dioxaphospholanes with an annelated 1,2-
dicarba-closo-dodecaborane unit. It is well known that
many 1,3,2-dioxaphospholane derivatives tend to dimerize
or polymerize.[13–17] In this context, the presence of the
three-dimensional rigid carborane framework might have a
distinctive influence.
Scheme 1. Synthesis of 1,2-dihydroxy-1,2-dicarba-closo-dodecabor-
ane(12) (1).
Results and Discussion
Synthesis and NMR Spectroscopy
Although reactions of 1 with phosphorus halides could
work, we preferred after some preliminary experiments
(Scheme 1; see the Supporting Information) the transfor-
mation of 1 into the dilithium derivatives 2 or 2(nEt2O)
(Scheme 2) prior to reactions with phosphorus halides
(Schemes 3, 4, 5, 6, and 7). The dilithium compounds are
colorless powders, slightly soluble in toluene, and were
characterized by their 13C and 7Li NMR spectroscopic data
(Table S1 in the Supporting Information). The broad
13C(carborane) NMR spectroscopic signals, which are at
higher frequency relative to 1, indicate changes in the C–
O bonding situation as well as association and exchange
equlibria in solution.
[a] Anorganische Chemie II, Universität Bayreuth,
95440 Bayreuth, Germany
E-mail: b.wrack@uni-bayreuth.de
[b] Anorganische Chemie I, Universität Bayreuth,
95440 Bayreuth, Germany
In all reactions of 2 with phosphorus trihalides, the for-
mation of the desired 1,3,2-dioxaphospholanes 3 was ac-
companied by 4, which became the major product after re-
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201301219.
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Scheme 2. Transformation of ortho-carborane–diol 1 into the dilithiated derivatives.
Scheme 3. Reaction of 2 with phosphorus trihalides.
moval of the volatile materials in a vacuum (Scheme 3). Fre- tives in various amounts (in repeated experiments) such as
quently, a small amount of compound 5 was present, be- diastereomers B10H10C2[OP(R)X]2 (see also 6), which give
cause of partial hydrolysis of 4. Some NMR spectroscopic 7–10 or the dimers 11–14, respectively (see Figure 2). Nei-
data of 3–5 could be obtained (Table 1). The equilibrium is ther the tert-butyl group nor the bulky 3,5-Me2-benzyl
slowly shifted towards 4 even in the absence of PX3, and as group prevented dimerization. Apparently, only one dia-
the result of the small scale of the preparative work, hydrol- stereomer of the dimers is formed, most likely for steric
ysis cannot be avoided and might even become dominant reasons. Purification of the dimers turned out to be diffi-
(see Figure 1). In the case of iodide 3c, the 31P NMR spec- cult. However, in the case of 13, crystalline material could
tra of the reaction solution clearly indicate the existence of be isolated that was suitable for X-ray structural analysis
6, which after some time is converted completely into 4, (see below).
accompanied by 5. In the cases of the reaction solutions
The reaction of 2 in toluene with diethylamino- or
that contain chloride 3a and bromide 3b, there are weak ethoxyphosphorus dichloride proceeds straightforwardly to
31P NMR spectroscopic signals of small intensity that give the 1,3,2-dioxaphospholanes 15 and 16, respectively
might belong to intermediates analogous to 6. Signals for (Scheme 5), which were sufficiently stable in solution to re-
an appreciable amount of oxidized products could not be cord a fairly complete set of NMR spectroscopic data
observed in the 31P NMR spectra.
(Table 1).
When some of reactions shown in Schemes 4 and 5 were
All attempts to obtain the P-organo-substituted 1,3,2-di-
oxaphospholanes 7–10 (Scheme 4) revealed their formation carried out using 2(nEt2O), only the dimers 11–14 were
followed by rather fast (a few hours) conversion, mainly formed immediately as major products instead of the
into dimers 11–14, together with small amounts of other monomers 7–10. Under these conditions (in the presence of
products, possibly oligomers, as readily shown by 31P NMR ether) even the P-diethylamino 15 or the P-ethoxy deriva-
spectroscopy (see also Tables 1 and 2). The formation of 7– tive 17 rearranged slowly into the respective dimers 17 or
10 is typically accompanied by noncyclic deriva- 18 (Scheme 6; NMR spectroscopic data in Table 2).
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Table 1. 13C and 31P NMR spectroscopic data[a] of the ortho-carborane derivatives (O2PR monomer).
R
AЈ (exp.)
A (calcd.)
AЈ (calcd.)
Solvent
δ13C
2J(31P,13Ccarb) other δ13C
δ31P
δ31P
δ13C
δ31P 2J(31P,13Ccarb
)
[C(carb)]
[C(carb)]
H
Cl (3a)
Br (3b)
I (3c)
(C2B10O2PO–)2(C2B10)
(4)
(C2B10O2PO–)(C2B10)OH
(5)
263.9[b]
no min.
no min.
–
no min.
105.2
105.1
–
[D8]toluene
[D8]toluene
[D8]toluene
[D8]toluene
100.5
100.6
n.o.
12.5
12.5
n.o.
12.5
11.0
12.7
10.3
–
–
–
–
238.3
265.5
312.7
183.8
300.2
343.3
–
–16.2
–15.9
–
99.4 (4COP)
95.5 (2COP)
99.9 (2COP)
97.2 (COP)
100.8 (COH)
[D8]toluene
–
184.4
no min.
110.5
103.4
104.5
107.0
107.4
214.7 not calcd.
Me
iPr (7)
no min.
no min.
356.0
357.3
–11.1
–11.3
[D8]toluene
[D8]toluene
102.6
101.8
12.3
10.4
12.8 (23.6)
35.7 (44.9)
23.2 (21.2)
36.7 (46.9)
n.o.
296.6
287.7
tBu (8)
no min.
106.2
347.8
–7.4
(3,5-Me2–C6H3)–CH2– (9) [D8]toluene
Ph (10)
n.o.
102.6
n.o.
10.3
287.7
264.2
no min.
no min.
107.6
107.2
341.3
316.1
–11.6
–11.2
[D8]toluene
129.0 (29.6)
Co
132.5 (7.0)
Cm
132.9 Cp
139.2 (54.8)
Ci
NH2
NEt2 (15)
no min.
no min.
104.5
103.2
226.2
237.9
–16.2
–10.0
[D8]toluene
CD2Cl2
99.9
99.8
7.7
7.5
14.8 (3.1)
39.8 (23.8)
15.2 (3.3)
40.3 (23.6)
16.6 (5.2)
63.1 (19.8)
194.2
194.6
192.8
OEt (16)
[D8]toluene
100.9
12.5
no min.
105.2
241.3
–15.6
[a] nJ(31P,13C) are given in parentheses (Ϯ0.5 Hz); n.o.: not observed; no min.: calculations did not converge. [b] 2J(31P,13Ccarb) = –11.7 Hz,
1J(31P,1H) = +107.2 Hz.
Figure 1. 202.5 MHz 31P{1H} and 125.8 MHz 13C{1H} NMR spectra of the reaction solution obtained from the reaction of 2 with PBr3.
(A) The mixture of 3b, 4, 5, and PBr3 (after 1 h at room temp. in [D8]toluene). (B) The mixture 4, 5, and 1 after 20 h at room temp. and
removing volatiles in a vacuum (in [D8]toluene).
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Scheme 4. Reaction of 2 with organophosphorus dihalides.
Table 2. 13C and 31P NMR spectroscopic data[a] of the ortho-carborane derivatives (O2PR dimer).
R
Dimer (exp.)
Dimer (calcd.)
13
Solvent
δ13C[C(carb)]
2J(31P,
C
)
Other δ13
C
δ31
P
δ13C[C(carb)]
δ31
P
carb
H
iPr (11)
107.6
109.5
215.6[b]
258.8
[D8]toluene
103.2
15.8
13.6 (17.9)
35.0 (16.1)
216.8
CD2Cl2
218.2
211.0
tBu dimer (12)
[D8]toluene
103.0
102.9
14.0
14.0
22.9 (19.7)
37.2 (30.5)
107.6
108.6
256.1
246.0
tBu trimer (12Ј)
[D8]toluene
22.9 (19.7)
37.9 (30.5)
210.5
(3,5-Me2–C6H3)–CH2– (13)
[D8]toluene
[D8]THF
102.8
103.5
16.4
15.6
206.6
208.3
21.4
45.1 (22.7)
128.9 (6.2) Co
129.7 (8.0) Ci
130.0 (3.4) Cp
139.5 (2.7) Cm
Ph dimer (14)
Ph trimer (14Ј)
CD2Cl2
CD2Cl2
102.5
103.4
19.0
19.5
129.5 (8.4) Cm
129.7 (27.0) Co
133.5 Cp
190.3
107.2
203.7
137.4 (14.3) Ci
129.8 (9.3) Cm
130.4 (27.9) Co
135.0 Cp
196.6 (br)
136.8 (14.7) Ci
NEt2 (17)
OEt (18)
[D8]toluene
[D8]toluene
102.2
99.6
19.7
16.0
14.3 (3.9)
38.7 (22.8)
152.2
134.0
107.8
104.8
182.6
190.9
16.1 (3.7)
64.7 (9.8)
1
3
[a] nJ(31P,13C) are given in parentheses (Ϯ0.5 Hz). [b] 2J(31P,13Ccarb) = +21.2 Hz, J(31P,1H) = +203.1 Hz, J(13Ccarb,1H) = –0.7 Hz.
In addition to marked differences in δ31P data for mono- tions of the lone-pair orientation and O–C bond vector are
mers and dimers, the 13C(carborane) NMR spectroscopic expected to give rise to large and positive values
2
signals show different splitting due to J(31PO13C) (see, for 2J(31PO13C), in contrast to ideal anti positions, for which
example, Figure 3). The values |2J(31PO13C)| in the mono- the values become absolutely smaller and negative[18] (see
mers appear to be smaller than for the dimers. Calculations also Figure S1 in the Supporting Information).
have indicated a negative sign for 2J(31PO13C) in the mono-
When samples that contain 17 in CD2Cl2 were left for
mers, opposite to that for dimers (Ͼ0). This can be traced some time, slow hydrolysis and decomposition took place
to the influence of the assumed orientation of the lone pair (Scheme 7) and small amounts of crystalline materials
of electrons at phosphorus. In phosphites, ideal syn posi- could be isolated that were suitable for X-ray structural
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towards the dimer. Apparently, oxidation and hydrolysis, to
a small extent, accompanied this experiment, and the for-
mation of 19 and 20 was observed, of which 19 could be
isolated as a crystalline material, which was just suitable for
X-ray analysis (see below).
MO Calculations: Molecular Geometries, NMR
Spectroscopic Parameters
The five-membered C2O2P rings in 3–5, 7–10, 15, and 16
can in principle adopt the structures A or AЈ (Scheme 9).
When the gas-phase structures were optimized at the
B3LYP/6-311+G(d,p) level of theory[19] minima in energy
were found only for AЈ. The compound with R = H, experi-
mentally not accessible as yet, is the sole exception, for
which the structure A was found as a minimum. This is
remarkable, since according to structural evidence so far
available for 1,3,2-dioxaphospholanes with an annelated
benzo ring[20] an envelope structure with phosphorus in the
flap is indicated, whereby the substituent R occupies the
axial position (as in A) and leaves equatorial space for the
lone pair of electrons at phosphorus.
The five-membered ring in 1,3,2-dioxaphospholanes is
strained for various reasons: (1) bond angles at phosphorus
are unfavorable; (2) short C–O bond lengths force the phos-
phorus into close distance to the carbon atoms and their
substituents; (3) this is tolerated to some extent by flat-
tening of the ring and the axial position of R; however,
the annelated carborane skeleton is rigid and cannot avoid
repulsive steric interactions with an axial group R, even if
R is of moderate size. Thus, R = H is the only substituent
that might prefer the axial position as in A. In AЈ, as a sort
of a bad compromise, the lone pair of electrons fills the
axial space around phosphorus, which might also increase
the ring strain. Increasingly bulky substituents R in an
equatorial position further increase the carborane/P lone-
pair repulsion, which explains why bulky substituents R fail
Figure 2. 202.5 MHz 31P{1H} NMR spectra of the reaction solu-
tion obtained from the reaction of 2 with PhPCl2. (A) 31P{1H}
NMR spectrum (in [D8]toluene, at 25 °C), the mixture of 10 and
B10H10C2[OP(Ph)Cl]2 together with unidentified intermediate
products (marked by an asterisk) (after 1 d at room temp. in [D8]-
toluene). (B) The same spectrum as in (A) after 20 h at room temp.
(C) After removing volatiles in a vacuum (in [D8]toluene). (D) The
same mixtures as in (C) in CD2Cl2 (at 25 °C). (E) The same spec-
trum as in (D) after 20 h at room temp. (in CD2Cl2, at 25 °C).
analysis. The crystal structure showed the 1,2-dihydroxy- to kinetically stabilize the monomers. Indeed, the calcula-
1,2-dicarba-closo-dodecaborane(12) (1) together with tions show that the energies of all dimers are significantly
HNEt2/HCl.
lower than those of two monomers. The smallest difference
The question of reversibility of the dimerization is ad- is observed for 16/18 (–5.4 kcalmol–1), followed by 15/17
dressed in Scheme 8 for the P-tBu derivatives 12 and 8. (–10.7 kcalmol–1), and the organo-substituted derivatives 7/
Upon prolonged heating of a solution of the dimer 12 in 11, 8/12, 9/13, and 10/14 (all Ͻ–15 kcalmol–1). The 31P nu-
boiling toluene, the 31P NMR spectroscopic signal of the clei in the five-membered rings are significantly deshielded
monomer 8 slowly grew. By keeping the solution at 80 °C with respect to those in the dimers, which might reflect in
for 2 d, the equilibrium was shifted completely again part the ring strain and repulsive effects in the small rings.
Scheme 5. Synthesis of the 1,3,2-dioxaphospholanes 15 and 16.
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Scheme 6. Slow dimerization of the P-diethylamino- and P-ethoxy derivatives 15 and 16.
Figure 3. (A) 125.8 MHz 13C{1H} NMR spectrum of 2-diethylamino-4,5-[1,2-dicarba-closo-dodecaborano(12)]-1,3,2-dioxaphospholane
(15) (in [D8]toluene, at 23 °C) (from the reaction of 2 with Et2NPCl2). (B) 125.8 MHz 13C{1H} NMR spectrum of 2,7-diethylamino-
4,5,9,10-bis[1,2-dicarba-closo-dodecaborano(12)]-2,7-diphospha-1,3,6,8-tetraoxacyclodecane (17) (in [D8]toluene, at 23 °C) [from the reac-
tion of 2(nEt2O) with Et2NPCl2].
Scheme 7. Hydrolysis of dimer 17 to 1,2 dihydroxy-1,2-dicarba-closo-dodecaborane(12) (1).
Scheme 8. Reversibility of dimerization accompanied by hydrolysis/oxidation.
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Figures 4, 5, and 6. The repulsion between the oxygen
atoms linked in vicinal positions to the rigid carborane
framework is evident by the fairly long C–C distances be-
tween the carborane carbon atoms. Indeed, the structures
determined here (see Table 3 for distances and angles) are
the first examples of this type of molecule. Data for com-
parison are listed in Table 4. For neutral ortho-carborane
derivatives with second-row substituents, the examples de-
scribed here possess the longest C–C bonds, and this can
be traced both to electronic and steric effects. The long C–
C distances were predicted by calculations for 1[4] and con-
firmed also by the results from calculations for 13 and 19,
which were carried out in this work. In the ten-membered
ring in 13, the four oxygen atoms are in a plane (mean devi-
ation 1.9 pm), and both phosphorus atoms are shifted out
of this plane (88.8, 88.5 pm). The substituents at the phos-
phorus atoms are symmetrically oriented in a way to mini-
mize contacts with the carborane units. Except for the C–
C distances, all other distances in the carborane moieties
are found in the usual range.[1,2] This is also true for 19 and
1·2(HNEt2/HCl).
Scheme 9. Conceivable conformations of 1,3,2-dioxaphospholanes
with an annelated carborane unit.
The linear correlation between calculated (keeping in mind
the shortcomings of the theoretical approach[21]) and exper-
imental δ31P values (Figure S2 and Table S2 in the Support-
ing Information) support the structural assignment for the
solution state of monomers and dimers.
X-ray Analyses
The molecular structure of dimer 13 and the hydrolysis/
oxidation products 1·2(HNEt2/HCl) and 19 are shown in
Figure 5. Molecular structures of 19 (ball-and-stick model). The
structure determination was carried out using a dataset from an
apparently slightly imperfect and rather small crystal [poor I/σ ra-
tio overall = 1.7; the position of the hydrogen atom at the terminal
C–O(2)H group of the carborane cage could not be determined].
For selected distances and angles, see Table 3.
Figure 4. ORTEP plot (50% probability; hydrogen atoms are omit-
ted for clarity) of the molecular structure of dimers 13. For selected
distances and angles, see Table 3.
Figure 6. Molecular structures of 1 together with 2 HNEt2/HCl. (A) ORTEP plot of the molecular structure of 1 [50% probability;
hydrogen atoms (except of OH) and HNEt2/HCl are omitted for clarity]. For selected distances and angles, see Table 3. (B) One view of
the arrangement of molecules of 1·2(HNEt2/HCl) in the crystal lattice (ball-and-stick model) showing close intermolecular contacts:
N(1)–HN1···Cl(2) 215 pm, N(3)–HN3···Cl(1A) 190 pm, N(3)–HN3A···Cl(4) 195 pm, N(4)–HN4···Cl(3) 236 pm, O(3)–H(3A)···Cl(4A)
219 pm. The direction of the O(3)–H3A bond is influenced by a hydrogen-bridge bonding to the neighboring Cl(4A) atom.
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Table 3. Selected bond lengths [pm] and angles [°] of the ortho-carborane derivatives 13, 13(calcd.), 19, 19(calcd.), 1·2(HNEt2/HCl), and
1(calcd.).
13
13(calcd.)
19
19(calcd.)
1·2(HNEt2/HCl) B10H10C2(OH)2
1 (calcd.)
C(1)–O(1)
C(2)–O(2)
C(3)–O(3)
C(4)–O(4)
136.9(5)
136.9(4)
136.6(4)
138.0(4)
136.2
136.6
136.6
136.2
139.2(12)
131.6(13)
136.9
136.4
133.4(11)
136.6(10)
132.4(10)
138.0(9)
136.3
136.3
C(1)–C(2)
C(3)–C(4)
171.7(5)
169.7(5)
174.4
174.4
173.9(14)
160.3(8)
173.7
166.5
178.5(11)
178.7(10)
177.2
O(1)–P(1)
O(2)–P(2)
O(3)–P(1)
O(4)–P
167.0(2)
168.2(3)
167.5(3)
167.3(3)
171.8
169.8
169.8
171.8
158.2(14)
147.7(7)
162.3
147.9
P(1)–C
P(2)–C
180.9(4)
181.4(4)
185.1
185.1
178.2(12)
183.5
P(1)–O(1)–C(1)
P(1)–O(3)–C(3)
P(2)–O(2)–C(2)
P(2)–O(4)–C(4)
121.9(2)
121.4(2)
120.8(2)
123.2(2)
124.49
126.06
126.06
124.49
126.7(6)
128.0
O(1)–C(1)–C(2)
O(2)–C(2)–C(1)
O(3)–C(3)–C(4)
O(4)–C(4)–C(3)
116.4(3)
115.8(3)
116.3(3)
115.8(3)
115.50
116.88
116.87
115.50
111.6(8)
115.7(9)
113.7
116.0
116.6(7)
112.5(7)
116.6(7)
113.3(7)
115.70
115.68
O(1)–P(1)–O(3)
O(2)–P(2)–O(4)
O(1)–P(1)–O(4)
O(3)–P(1)–O(4)
O(1)–P(1)–C(3)
O(3)–P(1)–C(3)
O(4)–P(1)–C(3)
95.24(12)
96.07(14)
95.90
95.91
109.4(7)
103.0
111.2(4)
112.6(7)
103.0(5)
103.0(7)
116.8(5)
114.7
114.1
100.1
104.2
118.7
Plane O(1)–C(1)–C(2)–O(2)
Plane O(3)–C(3)–C(4)–O(4)
0.46
0.41
0.4
1.7
1.6
Plane O(1)–O(2)–O(3)–O(4)
1.9
Distance [pm] of P(1) from the plane
O(1)–O(2)–O(3)–O(4)
Distance [pm] of P(2) from the plane
O(1)–O(2)–O(3)–O(4)
88.8
88.5
sphere of argon. All other solvents were distilled from Na metal in
an atmosphere of argon. The starting carborane 1 was prepared as
described.[3] Other starting materials were purchased from Kat-
Conclusion
For steric reasons, the annelated carborane skeleton in
1,3,2-dioxaphospholanes enhances the inherent strain in the Chem. (ortho-carborane), MCAT GmbH (3,5-dimethyl-benzyl-
phosphane dibromide), and Aldrich [butyllithium (1.6 m in hex-
ane), PCl3 (99.999%), PBr3 (Ͼ99.99%), PI3 (99%), iPrPCl2 (97%),
tBuPCl2 (97%), PhPCl2 (97%), EtOPCl2 (98%), Et2NPCl2 (97%)].
Most syntheses were carried out on a small scale sufficient for
NMR spectroscopic studies. Because of the small scale, the sensitiv-
ity to hydrolysis, and the multiple reaction pathways, it proved diffi-
cult to obtain analytically pure materials. NMR spectroscopic mea-
surements: Bruker DRX 500: 1H, 11B, 13C, and 31P; chemical shifts
five-membered rings. In the case of halogen substituents at
phosphorus, disproportionation towards phosphite deriva-
tives takes place, whereas with all organo substituents at
phosphorus, dimers that contain ten-membered rings are
the preferred products. One example of the latter was char-
acterized by X-ray analysis. The sensitivity of all products
towards hydrolysis/oxidation allowed us to isolate 1,2-dihy-
droxy-1,2-dicarba-closo-dodecaborane(12) (1) for the first
time in a crystalline matrix that was suitable for X-ray dif-
fraction studies.
are given relative to Me4Si [δ1H (CHDCl2)
= 5.33 ppm,
(C6D5CD2H) = (2.08Ϯ0.01) ppm ; δ13C (CD2Cl2) = 53.8 ppm,
(C6D5CD3) = 20.4 ppm, (C4D8O) = (25.4Ϯ0.1) ppm]; external
BF3·OEt2 [δ11B = (0Ϯ0.3) ppm for Ξ(11B) = 32.083971 MHz], ex-
ternal LiCl, D2O ≈ 9.7 m [δ7Li = (0Ϯ0.1) ppm for Ξ(7Li) =
38.863790 MHz], and external aqueous H3PO4 (85%) [δ31P =
0 ppm for Ξ(31P) = 40.480747 MHz]. Assignments of 1H and 11B
Experimental Section
General: All syntheses and the handling of the samples were carried
out observing necessary precautions to exclude traces of air and
moisture. Carefully dried solvents and oven-dried glassware were
used throughout. CD2Cl2 was distilled from CaH2 in an atmo-
1
NMR spectroscopic signals are based on H{11B} selective hetero-
nuclear decoupling experiments. Mass spectra (EI, 70 eV): Finni-
1
gan MAT 8500 with direct inlet (data for 12C, H, 11B, 16O, 31P).
Eur. J. Inorg. Chem. 0000, 0–0
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Table 4. Ccarb–Ccarb and Ccarb–O distances [pm] for selected Ccage-substituted ortho-carborane derivatives.
Ccarb–Ccarb
Ccarb–O
References
[22]
1,2-C2B10H12
162.9
[7c]
[7b]
[7d]
[7e]
[7f]
[7e]
1-OC(O)CH2R–C2B10H11
1-OH–2-COOH–C2B10H10
1-OC(O)CH3–2-COOH–C2B10H10
1-OH–2-Ph–C2B10H10·0.5H2O
[1-O–2-Ph–C2B10H10]–[C10H6(NMe2)2H]+
[1-O–2-Ph–C2B10H10]–[Ph3PMe]+
162.7
166.0
169.4
172.3
200.1(3)
206.5(7)
139.6
137.4
137.8
136.6
124.5(3)
122.8(7)
[B10H10C2O2PCH2(3,5-Me2–C6H3)]2 (13)
1-OH–2-[OPO(OH)(tBu)]–C2B10H10 (19)
1,2-(OH)2–C2B10H10·2(HNEt2/HCl)
171.7(5)
169.7(5)
173.9(14)
136.6(4)–138.0(4)
this work
this work
this work
131.6(13) (OH)
139.2(12) (OP)
133.4(11)
178.5(11)
178.7(10)
136.6(10)
132.4(10)
138.0(9)
[23a]
[23b]
[23c]
[23d]
[23e]
[23f]
[23g]
[23h]
[23i]
1,2-(COOH)2–C2B10H10·0.5C2H5OH
1,2-[CH(OH)(Ar)]2–C2B10H10·nROH
1,2-(SiMe3)2–C2B10H10
165.1(2)–166.0(2)
166.7–171.2
171.4(4)
172.2(4)
169.7 (4)
173.3(4)/172.0(4)
175.1(6)
179.9(3)
1,2-(PPh2)2–C2B10H10
1,2-(Ph)2–C2B10H10
1,2-(SeMe)2–C2B10H10
1,2-(SPh)2–C2B10H10
1,2-(SMe)2–C2B10H10
180.33(18)
Melting points (uncorrected) were determined with a Büchi 510
melting-point apparatus.
Dilithium
1,2-Dicarba-closo-dodecaborane-1,2-diolate
[(1,2-
C2B10H10)O2Li2](nEt2O) [2(nEt2O)]: Butyllithium (0.28 mL of a
1.6 m solution in hexane, 0.45 mmol) was added to a solution of
carborane 1 (39.6 mg, 0.225 mmol) in [D8]toluene (0.1 mL) and
Et2O (0.05 mL) at 0 °C. The reaction mixture was stirred for 1 h at
room temp., during which a layer of oil from 2(nEt2O) formed at
the bottom. The top layer was decanted after centrifugation, and
the oily residue was dried in a vacuum (2 h, 8ϫ10–3 Torr) to give
21.6 mg of 2(Et2O). The remaining oily solid was dissolved in
All quantum chemical calculations were carried out using the
Gaussian 09 program package.[24] Optimised geometries at the
B3LYP/6-311+G(d,p) level of theory[19] were found to be minima
by the absence of imaginary frequencies. NMR spectroscopic pa-
rameters were calculated[25,26] at the same level of theory. Calcu-
lated chemical shifts δ13C and δ31P were converted by δ13C (calcd.)
= σ(13C, TMS) – σ(13C), with σ(13C, TMS) = +181 ppm and δ13C
(TMS) = 0 ppm, 31P(calcd.) = σ[31P, P(OMe)3] – σ(31P) + 138 ppm;
with σ[31P, P(OMe)3] = 159.8 ppm [δ31P = 138 ppm and δ31P(aque-
ous H3PO4 (85%) = 0 ppm].
[D8]toluene. Compound 2(Et2O) (n
=
1): 1H{11B} NMR
(500.13 MHz, [D8]toluene, 25 °C): δ = 1.07, 3.30 (t, q, ≈10 H,
OEt2), 2.35 (br. s, 4 H), 2.60 (br. s, 6 H) ppm. 11B{1H} NMR
(160.5 MHz, [D8]toluene, 25 °C): δ = –18.2 (6 B), –14.3 (2 B), –8.5
(2 B) ppm.
1,2-Dihydroxy-1,2-dicarba-closo-dodecaborane(12) (1): 1H{11B}
NMR (500.13 MHz, [D8]toluene, 25 °C): δ = 1.94 [br. s, 2 H, HB
for δ(11B) = –10.9 ppm], 2.11 [br. s, 2 H, HB for δ(11B) =
–16.5 ppm], 2.38 [br. s, 2 H, HB for δ(11B) = –11.6 ppm], 2.45 [br.
s, 4 H, HB for δ(11B) = –12.8 ppm], 3.13 (s, 2 H, OH) ppm. 11B{1H}
NMR (160.5 MHz, [D8]toluene, 25 °C): δ = –16.5 (2 B), –12.8 (4
B), –11.6 (2 B), –10.9 (2 B) ppm. 11B NMR (160.5 MHz, [D8]tolu-
ene, 25 °C): δ = –16.5 [d, 1J(11B,1H) = 154 Hz, 2B], –12.8 [d,
1J(11B,1H) = 175 Hz, 4B], –11.6 [d, 1J(11B,1H) = 172 Hz, 2B], –10.9
Then the excess amount of Et2O (0.05 mL) was added in portions
to a suspension of 2(Et2O) in [D8]toluene. Compound 2(nEt2O) (n
1
= 40): H{11B} NMR (500.13 MHz, [D8]toluene, 25 °C): δ = 1.05,
3.30 (t, q, ≈400 H, OEt2), 2.00 (br. s, 4 H), 2.43 (br. s, 6 H) ppm.
11B{1H} NMR (160.5 MHz; [D8]toluene; 25 °C): δ = –18.9 (6 B),
–14.3 (2 B), –8.3 (2 B) ppm.
Reaction of 2 with PCl3
1
[d, J(11B,1H) = 160 Hz, 2B] ppm.
2-Chloro-4,5-[1,2-dicarba-closo-dodecaborano(12)]-1,3,2-dioxa-
phospholane (3a), 1,2-Bis{4,5-[1,2-dicarba-closo-dodecaborano(12)]-
1,3,2-dioxaphospholan-2-yl}oxy-1,2-dicarba-closo-dodecaborane(12)
(4), and 1-{4,5-[1,2-Dicarba-closo-dodecaborano(12)]-1,3,2-dioxa-
phospholan-2-yl}oxy-2-hydroxy-1,2-dicarba-closo-dodecaborane-
(12) (5): Freshly prepared [(1,2-C2B10H10)O2Li2] (2) (48.7 mg,
0.26 mmol) was dissolved in [D8]toluene (0.5 mL); the solution was
cooled to –30 °C, and PCl3 (0.023 mL, 0.26 mmol) was injected
through a microsyringe. After stirring the reaction mixture for 2 h
at room temp., insoluble materials were separated by centrifuga-
tion, and the clear liquid was collected. The mixture contained 3a
Dilithium
1,2-Dicarba-closo-dodecaborane-1,2-diolate
[(1,2-
C2B10H10)O2Li2] (2): Butyllithium (0.40 mL of a 1.6 m solution in
hexane, 0.64 mmol) was added to a solution of carborane 1
(55.8 mg, 0.32 mmol) in [D8]toluene (0.1 mL) at 0 °C. The reaction
mixture was stirred for 1 h at room temperature. The white precipi-
tate was separated using a centrifuge and by decanting the superna-
tant liquid. The residue as a white solid was dried in a vacuum
(2 h, 8ϫ10–3 Torr) to give 47.9 mg (80%) of 2 as a white powder.
1H{11B} NMR (500.13 MHz, [D8]toluene, 25 °C): δ = 2.00 (br. s, 2
H), 2.21 (br. s, 2 H), 2.27 (br. s, 4 H), 2.42 (br. s, 2 H) ppm. 11B{1H}
NMR (160.5 MHz, [D8]toluene, 25 °C): δ = –17.7 (6 B), –14.2 (2 (65%), 4 (25%), and 5 (10%), together with PCl3 (31P NMR spec-
B), –9.6 (2 B) ppm.
troscopy). Volatile materials were removed in a vacuum to give a
Eur. J. Inorg. Chem. 0000, 0–0
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mixture that contained 3a (15%), 4 (70%), and 5 (15%). After 3 d
at room temp., the mixture contained only 4 and 5. A white powder
that consisted of products 4 and 5 was formed that showed rather
H, PCH) ppm. 13C{1H} NMR (125.8 MHz, [D8]toluene, 25 °C): δ
= 14.7 [d, 2J(31P,13C) = 17.6 Hz, CH3], 14.8 [d, 2J(31P,13C) =
17.6 Hz, CH3], 36.1 [d, 1J(31P,13C) = 29.4 Hz, CH], 36.2 [d,
low solubility in [D8 ]toluene. Compound 5: 1 H NMR 1J(31P,13C) = 29.4 Hz, CH], 102.5 [d, 2J(31P,13C) = 14.0 Hz,
(500.13 MHz, [D8]toluene, 25 °C): δ = 3.88 (br. s, 1 H, OH) ppm. C(carb)], 102.6 [d, 2J(31P,13C) = 14.0 Hz, C(carb)] ppm. 31P{1H}
EI-MS (70 eV) for C4H21O4B20P (380.40): m/z (%) = 380 (5) [M+], NMR (202.5 MHz, [D8]toluene, 25 °C): δ = 213.4, 213.5 ppm.
222 (100) [C2H10B10O2POH], 176 (80) [C2H12B10O2].
2-(1,1-Dimethylethyl)-4,5-[1,2-dicarba-closo-dodecaborano(12)]-
Reaction of 2 with PBr3
1,3,2-dioxaphospholane (8) and 2,7-Bis(1,1-dimethylethyl)-4,5,9,10-
bis[1,2-dicarba-closo-dodecaborano(12)]-2,7-diphospha-1,3,6,8-tetra-
oxacyclodecane (12): Freshly prepared [(1,2-C2B10H10)O2Li2] 2
(24.9 mg, 0.132 mmol) was dissolved in [D8]toluene (0.4 mL); the
solution was cooled to –30 °C, and a solution of tBuPCl2
(0.021 mg, 0.132 mmol) in [D8]toluene (0.2 mL) was added. After
1 h at room temp., no reaction had taken place. After stirring the
reaction solution for 24 h at room temp., the mixture contained 8
(60%), 12 (30%), and 12Ј (10%, possibly a trimer), together with
tBuPCl2 (31P NMR spectroscopy). Insoluble materials were sepa-
rated by centrifugation, the clear liquid was collected, and volatile
materials were removed in a vacuum to give a mixture that con-
tained 8 (55%), 12 (35%), and 12Ј (trimer) (10%). After 2–3 d at
room temp., the mixture contained 12 (70 %) and 12Ј (trimer)
(30 %). A white powder that consisted of products 12/12Ј was
formed that showed rather low solubility in [D8]toluene and a
somewhat better solubility in CD2Cl2. Compound 8: 1H NMR
(500.13 MHz, [D8]toluene, 25 °C): δ = 0.58 [d, 3J(31P,1H) = 13.9 Hz,
2-Bromo-4,5-[1,2-dicarba-closo-dodecaborano(12)]-1,3,2-dioxa-
phospholane (3b), (4), and (5): The same procedure as for 3a was
applied, and after addition of PBr3 (0.014 mL, 0.148 mmol) a mix-
ture that contained 3b (75%), 4 (10%), and 5 (15%), together with
PBr3 and small amount of unidentified side products (31P NMR
spectroscopy) was obtained. Volatile materials were removed in a
vacuum to give the final mixture that contained 3b (70%), 4 (15%),
and 5 (15%). Compound 3b: 1H{11B} NMR (500.13 MHz, [D8]-
toluene, 25 °C): δ = 1.92 [br. s, 1 H, HB for δ(11B) = –4.2 ppm],
2.14 [br. s, 1 H, HB for δ(11B) = –14.1 ppm], 2.22 [br. s, 3 H, HB
for δ(11B) = –12.3, –13.5 ppm], 2.49 [br. s, 2 H, HB for δ(11B) =
–15.3 ppm], 2.54 [br. s, 2 H, HB for δ(11B) = –14.6 ppm], 2.33 [br.
s, 1 H, HB for δ(1 1 B) = –8.8 ppm] ppm. 1 1 B{1 H} NMR
(160.5 MHz, [D8]toluene, 25 °C): δ = –15.3 (2 B), –14.6 (2 B), –14.1
(1 B), –13.5 (1 B), –12.3 (2 B), –8.8 (1 B), –4.2 (1 B) ppm. 11B
NMR (160.5 MHz; [D8]toluene; 25 °C): δ = –15.3 (d, 2 B), –14.6
1
(d, 2 B), –14.1 (1 B), –13.5 (1 B), –12.3 [d, J(11 B,1H) = 165 Hz,
1
9 H, CH3] ppm. Compound 12Ј (trimer): H NMR (500.13 MHz,
2B], –8.8 [d, 1J(11 B,1H) = 179 Hz, 1B], –4.2 [d, 1J(11 B,1H) =
181 Hz, 1B] ppm.
3
[D8]toluene, 25 °C): δ = 0.76 [d, J(31P,1H) = 15.0 Hz, 27 H, CH3]
ppm.
Reaction of 2 with PI3
2-(3,5-Dimethylphenylmethyl)-4,5-[1,2-dicarba-closo-dodeca-
borano(12)]-1,3,2-dioxaphospholane (9) and 2,7-Bis(3,5-dimethyl-
phenylmethyl)-4,5,9,10-bis[1,2-dicarba-closo-dodecaborano(12)]-
2,7-diphospha-1,3,6,8-tetraoxacyclodecane (13): Freshly prepared
[(1,2-C2B10H10)O2Li2] (2) (33.3 mg, 0.177 mmol) was dissolved in
[D8]toluene (0.5 mL); the solution was cooled to –30 °C, and (3,5-
Me2–C6H3)CH2PBr2 (54.9 mg, 0.177 mmol) was injected through a
microsyringe. After 30 min at room temp., the mixture contained 9
(20%), 13 (10%), and unidentified intermediate products (70%),
together with (3,5-Me2–C6H3)CH2PBr2 (from 31P NMR spec-
troscopy). After stirring the reaction mixture for 24 h at room
temp., the mixture contained 13 (60%) and intermediate products
(40 %), together with (3,5-Me2–C6H3)CH2PBr2 (from 31P NMR
spectroscopy). Insoluble materials were separated by centrifuga-
tion, the clear liquid was collected, and volatile materials were re-
moved in a vacuum. The remaining white solid was dissolved in
[D8]toluene and the mixture was heated by 65 °C for 4 h. A white
powder that consisted of products 13 was formed that showed
rather low solubility in [D8]toluene and CD2Cl2. Insoluble materi-
als were separated by centrifugation and washed with [D8]toluene.
The residue was dissolved in CD2Cl2, the solid on the surface of
the solution was collected and dried in a vacuum to give 13 as a
white solid.
2-Iodo-4,5-[1,2-dicarba-closo-dodecaborano(12)]-1,3,2-dioxaphos-
pholane (3c), (4), (5), and 1,2-Bis(diiodophosphanyl)oxy-1,2-dicarba-
closo-dodecaborane(12) (6): Again the procedure described for 3a
was applied, and PI3 (90 mg, 0.22 mmol) was added. Insoluble ma-
terials were separated by centrifugation, and the clear liquid was
collected. The mixture contained 3c (25%) and 6 (75%) together
with PI3 (31P NMR spectroscopy). After 2 h at 100 °C, the mixture
contained 5 and 1 together with PI3. Compound 6: 13C{1H} NMR
13
(125.8 MHz, [D8]toluene, 25 °C): δ = 93.3 [2J(31P,
C
) =
carb
14.5 Hz] ppm. 31P{1H} NMR (202.5 MHz, [D8]toluene, 25 °C): δ
= 102.1 ppm.
Reactions of 2 with RPX2
2-(1-Methylethyl)-4,5-[1,2-dicarba-closo-dodecaborano(12)]-1,3,2-di-
oxaphospholane (7) and 2,7-Di(1-methylethyl)-4,5,9,10-bis[1,2-di-
carba-closo-dodecaborano(12)]-2,7-diphospha-1,3,6,8-tetraoxa-
cyclodecane (11): Freshly prepared [(1,2-C2B10H10)O2Li2] (2)
(25.4 mg, 0.135 mmol) was dissolved in [D8]toluene (0.5 mL); the
solution was cooled to –30 °C, and iPrPCl2 (19.6 mg, 0.017 mL,
0.135 mmol) was injected through a microsyringe. After stirring the
reaction mixture for 2 h at room temp., insoluble materials were
separated by centrifugation, and the clear liquid was collected. The
mixture contained 7 (80 %), 11 (10 %), B10H10C2[OPCl(iPr)]2
(10%), and a small amount of unidentified intermediate products
(from 31P NMR spectroscopy). After 24 h at room temp., the mix-
ture contained 7 (5%), 11 (85%), and B10H10C2[OPCl(iPr)]2 (10%).
Volatile materials were removed in a vacuum to give 11 as a white
solid that showed rather low solubility in [D8]toluene. The remain-
ing solid of 11 was washed with [D8]toluene and dried in a vacuum.
Compound 7: 1H NMR (500.13 MHz, [D8]toluene, 25 °C): δ = 0.51
2-Phenyl-4,5-[1,2-dicarba-closo-dodecaborano(12)]-1,3,2-dioxa-
phospholane (10) and 2,7-Diphenyl-4,5,9,10-bis[1,2-dicarba-closo-
dodecaborano(12)]-2,7-diphospha-1,3,6,8-tetraoxacyclodecane (14):
Freshly prepared [(1,2-C2B10H10)O2Li2] (2) (27.7 mg, 0.147 mmol)
was dissolved in [D8]toluene (0.5 mL); the solution was cooled to
–30 °C, and PhPCl2 (26.3 mg, 0.020 mL, 0.147 mmol) was injected
through a microsyringe. After stirring the reaction mixture for 2 h
[dd, J(31P,1H) = 17.7, J(1H,1H) = 7.1 Hz, 6 H, CH3], 1.23 [dsept at room temp., insoluble materials were separated by centrifuga-
3
3
2 J(3 1 P,1 H) = 3.5, 3 J(1 H,1 H) = 7.1 Hz, 1 H, PCH] ppm.
B10H10C2[OPCl(iPr)]2: 1H NMR (500.13 MHz, [D8]toluene,
25 °C): δ = 0.83 (m, 12 H, CH3), 1.54, 1.61 (dsept, dsept, 1 H, 1
tion, and the clear liquid was collected. The mixture contained 10
(50%), B10H10C2[OPCl(Ph)]2 (25%), and unidentified intermediate
products (25%) (from 31P NMR spectroscopy). After 24 h at room
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FULL PAPER
t e m p. , t h e m i x t u r e c o n t a i n e d 1 0 ( 5 % ) , 1 4 ( Ͻ 5 % ) , Reactions of 2(nEt2O) with RPX2
B10H10C2[OPCl(Ph)]2 (35 %), and intermediate products (55%).
2,7-Di(1-methylethyl)-4,5,9,10-bis[1,2-dicarba-closo-dodecaborano-
(12)]-2,7-diphospha-1,3,6,8-tetraoxacyclodecane (11): A suspension
of 2(nEt2O) (0.136 mmol) in [D8]toluene was cooled to –30 °C, and
iPrPCl2 (19.7 mg, 0.017 mL, 0.136 mmol) was injected through a
microsyringe. After stirring the reaction mixture for 2 h at room
temp., insoluble materials were separated by centrifugation, and
the clear liquid was collected. Volatile materials were removed in a
vacuum to give 11 as a white solid together with side products
B10H10C2[OPCl(iPr)]2 (ca. 5 %). The remaining solid of 11 was
washed with [D8]toluene and dried in a vacuum; m.p. 160–170 °C.
Volatile materials were removed in a vacuum, and the residue was
dissolved in CD2Cl2. The remaining mixture contained 10 (Ͻ5%),
14 (Ͻ35%), B10H10C2[OPCl(Ph)]2 (25%), and intermediate prod-
ucts (35%). After 24 h at room temp., the mixture contained 14
(80%), B10H10C2[OPCl(Ph)]2 (15%), and PhPCl2 (Figure 1).
2-Diethylamino-4,5-[1,2-dicarba-closo-dodecaborano(12)]-1,3,2-di-
oxaphospholane (15): Freshly prepared [(1,2-C2B10H10)O2Li2] (2)
(47.9 mg, 0.255 mmol) was dissolved in [D8]toluene (0.5 mL); the
solution was cooled to –30 °C, and Et2NPCl2 (44.3 mg, 0.037 mL,
0.255 mmol) was injected through a microsyringe. After stirring the
reaction mixture for 1 h at room temp., insoluble materials were
separated by centrifugation, and the clear liquid was collected. The
mixture contained 15 (95%) and 17 (Ͻ5%) as a white oil. After
two weeks in [D8]toluene at room temp., the mixture contained 15
(80%) and 17 (20%). Compound 15: 1H{11B} NMR (500.13 MHz,
[D8]toluene, 25 °C): δ = 0.64 [t, 3J(1H,1H) = 7.1 Hz, 6 H, CH3],
2.25 [br. s, 1 H, HB for δ(11B) = –15.8 ppm], 2.37 [br. s, 1 H, HB
for δ(11B) = –13.5 ppm], 2.45 [br. s, 2 H, HB for δ(11B) =
1
Compound 11: H{11B} NMR (500.13 MHz, [D8]toluene, 25 °C):
δ = 0.75 [dd, 3J(31P,1H) = 16.7, 3J(1H,1H) = 7.3 Hz, 12 H, CH3],
1.39 [dsept J(31P,1H) = 3.8, J(1H,1H) = 7.3 Hz, 2 H, PCH], 2.23,
2.26 [br. s, br. s, 2 H, 2 H, HB for δ(11B) = –16.0 ppm], 2.50 [br. s,
8 H, HB for δ(11B) = –10.6, –13.0 ppm], 2.54 [br. s, 4 H, HB for
δ(11B) = –13.0 ppm], 2.65 [br. s, 2 H, HB for δ(11B) = –9.5 ppm],
3.25 [br. s, 2 H, HB for δ(11B) = –13.0 ppm] ppm. 11B{1H} NMR
(160.5 MHz, [D8]toluene, 25 °C): δ = –16.0 (4 B), –13.0 (10 B),
–10.6 (4 B), –9.5 (2 B) ppm. 11B NMR (160.5 MHz, [D8]toluene,
25 °C): δ = –16.0 [d, 1J(11B,1H) = 144 Hz, 4B], –13.0 (d, 10B), –10.6
[d, 1J(11B,1H) = 160 Hz, 4B], –9.5 (d, 2 B) ppm. EI-MS (70 eV) for
2
3
3
3
–11.5 ppm], 2.62 [dq, J(1H,1H) = 7.1, J(31P,1H) = 10.9 Hz, 4 H,
PNCH2], 2.70 [br. s, 3 H, HB for δ(11B) = –15.3, –3.3 ppm], 2.80
[br. s, 2 H, HB for δ(11B) = –13.5 ppm], 2.97 [br. s, 1 H, HB for
δ(11B) = –8.1 ppm] ppm. 11B{1H} NMR (160.5 MHz, [D8]toluene,
25 °C): δ = –15.8 (1 B), –15.3 (2 B), –13.5 (3 B), –11.5 (2 B), –8.1
(1 B), –3.3 (1 B) ppm. 11B NMR (160.5 MHz, [D8]toluene, 25 °C):
δ = –15.8 [d, 1J(11B,1H) = 156 Hz, 1B], –15.3 [d, 1J(11B,1H) =
168 Hz, 2B], –13.5 [d, 1J(11B,1H) = 153 Hz, 3B], –11.5 [d,
1J(11B,1H) = 153 Hz, 2B], –8.1 [d, 1J(11B,1H) = 174 Hz, 1B], –3.3
C10H34O4B20P2 (496.5): m/z (%) = 496 (15) [M+], 453 (40) [M+
–
C3H7], 264 (10) [(M/2 + O)+], 248 (5) [M/2+], 238 (15), 232 (10)
[(M/2 – O)+], 205 (50) [M/2+ – C3H7], 176 (10) [C2H12B10O2], 146
(10), 44 (100) [C3H8].
2,7-Bis(1,1-dimethylethyl)-4,5,9,10-bis[1,2-dicarba-closo-dodeca-
borano(12)]-2,7-diphospha-1,3,6,8-tetraoxacyclodecane (12): A sus-
pension of 2(nEt2O) (0.195 mmol) in [D8]toluene was cooled to
–30 °C, and a solution of tBuPCl2 (0.031 mg, 0.195 mmol) in
[D8]toluene (0.2 mL) was added. After stirring the reaction mixture
for 2 h at room temp., insoluble materials were separated by centri-
fugation, and the clear liquid was collected. The mixture contained
12 (70%), 12Ј (possibly a trimer) (20%), a small amount of un-
identified products (10%) together with tBuPCl2 (31P NMR spec-
troscopy). The solution was heated by 80 °C for 5 d. A white pow-
der that consisted of products 12 was formed that showed rather
low solubility in [D8]toluene. Insoluble solids were separated by
centrifugation, washed with [D8]toluene and dried in a vacuum to
give 12 as a white solid; m.p. 185–195 °C. Compound 12: 1H NMR
(500.13 MHz, [D8]toluene, 25 °C): δ = 0.86 [d, 3J(31P,1H) = 15.1 Hz,
18 H, CH3] ppm. EI-MS (70 eV) for C12H38O4B20P2 (524.6): m/z
(%) = 524 (3) [M+], 467 (100) [M+ – C4H9], 412 (10) [M+ – C4H9 –
C4H8], 351 (3), 205 (5), 57 (100) [C4H9+].
1
[d, J(11B,1H) = 182 Hz, 1B] ppm.
Volatile materials were removed in a vacuum and the residue was
dissolved in CD2Cl2. This solution was left at room temperature
for two weeks, after which transparent colorless crystals of
1·2(HNEt2/HCl) (m.p. 260–270 °C) suitable for X-ray analysis
could be collected. 1H NMR (500.13 MHz, CD2Cl2, 25 °C): δ =
3
1.37 [t, 6 H, CH3, J(1H,1H) = 7.4 Hz], 3.04 (q, 4 H, NCH2), 8.48
(s, 2 H, COH) ppm.
2-Ethoxy-4,5-[1,2-dicarba-closo-dodecaborano(12)]-1,3,2-dioxaphos-
pholane (16): Freshly prepared [(1,2-C2B10H10)O2Li2] (2) (33.2 mg,
0.177 mmol) was dissolved in [D8]toluene (0.5 mL); the solution
was cooled to –30 °C, and EtOPCl2 (26.0 mg, 0.02 mL,
0.177 mmol) was injected through a microsyringe. After stirring the
reaction mixture for 1 h at room temp., insoluble materials were
separated by centrifugation, and the clear liquid was collected. The
mixture contained 16 (80%) and a small amount of unidentified
products. Volatile materials were removed in a vacuum to give the
mixture contained 16 (95%) and 18 (Ͻ5%) as a white oil. Com-
pound 16: 1H{11B} NMR (500.13 MHz, [D8]toluene, 25 °C): δ =
0.68 [t, 3J(1H,1H) = 7.0 Hz, 3 H, CH3], 2.25 [br. s, 1 H, HB for
2,7-Bis(3,5-dimethylphenylmethyl)-4,5,9,10-bis[1,2-dicarba-closo-do-
decaborano(12)]-2,7-diphospha-1,3,6,8-tetraoxacyclodecane (13): A
suspension of 2(nEt2O) (0.21 mmol) in [D8]toluene was cooled to
–30 °C, and (3,5-Me2–C6H3)CH2PBr2 (65.0 mg, 0.21 mmol) was in-
δ(11B) = –14.5 ppm], 2.31 [br. s, 1 H, HB for δ(11B) = –4.8 ppm], jected through a microsyringe. After stirring the reaction mixture
2.35 [br. s, 1 H, HB for δ(11B) = –13.5 ppm], 2.37 [br. s, 2 H, HB for 2 h at room temperature, insoluble materials were separated by
for δ(11B) = –12.4 ppm], 2.67 [br. s, 2 H, HB for δ(11B) =
centrifugation, and the clear liquid was collected. The mixture con-
–15.3 ppm], 2.76 [br. s, 2 H, HB for δ(11B) = –14.5 ppm], 2.85 [br. tained 13 (30%) and unidentified intermediate products (70%), to-
s, 1 H, HB for δ(11B) = –5.5 ppm], 3.27 [dq, 3J(1H,1H) = 7.0 Hz,
3 J(3 1 P,1 H) = 9.9 Hz, 2 H, POCH2 ] ppm. 1 1 B{1 H} NMR
(160.5 MHz, [D8]toluene, 25 °C): δ = –15.3 (2 B), –14.5 (3 B), –13.5
(1 B), –12.4 (2 B), –5.5 (1 B), –4.8 (1 B) ppm. 11 B NMR
(160.5 MHz, [D8]toluene, 25 °C): δ = –15.3 [d, 1J(11B,1H) = 162 Hz,
2B], –14.5 [d, 1J(11B,1H) = 142 Hz, 3B], –13.5 [d, 1J(11B,1H) =
160 Hz, 1B], –12.4 [d, 1J(11B,1H) = 164 Hz, 2B], –5.5 [d, 1J(11B,1H)
= 190 Hz, 1B], –4.8 [d, 1J(11B,1H) = 180 Hz, 1B] ppm. EI-MS
(70 eV) for C4H15O3B10P (250.2): m/z (%) = 250 (55) [M+], 222 (65)
[M+ – C2H4], 175 (100) [C2H11B10O2].
gether with (3,5-Me2–C6H3)CH2PBr2 (from 31P NMR spec-
troscopy). Volatile materials were removed in a vacuum. The resi-
due was dissolved in CD2Cl2, and the solid swimming on top of
the solution was collected and dried in a vacuum to give 13
(30.5 mg, 45%) as a white solid; m.p. 240–245 °C. Transparent col-
orless crystals of 13 for X-ray analysis were grown from the CD2Cl2
solution after one week at –30 °C. 1H{11B} NMR (500.13 MHz,
[D8]toluene, 25 °C): δ = 2.05 (s, 12 H, CH3), 2.23, 2.30 [br. s, br. s,
4 H, 2 H, HB for δ(11B) = –15.9 ppm], 2.42 [br. s, 10 H, HB for
δ(11B) = –11.0, –13.1 ppm], 2.71 [br. s, 2 H, HB for δ(11B) =
Eur. J. Inorg. Chem. 0000, 0–0
11
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

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/KAP1
Date: 21-11-13 17:13:57
Pages: 15
www.eurjic.org
FULL PAPER
2
–13.1 ppm], 2.74 [d, J(31P,1H) = 9.7 Hz, 4 H, PCH2], 3.24 [br. s, 2
microsyringe. After stirring the reaction mixture for 1 h at room
temp., insoluble materials were separated by centrifugation, and the
clear liquid was collected. The mixture contained 15 (70%) and
dimer 17 (30%), together with Et2NPCl2 (31P NMR spectroscopy).
H, HB for δ(11B) = –13.1 ppm], 6.58 (s, 4 H, CH, Ph), 6.66 (s, 2 H,
1
CH, Ph) ppm. H NMR (500.13 MHz, [D8]thf, 25 °C): δ = 2.30 (s,
2
12 H, CH3), 3.22 [d, J(31P,1H) = 9.1 Hz, 4 H, PCH2], 6.88 (s, 4 H,
CH), 6.95 (s, 2 H, CH) ppm. 11B{1H} NMR (160.5 MHz, [D8]- Volatile materials were removed in a vacuum to give the dimer 17
toluene, 25 °C): δ = –15.9 (6 B), –13.1 (10 B), –11.0 (4 B) ppm. EI-
MS (70 eV) for C22H42O4B20P2 (648.7): m/z (%) = 649 (3) [M+],
530 (70) [M+ – C9H11], 341 (5) [(M/2 + O)+], 325 (10) [M/2+], 361
(4), 206 (25) [M/2+ – C9H11], 176 (4) [C2H12O2B10], 147 (10), 119
(100) [C9H11].
as a white solid together with 15 (Ͻ5%); m.p. 120–125 °C (decom-
position). Compound 17: 1H{11B} NMR (500.13 MHz, [D8]tolu-
3
ene, 25 °C): δ = 0.79 [t, J(1H,1H) = 7.1 Hz, 12 H, CH3], 2.29 [br.
s, 6 H, HB for δ(11B) = –16.2 ppm], 2.51 [br. s, 10 H, HB for δ(11B)
= –11.0, –13.4 ppm], 2.71 [br. s, 2 H, HB for δ(11B) = –13.4 ppm],
2.75 [dq, J(1H,1H) = 7.1 Hz, J(31P,1H) = 11.2 Hz, 8 H, PNCH2],
3.22 [br. s, 2 H, HB for δ(11B) = –13.4 ppm] ppm. 11B{1H} NMR
(160.5 MHz, [D8]toluene, 25 °C): δ = –16.2 (6 B), –13.4 (8 B), –11.0
(6 B) ppm. 11B NMR (160.5 MHz, [D8]toluene, 25 °C): δ = –16.2
[d, 1J(11B,1H) = 140 Hz, 6B], –13.4 [d, 1J(11B,1H) = 157 Hz, 8B],
–11.0 [d, 1J(11B,1H) = 155 Hz, 6B] ppm. EI-MS (70 eV) for
3
3
2,7-Diphenyl-4,5,9,10-bis[1,2-dicarba-closo-dodecaborano(12)]-2,7-
diphospha-1,3,6,8-tetraoxacyclodecane (14): A suspension of
2(nEt2O) (0.145 mmol) in [D8]toluene was cooled to –30 °C, and
PhPCl2 (0.026 mg, 19.7 mL, 0.145 mmol) in [D8]toluene (0.2 mL)
was injected through a microsyringe. After stirring the reaction
mixture for 2 h at room temp., insoluble materials were separated
by centrifugation, and the clear liquid was collected. The mixture
contained 14 (85%) and 14Ј (possibly a trimer) (15%), together
with PhPCl2 (from 31P NMR spectroscopy). Volatile materials were
removed in a vacuum, washed with [D8]toluene and dried in a vac-
uum to give a mixture that contained 14 (90%) and 14Ј (trimer)
(10 %) as a white solid. 1H{11B} NMR (500.13 MHz, CD2Cl2,
25 °C): δ = 1.85, 1.89 [br. s, br. s, 2 H, 2 H, HB for δ(11B) =
–16.1 ppm], 2.00 [br. s, 4 H, HB for δ(11B) = –10.9 ppm], 2.29 [br.
s, 4 H, HB for δ(11B) = –13.4 ppm], 2.55 [br. s, 2 H, HB for δ(11B)
= –9.6 ppm], 2.60 [br. s, 4 H, HB for δ(11B) = –13.4 ppm], 3.45 [br.
s, 2 H, HB for δ(11B) = –13.4 ppm], 7.52 (m, 4 H, Ph), 7.63 (m, 2
H, Ph), 7.69 (m, 4 H, Ph) ppm. 11B{1H} NMR (160.5 MHz,
CD2Cl2, 25 °C): δ = –16.1 (4 B), –13.4 (10 B), –10.9 (4 B), –9.6
(2 B) ppm. 11B NMR (160.5 MHz, CD2Cl2, 25 °C): δ = –16.1 [d,
1J(11B,1H) = 162 Hz, 4B], –13.4 [d, 1J(11B,1H) = 150 Hz, 10B],
C12H40N2O4B20P2 (554.6): m/z (%) = 554 (5) [M+], 482 (25) [M+
–
NEt2], 277 (40) [M/2+], 262 (100) [(M/2 – CH3)+], 248 (10) [(M/2 –
C2H5)+], 233 (3) [(M/2 – C2H5 – CH3)+], 222 (5) [C2H11B10O3P],
205 (30) [(M/2 – NEt2)+], 175 (25) [C2H11B10O2].
2-Ethoxy-4,5-[1,2-dicarba-closo-dodecaborano(12)]-1,3-dioxa-2-
phospholane (16) and 2,7-Diethoxy-4,5,9,10-bis[1,2-dicarba-closo-
dodecaborano(12)]-2,7-diphospha-1,3,6,8-tetraoxacyclodecane (18):
A suspension of 2(nEt2O) (0.175 mmol) in [D8]toluene was cooled
to –30 °C, and EtOPCl2 (25.7 mg, 0.02 mL, 0.175 mmol) was in-
jected through a microsyringe. After stirring the reaction mixture
for 1 h at room temp., insoluble materials were separated by centri-
fugation, and the clear liquid was collected. The mixture contained
16 (90%), 18 (Ͻ5%), and a small amount of unidentified products
(5%), together with EtOPCl2 (from 31P NMR spectroscopy). After
24 h at room temp., the mixture contained 16 (80%), 18 (15%),
and a small amount of unidentified products (5%), together with
EtOPCl2. The products 16 and 18 decomposes slowly in [D8]tolu-
ene un de r A r at roo m t em p. Co mp ou nd 18: 1 H N MR
1
–10.9 [d, J(11B,1H) = 164 Hz, 4B], –9.6 (2B) ppm.
2,7-Diethylamino-4,5,9,10-bis[1,2-dicarba-closo-dodecaborano-
(12)]-2,7-diphospha-1,3,6,8-tetraoxacyclodecane (17): A suspension
of 2(nEt2O) (0.12 mmol) in [D8]toluene was cooled to –30 °C, and
Et2NPCl2 (20.9 mg, 0.017 mL, 0.12 mmol) was injected through a
3
(500.13 MHz, [D8]toluene, 25 °C): δ = 0.84 [t, J(1H,1H) = 7.0 Hz,
6 H, CH3], 3.27 [dq, 3J(1H,1H) = 7.0, 3J(31P,1H) = 7.0 Hz, 4 H,
Table 5. Crystallographic data of the ortho-carborane derivatives 13, 19, and 1·2(HNEt2/HCl).[a]
13
19
1·2(HNEt2/HCl)
Formula
C22H42B20O4P2
colorless prism
0.20ϫ0.18ϫ0.16
133(2) K
C6H19B10O4P
colorless prism
0.16ϫ0.12ϫ0.10
133(2) K
C10H36B10Cl2N2O2
colorless needle
0.20ϫ0.12ϫ0.10
133(2) K
Crystal
Dimensions [mm3]
T [K]
Crystal system
Space group
triclinic
P1
monoclinic
P21/c
triclinic
P1
¯
¯
a [pm]
b [pm]
c [pm]
α [°]
β [°]
γ [°]
Z
1101.2(2)
1349.9(3)
1386.9(3)
107.51(3)
107.54(3)
103.92(3)
2
1111.8(2)
1077.7(2)
1350.8(3)
719.31(14)
1110.5(2)
3127.1(6)
84.66(3)
87.64(3)
75.46(3)
4
98.27(3)
4
Absorption coefficient (μ) [mm–1]
Measuring range (ϑ) [°]
Reflections collected
Independent reflections [IՆ2σ(I)]
Absorption correction
Refined parameters
wR2/R1 [IՆ2σ(I)]
Max./min. residual electron density,
[epm–3 10–6]
0.156
1.68–25.71
11761
0.172
1.85–25.77
9022
0.276
1.90–25.66
8372
3855
1028
2892
none[b]
none[b]
190
none[b]
433
0.139/0.065
0.470/–0.352
470
0.308/0.118
0.493/–0.621
0.249/0.134
0.515/–0.595
[a] A STOE IPDS II diffractometer was used in all cases with graphite-monochromated Mo-Kα radiation (λ = 71.073 pm). [b] Absorption
corrections did not improve the parameter set.
Eur. J. Inorg. Chem. 0000, 0–0
12
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

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/KAP1
Date: 21-11-13 17:13:57
Pages: 15
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FULL PAPER
Michl, R. D. Miller, Inorg. Chem. 1997, 36, 6033–6038; e) M.
Tsuji, J. Org. Chem. 2003, 68, 9589–9597.
POCH2] ppm. EI-MS (70 eV) for C8H30O6B20P2 (500.4): m/z (%)
= 500 [M+].
[7]
a) M. E. El-Zaria, N. Janzen, M. Blacker, J. F. Valliant, Chem.
Eur. J. 2012, 18, 11071–11078; b) M. Scholz, G. N. Kal-
ueerovic´, H. Kommera, R. Paschke, J. Will, W. S. Sheldrick, E.
Hey-Hawkins, Eur. J. Med. Chem. 2011, 46, 1131–1139; c) M.
Scholz, A. L. Blobaum, L. J. Marnett, E. Hey-Hawkins, Bioorg.
Med. Chem. 2011, 19, 3242–3248; d) M. Scholz, K. Bensdorf,
R. Gust, E. Hey-Hawkins, ChemMedChem 2009, 4, 746–748;
e) L. A. Boyd, W. Clegg, R. C. B. Copley, M. G. Davidson,
M. A. Fox, T. G. Hibbert, J. A. K. Howard, A. Mackinnon,
R. J. Peace, K. Wade, Dalton Trans. 2004, 2786–2799; f) D. A.
Brown, W. Clegg, H. M. Colquhoun, J. A. Daniels, I. R. Ste-
phenson, K. Wade, J. Chem. Soc., Chem. Commun. 1987, 889–
891; g) L. I. Zakharkin, G. G. Zhigareva, Z. Obshch. Khim.
1975, 45, 1293–1301 [J. Gen. Chem. USSR 1975, 45 (Engl.
Transl.)].
a) S. E. Lyubimov, V. N. Kalinin, A. A. Tyutyunov, V. A. Olsh-
evskaya, Y. V. Dutikova, C. S. Cheong, P. V. Petrovskii, A. S.
Safronov, V. A. Davankov, Chirality 2009, 21, 2–5; b) S. E. Lyu-
bimov, A. A. Tyutyunov, P. A. Vologzhanin, A. S. Safronov,
P. V. Petrovskii, V. N. Kalinin, K. N. Gavrilov, V. A. Davankov,
J. Organomet. Chem. 2008, 693, 3321–3323.
a) B. Wrackmeyer, Z. García Hernández, R. Kempe, M. Herb-
erhold, Z. Anorg. Allg. Chem. 2007, 633, 851–857; b) Z.
García Hernández, B. Wrackmeyer, R. Kempe, M. Herberhold,
ARKIVOC 2008, 65–80.
a) B. Wrackmeyer, E. V. Klimkina, W. Milius, Eur. J. Inorg.
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a) J. P. Dutasta, J. Martin, J. B. Robert, Heterocycles 1980, 14,
1631–1648; b) J. P. Dutasta, A. Grand, A. C. Guimaraes, J. B.
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1519–1522.
1-[(1,1-Dimethylethyl)hydroxyphosphinyl]oxy-2-hydroxy-1,2-di-
carba-closo-dodecaborane(12) (19) and tButylphosphinic Acid (20):
The mixture of 14/14Ј (9:1) was dissolved in [D8]toluene, placed
into an NMR spectroscopy tube, and heated at 110 °C (oil bath)
for 4 h. The mixture contained 14 (50%), 14Ј (trimer) (15%), 8
1
(20%), 19 (10%), and 20 (5%), together with 1 (from 31P and H
NMR spectroscopy). After 2 d at 80 °C, the mixture contained 14
(60%), 14Ј (trimer) (10%), 8 (Ͻ5%), 19 (10%), and 20 (15%), to-
gether with 1. The [D8]toluene solution was cooled to –30 °C to
give 20 as a white powder. Volatile materials were removed in a
vacuum, and the residue was dissolved in CD2Cl2. This solution
was left at room temp. for one week, after which transparent crys-
tals of 19 (m.p. 160–165 °C) suitable for X-ray analysis could be
collected. Compound 19: 31P{1H} NMR (202.5 MHz, CD2Cl2,
25 °C): δ = 72.6 ppm. Compound 20: 1H NMR (500.13 MHz,
[8]
[9]
3
CD2Cl2, 25 °C): δ = 1.13 [d, J(31P,1H) = 18.1 Hz, 9 H, CH3], 6.74
[d, 1J(31P,1H)
= 540.2 Hz, 1
H, PH] ppm. 13C{1H} NMR
(125.8 MHz, CD2Cl2, 25 °C): δ = 22.2 [d, 2J(31P,13C) = 1.8 Hz,
CH3], 31.0 [d, 2J(31P,13C) = 94.7 Hz, PC] ppm. 31P{1H} NMR
(202.5 MHz, CD2Cl2, 25 °C): δ = 51.7 ppm. 31P NMR (202.5 MHz,
CD2Cl2, 25 °C): δ = 51.7 [dm, J(31P,1H) = 540.5 Hz] ppm.
1
Crystal Structure Determination of 13, 19, and 1·2(HNEt2/HCl):
Structure solutions and refinements were carried out with the pro-
gram package SHELXTL-PLUS V.5.1.[27] Details pertinent to the
crystal structure determination are listed in Table 5. Crystals of ap-
propriate size were sealed under argon in Lindemann capillaries,
and the data collections were carried out at 133 K.
[10]
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CCDC-961687 (13 at 133 K), -961685 (for 19 at 133 K), and
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supplementary crystallographic data for this paper. These data can
be obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Supporting Information (see footnote on the first page of this arti-
cle): Alternative synthetic pathway, NMR data of 2 and 2(nEt2O),
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Received: September 18, 2013
Published Online: ᭿
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FULL PAPER
Dioxaphospholanes
B. Wrackmeyer,* E. V. Klimkina,
W. Milius ........................................ 1–15
1,3,2-Dioxaphospholanes with an Annel-
ated 1,2-Dicarba-closo-dodecaborane(12)
Unit: Formation and Dimerization
Keywords: Carboranes / Dimerization
/
Heterocycles / NMR spectroscopy / Den-
sity functional calculations
Most of the title compounds were found
to be unstable as monomers and tend to
dimerize, even faster than comparable de-
rivatives without the annelated carborane
unit.
Eur. J. Inorg. Chem. 0000, 0–0
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© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim