Reactions of phosphonates with organohaloboranes: New route to molecular borophosphonates

Article abstract of DOI:10.1021/om000067v

Phosphonates RPO(OR′)₂ (R = Me, R′ = Et (1); R = CH₂Ph, R′ = Et (2); R = CH double bond CH₂, R′ = Et (3); R = CH₂-CH double bond CH₂, R′ = Me (4); R = CH₂N₃, R′ = Et (5)) react with CyBCl₂ (6; Cy = C₆H₁₁) in a 1:1 molar ratio in toluene at -30 °C to form the primary adducts CyBCl₂·O double bond PR(OR′)₂ (7-11). These products undergo a thermally induced bis-chlorodealkylation with the formation of mixtures of oligomers [-O-PR(O-)-O-BCy(O-)]_n (22-26) having isovalent P-O-B groupings. Under electron impact mass spectral conditions, the ions [RPO₃BCy]₄-Cy, which may be attributed to tetramers [RPO₃BCy]₄ (22′-26′), are detected. Compounds 22′-26′ presumably possess a central cubic M₄O₁₂P₄ framework that is analogous to those found in alumino- and gallophosphate materials. NMR monitoring shows that [CyBCl(μ₂-O)₂PR(OR′)]₂ (12-16) are formed as intermediates in these reactions. These unstable dimers 12-16 possess a cyclic core analogous to the single-four-ring (4R) secondary building units (SBUs) found in zeolites and phosphate molecular sieves. Hydrolysis of 12-16 and 22-26 with methanol at 30 °C gave respectively RPO(OH)(OR′) (17-21) and RPO(OH)₂ (27-31). NMR monitoring reveals that the cyclic dimer [Me₂B(μ₂-O)₂P(CH₂Ph)(OEt)]₂ (35a) is the primary adduct in the reaction of PhCH₂PO(OEt)₂ (2) with Me₂BBr (34). Heating or prolonged storage at room temperature leads to a mixture of 35a, cyclic borophosphonate Me₂BC(μ₂-O)₂P(CH₂Ph)(OEt) (35b), and the mixed anhydride of benzylphosphonic acid and dimethylborinic acid (35c).

Full text of DOI:10.1021/om000067v

4266
Organometallics 2000, 19, 4266-4275
Rea ction s of P h osp h on a tes w ith Or ga n oh a lobor a n es:
New Rou te to Molecu la r Bor op h osp h on a tes
J acques Mortier,*,† Ilya D. Gridnev,*,‡ and Pierre Gue´not§
Faculte´ des sciences, Laboratoire de synthe`se organique, Universite´ du
Maine and CNRS, avenue Olivier Messiaen, 72085 Le Mans Cedex 9, France,
A. N. Nesmeyanov Institute of Organoelement Compounds, Vavilova 28,
117813 Moscow, Russia, and Centre re´gional de mesures physiques de l'Ouest,
campus de Beaulieu, Universite´ Rennes-1, 35042 Rennes Cedex, France
Received J anuary 25, 2000
Phosphonates RPO(OR′)2 (R ) Me, R′ ) Et (1); R ) CH2Ph, R′ ) Et (2); R ) CHdCH2,
R′ ) Et (3); R ) CH2-CHdCH2, R′ ) Me (4); R ) CH2N3, R′ ) Et (5)) react with CyBCl2 (6;
Cy ) C6H11) in a 1:1 molar ratio in toluene at -30 °C to form the primary adducts CyBCl2‚
OdPR(OR′)2 (7-11). These products undergo a thermally induced bis-chlorodealkylation
with the formation of mixtures of oligomers [-O-PR(O-)-O-BCy(O-)]n (22-26) having
isovalent P-O-B groupings. Under electron impact mass spectral conditions, the ions [RPO3-
BCy]4-Cy, which may be attributed to tetramers [RPO3BCy]4 (22′-26′), are detected.
Compounds 22′-26′ presumably possess a central cubic M4O12P4 framework that is analogous
to those found in alumino- and gallophosphate materials. NMR monitoring shows that
[CyBCl(µ2-O)2PR(OR′)]2 (12-16) are formed as intermediates in these reactions. These
unstable dimers 12-16 possess a cyclic core analogous to the single-four-ring (4R) secondary
building units (SBUs) found in zeolites and phosphate molecular sieves. Hydrolysis of 12-
16 and 22-26 with methanol at 30 °C gave respectively RPO(OH)(OR′) (17-21) and RPO-
(OH)2 (27-31). NMR monitoring reveals that the cyclic dimer [Me2B(µ2-O)2P(CH2Ph)(OEt)]2
(35a ) is the primary adduct in the reaction of PhCH2PO(OEt)2 (2) with Me2BBr (34). Heating
or prolonged storage at room temperature leads to a mixture of 35a , cyclic borophosphonate
Me2BC(µ2-O)2P(CH2Ph)(OEt) (35b), and the mixed anhydride of benzylphosphonic acid and
dimethylborinic acid (35c).
In tr od u ction
It has been shown recently by us that the alkyl halide
elimination reaction involving haloboranes and phos-
phonates is a facile way for the formation of the P-O-B
groupings.5 A general synthesis of N-alkyl/aryl-R- and
N-alkyl/aryl-â-aminophosphonic acids based on reduc-
tive alkylation of R- and â-azidophosphonates with
organodichloroboranes has been proposed.5
Our experience in this field prompted us to explore
the possibility of synthesizing suitable molecular boro-
phosphonate clusters from organohaloboranes and phos-
phonates. The presence of reactive B-C and/or P-C
bonds at the corners of such cage models in principle
Although Al-, Ga-, and In-containing layered phos-
phates and phosphonates have been studied in detail
over the past few years, until two recent reports
published in 1997, no organic-soluble materials with
isovalent P-O-B groupings were known. Roesky and
co-workers have described the synthesis of the molec-
ular cage molecule [t-BuPO3BEt]4 from the reaction of
BEt3 and t-BuPO(OH)2 in refluxing toluene/1,4-diox-
ane.1 Kuchen and co-workers have reported the prepa-
ration in low yield (14%) of the cage borophosphonate
[t-BuPO3BPh]4 by reaction of PhBCl2 and t-BuPO-
(OSiMe3)2.2 In each case corners of the cubanoid P4B4
framework are alternately occupied by boron and phos-
phorus atoms, each of which is tetrahedrally coordinated
to three oxygen atoms and one carbon atom. The 12 O
atoms are located approximately in the middle of the
edges. These cage molecules show structures with
nearly equal P-O and B-O bond lengths, making them
structurally quite similar to silicate analogues.3,4
(3) Recent reviews on metal phosphates and phosphonates: (a)
Walawalkar, G. M.; Roesky, H. W.; Murugavel, R. Acc. Chem. Res.
1999, 32, 117. (b) Clearfield, A. In Progress in Inorganic Chemistry;
Karlin, K. D., Ed.; Wiley: New York, 1998; pp 371-510. (c) Zubieta,
J . Comments Inorg. Chem. 1994, 16, 153. (d) Cao, G.; Hong, H.-G.;
Mallouk, T. E. Acc. Chem. Res. 1992, 25, 420.
(4) For some recent work on phosphonates and phosphates, see: (a)
Byrd, H.; Clearfield, A.; Poojary, D. M.; Reis, K. P.; Thompson, M. E.
Chem. Mater. 1996, 8, 2239. (b) Song, P.; Xu, J .; Zhao, Y.; Yue, Y.; Xu,
Y.; Xu, R.; Hu, N.; Wie, G.; J ia, H. J . Chem. Soc., Chem. Commun.
1994, 1171. (c) Gendraud, P.; de Roy, M. E.; Besse, J . P. Inorg. Chem.
1996, 35, 6108. (d) Bonavia, G.; Haushalter, R. C.; O’Conner, C. J .;
Zubieta, J . Inorg. Chem. 1996, 35, 5603. (e) Soghomonian, V.; Haus-
halter, R. C.; Zubieta, J . Chem. Mater. 1995, 7, 1648. (f) Roca, M.;
Marcos, M. D.; Amoros, P.; Beltran-Porter, A.; Edwards, A. J .; Beltran-
Porter, D. Inorg. Chem. 1996, 35, 5613. (g) Bellito, C.; Federici, F.;
Ibrahim, S. A. J . Chem. Soc., Chem. Commun. 1996, 759. (h) Ganapati
Walawalkar, M.; Murugavel, R.; Voigt, A.; Roesky, H. W.; Schmidt,
H.-G. J . Am. Chem. Soc. 1997, 119, 4656.
† Universite´ du Maine and CNRS.
‡ A. N. Nesmeyanov Institute of Organoelement Compounds.
§ Universite´ Rennes-1.
(1) Ganapati Walawalkar, M.; Murugavel, R.; Roesky, H. W.;
Schmidt, H.-G. Organometallics 1997, 16, 516.
(2) Diemert, K.; Englert, U.; Kuchen, W.; Sandt, F. Angew. Chem.
1997, 109, 251; Angew. Chem., Int. Ed. Engl. 1997, 36, 241.
(5) Mortier, J .; Gridnev, I. D.; Fortineau, A.-D. Org. Lett. 1999, 1,
981.
10.1021/om000067v CCC: $19.00 © 2000 American Chemical Society
Publication on Web 09/19/2000

New Route to Molecular Borophosphonates
Organometallics, Vol. 19, No. 21, 2000 4267
Sch em e 1
Ta ble 1. P a r a m eter s of 11B a n d 31P NMR Sp ectr a
for th e Com p ou n d s 1-5, 7-11, 12-16, a n d 22-26
offers scope for using them as useful starting materials
for the preparationsthrough cage-fusionsof crystalline
solid-state boron phosphate materials with potential
catalytic and sorptive properties.3a,6 The preliminary
results of this investigation are reported in this paper.
R
R′
compd
δ(11B)a
δ(31P)b
Me
Et
1
7
12
22
30.58
37.55
24.38, 24.71
10
11.5
5.7
3
Resu lts a n d Discu ssion
PhCH2
Et
Et
Me
Et
2
8
13
23
27.70
30.05
18.51, 18.68
9
11.3
5.6
-4
Syn th esis a n d Ch a r a cter iza tion of Bor op h os-
p h on a tes 22-26. The interaction of dialkylphospho-
nates 1-5 with cyclohexyldichloroborane (6)7 in a 1:1
molar ratio in toluene at -30 °C afforded the corre-
sponding complexes 7-11, which were characterized by
1H, 13C, 11B, and 31P NMR spectra (Scheme 1). In all
complexes 7-11 the 11B chemical shifts are about 11
ppm, which corresponds to a tetracoordinated boron
atom (Table 1). The values of 31P chemical shifts in
complexes 7-11 are comparatively higher than those
of the corresponding phosphonates; therefore, the bond
between boron and phosphorus in complexes 7-11 is
coordinative.
CH2dCH
CH2dCHCH2
3
9
14
24
17.72
18.75
16.86, 16.95
-2
11.3
5.5
-4
4
10
15
25
30.15
34.3
21.27, 21.29
9
11.6
8.1
0
N3CH2
5
11
16
26
20.5
24.53
13.77, 13.83
0
11.7
7.3
-4
a
Referenced to external BF3‚Et2O. b Referenced to external 10%
Complexes 7-11 yielded mixtures of oligomers 22-
26 and 2 equiv of the corresponding alkyl chloride when
either heated for 12 h at 70 °C or stored for 2-3 days
at room temperature. The ESM microprobe analysis
showed for 22-26 an atomic ratio of phosphorus to
oxygen near 1:3 and a remaining chlorine content of less
than 0.5%. Borophosphonates 22-25 are insoluble in
common organic solvents, whereas 26 is soluble in
H3PO4.
hydrocarbons.8 We have managed to characterize 22-
25 with NMR, preparing them from diluted solutions
of the corresponding complexes. Clear gels first formed
in such experiments could be analyzed by NMR. How-
ever, the oligomers obtained from such gels after
evaporation of the solvent could not be solubilized.
All borophosphonates 22-26 were easily hydrolyzed
either by methanol at 30 °C or by refluxing with 10%
aqueous HCl, providing quantitative yields of the cor-
responding phosphonic acids 27-31 and cyclohexylbo-
ronic acid.9,10
(6) For general aspects of porous materials, see: (a) Zeolite Mi-
croporous Solids: Synthesis, Structure and Reactivity; Derouane, E.
G., Lemos, F., Naccache, C., Ribeiro, F. R., Eds.; Kluwer Academic:
Dordrecht, The Netherlands, 1992. (b) Catalytic Science and Technol-
ogy; Yoshida, S., Takezawa, N., Ono, T., Eds.; Kodansha: Tokyo, and
VCH: Weinheim, Germany, 1991; Vol. 1.
(7) 6 was prepared by the reaction of cyclohexene with dichlorobo-
rane ethyl etherate in the presence of boron trichloride: Brown, H.
C.; Ravindran, N. J . Am. Chem. Soc. 1973, 95, 2396.
(8) Gel chromatography of the soluble borophosphonate 26 showed
a broad mass distribution for n ) 3-7.

4268 Organometallics, Vol. 19, No. 21, 2000
Mortier et al.
F igu r e 1. 1H NMR spectra (300 MHz, toluene-d8, 297 K) of complex 10 and dimer 15. The inserts in the upper spectrum
show the appearance of the signal of aliphatic CH2 groups with decoupling from phosphorus (middle) and under the
conditions of triple resonance from phosphorus and the exo methylene group of the double bond.
NMR Mon itor in g of th e Rea ction s betw een Di-
a lk yl P h osp h on a tes a n d Cycloh exyld ich lor obo-
r a n e (7). To gain further insight into the mechanism
of these reactions and to be able to analyze their
individual steps, we have in each case monitored the
reaction by means of multinuclear NMR spectroscopy.
Overnight storage at room temperature of a sample
containing a solution of complex 7, 8, 10, or 11 led to
notable changes in the NMR spectra: the signals of the
different and was dependent on the solvent and con-
centration of the sample.
In the case of the complex of allyl dimethylphospho-
nate 10, the clean formation of 15swhose octahedral
core resembles the single-four-ring (4R) secondary
building unit (SBU) found in zeolites and phosphate
molecular sievesswas observed after 2 days at room
1
temperature. The monitoring of this process by H and
13C NMR showed that the transformation is direct and
quantitative: no stable intermediates were observed
between 10 and 15, and the dimer 15 does not react
further before all complex 10 is consumed (Figure 1 and
Figure 2a,b).
1
evolving alkyl chloride were detectable in the H and
13C NMR spectra, and new signals appeared in the 31P
and 11B NMR spectra. However, the complex 9, obtained
from vinylphosphonate 3, was unchanged under similar
conditions. Moreover, the character of the changes
observed for the complexes 7, 8, 10, and 11 was also
Compound 15 has been characterized by 1H, 13C, 11B,
and 31P NMR spectroscopy and by HRMS. While the
chemical shift of phosphorus is remarkably high-field-
shifted in 15 compared to complex 10, the same is valid,
although to a lesser extent, for the chemical shift of
boron (Table 1). The δ(31P) value of 21.3 is intermediate
between these in the starting phosphonate (δ 30.15) and
the resulting borophosphonate 25 (δ 9).2
(9) The initially formed dimethyl cyclohexylborate was further
hydrolyzed under these conditions.
(10) Dealkylation of phosphonate diisopropyl esters using Me3-
SiBr: (a) Salomon, C. J .; Breuer, E. Tetrahedron Lett. 1995, 36, 6759.
Phosphonate ester hydrolysis catalyzed by lanthanum ions: (b) Tsu-
bouchi, A.; Bruice, T. C. J . Am. Chem. Soc. 1995, 117, 7399. (c)
Tsubouchi, A.; Bruice, T. C. J . Am. Chem. Soc. 1994, 116, 11614.

New Route to Molecular Borophosphonates
Organometallics, Vol. 19, No. 21, 2000 4269
F igu r e 2. Evolution of the 31P NMR spectrum (121 MHz, toluene-d8, 300 K) of the sample obtained by mixing equivalent
amounts of dimethyl allylphosphonate (4) and cyclohexyldichloroborane (6): (a) initial spectrum; (b) after 2 days; (c) after
4 days; (d) after 1 week; (e) after 2 weeks.
Two isomers of 15 in a 1:1 ratio are found in the NMR
spectra. Thus, in the 31P NMR spectrum, two sharp
signals of equal intensity are observed (Table 1 and
Figure 2b). Similar splittings are found for the signal
the relative rates of several competitive processes and
is strongly dependent on the electronic properties of the
radicals of the phosphonate and the borane, as well as
on the solvent, concentration, temperature conditions,
etc.
1
of the CH2P group in the 13C NMR spectrum. In the H
NMR spectrum of 15 the protons of the CH2P group of
each isomer give an AB system, in contrast to complex
10, where the two protons of the CH2P group are
equivalent (Figure 1). Five isomers distinguishable by
NMR are possible for the molecule of 15. Fast dissocia-
tion-association of coordinative bonds in 15 averages
the signals of the isomers, which differ in the configu-
ration at the boron atoms.
Further transformation of 15 is not selective even at
room temperature (Figure 2c-e). Together with the
decrease of intensity of the signal corresponding to 15,
at least 10 signals of comparable intensity appear after
4 days (Figure 2c), and after 2 weeks the most intense
broad signal corresponds to oligomer 25 (Figure 2e).
Analysis of the values of the chemical shifts of boron
and phosphorus for the starting phosphonates, com-
plexes 7-11, dimers 12-16, and the resulting boro-
phosphonates 22-26 (Table 1) shows that the process
of oligomerization is characterized by a gradual shift of
the signals in the 11B and 31P NMR spectra toward zero
and even negative values, indicating that the resulting
oligomers are truly borophosphonates and not mixed
The characteristic NMR spectra of dimeric molecules
such as 15 allowed us to detect in the corresponding
reaction mixtures the signals of dimers 12-14 and 16
(Table 1). However, in these cases the dimers were
observed together with already formed oligomers 22-
24 and 26 and some unidentified intermediates. Appar-
ently, the possibility of observing a clear formation of a
dimer, as in the case of compound 15, is regulated by

4270 Organometallics, Vol. 19, No. 21, 2000
Mortier et al.
F igu r e 3. 11B (96 MHz, CDCl3, 300 K; left) 31P (121 MHz, CDCl3, 300 K; middle), and 14N (22 MHz, CDCl3, 300 K; right)
NMR spectra: (a) complex 11; (b) dimer 16 mixed with oligomer; (c) oligomer 26.
Sch em e 2
benzylphosphonic acid and dimethylborinic acid (35c)
in a 10:1:1 ratio was obtained quantitatively. Metha-
nolysis of 35a -c afforded benzylphosphonic acid mono-
methyl ester (18) and dimethylborinic acid.
The relative integral intensities in the 1H NMR
spectrum of 35 show the loss of one ethoxy group from
the starting phosphonate 2. In the high-resolution mass
spectrum molecular peaks at m/z 440 (35a ) and 220
(35b,c) with the expected isotopic distributions were
found. In the 31P spectrum (Figure 4) two close signals
at 17.65 and 17.66 ppm correspond to two isomers of
35a , whereas a broad resonance at 25.5 ppm originates
from 35b,c (Figure 4a). In 11B NMR 35a ,b resonate at
11.2 ppm, whereas 35c gives a signal at 32 ppm.
anhydrides, as had been proposed by Gerrard.11 This is
well illustrated by Figure 3, which displays the spectral
changes observed during the formation of the borophos-
phonate 26. It is of interest to note that the 14N NMR
spectrum is unchanged, attesting to the complete con-
servation of azido groups in the resulting oligomer,
although the organic azides are known to react rapidly
with dichloroboranes.12
The use of dibromoborane 32 in the reaction with
phosphonate 1 facilitates the formation of a borophos-
phonate. Thus, the high yield of [MePO3BMe]n (33) has
been obtained after overnight storage of the reaction
mixture at ambient temperature (Scheme 2).
Stu d y of th e Dyn a m ic Beh a vior of th e Cyclic
Dim er 35a . The main difficulty in studying the proper-
ties of cyclic dimers 12-16 is their easy further trans-
formation to the oligomeric borophosphonates 22-26.
To prepare a stable compound similar to 12-16, we
have treated diethyl benzylphosphonate (2) with di-
methylbromoborane (34)13 in deuteriochloroform (Scheme
3). After several minutes at room temperature 1 equiv
of ethyl bromide was formed, and a mixture of cyclic
borophosphonates 35a ,b and the mixed anhydride of
Storage of a sample containing the solution of 35 in
deuteriochloroform at room temperature for 2 weeks
resulted in a dramatic change of the relative concentra-
tions of 35a -c. The relative ratios of 35a -c could be
estimated now as 2:3:3, and in addition a new broad
signal at approximately 22 ppm appeared. From the
appearance of the spectrum shown in Figure 4b it is
clear that compounds 35a -c are in dynamic equilibrium
with each other. To study this phenomenon more
precisely, we have measured NMR spectra of 35 at
various temperatures (Figure 5).
Pronounced dynamic effects were found in the 1H, 13C,
and 31P NMR spectra of compound 35. Most informative
are temperature-dependent 31P NMR spectra at a
concentration of 1 mol/L. At 60 °C compound 35 gives a
single resonance at δ 25 (Figure 5f). Lowering the
temperature leads first to the broadening of this signal
(Figure 5e), which splits into three separate broad
(11) Gerrard, W.; Griffey, P. F. Chem. Ind. 1959, 55.
(12) Suzuki, A.; Sono, S.; Itoh, M.; Brown, H. C.; Midland, M. M. J .
Am. Chem. Soc. 1971, 93, 4329.
(13) Noth, H.; Vahrenkamp, H. J . Organomet. Chem. 1968, 11, 399.

New Route to Molecular Borophosphonates
Organometallics, Vol. 19, No. 21, 2000 4271
F igu r e 4. Evolution of the 31P NMR spectrum (121 MHz, CDCl3, 300 K) of compound 35: (a) immediately after preparation;
(b) after 2 weeks. Asterisks indicate an impurity of the starting phosphonate 2.
Sch em e 3
resonances at room temperature at δ values of ap-
proximately 18, 22, and 28 ppm, corresponding to 35a -
c, respectively (Figure 5d). Further lowering of the
temperature affects these three signals differently.
the elucidation of their structure is extremely compli-
cated due to their great number and low concentration.
On the basis of this temperature dependence of the
phosphorus spectrum we conclude that 35b,c are in a
fast equilibrium, whereas the equilibrium between 35c
and 35a is relatively slow (Scheme 4). Two peaks for
35b in the 31P spectrum at -55 °C probably correspond
to compounds with equatorial and axial orientations of
the benzyl group. Larger cycles similar to 35a are
probably involved in the equilibrium at high concentra-
tions.
The high-field signal of 35a at -20 °C is transformed
to two sharp signals of two isomers at 19.6 and 19.7
ppm (Figure 5c). The most intense low-field signal (δ
28 at 24 °C) gives at -20 °C a broad resonance of two
collapsed signals. At -40 °C two broad signals of equal
intensity are observed (Figure 5b), one of which is split
into two resonances at -55 °C (Figure 5a). Additionally,
the broad peak of low intensity observed in the 31P NMR
at room temperature at 22 ppm turns at -20 °C into
10 or 12 small peaks in the chemical shift interval 21-
25 ppm. From the temperature dependence of the line
shape it is clear that all compounds producing these
resonances are involved in the whole equilibrium, but
Thus, the dimer 35a is the primary product in the
reaction of phosphonate 2 with dimethylbromoborane
(32). Heating or prolonged storage at room temperature
transforms 35a into a mixture in equilibrium consisting
of 35a -c and other unidentified products. The equilib-
rium concentration of 35a is rather low (about 5%), but

4272 Organometallics, Vol. 19, No. 21, 2000
Mortier et al.
F igu r e 5. Temperature dependence of the 31P NMR spectrum (121 MHz, CDCl3, 1 mol/L) of compound 35; for discussion
see text. Asterisks indicate an impurity of the starting phosphonate 2.
its relatively high barrier of dissociation makes possible
the detection of 35a as a primary product.
gives a dimer, this may result in synthesis of a cubanoid
framework such as those described by Roesky1 and
Kuchen.2 However, only one isomer among five possible
is appropriate for that, whereas the other four would
again produce a statistical oligomer (Scheme 5). There-
fore, for the selective formation of the cubanoid frame-
work, the all-cis isomer of a dimer should be more stable
than the other four, react more quickly, or both. Since
all the known examples of cubanoid structures possess
a bulky substituent on phosphorus, one can propose that
these bulky substituents link the molecules of the all-
cis isomer of a dimer in a conformation, where they
occupy exclusively equatorial positions. This can result
both in stabilization of the all-cis isomer compared with
the other four and in higher reactivity, since all chlorine
atoms and alkoxy groups are axial and “ready-to-react”.
Although the borophosphonates 22-26 give in the
Our observations allow us to propose that dimers 12-
16 are also primary products in the oligomerization
reaction of complexes 7-11. Complexes 7-11 do not
react with an excess of 6 but react vigorously with an
additional amount of the corresponding phosphonate,
producing soluble oligomers. Therefore, the molecule of
a phosphonate incorporated into the complex is deacti-
vated, and the most probable result is a bimolecular
push-pull mechanism, resulting directly in a dimer
(Scheme 4). On the basis of the dynamic properties of
the dimer 35a we propose that similar equilibria operate
also in the case of dimers 12-16. Therefore, when the
dimer is formed, it may isomerize to a monomer, which
in turn would produce a statistical oligomer.
If the elimination of two molecules of alkyl chloride

New Route to Molecular Borophosphonates
Organometallics, Vol. 19, No. 21, 2000 4273
Sch em e 4
Sch em e 5
mass spectra the ions [RPO3BC6H11]4-C6H11, which
may be attributed to the cubanoid structures 22′-26′
(Scheme 1), their NMR spectra contain broad reso-
nances characteristic for statistical oligomers.1,14 An
interesting structural feature of these compounds is the
resemblance of their central M4O12P4 cubic core to the
D4R (double-four-tetrahedral-atom-ring) SBUs found in
cloverite, ULM-5,15 and gallophosphate-A.16 These com-
pounds can be regarded as potential precursors for the
preparation of molecular sieves and ion conductors.
We conclude therefore that structure of the oligomers
22-26 is not definite, and the peaks observed in the
mass spectra correspond to the lightest molecules
present in the mixture. Apparently, the molecules with
higher molecular weights are difficult to detect in the
EI mass spectra, whereas the measurement of the FAB
mass spectra is impossible due to hydrolysis of 22-26
by the matrix.
polyhedral structures. The cage molecules thus obtained
will serve us as precursors for the studies of their
transformation to three-dimensional borophosphonate
materials by nonaqueous routes. Alternatively, the
method should provide a convenient new route for
effective phosphonate deprotection.
Exp er im en ta l Section
All operations were performed under an atmosphere of dry
nitrogen using standard Schlenk techniques. Commercially
available phosphonates were used without additional purifica-
tion. Cyclohexyldichloroborane (6)7 and methyldibromoborane
(32)13 were prepared according to known procedures. NMR
spectra were recorded on Bruker ARX-200, Bruker AC-300,
1
and Bruker WM-300 spectrometers. Chemical shifts in the H
and 13C NMR spectra are referenced to internal standard TMS,
11B chemical shifts to external BF3‚Et2O, and 31P chemical
shifts to external 10% H3PO4. Electron impact mass spectra
were measured on a Finnigan-MAT instrument at 280-320
°C. Electron microscopy and microprobe analyses were carried
out on J EOL instruments.
Con clu sion
In this article, we have demonstrated the use of
phosphonates and organohaloboranes as precursors for
framework borophosphonates through a facile haloal-
kane elimination reaction. Small changes in the bulki-
ness of the substituents on boron or phosphorus should
allow the isolation of borophosphonates with different
Rea ction s of Alk ylp h osp h on a tes w ith Cycloh exyld i-
ch lor obor a n e (7). Gen er a l P r oced u r es. Syn th esis of
Bor op h osp h on a tes 22-26. Neat phosphonate (1 equiv) was
quickly added to a solution of cyclohexyldichloroborane (1
equiv) in 50 mL of toluene at -30 °C. The reaction mixture
was warmed to ambient temperature. The NMR analysis of
the reaction mixtures at this stage indicated the clear and
quantitative formation of the corresponding complex 7-11.
The subsequent heating of this solution for 12 h at 70 °C (48
h in the case of complex 9) led to evolution of 2 equiv of alkyl
chloride. Then all volatiles were removed under vacuum; the
(14) Only compounds that contain bulky alkyl groups on phosphorus
(e.g., t-Bu) are reported to be stable. See ref 3a, p 119.
(15) Loiseau, T.; Fe´rey, G. J . Solid State Chem. 1994, 111, 403.
(16) Merrouche, A.; Patarin, J .; Soulard, M.; Kessler, H.; Angelrot,
D. Synth. Microporous Mater. 1992, 1, 384.

4274 Organometallics, Vol. 19, No. 21, 2000
Mortier et al.
resulting solid oligomers were washed twice with ether and
dried under high vacuum.
3J HH ) 7.0 Hz), 1.2 (m, 10H of cyclohexyls), 1.6 (m, 10H of
cyclohexyls), 3.4 (m, 4H, 2CH2P), 4.1 (m, 4H, 2CH2O), 7.3 (m,
10H, 2C6H5). 13C NMR (50 MHz, CDCl3, 300 K): δ 15.69 (d,
2CH3, 3J CP ) 7.1 Hz), 27.24, 27.87, 28.79 (3CH2 of cyclohexyl),
Detection of Dim er s 12-16. If the solution of any complex
7-11 was stored for several days at ambient temperature, the
corresponding dimers 12-16 were observed in the NMR
spectra of the reaction mixtures. Only in the case of dimer 15
was the reaction clean and complete. In other cases dimers
12-14 and 16 were observed either in equilibria with mono-
mers or together with already formed oligomers.
Hyd r olysis of th e Mixtu r es of Oligom er s 22-26. A 100
mg portion of a mixture of oligomers was introduced in an
NMR tube, and 0.4 mL of CD3OD was added. Slight heating
of the resulting suspension with an air gun gave a clear
solution, which according to NMR analysis contained cyclo-
hexylboronic acid 9 and the corresponding phosphonic acids
27-31. Otherwise, 100 mg of an oligomeric borophosphonate
was heated for 10 min at 100 °C in 10% HCl. When the
resulting clear solution was cooled to room temperature,
cyclohexylboronic acid precipitated. The remaining solution
contained the corresponding phosphonic acids 27-31.
Reaction of methylphosphonate (2; 0.82 g, 5.4 mmol) and
cyclohexyldichloroborane (6; 0.89 g, 5.4 mmol) gave 0.95 g
(94%) of borophosphonate 22.
1
33.50 (d, 2CH2P, J CP ) 150.1 Hz), 34.6 (br, CHB), 66.65 (d,
3
3
CH2O, J CP ) 9.4 Hz), 66.70 (d, CH2O, J CP ) 8.3 Hz), 127.45
5
4
(d, p-C, J ) 3.4 Hz), 128.46 (d, m-C, J ) 3.5 Hz), 129.45 (d,
Cquat,
3J ) 10.8 Hz), 130.41 (d, o-C, 3J ) 7.4 Hz). 31P NMR
(121 MHz, C7D8, 297 K): δ 18.51 (1P), 18.68 (1P). 11B NMR
(96 MHz, C7D8, 297 K): δ 5.7.
1
Bor op h osp h on a te 23. H NMR (300 MHz, C7D8, 297 K):
δ 0.6-1.6 (unresolved multiplet, cyclohexyl), 2.8-3.6 (br,
CH2P), 7.0-7.4 (br, C6H5). 31P NMR (121 MHz, C7D8, 297 K):
δ 3.5 (ν1/2 ) 1000 Hz). 11B NMR (96 MHz, C7D8, 297 K): δ -1
(ν1/2 ) 900 Hz). Cubic tetramer 23′ was mainly observed in
MS (IE). HRMS (IE): calcd for C46H61O1211B4P4, 973.34855;
found, 973.3486. MS (IE): m/z 973 (M - C6H11).
Ben zylp h osp h on ic Acid (28). 1H NMR (200 MHz, CD3-
1
OD, 300 K): δ 3.11 (d, 2H, CH2P, J ) 21.7 Hz), 7.1-7.4 (m,
5H, C6H5). 13C NMR (50 MHz, CD3OD, 300 K): δ 34.44 (d,
1
5
CH2P, J ) 135.0 Hz), 126.12 (d, p-C, J ) 3.4 Hz), 127.95 (d,
m-C, 4J ) 2.9 Hz), 129.48 (d, o-C, 3J ) 6.3 Hz), 132.89 (d, Cquat
3J ) 9.3 Hz). 31P NMR (121 MHz, CD3OD, 297 K): δ 25.3.
,
Reaction of diethyl vinylphosphonate (3; 470 mg, 2.89 mmol)
with cyclohexyldichloroborane (6; 480 mg, 2.89 mmol) gave 435
mg (75%) of borophosphonate 24.
Dieth yl Meth ylp h osp h on a te-Cycloh exyld ich lor obo-
r a n e Com p lex (7). 1H NMR (300 MHz, CDCl3, 297 K): δ 0.61
3
(t, 1H, CHB, J aa ) 11.4 Hz), 1.06 (m, 2H of cyclohexyl), 1.19
(m, 3H of cyclohexyl), 1.44 (t, 6H, 2CH3, 3J ) 7.0 Hz), 1.70 (m,
3H of cyclohexyl), 1.81 (m, 2H of cyclohexyl), 2.03 (d, 3H, CH3P,
2J HP ) 18.3 Hz). 13C NMR (50 MHz, CDCl3, 300 K): δ 10.97
Diet h yl Vin ylp h osp h on a t e-Cycloh exyld ich lor ob o-
r a n e Com p lex (9). 1H NMR (200 MHz, CDCl3, 300 K): δ 1.21
(m, 6H of cyclohexyl), 1.39 (t, 6H, 2CH3, 3J ) 7.0 Hz), 1.75
(m, 3H of cyclohexyl), 1.89 (m, 2H of cyclohexyl), 6.2-6.8
(m, 3H, CHdCH2). 13C NMR (50 MHz, CDCl3, 300 K): δ 15.87
1
3
(d, CH3P, J CP ) 139.4 Hz), 16.00 (d, 2CH3, J CP ) 6.5 Hz),
27.26, 27.86, 28.75 (3CH2 of cyclohexyl), 35.5 (br, CHB), 66.58
2
3
(d, 2CH2, J CP ) 7.6 Hz). 31P NMR (121 MHz, CDCl3, 297 K):
(d, 2CH3, J CP ) 6.4 Hz), 27.02, 27.87, 28.53 (3CH2 of
2
δ 37.55. 11B NMR (96 MHz, CDCl3, 297 K): δ 11.5.
cyclohexyl), 37.2 (br, CHB), 67.22 (d, 2CH2, J CP ) 7.2 Hz),
1
120.08 (d, CHd, J CP ) 192.8 Hz), 141.05 (CH2d). 31P NMR
Dim er 12. 1H NMR (300 MHz, C7D8, 297 K): δ 0.92 (m,
2H, 2CHB), 1.20 (m, 10H of cyclohexyls), 1.25 (m, 6H, 2CH3),
(121 MHz, CDCl3, 297 K): δ 18.7. 11B NMR (96 MHz, CDCl3,
297 K): δ 11.3.
2
2
1.49 (d, 3H, CH3, J HP ) 19.1 Hz), 1.51 (d, 3H, CH3, J HP
)
18.8 Hz), 1.98 (m, 10H of cyclohexyls), 4.2 (m, 4H, 2CH2). 13C
Dim er 14. 13C NMR (75 MHz, C7D8, 297 K): δ 67.95 (d,
1
3
3
NMR (75 MHz, C7D8, 297 K): δ 12.25 (d, CH3P, J CP ) 150.2
CH2O, J CP ) 7.4 Hz), 68.37 (d, CH2O, J CP ) 7.4 Hz), 119.12
1 1
1
3
Hz), 12.31 (d, CH3P, J CP ) 154.4 Hz), 15.85 (d, 2CH3, J CP
)
(d, dCHP, J CP ) 189.0 Hz), 119.31 (d, dCHP, J CP ) 193.0
Hz), 143.33 (CH2d). 31P NMR (121 MHz, CDCl3, 297 K): δ
16.96 (1P), 17.61 (1P). 11B NMR (96 MHz, CDCl3, 297 K): δ
5.4.
7.3 Hz), 27.18, 27.60, 28.23 (3CH2 of cyclohexyl), 33.5 (br,
3
3
CHB), 65.18 (d, CH2O, J CP ) 8.6 Hz), 65.36 (d, CH2O, J CP
)
7.3 Hz). 31P NMR (121 MHz, C7D8, 297 K): δ 24.38 (1P), 24.71
(1P). 11B NMR (96 MHz, C7D8, 297 K): δ 5.7.
1
Bor op h osp h on a te 24. H NMR (300 MHz, C7D8, 297 K):
1
Bor op h osp h on a te 22. H NMR (300 MHz, C7D8, 297 K):
δ 1.0-2.2 (unresolved multiplet, cyclohexyl), 6.0-6.8 (br,
CHdCH2). 13C NMR (75 MHz, C7D8, 300 K): δ 26-29 (br,
cyclohexyl), 123 (br doublet, CHd), 137 (br, CH2).; 31P NMR
(121 MHz, C7D8, 297 K): δ 0.7 (ν1/2 ) 1000 Hz). 11B NMR (96
MHz, C7D8, 297 K): δ -0.5 (ν1/2 ) 1000).
δ 1.0-2.2 (unresolved multiplet, cyclohexyl, CH3P), 13C NMR
1
(75 MHz, C7D8, 300 K): δ 13 (br d, CH3P, J CP approximately
150 Hz), 28 (br, cyclohexyl). 31P NMR (121 MHz, C7D8, 297
K): δ 10 (br). 11B NMR (96 MHz, C7D8, 297 K): δ 3.0. High-
1
resolution EI mass spectrum: m/z 669 ([C7H14PO3B]4
-
Vin ylp h osp h on ic Acid (29). H NMR (200 MHz, CDCl3,
C6H11)+. HRMS (EI): calcd for C22H45O1211B4P4, 669.22335;
found, 669.2237. MS (IE): m/z 669 (M - C6H11).
300 K): δ 5.8-6.3 (m, 3H, CHdCH2). 13C NMR (50 MHz,
1
CDCl3, 300 K): δ 128.25 (d, CHd, J CP ) 184.3 Hz), 132.72
Meth ylp h osp h on ic Acid (27). 1H NMR (300 MHz, CD3-
(CH2d).
2
OD, 297 K): δ 1.44 (d, 3H, CH3P, J HP ) 17.6 Hz). 13C NMR
Reaction of dimethyl allylphosphonate (4; 135 mg, 0.90
mmol) with cyclohexyldichloroborane (6; 150 mg, 0.90 mmol)
gave 150 mg (78%) of borophosphonate 25.
(75 MHz, CD3OD, 297 K): δ 13.03 (d, CH3P, 1J CP ) 140.6 Hz).
31P NMR (121 MHz, CD3OD, 297 K): δ 30.55.
Reaction of diethyl benzylphosphonate (2; 584 mg, 2.56
mmol) with cyclohexyldichloroborane (6; 425 mg, 2.56 mmol)
gave 0.95 g (94%) of borophosphonate 23.
Dim eth yl Allylp h osp h on a te-Cycloh exyld ich lor obo-
r a n e Com p lex (10). 1H NMR (200 MHz, C7D8, 300 K): δ 1.09
(m, 1 H, CHB), 1.50 (m, 5H of cyclohexyl), 2.05 (m, 3H of
cyclohexyl), 2.30 (m, 2H of cyclohexyl), 2.99 (dd, 2H, CH2P,
2J HP ) 22.7 Hz, 3J HH ) 7.2 Hz), 3.76 (d, 6H, 2CH3, 3J HP ) 11.5
Hz) 5.20 (m, 2H, CHdCH2), 5.68 (m, 1 H, CHdCH2). 13C NMR
(50 MHz, C7D8, 300 K): δ 28.02, 29.31, 30.16 (3CH2 of
Dieth yl Ben zylp h osp h on a te-Cycloh exyld ich lor obo-
r a n e Com p lex (8). 1H NMR (200 MHz, CDCl3, 300 K): δ 0.72
(t, 1H, CHB, 3J aa ) 11.6 Hz), 1.2 (m, 5H of cyclohexyl), 1.40 (t,
6H, 2CH3, 3J ) 6.3 Hz), 1.8 (m, 5H of cyclohexyl), 3.82 (d, 2H,
2
1
CH2P, J HP ) 21.9 Hz), 7.5 (m, 5H, C6H5). 13C NMR (50 MHz,
cyclohexyl), 30.50 (d, CH3P, J CP ) 137.3 Hz), 37.6 (br, CHB),
CDCl3, 300 K): δ 15.86 (d, 2CH3, 3J CP ) 6.1 Hz), 27.16, 27.78,
57.38 (d, 2CH3, J CP ) 8.1 Hz); 123.83 (d, CH2d, J CP ) 15.9
2
3
1
2
28.70 (3CH2 of cyclohexyl), 32.74 (d, CH3P, J CP ) 132.1 Hz),
Hz), 124.53 (d, CHd, J CP ) 12.6 Hz). 31P NMR (121 MHz,
2
35.5 (br, CHB), 67.33 (d, 2CH2, J CP ) 7.4 Hz), 128.02 (p-C),
C7D8, 297 K): δ 34.31. 11B NMR (96 MHz, C7D8, 297 K): δ
3
128.83 (m-C), 129.95 (d, o-C, J CP ) 7.0 Hz), Cquat not found.
11.6.
31P NMR (121 MHz, CDCl3, 297 K): δ 30.05. 11B NMR (96
MHz, CDCl3, 297 K): δ 11.3.
1
Dim er 15. H NMR (300 MHz, C7D8, 297 K): δ 0.92 (m, 1
H, CHB), 1.50 (m, 5H of cyclohexyl), 2.08 (m, 5H of cyclohexyl),
1
Dim er 13. H NMR (200 MHz, CDCl3, 300 K): δ 0.40 (m,
2.97 and 2.98 (2 AB systems, 4H, 2CH2P, 2J HP ) 23.7 Hz, 2J HH
2H, 2CHB), 1.07 (t, 3H, CH3, 3J HH ) 6.9 Hz), 1.08 (t, 3H, CH3,
) 15.1 Hz, J HH ) 6.9 Hz), 3.80 (d, 3H, CH3, J HP ) 11.8 Hz),
3
3

New Route to Molecular Borophosphonates
Organometallics, Vol. 19, No. 21, 2000 4275
3.81 (d, 3H, CH3, 3J HP ) 11.8 Hz), 5.22 (m, 2H, CHdCH2), 5.80
(m, 1 H, CHdCH2). 13C NMR (50 MHz, C7D8, 300 K): δ 28.69,
29.17, 29.51 (3CH2 of cyclohexyl), 32.66 (d, CH3P, 1J CP ) 151.5
2J BP ) 12.6 Hz), 4.42 (m, 4H, 2CH2O). 13C NMR (50 MHz, C7D8,
3
300 K): δ 16.01 (d, 4 CH3, J CP ) 6.1 Hz), 27.65, 28.15, 29.10
1
(3CH2 of cyclohexyl), 32.5 (br, CHB), 44.51 (d, CH2P, J CP
)
1
1
Hz), 32.70 (d, CH3P, J CP ) 151.2 Hz), 34.5 (br, CHB), 56.80
172.1 Hz), 45.93 (d, CH2P, J CP ) 174.6 Hz), 67.86 (d, 2CH2,
2J CP ) 9.1 Hz). 31P NMR (121 MHz, C7D8, 297 K): δ 13.55
(1P), 13.48 (1P). 11B NMR (96 MHz, C7D8, 297 K): δ 8.1. 14N
NMR (22 MHz, CDCl3, 297 K): δ -332 (br), -164.8, -135.3.
2
3
(d, 2CH3, J CP ) 8.7 Hz), 122.57 (d, 2CH2d, J CP ) 15.3 Hz),
126.35 (d, 2CHd, J CP ) 13.1 Hz). 31P NMR (121 MHz, C7D8,
2
297 K): δ 21.27 (1P), 21.29 (1P). 11B NMR (96 MHz, C7D8, 297
K): δ 8.1. HRMS: calcd for C14H27O611B2P235Cl2, 445.08459;
found, 445.0831. MS (IE): m/z 493 (M - Cl), 445 (M - C6H11).
1
Bor op h osp h on a te 26. H NMR (300 MHz, C7D8, 297 K):
δ 1.0-2.2 (unresolved multiplet, cyclohexyl), 3.9-4.2 (br,
CH2P). 13C NMR (75 MHz, C7D8, 300 K): δ 26-29 (br,
cyclohexyl), 45 (br doublet, CH2P), 137 (br, CH2). 31P NMR (121
MHz, C7D8, 297 K): δ 3.7 (ν1/2 ) 300 Hz), -6.2 (sharp). 11B
NMR (96 MHz, C7D8, 297 K): δ -4 (ν1/2 ) 180 Hz). 14N NMR
(22 MHz, CDCl3, 297 K): δ -332 (br), -164.8, -135.3.
1
Bor op h osp h on a te 25. H NMR (300 MHz, C7D8, 297 K):
δ 0.6-1.6 (unresolved multiplet, cyclohexyl), 2.4 (br, CH2P),
4.9-5.2 (br, CHdCH2), 5.4-5.8 (br, CHd). 31P NMR (121 MHz,
C7D8, 297 K): δ 0.7 (ν1/2 ) 1000 Hz). 11B NMR (96 MHz, C7D8,
297 K): δ 0 (ν1/2 ) 600 Hz). The ion M+ - C6H11 corresponding
to tetramer 25′ was detected by high-resolution EIMS spec-
troscopy: HRMS: calcd for C30H53O1211B4P4, 773.28595; found,
773.2867. MS (IE): m/z 773 (M - C6H11).
1
Azid om eth ylp h osp h on ic Acid (31). H NMR (300 MHz,
2
CD3OD, 300 K): δ 3.40 (d, 2H, CH2P, J HP ) 12.0 Hz). 13C
NMR (50 MHz, CD3OD, 300 K): δ 45.37 (d, CH2P, 1J CP ) 157.1
Hz), 118.65 (d, CH2d, 3J CP ) 14.3 Hz). 31P NMR (81 MHz, CD3-
OD, 297 K): δ 15.29.
1
Allylp h osp h on ic Acid (30). H NMR (200 MHz, CD3OD,
2
3
300 K): δ 2.70 (dddd, 2H, CH2P, J HP ) 22.1 Hz, J HH ) 7.4
4
Hz, J HH ) 1.1 Hz), 5.30 (m, 2H, CHdCH2), 6.00 (m, 1 H,
Rea ction of Dieth yl Ben zylp h osp h on a te (2) w ith Di-
m eth ylbr om obor a n e (34). Diethyl benzylphosphonate (2;
187 mg, 0.82 mmol) was quickly added to a solution of Me2-
BBr (34; 100 mg, 0.82 mmol) in 1 mL of deuteriotoluene. The
reaction mixture was warmed to room temperature and left
overnight. The NMR analysis showed the clear formation of
equivalent amounts of ethyl bromide and an equilibrium
mixture of 35a -c. Evaporation of the volatiles under vacuum
gave 180 mg (91%) of a slightly yellow viscous oil.
CHdCH2). 13C NMR (50 MHz, CD3OD, 300 K): δ 32.74 (d,
1
3
CH2P, J CP ) 137.0 Hz), 118.65 (d, CH2d, J CP ) 14.3 Hz),
128.39 (d, CHd, J CP ) 11.1 Hz). 31P NMR (121 MHz, CDCl3,
2
297 K): δ 26.9.
Reaction of diethyl azidomethylphosphonate (5;17 294 mg,
1.52 mmol) with cyclohexyldichloroborane (6; 260 mg, 1.52
mmol) gave 330 mg (95%) of borophosphonate 26.
Dieth yl Azid om eth ylp h osp h on a te-Cycloh exyld ich lo-
r obor a n e Com p lex (11). 1H NMR (300 MHz, CDCl3, 297 K):
Equ ilibr iu m Mixtu r e 35a -c. 1H NMR (300 MHz, CDCl3,
3
3
δ 0.64 (tt, 1 H, CHB, J aa ) 11.7 Hz, J ae ) 2.7 Hz), 1.06 (m,
2H of cyclohexyl), 1.19 (m, 4H of cyclohexyl), 1.45 (t, 6H, 2CH3,
3J ) 7.1 Hz), 1.70 (br m, 4H of cyclohexyl), 1.81 (m, 2H of
cyclohexyl), 4.17 (d, 2H, CH2P, 2J ) 11.4 Hz), 4.55 (m, 4H,
2CH2O). 13C NMR (75 MHz, CDCl3, 300 K): δ 16.19 (d, 2CH3,
3J CP ) 5.4 Hz), 27.20, 27.79, 28.72 (3CH2 of cyclohexyl), 35.5
(br, CHB), 45.07 (d, CH3P, 1J CP ) 155.8 Hz), 66.5 (br, 2CH2O).
31P NMR (121 MHz, CDCl3, 297 K): δ 24.53. 11B NMR (96
MHz, CDCl3, 297 K): δ 11.7. 14N NMR (22 MHz, CDCl3, 297
K): δ -332 (br), -164.8, -135.3.
3
297 K): δ 0.61 (t, 1H, CHB, J aa ) 11.4 Hz), 0.35 (s, 6H,
3
2CH3B), 0.85 (t, CH3CH2O, J ) 6.9 Hz), 2.90 (d, 2H, CH2P,
2J HP ) 22.4 Hz), 3.64 (br 2H, CH3CH2O), 6.9-7.2 (m, 5H,
C6H5). 13C NMR (75 MHz, C7D8, 300 K): 9.89 (br, 2CH3B),
3
1
15.90 (d, CH3CH2O, J CP ) 6.5 Hz), 34.30 (d, CH3P, J CP
)
148.1 Hz), 63.96 (br, CH2). 31P NMR (121 MHz, CDCl3, 297
K): 17.66. 11B NMR (96 MHz, CDCl3, 297 K): 11.2. The high-
resolution mass spectrum supports the structure.
Methanolysis of 35 gave the benzylphosphonic acid mono-
ethyl ester 18.
1
Dim er 16. H NMR (300 MHz, CDCl3, 297 K): δ 0.64 (tt,
Ben zylp h osp h on ic Acid Mon oeth yl Ester (18). 1H NMR
3
3
1H, CHB, J aa ) 11.7 Hz, J ae ) 2.7 Hz), 1.06 (m, 2H of
cyclohexyl), 1.19 (m, 4H of cyclohexyl), 1.45 (t, 6H, 2CH3, 3J )
7.1 Hz), 1.70 (br m, 4H of cyclohexyl), 1.81 (m, 2H of
cyclohexyl), 3.84 (ABX system, 2H, CH2P, δA 3.81, δB 3.87, 2J AB
) 15.5 Hz, 2J AP ) 13.2 Hz, 2J BP ) 12.2 Hz), 3.86 (ABX system,
3
(200 MHz, C7D8 + CD3OD, 300 K): δ 1.32 (td, 3H, CH3, J HH
4
1
) 7.1 Hz, J HP ) 0.4 Hz), 3.25 (d, 2H, CH2P, J HP ) 21.6 Hz),
3
3
4.08 (dq, 2H, CH2O, J HH ) 7.1 Hz, J HP ) 0.7 Hz), 7.40 (m,
5H, C6H5). 13C NMR (50 MHz, C7D8 + CD3OD, 300 K): δ 33.20
1
2
2
2
(d, CH2P, J CP ) 136.5 Hz), 61.63 (d, CH2O, J CP ) 6.6 Hz),
2H, CH2P, δA 3.82, δB 3.90, J AB ) 15.3 Hz, J AP ) 13.2 Hz,
5
4
126.46 (d, p-C, J CP ) 3.6 Hz), 128.15 (d, m-C, J CP ) 3.1 Hz),
3
2
129.62 (d, o-C, J CP ) 6.5 Hz), 132.11 (d, Cquat, J CP ) 9.3 Hz).
(17) 5 was obtained by treatment of diethyl R-iodophosphonate
(Lancaster) with sodium azide in DMSO: Berte´-Verrando, S.; Nief,
F.; Patois, C.; Savignac, P. Phosphorus, Sulfur Silicon Relat. Elem.
1995, 103, 91.
31P NMR (121 MHz, C7D8 + CD3OD, 297 K): δ 25.5.
OM000067V