On the alkylation of Ph3PCHP(O)Ph2: Formation and crystal structures of neutral and cationic addition compounds

Article abstract of DOI:10.1002/ejic.201301427

Ylide Ph₃PCHP(O)Ph₂ (1) is the hydrolysis product of carbone C(PPh₃)₂ and reacts with MeI to produce the corresponding salt [Ph₃PCH(Me)P(O)Ph₂]I (2). Deprotonation of the cation of 2 with K[N(SiMe₃)₂] in methyl cyclohexane or toluene gives neutral ylide Ph₃PCMeP(O)Ph₂ (7). Addition of AlBr₃ at the oxygen atom of 7 involves simultaneous uptake of a proton along with formation of [Ph₃PCH(Me)P(OAlBr ₃)Ph₂][AlBr₄] (9). Small amounts of resultant proton bridged [H{Ph₂(O)PCH(Me)PPh₃}₂][I ₃]₃ (10) were isolated during attempts to silylate 2 with trimethylsilytriflate; the main product was found to be [Ph₃PCH(Me) P(O)Ph₂](O₃SCF₃) (8). In the course of our studies several by-products with cation [Ph₃PCH₂P(O) Ph₂]⁺ (4 to 6) were obtained. All compounds were characterized by multiple NMR and X-ray analyses. New cationic and neutral compounds were obtained by treating phosphonioylide Ph₃PCHP(O)Ph ₂ with MeI. The alkylated product can be deprotonated and gives an addition product with AlBr₃. Product characterizations were carried out using ³¹P NMR spectroscopy and single-crystal X-ray diffraction analyses. Copyright

Full text of DOI:10.1002/ejic.201301427

FULL PAPER
DOI:10.1002/ejic.201301427
On the Alkylation of Ph3PCHP(O)Ph2: Formation and
Crystal Structures of Neutral and Cationic Addition
Compounds
Wolfgang Petz*[a] and Bernhard Neumüller*[a]
Keywords: Carbenes / Ylides / Alkylation / Lewis acids / Carbodiphosphorane / Lewis acid adducts
Ylide Ph3PCHP(O)Ph2 (1) is the hydrolysis product of carbone
C(PPh3)2 and reacts with MeI to produce the corresponding
salt [Ph3PCH(Me)P(O)Ph2]I (2). Deprotonation of the cation
of 2 with K[N(SiMe3)2] in methyl cyclohexane or toluene
gives neutral ylide Ph3PCMeP(O)Ph2 (7). Addition of AlBr3 at
the oxygen atom of 7 involves simultaneous uptake of a pro-
ton along with formation of [Ph3PCH(Me)P(OAlBr3)Ph2]-
[AlBr4] (9). Small amounts of resultant proton bridged
[H{Ph2(O)PCH(Me)PPh3}2][I3]3 (10) were isolated during
attempts to silylate 2 with trimethylsilytriflate; the main prod-
uct was found to be [Ph3PCH(Me)P(O)Ph2](O3SCF3) (8). In
the course of our studies several by-products with cation
[Ph3PCH2P(O)Ph2]+ (4 to 6) were obtained. All compounds
were characterized by multiple NMR and X-ray analyses.
another two free pairs of electrons. This feature has strong
analogy to keto ylides, Ph3PCHC(O)R, wherein electron
pairs at C and O can both serve as anchor points for Lewis
acids, representing soft and hard donor sites, respectively.
A similar arrangement in 1 enables the formation of various
addition compounds as outlined in Scheme 1. For hard
Lewis acids coordination mode I is expected whereas soft
Lewis acids are envisioned to prefer coordination mode II.
In mode III two equal or different Lewis acids come into
account.
1. Introduction
Recent theoretical and experimental studies on double
ylides[1] revealed the presence of two lone pairs of electrons
with σ and π symmetry, respectively, at the carbon atom,
which are not involved in bonding. For electronic saturation
the carbon(0) atom gains an electron octet with help of two
neutral electron pair donors L.[2] For compounds of the ge-
neral type CL2 the name carbones has been established in
contrast to carbenes which bear a carbon(II) atom sharing
two electrons with neighboring atoms and for which one
electron remains free for donating properties.
With detection of the first carbone C(PPh3)2 by Ramirez
in 1961, the authors also mentioned hydrolysis product
PPh3CHP(O)Ph2 (1)[1] which quantitatively forms if a sus-
pension of C(PPh3)2 in toluene at room temperature is
brought into contact with wet air according to Equa-
tion (1).
Scheme 1. Expected coordination modes of 1 to Lewis acids A.
Despite its similarity to keto ylides, which adopt a rich
coordination chemistry,[3] reports on 1 are rare and only a
few studies of its chemical behavior have appeared. Twelve
years after the first description of 1, Goldberg and co-
workers reported for tungsten complex [Ph3PCHP-
{OW(CO)5}Ph2] binding mode I wherein the free pair of
electrons at the ylide carbon atom remains untouched.[4]
Some 30 years later, salt-like type III cation
[Ph3PCH2P(OAlBr3)Ph2]+ was obtained in our laboratories
(AЈ = AlBr3 and A = H+).[5] Both compounds were formed
accidentally as side products during attempts to study the
chemistry of C(PPh3)2 towards various Lewis acids. These
unusual rare reports on a potential ligand prompted us to
investigate the chemistry of 1 more intensively and in a pre-
ceding paper we reported on type I–III compounds re-
sulting from the reaction with various main group Lewis
(1)
Ylide 1 is endowed with one free pair of electrons at the
carbon atom and can be viewed as a derivative of ylide
Ph3P=CH2 where one proton is replaced by the P(O)Ph2
group to give a phosphonio ylide. Alongside the lone elec-
tron pair at the carbon atom, the oxygen atom provides
[a] Fachbereich Chemie der Universität Marburg,
35032 Marburg, Germany
E-mail: petz@staff.uni-marburg.de
neumuell@chemie.uni-marburg.de
http://www.uni-marburg.de/fb15/fachgebiete/anorganik/petz
http://www.uni-marburg.de/fb15/ag-neumueller/gruppe
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201301427.
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2
acids such as BX3 and SnCl2. All compounds, including (21.58, 20.79 ppm, JP,P = 14.33 Hz). Compound 6 formed
starting compound 1, were structurally elucidated by also as by-product when 1 was treated with HgI2 in THF;
X-ray analyses.[6] Subsequently, addition compound deprotonation of the solvent is envisioned. However, the
[Ph3PCH2P(OBeCl3)Ph2]·0.75CH2Cl2 with the anionic crystals obtained earlier from THF differ markedly in unit
–
Lewis acid BeCl3 was described.[7] As expected, Lewis ac- cell parameters and are therefore denoted as 6Ј.[6] An over-
ids of group 12 to group 14 elements were found to prefer view of the reaction products is depicted in Scheme 2.
associating with the electron pair at the oxygen atom of the
P=O group as depicted in coordination mode I; no tauto-
meric compound could be isolated when Lewis acids are
located at the carbon atom as in II. The free pair of elec-
trons at the ylide carbon atom appears to remain untouched
or, alternatively, is donating exclusively to a proton leading
to coordination mode III.
No attempts have been made thus far to alkylate 1. Such
reactions would indicate which of the two binding sites with
the free pairs of electrons, C or O, or both, are donating to
R+ groups. In this contribution we report on the results of
alkylation of 1 with various alkylation agents and on fur-
ther compounds displaying coordination modes I–III.
Scheme 2. New derivatives of ylides 1 and 7.
We have also studied the reaction of 1 with I(CH2)4I. No
2. Results and Discussion
reaction at room temperature was observed. If 1 was heated
For the transfer of a cationic methyl group the typical in neat I(CH2)4I for some minutes a yellow solution formed
alkylation agents MeI, [Me3O][BF4], MeSO3CF3, or from which yellow crystals separated. The solution showed
Me2SO4 are available. We found that 1 reacts quantitatively a set of doublets at δ = 52.24 and 17.30 ppm (2JP,P
=
in neat MeI with formation of [Ph3PCH(Me)P(O)Ph2]I salt 21.45 Hz) as the main signals along with a smaller set (2:1
(2) upon alkylation of the central ylidic carbon atom. No ratio) at 20.65 and 19.80 (2JP,P = 14.30 Hz) in the 31P NMR
addition of a second Me+ group at the oxygen atom of 1 spectrum. Unfortunately, the yellow crystals were unsuit-
could be observed. In the 31P NMR spectrum of a dichloro- able for X-ray structure analysis. Upon addition of DCM
methane (DCM) solution, the two doublets displayed a low to the mixture, the set of resonances at δ = 52.24 and
field shift from 25.34 and 18.68 ppm (2JP,P = 19.7 Hz) in 1 17.30 ppm disappeared in favor of the set at δ = 20.65 and
to 32.20 and 30.77 ppm (2JP,P = 5.09 Hz) in 2. C-methyl- 19.80 ppm which, it turns out, belong to cation
ation caused the shift difference Δ of the two doublets to [Ph3PCH2P(O)Ph2]+. This resonance transition is indicative
shrink from 6.66 to 1.43 ppm with simultaneous reduction of HI addition to 1, not an alkylation. However, the initial
of the P,P coupling constant. Unfortunately crystals ob- major set of doublets is indicative of transiently formed
tained from recrystallization in MeI, DCM, or THF were Type III addition compounds; the large signal difference Δ
not suitable for X-ray analysis. However, 2 could be easily amounting to about 35 ppm is typical for such compounds.
converted into mercury salt 3 by addition of equimolar Notably, Δ values between 16–35 ppm were recorded (see
amounts of HgI2 from which crystals suitable for X-ray also the NMR shifts of the addition compound 9, vide in-
analysis were obtained. The resulting new anion [Hg2I6]2– fra). The nature of the intermediate Type III compound is,
caused the 31P NMR signals to shift to 30.02 and thus far, unknown.
29.25 ppm (2JP,P Ն4 Hz); Δ = 0.77 ppm. We have observed
To deprotonate 2, a suspension of the salt in toluene was
that, in all cationic compounds evaluated, generation of heated with equimolar amounts of K[N(SiMe3)2]. The 31P
[Hg2I6]2– anion causes the 31P NMR signals to move to- NMR spectrum of the toluene solution showed new dou-
gether in all solvents applied.
blets at δ = 33.99 and 25.60 ppm (2JP,P = 41.12 Hz) which
Subjection of 1 to MeI in DCM and layering of the clear were assigned to neutral compound Ph3PCMeP(O)Ph2 (7).
solution of the reaction mixture with n-pentane produced Unfortunately, no crystals could be obtained upon layering
fibrous crystals of 2 as the main product. Among them, the toluene solution with n-pentane. Removal of the solvent
however, small amounts of thin plates were detected which gave an oily material from which no crystals could be
were identified as iodide salt [Ph3PCH2P(O)Ph2]I (4); the grown. If the reaction was carried out in methyl cyclohex-
proton probably originates from the DCM solvent. Related ane the resonances for 7 were found at δ = 35.36 and
chloride 5 was formed in small amounts as a by-product 24.28 ppm (2JP,P = 44.70 Hz). The solubility of 7 in hydro-
during reaction of C(PPh3)2 with 5,10,15-triphenylcorrol- carbons such as toluene or methyl cyclohexane and the new
atocopper in THF.[8] Chloride 5 was described previously to 31P NMR signals are suggesting of a neutral compound.
be obtained from hydrolysis of the carbone Ph3P=C=P(Cl)- Finally, on standing of the methyl cyclohexane solution for
Ph2.[9] To attain better crystals, 4 was treated with HgI2 to some days, X-ray crystallographic quality crystals separated
give crystals of 6, as shown by 31P NMR spectroscopic data leading to confirmation of proposed structure 7.
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Scheme 3. Envisoned generation of 9 and 10.
In order to activate O-coordination a solution of 7 in triflate behaves partly as an oxidation agent on I– to give
–
methyl cyclohexane was treated with excess AlBr3 in the elemental iodine and generating, in turn, I3 ion. Several
same solvent. A colorless precipitate formed quantitatively. runs afforded the same results. Even through spectroscopic
The precipitate was found to be insoluble in DCM but was means no hint of O-silylated product could be detected be-
soluble in 1-Br-2-F-C6H4; the 31P NMR spectrum of the cause a signal pattern of the 31P NMR spectrum close to
solution showed two new doublets at δ = 54.8 and 25.8 ppm that of the AlBr3 addition compound 9 was expected with
with 2JP,P = 10.7 Hz. From this solution several crystals sep- large distances of the two doublets of about 20 to 30 ppm.
arated in the NMR tube upon layering with n-pentane, The envisioned formation of 9 and 10 is depicted in
which turned out to be [Ph3PCH(Me)P(OAlBr3)Ph2][AlBr4] Scheme 3.
salt (9) in which coordination mode III of 1 was realized.
An explanation for the lack of O-silylation is not yet
However, the expected neutral adduct [Ph3PCMeP- clear since, in the case of 1, an O-silylated product could be
(OAlBr3)Ph2] displaying coordination mode II did not sepa- isolated.[10] We do not believe that the presence of the
rate during the crystallization process. No hints of such a methyl group at the carbon atom causes a significant steric
product could be detected in the 31P NMR spectrum of the or electronic obstacle for silylation. It is interesting to note
initial solution. As stated above, related salt that compounds 2, 3, 8, 9 and 10 all contain an asymmetric
[Ph3PCH2P(OAlBr3)Ph2][AlBr4] was reported earlier by us carbon atom. The corresponding unit cells contain pairs of
to be formed as a by-product during the reaction of AlBr3 enantiomers and, in the unit cell of 10, the single molecule
with double ylide C(PPh3)2.
of the H bridged dimer consists of a pair of enantiomers.
On standing of the NMR sample for some time, the 31P
NMR spectrum of this solution showed that the two signals
at δ = 54.8 and 25.8 ppm disappeared in favor of two new
signals at δ = 30.66 and 30.31 ppm assigned to cation
[Ph3PCH(Me)P(O)Ph2]+ (cation of 2) formed with loss of
AlBr3.
3. Crystal Structures
The structures of compounds [Ph3PCH(Me)P(O)Ph2]2-
[Hg2Cl6] (3), [Ph3PCH2P(O)Ph2]I·2CH2Cl2 (4·2CH2Cl2),
[Ph3PCH2P(O)Ph2]Cl·THF (5·THF), [Ph3PCH2P(O)Ph2]2-
Attempts to silylate alkyl compound 7 or cationic com-
pound 2 at the oxygen atom with Me3SiOSO2CF3 failed. If
a solution of freshly prepared 7 in methyl cyclohexane was
treated with trimethylsilyl triflate a colorless precipitate was
obtained which could be dissolved in 1-Br-2-F-C6H4. In the
31P NMR spectrum of the solution two sets of doublets A
and B in a 1:0.1 ratio were detected. The major set A at δ
= 30.76 and 30.45 ppm (2JP,P = 4.6 Hz) belongs to the cat-
ion of 8 (identical with the cation of 2) whereas the minor
set B at 22.06 and 21.26 was attributed to cation
[Ph3PCH2P(O)Ph2]+. Similarly, cationic alkylated com-
pound 2 and Me3SiOSO2CF3 in DCM did not lead to the
O-silylated product; we again could only isolate 8 and not
the expected dicationic compound [Ph3PCH(Me)P-
(OSiMe3)Ph2][OSO3CF3]2. From the orange solution, two
types of crystals were formed from DCM/n-pentane; aside
of the colorless crystals of 8, small amounts of orange
brown needles were detected, which turned out to be proton
Figure 1. Molecular structure of [Ph3PCH(Me)P(O)Ph2]2[Hg2Cl6]
(3). The phenyl rings are represented as thin lines. Selected bond
lengths [Å] and angles [°]: P(1)–O(1) 1.477(3), C(1)–C(2) 1.551(6),
P(1)–C(1) 1.841(4), P(2)–C(1) 1.826(4), C(1)–H(1) 0.93, Hg(1)–I(3)
2.6917(4), Hg(1)–I(2) 2.7015(5), Hg(1)–I(1) 2.8312(4), Hg(1)–I(1a)
3.0313(4); C(2)–C(1)–P(2) 108.4(3), C(2)–C(1)–P(1) 112.4(3), P(2)–
C(1)–P(1), 114.5(2), O(1)–P(1)–C(1) 113.8(2), I(3)–Hg(1)–I(2)
126.33(1), I(3)–Hg(1)–I(1) 110.20(1), I(2)–Hg(1)–I(1) 111.89(1),
–
bridged tricationic compound 10. The formation of the I3
anion in 10 is not yet clear; presumably the trimethylsilyl I(2)–Hg(1)–I(1a) 98.02(1), Hg(1)–I(1)–Hg(1a) 83.14(1).
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[Hg2I6] (6), Ph3PCMeP(O)Ph2 (7), [Ph3PCH(Me)P(O)Ph2]
(O3SCF3) (8), [Ph3PCH(Me)P(OAlBr3)Ph2][AlBr4] (9), and
{H[Ph2(O)PCH(Me)PPh3]2}[I3]3 (10) could be confirmed
by single-crystal X-ray diffraction analyses. The molecular
structures of compounds 3, 6, 7, 9, and 10, including bond
lengths and angles are shown in Figures 1, 2, 3, 4, and 5;
crystallographic data are collected in Table 1. The molecu-
lar structures of 4·2CH2Cl2, 5·THF, and 8 are found in the
Supporting Information.
Figure 4. Molecular structure of [Ph3PCH(Me)P(OAlBr3)-
Ph2][AlBr4] (9) showing the atom numbering scheme. The ellipsoids
are drawn at a 40% probability level. The phenyl rings are drawn
as thin lines. Selected bond lengths [Å] and angles [°]: C(1)–C(2)
1.555(7), P(2)–O(1) 1.533(4), P(1)–C(1) 1.839(4), P(2)–C(1)
1.834(6), Al(1)–O(1) 1.787(4); P(2)–C(1)–P(1), 115.1(3), C(2)–C(1)–
P(2) 111.0(3), C(2)–C(1)–P(1) 110.7(4), C(2)–C(1)–H(1) 106.5,
P(2)–C(1)–H(1) 106.5, P(1)–C(1)–H(1) 106.5, O(1)–P(2)–C(1)
107.7(2), P(2)–O(1)–Al(1) 141.7(2), O(1)–Al(1)–Br(1) 106.5(2),
O(1)–Al(1)–Br(2) 103.8(1), O(1)–Al(1)–Br(3) 107.0(1).
Figure 2. Molecular structure of [Ph3PCH2P(O)Ph2]2[Hg2I6] (6).
The phenyl rings are shown as thin lines. Selected bond lengths[Å]
and angles [°]: P(1)–O(1) 1.482(6), P(2)–C(1) 1.805(9), P(1)–C(1)
1.820(9), Hg(1)–I(3) 2.6720(7), Hg(1)–I(2) 2.7050(7), Hg(1)–I(1)
2.7818(3), Hg(1)–I(1a) 3.1656(8); P(2)–C(1)–P(1), 118.4(5), O(1)–
P(1)–C(1) 112.9(4), I(3)–Hg(1)–I(2) 120.89(2), I(3)–Hg(1)–I(1)
123.51(3), I(2)–Hg(1)–I(1) 109.48(2), I(3)–Hg(1)–I(1a) 96.79(2),
I(2)–Hg(1)–I(1a) 109.16(2), I(1)–Hg(1)–I(1a) 88.97(2), Hg(1)–I(1)–
Hg(1a) 82.46(2).
Figure 5. Molecular structure of {H[Ph2(O)PCH(Me)PPh3]2}[I3]3
(10) showing the atom numbering scheme. The ellipsoids are drawn
at a 40% probability level. The phenyl rings are drawn as thin lines.
Selected bond lengths [Å] and angles [°]: C(1)–C(2) 1.535(7), C(1)–
P(2) 1.837(5), C(1)–P(1) 1.838(5), O(1)–P(1) 1.529(4), O(1)–H(2)
1.199(3); C(2)–C(1)–P(2) 114.2(4), C(2)–C(1)–P(1) 113.1(4), P(2)–
C(1)–P(1) 112.7(3), P(1)–O(1)–H(2) 116.1(2), O(1)–P(1)–C(1)
105.0(2).
Figure 3. Molecular structure of Ph3PCMeP(O)Ph2 (7). The phenyl
rings are shown as thin lines. Selected bond lengths [Å] and angles
[°]: P(1)–O(1) 1.477(6), P(2)–C(1) 1.687(9), P(1)–C(1) 1.757(7),
C(1)–C(2) 1.51(1); P(2)–C(1)–P(1), 116.0(4), O(1)–P(1)–C(1)
112.3(4), C(2)–C(1)–P(2) 124.2(6), C(2)–C(1)–P(1) 119.8(6).
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Table 1. Crystallographic data and structure refinement details for [Ph3PCH(Me)P(O)Ph2]2[Hg2I6] (3) [Ph3PCH2P(O)Ph2]2[Hg2I6] (6),
Ph3PCMeP(O)Ph2 (7), [Ph3PCH(Me)P(OAlBr3)Ph2][AlBr4] (9), and {H[Ph2(O)PCH(Me)PPh3]2}[I3]3 (10).
3
6
7
9
10
Formula
C64H58Hg2I6O2P4
2145.56
1060.2(1)
1264.3(1)
1342.2(1)
93.13(1)
C64H54Hg2I6O2P4 C32H28OP2
C32H29Al2Br7OP2
1104.82
1589.4(1)
1472.1(1)
3294.7(1)
90
C64H59I9O2P4
2126.09
Mw [g/mol–1]
a [pm]
2117.51
11.021(1)
23.098(1)
25.174(1)
90
90
90
490.48
2098.7(2)
1114.9(1)
2373.5(3)
90
106.60(1)
90
1103.9(1)
1147.8(1)
1404.2(1)
81.59(1)
80.82(1)
84.24(1)
0.12ϫ0.08ϫ0.07
1732.1(3)
1
b [pm]
c [pm]
α [°]
β [°]
93.10(1)
90
90
γ [°]
109.92(1)
0.17ϫ0.07ϫ0.04
1683.9(2)
1
Crystal size [mm]
Volume [pm3·106]
Z
0.19ϫ0.14ϫ0.13 0.11ϫ0.07ϫ0.04
0.18ϫ0.10ϫ0.08
7708.8(8)
8
6408.4(7)
4
5322(1)
8
dcalcd. [gcm–3]
Crystal system
Space group (no.)
Diffractometer
Radiation
Temperature [K]
μ [cm–1]
2.116
2.195
1.224
1.904
2.038
triclinic
orthorhombic
Pccn (56)
IPDS II (Stoe)
monoclinic
C2/c (15)
IPDS II (Stoe)
Mo-Kα
100
1.86
orthorhombic
Pbca (61)
IPDS II (Stoe)
triclinic
¯
¯
P1 (2)
P1 (2)
IPDS II (Stoe)
IPDS II (Stoe)
100
74.39
51.80
100
78.17
51.84
100
74.40
51.96
100
41.60
51.76
2θmax [°]
51.84
Index range
–12ՅhՅ13
–15ՅkՅ15
–16ՅlՅ16
23951
–13ՅhՅ13
–28ՅkՅ26
–30ՅlՅ30
85285
–25ՅhՅ25
–12ՅkՅ13
–29ՅlՅ29
13074
–19ՅhՅ19
–18ՅkՅ15
–34ՅlՅ40
36226
–12ՅhՅ13
–14ՅkՅ14
–17ՅlՅ17
13946
Number of rflns collected
Number of indepentent re- 6539 (0.0406)
flections (Rint
Number of observed reflec- 5171
6233 (0.1402)
5124 (0.2467)
7474 (0.1091)
6680 (0.0455)
)
4340
1686
3945
4098
tions with Fo Ͼ4σ(Fo)
Parameters
358
344
310
399
360
Absorption correction
numerical
numerical
empirical
[X-red32/X-area
(Stoe)]
numerical
empirical
[X-red32/X-area
(Stoe)]
Structure solution
direct methods
SIR-92[11]
direct methods
SHELXS-97[12]
SHELXS-97[12]
direct methods
direct methods
SIR-92[11]
direct methods
SHELXS-98[13]
SHELXL-97[14]
SIR-92[11]
Refinement against F2
H atoms
SHELXL-97[14]
SHELXL-97[14]
SHELXL-97[14]
calculated positions with common displacement parameter
R1
0.0219
0.0449
0.969
0.0462
0.1013
2.132
0.0462
0.2145
0.403
0.0384
0.0532
0.648
0.03
0.0503
1.514
wR2 (all data)
Max. electron density left
[e/pm3·10–6]
3.1 Crystal Structure of [Ph3PCH(Me)P(O)Ph2]2[Hg2Cl6] (3) 3.2 Crystal Structures of Compounds 4–6
The molecular structure of 3 is depicted in Figure 1. The salt like compounds have the cation [Ph3PCH2P(O)-
Compounds 3 and 8 contain the same cation and nearly Ph2]+ in common; the Hg2Cl6 salt 6 was obtained earlier
identical bonding parameters are recorded. As expected the from addition of HgI2 to a solution of 1 with HgI2 in THF
C(1)–C(2) bond lengths are those of a typical single bond. but, according to structural differences, is denoted as 6Ј.[6]
The carbon atom C(1) is a stereogenic atom and the two The four-membered ring of the Hg2I6 anion in 6 shows an
enantiomers are part of the triple ion in 3. The distances of envelope configuration, whereas that in 6Ј obtained from
C(1) to the P atoms do not differ markedly [that to P(O) is THF is planar; both compounds differ in the parameters of
about 0.015 Å longer] and are in the range of normal P–C the unit cell and the numbers of molecules Z in it (Z = 2 in
single bonds. Nearly identical values are found in 8. The 6Ј, and Z = 4 in 6). The P–O bond lengths vary between
torsion angle C(2)C(1)P(1)O(1) amounts to 101° corrre- 1.479(6) Å (for 6Ј), 1.482(6) Å (for 6), and 1.488(5) Å (for
sponding to a gauche arrangement. The middle of the di- 4) and are close to that of Ph3PO [1.483(2) Å].[15] Different
anion forms an inversion center causing the four-membered P–C bond lengths to PPh3/P(O)Ph2 are found: 1.771(8)/
rhombic Hg–I–Hg–I ring to be completely planar. Anion 1.814(8) Å (4), 1.785(4)/1.830(4) Å (5), 1.797(8)/1.822(8) Å
and cations are held together by weak H····I bridges to (6Ј), 1.805(9)/1.820(9) Å (6); the molecular structure of 6
phenyl protons. Both Hg atoms are in a distorted tetrahe- is depicted in Figure 2; those of 4 and 5 are found in the
dral environment.
Supporting Information.
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3.3 Crystal Structure of Ph3PCMeP(O)Ph2 (7)
acids where O-coordination is preferred. The chemistry of
1 resembles that of the β-keto ylides R3PCHC(O)R dif-
fering from 1 by replacement of the C(O)R group with
P(O)Ph2. Alkylation of 1 proceeds exclusively at the carbon
atom, but uptake of a proton from various solvents is also
an option mainly in the presence of a Lewis acid. Proton-
ation in such a fashion leads to unexpected by-products.
Hints were found to suggest that O alkylation can occur in
some cases to give type III salts (Scheme 1). However, the
stabilities of such species in solution precluded rigorous
structure elucidation by crystallographic means. In the pres-
ent contribution, the chemistry of 1 is not brought to an
end. Clearly warranted, further studies are currently in pro-
gress and promising results, especially with regard to the
synthesis of mixed carbones, will be reported in due course.
The molecular structure of 7 is shown in Figure 3 and
can be compared with that of Ph3PCHP(O)Ph2 (1). The en-
vironment at the ylide carbon atom C(1) is exactly planar
(sum of angles of 360°) indicating an sp2 configuration. The
O atom is located approximately trans to the methyl group.
There is no remarkable difference between the P–O bond
length in 7 [1.477 (6) Å] and 1 [1.489(2) Å]. Compared to 1
the P(1)–C(1) distance is slightly longer [1.717 Å in 1 vs.
1.757 Å in 7] indicating decreased back bonding whereas
the related P(2)–C(1) distances are equivalent. However, the
bulkier methyl group at C(1) in 7 causes shrinking of the
P–C–P angle relative to that in 1 (116.0° in 7 vs. 127.5° in
1) containing the small H atom at C(1). The atoms O(1),
P(1), C(1), C(2), and P(2) are located in one plane. Only a
small shortening is found between the sp2 and sp3 carbon
atoms C(1)–C(2) in 7 [1.51(1) Å] relative to related sp3 and
sp3 carbon atoms in 3 and 9 [1.56 Å].
Experimental Section
General: All operations were carried out under an argon atmo-
sphere in dried and degassed solvents using Schlenk techniques.
The solvents were thoroughly dried and freshly distilled prior to
use. The IR spectra were run with a Nicolet 510 spectrometer in
Nujol mull. For the 31P NMR spectra we used Bruker AC 300 and
AC 250 spectrophotometers. The carbodiphosphorane C(PPh3)2 as
a precursor for 1, was prepared according to a modified literature
procedure[17] and MeI was commercially obtained and used with-
out further purification. Commercially available HgI2 was dried in
vacuo prior to use.
3.4 Crystal Structure of [Ph3PCH(Me)P(OAlBr3)Ph2]-
[AlBr4] (9)
The molecular structure of 9 is found in Figure 4. As in
3 C(1) is a stereogenic atom and the unit cell contains four
pairs of enantiomers. Anchoring of AlBr3 at the oxygen
atom of 3 resulting in 9 has no influence on the C–C bond
length but elongates the P–O distance by about 0.11 Å indi-
cating a dramatic disruption of the π character of this bond.
Anion and cation are linked by weak H···Br contacts [C(1)···
Br(4) = 4.020(5) Å; (C(1))···Br(5) = 4.279(5) Å]. The torsion
angle C(2)C(1)P(2)O(2) amounts to 159° which corre-
sponds to an approximately trans arrangement. Most of
the structural parameters are close to those of
[Ph3PCH2P(OAlBr3)Ph2][AlBr4] when H replaces Me and
previously reported by us.[5] Both compounds exhibit a flat
P–O–Al angle in the region of 142°. In the comparable
adduct Ph3POAlBr3 a linear arrangement is recorded along
with slightly shorter P–O [1.513(7) Å] and O–Al
[1.736(7) Å] bonds.[16]
[Ph3PCH(Me)P(O)Ph2]I (2): Compound 1 (0.21 g, 0.44 mmol) was
dissolved in MeI (1.5 mL). A clear colorless to pale yellow solution
was obtained. After about 20 min, precipitation of 2 occurred as
fine thin whiskers. Addition of n-pentane (2 mL) and filtration gave
2 in quantitative yields. Compound 2 is insoluble in pentane and
toluene, only slightly soluble in MeI and can be recrystallized from
warm THF. Compound 2 is soluble in dichloromethane, chloro-
form, 1,2-dichlorethane, acetone and acetonitrile. According to the
different phosphorus atoms two doublets were obtained in the 31P
NMR spectrum and the shifts depend on the choice of the solvent:
1H NMR (CDCl3): δ = 8.84–7.20 (m, 25 H), 6.00–5.85 (m, 1 H),
1.526, 1.502, 1.474, 1.465, 1.450, 1.442, 1.413, 1.390 (ddd, 3
H) ppm. 13C NMR (CDCl3): δ = 135.32 (d, JP,P = 10.33 Hz, Ph),
134.60 (d, JP,P = 2.71 Hz, Ph), 133.35–131.67 (m, Ph), 129.63 (d,
JP,P = 12.93 Hz, Ph), 128.94 (t, JP,P = 11.58 Hz, Ph), 117.56 (d, JP,P
3.5 Crystal Structure of {H[Ph2(O)PCH(Me)PPh3]2}[I3]3
(10)
2
2
= 86.29 Hz, Ph), 30.17 (d, JP,P = 41.86 Hz, Me), 29.63 (d, JP,P
=
41.80 Hz, Me), 14.21 (m, CH) ppm. 31P NMR: δ = 32.20, 30.77
The molecular structure of trication 10 is shown in Fig-
ure 5. The bridging H atom is located on an inversion cen-
tre leading to a linear O–H–O arrangement with a very
short O1··· O1A contact of 2.399(4) Å indicating strong hy-
drogen bonds. The bonding parameters do not differ mark-
edly from those observed in 9; the O-protonation in 10
elongates the P–O distance by about the same amount as
addition of AlBr3 to the oxygen atom in 9.
(d’s, JP,P = 5.1 Hz) ppm in DCM; δ = 31.51, 30.52 (2JP,P not re-
2
2
solved) ppm in 1,2-dichlorethane; δ = 32.04, 31.65 (d’s, JP,P
=
5.1 Hz) ppm in THF; δ = 31.73, 31.05 (2JP,P not resolved) ppm, in
acetone. IR (Nujol mull): ν = 1573 (w), 1483 (m), 1437 (s), 1242
˜
(w), 1194 (s), 1177 (m), 1163 (m), 1107 (s), 1072 (w), 1018 (m), 997
(w), 968 (w), 767 (s), 741 (s), 726 (s), 707 (s), 692 (s), 561 (s), 543
(s), 527 (w), 496 (s) cm–1. Attempts to grow crystals from various
solvents gave only thin crystals of 2 which were unsuitable for X-
ray analyses.
–
One of the I3 ions possesses only C1-symmetry (I1, I2,
–
I3) whereas the other I3 unit was formed around a center
[Ph3PCH(Me)P(O)Ph2]2[Hg2Cl6] (3): Compound
2
(0.12 g,
of symmetry (I4, I5, I5a).
0.19 mmol) was dissolved in 1,2-dichlorethane (4 mL). Addition of
HgI2 (0.086 g, 0.19 mmol) and treatment of the mixture in an ultra-
sonic bath for about 10 min gave a clear pale yellow solution. Lay-
ering the solution with n-pentane produced yellow crystals of 3 in
4. Conclusion and Outlook
The hydrolysis product of carbodiphosphorane
C(PPh3)2, ylide 1 is a versatile ligand for main group Lewis graphic analysis. H NMR (CDCl3): δ = 8.00–7.40 (m, 25 H), 4.87
about quantitative yields, which were suitable for X-ray crystallo-
1
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FULL PAPER
(m, 1 H), 1.608, 1.585, 1.557, 1.548, 1.533, 1.524, 1.497, 1.473 (ddd, CCDC-962504 (for 3), -965622 (for 4·2CH2Cl2), -965624 (for
2
3 H) ppm. 31P NMR: δ = 31.73, 29.80 (d’s, JP,P = 3.6 Hz) ppm
5·THF), -962505 (for 6), -962506 (for 7), -965623 (for 8), -962507
(for 9) and -962508 (for 10) contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
in CDCl3; δ = 29.86, 29.44 ppm in 1,2-dichlorethane; δ = 30.02,
29.25 ppm in DCM (all not resolved). IR (Nujol mull): ν = 1586
˜
(w), 1483 (m), 1437 (s), 1354 (w), 1335 (w), 1310 (w), 1206 (m), charge from The Cambridge Crystallographic Data Centre via
1182 (s), 1161 (m), 1109 (s), 1071 (w), 1049 (w), 1015 (m), 997 (m),
762 (m), 7450 (s), 739 (s), 727 (s), 719 (s), 698 (s), 687 (s), 559 (s),
542 (s), 522 (w), 500 (s) cm–1.
www.ccdc.cam.ac.uk/data_request/cif.
Supporting Information (see footnote on the first page of this arti-
cle): Preparation, NMR, and crystallographic details of 4·2CH2Cl2,
Figures S1, S2; crystallographic details of 5·THF, Figure S3; crys-
tallographic details of 8, Figures S4, S5; table of crystal data,
Table S1.
Ph3PCMeP(O)Ph2 (7): To a suspension of 2 (0.3 g, 0.63 mmol) in
methyl cyclohexane (≈ 5 mL) was added K[N(SiMe3)2] (0.15 g) and
the mixture stirred at room temperature for three h and heated to
reflux for about 10 min. The 31P NMR showed two doublets at
26.39 and 33.35 (2JP,P = 41.3 Hz) ppm. On standing of the solution
colorless crystals of 7 separated; yield ≈ 50%. If the reaction was
carried out in toluene, similarly a solution of 7 was obtained; the
Acknowledgments
31P NMR spectrum gave signals at 33.99 and 25.60 (2JP,P
=
The authors thank the Deutsche Forschungsgemeinschaft (DFG)
for financial support. W. P. is also grateful to the Max Planck Soci-
ety, Munich, Germany for supporting this research project.
41.1 Hz) ppm. Attempts to isolate 7 from toluene solution gave an
oily material which could not be crystallized. Attempts to dissolve
the oil again in toluene showed decomposition according to 31P
1
NMR signals. For H and 13C NMR spectra a solution of 7 was
1
prepared in C6D6: H NMR (C6D6): δ = 8.06–6.97 (m, Ph), 1.763,
[1] F. Ramirez, N. B. Desai, B. Hansen, N. McKelvie, J. Am.
Chem. Soc. 1961, 83, 3539–3540.
2
2
(d, JP,P = 13.78 Hz, Me) 1.740 (d, JP,P = 13.67 Hz) ppm. 13C
2
[2] G. Frenking, R. Tonner, Pure Appl. Chem. 2009, 81, 597–614.
[3] a) S. J. Sabounchei, A. Dadrass, F. Akhlaghi, Z. B. Nojini,
H. R. Khaasi, Polyhedron 2008, 27, 1963–1968; b) H. Koezuka,
G.-E. Matsubayashi, T. Tanaka, Inorg. Chem. 1976, 15, 417–
421; c) R. Uson, J. Fornies, R. Navarro, P. Espinet, C. Mendi-
vil, J. Organomet. Chem. 1985, 290, 125–131; d) J. Vicente,
M. T. Chicote, J. Femandez-Baeza, J. Martin, I. Saura-Llamas,
J. Turpin, J. Organomet. Chem. 1987, 331, 409–421; e) J. A.
Albanese, D. L. Staley, A. L. Rheingold, J. L. Burmeister, In-
org. Chem. 1990, 29, 2209–2213; f) M. Kalyanasundari, K.
Panchanatheswaran, W. T. Robinson, H. Wen, J. Organomet.
Chem. 1995, 491, 103–109.
[4] S. Z. Goldberg, K. N. Raymond, Inorg. Chem. 1973, 12, 2923–
2927.
[5] W. Petz, C. Kutschera, S. Tschan, F. Weller, B. Neumüller, Z.
Anorg. Allg. Chem. 2003, 629, 1235–1244.
[6] W. Petz, F. Öxler, K. Aicher, B. Neumüller, Z. Anorg. Allg.
Chem. 2010, 636, 1751–1759.
[7] W. Petz, K. Dehnicke, B. Neumüller, Z. Anorg. Allg. Chem.
2011, 637, 1761–1768.
NMR (C6D6): δ = 134–128 (m, Ph), 15.66 (pseudo t, JP,C
=
5.40 Hz), 2.039 (d, 1JP,C = 94.7 Hz), 1.776 (d, 1JP,C = 54.9 Hz) ppm.
31P NMR (C6D6): δ = 36.16, 27.57 (d’s, JP,P = 41.55 Hz) ppm.
2
Formation of [Ph3PCH(Me)P(O)Ph2](O3SCF3) (8): A solution of 7
in methyl cyclohexane {prepared in situ from 2 and K[N(SiMe3)2]}
was treated with a solution of Me3SiOSO2CF3 in the same solvent.
A colorless precipitate formed which was filtered and dried in
vacuo. The precipitate was dissolved in 1-Br-2-F-C6H4. In the 31P
NMR doublets at 30.75 and 30.50 (2JP,P = 4.6 Hz) ppm as major
signals were recorded, attributed to the signals of the cation
[Ph3PCH(Me)P(O)Ph2]+; additionally minor signals of the cation
[Ph3PCH2P(O)Ph2]+ (9:1 ratio) were detected. On standing, crystals
of 8 separated from solution.
Reaction of [Ph3PCH(Me)P(O)Ph2]I (2) with Me3SiOSO2CF3: To
a solution of 2 which was freshly prepared from 1 (0.226 g,
0.5 mmol) and excess MeI was added Me3SiOSO2CF3 (0.22 g,
1 mmol). The mixture was treated 1 min in an ultrasonic bath. A
slight yellow solution was obtained. The 31P NMR spectrum
showed signals at 34.40 (s, br) and 30.97 (s) ppm. Layering of the
solution in the NMR tube with n-pentane gave two sorts of crystal.
The colorless crystals were the main product and turned out to be
8. Minor amounts of orange brown crystals were found to be the
H bridged salt 10. 31P NMR in 1-Br-2-F-C6H4: δ = 41.86 (s, br),
29.18 (s) ppm.
[8] M. Funk, Ph. D. Thesis, University of Marburg, Germany,
2009.
[9] R. Appel, H.-Wihler, Chem. Ber. 1978, 111, 2054–2055.
[10] W. Petz, B. Neumüller, unpublished results.
[11] A. Altomare, G. Cascarano, C. Giacovazzo, A. Guagliardi,
M. C. Burla, G. Polidori, M. Camalli, Sir-92, Rome, 1992.
[12] G. M. Sheldrick, SHELXS-97, Program for the Solution of
Crystal Structures, University of Göttingen, Germany, 1997.
[13] G. M. Sheldrick, SHELXL-98, University of Göttingen, Ger-
many, 1998.
[Ph3PCH(Me)P(OAlBr3)Ph2][AlBr4] (9): A solution of 7 in methyl
cyclohexane {prepared in situ from 2 and K[N(SiMe3)2]} was
treated with a solution of AlBr3 in the same solvent at room tem-
perature. A flocky precipitate separated immediately and the mix-
ture was treated in an ultrasonic bath for 2 min. The precipitate
was then filtered and dried in vacuo. The colorless precipitate was
dissolved in 1-Br-2-F-C6H4 and the solution was layered with n-
[14] G. M. Sheldrick, SHELXL-97, University of Göttingen, Ger-
many, 1997.
[15] a) G. Ruban, V. Zabel, Cryst. Struct. Commun. 1976, 5, 671–
677; b) G. Bandoli, G. Bortolozzo, D. A. Clemente, U. Croatto,
C. Panaltoni, J. Chem. Soc. A 1970, 2778–2780.
[16] N. Burford, B. W. Royan, R. E. v. H. Spence, T. S. Cameron,
A. Linden, R. D. Rogers, J. Chem. Soc., Dalton Trans. 1990,
1521–1528.
[17] R. Appel, F. Knoll, H. Schöler, H.-D. Wihler, Angew. Chem.
1976, 88, 769; Angew. Chem. Int. Ed. Engl. 1976, 15, 702–703.
Received: November 7, 2013
pentane. Crystals separated from solution and were identified as
2
compound 9. 31P NMR (1-Br-2-F-C6H4): δ = 54.78 (d, JP,P
=
10.73 Hz), 25.76 (d, 2JP,P = 10.73 Hz) ppm. On the basis of the 31P
NMR spectrum 9 was obtained in near quantitative yield. Com-
pound 9 is insoluble in CD2Cl2 and decomposes in CDCl3, thus,
1
no H and 13C NMR spectra could be obtained.
Published Online: January 29, 2014
Eur. J. Inorg. Chem. 2014, 1218–1224
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© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim