New routes to diarsenes and arsaphosphenes involving fluorinated arsines

Article abstract of DOI:10.1016/S0022-328X(00)00671-9

The stable diarsene ArAs=AsAr (1) and arsaphosphene ArAs=PAr (6) (Ar=2,4,6-tri-tert-butylphenyl) have been synthesized in excellent yields from the difluoroarsine ArAsF₂ by reaction with ArAs(Li)SiMe₃ (for 1) and with ArP(H)Li follow

Full text of DOI:10.1016/S0022-328X(00)00671-9

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 619 (2001) 275–279
New routes to diarsenes and arsaphosphenes involving fluorinated
arsines
Mereyim Bouslikhane, Heinz Gornitzka, Jean Escudie´ *, Henri Ranaivonjatovo
He´te´rochimie Fondamentale et Applique´e, UMR 5069, Uni6ersite´ P. Sabatier, 118 route de Narbonne, 31062 Toulouse Cedex 04, France
Received 16 June 2000; accepted 15 September 2000
Abstract
The stable diarsene ArAsꢀAsAr (1) and arsaphosphene ArAsꢀPAr (6) (Ar=2,4,6-tri-tert-butylphenyl) have been synthesized in
excellent yields from the difluoroarsine ArAsF2 by reaction with ArAs(Li)SiMe3 (for 1) and with ArP(H)Li followed by t-BuLi
(for 6). Compound 1, previously prepared by other routes, as well as the new compound 6 were characterized by single-crystal
,
,
X-ray diffraction (d(AsꢀAs) 2.2634(3) A, d(PꢀAs) 2.141(5) A). © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Diarsene; Arsaphosphene; Fluorinated arsines; Fluoroarsinylphosphine
1. Introduction
substituted phosphorus and arsenic by the 2,4,6-tri-tert-
butylphenyl group, previously used for stabilization of
the first diphosphene by Yoshifuji [8], in order to
establish a comparison between structural data within a
complete series of diphosphene, arsaphosphene and
diarsene substituted by the same group on phosphorus
and arsenic.
Considerable interest has been directed toward the
synthesis of doubly bonded derivatives of Group 15
elements during the last two decades; various deriva-
tives of the type –EꢀE%– (E, E%=P, As, Sb, Bi) have
been synthesized [1].
The three main methods which have been used for
the preparation of diarsenes –AsꢀAs– or arsapho-
sphenes –AsꢀP– are dechlorination reactions by
lithium compounds [2], magnesium or potassium [3]
(route a), dehydrochlorination reactions with DBU [4]
or lithium compounds [5] (route b) and dechlorosilyla-
tion reactions involving disilylphosphines or disilylarsi-
nes [6] or lithium silylphosphides [4a,7] (route c)
(Scheme 1).
The yields in diarsenes and arsaphosphenes reported
in the literature vary from 7 to 72%. One problem is in
some cases the formation of by-products due to the
alkylation or the reduction of phosphorus or arsenic
precursors.
2. Results and discussion
2.1. Diarsene 1
The bis(2,4,6-tri-tert-butylphenyl)diarsene (1) is syn-
thesized by reaction between the difluoroarsine 2 [9]
and the lithium silylarsinide 3. The intermediate 4
cannot be isolated, immediately losing fluorotrimethyl-
silane to lead to the diarsene 1 in an excellent yield of
75% (Scheme 2).
It is not necessary to isolate 3 which is prepared by
successive addition of butyllithium, chlorotrimethylsi-
lane and butyllithium to the arsine 5. Thus, the reaction
can be performed in one pot from the arsine 5. 1 has
been obtained previously by Weber by reaction of
ArAsCl2 and magnesium (61% yield) [3a], and as a
by-product in the reaction between ArAsCl2 and
C5Me5(CO)2FeAs(SiMe3)2 (10% yield) [6b,6c].
We present here a new method of synthesis of di-
arsene and arsaphosphene using fluoroarsines. We have
* Corresponding author. Tel.: +33-5-61 55 83 47; fax: +33-5-61
55 82 04.
E-mail address: escudie@ramses.ups-tlse.fr (J. Escudie´).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(00)00671-9

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M. Bouslikhane et al. / Journal of Organometallic Chemistry 619 (2001) 275–279
Scheme 1.
2.2. Arsaphosphene 6
The bis(2,4,6-tri-tert-butylphenyl)arsaphosphene (6)
has been synthesized by a two step dehydrofluorination
reaction involving the intermediate formation of the
fluoroarsinylphosphine 7 in nearly quantitative yield
from the difluoroarsine 2 and the lithium phosphide 8.
7 was obtained in the form of two diastereoisomers
which present rather close 31P and 19F chemical shifts
Scheme 2.
1
(7a, 85%; l31P −30.5, l19F −126.4 ppm, JPH 218.1
1
Hz; 7b, 15%; l31P −43.7, l19F −113.4 ppm, JPH
2
211.6 Hz) but very different JPF (7a 89.0 Hz, 7b 34.6
Hz).
Addition of tert-butyllithium to 7 in pentane af-
forded the arsaphosphene 6 (Scheme 3).
Arsaphosphene 6 can be obtained directly from 2 and
8 without isolation of 7. It displays a 31P signal at 524.5
ppm, in the expected field for such a derivative (gener-
ally from 520 to 670 ppm [1c,10]).
Scheme 3.
Orange and orange–red crystals of diarsene 1 and
arsaphosphene 6 are thermally stable and can be han-
dled in air without decomposition.
2.3. X-ray structure analysis of 1 (Fig. 1) and 6 (Fig.
2)
Four diarsenes have been characterized by X-ray
analysis [2b,3b,4c]. They featured AsꢀAs distances be-
,
tween 2.224(3) [4c] and 2.285(3) A [3b]. The AsꢀAs
Fig. 1. Molecular structure of 1. The thermal ellipsoids are drawn at
50% probability.
,
bond length of 1 (2.2634(3) A) is in the middle of the
range. The shortening in relation to the standard As–
,
As single bond (2.34–2.45 A) is about 8%.
,
The As–P double-bond length of 6 (2.141(5) A) is
also close to the As–P distance reported for the two
arsaphosphenes previously structurally characterized
,
(2.124(2) A in (Me3Si)2CH–AsꢀPAr [4b] and 2.134 (2)
,
A in 2,6-Trip2C6H3AsꢀPMes (Trip=2,4,6-iPr3C6H2)
[5]). The shortening is about 8.5% in relation to the
,
standard As–P bond (2.33 A), roughly halfway be-
tween diarsenes (ꢀ8%) and diphosphenes (generally
9–9.5%). The synthesis of a complete homologous se-
ries of ArEꢀE%Ar derivatives (E, E%=P, As) allows
comparison of their structural data and determination
of their most significant features (Table 1). The AsP
double-bond length is exactly midway between the val-
ues found for As–As and P–P double bonds. A de-
crease is observed in the C–E–E% bond angle from
Fig. 2. Molecular structure of 6. The thermal ellipsoids are drawn at
50% probability.

M. Bouslikhane et al. / Journal of Organometallic Chemistry 619 (2001) 275–279
277
Table 1
Selected bond lengths, bond angles and torsion angles for 1, 6 and ArPꢀPAr [8]
ArAsꢀAsAr (1)
ArPꢀAsAr (6)
ArPꢀPAr
AsꢀAs
AsC1
2.2634(3)
2.0006(12)
PꢀAs
P–C1A
As–C1
2.141(5)
1.893(4)
1.9976(10)
PꢀP
P–C1
2.034(2)
1.862(2)
C1AsAsA
AsC1C6
AsC1C2
97.46(3)
119.49(8)
121.32(9)
C1AsP
98.59(9)
100.8(3)
120.89(12)
120.35(12)
116.5(3)
C1–P–PA
102.8(1)
C1APAs
AsC1C2
AsC1C6
PC1AC2A
PC1AC6A
C1AsPC1A
124.3(3)
175.2(4)
C1AsAsAC1A
180.0
C1PPAC1A
172.2(1)
102.8(1)° (CPP in ArPꢀPAr [8]) to 100.8(3)° and
98.59(9)° (CPAs and CAsP in 6) and 97.46(3)° (CAsAs
in 1) reflecting as expected the increasing p character of
the s and p bonding and s character of the lone pair.
By contrast, the torsion angle CEE%C% increases from
diphosphene (172.2(1)°) [8], to arsaphosphene
(175.2(4)°) and to diarsene (180.0°). A similar trend has
been reported in a series of diphosphene, diarsene,
distibene and dibismuthene [3b]. As expected, all of
them are in a E configuration.
trated. Recrystallization from pentane gave 1.01 g
(77%) of 1; m.p. 174°C. H-NMR (CDCl3): lppm 1.36
1
(s, 18H, p-t-Bu); 1.41 (s, 36H, o-t-Bu); 7.43 (s, 4H,
arom H). 13C-NMR (CDCl3): lppm 31.5 (p-C(CH3)3);
34.2 (o-C(CH3)3); 34.8 (p-C(CH3)3); 39.1 (o-C(CH3)3);
122.4 (m-CH); 141.9 (ipso-C); 148.8 (p-C); 154.5 (o-C).
MS (EI, m/z;%): 640, (1) [M+]; 584, (2) [M−t-Bu+1];
395, (1) [ArAsꢀAs]; 319, (22) [ArAs−1]; 57, (100)
[t-Bu].
3.2. Synthesis of fluroarsinylphosphine 7
3. Experimental
A solution of n-BuLi in hexane (1.58 ml, 2.53 mmol,
1.6 M) was added to ArPH2 (0.64 g, 2.30 mmol) in 10
ml of THF under stirring at −78°C. The solution
became brown and was transferred to a solution of
ArAsF2 (0.8 g, 2.30 mmol) in THF (15 ml) at −78°C.
Then the reaction mixture was warmed to room tem-
perature and solvents were removed in vacuo. The
residue was dissolved in pentane and LiF was filtered
out; 31P and 19F-NMR analysis showed the formation
of two diastereoisomers in the ratio 85:15. Only the
major one could be obtained in pure form by recrystal-
lization from pentane as pale yellow crystals (0.51 g,
All reactions were carried out under nitrogen or
argon with carefully dried solvents. NMR spectra (1H,
13C, 19F (CF3COOH), 31P (H3PO4)) were recorded on
Bruker AC 80 and AC 200 respectively at 80.130,
50.323, 188.298 and 81.015 MHz; mass spectra were
obtained from a Hewlett–Packard HP 5989 spectrome-
ter in the electron-impact mode (70 eV). Melting points
(m.p.) were measured on a Leitz microscope.
3.1. Preparation of diarsene 1
1
36%); m.p. 141°C. H-NMR: lppm 1.26–1.36 (m, 54H,
1
To ArAsH2 (1.10 g, 3.41 mmol) in 15 ml of THF at
−78°C was added dropwise a solution of n-BuLi in
hexane (2.34 ml, 3.74 mmol, 1.6 M). The reaction
mixture turned green. After 45 min at this temperature,
0.47 ml (3.78 mmol) of Me3SiCl was added giving a
yellow solution. THF and hexane were evaporated in
vacuo and replaced by 15 ml of THF. To this solution
cooled at −78°C were added 2.24 ml (3.58 mmol) of a
solution of n-BuLi in hexane. The reaction mixture was
then transferred via cannula to a solution of ArAsF2
(1.23 g, 3.44 mmol) in THF (10 ml) at −78°C giving
an orange suspension. The solvents were removed in
vacuo and the residue was dissolved in pentane; inor-
ganic salts were filtered out and the filtrate was concen-
p- and o-t-Bu (ArP and ArAs)); 5.03 (dd, JPH 217.2
3
4
Hz, JHF 3.0 Hz, 1H, PH); 7.25 (d, JPH 2.3 Hz, 2H,
arom H (ArP)); 7.36 (s, 2H, arom H (ArAs)). 31P-
1
2
NMR: lppm −30.5 (dd, JPH 218.1 Hz, JPF 89.0 Hz);
19F-NMR: lppm −126.5 (d, JPF 89.0 Hz); 13C-NMR:
2
lppm 31.4, 31.7 (p-C(CH3)3 (ArP and ArAs)); 33.9
(broad s, o-C(CH3)3 (ArP and ArAs)); 34.7, 35.0 (p-
C(CH3)3 (ArP and ArAs)); 38.0 (o-C(CH3)3 (ArP and
ArAs)); 122.8, 123.8 (m-C (ArP and ArAs)); 150.0,
150.8 (p-C (ArP and ArAs)); 154.6, 154.9 (o-C (ArP
and ArAs)). MS (EI, m/z,%): 616, (1) [M+]; 339, (2)
[ArAsF]; 319, (6) [ArAs−1]; 277, (18) [ArPH]; 275,
(12) [ArP−1], 264, (15) [ArAs−t-Bu+1], 208, (32)
[ArAs−2t-Bu+2]; 57, (100) [t-Bu].

278
M. Bouslikhane et al. / Journal of Organometallic Chemistry 619 (2001) 275–279
4
(p-C(CH3)3 (ArP and ArAs)); 34.1 (d, JCP 3.6 Hz,
o-C(CH3)3 (ArP)); 34.4 (o-C(CH3)3 (ArAs)); 34.7 (p-
C(CH3)3 (ArP and ArAs)); 38.7, 39.0 (o-C(CH3)3 (ArP
and ArAs)); 122.1, 122.6 (m-C (ArP and ArAs)); 148.7,
148.9 (p-C (ArP and ArAs)); 153.8 (o-C (ArAs)); 154.6
3.3. Preparation of arsaphosphene 6
To a solution of 7 (0.5 g, 0.80 mmol) in pentane (10
ml) cooled at −78°C, was added a solution of one
equivalent of t-BuLi in pentane (0.47 ml, 1.7 M). The
reaction mixture became red and then was slowly
warmed to room temperature; the solvent was evapo-
rated in vacuo, LiF was filtered out and the residue was
extracted with 15 ml of pentane. 6 crystallized in the
form of orange red crystals (0.35 g, 75%); m.p. 173°C.
1H-NMR: lppm 1.36 (s, 18H, p-t-Bu (ArAs and ArP));
1.43, 1.45 (2s, 2×18H, o-t-Bu (ArAs and ArP)); 7.39
2
(d, JCP 5.9 Hz, o-C (ArP)); MS (EI, m/z, %): 596, (6)
[M+]; 539, (1) [M−t-Bu]; 319, (6) [ArAs−1]; 208, (32)
[ArAs−2t-Bu+2]; 57, (100) [t-Bu].
3.4. X-ray data collection and structure refinement
Crystal data for 1 and 6 are presented in Table 2. All
data were collected at low temperature on a Bruker-
AXS CCD 1000 diffractometer with Mo–Ka radiation
4
(d, JPH 1.1 Hz, 2H, arom H (ArP)); 7.44 (s, 2H, arom
H (ArAs)). 31P-NMR: lppm 524.5. 13C-NMR: lppm 31.5
,
(u=0.71073 A). The structures were solved by direct
Table 2
methods by means of SHELXS-97 [11] and refined with
all data on F2 by means of SHELXL-97 [12]. All non-hy-
drogen atoms were refined anisotropically. The hydro-
gen atoms of the molecules were geometrically idealized
and refined using a riding model. The inversion centre
between the P and the As atoms in 6 leads to a
disorder, which has been refined with the help of ADP
and distance restraints with an occupancy of 0.5 for
each atom by ignoring the symmetry (PART-1).
Crystal data and structure refinement for 1 and 6
Empirical formula
C36H58As2 (1)
C36H58AsP (6)
Formula weight
Temperature (K)
Wavelength (A)
Crystal system
Space group
Unit cell dimensions
640.66
193(2)
0.71073
Triclinic
596.72
193(2)
0.71073
Triclinic
,
(
(
P1
P1
,
a (A)
9.9082(2)
9.9274(2)
,
b (A)
10.1943(2)
10.6758(2)
94.5880(10)
109.1560(10)
116.9730(10)
873.64(3), 1
1.218
10.2828(2)
10.5872(2)
93.9980(10)
109.0350(10)
117.6710(10)
872.66(3), 1
1.135
,
c (A)
4. Supplementary material
h (°)
i (°)
l (°)
Crystallographic data (excluding structure factors)
have been deposited with the Cambridge Crystallo-
graphic Data Centre as supplementary publications
CCDC nos. 145883 (1) and 145884 (6). Copies of the
data can be obtained free of charge on application to
The Director, CCDC, 12 Union Road, Cambridge CB2
1 EZ, UK (Fax: +44-1223-336033; e-mail: deposit@
ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk).
3
,
Volume (A ), Z
Density (calculated) (Mg
m−3
)
Absorption coefficient
(mm−1
F(000)
Crystal size (mm)
q range for data collection 2.10–30.51
(°)
1.933
1.041
)
340
0.6×0.5×0.1
322
0.3×0.5×0.6
2.11–31.05
Limiting indices
−145h514
−145k514
−155l515
15792
−145h513
−145k514
−145l515
13216
Acknowledgements
Reflections collected
Independent reflections
5298
(Rint=0.0257)
4960
(Rint=0.0282)
88.7
The authors thank the Comite´ Mixte Interuniversi-
taire Franco-Marocain for the Action Integre´e no. 216/
SM/00.
Completeness to q=30.51° 99.4
(%)
Absorption correction
Max. and min.
transmission
Semi-empirical
1.000000 and
0.781077
Full-matrix
least-squares on
F2
None
References
Refinement method
Full-matrix
least-squares on
F2
4960/54/190
1.079
R1=0.0318,
wR2=0.0878
R1=0.0372,
wR2=0.0900
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0.978
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R1=0.0257,
wR2=0.0644
R1=0.0319,
wR2=0.0663
0.742 and −0.251 0.393 and
−0.233
R indices (all data)
Largest difference peak
−3
,
and hole (e A
)

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