Arsinophosphonium cations from arsenium-phosphine and -bisphosphine coordination chemistry

Article abstract of DOI:10.1021/ic050989w

A new 14π-electron tricyclic organoarsenium cation (5- hydrophenarsazinium, AN, C₁₂H₉AsN⁺) has been prepared in situ and used as a Lewis acceptor with trimethylphosphine, triphenylphosphine, bis(diphenylphosphino)methane (dppm), bis(dimethylphosphino) methane (dmpm), and 1,4-bis(diphenylphosphino)benzene (dppb) ligands. Solid-state structures and spectroscopic characterization data are reported for complexes of the general formula [AN-PMe₃]⁺, [AN-PPh ₃]⁺, [AN-dppm]⁺, [AN-dppm-AN]²⁺, [AN-dmpm-AN]²⁺, and [AN-dppb-AN]²⁺ as tetrachlorogallate salts. Depending on reaction stoichiometry, dppm forms adducts at one or both of the donor sites. Structural comparisons with analogous complexes of phosphenium cations provide interesting similarities and differences.

Full text of DOI:10.1021/ic050989w

Inorg. Chem. 2005, 44, 9453−9460
Arsinophosphonium Cations from Arsenium-phosphine and
-bisphosphine Coordination Chemistry
Neil Burford,* Paul J. Ragogna, and Kendall Sharp
Department of Chemistry, Dalhousie UniVersity, Halifax, NoVa Scotia, B3H 4J3, Canada
Robert McDonald and Michael J. Ferguson
X-ray Crystallography Laboratory, Department of Chemistry, UniVersity of Alberta,
Edmonton, Alberta T6G 2G2, Canada
Received June 16, 2005
A new 14π
-electron tricyclic organoarsenium cation (5-hydrophenarsazinium, AN, C12H9AsN+) has been prepared
in situ and used as a Lewis acceptor with trimethylphosphine, triphenylphosphine, bis(diphenylphosphino)methane
(dppm), bis(dimethylphosphino)methane (dmpm), and 1,4-bis(diphenylphosphino)benzene (dppb) ligands. Solid-
state structures and spectroscopic characterization data are reported for complexes of the general formula [AN
−
PMe3]+, [AN PPh3]+, [AN dppm]+, [AN AN]2+, [AN AN]2+, and [AN AN]2+ as tetrachlorogallate
−
−
−
dppm dmpm dppb
−
−
−
−
−
salts. Depending on reaction stoichiometry, dppm forms adducts at one or both of the donor sites. Structural
comparisons with analogous complexes of phosphenium cations provide interesting similarities and differences.
Introduction
or selenium.19 Solid-state structural characterization data or
NMR data that have been reported for examples of com-
plexes involving electron-rich arsenic Lewis acceptors30-40
The coordination chemistry of electron-rich (lone-pair
bearing) phosphorus centers as Lewis acceptors1 is well
established and provides a new approach to forming bonds
between phosphorus and carbon,2-9 nitrogen,10-18 oxygen,19
phosphorus,17,20-28 sulfur,19 chlorine,8 gallium,29 bromine,8
(12) Burford, N.; Losier, P.; Bakshi, P. K.; Cameron, T. S. Chem. Commun.
1996, 307-308.
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1171.
* To whom correspondence should be addressed. E-mail:
Neil.Burford@dal.ca.
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1995, 6, 371-375.
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H. A. Chem. Commun. 2000, 2087-2088.
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10.1021/ic050989w CCC: $30.25
Published on Web 11/02/2005
© 2005 American Chemical Society
Inorganic Chemistry, Vol. 44, No. 25, 2005 9453

Burford et al.
highlight the potential for application of this methodology
to arsenic chemistry. Moreover, the intramolecular phosphine
complex, 1,39
phenium cations has been extended using bisphosphine
ligands dppm, dmpm, dppe, dmpe, dpph, and dppb, which
give triphosphorus monocations, 4, and tetraphosphorus
dications, 5, 6, and 7,20 depending on the ligand backbone
and the steric crowding of the donor and the acceptor sites.
and the prototypical arsenium-phosphine complexes, 2,40
are analogues of the phosphenium-phosphine cations, 3,41,20
and were first proposed as “arsinophosphonium” cations, 2′,
for solids with appropriate elemental composition that were
isolated from reactions of dialkylhaloarsines with triarylphos-
phines.42
Attempts to isolate complexes of the diphenylarsenium cation
have been unsuccessful, but the closely related tricyclic
5-hydrophenarsazinium cation (AN, [C12H9AsN]+) has been
prepared in situ from 10-chloro-5-hydrophenarsazine (ANCl
8)44 and a number of arsinophosphonium, arsinophosphoni-
umphosphine, and bisarsinobisphosphonium tetrachloro-
gallate salts have been isolated and comprehensively char-
acterized.
The extensive ligand exchange chemistry that has been
observed for derivatives of 3′ 15,20,29,43 defines the reactivity
of the phosphorus derivatives as ligand stabilized phosphe-
nium cations, 3, but the coordination sphere of the phos-
phenium Lewis acceptor is apparently restricted to a single
ligand. Nevertheless, the coordination chemistry of phos-
Cations with the abbreviated formulas [AN-PR3]+ (R ) Me,
Ph), [AN-dppm]+, [AN-dppm-AN]2+, [AN-dmpm-
AN]2+, and [AN-dppb-AN]2+ demonstrate a versatile
Lewis acid behavior for the new 14π-electron arsenium
cation (AN). The complexes exploit a new avenue of
phosphorus-arsenic chemistry in a rational and systematic
manner, offering interesting structural comparisons, and the
observation that both [AN-dppm]+ and [AN-dppm-AN]2+
demonstrate some control of ligand stoichiometry.
(27) Burford, N.; Cameron, T. S.; Clyburne, J. A. C.; Eichele, K.; Robertson,
K. N.; Sereda, S.; Wasylishen, R. E.; Whitla, W. A. Inorg. Chem.
1996, 35, 5460-5467.
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Int. Ed. Engl. 1985, 24, 226-227.
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Hardman, N. J.; Power, P. P. J. Am. Chem. Soc. 2002, 124, 382-
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31-33.
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17, 2071-2073.
Experimental Section
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(34) Coates, G. E.; Braddock, J. M. F. J. Chem. Soc. 1961, 3208-3211.
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Wolf, R.; Sanchez, M. Heteroat. Chem. 1992, 3, 157-162.
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S.; Richardson, J. F.; Gabe, E. J.; Hynes, R. J. Am. Chem. Soc. 1992,
114, 8147-8153.
General. All manipulations were carried out in a N2-filled
Innovative Technologies drybox. Solvents were purified using an
MBraun Solvent Purification System and were degassed with three
freeze-pump-thaw cycles prior to use. Arsenic trichloride was
purchased from BDH. Triphenylphosphine, gallium chloride, tri-
methylsilyltrifluoromethanesulfonate (TMS-OTf), bis(diphenylphos-
phino)methane (dppm), and bis(dimethylphosphino)methane (dmpm)
were purchased from Aldrich Chemical Co., and 1,4-bis(diphen-
ylphosphino)benzene (1,4-dppb) was purchased form Kodak Chemi-
cal Company. All reagents were used as received without further
purification. 10-Chloro-5-hydrophenarsazine (ANCl 8, “adamsite”)
was prepared by a literature procedure.44 IR spectra were recorded
(39) Vogt, R.; Jones, P. G.; Schmutzler, R. Chem. Ber. 1993, 126, 1271-
1281.
(40) Porter, K. A.; Willis, A. C.; Zank, J.; Wild, S. B. Inorg. Chem. 2002,
41, 6380-6386.
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Gee, M.; McDonald, R.; Wasylishen, R. E. J. Am. Chem. Soc. 2001,
123, 7947-7948.
(42) Braddock, J. M. F.; Coates, G. E. J. Chem. Soc. 1961, 3208-3211.
(43) Burford, N.; Herbert, D. E.; Ragogna, P. J.; McDonald, R.; Ferguson,
G. J. Am. Chem. Soc. 2004, 126, 17067-17073.
(44) Burton, H.; Gibson, C. S. J. Chem. Soc. 1926, 450.
9454 Inorganic Chemistry, Vol. 44, No. 25, 2005

Arsinophosphonium Cations
Table 1. Crystal Data
[AN-PMe3] 9a
[AN-PMe3] 9a
[AN-PPh3] 9b
[GaCl4]
[OTf]
[OTf]
formula
C15H18AsCl4GaNP
529.71
triclinic
C16H18AsF3NO3PS
C31H24AsF3NO3PS
653.46
triclinic
fw (g mol-1
cryst syst
space group
a (Å)
)
467.26
orthorhombic
Pbca
P1h
P1h
8.9063(6)
10.4349(7)
11.5512(7)
87.2939(9)
83.2283(9)
80.7053(8)
1051.61(12)
2
12.4041(11)
14.4224(13)
21.608(2)
-
10.9114(6)
11.2816(6)
14.0864(8)
68.8860(10)
69.0570(10)
66.4330(10)
1435.75(14)
2
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
-
-
3865.5(6)
8
Z
Dc (Mg m3)
R1
1.673
0.0276
1.606
0.0899
1.512
0.0330
(I > 2σ(I))
wR2
0.0643
1.072
0.0890
1.049
0.0759
1.030
(I > 2σ(I))
GOF
[AN-dppm] 10
[AN-dppm-AN] 11a
[AN-dmpm-AN] 11b
[AN-dppb-AN]12
[GaCl4]2 [CH2Cl2]
[GaCl4]
[GaCl4]2
[GaCl4]2
formula
C37H31AsCl4GaNP2
838.01
triclinic
C49H40As2Cl8Ga2N2P2
1291.65
triclinic
C29H32As2Cl8Ga2N2P2
1043.39
triclinic
C55H44As2Cl10Ga2N2P2
1438.64
monoclinic
P21/n
12.973(2)
21.727(3)
21.088(3)
-
97.109(2)
-
fw (g mol-1
cryst syst
space group
a (Å)
)
P1h
P1h
P1h
10.8267(8)
11.0873(8)
16.9738(12)
93.6919(10)
105.8446(10)
107.4575(10)
1845.9(2)
2
11.9023(6)
12.1996(6)
19.0401(10)
80.5845(9)
79.7616(9)
78.9139(9)
2645.8(2)
2
10.2840(9)
11.5340(10)
17.5873(15)
75.9930(10)
85.1000(10)
76.6770(10)
1968.7(3)
2
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
5898.2(16)
4
1.620
Z
Dc (Mg m3)
R1
1.508
0.0501
1.621
0.0627
1.760
0.0503
0.0528
(I > 2σ(I))
wR2
0.1026
1.034
0.1207
1.064
0.0734
0.993
0.0831
1.026
(I > 2σ(I))
GOF
on a Bruker VECTOR 22 FT-IR using Nujol mulls and are reported
with ranked intensities in parentheses. Solution NMR data were
obtained on a Bruker AC-250 NMR spectrometer at room temper-
ature unless otherwise indicated. Chemical shifts are reported in
ppm relative to a reference standard [TMS (1H); 85% H3PO4 (31P)]
and J values are reported in Hz. Unless otherwise indicated,
crystalline samples were obtained by vapor diffusion, in which the
sample (0.050 to 0.100 g) was dissolved in a minimal amount of
CH2Cl2 in an uncapped 1 dram vial that was placed inside a 4 dram
vial containing Et2O, hexane, or pentane (2 mL). The larger vial
was capped tightly, and the system was allowed to stand at room
temperature. Crystals were mounted under oil (perfluoropolyether
or Paratone). X-ray diffraction data (Table 1) were collected at 193-
(2) K on a Bruker PLATFORM diffractometer with a sealed tube
generator and a SMART 1000 CCD detector using graphite-
monochromated Mo KR (λ ) 0.71073) radiation.
Preparative Procedures and Characterization Data. [AN-
PMe3][GaCl4]. A solution of GaCl3 (0.032 g, 0.18 mmol) in CH2-
Cl2 (2 mL) was added to a solution of ANCl (0.050 g, 0.18 mmol)
in CH2Cl2 (5 mL). PMe3 (1.0 M in hexane, 180 µL, 0.18 mmol)
was added after 1 h, and the mixture was stirred for 48 h. The
solvent was reduced in vacuo to 2 mL, and the addition of hexanes
gave a white precipitate. Crystallization was by hexane vapor
diffusion into a CH2Cl2 solution. Yield: 0.089 g, 93%. mp: 152
°C. Elemental analyses were not determined. IR (cm-1): 300 (13),
361 (15), 375 (1), 445 (3), 560 (10), 802 (6), 958 (2), 1027 (4),
1235 (14), 1261 (8), 1342 (11), 1576 (5), 1595 (9), 2360 (12), 3375
(7). 1H NMR (CD2Cl2): δ 8.2 (s, 1H, NH), 7.6-7.1 (m, 8H,
aromatic), 1.6 (d, 9H, CH3, 2JPH ) 13.7 Hz). 31P{1H} NMR (CH2-
Cl2): δ 7.
[AN-PMe3][OTf]. PMe3 (1.0 M in hexane, 77 µL, 0.077 mmol)
was added to a solution of [AN-PPh3][OTf] (0.050 g, 0.077 mmol)
in CH2Cl2 (5 mL). The solvent was reduced in vacuo to 2 mL, and
the addition of hexane gave an off-white precipitate. Crystallization
was by Et2O vapor diffusion into a CH2Cl2 solution. Yield 0.043
g, 91%. mp: 183-184 °C. Elemental analyses were not determined.
IR (cm-1): 450 (15), 517 (13), 636 (8), 750 (7), 962 (5), 1028 (4),
1156 (2), 1224 (6), 1249 (1), 1282 (3), 1344 (9), 1522 (14), 1576
(10), 1601 (11), 3314 (12). 1H NMR (CD2Cl2): δ 8.2 (s, 1H, NH),
7.6-7.1 (m, 8H, aromatic), 1.5 (d, 9H, CH3, 2JPH ) 13.7 Hz). 31P-
{1H} NMR (CH2Cl2): δ 7.
[AN-PPh3][OTf]. TMS-OTf (0.33 mL, 1.80 mmol) was added
to ANCl (0.499 g, 1.80 mmol) in CH2Cl2 (15 mL). Ph3P (0.473 g,
1.80 mmol) in CH2Cl2 (10 mL) was added after 1 h and stirred for
5 h. Solvent was removed in vacuo giving a yellow precipitate that
was filtered and washed with 2 × 10 mL hexane. Crystallization
was by Et2O vapor diffusion into a CH2Cl2 solution. Yield: 1.06
g, 90%. mp: 170-171 °C. Elemental analyses were not determined.
IR (cm-1): 495 (14), 517 (13), 634 (10), 692 (12), 720 (18), 746
(5), 755 (7), 995 (15), 1029 (3), 1096 (11), 1151 (4), 1223 (6),
1257 (1), 1282 (2), 1346 (9). 31P{1H} NMR: δ 6.
[AN-dppm][GaCl4]. Dppm (0.038 g, 0.10 mmol) in CH2Cl2
(2 mL) was added to a solution of ANCl (0.028 g, 0.10 mmol) in
CH2Cl2 (2 mL) and GaCl3 (0.018 g, 0.10 mmol) in CH2Cl2 (2 mL).
Inorganic Chemistry, Vol. 44, No. 25, 2005 9455

Burford et al.
Table 2. Selected As-P and As-C Distances (Å), C-As-C and C-As-P Angles (deg), and the Shortest Intermolecular and Intramolecular Distances
(Å) Between the Centroids of AN and Aryl Planes and Angles (deg) between the Planes for Derivatives of 1, 2, 9, 10, 11, and 12
AN‚‚‚AN
(angle)
iPh‚‚‚AN
(angle)
As-P
As-C
C-As-C
98.8(3)
C-As-P
96.6 (3)
ref
39
1 [BPh4]
2.346(2)
1.975(7)
1.877(5)
(As-N)
1.959(2)
1.955(2)
1.956(2)
1.957(2)
As1-C1
1.913(2)
As1-C7
1.914(2)
As1-C11
1.928(2)
As1-C21
1.934(2)
As1-C1
1.937(4)
As1-C1
1.931(4)
As1-C1
1.922(3)
As1-C12
1.928(3)
As1-C11
1.928(4)
As1-C21
1.920(4)
As2-C41
1.921(5)
As2-C31
1.924(5)
As1-C1
1.931(3)
As1-C7
1.927(3)
As2-C21
1.917(3)
As2-C27
1.919(3)
(C-As-N)
101.73(7)
100.35(8)
83.9(2)
(N-As-P)
92.31(8)
997.04(6)
95.59(6)
96.99(5)
C1-As1-P1
95.76(6)
C7-As1-P1
99.38(5)
C11-As1-P1
94.30(6)
C21-As1-P1
94.03(6)
C11-As1-P1
95.9(1)
C21-As1-P1
94.1(1)
C1-As1-P1
93.82(9)
C12-As1-P1
94.29(9)
[PhMeAs-PPh3]
2a [PF6]
[PhMeAs-PPh2 {2-(MeO)C6H4}] 2.3703(5)
2b [PF6]
[AN-PPh3]
9b [OTf]
2.3480(5)
40
40
a
As1-P1
2.4121(5)
C1-As1-C7
97.31(8)
3.361 (0)
3.334 (0)
3.322 (0)
3.402 (0)
3.335 (0)
[AN-PMe3]
9a [GaCl4]
As1-P1
2.3393(6)
C11-As1-C21
97.36(9)
a
a
a
a
[AN-PMe3]
9a [OTf]
As1-P1
2.342(1)
C21-As1-C11
96.9(2)
[AN-dppm]
10 [GaCl4]
As1-P1
2.3753(8)
C1-As1-C12
97.5(1)
3.683 (22.7)
[AN-dppm-AN]
11a [GaCl4]2
As1-P1
2.414(1)
As2-P2
2.417(1)
C21-As1-C11
97.8(2)
C11-As1-P1
94.1(1)
3.502 (15.5)
3.437 (18.0)
C41-As2-C31
97.2(2)
C21-As1-P1
92.6(1)
C41-As2-P2
93.2(1)
C31-As2-P2
91.7(1)
[AN-dmpm-AN]
11b [GaCl4]2
As1-P1
2.3755(8)
As2-P2
2.3663(9)
C11-As1-C11
97.1(1)
C21-As2-C27
97.6(1)
C1-As1-P1
3.371 (0)
a
a
91.09(9)
C7-As1-P1
95.78(9)
C21-As2-P2
94.62(9)
C27-As2-P2
93.72(9)
[AN-dppb-AN]
As1A-P1A As1A-C11A C11A-As1A-C21A C11A-As1A-P1A 3.503 (4.2) A 3.632 (20.6)
b
12 [GaCl4]2
2.3925(8)
1.926(4)
97.7(1)
96.08(9)
B: 3.641 (20.5)
As1A-C21A
1.930(3)
C21A-As1A-P1A
92.54(9)
a This work. b One of two essentially identical asymmetric units.
After 1 h, the solvent was reduced in vacuo to 2 mL, and the
addition of Et2O (10 mL) gave a yellow precipitate, which was
recrystallized by liquid-liquid diffusion (CH2Cl2/hexane). Yield:
0.051 g, 61%. mp: 179-180 °C. Anal. Calcd for C37H31AsCl4-
GaNP2 (Found): C, 53.03 (52.92); H, 3.73 (3.52); N, 1.67 (1.57).
IR (cm-1): 461 (4), 480 (19), 502 (7), 519 (13), 586 (17), 658
(16), 687 (2), 891 (14), 997 (15), 1027 (8), 1105 (5), 1160 (9),
1235 (12), 1307 (18), 1351 (20), 1513 (10), 1574 (6), 1595 (1),
2725 (11), 3358 (3). 1H NMR (CD2Cl2): δ 8.2 (s, 1H, NH), 7.6-
7.6-6.8 (m, 36H, aromatic), 3.0 (t, 2H, CH2, 2JPH ) 9.5 Hz). 31P-
{1H} NMR (CH2Cl2): δ 4.
[AN-dmpm-AN][GaCl4]2. GaCl3 (0.018 g, 0.10 mmol) in
CH2Cl2 (2 mL) was added to ANCl (0.028 g, 0.10 mmol) in CH2-
Cl2 (5 mL). The resulting purple solution was then added dropwise
to a solution of dmpm (0.014 g, 0.10 mmol) in CH2Cl2 (5 mL),
giving a pale yellow solution which was stirred for 24 h.
Crystallization by liquid-liquid diffusion (CH2Cl2/hexane) gave
yellow crystals. Yield 0.05 g, 60%. mp 174-175 °C. Elemental
analyses were not determined. IR (cm-1): 801 (14), 893 (1), 952
(6), 1025 (3), 1178 (8), 1261 (4), 1507 (11), 1541 (15), 1559 (12),
2
6.6 (m, 28H, aromatic), 2.9 (t, 2H, CH2, JPH ) 6.3 Hz). 31P{1H}
NMR (CH2Cl2, 200 K): δ 11 (d, 2JPP ) 75 Hz), -30 (d, 2JPP ) 75
Hz).
1
1576 (5), 1595 (2), 1653 (9), 3375 (10), 3750 (13), 3853 (7). H
[AN-dppm-AN][GaCl4]2. GaCl3 (0.035 g, 0.20 mmol) in CH2-
Cl2 (2 mL) was added to a ANCl (0.056 g, 0.20 mmol) in CH2Cl2
(2 mL). The resulting purple solution was then slowly added
dropwise to a solution of dppm (0.038 g, 0.01 mmol) in CH2Cl2 (2
mL). Orange crystalline material slowly precipitated. Yield 0.099
g, 77%. mp 223 °C. Anal. Calcd for C49H40As2Cl8Ga2N2P2
(Found): C, 45.56 (45.04); H, 3.12 (2.88); N, 2.17 (1.95). IR
(cm-1): 453 (6), 494 (15), 585 (11), 685 (3), 890 (14), 1024 (10),
1063 (12), 1102 (4), 1164 (7), 1235 (8), 1317 (13), 1515 (9), 1573
NMR (CD2Cl2): δ 8.2 (s, 2H, NH), 7.7-7.1 (m, 16H, aromatic),
2
2
1.4 (d, 12H, CH3, JPH ) 5 Hz), 2.0 (t, 2H, CH2, JPH ) 7 Hz).
31P{1H} NMR (CH2Cl2, 200 K): δ 16, -43.
[AN-dppb-AN][GaCl4]2. A solution of dppb (0.045 g., 0.10
mmol) in CH2Cl2 (2 mL) was added to ANCl (0.028 g, 0.10 mmol)
in CH2Cl2 (2 mL) and GaCl3 (0.018 g, 0.1 mmol) in CH2Cl2 (2
mL). Red-orange crystals formed when the solution stood at room
temperature. Yield: 0.046 g, 51. mp: 253-254 °C. Anal. Calcd
for C54H42As2Cl8Ga2N2P2 (Found): C, 47.91 (45.92); H, 3.13 (3.08);
N, 2.07 (1.95). IR (cm-1): 282 (12), 374 (2), 441 (10), 496 (13),
1
(5), 1596 (1), 3357 (2). H NMR (CD2Cl2): δ 8.2 (s, 2H, NH),
9456 Inorganic Chemistry, Vol. 44, No. 25, 2005

Arsinophosphonium Cations
Table 3. Comparison of P-C-P-Pn and C-Pn-P-C Torsional Angles (deg) for derivatives of 4, 5, 7, 10, 11, and 12
P-C-P-Pn
CA-Pn-P-C
C-Pn-P-C
ref
43
[Me2P-dppm] 4a [OTf]
[Me2P-dppm] 4a [GaCl4]
[Ph2P-dppm] 4b [OTf]
P(3)-C(3)-P(2)-P(1)
-52.3(2)
C(1)-P(1)-P(2)-C(3)
-147.4(2)
C(2)-P(1)-P(2)-C(3)
-44.9(2)
C(2)-P(1)-P(2)-C(3)
P(3)-C(3)-P(2)-P(1)
C(1)-P(1)-P(2)-C(3)
43
43
43
60.4(2)
65.3(2)
167.4(2)
P(1)-C(1)-P(2)-P(3)
-61.3(1)
C(51)-P(3)-P(2)-C(1)
-163.6(1)
C(61)-P(3)-P(2)-C(1)
-54.7(1)
C(21)-P(2)-P(1)-C(1)
-86.8(2)
C(21′)-P(2′)-P(1′)-C(1)
-86.8(2)
C(21)-P(1)-P(2)-C(1)
[Ph2P-dmpm-PPh2] 5 [GaCl4]2
P(1′)-C(1)-P(1)-P(2)
-38.05(6)
C(11)-P(2)-P(1)-C(1)
166.3(2)
P(1)-C(1)-P(1′)-P(2′)
-38.05(6)
C(11′)-P(2′)-P(1′)-C(1)
166.3(2)
[Ph2P-dmpm-PPh2] 5 [OTf]2
[Me2P-dppb-PMe2] 7 [GaCl4]2
P(3)-C(1)-P(2)-P(1)
-68.6(2)
P(2)-C(1)-P(3)-P(4)
170.1(1)
C(11)-P(1)-P(2)-C(1)
43
43
-106.3(1)
143.9(1)
C(31)-P(4)-P(3)-C(1)
-79.7(1)
C(41)-P(4)-P(3)-C(1)
167.8(1)
C(12)-P(1)-P(2)-C(1)
C(11)-P(1)-P(2)-C(1)
-42.0(4)
60.3(4)
C(61)-P(4)-P(3)-C(4)
165.6(4)
C(62)-P(4)-P(3)-C(4)
63.5(4)
C(71′)-P(5′)-P(6′)-C(7′)
164.8(7)
C(72)-P(5)-P(6)-C(7)
67.2(6)
C(71)-P(5)-P(6)-C(7)
164.8(7)
C(72′)-P(5′)-P(6′)-C(7′)
67.2(6)
[AN-dppm] 10 [GaCl4]
P(2)-C(20)-P(1)-As
-176.1(1)
C(1)-As-P(1)-C(20)
C(12)-As-P(1)-C(20)
a
a
65.2(1)
-163.0(1)
[AN-dppm-AN] 11a [GaCl4]2
P(2)-C(1)-P(1)-As(1)
-176.6(2)
C(11)-As(1)-P(1)-C(1)
-179.2(2)
C(21)-As(1)-P(1)-C(1)
-81.2(2)
P(1)-C(1)-P(2)-As(2)
-174.3(2)
C(31)-As(2)-P(2)-C(1)
-74.7(2)
C(41)-As(2)-P(2)-C(1)
-172.0(2)
[AN-dmpm-AN] 11b [GaCl4]2
P(2)-C(40)-P(1)-As(1)
C(1)-As(1)-P(1)-C(40)
C(7)-As(1)-P(1)-C(40)
a
a
166.8(1)
174.5(2)
77.3(2)
P(1)-C(40)-P(2)-As(2)
161.9(1)
C(21)-As(2)-P(2)-C(40)
70.5(2)
C(11A)-As(1A)-P(1A)
-C(51A) -46.8(1)
C(27)-As(2)-P(2)-C(40)
-27.5(1)
C(21A)-As(1A)-P(1A)-C(51A)
51.2(1)
b
[AN-dppb-AN] 12 [GaCl4]2
a This work. b One of two essentially identical asymmetric units.
519 (1), 577 (4), 693 (6), 801 (5), 1023 (3), 1098 (7), 1164 (15),
1261 (8), 1573 (14), 1595 (9), 3357 (11). The compound is sparingly
soluble, and NMR data could not be obtained.
Yellow solutions of 10-chloro-5-hydrophenarsazine (8
ANCl, “adamsite”)44 react rapidly with trimethylsilyltri-
fluoromethanesulfonate (TMSOTf) or gallium chloride to
give purple solutions. Attempts to isolate and characterize
products from these reactions have been unsuccessful.
Nevertheless, introduction of Ph3P, Me3P, or the tethered
bisphosphines dppm, dmpm, or dppb, has enabled isolation
of complexes containing the cationic unit AN with phosphine
or bisphosphine ligands, which exhibit similar 31P NMR
Results and Discussion
The bisphosphines dppm, dmpm, dppe, dmpe, dpph, and
dppb are traditionally employed as chelate ligands or bridging
ligands for transition metals. They have recently been used
to effect ligand exchange of the phosphine in phosphenium-
phosphine 3 (phosphinophosphonium cations 3′) to give
phosphenium-bisphosphine 4 (phosphinophosphoniumphos-
phine 4′) and bisphosphenium-bisphosphine 5, 6, and 7
cations (bisphosphinobisphosphonium 5′, 6′, and 7′).43 Tetra-
chlorogallate salts of arsenium-bisphosphine 10 (arsino-
phosphoniumphosphine 10′) and bisarsenium-bisphosphine
11 and 12 (bisarsinobisphosphonium 11′, 12′) have now been
prepared using an in situ generation of arsenium cation AN,
and the comparative characterization data for the prototypical
arsenium-phosphine 9 cations (arsinophosphonium 9′),
prepared in the same manner, provide a systematic means
of developing new As-P bonded compounds.
chemical shifts to the quantitative products observed by 31
P
NMR spectroscopy in each reaction mixture. Except in the
case of reactions involving dppm, the 31P NMR spectra of
the reaction mixtures are independent of the imposed reaction
stoichiometry, and chemical shifts for all derivatives of 9,
Inorganic Chemistry, Vol. 44, No. 25, 2005 9457

Burford et al.
Figure 1. Representative structural view of the cation in (a) [AN-PPh3]
9b [OTf] and (b) [Ph2P-PPh3] 3 (R ) R′ ) R′′ ) Ph) [OTf].20 Ellipsoids
are drawn to 50% probability. Hydrogen atoms are not shown.
10, 11, and 12 are consistent with the distinctive shifts for
phosphorus analogues 4, 5, 6, and 720 and the phosphonium
cations (e.g., Ph4P+, δ 20).45
Figure 2. Representative structural views of the cations in (a) [AN-dppm]
10 [GaCl4] and (b) [Me2P-dppm] 4a [GaCl4].43 Ellipsoids are drawn to 50%
probability. Hydrogen atoms are not shown.
X-ray crystallographic studies (Table 1) have confirmed
the ionic formulations for tetrachlorogallate (gallate) and
trifluoromethanesulfonate (triflate) salts of [AN-PMe3] (9a),
[AN-PPh3] (9b), [AN-dppm] (10), [AN-dppm-AN]
(11a), [AN-dmpm-AN] (11b), and [AN-dppb-AN] (12).
Table 2 lists P-As distances and angles at the arsenic center
for each compound together with values for the related
cations in 1 [BPh4],39 2a [PF6], and 2b [PF6],40 which contain
examples of previously reported As-P coordinate bonds.
Table 3 provides a comparison of important torsional angles
for cations involving bisphosphine ligands with arsenium or
phosphenium cation acceptors.
angles close to 90° (range 91.1-99.4°). The As-P distance
is slightly shorter in [AN-PMe3] 9a [GaCl4] and [AN-
PMe3] 9a [OTf] than in [AN-PPh3] 9b [OTf], consistent
with the relative inductive basicity of the respective phos-
phine ligands. The pyramidal geometry about the three-
coordinate arsenic center in all cations is consistent with an
arsine-like environment, and the donor phosphorus centers
have a phosphonium-like distorted tetrahedral geometry. The
As-P distances in [AN-PMe3] 9a and [AN-PPh3] 9b are
the same as those in 2a [PF6] and 2b [PF6].40
Differences in As-C bond lengths between 2a, 2b, 9a,
and 9b, as well as differences in the angles (C-As-C and
C-As-P) at arsenic, can be rationalized in terms of the
restrictions imposed by the heterocyclic framework of AN.
The As-C bonds are slightly shorter in derivatives of 9 than
those in 2a and 2b40 because of the involvement of the
arsenic center in the π framework of anthracenic unit AN.
In addition, the C-As-C angle is slightly smaller in 9a and
9b, and the C-As-P angles are larger than those in 2a and
2b,40 which represent complexes of acyclic arsenium accep-
tors. Although the As-P distance in 1[BPh4]39 is comparable
with the those described above, it is not reasonable to
compare the other structural features as the arsenic center
The cations in [AN-PMe3]9a[GaCl4] and [AN-PMe3]-
9a[OTf] are essentially identical, indicating that the anion
has no influence on the structure of the cation. A representa-
tive view of cation 9b in [AN-PPh3][OTf] is shown in
Figure 1a, and it confirms the interaction of the donor
phosphine center with the arsenic center with an approach
that is perpendicular to the plane of AN and analogous to
those in the phosphorus derivatives 3, as shown in Figure
1b for [Ph2P-PPh3][GaCl4]. Consequently, the arsenic
centers adopt a pyramidal geometry in all compounds, with
(45) Kosolapoff, G. M.; Maier, L. Organic Phosphorus Compounds; Wiley-
Interscience: Toronto, 1972.
9458 Inorganic Chemistry, Vol. 44, No. 25, 2005

Arsinophosphonium Cations
Figure 4. Representative structural views of the cations in (a) [AN-dppb-
AN] 12 [GaCl4]2, (b) gauche-[Ph2P-dppb-PPh2] 7 [GaCl4]2,43 and (c) anti-
[Ph2P-dppb-PPh2] 7 [GaCl4]2. Ellipsoids are drawn to 50% probability.
Hydrogen atoms are not shown.
Figure 3. Representative structural views of the cations in (a) [AN-
dppm-AN] 11a [GaCl4]2, (b) [AN-dmpm-AN] 11b [GaCl4]2, and (c)
[Ph2P-dmpm-PPh2] 5 [GaCl4]2.43 Ellipsoids are drawn to 50% probability.
Hydrogen atoms are not shown.
perhaps resulting from the alignment and intramolecular
stacking of one of the phenyl substituents at P(1) with the
central ring of AN. Nevertheless, it is interesting to note that
intermolecular distances between the centroids of the AN
units are generally shorter than intramolecular distances
between the aryl centroid and that of the AN unit (Table 2).
Figure 3 shows representative views of the dications in
[AN-dppm-AN] 11a [GaCl4]2 and [AN-dmpm-AN] 11b
[GaCl4]2, confirming association of two arsenium centers by
the tethered bisphosphine (dppm or dmpm) ligand in each
case. Both dications adopt an anti-anti conformation with
P-C-P-As torsional angles close to 180°. The anti
conformation is extended to include the carbon centers
attached to arsenic to give an anti-anti-anti conformation
for 11b and an anti-anti-anti-anti conformation for 11a,
with C(41), As(2), P(2), C(1), P(1), As(1), and C(11)
essentially coplanar, as illustrated in Figure 3a. In addition,
the tricyclic arsine units adopt an anti conformation with
in this compound is bound to a nitrogen center and is
encumbered by the intramolecular coordinative cyclic ar-
rangement.
A representative view of monocation 10 in the solid-state
structure of [AN-dppm][GaCl4] is shown in Figure 2a, and
it illustrates the interaction of arsenic with a single phos-
phorus donor and the consequential pendant tricoordinate
phosphine. The structure of this arsenium-bisphosphine
cation is analogous to that of cation 4a in [Me2P-dppm]-
[GaCl4], shown in Figure 2b.43 The As-P and As-C
distances, as well as the angles at arsenic in 10, are within
the narrow range exhibited in 1[BPh4],39 2a [PF6],40 2b
[PF6],40 9a [GaCl4], 9a [OTf], and 9b [OTf]. The conforma-
tion of the P-C-P-Pn backbones in 4a and 10 are notably
different, with the P-C-P-P angle of 61.3(1)° in 4a best
considered gauche, while 10 adopts an anti arrangement
involving a P-C-P-As torsional angle of 176.6(2)°,
Inorganic Chemistry, Vol. 44, No. 25, 2005 9459

Burford et al.
respect to each other. Intramolecular interplane interactions
between the phenyl substituents of the ligand and the plane
of the arsenium cation are evident in 11a, while the methyl
substituents in 11b apparently allow for more flexibility of
the As-P-C-P-As backbone. By comparison with 11b,
bisphosphenium-bisphosphine 5 adopts a gauche-gauche
conformation in the gallate salt, illustrated in Figure 3c, and
a gauche-anti conformation in the triflate salt. We rationalize
the differences between 11b and 5 in terms of the greater
steric flexibility allowed by two phenyl substituents at the
phosphorus acceptor centers relative to that of the tricyclic
unit AN.
The existence of both a monocationic arsenium-bis-
phosphine 10 and a dicationic bisarsenium-bisphosphine
11a, employing the dppm ligand, indicates the potential to
stoichiometrically control the association of arsenium centers
by bifunctional ligands. In contrast, dppm is observed to form
only phosphenium-bisphosphine cations, 4, and the sterically
less inhibited dmpm is observed to form only bisphos-
phenium-bisphosphine cations, 5.43 We speculate that the
slightly longer As-P coordinate bonds in comparison to the
P-P coordinate bonds provides for sufficient relief of the
steric strain within the ligand to enable incorporation of the
second Lewis acid.
the existence of interplane stacking. In comparison, 7 displays
both anti (Figure 4b) and gauche (Figure 4c) conformations.
Conclusions
The facile in situ preparation of a tricyclic arsenium species
provides a versatile synthetic approach to arsinophospho-
nium, and the first arsinophosphoniumphosphine and bisarsi-
nobisphosphonium salts. Spectroscopic and structural data
show that the tricyclic (anthracenic) arsenium cation engages
bifunctional ligands in pendant and tethered complexation.
The new complexes highlight a versatile approach to As-P
bond formation, and the demonstrated control of stoichiom-
etry with bifunctional tethering ligands bodes well for the
development of extended arrays and the potential for
extrapolation to supramolecular or coordination polymeric
systems.
Acknowledgment. We thank the Natural Sciences and
Engineering Research Council of Canada, the Killam Foun-
dation, the Canada Research Chairs Program, the Canada
Foundation for Innovation, the Nova Scotia Research and
Innovation Trust Fund, and the Walter C. Sumner Foundation
for funding, the Atlantic Region Magnetic Resonance Centre
for use of instrumentation, and Dr. M. Lumsden (ARMRC)
for the collection of solid state NMR data.
The structure of cation 12 in [AN-dppb-AN][GaCl4]2
is shown in Figure 4a together with views of the gauche
and anti conformations of cation 7 in [Me2P-dppb-PMe2]-
[GaCl4]2. The arsine units (AN) of 12 adopt a distinct anti
conformation with respect to the benzo plane of the ligand
backbone, and the endo orientation of the AN units implies
Supporting Information Available: Crystallographic informa-
tion files (CIF) for all of the compounds presented above.
This material is available free of charge via the Internet at
http://pubs.acs.org.
IC050989W
9460 Inorganic Chemistry, Vol. 44, No. 25, 2005