Phosphinopnictonium cations: High yield and general preparative procedures for new interpnictogen frameworks exploiting As→P and Sb→P coordinate bonds

Article abstract of DOI:10.1021/ja907613c

Reactions of R₃Pn (Pn = As or Sb; R = Me, Et or Ph) with R′₂PCl or R′PCl₂ (R′ = Me, Et, Ph, Cy, ⁱPr), in the presence of a halide abstracting agent (Me ₃SiOSO₂CF₃, GaCl₃

Full text of DOI:10.1021/ja907613c

Published on Web 11/03/2009
Phosphinopnictonium Cations: High Yield and General
Preparative Procedures for New Interpnictogen Frameworks
Exploiting AsfP and SbfP Coordinate Bonds
Eamonn Conrad,† Neil Burford,*,† Robert McDonald,‡ and Michael J. Ferguson‡
Department of Chemistry, Dalhousie UniVersity, Halifax, NoVa Scotia B3H 4J3, Canada, and
X-ray Crystallography Laboratory, Department of Chemistry, UniVersity of Alberta, Edmonton,
Alberta T6G 2G2, Canada
Received September 9, 2009; E-mail: Neil.Burford@dal.ca
Abstract: Reactions of R3Pn (Pn ) As or Sb; R ) Me, Et or Ph) with R′2PCl or R′PCl2 (R′ ) Me, Et, Ph,
i
Cy, Pr), in the presence of a halide abstracting agent (Me3SiOSO2CF3, GaCl3, or AlCl3), give salts with
cations containing Pn-P bonds. The bond formation is envisaged to proceed by activation of the P-Cl
bond and coordination of the pnictine to the resulting phosphorus cation (R′2P+ or R′P2+, respectively).
Salts of the first phosphinoarsonium cations, [R3As-PR′2]+, and the first 2-phosphino-1,3-diarsonium
dications, [R3AsP(R′)AsR3]2+, have been isolated and comprehensively characterized. In contrast, reactions
involving Ph3Sb give 2,3-diphosphino-1,4-distibonium dications, [R3SbP(R′)P(R′)SbR3]2+, resulting from a
single P-Cl activation (abstraction) at each of two phosphorus centers and reductive P-P coupling effected
by Ph3Sb. The analogous 2,3-diphosphino-1,4-diarsonium dication [R3AsP(R′)P(R′)AsR3]2+ can be accessed
from the 2,3-diphosphino-1,4-distibonium cation by a ligand exchange reaction, which also provides the
phosphorus derivative 2,3-diphosphino-1,4-diphosphonium [R3PP(R′)P(R′)PR3]2+. The versatile synthetic
methodologies toward the new P-As and P-Sb frameworks demonstrate the potential for diversification
and systematic expansion of interpnictogen compounds.
Interpnictogen compounds are promising as materials that
exhibit new properties;1 however, examples of compounds based
on a Pn-Pn′ bonded backbone (Pn or Pn′ ) P, As, Sb or Bi)
are rare. The formation of P-P bonds using homoatomic
coordination chemistry between neutral and cationic phosphorus
centers represents a high yield and versatile new synthetic
method that provides access to series of catena-phosphorus
cations.2-9 Application of this approach to the heavier pnictogen
elements (As, Sb, Bi) offers the potential for diverse and
extensive development of interpnictogen compounds.
(e.g., A ) Me3SiOSO2CF3, AlCl3, GaCl3). The reaction is
envisaged to proceed by the heterolytic cleavage of the P-Cl
bond and coincident or subsequent PfP coordination of the
phosphine R3P (Lewis donor) to the phosphenium R′2P+ center
(Lewis acceptor) to give the salt [R3PPR′2][anion]. The PfP
adduct can also be viewed as a phosphinophosphonium cation,
as illustrated for [R3PPR′2]+ by the molecular frameworks
presented above reaction 1.10
The PfP homoatomic coordination chemistry is fundamen-
tally described by reaction 1 involving the combination of a
phosphine, a chlorophosphine and a halide abstracting agent
† Dalhousie University.
‡ University of Alberta.
(1) Chivers, T.; Manners, I. Inorganic Rings and polymers of the p-Block
Elements: From Fundamentals to Applications; The Royal Society of
Chemistry: Cambridge, UK, 2009.
(2) Schmidpeter, A.; Lochschmidt, S.; Karaghiosoff, K.; Sheldrick, W. S.
Chem.Commun. 1985, 1447–1448.
(3) Schmidpeter, A.; Lochschmidt, S.; Sheldrick, W. S. Angew. Chem.,
Int. Ed. 1985, 24, 226–227.
(4) Burford, N.; Ragogna, P. J.; McDonald, R.; Ferguson, M. J. Am. Chem.
Soc. 2003, 125, 14404–14410.
Reaction 2 describes the potential generic application of eq
1 to form bonds between the heavy pnictogen elements (Pn or
Pn′ ) P, As, Sb or Bi). This has been successfully exploited to
obtain examples of pnictinophosphonium cations containing
formal PfPn coordinate bonds for Pn ) As, Sb or Bi,11,12 as
well as examples of stibinoarsonium and bismuthinoarsonium
(5) Dyker, C. A.; Burford, N. Chem. Asian J. 2008, 3, 28–36.
(6) Weigand, J. J.; Burford, N.; Decken, A. Eur. J. Inorg. Chem. 2008,
4868–4872.
(7) Dyker, C. A.; Riegel, S. D.; Burford, N.; Lumsden, M. D.; Decken,
A. J. Am. Chem. Soc. 2007, 129, 7464–7474.
(8) Dyker, C. A.; Burford, N.; Menard, G.; Lumsden, M. D.; Decken, A.
Inorg. Chem. 2007, 46, 4277–4285.
(9) Carpenter, Y.; Dyker, C. A.; Burford, N.; Lumsden, M. D.; Decken,
A. J. Am. Chem. Soc. 2008, 130, 15732–15741.
(10) Burford, N.; Ragogna, P. J. Dalton Trans. 2002, 4307–4315.
9
17000 J. AM. CHEM. SOC. 2009, 131, 17000–17008
10.1021/ja907613c CCC: $40.75  2009 American Chemical Society

Phosphinopnictonium Cations
A R T I C L E S
and distilled prior to use. All other chemicals were purchased from
Aldrich and used as received.
cations containing examples of AsfSb and AsfBi coordinate
bonds, respectively.13,14 Here we describe the preparation and
characterization of the first examples of salts containing
phosphinoarsonium and phosphinostibonium cations, represent-
ing the first compounds with formal AsfP (Preliminary
Communication)15 and SbfP coordinate bonds, in which the
traditionally less basic pnictogen center is a donor on the more
basic phosphorus center.
Consideration of the number of Pn′-Pn (Pn or Pn′ ) As,
Sb, Bi) bonds in an interpnictogen framework, the variety of
connectivities (isomers) and the accommodation of more than
one molecular charge, introduces potential for vast diversifica-
tion. In this context, activation of both P-Cl bonds of a
dichlorophosphine by a halide abstracting agent in the presence
NMR spectra were obtained at room temperature, unless
otherwise stated, on a Bruker AVANCE 500 1H (500.13 MHz, 11.7
T) and Bruker/Tecmag AC250 1H (250.06 MHz, 5.9 T). Chemical
shifts (δ) are reported in ppm.13C{1H} (125.76 MHz) chemical shifts
are referenced to δTMS ) 0.00 ppm, 31P{1H} (202.46 MHz, 101.26
MHz) chemical shifts are referenced to δH3PO4(85%) ) 0.00 ppm.
NMR spectra were obtained on aliquots of reaction mixture in
appropriate deuterated solvent in a 5 mm tube. The tubes were
capped and sealed with parafilm prior to removal from the inert
atmosphere.
IR spectra were obtained on powdered and ground crystalline
samples dissolved in CH2Cl2 and spotted on CsI plates. Data
collection was on a Bruker Vector FT-IR spectrometer. Peaks are
reported in wavenumbers (cm-1) with ranked intensities in paren-
theses, where a value of one is indicative of the most intense peak
in the spectrum. Melting points were recorded on an Electrothermal
apparatus in sealed capillary tubes under N2. Elemental analyses
of selected samples were performed by Canadian Microanalytical
Services Ltd. Delta, British Columbia, Canada.
of a phosphine according to reaction 3 gives the 2-phosphino-
2,3
1,3-diphosphonium framework [R3PP(R′)PR3]2+
.
We have
now evolved this methodology to prepare and characterize salts
containing the first examples of phosphinodiarsonium dications
according to reaction 4. In contrast, halide abstraction is
accompanied by a reduction of the dichlorophosphine upon
reaction with a stibine to give the first examples of diphosphi-
nodistibonium dications according to reaction 5. Moreover,
diphosphinodistibonium represents a precursor to diphosphino-
diarsonium dications according to reaction 6, involving a ligand
exchange process. The versatility and generality of these
reactions bodes well for the extensive and diverse development
of interpnictogen frameworks that provide opportunities for the
discovery of new inorganic materials.
Preparation of [Ph2PAsMe3][OSO2CF3]. Me3As (10.7 µL,
0.100 mmol) in CH2Cl2 (1 mL) was added to a mixture of
Me3SiOSO2CF3 (75.4 µL, 0.300 mmol) and Ph2PCl (13.5 µL, 0.100
mmol) in CH2Cl2 (1 mL) and stirred for 10 min. The mixture
exhibited one signal in the 31P{1H} NMR spectra. Addition of ether
(3 mL) effected precipitation of a white solid that was recrystallized
from CH2Cl2 by diffusion of ether vapor into the solution at room
temperature, giving large white crystals that were isolated by
decantation and washed with ether (3 × 3 mL). Yield: 40.9 mg,
90%; mp 88-90 °C; elemental analysis calcd. (found): C 42.30
(40.80), H 4.22 (4.22); FTIR (cm-1, ranked intensities): 3164 (17),
2942 (16), 2627 (19), 2409 (20), 2292 (8), 2253 (4), 1438 (12),
1375 (15), 1262 (3), 1225 (14), 1157 (6), 1032 (2), 918 (10), 800
1
(18), 749 (7), 696 (11), 640 (1), 573 (13), 518 (9), 378 (5); H
NMR (CD3CN, 500 MHz, 293 K): 1.79 (s, 9H), 7.61-7.71 (m,
10H); 13C{1H} NMR (CD3CN, 125.8 MHz, 293 K): 14.2 (s),
1
119.1(d, JPC ) 25 Hz), 129.1 (s), 131.1 (s), 133.2 (s); 31P{1H}
NMR (CD3CN, 101.3 MHz, 293 K): -2.2 (s). The 31P{1H} NMR
spectra observed for reaction mixtures are independent of the order
that the reactants are combined.
Preparation of [Me2PAsMe3][OSO2CF3]. Me3As (10.7 µL,
0.100 mmol) in CH2Cl2 (1 mL) was added to a mixture of
Me3SiOSO2CF3 (75.4 µL, 0.300 mmol) and Me2PCl (9 µL, ∼0.100
mmol) in CH2Cl2 (1 mL) and stirred for 10 min. The mixture
exhibited one signal in the 31P{1H} NMR spectra. Addition of ether
(3 mL) effected precipitation of a white solid that was redissolved
in CH2Cl2 and diffusion of ether vapor into the solution gave a
white powder that was isolated by decantation and washed with
ether (3 × 3 mL). Yield: 8.25 mg, 25%; mp. 100-102; FTIR (cm-1
,
ranked intensities): 3017 (9), 2930 (10), 2875 (15), 1423 (8), 1259
(1), 1225 (5), 1155 (3), 1031 (2), 934 (7), 898 (6), 855 (13), 756
(12), 736 (11), 709 (14), 638 (4). 31P{1H}NMR (CD3CN, 101.3
1
MHz, 293 K): -15.8 (s); H NMR (CDCl3, 500 MHz, 293 K):
2
1.21 (s, 9H), 1.82 (d, 6H, JPH ) 25 Hz); 13C{1H} NMR (CDCl3,
125.8 MHz, 293 K): 15.3 (s), 65.8 (s).
Preparation of [Ph2PAsPh3][AlCl4]. Ph3As (30.4 mg, 0.100
mmol) in CH2Cl2 (2 mL) was added to a mixture of AlCl3 (26.7
mg, 0.200 mmol) and Ph2PCl (13.5 µL, 0.100 mmol) in benzene
Synthetic Procedures and Characterization Data
General. Reactions were carried out in an MBraun Glovebox
under atmosphere of dry N2. Solvents were dried on an MBraun
solvent purification system and stored over 4 Å molecular sieves.
MeCN was purchased from Aldrich and degassed with argon and
stored over 4 Å molecular sieves. Et2O was dried over sodium/
benzophenone and distilled prior to use. Deuterated solvents were
purchased from Aldrich and were used as received. Me3As, Et3As,
Me2PCl, and MePCl2 were purchased from Strem Chemicals and
used as received. GaCl3 was purchased from Strem Chemicals
and sublimed before use. AlCl3 was purchased from Aldrich and
sublimed before use. Me3SiOSO2CF3 was purchased from Aldrich
(11) Burford, N.; Ragogna, P. J.; Sharp, K.; McDonald, R.; Ferguson, M. J.
Inorg. Chem. 2005, 44, 9453–9460.
(12) Coote, M. L.; Krenske, E. H.; Porter, K. A.; Weir, M. L.; Willis, A. C.;
Zhou, X.; Wild, S. B. Organometallics 2008, 27, 5099–5107.
(13) Conrad, E.; Burford, N.; McDonald, R.; Ferguson, M. J. J. Am. Chem.
Soc. 2009, 131, 5066–5067.
(14) Genge, A. R. J.; Hill, N. J.; Levason, W.; Reid, G. Dalton Trans.
2001, 1007–1012.
(15) Conrad, E.; Burford, N.; McDonald, R.; Ferguson, M. J. Inorg. Chem.
2008, 47, 2952–2954.
9
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A R T I C L E S
Conrad et al.
(1 mL) and stirred for 10 min. The mixture exhibited a new signal
18H); 13C{1H} NMR (DMSO-d6, 125.8 MHz, 293 K): 11.5 (s),
12.1 (s), 13.4 (d, 1JPC ) 25 Hz). The 31P{1H} NMR spectra observed
for reaction mixtures are independent of the order that the reactants
are combined.
in the 31P{1H} NMR spectra and low intensity signals at 58.1 (d,
1
1JPP ) 182 Hz) and -17.8 (d, JPP ) 182 Hz corresponding to
[Ph2(Cl)PPPh2][AlCl4].16 Addition of hexanes (3 mL) effected
precipitation of a white solid that was redissolved in CH2Cl2 and
precipitated by diffusion of hexane vapor into the solution. The
solution was decanted and the solid was washed with ether (3 × 2
mL). Yield: 22.1 mg, 35%; mp 52-55 °C; FTIR (cm-1, ranked
intensities): 3155 (25), 3058 (7), 2993 (18), 2957 (15), 2927 (17),
2870 (20), 2670 (30), 2576 (28), 2326 (29), 1971 (23), 1898 (24),
1816 (22), 1777 (27), 1670 (26), 1582 (9), 1481 (6), 1438 (1), 1392
(19), 1337 (11), 1312 (12), 1265 (8), 1187 (10), 1163 (13), 1101
(4), 1024 (14), 997 (5), 919 (21), 740 (2), 688 (3), 619 (16); 31P{1H}
Preparation of [Me3AsP(iPr)AsMe3][OSO2CF3]2. Me3As (21.4
µL, 0.200 mmol) in CH2Cl2 (1 mL) was added to a mixture of
Me3SiOSO2CF3 (75.4 µL, 0.300 mmol) and iPrPCl2 (12.3 µL, 0.100
mmol) in CH2Cl2 (1 mL) and stirred for 10 min, and the mixture
exhibited one signal in the 31P{1H} NMR spectra. Addition of ether
(3 mL) effected precipitation of a white solid that was recrystallized
from CDCl3 by diffusion of ether vapor in the solution, giving pale-
white powder. Yield: 51.5 mg, 85%; mp 91-93; FTIR (cm-1
,
ranked intensities): 3054 (9), 2986 (10), 2685 (15), 2305 (14), 1605
(18), 1421 (11), 1264 (1), 1232 (5), 1160 (4), 1040 (6), 896 (13),
740 (2), 705 (3), 643 (7), 579 (12), 514 (8), 349 (17), 286 (16);
1
NMR (CD2Cl2, 101.3 MHz, 293 K): 17.1 (s). H NMR (CD2Cl2,
500 MHz, 293 K): 7.29-7.49 (m, 25H), 13C{1H} NMR (CD2Cl2,
125.8 MHz, 293 K): 129.1 (s), 129.2 (s), 130.5 (d, 1JPC ) 14 Hz),
1
31P{1H} NMR (CH2Cl2, 101.3 MHz, 293 K): 2.7 (s); H NMR
1
(CDCl3, 500 MHz, 293 K): 1.46 (dd, 6H, 3JHH ) 10 Hz, 3JPH ) 20
132.5 (d, JPC ) 15 Hz), 134.2 (s, 2C), 136.3 (s), 140.0 (s).
3
2
Preparation of [Ph3AsP(Me)AsPh3][AlCl4]2. Ph3As (60.4 mg,
0.200 mmol) in CH2Cl2 (1 mL) was added to a mixture of AlCl3
(39.8 mg, 0.300 mmol) and MePCl2 (9.0 µL, 0.100 mmol) in
CH2Cl2 (1 mL) and stirred for 10 min. The mixture exhibited one
signal in the 31P{1H} NMR spectra. Addition of ether (3 mL)
effected precipitation of a white solid that was isolated and
recrystallized from CH2Cl2 by diffusion of ether vapor into the
solution, giving pale-yellow crystals. Yield: 78.6 mg, 95%; mp:
35-37 °C; FTIR (cm-1, CsI, ranked intensities): 3057 (16), 2988
(17), 2646 (20), 1481 (9), 1437 (5), 1393 (10), 1309 (18), 1190
(12), 1150 (13), 1074 (11), 997 (4), 876 (7), 834 (15), 766 (8), 738
(2), 694 (6), 533 (1), 493 (3), 409 (14), 317 (19; 31P{1H} NMR
(CH2Cl2, 101.3 MHz, 293 K): -18.3 (s);1H NMR (CDCl3, 500
Hz), 2.35 (s, 18H), 3.18 (dsept, 1H, JHH ) 10 Hz, JPH ) 5 Hz);
13C{1H} NMR (CDCl3, 125.8 MHz, 293 K): 12.8 (s), 22.3 (s), 25.3
(d, 1JPC ) 25 Hz). The 31P{1H} NMR spectra observed for reaction
mixtures are independent of the order that the reactants are
combined.
Preparation of [Me3AsP(Cy)AsMe3][OSO2CF3]2. Me3As (21.4
µL, 0.200 mmol) in CH2Cl2 (1 mL) was added to a mixture of
Me3SiOSO2CF3 (75.4 µL, 0.300 mmol) and CyPCl2 (0.100 mmol,
12.3 µL) in CH2Cl2 (1 mL) and stirred for 10 min, and the mixture
exhibited one signal in the 31P{1H} NMR spectra. Addition of ether
(3 mL) effected precipitation of a white solid that was redissolved
in CDCl3 and precipitated by diffusion of ether vapor into the
solution, giving pale-white powder. Yield: 47.1 mg, 73%; mp
85-87 °C; FTIR (cm-1, ranked intensities): 3029 (14), 2933 (7),
2870 (15), 1633 (13), 1454 (3), 1414 (6), 1360 (10), 1259 (2), 1151
(9), 1027 (8), 907 (16), 795 (17), 702 (4), 666 (1), 623 (11), 513
2
MHz, 293 K): 2.23 (d, 3H, JPH ) 25 Hz), 7.30-7.40 (m, 30H);
1
13C{1H} NMR (CDCl3, 125.8 MHz, 293 K): 30.5 (d, JPC ) 25
Hz), 118.2 (s), 129.2 (s), 133.3 (s), 139.8 (s). The 31P{1H} NMR
spectra observed for reaction mixtures are independent of the order
that the reactants are combined.
1
(12); 31P{1H} NMR (CH2Cl2, 101.3 MHz, 293 K): -2.0 (s); H
NMR (CDCl3, 500 MHz 293 K): 1.33-1.37 (m, 2H), 1.96-2.00
(m, 4H), 2.12 (t, 3JHH ) 15 Hz, 4H), 2.28 (s, 18H), 2.45-2.49 (m,
1H); 13C{1H} NMR (CDCl3, 125.8 MHz, 293 K): 10.5 (s), 24.1
Preparation of [Me3AsP(Me)AsMe3][OSO2CF3]2. Me3As (21.4
µL, 0.200 mmol) in CH2Cl2 (1 mL) was added to a mixture of
Me3SiOSO2CF3 (75.4 µL, 0.300 mmol) and MePCl2 (9 µL, 0.100
mmol) in CH2Cl2 (1 mL) and stirred for 10 min. The mixture
exhibited one signal in the 31P{1H} NMR spectra. Addition of ether
(3 mL) effected precipitation of a white solid that was isolated and
recrystallized from CD3CN by diffusion of ether vapor into the
solution, giving pale-white crystals. Yield: 40.4 mg, 93%; mp
153-155; elemental analysis calcd. (found): C 18.60 (18.31), H
3.12 (3.63); FTIR (cm-1, ranked intensities): 3369 (16), 3280 (18),
3092 (15), 2966 (19), 2261 (1), 2115 (13), 1274 (3), 1225 (9), 1192
(10), 1159 (7), 1101 (8), 1032 (2), 927 (14), 832 (4), 736 (20), 689
(13), 640 (6), 573 (12), 518 (11), 347 (5); 31P{1H} NMR (CD3CN,
101.3 MHz, 293 K): -15.1 (s); 1H NMR (CD3CN, 500 MHz, 293
1
(s), 26.1 (s), 32.2 (s), 34.2 (d, JPC ) 25 Hz). The 31P{1H} NMR
spectra observed for reaction mixtures are independent of the order
that the reactants are combined.
Preparation of [Ph3SbP(Ph)P(Ph)SbPh3][AlCl4]2. AlCl3 (39.8
mg, 0.300 mmol) was added to a mixture of PhPCl2 (27.4 µL, 0.200
mmol) and Ph3Sb (106.0 mg, 0.300 mmol) in CH2Cl2 (2 mL) and
stirred for 2.5 h, and the mixture exhibited one signal in the 31P{1H}
NMR spectra. The solution became pale yellow and crystals were
obtained by layering hexane on the solution and storing at -25
°C. The solid was washed with ether (3 × 2 mL). The solid was
recrystallized by diffusion of ether into a solution in CH2Cl2, giving
pale-yellow crystals. Yield: 52%, 63.0 mg; mp: 127-129 °C.;
elemental analysis: calcd (found): C 45.69 (43.37), H 3.19 (3.16);
light sensitive; 31P{1H} NMR (101.3 MHz, 293 K, CD2Cl2): -29.2
2
K): 1.49 (d, 3H, JPH ) 25 Hz), 2.55 (s, 18H); 13C{1H} NMR
(DMSO-d6, 125.8 MHz, 293 K): 15.2 (t, 1JPC ) 62.9 Hz), 21.5 (s).
The 31P{1H} NMR spectra observed for reaction mixtures are
independent of the order that the reactants are combined.
1
(s); H NMR (500 MHz, 293 K, CD2Cl2): 7.35-7.39 (m, 30 H),
7.45-7.49 (m, 10 H); 13C{1H} NMR (125.8 MHz, 293 K, CD2Cl2):
131.2 (s), 131.6 (s), 132.1 (s), 132.6 (s), 134.9 (s), 135.2 (s), 135.8
(s), 136.3 (s); FTIR (cm-1, CsI, ranked intensities): 3054 (4), 2987
(9), 2685 (15), 2305 (12), 1479 (13), 1437 (6), 1422 (7), 1265 (2),
1066 (14), 966 (11), 896 (8), 740 (1), 705 (3), 493 (5), 286 (10).
Reaction mixtures prepared by addition of Ph3Sb to a mixture of
AlCl3 and PhPCl2 showed no evidence for the formation of
[Ph3SbP(Ph)P(Ph)SbPh3][AlCl4]2.
Preparation of [Me3AsP(Et)AsMe3][OSO2CF3]2. Me3As (21.4
µL, 0.200 mmol) in CH2Cl2 (1 mL) was added to a mixture of
Me3SiOSO2CF3 (75.4 µL, 0.300 mmol) and EtPCl2 (12.3 µL, 0.100
mmol) in CH2Cl2 (1 mL) and stirred for 10 min, and the mixture
exhibited one signal in the 31P{1H} NMR spectra. Addition of ether
(3 mL) effected precipitation of a white solid that was recrystallized
from CH2Cl2 by diffusion of ether vapor into the solution, giving
blocklike white crystals. Yield: 55.1 mg, 93%; mp 122-24; FTIR
(cm-1, ranked intensities): 3021 (12), 2934 (14), 2305 (17), 1604
(18), 1463 (15), 1422 (11), 1261 (1), 1232 (3), 1160 (2), 1034 (4),
922 (6), 857 (13), 739 (8), 703 (10), 639 (5), 574 (9), 516 (7), 349
Preparation of [Ph3SbP(Me)P(Me)SbPh3][AlCl4]2. AlCl3 (39.8
mg, 0.300 mmol) was added to a mixture of MePCl2 (18.0 µL,
0.200 mmol) and Ph3Sb (106.0 mg, 0.300 mmol) in CH2Cl2 (2 mL)
and stirred for 2 h in the dark, and the mixture exhibited one signal
in the 31P{1H} NMR spectra. A pale yellow powder precipitated
on standing that was isolated and recrystallized by diffusion of ether
into a solution in CH2Cl2 to give pale-yellow crystals. Yield: 48%,
54.5 mg; mp: Decomposed above 205 °C; light sensitive; FTIR
(cm-1, CsI, ranked intensities): 3055 (13), 2982 (22), 2876 (21),
1
(16); 31P{1H} NMR (CH2Cl2, 101.3 MHz, 293 K): -17.2 (s); H
2
NMR (DMSO-d6, 500 MHz, 293 K): 1.12 (dt, 3H, JPH ) 69 Hz,
3JHH ) 10 Hz), 1.75 (dq, 2H, 2JPH ) 69 Hz, 3JHH) 10 Hz), 2.55 (s,
(16) Burford, N.; Cameron, T. S.; LeBlanc, D. J.; Losier, P.; Sereda, S.;
Wu, G. Organometallics 1997, 16, 4712–4717.
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A R T I C L E S
1699 (20), 1652 (16), 1575 (18), 1558 (19), 1478 (7), 1436 (3),
1334 (12), 1096 (17), 1065 (9), 1018 (14), 730 (1), 687 (4), 492
(2), 444 (5), 384 (10), 326 (15), 280 (8), 247 (11); 31P{1H} NMR
(101.3 MHz, 293 K, CD2Cl2): -78.8 (s); 1H NMR (500 MHz, 293
K, CD2Cl2): 7.51-7.92 (m, 30 H), 2.91 (s, 6H); 13C{1H} NMR
(125.8 MHz, 293 K, CD2Cl2): 29.7 (s), 132.4 (s), 132.5 (s), 135.3
(s), 136.2 (s); Reaction mixtures prepared by addition of Ph3Sb to
a mixture of AlCl3 and MePCl2 showed no evidence for the
formation of [Ph3SbP(Me)P(Me)SbPh3][AlCl4]2.
(16), 895 (13), 738 (2), 703 (7), 685 (10), 609 (19), 490 (5), 455
(12), 287 (9), 254 (8); 31P{1H} NMR (101.3 MHz, 293 K, CD3CN):
-27.2 (s); 1H NMR (500 MHz, 293 K, CD3CN): 1.35 (dd, 3JHH
)
4
18 Hz, JHP ) 7 Hz), 1.49 (s, signals at 1.35 and 1.49 overlap,
total integration 30H); 2.77 (sept, not well resolved, connectivity
confirmed through 2D COSY, 2H). 13C NMR{1H} (125.8 MHz,
293 K, CD3CN): 10.4 (s), 18.6 (s), 31.5 (s).
NMR Identification of Compounds Prepared in Situ.
[Ph2PAsMe3][GaCl4]. Me3As (10.7 µL, 0.100 mmol) in CH2Cl2
(1 mL) was added to a solution of GaCl3 (52.8 mg, 0.300 mmol)
and Ph2PCl (13.5 µL, 0.100 mmol) in CH2Cl2 (1 mL) and stirred
for 10 min, and the mixture exhibited one signal in the 31P{1H}
NMR spectra: 1.0 (s);1H NMR (CD2Cl2, 500 MHz, 293 K): 2.02
(s, 9H), 7.37-7.70 (m, 10H); 13C{1H} NMR (CD2Cl2, 125.8 MHz,
293 K): 31.2 (s), 126.1 (s), 132.5 (s), 133.6 (s), 135.1 (s).
Preparation of [Ph3AsP(Ph)P(Ph)AsPh3][AlCl4]2. Ph3As (151.5
mg, 0.500 mmol) in CH2Cl2 (4 mL) was added dropwise to a
solution of [Ph3SbP(Ph)P(Ph)SbPh3][AlCl4]2 (251 mg, 0.200 mmol)
in CH2Cl2 (2 mL) and stirred for 10 min and the mixture exhibited
one signal in the 31P{1H} NMR spectra. The reaction mixture was
concentrated and diffusion of ether vapor into the solution at -25
°C gave pale-white crystals that were washed with ether (3 × 3
mL). Yield: 68%, 158 mg; mp: 153-155 °C; FTIR (cm-1, CsI,
ranked intensities): 3055 (9), 1965 (22), 1887 (21), 1815 (20), 1577
(10), 1480 (6), 1436 (3), 1334 (11), 1307 (13), 1265 (19), 1185
(12), 1162 (14), 1067 (7), 1021 (8), 997 (5), 802 (18), 733 (2), 688
(4), 564 (17), 491 (1), 329 (16), 288 (15); 31P{1H} NMR (101.3
[Ph2PAsEt3][OSO2CF3]. Et3As (14.0 µL, 0.100 mmol) in
benzene (2 mL) was added to a solution of Me3SiOSO2CF3 (52.1
µL, 0.200 mmol) and Ph2PCl (13.5 µL, 0.100 mmol) in benzene
(1 mL) and stirred for 10 min, and the mixture exhibited one signal
in the 31P{1H} NMR spectra: -15.1 (s); 1H NMR (C6D6, 500 MHz,
3
3
293 K): 1.73 (t, 9H, JHH ) 30 Hz), 1.26 (q, 6H, JHH ) 10 Hz),
1
3
MHz, 293 K, CD2Cl2): -11.9 (s); H NMR (500 MHz, 293 K,
6.96-7.00 (m, 2H), 7.11-7.17 (m, 4H), 7.48 (t, 4H, JHH ) 10
Hz); 13C{1H} NMR (C6D6, 125.8 MHz, 293 K): 10.6 (s), 16.4 (s),
CD2Cl2): 7.12 (d, JHH ) 7 Hz, 8H), 7.34-7.55 (m, 25 H), 7.56 (t,
JHH ) 6 Hz, 5H), 7.68-7.88 (m, 32H); 13C{1H} NMR (125.8 MHz,
293 K, CDCl3): 131.7 (s), 131.9 (s), 132.1 (s), 133.1 (s), 134.9 (s),
135.5 (s), 135.6 (s), 135.8 (s).
2
1
128.6 (s), 130.1 (s), 131.5 (d, JPC ) 25 Hz), 139.0 (d, JPC ) 63
Hz).
[Cy2PAsMe3][OSO2CF3]: Me3As (10.7 µL, 0.100 mmol) in
benzene (1 mL) was added to a solution of TMSOTf (25 µL, 0.300
mmol) and Cy2PCl (22,1.5 µL, 0.100 mmol) in benzene (1 mL)
and stirred for one hour, resulting in a clear colorless solution. The
mixture exhibited two signals in the 31P{1H} NMR spectra: 24.6
(s) ([Cy2PAsMe3][OSO2CF3], 70%), and 131.4 (s) Cy2PCl (30%).
[iPr2PAsMe3][OSO2CF3]. Me3As (10.7 µL, 0.100 mmol) in
CH2Cl2 (1 mL) was added to a solution of TMSOTf (25 µL, 0.300
Preparation of [Me3AsP(Ph)P(Ph)AsMe3][AlCl4]2. Me3As
(53.5 µL, 0.500 mmol) in CH2Cl2 (3 mL) was added dropwise to
a solution of [Ph3SbP(Ph)P(Ph)SbPh3][AlCl4]2 (251 mg, 0.200
mmol) in CH2Cl2 (3 mL) and the mixture exhibited one signal in
the 31P{1H} NMR spectra. The reaction mixture was concentrated
and pale-white crystals were formed by diffusion of ether vapor
into a solution in CH2Cl2 at -25 °C. Crystals were washed with
ether (3 × 3 mL). Yield: 82%, 130 mg; mp: 182-184 °C; elemental
i
mmol) and Pr2PCl (15.9 µL, 0.100 mmol) in CH2Cl2 (1 mL) and
analysis calcd (found): C 27.23 (27.64), H 3.56 (3.54); FTIR (cm-1
,
stirred for one hour, resulting in a clear colorless solution. The
mixture exhibited two signals in the 31P{1H} NMR spectra: 28.1
CsI, ranked intensities): 3943 (20), 3055 (3), 2986 (4), 2305 (12),
1650 (16), 1575 (17), 1478 (8), 1436 (6), 1331 (15), 1265 (2), 1184
(18), 1065 (19), 997 (19), 912 (3), 895 (11), 739 (1), 704 (5), 494
(7), 456 (9), 288 (10); 31P{1H} NMR (101.3 MHz, 293 K, CD3CN):
i
(s) ([iPr2PAsMe3][OSO2CF3], 50%), and 137.8 (s) Pr2PCl (50%).
[Et2PAsMe3][OSO2CF3]. Me3As (10.7 µL, 0.100 mmol) in
CH2Cl2 (1 mL) was added to a solution of TMSOTf (25 µL, 0.300
mmol) and Et2PCl (µL, 0.100 mmol) in CH2Cl2 (1 mL) and stirred
for one hour, resulting in a clear colorless solution. The mixture
exhibited signals in the 31P{1H} NMR spectra that are assigned to
three compounds: -5.1 (s) ([Et2PAsMe3][OSO2CF3], 30%), [Et2PCl-
PEt2][OSO2CF3] (40%), and 119.0 (s) Et2PCl (20%), [Et2PAsMe3]-
[OSO2CF3] -5.1 (broad).
[Ph3AsP(Ph)AsPh3][AlCl4]2. Ph3As (60.4 mg, 0.200 mmol) in
CH2Cl2 (1 mL) was added to a solution of AlCl3 (39.8 mg, 0.300
mmol) and PhPCl2 (13.7 µL, 0.100 mmol) in CH2Cl2 (1 mL) and
stirred for 10 min, and the mixture exhibited one signal in the
31P{1H} NMR spectra: -4.1 (s); 1H NMR (CDCl3, 500 MHz, 293
K): 7.25-7.99 (m, 35H).13C{1H} NMR (CDCl3, 125.8 MHz, 293
K): 118.2 (s), 129.7 (s), 130.1 (s), 130.9 (s), 131.1 (s), 134.2 (s),
134.5 (s), 140.6 (s).
1
-31.6 (s); H NMR (500 MHz, 293 K, CD3CN): 1.33 (s, 18H),
7.60-7.68 (m, 10H); 13C{1H} NMR (125.8 MHz, 293 K, CD3CN):
10.0 (s), 129.7 (s), 132.0 (s), 134.1 (s), 140.1 (s).
Preparation of [Et3AsP(Ph)P(Ph)AsEt3][AlCl4]2. Et3As (70.0
µL, 0.500 mmol) in CH2Cl2 (3 mL) was added dropwise to a
solution of [Ph3SbP(Ph)P(Ph)SbPh3][AlCl4]2 (251 mg, 0.200 mmol)
in CH2Cl2 (3 mL) and stirred for 10 min, giving a white precipitate.
The white solid was dissolved in CD3CN and exhibited one signal
in the 31P{1H} NMR spectra. The powder was washed with CH2Cl2
(3 × 3 mL) and recrystallized by diffusion of ether vapor into a
CH2Cl2 solution giving pale yellow crystals. Yield: 67%, 114 mg;
mp: 172-174 °C; FTIR (cm-1, CsI, ranked intensities): 3055 (19),
2969 (12), 2938 (13), 2878 (22), 1964 (24), 1891 (25), 1818 (26),
1576 (23), 1479 (6), 1456 (8), 1437 (3), 1408 (15), 1388 (14), 1335
(18), 1238 (17), 1164 (16), 1067 (9), 1931 (10), 996 (5), 810 (21),
734 (2), 688 (4), 491 (1), 445 (7), 287 (11), 256 (20); 31P{1H}
NMR (101.3 MHz, 293 K, CD3CN): -36.1 (s); 1H NMR (500 MHz,
[Ph3AsP(Et)AsPh3][AlCl4]2. Ph3As (60.4 mg, 0.200 mmol) in
CH2Cl2 (1 mL) was added to a solution of AlCl3 (39.8 mg, 0.300
mmol) and EtPCl2 (10.1 µL, 0.100 mmol) in CH2Cl2 (1 mL) and
stirred for 10 min, and the mixture exhibited one signal in the
31P{1H} NMR spectra: -7.7 (s); 1H NMR (CDCl3, 500 MHz, 293
3
3
293 K, CD3CN): 1.44 (t, JHH ) 8 Hz, 18 H), 2.99 (q, JHH ) 8
Hz, 12H), 7.75 (bs, 6 H), 8.10 (bs, 4H); 13C{1H} NMR (125.8 MHz,
293 K, CD3CN): 17.2 (s), 26.5 (s), 128.8 (s), 129.0 (s), 131.2 (s),
136.5 (s).
3
3
K): 1.59 (t, 3H, JHH ) 10 Hz), 4.55, (q, 2H, JHH ) 10 Hz),
7.41-7.62 (m, 20H); 13C{1H} NMR (CDCl3, 125.8 MHz, 293 K):
12.3 (s),71.8(s), 129.2(s), 129.8(s), 132.1(s), 133.8(s).
Preparation of [Me3AsP(iPr)P(iPr)AsMe3][AlCl4]2. Me3As
(53.5 µL, 0.500 mmol) in CH2Cl2 (3 mL) was added dropwise to
a solution of [Ph3SbP(iPr)P(iPr)SbPh3][AlCl4]2 (0.200 mmol) in
CH2Cl2 (3 mL) and stirred for 10 min, giving a white precipitate.
The white solid was dissolved in CD3CN and exhibited one signal
in the 31P{1H} NMR spectra. The powder was washed with CH2Cl2
[Ph3AsP(iPr)AsPh3][AlCl4]2. Ph3As (60.4 mg, 0.200 mmol) in
CH2Cl2 (1 mL) was added to a solution of AlCl3 (39.8 mg, 0.300
i
mmol) and PrPCl2 (12.3 µL, 0.100 mmol) in CH2Cl2 (1 mL) and
stirred for 10 min, and the mixture exhibited one signal in the
31P{1H} NMR spectra: 7.7 (s); H NMR (CDCl3, 500 MHz, 293
1
(3 × 3 mL). Yield: 71%, 103 mg; mp: 129-130 °C; FTIR (cm-1
,
K): 1.26 (d, 6H, JHH ) 20 Hz), 2.70 (sept, 1H, JHH ) 21 Hz)
3
3
CsI, ranked intensities): 3055 (1), 2987 (3), 2305 (18), 1644 (14),
1477 (11), 1434 (6), 1265 (4), 1154 (20), 1065 (17), 996 (15), 918
7.5-8.0 (m, 30H); 13C{1H} NMR (CDCl3, 125.8 MHz, 293 K):
2
1
23.9 (d, JPC ) 15 Hz), 33.0 (d, JPC ) 49 Hz).
9
J. AM. CHEM. SOC. VOL. 131, NO. 46, 2009 17003

A R T I C L E S
Conrad et al.
Table 1. Crystal Data for [Me3AsPPh2][OSO2CF3], [Me3AsP(Me)AsMe3][OSO2CF3]2, [Ph3AsP(Me)AsPh3][AlCl4]2, and Derivatives of
[R′3PnP(R)P(R)PnR′3][AlCl4]2 (Pn ) As or Sb)
[Me3AsP(Me)
AsMe3]
[OSO2CF3]2
[Ph3SbP(iPr)P
(iPr)SbPh3]
[AlCl4]2
[Me3AsPPh2]
[OSO2CF3]
[Ph3AsP(Me)
AsPh3][AlCl4]2
[Ph3SbP(Ph)P(Ph)
SbPh3][AlCl4]2
[Ph3AsP(Ph)P(Ph)
AsPh3][AlCl4]2
[Me3AsP(Ph)P(Ph)
AsMe3][AlCl4]2
empirical formula C16H19AsF3O3PS C9H21As2F6O6PS2
C37H33Al2As2Cl8P C48H40Al2Cl8P2Sb2 C42H44Al2Cl8P2Sb2•CH2Cl2 C48H40Al2As2Cl8P2 C18H28Al2As2Cl8P2
formula weight
crystal system
space group
454.26
monoclinic
P21/c (No. 14)
584.19
monoclinic
P21/n
(an alternate setting
of P21/c [No. 14])
996.00
monoclinic
P21/c (No. 14)
1259.80
monoclinic
P21/c (No. 14)
1276.70
triclinic
P (No. 2)
1166.14
triclinic
P (No. 2)
793.74
monoclinic
P21/c (No. 14)
a (Å)
b (Å)
c (Å)
11.7585 (8)
12.8289 (9)
12.9423 (9)
90
96.4800 (10)
90
13.4659 (12)
11.5349 (11)
14.0530 (13)
90
109.1230 (10)
90
20.132 (3)
14.3110 (18)
15.4865 (19)
90
101.1671 (18)
90
11.5699 (5)
10.8660 (5)
21.0827 (9)
90
101.3290 (10)
90
10.142 (2)
11.858 (3)
22.810 (5)
81.329 (3)
79.316 (3)
85.433 (3)
1276.70
1.593
11.327 (3)
11.345 (3)
20.433 (6)
90.271 (4)
98.929 (4)
90.595 (4)
2593.7 (13)
1.493
28.143 (4)
15.696 (2)
11.3857 (15)
90
97.8153 (17)
90
R (deg)
ꢀ (deg)
γ (deg)
V (Å3)
1939.9 (2)
1.555
2062.4 (3)
1.881
4377.3 (9)
1.511
2598.8 (2)
1.610
4982.9 (12)
1.587
Dc (g cm-3
)
radiation, λ (Å)
temp (K)
GoF
R1
wR2
0.71073
193
0.71073
193
0.71073
193
0.71073
173
0.71073
173
0.71073
0.71073
173
173
1.066
a
a
a
a
a
a
a
1.044
0.0335
1.043
0.0283
1.049
0.0376
1.044
0.0232
1.208
0.0861
1.047
0.0425
b
b
b
b
b
b
b
0.0813
0.2448
c
c
c
c
c
c
c
0.0889
0.0748
0.0978
0.0620
0.2094
0.1104
a
2
2
S ) [Σw(Fo s Fc2)2/(n s p)]1/2 (n ) number of data; p ) number of parameters varied; w ) [σ2(Fo ) + (0.0496P)2 + 0.7515P]-1 where P )
[Max(Fo , 0) + 2Fc2]/3). b Σ|Fo| s |Fc|/Σ|Fo|. wR2 ) [Σw(Fo s Fc2)2/Σw(Fo )]1/2
.
c
2
2
4
Table 2. Coordinate Bonds between the Heavy Pnictogen Elementsa
ref
ref
ref
ref
PfP
4, 5
11, 12
12
AsfP
SbfP
BifP
PfAs
PfSb
PfBi
AsfAs
AsfSb
AsfBi
19
13
13
SbfAs
SbfSb
SbfBi
BifAs
BifSb
BifBi
20
12
a Bold font highlights bonds for which examples of representative compounds have been isolated and characterized.
[Ph3AsP(Cy)AsPh3][AlCl4]2. Ph3As (60.4 mg, 0.200 mmol) in
CH2Cl2 (1 mL) was added to a solution of AlCl3 (39.8 mg, 0.300
mmol) and CyPCl2 (12.3 µL, 0.100 mmol) in CH2Cl2 (1 mL) and
stirred for 10 min, and the reaction mixture exhibited one signal in
the 31P{1H} NMR spectra: 3.8 (s).
APEX II CCD diffractometer. All data collections employed
graphite-monochromated Mo KR (0.71073 Å) radiation. Crystals
were selected under oil, mounted on glass fibers, and placed in a
cold stream of N2. Structures were solved by direct methods17
([Ph3SbP(Ph)P(Ph)SbPh3][AlCl4]2) or Patterson location of heavy
atoms18 (all others) and refined using full matrix least-squares on
F2.17 Refinement details are summarized in Table 1.
[Me3AsP(Ph)AsMe3][OSO2CF3]2. Me3As (21.4 µL, 0.200 mmol)
in CH2Cl2 (1 mL) was added to a solution of Me3SiOSO2CF3 (75.4
µL, 0.300 mmol) and PhPCl2 (13.7 µL, 0.100 mmol) in CH2Cl2 (1
mL) and stirred for 10 min, and the mixture exhibited one signal
Results and Discussion
1
in the 31P{1H} NMR spectra: -6.2 (s); H NMR (CD3CN, 500
MHz, 293 K): 1.95 (s, 18H), 7.61-7.81 (m, 5H); 13C{1H} NMR
(CD3CN, 125.8 MHz, 293 K): 12.5 (s), 130.7 (s), 131.2 (s), 134.1
While the bond energies of bonds between the pnictogen
elements are viable, reports of compounds containing bonds
between heavy pnictogen elements are rare, perhaps due to the
limited availability of synthetic approaches for Pn′-Pn bond
formation. Application of the generic reaction eq 2 using
phosphines as ligands on pnictogenium centers has enabled the
facile preparation of compounds containing PfPn coordinate
bonds4,12,15 as well as compounds containing AsfAs,19
AsfSb,13,14 AsfBi,13,14 and SbfSb coordinate bonds.20
Nevertheless, only half of the possible interpnictogen coordinate
bonds have been identified in examples of representative
compounds, as illustrated by the bolded entries in Table 2, which
lists all possible coordinate bonds between pnictogen elements.
Moreover, all examples of isolated compounds containing a
Pn′fPn coordinate bond involve a pnictogen donor center (Pn′)
that is a stronger base than the pnictogen acceptor center (Pn).
1
(s), 137.8 (d, JPC ) 25 Hz).
[Ph3SbP(Et)P(Et)SbPh3][AlCl4]2. AlCl3 (39.8 mg, 0.300 mmol)
was added to a solution of EtPCl2 (20.2 µL, 0.200 mmol) and Ph3Sb
(106.0 mg, 0.300 mmol) in CH2Cl2 (2 mL) and stirred for 2 h in
the dark, and the mixture exhibited one signal in the 31P{1H} NMR
spectra; -58.2 (s); 1H NMR (500 MHz, 293 K, CD2Cl2): 1.29 (dt,
2JPH ) 15 Hz, 3JHH ) 7 Hz, 6H), 2.37 (dq, 3JHH ) 7 Hz, 4JPH ) 13
Hz, 4H), 7.46-7.49 (m); 13C{1H} NMR (125.8 MHz, 293 K,
CD2Cl2): 14.3 (s), 23.1 (s), 125.1 (s), 127.9 (s), 128.8 (s), 137.5
(s).
[Ph3SbP(iPr)P(iPr)SbPh3][AlCl4]2. AlCl3 (39.8 mg, 0.300 mmol)
was added to a solution of iPrPCl2 (24.6 µL, 0.200 mmol) and Ph3Sb
(106.0 mg, 0.300 mmol) in CH2Cl2 (2 mL) and stirred for 2 h in
the dark, and the mixture exhibited one signal in the 31P{1H} NMR
spectra: -31.7 (s), 1H NMR (500 MHz, 293 K, CD2Cl2): 1.55 (dd,
4
3JHH ) 30 Hz, JPH ) 10 Hz, 12H), 2.50 (m, 2H), 7.32-7.55 (m,
30 H); 13C{1H} NMR (125.8 MHz, 293 K, CD2Cl2): 20.2 (s), 39.2
(s), 130.1 (s), 132.5 (s), 135.6 (s), 137.2 (s).
(17) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112–122.
(18) Beurskens, P. T.; Beurskens, G.; de Gelder, R.; Garcia-Granda, S.;
Isreal, R.; Gould, R. O.; Smits, J. M. M. Patterson. (DIRDIF-99);
Crystallography Laboratory: Nijmegen, 1999.
Crystallography. X-ray diffraction data for [Ph3AsP(Me)AsPh3]-
[AlCl4]2, [Me3AsP(Me)AsMe3][OSO2CF3]2 and [Ph2PasMe3][OSO2-
CF3] were collected on a Bruker PLATFORM/SMART 1000 CCD
diffractometer. Data for [Ph3SbP(Ph)P(Ph)SbPh3][AlCl4]2, [Ph3SbP-
(iPr)P(iPr)SbPh3][AlCl4]2, [Ph3AsP(Ph)P(Ph)AsPh3][AlCl4]2, and
[Me3AsP(Ph)P(Ph)AsMe3][AlCl4]2 were collected on Bruker D8/
(19) Kilah, N. L.; Weir, M. L.; Wild, S. B. Dalton Trans. 2008, 2480–
2486.
(20) Althaus, H.; Breunig, H. J.; Lork, E. Chem. Commun. 1999, 1971–
1972.
9
17004 J. AM. CHEM. SOC. VOL. 131, NO. 46, 2009

Phosphinopnictonium Cations
A R T I C L E S
1
Table 3. 31P{1H} and H NMR Data for Derivatives of [R′3PnP(R)PnR′3][AlCl4]2, [R′3PnP(R)PnR′3][OSO2CF3]2, [R′3PnP(R)P(R)PnR′3][AlCl4]2,
and [R′3PnP(R)P(R)PnR′3][OSO2CF3]2
δ31P{1H} (ppm)
δ
1H (ppm), [integ.]a
ref
[Me3AsPPh2][OSO2CF3]
-2.2 (s)
-15.8 (s)
1.0 (s)
24.6 (s)
-5.1 (s)
28.1 (s)
-15.1 (s)
17.1 (s)
-15.1 (s)
-6.2 (s)
-17.2 (s)
-2.0 (s)
2.7(s)
7.61-7.71 [10]
1.82 [6]
7.37-7.70 [10]
N/A
N/A
N/A
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
9
9
9
9
9
9
9
[Me3AsPMe2][OSO2CF3]
[Me3AsPPh2][GaCl4]e
[Me3AsPCy2][OSO2CF3]
[Me3AsPEt2][OSO2CF3]
[Me3AsPiPr2][OSO2CF3]
[Et3AsPPh2][OSO2CF3]e
1.73 [9], 1.26 [6]
[Ph3AsPPh2][AlCl4]
N/Ab
[Me3AsP(Me)AsMe3][OSO2CF3]2
[Me3AsP(Ph)AsMe3][OSO2CF3]2
[Me3AsP(Et)AsMe3][OSO2CF3]2
[Me3AsP(Cy)AsMe3][OSO2CF3]2
[Me3AsP(iPr)AsMe3][OSO2CF3]2
[Ph3AsP(Me)AsPh3][AlCl4]2
1.49 [3]
7.8-8.0 [5]
1.12 [3], 1.75 [2]
1.35 [2], 1.98 [4], 2.12 [4], 2.47 [1]
1.46 [6], 3.18 [1]
2.23 [3]
-18.3 (s)
e
[Ph3AsP(Ph)AsPh3][AlCl4]2
[Ph3AsP(Et)AsPh3][AlCl4]2
-4.1 (s)
N/Ab
1.59 [3], 4.55, [2]
N/A
e
-7.7 (s)
e
[Ph3AsP(Cy)AsPh3][AlCl4]2
3.8 (s)
[Ph3AsP(iPr)AsPh3] [AlCl4]2
7.7 (s)
1.26 [6], 2.70 [1]
[Ph3SbP(Ph)P(Ph)SbPh3][AlCl4]2
[Ph3SbP(Me)P(Me)SbPh3][AlCl4]2
-29.2 (s)
-78.8 (s)
-58.2 (s)
-31.7 (s)
-11.9 (s)
-31.6 (s)
-33.4 (s)
-27.2 (s)
-33 (m), 24 (m)
-52 (m), 25 (m)
-71 (m), 26 (m)
-73 (m), 26 (m)
-54 (m), 24 (m)
-26 (m), 22 (m)
-34 (m), 20 (m)
N/Ab
2.91 [6]
e
[Ph3SbP(Et)P(Et)SbPh3][AlCl4]2
5.02 [6], 5.38 [4]
1.55 [12], 2.50 [2]
N/Ab
7.60-7.68 [10]
7.75 [6], 2,99 [4]
see exptl section
N/Ab
7.74 [4], 7.84 [2], 8.05 [4]
0.76 [6]
1.93 [6]
e
[Ph3SbP(iPr)P(iPr)SbPh3][AlCl4]2
[Ph3AsP(Ph)P(Ph)AsPh3][AlCl4]2
[Me3AsP(Ph)P(Ph)AsMe3][AlCl4]2
[Et3AsP(Ph)P(Ph)AsEt3][AlCl4]2
[Me3AsP(iPr)P(iPr)AsMe3][AlCl4]2
[Ph3PP(Ph)P(Ph)PPh3][OSO2CF3]2
[Me3PP(Ph)P(Ph)PMe3][OSO2CF3]2
[Ph3PP(Me)P(Me)PPh3][OSO2CF3]2
[Me3PP(Me)P(Me)PMe3][OSO2CF3]2
[Ph3PP(Et)P(Et)PPh3][OSO2CF3]2
[Ph3PP(iPr)P(iPr)PPh3][OSO2CF3]2
[Me3PP(Cy)P(Cy)PMe3][OSO2CF3]2
1.93 [4], 0.55 [6]
0.93 [12], 3.26 [2]
N/Ac
a Integrations are relative to signals for R′. b Indistinguishable aromatic regions. c Not reported. d This work. e Not isolated.
The use of a cationic charge at the acceptor site offers the
potential to extrapolate coordination chemistry as a synthetic
methodology to access compounds with interpnictogen coor-
dinate bonds that have not yet been observed (Table 2).
Consequently, the implementation of reaction 2 has broad scope
in terms of the discovery of new interpnictogen compounds.
To this end we have used three component reaction mixtures
of a chlorophosphine, a pnictine, and a halide abstracting agent
as a versatile and high yield approach to the first compounds
containing coordinate AsfP and SbfP bonds, representing the
first examples of bonds involving the less basic pnictogen center
(As or Sb) as the donor to the more basic pnictogen center (P).
Reaction mixtures composed of chlorophosphines (ClPR′2,
i
R′ ) Me, Ph, Pr, Cy), Me3As and Me3SiOSO2CF3 in CH2Cl2
exhibit one product signal in the 31P{1H} NMR spectra,
Figure 1. Crystallographic view of the cation in [Me3AsPPh2][OSO2CF3].
Ellipsoids presented at 50%, hydrogen atoms and counteranions removed
for clarity. All nonlabeled atoms are carbon.
independent of the imposed reaction stoichiometry (Table 3).
For R′ ) Ph, the compound has been isolated and crystallo-
graphically characterized as [Me3AsPPh2][OSO2CF3], and the
structure of the cation in the solid state is shown in Figure 1.
The compound can be described as a salt of a phosphinoarso-
nium cation formed according to reaction 2 (Pn ) P, Pn′ )
As). The cation may also be considered as a complex of an
arsine ligand on a phosphenium cationic Lewis acceptor, as
illustrated by molecular frameworks presented above reaction
2. Reaction mixtures containing the less basic Ph3As (relative
to Me3As) with AlCl3 as the halide abstracting agent show
analogous formation of the AsfP bond. However, no reaction
is observed in mixtures of chlorophosphines, Ph3As and
Me3SiOSO2CF3 probably demonstrating the kinetic limitations
of Me3SiOSO2CF3 as a chloride abstracting agent.
Reaction mixtures composed of dichlorophosphines (R′PCl2,
i
R′ ) Ph, Et, Pr, Me, Cy), Ph3As and AlCl3 in CH2Cl2 exhibit
one product signal in the 31P{1H} NMR spectra (Table 3),
independent of the imposed reaction stoichiometry. For R )
Me, the product has been isolated and crystallographically
characterized as the 2-phosphino-1,3-diarsonium tetrachloro-
aluminate [Ph3AsP(Me)AsPh3][AlCl4]2, which is spectroscopi-
cally identical to the compound identified in the reaction
1
mixture, and implicates reaction 4. Integrated H NMR data
(Table 3) for all derivatives of [Ph3AsP(R)AsPh3][AlCl4]2 are
consistent with the solid state structure of the cation in
[Ph3AsP(Me)AsPh3][AlCl4]2, which is illustrated in Figure 2a,
9
J. AM. CHEM. SOC. VOL. 131, NO. 46, 2009 17005

A R T I C L E S
Conrad et al.
Figure 2. Crystallographic views of the dications in (a) [Ph3AsP(Me)AsPh3][AlCl4]2 and in (b) [Me3AsP(Me)AsMe3][OSO2CF3]2. Ellipsoids presented at
50%, hydrogen atoms and counteranions removed for clarity. All nonlabeled atoms are carbon.
Figure 3. Crystallographic views of the dications in (a) [Ph3SbP(Ph)P(Ph)SbPh3][AlCl4]2 and in (b) [Ph3SbP(iPr)P(iPr)SbPh3][AlCl4]2. Ellipsoids presented
at 50%, hydrogen atoms and counteranions removed for clarity. All nonlabeled atoms are carbon.
and can be described as a phosphinodiarsonium cation. Alter-
natively, the cation can be described as a complex of two arsine
ligands on a formal R′P2+ dication (phosphinidenium) Lewis
acceptor, as illustrated by molecular frameworks presented
above eq 4. In contrast to phosphenium21,22,22-25 and arsenium
cations,26-29 examples of salts containing phosphinidenium
dications have not been reported.
As for mixtures of ClPR′2, Ph3As and Me3SiOSO2CF3,
mixtures of R′PCl2 with Ph3As and Me3SiOSO2CF3 show no
evidence of reaction in the 31P{1H} NMR spectra after 24 h.
Nevertheless, the more basic ligand Me3As enables formation
of derivatives of [Me3AsP(R′)AsMe3][OSO2CF3]2 (R′ ) Me,
Ph, Et, iPr, Cy) using reaction 4 as evidenced by 31P{1H} NMR
spectra (Table 3) of reaction mixtures. The identity of the triflate
salts is also confirmed by the solid state structure of
[Me3AsP(Me)AsMe3][OSO2CF3]2, the cation of which is shown
in Figure 2b. It has not been possible to identify the chloro-
phosphinoarsonium cation [R′3AsP(Cl)R]+ intermediate, which
is inevitable in these reactions based on the observed products,
even though salts of the corresponding chlorophosphinophos-
phonium cations have been previously isolated.4
(21) Burford, N.; Losier, P.; Macdonald, C.; Kyrimis, V.; Bakshi, P. K.;
Cameron, T. S. Inorg. Chem. 1994, 33, 1434–1439.
(22) Burck, S.; Gudat, D. Inorg. Chem. 2008, 47, 315–321.
(23) Gudat, D.; Haghverdi, A.; Nieger, M. Phosphorus, Sulfur, Silicon Relat.
Elem. 2001, 168-169, 203–208.
Reaction mixtures composed of dichlorophosphines (R′PCl2,
i
R ) Ph, Et, Pr, Me), Ph3Sb and AlCl3 in CH2Cl2 also exhibit
one product signal in the 31P{1H} NMR spectra, independent
of the imposed reaction stoichiometry. In contrast to reaction
mixtures involving arsine donors, crystallographic characteriza-
(24) Spinney, H. A.; Yap, G. P. A.; Korobkov, I.; DiLabio, G.; Richeson,
D. S. Organometallics 2006, 25, 3541–3543.
(25) Burck, S.; Daniels, J.; Gans-Eichler, T.; Gudat, D.; Naettinen, K.;
Nieger, M. Z. Anorg. Allg. Chem. 2005, 631, 1402–1412.
(26) Burford, N.; Parks, T. M.; Royan, B. W.; Borecka, B.; Cameron, T. S.;
Richardson, J. F.; Gabe, E. J.; Hynes, R. J. Am. Chem. Soc. 1992,
114, 8147–8153.
i
tion of the product from the reaction of PhPCl2 (or PrPCl2),
Ph3Sb and AlCl3 reveal the first salts of 2,3-diphosphino-1,4-
distibonium cations, resulting from reaction 5. Views of the solid
state structures of the dications in [Ph3SbP(Ph)P(Ph)SbPh3]-
[AlCl4]2 and [Ph3SbP(iPr)P(iPr)SbPh3][AlCl4]2 are shown in
Figure 3. Other derivatives of [Ph3SbP(R′)P(R′)SbPh3][AlCl4]2
have been prepared in situ as evidenced by 31P{1H} NMR
spectra (Table 3) of reaction mixtures. Integrated 1H NMR data
(27) Burford, N.; Parks, T. M.; Royan, B. W.; Richardson, J. F.; White,
P. S. Can. J. Chem. 1992, 70, 703–709.
(28) Spinney, H. A.; Korobkov, I.; DiLabio, G.; Yap, G. P. A.; Richeson,
D. S. Organometallics 2007, 26, 4972–4982.
(29) Spinney, H. A.; Korobkov, I.; Richeson, D. S. Chem. Commun. 2007,
1647–1649.
9
17006 J. AM. CHEM. SOC. VOL. 131, NO. 46, 2009

Phosphinopnictonium Cations
A R T I C L E S
Table 4. Selected Interatomic Distances in Phosphinopnictonium Compounds
P-P (Å)
Pn-P (Å)
ref
[Me3AsPPh2][OSO2CF3]
[Me3AsP(Me)AsMe3][OSO2CF3]2
[Ph3AsP(Me)AsPh3][AlCl4]2
[Ph3PP(Ph)P(Ph)PPh3][OSO2CF3]2
[Me3PP(Ph)P(Ph)PMe3][OSO2CF3]2
[Ph3PP(Me)P(Me)PPh3][OSO2CF3]2
[Me3PP(Me)P(Me)PMe3][OSO2CF3]2
[Ph3PP(Et)P(Et)PPh3][OSO2CF3]2
-
-
2.3239(7)
2.3267(6), 2.3283(6)
2.3247(7), 2.3198(7)
N/A
N/A
N/A
N/A
N/A
2.379(2), 2.365(2)
2.3106(10), 2.3199(9), 2.3118(10)
2.523(3), 2.503(3)
2.5387(5)
d
d
d
9
9
9
9
9
d
d
d
d
-
2.258(1), 2.221(1)
2.2041(9), 2.2318(12)
2.206(13), 2.2284(12)
2.192(2), 2.243(2), 2.191(2)
2.2048(8), 2.2153(11)
2.221(4), 2.241(5)
2.2271(12), 2.2215(18)
2.226(4)
a
[Ph3AsP(Ph)P(Ph)AsPh3][AlCl4]2
c
[Me3AsP(Ph)P(Ph)AsMe3][AlCl4]2
[Ph3SbP(iPr)P(iPr)SbPh3][AlCl4]2
b
[Ph3SbP(Ph)P(Ph)SbPh3][AlCl4]2
2.2357(10)
a Two independent cations, both inversion-symmetric. b Cation is inversion-symmetric. c Two independent cations, one is inversion-symmetric. d This
work.
Table 5. Selected Angles in Phosphinopnictonium Compounds
Pn-P-Pn (deg)
Pn-P-P-Pn (deg)
ΣR-Pn-Pn (deg)
ref
[Me3AsPPh2][OSO2CF3]
[Me3AsP(Me)AsMe3][OSO2CF3]2
[Ph3AsP(Me)AsPh3][AlCl4]2
[Ph3PP(Ph)P(Ph)PPh3][OSO2CF3]2
[Me3PP(Ph)P(Ph)PMe3][OSO2CF3]2
[Ph3PP(Me)P(Me)PPh3][OSO2CF3]2
-
-
-
-
301.1
306.2
304.0
299.5
295.2
298.4
303.9
295.2
298.7
309.3
293.8
295.7
295.7
294.7
294.8
306.7
308.5
290.5
d
d
d
9
9
9
106.80(2)
102.77(3)
97.20(3)b
96.41(3)b
180
180
96.66(4), 91.45(4)
-159.98(4)
[Me3PP(Me)P(Me)PMe3][OSO2CF3]2
[Ph3PP(Et)P(Et)PPh3][OSO2CF3]2
95.20(3), 94.45(3)
-126.72(3)
9
95.83(3)b
-142.35(3)
180.0, 180.0
9
d
a
[Ph3AsP(Ph)P(Ph)AsPh3][AlCl4]2
95.16(12), 96.60(13)
c
[Me3AsP(Ph)P(Ph)AsMe3][AlCl4]2
97.58(4), 94.54(4), 95.86(5)
173.36(3), 180.0
d
[Ph3SbP(iPr)P(iPr)SbPh3][AlCl4]2
93.63(13), 93.77(13)
93.62(3)
-5.0(6)
d
d
b
[Ph3SbP(Ph)P(Ph)SbPh3][AlCl4]2
180.0
a Two independent cations, both inversion-symmetric. b Cation is inversion-symmetric. c Two independent cations, one is inversion-symmetric. d This
work.
(Table 3) for derivatives of [R3SbP(R′)P(R′)SbR3][AlCl4]2 are
these reactions. Nevertheless, as the basicity of Ph3Sb is lower
than that of R3As (R ) Me, Et, Ph) or Ph3P, reactions of
[Ph3SbP(Ph)P(Ph)SbPh3][AlCl4]2 with excess Ph3P or R3As (R
) Me, Et, Ph) result in quantitative formation of [Ph3PP-
(Ph)P(Ph)PPh3][AlCl4]2 and [R3AsP(Ph)P(Ph)AsR3][AlCl4]2,
respectively, according to reaction 6, as evidenced by the
31P{1H} NMR spectra of reaction mixtures. The solid state
structures of [Me3AsP(Ph)P(Ph)AsMe3][AlCl4]2 and [Ph3AsP-
(Ph)P(Ph)AsPh3][AlCl4]2 have been determined by X-ray crys-
tallography and views of the structures of the dications are
shown in Figure 4. It was not possible to observe the anticipated
nonsymmetric cation in salts of the form [R3AsP(R′)P(R′)SbR3]-
[AlCl4]2 for a reaction stoichiometry with less than the 2 equiv
of arsine or phosphine. Instead, the reaction mixture contains
consistent with the 2,3-diphosphino-1,4-distibonium formula.
Formation of the 2,3-diphosphino-1,4-distibonium bis(tetra-
chloroaluminate) salts from the assembly of two molecules of
R′PCl2 with two molecules of Ph3Sb and two molecules of AlCl3
involves a chloride abstraction from the phosphine with
subsequent coordination of a stibine to the resulting chloro-
phosphenium cation and reductive P-P coupling of two cationic
phosphorus centers. There is no evidence for the intermediate
existence of the chlorophosphinostibonium cation [Ph3SbP(Cl)-
R′]+, perhaps indicating that the P-P reductive coupling reaction
precedes the chloride abstraction and SbfP coordination.
Formation of [Ph3SbP(R′)P(R′)SbPh3]2+ is analogous to that
reported for reactions of a dichlorophosphine with a phosphine
and MeSi3OSO2CF3 to give derivatives of [R3PP(R′)P(R′)-
PR3][OSO2CF3]2, examples of which are listed in Tables 3, 4,
and 5.9 Analogous reaction mixtures containing Ph3Bi in place
of Ph3Sb render yellow reaction mixtures which show many
signals in the 31P{1H} NMR spectra, but it has not been possible
to isolate or identify the products.
`
unreacted [Ph3SbP(R)P(R′)SbPh3][AlCl4]2 and the symmetric
2,3-diphosphino-1,4-diarsonium cation [R3AsP(R′)P(R′)AsR3]2+,
suggesting that the inevitable nonsymmetric intermediate
[R3AsP(R′)P(R′)SbPh3]2+ is more susceptible to ligand exchange
than [Ph3SbP(R′)P(R′)SbPh3]2+
.
Selected solid state structural parameters for [Me3AsPPh2]+
and derivatives of [R3AsP(R′)AsR3]2+ and [R3PnP(R′)-
P(R′)PnR3]2+ (Pn ) P, As, Sb) are presented in Tables 4 (bond
lengths) and Table 5 (bond angles). In all cases, the terminal
pnictonium environments adopt the predictable distorted tetra-
hedral geometry as shown in Figures 1-4. The trigonal
pyramidal geometry for the phosphine centers exhibit smaller
Pn-P-Pn angles in [Me3AsPPh2]+ and derivatives of
We attribute the distinct difference in outcome for reactions
4 and 5 to the relative redox properties of arsenic and antimony.
In contrast to Ph3Sb, R3As is an ineffective reducing agent.
Adjustment of the stoichiometry of the reaction mixtures
described by reactions 4 and 5 does not influence the cations
formed. It has not been possible to observe derivatives of
[Ph3SbP(R′)SbPh3][AlCl4]2 or [R3AsP(R′)P(R′)AsR3][AlCl4]2 in
9
J. AM. CHEM. SOC. VOL. 131, NO. 46, 2009 17007

A R T I C L E S
Conrad et al.
Figure 4. Crystallographic views of the dications in (a) [Me3AsP(Ph)P(Ph)AsMe3][AlCl4]2 and in (b) [Ph3AsP(Ph)P(Ph)AsPh3][AlCl4]2. Ellipsoids presented
at 50%, hydrogen atoms and counteranions removed for clarity. All nonlabeled atoms are carbon.
[R3PnP(R′)P(R′)PnR3]2+ than in derivatives of [R3AsP(R′)-
AsR3]2+, likely due to the steric imposition of the two arsonium
centers. All of the interpnictogen bond lengths are within a
narrow range, are typical for single bonds and are essentially
independent of the molecular charge or the substitution (Table
4). The cation in [Ph3SbP(Ph)P(Ph)SbPh3][AlCl4]2 (Figure 2a)
adopts an R,S configuration and a torsional angle of 180.0° for
the Sb-P-P-Sb framework, consistent with the P-P-P-P
framework of the phosphorus analogue [Ph3PP(Ph)P(Ph)PPh3]-
[OSO2CF3]2.9 The cation in [Ph3SbP(iPr)P(iPr)SbPh3][AlCl4]2
(Figure 2b) shows an S,S configuration with an eclipsed
conformation [C-P-P-C torsional angle ) -5.0(6)°], con-
sistent with the calculated gas phase structure of [H3PP(iPr)P-
(iPr)PH3]2+.9 Only one isomer is observed in the solid state
frameworks containing two, three or four pnictogen centers. The
compounds represent the first examples of salts containing
phosphinoarsonium, 2-phosphino-1,3-diarsonium, 2,3-diphos-
phino-1,4-diarsonium and 2,3-diphosphino-1,4-distibonium cat-
ions. The bonding in the cations can be viewed as interpnictogen
coordination and are the first examples of AsfP and SbfP
bonding. As such, the complexes demonstrate the possibility
of the interaction between a donor that is a weaker base than
the acceptor by virtue of a cationic charge on the acceptor. The
high yield and generic nature of these new preparative reactions
bodes well for the discovery of interpnictogen compounds
representing building blocks in the development of new
materials.
structure for both derivatives of [Ph3SbP(R)P(R)SbPh3]2+
,
Acknowledgment. We thank the Natural Sciences and Engi-
neering Research Council of Canada, the Canada Research Chairs
Program, the Canada Foundation for Innovation, the Walter C.
Sumner Foundation and the Nova Scotia Research and Innovation
Trust Fund for funding, and the Atlantic Region Magnetic
Resonance Centre for use of instrumentation.
consistent with the observed 31P{1H} NMR spectra (Table 3).
The solid state structures for both derivatives of [R3AsP(Ph)P-
(Ph)AsR3]2+ adopt anti conformations consistent with the
structures of the dications in [Ph3SbP(Ph)P(Ph)SbPh3][AlCl4]2
and [Ph3PP(Ph)P(Ph)PPh3][OSO2CF3]2.
Conclusion
Supporting Information Available: CIF files with crystal-
lographic data. This material is available free of charge via the
Internet at http://pubs.acs.org.
Reactions of chlorophosphines or dichlorophosphine with
arsines (R3As, R ) Me, Et, Ph) or Ph3Sb in the presence of a
chloride ion abstracting agent (AlCl3, GaCl3, Me3SiOSO2CF3)
provide a versatile one pot synthetic approach to interpnictogen
JA907613C
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17008 J. AM. CHEM. SOC. VOL. 131, NO. 46, 2009