HL2[(1,2-O2C6H4)3] (L = DMSO or DMF): A convenient proton source with a weakly basic phosphorus(V) Anion

Article abstract of DOI:10.1021/om9003187

Treating phosphorus pentachloride with catechol (3 equiv) followed by the addition of dimethyl -sulfoxide (DMSO) or dimethylformamide (DMF) affords isolable Bronsted acids of the tris-(o-phenylenedioxy)phosphate anion, [P(1,2-O₂C₆H

Full text of DOI:10.1021/om9003187

Organometallics 2009, 28, 4491–4499 4491
DOI: 10.1021/om9003187
HL2[P(1,2-O2C6H4)3] (L=DMSO or DMF): A Convenient Proton
Source with a Weakly Basic Phosphorus(V) Anion
Paul W. Siu and Derek P. Gates*
Department of Chemistry, University of British Columbia, Vancouver, 2036 Main Mall, British Columbia,
Canada V6T 1Z1
Received April 26, 2009
Treating phosphorus pentachloride with catechol (3 equiv) followed by the addition of dimethyl-
sulfoxide (DMSO) or dimethylformamide (DMF) affords isolable Brønsted acids of the tris-
(o-phenylenedioxy)phosphate anion, [P(1,2-O2C6H4)3]-. Specifically, H(DMSO)2[P(1,2-O2C6H4)3]
and H(DMF)2[P(1,2-O2C6H4)3] have been isolated as crystalline solids. The downfield shifts of the
acidic proton in their 1H NMR spectra are consistent with its expected high acidity. The molecular
structures of H(DMSO)2[P(1,2-O2C6H4)3] and H(DMF)2[P(1,2-O2C6H4)3] reveal that the protons in
each are O-bound by either DMSO (ꢀ2) or DMF (ꢀ2). The N-H stretching frequency for the
Oct3NH[P(1,2-O2C6H4)3] (νN-H=3129 cm-1) is identical to that observed for trioctylammonium
h
tetrafluoroborate (νN-H=3129 cm-1), suggesting that the basicity of these two weakly coordinating
h
anions is similar. A preliminary investigation of the effectiveness of H(DMF)2[P(1,2-O2C6H4)3] in the
protonolysis of metal-alkyl bonds was undertaken. Treating (dppe)PdMe2 [dppe=1,2-bis(diphe-
nylphosphino)ethane] with H(DMF)2[P(1,2-O2C6H4)3] affords either [(dppe)Pd(NCMe)Me][P(1,2-
O2C6H4)3] (1:1 ratio) or [(dppe)Pd(NCMe)2][P(1,2-O2C6H4)3]2 (1:2 ratio), both of which are
structurally characterized.
Introduction
ing anions (WCAs).1 A number of sophisticated approaches
have been designed to prepare large, charge-delocalized WCAs
such as fluoroarylborates, carboranes, fluoroalkoxyalumi-
nates, and teflates, among others.2-5 Classical WCAs have
often served as inspiration for the design of improved WCAs.
For example, the classical anion [BF4]- may be envisaged, at
least formally, as the predecessor to the larger and more charge
delocalized [BPh4]-. The formal evolution of [BF4]- ultimately
led to the popular fluoroarylborate anions [B(3,5-(CF3)2-
C6H3)4]- and [B(C6F5)4]-.6,7 Although fluoroarylborates have
permitted important advancements in both fundamental and
The stabilization of coordinatively unsaturated cations,
which are often found as reactive intermediates or active
catalysts, necessitates the presence of charge-balancing anions
with minimal nucleophilicity, the so-called weakly coordinat-
*Corresponding author. E-mail: dgates@chem.ubc.ca.
(1) For general reviews on WCAs, see (a) Krossing, I.; Raabe, I.
Angew. Chem., Int. Ed. 2004, 43, 2066. (b) Reed, C. A. Acc. Chem. Res.
1998, 31, 133. (c) Strauss, S. H. Chem. Rev. 1993, 93, 927.
(2) For recent developments of carborane-based WCAs, see, for
€
example: (a) Korbe, S.; Schreiber, P. J.; Michl, J. Chem. Rev. 2006,
106, 5208. (b) K€uppers, T.; Bernhardt, E.; Eujen, R.; Willner, H.; Lehmann,
C. W. Angew. Chem., Int. Ed. 2007, 46, 6346. (c) Douvris, C.; Stoyanov, E.
S.; Tham, F. S.; Reed, C. A. Chem. Commun. 2007, 1145. (d) Reed, C. A.
Chem. Commun. 2005, 1669. (e) Clarke, A. J.; Ingleson, M. J.; Kociok-
(5) For recent developments of teflates and other WCA motifs, see,
for example: (a) Mercier, H. P. A.; Moran, M. D.; Schrobilgen, G. J.;
Steinberg, C.; Suontamo, R. J. J. Am. Chem. Soc. 2004, 126, 5533.
(b) Cameron, T. S.; Krossing, I.; Passmore, J. Inorg. Chem. 2001, 40, 4488.
(c) Metz, M. V.; Sun, Y. M.; Stern, C. L.; Marks, T. J. Organometallics 2002,
21, 3691. (d) Finze, M.; Bernhardt, E.; Willner, H. Angew. Chem., Int. Ed.
2007, 46, 9180. (e) Richardson, C.; Reed, C. A. Chem. Commun. 2004, 706.
(f) Chen, M. C.; Roberts, J. A. S.; Seyam, A. M.; Li, L. T.; Zuccaccia, C.;
Stahl, N. G.; Marks, T. J. Organometallics 2006, 25, 2833. (g) Geis, V.;
Guttsche, K.; Knapp, C.; Scherer, H.; Uzun, R. Dalton Trans. 2009, 2687.
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€
Kohn, G.; Mahon, M. F.; Patmore, N. J.; Rourke, J. P.; Ruggiero, G. D.;
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C.; Sze, E. T. P.; Mak, T. C. W.; Chan, D. T. W.; Xie, Z. W. Inorg. Chem.
2000, 39, 5851.
(3) For recent developments of fluoroarylborates as WCAs, see, for
example: (a) Chai, J. F.; Lewis, S. P.; Collins, S.; Sciarone, T. J. J.;
Henderson, L. D.; Chase, P. A.; Irvine, G. J.; Piers, W. E.; Elsegood, M.
R. J.; Clegg, W. Organometallics 2007, 26, 5667. (b) Hannant, M. H.;
Wright, J. A.; Lancaster, S. J.; Hughes, D. L.; Horton, P. N.; Bochmann, M.
Dalton Trans. 2006, 2415. (c) Bavarian, N.; Baird, M. C. Organometallics
2005, 24, 2889. (d) Lancaster, S. J.; Rodriguez, A.; Lara-Sanchez, A.;
Hannant, M. D.; Walker, D. A.; Hughes, D. H.; Bochmann, M. Organome-
tallics 2002, 21, 451. (e) LaPointe, R. E.; Roof, G. R.; Abboud, K. A.; Klosin,
J. J. Am. Chem. Soc. 2000, 122, 9560. (f) Rodriguez, G.; Brant, P.
Organometallics 2001, 20, 2417. (g) Chen, E. Y. X.; Marks, T. J. Chem.
Rev. 2000, 100, 1391.
(4) For recent developments of fluoroalkoxyaluminates as WCAs,
see, for example: (a) Krossing, I.; Reisinger, A. Eur. J. Inorg. Chem.
2005, 1979. (b) Ivanova, S. M.; Nolan, B. G.; Kobayashi, Y.; Miller, S. M.;
Anderson, O. P.; Strauss, S. H. Chem.;Eur. J. 2001, 7, 503. (c) Tsujioka, S.;
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2004, 151, A1418. (d) Timofte, T.; Pitula, S.; Mudring, A. V. Inorg. Chem.
2007, 46, 10938.
(7) Typical sources of [B(3,5-(CF3)2C6H3)4]- and [B(C6F5)4]- include
H(Et2O)2 salts: (a) Brookhart, M.; Grant, B.; Volpe, A. F. Organome-
tallics 1992, 11, 3920. (b) Jutzi, P.; Muller, C.; Stammler, A.; Stammler, H. G.
Organometallics 2000, 19, 1442. Alkali metal salts: (c) Nishida, H.; Takada,
N.; Yoshimura, M.; Sonoda, T.; Kobayashi, H. Bull. Chem. Soc. Jpn. 1984, 57,
2600. (d) Massey, A. G.; Park, A. J. J. Organomet. Chem. 1964, 2, 245. Silver
(I) salts: (e) Golden, J. H.; Mutolo, P. F.; Lobkovsky, E. B.; DiSalvo, F. J. Inorg.
Chem. 1994, 33, 5374. (f) Mukaiyama, T.; Maeshima, H.; Jona, H. Chem. Lett.
2001, 388. Thallium(I) salts: (g) Hughes, R. P.; Lindner, D. C.; Rheingold, A.
L.; Yap, G. P. A. Inorg. Chem. 1997, 36, 1726. (h) Alberti, D.; Porschke, K. R.
Organometallics 2004, 23, 1459. Trityl salts: (i) Bahr, S. R.; Boudjouk, P. J.
Org. Chem. 1992, 57, 5545. (j) Chien, J. C. W.; Tsai, W. M.; Rausch, M. D. J.
Am. Chem. Soc. 1991, 113, 8570. Dimethylanilinium salts: (k) Taube, R.;
Wache, S. J. Organomet. Chem. 1992, 428, 431. (l) Pellecchia, C.; Proto, A.;
Longo, P.; Zambelli, A. Makromol. Chem., Rapid Commun. 1991, 12, 663.
r
2009 American Chemical Society
Published on Web 07/06/2009
pubs.acs.org/Organometallics

4492 Organometallics, Vol. 28, No. 15, 2009
Siu and Gates
applied chemistry,8,9 their often difficult preparation leaves
open the possibility to develop alternative WCAs with simple
and convenient preparative routes.
We have been inspired by the aforementioned evolution of
[BF4]- to explore the possible analogous evolution of classi-
cal WCA [PF6]-, which has thus far received very little
attention for improvement. Investigation of [PF6]- deriva-
tives could potentially pave the way to new classes of weakly
nucleophilic anions with poor coordinating ability. A logical
first step in the evolution of [PF6]- is the preparation of
[PPh6]-; however, this unknown species would likely suffer
from undesirable redox chemistry. Therefore, we have cho-
sen the relatively large tris(o-phenylenedioxy)phosphate an-
ion [1]- 10-12 as a candidate for our preliminary studies of the
WCA properties of hexacoordinated phosphorus. Despite
the fact that anion [1]- has been studied extensively,13-17 it
has not yet been explored for WCA applications. We are
particularly interested in preparing Brønsted acids contain-
ing [1]- due to their potential to serve as catalyst activators
through the protonolysis of metal-alkyl bonds, particularly
when more sophisticated WCAs are not necessarily essential.
Herein, we describe the preparation and characterization
of two solid Brønsted acids containing the tris(o-phenylene-
dioxy)phosphate anion [1]-. Specifically, H(DMF)2[1] and
H(DMSO)2[1] have been prepared and structurally charac-
terized. In contrast to the preparation of other protic salts of
WCAs, the route to these new Brønsted acids is simple and
straightforward, beginning with conveniently available
Figure 1. Molecular structure of H(DMSO)2[1]. Ellipsoids are
drawn at the 50% probability level. All hydrogen atoms are
omitted for clarity, except for H(1), H(19a), H(19b), and H(19c).
˚
Selected bond lengths (A) and angles (deg): O(1)-P(1)=1.726(1);
O(2)-P(1)=1.716(1); O(3)-P(1)=1.725(1); O(4)-P(1)=1.709(1);
O(5)-P(1)=1.705(1); O(6)-P(1)=1.713(1); O(7)-H(1)=1.00(3);
O(8)-H(1)=1.45(3); O(7)-O(8)=2.445(6); O(6)-H(19c)=2.421
(1); O(2)-P(1)-O(1)=90.85(5); O(2)-P(1)-O(3)=87.11(5); O
(3)-P(1)-O(1)=92.00(5); O(4)-P(1)-O(3)=90.60(5); O(4)-P
(1)-O(6) = 92.85(5); O(4)-P(1)-O(1) = 88.62(5); O(5)-P(1)-
O(2)=93.42(5); O(5)-P(1)-O(4)=88.86(5); O(5)-P(1)-O(6)=
91.27(5); O(5)-P(1)-O(1)=87.89(5); O(6)-P(1)-O(3)=88.86(5);
O(6)-P(1)-O(2)=87.71(5); O(7)-H(1)-O(8)=171(3).
inexpensive precursors: phosphorus(V) chloride, catechol,
and DMF or DMSO. It will be shown that H(DMF)2[1] is
effective in the stoichiometric activation of the metal-alkyl
bonds of (dppe)PdMe2 and that the coordinating nature of
the anion [1]- is comparable to the classical WCA [BF4]-.
(8) For selected examples where WCAs have been employed to
facilitate the isolation of novel cationic species, see: (a) Jutzi, P.; Mix,
A.; Rummel, B.; Schoeller, W. W.; Neumann, B.; Stammler, H. G.
Science 2004, 305, 849. (b) Yang, J.; White, P. S.; Schauer, C. K.; Brookhart,
M. Angew. Chem., Int. Ed. 2008, 47, 4141. (c) Bonnier, C.; Piers, W. E.;
Parvez, M.; Sorensen, T. S. Chem. Commun. 2008, 4593. (d) Stoyanov, E. S.;
Stoyanova, I. V.; Reed, C. A. Chem.;Eur. J. 2008, 14, 7880. (e) Jones, J. N.;
Moore, J. A.; Cowley, A. H.; Macdonald, C. L. B. Dalton Trans. 2005, 3846.
(f) Yao, S. L.; Xiong, Y.; van W€ullen, C.; Driess, M. Organometallics 2009,
28, 1610. (g) Yang, Y.; Panisch, R.; Bolte, M.; M€uller, T. Organometallics
2008, 27, 4847. (h) Brownie, J. H.; Baird, M. C. Organometallics 2007, 26,
5890. (i) Filippou, A. C.; Philippopoulos, A. I.; Portius, P.; Schnakenburg, G.
Organometallics 2004, 23, 4503. (j) Koppe, K.; Frohn, H. J.; Mercier, H. P.
A.; Schrobilgen, G. J. Inorg. Chem. 2008, 47, 3205. (k) Avelar, A.; Tham, F.;
Reed, C. Angew. Chem., Int. Ed. 2009, 48, 3491.
(9) For use of WCAs in applied chemistry, see, for example: (a) Ono, T.;
Sugimoto, T.; Shinkai, S.; Sada, K. Nat. Mater. 2007, 6, 429. (b) Uyeda, C.;
Jacobsen, E. N. J. Am. Chem. Soc. 2008, 130, 9228. (c) Friesen, D. M.; Piers, W.
E.; Parvez, M. Organometallics 2008, 27, 6596. (d) Broene, R. D.; Brookhart,
M.; Lamanna, W. M.; Volpe, Jr. A. F. J. Am. Chem. Soc. 2005, 127, 17194.
(10) Allcock, H. R. J. Am. Chem. Soc. 1963, 85, 4050.
(11) Allcock, H. R.; Bissell, E. C. Chem. Commun. 1972, 676.
(12) Allcock, H. R.; Bissell, E. C. J. Am. Chem. Soc. 1973, 95, 3154.
(13) Handa, M.; Suzuki, M.; Suzuki, J.; Kanematsu, H.; Sasaki, Y.
Electrochem. Solid-State Lett. 1999, 2, 60.
(14) Koenig, M.; Klaebe, A.; Munoz, A.; Wolf, R. J. Chem. Soc.,
Perkin Trans. 2 1979, 40.
(15) Munoz, A.; Gallagher, M.; Klaebe, A.; Wolf, R. Tetrahedron
Lett. 1976, 17, 673.
(16) Ramirez, F.; Nowakowski, M.; Marecek, J. F. J. Am. Chem. Soc.
Results and Discussion
The tris(o-phenylenedioxy)phosphate anion [1]- was first
isolated as its triethylammonium salt,10 and the presence of
hexacoordinate phosphorus in its structure was confirmed by
X-ray diffraction.11,12 Recently, the salt Li[1] has attracted
attention as an electrolyte for use in lithium batteries and was
reported to have good thermal stability (up to 150 °C).13 We
postulated that its large size combined with high thermal stability
should make [1]- a promising candidate for WCA applications.
Particularly attractive, from the standpoint of the activation of
metal-carbon bonds, would be the preparation of Brønsted
acids containing the tris(o-phenylenedioxy)phosphate anion
[1]-. Consequently, we set out to prepare H[1] in the presence
of weakly basic solvents in an effort to prepare isolable com-
pounds that would serve as solid, weighable, proton sources.
Brønsted Acids of Tris(o-phenylenedioxy)phosphate.
1. Synthesis and Spectroscopic Characterization. It has been
reported that the treatment of PCl5 with catechol (3 equiv)
affords an equilibrium mixture of monomer 2 and catechol-
bridged 3.14 Interestingly, previous studies of catechol-con-
taining phosphorus(V) compounds in DMF or DMSO
provided evidence for the formation of protic acids of [1]-,
1977, 99, 4515.
(17) (a) Eberwein, M.; Schmid, A.; Schmidt, M.; Zabel, M.;
Burgemeister, T.; Barthel, J.; Kunz, W.; Gores, H. J. J. Electrochem.
Soc. 2003, 150, A994. (b) Gallagher, M.; Munoz, A.; Gence, G.; Koenig, M.
Chem. Commun. 1976, 321. (c) Gloede, J.; Gross, H.; Engelhardt, G. J.
Prakt. Chem. 1977, 319, 188. (d) Hellwinkel, D.; Wilfinger, H.-J. Chem.
Ber. 1970, 103, 1056. (e) Kabachnik, M. I.; Lobanov, D. I.; Matrosova, N. V.;
Petrovskii, P. V. Zh. Obshch. Khim. 1986, 56, 1464. (f) Kostin, V. P.;
ꢀ
Sinyashin, O. G.; Batyeva, E. S.; Pudovik, A. N. Zh. Obshch. Khim. 1984,
54, 218. (g) Kukhar, V. P.; Grishkun, E. V.; Khristich, A. I.; Rudavskii, V. P.
Zh. Obshch. Khim. 1979, 49, 1671. (h) Liu, L. Z.; Cai, B. Z.; Chen, R. Y.
Acta Chim. Sin. 1986, 44, 1249. (i) Riesel, L.; Lindemann, D. Z. Anorg.
Allg. Chem. 1991, 606, 219. (j) Schmidpeter, A.; Criegern, T. V.; Sheldrick,
W. S.; Schomburg, D. Tetrahedron Lett. 1978, 19, 2857.

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Organometallics, Vol. 28, No. 15, 2009 4493
however no compounds were isolated nor were structural
data obtained. The presence of HL[1] was inferred on the
basis of 31P NMR spectroscopic data, which suggested the
presence of [1]- (δ=-83.5).15,16
Inspired by this previous work, a solid mixture of 2 and 3 was
prepared from PCl5 and catechol (3 equiv), and subsequently,
the mixture was dissolved in DMSO. Following an identical
procedure, the mixture of 2 and 3 was dissolved in DMF.
Analysis of each reaction mixture using 31P NMR spectroscopy
revealed that the resonances at -28.8 and -29.4 ppm, attrib-
uted to 2 and 3, respectively, had been consumed and were
replaced by a signal at ca. -80 ppm (DMSO: δ=-80.5; DMF:
δ=-80.0), which is similar to those reported previously.15,16
Figure 2. Molecular structure of H(DMF)2[1]. Ellipsoids are
drawn at the 50% probability level. All hydrogen atoms are
omitted for clarity, except for H(1), H(20a), H(20b), and H(20c).
˚
Selected bond lengths (A) and angles (deg): O(1)-P(1)=1.706(1);
O(2)-P(1)=1.715(1); O(3)-P(1)=1.708(1); O(4)-P(1)=1.708(1);
O(5)-P(1)=1.700(1); O(6)-P(1)=1.730(1); O(7)-H(1)=1.13(4);
O(8)-H(1)=1.31(4); O(7)-O(8)=2.438(2); O(3)-H(20c)=2.375-
(1); O(1)-P(1)-O(2)=90.96(6); O(1)-P(1)-O(4)=88.78(7); O-
(1)-P(1)-O(6) = 92.32(7); O(2)-P(1)-O(6) = 87.79(6); O(3)-
P(1)-O(2)=87.54(6); O(3)-P(1)-O(6)= 87.86(6); O(4)-P(1)-
O(2)=92.66(7); O(4)-P(1)-O(3)=91.05(6); O(5)-P(1)-O(1)=
89.23(6); O(5)-P(1)-O(3)=92.27(7); O(5)-P(1)-O(4)=89.08(7);
O(5)-P(1)-O(6)=90.46(6); O(7)-H(1)-O(8)=176(4).
In contrast to previous studies, we have successfully iso-
lated and crystallographically characterized protic salts of
[1]- with [H(DMSO)2]þ and [H(DMF)2]þ as counterion. The
molecular structures are presented in Figures 1 and 2, and the
metrical parameters will be discussed later. In addition to 31P
NMR spectroscopy, each compound was characterized
using 1H and 13C NMR spectroscopy and elemental analysis.
The 1H NMR spectra of CD3CN solutions of the crystalline
solids are shown in Figures 3 and 4. Of particular importance
is the broad downfield signal that is assigned to the acidic
proton of H(DMSO)2[1] (δ = 13.3) and H(DMF)2[1] (δ =
15.3). Importantly, the integrated ratio of the signal assigned
to acidic proton and the DMSO protons (δ=2.83) or the
DMF signals (δ=8.06, 3.07, and 2.95) are consistent with the
molecular structure determined by X-ray crystallography
(vide infra). The slight downfield shift observed for the
complex in comparison to free DMSO (δ = 2.50) or free
DMF (δ=7.92, 2.89, and 2.77) provides evidence that the
[HL2]þ moiety is retained in solution (L=DMSO or DMF).
A rough indication of the acidity of the H in the [H
(DMSO)2]þ and [H(DMF)2]þ cations and the innocence of
the [1]- anion may be obtained from the 1H NMR chemical
shift for the acidic proton. At room temperature the chemical
shift for [H(DMSO)2]þ is 13.3 ppm, whereas for [H(DMF)2]þ
it is observed further downfield at 15.3 ppm, suggesting
a higher acidity for the latter, which is inconsistent with
the relative pKa’s for [HDMSO]þ (pKa = -2.0118) and
Figure 3. 1H NMR (300 MHz) spectrum of H(DMSO)2[1] in
CD3CN at room temperature (* = residual protonated solvent).
[HDMF]þ (pKa =-1.2 ( 0.519). A plausible rationale for
this inconsistency has been proposed previously by consider-
ing that the positive charge is better delocalized through
resonance stabilization in monosolvated protons when com-
pared to disolvated protons.20 The significant deshielding of
the acidic proton is consistent with that observed for acids of
other weakly coordinating anions. For comparison, chemical
shifts of the acidic proton in related compounds such as
(19) Grant, H. M.; McTigue, P.; Ward, D. G. Aust. J. Chem. 1983, 36,
2211.
(18) Reynolds, W. L.; Lampe, K. A. J. Inorg. Nucl. Chem. 1968, 30,
(20) Larson, J. W.; McMahon, T. B. J. Am. Chem. Soc. 1982, 104,
2860.
6255.

4494 Organometallics, Vol. 28, No. 15, 2009
Siu and Gates
and DMSO.23,24 The O O distance in the O-H-O moiety
3 3 3
of the [HL2]þ ion is generally accepted as being more indicative
of the strength of hydrogen bonding than the H-O distance,
which is difficult to determine accurately.23,25-29 The O
O
3 3 3
distance for the O-H-O moiety in H(DMSO)2[1] is 2.445(6)
A and in H(DMF)2[1] is 2.438(2) A, which are comparable to
˚
˚
those observed in related compounds {H(DMSO)2[trans-
25
RuCl4(DMSO)2] (2.423(5) A ), [H(DMSO)2]2[TeBr6] (2.448
˚
29
21
˚
˚
(4) A ), and [H(DMF)2]2[TeBr6] (2.44(2) A) }. Noteworthy,
is the fact that the distance between the oxygen atoms of the
two DMF molecules in H(DMF)2[1] [O(7) O(8)=2.438(2)
3 3 3
˚
A] is longer than partially chlorinated tris(o-phenylenedioxy)
phosphate, H(DMF)2[P(1,2-O2C6H4)(1,2-O2C6Cl4)2] (2.413
30
A). The above data suggest that there is strong hydrogen
˚
bonding present in the Brønsted acids of [1]-.
Figure 4. 1H NMR (300 MHz) spectrum of H(DMF)2[1] in
CD3CN at room temperature (* = residual protonated solvent).
Importantly, the metrical parameters for H(DMSO)2[1]
and H(DMF)2[1] reveal that there are weak interactions
between the cation and anion [1]-. Specifically, the closest
contact between [H(DMSO)2]þ and [1]- involves an oxygen
atom in the catecholate anion and an H atom of the methyl
H2(DMF)4[TeBr6] and H(DMF)2[OTf] are 16.8 and 16.9,
respectively,21 whereas those of the widely used [H(OEt)2]-
[B(3,5-(CF3)2C6H3)4] and [H(OEt)2][B(C6F5)4] are 11.1 and
15.5, respectively.7a,7b
˚
group of DMSO [O(6) H(19c)=2.421(1) A]. Likewise, the
3 3 3
The Brønsted acid H(DMF)2[1] exhibits excellent stabi-
lity. For example, a solid sample of H(DMF)2[1] that was
stored at room temperature in a glovebox showed no change
in its 1H or 31P NMR spectrum when monitored for over one
month. Remarkably, neither the 1H nor the 31P NMR
spectra of a solution of H(DMF)2[1] in CD3CN show any
change when monitored for one month. In contrast, the 31P
NMR spectrum of a solution of H(DMSO)2[1] in CD3CN
shows evidence of decomposition after several hours.
2. X-ray Crystallography. Details of the solution and
refinement for H(DMSO)2[1] and H(DMF)2[1] are given in
Table 1 and in the Experimental Section. The phosphorus
atom of anion [1]- in each compound shows very minor
deviation from perfect octahedral geometry. The P-O bond
closest contact between [H(DMF)2]þ and [1]- involves a
methyl group of DMF and an oxygen atom of [1]- [O
˚
(3) H(20c)=2.375(1) A]. In both cases, the closest ion-
pair distances are within the sum of van der Waals radii for
3 3 3
˚
oxygen and hydrogen [rvdw=2.72 A], consistent with weak
cation-anion interactions.31
3. Placement of [1]- on an Infrared Scale for Weakly Basic
Anions. Given our interest in the potential use of [1]- as a
weakly coordinating anion, we are interested in comparing
the coordinating ability [1]- with other anions. A convenient
scale of coordinating ability in solution has been proposed
that involves measuring the N-H stretching frequency for
ammonium salts of different anions.32 In an effort to place
[1]- on this scale, we synthesized and characterized the
trioctylammonium salt of [1]-. Analysis of a CCl4 solution
of Oct3NH[1] by infrared spectroscopy following the litera-
ture protocol revealed a N-H stretching frequency of 3129
cm-1. Interestingly, this value is comparable to Oct3NH
˚
˚
lengths in HL2[1] [av: 1.711(3) A, L=DMF; 1.716(3) A, L=
DMSO] are longer than those typically observed for P-O
single bonds in triarylphosphates [1.59(1) A] and are
22
˚
similar to those found in the ammonium salt Et3NH[1]
[av: 1.715(6)].12
[BF4] [νN-H=3133 cm-1 32 3129 cm-1 (our data)], suggest-
,
Consistent with the 1H NMR spectroscopic data, the
molecular structures of the Brønsted acids of [1]- revealed
that their cationic components consist of a single proton
coordinated through the oxygen atom of two ligand mole-
cules. In each case the acidic hydrogen atom, H(1), was
located in the difference map and was refined isotropically.
The H-O bond lengths in the [H(DMSO)2]þ cation differ
h
ing that [1]- has a similar basicity to [BF4]-. For comparison,
the most likely candidates for the title of “weakest coordi-
nating anion”, [B(C6F5)4]- and [CMeB11F11]-, have N-H
stretching frequencies of 3233 and 3219 cm-1, respectively.32
In contrast, the chloride anion is the most basic of those
previously measured, and Oct3NHCl possesses an N-H
stretching frequency of 2330 cm-1 32
.
˚
considerably [O-H=1.00(3) and 1.45(3) A], which is consis-
Application of HL2[1] in Metal-Carbon Bond Protonolysis.
The results from the previous section suggest that the
coordinating ability of tris(o-phenylenedioxy)phosphate an-
ion [1]- should be comparable to tetrafluoroborate.
Although more coordinating than perfluoroarylborate
and carborane anions, the relative ease of synthesis of
tent with that observed in related compounds: [H(DMSO)2]2-
[TeCl6], H(DMSO)2[7,8-C2B9H12], and H(DMSO)2[trans-
23
˚
RuCl4(DMSO)2] [O-H=0.9(1), and 1.5(1) A; 0.95(4) and
1.45(4) A; 1.12(6) and 1.30(6) A, respectively]. Similarly,
24
25
˚
˚
the [H(DMF)2]þ cation is also bound asymmetrically [O-H=
1.13(4) and 1.31(4) A]. Asymmetric hydrogen bonding is quite
common for protons bound by oxygen donors such as DMF
˚
(26) Cartwright, P. S.; Gillard, R. D.; Sillanpaa, E. R. J.; Valkonen, J.
Polyhedron 1988, 7, 2143.
(27) Emsley, J. Chem. Soc. Rev. 1980, 9, 91.
(28) Keefer, L. K.; Hrabie, J. A.; Ohannesian, L.; Flippen-Anderson,
J. L.; George, C. J. Am. Chem. Soc. 1988, 110, 3701.
(29) Rudd, M. D.; Kokke, G.; Lindeman, S. V. Acta Crystallogr.,
Sect. E: Struct. Rep. Online 2008, 64, O1161.
(21) Behmel, P.; Jones, P. G.; Sheldrick, G. M.; Ziegler, M. J. Mol.
Struct. 1980, 69, 41.
(22) Lide, D. R. CRC Handbook of Chemistry and Physics, 88th ed.;
CRC Press/Taylor and Francis: Boca Raton, FL, 2008.
€
(23) Pietkainen, J.; Maaninen, A.; Laitinen, R. S.; Oilunkaniemi, R.;
Valkonen, J. Polyhedron 2002, 21, 1089.
(24) Buchanan, J.; Hamilton, E. J. M.; Reed, D.; Welch, A. J. Dalton
(30) Krill, J.; Shevchenko, I. V.; Fischer, A.; Jones, P. G.; Schmutzler,
R. Chem. Ber. 1997, 130, 1479.
Trans. 1990, 677.
(31) Bondi, A. J. Phys. Chem. 1964, 68, 441.
(32) Stoyanov, E. S.; Kim, K. C.; Reed, C. A. J. Am. Chem. Soc. 2006,
128, 8500.
(25) Jaswal, J. S.; Rettig, S. J.; James, B. R. Can. J. Chem. 1990, 68,
1808.

Article
Organometallics, Vol. 28, No. 15, 2009 4495
Table 1. X-ray Crystallographic Data of H(DMSO)2[1], H(DMF)2[1], [(dppe)Pd(NCMe)Me][Λ-1], [(dppe)Pd(NCMe)Me][Δ-1], and
[(dppe)Pd(NCMe)2][1]2
[(dppe)Pd(NCMe)Me]-
[Λ-1] CH3CN
[(dppe)Pd(NCMe)Me]-
[Δ-1] CH3CN
[(dppe)Pd(NCMe)2]
[1]2 2CH3CN
H(DMSO)2[1]
22H25O8PS2
512.51
monoclinic
P21/n
H(DMF)2[1]
3
3
3
formula
fw
C
C24H27N2O8P
502.45
monoclinic
P21/n
C49H45N2O6P3Pd
957.18
monoclinic
P21
C49H45N2O6P3Pd
957.18
monoclinic
P21
C70H60N4O12P4Pd
1379.50
triclinic
P1
cryst syst
space group
color
colorless
12.767(3)
13.932(3)
13.625(3)
90
108.507(7)
90
2298.2(9)
173(2)
4
colorless
11.5961(9)
14.877(1)
13.831(1)
90
97.807(4)
90
2364.0(3)
173(2)
colorless
10.036(1)
17.318(2)
13.035(2)
90
95.200(5)
90
2256.2(5)
173(2)
colorless
10.030(2)
17.331(3)
13.073(3)
90
95.079(7)
90
2263.6(8)
173(2)
yellow
˚
a (A)
12.173(1)
15.673(2)
18.048(2)
81.711(5)
83.998(5)
68.021(5)
3154.8(6)
173(2)
˚
b (A)
˚
c (A)
R (deg)
β (deg)
γ (deg)
3
˚
V (A )
T (K)
Z
4
0.169
2
0.569
2
0.567
2
0.463
μ(Mo KR) (mm-1
)
0.349
1.1 ꢀ 0.7 ꢀ 0.5
cryst size (mm3)
0.5 ꢀ 0.3 ꢀ 0.2
0.9 ꢀ 0.8 ꢀ 0.3
0.8 ꢀ 0.6 ꢀ 0.5
0.40 ꢀ 0.35 ꢀ 0.15
Dcalcd (Mg m-3
2θ(max) (deg)
no. of reflns
)
1.481
55.8
1.406
55.88
1.409
56.0
1.404
55.82
1.452
56.7
39 445
5373
0.0319
14.37
0.0324
0.0836
1.019
38 168
5664
0.0493
17.48
0.0423
0.1131
1.020
19 836
9813
0.0205
17.75
0.0245
0.0621
1.042
37 561
10 816
0.0216
19.56
0.0216
0.0518
1.032
67 930
15 158
0.0476
18.40
0.0375
0.0816
1.004
no. of unique data
R(int)
refln/param ratio
R1 [I > 2σ(I)]a
wR2 [all data]b
GOF
P
P
P
P
a R1 =
Fo| - |Fc
/
|Fo|. b wR2(F2[all data]) = { [w(F2o - Fc2)2]/ [w(F2o)2]}1/2
.
H(DMSO)2[1] and H(DMF)2[1] compared to protic salts of
fluoroarylborate or carboranes makes them attractive as
catalyst activators where a moderately coordinating anion
can be tolerated. Moreover, they represent convenient pro-
tonating agents because they are isolable in solid form and
may be readily weighed.33 Protic acids of weakly coordinat-
ing anions are of importance for the protonolysis of metal-
alkyls to generate active catalysts. Readily available anhy-
drous Brønsted acids, such as HOSO2CF3, HOSO2F, HBF4/
Et2O, and HF SbF5, can be effective in metal-alkyl bond
3
activation; however, they are available only in solution or in
liquid form. Weighable solid Brønsted acids of moderate
molecular weight, such as H(DMSO)2[1] and H(DMF)2[1],
are less common; however, they are attractive for catalytic
applications since, due the small amount of catalyst typically
used, they enable more precise control of stoichiometry. In
this section, the activation of palladium(II)-methyl bonds
using H(DMF)2[1] will be explored.
Figure 5. (a) 31P NMR (162 MHz) spectrum of (dppe)PdMe2 in
CD3CN at room temperature. (b) 31P{1H} NMR (121 MHz)
spectrum of [(dppe)Pd(NCMe)Me][1] in CD3CN at room tem-
perature. (c) 31P NMR (162 MHz) spectrum of [(dppe)Pd
(NCMe)2][1]2 in CH3CN at room temperature.
It is known that the reaction of (P∧P)PdMe2 (where P∧P is a
bidentate ligand) with H(OEt2)2[B(3,5-(CF3)2C6H3)4] affords
[(P∧P)Pd(solvent)Me][B(3,5-(CF3)2C6H3)4],34,35 an active cat-
alyst for alternating polymerization of carbon monoxide and
ethylene.36-38 Consequently, we investigated the reaction of
(dppe)PdMe2 (dppe=1,2-bis(diphenylphosphino)ethane) with
H(DMF)2[1] in Et2O/CH3CN solution as a starting point to
test the effectiveness of acids of [1]- to protonate metal-alkyl
moieties. We chose to study the use of H(DMF)2[1] rather than
H(DMSO)2[1] due to the greater stability of the former at
room temperature. Cooling the reaction mixture to -30 °C
resulted in the precipitation of a colorless solid. The 31P NMR
spectrum of a CD3CN solution of the powder is shown in
Figure 5 and is consistent with the successful formation of
[(dppe)Pd(NCMe)Me][1]. Importantly, the spectrum reveals
two inequivalent coupled phosphine moieties [δ=62.5, 40.7;
2JPP=28 Hz] and a singlet resonance assigned to the anion [1]-
[δ=-82.0]. For comparison, similar resonances are observed
for the phosphine moieties in [(dppe)Pd(NCMe)Me][OTf] [δ=
(33) The need for weighable solid protonating agents is discussed in
the following paper: Stasko, D.; Hoffmann, S. P.; Kim, K. C.; Fackler,
N. L. P.; Larsen, A. S.; Drovetskaya, T.; Tham, F. S.; Reed, C. A.;
Rickard, C. E. F.; Boyd, P. D. W.; Stoyanov, E. S. J. Am. Chem. Soc.
2002, 124, 13869.
(34) Ledford, J.; Shultz, C. S.; Gates, D. P.; White, P. S.; DeSimone,
J. M.; Brookhart, M. Organometallics 2001, 20, 5266.
(35) Shultz, C. S.; Ledford, J.; DeSimone, J. M.; Brookhart, M. J.
Am. Chem. Soc. 2000, 122, 6351.
2
60.4, 35.2; JPP = 27 Hz]39 and [(dppe)Pd(NCMe)Me][PF6]
(36) Bianchini, C.; Meli, A.; Oberhauser, W.; Claver, C.; Suarez, E. J.
G. Eur J. Inorg. Chem. 2007, 2702.
(37) Drent, E.; Budzelaar, P. H. M. Chem. Rev. 1996, 96, 663.
(38) Drent, E.; van Broekhoven, J. A. M.; Doyle, M. J. J. Organomet.
Chem. 1991, 417, 235.
(39) Dekker, G.; Elsevier, C. J.; Vrieze, K.; van Leeuwen, P. W. N. M.
Organometallics 1992, 11, 1598.

4496 Organometallics, Vol. 28, No. 15, 2009
Siu and Gates
Figure 6. Molecular structures of [(dppe)Pd(NCMe)Me][Λ-1] and [(dppe)Pd(NCMe)Me][Δ-1]. Ellipsoids are drawn at the 50%
probability level. All hydrogen atoms are omitted for clarity, except for H(28) for [(dppe)Pd(NCMe)Me][Λ-1] and H(22) for [(dppe)Pd
˚
(NCMe)Me][Δ-1]. In both cases, solvents of crystallization (CH3CN) are also omitted for clarity. Selected bond lengths (A) and angles
(deg): [(dppe)Pd(NCMe)Me][Λ-1]: O(1)-P(1)=1.705(2); O(2)-P(1)=1.703(2); O(3)-P(1)=1.712(2); O(4)-P(1)=1.708(2); O(5)-
P(1)=1.712(2); O(6)-P(1)=1.707(2); P(2)-Pd(1)=2.3368(6); P(3)-Pd(1)=2.2022(6); N(1)-Pd(1)=2.063(2); C(45)-Pd(1)=2.084(2);
O(6)-H(28)=2.551(2); O(1)-P(1)-O(3)=88.60(9); O(1)-P(1)-O(5)=88.68(8); O(1)-P(1)-O(6)=92.10(8); O(2)-P(1)-O(1)=
91.28(8); O(2)-P(1)-O(3)=92.01(9); O(2)-P(1)-O(4)=88.54(8); O(2)-P(1)-O(6)=88.23(8); O(4)-P(1)-O(3)=90.74(8); O(4)-
P(1)-O(5)=91.51(8); O(5)-P(1)-O(3)=88.59(9); O(6)-P(1)-O(4)=88.56(8); O(6)-P(1)-O(5)=91.17(8); N(1)-Pd(1)-C(45)=
89.17(9); C(45)-Pd(1)-P(3)=87.26(7); N(1)-Pd(1)-P(2)=96.76(6); P(3)-Pd(1)-P(2)=86.73(2); [(dppe)Pd(NCMe)Me][Δ-1]: O(1)-
P(1)=1.706(1); O(2)-P(1)=1.708(1); O(3)-P(1)=1.716(1); O(4)-P(1)=1.711(1); O(5)-P(1)=1.710(1); O(6)-P(1)=1.714(2); P(2)-
Pd(1)=2.3381(6); P(3)-Pd(1)=2.2076(6); N(1)-Pd(1)=2.069(2); C(45)-Pd(1)=2.087(2); O(4)-H(22)=2.550(1); O(1)-P(1)-O(2)=
91.06(7); O(1)-P(1)-O(4)=88.38(7); O(1)-P(1)-O(5)=88.80(6); O(1)-P(1)-O(6)=92.08(7); O(2)-P(1)-O(3)=88.92(7); O(2)-P-
(1)-O(4)=92.25(7); O(2)-P(1)-O(6)=88.38(7); O(4)-P(1)-O(3)=90.99(7); O(5)-P(1)-O(3)=91.23(7); O(5)-P(1)-O(4)=88.50-
(7); O(5)-P(1)-O(6)=90.87(7); O(6)-P(1)-O(3)=88.56(7); N(1)-Pd(1)-C(45)=89.36(7); C(45)-Pd(1)-P(3)=87.31(6); N(1)-Pd-
(1)-P(2)=96.52(5); P(3)-Pd(1)-P(2)=86.75(2).
[δ=61.2, 39.5; 2JPP=27 Hz].40 Further analysis of the product
by 1H and 13C NMR spectroscopy provided further evidence
for the formulation of the product as [(dppe)Pd(NCMe)Me][1].
was consistent with the quantitative formation of [(dppe)Pd
(NCMe)2][1]2 [δ = 76.5 (s), -82.1 (s), respectively] (see
Figure 5). Upon standing, a pale yellow solid precipitated
from the reaction solution, and this solid was separated,
washed, and dried. Analyses of a DMSO-d6 solution of the
solid product by 31P, 1H, and 13C NMR spectroscopy were
consistent with the dication salt [(dppe)Pd(NCMe)2][1]2. For
comparison, we treated (dppe)PdMe2 with hydrogen chlor-
ide in acetonitrile solution, which afforded (dppe)PdCl2
rather than [(dppe)Pd(NCMe)2]Cl2
We were also interested in whether or not H(DMF)2[1]
could doubly activate (dppe)PdMe2 and whether or not the
dication [(dppe)Pd(NCMe)2]2þ would be stable in the pre-
sence of [1]-. Complexes containing the [(dppe)Pd
(solvent)2]2þ are effective for numerous catalytic transfor-
mations.41 A solid mixture of (dppe)PdMe2 and H(DMF)2[1]
(2 equiv) was dissolved in acetonitrile, and an immediate
color change to yellow was observed. After the reaction
mixture was stirred for a total of 3 h, the 31P NMR spectrum
The molecular structures of [(dppe)Pd(NCMe)Me][1] and
[(dppe)Pd(NCMe)2][1]2 determined using X-ray crystallo-
graphy (Figures 6 and 7, respectively) confirmed the for-
mulations proposed from NMR spectroscopy. Details of the
solution and refinement are provided in Table 1 and in the
Experimental Section. The metrical parameters within the
anion [1]- in each molecular structure are similar to those
found in the HLþ2 salts discussed above and will not be
discussed further. Noteworthy is the fact that [(dppe)Pd
(NCMe)Me][1] crystallizes in a chiral space group, P21.
Remarkably, the analysis of two different crystals revealed
that the Λ- and Δ-isomers of [1]- are resolved in the presence
of [(dppe)Pd(NCMe)Me]þ. Careful comparison of the mo-
lecular structures of [(dppe)Pd(NCMe)Me][Λ-1] with
[(dppe)Pd(NCMe)Me][Δ-1] reveals an asymmetrical twist
(40) Bianchini, C.; Lee, H. M.; Meli, A.; Oberhauser, W.; Peruzzini,
M.; Vizza, F. Organometallics 2002, 21, 16.
(41) The dicationic [(dppe)Pd(solvent)2]2þ has been employed as a
catalyst for the following reactions: polymerization of norbornene:
(a) Abu-Surrah, A. S.; Lappalainen, K.; Kettunen, M.; Repo, T.;
€
Leskela, M.; Hodali, H. A.; Rieger, B. Macromol. Chem. Phys. 2001,
202, 599. (b) Abu-Surrah, A. S.; Lappalainen, K.; Repo, T.; Klinga, M.;
€
Leskela, M.; Hodali, H. A. Polyhedron 2000, 19, 1601. Hydrosulfination of
propene: (c) Herwig, J.; Keim, W. Inorg. Chim. Acta 1994, 222, 381.
(d) Keim, W.; Herwig, J. Chem. Commun. 1993, 1592. Hydrogenation of
olefins: (e) Davies, J. A.; Hartley, F. R.; Murray, S. G. Dalton Trans. 1980,
2246. (f) Davies, J. A.; Hartley, F. R.; Murray, S. G.; Marshall, G. J. Mol.
Catal. A: Chem. 1981, 10, 171. 1,4-Addition of aryl boronic acids to R,β-
unsaturated carbonyl compounds: (g) Nishikata, T.; Yamamoto, Y.; Miyaura,
N. Angew. Chem., Int. Ed. 2003, 42, 2768.

Article
Organometallics, Vol. 28, No. 15, 2009 4497
Figure 7. Molecular structure of [(dppe)Pd(NCMe)2][1]2. Ellipsoids are drawn at the 50% probability level. All hydrogen atoms are
omitted for clarity, except for H(28a), H(28b), and H(28c). Solvents of crystallization (2 ꢀ CH3CN) are also omitted for clarity. Selected
˚
bond lengths (A) and angles (deg): O(1)-P(3)=1.708(2); O(2)-P(3)=1.709(2); O(3)-P(3)=1.715(2); O(4)-P(3)=1.708(2); O(5)-
P(3)=1.720(2); O(6)-P(3)=1.723(2); O(7)-P(4)=1.711(2); O(8)-P(4)=1.713(2); O(9)-P(4)=1.703(2); O(10)-P(4)=1.717(2); O
(11)-P(4)=1.717(2); O(12)-P(4)=1.711(2); P(1)-Pd(1)=2.2492(6); P(2)-Pd(1)=2.2370(7); N(1)-Pd(1)=2.080(2); N(2)-Pd(1)=
2.093(2); O(8)-H(28a)=2.318(2); O(1)-P(3)-O(2)=90.84(8); O(1)-P(3)-O(3)=88.38(8); O(1)-P(3)-O(5)=88.59(8); O(1)-P(3)-O
(6)=92.96(8); O(2)-P(3)-O(3)=93.60(8); O(2)-P(3)-O(6)=88.72(8); O(3)-P(3)-O(5)=87.46(8); O(4)-P(3)-O(2)=87.11(8); O
(4)-P(3)-O(3)=91.17(8); O(4)-P(3)-O(5)=93.46(8); O(4)-P(3)-O(6)=87.57(8); O(5)-P(3)-O(6)=90.24(7); O(7)-P(4)-O(11)=
88.65(8); O(7)-P(4)-O(8) = 90.85(8); O(8)-P(4)-O(10) = 87.43(8); O(9)-P(4)-O(10) = 91.02(8); O(9)-P(4)-O(11) = 88.16(8);
O(9)-P(4)-O(7)=88.04(8); O(9)-P(4)-O(8)=93.11(9); O(11)-P(4)-O(10)=93.09(8); O(12)-P(4)-O(10)=88.46(8); O(12)-P(4)-
O(11)=90.47(8); O(12)-P(4)-O(7)=92.53(9); O(12)-P(4)-O(8)=88.26(8); N(1)-Pd(1)-N(2)=87.38(8); N(2)-Pd(1)-P(2)=93.50-
(6); N(1)-Pd(1)-P(1)=93.74(6); P(2)-Pd(1)-P(1)=85.09(2).
conformation of the palladacycle, which results in the oppo-
site enantiomer for the cation in each structure. Such twisting
is commonly observed for square-planar palladium(II) com-
pounds containing the dppe ligand.42 The molecular struc-
ture of [(dppe)Pd(NCMe)2][1]2 shows similar behavior;
however, both enantiomers of the cation and anion are
present and are related by symmetry in the P1 space group.43
The metrical parameters within the [(dppe)Pd(NCMe)
Me]þ and [(dppe)Pd(NCMe)2]2þ cations are comparable to
those observed in analogous species. As represented by a
dashed line in Figure 6, the closest ion contact in [(dppe)Pd
(NCMe)Me][Λ-1] and [(dppe)Pd(NCMe)Me][Δ-1] is be-
tween a phenyl-H of the dppe ligand and an oxygen atom
slightly less than the sum of the van der Waals radii for
31
oxygen and hydrogen [rvdw = 2.72 A] and suggest weak
interactions between the cation and anion.
˚
Summary
The preparation of two novel Brønsted acids containing the
tris(o-phenylenedioxy)phosphate anion [1]-, H(DMF)2[1]
and H(DMSO)2[1], was accomplished following a straightfor-
ward procedure from PCl5, catechol, and the appropriate
solvent (DMF or DMSO). Both compounds were character-
ized spectroscopically and through X-ray crystallographic
analysis. Their high acidities were suggested by the downfield
˚
from the catecholate anion [ca. 2.55 A]. In contrast, Figure 7
shows that the closest contact in [(dppe)Pd(NCMe)2][1]2 is
1
shifts of the acidic proton in their H NMR spectra. The
basicity of anion [1]- was determined to be similar to the
classical weakly coordinating anion [BF4]-, based on identical
N-H stretching frequency for the Oct3NH[1], and to that
observed for Oct3NH[BF4]. H(DMF)2[1] was shown to be
effective in the stoichiometric activation of the metal-alkyl
bonds of (dppe)PdMe2 to afford either [(dppe)Pd(NCMe)Me]
[1] (1:1 ratio) or [(dppe)Pd(NCMe)2[1] (1:2 ratio), both of which
were structurally characterized. Future work is underway to
determine the effectiveness of H(DMF)2[1] in the protonolysis
of other metal-alkyls to generate catalytically active species.
The potential resolution of [1]-, or its derivatives, to afford
compounds containing enantiomerically pure anions may lead
to exciting possibilities in enantioselective synthesis.
between an acetonitrile hydrogen and an oxygen atom of the
[1]- [2.318(2) A]. In both compounds, these approaches are
˚
(42) (a) Batsanov, A. S.; Howard, J. A. K.; Robertson, G. S.; Kilner,
M. Acta Crystallogr. Sect. E: Struct. Rep. Online 2001, 57, m301.
(b) Oberhauser, W.; Bachmann, C.; Stampfl, T.; Haid, R.; Bruggeller, P.
Polyhedron 1997, 16, 2827. (c) Capdevila, M.; Clegg, W.; Gonzalez-Duarte,
P.; Harris, B.; Mira, I.; Sola, J.; Taylor, I. C. Dalton Trans 1992, 2817.
(d) Bachechi, F.; Lehmann, R.; Venanzi, L. M. J. Crystallogr. Spectrosc.
Res. 1988, 18, 721.
(43) Theabsolute configuration ofanion [1]- components of 5(Λ) and 5
(Δ) were determined on the basis of their Flack values. Their final Flack
values were refined to be 0.006(12) for 5(Λ) and -0.012(10) for 5(Δ).
Flack, H. D. Acta Crystallogr., Sect. A: Found. Crystallogr. 1983, 39, 876.

4498 Organometallics, Vol. 28, No. 15, 2009
Siu and Gates
Experimental Section
was added dropwise to the stirred suspension until all the solids
dissolved (ca. 10 drops). The solution was stirred at room
temperature for 15 min, after which it was cooled -30 °C to
afford a colorless precipitate. The supernatant liquid was
decanted from the precipitate and the solid was dried in vacuo.
Yield = 72 mg (85%). Crystals suitable for X-ray diffraction
were grown by slow evaporation of a solution of [(dppe)Pd
(NCMe)Me][1] in Et2O/CH3CN.
General Procedures. All manipulations were performed using
standard Schlenk or glovebox techniques under nitrogen at-
mosphere. Toluene and Et2O were deoxygenated with nitrogen
and dried by passing through a column containing activated
alumina. CD3CN, CD2Cl2, and DMSO-d6 were purchased
from Cambridge Isotope Laboratories Inc. in 1 g sealed
31P{1H} NMR (121 MHz, CD3CN): δ 62.5 (d, 2JPP=28 Hz,
dppe), 40.7 (d, 2JPP=28 Hz, dppe), -82.0 (s, anion). 1H NMR
(300 MHz, CD3CN): δ 7.69-7.52 (m, 20H, Ar-H of dppe),
6.65-6.58 (m, 12H, Ar-H of anion), 2.73-2.55, 2.41-2.24 (m,
4H, CH2CH2), 1.96 (s, 3H, Pd-NCCH3), 0.52 (dd, 3JHP=6 Hz,
3JHP=3 Hz, 3H, Pd-CH3). 13C{1H} NMR (101 MHz, CD2Cl2):
146.3 (d, JCP=5 Hz), 133.8 (d, JCP=12 Hz), 133.2 (d, JCP=14
Hz), 132.8 (d, JCP=3 Hz), 132.3 (s), 130.1 (d, JCP=9 Hz), 130.4
(d, JCP=34 Hz), 130.0 (d, JCP=12 Hz), 127.9 (d, JCP=57 Hz),
123.7 (s), 119.4 (s), 109.9 (d, JCP=18 Hz), 31.3 (dd, JCP=35 Hz,
˚
ampules and dried over 3 A molecular sieves before use.
Trioctylamine and HPLC grade carbon tetrachloride were
˚
purchased from Aldrich and dried over 3 A molecular sieves
˚
before use. DMSO and DMF were dried over 3 A molecular
sieves and distilled before use. Acetonitrile was distilled from
CaH2 before use. PCl5 (Aldrich) was sublimed prior to use.
Anhydrous HCl (BOC Gases) and catechol (Aldrich) were
used as received. Mixture 2/314 and [(dppe)Pd(CH3)2]44 were
prepared following literature procedures. 1H, 13C{1H}, 31P,
and 31P{1H} NMR spectra were recorded at room temperature
on Bruker Avance 300 or 400 MHz spectrometers. 85% H3PO4
was used as an external standard (δ 0.0) for 31P and 31P{1H}
JCP=21 Hz), 24.2 (dd, JCP=28 Hz, JCP=8.1 Hz), 8.6 (d, JCP=88
Hz), 3.0 (s).
1
NMR spectra. H NMR spectra were referenced to residual
[(dppe)Pd(NCMe)2][1]2. To a solid mixture of (dppe)PdMe2
(45 mg, 0.084 mmol) and H(DMF)2[1] (85 mg, 0.17 mmol) was
added CH3CN (2 mL). The resulting cloudy yellow mixture was
stirred for 3 h, and the supernatant was decanted to afford a
yellow solid. The solid was washed with cold CH3CN (3 ꢀ 2 mL)
and was dried in vacuo. Yield=66 mg (61%). Crystals, suitable
for X-ray diffraction, were obtained after a concentrated solu-
tion of [(dppe)Pd(NCCH3)2][1]2 in CH3CN was left in the
glovebox overnight.
protonated solvent, and 13C{1H} NMR spectra were refer-
enced to the deuterated solvent. Elemental analyses were
performed in the University of British Columbia Chemistry
Microanalysis Facility. Infrared spectra were recorded on a
Thermo Nicolet Nexus 670 FT-IR spectrometer equipped with
an inlet attached to a nitrogen supply. The sample chamber was
purged with nitrogen until a constant concentration level of
moisture, and carbon dioxide was obtained for the back-
ground. IR spectra of 0.005-0.01 M solutions of trioctylam-
monium salts in carbon tetrachloride were obtained using a cell
with KBr windows and recorded in the 4000-500 cm-1 range
under a flow of nitrogen.
31P NMR (162 MHz, CH3CN): δ 76.5 (s, dppe), -82.1 (s,
1
anion). H NMR (400 MHz, CD3CN): δ 7.79-7.61 (m, 20H,
Ar-H on dppe), 6.64-6.58 (m, 24H, Ar-H on anion), 2.92-2.77
(m, 4H, CH2CH2 on dppe), 1.96 (s, 6H, PdNCCH3). 13C{1H}
NMR (101 MHz, DMSO-d6): 145.5 (d, JCP=4 Hz), 133.5 (d,
H(DMSO)2[1]. To a solid mixture of 2 and 3 (1.0 g, 2.8 mmol)
was added DMSO (5.0 g, 64 mmol), and the resultant pale
purple solution was stirred for 20 min. Subsequently, toluene
(90 mL) was added to afford a colorless precipitate, which was
collected by filtration. The solid was redissolved in CH3CN
(10 mL), reprecipitated with toluene (90 mL), and collected by
filtration. The crude product was dried in vacuo. Yield=1.4 g
(98%). Crystals suitable for X-ray crystallography were ob-
tained from slow diffusion of toluene into a DMSO solution of
H(DMSO)2[1] (ca. 5 days).
J
(s), 118.0 (s), 108.9 (d, JCP=17 Hz), 26.9 (dd, JCP=39 Hz, JCP
CP=12 Hz), 129.7 (d, JCP=12 Hz), 125.3 (d, JCP=55 Hz), 118.6
=
8 Hz), 1.1 (s).
Reaction of (dppe)PdMe2 with HCl. Anhydrous HCl was
bubbled through a stirred solution of (dppe)PdMe2 in CH3CN
(10 mL) at 0 °C for a few minutes. The solvent was removed in
vacuo to afford a white solid. The 31P NMR spectrum of the
isolated solid was identical to that of an authentic sample of
(dppe)PdCl2 [δ=68.1 in CH3CN].45
[(C8H17)3NH][1]. Trioctylamine (1.7 g, 4.8 mmol) and a solid
mixture of 2 and 3 (1.0 g, 2.8 mmol) were dissolved in CH2Cl2
(5 mL). After 3 h, the solvent was removed in vacuo and the
resultant colorless oil was heated in vacuo at 140 °C. Subse-
quently, hexanes (15 mL) was added to the colorless oil, and this
mixture was ultrasonicated for 15 min to afford a white solid.
[(C8H17)3NH][1] was isolated by filtered, washed with hexanes
(10 mL), and dried in vacuo. Yield=1.3 g (63%).
31P NMR (162 MHz, CH3CN): δ -80.5. 1H NMR (300 MHz,
CD3CN): δ 13.3 (s, 1H, H-DMSO2), 6.65 (s, 12H, Ar-H), 2.83 (s,
12H, CH3). 13C{1H} NMR (101 MHz, DMSO-d6): 145.4 (d,
J
CP=4 Hz), 118.6 (s), 108.9 (d, JCP=17 Hz), 40.4 (s). Anal. Calcd
for C22H25O8PS2: C, 51.55; H, 4.92. Found: C, 51.68; H, 4.93.
H(DMF)2[1]. To a solid mixture of 2 and 3 (1.0 g, 2.8 mmol)
was added DMF (5.0 g, 68 mmol), and the resultant white
suspension was stirred for 60 min. Subsequently, toluene
(40 mL) was added and the colorless precipitate was collected
by filtration. The solid was redissolved in CH3CN (10 mL),
reprecipitated with toluene (90 mL), and collected by filtration.
The crude product was dried in vacuo. Yield=1.1 g (78%). Crystals
suitable for X-ray diffraction were obtained from slow diffusion of
toluene into a solution of H(DMF)2[1] in DMF.
31P NMR (121 MHz, CDCl3): δ -83.8. 1H NMR (300 MHz,
CDCl3): δ 8.61 (br s, 1H, H-N), 6.70 (s, 12H, Ar-H), 3.20-3.12
(m, 6H, N-CH2), 1.74-1.63 (m, 6H, NCH2-CH2), 1.26-1.17 (m,
30H, NC2H4-C5H10), 0.87 (t, 3JHH=7 Hz, 9H, CH3). 13C{1H}
NMR (100 MHz, CDCl3): 145.0 (d, JCP=4 Hz), 119.5 (s), 109.7
(d, JCP=19 Hz), 53.4 (s), 31.5 (s), 28.8 (s), 28.7 (s), 26.5 (s), 23.1
(s), 22.4 (s), 14.0 (s). Anal. Calcd for C42H64NO6P: C, 71.06; H,
9.09; N, 1.97. Found: C, 71.12; H, 9.21; N, 2.12.
X-ray Crystallography. All single crystals were immersed in
oil and were mounted on a glass fiber. Data were collected on a
Bruker X8 APEX II diffractometer with graphite-monochro-
mated Mo KR radiation. All structures were solved by direct
methods and subsequent Fourier difference techniques. Unless
noted, all non-hydrogen atoms were refined anisotropically,
whereas all hydrogen atoms were included in calculated posi-
tions but not refined. All data sets were corrected for Lorentz
31P NMR (162 MHz, CH3CN): δ -80.0. 1H NMR (300 MHz,
CD3CN): δ 15.3 (br s, 1H, H-DMF2), 8.06 (s, 2H, HCdO),
6.69-6.65 (m, 12H, Ar-H), 3.07 (s, 6H, CH3), 2.95 (s, 6H, CH3).
13C{1H} NMR (101 MHz, CD3CN): 165.5 (s), 146.6 (d, JCP=4
Hz), 120.3 (s), 110.4 (d, JCP =16 Hz), 39.3 (s), 33.8 (s). Anal.
Calcd for C24H27N2O8P: C, 57.37; H, 5.42; N, 5.58. Found: C,
57.52; H, 5.45; N, 5.64.
[(dppe)Pd(NCMe)Me][1]. To a solid mixture of [(dppe)
PdMe2] (50 mg, 0.093 mmol) and H(DMF)2[P(1,2-O2C6H4)3]
(47 mg, 0.094 mmol) was added Et2O (ca. 1 mL). Acetonitrile
(44) Spaniel, T.; Schmidt, H.; Wagner, C.; Merzweiler, K.; Steinborn,
D. Eur. J. Inorg. Chem. 2002, 2868.
(45) Lindsay, C. H.; Benner, L. S.; Balch, A. L. Inorg. Chem. 1980, 19,
3503.

Article
Organometallics, Vol. 28, No. 15, 2009 4499
and polarization effects. Calculations were performed using
PARST46,47 and SHELXL-97.48,49 All refinements were per-
formed using the SHELXTL49,50 crystallographic software
package from Bruker-AXS.
DMF bound to H(1). H(1) was located using the difference
map and refined isotropically. Crystal data and refinement
paramenters are listed in Table 1. Additional data are available
in the Supporting Information.
Compound H(DMSO)2[1] has two disordered molecules of
DMSO bound to H(1). H(1) was located using the difference
map and refined isotropically. Each of the disordered DMSO
molecules was modeled in two orientations. Their respective
populations were refined to the final occupancy of 0.926(2),
0.074(2), 0.8570(16), and 0.1430(16). Due to the low occupancy
values (0.074(2)) for C(19b) and C(20b), they were refined
isotropically. Compound H(DMF)2[1] has two molecules of
Acknowledgment. This work was supported by the
Natural Science and Engineering Research Council
(NSERC) of Canada, the Canada Foundation for Inno-
vation (CFI), and the British Columbia Knowledge De-
velopment Fund (BCKDF). P.W.S. is grateful for an
NSERC PGS D3 scholarship. We thank Joshua I. Bates
for determining the crystal structure of H(DMSO)2[1].
(46) Nardelli, M. Comput. Chem. 1983, 7, 95.
(47) Nardelli, M. J. Appl. Crystallogr. 1995, 28, 659.
(48) Sheldrick, G. M. SHELXL-97 (Release 97-2); University of
Supporting Information Available: CIF files giving supple-
mentary crystallographic data for the structures reported are
available free of charge via the Internet at http://pubs.acs.org.
These data can also be obtained free of charge from The
Cambridge Crystallographic Data Centre as CCDC-727172 to
CCDC-727176 via www.ccdc.cam.ac.uk/data_request/cif.
€
Gottingen: Germany, 1997.
(49) Sheldrick, G. M. Acta Crystallogr., Sect. A: Found. Crystallogr.
2008, 64, 112.
(50) Sheldrick, G. M. SHELXTL, 5.1 ed.; Bruker AXS Inc.: Madison,
WI, 1997.