Gold(I) and silver(I)/gold(I) complexes derived from C6Me 4(C≡CH)2-1,2

Article abstract of DOI:10.1021/om050418b

C₆Me₄(C≡CH)₂-1,2 [Ar(C≡CH)₂] reacts with PPN[Au(acac)₂] (acac = acetylacetonato, PPN = (Ph₃P)₂N) (2:1) or with [AuCl(SMe₂)] and NEt₃ (1:2:2) to give PPN[Au{C≡ CArC≡CH}₂] (1) or [Au₂{μ-Ar(C≡C) ₂})]_n (2), respectively. Dinuclear complexes of general formula [Au₂L₂{μ-Ar(C≡C)₂}] can be obtained by reacting 2 with the appropriate ligand L (1:2) [L = ^tBuNC (3), PMe₃ (4), PTo₃ (5, To = C₆H ₄Me-4)] or L₂ (1:1) (L₂ = Ph ₂P(CH₂)_nPPh₂, n = 4 (6), 6 (7)]. The analogous complexes [(AuNHEt₂)₂{μ-Ar(C≡C) ₂}] (8) and [{AuC(NH^tBu)(NEt₂)} ₂{μ-Ar(C≡C)₂}] (9) result from the reactions of Ar(C≡CH)₂ with PPN[AuCl₂] and NHEt₂ (1: 2:4) or 3 with an excess of NHEt₂, respectively, The reaction of 5 with AgClO₄ (2:1) gives the heteropentanuclear "AgAu ₄" complex [Ag{(AuPTo₃)₂{μ- Ar(C≡C)₂}}₂]ClO₄ (10). The X-ray crystal structures of 3, 7, 9·1/3CHCl₃, and 10·2CHCl ₃ have been determined.

Full text of DOI:10.1021/om050418b

4666
Organometallics 2005, 24, 4666-4675
Gold(I) and Silver(I)/Gold(I) Complexes Derived from
C6Me4(CtCH)2-1,2
Jose´ Vicente,† Mar´ıa-Teresa Chicote,*,† and Miguel M. Alvarez-Falco´n
Grupo de Quı´mica Organometa´lica, Departamento de Quı´mica Inorga´nica,
Universidad de Murcia, Apartado 4021, Murcia, 30071 Spain
Peter G. Jones*,‡
Institut fu¨r Anorganische und Analytische Chemie der Technischen Universita¨t,
Postfach 3329, 38023 Braunschweig, Germany
Received May 26, 2005
C6Me4(CtCH)2-1,2 [Ar(CtCH)2] reacts with PPN[Au(acac)2] (acac ) acetylacetonato, PPN
) (Ph3P)2N) (2:1) or with [AuCl(SMe2)] and NEt3 (1:2:2) to give PPN[Au{CtCArCtCH}2]
(1) or [Au2{µ-Ar(CtC)2})]n (2), respectively. Dinuclear complexes of general formula [Au2L2-
t
{µ-Ar(CtC)2}] can be obtained by reacting 2 with the appropriate ligand L (1:2) [L ) -
BuNC (3), PMe3 (4), PTo3 (5, To ) C6H4Me-4)] or L2 (1:1) (L2 ) Ph2P(CH2)nPPh2, n ) 4 (6),
6 (7)]. The analogous complexes [(AuNHEt2)2{µ-Ar(CtC)2}] (8) and [{AuC(NHtBu)(NEt2)}2-
{µ-Ar(CtC)2}] (9) result from the reactions of Ar(CtCH)2 with PPN[AuCl2] and NHEt2 (1:
2:4) or 3 with an excess of NHEt2, respectively. The reaction of 5 with AgClO4 (2:1) gives
the heteropentanuclear “AgAu4” complex [Ag{(AuPTo3)2{µ-Ar(CtC)2}}2]ClO4 (10). The X-ray
crystal structures of 3, 7, 9‚1/3CHCl3, and 10‚2CHCl3 have been determined.
Introduction
and displayed interesting photophysical properties.7 The
latter have been attributed in part8,9 to the short
intermolecular Au‚‚‚Au contacts that are present in
most of the structurally characterized luminescent gold-
(I) complexes.5,7,8,10 Puddephatt has recently reviewed
the synthesis and characterization of polymers, rings,
and oligomers containing gold(I) centers.11
On the basis of our previous experience on the
synthesis of alkynylgold(I) complexes12-16 by the “acac
method”,17 we have described some new arenediethyn-
ylgold(I) complexes of the types i and ii,18,19 R being C6-
Me4-1,4, C6H4-1,3, C6HMe3-2,4,6, and also PPN[Au{Ct
CC6H4CtCAuPPh3-3}2], (PPN)2[(AuX)2{µ-C6HR3-2,4,6-
(CtC)2}] (R ) H, X ) Cl; R ) Me, X ) Cl, SCN),
(PPN)3[Au{CtCC6H4CtCAuCl-3}2],18 and [{AuC(NEt2)-
2-
Metal complexes with bridging R(CtC)2 spacers
(-R- being various aromatic rings) have been shown
to display electrical conductivity and nonlinear optical
or liquid crystalline properties.1 Among the many arene-
diethynyl metal complexes described so far, there is no
ortho-disubstituted derivative of gold and few such
derivatives of other metals; thus, only three of them
have been structurally characterized by X-ray diffrac-
tion methods, namely, [C6H4(CtCSnMe3)2)-1,2],2 [C6H4-
{CtCPdCl(PEt3)2}2-1,2], and [C6H4{CtCPd(PEt3)2}2-
1,2]4.3 The known neutral arenediethynyl gold complexes
are of the types (i) [Au2{µ-R(CtC)2}]n,4,5 (ii) [(AuL)2-
{µ-R(CtC)2}] (L ) phosphine,5,6 isocyanide4,5), (iii)
[(Au2L2){µ-R(CtC)2}]n (L2 ) diphosphine,1,5 diisocya-
nide),4,5 (iv) [AuCl{{(µ-PP)Au{µ-R(CtC)2}Au}n(µ-PP)-
AuCl] (PP ) diphosphine),1 and (v) [{Au2{µ-R(Ct
C)2}}2(µ-PP)2}],6 derived from the dialkynes R(CtCH)2
[R ) C6H4-1,4, (C6H2Me2-2,5)-1,4 or (C6H3Me)-3,5].
Three of them were characterized by X-ray crystal-
lography,5,7 showing infinite chain or ribbon structures,
(8) Xiao, H.; Cheung, K. K.; Che, C. M. J. Chem. Soc., Dalton Trans.
1996, 3699.
(9) Tzeng, B.-C.; Lo, W.-C.; Che, C.-M.; Peng, S.-M. Chem. Commun.
1996, 181. Li, D.; Hong, X.; Che, C. M.; Lo, W. C.; Peng, S. M. J. Chem.
Soc., Dalton Trans. 1993, 2929. Che, C. M.; Yip, H. K.; Lo, W. C.; Peng,
S. M. Polyhedron 1994, 13, 887.
(10) Che, C. M.; Chao, H. Y.; Miskowski, V. M.; Li, Y. Q.; Cheung,
K. K. J. Am. Chem. Soc. 2001, 123, 4985.
(11) Puddephatt, R. J. Coord. Chem. Rev. 2001, 216, 313.
(12) Vicente, J.; Chicote, M. T.; Abrisqueta, M. D. J. Chem. Soc.,
Dalton Trans. 1995, 497.
† E-mail: mch@um.es; jvs1@um.es. Web: http://www.um.es/gqo.
‡ E-mail: p.jones@tu-bs.de.
(13) Vicente, J.; Chicote, M.-T.; Abrisqueta, M.-D.; Guerrero, R.;
Jones, P. G. Angew. Chem., Int. Ed. Engl. 1997, 36, 1203.
(14) Vicente, J.; Chicote, M. T.; Abrisqueta, M. D.; Jones, P. G.
Organometallics 2000, 19, 2629.
(1) Jia, G. C.; Puddephatt, R. J.; Scott, J. D.; Vittal, J. J. Organo-
metallics 1993, 12, 3565.
(2) Adiwidjaja, G.; Grouhi-Witte, G. J. Organomet. Chem. 1980, 188,
91.
(15) Vicente, J.; Chicote, M. T.; Abrisqueta, M. D.; Jones, P. G.
Organometallics 1997, 16, 5628.
(3) Onitsuka, K.; Yamamoto, S.; Takahashi, S. Angew. Chem., Int.
Ed. 1999, 38, 174.
(16) Vicente, J.; Chicote, M. T.; Abrisqueta, M. D.; Jones, P. G.;
Humphrey, M. G.; Cifuentes, M. P.; Samoc, M.; Luther-Davies, B.
Organometallics 2000, 19, 2968.
(4) Irwin, M. J.; Jia, G. C.; Payne, N. C.; Puddephatt, R. J.
Organometallics 1996, 15, 51.
(5) MacDonald, M. A.; Puddephatt, R. J.; Yap, G. P. A. Organome-
tallics 2000, 19, 2194.
(17) Vicente, J.; Chicote, M. T. Coord. Chem. Rev. 1999, 193-195,
1143.
(6) Irwin, M. J.; Rendina, L. M.; Vittal, J. J.; Puddephatt, R. J. J.
Chem. Soc., Chem. Commun. 1996, 1281.
(7) Irwin, M. J.; Vittal, J. J.; Puddephatt, R. J. Organometallics
1997, 16, 3541.
(18) Vicente, J.; Chicote, M. T.; Abrisqueta, M. D.; Alvarez-Falco´n,
M. M. J. Organomet. Chem. 2002, 663, 40.
(19) Vicente, J.; Chicote, M. T.; Alvarez-Falco´n, M. M.; Abrisqueta,
M. D.; Herna´ndez, F. J.; Jones, P. G. Inorg. Chim. Acta 2003, 347, 67.
10.1021/om050418b CCC: $30.25 © 2005 American Chemical Society
Publication on Web 08/12/2005

Gold(I) and Silver(I)/Gold(I) Complexes
Organometallics, Vol. 24, No. 19, 2005 4667
Ag,35 Au,36 and Hg37). Two or three η2-RCtCM′ ligands
per Ag(I) are generally involved in such interactions,
and only three complexes with four such alkynyl ligands
disposed around one Ag(I), none of them containing gold
as does our complex, have been structurally character-
ized.27,33 Taking into account the isolobal character of
H and AuPR3,38 our pentanuclear “Au4Ag” complex can
be considered as containing four C-(AuPR3)‚‚‚Ag “agos-
tic” interactions,39 which could be termed “metalagostic”
contacts (see Chart 1). Although Au‚‚‚Ag interactions
are not as common as the Au‚‚‚Au aurophilic interac-
tions, they have been observed previously.40,41
Chart 1
Experimental Section
(NHtBu)}2{CtCC6H4CtC-3}].20 Using the same method,
we have recently reported the synthesis and crystal
structure of the heteronuclear metallamacrocyclic tri-
angle PPN[{Au{Pt(PMe3)2}2}{µ-Ar(CtC)2}3]21 (Ar ) C6-
Me4-3,4,5,6) by reacting trans-[Pt(CtCArCtCH-2)2-
(PMe3)2] with PPN[Au(acac)2]. The growing interest in
the search for novel metallamacrocycles is associated
with their ability to mimic biological systems and their
relationship with supramolecular chemistry, intramo-
lecular self-assembly, molecular recognition, crystal
engineering, nanotechnology, and catalysis. The con-
cepts, principles, and strategies on which the develop-
ment of this chemistry is based have recently been
widely reviewed.22-24 Despite the connection of metal-
lamacrocyclic complexes with such varied and interest-
ing fields, the triangular architecture is surprisingly
scarce24 compared to the number of molecular polygons
described to date.23-25 Therefore, ortho-arenediethynyl
complexes could serve as building blocks to construct
molecular triangles selectively, or at least preferentially,
if the CtC-M-CtC group is linear, because the ligand
has the appropriate disposition [CtCM-(aryl cen-
troid)-MCtC angle ) 60°].
General Comments. IR spectroscopy, mass spectrometry
(FAB+/-), elemental analyses, conductance measurements in
acetone, and melting point determinations were carried out
as described elsewere.42 The molar conductivity of the neutral
complexes gave very low values (0-5 Ω-1 cm2 mol-1). The NMR
spectra were measured on Bruker Avance 200, 300, or 400
MHz spectrometers. Chemical shifts are referred to TMS (1H,
13C) or H3PO4 (31P). Unless otherwise stated the reactions were
carried out at room temperature without any precautions to
avoid oxygen or moisture. The syntheses of C6Me4(CtCH)2-
1,2,43 PPN[Au(acac)2],44 and [AuCl(SMe2)]45 were previously
reported. All other chemicals were obtained from commercial
sources and used as received. The solvents were distilled before
use.
(29) Yam, V. W. W.; Chong, S. H. F.; Wong, K. M. C.; Cheung, K. K.
Chem. Commun. 1999, 1013. Mihan, S.; Sunkel, K.; Beck, W. Chem.
Eur. J. 1999, 5, 745.
(30) Bruce, M. I.; Zaitseva, N. N.; Skelton, B. W.; Somers, N.; White,
A. H. Aust. J. Chem. 2003, 56, 509.
(31) Churchill, M. R.; DeBoer, B. G. Inorg. Chem. 1975, 14, 2630.
(32) Espinet, P.; Fornie´s, J.; Martinez, F.; Sotes, M.; Lalinde, E.;
Moreno, M. T.; Ruiz, A.; Welch, A. J. J. Organomet. Chem. 1991, 403,
253. Espinet, P.; Fornie´s, J.; Mart´ınez, F.; Toma´s, M.; Lalinde, E.;
Moreno, M. T.; Ruiz, A.; Welch, A. J. J. Chem. Soc., Dalton Trans.
1990, 791. Yam, V. W. W.; Hui, C. K.; Wong, K. M. C.; Zhu, N. Y.;
Cheung, K. K. Organometallics 2002, 21, 4326. Adams, C. J.; Raithby,
P. R. J. Organomet. Chem. 1999, 578, 178.
(33) Ara, I.; Berenguer, J. R.; Fornie´s, J.; Lalinde, E.; Moreno, M.
T. J. Organomet. Chem. 1996, 510, 63. Wong, W. Y.; Lu, G. L.; Choi,
K. H. J. Organomet. Chem. 2002, 659, 107.
(34) Abu-Salah, O. M.; Hussain, M. S.; Schlemper, E. O. J. Chem.
Soc., Chem. Commun. 1988, 212.
In this paper, we report the first ortho-arenediethynyl
gold(I) complexes including neutral and anionic species
and a cationic pentanuclear “Au4Ag” complex resulting
from the use of two molecules of [(AuPTo3)2{µ-Ar(Ct
C)2}] acting as ligands toward Ag(I). Related alkynyl-
metal complexes have been structurally characterized,
showing η2-(RCtCM′)-M interactions (see Chart 1; M
) Ag, M′ ) Ti,26,27 Ru,28 Re,29 Rh,30,31 Ir,30 Pt,32,33 Cu,34
(35) Al-Farhan, K. A.; Abu-Salah, O. M.; Mukhalalati, M.; Jaafar,
M. Acta Crystallogr., Sect. C 1995, 51, 1089. Rais, D.; Yau, J.; Mingos,
D. M. P.; Vilar, R.; White, A. J. P.; Williams, D. J. Angew. Chem., Int.
Ed. 2001, 40, 3464. Brasse, C.; Raithby, P. R.; Rennie, M. A.; Russell,
C. A.; Steiner, A.; Wright, D. S. Organometallics 1996, 15, 639.
(36) Mazar-Ul-Haque; Horne, W.; Abu-Salah, O. M. J. Crystallogr.
Spectrosc. Res. 1992, 22, 421. Hussain, M. S.; Mazar-Ul-Haque; Abu-
Salah, O. M. J. Cluster Sci. 1996, 7, 167.
(20) Vicente, J.; Chicote, M. T.; Abrisqueta, M. D.; Alvarez-Falco´n,
M. M.; Ram´ırez de Arellano, M. C.; Jones, P. G. Organometallics 2003,
22, 4327.
(21) Vicente, J.; Chicote, M. T.; AÄ lvarez-Falco´n, M. M.; Jones, P. G.
Chem. Commun. 2004, 2658.
(22) Schweiger, M.; Seidel, S. R.; Arif, A. M.; Stang, P. J. Inorg.
Chem. 2002, 41, 2556. Wu¨rthner, F.; You, C.-C.; Saha-Mo¨ller, C. R.
Chem. Soc. Rev. 2004, 33, 133.
(23) Stang, P. J. Chem. Eur. J. 1998, 4, 19. Severin, K. Coord. Chem.
Rev. 2003, 245, 3. Navarro, J. A. R.; Lippert, B. Coord. Chem. Rev.
1999, 185-186, 653. Leininger, S.; Olenyik, B.; Stang, P. J. Chem. Rev.
2000, 100, 853. Holliday, B. J.; Mirkin, C. A. Angew. Chem., Int. Ed.
2001, 40, 2022. Fujita, M. Chem. Soc. Rev. 1998, 27, 417. Bodwin, J.
J.; Cutland, A. D.; Malkani, R. G.; Pecoraro, V. L. Coord. Chem. Rev.
2001, 216-217, 489.
(24) Olenyuk, B.; Fechtenko¨tter, A.; Stang, P. J. J. Chem. Soc.,
Dalton Trans. 1998, 1707.
(25) Swiegers, G. F.; Malefeste, T. J. Chem. Rev. 2000, 100, 3483.
(26) Lang, H.; Weinmann, S.; Wu, I. Y.; Stein, T.; Jacobi, A.; Huttner,
G. J. Organomet. Chem. 1999, 575, 133. Stein, T.; Lang, H. Chem.
Commun. 2001, 1502.
(37) Rais, D.; Mingos, D. M. P.; Vilar, R.; White, A. J. P.; Williams,
D. J. Organometallics 2000, 19, 5209.
(38) Mingos, D. M. P. Essential Trends in Inorganic Chemistry;
Oxford University Press: Oxford, 1998; p 246.
(39) Mart´ın, A. J. J. Chem. Educ. 1999, 76, 578.
(40) Vicente, J.; Chicote, M. T.; Saura-Llamas, I.; Lagunas, M. C.;
Ram´ırez de Arellano, M. C.; Gonza´lez-Herrero, P.; Abrisqueta, M. D.;
Guerrero, R. Au(I)‚‚‚Au(I) and Au(I)‚‚‚Ag(I) Loose Clusters. In Metal
Clusters in Chemistry; Braunstein, P., Oro, L. A., Raithby, P. R., Eds.;
Wiley-VCH: Weinheim (Germany), 1999; Vol. 1, p 493. Vicente, J.;
Chicote, M. T.; Lagunas, M. C.; Jones, P. G. J. Chem. Soc., Chem.
Commun. 1991, 1730. Rawashdeh-Omary, M. A.; Omary, M. A.;
Fackler, J. P. Inorg. Chim. Acta 2002, 334, 376. Crespo, O.; Fernandez,
E. J.; Gil, M.; Gimeno, M. C.; Jones, P. G.; Laguna, A.; Lopez de
Luzuriaga, J. M.; Olmos, M. E. J. Chem. Soc., Dalton Trans. 2002,
1319. Catalano, V. J.; Horner, S. J. Inorg. Chem. 2003, 42, 8430.
Catalano, V. J.; Malwitz, M. A.; Etogo, A. O. Inorg. Chem. 2004, 43,
5714. Rombke, P.; Schier, A.; Schmidbaur, H.; Cronje, S.; Raubenhe-
imer, H. Inorg. Chim. Acta 2004, 357, 235. Fernandez, E. J.; Laguna,
A.; Lopez de Luzuriaga, J. M.; Monge, M.; Olmos, M. E.; Perez, J.;
Puelles, R. C.; Sa´enz, J. C. J. Chem. Soc., Dalton. Trans. 2005, 1162.
(41) Vicente, J.; Chicote, M. T.; Lagunas, M. C. Inorg. Chem. 1993,
32, 3748.
(27) Hayashi, Y.; Osawa, M.; Kobayashi, K.; Sato, T.; Sato, M.;
Wakatsuki, Y. J. Organomet. Chem. 1998, 569, 169.
(28) Rios, I.; Tenorio, M. J.; Puerta, M. C.; Valerga, P. Organome-
tallics 1998, 17, 3356.
(42) Vicente, J.; Chicote, M. T.; Guerrero, R.; Saura-Llamas, I. M.;
Jones, P. G.; Ram´ırez de Arellano, M. C. Chem. Eur. J. 2001, 7, 638.

4668 Organometallics, Vol. 24, No. 19, 2005
Vicente et al.
2
Synthesis of PPN[Au{CtCArCtCH}2]‚0.5H2O (1). To a
solution of C6Me4(CtCH)2-1,2 [Ar(CtCH)2] (204 mg, 1.12
mmol) in CH2Cl2 (5 mL) was added a solution of PPN[Au-
(acac)2] (261 mg, 0.28 mmol) in the same solvent (5 mL). The
mixture was stirred for 5 h and then filtered through a short
pad of anhydrous MgSO4. The solution was concentrated under
reduced pressure to dryness and the solid residue stirred with
Et2O (3 × 20 mL). The suspension was filtered to give a brown
powder, which was dried under reduced pressure (ca. 1 mbar)
to give 1. Yield: 187 mg, 61%. Mp: 163 °C (dec). Anal. Calcd
for C64H57AuNO0.5P2: C, 69.44; H, 5.19; N, 1.27. Found: C,
69.42; H, 4.89; N, 1.14. IR (cm-1): ν(CH), 3305(w); ν(CtC),
2093(w). ΛM (Ω-1 cm2 mol-1): 76. 1H NMR (400 MHz, CDCl3):
δ 7.61-7.37 (m, 30 H, PPN), 3.21 (s, 2 H, tCH), 2.44 (s, 6 H,
Me), 2.36 (s, 6 H, Me), 2.14 (s, 12 H, Me) 1.8 (br, 1 H, H2O).
13C{1H} NMR (100 MHz, CDCl3): δ 133.9 (m, p-PPN), 131.9
p-PTo3), 135.6, 134.3 (d, o-PTo3, JCP ) 14 Hz), 132.9, 129.5
(d, m-PTo3, 3JCP ) 6 Hz), 127.5 (d, i-PTo3, 1JCP ) 56 Hz), 125.4,
103.0 (d, CAu, 2JCP ) 25 Hz), 65.8 (Et2O), 21.4 (Me, PTo3), 19.5
(Me), 16.8 (Me), 15.2 (Et2O). 31P{1H} NMR (81 MHz, CDCl3):
δ 40.79 (s, PTo3).
Synthesis of [Au2{µ-Ar(CtC)2}{µ-Ph2P(CH2)nPPh2}] [n
) 4 (6), 6 (7)]. To a suspension of 2 (6: 380 mg, 0.66 mmol; 7:
133 mg, 0.23 mmol) in CH2Cl2 (20 mL) was added the
appropriate diphosphine (6: dppb, 282 mg, 0.66 mmol; 7:
dpph, 105 mg, 0.23 mmol). The reaction mixture was stirred
for 30 min (7) or 1 h (6) and filtered through a short column
of Celite. The solution was concentrated to dryness (6) or to 1
mL (7), and Et2O (20 mL) was added. The resulting suspension
was filtered, and the white solid thus collected was air-dried.
6: Yield: 580 mg, 88%. Mp: 211 °C. Anal. Calcd for C42H40-
Au2P2: C, 50.41; H, 4.03. Found: C, 50.66; H, 3.97. IR (cm-1):
1
1
(m, o-PPN), 129.5 (m, m-PPN), 126.8 (d, i-PPN, JCP ) 108
No ν(CtC) band is observed. H NMR (400 MHz, CDCl3): δ
Hz), 96.6 (CtC), 83.6 (tCH), 82.5 (CtCH), 19.1 (Me), 18.7
7.69-7.40 (m, 20 H, PPh2), 2.55 (s, 6 H, Me), 2.39 (m, 4 H,
(Me), 16.9 (Me), 16.5 (Me). MS-FAB- (m/z, %): 559 (M-, 50%).
CH2), 2.18 (s, 6 H, Me), 1.93 (m, 4 H, CH2). 13C{1H} NMR (50
2
Synthesis of [Au2{µ-Ar(CtC)2}]n (2). A suspension of
[AuCl(SMe2)] (1.480 g, 5 mmol) and Ar(CtCH)2 (458 mg, 2.5
mmol) in a mixture of CH2Cl2 (20 mL) and NEt3 (0.750 mL)
was stirred for 15 min. The suspension was filtered and the
solid washed with CH2Cl2 (2 × 10 mL) and Et2O (10 mL) and
dried under reduced pressure (ca. 1 mbar) to give 4 as a pale
brown solid, which proved to be insoluble in all common
solvents. Yield: 1.31 g, 91%. Mp: 120 °C (dec). Anal. Calcd
for C14H12Au2: C, 29.29; H, 2.11. Found: C, 30.42; H, 2.29 (see
Discussion). IR (cm-1): ν(CtC), 2018(w), 1970(br).
Synthesis of [(AuL)2{µ-Ar(CtC)2}] [L ) tBuNC (3),
PMe3 (4), PTo3 (5, To ) C6H4Me-4)]. To a suspension of 2
(3: 435 mg, 0.76 mmol; 4: 506 mg, 0.88 mmol; 5: 417 mg,
0.73 mmol) in CH2Cl2 (20 mL) was added the appropriate
ligand (3, tBuNC: 0.180 mL, 1.6 mmol; 4, PMe3: 1 M in
toluene, 2.2 mL, 2.2 mmol; 5, PTo3: 464 mg, 1.5 mmol). The
resulting solution (3, 5) or suspension (4) was stirred at room
temperature for 10 (3) or 30 min (4, 5) (4, under a nitrogen
atmosphere). The solution was filtered thorugh a short pad of
Celite, the solvent was removed under vacuum to dryness, and
the solid residue was stirred with 2 × 20 mL of n-pentane (3)
or Et2O (5) and filtered. Pale yellow microcrystals of 3 or a
white amorphous powder of 5‚0.6Et2O were obtained after
recrystallizing the crude solids from CH2Cl2/n-pentane or CH2-
Cl2/Et2O, respectively, and drying at reduced pressure for 1
h. The bright yellow suspension of 4 was filtered and the solid
washed with Et2O (2 × 15 mL) and dried at reduced pressure
for 1 h. 4 is insoluble in all common solvents.
MHz, CDCl3): δ 134.5, 133.3 (d, o-Ph, JCP ) 12 Hz), 132.8,
1
131.4 (p-Ph), 130.5 (d, i-Ph, JCP ) 53 Hz), 129.0 (d, m-Ph,
3JCP ) 10 Hz), 126.8, 103.8 (CtC), 28.1 (d, AuPCH2, JCP
)
1
26 Hz), 25.9 (CH2), 19.5 (Me), 16.6 (Me). 31P{1H} NMR (162
MHz, CDCl3): δ 36.01 (s). MS-FAB+ (m/z, %): 1001 (M+,
100%).
7: Yield: 168 mg, 71%. Mp: 233 °C (dec). Anal. Calcd for
C44H44Au2P2: C, 51.37; H, 4.31. Found: C, 51.13; H, 4.35. IR
(cm-1): No ν(CtC) band is observed. 1H NMR (400 MHz,
CDCl3): δ 7.71-7.43 (m, 20 H, Ph), 2.57 (s, 6 H, Me), 2.33 (m,
4 H, CH2), 2.19 (s, 6 H, Me), 1.71 (m, 4 H, CH2), 1.45 (m, 4 H,
CH2). 13C{1H} NMR (100 MHz, CDCl3): δ 141.5, 135.8, 133.8
2
4
(d, o-Ph, JCP ) 13 Hz), 133.4, 131.7 (d, p-Ph, JCP ) 3 Hz),
1
3
131.5 (d, i-Ph, JCP ) 52 Hz), 129.4 (d, m-Ph, JCP ) 10 Hz),
126.3 (d, CtCAu, 3JCP ) 3 Hz), 103.0 (d, CAu, 2JCP ) 27 Hz),
2
1
30.4 (d, CH2, JCP ) 17 Hz), 29.2 (d, CH2, JCP ) 34 Hz), 25.2
(d, CH2, 3JCP ) 6 Hz), 20.0 (Me), 17.2 (Me). 31P{1H} NMR (162
MHz, CDCl3): δ 37.51 (s). MS-FAB+ (m/z, %): 1029 (M+, 85%).
Crystals of 7 suitable for an X-ray diffraction study were
obtained by the liquid diffusion method using CH2Cl2 and
Et2O.
Synthesis of [(AuNHEt2)2{µ-Ar(CtC)2}] (8). To a mixture
of Ar(CtCH)2 (85 mg, 0.46 mmol) and PPN[AuCl2] (748 mg,
0.93 mmol) in degassed CH2Cl2 (15 mL) was added NHEt2 (3
mL), and the solution was stirred under a nitrogen atmosphere
for 2 h. The solvent was removed under reduced pressure, and
the dry residue was stirred with a mixture of CH2Cl2 (5 mL)
and NHEt2 (10 mL). The suspension was filtered, and the
white microcrystalline solid collected was dried under reduced
pressure for 0.5 h. The limited stability of 8 in solution in the
absence of NHEt2 prevented measurement of its 13C NMR
spectrum. Yield: 274 mg, 83%. Mp: 113 °C (dec). Anal. Calcd
for C22H34Au2N2: C, 36.68; H, 4.76; N, 3.89. Found: C, 36.70;
H, 4.79; N, 3.95. IR (cm-1): ν(NH), 3180(s); ν(CtC), 2098(w).
1H NMR (300 MHz,CDCl3): δ 5.15 (m, 2 H, NH), 3.28 (m, 8
H, CH2), 2.44 (s, 6 H, Me), 2.15 (s, 6 H, Me), 1.12 (m, 12 H,
CH2Me). Single crystals suitable for an X-ray diffraction study
were obtained by slow diffusion of n-pentane into a solution
of 8 in a mixture of NHEt2 and CH2Cl2. Although the
crystallographic data showed the structure to be as expected,
it could not be refined satisfactorily because of disordered ethyl
groups.
3: Yield: 430 mg, 76%. Mp: 142 °C (dec). Anal. Calcd for
C24H30Au2N2: C, 38.93; H, 4.08; N, 3.78. Found: C, 38.57; H,
3.94; N, 3.65. IR (cm-1): ν(CtN), 2216(s); ν(CtC), 2134(w).
1H NMR (200 MHz, CDCl3): δ 2.48 (s, 6 H, Me), 2.16 (s, 6 H,
t
Me), 1.48 (s, 18 H, Bu). 13C{1H} NMR (50 MHz, CDCl3): δ
147.7 (CN), 135.1, 132.8, 130.1, 126.1, 103.4 (CtC), 57.8
(CMe3), 29.5 (CMe3), 18.6 (Me), 16.6 (Me). Crystals of 3 suitable
for an X-ray diffraction study were obtained by slow diffusion
of Et2O into a solution of the compound in CDCl3.
4: Yield: 0.533 g, 83%. Mp: 174 °C (dec). Anal. Calcd for
C20H30Au2P2: C, 33.07; H, 4.16. Found: C, 33.44; H, 4.27. IR
(cm-1): ν(CtC), 2090 (w).
5‚0.6Et2O: Yield: 612 mg, 71%. Mp: 174 °C. Anal. Calcd
for C58.4H60Au2O0.6P2 (7‚0.6Et2O): C, 57.15; H, 4.93. Found:
C, 57.54; H, 4.72. IR (cm-1): No ν(CtC) band is observed. 1H
NMR (200 MHz, CDCl3): δ 7.49-7.39 (m, 12 H, PTo3), 7.16-
7.11 (m, 12 H, PTo3), 3.46 (q, 2.4 H, CH2, Et2O), 2.57 (s, 6 H,
Me), 2.32 (s, 18 H, Me, PTo3), 2.19 (s, 6 H, Me), 1.21 (t, 3.6 H,
Me, Et2O). 13C{1H} NMR (50.3 MHz, CDCl3): δ 141.3 (m,
Synthesis of [{AuC(NHtBu)NEt2}2{µ-Ar(CtC)2}] (9). A
solution of 3 (315 mg, 0.43 mmol) in a mixture of CH2Cl2 (10
mL) and NHEt2 (2 mL) was stirred for 2 h and then filtered
through Celite. The solution was concentrated under vacuum
(to ca. 3 mL), and n-pentane (30 mL) was added. Upon stirring
the resulting oily material with n-pentane (3 × 10 mL), a
bright yellow powder formed, which was filtered and air-dried.
Yield: 240 mg, 63%. Mp: 131 °C (dec). Anal. Calcd for C32H52-
Au2N4: C, 43.34; H, 5.91; N, 6.32. Found: C, 43.47; H, 5.89;
N, 6.37. IR (cm-1): ν(NH), 3338(s); ν(CtC), 2097(s). 1H NMR
(43) Vicente, J.; Chicote, M. T.; Alvarez-Falco´n, M. M.; Jones, P. G.
Organometallics 2005, 24, 2764.
(44) Vicente, J.; Chicote, M. T. Inorg. Synth. 1998, 32, 172.
(45) Tamaki, A.; Kochi, J. K. J. Organomet. Chem. 1974, 64, 411.

Gold(I) and Silver(I)/Gold(I) Complexes
Organometallics, Vol. 24, No. 19, 2005 4669
Table 1. Crystallographic Data for Complexes 3, 7, 9‚1/3CHCl3, and 10‚2CHCl3
3
7
9‚1/3CHCl3
10‚2CHCl3
formula
Mr
cryst size (mm)
cryst syst
space group
cell constants
a, Å
C
24H30Au2N2
C
44H44Au2P2
C
32.33H52.33Au2ClN4
C
114H110AgAu4Cl7O4P4
740.43
1028.67
926.50
2811.79
0.13 × 0.05 × 0.03
monoclinic
C2/c
0.28 × 0.09 × 0.08
orthorhombic
Pnna
0.26 × 0.12 × 0.10
rhombohedral
R3h
0.25 × 0.10 × 0.05
triclinic
P1h
14.6653(16)
12.0080(14)
15.0930(16)
90
114.840(5)
90
19.1819(14)
25.361(2)
15.9512(11)
90
90
90
36.7765(16)
36.7765(16)
14.4639(11)
90
90
120
15.0818(8)
17.2044(11)
42.493(3)
90.689(5)
98.936(5)
102.289(5)
10630.8(12), 4
0.71073
b, Å
c, Å
R, deg
â, deg
γ, deg
V (Å3), Z
λ (Å)
2412.0(5), 4
0.71073
2.039
7759.8(10), 8
0.71073
1.761
16941.7(17), 18
0.71073
1.635
F(calc) (Mg m-3
)
1.757
µ (mm-1
F(000)
T (K)
)
12.162
7.666
7.879
5.970
1384
3968
8088
5472
133(2)
133(2)
133(2)
133(2)
2θmax (deg)
60.06
50.06
60.08
50.06
no. of reflns measd
no. of indep reflns
transmissions
Rint
15549
78323
90439
134650
3530
6871
11010
37232
0.746 and 0.426
0.0476
0.648 and 0.370
0.0712
0.494 and 0.301
0.0413
0.7545 and 0.3168
0.1004
no. of data/rest/params
Rw(F2, all reflns)
R(F, > 4σ(F)
3530/24/132
0.0520
6871/110/433
0.1399
11010/81/377
0.0693
37232/141/985
0.0878
0.0248
0.0609
0.0238
0.0491
max ∆F (e Å-3
)
1.526/-0.893
3.108/-1.887
2.288/-1.674
1.761/-1.107
(400 MHz, CDCl3): δ 5.81 (s, 2 H, NH), 4.06 (q, 4 H CH2, 3JHH
pound 7 displays U values that are rather high for low-
temperature data (Ueq for C atoms up to 0.12 Å2). Its methyl
hydrogens were not found in difference syntheses and were
therefore not included in the refinement (note that there is
no reliable method of geometrically placing methyl hydrogens
in the absence of a significant torsional energy barrier). The
NH hydrogens of compound 9 were refined freely but with
N-H distances restrained equal. The methyl hydrogen atoms
at C12 and C13 were indistinct but were included in the
refinement with higher U values. The chloroform molecule is
ordered (with 3-fold symmetry) but has high U values. There
is significant residual electron density near the 3-fold axis that
might correspond to further (disordered) solvent, but no
corresponding model could be refined, and these peaks were
therefore neglected. For compound 10, carbon atoms were
refined isotropically and tolyl rings were refined as rigid
groups with idealized geometry. All methyl hydrogen positions
should be interpreted with caution. The four chloroform and
two perchlorate residues were ordered, but some atoms
displayed high U values.
3
) 7 Hz,), 3.22 (q, 4 H, CH2, JHH ) 7 Hz), 2.52 (s, 6 H, Me),
t
3
2.15 (s, 6 H, Me), 1.64 (s, 18 H, Bu), 1.27 (t, 6 H, Me, JHH
)
7 Hz), 1.15 (t, 6 H, Me, 3JHH ) 7 Hz). 13C{1H} NMR (50 MHz,
CDCl3): δ 206.97 (AuCN2), 135.6, 134.1, 132.2, 126.6, 105.4
(CtC), 54.5 (CMe3), 54.3 (CH2), 54.2 (CH2), 32.4 (CMe3), 19.8
(Me), 17.2 (Me), 15.4 (CH2Me), 15.3 (CH2Me). Crystals of 9‚1/
3CHCl3 suitable for an X-ray diffraction study were obtained
by the liquid diffusion method using CHCl3 and n-pentane.
Synthesis of [Ag{(AuPTo3)2{µ-Ar(CtC)2}}2]ClO4 (10).
To a solution of 5 (0.160 g, 0.14 mmol) in degassed CH2Cl2 (10
mL) was added a solution of AgClO4 (0.014 g, 0.07 mmol) in
Et2O (5 mL), and the mixture was stirred under nitrogen
atmosphere for 23 h, filtered through Celite, and concentrated
to dryness under reduced pressure. The residue was stirred
with Et2O (20 mL) for 0.5 h, and the suspension was filtered.
The microcrystalline yellow powder collected was washed with
Et2O (10 mL) and dried under vacuum. Yield: 155 mg, 86%.
Mp: 207 °C (dec). Anal. Calcd for C112H108AgAu4ClO4P4: C,
52.28; H, 4.23. Found: C, 52.03; H, 4.23. IR (cm-1): ν(ClO),
1096(s). No ν(CtC) band is observed. ΛM (Ω-1 cm2 mol-1): 129.
1H NMR (400 MHz, CDCl3): δ 7.37-7.22 (m, 24 H, Ar, PTo3),
6.96-6.95 (m, 24 H, Ar, PTo3), 2.27 (s, 36 H, Me, PTo3), 2.04
(s, 12 H, Me), 1.99 (s, 12 H, Me). 13C{1H} NMR (100 MHz,
Results and Discussion
CDCl3): δ 141.2 (d, p-PTo3, 4JC ) 3 Hz), 135.0, 134.1 (d,
Synthesis. The synthesis of PPN[Au{CtCArCt
CH}2] (Ar ) C6Me4-3,4,5,6, 1) from Ar(CtCH)2 and
PPN[Au(acac)2] required a 2-fold excess of the alkyne
over the stoichiometric 2:1 molar ratio (Scheme 1). In
an attempt to prepare the triangular (PPN)3[AuCt
CArCtC]3 we reacted Ar(CtCH)2 with PPN[Au(acac)2]
(1:1), but, unfortunately, extensive decomposition to
metallic gold took place.
P
2
3
o-PTo3, JCP ) 14 Hz), 133.7, 130.3, 129.3 (d, m-PTo3, JCP
)
1
12 Hz), 126.7 (d, i-PTo3, JCP ) 59 Hz), 123.5, 109.9 (d, CAu,
2JCP ) 25 Hz), 21.4 (Me, PTo3), 19.1 (Me), 16.7 (Me). 31P{1H}
NMR (162 MHz, CDCl3): δ 37.52 (s, AuPTo3). Crystals of 10‚
2CHCl3 suitable for an X-ray diffraction study were obtained
by slow diffusion of Et2O into a 1:1 acetone/CH2Cl2 solution.
X-ray Structure Determinations. Data were registered
using Mo KR radiation on a Bruker SMART 1000 CCD
diffractometer. Absorption corrections were based on multiple
scans (program SADABS). Structures were refined anisotro-
pically on F 2 (program SHELXL-97, G. M. Sheldrick, Univer-
sity of Go¨ttingen, Germany). To improve stability of refine-
ment, restraints to local ring symmetry and to light atom
displacement factors were employed. Methyl hydrogens were
identified in difference syntheses (for exceptions see below)
and refined as rigid groups allowed to rotate but not tip; other
hydrogens were included using a riding model. Crystal data
are presented in Table 1. Special features/exceptions: Com-
Complex [Au2{µ-Ar(CtC)2})]n (2) was obtained by
reacting Ar(CtCH)2 with [AuCl(SMe2)] and NEt3 (1:2:
2); Cl and SMe2 ligands are displaced from the coordi-
2-
nation sphere of gold by the Ar(CtC)2 ligand gener-
ated in situ by deprotonation of the dialkyne with the
amine. The insolubility of complex 2 in all common
organic solvents suggests it to be a polymer in which
gold would complete its usual linear dicoordination with
η2-(RCtCAu)-Au interactions, as found in related

4670 Organometallics, Vol. 24, No. 19, 2005
Table 2. Selected Bond Lengths and Angles in 10‚2CHCl3
Bond Lengths (Å)
Vicente et al.
Au(1)-C(1)
Au(1)-P(1)
Au(1)-Ag(1)
Au(2)-C(10)
Au(2)-P(2)
Au(2)-Ag(1)
Au(3)-C(15)
Au(3)-P(3)
Au(3)-Ag(1)
Au(4)-C(24)
Au(4)-P(4)
1.994(9)
2.275(3)
3.2240(9)
1.997(10)
2.270(3)
3.1950(9)
1.967(10)
2.275(3)
3.3397(9)
2.004(10)
2.277(3)
Au(4)-Ag(1)
3.2009(9)
2.451(9)
2.476(9)
2.482(9)
2.482(9)
1.983(10)
2.269(3)
3.4457(9)
1.999(10)
2.282(3)
3.1662(9)
Au(6)-C(160)
Au(6)-P(6)
Au(6)-Ag(2)
Au(7)-C(165)
Au(7)-P(7)
Au(7)-Ag(2)
Ag(2)-C(160)
Ag(2)-C(165)
Ag(2)-C(174)
Ag(2)-C(151)
1.995(10)
2.273(3)
3.3328(9)
1.984(10)
2.278(3)
3.5134(9)
2.463(9)
2.468(10)
2.480(9)
2.498(10)
Ag(1)-C(1)
Ag(1)-C(10)
Ag(1)-C(15)
Ag(1)-C(24)
Au(5)-C(151)
Au(5)-P(5)
Au(5)-Ag(2)
Au(8)-C(174)
Au(8)-P(8)
Au(8)-Ag(2)
Bond Angles (deg)
C(1)-Au(1)-P(1)
173.3(3)
175.3(3)
175.8(3)
179.7(3)
171.9(3)
171.6(3)
172.0(3)
173.5(3)
110.4(3)
103.0(3)
112.8(3)
108.9(3)
107.5(3)
108.5(3)
105.0(3)
116.6(3)
109.0(3)
112.3(3)
C(15)-Ag(1)-C(24)
C(174)-Ag(2)-C(151)
Au(2)-Ag(1)-Au(4)
Au(8)-Ag(2)-Au(6)
Au(2)-Ag(1)-Au(1)
Au(8)-Ag(2)-Au(5)
Au(2)-Ag(1)-Au(3)
Au(6)-Ag(2)-Au(5)
Au(4)-Ag(1)-Au(1)
Au(8)-Ag(2)-Au(7)
Au(4)-Ag(1)-Au(3)
Au(6)-Ag(2)-Au(7)
Au(1)-Ag(1)-Au(3)
Au(5)-Ag(2)-Au(7)
C(2)-C(1)-Au(1)
112.0(3)
107.2(3)
89.06(2)
73.63(2)
162.09(3)
74.80(2)
72.15(2)
148.29(3)
108.29(2)
159.08(3)
160.39(3)
86.62(2)
90.93(2)
124.24(3)
172.7(9)
167.4(9)
94.3(7)
C(1)-C(2)-C(3)
178.8(11)
176.8(11)
174.6(9)
176.0(11)
92.6(7)
C(151)-Au(5)-P(5)
C(10)-Au(2)-P(2)
C(174)-Au(8)-P(8)
C(15)-Au(3)-P(3)
C(160)-Au(6)-P(6)
C(24)-Au(4)-P(4)
C(165)-Au(7)-P(7)
C(1)-Ag(1)-C(10)
C(160)-Ag(2)-C(165)
C(1)-Ag(1)-C(15)
C(160)-Ag(2)-C(174)
C(1)-Ag(1)-C(24)
C(160)-Ag(2)-C(151)
C(10)-Ag(1)-C(15)
C(165)-Ag(2)-C(174)
C(10)-Ag(1)-C(24)
C(165)-Ag(2)-C(151)
C(151)-C(152)-C(153)
C(9)-C(10)-Au(2)
C(160)-C(159)-C(158)
C(9)-C(10)-Ag(1)
C(159)-C(160)-Au(6)
C(16)-C(15)-Au(3)
C(159)-C(160)-Ag(2)
C(16)-C(15)-Ag(1)
C(166)-C(165)-Au(7)
C(15)-C(16)-C(17)
C(174)-C(173)-C(172)
C(24)-C(23)-C(22)
C(173)-C(174)-Au(8)
C(23)-C(24)-Au(4)
C(173)-C(174)-Ag(2)
C(23)-C(24)-Ag(1)
172.2(9)
173.0(8)
91.6(7)
89.4(6)
165.9(9)
175.2(10)
176.6(11)
176.8(11)
178.0(9)
172.3(9)
89.2(7)
C(152)-C(151)-Au(5)
C(2)-C(1)-Ag(1)
92.1(7)
C(152)-C(151)-Ag(2)
91.7(7)
complexes;46 the insolubility prevented us from measur-
ing its NMR spectra and recrystallizing it to obtain good
elemental analyses. However, its nature was proved by
its reactivity toward different neutral ligands. Thus, 2
reacted with L (1:2) or L2 (1:1) ligands to give complexes
failed since complex 2 precipitated instead. This result
seems reasonable in view of the above-mentioned de-
composition of 8 in the absence of excess NHEt2 to give
2, which only reacts with tBuNC to give 3 if the
isocyanide is used in a large excess.
t
[Au2L2{µ-Ar(CtC)2}] [L ) BuNC (3), PMe3 (4), PTo3
The reaction of 5 with AgClO4 (2:1) gave the hetero-
pentanuclear complex [Ag{(AuPTo3)2{µ-Ar(CtC)2}}2]-
ClO4 (10) (Scheme 2) favored by both the limited
coordinative ability of the perchlorate anion and the
appropriate ortho disposition of the CtCAuPTo3 groups
in 5. Complex 10 behaves in acetone solution as a 1:1
electrolyte (ΛM ) 129 Ω-1 cm2 mol-1).48 The related
reaction between 3 and AgClO4 gave a mixture of
products in which [Ag{(AuCNtBu)2{µ-Ar(CtC)2}}2]ClO4
was shown by NMR to be the major species, but
unfortunately we could not obtain it pure even after
repeated recrystallization. A complex mixture was also
obtained when complex 6 was reacted with AgClO4 (2:
1).
X-ray Crystal Structures. The crystal structures of
[(AuCNtBu)2{µ-Ar(CtC)2}] (3; Figures 1-3), [Au2{µ-Ar-
(CtC)2}{µ-Ph2P(CH2)6PPh2}] (7; Figure 4), [{AuC(NHt-
Bu)NEt2}2{µ-Ar(CtC)2}]‚1/3CHCl3 (9‚1/3CHCl3; Fig-
ures 5 and 6), and [Ag{(AuPTo3)2{µ-Ar(CtC)2}}2]ClO4‚
2CHCl3 (10‚2CHCl3; Figure 7) have been determined.
A comparative study of the structural data reveals many
similarities regarding various structural parameters
that vary only very slightly within these complexes.
Thus, (i) the gold atoms are in essentially linear
environments [angles at gold: 174.28(16)-178.96(14)°],
(ii) the CtC bond distances are in the narrow range of
1.184(11)-1.214(5) Å, (iii) the Au-Calkynyl bond dis-
tances [1.979(4)-2.031(15) Å] are similar for all com-
plexes and seem to depend only slightly on the nature
of the other ligands, (iv) the Au-P distances in the
(5, To ) C6H4Me-4); L2 ) Ph2P(CH2)nPPh2, n ) 4 (6), 6
(7)]. The analogous complex [(AuNHEt2)2{µ-Ar(CtC)2}]
(8) was obtained by reacting PPN[AuCl2] with Ar(Ct
CH)2 and NHEt2 in CH2Cl2 using a 2:1:4 molar ratio.
One possible reaction pathway for this process would
be the deprotonation of the alkyne by the base to give a
monoalkynyl ligand, capable of replacing one of the
chloro ligands in PPN[AuCl2] to give [NH2Et2]Cl and
PPN[Au{CtCArCtCH}Cl], in which the chloro ligand
would be substituted by NHEt2 to give 8 and (PPN)Cl.
This last step could be favored by the excess of base and
the poor solubility of 8, probably attributable to the
formation of intermolecular hydrogen bonds. When
complex 8 is dissolved in the absence of excess NHEt2,
it gradually decomposes to give 2 with liberation of
NHEt2, which prevented the measuring of its 13C NMR
spectrum. Although these results suggest the possibility
of obtaining 8 by reacting 2 with NHEt2, we have
established that once it precipitates, 2 does not react
with NHEt2 even when it is used as the solvent.
The synthesis of carbenegold(I) complexes from the
homologous isocyanide derivatives and primary or
secondary amines is well documented,15,47 and we have
used this method to prepare [{AuC(NHtBu)NEt2}2{µ-
Ar(CtC)2}] (9) from (3) and NHEt2. The alternative
t
synthesis of 9 from the amine complex 8 and BuNC
(46) Chui, S. S. Y.; Ng, M. F. Y.; Che, C. M. Chem. Eur. J. 2005, 11,
1739, and references therein.
(47) Parks, J. E.; Balch, A. L. J. Organomet. Chem. 1974, 71, 453.
Bonati, F.; Minghetti, G. J. Organomet. Chem. 1973, 59, 403. Ming-
hetti, G.; Baratto, L.; Bonati, F. J. Organomet. Chem. 1975, 102, 397.
(48) Geary, W. J. Coord. Chem. Rev. 1971, 7, 81.

Gold(I) and Silver(I)/Gold(I) Complexes
Organometallics, Vol. 24, No. 19, 2005 4671
Scheme 1
Figure 1. Thermal ellipsoid plot (30% probability) of 3.
Selected bond lengths (Å) and angles (deg): Au-C(8) 1.970-
(4), Au-C(1) 1.979(4), N-C(8) 1.148(5), N-C(9) 1.472(5),
C(1)-C(2) 1.197(5), C(8)-Au-C(1) 174.28(16), C(8)-N-
C(9) 172.9(4), C(2)-C(1)-Au 176.5(3), C(1)-C(2)-C(3)
174.1(4), N-C(8)-Au 173.5(4).
Figure 2. One of the layers in the crystal of 3. The
shortest intermolecular distances in the sheets correspond
to C-H‚‚‚Au contacts (H‚‚‚Au ) 2.95 Å, C-H‚‚‚Au ) 159°).
Scheme 2
Figure 3. Packing diagram for complex 3 viewed parallel
to the layers. The shortest distances between layers cor-
respond to C-H‚‚‚Au (H‚‚‚Au ) 2.94, 3.06 Å, C-H‚‚‚Au )
161, 136°), and Au‚‚‚Au [3.5692(4) Å] contacts.
The molecule of 3 (Figure 1) displays crystallographic
2-fold symmetry. The molecules pack in sheets (Figure
2), parallel to the planes (40-2), which, in turn, stack
to give a three-dimensional supramolecular structure
alkynyl(phosphine)gold(I) are in the range 2.270(3)-
2.278(3) Å, and (v) the distances Au-Ctrans to alkynyl are
in the range 1.970(4)-2.046(3) Å. All these values are
consistent with those found for other (alkynyl)Au(I)
complexes.49
(49) CCDC CSD version 5.25, December 2004.

4672 Organometallics, Vol. 24, No. 19, 2005
Vicente et al.
Figure 6. Short intermolecular contacts in the packing
of complex 9. Only the relevant molecular fragments are
shown; the parent molecule is in the middle. For further
explanation see text.
intralayer [C(12)-H(12B)‚‚‚Au#5; H‚‚‚Au ) 2.95 Å,
C‚‚‚Au ) 3.982(4) Å, C-H‚‚‚Au ) 159°, Figure 2] or
interlayer interactions [C(10)-H(10A)‚‚‚Au#3; H‚‚‚Au )
2.94 Å, C‚‚‚Au ) 3.979(5) Å, C-H‚‚‚Au ) 161° and
C(10)-H(10B)‚‚‚Au#4; H‚‚‚Au ) 3.06 Å, C‚‚‚Au ) 3.912-
(4) Å, C-H‚‚‚Au ) 136°, Figures 2 and 3]. Weak
Au‚‚‚Au contacts [3.5692(4) Å] are also observed. These
H‚‚‚Au and Au‚‚‚Au distances are slightly longer than
the sum of the van der Waals radii of the corresponding
elements (H‚‚‚Au ) 2.86 Å; Au‚‚‚Au ) 3.32 Å),50 but the
C-H‚‚‚Au bond angles are in the range found in
“classical” C-H‚‚‚E (E ) O,51 N)52 or O-H‚‚‚OdC51 and
N-H‚‚‚O53 hydrogen bonds. The distinction between
hydrogen bonds and van der Waals interactions is
mainly based on the directionality of the former versus
the isotropic character of the latter, while the lengthen-
ing of the H‚‚‚E distance by less than 0.3 Å, as in 3, has
not been considered critical.51 In the past few years an
increasing number of nonclassical hydrogen bond in-
teractions, including X-H‚‚‚M,54,55 have been reported,
M being an electron-rich metal and X being, in most
cases, N or O but also C. Some of the latter involve
gold.20,56,57 They are different from agostic interactions,
which produce narrower angles.39 Although the search
Figure 4. Thermal ellipsoid plot (20% probability) of 7.
Hydrogen atoms are omitted for clarity. Selected bond
lengths (Å) and angles (deg): Au(1)-C(1) 1.990(13), Au-
(1)-P(1) 2.275(4), Au(2)-C(31) 2.031(15), Au(2)-P(2) 2.278-
(3), C(1)-C(2) 1.211(18), C(31)-C(32) 1.169(19), C(1)-
Au(1)-P(1) 175.1(4), C(31)-Au(2)-P(2) 176.9(4), C(2)-
C(1)-Au(1) 170.8(13), C(1)-C(2)-C(3) 178.0(15), C(32)-
C(31)-Au(2) 178.0(13), C(31)-C(32)-C(33) 178.7(16).
(50) Bondi, A. J. Phys. Chem. 2001, 68, 441.
(51) Steiner, T.; Desiraju, G. R. Chem. Commun. 1998, 891.
(52) Mascal, M. Chem. Commun. 1998, 303.
Figure 5. Thermal ellipsoid plot (50% probability) of 9‚
1/3CHCl3 (solvent omitted). Selected bond lengths (Å) and
angles (deg): Au(1)-C(1) 1.986(3), Au(1)-C(15) 2.046(3),
Au(2)-C(3) 1.980(3), Au(2)-C(24) 2.046(3), N(1)-C(15)
1.338(4), N(2)-C(15) 1.345(4), N(3)-C(24) 1.342(4), N(4)-
C(24) 1.334(5), C(1)-C(2) 1.214(4), C(3)-C(4) 1.214(5),
C(1)-Au(1)-C(15) 177.05(13), C(3)-Au(2)-C(24) 178.96-
(14), C(2)-C(1)-Au(1) 173.5(3), C(4)-C(3)-Au(2) 176.0-
(3).
(53) Taylor, R.; Kennard, O. J. Am. Chem. Soc. 1982, 104, 5063.
(54) Brammer, L.; Zhao, D.; Ladipo, F. T.; Braddock-Wilking, J. Acta
Crystallogr., Sect. B 1995, 28, 406. Canty, A. J.; van Koten, G. Acc.
Chem. Res. 1995, 28, 406. Brammer, L.; Charnock, J. M.; Goggin, P.
L.; Goodfellow, R. J.; Orpen, A. G.; Koetzle, T. F. J. Chem. Soc., Dalton
Trans. 1991, 1789. Calhorda, M. J. Chem. Commun. 2000, 801.
Brammer, L.; McCan, M. C.; Bullock, R. K.; McMullan, R. K.;
Sherwood, P. Organometallics 1992, 11, 2339. Hascall, T.; Baik, M.
H.; Bridgewater, B. M.; Shin, J. H.; Churchill, D. G.; Friesner, R. A.;
Parkin, G. Chem. Commun. 2002, 2644.
(55) Braga, D. J. Chem. Soc., Dalton Trans. 1999, 1.
(56) Wong, W. Y.; Choi, K. H.; Lu, G. L.; Shi, J. X.; Lai, P. Y.; Chan,
S. M.; Lin, Z. Y. Organometallics 2001, 20, 5446. Bardaji, M.; Jones,
P. G.; Laguna, A. J. Chem. Soc., Dalton Trans. 2002, 3624. Barranco,
E. N.; Crespo, O.; Gimeno, M. C.; Laguna, A.; Jones, P. G.; Ahrens, B.
Inorg. Chem. 2000, 39, 680. Vicente, J.; Chicote, M. T.; AÄ lvarez-Falco´n,
M. M.; Fox, M. A.; Bautista, D. Organometallics 2003, 22, 4792.
(57) Vicente, J.; Singhal, A. R.; Jones, P. G. Organometallics 2002,
21, 5887.
(Figure 3). This packing seems to be attributable to
C-H‚‚‚Au intermolecular interactions, which could be
established since the methyl hydrogen sites were clearly
identified in the X-ray analysis. Thus, the shortest
intermolecular distances, normalized to C-H 1.08 Å for
all structures in this paper, correspond to C-H‚‚‚Au

Gold(I) and Silver(I)/Gold(I) Complexes
Organometallics, Vol. 24, No. 19, 2005 4673
t
involved in C-H‚‚‚Au interactions belong to BuNC
ligands, suggesting that the polarity of the C-H bond
could be enhanced by the proximity of the electroneg-
ative nitrogen atom. In addition, it has been shown that
aurophilicity and hydrogen bonding can work coopera-
tively in assembling gold complexes into dimers, oligo-
mers, three-dimensional structures, or even, despite
unfavorable electrostatic interactions, infinite chains of
cations.13,42,57,62
The crystal structure of 7 involves two independent
molecules, each with 2-fold symmetry (Figure 4); for the
lower numbered molecule, the 2-fold axis is parallel to
the x axis and for the higher numbered molecule to the
z axis. The connectivities are identical, but the confor-
mations of the (CH2)6 chains are different; the torsion
angles along the atom sequence P1-C8-C9-C10-
C10′-C9′ are 176°, -70°, and -68°, but the correspond-
ing values in the other molecule are 179°, 179°, and 77°.
Each gold atom is bonded to one of the CtC fragments
of the Ar(CtC)2 ligand and to one of the phosphorus
atoms of the 1,6-bis(diphenylphosphino)hexane ligand,
resulting in a 16-membered metallamacrocycle. The
great bite and flexibility of the diphosphine ligand, along
with the ortho disposition of both ethynyl fragments,
allow the gold atoms to be in essentially linear environ-
ments. The absence of reliable positions for the methyl
hydrogens precludes the analysis of any associated short
contacts that might be present.
The crystal structure of 9‚1/3CHCl3 (Figure 5) shows
a dinuclear complex in which both gold atoms are
linearly coordinated. The Au-Ccarbene bond distance
[2.046(3) Å] is similar to those found in other gold(I)
carbene complexes previously described.20,63,64 The skel-
eton of the carbene ligands is almost planar, the mean
deviation of the seven-atom fragments C(NC2)NHC from
their respective mean planes being only 0.02 and 0.03
Å, whereby the gold atoms lie marginally outside these
planes by 0.035(2) and 0.0557(2) Å. The C-NHBut
distances [1.334(5), 1.345(4) Å] and C-NEt2 [1.342(4),
1.338(4) Å] are similar to each other and intermediate
between those corresponding to single and double
C(sp2)-N(sp2) bonds.65 Both the planar geometry and
the similar C-N distances suggest extensive electronic
delocalization in the fragment CN2, analogous to that
previously found in other carbene complexes.16 Although
the partial double character of the C-NHBut bond
allows two possible conformations for the carbene ligand
(E or Z), the crystal structure of 9 shows that only the
Z-isomer is present, as has previously been found in
other gold complexes with the same carbene.16 This
could have steric reasons since, in this isomer, the most
bulky substituent (tBu) is cis with respect to the metallic
fragment, thus avoiding contact with the more con-
gested NEt2 group.
Figure 7. Ball-and-stick plot of both cations of 10‚2CHCl3.
For clarity, hydrogen atoms are omitted and the To groups
are represented by the ipso carbon. Selected bond lengths
(Å) and angles (deg) are listed in Table 2.
for C-H‚‚‚M interactions is not well integrated into
common program systems and, in many cases, such
interactions fail to be reported,58 we suggest that they
should be routinely taken into account since by them-
selves, or acting cooperatively with Au‚‚‚Au,55,59 they
could explain the packing architecture in many com-
plexes, particularly when no other stronger intermo-
lecular interactions are present. We point out however
the criterion that the hydrogen positions must be
reliable, which is often not the case for methyl groups
lacking significant torsional barriers; in the absence of
significant electron density maxima corresponding to
the hydrogen atoms, the refinement program will choose
apparently sensible hydrogen positions that are, how-
ever, quite inappropriate. It should be noticed that in 3
and in [AuX(CNBut)] (X ) Cl,60 Br61), the C-H bonds
(62) Hollatz, C.; Schier, A.; Schmidbaur, H. J. Am. Chem. Soc. 1997,
119, 8115. Mingos, D. M. P.; Yau, J.; Menzer, S.; Williams, D. J. J.
Chem. Soc., Dalton Trans. 1995, 319. Tzeng, B. C.; Schier, A.;
Schmidbaur, H. Inorg. Chem. 1999, 38, 3978. Ahrens, B.; Jones, P.
G.; Fischer, A. K. Eur. J. Inorg. Chem. 1999, 1103. Schneider, W.;
Bauer, A.; Schmidbaur, H. Organometallics 1996, 15, 5445.
(63) Banditelli, G.; Bonati, F.; Calogero, S.; Valle, G. J. Organomet.
Chem. 1984, 275, 153.
(64) Lee, K. M.; Lee, C. K.; Lin, I. J. B. Angew. Chem., Int. Ed. Engl.
1997, 36, 1850. Uson, R.; Laguna, A.; Villacampa, M. D.; Jones, P. G.;
Sheldrick, G. M. J. Chem. Soc., Dalton Trans. 1984, 2035. Britten, J.
F.; Lock, C. J. L.; Wang, Z. X. Acta Cristallogr., Sect. C 1992, 48, 1600.
(65) Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen,
A. G.; Taylor, R. J. Chem. Soc., Perkin Trans. 2 1987, S1.
(58) Jones, P. G.; Ahrens, B. Chem. Commun. 1998, 2307.
(59) Braga, D.; Grepioni, F.; Desiraju, G. R. Chem. Rev. 1998, 98,
1375. Prins, L. J.; Reinhoudt, D. N.; Timmerman, P. Angew. Chem.,
Int. Ed. 2001, 40, 2383.
(60) Eggleston, D. S.; Chodosh, D. F.; Webb, R. L.; Davies, L. L. Acta
Crystallogr., Sect. C 1986, 42, 36.
(61) Schneider, W.; Angermaier, K.; Sladek, A.; Schmidbaur, H. Z.
Naturforsch., B 1996, 51, 790.

4674 Organometallics, Vol. 24, No. 19, 2005
Vicente et al.
It is noticeable in Figure 5 that the butyl groups
approach the gold atoms quite closely; the intramolecu-
lar 1,6-contacts are H(23A)‚‚‚Au1 2.50, H(22C)‚‚‚Au1
2.66, H(30C)‚‚‚Au2 2.65, and H(32A)‚‚‚Au2 2.59 Å. The
angles at hydrogen are necessarily quite narrow (126-
134°). The intermolecular contacts of 9 are complicated
(Figure 6). In the absence of classical acceptors, the NH
donors would be expected to seek regions of higher
electron density such as multiple bonds. The donor
N(2)-H(02), normalized to N-H 1.01 Å, approaches the
bond C(3)-Au(2) with H‚‚‚Cent 2.91 Å, angle 133°,
operator (i) 2/3-y, 1/3+x-y, 1/3+z (Cent ) bond mid-
point). Similarly N(4)-H(04) is associated with the bond
C(1)-C(2) with H‚‚‚Cent 2.93 Å, angle 136°, operator
(ii) 2/3+x-y, 1/3+x, 1/3-z. Short C-H‚‚‚π contacts are
observed for C(27)-H(27A) to C(1)-C(2) [H‚‚‚Cent 2.59
Å, angle 174°, operator (ii)] and C(16)-H(16A) to C(3)-
C(4) [H‚‚‚Cent 2.62 Å, angle 148°, operator (i)]. Finally,
Au(2) is involved in three short C-H‚‚‚Au contacts:
from H(21C) (2.75 Å, 155°, operator (i)), H(22A) (2.99
Å, 146°, operator (i)), and H(27B) (2.98 Å, 157°, operator
(ii)). The net effect of all these contacts is seen in Figure
6; the central molecule is connected with two neighbor-
ing molecules.
This plethora of contacts deserves further comment.
First, any contact taken for itself might be considered
marginally significant. Second, it is not clear in some
cases whether a single atom or a bond should be
regarded as the acceptor for the contact. Third, it is
conceivable that the steric accessibility of the linear
regions of the molecule enable closer packing, rather
than that attractive interactions are involved. Never-
theless, the overall effect is impressive. Finally, the
atom Au(1) may be involved in intermolecular interac-
tions to methyl hydrogens at C(13) and C(14), but we
are not convinced of the complete reliability of these
hydrogen positions and so present no numerical values.
The asymmetric unit in the crystal structure of 10‚
2CHCl3 contains two pentanuclear “AgAu4” cations, two
perchlorate anions, and four molecules of chloroform.
The two cations are qualitatively similar, consisting of
a silver ion encased by four AuCtC fragments (Figure
7), but nonetheless display some important differences,
the second cation being less regular. The silver atom
contacts with the four gold atoms [Ag(1)‚‚‚Au: 3.2240-
(9), 3.1950(9), 3.3397(9), 3.2009(9) Å; Ag(2)‚‚‚Au: 3.4457-
(9), 3.1662(9), 3.3328(9), 3.5134(9) Å] at distances
shorter, with two exceptions for Ag(2), than the sum of
the van der Waals radii of the elements (3.38 Å).66 There
are no Au‚‚‚Au contacts at distances shorter than 4 Å.
The four silver to R-carbon atoms distances [Ag(1)‚‚‚CR:
2.451(9), 2.476(9), 2.482(9), 2.482(9) Å; Ag(2)‚‚‚CR: 2.463-
(9), 2.468(10), 2.480(9), 2.498(10) Å] are in the range
found in other complexes where the CtC-Ag angle is,
as in 10, in the range 80-100° (2.242-2.595 Å; mean
value 2.412 Å).67 The Ag‚‚‚Câ distances are appreciably
longer (Ag(1): 2.755-2.808 Å; Ag(2): 2.633-2.803 Å).
This unsymmetrical disposition of the silver atom with
respect to the CtC fragments is probably forced by the
existing numismophilic41 Ag‚‚‚Au contacts. In fact, in
Ag(η2-RCtCR′) complexes the Ag-C distances are
similar and in the range 2.2-2.5 Å (mean value 2.295
Å).68
The gold atoms are disposed around the Ag(1) atom
in a distorted square planar environment [mean devia-
tion from least-squares plane: 0.11 Å; deviations of C
atoms from plane: C(1), C(10) 1.4, C(15), C(24) -1.4 Å;
Au(1)-Ag(1)-Au(3) 90.93(2)°, Au(2)-Ag(1)-Au(4) 89.06-
(2)°, Au(2)-Ag(1)-Au(1) 162.09(3)°, Au(4)-Ag(1)-Au-
(1) 108.29(2)°, Au(2)-Ag(1)-Au(3) 72.15(2)°, Au(4)-
Ag(1)-Au(3) 160.39(3)°], while around Ag(2) the geometry
is more distorted but still planar [mean deviation from
least-squares plane: 0.06 Å; deviations of C atoms from
plane: C(151) 1.2, C(160) 1.3, C(165) -1.4, C(174) -1.6
Å; Au(8)-Ag(2)-Au(6) 73.63(2)°, Au(8)-Ag(2)-Au(5)
74.80(2)°, Au(6)-Ag(2)-Au(5) 148.29(3)°, Au(8)-Ag(2)-
Au(7) 159.08(3)°, Au(6)-Ag(2)-Au(7) 86.62(2)°, Au(5)-
Ag(2)-Au(7) 124.24(3)°]. The four R-carbon atoms are
in a pseudo-tetrahedral disposition with respect to the
Ag(1) [range 105.0(3)-112.8(3)°, mean value 109.5°] or
Ag(2) centers [range 103.0(3)-116.6(3)°, mean value
109.4°]. The mean Au-C‚‚‚Ag angle is 96°. Taking into
account the above data and the isolobal character of H
and AuPR3,38 complex 10 can be considered as contain-
ing four C-(AuPR3)‚‚‚Ag “agostic” interactions, which
could be termed “metalagostic” contacts to distinguish
them from the normal C-H‚‚‚M agostic interactions (see
Chart 1).39
Complex 10 shows for the first time the coordination
of one Ag(I) to four “CtCAu” fragments, although three
silver complexes have been reported in which, as in 10,
four “CtCM” (M ) Pt, Ti)27,33 fragments are disposed
around silver. In [{Au(C2Ph)2}2(AgPPh3)2] each AgPPh3
group is bonded to two AuCtCPh moieties.34
NMR Spectra. The insolubility of 2 precluded the
measurement of its NMR spectra, while the slow
decomposition of 8 in solution (see above) allowed us to
1
measure only the H NMR spectrum. In the 13C NMR
spectrum of 1 four resonances are observed for all the
inequivalent Me groups (see Experimental Section),
1
while in the H NMR spectrum only three resonances
are observed, one of them being twice the intensity of
the others. As expected, in the spectra of complexes 2,
3, and 5-10 the Me groups in the C6Me4 fragment give
1
rise to two singlets (∆δ ) 0.05-0.38 ppm). In the H
NMR spectra, the resonances at lower field can be
assigned to the Me groups in ortho position with respect
to the CtCAu fragments since the spectra of some
(alkynyl)gold(I) complexes containing C6H4(CtC)2-1,3,
C6HMe3-2,4,6-(CtC)2-1,319 and C6H3N(CtC)2-3,569
ligands allowed us to conclude that the CtCAu frag-
ments produce the deshielding of the H or CH3 in ortho
position with respect to those in meta position. The
spectra show also the expected resonances for the
auxiliary ligands in the ranges previously found for
other alkynylgold(I) complexes with isocyanide,4,19 phos-
phino,12,15,70 carbene,15,63 or diethylamino ligands.15
(68) Iyoda, M.; Horino, T.; Takahashi, F.; Hasegawa, H.; Yoshida,
M.; Kuwatani, Y. Tetrahedron Lett. 2001, 42, 6883. Chi, K. M.; Lin, C.
T.; Peng, S. M.; Lee, G. H. Organometallics 1996, 15, 2660. Schulte,
P.; Behrens, U. J. Organomet. Chem. 1998, 563, 235.
(69) Vicente, J.; Chicote, M. T.; AÄ lvarez-Falco´n, M. M.; Bautista, D.
Organometallics 2004, 23, 5707.
(66) Bondi, A. J. Phys. Chem. 1964, 68, 441.
(67) Zhao, X.-L.; Wang, Q.-M.; Mak, T. C. W. Inorg. Chem. 2003,
42, 7872. Lin, Y.-Y.; Lai, S.-W.; Che, C.-M.; Cheung, K.-K.; Zhou, Z.-
Y. Organometallics 2002, 21, 2275. Wang, Q.-M.; Mak, T. C. W. J. Am.
Chem. Soc. 2001, 123, 7594. Wang, Q.-M.; Mak, T. C. W. J. Am. Chem.
Soc. 2000, 122, 7608.
(70) Wong, W. Y.; Ho, K. Y.; Choi, K. H. J. Organomet. Chem. 2003,
670, 17.

Gold(I) and Silver(I)/Gold(I) Complexes
Organometallics, Vol. 24, No. 19, 2005 4675
The NMR spectra (1H, 13C, 31P) of complex 10 show
the equivalence of the four AuPTo3 and the two C6Me6
groups.
Acknowledgment. We are grateful for the financial
support of Ministerio de Ciencia y Tecnolog´ıa, FEDER
(CTQ2004-05396) and Fundacio´n Se´neca (Comunidad
Auto´noma de la Regio´n de Murcia, Spain) for a grant
to M.A.A.F.
IR Spectra. In the IR spectra of complexes 1-10 the
ν(CtC) stretching modes give rise to one (1, 3, 4, 8, 9,
in the range 2090-2134 cm-1) or two (2: 2108, 1970
cm-1) weak absorptions (strong for 9) or are not ob-
served (5-7, 10). The spectrum of 1 shows a weak
absorption at 3305 cm-1 assignable to ν(C-H) in the
CtCH fragments. In the spectrum of 3 the strong band
at 2216 cm-1 corresponds to the ν(CtN) in the isocya-
nide ligand, while in those of 8 and 9, one strong band
at 3180 and 3338 cm-1, respectively, are assignable to
ν(N-H).
Supporting Information Available: Listing of all refined
and calculated atomic coordinates, anisotropic thermal pa-
rameters, and bond lengths and angles for 3, 7, 9‚1/3CHCl3,
and 10‚2CHCl3. This material is available free of charge via
the Internet at http://pubs.acs.org.
OM050418B