Alkynyl gold(I) rigid-rod molecules from 1,12-bis(ethynyl)-1,12-dicarba-closo-dodecarborane(12)

Article abstract of DOI:10.1021/om0304311

Reactions of 1,12-bis(ethynyl)-1,12-dicarba-closo-dodecaborane(12), 1,12-(HC≡C)₂-1,12-C₂B₁₀H₁₀ (diethynylcarborane, decH₂), with gold complexes of type [Au(acac)L] (acac = acetylacetonate) gave the ne

Full text of DOI:10.1021/om0304311

4792
Organometallics 2003, 22, 4792-4797
Alk yn yl Gold (I) Rigid -Rod Molecu les fr om
1,12-Bis(eth yn yl)-1,12-d ica r ba -closo-d od eca bor a n e(12)
J ose´ Vicente,*,† Mar´ıa-Teresa Chicote, and Miguel M. Alvarez-Falco´n
Grupo de Qu´ımica Organometa´lica, Departamento de Quı´mica Inorga´nica, Universidad de
Murcia, Apartado 4021, Murcia, 30071 Spain
Mark A. Fox*,‡
Department of Chemistry, University of Durham, South Road, Durham DH1 3LE, U.K.
Delia Bautista
SACE, Universidad de Murcia, Apartado 4021, Murcia, 30071 Spain
Received J une 4, 2003
Reactions of 1,12-bis(ethynyl)-1,12-dicarba-closo-dodecaborane(12), 1,12-(HCtC)2-1,12-
C2B10H10 (diethynylcarborane, decH2), with gold complexes of type [Au(acac)L] (acac )
acetylacetonate) gave the neutral digold complexes [(AuL)2(µ-dec)] [L ) PPh3 (1), P(C6H4-
OMe-4)3 (2), C(NHtBu)(NEt2) (3)]. The neutral complex [(AuCNtBu)2(µ-dec)] (5) was obtained
t
by adding BuNC to the complex [Au2(µ-dec)]n (4) resulting from the reaction of decH2 with
[AuCl(SMe2)] and NEt3. The anionic complex PPN[Au(decH)2] (6) (PPN ) Ph3PdNdPPh3)
was isolated from its mixture with (PPN)2[{Au(decH)}2(µ-dec)] (7) by reacting PPN[Au(acac)2]
and decH2 in 1:4 molar ratio. The rigid-rod structures of the digold compound 2‚CH2Cl2 and
the salt 6‚CHCl3 were determined by X-ray crystallography.
In tr od u ction
plexes,2,3,11 the recently reported12 compound 1,12-
bis(ethynyl)-1,12-dicarba-closo-dodecaborane(12) (di-
ethynylcarborane, decH2) may be considered as a pre-
cursor for the same purpose. Monoethynyl ortho- and
meta-carboranes have been shown to form alkynylmet-
als with the acetylenic hydrogen replaced by metals.13
As the robust cage in para-carborane has a 5-fold
symmetry through the axis of the cage carbons and the
hydrogens at the cage carbons are easily substituted,
there has been substantial interest in the para-carbo-
rane unit -CB10H10C- as a linker/building block for
rigid-rods,14 liquid crystals,15 and materials with large
hyperpolarizabilities.16 Recent studies of various para-
carborane derivatives show evidence of electronic trans-
mission via the para-carborane cage.17
Together with the linearity of the CtC bond in
alkynyl ligands, the preference of gold(I) for linear
dicoordination makes alkynylgold(I) compounds attrac-
tive candidates for the design of linear-chain metal-
containing polymers with extended electronic conjuga-
tion along the backbone.1-6 Among the many alkynyl-
gold(I) compounds described, some show liquid crystal-
line properties7 or nonlinear-optical behavior.8,9 In ad-
dition, some alkynylgold(I) derivatives belong to a new
class of luminophores with interesting photophysical
and photochemical properties.10
Since 1,4-bis(ethynyl)benzene is a widely used precur-
sor in the syntheses of many rigid-rod metal com-
Here we describe the syntheses of new rigid-rod
alkynylgold(I) derivatives from 1,12-bis(ethynyl)-1,12-
† E-mail: jvs@um.es. www: http://www.um.es/gqo.
‡ E-mail: m.a.fox@durham.ac.uk.
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10.1021/om0304311 CCC: $25.00 © 2003 American Chemical Society
Publication on Web 10/15/2003

Alkynyl Gold(I) Rigid-Rod Molecules
Organometallics, Vol. 22, No. 23, 2003 4793
2614 (s), v(CtC) 2132 (w). 1H{11B} NMR: δ 7.32, 6.90 (AA′BB′,
24 H, C6H4), 3.81 (s, 18 H, Me), 2.54 (s, 10 H, BH). 13C{1H}
dicarba-closo-dodecaborane(12). The crystal structures
of two rigid-rod molecules containing two metal centers
and a -CtC-CB10H10C-CtC- carborane linker or a
gold center with two -CtC-CB10H10C-CtCH groups
are also discussed.
2
NMR: δ 162.1 (s, p-C), 135.6 (d, J CP ) 15 Hz, o-CH), 124.2
1
3
(s, CtCAu), 121.3 (d, J CP ) 60 Hz, i-C), 114.6 (d, J CP ) 13
Hz, m-CH), 100.0 (d, 2J CP ) 33 Hz, CAu), 66.6 (s, C cage), 55.4
(s, Me). 31P{1H} NMR: δ 38.61 (s). 11B NMR: δ -11.3 (d, J BH
) 161 Hz). Crystals of 2‚2CH2Cl2 suitable for X-ray analysis
were obtained by slow diffusion of n-pentane into a CH2Cl2
solution of 2.
Exp er im en ta l Section
1H, 11B, 13C, and 31P NMR spectra were recorded in CDCl3
solutions with a Varian Unity 300 at room temperature.
Chemical shifts are referenced to BF3‚Et2O (11B), H3PO4 (31P),
or TMS (1H, 13C). The gold complexes [Au(acac)L],18,19 [AuCl-
(SMe2)],20 PPN[Au(acac)2]18 (acacH ) acetylacetone, PPN )
Syn th esis of [{Au {C(NHtBu )(NEt2)}}2(µ-d ec)] (3). To a
solution of [Au(acac){C(NHtBu)(NEt2)}] (183 mg, 0.4 mmol)
in degassed acetone (10 mL) was added a solution of decH2
(25 mg, 0.13 mmol) in the same solvent (10 mL). The mixture
was stirred for 9.25 h and filtered through Celite, and the
solution was concentrated under reduced pressure to dryness.
The residue was then stirred with Et2O (30 mL), filtered off,
washed with Et2O (5 mL), and recrystallized from CH2Cl2/Et2O
to give a white powder. Yield: 19 mg (16%). Mp: 164 °C (dec).
Anal. Calcd for C24H50N4B10Au2: C, 32.14; H, 5.62; N, 6.25.
Found: C, 31.68; H, 5.41; N, 5.95. IR (cm-1): ν(NH) 3368 (s),
ν(BH) 2657 (s), 2606 (s), ν(CtC) 2128 (s). 1H{11B} NMR δ 5.74
12
Ph3PdNdPPh3), and decH2 were prepared as described in
the literature.
Syn th esis of [(Au P P h 3)2(µ-d ec)] (1). To a solution of
decH2 (20 mg, 0.1 mmol) in degassed CH2Cl2 (5 mL) was added
[Au(acac)PPh3] (114 mg, 0.2 mmol). The resulting light sus-
pension was stirred for 5 h and filtered through Celite. The
pale yellow solution was concentrated under reduced pressure
(to ca. 1 mL). By addition of Et2O (20 mL) a white microcrys-
talline solid was obtained, which was filtered off, washed with
Et2O (5 mL), and air-dried. Yield: 32 mg (29%). Mp: 258 °C
(dec). Anal. Calcd for C42H40Au2B10P2: C, 45.50; H, 3.64.
Found: C, 45.62; H, 3.75. IR (cm-1): v(BH) 2666 (s), 2614 (s),
v(CtC) 2146 (w). 1H{11B} NMR: δ 7.42 (m, 30 H, Ph), 2.55 (s,
3
(s, 2 H, NH), 3.92 (q, 4 H, J HH ) 7 Hz, CH2), 3.18 (q, 4 H,
3J HH ) 7 Hz, CH2), 2.52 (s, 10 H, BH), 1.54 (s, 18 H, tBu), 1.21
3
3
(t, 6 H, J HH ) 7 Hz, CH2Me), 1.13 (t, 6 H, J HH ) 7 Hz,
CH2Me). 11B NMR: δ -11.4 (d, J BH ) 168 Hz).
[(Au CNtBu )2(µ-d ec)] (5). To a solution of decH2 (21 mg,
0.11 mmol) in degassed CH2Cl2 (6 mL) were added [AuCl-
(SMe2)] (65 mg, 0.22 mmol) and NEt3 (0.061 mL, 0.44 mmol).
No changes were observed after 1.5 h of stirring. The solution
was concentrated to dryness, the residue was stirred with
acetone (0.5 mL) and water (10 mL), the resulting suspension
was filtered, and the pale yellow solid was washed with water
(8 mL) and air-dried. The color of this solid, presumed to be
the polymer [Au2(µ-dec)]n (4), slowly darkened, suggesting that
decomposition to metallic gold was taking place. The dried
2
10 H, BH). 13C{1H} NMR: δ 134.2 (d, J CP ) 14 Hz, o-CH),
131.5 (d, 4J CP ) 2 Hz, p-CH), 129.6 (d, 1J CP ) 56 Hz, i-C), 129.1
3
2
(d, J CP ) 11 Hz, m-CH), 121.8 (s, CtCAu), 100.0 (d, J CP
)
31 Hz, CAu). 31P{1H} NMR: δ 42.25 (s). 11B NMR: δ -11.4
(d, J BH ) 165 Hz).
Syn th esis of [{Au P (C6H4OMe-4)3}2(µ-d ec)] (2). To a
solution of decH2 (20 mg, 0.1 mmol) in acetone (15 mL) was
added[Au(acac)P(C6H4OMe-4)3] (149 mg, 0.23 mmol), and the
mixture was stirred for 4.25 h and filtered through Celite. The
solution was concentrated under vacuum (to ca. 1 mL), and
Et2O (10 mL) was added to precipitate a white microcrystalline
solid, which was filtered off and air-dried. Yield: 87.5 mg
(64%). Mp: 232 °C (dec). Anal. Calcd for C48H52Au2B10O6P2:
C, 44.73; H, 4.07. Found: C, 44.46; H, 4.08. IR (cm-1): v(BH)
t
solid was suspended in CH2Cl2 (3 mL), and BuNC (0.1 mL,
0.89 mmol) was added. A pale yellow solution immediately
formed, which was stirred for 2.5 h and then filtered through
a short column of Celite. The solution was concentrated under
reduced pressure (to ca. 1 mL), and Et2O (5 mL) was added to
give a white microcrystalline solid. This solid was filtered off,
washed with Et2O (2 × 5 mL), and air-dried. Yield: 30 mg
(36%). Mp 162 °C. Anal. Calcd for C16H28Au2B10N2: C, 25.61;
H, 3.76; N, 3.73. Found: C, 26.03; H, 3.86; N, 3.77. IR (cm-1):
v(BH) 2618 (s), v(NtC) 2234 (s), v(CtC) 2140 (w). 1H{11B}
NMR: δ 2.47 (s, 10 H, BH), 1.51 (s, 18 H, tBu). 13C{1H} NMR:
δ 112.6 (CtCAu), 99.4 (CAu), 66.2 (C cage), 58.6 (CMe), 29.8
(Me). 11B NMR: δ -11.5 (d, J BH ) 166 Hz).
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Young, V. G., J r. Inorg. Chem. 2001, 40, 6622. Douglass, A. G.;
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Yamamoto, Y. Chem. Commun. 2000, 1595. Tsuboya, N.; Lamrani, M.;
Hamasaki, R.; Ito, M.; Mitsuishi, M.; Miyashita, T.; Yamamoto, Y. J .
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Y.; Iyoda, T. Inorg. Chem. 1998, 37, 172. Allis, D. G.; Spencer, J . T.
Inorg. Chem. 2001, 40, 3373.
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2001, 42, 6327. Bitner, T. W.; Wedge, T. J .; Hawthorne, M. F.; Zink,
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Commun. 2001, 1610.
Syn th esis of P P N[Au (d ecH)2] (6). To a solution of decH2
(0.039 g, 0.2 mmol) in degassed CH2Cl2 (5 mL) was added a
solution of PPN[Au(acac)2] (0.048 g, 0.05 mmol) in the same
solvent (10 mL). The mixture was stirred for 8 h and filtered
through Celite. The solution was then concentrated to dryness
under reduced pressure, giving a residue, which was stirred
with n-hexane (15 mL), filtered off, washed with n-hexane (10
mL), and finally air-dried to give a white microcrystalline solid
shown by NMR to be a mixture of 6 and (PPN)2[{Au(decH)}2-
(µ-dec)] (7) [41 mg, 71% yield; 6/7 ) 80/20; mp 176 °C]. Anal.
Calcd for C48H52AuB20NP2: C, 51.56; H, 4.69; N, 1.25. Found:
C, 50.60; H, 5.04; N, 1.09. IR (cm-1): v(CH) 3302 (w), 3238 (s),
v(BH) 2616 (s); v(CtC) 2114 (s). PPN: 1581 (m), 1320-1220
(s,br), 544 (s), 527 (s), 491 (s). Slow evaporation of a solution
of the above-mentioned mixture in chloroform gave very small
crystals identified by X-ray crystallography as the anionic
complex 6‚CHCl3. Attempts to purify the minor complex 7 by
recrystallization have not proved successful, and it was
characterized by NMR and FAB-MS as a mixture with 6.
Com p lex 6. 1H{11B} NMR: δ 7.45-7.76 (m, 30 H, PPN),
2.43 (s, 10 H, BH), 2.27 (s, 10 H, BH), 1.96 (s, 2 H, CtCH)
(18) Vicente, J .; Chicote, M. T. Inorg. Synth. 1998, 32, 172.
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de Arellano, M. C. Inorg. Chem. 1997, 36, 4438. Vincente, J .; Chicote,
M.-T.; Abrisqueta, M. D.; Alvarez-Falco´n, M. M.; Ram´ırez de Arellano,
M. C.; J ones, P. G. Organometallics 2003, 22, 4327.
ppm. 31P{1H} NMR: δ 21.71 (s). 11B NMR: δ -11.2 (d, J BH
158 Hz, 10 B), -12.5 (d, J BH ) 158 Hz, 10 B). 13C{1H} NMR:
)
(20) Tamaki, A.; Kochi, J . K. J . Organomet. Chem. 1974, 64, 411.

4794 Organometallics, Vol. 22, No. 23, 2003
Vicente et al.
Ta ble 1. Cr ysta l Da ta a n d Str u ctu r e Refin em en ts
Sch em e 1
for 2‚CH2Cl2 a n d 6‚CHCl3
2‚CH2Cl2
6‚CHCl3
formula
fw
T (K)
C50H56Au2B10Cl4O6P2 C49H53AuB20Cl3NP2
1458.72
173(2)
1237.38
100(2)
wavelength (Å)
cryst syst
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
0.71073
monoclinic
P2(1)/c
13.2942(9)
12.0671(13)
19.2784(13)
90
105.662(5)
90
2977.9(4)
2
0.71073
monoclinic
P2(1)/c
22.9998(15)
14.5902(10)
17.1371(11)
90
91.6690(10)
90
5748.3(7)
4
Z
Fcalcd (g cm-3
)
1.627
5.199
1420
1.430
2.791
2456
µ (mm-1
F(000)
)
cryst size (mm3)
θ range for data
collection (deg)
index ranges
0.42 × 0.40 × 0.26
0.18 × 0.07 × 0.05
3.04 to 25.00
1.65 to 26.37
-15 e h e 2
0 e k e 14
-22 e l e 22
5979
25 e h e 28
-18 e k e 15
-21 e l e 21
33 615
no. of reflns
collected
no. of ind reflns
5239 [R(int) )
0.0220]
11 702 [R(int) )
0.0772]
completeness to θ ()25.00°) 99.8%
()26.00°) 99.7%
full-matrix least-
squares on F2
refinement
method
full-matrix least-
squares on F2
psi-scans
abs correction
max. and min.
transmn
does not have any effect, it is probably a genuine disorder
effect. In this compound the solvent molecules (CHCl3) in the
crystal are disordered over two sites (ca. 56:44).
0.901 and 0.470
no. of data/
restraints/
params
5239/7/342
0.919
11702/72/682
0.953
Resu lts a n d Discu ssion
goodness-of-fit
on F2
Syn th esis. A summary of the reactions carried out
in this study is depicted in Scheme 1. Reactions of the
carborane, decH2, with (acetylacetonato)gold(I) com-
plexes, [Au(acac)L], gave the neutral digold compounds
[(AuL)2(µ-dec)] where L is a phosphine, PPh3 (1) or
P(C6H4OMe-4)3 (2), or a carbene, C(NHtBu)(NEt2) (3).
These are new examples of the synthetic utility of
(acetylacetonato)gold(I) complexes, which have been
shown to be versatile and efficient reagents for the
synthesis of a variety of coordination and organometallic
complexes.9,21-23
The reaction in CH2Cl2 between decH2 and [AuCl-
(SMe2)], in the presence of an excess of NEt3 (1:2:4), led
to a solution that, after concentrating to dryness and
washing successively with acetone and water, gave a
pale yellow solid, which in view of its insolubility and
reactivity (see below) we believe to be [Au2(µ-dec)]n (4),
similar to the stable polymeric complexes [AuCtC(R)Ct
CAu]x [R ) C6H4C6H4-4,4′, (C6H2Me2-2,5)-4,11 C6H4-1,3,
(C6HMe3-2,4,6)-1,3, and (C6Me4-2,3,5,6)-1,4], which we
have previously prepared24 by the same method. In
these polymers, the dicoordination at gold must be
R(F)a
0.0306
0.0704
1.029 and -0.833
0.0613
0.1515
4.194 and -1.400
Rw(F2)b
∆F (e Å-3
)
a
R(F) ) ∑||Fo| - |Fc||/∑|Fo| for reflections with F > 2σ(F).
Rw(F2) ) [∑{w(Fo - Fc2)2}/∑{w(Fo2)2}]0.5 for all reflections; w-1
b
2
) σ2(Fo2) + (aP)2 + bP, where P ) [Fo + 2Fc2]/3 and a and b are
2
constants adjusted by the program.
δ 134.0 (m, p-CH), 132.2 (m, m-CH), 129.7 (m, o-CH), 127.0
(m, ipso-C), 117.06 (CtCAu), 97.84 (CAu), 66.8 (C cage) ppm.
MS (FAB-): m/z 580 (M-, 100).
Com p lex 7 (in 1:4 mixture with 6). H{11B} NMR: δ 2.32
1
(s, BH) ppm. 11B NMR: δ -12.0 ppm. Other peaks correspond-
ing to 7 are presumed hidden in peaks assigned to 6. MS
(FAB-): m/z 968 (MH-, 6).
Cr ysta llogr a p h y. Crystal data and refinement details are
presented in Table 1. Crystals were mounted on glass fibers
and transferred to the cold gas stream of the diffractometer
(2‚CH2Cl2 Siemens P4 and 6‚CHCl3 Bruker Smart APEX).
Data were recorded with Mo KR radiation (λ ) 0.71073 Å) in
ω-scan mode. Absorption corrections were applied to 2‚CH2-
Cl2 on the basis of Ψ-scans.
Structures were solved by the heavy-atom method and
refined anisotropically on F2 (program SHELXL-97, G. M.
Sheldrick, University of Go¨ttingen, Germany). Hydrogen
atoms were included using a riding model. Special features of
refinement: In compound 2‚CH2Cl2, the solvent molecules
(CH2Cl2) in the crystal are disordered over two sites (ca. 73:
27). In compound 6‚CHCl3, the residual electron density near
the gold atoms is high. To solve this problem, different crystals
were measured. Despite very careful measurements, the large
difference peak remains. Because absorption corrections (mul-
tiscan with SADABS or face-indexing) or no correction at all
(21) Vicente, J .; Chicote, M. T.; Abrisqueta, M. D.; AÄ lvarez-Falco´n,
M. M. J . Organomet. Chem. 2002, 663, 40.
(22) Vicente, J .; Singhal, A. R.; J ones, P. G. Organometallics 2002,
21, 5887.
(23) Vicente, J .; Chicote, M. T. Coord. Chem. Rev. 1999, 193-195,
1143. Vicente, J .; Chicote, M. T.; Abrisqueta, M. D.; J ones, P. G.
Organometallics 2000, 19, 2629. Vicente, J .; Chicote, M. T.; Guerrero,
R.; Saura-Llamas, I. M.; J ones, P. G.; Ramı´rez de Arellano, M. C. Chem.
Eur. J . 2001, 7, 638.
(24) Vicente, J .; Chicote, M. T.; Alvarez-Falco´n, M. M.; Abrisqueta,
M. D.; Herna´ndez, F. J .; J ones, P. G. Inorg. Chim. Acta 2003, 347, 67.

Alkynyl Gold(I) Rigid-Rod Molecules
Organometallics, Vol. 22, No. 23, 2003 4795
F igu r e 1. Crystal structure of 2‚2CH2Cl2 (30% thermal ellipsoids). Hydrogen atoms and solvent molecules are omitted.
Selected distances (Å) and angles (deg): Au1-C3 2.007(5), Au1-P1 2.2743(14), C2-C3 1.181(7), C1-C2 1.455(7), average
C-P 1.811(5), av C-B 1.715(8), av B-B(tropical) 1.777(10), av B-B(meridianal) 1.758(9), C1‚‚‚C1A 3.112, Au1‚‚‚Au1A
12.36, C1-C2-C3 170.0(6), C2-C3-Au1 174.3(15), C3-Au1-P 179.26(15).
completed by π (CtC) f Au interactions which are
separated by strong donors such as phosphine or iso-
cyanide ligands. On the basis of the recent isolation by
us25 of some [(AuNHEt2)2{(CtC)2-µ-R}] complexes (R )
different arylene radicals) we suggest that the solution
initially formed in the reaction of decH2 with [AuCl-
(SMe2)] and NEt3 is likely to contain the neutral
complex [(AuNEt3)2(µ-dec)], which would be stable only
in the presence of an excess of NEt3. When the excess
is removed by concentration to dryness and washing,
[(AuNEt3)2(µ-dec)] transforms into the insoluble polymer
since π (CtC) f Au bonds would replace the labile Et3N
f Au ones. The byproduct NHEt3Cl is separated by
washing with water. In view of the surprisingly poor
stability of [Au2(µ-dec)]n (4) we decided not to character-
ize it but to suspend it in CH2Cl2 and treat it with a 4:1
excess of tBuNC. The suspension immediately dissolved,
and [(AuCNtBu)2(µ-dec)] (5) was obtained from the
solution.
In an attempt to obtain pure 6, we used a decH2/PPN-
[Au(acac)2] 6:1 molar ratio, but in this case, the NMR
of the isolated product showed the presence of not only
both components of the previous mixture but also ca.
10% of decH2.
Cr ysta l Str u ctu r e of th e Rigid -Rod Com p ou n d s
2‚2CH2Cl2 a n d 6‚CHCl3. The crystal structure of 2‚
2CH2Cl2 (Figure 1) has an inversion center at the center
of the carborane cage. Both in 2‚2CH2Cl2 and in 6‚CHCl3
(Figures 2, 3) the coordination environment of the gold
centers is, as usual, almost linear [2, C(3)-Au(1)-P
179.26(15)°; 6, 178.3(3)°]. Additionally, the anion
[Au(decH)2]- in 6 is very long [C(6)-C(16) 20.51 Å] and
almost linear since the segments C(6)-Au and Au-
C(16) form an angle of 174.9°. Despite the greater trans-
influence of the C-donor with respect to P-donor ligands,
the Au-C bond distances [2, Au(1)-C(3) 2.007(5); 6, Au-
(1)-C(3) 1.999(7), Au(1)-C(13) 2.002(7) Å] are all
similar.
We have reported the syntheses of some anionic
alkynylgold(I) complexes from the reactions of the salt
PPN[Au(acac)2] with alkynes.21,26 In the reaction of
PPN[Au(acac)2] with decH2 designed to give PPN[Au-
(decH)2] (6), we decided to use an excess of the dialkyne
(4:1) over the 2:1 stoichiometric ratio in order to avoid
the formation of the polymer (PPN)n[Au(µ-dec)]n. How-
ever, although the desired complex 6 was obtained in
good yield (71%), its NMR spectra showed the presence
of a second product (ca. 20%, identified as (PPN)2[{Au-
(decH)}2(µ-dec)] (7) by NMR and FAB mass spectros-
copy) that we could not separate. By slow evaporation
of a solution of the mixture in CHCl3, a small amount
of crystals formed. Many of these poor-quality crystals
were subjected to X-ray crystallography and the identity
of 6 was confirmed. Despite repeated recrystallization,
complex 7 could not be isolated pure.
In both complexes, the CtC bond distances [2, 1.181-
(7); 6, 1.188(10), 1.166(9) Å)] are similar to those found
in decH2 [1.179(3), 1.180(3) Å]12 and dec(SiMe3)2 [1.193-
(3) Å].27 However, the average C-B and tropical B-B
bond lengths [2, 1.715(8) and 1.777(10) Å, respectively;
6, 1.714(11) and 1.778(13) Å, respectively] in the C2B10
cages of 2 and 6 differ from the cages in the reported
structures [1.726(3) and 1.793(3) Å, respectively for
decH2,12 or 1.726(2) and 1.789(2) Å, respectively, for dec-
(SiMe3)227]. These differences are likely due to the less
accurate data obtained for 2‚2CH2Cl2 and 6‚CHCl3,
rather than to the gold substituents, as the thermal
motion in para-carboranes mostly takes the form of
rotation around the cage C‚‚‚cage‚‚‚C axis [2, C(1)‚‚‚
C(1A) (Figure 1); 6, C(1)‚‚‚C(4) and C(11)‚‚‚C(14) (Figure
2), and the resulting systematic error is largest for the
tropical B-B bonds.12
In 2‚CH2Cl2 there are no intermolecular contacts
between gold atoms and the gold-phosphine fragments
display geometric parameters similar to those in other
(25) Vicente, J .; Chicote, M. T.; Alvarez-Falco´n, M. M.; J ones, P. G.
Unpublished studies.
(26) Vicente, J .; Chicote, M. T.; Abrisqueta, M. D.; J ones, P. G.
Organometallics 1997, 16, 5628. Vicente, J .; Chicote, M. T.; Saura-
Llamas, I.; Lagunas, M. C. J . Chem. Soc., Chem. Commun. 1992, 915.
Vicente, J .; Chicote, M. T.; Abrisqueta, M. D. J . Chem. Soc., Dalton
Trans. 1995, 497.
(27) Kaszynski, P.; Pakhomov, S.; Young, V. G., J r. Collect. Czech.
Chem. Commun. 2002, 67, 1061.

4796 Organometallics, Vol. 22, No. 23, 2003
Vicente et al.
F igu r e 2. Crystal structure of the anion in 6‚CHCl3 (30% thermal ellipsoids). Solvent molecules, hydrogen atoms, except
CtCH, and the cation are omitted. Selected distances (Å) and angles (deg): Au(1)-C(3) 1.999(7), Au(1)-C(13) 2.002 (7),
C(1)-C(2) 1.461(10), C(11)-C(12) 1.472(10), C(2)-C(3) 1.188(10), C(12)-C(13) 1.166(9), average C-B 1.714(11), av
B-B(tropical) 1.778(13), av B-B(meridianal) 1.764(13), C(6)‚‚‚C(16), 20.51, C(3)-Au(1)-C(13) 178.3(3), torsion angle Au-
(1)-C(6)//Au(1)-C(16) 174.9.
P(C6H4OMe-4)3 complexes containing linearly dicoordi-
nated gold(I).19,28 Although many dimetal complexes
with the 1,4-bis(ethynyl)benzene bridge have been
prepared, only three crystal structures of these com-
pounds are reported in the literature,2,29 and one is of
a digold compound, namely, Me3PAuCtCC6H2Me2Ct
CAuPMe3.22 Comparison of its structure with that of
complex 2 revealed the bond distances along the P-Au-
C-C-C rod to be similar. The average Au-Au distance
of 12.06 Å in the structure of the para-phenylene
complex is shorter than in the structure of 2‚2CH2Cl2
by 0.30 Å, as expected from the bigger carborane unit
in the latter. The structure of compound 2 contains the
longest rigid Au-Au distance yet reported for a digold
compound.
The packing diagram of 6‚CHCl3 displays self-as-
sembling of the [Au(decH)2]- anions through two Ct
C-H‚‚‚Au and one CtC-H‚‚‚π(CtC) intermolecular
hydrogen bonding (Figure 3), while no Au‚‚‚Au auro-
philic contacts are observed. The data involving the
H‚‚‚Au interaction are not very reliable because of
the residual electron density found at gold, but the C‚
‚‚Au [C(6AA)‚‚‚Au(1) 3.53 Å, C(16B)‚‚‚Au(1) 3.72 Å],
H(16H)‚‚‚M (M ) midpoint of the π-system; 2.67 Å; the
F igu r e 3. Packing diagram of the anions of 6‚CHCl3
ethynyl C-H distance is normalized to 1.08 Å), and
C(16B)‚‚‚M (3.51 Å) distances and the C(16B)-
H(16B)‚‚‚M (134.3°) angle point to the existence of
hydrogen bonds that justify the formation of the ob-
served infinite sheet of anions (Figure 4). There are
many examples of C-H‚‚‚Au (C‚‚‚Au: 3.0-3.9 Å) and
CtC-H‚‚‚π(CtC) hydrogen bonding (H‚‚‚M 2.3-2.8 Å,
C‚‚‚M 3.4-3.9 Å, C-H‚‚‚M 123.3-177.5°),30 although
only one complex with a CtC-H‚‚‚π(CtC-Au) hydro-
gen bond has been reported.33 1,4-Bis(ethynyl)benzene
shows CtC-H‚‚‚π(CtC) hydrogen bonds (H‚‚‚M 2.596
Å, C‚‚‚M 3.67 Å, C-H‚‚‚M 174.8°) that give a packing
similar to that in 6‚CHCl3.31 Despite the existence of
many complexes containing intermolecular C-H‚‚‚Au
interactions, just a few papers have reported such
showing the CtC-H‚‚‚Au and CtC-H‚‚‚π(CtC) intermo-
lecular hydrogen bonding.
contacts,5,22,32,33 and only one corresponds to an ethynyl
CtC-H‚‚‚Au interaction with a C‚‚‚Au distance of 3.99
Å.32
NMR a n d IR Sp ect r oscop y. The 11B and 1H{11B
broad-band decoupled} NMR spectra of complexes show
one or two (in the case of 6) doublets at frequencies
similar to those reported for the starting carborane and
its SiMe3 derivative.12 In 6, the 1H{11B selective}
spectrum indicates the BH peak at 2.43 ppm to cor-
respond to the borons at -11.2 ppm. Because the
δ(1H{11B}) of decH2 (2.49 ppm) is similar to that at 2.43
ppm in 6, the peak at 2.27 ppm in this complex could
be assigned to the protons facing the gold atom. Con-
sequently, the greater shielding of these protons [and
that of their B nuclei, resonating also at higher field
(-12.5 ppm)] indicates that the negative charge is
located around the gold atom. A sharp peak at 1.96 ppm
in the proton spectrum of 6 is assigned to the acetylenic
hydrogens.
(28) Cerrada, E.; Laguna, M.; Villacampa, M. D. Acta Crystallogr.
C 1998, 54, 201. Ho, S. Y.; Tiekink, E. R. T. Acta Crystallogr., Sect. E
2001, 57, M549.
(29) Behrens, U.; Hoffman, K.; Kopf, J .; Moritz, J . J . Organomet.
Chem. 1976, 117, 91. Fyfe, H. B.; Mlekuz, M.; Zargarian, D.; Taylor,
N. J .; Marder, T. B. J . Chem. Soc., Chem. Commun. 1991, 188.
(30) Survey of the Cambridge Crystallographic Database May 2003;
Allen, F. H.; Kennard, O. Chem. Des. Autom. News 1993, 8, 31.
(31) Weiss, H.-C.; Bla¨ser, D.; Boese, R.; Doughan, B.; Haley, M. M.
Chem. Commun. 1997, 1703.
(32) Bardaji, M.; J ones, P. G.; Laguna, A. J . Chem. Soc., Dalton
Trans. 2002, 3624.
(33) Barranco, E. N.; Crespo, O.; Gimeno, M. C.; Laguna, A.; J ones,
P. G.; Ahrens, B. Inorg. Chem. 2000, 39, 680.
The inequivalence of the Et groups and the presence
of only one NH and tBu resonances in the proton
spectrum of 3 are indicative of the multiple character
of the C-NEt2 bond in the carbene ligand and the free
rotation around the C-NHtBu one.

Alkynyl Gold(I) Rigid-Rod Molecules
Organometallics, Vol. 22, No. 23, 2003 4797
F igu r e 4. Layers of anions in 6‚CHCl3
The 13C{1H} NMR spectra of 3 could not be measured
even after prolonged accumulation due to its low
solubility. In the remaining neutral complexes, the 13C-
Au resonance (99.4-100 ppm) is highfield shifted with
respect to those in 6 (97.84 ppm) in support of the above
assignments. The resonance due to the cage carbons is
observed in the 13C{1H} spectra of these complexes
toward 66 ppm, but this peak is not observed in the
spectrum of 1, as well as one of the two peaks expected
for 6. Regarding the CtCAu moiety, we have tentatively
assigned the carbon bound to gold (R-C) at higher field
with respect to the â-C due to the coupling of the former
with 31P observed in 1 and 2.
The IR spectra of all these complexes show bands
characteristic of the fragments they contain. Thus, in
the spectra of 1-3, 5, and 6 the bands in the regions
2606-2666 and 2114-2146 are respectively due to the
B-H and CtC stretching modes in the carborane
fragment. Additionally, the spectra show bands due to
N-H (3, 3368 cm-1), CtN (5, 2234 cm-1), C-H (6, 3238,
3302 cm-1), and PPN (6, 1581, 1320-1220, 544, 527,
491 cm-1).
Ack n ow led gm en t. We thank the Direccio´n General
de Investigacio´n Cient´ıfica y Te´cnica and FEDER
(Grant BQU 2001-0113) for financial support. M.A.F.
thanks EPSRC for an Advanced Research Fellowship
(Grant AF/98/2454). M.M.A.-F. thanks Fundacio´n Se´n-
eca (Comunidad Auto´noma de la Regio´n de Murcia,
Spain) for a grant.
Su p p or tin g In for m a tion Ava ila ble: Listing of all refined
and calculated atomic coordinates, anisotropic thermal
parameters, and bond lengths and angles for 2‚CH2Cl2 and
6‚CHCl3. This material is available free of charge via the
Internet at http://pubs.acs.org.
OM0304311