Synthesis and formation of metal complexes of 4-alkynyl and 4-cyano-2,6-diisopropylphenylisocyanides

Article abstract of DOI:10.1016/S0020-1693(98)00288-6

The 4-halo-2,6-diisopropyl-N-formylanilides HC(O)NH-C₆H₂-i-Pr₂-2,6-X-4, (2a) (X = Br) and 2b (X = I), serve as precursors for the bromo-, iodo-, alkynyl- and cyano-substituted diisopropylphenylisocyanides CN-C₆H

Full text of DOI:10.1016/S0020-1693(98)00288-6

Inorganica Chimica Acta 284 (1999) 205±214
Synthesis and formation of metal complexes of 4-alkynyl and
4-cyano-2,6-diisopropylphenylisocyanides
Zhong-lin Lua, Andreas Mayrb,*, Kung-Kai Cheunga
aDepartment of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, China
bDepartment of Chemistry, State University of New York at Stony Brook, Stony Brook, NY 11794-3400, USA
Received 2 February 1998; accepted 6 May 1998
Dedicated to Professor Warren R. Roper on the occasion of his 60th birthday
Abstract
The 4-halo-2,6-diisopropyl-N-formylanilides HC(O)NH-C6H2-i-Pr2-2,6-X-4, (2a) (X ˆ Br) and 2b (X ˆ I), serve as precursors for the
bromo-, iodo-, alkynyl- and cyano-substituted diisopropylphenylisocyanides CN-C6H2-i-Pr2-2,6-X-4, (3a) (X ˆ Br) and 3b (X ˆ I), CN-
C6H2-i-Pr2-2,6-R-4, (6) (R ˆ CꢀCSiMe3), (7) (R ˆ C>CH), (9) (R ˆ C>C-C6H4-C>CSiMe3-4), 10 (R ˆ C>C-C6H4-C>CH-4) and 12
(R ˆ CN). The new isocyanides readily form complexes with several metal iodides: CoI2L4, 13 (L ˆ 7), MI2L2, 14±23 (M ˆ Pd and Pt,
L ˆ 3a, 3b, 7, 10, 12), and AuIL, 24 and 25 (L ˆ 10 and 12). The crystal structures of the complexes 13, 15 (M ˆ Pt, L ˆ 3a), and 22
(M ˆ Pd, L ˆ 12) have been determined by X-ray crystallography. # 1999 Elsevier Science S.A. All rights reserved.
Keywords: Isocyanide complexes; Alkyne complexes; Nitrile complexes; Crystal structures; Transition metal
1. Introduction
complexes bearing hydrogen-bonding sites was based on the
attachment of entire hydrogen-bonding groups to formyl-
substituted arylisocyanides [34]. The signi®cance of this
procedure lies in its wide range of applicability. Due to the
selective reactivity of aldehyde functionality, the procedure
is suitable for the introduction of many types of functional
groups into isocyanide metal complexes, before or after the
establishment of the isocyanide metal complex core. In the
course of this work, we found functionalized derivatives of
2,6-diisopropylphenylisocyanide to be particularly useful
because of the relatively good solubility of metal complexes
of this type of ligand. In an effort to further broaden the
synthetic basis for the design of isocyanide metal complexes
as building blocks for molecular materials, we present here
several procedures for the introduction of functional groups
into 2,6-diisopropylphenyl-isocyanides based on well-estab-
lished transformations of bromo- and iodo-aryl compounds
[35±39]. These types of transformations are particularly well
suited to complement the previously developed method as
far as the extension of the length and variation of the shapes
of functionalized isocyanides is concerned.
On account of their favorable steric and electronic proper-
ties, isocyanide metal complexes [1±10] are promising as
building blocks for organometallic molecular materials. The
most important structural and electronic element of metal
isocyanides in this context is the presence of partial metal±
carbon multiple bonds. Metal±carbon p interactions con-
tribute towards the stability of metal±isocyanide linkages
and they provide a mechanism for the electronic commu-
nication between the metal center and unsaturated isocya-
nide ligands [11±14]. Thus the metal center, as a single atom
not only controls the overall geometry, but also exerts a
dominant in¯uence on the electronic properties of the
building blocks. By connecting such isocyanide metal com-
plexes in a stereochemically controlled and electronically
coupled manner, one can expect to gain access to a variety of
molecular materials with novel properties [15±31]. The type
of molecular components most needed at present for the
development of this type of materials chemistry are suitably
functionalized isocyanides. We have recently demonstrated
that metal complexes of isocyanides carrying nitrogen donor
groups [32,33] or hydrogen-bonding groups [34] can serve
as building blocks for the self-assembly of coordination
polymers. The strategy for the synthesis of isocyanide metal
2. Experimental
2,6-Diisopropylaniline, Me3SiCCH, ICl, CoI2, CuI,
CuCN, PdI2, Pd(dba)2, PdCl2(PPh3)2, PtI2, and AuI were
*Corresponding author. Tel.: +1-516-632-7951; fax: +1-516-632-7960.
0020-1693/99/$ ± see front matter # 1999 Elsevier Science S.A. All rights reserved.
PII: S0020-1693(98)00288-6

206
Z. Lu et al. / Inorganica Chimica Acta 284 (1999) 205±214
purchased from commercial sources. 4-Iodo-1-trimethylsi-
lylethynylbenzene was prepared as described in the litera-
ture [40]. 2,6-Diisopropylaniline was distilled prior to use.
The metal halides were dried under vacuum for 1 h prior to
use. THF, ether, CH2Cl2, and n-hexane were distilled under
N2 from appropriate drying agents. All other solvents and
reagents were of analytical grade and were used as received,
unless otherwise noted. The syntheses of the transition
metal complexes were performed under an atmosphere of
2.1.2. 2,6-Diisopropyl-4-iodo-1-formamidobenzene (2b)
First, 2,6-diisopropyl-4-iodoaniline (1b) is prepared fol-
lowing the procedure described for compound 1a, using
iodine monochloride instead of bromine: 2,6-diisopropyl-
aniline (10 ml, 53 mmol), iodine monochloride (3 ml). The
product is obtained as a light brown oil (14.0 g). Yield:
87.5%. 1H NMR (CDCl3): ꢀ 7.28 (s, 2H, C6H2), 3.73 (br, s,
2H, NH2), 2.84 (m, J ˆ 6.8 Hz, 2H, CH), 1.24 (d,
J ˆ 6.8 Hz, 12H, CH3). 13C NMR (CDCl3), 140.1, 135.0,
131.7, 81.1, 27.9, 22.2. Compound 2b is then obtained
following the procedure described for 2a: 1b (5.2 g,
17.2 mmol), acetic anhydride (3 ml) and formic acid
(3 ml). The product is obtained as white crystalline solid
1
N2. The NMR spectra were recorded at 300 MHz for H
NMR and 75.4 MHz for 13C NMR. The elemental analyses
were performed by the Analytical Laboratory of Peking
University.
1
(4.8 g). Yield: 84.5%. H NMR (CDCl3), two isomers: ꢀ
2.1. Syntheses
8.43 (s) and 7.98 (d) (1H), 7.50 (s) and 7.49 (s) (2H), 7.27 (d)
and 6.77 (s) (1H), 3.19±2.98 (m, 2H), 1.19 (d, 12H). 13C
NMR (CDCl3): ꢀ 164.7 and 160.4 (NHCHO), 149.1, 148.6,
133.3, 133.1, 95.4, 28.8, 28.4, 23.4. IR (CH2Cl2, cm 1):
2.1.1. 2,6-Diisopropyl-4-bromo-1-formamidobenzene (2a)
To a stirred solution of 2,6-diisopropylaniline (20 ml,
106 mmol) in dichloromethane/methanol (1:1, v/v,
100 ml) is added a solution of bromine (5.5 ml, 108 mmol)
in dichloromethane/methanol (1:1, v/v, 50 ml) dropwise via
a pressure funnel at room temperature. After stirring for 12 h
(reaction monitored by TLC), the solvent is evaporated. The
solid is recrystallized with dichloromethane/n-hexane (2:1,
v/v). 2,6-Diisopropyl-4-bromo-aniline hydrobromide is
obtained as a white crystalline solid (28.7 g). Yield
‡
1697 (CˆO). MS (EI): 331 (100%, M ).
2.1.3. 2,6-Diisopropyl-4-bromo-1-isocyanobenzene (3a)
To a stirred mixture of 2a (1.0 g, 3.52 mmol) and Et3N
(0.6 ml) in THF (70 ml) is added a solution of triphosgene
(0.349 g, 1.18 mmol) in THF (15 ml) at 788C. The mix-
ture is allowed to warm slowly to room temperature and is
continued to be stirred for 20 h. Then aqueous sodium
carbonate (10%, 25 ml) is added and the mixture is stirred
for another hour. The mixture is evaporated under reduced
pressure to remove THF. After adding more water, the
mixture is extracted with chloroform (3 Â 100 ml). The
organic layers are combined, washed with water
(2 Â 50 ml), dried over magnesium sulfate, and the solvent
is removed under vacuum. The compound is puri®ed by
chromatography on silica gel using n-hexane/dichloro-
methane (v/v, 100:5) as the eluent to afford a white crystal-
line solid (0.51 g, yield: 54%). 1H NMR (CDCl3): ꢀ 7.29 (s,
2H, C6H2), 3.34 (h, J ˆ 6.9 Hz, 2H, CH), 1.27 (d,
J ˆ 6.9 Hz, 12H, CH3). 13C NMR (CDCl3): ꢀ 170.0,
147.0, 126.8, 123.9, 29.9, 22.4. IR (CH2Cl2, cm 1): 2120
(s, NC). Anal. Calc. for C13H16BrN: C, 58.66; H, 6.06; N,
5.26. Found: C, 58.57; H, 5.88; N, 5.26%.
1
80.3%. H NMR (CDCl3): ꢀ 10.06 (br, 2H), 7.36 (s, 2H),
6.95 (br, 1H), 3.69 (m, 2H), 1.30 (d, 12H). 2,6-Diisopropyl-
4-bromo-aniline hydrobromide (5.0 g, 15.0 mmol) is neu-
tralized with 20% aqueous sodium hydroxide (25 ml) at
room temperature for 1 h. The mixture is extracted with
diethyl ether (3Â60 ml). The combined extracts are dried
over magnesium sulfate. After ®ltration and evaporation of
the solvent, 2,6-diisopropyl-4-bromoaniline (1a) is obtained
1
as a yellow oil (3.5 g). Yield 91.5%. H NMR (CDCl3): ꢀ
7.11 (s, 2H), 3.68 (br, s, 2H), 2.89 (h, 2H), 1.25 (d, 12H).
A mixture of acetic anhydride (10.5 ml) and formic acid
(10.5 ml) is heated for 2 h under 50±608C with stirring.
Then the solution is cooled to room temperature. 2,6-
Diisopropyl-4-bromoaniline (13.9 g, 54.3 mmol) is dropped
into this solution within a few minutes. Then diethyl ether
(150 ml) is added. The resulting solution is stirred at room
temperature for 24 h and neutralized to pH 7 with 10%
aqueous sodium carbonate. The organic phase is dried over
magnesium sulfate. After ®ltration and evaporation of the
solvent, the product is obtained as a white solid which can be
recrystallized from diethyl ether (13.5 g). Yield: 87.5%. 1H
NMR (CDCl3), two isomers: ꢀ 8.46 (d, J ˆ 1.32 Hz) and
7.98 (d, J ˆ 11.79 Hz) (CHO), 7.31 (s) and 7.30 (s) (2H,
C6H2), 7.07 (d, J ˆ 11.85 Hz) and 6.72 (s) (1H, NH), 3.17
(h) and 3.09 (h) (2H, CH); 1.20 (d, J ˆ 6.84 Hz) and 1.19 (d,
J ˆ 6.91 Hz, 12H, CH3). 13C NMR (CDCl3), two isomers: ꢀ
164.7, 160.4, 149.2, 148.6, 129.0, 128.6, 127.9, 127.3,
127.1, 123.9, 123.3, 29.0, 28.6, 23.8, 23.4. IR (CH2Cl2,
cm 1): 1701, 1687 (NHCH=O). MS (EI): 283/285 (100%,
2.1.4. 2,6-Diisopropyl-4-iodo-1-isocyanobenzene (3b)
3b is obtained following the procedure described for 3a.
2b, triphosgene (0.74 g, 2.49 mmol), Et3N (1.4 ml), reaction
time: 12 h, sodium carbonate (10%, 50 ml). The compound
is puri®ed by chromatography on silica gel using n-hexane/
dichloromethane (v/v, 9:1) as the eluent to afford a white to
very light yellow waxy or oily product (1.66 g, yield:
1
87.7%). H NMR (CDCl3): ꢀ 7.48 (s, 2H, C6H2), 3.54±
3.24 (h, J ˆ 6.9 Hz, 2H, CH), 1.26 (d, J ˆ 6.9 Hz, 12H,
CH3). 13C NMR (CDCl3): ꢀ 170.2 (CN), 146.9, 132.8,
123.3, 96.1, 29.8, 22.5. IR (CH2Cl2, cm 1): 2120 (NC).
‡
FAB-MS: 314 (100%, (M‡1) ). Anal. Calc. for C13H16IN:
C, 49.86; H, 5.15; N, 4.47. Found: C, 50.04; H, 5.15; N,
4.37%.
‡
M ).

Z. Lu et al. / Inorganica Chimica Acta 284 (1999) 205±214
207
2.1.5. 3,5-Diisopropyl-4-formamido-1-
trimethylsilylethynylbenzene (4)
2.1.8. 3,5-Diisopropyl-4-isocyano-1-ethynylbenzene (7)
To a methanol (15 ml) solution of 6 (2.5 g, 10.1 mmol)
potassium hydroxide (1 M, 15 ml) is added. The mixture is
stirred for 2 h. Then the solvent is removed under vacuum,
and the residue is extracted with diethyl ether (3 Â 50 ml).
The combined extracts are washed three times with water
and dried over magnesium sulfate. After ®ltration, the
solvent is evaporated to afford 2.0 g of the product. Yield:
93%. 1H NMR (CDCl3): ꢀ 7.29 (s, 2H), 3.35 (h, J ˆ 6.9 Hz,
2H), 3.16 (s, 1H), 1.27 (d, J ˆ 6.9 Hz, 12H). 13C NMR: ꢀ
170.1, 145.2, 127.3, 123.2, 83.0, 78.8, 29.8, 22.4. IR
(CH2Cl2, cm 1): 3299 (CC±H), 2158 (CC), 2118 (±NC).
A ¯ask containing 2a (5.0 g, 17.6 mmol), bis(dibenzyli-
deneacetone)palladium(0) (0.206 g), triphenylphosphine
(0.472 g) and CuI (0.078 g) is evacuated and back-®lled
with nitrogen several times. Then triethylamine (60 ml) and
trimethylsilylacetylene (3.0 ml) are added via a syringe. The
mixture is stirred at 60±708C for about 24 h under nitrogen.
After the reaction is complete (monitored by TLC), the
resulting mixture is cooled to room temperature, ®ltered
through a plug of silica gel, and washed with diethyl ether
(120 ml). The combined ®ltrates are washed with water and
dried over magnesium sulfate. After evaporation of the
solvent, the crude product is recrystallized from n-hexane
to give an off-white crystalline solid, 4.12 g. Yield: 77.8%.
The product can also be obtained in higher yields by using
2b as the starting material. 1H NMR (CDCl3), two isomers:
ꢀ 8.47 (s) and 7.99 (d) (1H), 7.30 (s) and 7.29 (s) (2H), 6.85
(d) and 6.66 (s) (1H), 3.2±3.0 (m, 2H), 1.21 (d, 12H), 0.27 (s,
9H). 13C NMR: ꢀ 163.5, 147.3, 145.9, 128.1, 125.4, 104.7,
95.5, 29.0, 23.8, 0.1. IR (CH2Cl2, cm 1): 2154 (C>C),
‡
FAB-MS: 212 (38%, (M‡1) ).
2.1.9. 4-(3,5-Diisopropyl-4-formamidophenyl)ethynyl-1-
trimethylsilylethynylbenzene (8)
To a mixture of 5 (0.43 g, 1.88 mmol) and 4-iodo-1-
trimethylsilylethynylbenzene (0.565 g, 1.99 mmol) in
triethylamine (20 ml) are added bis(triphenylphosphine)-
palladium dichloride (0.026 g, 0.038 mmol) and copper(I)
iodide (0.007 g, 0.038 mmol). The reaction mixture is stir-
red at room temperature for 6 h under nitrogen. Then the
solvent is removed under reduced pressure. The residue is
extracted with diethyl ether (150 ml) and puri®ed by chro-
matography on silica gel using ethyl acetate/n-hexane (1:2,
v/v) as the eluent to afford 0.61 g of product. Yield: 81%. 1H
NMR (CDCl3), two isomers: ꢀ 8.48 (s) and 8.3 (d) (1H),
7.50±7.43 (m, 4H), 7.35 (s, 2H), 6.80 (d) and 6.68 (s) (1H),
3.24±3.06 (m, 2H), 1.23 (d, 12H), 0.26 (s, 9H). 13C NMR
(CDCl3): ꢀ 164.8, 160.4, 146.9, 146.5, 137.6, 133.1, 131.9,
131.4, 130.2, 129.9, 127.3, 127.1, 123.5, 123.4, 123.3,
123.1, 123.0, 122.5, 104.6, 96.5, 94.4, 91.4, 91.0, 90.4,
89.4, 89.0, 28.8, 28.4, 23.5. IR (CH2Cl2, cm 1): 3408
(N±H), 2156 (CC), 1697 (C=O). FAB-MS: 402 (100%,
‡
1697 (C=O). MS (EI): 301 (75%, M ), 329 (100%,
‡
(M‡28) ).
2.1.6. 3,5-Diisopropyl-4-formamido-1-ethynylbenzene (5)
A methanol solution (15 ml) of 4 (1.63 g, 5.42 mmol) is
treated with potassium hydroxide (0.38 g/8 ml H2O) for 2 h
at room temperature. After hydrolysis is complete (mon-
itored by TLC), methanol is removed under reduced pres-
sure. Then more water is added, and the mixture is extracted
with diethyl ether (2Â50 ml). The combined extracts are
washed with water and dried over magnesium sulfate. After
evaporation of the solvent under reduced pressure, the
product is obtained as a white or very light yellow solid
(1.19 g, yield: 96%). 1H NMR (CDCl3), two isomers: ꢀ 8.48
(s) and 8.01 (d, J ˆ 11.81 Hz) (1H, 7.33 (s, 2H, C6H2), 7.13
(d, J ˆ 11.6 Hz) and 6.77 (s) (1H), 3.23±3.00 (m, 3H, CH,
CCH), 1.21 (d, J ˆ 6.9 Hz, 12H, CH3). 13C NMR (CDCl3):
ꢀ 165.1, 160.5 (NHCHO), 146.9, 146.5, 130.7, 129.3, 127.8,
127.6, 122.6, 122.4, 83.8, 83.4, 28.8, 28.4, 23.47. FAB-MS:
‡
(M‡1) ).
2.1.10. 4-(3,5-Diisopropyl-4-isocyanophenyl)ethynyl-1-
trimethylsilylethynyl benzene (9)
To a stirred mixture of 8 (0.71 g, 1.77 mmol) and Et3N
(0.84 ml) in dichloromethane (30 ml) is added triphosgene
(0.200 g, 0.67 mmol) in dichloromethane (10 ml) at
1988C. The mixture is gradually warmed to room tem-
perature and stirred for 6 h. Then 10% aqueous sodium
carbonate (25 ml) is added and stirring is continued for
another hour. The organic phase is separated and the aque-
ous layer is extracted with diethyl ether (3 Â 50 ml). The
combined organic layers are washed with water
(2 Â 40 ml), dried over magnesium sulfate, and evaporated.
The residue is puri®ed on a silica gel column using n-
hexane/ethylacetate (1:4, v/v) as the eluent to give 0.61 g of
‡
230 (100%, (M‡1) ).
2.1.7. 3,5-Diisopropyl-4-isocyano-1-
trimethylsilylethynylbenzene (6)
The compound is obtained following the procedure
described for 3a. Compound 4 (1.200 g, 3.98 mmol),
triphosgene (0.45 g, 1.52 mmol), Et3N (1.0 ml), reaction
time: 17 h, potassium carbonate (10%, 30 ml). The com-
pound is puri®ed by chromatography on silica gel using n-
hexane as the eluent (white solid, 0.906 g, yield: 80.3%). 1H
NMR (CDCl3): ꢀ 7.25 (s, 2H, C6H2), 3.33 (m, J ˆ 6.9 Hz,
2H, CH), 1.26 (d, J ˆ 6.9 Hz, 12H, CH3), 0.28 (s, 9H, Si-
CH3). 13C NMR (CDCl3): ꢀ 170.0 (CN), 145.2, 127.2,
124.2, 104.4, 96.2, 29.9, 22.55, 0.1. IR (CH2Cl2, cm 1):
2147 (w, CC), 2118 (s, NC). FAB-MS: 284 (100%,
1
product. Yield: 90%. H NMR (CDCl3): ꢀ 7.46 (m, 4H),
7.31 (s, 2H), 3.41±3.32 (m, 2H), 1.30 (d, 12H), 0.26 (s, 9H).
13C NMR (CDCl3): ꢀ 170.1, 145.3, 132.0, 131.5, 126.7,
124.1, 123.4, 122.8, 104.5, 96.6, 90.6, 29.8, 22.5, 0.3. IR
(CH2Cl2, cm 1): 2152 (CC), 2116 (NC). FAB-MS: 384
‡
‡
(M‡1) ).
(30%, (M‡1) ).

208
Z. Lu et al. / Inorganica Chimica Acta 284 (1999) 205±214
2.1.11. 4-(3,5-Diisopropyl-4-isocyanophenyl)ethynyl-1-
ethynylbenzene (10)
2.1.14. trans-[CoI2(4-CN-3,5-diisopropyl-C6H2CCH)4]
(13)
The compound is prepared according to the procedure
described for 7. Thus 9 (0.61 g, 1.57 mmol) and 5 ml 1 M
potassium hydroxide aqueous solution afford 0.45 g of
CoI2 (18.0 mg, 0.058 mmol) is dissolved in absolute
ethanol to give a blue solution. Upon addition of 7
(50.0 mg, 0.237 mmol), the solution turns dark brown
immediately. After the mixture is stirred for 12 h, the
solvent is removed under reduced pressure, and the residue
is washed with n-hexane/diethyl ether. A dark brown solid
is isolated by ®ltration (48.0 mg, yield: 71%). Brown
crystals are obtained from CH2Cl2/hexane. 1H NMR
(CDCl3): ꢀ 3.5. (br), 1.4 (br). IR (CH2Cl2, cm 1): 3300
(C±H), 2170 (NC).
1
product as a yellow solid. Yield: 91%. H NMR (CDCl3):
ꢀ 7.49 (m, 4H), 7.32 (s, 2H), 3.47±3.32 (m, 2H), 3.19 (s, 1H),
1.30 (d, 12H). 13C NMR (CDCl3): ꢀ 170.0, 145.3, 132.1,
131.5, 126.7, 124.0, 123.2, 122.3, 90.7, 90.4, 83.1, 79.2,
29.8, 22.5. IR (CH2Cl2, cm 1): 3300 (C±H), 2117 (NC).
‡
FAB-MS: 312 (100%, (M‡1) ).
2.1.12. 2,6-Diisopropyl-4-cyano-1-formamidobenzene (11)
A stirred mixture of 2a (4.05 g, 17.6 mmol), cuprous
cyanide (1.81 g, 20.2 mmol) and dimethylformamide
(50.0 ml) is re¯uxed for 6 h. The resulting brown mixture
is poured (residues are transferred with hot dimethylforma-
mide) into a solution of hydrated ferric chloride (12.0 g) and
concentrated hydrochloric acid (20 ml) in water (120 ml),
whereby the mixture is maintained at 60±708C for 20 min.
After cooling to room temperature, the mixture is extracted
with diethyl ether (3 Â 100 ml). The combined extracts are
washed with dilute hydrochloric acid, water, and 10%
aqueous sodium hydroxide. The organic layer is dried,
®ltered, and the solvent is removed under reduced pressure.
The crude product is puri®ed on a silica gel column using n-
hexane/ethyl acetate (2:1, v/v) as the eluent to afford 2.74 g
of white solid product. Yield: 84%. 1H NMR (CDCl3), two
isomers: ꢀ 8.49 (d) and 8.04 (d, J ˆ 11.47 Hz) (1H, CHO),
7.49 and 7.48 (2H, C6H2); 7.28 (d, J ˆ 12.67 Hz) and 6.92
(s) (1H, NH), 3.27±3.08 (m, 2H), 1.22±1.19 (d, 12H). 13C
NMR (CDCl3): ꢀ 146.5, 127.5, 118.2, 113.3, 30.0, 22.3. IR
(CH2Cl2, cm 1): 3408 (N±H), 2233 (CN), 1699 (C ˆ O).
2.1.15. trans-[PdI2(CN-C6H2-3,5-diisopropyl-4-Br)2] (14)
A 50 ml ¯ask is charged with 3a (48.3 mg, 0.18 mmol)
and PdI2 (33 mg, 0.09 mmol). The ¯ask is evacuated and
back-®lled with nitrogen three times, and CH2Cl2 (20 ml) is
added. The mixture is stirred at room temperature for 12 h.
The solution is ®ltered, and the solvent is removed under
vacuum. The brown residue is washed with n-hexane and
collected by ®ltration (65 mg). Yield: 70%. 1H NMR
(CDCl3): ꢀ 7.35 (s, 2H, C6H2), 3.52 (h, 2H, CH), 1.32 (d,
12H, CH3). 13C NMR (CDCl3): ꢀ 148.9, 127.3, 126.2, 29.8.
IR (CH2Cl2, cm 1): 2197 (s, ±NC). Anal. Calc. for
C26H32Br2I2N2Pd: C, 34.96; H, 3.59; N, 3.14. Found: C,
35.22; H, 3.50; N, 2.97%.
2.1.16. trans-[PtI2(CN-C6H2-2,6-diisopropyl-4-Br)2] (15)
The procedure for the synthesis of 14 is followed. Thus,
reaction of PtI2 (30.0 mg, 0.067 mmol) and 3a (35.6 mg,
0.134 mmol) in 20 ml methylene chloride gives an orange
solid (32 mg). Yield: 49%. 1H NMR (CDCl3): ꢀ 7.35, 3.52,
1.32. 13C NMR (CDCl3): ꢀ 149.3, 127.2, 126.2, 30.0, 22.7.
IR (CH2Cl2, cm 1): 2191 (s, ±NC). Anal. Calc. for
C26H32Br2I2N2Pt: C, 31.80; H, 3.26; N, 2.85. Found: C,
31.86; H, 3.10; N, 2.66%.
‡
MS (EI): 230 (100%, M ).
2.1.13. 3,5-Diisopropyl-4-isocyanobenzonitrile(12)
To a solution of 11 (2.0 g, 8.8 mmol) and diisopropyl-
amine (3.3 ml, 23.2 mmol) in CH2Cl2 (100 ml), phosphoryl
oxychloride (0.85 ml, 9.1 mmol) in CH2Cl2 (10 ml) is added
dropwise with stirring at 5±08C and stirred for another 1 h.
Then a solution of sodium carbonate (3.0 g) in water (30 ml)
is added at a slow rate to ensure that the temperature of the
mixture does not rise above 308C. After stirring for 1 h at
room temperature, more water (50 ml) and CH2Cl2 (100 ml)
are added. The organic layer is separated and washed with
water (3 Â 50 ml). The solvent is removed under reduced
pressure and the residue is puri®ed by column chromato-
graphy on silica gel, using n-hexane/CH2Cl2 (1:1, v/v) as the
eluent (1.37 g, yield: 74%). The product can also be
obtained in a similar yield by dehydration of 11 with
2.1.17. trans-[PdI2(CN-C6H2-2,6-diisopropyl-4-I)2] (16)
1
The procedure for the synthesis of 14 is followed. H
NMR (CDCl3): ꢀ 7.35, 3.48, 1.32. 13C NMR (CDCl3): ꢀ
148.6, 133.4, 98.7, 29.6, 22.8. IR (CH2Cl2, cm 1): 2195
(s, ±NC). Anal. Calc. for C26H32I4N2Pd: C, 31.63; H,
3.24; N, 2.84. Found: C, 31.77; H, 3.18; N, 2.49%.
2.1.18. trans-[PtI2(CN-C6H2-2,6-diisopropyl-4-I)2] (17)
1
The procedure for the synthesis of 14 is followed. H
NMR (CDCl3): ꢀ 7.55, 3.48, 1.31. 13C NMR (CDCl3): ꢀ
148.6, 133.4, 98.5, 29.6, 22.8. IR (CH2Cl2, cm 1): 2189
(s, ±NC). Anal. Calc. for C26H32I4N2Pt: C, 29.02; H,
2.98; N, 2.60. Found: C, 29.26; H, 2.95; N, 2.23%.
1
triphosgene/NEt3. H NMR (CDCl3): ꢀ 7.47 (s, 2H), 3.40
(h, 2H), 1.30 (d, 12H). 13C NMR (CDCl3): ꢀ 146.5, 127.5,
2.1.19. trans-[PdI2(4-CN-3,5-diisopropyl-
C6H2CCH)2](18)
The procedure for the synthesis of 14 is followed. Thus,
reaction of PdI2 (45.0 mg, 0.125 mmol) and 7 (55.0 mg,
0.260 mmol) in 20 ml methylene chloride gives an orange
118.2, 113.3, 30.0, 22.3. IR (CH2Cl2, cm 1): 2233 (w, ±CN),
‡
2115 (s, ±NC). MS (EI): 212 (34%, M ), 197 (100%,
‡
(M 15) ).

Z. Lu et al. / Inorganica Chimica Acta 284 (1999) 205±214
209
1
solid (60.0 mg). Yield: 61%. H NMR (CDCl3): ꢀ 7.34 (s,
0.150 mmol) in dichloromethane to give 36 mg green±yel-
1
2H), 3.53 (h, 2H), 3.23 (s, 1H), 1.33 (d, 12H). 13C NMR
(CDCl3): ꢀ 147.2, 127.6, 125.1, 123.4, 82.7, 80.0, 29.6, 22.8.
IR (CH2Cl2, cm 1): 3300 (C±H), 2196 (NC). Anal. Calc. for
C30H34I2N2Pd: C, 46.01; H, 4.35; N, 3.59. Found: C, 46.08;
H, 4.34; N, 3.47%.
low solid. Yield: 56%. H NMR (CDCl3): ꢀ 7.53 (s, 2H),
3.58 (h, 2H), 1.36 (d, 12H). 13C NMR (CDCl3): ꢀ 148.4,
127.9, 117.8. 115.0, 29.8, 22.7. IR (CH2Cl2, cm 1): 2187
(±NC), 2234 (CN). Anal. Calc. for C28H32I2N4Pt: C, 38.48;
H, 3.67; N, 6.41. Found: C, 38.31; H, 3.53; N, 6.30%.
2.1.20. trans-[PtI2(4-CN-3,5-diisopropyl-C6H2CCH)2]
(19)
2.1.25. [AuI(4-(4-CN-3,5-diisopropyl-C6H2CC)-
C6H4-CCH)] (24)
The procedure for the synthesis of 14 is followed. Thus
PtI2 (33.0 mg, 0.074 mmol) and 7 (31.5 mg, 0.260 mmol)
in 20 ml methylene chloride afford an orange solid
A 50 ml ¯ask is charged with 10 (21.0 mg, 0.067 mmol)
and AuI (20 mg, 0.062 mmol). The ¯ask is evacuated and
back-®lled with nitrogen three times, and THF (20 ml) is
added. The mixture is stirred at room temperature for 4 h.
The solution is ®ltered, and the solvent is removed under
vacuum. The off-white residue is washed with n-hexane and
collected by ®ltration (30.5 mg). Yield: 78%. 1H NMR
(CDCl3): ꢀ 7.50 (s, 4H), 7.37 (s, 2H), 3.28±3.18 (m, 2H),
3.20 (s, 1H), 1.34±1.32 (d, 12H). 13C NMR (CDCl3): ꢀ
146.6, 132.2, 131.6, 127.3, 126.7, 122.8, 122.7, 92.3, 83.0,
79.5, 30.1, 22.5. IR (CH2Cl2, cm 1): 3300 (w, CH), 2197 (s,
NC).
1
(40.0 mg). Yield: 62%. H NMR (CDCl3): ꢀ 7.37 (s, 2H),
3.53 (h, 2H), 3.30 (s, 1H), 1.32 (d, 12H). 13C NMR (CDCl3):
ꢀ 147.6, 128.1, 125.3, 83.0, 80.1, 30.0, 22.9. IR (CH2Cl2,
cm 1): 3300 (C±H), 2189 (NC). Anal. Calc. for
C30H34I2N2Pt: C, 41.33; H, 3.90; N, 3.21. Found: C,
41.55; H, 3.91; N, 2.62%.
2.1.21. trans-[PdI2(4-(4-CN-3,5-diisopropyl-C6H2CC)-
C6H4-CCH)2 ] (20)
The procedure for the synthesis of 14 is followed. Reac-
tion of PdI2 (20.0 mg, 0.055 mmol) and 10 (34.6 mg,
0.111 mmol) affords a yellow product (32.0 mg). Yield:
2.1.26. [AuI(4-CN-3,5-diisopropyl-C6H2CN)] (25)
The complex is synthesized according to the method for
24. Thus AuI (34.6 mg, 0.107 mmol) and 12 (25.6 mg,
0.120 mmol) in 50 ml THF afford 34.0 mg of product.
1
51%. C46H42PdI2N2, FW: H NMR (CDCl3): ꢀ 7.50 (m,
4H), 7.37 (s, 2H), 3.54 (m, 2H), 3.20 (s, 1H), 1.27 (d, 12H).
13C NMR (CDCl3): ꢀ 147.2, 132.2, 131.6, 127.1, 126.0,
122.9, 122.6, 91.6, 90.4, 83.1, 79.3, 29.7, 22.9. IR (CH2Cl2,
cm 1): 2193 (±NC), 3290 (CC±H). Anal. Calc. for
C46H42Br2I2N2PdÁ0.5 C6H4: C, 57.33; H, 4.78; N, 2.73.
Found: C, 57.75; H, 4.75; N, 2.22%.
1
Yield: 60%. H NMR (CDCl3): ꢀ 7.53 (s, 2H), 3.32±3.23
(m, 2H), 1.35±1.32 (d, 12H). IR (CH2Cl2, cm 1): 2200
(±NC), 2233 (CN).
2.2. Crystal structure determinations
2.1.22. trans-[PtI2(4-(4-CN-3,5-diisopropyl-C6H2CC)-
C6H4-CCH)2] (21)
The procedure for the synthesis of 14 is followed. H
NMR (CD2Cl2): ꢀ 7.43 (m, 4H), 7.34 (s, 2H), 3.48 (m, 2H),
3.19 (s, 1H), 1.27 (d, 12H). 13C NMR (CD2Cl2): ꢀ 147.6,
132.6, 132.1, 127.6, 126.2, 123.4, 122.9, 110.1, 91.7, 90.8,
83.3, 79.6, 30.0, 23.0. IR (CH2Cl2, cm 1): 3292, (w, CC±H),
2189 (NC). Anal. Calc. for C46H42Br2I2N2PtÁ0.5 C6H4: C,
52.78; H, 4.39; N, 2.51. Found: C, 52.35; H, 4.32; N, 1.93%.
The diffraction data for compound 22 were collected on
an MAR Imaging Plate Detector System using X-ray radia-
tion from a MAR generator (sealed tube 50 kVand 50 mA),
and processed by DENZO [41]. The diffraction data for
compound 13 were collected on a Rigaku AFC7R four-
circle diffractometer using X-ray radiation from a Rigaku
RU-200 rotating-anode generator at 50 kVand 160 mA and
processed by the MSC/RIGAKU diffractometer control
software. The diffraction data for compound 15 were col-
lected on a Enraf-Nonius CAD4 four-circle diffractometer
using X-ray radiation from a sealed tube (50 kVand 26 mA)
and processed by the CAD4 software (PC version). The X-
ray radiation from all three generators was graphite-mono-
1
2.1.23. trans-[PdI2(4-CN-3,5-diisopropyl-C6H2CN)2] (22)
The procedure for the synthesis of 14 is followed.
Reaction of PdI2 (33.9 mg, 0.094 mmol) and 12 (42 mg,
0.197 mmol) in dichloromethane to give 53.0 mg
orange±yellow solid. Yield: 72%. 1H NMR (CDCl3): ꢀ
7.53 (s, 2H), 3.58 (h, 2H), 1.36 (d, 12H). 13C NMR (CDCl3):
ꢀ 148.5, 127.9, 117.7, 115.2, 29.9, 22.7. IR (CH2Cl2, cm 1):
2196 (±NC), 2233 (CN). Anal. Calc. for C28H32I2N4Pd:
C, 42.83; H, 4.08; N, 7.14. Found: C, 42.64; H, 3.91; N,
7.03%.
Ê
chromatized Mo Ka X-ray radiation (ꢁ ˆ 0.71073A).
Empirical absorption corrections from -scans were applied
to the data for compounds 13 and 15 and no absorption
correction was made on compound 22. All structure deter-
minations and numerical calculations were made using the
MSC crystal structure analysis package-TeXsan [42] using a
Silicon Graphic Computer, and the full-matrix least±squares
re®nements were on F using re¯ections with I > 3ꢂ(I).
Hydrogen atoms at calculated positions with thermal para-
meters equal to 1.3 times that of the attached C atoms were
included in the calculations, but not re®ned.
2.1.24. trans-[PtI2(4-CN-3,5-diisopropyl-C6H2CN)2] (23)
The procedure for the synthesis of 14 is followed. Reac-
tion of PtI2 (33.3 mg, 0.074 mmol) and 12 (32.0 mg,

210
Z. Lu et al. / Inorganica Chimica Acta 284 (1999) 205±214
3. Results and discussion
Substitution of the halogens in 2a and 2b by the trimethyl-
silylalkynyl group to afford 4 is achieved by cross-coupling
with trimethylsilyacetylene in the presence of catalytic
amounts of bis(dibenzylideneacetone)palladium(0) and
copper(I) iodide [39±41]. Treatment of 4 with aqueous
KOH affords acetylene 5, which is dehydrated to give the
4-isocyanophenylacetylene 7. Compound 7 can also be
obtained from 4 by reversing the hydrolysis and dehydration
steps, via the 4-isocyano-1-trimethylsilylethynylbenzene 6.
The extended trimethylsilylphenylacetylene derivative 8 is
obtained by reaction of 5 with 4-iodophenyl(trimethyl-
silyl)acetylene [40] under conditions similar to those
employed in the synthesis of compound 4. Dehydration
of 8 and subsequent desilylation affords the extended
isocyanophenylacetylene derivatives 9 and 10. The 4-iso-
cyanobenzonitrile 12 is obtained in two steps from 2a by
sequential treatment with copper(I) cyanide and dehydra-
tion with triphosgene/triethylamine.
The 4-bromo- and 4-iodo-2,6-diisopropylanilines 1a and
1b were chosen as the starting materials for the present
study and prepared by treatment of 2,6-diisopropylaniline
with bromine and iodine monochloride [43], respectively
(Scheme 1). Formylation of 1a and 1b with formic acetic
anhydride affords the formamides 2a and 2b, which are
dehydrated to give the isocyanides 3a and 3b [44,45].
The new isocyanides 3, 6, 7, 9, 10, and 12 are character-
ized by a strong absorption in the IR near 2120 cm 1 [1±10].
The acetylene groups of compounds 4±10 give rise to weak
bands near 2150 cm 1 [46]. The nitrile derivatives 11 and 12
exhibit weak absorptions at around 2230 cm 1 for the nitrile
groups [47,48].
In contrast to the isocyanide ligands bearing nitrogen
donor groups or hydrogen-bonding groups which we have
synthesized previously, the alkynyl groups of the ligands 7
and 10 are not suitable for reversible self-assembly pro-
cesses. These ligands are, however, useful for the construc-
tion of larger discrete polymetallic units or polymeric metal
complexes by means of establishing metal±alkynyl links
[31,49±54]. Several oligomeric and polymeric metal com-
plexes based on the isocyanophenylacetylide ligands 4-
CNC6H4CC and 3-Me-4-CNC6H3CC have recently been
described by Puddephatt and co-workers [24].
Due to the presence of the bulky isopropyl substituents,
metal complexes of the new isocyanides can be expected to
possess both increased stability and higher solubility than
complexes of isocyanides without alkyl substituents. The
relatively low solubility of some metal complexes of unsub-
stituted isocyanobenzonitriles has previously made it dif®-
cult, in several cases, to obtain coordination polymers. It is
hoped that the higher solubility of metal complexes of the
bulkier isocyanide 12 will facilitate the formation of crystal-
line coordination polymers by molecular self-assembly.
As expected, the new isocyanides readily form transition
metal complexes (Scheme 2). The isocyanide 7 combines
with cobalt(II) iodide to afford complex 13. The isocyanides
3, 7, 10, and 12 combine with palladium(II) iodide and
platinum(II) iodide to afford the complexes 14±23. The gold
complexes 24 and 25 were prepared by addition of 10 and 12
to gold(I) iodide.
Due to the trans arrangement of the iodide ligands in
complexes 13±23, the four isocyanide ligands in 13 are
arranged in equatorial fashion and the two isocyanide
ligands in complexes 14±23 are mutually trans. Thus the
Scheme 1. (i) formic acetic anhydride; (ii) triphosgene/triethylamine; (iii)
4-IC6H4CCSiMe3/PdCl2(PPh3)2/CuI; (iv) KOH; (v) CuCN.

Z. Lu et al. / Inorganica Chimica Acta 284 (1999) 205±214
211
Scheme 2.
IR spectra of these compounds exhibit only single absorp-
tions for the isocyanide ligands. Upon coordination to the
metal centers, the stretching frequencies of the isocyanide
ligands experience a characteristic shift to higher energies,
1
1
by about 50 cm for Co(II) and 70±80 cm for Pd(II),
Pt(II), and Au(I) [1±10]. Only single sets of NMR signals
are observed for the isocyanide ligands in all complexes
13±25.
The molecular structures of complexes 13, 15, and 22
were established by X-ray crystallography. The crystallo-
graphic data are collected in Table 1, selected bond dis-
tances and bond angles are listed in Table 2. Drawings of the
molecular structures are shown in Fig. 1. The intramole-
cular geometric parameters of the compounds 13, 15, and 22
are unexceptional. All bond distances and bond angles are
within the ranges established for the respective types of
isocyanide metal complex [55±57]. Noteworthy is a special
feature of the crystal packing of the cobalt complex 13. As
shown in Fig. 2, the molecular units are arranged in a way
that the alkynyl carbon atoms C(9), C(24), and the iodide
atom I(1) of three adjacent molecular units form a close
triangle with intermolecular distances of I(1)Á Á ÁC(9)
Fig. 1. (a) Molecular structure of complex 13. (b) Molecular structure of
complex 15. (c) Molecular structure of complex 22. The thermal ellipsoids
are shown at the 50% probability level.
Ê
Ê
3.845(0) A, I(1)Á Á ÁC(24) 4.37(1) A, and C(9)Á Á ÁC(24)
Ê
3.98(1) A. The two shorter of these distances, namely,
I(1)Á Á ÁC(9) and C(9)Á Á ÁC(24), suggest the presence of
hydrogen bonds involving the C>C±H groups. The orienta-
tions of the terminal acetylene groups indicate that
C(8)>C(9)±H serves as a hydrogen bond donor towards
I(1) [I(1)±C(9)±C(8) ˆ 158.3(7)8] and C(23)>C(24)±H as
a hydrogen bond donor towards p(C(8)>C(9)) [C(8)±
C(24)±C(23) ˆ 165.1(9)8 C(8)±C(9)±C(24) ˆ 95.8(7)8].
Thus the acetylene group C(8)>C(9)±H acts both as a
hydrogen bond donor and acceptor. Hydrogen bonds invol-
ving C>C triple bonds as acceptors and CC±H groups as
donors are very weak, but several examples have been well
documented in recent studies [58,59]. The ability of iodide
ligands in iodometal isocyanide complexes to serve as
hydrogen bond acceptors has previously been found in
the complex [FeI2(CN-C6H3-2,6-Me2-4-CHNOH)4], where

212
Z. Lu et al. / Inorganica Chimica Acta 284 (1999) 205±214
Table 1
Crystal and data collection parameters for complexes 13, 15, and 22
13
15
22
Formula
C
60H68CoI2N4O4ÁCH2Cl2
C26H32Br2N2Pt
981.26
C28H32I2N4Pd
784.80
triclinic
P1 (No. 2)
8.578(2)
9.585(2)
10.770(2)
66.80(2)
67.45(2)
83.06(2)
751.2(4)
1
Formula weight
Crystal system
Space group
1242.90
monoclinic
P21/c (No. 14)
11.36(1)
monoclinic
C2/c (No. 15)
20.015(4)
Ê
a (A)
Ê
b (A)
21.351(9)
13.649(10)
8.478(2)
Ê
c (A)
18.880(2)
ꢃ (8)
ꢄ (8)
ꢅ (8)
102.04(6)
110.32(2)
3
Ê
V (A)
3236(3)
2
301
3004.4(9)
4
301
Z
T (K)
301
Crystal color
reddish brown
0.20Â0.10Â0.40
1.275
yellow
0.20Â0.05Â0.35
2.169
93.92
!-2ꢇ
orange
0.15Â0.05Â0.30
1.735
Crystal dimensions (mm)
3
d (calc) (g cm
1
)
ꢆ (cm
Scan mode
)
13.38
26.96
!-2ꢇ
50.0
!-2ꢇ
51.2
2ꢇ max. (8)
Unique reflections
Reflections (I>3ꢂ(I)) used in least-squares refinement
49.9
5869
3041
2833
2056
2453
1733
No. of variables
R
Rw
316
151
160
0.032a
0.042a
0.051b
0.021
0.028a
0.036b
0.016
0.01
0.040b
p-factor
0.019
(Á/ꢂ) max
Goodness-of-fit
0.05
0.01
1.72
2.24
1.62
3
Ê
Áꢈ, e A
0.55/0.77
1.33/0.48
0.35/0.65
a R ˆ Æ||Fo| |Fc||/Æ|Fo|.
b Rw ˆ [Æw(|Fo| |Fc|)2/ÆwFo
]
2 1/2, where w ˆ Fo2/[ꢂ2(I)‡(pFo2)2].
the oxime groups of one pair of mutually trans isocyanide
Ê
ligands form OÁ Á ÁI contacts of 3.59(1) A [34]. The hydrogen
bond distances found in the structure of 13 are perhaps
somewhat longer than one might expect for the respective
types of interactions. Also, the hydrogen bonds are probably
not optimized in terms of the intermolecular distances and
the direction of the approach of the C±H bonds towards the
acceptor groups, that is, C(23)C(24)±H does not point
towards the midpoint of the C(8)>C(9) triple bond, and
C(8)C(9)±H does not point directly towards the iodide
ligand.
Table 2
Ê
(a) Selected bond lengths (A) and bond angles (8) for complex 13
Co(1)±I(1)
Co(1)±C(16)
N(1)±C(2)
N(2)±C(17)
C(8)±C(9)
2.8448(7)
1.849(7)
1.414(8)
1.410(8)
1.148(9)
1.137(10)
Co(1)±C(1)
N(1)±C(1)
N(2)±C(16)
C(5)±C(8)
C(20)±C(23)
1.850(6)
1.139(7)
1.151(7)
1.441(9)
1.43(1)
C(23)±C(24)
I(1)±Co(1)±C(1)
C(1)±Co(1)±C(16)
Co(1)±C(16)±N(2)
89.7(2)
92.6(3)
I(1)±Co(1)±C(16)
Co(1)±C(1)±N(1)
91.4(2)
175.5(6)
175.6(6)
4. Conclusions
Ê
(b) Selected bond lengths (A) and bond angles (8) for complex 15
Pt(1)±I(1)
Br(1)±C(5)
N(1)±C(2)
2.6054(7)
1.900(6)
1.395(7)
Pt(1)±C(1)
1.946(6)
Several new alkynyl- and cyano-substituted diisopropyl-
phenylisocyanides have been prepared from 4-bromo- and
4-iodo-2,6-diisopropylphenylformamide as precursors, uti-
lizing palladium-catalyzed cross-coupling and copper-
mediated substitution reactions. The 4-alkynylphenyliso-
cyanide ligands in complexes 13 and 14±23 are arranged
in square planar and linear arrangements, respectively. The
terminal acetylene groups are oriented exactly along the
extended coordination axes of the transition metal centers.
Thus it should be possible, via established metal acetylide
N(1)±C(1)
1.146(8)
I(1)±Pt(1)±C(1)
90.7(2)
Ê
Pt(1)±C(1)±N(1)
179.2(6)
(c) Selected bond lengths (A) and bond angles (8) for compound 22
Pd(1)±I(1)
N(1)±C(1)
N(2)±C(8)
2.5905(3)
1.137(6)
1.020(6)
Pd(1)±C(1)
N(1)±C(2)
C(5)±C(8)
1.960(5)
1.406(6)
1.517(7)
I(1)±Pd(1)±C(1)
89.7(1)
Pd(1)±C(1)±N(1)
179.6(4)

Z. Lu et al. / Inorganica Chimica Acta 284 (1999) 205±214
213
[10] D. Lentz, Angew. Chem., Int. Ed. Engl. 33 (1994) 1315.
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È
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25 (1984) 3679.
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Fig. 2. Three adjacent molecular units in the solid-state structure of 13.
The intermolecular contacts involving the terminal acetylene groups are
indicated by dotted lines.
Â
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Acknowledgements
Support for this work by the Research Grants Council of
Hong Kong (RGC) and by the Committee on Research and
Conference Grants (CRCG) of The University of Hong
Kong is gratefully acknowledged. Crystallographic data
have been deposited at the CCDC, 12 Union Road, Cam-
bridge CB2 1EZ, UK, and copies can be obtained on
request, free of charge, by quoting the publication citation.
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