Synthesis of Long, Palladium End-Capped Polyynes through the Use of Asymmetric 1-Iodopolyynes

Article abstract of DOI:10.1002/chem.201502737

The synthesis of a unique series of long, asymmetric 1-iodopolyynes (1-C_nI and 2-C_nI) with the sp-hybridized carbon chain up to a decapentayne is reported. These compounds were then used as substrates in reactions with Pd(PPh₃

Full text of DOI:10.1002/chem.201502737

DOI: 10.1002/chem.201502737
Full Paper
&
Polyynes
Synthesis of Long, Palladium End-Capped Polyynes through the
Use of Asymmetric 1-Iodopolyynes
Bartłomiej Pigulski, Nurbey Gulia, and Sławomir Szafert*[a]
Abstract: The synthesis of a unique series of long, asymmet-
ric 1-iodopolyynes (1-CnI and 2-CnI) with the sp-hybridized
carbon chain up to a decapentayne is reported. These com-
pounds were then used as substrates in reactions with
Pd(PPh3)4 leading to another series of palladium end-capped
polyynes, which were unstable in solution. Organometallic
octatetraynes 1-C8[Pd]I, 2-C8[Pd]I, and decapentayne 1-
C10[Pd]I are palladium end-capped polyyne compounds with
the longest carbon chains reported so far. All the complexes
as well as their organic precursors were fully characterized
by NMR, HRMS(ESI), IR, TGA-DTA, and UV/Vis techniques, and
the X-ray crystal structures of two silyl-protected precursors
and one palladium complex are presented. The synthetic ap-
proach for palladium species is envisioned as a general
route for the synthesis of labile organometallic polyynes.
Introduction
extensive and ongoing studies of polyynic palladium com-
plexes, they are rarely reported and, before this report, only
a few examples of compounds with butadiyne carbon chain
were known.[14] Recently, we reported the use of 1-halopo-
lyynes (mostly 1-bromobutadiynes) as substrates for palladium
end-capped polyynes with a carbon chain up to the hexa-
triyne.[15] To date, this reported palladium compound with a C6
carbon chain is the only known palladium end-capped hexa-
triyne.
Organic, organometallic, and metal-containing polyynes have
attracted interest from the scientific community for more than
half a century.[1] Such species may be regarded as model com-
pounds of the hypothetical linear allotropic form of carbon—
carbyne—however, polyynes also possess considerable poten-
tial for a number of applications. Such molecules have been
explored as molecular wires and switches in nanoelectronics,[2]
as materials for optoelectronics because of their nonlinear op-
tical response[3] or as precursors for conducting polymers.[4] It
is also noteworthy that polyynes and cyanopolyynes are
among the largest molecules that have been found in interstel-
lar matter.[5]
The lack of long palladium polyynes is a consequence of the
fact that it is impossible to use the most common synthetic
strategy leading to polyynes; that is, chain elongation starting,
for instance, from an ethynyl complex. Alkynyl palladium com-
plexes have proven to be highly unstable in solution because
of ligand exchange[15] and, therefore, it is not possible to carry
out C(sp)–C(sp) cross-coupling reactions for s-alkynyl palladi-
um complexes. This is why long, palladium end-capped poly-
ynes are not reported whereas their platinum analogues are
well explored. For this reason, the synthetic approach in which
the polyyne chain with the target length is attached to the
metal in the final step seems to be the only rational way to ap-
proach such unstable organometallic polyynes. Moreover, pal-
ladium end-capped polyynes may be a versatile starting mate-
rial for numerous new coupling products.
Organometallic polyynes are an important class of poly-
ynes[6] and, to date, the most intense research has concerned
rhenium,[7] ruthenium,[8] iron,[9] and especially platinum[10] com-
plexes. Alkynyl palladium complexes are well known and have
been studied for many years; this is because such compounds
may be regarded as key intermediates in many coupling reac-
tions[11] and are known as active catalysts for living polymeri-
zation of isocyanides.[12] Recently, the use of palladium end-
capped butadiynes as highly active initiators for this reaction
was reported.[12c] Moreover, organometallic polymers with
a PdCꢀC moiety exhibit nonlinear optical, luminescence, and
liquid crystalline properties, all of which make them attractive
for use in numerous commercial applications.[13] Despite the
In this work, we present the synthesis of a series of unique,
fully conjugated 1-iodopolyynes with carbon chain up to the
decapentayne and describe their use as substrates for the syn-
thesis of palladium end-capped polyynes.[15–16] This approach
led to the longest known palladium end-capped polyynes with
a carbon chain up to C10. The new compounds were character-
[a] Dr. B. Pigulski, Dr. N. Gulia, Dr. S. Szafert
Department of Chemistry
1
ized by H, 13C, 31P NMR, IR, TGA-DTA, UV/Vis and HRMS (ESI)
University of Wrocław
14 F. Joliot-Curie, 50-383 Wrocław (Poland)
E-mail: slawomir.szafert@chem.uni.wroc.pl
Homepage: http://www.zb1.chem.uni.wroc.pl
techniques. Furthermore, the X-ray crystal structures of hexa-
triyne 2-C6[Pd]I and silyl-protected precursors 1-C8TMS and 1-
C10-TIPS are presented.
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/chem.201502737.
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cedure with the Cadiot–Chodkiewicz cross-coupling as the
carbon chain elongation step. As mentioned in the introduc-
tion, long 1-halopolyynes are extremely rare and the only
known examples are octatetrayne I(CꢀC)8I[18a] and decapen-
tayne I(CꢀC)10I.[18b]
Results and Discussion
Synthesis of long 1-halopolyynes
1-Iodopolyynes and 1-halopolyynes in general are a rare class
of compounds that exhibit several fascinating properties. The
history of 1-halopolyynes begins in the second half of the 19th
century with von Baeyer’s synthesis of diiodobutadiyne.[17]
However, the synthesis of longer homologues was not ach-
ieved until I(CꢀC)nI (n=3, 4, 5) carbon rods were obtained in
Goroff’s group (see Figure 1) from which I(CꢀC)10I is the lon-
All of our syntheses started from para-bromonitrobenzene
or para-bromobenzonitrile according to the synthetic strategy
involving Sonogashira cross-coupling in the first step, followed
by bromination with deprotection in situ and Cadiot–Chodkie-
wicz cross-coupling with TMSC2H or TMSC4H, as shown in
Scheme 1 (TMSC4H was obtained according to a reported pro-
cedure;[27] synthetic route to 1-C4Br, 2-C4Br, and 1-C6TMS was
reported in our previous work;[15,28] compound 2-C6TMS was
obtained as described for 1-C6TMS). The choice of aryl substitu-
ents was based on the greater stability of 1-iodopolyynes with
these groups compared with, for instance, para-fluorophenyl
or perfluorophenyl groups. Polar end-groups such as nitro and
nitrile groups also allowed column chromatography after cou-
pling reactions to be performed more easily. Cadiot–Chodkie-
wicz cross-coupling of 1-C4Br and 2-C4Br with TMSC4H gave
new octatetraynes 1-C8TMS and 2-C8TMS. Iodination of all
TMS-protected polyynes gave new 1-iodohextatriynes (1-C6I
and 2-C6I) and 1-iodooctatetraynes (1-C8I and 2-C8I) with good
yields (75–95%). Synthesis of the C10I type compound present-
ed a greater challenge. We have noticed that elongation of the
carbon chain strongly decreases the solubility of 1-iodopo-
lyynes. Compound 2-C8I was very poorly soluble in CH2Cl2,
CHCl3, tetrahydrofuran (THF), and MeCN, and consequently its
use in further chain elongation was challenging. The solubility
of compounds with a benzonitrile end-group was better, so
we attempted to obtain the silyl-protected precursor of 1-C10I.
In the first thrust, Cadiot–Chodkiewicz cross-coupling of 1-C8I
with TMSC2H was performed, but we observed only traces of
Figure 1. 1-Haloalkynes, 1-halopolyynes (top), and examples of 1,n-diiodopo-
lyynes from Goroff’s group (bottom).
gest known 1-halopolyyne to date.[18] 1-Halopolyynes may be
used as precursors of an interesting group of carbon-rich mol-
ecules. It has been shown that diiodobutadiyyne and dibromo-
butadiyne may be substrates for easy preparation of tetrahalo-
butatrienes[19] but the most fascinating example of their reac-
tivity is topochemical crystal-to-crystal polymerization of diio-
dobutadiyne yielding the conducting poly(diiododiacetylene)
(PIDA).[4,20] Furthermore, PIDA undergoes carbonization under
treatment of Lewis bases, giving conducting carbon nanofib-
ers.[21] Another interesting reactivity of 1-halopolyynes is
a unique single-crystal-to-single-crystal topochemical dimeriza-
tion.[22] Moreover, 1-halopolyynes are used in the iterative syn-
thesis of longer polyynes by Negishi[23] or Stille reaction[18b] or
in the synthesis of butadiyne-substituted pyrroles.[24] Despite
sparse experimental data on their synthesis, modern computa-
tional studies of halogen end-capped polyynes are fairly nu-
merous.[25]
1
the desired product in the H NMR spectrum. Analogous reac-
tion with TESC2H (triethylsilylacetylene) gave 1-C10TES with low
yields (5–7%). Finally, we stepped down with chain length to
maintain a better solubility and performed a reaction of 1-C6I
with TIPSC4H (triisopropylsilylbutadiyne) to finally obtain 1-
C10TIPS in 20% yield. TIPSC4H is a known compound[29] but for
its synthesis we designed a modified, very effective synthetic
procedure (starting from TMSC4TMS; see the Supporting Infor-
mation). Iodination of 1-C10TIPS proceeded smoothly and gave
1-C10I in good yield (58%).
The unsymmetrical 1-iodopolyynes reported in this work are
significantly more stable than those previously described. The
only known octatetrayne I(CꢀC)8I explodes at 858C[18a] and the
only known decapentayne I(CꢀC)10I decomposes rapidly above
08C and explodes above 55–568C,[18b] so both must be stored
in solution below 08C. The newly synthesized 1–2-C8I decom-
pose rapidly at 1258C (1-C8I) and 1298C (2-C8I) and longer 1-
C10I decomposes at 988C. Moreover, 1-C10I may be handled at
room temperature for several hours without significant decom-
position and may be stored for months as a solid at tempera-
tures below À258C. Although diiodopolyynes have been re-
ported to be explosive,[18b] we did not experience any danger-
ous incident during our work with the 1-iodopolyynes report-
ed in this work. However, careful handling and small-scale syn-
Accordingly, the initial step of our research strategy was the
synthesis of long, fully conjugated 1-halopolyynes. During our
previous work with 1-halopolyynes we noted that iodides are
usually more stable than the corresponding chlorides and bro-
mides upon chain elongation, although no clear evidence for
this has been reported. We suppose that the reason may be
lower polarization of the polyyne chain or the size of the halo-
gen atom. To investigate this observation in more detail, we
performed TGA-DTA measurements for a series of known[15,26]
4-(halobutadiynyl)benzonitriles. The data have shown the de-
composition temperatures for chloride, bromide, and iodide
derivatives to be 128, 147, and 1838C, respectively. With this
result in mind, we selected iodides as targets for the synthesis
of long 1-halopolyynes, and compounds with carbon chains
up to decapentayne were obtained by using an iterative pro-
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good to excellent yields, as
shown in Scheme 2, but it was
necessary to avoid reaction
times longer than 5 to 10 min.
As was noted previously, alkynyl
palladium complexes are highly
unstable in solution[15] and
longer reaction times initiate the
formation of byproducts and
a black tar-like precipitate. Nota-
bly, the use of 1-iodopolyynes
instead of 1-bromopolyynes al-
lowed the formation and isola-
tion of compounds with longer
carbon chains, but the stability
of resulting complexes with
iodine in solution was lower
than the stability of analogous
complexes with bromine.[15]
None of the complexes in the
solid form exhibited significant
sensitivity towards air or mois-
ture.
Characterization of 1-iodopo-
lyynes and palladium com-
plexes
All 1-iododopolyynes and palla-
dium complexes were character-
1
ized through the use of H and
13C NMR, IR and UV/Vis spectros-
copy, and by using TGA-DTA and
HRMS (ESI) techniques. More-
over, for all the complexes,
31P NMR spectra were obtained.
1H NMR spectra of 1-iodopo-
lyynes are quite simple, with
only multiplets from the para
substituted phenyl groups being
observed. The 13C NMR spectra
contained much more structural
information. The 13C NMR spec-
tra of 1-CnI (n=3–5) are shown
Scheme 1. Synthesis of 1-iodohexatriynes, 1-iodooctatetraynes, and 1-iododecapentayne.
thesis should always be applied
when working with 1-halopo-
lyynes.
Synthesis of palladium com-
plexes
With 1-iodopolyynes in hand,
their reactions with [Pd(PPh3)4] in
CH2Cl2 were then carried out.
Oxidative addition gave palladiu-
m(II) end-capped polyynes in Scheme 2. Synthesis of palladium end-capped polyynes.
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in Figure 2 and all the data for carbon spectra of 1-iodopo-
lyynes and palladium complexes (acetylenic range) are given in
Table 1. The carbon atoms directly attached to the iodine are
shifted strongly upfield and exhibit chemical shifts that are un-
13C NMR spectrum of 1-C8I in [D6]DMSO is also presented (ICꢀC
resonance: 20.4 ppm). Full assignment of acetylenic signals
was problematic, but HMBC data recorded in CDCl3 suggested
that signals at 73.5–74.7 ppm may be assigned to ArCꢀC
carbon centers. A comparison with the literature data for ICnI
suggests that the most downfield shifted signals arise from
ICꢀC carbon atoms. An upfield shift of ICꢀC signals is visible as
the length of the carbon rods is increased for the 1-CnI series
(4.2 ppm for 1-C6I, 3.7 ppm for 1-C8I, 3.6 ppm for 1-C10I) and
these data are consistent with the chemical shift of the ICꢀC
signal (6.5 ppm) of 1-C4I reported previously.[15]
1
The H NMR spectra of the palladium complexes also pro-
vide very little structural information, and the 13C NMR spectra
are much more informative. Resonances of the PdCꢀC carbon
atoms resonate as strongly downfield shifted triplets (J(C,P)=
14.3–14.5 Hz) with chemical shift between 107.0 (1-C6[Pd]I) and
107.7 ppm (2-C8[Pd]I). Triplets (J(C,P)=6.5–6.7 Hz) of PdCꢀC
carbon atoms exhibit chemical shifts between 90.4 and
90.8 ppm. It is also possible to assign the signals of PdCꢀCCꢀC
carbon atoms (from 67.0 ppm for 1-C10[Pd]I to 71.9 ppm for 1-
C6[Pd]I) due to a weak J(C,P) coupling constant (2.3–2.4 Hz).
The acetylenic range of the 13C NMR spectra of 1-Cn[Pd]I series
is shown in Figure 3. Full assignment of resonances of carbon
Figure 2. 13C NMR spectra (acetylene range) of 1-CnI (n=6, 8, 10) in CDCl3.
Table 1. 13C NMR spectra (acetylenic range) of 1-iodopolyynes and palla-
dium complexes in CDCl3.[a]
Compound C1
C2 C3 to C9
CXÀAr
1-C6I
2-C6I
1-C8I
1-C8I[b]
2-C8I[b]
1-C10I
4.2
4.6
3.7
78.9 57.9 69.8 77.9
78.9 57.9 70.2 78.7
79.1 59.1 60.2 66.1 69.0 78.2
73.8
73.5
74.2
75.0
74.7
20.4 76.6 57.3 59.6 66.2 68.1 76.5
20.7 77.2 57.2 59.6 66.4 68.5 76.6
3.6
C1
107.0 90.8 72.4 80.7 55.6
107.6 90.8 73.0 81.7 55.6
107.3 90.5 68.4 79.7 72.7 58.1 57.0
107.7 90.5 68.7 80.5 72.5 58.0 57.0
107.5 90.4 67.0 79.1 73.5 68.2 59.5 59.1 57.3 70.8
79.2 59.3 60.6 61.4 64.8 65.4 69.3 78.2 74.5
C2 C3 C4 to C9
CXÀAr
1-C6[Pd]I
2-C6[Pd]I
1-C8[Pd]I
2-C8[Pd]I
1-C10[Pd]I
71.9
71.7
71.8
72.3
[a] All chemical shifts are given in ppm. [b] Spectrum recorded in
[D6]DMSO. [c] Unambiguous assignment is possible only for carbon
atoms near to the end-groups.
Figure 3. 13C NMR spectra (acetylene range) of 1-Cn[Pd]I (n=3,4,5); CDCl3,
300 K, 151 MHz.
usual for acetylenes (in CDCl3 slightly above 0 ppm); this phe-
nomenon has also been reported for 1-iodopolyynes.[30] For in-
stance, chemical shifts of the ICꢀC carbon for ICnI (n=3–5) are
0.9, 1.9, and 2.3 ppm (in CDCl3), respectively.[18] Compound 2-
C8I was almost insoluble in CDCl3 and the carbon NMR spec-
trum was recorded in [D6]DMSO. Due to the different Lewis ba-
sicity of [D6]DMSO, the chemical shift of ICꢀC carbon for this
compound changed dramatically to 20.7 ppm. It is known for
1-iodoalkynes that in Lewis-base solvents, the chemical shift of
the alpha carbon is shifted strongly downfield because of the
formation of Lewis acid–base complex.[30] For comparison, the
atoms from polyyne chain was once again not possible. Three
signals (ipso, ortho, and meta) of the phosphine groups are
split into triplets. Such phenomena was described previously
as a ‘virtual coupling’ and is known for trans square planar
complexes.[31] In the phosphorus NMR spectra we observed
only one resonance near 22 ppm, which confirmed the trans
configuration of products and is typical for s-alkynyl bis(triphe-
nylphosphine)palladium complexes.[32] Nevertheless, it should
be noted that the cis product is likely initially generated during
oxidative addition, which isomerizes over time to the final
trans coordination.
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that 1-iodopolyynes are less stable and that their decomposi-
tion temperatures decrease as the length of the carbon chain
increases. Hexatriynes decompose near 1608C (1618C for 1-C6I,
1588C for 2-C6I), octatetraynes decompose below 1308C
(1258C for 1-C8I, 1298C for 2-C8I), and decapentayne 1-C10I de-
composes at 988C. We did not observe noticeable light-sensi-
tivity for any reported polyyne; however, all compounds were
stored in the dark.
X-ray Crystallography
As noted above, polyyne palladium complexes are unstable in
solution[15] and therefore single crystals suitable for X-ray analy-
sis are extremely difficult to obtain. If the crystallization time is
too long (several hours) only the decomposition products
(Pd(PPh3)2I2, most probably Pd(PPh3)2((CꢀC)nR)2 and some other
unidentified compounds) are observed. Nevertheless, in case
of 2-C6[Pd]I, our efforts were eventually successful. Clearly, silyl-
protected precursors are far more stable and their crystalliza-
tion was much easier.
X-ray crystal structures of two silyl-protected polyynes 1-
C8TMS and 1-C10TIPS and one palladium complex 2-C6[Pd]I
were solved. Crystals of 1-C8TMS and 1-C10TIPS were obtained
by slow evaporation of their solutions in n-hexane and 2-
C6[Pd]I was crystallized from a mixture of n-hexane and CH2Cl2.
1-C8TMS crystallizes in the Pbcma space group in the ortho-
rhombic system with Z=4, whereas 1-C10TIPS and 2-C6[Pd]I
¯
crystallize in the P1 space group in the triclinic system with
Z=4 and Z=2, respectively (for further details see the Sup-
porting Information). Molecular structures of the compounds
are given in Figure 5 and Figure 6.
Figure 4. UV/Vis spectra of 1-CnI (top) and 1-Cn[Pd]I (bottom) compounds.
Selected bond lengths of the compounds are given in the
Table 2. The PdÀC bond in 2-C6[Pd] (1.971(7) Š) is in a lower
region of a typical range for neutral s-alkynyl palladium com-
plexes (usually 1.94–2.07 Š)[32–33] and is consistent with our pre-
Example UV/Vis spectra of 1-iodopolyynes and the corre-
sponding Pd complexes are shown in Figure 4 (for all UV/Vis
spectra see the Supporting Information). Vibronic structure is
clearly visible and a series of narrow peaks can be observed,
especially for the benzonitrile derivatives. A bathochromic shift
in lmax is clearly visible as the length of the carbon rods is in-
creased (as well as a hyperchromic shift), which is a known de-
pendence for polyynes.[3a] The spectra of the Pd complexes are
slightly more bathochromic shifted than the spectra of 1-iodo-
polynes and have higher molar absorptivity values (17000–
93000mÀ1 cmÀ1).
IR CꢀC stretching bands for all palladium complexes and the
1-iodopolyynes are within the typical acetylenic range (see the
Experimental Section). These data are in good agreement with
those of the previously reported palladium complexes and 1-
halopolyynes.[15] The HRMS characterization of the palladium
complexes was relatively straightforward. The signals from
[MÀI]+ with a characteristic palladium isotope pattern could
be observed with the use of an ESI ion source. The thermal sta-
bility of the palladium complexes was investigated by using
TGA-DTA techniques. The complexes possess high thermal sta-
bility, ranging from 1778C for 1-C10[Pd]I to 2088C for 2-C8[Pd]I.
High decomposition temperatures were previously noted for
shorter palladium end-capped polyynes.[15] It is not surprising
Figure 5. Molecular structures of silyl-protected polyynes 1-C8TMS and 1-
C10TIPS. Hydrogen atoms are omitted for clarity. Thermal ellipsoids are
drawn with 50% probability. In the case of 1-C10TIPS, there are two different
molecules in the asymmetric unit.
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Table 3. Contraction coefficients for 1-C8TMS, 1-C10TIPS, and 2-C6[Pd]I
compounds.
Contraction[a] C1ÀCx [%]
Contraction[b] XÀCAr [%]
1-C8TMS
0.00
0.19
1.01
0.09
0.60
0.61
1.98
0.19
1-C10TIPS[b]
1-C10TIPS[b]
2-C6[Pd]I
[a] Contraction C1ÀCx=(C1ÀCx sum of bond lengthsÀC1ÀCx distance)/
C1ÀCx sum of bond lengths”100%. [b] Contraction XÀCAr =(XÀCAr sum
of bond lengthsÀX-CAr distance)/XÀCAr sum of bond lengths”100%.
[c] X=Si, Pd.
Figure 6. Molecular structure of 2-C6[Pd]I. Hydrogen atoms are omitted for
clarity. Thermal ellipsoids are drawn with 50% probability.
vious work.[15] In all the compounds the length of triple bonds
are usually below 1.22 Š, which is a typical value for polyynes
with a carbon chain of such a length.[6]
The conformations of the polyyne chains were then ana-
lyzed. In the case of 1-C10TIPS it is possible to observe confor-
mational flexibility of the carbon chain that is known for
longer polyynes.[6] Two molecules in the asymmetric unit pos-
sess different conformation of the carbon chain and different
contraction coefficients (see Table 3). The molecule with the
bigger distortion from linearity possesses ‘unsymmetrical bow’
conformation, whereas the second is ‘S-shaped’. The carbon
chains in 1-C8TMS and 2-C6[Pd]I are only slightly distorted from
linearity.
The packing motifs for all the reported structures were ana-
lyzed (two packings are shown in Figure 7). As mentioned
before, polyynes have great potential for 1,n-topochemical
polymerization[4,34] so we analyzed the packing diagrams in
search for good candidates for such a process. Compound 1-
C8TMS crystallizes in the Pnma space group with 0.5 molecule
in the asymmetric unit so, consequently, its molecules form
two sets of parallel chains (with head-to-tail orientation within
Figure 7. Packing motifs for 1-C8TMS (top) and 1-C10TIPS (bottom). The dis-
tances [Š] for 1-C8TMS are: C8ÀC6(i) 3.530, C7ÀC7(i) 3.540. Symmetry opera-
tions for related atoms are: (i) Àx, 1/2+y, Àz; (ii): Àx. À1/2+y, Àz. The dis-
tances [Š] for 1-C10TIPS are: C8ÀC3(iii) 4.193, C1ÀC10(iv) 5.334, C10ÀC5’(v)
3.462, C4’(v)ÀC9’(vi) 3.681, C10’(vi)ÀC1(vii) 5.334. Symmetry operations for re-
lated atoms are: (iii): À1+x, 1Ày, 1Àz, (iv): 2Àx, 1Ày, 1Àz, (v): 1Àx, 2Ày, 1Àz,
(vi): 2Àx, 2Ày, 1Àz, (vii): À1+x, 1+y, z.
¯
a set). Instead, 1-C10TIPS and 2-C6[Pd]I crystallize in P1 space
group. There are two molecules in the asymmetric unit for 1-
C10TIPS, which means that the compound also forms two sets
of parallel chains (head-to-head within each set) and only 2-
C6[Pd]I forms one set of parallel chains (with head to-tail orien-
tation).
The closest chain–chain separation was then analyzed for
each structure, which was understood as the closest carbon–
carbon distance from two neighboring carbon chains. In the
case of 2-C6[Pd]I, the geometrical parameters appeared far
from those necessary for topochemical polymerization (3.5 Š)[6]
and the closest carbon–carbon contact was as high as 5.04 Š,
which is most probably an effect of the bulky end-group. In-
stead, as revealed by a detailed analysis (see Figure 6), the
closest distances between two chain carbon atoms for 1-
C8TMS (3.53 Š) and 1-C10TIPS (3.46 Š) were slightly lower than
the sum of van der Waals radii (3.56 Š). Nevertheless, only in
the case of 1-C8TMS was it possible to define an infinite chain
with such short contacts. In the case of 1-C10TIPS, the shortest
carbon–carbon distances formed between atoms from two
chain sets whereas contacts within one set were much longer
(5.33 Š) than is necessary for topochemical polymerization.
Table 2. Selected bond lengths for 1-C8TMS, 1-C10TIPS, and 2-C6[Pd]I polyynes.
X[c]ÀC1
C1ÀC2
C2ÀC3
C3ÀC4
C4ÀC5
C5ÀC6
C6ÀC7
C7ÀC8
C8ÀC9
C9ÀC10
ꢀCÀAr
1-C8TMS
1.8507(14)
1.849(2)
1.845(2)
1.971(7)
1.216(2)
1.214(2)
1.213(2)
1.167(8)
1.369(2)
1.373(2)
1.370(2)
1.387(10)
1.210(2)
1.209(2)
1.211(2)
1.220(9)
1.361(2)
1.360(2)
1.357(2)
1.360(9)
1.212(2)
1.213(2)
1.213(2)
1.202(9)
1.364(2)
1.357(2)
1.355(2)
1.207(2)
1.210(2)
1.214(2)
1.428(2)
1.429(2)
1.424(2)
1.439(10)
1-C10TIPS[b]
1-C10TIPS[b]
2-C6[Pd]I
1.364(2)
1.364(2)
1.204(2)
1.206(2)
[a] All lengths in Š. [b] Two molecules in the asymmetric unit. [c] X=Si, Pd.
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ment. Lorentz and polarization corrections were applied. The struc-
tures were solved by direct methods and refined by full-matrix,
least-squares on F2 by use of the SHELXTL Package.[35] Non-hydro-
gen atoms were refined with anisotropic thermal parameters. Hy-
drogen atom positions were calculated and added to the structure
factor calculations, but were not refined.
Based on the analysis, only 1-C8TMS could be considered as
a good candidate for 1,n-topochemical polymerization.
Conclusion
We have described the synthesis of a series of fully conjugated
long 1-iodopolyynes with carbon chains up to the decapen-
tayne by using an iterative procedure with Cadiot–Chodkiewicz
cross-couplings and halogenations with deprotection in situ.
The development of 1-C8I, 2-C8I, and 1-C10I significantly enrich-
es the family of known 1-halopolyynes. The oxidative addition
of Pd(PPh3)4 to resulting 1-iodopolyynes was then carried out
and the corresponding palladium end-capped polyynes were
obtained. To our knowledge, decapentayne 1-C10[Pd]I is the
palladium polyynyl complex with the longest carbon chain for
this class of compounds reported to date. All the complexes
were characterized by using 1H, 13C, 31P NMR, IR, HRMS(ESI),
TGA-DTA and UV/Vis techniques. Moreover, X-ray crystal struc-
tures of two silyl protected precursors (1-C8TMS and 1-C10TIPS)
and one palladium complex (2-C6[Pd]I) were determined.
General procedure for Cadiot–Chodkiewicz cross-coupling
Trimethyl((4-nitrophenyl)hexa-1,3,5-triyn-1-yl)silane (2-C6TMS):
Under a N2 atmosphere 1-(bromoethynyl)-4-nitrobenzene (2-C2Br;
655 mg, 2.90 mmol) was dissolved in anhydrous THF (25 mL). Buta-
1,3-diyn-1-yltrimethylsilane (533 mg, 4.36 mmol), Pd(PPh3)2Cl2
(102 mg, 0.145 mmol), and CuI (28 mg, 0.147 mmol) were added
and the mixture was degassed by using the freeze-pump-thaw
technique. Diisopropylamine (1.02 mL, 7.25 mmol) was then added
and the mixture was stirred for 40 min. Solvent was removed and
the product was purified by silica gel chromatography (hexane/
CH2Cl2, 3:1 v/v) to give the product. Yield: 398 mg (1.49 mmol,
51%); yellow solid. 1H NMR (500 MHz, CDCl3, 258C): d=8.22–8.18
(m, 2H), 7.69–7.64 (m, 2H), 0.24 ppm (s, 9H); 13C NMR (126 MHz,
CDCl3, 258C): d=147.9 (s, CNO2), 134.0 (s, CH of C6H4), 128.0 (s,
CArCꢀC), 123.8 (s, CH of C6H4), 91.3 (s, CꢀC), 87.7 (s, CꢀC), 79.2 (s,
CꢀC), 74.3 (s, CꢀC), 69.5 (s, CꢀC), 60.6 (s, CꢀC), À0.5 ppm (SiMe3);
elemental analysis calcd (%) for C15H13NO2Si: C 67.50, H 4.90, N
5.24; found: C 67.41, H 4.85, N 5.15.
Experimental Section
Experimental details
Typical procedure for iodination of silyl-protected polyynes
For full details, including additional experimental procedures,
1
4-(Iodohexa-1,3,5-triyn-1-yl)benzonitrile (1-C6I): Under a N2 at-
mosphere 1-C6TMS (751 mg, 3.04 mmol), AgF (393 mg, 3.01 mmol),
NIS (845 mg, 3.64 mmol), and H2O (109 mL) were dissolved in MeCN
(40 mL). The flask was wrapped with aluminum foil and the mix-
ture was stirred for 5.5 h. After this time the solvent was removed
under reduced pressure. The crude product was purified by elution
through a silica gel plug (hexane/CH2Cl2, 1:1 v/v) to give the prod-
uct. Yield: 840 mg (2.79 mmol, 92%); yellow solid; decomposition:
copies of H, 13C and 31P NMR spectra and X-ray crystallography de-
tails, see the Supporting Information. CCDC 1056226 (1-C8TMS),
1056227 (1-C10TIPS), and 1056228 (2-C6[Pd]I) contain the supple-
mentary crystallographic data for this paper. These data are provid-
ed free of charge by The Cambridge Crystallographic Data Centre.
General
1
1618C; H NMR (500 MHz, CDCl3, 258C): d=7.64–7.58 ppm (m, 4H);
All reactions were conducted under N2 by using standard Schlenk
techniques. Glassware was pre-dried at 1208C. Solvents were treat-
ed as follows: hexane was distilled from Na, THF was distilled from
Na/benzophenone, CH2Cl2 was distilled from P2O5, and CH3CN
(HPLC grade) was used as received. Pd(PPh3)4 (Aldrich, 99%), N-io-
dosuccinimide (NIS) (Alfa Aesar, 97%), AgF (Alfa Aesar, 98%) were
used as received. 2-C2Br, 1-C4Br, 2-C4Br, 1-C6TMS, and TMSC4H were
obtained according to the known procedures.[15,27]
13C NMR (126 MHz, CDCl3, 258C): d=133.8 (s, CH of C6H4), 132.3 (s,
CH of C6H4), 125.8 (s, CCꢀN), 118.2 (s, CꢀN), 113.2 (s, CArCꢀC), 78.9
(s, CꢀC), 77.9 (s, CꢀC), 73.76 (s, CꢀC), 69.8 (s, CꢀC), 57.9 (s, CꢀC),
4.2 ppm (s, CꢀCI). IR (fluorinated oil mull): n˜ =1920 (CꢀC), 2072 (Cꢀ
C), 2159 (CꢀC), 2237 cmÀ1 (CꢀN). UV/Vis (CH2Cl2): lmax (e,
dm3 molÀ1 cmÀ1)=356 (11000), 332 (16000), 310 (12000), 291
(10000), 275 (37000), 262 nm (25000). HRMS (ESI): m/z calcd for
C13H4INAg: 407.8434 [M+Ag]+; found: 407.8417.
1H, 13C and 31P NMR spectra were recorded with Bruker Avance 500
1
1-(Iodohexa-1,3,5-triyn-1-yl)-4-nitrobenzene (2-C6I): According to
the general procedure for iodination of silyl-protected polyynes, 2-
C6TMS (166 mg, 0.621 mmol), NIS (173 mg, 0.746 mmol), AgF
(82 mg, 0.63 mmol), and MeCN (20 mL) were used. Time: 2 h.
Workup on silica gel plug (hexane/CH2Cl2, 1:1 v/v) gave the prod-
uct. Yield: 149 mg (0.464 mmol, 75%); yellow solid; decomposi-
and Avance III 600 MHz spectrometers. For all the H NMR spectra,
the chemical shifts are given in ppm relative to the solvent residual
peaks (CDCl3, 1H: 7.26 ppm, 13C: 77.2 ppm; [D6]DMSO, 1H:
2.50 ppm, 13C: 39.5 ppm,). For the 31P NMR spectra, H3PO4(aq)
(85%) was used as an external standard (0 ppm). Coupling con-
stants are given in Hz. HRMS spectra were recorded with Bruker
apex ultra FT-ICR and MicOTOF-Q spectrometers with ESI ion
source. IR spectra were recorded with a Bruker 66s FTIR spectrome-
ter. UV/Vis spectra were recorded with an Agilent Cary 60 spectro-
photometer. TGA-DTA data were collected with a Setaram SETSYS
16/18 thermal analyzer. Microanalyses were conducted with an Ele-
mentar CHNS Vario ELIII analyzer.
1
tion: 1588C; H NMR (600 MHz, CDCl3, 258C): d=8.23–8.17 (m, 2H),
7.70–7.64 ppm (m, 2H); 13C NMR (151 MHz, CDCl3, 258C): d=148.0
(s, CNO2), 134.1 (s, CH of C6H4), 127.7 (s, CArCꢀC), 123.9 (s, CH of
C6H4), 78.9 (s, CꢀC), 78.7 (s, CꢀC), 73.5 (s, CꢀC), 70.2 (s, CꢀC), 57.9
(s, CꢀC), 4.6 ppm (s, CꢀCI); IR (fluorinated oil mull): n˜ =1931 (CꢀC),
2075 (CꢀC), 2162 cmÀ1 (CꢀC); UV/Vis (CH2Cl2): lmax (e,
dm3 molÀ1 cmÀ1)=367 (8000), 342 (9000), 319 (8000), 292 (9000),
279 (8000), 237 nm (18000); HRMS (ESI) m/z calcd for C12H4INNa:
343.9185 [M+Na]+; found: 343.9188.
Details of X-ray data collection and reduction
X-ray diffraction data were collected with a KUMA KM4 CCD (w
scan technique) diffractometer. The space groups were determined
from systematic absences and subsequent least-squares refine-
4-((Trimethylsilyl)octa-1,3,5,7-tetrayn-1-yl)benzonitrile (1-C8TMS):
According to the general procedure for Cadiot–Chodkiewicz cross-
coupling, 1-C4Br (200 mg, 0.869 mmol), [Pd(PPh3)2Cl2] (32 mg,
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0.046 mmol), CuI (9 mg, 0.047 mmol), TMSC4H (163 mg,
1.33 mmol), NH(iPr)2 (0.30 mL, 2.12 mmol), and anhydrous THF
(20 mL) were used. Time: 20 min. Silica gel chromatography
(hexane/CH2Cl2, 1:1 v/v) gave the product. Yield: 116 mg
(0.427 mmol, 48%); yellow solid. 1H NMR (500 MHz, CDCl3, 258C):
d=7.64–7.58 (m, 4H), 0.23 ppm (s, 9H); 13C NMR (126 MHz, CDCl3,
258C): d=133.8 (s, CH of C6H4), 132.4 (s, CH of C6H4), 125.7 (s, CCꢀ
N), 118.2 (s, CꢀN), 113.4 (s, CArCꢀC), 90.1 (s, CꢀC), 87.8 (s, CꢀC), 78.4
(s, CꢀC), 74.5 (s, CꢀC), 69.5 (s, CꢀC), 65.4 (s, CꢀC), 61.9 (s, CꢀC),
61.0 (s, CꢀC), À0.5 ppm (s, SiMe3); HRMS (ESI) m/z calcd for
C18H14NSi: 272.0890 [M+H]+; found: 272.0892.
(hexane/CH2Cl2, 1:1 v/v) gave the product. Yield: 48 mg
(0.126 mmol, 20%); yellow solid; 1H NMR (500 MHz, CDCl3, 258C):
d=7.65–7.59 (m, 4H; C6H4), 1.08–1.10 ppm (m, 21H; TIPS);
13C NMR (126 MHz, CDCl3, 258C): d=133.9 (s, CH of C6H4), 132.3 (s,
CH of C6H4), 125.5 (s, CCꢀN), 118.1 (s, CꢀN), 113.5 (s, CArCꢀC), 89.5
(s, CꢀC), 88.0 (s, CꢀC), 78.3 (s, CꢀC), 74.5 (s, CꢀC), 69.6 (s, CꢀC),
66.0 (s, CꢀC), 64.4 (s, CꢀC), 61.8 (s, CꢀC), 61.1 (s, CꢀC), 60.7 (s, Cꢀ
C), 18.6 (s, CH(CH3)), 11.4 ppm (s, CH(CH3)); HRMS (ESI): m/z calcd
for C26H26NSi: 402.1654 [M+H]+; found: 402.1661.
4-(Iododeca-1,3,5,7,9-pentayn-1-yl)benzonitrile (1-C10I): Accord-
ing to the general procedure for iodination of silyl-protected poly-
ynes, 1-C10TIPS (21 mg, 0.055 mmol), AgF (7.2 mg, 0.056 mmol), NIS
(15 mg, 0.067 mmol), and MeCN (5 mL) were used. Time: 4 h.
Workup on silica gel plug (hexane/CH2Cl2, 1:1) gave the product.
Yield: 11 mg (0.032 mmol, 58%); yellow solid; decomposition:
Trimethyl((4-nitrophenyl)octa-1,3,5,7-tetrayn-1-yl)silane
(2-
C8TMS): According to the general procedure for Cadiot–Chodkie-
wicz cross-coupling, 2-C4Br (542 mg, 2.17 mmol), [Pd(PPh3)2Cl2]
(30 mg, 0.043 mmol), CuI (15 mg, 0.079 mmol), TMSC4H (318 mg,
2.60 mmol), NH(iPr)2 (0.76 mL, 5.38 mmol), and anhydrous THF
(15 mL) were used. Time: 3 h. Silica gel chromatography (hexane/
CH2Cl2, 1:1 v/v) gave the product. Yield: 267 mg (0.916 mmol,
42%); yellow solid. 1H NMR (500 MHz, CDCl3, 258C): d=8.22–8.19
(m, 2H; C6H4), 7.69–7.66 (m, 2H; C6H4), 0.23 ppm (s, 9H; SiMe3);
13C NMR (126 MHz, CDCl3, 258C): d=148.1 (s, CNO2), 134.1 (s, CH of
C6H4), 127.6 (s, CArCꢀC), 123.9 (s, CH of C6H4), 90.3 (s, CꢀC), 87.7 (s,
CꢀC), 79.1 (s, CꢀC), 74.2 (s, CꢀC), 69.8 (s, CꢀC), 65.6 (s, CꢀC), 61.7
(s, CꢀC), 60.9 (s, CꢀC), À0.5 ppm (s, SiMe3); HRMS (ESI) m/z calcd
for C17H13NO2SiNa: 314.0619 [M+Na]+; found: 314.0617.
1
988C; H NMR (600 MHz, CDCl3, 258C): d=7.65–7.60 ppm (m, 4H);
13C NMR (151 MHz, CDCl3, 258C): d=133.9 (s, CH of C6H4), 132.3 (s,
CH of C6H4), 125.3 (s, CCꢀN), 118.1 (s, CꢀN), 113.6 (s, CArCꢀC), 79.2
(s, CꢀC), 78.2 (s, CꢀC), 74.5 (s, CꢀC), 69.3 (s, CꢀC), 65.4 (s, CꢀC),
64.8 (s, CꢀC), 61.4 (s, CꢀC), 60.6 (s, CꢀC), 59.3 (s, CꢀC), 3.6 ppm (s,
CꢀCI); IR (fluorinated oil mull): n˜ =1919 (CꢀC) (weak), 2044 (CꢀC),
2087 (CꢀC), 2169 (CꢀC), 2235 cmÀ1 (CꢀN); UV/Vis (CH2Cl2): lmax (e,
dm3 molÀ1 cmÀ1)=430 (3000), 396 (6000), 367 (7000), 343 (6000),
322 (60000), 302 (45000), 285 (38000), 272 nm (25000); HRMS
(ESI): m/z calcd for C17H5IN: 349.9461 [M+H]+; found: 349.9465.
4-(Iodoocta-1,3,5,7-tetrayn-1-yl)benzonitrile (1-C8I): According to
the general procedure for iodination of silyl-protected polyynes, 1-
C8TMS (100 mg, 0.368 mmol), AgNO3 (19 mg, 0.112 mmol), KF
(22 mg, 0.379 mmol), NIS (103 mg, 0.444 mmol), H2O (14 mL), and
MeCN (10 mL) were used. Time: 2 h. Workup on silica gel plug
(hexane/CH2Cl2, 1:1 v/v) gave the product. Yield: 114 mg
(0.351 mmol, 95%); yellow solid; decomposition: 1258C; 1H NMR
(500 MHz, CDCl3, 258C): d=7.64–7.59 ppm (m, 4H); 13C NMR
(126 MHz, CDCl3, 258C): d=133.9 (s, CH of C6H4), 132.3 (s, CH of
C6H4), 125.5 (s, CCꢀN), 118.1 (s, CꢀN), 113.4 (s, CArCꢀC), 79.1 (s, Cꢀ
C), 78.2 (s, CꢀC), 74.2 (s, CꢀC), 69.0 (s, CꢀC), 66.1 (s, CꢀC), 60.2 (s,
CꢀC), 59.1 (s, CꢀC), 3.7 ppm (s, CꢀCI); IR (fluorinated oil mull): n˜ =
2058 (CꢀC), 2122 (CꢀC), 2190 (CꢀC), 2234 cmÀ1 (CꢀN); UV/Vis
(CH2Cl2): lmax (e, dm3 molÀ1 cmÀ1)=394 (5000), 365 (9000), 340
(8000), 319 (7000), 300 (44000), 283 nm (29000); HRMS (ESI) m/z
calcd for C15H5IN: 325.9461 [M+H]+; found: 325.9458.
Typical procedure for the synthesis of palladium complexes
trans-Iodo((4-cyanophenyl)hexatriynyl)bis(triphenyphosphine)-
palladium (1-C6[Pd]I): Under a N2 atmosphere, 1-C6I (57 mg,
0.189 mmol) was added to a solution of [Pd(PPh3)4] (222 mg,
0.190 mmol) in anhydrous CH2Cl2 (10 mL). The mixture was stirred
for 5 min and then part of the solvent was removed under reduced
pressure. A solid was precipitated with hexane and then filtered
off. The crude product was dissolved in CH2Cl2 and reprecipitated
with hexane to give the product. Yield: 141 mg (0.151 mmol,
80%); yellow solid; decomposition: 1868C; 1H NMR (600 MHz,
CDCl3, 258C): d=7.71 (dd, J=12.5, 5.9 Hz, 12H; PPh3), 7.53 (d, J=
8.4 Hz, 2H; C6H4), 7.47–7.38 ppm (m, 20H; PPh3 and C6H4); 13C NMR
(151 MHz, CDCl3, 258C): d=135.1 (t, J=6.3 Hz; ortho of PPh3),
133.1 (s, CH of C6H4), 132.0 (s, CH of C6H4), 131.9 (t, J=25.8 Hz; ipso
of PPh3), 130.7 (s, para of PPh3), 128.2 (t, J=5.4 Hz; meta of PPh3),
127.6 (s, CCꢀN), 118.5 (s, CꢀN), 111.7 (s, CArCꢀC), 107.0 (t, J=
14.3 Hz, CꢀCPd), 90.8 (t, J=6.7 Hz; CꢀCPd), 80.7 (s, CꢀC), 72.4 (t,
J=2.3 Hz; CCꢀCPd), 71.9 (s, CꢀC), 55.6 ppm (s, CꢀC); 31P NMR
(243 MHz, CDCl3, 258C): d=22.2 ppm (s); IR (fluorinated oil mull):
n˜ =2034 (CꢀC), 2135 (CꢀC), 2162 (CꢀC), 2225 cmÀ1 (CꢀN); UV/Vis
(CH2Cl2): lmax (e, dm3 molÀ1 cmÀ1)=380 (30000), 352 (41000), 329
(37000), 292 nm (83000); HRMS (ESI): m/z calcd for C49H34NP2Pd:
804.1201 [MÀI]+; found: 804.1211.
trans-Iodo((4-nitrophenyl)hexatriynyl)bis(triphenyphosphine)pal-
ladium (2-C6[Pd]I): 2-C6I (40 mg, 0.13 mmol), [Pd(PPh3)4] (144 mg,
0.123 mmol), and CH2Cl2 (10 mL) were used according to the gen-
eral procedure for the synthesis of palladium complexes. Time:
10 min. Workup gave the product as a yellow solid (73%, 90 mg,
0.095 mmol); decomposition: 1868C; 1H NMR (600 MHz, CDCl3,
258C): d=8.14–8.10 (m, 2H; C6H4), 7.73–7.68 (m, 12H; PPh3), 7.52–
7.49 (m, 2H; C6H4), 7.47–7.38 ppm (m, 18H; PPh3); 13C NMR
(151 MHz, CDCl3, 258C): d=147.1 (s, CNO2), 135.1 (t, J=6.3 Hz;
ortho of PPh3), 133.4 (s, CH of C6H4), 131.9 (t, J=25.8 Hz; ipso of
PPh3), 130.7 (s, para of PPh3), 129.7 (s, CCꢀC), 128.2 (t, J=5.4 Hz;
meta of PPh3), 123.7 (s, CH of C6H4), 107.6 (t, J=14.4 Hz; CꢀCPd),
90.8 (t, J=6.5 Hz; CꢀCPd), 81.7 (s, CꢀC), 73.0 (t, J=2.3 Hz; CCꢀ
1-(Iodoocta-1,3,5,7-tetrayn-1-yl)-4-nitrobenzene (2-C8I): Accord-
ing to the general procedure for iodination of silyl-protected poly-
ynes, 2-C8TMS (100 mg, 0.343 mmol), AgF (44 mg, 0.347 mmol), NIS
(95 mg, 0.410 mmol), H2O (12 mL), and MeCN (30 mL) were used.
Time: 4 h. Workup on silica gel plug (CH2Cl2) gave the product.
Yield: 98 mg (0.284 mmol, 83%); yellow solid; decomposition:
1298C; 1H NMR (500 MHz, DMSO, 258C): d=8.28–8.24 (m, 2H),
7.95–7.91 ppm (m, 2H); 13C NMR (126 MHz, DMSO, 258C): d=148.0
(s, CNO2), 134.8 (s, CH of C6H4), 125.6 (s, CArCꢀC), 124.0 (s, CH of
C6H4), 77.2 (s, CꢀC), 76.6 (s, CꢀC), 74.7 (s, CꢀC), 68.5 (s, CꢀC), 66.4
(s, CꢀC), 59.6 (s, CꢀC), 57.2 (s, CꢀC), 20.7 ppm (s, CꢀCI); IR (fluori-
nated oil mull): n˜ =1930 (CꢀC), 2119 (CꢀC), 2192 cmÀ1 (CꢀC); UV/
Vis (CH2Cl2): lmax (e, dm3 molÀ1 cmÀ1)=400 (7000), 370 (13000), 345
(14000), 318 (18000), 303 (19000), 289 (15000), 263 (23000), 252
(24000), 242 nm (23000); HRMS (ESI): m/z calcd for C14H4INO2Na:
367.9190 [M+Na]+; found: 367.9191.
4-((Triisopropylsilyl)deca-1,3,5,7,9-pentayn-1-yl)benzonitrile (1-
C10TIPS): According to the general procedure for Cadiot–Chodkie-
wicz cross-coupling, 1-C6I (193 mg, 0.641 mmol), [Pd(PPh3)2Cl2]
(9 mg, 0.013 mmol), CuI (2.4 mg, 0.013 mmol), TIPSC4H (199 mg,
0.964 mmol), NH(iPr)2 (0.23 mL, 1.63 mmol), and anhydrous THF
(15 mL) were used. Time: 30 min. Silica gel chromatography
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Full Paper
CPd), 71.7 (s, CꢀC), 55.6 ppm (s, CꢀC); 31P NMR (243 MHz, CDCl3,
258C): d=22.2 ppm (s); IR (fluorinated oil mull): n˜ =2037 (CꢀC),
2137 cmÀ1 (CꢀC); UV/Vis (CH2Cl2): lmax (e, dm3 molÀ1 cmÀ1)=400
(16000), 373 nm (17000); HRMS (ESI): m/z calcd for C48H34NO2P2Pd:
824.1099 [MÀI]+; found: 824.1102.
(72000), 279 nm (67000); HRMS (ESI): m/z calcd for C53H34NP2Pd:
852.1201 [MÀI]+; found: 828.1199.
Acknowledgements
trans-Iodo((4-cyanophenyl)octatetraynyl)bis(triphenyphosphine)-
palladium (1-C8[Pd]I): 1-C8I (9.0 mg, 0.028 mmol), [Pd(PPh3)4]
(32 mg, 0.027 mmol), and CH2Cl2 (10 mL) were used according to
the general procedure for the synthesis of palladium complexes.
Time: 5 min. Workup gave the product as a beige solid (15 mg,
0.016 mmol, 57%). Decomposition: 1858C; 1H NMR (600 MHz,
CDCl3, 258C): d=7.69 (dd, J=12.5, 5.9 Hz, 12H; PPh3), 7.57 (d, J=
8.4 Hz, 2H; C6H4), 7.52 (d, J=8.4 Hz, 2H; C6H4), 7.47–7.36 ppm (m,
18H; PPh3); 13C NMR (151 MHz, CDCl3, 258C): d=135.1 (t, J=
6.2 Hz; ortho of PPh3), 133.5 (s, CH of C6H4), 132.2 (s, CH of C6H4),
131.8 (t, J=25.8 Hz; ipso of PPh3), 130.8 (s, para of PPh3), 128.2 (t,
J=5.4 Hz; meta of PPh3), 126.7 (s, CCꢀN), 118.4 (s, CꢀN), 112.5 (s,
CArCꢀC), 107.3 (t, J=14.5 Hz; CꢀCPd), 90.5 (t, J=6.7 Hz; CꢀCPd),
79.7 (s, CꢀC), 72.7 (s, CꢀC), 71.8 (s, CꢀC), 68.4 (t, J=2.0 Hz; CCꢀ
CPd), 58.1 (s, CꢀC), 57.0 ppm (s, CꢀC); 31P NMR (243 MHz, CDCl3,
258C): d=22.1 ppm (s); IR (fluorinated oil mull): n˜ =2032 (CꢀC),
2097 (CꢀC), 2133 (CꢀC), 2226 cmÀ1 (CꢀN); UV/Vis (CH2Cl2): lmax (e,
dm3 molÀ1 cmÀ1)=417 (16000), 385 (24000), 356 (29000), 319
(90000), 306 nm (84000); HRMS (ESI): m/z calcd for C51H34NP2Pd:
828.1201 [MÀI]+; found: 828.1210.
trans-Iodo((4-nitrophenyl)octatetraynyl)bis(triphenyphosphine)-
palladium (2-C8[Pd]I): 2-C8I (9.5 mg, 0.028 mmol), [Pd(PPh3)4]
(32 mg, 0.027 mmol), and CH2Cl2 (10 mL) were reacted according
to the general procedure for the synthesis of palladium complexes.
Time: 5 min. Workup gave the product as a yellow solid (26 mg,
0.027 mmol, 96%). Decomposition: 2088C; 1H NMR (600 MHz,
CDCl3, 258C): d=8.16 (d, J=8.8 Hz, 2H; C6H4), 7.69 (dd, J=12.6,
5.9 Hz, 12H; PPh3), 7.59 (d, J=8.8 Hz, 2H; C6H4), 7.47–7.38 ppm (m,
18H; PPh3); 13C NMR (151 MHz, CDCl3, 258C): d=147.6 (s, CNO2),
135.1 (t, J=6.2H, ortho of PPh3), 133.7 (s, CH of C6H4), 131.8 (t, J=
25.8 Hz; ipso of PPh3), 130.8 (s, para of PPh3), 130.4 (s, CArCꢀC),
128.2 (t, J=5.4 Hz; meta of PPh3), 123.8 (s, CH of C6H4), 107.7 (t, J=
14.5 Hz; CꢀCPd), 90.5 (t, J=6.5 Hz; CꢀCPd), 80.5 (s, CꢀC), 72.5 (s,
CꢀC), 72.3 (s, CꢀC), 68.7 (t, J=2.4 Hz; CCꢀCPd), 58.0 (s, CꢀC),
57.0 ppm (s, CꢀC); 31P NMR (243 MHz, CDCl3, 258C) d=22.1 ppm
(s); IR (fluorinated oil mull): n˜ =2122 (CꢀC), 2195 (CꢀC), 2186 cmÀ1
(CꢀC); UV/Vis (CH2Cl2): lmax (e, dm3 molÀ1 cmÀ1)=428 (26000), 394
(36000), 330 (63000), 311 (63000), 278 nm (77000); HRMS (ESI): m/
z calcd for C50H34NO2P2Pd: 848.1099 [MÀI]+; found: 848.1099.
trans-Iodo((4-cyanophenyl)decapentaynyl)bis(triphenylphosphi-
ne)palladium (1-C10[Pd]I): 1-C10I (13 mg, 0.037 mmol), [Pd(PPh3)4]
(42 mg, 0.036 mmol), and CH2Cl2 (10 mL) were reacted according
to the general procedure for the synthesis of palladium complexes.
Time: 5 min. Workup gave the product as a yellow solid (26 mg,
0.027 mmol, 73%). Decomposition: 1778C; 1H NMR (600 MHz,
CDCl3, 258C): d=7.69 (dd, J=12.4, 6.0 Hz, 12H; PPh3), 7.61 (d, J=
8.4 Hz, 2H; C6H4), 7.58 (d, J=8.3 Hz, 2H; C6H4), 7.48–7.38 ppm (m,
18H; PPh3); 13C NMR (151 MHz, CDCl3, 258C): d=135.1 (t, J=
6.2 Hz; ortho of PPh3), 133.7 (s, CH of C6H4), 132.2 (s, CH of C6H4),
131.7 (t, J=25.8 Hz; ipso of PPh3), 130.8 (s, para of PPh3), 128.2 (t,
J=5.4 Hz; meta of PPh3), 126.1 (s, CCꢀN), 118.2 (s, CꢀN), 113.0 (s,
CArCꢀC), 107.5 (t, J=14.5 Hz; CꢀCPd), 90.4 (t, J=6.5 Hz; CꢀCPd),
79.1 (s, CꢀC), 73.5 (s, CꢀC), 70.8 (s, CꢀC), 68.2 (s, CꢀC), 67.0 (t, J=
2.4 Hz; CCꢀCPd), 59.5 (s, CꢀC), 59.1 (s, CꢀC), 57.3 ppm (s, CꢀC);
31P NMR (243 MHz, CDCl3, 258C): d=22.1 ppm (s); IR (fluorinated
oil mull): n˜ =2015 (CꢀC), 2067 (CꢀC), 2145 (CꢀC), 2122 (CꢀC),
2226 cmÀ1 (CꢀN); UV/Vis (CH2Cl2): lmax (e, dm3 molÀ1 cmÀ1)=451
(11000), 415 (16000), 383 (21000), 336 (93000), 318 (84000), 297
The authors would like to thank the National Science Centre
(Grants UMO-2012/05/N/ST5/00665 and UMO-2013/08M/ST5/
00942) for support of this research.
Keywords: alkynes
iodine · palladium
· cross-coupling · hyperconjugation ·
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Received: July 12, 2015
Published online on October 22, 2015
Chem. Eur. J. 2015, 21, 17769 – 17778
www.chemeurj.org
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ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim