Reaction of the butadiynyl complex (η5-C5Me5)Re(NO)(PPh3)(C⋮CC⋮CH) (ReC
4
H) with Cu(OAc)2 (pyridine, 80 °C) gives the μ-octatetraynediyl complex ReC
8
Re (70%). Analogous cross-coupling of
ReC
4
H and ReC
2
H gives (after chromatography) ReC
4
Re (14%), ReC
6
Re (44%), and ReC
8
Re (15%). Longer
sp carbon chains are accessed by reactions of ReC
4
H with n-BuLi and CuI, which give ReC
4
Cu. This isolable
species is treated in situ with BrC⋮CSiEt3 or BrC⋮CC⋮CSiMe3 (excess EtNH2, THF) to give ReC
6
SiEt
3
or
ReC
8
SiMe
3
(84−77%). Desilylations (wet n-Bu4N+F-) yield ReC
6
H or ReC
8
H (88−73%). Then Cu(OAc)2
(pyridine, 50 °C) gives ReC
12
Re or ReC
16
Re (71−67%). The former is also available from ReC
4
Cu and
BrC⋮CC⋮CBr (45%), and ReC
10
Re can be accessed by cross-coupling. ReC
6
H and ReC
8
H are similarly
converted to ReC
10
SiR
3
(R = Me, Et; 51−26%) and ReC
12
SiMe
3
(43%). Desilylation of ReC
10
SiR
3
gives
labile ReC
10
H, but only black powder is obtained from ReC
12
SiMe
3
. In situ coupling of ReC
10
H gives ReC
20
Re
(52−34%), which unlike lower homologues is not obtained in analytically pure form. The effects of chain
length upon visible spectra (progressively red-shifted and more intense bands; ε >190 000 M-1 cm-1), IR/Raman νC
⋮
C patterns (progressively more bands), 13C NMR chemical shifts (asymptotic limit of 64−67 ppm
for ReC⋮C(
C
⋮
C
)
n
), cyclic voltammetry (decreased reversibility of two oxidations; a gradual shift of the first
to thermodynamically less favorable potentials, so that only a single oxidation is observed for ReC
20
Re), and
thermal stabilities (solid-state decompositions at 155 °C, ReC
20
Re, and 178−217 °C, lower homologues) are
studied in detail.
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