ation). Since the broad range of half-wave potentials implies a
Ru2[(p-MeOC6H4)NCHN(p-MeOC6H4)]4(CCPh)2 1. Eluent:
1
significant variation in the electron-richness of the RuIII core
CH2Cl2. Yield: 5%. H NMR: δ 8.17 (s, 4 H, NCHN), 7.09 (t,
2
for compounds 1–7, a substantial influence on the C᎐C bond
4 H, CCC6H5, 3J = 7.7), 6.84 (t, 2 H, CCC6H5, 3J = 7.4), 6.77 (d,
᎐
᎐
3
᎐
strength would be anticipated. However, the ν(C᎐C) values
16 H, phenyl ring of bridging ligand, J = 8.8), 6.62 (d, 16 H,
᎐
across the series [mean 2100(2) cmϪ1] show no substituent
dependence at all. While in-depth understanding of such a sub-
stituent independence awaits more accurate theoretical model-
ing, a plausible explanation is that the inductive and π-back
donation effects cancel each other.
phenyl ring of bridging ligand, 3J = 8.8), 6.35 (d, 4 H, CCC6H5,
3J = 7.1 Hz) and 3.68 (s, 24 H, OCH3). UV/VIS: λmax/nm (ε/Ϫ1
cmϪ1) 694 (sh), 574 (12 460), 507 (14 370) and 426 (sh). ν(C᎐C):
᎐
᎐
2099 cmϪ1
.
Ru2(PhNCHNPh)4(CCPh)2 2. Eluent: CH2Cl2–hexane (9:1
1
v/v). Yield: 36%. H NMR: δ 8.28 (s, 4 H, NCHN), 7.12–7.04
Conclusion
(m, 28 H, phenyl ring of bridging ligand and CCC6H5), 6.88–
6.83 (m, 18 H, phenyl ring of bridging ligand and CCC6H5) and
A facile synthesis of a series of diruthenium() compounds
bearing two axial phenylacetylides in satisfactory yields is
reported, which implies the general accessibility of this type of
compound with other transition-metal centers. As the first
example of linear substituent redox-tuning for dinuclear
organometallic compounds, the linear free-energy relationship
reported complements the early studies of dimolybdenum,19
dinickel,20 and diruthenium compounds.1 In addition, the
origin of unusual geometric distortions observed for diruthe-
nium() paddlewheel compounds has been attributed to a
second-order Jahn–Teller effect. The conversion of the reported
compounds into the corresponding vinylidene compounds is
being investigated. A complete list of IR and 13C NMR data is
provided in the supplementary data (SUP 57330).
6.28 (d, 4 H, CCC6H5, J = 7.2 Hz). UV/VIS: λmax/nm (ε/Ϫ1
3
cmϪ1) 694 (sh), 534 (16 200), 510 (sh) and 416 (sh). ν(C᎐C):
᎐
᎐
2101 cmϪ1
.
Ru2[(p-ClC6H4)NCHN(p-ClC6H4)]4(CCPh)2
3.
Eluent:
CH2Cl2. Yield: 73%. 1H NMR: δ 8.21 (s, 4 H, NCHN), 7.22 (t,
3
4 H, CCC6H5, J = 7.7), 7.11 (d, 16 H, phenyl ring of bridging
ligand, 3J = 8.6), 6.96 (t, 2 H, CCC6H5, 3J = 7.4), 6.77 (d, 16 H,
3
phenyl ring of bridging ligand, J = 8.6) and 6.25 (d, 4 H,
CCC6H5, 3J = 7.2 Hz). UV/VIS: λmax/nm (ε/Ϫ1 cmϪ1) 690 (sh),
Ϫ1
᎐
526 (17 310), 504 (sh) and 424 (sh). ν(C᎐C): 2099 cm
.
᎐
Ru2[(m-ClC6H4)NCHN(m-ClC6H4)]4(CCPh)2 4. Eluent:
CH2Cl2–hexane (1:3 v/v). Yield: 39%. 1H NMR: δ 8.29 (s, 4 H,
NCHN), 7.12–7.08 (m, 20 H, phenyl ring of bridging ligand
and CCC6H5), 6.92 (s, 8 H, phenyl ring of bridging ligand), 6.89
Experimental
All the chlorotetrakis(diarylformamidinato)diruthenium(,)
compounds were prepared as previously described.1 Phenyl-
acetylene, lithium phenylacetylide and n-butyllithium [1.6 in
tetrahydrofuran (thf)] were from Aldrich. Tetrahydrofuran was
distilled over sodium–benzophenone under a nitrogen atmos-
phere prior to use. Proton and 13C NMR spectra were recorded
on a Bruker AMX-360 spectrometer, with chemical shifts (δ)
referenced to the residual CHCl3 and the solvent CDCl3,
respectively, infrared spectra on a Nicolet system 550 (Magna
series) FTIR spectrometer using KBr discs and UV/VIS spec-
tra in CH2Cl2 with an IBM 9420 spectrophotometer. Cyclic
voltammograms were recorded in 0.1 NBu4BF4 solution
(CH2Cl2, N2-degassed) on a BAS CV-50W voltammetric ana-
lyzer with platinum working and auxiliary electrodes and a Ag–
AgCl reference electrode. The ferrocenium–ferrocene couple
(added as internal reference) was measured at 0.625 V under the
experimental conditions.
3
(t, 2 H, CCC6H5, J = 7.2), 6.77–6.73 (m, 8 H, phenyl ring
3
of bridging ligand) and 6.40 (d, 4 H, CCC6H5, J = 7.6 Hz).
UV/VIS: λmax/nm (ε/Ϫ1 cmϪ1) 680 (sh), 533 (17 650), 506 (sh)
Ϫ1
᎐
and 419 (sh). ν(C᎐C); 2099 cm
.
᎐
Ru2[(m-F3CC6H4)NCHN(m-F3CC6H4)]4(CCPh)2 5. Eluent:
CH2Cl2–hexane (1:3 v/v). Yield: 52%. 1H NMR: δ 8.38 (s, 4 H,
NCHN), 7.41 (d, 8 H, phenyl ring of bridging ligand, 3J = 7.8),
7.31 (t, 8 H, phenyl ring of bridging ligand, J = 7.8), 7.11 (s,
8 H, phenyl ring of bridging ligand), 7.08 (d, 8 H, phenyl ring
3
3
3
of bridging ligand, J = 8.0), 7.03 (t, 4 H, CCC6H5, J = 7.7),
3
6.86 (t, 2 H, CCC6H5, J = 7.4) and 6.02 (d, 4 H, CCC6H5,
3J = 7.5 Hz). UV/VIS: λmax/nm (ε/Ϫ1 cmϪ1) 682 (sh), 529
Ϫ1
᎐
(14 380), 502 (sh) and 420 (sh). ν(C᎐C): 2102 cm
.
᎐
Ru2[(3,4-Cl2C6H3)NCHN(3,4-Cl2C6H3)]4(CCPh)2 6. Eluent:
CH2Cl2–hexane (3:2 v/v). Yield: 54%. 1H NMR: δ 8.29 (s, 4 H,
NCHN), 7.27 (d, 8 H, phenyl ring of bridging ligand, 3J = 8.1),
Synthesis
3
7.19 (t, 4 H, CCC6H5, J = 7.6), 7.03 (d, 8 H, phenyl ring of
All the compounds were prepared by the following method:
the parent compound chlorotetrakis(diarylformamidinato)-
diruthenium(,)1 (0.20 mmol) was dissolved/suspended in
dry thf (30 cm3) under argon. To this solution at 0 ЊC was added
PhCCLi (10 mmol, freshly prepared by treating PhCCH with
an equal amount of LiBu in dry thf at Ϫ78 ЊC under argon) with
stirring, whereupon it immediately changed from dark green to
dark red. After being stirred for 20 min, the reaction mixture
was allowed to warm to room temperature and stirred under
argon until it became yellowish brown. It was further stirred in
the air for 30 min before the volatiles were removed under vac-
uum. The purple residue was dissolved in CH2Cl2 (10 cm3),
loaded onto a short plug of silica, then eluted with CH2Cl2. The
solvent was removed from the purple fraction by bubbling air
through it at ambient temperature. The crude product was fur-
ther purified on a silica gel column with CH2Cl2–hexane as the
eluent (the exact ratio for individual compounds is given
below). Evaporation of solvents from the purple band yielded
the crystalline product. (Note: while satisfactory yields were
achieved with the PhCCLi prepared in situ, little or no products
were isolated when the same procedure was repeated using the
commercial PhCCLi reagent from Aldrich).
5
3
bridging ligand, J = 1.9), 6.96 (t, 2 H, CCC6H5, J = 7.4), 6.72
(dd, 8 H, phenyl ring of bridging ligand, 3J = 8.4, 5J = 2.0) and
6.29 (d, 4 H, CCC6H5, J = 7.6 Hz). UV/VIS: λmax/nm (ε/Ϫ1
3
cmϪ1) 690 (sh), 549 (13 710), 510 (sh) and 420 (sh). ν(C᎐C):
᎐
᎐
2099 cmϪ1
.
Ru2[(3,5-Cl2C6H3)NCHN(3,5-Cl2C6H3)]4(CCPh)2 7. Eluent:
CH2Cl2. Yield: 20%. 1H NMR: δ 8.34 (s, 4 H, NCHN), 7.19 (s,
8 H, phenyl ring of bridging ligand), 7.13 (t, 4 H, CCC6H5,
3J = 7.6), 6.93 (t, 2 H, CCC6H5, J = 7.4), 6.85 (s, 16 H, phenyl
3
ring of bridging ligand) and 6.49 (d, 4 H, CCC6H5, 3J = 7.5 Hz).
UV/VIS: λmax/nm (ε/Ϫ1 cmϪ1) 688 (sh), 539 (12 890), 503 (sh)
Ϫ1
᎐
and 423 (sh). ν(C᎐C): 2099 cm
.
᎐
X-Ray crystallography
Crystal data. C92H70Cl8N8Ru2 3ؒ2C6H6, M = 1773.30, mono-
clinic, space group P21/n, a = 16.290(7), b = 15.700(6),
c = 16.946(8) Å, β = 107.43(3)Њ, U = 4135(3) Å3, Z = 2 (the
molecule has crystallographic inversion symmetry), Dc = 1.424
g cmϪ3, Mo-Kα radiation, λ = 0.710 73 Å. µ(Mo-Kα) = 6.75
cmϪ1, F(000) = 3608.
J. Chem. Soc., Dalton Trans., 1998, Pages 571–576
575
Lin, Chun
