Inorganic Chemistry
Article
with dry pentane (10 mL), centrifuged and the washing solution was
significantly smaller half-width compared to the high-temper-
ature limit of a Class II MV system. For Rc-Ruacac+ and Rc*-
RuCl, which constitute the electronically most strongly coupled
systems of this series, the IVCT band is skewed and has a
distinctly smaller half-width at the low energy side. The low-
energy cutoff becomes even more prominent at lower T. Such
behavior is typical of (almost) delocalized MV systems of class
III or at the class II/III borderline and is due to coupling of the
electronic IVCT transition to symmetrical vibrational modes of
the bridge. The present findings complement our previous
study on the MV radical cations of vinylruthenium triarylamine
conjugates (4-RC6H4)2N−C6H4−CHCH−{RuCl}, where
skewed IVCT bands were also observed for those congeners
situated at the class II/III borderline.31
removed via decanting. After evaporating to dryness, compound 4 was
1
isolated as reddish gray solid in 56% yield (250 mg, 0.34 mmol). H
3
NMR (400 MHz, CD2Cl2): δ 7.64 (dt, 1H, JHH = 13.3 Hz, H-1),
5.39 (dt, 1H, 3JHH = 13.3 Hz, 3JHP = 2.2 Hz, H-2), 4.44 (vt, 2H, 3JHH
=
3
1.6 Hz, H-5), 4.42 (s, 5H, H-6), 4.36 (vt, 2H, JHH = 1.6 Hz, H-4),
2.66−2.78 (m, 6H, P(CH(CH3)2)3), 1.25−1.32 (m, 36H, P(CH-
2
(CH3)2)3). 13C NMR (100.6 MHz, CD2Cl2): δ 203.5 (t, JCP = 13.3
Hz, C-7), 144.0 (t, 2JCP = 10.8 Hz, C-1), 129.3 (t, 3JCP = 3.4 Hz, C-2),
93.2 (t, 4JCP = 1.7 Hz, C-3), 70.6 (s, C-6), 69.2 (s, C-4), 67.4 (s, C-5),
24.9 (t, 1JCP = 9.8 Hz, P(CH(CH3)2)3), 20.3 (s, P(CH(CH3)2)3), 20.2
(s, P(CH(CH3)2)3). 31P NMR (162 MHz, CD2Cl2): δ 38.3 (s, 2P,
PiPr3). Anal. Calcd for C31H53ClOP2Ru2: C, 50.23; H, 7.21. Found: C,
50.02; H: 7.11.
(η5-C5H5)Ru(η5-C5H4−CHCH−){Ru(acac)(CO)(PiPr3)2}, Rc-
Ruacac. To a solution of potassium hydroxide (20 mg, 0.36 mmol,
2.6 equiv) in dry methanol (10 mL) was added acetylacetone (0.08
mL, 74 mg, 0.74 mmol, 5.5 equiv). The mixture was stirred at 50 °C
for 1.5 h. The resulting solution was added to a solution of Rc-RuCl
(100 mg, 0.14 mmol, 1 equiv) in dry CH2Cl2 (10 mL) at room
temperature. The reaction mixture was stirred for 1 h at 40 °C. Then,
the solvents were removed under reduced pressure. The residue was
dissolved in CH2Cl2 and filtered via syringe filtration into a falcon
tube under inert gas conditions. The solvent was removed and the
crude product was dried under reduced pressure. The solid was
washed with dry methanol (5 mL). After evaporating to dryness,
compound 5 was obtained as yellow powder in 62% yield (67 mg,
The MV radical cations of their ferrocene analogs Fc-RuCl+
and Fc-Ruacac+ are electronically less strongly coupled and their
IVCT bands are adequately represented by a single Gaussian.
Quite interestingly, the HOMO of the ferrocene vinyl
ruthenium conjugates appears to be as delocalized as that of
their ruthenocene analogs. This does, however, not pertain to
their radical cations. For the ruthenocene derivatives, the β-
LUSO of the associated radical cations has the same character
as the HOMO of their neutral precursors. In the ferrocene
analogs, however, the β-LUSO, which represents the spin
orbital from where the electron is taken, is strongly biased
toward the ferrocenyl entity.
Perhaps the most stunning finding of this study comes from
the comparison between the ruthenocene derivatives and their
ferrocene analogs. We have identified several pairs of
ferrocene/ruthenocene vinylruthenium conjugates where the
free enthalpy differences ΔG0 for oxidation of the vinyl-
ruthenium or the metallocene site are largely identical or very
similar. Even in these cases, the ΔE1/2 values of the
ruthenocene complexes are by 400 to over 600 mV smaller
than for their ferrocene analogs despite the stronger electronic
coupling of the former. A different positioning of the
associated counterion either close to the metallocene site in
the case of a more localized charge or within the cleft in
between the metallocene and the vinylruthenium sites in the
more delocalized congeners may explain these unexpected
observations.
1
3
0.08 mmol). H NMR (400 MHz, CD2Cl2): δ 8.07 (dt, 1H, JHH
=
16.6 Hz, 3JHP = 1.6 Hz, H-1), 5.74 (dt, 1H, 3JHH = 16.6 Hz, 4JHP = 1.8
Hz, H-2), 5.28 (s, 1H, H-10), 4.52 (vt, 2H, 3JHH = 1.6 Hz, H-5), 4.43
3
(s, 5H, H-6), 4.35 (vt, 2H, JHH = 1.6 Hz, H-4), 2.25−2.38 (m, 6H,
P(CH(CH3)2)3), 1.87 (s, 3H, H-8/8′), 1.76 (s, 3H, H-8/8′), 1.21−
1.30 (m, 36H, P(CH(CH3)2)3). 13C NMR (100.6 MHz, CD2Cl2): δ
2
210.6 (t, JCP = 15.3 Hz, C-7), 188.9 (s, C-9/9′), 187.1 (s, C-9/9′),
160.6 (t, 2JCP = 11.9 Hz, C-1), 128.0 (t, 3JCP = 2.4 Hz, C-2), 100.4 (s,
4
C-10), 97.4 (t, JCP = 1.4 Hz, C-3), 70.3 (s, C-6), 68.8 (s, C-4), 67.3
1
(s, C-5), 28.9 (s, C-8/8′), 24.7 (t, JCP = 8.7 Hz, P(CH(CH3)2)3),
20.1 (s, P(CH(CH3)2)3), 19.9 (s, P(CH(CH3)2)3). 31P NMR (162
MHz, CD2Cl2): δ 36.3 (s, 2P, PiPr3). Anal. Calcd for C36H60O3P2Ru2:
C, 53.72; H, 7.51. Found: C, 53.60; H, 7.53.
C6H5CHCH−){Ru(acac)(CO)(PiPr3)2}, Ph-Ruacac. Complex Ph-
45
Ruacac was prepared from the literature-known complex Ph-RuCl
according to the procedure described for complex Rc-Ruacac 1H
.
NMR (400 MHz, CD2Cl2): δ 8.96 (dt, 1H, 3JHH = 16.6 Hz, 3JHP = 1.6
Hz, H-1), 7.20−7.11 (m, 4H, H-Ph), 6.98 (tt, 1H, 3JHH = 6.5, 2.1 Hz
3
3
H-Ph), 6.40 (dt, 1H, JHH = 16.7 Hz,, JHP = 1.9 Hz, H-2), 5.33 (s,
1H, H-12), 2.34 (m, 6H, P(CH(CH3)2)3), 1.93 (s, 3H, H-11/11′),
1.79 (s, 3H, H-11/11′), 1.35−1.16 (m, 36H, P(CH(CH3)2)3). 13C
EXPERIMENTAL SECTION
■
2
General methods and procedures are detailed in the Supporting
Information. Scheme 2 provides the atomic numbering used for the
assignment of NMR signals.
NMR (100.6 MHz, CD2Cl2): δ 210.5 (t, JCP = 15.4 Hz, C-7), 189.1
2
(s, C-9/C-9′), 187.2 (s, C-9/C-9′), 166.5 (t, JCP = 12.3 Hz, C-1),
3
3
142.5 (t, JCP = 1.50 Hz, C-ipsoPh), 134.4 (t, JCP = 2.3 Hz, C-2),
128.7 (s, C-o/mPh), 124.2 (s, C-o/mPh), 123.2 (s, C-pPh), 100.6 (s,
1
C-10), 28.9 (s, C-11/C-11′) 24.9 (t, JCP = 8.7 Hz, P(CH(CH3)2)3),
Scheme 2. General Atomic Numbering for the Cp- and Cp*-
Substituted Metallocenes−Vinyl Ruthenium Conjugates
20.0 (s, P(CH(CH3)2)3), 19.9 (s, P(CH(CH3)2)3. 31P NMR (162
MHz, CD2Cl2): δ 35.6 (s, 2P, PiPr3). Anal. Calcd for C32H56O3P2Ru:
C, 58.97; H, 8.66. Found: C, 58.72; H, 8.42.
(η5-C5Me5)Ru(η5-C5H4−CHCH−){Ru(CO)Cl(PiPr3)2}, Rc*-RuCl. 1-
Ethynyl-1′,2′,3′,4′,5′-pentamethylruthenocene was prepared accord-
ing to the literature.103 Hydroruthenation was carried out as for
complex Rc-RuCl. Complex Rc*-RuCl was isolated as a red solid in
1
57% yield (250 mg, 0.34 mmol). H NMR (400 MHz, CD2Cl2): δ
7.39 (dt, 1H, 3JHH = 13.2 Hz, 3JHP = 1.6 Hz H-1), 5.29 (dt, 1H, 3JHH
=
13.2 Hz, 3JHP = 1.9 Hz, H-2), 3.94 (vt, 2H, 3JHH = 1.7 Hz, H-5), 3.90
(vt, 2H, 3JHH = 1.7 Hz, H-4), 1.87 (s, 15H, C5(CH3)5), 2.77−2.66 (m,
6H, P(CH(CH3)2)3), 1.34−1.22 (m, 36H, P(CH(CH3)2)3). 13C
Synthesis and Characterization. (η5-C5H5)Ru(η5-C5H4−CH
CH−){Ru(CO)Cl(PiPr3)2}, Rc-RuCl. Ethynylruthenocene (151 mg, 0.59
mmol, 1 equiv) and HRu(CO)Cl(PiPr3)2 (287 mg, 0.59 mmol, 1
equiv) were put into a falcon tube and dissolved in 10 mL of dry
CH2Cl2 under inert gas conditions. The solution was stirred for 30
min. After evaporating most of the solvent under nitrogen, the crude
product was dried under reduced pressure. The residue was washed
2
NMR (100.6 MHz, CD2Cl2): δ 203.7 (t, JCP = 13.3 Hz, C-8), 143.7
(t, JCP = 10.5 Hz, C-1), 129.3 (t, JCP = 3.4 Hz, C-2), 93.2 (t, JCP
2
3
4
=
1.70 Hz, C-3), 84.9 (s, C5(CH3)5), 71.8 (s, C-4), 69.9 (s, C-5), 24.6
1
(t, JCP = 9.8 Hz, P(CH(CH3)2)3), 20.2 (s, P(CH(CH3)2)3), 20.2 (s,
P(CH(CH3)2)3), 12.4 (s, C5(CH3)5). 31P NMR (162 MHz, CD2Cl2):
I
Inorg. Chem. XXXX, XXX, XXX−XXX