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N. Zabarska et al. / Polyhedron 102 (2015) 173–175
2.2. Synthesis of 2a
2.5. Synthesis of 3b
30 mg (0.06 mmol) of [Ru(H-bpy)2(CO)Cl]Cl (1a) was dissolved
in 2 ml MeOH. Then 2 ml of an aqueous KOH-solution
(nKOH = 2.40 mmol) was added and the brown reaction mixture
was refluxed at 70 °C for 2 h. Afterwards the solvent was
evaporated from the violet solution. The dark violet residue was
repetitively dissolved in DCM and the remaining salts removed
by filtration, until the filtrate was colorless. After subsequent
solvent evaporation, 2a was obtained as a dark violet solid. Yield:
32 mg (complete conversion). 1H NMR (400 MHz, CDCl3): complex,
This synthesis was performed in accordance with the literature
procedure [15]. 20 mg (0.03 mmol) of 2b were dissolved in 4 ml
EtOH/H2O 3:1 and the ligand tb-bpy was added. After refluxing
for 3 h a color change from purple to red occurred. Afterwards
NH4PF6 was added for precipitation of 3b as an orange solid, which
was washed with circa 20 ml water and 40 ml diethyl ether. Then it
was repetitively dissolved in chloroform and filtrated until the fil-
trate was colorless. 3b was obtained as a red solid after solvent
evaporation. Yield: 28 mg (complete conversion). 1H NMR
(400 MHz, CDCl3) d = 8.23–8.11 (m, 6H, 3), 7.63 (d, J = 6.0 Hz, 6H,
6), 7.52 (dd, J = 6.1, 2.0 Hz, 6H, 5), 1.41 (s, 54H, CH3) (1H NMR is
in accordance with the literature) [17]. MS-ESI: m/z = 452
[M2+/2], 1051 [M2++PFÀ6 ].
overlapping
signals,
see
Fig.
S3.
MS–ESI:
m/z = 489
[M2+ÀClÀ + MeCN]+.
2.3. Synthesis of 2b
3. Results and discussion
50 mg (0.07 mmol) of [Ru(tbbpy)2(CO)Cl]Cl (1b) was dissolved
in 2 ml MeOH and 2 ml of KOH(aq) (nKOH = 2.80 mmol) was added.
After heating at 70 °C for 2 h a color change of the solution arose
from light brown to purple. Then the solvent was evaporated and
the solid repetitively dissolved in chloroform and the
remaining salts removed by filtration, until the filtrate was
colorless. Thereafter, the solvent was evaporated remaining a dark
purple solid. Yield: 43 mg (complete conversion). Main product is
2b. 1H NMR (400 MHz, CDCl3) d = 9.40 (d, J = 6.0 Hz, 2H), 8.09
(m, 2H), 7.94 (t, m, 2H), 7.60 (dd, J = 6.0, 1.8 Hz, 2H), 7.41
(d, J = 6.1 Hz, 2H), 6.88 (dd, J = 6.1, 2.0 Hz, 2H), 1.50 (s, 18H), 1.29
(s, 18H). MS–ESI: m/z = 708.23 [Ru(tbbpy)2Cl2]1À (reduction during
MS measurement analogue to MacDonnell et al.).[14].
The reactivity of compounds such as [Ru(R-bpy)2(CO)Cl]+ has
been investigated in the past. Upon irradiation of a solution of
the compound with UV light, the CO ligand can be removed whilst
the chloro ligand remains coordinated and a range of [Ru(bpy)2(Cl)
X]+ species can be prepared [18]. On the other hand, upon heating
the reaction solution at reflux, the chloro ligand is removed and
can be exchanged with a range of monodentate ligands [18]. In
addition, analogues of the type [Ru(bpy)2(CO)H]+ can also be pre-
pared [19]. To the best of our knowledge, the efficient removal of
both ligands in a single reaction has not been reported so far.
The new approach we propose is based on a method related to
the reaction conditions reported by Hieber [20,21]. After stirring
[Ru(R-bpy)2(CO)Cl]Cl (1) with 40 eq. KOH in MeOH/H2O at 70 °C,
conversion into [Ru(R-bpy)2Cl2] (2) was observed (see Fig. 1).
IR spectroscopy indicated a complete removal of the CO stretch-
ing vibration (see Figs. 2 and 3) that is present for the starting
material 1 between 1960 cmÀ1 and 1970 cmÀ1. Compound 2 was
detected by ESI–MS (see Figs. S1 and S2). Since labile Cl-ligands
can be substituted by solvent molecules, signal complexity is
observed in the 1H NMR spectrum, indicative of the presence of
several complexes of general type 2 having 2, 1 or 0 chloro ligands
(see Figs. S3 and S4). However, the solution of crude 2 obtained,
can be used without further purification in the following reaction
step.
2.4. Synthesis of 3a
This synthesis was performed in accordance with the literature
procedure [15]. 16 mg (0.03 mmol) of 2a was dissolved in 4 ml
EtOH/H2O 3:1 and 9.4 mg (0.06 mmol) of the ligand H-bpy was
added. Afterwards the violet solution was refluxed for 3 h. Then
3a precipitated after mixing the brown solution with NH4PF6(aq).
Afterwards the product was filtrated, washed with circa 20 ml
water and 40 ml diethyl ether. Then the orange solid was
repetitively dissolved in MeCN and filtrated until the filtrate was
colorless, in order to remove remaining salts. 2a was obtained after
solvent evaporation as a red solid. Yield: 16 mg (complete conver-
sion). 1H NMR (400 MHz, CDCl3) d = 8.50 (d, J = 8.1 Hz, 6H, 3), 8.05
(td, J = 8.0, 1.5 Hz, 6H, 4), 7.73 (dd, J = 5.6, 0.7 Hz, 6H, 6), 7.43–7.34
(m, 6H, 5) (1H NMR is in accordance with the literature) [16].
13C NMR (400 MHz, CDCl3) d = 157.89, 152.60, 138.71, 128.49,
125.17. MS–ESI: m/z = 284 [M2+/2].
R-bpy with R = H or tert-butyl was then coordinated onto 2a or
2b respectively using standard conditions [15]. After precipitation
with PFÀ6 , complete conversion into [Ru(R-bpy)3](PF6)2 3 was
observed (see Fig. 1). Clear 1H NMR (see Figs. S5 and S6) spectra
and the absence of a CO-band in the IR spectrum (see Fig. S7)
indicates the absence of any Ru(II)–CO species.
2+
R
R
R
R-bpy
EtOH/H2O 3:1
NH4PF6
40 eq. KOH,
MeOH/H2O
70°C, 2h
R
R
R
R
R
R
R
R
N
Ru
N
N
Ru
N
N
Ru
N
N
N
Cl
N
N
Cl/solvent
Cl/solvent
N
N
N
N
-
Cl-
(PF6 )2
CO
complete
conversion
complete
conversion
3a-b
R
R
2a-b
R
1a-b
a) R = H
b) R = tert -butyl
Fig. 1. Complete conversion of the Ru(II)-(CO)Cl species 1 forming 2 and following coordination of a third R-bpy ligand yielding [Ru(R-bpy)3]2+ compounds 3a with R = H and
3b with R = tert-butyl.
Zabarska, Natalia
