Synthesis of the half-sandwich ruthenium complexes [Cp?RuL3]+ via naphthalene replacement in [Cp?Ru(C10H8)]+

Article abstract of DOI:10.1016/j.mencom.2015.01.010

The cation [Cp?Ru(C₁₀H₈)]⁺ exchanges naphthalene for various ligands under near-UV (365 nm) or visible light irradiation giving the half-sandwich complexes [Cp?RuL₃]⁺ [L = P(OMe)₃, 1,3,5-tr

Full text of DOI:10.1016/j.mencom.2015.01.010

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Mendeleev
Communications
Mendeleev Commun., 2015, 25, 29–31
Synthesis of the half-sandwich ruthenium complexes
[Cp*RuL3]+ via naphthalene replacement in [Cp*Ru(C10H8)]+
Dmitry S. Perekalin, Nikita V. Shvydkiy, Yulia V. Nelyubina and Alexander R. Kudinov*
A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 119991 Moscow,
Russian Federation. Fax: +7 499 135 5085; e-mail: arkudinov@ineos.ac.ru
DOI: 10.1016/j.mencom.2015.01.010
The cation [Cp*Ru(C10H8)]+ exchanges naphthalene for various ligands under near-UV (365 nm) or visible light irradiation giving
the half-sandwich complexes [Cp*RuL3]+ [L = P(OMe)3, 1,3,5-triaza-7-phosphaadamantane, ButNC], [Cp*Ru(dppe)(MeCN)]+,
Cp*Ru(CO)2Cl, Cp*Ru[tris(pyrazolyl)borate] and [Cp*Ru(C6H6)]+ in 80–95% yields.
The half-sandwich cyclopentadienyl ruthenium complexes
[(C5R5)RuL3]+ attract a considerable attention owing to their use
in homogeneous catalysis.1,2 They are commonly synthesized
from the air-sensitive precursors [(C5R5)Ru(MeCN)3]+.3 Recently,
it was found that the cations [CpRuL3]+ (with the unsubstituted
cyclopentadienyl ligand) are more conveniently prepared via the
replacement of a naphthalene ligand in the air-stable complex
[CpRu(C10H8)]+ 1a.4 Here, we report the extension of this
approach to the synthesis of the pentamethyl-substituted deri-
vatives [Cp*RuL3]+ from the air-stable and readily available5
naphthalene complex [Cp*Ru(C10H8)]+ 1b.
We found that heating 1b with P(OMe)3 in acetone at
60°C for 5 h does not lead to naphthalene replacement.
However, the same reaction under near-UV irradiation (365 nm)
at room temperature gives the target half-sandwich complex
{Cp*Ru[P(OMe)3]3}+ 2a in 96% yield (Scheme 1).† Naphthalene
Me
Me
Me
Me
Me
Me
Me
Me
Ph2P
Me
Me
Ru
L
Ru
L
L
NCMe
PPh2
2a L = P(OMe)3, 96%
2b L = PTA, 88%
3, 86%
2c L = ButNC, 79%
dppe
MeCN
hv
hv
L
Me
Ru
Me
Me
Me
Me
Me
Me
Me
Me
Cl–, CO
Me
OC
Ru
hv
Cl
CO
1b
4, 84%
†
All reactions were carried out under argon, in anhydrous solvents,
[(C3N2H3)3BH]–
hv
C6H6
which were purified using standard procedures. The products were isolated
in air. Complex [1b]PF6 was obtained using a published procedure.5
Irradiation was performed by a household nail curing lamp (365 nm,
36 W). Column chromatography was performed on Acros silica gel
(0.060–0.200 mm). The 1H and 31P NMR spectra were measured with a
Bruker Avance 400 spectrometer at 20°C in acetone-d6 solutions unless
otherwise stated. Chemical shifts are given in ppm relative to the residual
signal of acetone-d5 (1H, d 2.05 ppm) or an external standard of 85%
H3PO4 (31P).
[Cp*RuL3]PF6 [2a–c]PF6 (general procedure). A solution of [1b]PF6
(25 mg, 0.05 mmol) and an excess of ligand L [P(OMe)3, 59 ml, 0.5 mmol;
1,3,5-triaza-7-phosphaadamantane, 27 mg, 0.17 mmol; ButNC, 37 ml,
0.5 mmol] in acetone (5 ml) was irradiated for 5 h. The solvent was
evaporated; the residue was washed with Et2O, dissolved in a minimal
volume of CH2Cl2 (MeNO2 in the case of 2b), precipitated by an excess
of a hexane–Et2O mixture and dried in vacuo.
hv
Me
Me
Ru
Me
Me
Me
Me
Me
Me
Me
Me
Ru
N
N
N
N
N
N
5, 90%
B
H
6, 82%
Scheme 1
a 5 cm silica gel column with a CH2Cl2–acetone mixture. The yellow
band was collected and dried in vacuo to give [3]PF6, 69 mg (86%). 1H NMR,
d: 1.51 (s, 15H, Cp*), 1.83 (s, 3H, MeCN), 2.57 (br.s, 4H, CH2), 7.63
(m, 20H, Ph). 31P NMR, d: 75.1 (cf. ref. 13).
2a: yield 32 mg (96%). 1H NMR, d: 1.84 (q, 15H, Cp*, JHP 2 Hz), 3.79
[m, 27H, (MeO)3P]. 31P NMR, d: 148.2 (cf. ref. 12).
1
2b: yield 42 mg (88%). H NMR, d: 2.01 (m, 15H, Cp*), 4.13 (br.s,
Cp*Ru(CO)2Cl 4: Carbon monoxide was bubbled through an irradiated
18H, CH2), 4.52 (d, 9H, CH2, J 13 Hz), 4.60 (d, 9H, CH2, J 13 Hz).
31P NMR, d: –37.2. Found (%): C, 36.92; H, 5.91. Calc. for C28H51F6N9P4Ru·
2MeNO2 (%): C, 36.96; H, 5.89. Note that crystals submitted for X-ray
diffraction correspond to the formula [2b]PF6·4MeNO2.
solution of [1b]PF6 (71 mg, 0.14 mmol), [Et3NCH2Ph]Cl (37 mg, 0.16 mmol)
in CH2Cl2 (5 ml) for 6 h. The solvent was evaporated, the residue was
purified by elution through a 5 cm silica gel column first with hexane
(to remove naphthalene) and then with a CH2Cl2–hexane (1:1) mixture.
The yellow band was collected and dried in vacuo to give 4 (39 mg,
84%). 1H NMR (CDCl3) d: 1.90 (s, 15H, Cp*) (cf. ref. 14).
[Cp*Ru(C6H6)]PF6 [5]PF6. A solution of [1b]PF6 (57 mg, 0.11 mmol)
and C6H6 (500 ml, 5.6 mmol) in acetone (5 ml) was irradiated for 18 h.
The solvent was evaporated; the residue was washed with Et2O, dissolved
in a minimal volume of CH2Cl2, precipitated by Et2O and dried in vacuo
to give colorless [5]PF6 (46 mg, 90%). 1H NMR, d: 2.09 (s, 15H, Cp*),
6.06 (s, 6H, C6H6) (cf. ref. 15).
2c: yield 24 mg (79%). 1H NMR, d: 1.98 (s, 15H, Cp*), 1.56 (s, 27H,
Me3CNC). Found (%): C, 47.35; H, 7.00. Calc. for C25H42F6N3PRu (%):
C, 47.61; H, 6.71.
[Cp*Ru(dppe)(MeCN)]PF6 [3]PF6. A solution of [1b]PF6 (50 mg,
0.1 mmol) and dppe (51 mg, 0.13 mmol) in acetonitrile (5 ml) was
irradiated for 12 h. The solvent was evaporated, the residue was dissolved
in a minimal volume of CH2Cl2 and precipitated by a mixture of hexane–
Et2O (1:1). The precipitate was dissolved in CH2Cl2 and eluted through
© 2015 Mendeleev Communications. Published by ELSEVIER B.V.
on behalf of the N. D. Zelinsky Institute of Organic Chemistry of the
Russian Academy of Sciences.
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Mendeleev Commun., 2015, 25, 29–31
replacement in 1b also proceeds under visible light irradiation
(>400 nm), although notably slower because the absorption of
1b is maximal at 365 nm.6
Similar reactions of 1b with ButNC or 1,3,5-triaza-7-phos-
phaadamantane (PTA) produce tris-ligand complexes [Cp*Ru-
(ButNC)3]+ 2c or [Cp*Ru(PTA)3]+ 2b, respectively. The reaction
with 1,2-bis(diphenylphosphino)ethane (dppe) in acetonitrile
affords the mixed-ligand complex [Cp*Ru(dppe)(MeCN)]+ 3.
An attempt to prepare the tris-acetonitrile complex [Cp*Ru-
(MeCN)3]+ 2d by the irradiation of 1b in MeCN has failed,
probably, because the strong absorption of formed product 2d
(lmax = 370 nm, e = 1287 dm3 mol–1 cm–1) prevents the absorption
by starting complex 1b (lmax = 365 nm, e = 760 dm3 mol–1 cm–1).6
At the same time, refluxing 1b in acetonitrile slowly produced
2d. Unfortunately, we could not achieve 100% conversion in this
reaction even after 20 h of reflux with the continuous extraction
of released naphthalene by heptane. Note that an analogous
reaction of unsubstituted naphthalene complex 1a with MeCN
reached 100% conversion within 35 h at room temperature.
In contrast to 1a,4(b) complex 1b does not react with carbon
monoxide or chloride anion alone. The reaction with CO is
presumably too slow, while naphthalene replacement by Cl–
can be reversible.8 However, 1b readily reacts with Cl– and CO
together giving Cp*Ru(CO)2Cl 4 in 84% yield.
N(3)
Ru(1)
N(6)
P(2)
P(3)
P(1)
N(4)
N(2)
N(8)
N(1)
N(7)
N(5)
N(9)
Figure 1 Structure of cation 2b with ellipsoids at a 50% probability level.
All hydrogen atoms are omitted for clarity. Selected interatomic distances
(Å): Ru(1)–P(1) 2.2997(11), Ru(1)–P(2) 2.2973(11), Ru(1)–P(3) 2.2926(11),
Ru···C5 1.915.
Ru(1)
P(2)
P(1)
N(1S)
Complex 1b also exchanges naphthalene for six-electron
ligands. For example, the prolonged irradiation of 1b with benzene
leads to arene exchange resulting in thermodynamically more
stable9 complex [Cp*Ru(C6H6)]+ 5 in 90% yield. The reaction
with the tris(pyrazolyl)borate anion produces the neutral com-
pound Cp*RuTp 6 [Tp = (C3N2H3)3BH] in 82% yield. However,
a similar reaction with the substituted tris(3,5-dimethylpyrazolyl)-
borate anion does not proceed, presumably, because of steric
hindrances.
Figure 2 Structure of cation 3 with ellipsoids at a 50% probability level.
All hydrogen atoms are omitted for clarity. Selected interatomic distances
(Å): Ru(1)–N(1S) 2.0455(17), Ru(1)–P(1) 2.3013(5), Ru(1)–P(2) 2.3054(5),
Ru···C5 1.870.
we suggest that this general approach can be still applied to other
ruthenium naphthalene complexes.4(a),11
All of the compounds obtained were characterized by 1H NMR
spectroscopy. New complexes [2b]PF6 and [2c]PF6 were addi-
tionally characterized by elemental analysis. The structures
of [2b]PF6 and [3]PF6 were established by X-ray diffraction
(Figures 1 and 2).‡ The distance Ru···Cp* in cation 2b (1.915 Å)
is notably longer than that in 3 (1.870 Å), probably, because of
steric effects imposed by large PTA ligands in 2b. Interestingly,
the Ru···Cp* distances in both 2b and 3 are longer than that in
the starting sandwich complex [Cp*Ru(C10H8)]+ (1.803 Å),5 which
can be attributed to the strong trans influence of phosphorous
ligands. The geometry of cation 3 is generally similar to that of
the benzonitrile complex [Cp*Ru(dppe)(PhCN)]+.10
In overall, we have developed a convenient method for the
synthesis of Cp*Ru complexes via naphthalene replacement in
[Cp*Ru(C10H8)]+ 1b under photochemical conditions. Compared
to the unsubstituted complex [CpRu(C10H8)]+, cation 1b reacts
less readily apparently because of steric hindrances. Nevertheless,
This work was supported by the Russian Science Foundation
(project no. 14-13-00724).
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‡
Crystallographic data. Crystals of [2b]PF6·4MeNO2 (C32H63F6N13O8P4Ru,
M = 1096.90) are monoclinic, space group C2/c, at 120 K: a = 23.1405(14),
b = 18.2330(11) and c = 22.0670(13) Å, b = 90.0410(10)°, V = 9310.5(10) Å3,
Z = 8 (Z' = 1), dcalc = 1.565 g cm–3, m(MoKa) = 5.59 cm–1, F(000) = 4544.
Crystals of [3]PF6 (C38H42F6NP3Ru, M = 820.71) are monoclinic, space
group P21/c, at 120 K: a = 11.4436(6), b = 17.3250(9) and c = 19.1253(9) Å,
b = 104.4260(10)°, V = 3672.2(3) Å3, Z = 4 (Z' = 1), dcalc = 1.484 g cm–3,
m(MoKa) = 6.17 cm–1, F(000) = 1680.
CCDC 994750 and 994751 contain the supplementary crystallographic data
forthispaper.ThesedatacanbeobtainedfreeofchargefromTheCambridge
Crystallographic Data Centre via http://www.ccdc.cam.ac.uk.
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Mendeleev Commun., 2015, 25, 29–31
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Received: 1st April 2014; Com. 14/4339
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