Cationic vinyl and dicationic carbene ruthenium(II) complexes from a vinylidene(hydrido) precursor

Article abstract of DOI:10.1021/om0100737

The reaction of the vinylidene(hydrido)ruthenium(II) compound [RuHCl(=C=CH₂)(PCy₃)₂] (1a) with excess KPF₆ in CH₂Cl₂/CH₃CN affords the five-coordinate vinyl complex [Ru(CH=CH₂)(CH₃CN)₂ (PCy₃)₂]PF₆ (2a), which on treatment with NaBPh₄ or NaB(Ar_f)₄ gives the tetraaryloborate salts 2b and 2c in excellent yields. The six-coordinate compounds [Ru(CH=CHPh)- (CH₃CN)₃(PiPr₃)₂]X (3a, X = Cl; 3b, X = PF₆) were obtained in a similar route using [RuHCl(=C=CHPh)- (PiPr₃)₂] (1b) as the starting material. Protonation of 2c or 2d (X = BF₄) with, respectively, [H(OEt₂)₂]B(Ar_f)₄ or HBF₄ yields [Ru(=CHCH₃)(CH₃CN)₂ (PCy₃)₂]X₂ (4a,b), which to the best of our knowledge represent the first dicationic carbeneruthenium(II) complexes.

Full text of DOI:10.1021/om0100737

© Copyright 2001
Volume 20, Number 11, May 28, 2001
American Chemical Society
Communications
Ca tion ic Vin yl a n d Dica tion ic Ca r ben e Ru th en iu m (II)
Com p lexes fr om a Vin ylid en e(h yd r id o) P r ecu r sor
Stefan J ung, Kerstin Ilg, J ustin Wolf, and Helmut Werner*
Institut fu¨r Anorganische Chemie, Universita¨t Wu¨rzburg, Am Hubland,
D-97074 Wu¨rzburg, Germany
Received J anuary 30, 2001
Summary: The reaction of the vinylidene(hydrido)ruthe-
nium(II) compound [RuHCl(dCdCH2)(PCy3)2] (1a ) with
excess KPF6 in CH2Cl2/ CH3CN affords the five-coordi-
nate vinyl complex [Ru(CHdCH2)(CH3CN)2(PCy3)2]PF6
(2a ), which on treatment with NaBPh4 or NaB(Arf)4
gives the tetraaryloborate salts 2b and 2c in excellent
yields. The six-coordinate compounds [Ru(CHdCHPh)-
(CH3CN)3(PiPr3)2]X (3a , X ) Cl; 3b, X ) PF6) were
obtained in a similar route using [RuHCl(dCdCHPh)-
(PiPr3)2] (1b) as the starting material. Protonation of 2c
or 2d (X ) BF4) with, respectively, [H(OEt2)2]B(Arf)4 or
HBF4 yields [Ru(dCHCH3)(CH3CN)2(PCy3)2]X2 (4a ,b),
which to the best of our knowledge represent the first
dicationic carbeneruthenium(II) complexes.
lower than that of the corresponding neutral carbene
[RuCl2(dCHCH3)(PCy3)2],2 we attempted to prepare
more stable carbyneruthenium(II) species by using
stronger σ-donors than diethyl ether. In the context of
these studies we observed that the starting material 1a
can be easily converted, in the presence of acetonitrile,
to cationic vinylruthenium(II) compounds which react
with acids HA to give dicationic five-coordinate ruthe-
nium carbenes.
Treatment of a solution of 1a in CH2Cl2/CH3CN with
excess KPF6 leads to a gradual change of color from
brown-yellow to brown and results in the formation of
the vinyl complex 2a in 87% isolated yield.3 Salt
metathesis of 2a with NaBPh4 in methanol affords 2b
(Scheme 1), the molecular structure of which has been
determined by X-ray crystallography.4
Recently, we reported1 that the reaction of the hydri-
do(vinylidene) compound [RuHCl(dCdCH2)(PCy3)2] (1a )
with acids HA, containing an anion that does not
coordinate to the metal center, in diethyl ether affords
instead of the anticipated cationic carbene derivative
[RuCl(dCHCH3)(PCy3)2]+ the corresponding carbyne-
(hydrido) complex [RuHCl(tCCH3)(PCy3)2(OEt2)]+. This
cation catalyzes with high efficiency not only the ring-
opening metathesis polymerization of cyclooctene but
also the cross-olefin metathesis of cyclopentene with
methylacrylate.1 Since the lifetime of the carbyne-
(hydrido)ruthenium cation is limited and significantly
As shown in Figure 1, the coordination geometry
around the metal center of the cation corresponds to
that of a square pyramid with the two phosphines and
the two acetonitriles trans disposed. The atoms C5 and
C6 of the vinyl ligand (which occupies the apical
position) lie in the same plane as the nitrogen and
carbon atoms of the CH3CN units. In contrast to the
almost linear N1-Ru-N2 axis, the P1-Ru-P2 axis is
slightly bent with the phosphorus atoms pointing away
(2) (a) Schwab, P.; France, M. B.; Ziller, J . W.; Grubbs, R. H. Angew.
Chem. 1995, 107, 2179-2181; Angew. Chem., Int. Ed. Engl. 1995, 34,
2039-2041. (b) Schwab, P.; Grubbs, R. H.; Ziller, J . W. J . Am. Chem.
Soc. 1996, 118, 100-110.
(1) Stu¨er, W.; Wolf, J .; Werner, H.; Schwab, P.; Schulz, M. Angew.
Chem. 1998, 110, 3603-3606; Angew. Chem., Int. Ed. 1998, 37, 3421-
3423.
10.1021/om0100737 CCC: $20.00 © 2001 American Chemical Society
Publication on Web 05/04/2001

2122 Organometallics, Vol. 20, No. 11, 2001
Communications
dinated to the metal center. The smaller cone angle of
PiPr3 (160°) compared to PCy3 (170°)7 probably favors
the increase of the coordination number from five to six
in the Ru(PiPr3)2 derivative. An uncharged six-coordi-
nate ruthenium compound of composition [RuCl2(CH3-
CN)2(PiPr3)2] has recently been prepared by Ozawa et
al. from [(p-cymene)RuCl2]2 and PiPr3 in toluene/aceto-
nitrile.8 Moreover, Caulton et al. found that the hydrido-
(iodo) complex [RuHI(dCdCHSiMe3)(PtBu2Me)2] reacts
with excess methylisocyanide to give the substituted
vinylruthenium(II) derivative [Ru(CHdCHSiMe3)(CN-
Me)3(PtBu2Me)2]I.9
While the protonation of 2a or 2b with excess HBF4/
OEt2 gives a saltlike product with [Ru(dCHCH3)(CH3-
CN)2(PCy3)2]2+ as the cation and different ratios of,
-
-
respectively, PF6-/BF4 and BPh4-/BF4 as the anion,
the reaction of 2c3 with Brookhart’s acid10 [H(OEt2)2]B-
(Arf)4 (Arf ) 3,5-bis(trifluoromethyl)phenyl) affords
cleanly the bis(tetraaryloborate) 4a in 91% yield (Scheme
F igu r e 1. Molecular structure (ORTEP plot) of compound
2b, with anisotropic uncertainty parameters depicting 50%
probability. Selected bond distances (Å) and angles (deg):
Ru-C6 2.001(5), Ru-N1 2.008(4), Ru-N2 2.006(4), Ru-
P1 2.3975(13), Ru-P2 2.3979(12), C5-C6 1.340(7), N1-
C1 1.160(6), N2-C3 1.142(6); C6-Ru-P1 92.48(12), C6-
Ru-P2 96.24(12), C6-Ru-N1 92.35(16), C6-Ru-N2
89.52(16), N1-Ru-N2 178.05(15), P1-Ru-P2 171.04(4),
N1-C1-C2 178.7(5), N2-C3-C4 179.0(5).
(3) The preparation of 2a is as follows. A solution of 1a (270 mg,
0.30 mmol) in 30 mL of CH2Cl2/CH3CN (1:1) was treated with KPF6
(250 mg, 1.36 mmol) and stirred for 35 min at room temperature. The
solvent was removed, and the residue was extracted twice with 10 mL
of CH2Cl2 each. The combined extracts were evaporated in vacuo, and
the remaining red-brown solid was washed twice with pentane (8 mL)
and dried: yield 307 mg (87%); mp 55 °C dec; Λ (CH3NO2) 68.6 cm2
Sch em e 1
Ω-1 mol-1; IR (KBr) ν(CN) 2253 cm-1 1H NMR (400 MHz, CD2Cl2) δ
;
7.38 (dd, J (HH) ) 7.9 and 15.8 Hz, 1H, CHdCH2), 4.84 (d, J (HH) )
7.9 Hz, 1H, one H of CH2, cis to CH), 4.70 (d, J (HH) ) 15.8 Hz, 1H,
one H of CH2, trans to CH), 2.49 (s, 6H, CH3CN), 2.24-1.22 (m, 66H,
C6H11); 13C NMR (100.6 MHz, CD2Cl2) δ 150.2 (br s, RuCH), 125.5 (s,
CN), 117.3 (s, dCH2), 34.3 (vt, N ) 16.2 Hz, CH of C6H11), 29.7, 26.5
(both s, C6H11), 28.1 (vt, N ) 10.2 Hz, CHCH2 of C6H11), 5.0 (s, CH3-
CN); 31P NMR (162.0 MHz, CD2Cl2) δ 22.4 (s, PCy3), -144.0 (sept, J (PF)
) 709.4 Hz, PF6-). Compound 2b was prepared from 2a (450 mg, 0.40
mmol) and NaBPh4 (200 mg, 0.58 mmol) in 20 mL of methanol: orange
solid; yield 416 mg (78%); mp 100 °C dec; Λ (CH3NO2) 62.5 cm2 Ω-1
mol-1. Compound 2c was prepared from 2a (54 mg, 0.06 mmol) and
NaB(Arf)4 (55 mg, 0.06 mmol) in 10 mL of ether at 0 °C: red-brown
solid; yield 94 mg (97%); mp 70 °C dec; Λ (CH3NO2) 78.2 cm2 Ω-1 mol-1
.
Compound 2d was prepared analogously as described for 2a , from 1a
(101 mg, 0.14 mmol) and NaBF4 (250 mg, 2.28 mmol) in 15 mL of CH2-
Cl2/CH3CN (2:1): orange-red solid; yield 109 mg (91%); mp 52 °C dec;
Λ (CH3NO2) 57.8 cm2 Ω-1 mol-1
.
Sch em e 2
(4) Crystal data for 2b: crystals from CH2Cl2; triclinic, P1h (No. 2),
a ) 12.7193(17) Å, b ) 15.482(2) Å, c ) 17.447(2) Å, R ) 88.771(16)°,
â ) 79.931(15)°, γ ) 69.452(15)°, V ) 3164.3(7) Å3, Z ) 2, Dcalcd
)
1.227 g cm-3, T ) 173(2) K, µ(Mo KR) ) 0.423 cm-1; data collected on
a Stoe IPDS diffractometer using Φ scan mode (2θmax ) 50.06°); 25 291
reflections scanned, 10 533 unique, 6204 observed (I > 2σ(I)); extinction
parameter 0.0051(5), 686 parameters refined to give R ) 4.95% and
Rw ) 12.80% with a reflex-parameter ratio of 15.4 and a residual
electron density +1.064/-0.948 e Å-3
.
(5) Daniel, T.; Mahr, N.; Braun, T.; Werner, H. Organometallics
1993, 12, 1475-1477.
(6) The preparation of 3a and 3b is as follows. A solution of 1b (81
mg, 0.14 mmol) in 8 mL of CH2Cl2 was treated with acetonitrile (3
mL) and stirred for 5 min at room temperature. The solvent was
evaporated in vacuo, and the residue was washed repeatedly with
pentane (5 mL) and dried. A light yellow solid of 3a was obtained:
yield 87 mg (93%); mp 59 °C dec; Λ (CH3NO2) 55.8 cm2 Ω-1 mol-1. A
sample of 3a (85 mg, 0.12 mmol) was dissolved in 8 mL of CH2Cl2/
CH3CN (5:3) and then treated with KPF6 (150 mg, 0.81 mmol). After
stirring for 30 min at room temperature, the reaction mixture was
worked up as described for 2a : orange solid; yield 73 mg (75%); mp
from the CHdCH2 moiety. The distance Ru-C6 of 2.001
(5) Å is relatively short but comparable to that found
in other ruthenium compounds with a Ru-C(sp2) bond.5
36 °C dec; IR (KBr) ν(CN) 2260 cm-1 1H NMR (200 MHz, CD2Cl2) δ
;
8.56 (d, J (HH) ) 16.8 Hz, 1H, CHdCHPh), 7.14, 6.92 (both m, 5H,
C6H5), 6.34 (d, J (HH) ) 16.8 Hz, 1H, CHdCHPh), 2.46 (m, 6H,
PCHCH3), 2.42 (s, 6H, CH3CN), 2.31 (s, 3H, CH3CN), 1.27 (m, 36H,
PCHCH3); 13C NMR (50.3 MHz, CD2Cl2) δ 159.7 (br s, RuCH), 141.2
(s, ipso-C of C6H5), 133.3 (s, dCHPh), 128.2, 123.6, 123.1 (all s, C6H5),
125.4 (s, CN), 24.1 (vt, N ) 17.1 Hz, PCHCH3), 19.1 (s, PCHCH3), 5.0,
3.3 (both s, CH3CN); 31P NMR (81.0 MHz, CD2Cl2) δ 28.3 (s, PiPr3),
-144.0 (sept, J (PF) ) 709.4 Hz, PF6-).
The bis(triisopropylphosphine) complex 1b behaves
similarly to 1a and reacts with acetonitrile in CH2Cl2
to give 3a (Scheme 2). Treatment of 3a with KPF6
affords the more stable PF6 salt 3b, which was isolated
as an orange solid in 75% yield.6 Both the elemental
analyses and the spectroscopic data of 3a ,b confirm that
in contrast to 2a ,b three acetonitrile ligands are coor-
(7) Tolman, C. A. Chem. Rev. 1977, 77, 313-348.
(8) Katayama, H.; Ozawa, F. Organometallics 1998, 17, 5190-5196.
(9) Oliva´n, M.; Clot, E.; Eisenstein, O.; Caulton, K. G. Organome-
tallics 1998, 17, 3091-3100.
(10) Brookhart, M.; Grant, B.; Volpe, A. F. Organometallics 1992,
11, 3920-3922.

Communications
Organometallics, Vol. 20, No. 11, 2001 2123
Sch em e 3
best of our knowledge, compounds 4a and 4b are the
first dicationic five-coordinate carbeneruthenium com-
plexes described as yet.
The formation of a metal carbene from a metal vinyl
precursor is not without precedence. Casey and Helquist
showed already in 1982 that neutral cyclopentadienyl-
iron compounds with CRdCH2 as ligand can be con-
verted with HBF4 to corresponding cationic carbene
derivatives.12 Similar transformations of neutral vinyl
to monocationic carbene complexes via attack of an
electrophile at the â-carbon atom of the vinyl ligand
have since been carried out by Gladysz and others.13
We note, however, that as far as we know, there is no
report about the preparation of a dicationic carbene
complex from a monocationic vinylmetal precursor by
protonation. Our present interests are aimed to find out
whether 4a or 4b can be used, in the absence or in the
presence of a Lewis acid, as catalysts for olefin metath-
esis.
3).11 Analogously, the bis(tetrafluoroborate) 4b was
prepared on treatment of 2d with an excess of a solution
of HBF4 in ether. Both 4a and 4b are yellow, moderately
air-stable solids, the conductivity of which (in ni-
tromethane) corresponds to that of 1:2 electrolytes.
Regarding the spectroscopic data, the most typical
features are the signal for the dCH carbene proton at
δ 17.20 (4a ) or 17.70 (4b) in the 1H NMR and the
multiplet for the carbene carbon atom at δ 335.1 (4a )
in the 13C NMR spectrum. The single resonance for the
phosphorus nuclei at δ 41.0 (4a ) or 38.0 (4b) in the 31P
NMR spectra indicates that the phosphine ligands are
stereochemically equivalent and therefore in trans
disposition. Attempts to generate the dication [Ru(d
CHCH3)(CH3CN)2(PCy3)2]2+ from [RuCl2(dCHCH3)-
(PCy3)2] by substitution of the chloride ligands for
acetonitrile failed. It should be mentioned that, to the
Ack n ow led gm en t. We gratefully acknowledge fi-
nancial support from the Deutsche Forschungsgemein-
schaft (Grant No. 347), the Fonds der Chemischen
Industrie, and the BASF AG. We also thank Mr. S.
Stellwag for valuable experimental assistance.
Su p p or tin g In for m a tion Ava ila ble: A table with the
elemental analysis of compounds 2a -2d , 3a , 3b, and 4a as
well as fully labeled diagrams and tables of crystallographic
data, data collection and solution and refinement details,
positional and thermal parameters, and both distances and
angles for 2b. This material is available free of charge via the
Internet at http://pubs.acs.org.
(11) The preparation of 4a was as follows. A solution of 2c (94 mg,
0.06 mmol) in
8 mL of CH2Cl2 was treated with a solution of
[H(OEt2)2]B(Arf)4 (58 mg, 0.06 mmol) in 4 mL of CH2Cl2 at 0 °C. After
the solution was stirred for 5 min, it was warmed to room temperature
and the solvent was removed in vacuo. The yellow residue was washed
three times with 5 mL portions of pentane and dried: yield 130 mg
(91%); mp 130 °C dec; Λ (CH3NO2) 138.9 cm2 Ω-1 mol-1; 1H NMR (400
MHz, CD2Cl2) δ 17.20 (q, J (HH) ) 5.9 Hz, 1H, dCHCH3), 7.72 (s, 16H,
ortho-H of Arf), 7.57 (s, 8H, p-H of Arf), 2.87 (d, J (HH) ) 5.9 Hz, 3H,
dCHCH3), 2.75 (s, 6H, CH3CN), 2.17-1.23 (m, 66H, C6H11); 13C NMR
(100.6 MHz, acetone-d6) δ 335.1 (m, RudC), 163.0 (d, J (BC) ) 49.6
Hz, ipso-C of Arf), 135.9 (s, ortho-C of Arf), 130.4, 118.8 (both m, meta-
and para-C of Arf), 125.7 (q, J (FC) ) 272.1 Hz, CF3), 48.5 (s, dCHCH3),
35.3 (vt, N ) 19.1 Hz, CH of C6H11), 30.8, 26.1 (both s, C6H11), 28.5
(vt, N ) 10.2 Hz, CHCH2 of C6H11), 5.7 (s, CH3CN); 31P NMR (162.0
MHz, acetone-d6) δ 41.0 (s). Compound 4b was prepared from 2d (275
mg, 0.32 mmol) in CH2Cl2 (8 mL) and an excess of HBF4 (ca. 1.60 mmol)
in ether: yellow solid; yield 225 mg (75%); mp 55 °C dec; Λ (CH3NO2)
OM0100737
(12) (a) Casey, C. A.; Miles, W. H.; Tukada, H.; O’Connor, J . M. J .
Am. Chem. Soc. 1982, 104, 3761-3762. (b) Kremer, K. A. M.; Kuo,
G.-H.; O’Connor, E. J .; Helquist, P.; Kerber, R. C. J . Am. Chem. Soc.
1982, 104, 6119-6121.
(13) (a) Bodner, G. S.; Smith, D. E.; Hatton, W. G.; Heah, P. C.;
Georgiou, S.; Rheingold, A. L.; Geib, S. J .; Hutchinson, J . P.; Gladysz,
J . A. J . Am. Chem. Soc. 1987, 109, 7688-7705. (b) Esteruelas, M. A.;
Lahoz, F. J .; Onate, E.; Oro, L. A.; Zeier, B. Organometallics 1994, 13,
4258-4265. (c) J ia, G.; Wu, W. F.; Yeung, R. C. Y.; Xia, H. J .
Organomet. Chem. 1997, 538, 31-40. (d) Alias, F. M.; Poveda, M. L.;
Sellin, M.; Carmona, E. J . Am. Chem. Soc. 1998, 120, 5816-5817. (e)
Alias, F. M.; Poveda, M. L.; Sellin, M.; Carmona, E.; Gutie´rrez-Puebla,
E.; Monge, A. Organometallics 1998, 17, 4124-4126.
98.8 cm2 Ω-1 mol-1; IR (KBr) ν(CN) 2275 cm-1
.