Regioselective nucleophilic addition to vinyl carbenes (metallabutadienes): Crystal structure of [Ru{CH(CH=CPh2)SC(NMe2)S}(S2CNMe 2)(CO)(PPh3)]

Article abstract of DOI:10.1021/om980091x

The new vinyl carbene salt [Ru(=C_αHC_βH=C_γ - Ph₂)(CO)(S₂CNMe₂)(PPh₃) ₂]PF₆ (obtained from [RuH-Cl(CO)(PPh₃)₃], HC=CCPh₂OH, N

Full text of DOI:10.1021/om980091x

1916
Organometallics 1998, 17, 1916-1918
Regioselective Nu cleop h ilic Ad d ition to Vin yl Ca r ben es
(Meta lla bu ta d ien es): Cr ysta l Str u ctu r e of
[Ru {CH(CHdCP h 2)SC(NMe2)S}(S2CNMe2)(CO)(P P h 3)]
Karsten J . Harlow, Anthony F. Hill,* Thomas Welton,* Andrew J . P. White, and
David J . Williams
Centre for Chemical Synthesis, Department of Chemistry, Imperial College of Science
Technology and Medicine, South Kensington, London SW7 2AY, United Kingdom
Received February 11, 1998
Sch em e 1
Summary: The new vinyl carbene salt [Ru(dCRHCâHdCγ-
Ph2)(CO)(S2CNMe2)(PPh3)2]PF6 (obtained from [RuH-
Cl(CO)(PPh3)3], HCtCCPh2OH, Na[S2CNMe2], and
HPF6) reacts with fluoride, alkoxide, borohydride and
hydroxide at Cγ to give γ-functionalized σ-vinyl com-
plexes, but with dithiocarbamate salts, attack occurs at
CR to provide the structurally characterized metallacycle
[Ru {CH (CH dCP h 2)S C(NMe2)S }(S 2CNMe2)(CO)(P -
Ph3)].
With the advent of Grubbs’ ROMP catalyst [Ru-
(dCHCHdCPh2)Cl2(PPh3)2],1 interest has grown in the
synthesis of vinyl carbene complexes2 and in their
applications to organic synthesis.3 The Grubbs’ ap-
proach involves the ring opening of diphenylcyclopro-
pene, the synthesis of which is nontrivial;4 however,
more recently, the hydrometalation of propargylic al-
cohols has provided an alternative and more expedient
approach, particularly appropriate for ruthenium.2 If
viewed as metallabutadienes, such complexes raise the
question of the regioselectivity of attack by nucleophiles,
the primary concern of this paper. Typically, alkylidene
complexes of coordinatively saturated divalent ruthe-
nium are prone to nucleophilic attack at the alkylidene
carbon.5 In the case of vinyl carbene complexes, how-
ever, attack at Cγ (Scheme 1) is also plausible and
reflects by microreversibility their synthesis via γ-dehy-
droxylation of γ-hydroxyvinyl ligands. Herein, we
report (i) the synthesis of the salt [Ru(dCHCHdCPh2)-
(CO)(S2CNMe2)(PPh3)2]PF6; (ii) the reactions of this salt
with a range of nucleophiles, all but one of which attack
at Cγ; and (iii) the crystal structure of the metallacycle
[Ru {CH (CH dCP h 2)SC(NMe2)S}(S2CNMe2)(CO)(P -
Ph3)] which results from nucleophilic attack at CR by
dithiocarbamate salts.
For this study, the new salt [Ru(dCHCHdCPh2)(CO)-
(S2CNMe2)(PPh3)2]PF6 (1) was chosen for the following
reasons: (i) It is air and thermally stable and easily
prepared on a large scale via the synthetic procedure
outlined in Scheme 2; (ii) the co-ligand set is substitu-
tion-inert, precluding complications in mechanistic in-
terpretation which might result from direct attack at
the ruthenium center; (iii) the cationic charge on the
complex is expected to activate the alkylidene toward
nucleophilic attack. The synthesis from [RuHCl(CO)-
(PPh3)3] proceeds in high yield to provide deep red
crystals of 1, the formulation and stereochemistry of
which rests firmly on spectroscopic data.6 Most notable
among these are the NMR data associated with the
* To whom correspondence should be addressed. E-mail: a.hill@
ic.ac.uk; t.welton@ic.ac.uk.
(1) Nguyen, S. T.; J ohnson, L. K.; Grubbs, R. H.; Ziller, J . W. J .
Am. Chem. Soc. 1992, 114, 3974. (b) Nguyen, S. T.; Grubbs, R. H.;
Ziller, J . W. Ibid. 1993, 115, 9858. (c) Wu, Z.; Nguyen, S. T.; Grubbs,
R. H.; Ziller, J . W. Ibid. 1995, 117, 5503. (d) Dias, E. L.; Nguyen, S.
T.; Grubbs, R. H. Ibid. 1998, 119, 3887. (e) Kanaoka, S.; Grubbs, R.
H. Macromolecules 1995, 28, 4707. (f) Hillmyer, M. A.; Laredo, W. R.;
Grubbs, R. H. Ibid. 1995, 28, 6311. (g) Nguyen, S. T.; Grubbs, R. H. J .
Organomet. Chem. 1995, 497, 195.
(2) Esteruelas, M. A.; Lahoz, F. J .; On˜ate, E.; Oro, L. A.; Valero, C.;
Zeiter, B. J . Am. Chem. Soc. 1995, 117, 7935. (b) Esteruelas, M. A.;
Lahoz, F. J .; On˜ate, E.; Oro, L. A.; Zeier, B. Organometallics 1994, 13,
0.4258. (c) Esteruelas, M. A.; Lahoz, F. J .; On˜ate, E.; Oro, L. A.; Zeier,
B. Ibid. 1994, 13, 1662. (d) Albeniz, M. J .; Esteruelas, M. A.; Lledos,
A.; Maseras, F.; On˜ate, F.; Oro, L. A.; Sola, E.; Zeier, B. J . Chem. Soc.,
Dalton Trans. 1997, 181. (e) J ia, G. C.; Wu, W. F.; Yeung, R. C. Y.;
Xia, H. P. J . Organomet. Chem. 1997, 538, 31. (f) Binger, P.; Muller,
P.; Benn, R.; Mynott, R. Angew. Chem., Int. Ed. Engl. 1989, 28, 610.
(g) Nishiyama, H.; Park, S. B.; Itoh, K. Chem. Lett. 1995, 599.
(3) Barluenga, J .; Aznar, F.; Martin, A.; Barluenga, S.; Garcia-
Granda, S.; Panaque-Quevedo, A. A. J . Chem. Soc., Chem. Commun.
1994, 843. (b) Chamberlin, S.; Wulff, W. D. J . Org. Chem. 1994, 59,
3047. (c) Park, J .; Kim, J . Organometallics 1995, 14, 4431. (d) Gibson,
S. E.; Saberi, S. P.; Slawin, A. M. Z.; Stanley, P. D.; Ward, M. F.;
Williams, D. J .; Worthington, P. J . Chem. Soc., Perkin Trans. 1 1995,
2147. (e) Benyunes, S. A.; Gibson, S. E.; Ward, M. F. Tetrahedron:
Assymetry 1995, 6, 2517. (f) Benyunes, S. A.; Gibson, S. E.; Peplow,
M. A. Ibid. 1997, 8, 1535. (g) Gibson, S. E.; Ward, M. F.; Kipps, M.;
Stanley, P. D.; Worthington, P. A. Chem. Commun. 1996, 263.
(4) Hughes, D. L.; Leigh, G. J .; McMahon, C. M. J . Chem. Soc.,
Dalton Trans. 1977, 1301.
(5) For a recent review of alkylidene complexes of ruthenium, see:
Hill, A. F. In Comprehensive Organometallic Chemistry II; Abel, E.
W., Stone, F. G. A., Wilkinson, G., Eds.; Pergamon Press: Oxford, 1996;
Vol. 7. (b) Gallop, M. A.; Roper, W. R. Adv. Organomet. Chem. 1986,
25, 121.
S0276-7333(98)00091-0 CCC: $15.00 © 1998 American Chemical Society
Publication on Web 04/14/1998

Communications
Organometallics, Vol. 17, No. 10, 1998 1917
alkylidene ligand: The metallacumulene gives rise to
three 13C NMR resonances attributable to CR (t, 311.8
ppm), Câ (148.2 ppm), and Cγ (161.4 ppm). The low-
1
field region of the H NMR spectrum features a double
triplet at 14.72 ppm, showing discernible though not
resolved coupling to two chemically equivalent phos-
phorus nuclei and Hâ (J (HRHâ) ) 13.9 Hz). The gross
composition is confirmed by the appearance of a well-
resolved isotopic distribution consistent with the com-
plex molecular ion.
The reactions of 1 with a range of nucleophiles were
investigated: Initially, the reaction with hydroxide
([nBu4N]OH) was investigated and shown to regenerate
the precursor complex [Ru(CHdCHCPh2OH)(CO)(S2-
CNMe2)(PPh3)2] (2)6 in high yield (spectroscopically
quantitative by 31P{1H} NMR), clearly resulting from
nucleophilic attack at Cγ. In a similar manner, the
reaction 1 with sodium ethoxide provided [Ru(CHdCH-
CPh2OEt)(CO)(S2CNMe2)(PPh3)2] (3).6 The alkoxide
group is readily cleaved by HPF6 to regenerate 1.
Treating 1 with [Bu4N]F in thf provided the γ-fluorovi-
nyl complex [Ru(CHdCHCPh2F)(CO)(S2CNMe2)(PPh3)2]
(4).6 This complex is readily converted to 3 or 2 upon
treatment with ethanol or water. The activation of C-F
bonds of metal-bound trifluoromethyl groups is a no-
table feature of organoruthenium chemistry which has
been extensively exploited by Roper;7 however, the
activation of a remote C-F bond as in the present case
is, we believe, unprecedented. The reaction of 1 with
ethanolic NaBH4 provides exclusively the vinyl complex
[Ru(CHdCHCHPh2)(CO)(S2CNMe2)(PPh3)2] (5),6 once
again arising from attack at Cγ. No major tractable
organometallic products have, however, been identified
F igu r e 1. Geometry of 6t. Phenyl hydrogen atoms have
been omitted.
from the reactions of 1 with carbon nucleophiles includ-
ing [Bu4N]CN, LiPh, LiMe, LiCtCPh, and BrMgC6H4-
Me-4.
The reactions of 1 with a range of thiols and thiolates
were investigated but failed to provide definitive results.
In the case of sodium dimethyldithiocarbamate, how-
ever, a clean reaction ensued to initially provide the
kinetic isomer (6k ) which, however, slowly converted
to the thermodynamic isomer (6t) of the metallacycle
[Ru {CH (CH dCP h 2)SC(NMe2)S}(S2CNMe2)(CO)(P -
Ph3)] (6). The thermodynamic isomer (6t) was charac-
terized by a crystallographic study (Figure 1).8 The
geometry at ruthenium is distorted octahedral, with cis
angles at ruthenium in the range 71.8(1)-98.8(1)°, the
smaller value being associated with the bite of the
dithiocarbamate ligand, which despite a normal pattern
of delocalization (C(2)-S(3) 1.729(5) Å, C(2)-S(4) 1.715-
(5) Å) is noticeably asymmetrically bound to the ruthe-
nium center (Ru-S(3) 2.486(1) Å, Ru-S(4) 2.453(1) Å).
The larger of these is trans to the phosphine, whereas
the shorter is trans to C(3), which might have been
expected to show a pronounced trans influence. The
Ru-S(1) separation at 2.434(1) Å is the shortest,
consistent with it being trans to CO, the strongest
π-acceptor ligand present. The C-S distances in the
dithiocarbamatoalkylmetallacycle are distinctly asym-
metric, in agreement with the valence bond description
shown in Scheme 2. The Ru-C(3) bond at 2.148(5) Å
is typical for alkyls of ruthenium(II). The chelate ring
is clearly nonplanar, being folded out of plane by 25°
about the C(3)-S(1) vector. While C(3)-C(4) is typical
of a C(sp2)-C(sp2) single bond (being 1.492(7) Å), the
(6) Selected data for new complexes (satisfactory microanalytical
data obtained; IR (Nujol, 25 °C), NMR (CDCl3, 25 °C), FAB-MS (nba);
Cumulene designation: Ru-CR-Câ-Cγ; with the exception of 1 which
was prepared on a 3 g scale, yields are based on 0.2 mmol scales). 1:
Yield 71%. IR: 1956 (ν(CO)), 1712, 1590 (CdCCdRu) cm-1 1H NMR:
.
δ 2.34, 2.48 (s × 2, 6 H, NMe2), 6.19 (d, 2 H, H2,6(CC6H5), J (HH) ) 8.0
Hz), 7.06 (d, 2 H, H2,6(CC6H5), J (HH) ) 6.9 Hz), 7.21-7.66 (m × 3, 36
H, C6H5), 8.06 (d, 1 H, Hâ, J (HRHâ) ) 13.9 Hz), 14.72 (d, 1 H, J (HRHâ)
) 13.9 Hz, J (PH) not resolved) ppm. 13C{1H} NMR (CD2Cl2): 311.8
(RudC), 203.2 (t, RuCO, J (PC) ) 13.4 Hz), 161.4 (Cγ), 148.2 (Câ),
141.7-130.0 (C6H5), 40.5 (NCH3) ppm. 31P{1H} NMR: δ 33.9 ppm.
FAB-MS: m/z 966 [M]+, 774 [M - C3H2Ph2]+, 704 [M - PPh3]+. 2:
Yield spectroscopically quantitative (31P NMR). IR: 3562 (νOH), 1907
(ν(CO)) cm-1
.
1H NMR: δ 2.25, 2.53 (s × 2, 6 H, NMe2), 5.44 (dt, 1 H,
J (HRHâ) ) 16.9 Hz, J (PHâ) not resolved), 6.78 (m, 4 H, H2,6(CC6H5))
6.93 (dt, 1 H, HR, J (HRHâ) ) 16.8 Hz), 6.07 (m, 6 H, H3-5(CC6H5)),
6.24 (m, 18 H, H3-5(PC6H5)), 6.49 (m, 12 H, H2,6(PC6H5)) ppm. 31P-
{1H} NMR: δ 41.0 ppm. FAB-MS: m/z 983 [M]+, 966 [M - OH]+, 774
[M - vinyl]+, 704 [M - OH - PPh3]+. 3: Yield 99%. IR: 1909 (ν(CO))
cm-1
.
1H NMR: δ 1.04 (t, 3 H, CH2CH3, J (HH) ) 6.6), 2.19, 2.52 (s ×
2, 3 H × 2, NCH3), 2.81 (q, 2 H, OCH2, J (HH) ) 6.6), 5.30 (d, 1 H, Hâ,
J (HâHR) ) 13.2 Hz), 6.73, 7.05, 7.27, 7.51 (m × 4, 40 H, C6H5). 13C-
{1H} NMR: 206.4 (t, RuCO, J (PC) ) 16.1), 206.1 (CS2), 146.7 (t, CR),
146.6-125.4 (C6H5 + Câ), 85.7 (Cγ), 58.0 (OCH2), 38.5, 37.8 (NCH3),
15.7 (CCH3) ppm. 31P{1H} NMR: 41.64 ppm. FAB-MS: m/z 1011 [M]+.
4: Yield 91%. IR: 1905 (ν(CO)), 1144m (ν(CF)) cm-1. FAB-MS: m/z
985 (1, [M]+), 966 (8, [M - F]+). The complex was insufficiently soluble
for NMR analysis. 5: Yield 97%. IR: 1905vs, 1893sh (ν(CO)) cm-1 1H
.
NMR: δ 2.21, 2.60 (s × 2, 3 H × 2, NCH3), 4.13 (d, 1 H, Hγ, J (HγHâ)
) 7.3 Hz), 4.98 (dd, 1 H, Hâ, J (HγHâ) ) 7.3, J (HâHR) ) 15.6), 6.67 (dt,
1 H, HR, J (HâHR) ) 15.6 Hz, J (PHR) not resolved), 6.55, 7.04, 7.22,
7.51 (m × 4, 40 H, C6H5). 31P{1H} NMR: 40.77 ppm. FAB-MS: m/z
(8) Crystal data for 6t: C40H39N2OPRuS4‚2CHCl3, M ) 1062.8,
monoclinic, space group C2/c (No.15), a ) 18.627(2) Å, b ) 19.801(2)
Å, c ) 25.717(4) Å, â ) 95.34(1)°, U ) 9444(2) Å3, Z ) 8, Dc ) 1.495 g
cm-3, µ(Mo KR) ) 9.17 cm-1, F(000) ) 4320. An orange prism of
dimensions 0.67 × 0.40 × 0.30 mm was used. Independent reflections
(8280) were measured on a Siemens P4/PC diffractometer (graphite-
monochromated Mo KR radiation) using ω-scans. The structure was
solved by direct methods, and all of the non-hydrogen atoms were
refined anisotropically using full-matrix least squares based on F 2 and
absorption-corrected data to give R1 ) 0.053 and wR2 ) 0.106 for 5810
observed reflections [|Fo| > 4σ(|Fo|), 2θ e 50°] and 477 parameters.
Atomic coordinates, bond lengths and angles, and thermal parameters
have been deposited at the Cambridge Crystallographic Data Centre.
967 [M]+. 6t: Yield 86%. IR: 1928 (ν(CO)) cm-1 1H NMR: δ 3.11 (3
.
H), 3.29 (6 H), 3.36 (3 H) (s × 3, 12 H, NCH3), 4.36 (dd, 1 H, HR, J (HRHâ)
) 12.3, J (PHR) ) 5.4), 6.55 (d, 1 H, Hâ, J (HRHâ) ) 12.3 Hz), 7.10, 7.20,
7.36 (m × 3, 25 H, C6H5). 13C{1H} NMR: 213.6 (d, S2C, J (PC) ) 1.9
Hz), 209.5 (s, S2C), 201.5 (d, RuCO, J (PC) ) 14.0), 143.7 (C1(CC6H5)),
141.9 (Câ), 141.1-125.8 (C6H5), 129.5 (Cγ), 46.9, 44.2, 39.5, 39.3 (NCH3),
35.1 (d, CR, J (PC) ) 6.5 Hz) ppm. 31P{1H} NMR: 53.2 ppm. FAB-MS:
m/z 824 [M]+, 796 [M - CO]+, 736 [M - SCNMe2]+, 704 [M -
S2CNMe2]+.
(7) Brothers, P. J .; Roper, W. R. Chem. Rev. 1988, 88, 1293.

1918 Organometallics, Vol. 17, No. 10, 1998
Communications
Sch em e 2a
a
Reagents and conditions (25 °C unless otherwise stated): (i) HCtCCPh2OH (CH2Cl2, 30 min); (ii) Na[S2CNMe2] (CH2Cl2/
EtOH, 15 min); (iii) HPF6 (Et2O, 30 min); (iv) [Bu4N]OH (CH2Cl2, 15 min); (v) H2O (thf, 30m); (vi) [Bu4N]F (CH2Cl2, 1 h); (vii)
NaOEt (CH2Cl2/EtOH, 30 min); (viii) EtOH (30 min); (ix) Na[S2CNMe2] (CHCl3, reflux, 12 h); (x) NaBH4 (CH2Cl2/EtOH, 30 min).
C(4)-C(5) “double” bond is long at 1.347(7) Å, despite
the absence of any apparent conjugation with the phenyl
rings which, are rotated out of the plane of the double
bond and its immediate substituents by 30° and 71°,
respectively, for the rings based on C(17) and C(11).
The results discussed above indicate a general though
not exclusive preference for nucleophilic attack to occur
γ to the ruthenium in the present system. It might be
argued that the steric bulk of the Ru(S2CNMe2)(CO)-
(PPh3)2 auxiliary predisposes the complex to attack
remote from the metal; however, it should be noted that
dithiocarbamate salts were the largest nucleophiles
employed and these were nevertheless capable of attack
at CR. The possibility that the complex (6t) arises from
coupling of the precoordinated dithiocarbamate and
alkylidene ligands may be discounted since reaction of
1 with [NH4][S2CN(CH2)4] provides the analogue of 6t
wherein the pyrollidinyl group resides exclusively on the
metallacycle. The regioselectivity of attack at metal-
lacumulenes is perhaps reminiscent of the more familiar
1,2 vs 1,4 regioselectivity encountered for R,â-unsatur-
ated ketones (Scheme 1). Clearly, such regioselectivity
will also be a function of the nature of the metallabu-
tadiene in question, and we are extending our studies
accordingly to address this question.
Ack n ow led gm en t. We wish to thank the Engineer-
ing and Physical Sciences Research Council (U.K.) and
the Wolfson Foundation for financial support. A.F.H.
gratefully acknowledges the award of a Senior Research
Fellowship by The Royal Society and The Leverhulme
Trust. Ruthenium salts were generously provided by
J ohnson Matthey Ltd.
Su p p or tin g In for m a tion Ava ila ble: Tables of final
atomic positional parameters and isotropic thermal param-
eters and an ORTEP representation for the structural analysis
(9 pages). Ordering information is given on any current
masthead page.
OM980091X