Alkyne insertion reactions of [RuH(κ2-S2CNEt2)(CO)(PPh 3)2]: Synthesis of alkenyl, alkynyl and enynyl complexes

Article abstract of DOI:10.1016/S0022-328X(99)00664-6

The diethyldithiocarbamate hydride ruthenium complex [RuH(κ²-S₂CNEt₂)(CO)(PPh ₃)₂] reacts with excess phenylacetylene to give the alkynyl complex [Ru(CCPh)(κ²-S₂CNEt₂)(CO)(PPh ₃)₂] via the intermediate alkenyl complex [Ru(CH=CHPh)(κ²-S₂CNEt₂)(CO)(PPh ₃)₂] and with 1,4-diphenylbutadiyne to give the enynyl complex [Ru{η¹-C(CCPh)=CHPh}(κ²-S₂CNEt ₂)(CO)(PPh₃)₂]. The alkenyl complex [Ru(CH=CHPh)(κ²-S₂CNEt₂)(CO)(PPh ₃)₂] is a convenient precursor for alkynyl complexes of the type [Ru(CCR)(κ²-S₂CNEt₂)(CO)(PPh ₃)₂] (R=aryl, alkyl, C₆H₄-4-CCH).

Full text of DOI:10.1016/S0022-328X(99)00664-6

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 598 (2000) 20–23
Alkyne insertion reactions of [RuH(k2-S2CNEt2)(CO)(PPh3)2]:
synthesis of alkenyl, alkynyl and enynyl complexes
Robin B. Bedford *, Catherine S.J. Cazin
School of Chemistry, Uni6ersity of Exeter, Exeter EX4 4QD, UK
Received 29 September 1999; received in revised form 21 October 1999
Abstract
The diethyldithiocarbamate hydride ruthenium complex [RuH(k2-S2CNEt2)(CO)(PPh3)2] reacts with excess phenylacetylene to
give the alkynyl complex [Ru(CꢀCPh)(k2-S2CNEt2)(CO)(PPh3)2] via the intermediate alkenyl complex [Ru(CHꢁCHPh)(k2-
S2CNEt2)(CO)(PPh3)2] and with 1,4-diphenylbutadiyne to give the enynyl complex [Ru{h1-C(CꢀCPh)ꢁCHPh}(k2-S2CNEt2)-
(CO)(PPh3)2]. The alkenyl complex [Ru(CHꢁCHPh)(k2-S2CNEt2)(CO)(PPh3)2] is a convenient precursor for alkynyl complexes of
the type [Ru(CꢀCR)(k2-S2CNEt2)(CO)(PPh3)2] (R=aryl, alkyl, C6H4-4-CꢀCH). © 2000 Elsevier Science S.A. All rights reserved.
Keywords: Ruthenium; Hydride; Alkynes; Alkenyl; Enynyl; Diethynylbenzene
1. Introduction
cause the strong chelation of the dithiocarbamate lig-
and precludes the facile formation of coordinatively
unsaturated intermediates.
The hydroruthenation of alkynes is a powerful
methodology for the synthesis of s-alkenyl ruthenium
complexes. In particular the complex [RuHCl-
(CO)(PPh3)3] (1) has been exploited because the re-
versible de-coordination of one of the triphenyl-
phosphine ligands gives a 16-electron species. This facil-
itates migratory insertion of alkynes and diynes into the
ruthenium-hydride bond generating 16-electron s-
alkenyl and s-enynyl complexes respectively [1,2]. The
ruthenium hydride carboxylate complexes [RuH(k2-
O2CR)(CO)(PPh3)2] (2) also react with alkynes to gen-
erate [Ru{h1-C(CꢀCR)ꢁCHR}(k2-O2CR)(CO)(PPh3)2]
[3,4] or [Ru(h1-CHꢁCR)(k2-O2CR)(CO)(PPh3)2] [4]
complexes depending on the alkyne and the reaction
conditions. In these cases the reaction probably pro-
ceeds via a 16-electron intermediate formed by the
de-coordination of one end of the moderately labile
carboxylate ligand. To the best of our knowledge no
reports have appeared on migratory insertion reactions
of alkynes with the analogous dithiocarbamate complex
[RuH(k2-S2CNEt2)(CO)(PPh3)2] (3) [5], presumably be-
2. Results and discussion
Perhaps unsurprisingly in view of its low lability, the
complex 3 shows no reaction with excess phenyl-
acetylene in dichloromethane at room temperature. In-
creasing the temperature did lead to reaction, however
the product formed after 3 h in toluene at reflux
temperature proved not to be the expected s-alkenyl
complex [Ru(CHꢁCHPh)(k2-S2CNEt2)(CO)(PPh3)2] (4)
but rather the s-alkynyl complex [Ru(CꢀCPh)(k2-
S2CNEt2)(CO)(PPh3)2] (5a) (Scheme 1). The IR spec-
trum of 5a shows peaks at 2091 and 1942 cm−1
corresponding to w(CꢀC) and w(CO), respectively. The
trans-disposition of the phosphine ligands is indicated
by the appearance of a singlet in the 31P-NMR spec-
trum at l 40.2 ppm, whilst characteristic peaks for the
two distinct ethyl groups of the diethyldithiocarbamate
1
ligand are seen in the H-NMR spectrum. The spectro-
scopic data for this compound compare well with those
reported for this type of complex prepared previous-
ly from [RuCl(CꢀCR)(CO)(BSD)(PPh3)2] and Na[S2-
* Corresponding author. Fax: +44-1392-263-434.
E-mail address: r.bedford@ex.ac.uk (R.B. Bedford)
0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00664-6

R.B. Bedford, C.S.J. Cazin / Journal of Organometallic Chemistry 598 (2000) 20–23
21
Scheme 3. (i) HCCR (excess), toluene, reflux temperature.
CNEt2)(CO)(PPh3)] [8]. The formation of 5a from 3 is
in contrast to the analogous reaction of phenylacetylene
with the carboxylate complex 2, which generates a
s-enynyl complex [4]. However, the comparable enynyl
complex [Ru{h1-C(CꢀCPh)ꢁCHPh}(k2-S2CNEt2)(CO)-
(PPh3)2] (6) can be synthesized from 3 and 1,4-
diphenylbutadiyne in toluene at reflux temperature in
54% yield. Similar reactions have been reported previ-
ously with the more labile carboxylate complexes 2 and
1,4-diphenylbutadiyne giving the complex [Ru{h1-
C(CꢀCPh)ꢁCHPh}(k2-O2CR)(CO)(PPh3)2], 7 [4]. The
complex 6 can also be prepared in 68% yield by the
reaction of 1 with 1,4-diphenylbutadiyne [2] followed
by addition of sodium diethyldithiocarbamate. The IR
spectrum of 6 shows a peak at 1913 cm−1 correspond-
ing to the w(CO). As would be expected this stretch is
about 30 cm−1 lower than those of the complexes 7 [4]
as a result of the greater electron donation of the
dithiocarbamate ligand. However, the w(CꢀC) of 6 is
about 45 cm−1 higher than those of 7. This indicates
that the coordination environment of the enynyl ligand
Scheme 1. (i) Phenylacetylene (excess), toluene, reflux temperature;
(ii) 1,4-diphenylbutadiyne, toluene, reflux temperature; (iii) 1,4-
diphenylbutadiyene, CH2Cl2; (iv) Na[S2CNEt2], CH2Cl2–EtOH; (v)
phenylacetylene, CH2Cl2.
CNEt2] (BSD=2,1,3-benzoselenadiazole) [6]. The most
likely explanation for the isolation of 5a rather than 4
was that 4 did indeed form but subsequently reacted
with the excess phenylacetylene to generate 5a and
styrene. In order to test this hypothesis, 4 was prepared
according to a published method by the reaction of 1
with phenylacetylene and then Na[S2CNEt2] [7]. Heat-
ing 4 with excess phenylacetylene in toluene did indeed
generate complex 5a in 86% yield.
1
of 6 may be different from that of 7. The H-NMR
It is highly unlikely that the transformations of 3 to
4 and 4 to 5a proceed via 20-electron intermediates,
therefore it is reasonable to assume that both 3 and 4
are in equilibrium with 16-electron species at elevated
temperature. Such species could conceivably be gener-
ated either by the loss of a triphenylphosphine ligand or
by reversible de-coordination of one sulfur donor of the
dithiocarbamate ligand (Scheme 2).
The exchange of a s-alkenyl for a s-alkynyl ligand
presumably occurs via a Ru(IV) intermediate with sub-
sequent reductive elimination of styrene. Such a mecha-
nism has recently been postulated for the reaction of
the osmium complex [Os(CHꢁCHC6H4Me)(k2-S2-
CNEt2)(CO)(PPh3)2] with HCꢀCC6H4Me, which gener-
ates the alkynyl complex [Os(CꢀCC6H4Me)(k2-S2-
spectrum of 6 at r.t. shows a broad singlet at l 6.24
ppm corresponding to the alkenic proton, whilst the
31P-NMR shows a very broad peak at l 38.7 ppm. This
is in contrast to the complexes 7 for which no peak
broadenings were reported [4]. At −50°C two peaks
corresponding to alkenic protons are observed at l 6.38
and 6.09 ppm in a 1:3.4 ratio, respectively. The 31P
spectrum recorded at this temperature shows two sharp
singlets in the same ratio at l 39.1 (major) and 37.9
ppm (minor). These data indicate that there is restricted
rotation about the RuꢂC bond of the enynyl ligand in
6 giving two isomers. This may explain why in the IR
spectrum the w(CꢀC) of 6 is so different from that of 7.
Based on the observation with phenylacetylene, the
reaction of 4 with terminal alkynes seemed as if it might
provide a relatively facile route to s-alkynyl complexes.
Accordingly we investigated the reaction of 4 with
excess 1-pentyne which gave the alkynyl complex
[Ru(CꢀCC3H7)(k2-S2CNEt2)(CO)(PPh3)2] (5b) in 76%
yield, demonstrating that this reaction could be ex-
tended to alkyl-substituted alkynes (Scheme 3). The
spectroscopic data for 5b were comparable with those
of 5a with the exception of those associated with the
C3H7 group.
Scheme 2.

22
R.B. Bedford, C.S.J. Cazin / Journal of Organometallic Chemistry 598 (2000) 20–23
The reaction of 4 with excess 1,4-diethynylbenzene
3.1. Preparation of [Ru(CꢀCPh)(s2-S2CNEt2)-
(CO)(PPh3)2] (5a)
gave the mono-ruthenated diyne complex [Ru(Cꢀ
CC6H4–4-CꢀCH)(k2-S2CNEt2)(CO)(PPh3)2] (5c) in 91%
yield. Again the spectroscopic data for 5c are broadly
similar to those of 5a. In addition to the w(CꢀC) for the
ruthenated alkyne function at 2083 cm−1 in the IR
spectrum, a peak was also seen at 3294 cm−1 corre-
sponding to the w(ꢀCꢂH) of the terminal alkyne func-
tion. These data compare well with those reported
for [Ru(CꢀCC6H4-4-CꢀCH)2(dppe)2] [9] and [RuCl-
(CꢀCC6H4-4-CꢀCH)(dppe)2] [10]. The presence of both
a metallated and a free alkyne function for the di-
ethynylbenzene ligand was confirmed by 1H-NMR
spectroscopy which showed two doublets at l 7.12 and
6.48 ppm, with a mutual coupling of 8.3 Hz, corre-
sponding to the two aromatic environments of the
ligand and a singlet at l 3.04 ppm for the terminal
proton. Ruthenium complexes with mono-metallated
diethynylbenzene ligands are of interest as they can act
as building blocks for the synthesis of hetero-poly-
metallic assemblies which allow communication be-
tween the metal centers [9–11]. Ordinarily such
mono-ruthenated complexes of diethynylbenzene are
generated by first protecting one end of the diyne,
ruthenating the other end and then de-protecting [9,10].
The methodology reported here therefore provides an
attractive alternative as direct mono-metallation of the
diyne can be achieved in high yield. Preliminary investi-
gations show that 5c can indeed be used to fabricate bi-
and tri-metallic assemblies and this chemistry will be
reported in full elsewhere.
3.1.1. Method A
A mixture of [RuH(k2-S2CNEt2)(CO)(PPh3)2] (0.100
g, 0.125 mmol) and phenylacetylene (0.07 ml, 0.637
mmol) in toluene (20 ml) was heated at reflux tempera-
ture for 3 h. The volatiles were then removed on a
rotary evaporator and the resultant solid was recrystal-
lized from dichloromethane–ethanol to give 5a as a
yellow powder (0.093 g, 82%).
3.1.2. Method B
A
mixture of [Ru(CHꢁCHPh)(k2-S2CNEt2)(CO)-
(PPh3)2] (0.500 g, 0.552 mmol) and phenylacetylene
(0.25 ml, 2.28 mmol) in toluene (20 ml) was heated at
reflux temperature for 3 h. The solvent was then re-
moved on a rotary evaporator and the residual solid
was recrystallized from dichloromethane–ethanol to
give 5a (0.427 g, 86%). Found: C, 65.0; H, 4.9; N 1.4%.
C50H45NOP2RuS.2CH2Cl2. Anal. Calc.: C, 64.15; H, 4.9;
N, 1.5%. IR (wmax/cm−1): 2091 (CꢀC), 1942 (CO) and
1261 (SCS) (KBr). P-NMR (CDCl3): l 40.2. H-NMR
3
(CDCl3): l 0.61 (t, 3H, CH3, J(HH) 7.2 Hz), 0.74 (t,
3
3
3H, CH3, J(HH) 7.2 Hz), 2.79 (q, 2H, CH2, J(HH)
3
7.2 Hz), 2.98 (q, 2H, CH2, J(HH) 7.2 Hz), 6.57 (m,
2H, ortho-Hs of ꢀCC6H5), 6.97 (m, 3H, meta and
para-Hs of ꢀCC6H5), 7.32 (m, 18H, PPh3) and 7.88 (m,
12H PPh3).
3.2. Synthesis of [Ru{p1-C(CꢀCPh)ꢁCHPh}-
(s2-S2CNEt2)(CO)(PPh3)2] (6)
In conclusion we have shown that whilst the 18e
ruthenium dithiocarbamate hydride complex 3 is essen-
tially non-labile at r.t., at elevated temperatures it is
able to undergo reaction with excess phenylacetylene to
generate the s-alkynyl complex 5a via the s-alkenyl
species 4, or with 1,4-diphenylbutadiyne to give the
enynyl complex 6. The complex 4 proves to be a useful
building block for the facile generation of s-alkynyl
complexes with aryl, alkyl and alkynyl substituted ter-
minal alkynes.
3.2.1. Method A
A mixture of [RuH(k2-S2CNEt2)(CO)(PPh3)2] (0.200
g, 0.250 mmol) and 1,4-diphenylbutadiyne (0.063 g,
0.311 mmol) in toluene (20 ml) was heated at reflux
temperature for 4 h. The volatiles were removed in
vacuo and the brown residue was recrystallized from
dichloromethane–ethanol giving 6 as a yellow–ochre
powder (0.135 g, 54%).
3.2.2. Method B
A mixture of [RuHCl(CO)(PPh3)3] (0.504 g, 0.530
mmol) and 1,4-diphenylbutadiyne (0.125 g, 0.618
mmol) in dichloromethane (40 ml) was stirred for 10
min. Then Na[S2CNEt2]·3H2O (0.125 g, 0.550 mmol)
and ethanol (60 ml) was added and the mixture was left
to stir for 1 h. Concentration of the solution on a
rotary evaporator gave 6, which was collected by filtra-
tion and washed with water (2×10 ml) and then
ethanol (4×10 ml) (0.364 g, 68%). Found: C, 67.9; H,
4.9; N 1.25. C58H51NOP2RuS2·0.5CH2Cl2. Anal. Calc.:
C, 67.1; H, 5.0; N, 1.3%. IR (wmax/cm−1): 2148 (CꢀC),
1913 (CO) and 1271 (SCS) (KBr). P-NMR (CDCl3,
30°C): l 38.7 (s, broad); (CDCl3, −50°C) 39.1 (s) and
3. Experimental
The compounds [RuH(k2-S2CNEt2)(CO)(PPh3)2] [5],
[Ru(CHꢁCHPh)(k2-S2CNEt2)(CO)(PPh3)2] [7] and 1,4-
diethynylbenzene [12] were prepared according to litera-
ture methods. All reactions were performed under
nitrogen using degassed solvents. 1H- and 31P-NMR
spectra were recorded on a Bruker AC300 spectrometer
calibrated against internal CDCl3 (1H) or external
H3PO4 (31P). IR spectra were recorded on a Nicolet
Magna-IR 550 spectrometer.

R.B. Bedford, C.S.J. Cazin / Journal of Organometallic Chemistry 598 (2000) 20–23
23
37.9 (s). H-NMR (CDCl3, 30°C): l 0.71 (t, 3H, CH3,
(k2-S2CNEt2)(CO)(PPh3)2] (0.940 g, 1.04 mmol) and
1,4-diethynylbenzene (0.655 g, 5.19 mmol) to give 5b as
a tan solid (0.847 g, 91%). Found: C, 66.9; H, 4.9; N
1.05. C52H45NOP2RuS2. Anal. Calc.: C, 67.4; H, 4.9; N,
1.5%. IR (wmax/cm−1): 3294 (ꢀCꢂH), 2083 (CꢀC),1938
(CO) and 1271 (SCS) (KBr). P-NMR (CDCl3): l 40.3.
3
3J(HH) 7.1 Hz), 0.74 (t, 3H, CH3, J(HH) 7.2 Hz), 2.94
(q, 2H, CH2, 3J(HH) 7.1 Hz), 3.05 (q, 2H, CH2, 3J(HH)
7.1 Hz), 6.24 (s, br, 1H, ꢁCHPh), 6.94 (m, 1H, aro-
matic), 7.04 (m, 4H, aromatic), 7.18 (m, 12H, aromatic),
7.24 (m, 6H aromatic), 7.31 (m, 5H aromatic) and 7.60
(m, 12H, aromatic); (CDCl3, −50°C) selected peaks for
minor isomer, 0.59 (t, 3H, CH3, 3J(HH), 7.4 Hz), (triplet
for second CH3 obscured), 2.77 (q, br, 2H, CH2, 3J(HH)
ꢀ 7 Hz), (quartet for second CH2 obscured), 3.05 (q,
3
H-NMR (CDCl3): l 0.61 (t, 3H, CH3, J(HH) 7.2 Hz),
3
0.73 (t, 3H, CH3, J(HH) 7.2 Hz), 2.79 (q, 2H, CH2,
3
3J(HH) 7.2 Hz), 2.97 (q, 2H, CH2, J(HH) 7.2 Hz),
3.04 (s, 1H, CꢀCH), 6.48 (d, 2H, two of ꢀCC6H4Cꢀ,
3
2H, CH2, J(HH)=7.1 Hz) and 6.38 (s, 1H, ꢁCHPh);
3J(HH) 8.3 Hz), 7.12 (d, 2H, two of ꢀCC6H4-
3
selected peaks for major isomer, 0.68 (t, 3H, CH3,
3J(HH) 7.1 Hz), 0.74 (t, 1×CH3, 3J(HH) 7.1 Hz+1×
CH3 of minor isomer), 2.93 (m, 2×CH2+1×CH2 of
minor isomer) and 6.09 (s, 1H, ꢁCHPh).
Cꢀ, J(HH), 8.3 Hz), 7.35 (m, 18H, PPh3) and 7.86 (m,
12H, PPh3).
3.3. Preparation of [Ru(CꢀCC3H7)(s2-S2CNEt2)-
(CO)(PPh3)2] (5b)
References
[1] M.R. Torres, A. Vegas, A. Santos, J. Organomet. Chem. 309
(1986) 169.
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[9] O. Lavastre, M. Even, P.H. Dixneuf, Organometallics 15 (1996)
1530.
As for 5a above (Section 3.2.2) with [Ru(CHꢁCHPh)-
(k2-S2CNEt2)(CO)(PPh3)2] (0.500 g, 0.552 mmol) and
1-pentyne (0.20 ml, 2.0 mmol) to give 5b as golden
flakes (0.366 g, 76%). Found: C, 62.9; H, 5.4; N 1.45.
C47H47NOP2RuS.20.5CH2Cl2. Anal. Calc.: C, 62.6; H,
5.3; N, 1.5%. IR (wmax/cm−1):2112 (CꢀC), 1946 (CO)
and 1267 (SCS) (KBr). P-NMR (CDCl3): l 39.8. H-
NMR (CDCl3): l 0.57 (t, 3H, CH2CH2CH3, 3J(HH) 7.2
Hz), 0.75 (t, 6H, N(CH2CH3)2, 3J(HH) 7.2 Hz), 1.13 (m,
3
2H, CꢀCCH2CH2), 1.92 (tt, 2H, CꢀCCH2, J(HH) 6.9
5
3
Hz, J(PH) 1.8 Hz), 2.76 (q, 2H, NCH2, J(HH) 7.2
Hz), 3.01 (q, 2H, NCH2, 3J(HH) 7.2 Hz), 7.29 (m, 18H,
aromatic) and 7.87 (m, 12H, aromatic).
[10] O. Lavastre, J. Plass, P. Bachmann, S. Guesmi, C. Moinet, P.H.
Dixneuf, Organometallics 16 (1997) 184.
[11] N. Le Narvor, C. Lapinte, Organometallics 14 (1995) 634 and
references therein.
3.4. Preparation of [Ru(CꢀCC6H4-4-CꢀCH)-
(s2-S2CNEt2)(CO)(PPh3)2] (5c)
As for 5a above (Section 3.2.2) with [Ru(CHꢁCHPh)-
[12] A.S. Hay, J. Org. Chem. 25 (1960) 637.
.