What are the primary products of reactions between anionic hydrides and HC≡CPh?

Article abstract of DOI:10.1039/a807554i

Reactions of phenylacetylene with [RuH₂(CO)L]^- [L is the pincer ligand C₆H'3-2,6-(CH₂PBu'2/(t))₂], [RuH₃(CO)(PPr₃/¹)₂[^- and [ReH₃(NO)(

Full text of DOI:10.1039/a807554i

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What are the primary products of reactions between anionic hydrides
and HCy CPh?
Brandon Reinhart and Dmitry G. Gusev*
Department of Chemistry, W ilfrid L aurier University, W aterloo, ON, Canada N2L 3C5.
E-mail: dgoussev=mach1.wlu.ca; FAX: ]1 519 746 0677
L e t t e r
Recei¿ed (in Montpellier, France) 16th September 1998, Accepted 5th October 1998
Reactions of phenylacetylene with [RuH (CO)L]— [L is the
2
pincer ligand C H -2,6-(CH PBut ) ], [RuH (CO)(PPri ) ]—
6
3
2
2 2
3
3 2
and [ReH (NO)(PPri ) ]— have a†orded the new anionic r-
3
3 2
alkynyl and vinyl complexes trans-[RuH(Cy CPh)(CO)L]—,
cis-[RuH (Cy CPh)(CO)(PPri ) ]—, cis-[RuH (CPhxCH )-
2
3 2
3 2
2
2
2
(CO)(PPri ) ]— and cis-[ReH (CPhxCH )(NO)(PPri ) ]—,
2
3 2
all as the [K(18-crown-6)]‘ salts. Formation of the acetylides
does not involve unsaturated species and takes place via
[MwC(Ph)xCH ] vinyl intermediates.
2
Chemistry of anionic transition metal hydrides has attracted
little attention in contrast to the related neutral and cationic
species.1 We decided to investigate the reactivity of trans-
[RuH (CO)L]~ (1)2a [L is the pincer ligand C H -2,6-
2
6 3
(CH PBut ) ], [RuH (CO)(PPri ) ]~ (2)2b and [ReH (NO)-
2
2 2
3
3 2
3
(PPri ) ]~ (3)2b Mall are [K(18-crown-6)]` saltsN in a typical
3 2
reaction of metal hydridesÈinsertion of alkynes into the
MwH bond. Three primary organometallic products could be
anticipated with HCy CPh (Scheme 1). Product a can be
formed by H /PhC ~ replacement after protonation of
2
2
[HML ]~ by HCy CPh.3 Species b and c are insertion pro-
n
ducts with vinyl ligands attached via the a or b-carbon atoms,
respectively. This communication reports the Ðnding that c is
the primary product with complexes 1È3.
Scheme 1
A fast NMR tube reaction of trans-[RuH (CO)L]~ (1) and
Fig. 1 (A) Regular 1H NMR and (B, C) di†erence NOE spectra of
the acetylide 4. The RuH and wCy CwC H fragments are trans
2
two equivalents of HCy CPh in pyridine-d cleanly a†orded a
5
ruthenium product and one equivalent of H CxCHPh. The
2
6
5
since their enhancements in B and C originate from inequivalent CH
3
groups on the opposite sides of the PwCwP plane in 4. Solvent reso-
product could be isolated from pyridine or THF and charac-
nances (THF-d ) are shown by stars, the one at d 3.58 is overlapped
terized as trans-[RuH(CCPh)(CO)L]~ (4) by 1H, 31P and 13C
NMR, IR spectroscopy and elemental analysis. The trans-
HwRuwCy CPh disposition was conÐrmed by the di†erence
1H NOE (nuclear Overhauser e†ect) spectra (Fig. 1). The
anion 4 is not a very strong base and no protonation was
observed with 2È4 equivalents of methanol in THF.
8
with the intense line of [K(18-crown-6)]`.
Table 1 Selected spectroscopic data for complexes 4È7
A
second anionic complex, [RuH (CO)(PPri ) ]~ (2),
3
3 2
Complex
d(MwH)
d(MwCy )
151.59
148.24
d(y CPh)
113.88
113.24
d(C
)
)
reacted with phenylacetylene to a†ord an isolated mixture of
two products in a 1 : 2 ratio. The minor product is of the a
type, cis-[RuH (Cy CPh)(CO)(PPri ) ]~ (5), and was identi-
ipso
4a
5b
[9.67
134.91
135.30
[11.10, [8.27
2
3 2
Ðed by NMR and IR spectroscopy. Complexes 4 and 5 have
very similar wCy CPh 13C NMR and IR features (Table 1).
The major component of the mixture is the vinyl complex cis-
[RuH (CPhxCH )(CO)(PPri ) ]~ (6) according to the 1H
d(MwH)
d(MwCPh)
191.96
182.06
d(xCH )
2
d(C
167.82
165.75
ipso
6
7
[12.39, [7.52
[5.45, [3.78
121.62
120.30
a m
C. C
\ 2065 cm~1. b m
\ 2058 cm~1.
2
2
3 2
C. C
and 13C NMR data.
New J. Chem., 1999, 1È3
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Scheme 2
Finally, when rhenium trihydride, [ReH (NO)(PPri ) ]~ (3),
d 5.12 (3J \ 1.6 Hz), respectively. Thus, only one hydride
3
3 2
HvD
was reacted with phenylacetylene, slow and clean formation of
took part in the reaction and it was transferred to the C atom
a
cis-[ReH (CPhxCH )(NO)(PPri ) ]~ (7) was complete in 6 h.
of phenylacetylene, a†ording the vinyl intermediate shown in
2
2
3 2
No intermediates could be detected in the reaction solution by
31P NMR. The isolated product was characterized by 1H, 31P
and 13C NMR, IR spectroscopy, and elemental analysis.
Facile protonation of 7 cleanly a†orded a stable styrene
complex, ReH (CH xCHPh)(NO)(PPri ) , which will be
Scheme 3.
All of the above indicate that generally (a) reactions of ter-
minal acetylenes with metal hydrides may not require forma-
tion of unsaturated intermediates, (b) r-acetylide complexes
may not be intermediate species in hydrogenation of acety-
lenes, but (c) their formation might take place via intermediate
c-type vinyl complexes.
2
2
3 2
reported elsewhere.
The results of three di†erent reactions of the ruthenium and
rhenium complexes allow mechanistic considerations. The
interaction that brings together coordinatively saturated, ther-
mally stable hydrides 1È3 and an alkyne molecule could be
the MwHd~É É Éd`HwC hydrogen (also termed “dihydrogenÏ)
bonding shown in Scheme 2.4 The experimental evidence for a
reversible formation of the [L M(l-H )CCPh]~ transient
Experimental
All reactions and sample preparations were carried out in dry
solvents under puriÐed nitrogen in an Innovative Technology
glovebox equipped with a vacuum line and a [35 ¡C refriger-
ator. Throughout this paper, the NMR data are reported with
the apparent coupling of virtual triplets (vt) denoted as vJ.
n
2
species is represented by the reported H/D scrambling in a
FeH (dippe) /PhCy CD system.5 Scheme 2 shows further
2
2
feasible rearrangements of [L M(l-H )CCPh]~, which are
n
2
either protonation of the metal fragment or hydride transfer
Preparation of trans-[RuH(Cy CPh)(CO){C H -2,6-
6
3
to the C atom of phenylacetylene. An alternative C wH bond
(CH PBut ) } ] [K(18-crown-6)] (4)
a
b
2
2 2
PhCy CH (74 mg, 0.72 mmol) was added to a solution of
[RuH (CO)MC H -2,6-(CH PBut ) N][K(18-crown-6)] (300
mg, 0.36 mmol) in THF (3 mL) or pyridine (1.5 mL). The
mixture was stirred for 1 h. Addition of 12 mL of hexane
caused the product to crystallize out as a white solid. It was
isolated by Ðltration, washed with 3 ] 3 mL of hexane and
dried under vacuum. Yield from THF: 278 mg (ca. 82%).
Yield from pyridine: 316 mg (ca. 94%). Anal. calcd for
formation (not shown) appears less likely for geometric
reasons. In agreement with this, no b-type product has been
detected in the reactions of complexes 1È3.
2
6
3
2
2 2
The acetylides 4 and 5 apparently do not result from proto-
nation of 1 and 2 by phenylacetylene. For example, complex 4
is not a primary organometallic product since it is formed
along with styrene. Furthermore, for 4, the interpretation of
Scheme 2 invoking H loss and a 16-electron intermediate is
2
implausible in neat pyridine where the intermediate would
C
H
KO P Ru (928.195): C, 58.23; H, 7.93. Found: C,
a†ord a pyridine complex.
45 73
7 2
57.83; H, 8.05. IR (Nujol): m
2065 cm~1, m 1852 cm~1,
A
deuterium-labeling
phenylacetylene-d clearly indicated that formation of the
acetylide involved
experiment
with
1
and
C. C
CO
m
1583 cm~1. 1H NMR (200 MHz, THF-d ): d [9.67 (t,
RuH
8
2J \ 21.7 Hz, 1H, RuH), 1.22, 1.50 (vt, vJ \ 5.6 Hz,
4
a c-type primary product. trans-
HhP
HhP
\ 14.9 Hz, vJ \ 3.7 Hz, 2H,
HhH HhP
36H, CH ), 3.07 (dvt, 2J
[RuH (CO)L]~ and two equivalents of DCy CPh reacted on
mixing in an NMR tube, cleanly a†ording the monohydride 4
3
2
CH ), 3.51 (s, 24H, crown-CH ), 3.55 (overlapped with the
2
2
crown resonance, 2H, CH ), 6.31 (m, 1H, C H ), 6.57 (m, 3H,
Ar), 6.86 (m, 4H, C H ). 31PM1HN NMR (80 MHz, THF-d ): d
107.4. 13CM1HN NMR (50 MHz, THF-d ): d 30.23, 29.88 (vt,
and one equivalent of HCDxCDPh (Scheme 3). The deuter-
iated styrene showed two terminal CH triplets in the 1H
2
6 3
6
5
8
NMR spectrum in a 3.5 : 1 ratio at d 5.68 (3J \ 2.7 Hz) and
8
HvD
vJ
\ 2.2 Hz, CH ), 35.55 (vt, vJ \ 8.1 Hz, PC), 37.61 (vt,
CvP
3
ChP
vJ \ 3.4 Hz, PC), 42.04 (vt, vJ \ 10.0 Hz, PCH ), 71.12
ChP ChP
2
(s, crown-CH ), 113.88 (s, y CPh), 118.41 (vt, vJ \ 7.6 Hz,
2
ChP
CH, RuwAr), 120.13 (s, CH, RuwAr), 120.23, 127.41, 130.68
(s, CH, C H ), 134.91 (s, C , C H ), 149.04 (vt, vJ \ 10.3
6
5
ipso
ChP
6
5
ChP
Hz, C, RuwAr), 151.59 (t, 2J \ 10.7 Hz, RuwCy ), 188.57
(t, 2J \ 7.6 Hz, RuC), 212.46 (t, 2J \ 10.1 Hz, CO).
ChP
ChP
Assignment of the 13C signals was conÐrmed by gated-
decoupled 13C NMR. Hydride-coupled 13C NMR: the car-
bonyl and ligand metal-bound carbon atoms both showed
small 2J
couplings of 5.2 and ca. 5 Hz, respectively. The
wCy CPh carbons showed two- and three-bond couplings of
ChH
14.5 and 8.9 Hz, respectively.
Isolation of a mixture of cis-[RuH (Cy CPh)(CO)(PPri ) ]-
2
2
3 2
3 2
[K(18-crown-6)] (5) and cis-[RuH (CPhxCH )(CO)(PPri ) ]-
2
[K(18-crown-6)] (6)
PhCy CH (338 mg, 3.31 mmol) was added to a cold ([35 ¡C)
solution of [RuH (CO)(PPri ) ][K(18-crown-6)] (1000 mg,
Scheme 3
3
3 2
2
New J. Chem., 1999, 1È3

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1.32 mmol) in THF (3 mL). The mixture was left at [35 ¡C
for 5 h. Addition of 12 mL of cold ([35 ¡C) hexane precipi-
tated a white solid. It was isolated by Ðltration, washed with
3 ] 3 mL of hexane and dried under vacuum. Yield: 684 mg
Found: C, 47.89; H, 7.85; N, 1.54. IR (Nujol): m
1790, m
ReH
ReH
or/and m
1597, m 1500 cm~1. 1H NMR (200 MHz, THF-
C/C
NO
d ): d [5.45 (td, 2J \ 22.1 Hz, 2J
\ 8.3, 1H, ReH),
8
HhP
HhH
[3.78 (td, 2J \ 31.4 Hz, 1H, ReH), 1.15, 1.19 (dvt, vJ
HhP
\
HhP
(60%). IR (Nujol): m
2058, m and m
1852, m
or/and
6.3 Hz, 3J
\ 5.3 Hz, 36H, CH ), 2.36 (m, 6H, CH), 3.57 (s,
C. C
CO
RhH
RuH
HhH
3
m
1597 cm~1. 5: 1H NMR (200 MHz, THF-d ): d [11.10
24H, crown-CH ), 4.81, 5.83 (d, 2J
\ 7.1 Hz, 2H, xCH )
C/C
8
2
HhH
2
(td, 2J \ 22.3 Hz, 2J
\ 7.0, 1H, RuH), [8.27 (td,
6.60, 6.86, 7.40 (m, 5H, C H ). 31PM1HN NMR (80 MHz, THF-
HhP
HhH
6 5
2J \ 26.1 Hz, 1H, RuH), 1.30 (dvt, vJ \ 6.3 Hz,
d ): d 42.7. 13CM1HN NMR (50 MHz, THF-d ): d 20.78, 21.64
HhP
HhH
HhP
8
8
3J
\ 6.0 Hz, 36H, CH ), 2.21 (m, 6H, CH), 3.55 (s, 24H,
(s, CH ), 29.51 (vt, vJ \ 10.1 Hz, PCH), 71.12 (s, crown-
ChP
CH ), 120.30 (s, xCH ), 121.18, 126.07, 128.96 (s, CH, Ph),
3
3
crown-CH ), 6.5È7.4 (m, 5H, C H ). 31PM1HN NMR (80 MHz,
2
6
5
2
2
THF-d ): d 84.0. 13CM1HN NMR (50 MHz, THF-d ): d 21.45,
165.75 (s, C , Ph), 182.06 (t, 2J \ 5.0 Hz, RewCPh).
ipso ChP
8
8
21.61 (s, CH ), 28.79 (vt, vJ \ 9.1 Hz, PCH), 71.12 (s,
Assignment of the 13C signals is conÐrmed by a gated-
3
ChP
crown-CH ), 113.24 (s, y CPh), 119.84, 127.64, 130.86 (s, CH,
decoupled 13C experiment: d 120.30 (dd, 1J
\ 142, 145 Hz,
2
ChH
Ph), 135.30 (s,
C
,
Ph), 148.24 (t, 2J \ 13.3 Hz,
xCH ).
ipso
ChP
2
RuwCy ), 212.35 (t, 2J \ 9.5 Hz, RuwCO). 6: 1H NMR
ChP
(200 MHz, THF-d ): d [12.39 (td, 2J \ 25.7 Hz, 2J
\
8
HhP
HhH
Acknowledgements
7.0, 1H, RuH), [7.52 (td, 2J \ 27.8 Hz, 1H, RuH), 1.17
HhP
(dvt, vJ \ 6.3 Hz, 3J
HhP
\ 6.0 Hz, 36H, CH ), 2.12 (m, 6H,
HhH
3
Wilfrid Laurier University supported this research in the form
of a start-up grant to D.G.G. We thank the Natural Sciences
and Engineering Research Council (NSERC) of Canada for
the undergraduate student research award to B.R. The com-
petent technical assistance of Ms. Margaret Szymanska is
gratefully acknowledged.
CH), 3.55 (s, 24H, crown-CH ), 5.20, 5.55 (d, 2J
\ 7.6 Hz,
2
HhH
2H, xCH ) 6.5È7.4 (m, 5H, C H ). 31PM1HN NMR (80 MHz,
2
6 5
THF-d ): d 81.2. 13CM1HN NMR (50 MHz, THF-d ): d 21.05,
8
8
21.97 (s, CH ), 28.92 (vt, vJ \ 8.4 Hz, PCH), 71.12 (s,
ChP
crown-CH ), 121.62 (t, 3J \ 2.1 Hz, xCH ), 120.40, 125.79,
ChP
3
2
2
128.93 (s, CH, Ph), 167.82 (s, C , Ph), 191.96 (t, 2J \ 9.3
ipso
ChP
Hz, RuwCPh), 212.59 (t, 2J \ 10.5 Hz, RuwCO). Assign-
ChP
ment of the 13C signals is conÐrmed by an APT (attached
References
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2
3 2
6)] (7)
unstable by H loss.
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[ReH (NO)(PPri ) ][K(18-crown-6)] (600 mg, 0.71 mmol) in
2
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3 2
THF (6 mL). The mixture was stirred for 6 h. Addition of 20
mL of hexane precipitated a yellow solid. It was isolated by
Ðltration, washed with 2 ] 5 mL of hexane and dried under
vacuum. Yield: 500 mg (75%). Anal. calcd for
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H
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38 75
7 2
New J. Chem., 1999, 1È3
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