Control of intramolecular acetate-allenylidene coupling by spectator co-ligand π-acidity

Article abstract of DOI:10.1039/a902021g

The reactions of [RuHX(PPh₃)₃] (X = Cl, O₂CMe) and [MHCl(CO)(PPh₃)₃] (M = Ru, Os) with 1,1-diphenylprop-2-yn-1-ol provide convenient access to alkynyl, alkenyl, propenylidene, and acetoxyallenyl complexes of divalent ruthenium and osmium, including [RuCl₂(=CHCH= CPh₂)(PPh₃)₂] and the complexes [Ru(C=CCPh₂OH)-(O₂CMe)(CA)₂(PPh ₃)₂] (A = NCMe₃, O), protonation (HPF₆) of which provides [Ru(O₂CMe)(=C=C=CPh₂)-(CNCMe₃) ₂(PPh₃)₂]PF₆ or the metallacycle [Ru{κ²C,O-C(=C=CPh₂)O₂CMe}(CO) ₂(PPh₃)₂]PF₆, respectively.

Full text of DOI:10.1039/a902021g

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Control of intramolecular acetate–allenylidene coupling by
spectator co-ligand ð-acidity
Karsten J. Harlow, Anthony F. Hill* and Thomas Welton*
Department of Chemistry, Imperial College of Science Technology and Medicine,
South Kensington, London, UK SW7 2AY. E-mail: a.hill@ic.ac.uk
Received 15th March 1999, Accepted 7th May 1999
Ph
Ph
The reactions of [RuHX(PPh3)3] (X = Cl, O2CMe) and
[MHCl(CO)(PPh3)3] (M = Ru, Os) with 1,1-diphenylprop-
PPh3
M
CO
PPh3
Cl
Cl
(i) HC≡CCPh2OH 1
[MHCl(CO)(PPh3)3]
2-yn-1-ol provide convenient access to alkynyl, alkenyl,
(ii) Cl2PPh3
propenylidene, and acetoxyallenyl complexes of divalent
M = Ru 2a
M = Os 2b
ruthenium and osmium, including [RuCl (᎐CHCH᎐
᎐
᎐
2
M = Ru 6a
M = Os 6b
᎐
CPh2)(PPh3)2] and the complexes [Ru(C᎐CCPh OH)-
᎐
2
(O2CMe)(CA)2(PPh3)2] (A = NCMe3, O), protonation
Cl2PPh3
1
(HPF6) of which provides [Ru(O CMe)(᎐C᎐C᎐CPh )-
᎐ ᎐ ᎐
2
2
(CNCMe3)2(PPh3)2]PF6 or the metallacycle [Ru{κ2C,O-
Ph
Ph
Ph
Ph
OH
C(᎐C᎐CPh )O CMe}(CO) (PPh ) ]PF , respectively.
PPh3
PPh3
᎐ ᎐
2
2
2
3
2
6
Cl
Cl
MeCN
OH
Ru
Ru
There is currently enormous interest in the chemistry of alkyl-
idene complexes of divalent ruthenium.1 This is inspired
primarily by Grubbs’ ground-breaking discovery of highly
effective and remarkably tolerant alkene metathesis catalysts of
MeCN
CO
PPh3
CO
PPh3
5
9b
the form [RuCl (᎐CHR)(PRЈ ) ] (R = Ph, CH᎐CPh ; RЈ = Ph,
᎐
᎐
2
3
2
2
Ph
Cy)2 which are currently enjoying increasingly wide application
in a variety of synthetically useful C–C bond-forming pro-
cesses.3 We have recently shown that [RuCl2(PPh3)3] reacts with
1,1-diphenylprop-2-yn-1-ol 1 to provide the coordinatively
PPh3
Ph
[RuHCl(PPh3)3] 3
1, MeCN
Cl
OH
Ru
NCMe
PPh3
OC
CO
9a
unsaturated allenylidene complex [RuCl (᎐C᎐C᎐CPh )(P-
᎐ ᎐ ᎐
2
Ph3)2].4a This complex may be easily conv2erted to [RuCl2-
Ph
Ph
Ph
(᎐C᎐C᎐CPh )(PCy ) ] which serves as a conveniently accessible
PPh3
PPh3
᎐ ᎐ ᎐
2
3 2
Ph
HCl
Cl
Cl
alternative to Grubbs’ catalysts for the ring-closure alkene
metathesis of α,ω-dienes and dienynes.4b The reactions of prop-
argylic alcohols with metal hydride complexes however, take a
different course, viz. hydrometallation of the alkyne to provide
γ-hydroxyvinyl complexes which have been shown to be particu-
larly prone to dehydroxylation, providing either σ-butadienyl5
or propenylidene6,7 complexes depending, respectively, on the
presence or absence of protons δ to the metal. In search of
alternative routes to coordinatively unsaturated alkylidenes
of ruthenium and osmium, we have investigated the reactions
of the complexes [MHCl(CO)(PPh3)3] (M = Ru 2a, Os 2b),
[RuHCl(PPh3)3] 3, and [RuH(O2CMe)(PPh3)3] 4 with 1. The
results which include convenient routes to alkenyl, alkynyl,
allenylidene, propenylidene and acetoxyallenyl complexes are
reported herein.
OH
Ru
Ru
MeCN
NCMe
Cl
PPh3
PPh3
8
7
Scheme 1
isomer (CO trans to vinyl) of 9b (MeCN trans to vinyl)
obtained from 5 and acetonitrile.
The acetate complex 4 reacts with 1 via a quite different
sequence, to ultimately provide the alkynyl complex mer-
[Ru(C᎐CCPh OH)(O CMe)(PPh ) ] 10 (Scheme 2).† The
mechanism presumably involves alkyne hydrometallation, as
above, followed by oxidative addition of a second alkyne C–H
᎐
᎐
2
2
3 3
᎐
bond to provide [RuH(C᎐CCPh OH)(CH᎐CHCPh OH)-
᎐
᎐
2
2
The γ-hydroxyvinyl complex [Ru(CH᎐CHCPh OH)Cl(CO)-
(O2CMe)(PPh3)2] which undergoes reductive elimination of
alkene and re-coordination of phosphine to provide 10. The
facility of the proposed sequence is consistent with the increase
in basicity of the acetate ligand in 4 relative to the chloride in 3,
favouring the involvement of tetravalent ruthenium intermedi-
ates. The formulation of 10 rests firmly on spectroscopic and
FAB-MS data with the mer stereochemistry at ruthenium fol-
lowing unequivocally from 13C-{1H} and 31P-{1H} NMR data.†
Both the acetate chelation and the phosphine coordination in
᎐
(PPh3)2] 5 forms in high yield from the reaction2of 2a with 1
(Scheme 1).† Treating 5 with Cl2PPh3 results in the high yield
conversion to the propenylidene complex [RuCl (᎐CHCH᎐
᎐
᎐
2
CPh2)(CO)(PPh3)2] 6a.†,‡ The analogous osmium complex 6b†
may be similarly obtained in 75% yield directly from 2b, 1 and
Cl2PPh3. The complexes 6 may be viewed as analogues of the
benzylidene complexes [MCl (᎐CHR)(CO)(PPh ) ] long since
᎐
2
3 2
described by Roper.1a,b,9
The coordinatively unsaturated, carbonyl-free complex
10 are labile. Thus treating 10 with carbon monoxide (1 atmos-
᎐
[RuCl (᎐CHCH᎐CPh )(PPh ) ] 7 was shown by Grubbs to
phere, 25 ЊC) results in clean conversion to [Ru(C᎐CCPh -
᎐
᎐
᎐
2
2
2
result 2from the reaction of3[RuCl2(PPh3)3] with 3,3-diphenyl-
cyclopropene2a but required the non-trivial preparation and
handling of 3,3-diphenylcyclopropene. We find that the reac-
tion of 3 with 1 in acetonitrile followed by acid (HCl) work-up
provides 7 conveniently and in high yield (83%).† The presumed
γ-hydroxyvinyl intermediate 8 in this sequence (Scheme 1) has
not been fully characterised due to its sensitivity, however
carbonylation (1 atmosphere) provides the air stable adduct
OH)(O2CMe)(CO)2(PPh3)2] 11. Similarly, addition of two
equivalents of 1,1-dimethylethyl isocyanide leads to formation
᎐
of [Ru(C᎐CCPh OH)(O CMe)(CNCMe ) (PPh ) ] 12, whilst
᎐
2
2
3
2
3 2
᎐
excess isocyanide provides the cationic complex mer-[Ru(C᎐
᎐
CCPh2OH)(CNCMe3)3(PPh3)2]ϩ 13ϩ, readily isolated as the
tetrafluoborate salt [13]BF4. By analogy with the dehydroxyl-
ation of γ-hydroxyvinyl ligands, the γ-hydroxyalkynyl ligands in
11 and 12 are also prone to dehydroxylation although the final
products differ depending on the nature (π-acidity) of the co-
[Ru(CH᎐CHCPh OH)Cl(CO)(NCMe)(PPh ) ] 9a, which is an
᎐
2
3 2
J. Chem. Soc., Dalton Trans., 1999, 1911–1912
1911

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δ 80.0 [CPh2OH], 139.7 [RuCH᎐CH], 144.6 [RuCH᎐CH], 202.3 [t, CO;
Ph
Ph
OH
᎐
᎐
J(PC) = 14.3 Hz]. This complex was also crystallographically character-
C
PPh3
ised.12 6a: yield 95%. IR: 1955 (CO). NMR 1H: δ 8.01 [d, 1 H, Ru᎐
C
1
᎐
O
O
C
CHCH; J(HH) = 13.8], 15.93 [d, 1 H, Ru᎐CH; J(HH) = 13.9 Hz]. 31P-
[RuH(O2CCH3)(PPh3)3] 4
Me C
Ru
᎐
PPh3
{1H}: δ 16.7. 13C-{1H}: δ 146.9 [Ru᎐CHCH], 154.2 [᎐CPh2], 199.0 [t,
᎐
᎐
PPh3
CO; J(PC) = 13.4], 322.1 [t, Ru=CH; J(PC) = 10.7 Hz]. 6b: yield 75%.
10
1
IR 1932 (CO). NMR H: δ 17.50 [dt, 1 H, Os᎐CHCH; J(HH) = 13.5;
CNR
᎐
J(PH) = 2.0 Hz] (OsCH᎐CH obscured by Ph resonances). 31P-{1H}:
᎐
CO
δ Ϫ8.0. 13C-{1H}: δ 151.2 [Os᎐CHCH], 152.4 [᎐CPh2], 177.6 [t, CO;
Ph
Ph
OH
Ph
᎐
᎐
1
Ph
J(PC) = 9.7 Hz], 278.1 [m, Os᎐CH]. 7: yield 83%. NMR H: δ 8.20 [d,
᎐
C
C
PPh3
C
PPh3
OH
C
1 H, Ru᎐CHCH; J(HH) = 9.9], 17.74 [dt, 1 H, Ru᎐CH; J(HH) = 9.9;
᎐
᎐
RNC
RNC
C
OC
OC
C
J(PH) = 9.6 Hz]. 31P-{1H}: δ 28.9. These data correspond to those pre-
viously reported.2a 9a: yield 75%. IR: 3564 (OH), 2283 (CN), 1949
Ru
Ru
O2CMe
O2CMe
PPh3
PPh3
12
(CO). NMR 1H: δ 0.82 [s, 3 H, CH3], 5.32 [d, 1 H, RuCH᎐CH;
᎐
11
HPF6
J(HH) = 17.8], 7.59 [d, 1 H, RuCH; J(HH) = 18.5 Hz]. 31P-{1H}: δ 29.3.
13C-{1H}: δ 2.6 [CH ], 80.2 [CPh OH], 119.6 [NC], 136.4 [t, RuCH᎐CH;
HPF6
3
᎐
J(PC) = 4.3], 153.2 [t, RuCH; J(2PC) = 15.1], 198.9 [t, CO; J(PC) = 10.3
Hz]. 9b: yield 86%. IR: 3564 (OH), 1944 (CO). NMR 1H: δ 1.60 [s, 3 H,
Ph
O
Ph
C
C
Ph
CH3], 5.48 [dt, 1 H, RuCH᎐CH; J(HH) = 15.9; J(PH) = 2.0], 7.40 [d, 1
᎐
H, RuCH, J(HH) = 15.9 Hz]. 31P-{1H}: δ 27.3. 10: yield 71%. IR: 3558
C
PPh3
Ru
PPh3
Ph
C
(OH), 2057(C᎐C), 1531 (CO2). NMR H: δ 0.92 [s, 3H, CH3]. 31P-{1H}:
1
OC
OC
C
O
RNC
RNC
᎐
C
᎐
Ru
δ35.5[d, 2PA, J(PAPB) = 26.8], 50.9[t, 1PB, J(PAPB) = 26.8Hz]. 13C-{1H}:
O2CMe
C
Me
᎐
PPh3
15+
PPh3
14+
δ
24.3 [O2CCH3], 76.7 [CPh2OH], 110.5 [dt, RuC᎐C; J(PaxC)
᎐
᎐
≈ J(PeqC) = 17.3], 118.3 [RuC᎐C], 185.1 [CO2]. 11: yield 88%. IR:
᎐
1
᎐
3579, 3561 (OH), 2121(C᎐C), 2051, 1978 (CO). NMR H: δ 1.20 [s, 3 H,
Ph
S
᎐
Ph
CH3]. 31P-{1H}: δ 31.4. 13C-{1H}: δ 22.8 [CH3], 75.0 [CPh2OH], 106.8 [t,
C
C
C
᎐
᎐
RuC᎐C; J(PC) = 20.0], 116.2 [t, RuC᎐C; J(PC) = 2.4], 176.2 [CO2],
H2
C
᎐
᎐
194.3 [t, CO; J(PC) = 9.2], 198.5 [t, CO; J(PC) = 11.9 Hz]. 12: yield
(Ph3P)(OC)(Me2NCS2)Ru
O
(Ph3P)2(OC)(Ph)Ru
᎐
87%. IR: 3567 (OH), 2150 (CN), 2105 (CN), 2073 (C᎐C), 1606 (CO2).
S
᎐
C
O
C
NMR 1H: δ 0.81, 0.89 [s × 2, 9 H × 2, CNC(CH3)3], 1.25 [s, 3 H,
NMe2
Me
A10
B11
O2CCH3]. 31P-{1H}: δ 38.3. 13C-{1H}: δ 24.5 [O2CCH3], 29.8, 30.6
᎐
[CNC(CH3)3], 55.6, 56.1 [CNC(CH3)3], 75.1 [CPh2OH], 115.2 [RuC᎐C],
᎐
Scheme 2 R = CMe3.
176.3 [CO2]. [13]BF4: yield 65%. IR: 3563 (OH), 2194 (CN), 2150 (CN),
1
᎐
2111 (C᎐C). NMR H: δ 0.81 [s, 9 H, C(CH3)3], 0.93 [s, 18 H, C(CH3)3].
᎐
ligands. Thus the reaction of 12 with HPF6 provides an allen-
31P-{1H}: δ 34.8. [14]PF6: yield 79%. IR: 2184 (CN), 2148 (CN), 1970
(C᎐C᎐C), 1587 (CO2). NMR 1H: δ 0.96 [s, 9 H, C(CH3)3], 1.08 [s, 9 H,
ylidene complex viz. [Ru(O CMe)(᎐C᎐C᎐CPh )(CNCMe ) -
᎐ ᎐ ᎐
2
2
2
(PPh3)2]PF6 ([14]PF6). Amongst the spectroscopic data for 134ϩ,
the intense infrared absorption at 1970 cmϪ1 is characteristic of
the allenylidene ligand.
᎐
᎐
C(CH3)3], 1.11 [s, 3 H, O2CCH3]. 31P-{1H}: δ 34.3. [15]PF6: yield 88%.
IR: 2071 (CO), 2003 (CO), 1598 (C᎐C᎐C). NMR 1H: 1.32 [s, 3H,
᎐
᎐
O2CCH3]. 31P-{1H}: δ 22.4. 13C-{1H}: δ 18.4 [O2CCH3], 118.6 [᎐CPh2],
᎐
The protonation of 11 with HPF6 however takes a different
course although an allenylidene complex akin to 14ϩ is clearly
involved. The product obtained is formulated as the metalla-
147.4 [t, RuC(OCO), J(PC) = 15.1], 183.6 [O2CCH3], 192.0 [t, CO;
J(PC) = 9.7], 198.7 [t, CO; J(PC) = 11.3], 201.8 [t, RuC᎐C, J(PC) = 4.9
᎐
Hz].
cyclic complex [Ru{κ2C,O-C(᎐C᎐CPh )O CMe}(CO) (PPh ) ]-
‡ Whilst Cl2PPh3 was found to be the most convenient dehydroxylating
᎐ ᎐
PF6 [15]PF6) on the basis of spectroscopic data.† 2We ha2ve
recently observed the formation of a related metallacycle (A,
Scheme 2) derived from the intermolecular coupling of an
allenylidene ligand with dithiocarbamate,10 whilst Roper has
shown that the coupling of methylene and acetate ligands
provides the metallacycle B.11 Complex 15ϩ may therefore be
usefully viewed as a hybrid of A and B. The reason for the
dichotomy in products arising from the protonation of 11 and
12 may be understood by considering the π-acidity of the co-
ligands CO and CNCMe3. By far the majority of allenylidene
complexes of Group 8 metals involve strong donor co-ligands
coordinated trans to the allenylidene,1c a feature which may be
expected to deactivate the allenylidene towards nucleophilic
attack. Whilst the isocyanide ligands in 12 and 14ϩ are only
modest π-acids, the carbonyl ligand coordinated trans to the
allenylidene in the carbonyl analogue of 14ϩ may be expected to
strongly activate the allenylidene towards attack by the internal
acetate nucleophile.
2
2
3
agent,8 similar yields were obtained using anhydrous HCl, OSCl2 or
PhSeCl and the complexes [Ru(CH᎐CHCR2OH)Cl(CO)(PPh3)2]
᎐
(CR2 = cyclo-C6H10, CMe2, C13H8), obtained from 2a and the appropri-
ate propargylic alcohol.
1 For reviews on the chemistry of alkylidenes of Group 8 metals see
(a) M. A. Gallop and W. R. Roper, Adv. Organomet. Chem., 1986,
25, 121; (b) W. R. Roper, J. Organomet. Chem., 1986, 300, 167; (c)
A. F. Hill, in Comprehensive Organometallic Chemistry II, ed. E. W.
Abel, F. G. A. Stone and G. Wilkinson, Pergamon, Oxford, 1995,
vol. 7.
2 (a) S. T. Nguyen, R. H. Grubbs and J. W. Ziller, J. Am. Chem. Soc.,
1993, 115, 9858; (b) P. Schwab, M. B. France, J. W. Ziller and R. H.
Grubbs, Angew. Chem., Int. Ed. Engl., 1995, 34, 2039; (c) E. L. Dias,
S. T. Nguyen and R. H. Grubbs, J. Am. Chem. Soc., 1997, 119, 3887.
3 A. Fürtsner, Top. Organomet. Chem., 1998, 1, 37.
4 (a) K. J. Harlow, A. F. Hill and J. D. E. T. Wilton-Ely, J. Chem. Soc.,
Dalton Trans., 1999, 285; (b) A. Fürstner, A. F. Hill, M. Liebl and
J. D. E. T. Wilton-Ely, Chem. Commun., 1999, 601.
5 M. C. J. Harris and A. F. Hill, J. Organomet. Chem., 1992, 438, 209.
6 (a) M. A. Esteruelas, F. J. Lahoz, E. Oñate, L. A. Oro and B. Zeier,
Organometallics, 1994, 13, 4258; (b) M. A. Esteruelas, F. J. Lahoz,
E. Oñate, L. A. Oro and B. Zeier, B., ibid., 1994, 13, 1662.
7 K. J. Harlow, A. F. Hill, T. Welton, A. J. P. White and D. J. Williams,
Organometallics, 1998, 17, 1916.
Acknowledgements
We wish to thank the Engineering and Physical Sciences
Research Council (U.K.) for the award of a studentship (to
K. J. H.). 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 Johnson Matthey Chemicals Ltd.
8 S. Anderson, D. J. Cook and A. F. Hill, J. Organomet. Chem., 1993,
463, C3.
9 G. R. Clark, K. Marsden, W. R. Roper and L. J. Wright, J. Am.
Chem. Soc., 1980, 102, 6570.
10 B. Buriez, K. J. Harlow, A. F. Hill, T. Welton, A. J. P. White,
D. J. Williams and J. D. E. T. Wilton-Ely, J. Organomet. Chem.,
1999, 578, 264.
11 D. S. Bohle, G. R. Clark, C. E. F. Rickard, W. R. Roper, W. E. B.
Shepard and L. J. Wright, J. Chem. Soc., Chem. Commun., 1987,
563; D. S. Bohle, G. R. Clark, C. E. F. Rickard, W. R. Roper and
L. J. Wright, J. Organomet. Chem., 1989, 358, 411.
Notes and references
† Selected data for new complexes (satisfactory microanalytical and/or
FAB-MS data obtained); IR (Nujol, cmϪ1), NMR (CDCl3, 25 ЊC, ppm)
1H (270), 31P (109), 13C (68 MHz). 5: yield 97%. IR: 3573 (OH), 1917
12 A. J. P. White and D. J. Williams, unpublished work.
1
(CO). NMR H: δ 5.40 [d, 1 H, RuCH᎐CH; J(HH) = 12.9 Hz], 6.94–
᎐
7.45 [m, 41 H, Ph ϩ RuCH (obscured)]. 31P-{1H}: δ 33.2. 13C{1H}:
Communication 9/02021G
1912
J. Chem. Soc., Dalton Trans., 1999, 1911–1912