L′ = CO vs Cl- transposition: Remarkable consequences for the product of (L′)-Ru(L)2-(H) and vinyl ether

Article abstract of DOI:10.1021/om990649g

The products of reaction of H₂C=CH(OR) with RuH(Cl)L₂ (L = PⁱPr₃) and RuH(CO)L₂⁺ (L = P^t-Bu₂Me) are RuH(Cl)(=C(OR)Me)L₂ and Ru(CO)(CH₂-CH₂OR)L₂⁺, respectively. Spectroscopic data and X-ray analysis (R -Me, B[C₆H₃(CF₃)₂]₄ salt, hemi(pentane) solvate) reveal the presence, in the latter, of a β-alkoxy ethyl ligand with a Ru-O bond. DFT (B3PW91) calculations show that the observed products correspond to the thermodynamic preference.

Full text of DOI:10.1021/om990649g

Organometallics 1999, 18, 5441-5443
5441
-
L′ ) CO vs Cl Tr a n sp osition : Rem a r k a ble Con sequ en ces
for th e P r od u ct of (L′)-Ru (L) -(H) a n d Vin yl Eth er
2
†
‡
‡
§
Dejian Huang, H e´ l e` ne G e´ rard, Eric Clot, Victor Young, J r.,
†
,‡
,†
William E. Streib, Odile Eisenstein,* and Kenneth G. Caulton*
Department of Chemistry and Molecular Structure Center, Indiana University,
Bloomington, Indiana 47405-7102, LSDSMS (UMR 5636), Universit e´ de Montpellier 2,
4095 Montpellier Cedex 5, France, and Department of Chemistry, University of Minnesota,
Minneapolis, Minnesota 55455
3
Received August 12, 1999
Summary: The products of reaction of H2CdCH(OR)
i
+
t
with RuH(Cl)L2 (L ) P Pr3) and RuH(CO)L2 (L ) P -
Bu2Me) are RuH(Cl)(dC(OR)Me)L2 and Ru(CO)(CH2-
CH2OR)L2 , respectively. Spectroscopic data and X-ray
+
analysis (R ) Me, B[C6H3(CF3)2]4 salt, hemi(pentane)
solvate) reveal the presence, in the latter, of a â-alkoxy
ethyl ligand with a Ru-O bond. DFT (B3PW91) calcu-
lations show that the observed products correspond to
the thermodynamic preference.
We have reported earlier that the fragment RuHClL2
i
(
L ) P( Pr)3), which exists as a dimer in noncoordinating
solvents, isomerizes vinyl ethers to coordinated carbenes
A (eq 1). This is enabled kinetically by the hydride
1
2
RuHClL + H CdCH(OMe) f
2
2
b
c
L ClHRu(H CdCH(OMe)) f
at 4.09 ppm (H ) and a singlet at 3.04 ppm for H .
2
2
1
3
1
Correspondingly, the C{ H} NMR spectrum gives
singlets at 89.6 (CH2O) and 60.6 ppm (OCH3) and a
triplet at -1.18 ppm (J PC ) 5.5 Hz) for Ru-CH2. These
data do not provide evidence for or against ether oxygen
coordination. However, the CO stretching frequency
L ClHRudCMe(OMe) (1)
2
A
ligand (eq 1), and the carbene is calculated to be
isoenergetic with the π-olefin complex (an observed
intermediate) due to the π-basicity of Ru(II) in this
ligand environment;3 that is, the π-acidic carbene
benefits from back-donation by the RuHClL2 substruc-
-
1
(1939 cm ) of 1 is significantly lower than that of [Ru-
+
-1
(CH3)(CO)L2] (1951 cm ), consistent with ether oxygen
coordination in 1 (eq 2). Vinyl ethyl ether reacts
similarly to give 2, although sterically more demanding
vinyl tert-butyl ether does not react.
A crystal structure determination (Figure 1) confirms
what is deduced from the spectroscopic study: the vinyl
1
ture. We now report experimental observations show-
-
ing that replacement of Cl by CO leads to an isomeric
5
product (eq 2), together with computational studies that
help explain the newly observed product.
Addition of CH2dCH(OCH3)(excess) to [RuH(CO)(P -
t
ligand has inserted into the hydride-Ru bond, and the
resulting â-methoxy ethyl ligand binds in an η fashion
2
Bu2Me)2]BAr′4 (Ar′ ) 3,5-bis(trifluoromethyl)phenyl) in
fluorobenzene (20 °C, <5 min) causes an immediate
color change from light orange to bright orange. When
the solution is layered with pentane at -20 °C for 2
days, large orange crystals are isolated in almost
quantitative yield. NMR spectral data reveal clean
2
t
(
4) [Ru (η -CH ]BAr ′
2
CH
2
OCH
3
)(CO)(P Bu
2
Me)
2
4 2
. [RuH(CO)L ]-
BAr′ (200 mg, 152 mmol) was dissolved in C H F (5 mL); an excess of
4
6 5
methyl vinyl ether was vacuum-transferred into this solution, and the
mixture was stirred for 5 min. The volatiles were evaporated, and the
residue was recrystallized in C
6
H
5
F layered with pentane. Yield: 190
12 ) 10:1, 20 °C, 400 MHz): δ 4.09 (t,
) 7.7 )
1
6 5 6
mg (92%). H NMR (C H F:C D
2
a
b
c
t
+
formation of [Ru(η -CH 2CH 2OCH 3)(CO)(P Bu2Me)2]
(
J HH ) 7.7 Hz, 2H, CH O), 3.04 (s, 3H, OCH ), 2.07 (tt, J
2
3
HH
4
1
J PH ) 7.7 Hz, Ru-CH ), 1.13 (vt, N ) 13.7 Hz, 18H, PC(CH ) ), 1.09
1). The H NMR spectrum of 1 has an apparent quintet
2
3 3
(
vt, N ) 5.0 Hz, 6H, PCH ), 0.90 (vt, N ) 13.0 Hz, 18H, PC(CH ) ).
3
3
3
a
at 2.07 ppm (J HH ) J PH ) 7.7 Hz) for H and a triplet
31
1
13 1
P{ H} NMR (162 MHz): δ 45.0 (s). C{ H} NMR (100 MHz): δ 205.4
(
t, J PC ) 15 Hz, Ru-CO), 89.6 (s, CH
2
O), 60.6 (s, OCH
), 36.6 (vt, N ) 18 PC(CH ), 29.3 and 29.0 (s, PC-
), -1.18 (t, J PC ) 5.5 Hz). IR
F): 1939 cm (ν(CO)). Elemental analyses, which will differ
3
), 38.0 (vt, N )
*
To whom correspondence should be addressed. E-mail: O.E.,
18 Hz, PC(CH
3
)
3
3 3
)
eisenst@lsd.univ-montp2.fr; K.G.C., caulton@indiana.edu.
(CH
(C
3
H
)
5
3
), 2.9 (vt, N ) 17.4 Hz, PCH
3
†
-1
Indiana University.
Universit e´ de Montpellier 2.
University of Minnesota.
6
‡
insignificantly from the reagent complex, were not obtained.
(5) Crystal data (-174 °C) for C57 Ru (which is the salt
together with 0.5 molecule of pentane, disordered by a C axis): a )
13.622(2) Å, c ) 34.616(3) Å, with Z ) 4 in space group P4 2. R(F)
(F ) ) 0.1574 for 3819 observed (F > 4σ(F)) data out
of 5679 unique intensities measured. The cation is disordered around
a C axis, and restraints are required to obtain a satisfactory refine-
§
2 2
H61BF24O P
(
1) Coalter, J . N., III; Spivak, G. J .; G e´ rard, H.; Clot, E.; Davidson,
E. R.; Eisenstein, O.; Caulton, K. G. J . Am. Chem. Soc. 1998, 120, 9388.
2) Coalter, J . N., III; Bollinger, J . C.; Huffman, J . C.; Werner-
2
1 1
2
2
(
) 0.0663 and R
w
Zwanziger, U.; Caulton, K. G.; Davidson, E. R.; G e´ rard, H.; Clot, E.;
Eisenstein, O. New J . Chem., in press.
2
(
3) Harman, W. D. Chem. Rev. 1997, 97, 1953. Taube, H. Pure Appl.
ment. Structural parameters are thus to be interpreted with great
caution.
Chem. 1979, 51, 901.
1
0.1021/om990649g CCC: $18.00 © 1999 American Chemical Society
Publication on Web 12/03/1999

5
442 Organometallics, Vol. 18, No. 26, 1999
Communications
F igu r e 1. ORTEP drawing (30% probability ellipsoids) of
2
t
the non-hydrogen atoms of Ru(η -CH
2
CH
2
OMe)(CO)(P Bu
2
-
+
Me)
2
. Unlabeled atoms are phosphine substituent carbons.
Ru-C1 ) 1.796(15) Å, Ru-C2 ) 2.068(13) Å; C1-Ru-C2
)
94.0(7)°, C2-Ru-O2 ) 63.2(14)°.
through an alkyl carbon and the methoxy oxygen. The
F igu r e 2. DFT(B3PW91) optimized structure for the most
Ru-O distance is 2.226(8) Å.
The DFT(B3PW91) calculations
favorable alkyl complexes: (top) RuL′(PH
3 2
) (CH(OMe)-
6
-12
show that the
(
CH )); (bottom) RuL′(PH (CH CH OMe). Energies are
3
3
)
2
2
2
significant binding energy of the π-olefin adduct to
RuHL′(PH3)2 is remarkably insensitive to the nature of
given in kcal/mol, relative to the vinyl methyl ether adduct,
and distances are given in Å.
-
L′, since they differ by less than 3 kcal/mol (Cl , 35.7
kcal/mol; CO, 33.1 kcal/mol). The relative energy of the
carbene and the π-olefin adduct is also insensitive to
thermodynamics of the transformation of the vinyl ether
into alkoxycarbene complexes. In contrast, the energy
and structure of the alkyl isomers (Figure 2) resulting
from the insertion of the CdC bond in the Ru-H bond
in the two possible orientations depend significantly on
the nature of L′. The most stable carbene complexes are
-
1
.6 kcal/mol (L′ ) Cl ) or 2.2 kcal/mol (L′ ) CO) above
-
the most stable π-olefin adduct. Therefore, replacing Cl
-
by CO does not change in any significant manner the
L′. With L′ ) Cl , the π-olefin adduct (used as reference
for energy) is below the most stable alkyl isomer (OMe
on the R-carbon and â-C-H agostic bond: a , +3.5 kcal/
mol) and below isomer c (OMe on the â-carbon; +9.2
kcal/mol). With L′ ) CO, the π-olefin adduct is above
the most stable alkyl isomer (OMe on the â-carbon: d ,
(
6) The calculations were carried out with the Gaussian 98 suite of
programs: Frisch, M. J .; Trucks, G. W.; Schlegel, H. B.; Scuseria, G.
E.; Robb, M. A.; Cheeseman, J . R.; Zakrzewski, V. G.; Montgomery, J .
A., J r.; Stratmann, R. E.; Burant, J . C.; Dapprich, S.; Millam, J . M.;
Daniels, A. D.; Kudin, K. N.; Strain, M. C.; Farkas, O.; Tomasi, J .;
Barone, V.; Cossi, M.; Cammi, R.; Mennucci, B.; Pomelli, C.; Adamo,
C.; Clifford, S.; Ochterski, J .; Petersson, G. A.; Ayala, P. Y.; Cui, Q.;
Morokuma, K.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.;
Foresman, J . B.; Cioslowski, J .; Ortiz, J . V.; Stefanov, B. B.; Liu, G.;
Liashenko, A.; Piskorz, P.; Komaromi, I.; Gomperts, R.; Martin, R. L.;
Fox, D. J .; Keith, T.; Al-Laham, M. A.; Peng, C. Y.; Nanayakkara, A.;
Gonzalez, C.; Challacombe, M.; Gill, P. M. W.; J ohnson, B.; Chen, W.;
Wong, M. W.; Andres, J . L.; Gonzalez, C.; Head-Gordon, M.; Replogle,
E. S.; Pople, J . A. Gaussian 98, Revision A.6; Gaussian, Inc., Pitts-
burgh, PA, 1998. Ru was represented with the Hay-Wadt relativistic
core potential (ECP) for the 28 innermost electrons and its associated
double-ú basis set.7 Cl and P are also described with the Los Alamos
ECPs and their associated double-ú basis set augmented by a d
-
4.4 kcal/mol) and isomer b (-2.2 kcal/mol). Thus, the
-
primary consequence of the replacement of Cl by CO
is to stabilize the alkyl isomers regardless of the
direction of insertion of the CdC bond into the Ru-H
bond. This leads to an alkyl complex which can ef-
fectively compete with the isomeric olefin or carbene
adducts. The structure of d compares very well with the
experimental structure (Figure 1).
To assess the role of L′ in lowering the energy of
8
,9
10
-
polarization function. A 6-31G(d,p) basis set was used for all other
atoms. Full optimizations without symmetry constraint have been
carried out at the B3PW91 level.
isomer d , alkyl rotamers (e for L′ ) Cl and f for L′ )
CO) deprived of any Ru‚‚‚O or C-H agostic interactions
were considered as true 14-electron complexes.13 The
alkyl isomers e and f are 24.2 and 19.3 kcal/mol above
the corresponding π-olefin adduct. This shows that the
1
1,12
(7) Hay, P. J .; Wadt, W. R. J . Chem. Phys. 1985, 82, 299.
(8) Wadt, W. R.; Hay, P. J . J . Chem. Phys. 1985, 82, 284.
(9) H o¨ lwarth, A.; B o¨ hme, M.; Dapprich, S.; Ehlers, A. W.; Gobbi,
A.; J onas, V.; K o¨ hler, K.; Stegmann, R.; Veldkamp, A.; Frenking, G.
Chem. Phys. Lett. 1993, 208, 237.
(
(
(
10) Hariharan, P. C.; Pople, J . A. Theor. Chim. Acta 1973, 28, 213.
11) Becke, A. D. J . Chem. Phys. 1993, 98, 5648.
12) Perdew, J . P.; Wang, Y. Phys. Rev. B 1992, 45, 13244.
(13) The alkyl chain is constrained to have eclipsed R-C-H and Ru-
3
L′ bonds, which puts the two other CH and OMe substituents away
from the empty sites of Ru.

Communications
Organometallics, Vol. 18, No. 26, 1999 5443
alkyl complex is intrinsically more energetically acces-
Ack n ow led gm en t. This work was supported by the
U.S. National Science Foundation, the French CNRS,
and the Universit e´ de Montpellier 2. We thank J ohn C.
Bollinger for assistance with the structure refinement
and J oseph N. Coalter for stimulating this work.
-
sible for L′ ) CO than for L′ ) Cl . While they have
essentially identical geometrical features, cleaving the
-
Ru-O bond (going from c to e for L′ ) Cl and from d
to f for L′ ) CO) to give a 14-electron complex costs 15.0
-
kcal/mol for L ) Cl but 23.7 kcal/mol for L′ ) CO. This
significant difference in Ru-O binding energy could be
due to orbital interactions involving the π-donor or
Su p p or tin g In for m a tion Ava ila ble: Tables giving crys-
tallographic details, positional and thermal parameters, and
bond distances and angles and figures giving NMR spectra.
This material is available free of charge via the Internet at
http://pubs.acs.org..
-acceptor L′ ligand and/or to electrostatic factors. The
factors that control the role of L′ on the relative energies
of the alkyl, carbene, and olefin isomers are under study.
This result is another example where replacement of
Cl- by CO induces ligand coupling instead of metal-
ligand bond formation. This principle thus has some
generality.14
OM990649G
(14) Huang, D.; Oliv a´ n, M.; Huffman, J . C.; Eisenstein, O.; Caulton,
K. G. Organometallics 1998, 17, 4700.