Redox isomerization of allylic alcohols catalyzed by osmium and ruthenium complexes containing a cyclopentadienyl ligand with a pendant amine or phosphoramidite group: X-ray structure of an η3-1-hydroxyallyl- metal-hydride intermediate

Article abstract of DOI:10.1021/om100126t

Complexes [MCl₂(η⁶-p-cymene)]₂ (M = Os (1a), Ru (1b)) react with Li(C₅H₄CH₂CH ₂NHMe) (LiCp^N) and KPF₆ to give the sandwich derivatives [M(η⁵-Cp^N)(η⁶-p-cymene)] PF₆ (M = Os (2a), Ru (2b)). Treatment of 2a and 2b with (2,2--biphenol)PCl leads to [M(η⁵-Cp^P) (η⁶-p-cymene)]PF₆ (M = Os (3a), Ru (3b); Cp ^P = C₅H₄CH₂CH₂N(Me)P(2,2- -biphenol)). The photolysis of 2a, 2b, 3a, and 3b in acetonitrile produces the release of the p-cymene group and the coordination of the cyclopentadienyl pendant substituent to the metal center to afford [M(η⁵-C ₅,κ-N-Cp^N)(CH₃CN)₂]PF ₆ (M = Os (4a), Ru (4b)) and [M(η⁵-C ₅,κ-P-Cp^P)(CH₃CN)₂]PF ₆ (M = Os (5a), Ru (5b)). Complex 4a, which has been characterized by X-ray diffraction analysis, is a more efficient catalyst precursor than 4b for the redox isomerization of primary allylic alcohols, while the latter is more efficient than the former for the redox isomerization of secondary allylic alcohols. From the catalytic solutions containing 4a and 2-methyl-2-propen-1-ol, the η³-1-hydroxyallyl complex [OsH(η⁵-C ₅,κ-N-Cp^N){η³-CH₂C(CH ₃)CHOH}]PF₆ (6) has been crystallized and characterized by spectroscopic methods and X-ray diffraction analysis. The structure shows a N-HO hydrogen bond (2.22 a) between the NH-hydrogen atom of the coordinated pendant amine group and the oxygen atom of the hydroxy substituent of the allyl ligand.

Full text of DOI:10.1021/om100126t

2166 Organometallics 2010, 29, 2166–2175
DOI: 10.1021/om100126t
Redox Isomerization of Allylic Alcohols Catalyzed by Osmium and
Ruthenium Complexes Containing a Cyclopentadienyl Ligand with a
Pendant Amine or Phosphoramidite Group: X-ray Structure of an
η3-1-Hydroxyallyl-Metal-Hydride Intermediate
~
Marıa Batuecas, Miguel A. Esteruelas,* Cristina Garcıa-Yebra,* and Enrique Onate
´ ꢀ ꢀ
Departamento de Quımica Inorganica, Instituto de Ciencia de Materiales de Aragon,
Universidad de Zaragoza, CSIC, 50009 Zaragoza, Spain
Received February 16, 2010
Complexes [MCl2(η6-p-cymene)]2 (M = Os (1a), Ru (1b)) react with Li(C5H4CH2CH2NHMe)
(LiCpN) and KPF6 to give the sandwich derivatives [M(η5-CpN)(η6-p-cymene)]PF6 (M = Os (2a), Ru
(2b)). Treatment of 2a and 2b with (2,20-biphenol)PCl leads to [M(η5-CpP)(η6-p-cymene)]PF6 (M =
Os (3a), Ru (3b); CpP = C5H4CH2CH2N(Me)P(2,20-biphenol)). The photolysis of 2a, 2b, 3a, and 3b
in acetonitrile produces the release of the p-cymene group and the coordination of the cyclopenta-
dienyl pendant substituent to the metal center to afford [M(η5-C5,κ-N-CpN)(CH3CN)2]PF6 (M = Os
(4a), Ru (4b)) and [M(η5-C5,κ-P-CpP)(CH3CN)2]PF6 (M = Os (5a), Ru (5b)). Complex 4a, which has
been characterized by X-ray diffraction analysis, is a more efficient catalyst precursor than 4b for the
redox isomerization of primary allylic alcohols, while the latter is more efficient than the former for
the redox isomerization of secondary allylic alcohols. From the catalytic solutions containing 4a and
2-methyl-2-propen-1-ol, the η3-1-hydroxyallyl complex [OsH(η5-C5,κ-N-CpN){η3-CH2C(CH3)CH-
OH}]PF6 (6) has been crystallized and characterized by spectroscopic methods and X-ray diffraction
˚
analysis. The structure shows a N-H O hydrogen bond (2.22 A) between the NH-hydrogen atom
of the coordinated pendant amine group and the oxygen atom of the hydroxy substituent of the allyl
ligand.
3 3 3
Introduction
aldol condensation products.5 Furthermore, the products
may also undergo decarbonylation reactions, which cause
catalyst deactivation by coordination of carbon monoxide to
The one-pot internal redox isomerization of allylic alco-
hols mediated by transition metal complexes represents a
useful and elegant shortcut to carbonyl compounds (eq 1),
which otherwise would require a two-step sequence of oxida-
tion and reduction reactions.1
(3) (a) Alper, H.; Hachem, K. J. Org. Chem. 1980, 45, 2269. (b)
€
Backvall, J.-E.; Andreasson, U. Tetrahedron Lett. 1993, 34, 5459. (c) Trost,
B. M.; Kulawiec, R. J. J. Am. Chem. Soc. 1993, 115, 2027. (d) Stunnenberg,
F.; Niele, F. G. M.; Drent, E. Inorg. Chim. Acta 1994, 222, 225. (e) Slugovc,
C.; R€uba, E.; Schmid, R.; Kirchner, K. Organometallics 1999, 18, 4230.
(f) Slugovc, C.; R€uba, E.; Schmid, R.; Kirchner, K.; Mereiter, K. Monatsh.
ꢀ
ꢀ
Chem. 2000, 131, 1241. (g) Uma, R.; Davies, M. K.; Crevisy, C.; Gree, R.
Eur. J. Org. Chem. 2001, 3141. (h) van der Drift, R. C.; Sprengers, J. W.;
Bouwman, E.; Mul, W. P.; Kooijman, H.; Spek, A. L.; Drent, E. Eur. J. Inorg.
Chem. 2002, 2147. (i) Cadierno, V.; Crochet, P.; García-Garrido, S. E;
Gimeno, J. Dalton Trans. 2004, 3635. (j) Cadierno, V.; García-Garrido, S.
E; Gimeno, J. Chem. Commun. 2004, 232. (k) Ganchegui, B.; Bouquillon,
Primary allylic alcohols2 are harder to isomerize success-
fully than secondary allylic alcohols,3 due to the side reac-
tions that may occur during the process, in particular when a
basic medium is used. In addition to metal-promoted C-H
bond activation,4 the R-CH group of the resulting aldehyde is
susceptible to deprotonation, which may degenerate into
ꢀ
S.; Henin, F.; Muzart, J. J. Mol. Catal. A: Chem. 2004, 214, 65. (l) Martín-
ꢀ
€
Matute, B.; Bogar, K.; Edin, M.; Kaynak, F. B.; Backvall, J.-E. Chem.;Eur.
J. 2005, 11, 5832. (m) van der Drift, R. C.; Gagliardo, M.; Kooijman, H.;
Spek, A. L.; Bouwman, E.; Drent, E. J. Organomet. Chem. 2005, 690, 1044.
(n) Ito, M.; Kitahara, S.; Ikariya, T. J. Am. Chem. Soc. 2005, 127, 6172. (o)
Takai, Y.; Kitaura, R.; Nakatani, E.; Onishi, T.; Kurosawa, H. Organome-
ꢀ
tallics 2005, 24, 4729. (p) Díaz-Alvarez, A. E.; Crochet, P.; Zablocka, M.;
*Corresponding authors. E-mail: maester@unizar.es (M.A.E.),
cgaryeb@unizar.es (C.G.-Y.).
(1) (a) van der Drift, R. C.; Bouwman, E.; Drent, E. J. Organomet.
Duhayon, C.; Cadierno, V.; Gimeno, J.; Majoral, J. P. Adv. Synth. Catal.
ꢀ
2006, 348, 1671. (q) Crochet, P.; Díez, J.; Fernandez-Zuꢀmel, M. A.; Gimeno,
J. Adv. Synth. Catal. 2006, 348, 93. (r) Cadierno, V.; García-Garrido, S. E.;
ꢀ
ꢀ
ꢀ
Chem. 2002, 650, 1. (b) Uma, R.; Crevisy, C.; Gree, R. Chem. Rev. 2003,
103, 27. (c) Cadierno, V.; Crochet, P.; Gimeno, J. Synlett 2008, 1105.
(2) For efficient catalysts that isomerize primary allylic alcohols to
aldehydes see for example: (a) Tanaka, K.; Fu, G. C. J. Org. Chem. 2001,
66, 8177. (b) Mantilli, L.; Mazet, C. Tetrahedron Lett. 2009, 50, 4141. (c)
Gimeno, J.; Varela-Alvarez, A.; Sordo, J. A. J. Am. Chem. Soc. 2006, 128,
ꢀ
1360. (s) Crochet, P.; Fernandez-Zꢀumel, M. A.; Gimeno, J.; Scheele,
M. Organometallics 2006, 25, 4846. (t) Bouziane, A.; Carboni, B.;
Bruneau, C.; Carreaux, F.; Renaud, J.-L. Tetrahedron 2008, 64, 11745. (u)
Lastra-Barreira, B.; Díez, J.; Crochet, P. Green Chem. 2009, 11, 1681.
ꢀ
ꢀ
~
Mantilli, L.; Gerard, D.; Torche, S.; Besnard, C.; Mazet, C. Angew. Chem.,
(4) Eguillor, B.; Esteruelas, M. A.; Olivan, M.; Onate, E. Organome-
Int. Ed. 2009, 48, 5143.
tallics 2004, 23, 6015.
r
pubs.acs.org/Organometallics
Published on Web 04/08/2010
2010 American Chemical Society

Article
Organometallics, Vol. 29, No. 9, 2010 2167
Figure 1
the metal center.6 The development of efficient catalysts for
the isomerization of primary allylic alcohols to aldehydes is
of great interest.
Three types of mechanisms have been proposed for
these reactions1,3c,l (Figure 1). A metal hydride addition-
elimination mechanism is usually invoked for metal-hydride
catalysts (a), while a π-allyl-metal-hydride mechanism
has been proposed for low-valent metal complexes that
can accommodate a π-allyl ligand (b). The third type of
mechanism involves alcoholate species, which are generated
in a basic reaction medium (c). These mechanisms have,
however, been proposed with scarce experimental evidence,
and all previous attempts to isolate and characterize catalytic
intermediates unambiguously have been unsuccessful.
The overwhelming majority of catalysts belong to either
group 8 or 9.1,3g From the iron triad, ruthenium dominates
these reactions.3b-f,h-j,l-t Osmium has received little atten-
tion.7 It is more reducing than ruthenium and prefers coordi-
nation saturation and redox isomers with more metal-carbon
bonds.8 This appears to be a handicap from a catalytic point of
view. Thus, the catalytic osmium chemistry is poor. In addition
to the Sharpless osmium-catalyzed asymmetric olefin dihy-
droxylation,9 only a few homogeneous processes have been
reported.5,7,10,11
~
(5) Barrio, P.; Esteruelas, M. A.; Onate, E. Organometallics 2004, 23,
1340.
ꢀ
ꢀ
ꢀ
(6) Esteruelas, M. A.; Hernandez, Y. A.; Lopez, A. M.; Olivan, M.;
Rubio, L. Organometallics 2008, 27, 799.
(7) Deeming, A. J.; Hasso, S. J. Organomet. Chem. 1976, 114, 313.
~
(8) (a) Caulton, K. G. J. Organomet. Chem. 2001, 617, 56. (b) Bolano,
Ruthenium-cyclopentadienyl complexes have been found
to be very efficient catalysts for the redox isomerization of
allylic alcohols, in particular for secondary alcohols.3c,e,f,l-n,t
A modification of the cyclopentadienyl system is the use of a
pendant donor substituent. The complexes containing this
type of ligands are expected to perform chemistry different
from that of usual cyclopentadienyl complexes. Indeed, the
reversible coordination of the pendant donor group in-
creases the stability of highly reactive centers.12 This has a
strong influence on the catalytic properties of the active
systems and facilitates the study of the catalytic mecha-
nisms.13 As a consequence of this, complexes containing
~
T.; Castarlenas, R.; Esteruelas, M. A.; Modrego, F. J.; Onate, E. J. Am. Chem.
ꢀ
ꢀ
Soc. 2005, 127, 11184. (c) Esteruelas, M. A.; Lopez, A. M.; Olivan, M.
Coord. Chem. Rev. 2007, 251, 795. (d) Jia, G. C. Coord. Chem. Rev. 2007,
251, 2167.
(9) (a) Berrisford, D. J.; Bolm, C.; Sharpless, K. B. Angew. Chem., Int.
Ed. Engl. 1995, 34, 1059. (b) Sharpless, K. B. Angew. Chem., Int. Ed. 2002,
41, 2024. (c) Zaitsev, A. B.; Adolfsson, H. Synthesis 2006, 1725. (d)
Franc-ais, A.; Bedel, O.; Haudrechy, A. Tetrahedron 2008, 64, 2495.
(10) (a) Esteruelas, M. A.; Sola, E.; Oro, L. A.; Werner, H.; Meyer, U.
J. Mol. Catal. 1988, 45, 1. (b) Esteruelas, M. A.; Sola, E.; Oro, L. A.; Meyer,
U.; Werner, H. Angew. Chem., Int. Ed. Engl. 1988, 27, 1563. (c) Werner, H.;
Meyer, U.; Esteruelas, M. A.; Sola, E.; Oro, L. A. J. Organomet. Chem.
1989, 366, 187. (d) Esteruelas, M. A.; Sola, E.; Oro, L. A.; Werner, H.; Meyer,
U. J. Mol. Catal. 1989, 53, 43. (e) Andriollo, A.; Esteruelas, M. A.; Meyer,
U.; Oro, L. A.; Sanchez-Delgado, R. A.; Sola, E.; Valero, C.; Werner, H. J.
Am. Chem. Soc. 1989, 111, 7431. (f) Aracama, M.; Esteruelas, M. A.; Lahoz,
F. J.; Lopez, J. A.; Meyer, U.; Oro, L. A.; Werner, H. Inorg. Chem. 1991, 30,
288. (g) Esteruelas, M. A.; Oro, L. A.; Valero, C. Organometallics 1991, 10,
462. (h) Esteruelas, M. A.; Valero, C.; Oro, L. A.; Meyer, U.; Werner, H.
Inorg. Chem. 1991, 30, 1159. (i) Esteruelas, M. A.; Oro, L. A.; Valero, C.
ꢀ
ꢀ
~
~
(11) (a) Bolano, T.; Castarlenas, R.; Esteruelas, M. A.; Onate, E.
J. Am. Chem. Soc. 2007, 129, 8850. (b) Esteruelas, M. A.; García-Yebra, C.;
~
Onate, E. Organometallics 2008, 27, 3029. (c) Castarlenas, R.; Esteruelas,
ꢀ
~
M. A.; Onate, E. Organometallics 2008, 27, 3240. (d) Esteruelas, M. A.;
Organometallics 1992, 11, 3362. (j) Esteruelas, M. A.; García, M. P.; Lopez,
ꢀ ~
García-Yebra, C.; Olivan, M.; Onate, E.; Valencia, M. Organometallics
A. M.; Oro, L. A.; Ruiz, N.; Schl€unken, C.; Valero, C.; Werner, H. Inorg.
Chem. 1992, 31, 5580. (k) Esteruelas, M. A.; Oro, L. A.; Ruiz, N.
ꢀ
2008, 27, 4892. (e) Eguillor, B.; Esteruelas, M. A.; García-Raboso, J.; Olivan,
ꢀ
~
Organometallics 1994, 13, 1507. (l) Sanchez- Delgado, R. A.; Rosales,
M.; Onate, E. Organometallics 2009, 28, 3700.
M.; Esteruelas, M. A.; Oro, L. A. J. Mol. Catal. A: Chem. 1995, 96, 231. (m)
Hafner, A.; M€uhlebach, A.; van der Schaaf, P. A. Angew. Chem., Int. Ed.
Engl. 1997, 36, 2121. (n) Esteruelas, M. A.; Oro, L. A. Chem. Rev. 1998, 98,
577. (o) Brumaghim, J. L.; Girolami, G. S. Organometallics 1999, 18, 1923.
(12) See for example: (a) Chu, H. S.; Lau, C. P.; Wong, K. Y.; Wong,
W. T. Organometallics 1998, 17, 2768. (b) Ayllon, J. A.; Sayers, S. F.;
Sabo-Etienne, S.; Donnadieu, B.; Chaudret, B.; Clot, E. Organometallics
1999, 18, 3981. (c) Lam, Y. F.; Yin, C.; Yeung, C. H.; Ng, S. M.; Jia, G.; Lau,
C. P. Organometallics 2002, 21, 1898. (d) Matsubara, T.; Hirao, K.
Organometallics 2001, 20, 5759.
(13) See for example: (a) Dohring, A.; Gohre, J.; Jolly, P. W.; Kryger,
B.; Rust, J.; Verhovnik, G. P. J. Organometallics 2000, 19, 388. (b)
Deckers, P. J. W.; Hessen, B.; Teuben, J. H. Angew. Chem., Int. Ed. 2001, 40,
2516. (c) Deckers, P. J. W.; Hessen, B.; Teuben, J. H. Organometallics 2002,
21, 5122. (d) de Bruin, T. J. M.; Magna, L.; Raybaud, P.; Toulhoat, H.
Organometallics 2003, 22, 3404. (e) Zhang, H.; Ma, J.; Qian, Y.; Huang, J.
Organometallics 2004, 23, 5681.
ꢀ
(p) Díaz, J.; Esteruelas, M. A.; Herrero, J.; Moralejo, L.; Olivan, M. J. Catal.
ꢀ
~
2000, 195, 187. (q) Esteruelas, M. A.; García-Yebra, C.; Olivan, M.; Onate,
E.; Tajada, M. A. Organometallics 2000, 19, 5098. (r) Esteruelas, M. A.;
€
€
ꢀ
ꢀ
Herrero, J.; Lopez, A. M.; Olivan, M. Organometallics 2001, 20, 3202. (s) Li,
Y.; Huang, J.-S.; Zhou, Z.-Y.; Che, C.-M. J. Am. Chem. Soc. 2001, 123,
€
4843. (t) Dobler, C.; Mehltretter, G. M.; Sundermeier, U.; Eckert, M.;
Militzer, H.-C.; Beller, M. Tetrahedron Lett. 2001, 42, 8447. (u) Cobo,
ꢀ
ꢀ
N.; Esteruelas, M. A.; Gonzalez, F.; Herrero, J.; Lopez, A. M.; Lucio, P.;
ꢀ
Olivan, M. J. Catal. 2004, 223, 319. (v) Schl€unken, C.; Esteruelas, M. A.;
Lahoz, F. J.; Oro, L. A.; Werner, H. Eur. J. Inorg. Chem. 2004, 2477. (w)
(14) (a) Jutzi, P.; Siemeling, U. J. Organomet. Chem. 1995, 500, 175.
(b) Jutzi, P.; Redeker, T. Eur. J. Inorg. Chem. 1998, 663. (c) Siemeling, U.
~
Castarlenas, R.; Esteruelas, M. A.; Onate, E. Organometallics 2005, 24,
€
4343. (x) Carmona, D.; Vega, C.; García, N.; Lahoz, F. J.; Elipe, S.; Oro,
Chem. Rev. 2000, 100, 1495. (d) Butenschon, H. Chem. Rev. 2000, 100,
L. A.; Lamata, M. P.; Viguri, F.; Borao, R. Organometallics 2006, 25, 1592.
1527. (e) M€uller, C.; Vos, D.; Jutzi, P. J. Organomet. Chem. 2000, 600, 127.
(f) Qian, Y.; Huang, J.; Bala, M. D.; Lian, B.; Zhang, H.; Zhang, H. Chem.
Rev. 2003, 103, 2633.
ꢀ
ꢀ
(y) Esteruelas, M. A.; Gonzalez, F.; Herrero, J.; Lucio, P.; Olivan, M.;
Ruiz-Labrador, B. Polym. Bull. 2007, 58, 923.

2168 Organometallics, Vol. 29, No. 9, 2010
Batuecas et al.
cyclopentadienyl ligands with a pendant donor substituent
are attracting increased interest from those who study the
chemistry of metals.14
Scheme 1
Our group is actively interested in this type of com-
pounds.15 As a part of our work in this field, we now report
the preparation and characterization of new osmium and
ruthenium complexes containing cyclopentadienyl ligands
with pendant amine and phosphoramidite groups and their
catalytic behavior in the isomerization of primary and
secondary allylic alcohols. Furthermore, we propose a cat-
alytic cycle on the basis of the isolation and full characteri-
zation of a hydroxyallyl intermediate.
Results and Discussion
1. Osmium and Ruthenium Complexes Containing Cyclo-
pentadienyl Ligands with Pendant Amine and Phosphorami-
dite Groups. Osmium-cyclopentadienyl compounds15d are
harder to prepare than the ruthenium counterparts. This is
due to the greater inertness of the octahedral osmium(II)
complexes, which is a consequence of the dependence of the
crystal field activation energy on Δo. Two successful meth-
ods have been used to obtain this type of derivative: (i) the
treatment of phosphine-metal-halide complexes with cyclo-
pentadiene or a cyclopentadienyl derivative of an s- or p-
block element15b,c,16 and (ii) the photolysis of sandwich
cyclopentadienyl-metal-arene derivatives in acetonitrile.17
The former method has a major disadvantage in that dis-
placement of the phosphine ligands is often difficult. There-
fore, we have used the latter as it also allows the ruthenium
counterparts to be obtained (Scheme 1).
The 13C{1H} and 1H NMR spectra of 2a and 2b are
consistent with the presence of a free pendant substituent
in the complexes. This allows, in solution, the five-membered
ring to rotate around the M-Cp axis. Thus, the 13C{1H}
NMR spectra in dichloromethane-d2 shows three Cp singlets
for each complex, at 75.8, 76.5, and 98.1 (2a) and 66.2, 80.4,
and 81.5 (2b) ppm, whereas in the 1H NMR spectra two Cp
signals, at 5.48 and 5.60 (2a) and 5.08 and 5.17 (2b) ppm, are
observed. The free character of the pendant substituent is
also revealed by the CH2 resonances of the CH2-CH2 chain
in the 1H NMR spectra, which appear as triplets, at 2.50 and
2.71 (2a) and 2.34 and 2.64 (2b) ppm, with H-H coupling
constants of 6.6 (2a) and 7.1 (2b) Hz.
An effective method to prepare phosphoramidite ligands
involves the reaction of (RO)2PCl compounds with primary
or secondary amines in the presence of a base.18 In agreement
with this, the treatment at 0 °C of dichloromethane solutions
of 2a and 2b with 1.3 equiv of (2,20-biphenol)PCl in the
presence of 2.4 equiv of piperidinomethyl polystyrene for
12 h leads to [M(η5-CpP)(η6-p-cymene)]PF6 (M = Os (3a),
Ru (3b); CpP = C5H4CH2CH2N(Me)P(2,20-biphenol)) con-
taining a phosphoramidite pendant substituent at the cyclo-
pentadienyl group. Complexes 3a and 3b were isolated as
pale brown solids in 75% and 68% yield, respectively. The
formation of the phosphoramidite group is strongly sup-
ported by the 31P{1H} NMR spectra of these compounds, in
acetonitrile-d3 at room temperature, which show singlets at
150 (3a) and 148 (3b) ppm.
Treatment at room temperature of the dimer [OsCl2(η6-p-
cymene)]2 (1a) with 2.5 equiv of Li(C5H4CH2CH2NHCH3)
(LiCpN) in tetrahydrofuran for 4 h and the subsequent
addition of 2.0 equiv of KPF6 to the dichloromethane/
acetone (1:1) solution of the resulting residue affords the
sandwich derivative [Os(η5-CpN)(η6-p-cymene)]PF6 (2a).
Under the same conditions, the reaction of the ruthenium
dimer [RuCl2(η6-p-cymene)]2 (1b) with LiCpN and KPF6
yields [Ru(η5-CpN)(η6-p-cymene)]PF6 (2b). Both com-
pounds were isolated as brown oils in 80% yield.
ꢀ
ꢀ
~
(15) Esteruelas, M. A.; Fernandez, F. J.; Lopez, A. M.; Onate, E.
ꢀ
~
Organometallics 2003, 22, 1787. (b) Esteruelas, M. A.; Lopez, A. M.; Onate,
ꢀ
E.; Royo, E. Organometallics 2004, 23, 3021. (c) Esteruelas, M. A.; Lopez,
~
A. M.; Onate, E.; Royo, E. Organometallics 2004, 23, 5633. (d) Esteruelas,
ꢀ
M. A.; Lopez, A. M. Organometallics 2005, 24, 3584. (e) Esteruelas, M. A.;
ꢀ
~
Lopez, A. M.; Mateo, A. C.; Onate, E. Organometallics 2005, 24, 5084. (f)
ꢀ
~
Esteruelas, M. A.; Lopez, A. M.; Onate, E.; Royo, E. Inorg. Chem. 2005, 44,
ꢀ
~
4094. (g) Esteruelas, M. A.; Lopez, A. M.; Mateo, A. C.; Onate, E.
ꢀ
Organometallics 2006, 25, 1448. (h) Buil, M. L.; Esteruelas, M. A.; Lopez,
A. M.; Mateo, A. C. Organometallics 2006, 25, 4079. (i) Esteruelas, M. A.;
ꢀ
ꢀ
~
ꢀ
Fernandez-Alvarez, F. J.; Lopez, A. M.; Onate, E.; Ruiz-Sanchez, P. Orga-
ꢀ
nometallics 2006, 25, 5131. (j) Buil, M. L.; Esteruelas, M. A.; Lopez, A. M.;
~
Mateo, A. C.; Onate, E. Organometallics 2007, 26, 554.
The photolysis at -5 °C of acetonitrile solutions of 2a, 2b,
3a, and 3b for 6 h, with a 400 W medium-pressure mercury
lamp, produces the release of the p-cymene group and the
coordination to the metal center of the pendant substituent
of the cyclopentadienyl groups. The resulting unsaturated
metal fragments are stabilized by coordination of two sol-
vent molecules. The formed half-sandwich derivatives
[M(η5-C5,κ-N-CpN)(CH3CN)2]PF6 (M = Os (4a), Ru (4b))
and [M(η5-C5,κ-P-CpP)(CH3CN)2]PF6 (M = Os (5a),
(16) (a) Blackmor, T.; Bruce, M. I.; Stone, F. G. A. J. Chem. Soc. A
1971, 2376. (b) Marshman, R. W.; Shusta, J. M.; Wilson, S. R.; Shapley, P. A.
Organometallics 1991, 10, 1671. (c) Shapley, P. A.; Shusta, J. M.; Hunt, J. L.
Organometallics 1996, 15, 1622. (d) Esteruelas, M. A.; Gomez, A. V.;
Lopez, A. M.; Oro, L. A. Organometallics 1996, 15, 878. (e) Esteruelas,
M. A.; Lopez, A. M.; Ruiz, N.; Tolosa, J. I. Organometallics 1997, 16, 4657.
(f) Koch, J. L.; Shapley, P. A. Organometallics 1997, 16, 4071. (g) Koch,
J. L.; Shapley, P. A. Organometallics 1999, 18, 814. (h) Esteruelas, M. A.;
ꢀ
ꢀ
ꢀ
ꢀ
~
Lopez, A. M.; Onate, E.; Royo, E. Organometallics 2005, 24, 5780.
(17) (a) Freedman, D. A.; Magneson, D. J.; Mann, K. R. Inorg.
Chem. 1995, 34, 2617. (b) Mann, K. R.; Blough, A. M.; Schrenk, J. L.;
Koefod, R. S.; Freedman, D. A.; Matachek, J. R. Pure Appl. Chem. 1995, 67,
95. (c) Freedman, D. A.; Gill, T. P.; Blough, A. M.; Koefod, R. S.; Mann,
K. R. Inorg. Chem. 1997, 36, 95.
(18) See for example: Bartels, B.; Garcıa-Yebra, C.; Helmchen, G.
Eur. J. Org. Chem. 2003, 1097, and references therein.

Article
Organometallics, Vol. 29, No. 9, 2010 2169
Table 1. a
Figure 2. Molecular diagram of complex 4a. Selected bond
˚
lengths (A) and angles (deg): Os-C(1) 2.095(8); Os-C(2)
2.144(6); Os-C(3) 2.161(6); Os-N(1) 2.049(5); Os-N(2)
2.176(8); C(1)-Os-N(2) 82.3(3); N(1)-Os-N(2) 83.3(3).
Ru (5b)) were obtained as yellow (4a, 4b, and 5a) or white
(5b) solids in 40-44% yield.
The coordination of the pendant group to the metal center
of these compounds was confirmed by an X-ray diffraction
study of 4a (Figure 2). The geometry around the osmium
center can be described as a distorted octahedron, with the
cyclopentadienyl ring occupying the three sites of a face. The
N-Os-N angles are close to 90°, whereas the separation
between the pendant amine group and the metal center
˚
(Os-N(2)) is 2.176(8) A.
The 13C{1H} and 1H NMR spectra in acetonitrile-d3 of 4a
and 4b are temperature invariant between 25 and 80 °C. They
are consistent with the structure shown in Figure 2 and reveal
that the bond between the metal center and the amine
nitrogen atom is strong; therefore the metal-pendant inter-
action remains in acetonitrile solution. In agreement with
this the 13C{1H} NMR spectra contain five cyclopentadienyl
resonances at 52.1, 58.7, 60.0, 68.3, and 96.6 (4a) and 57.4,
62.9, 67.0, 74.6, and 102.5 (4b) ppm, whereas the 1H NMR
spectra show ABCD spin systems between 4.10 and 4.78 (4a)
and between 3.85 and 4.30 (4b) ppm for the cyclopentadienyl
a All reactions were performed in THF-d8 (0.08 M in substrate) at
60 °C in an NMR tube. b Yields referred to starting alcohol. c Turnover
frequencies calculated at 50% of conversion.
2. Isomerization of Primary Allylic Alcohols. The osmium
complex 4a is an efficient catalyst precursor for the redox
isomerization of 2-propen-1-ol, 2-methyl-2-propen-1-ol,
3-methyl-2-buten-1-ol, and 2-methyl-3-phenyl-2-propen-
1-ol into the corresponding aldehydes. The reactions
were performed under argon atmosphere in tetrahydrofu-
ran at 60 °C.
1
ring protons. The H NMR spectra also reflect the rigidity
The results collected in Table 1 clearly show that this
osmium catalyst is very sensitive to the number of substitu-
ents at the carbon-carbon double bond of the alcohol, their
positions, and their aliphatic or aromatic nature. Using 4
mol % of catalyst precursor, the almost quantitative forma-
tion of propanal occurs after 6 min (entry 1), while the
isomerization of the trisubstituted substrates requires hours.
3-Methylbutanal, resulting from a double C3-alkyl-substi-
tuted alcohol, is formed in 93% yield after 1.3 h (entry 3),
whereas 2-methyl-3-phenylpropanal, resulting from a C2-
alkyl,C3-aryl-substituted alcohol, is obtained in 98% after
13 h (entry 4). The isomerization of the disubstituted
2-methyl-2-propen-1-ol into 2-methylpropanal is not a clean
process. In this case, the metal center catalyzes not only the
redox isomerization but also the aldol-type reaction. Thus,
after 3 h, 2-methylpropanal is obtained in only 69% yield; the
rest of the substrate (31%) is transformed into 3-hydroxy-
2,2,4-trimethylpentanal (entry 2). The formation of the
latter, which can be rationalized according to Scheme 2,
involves the initial isomerization of the starting alcohol to
both the aldehyde and the enol, followed by the formal
of the CH2-CH2 chain, which is a consequence of the
coordination of the amine pendant group. Thus, they show
four resonances at 2.03, 2.21, 3.24, and 3.87 (4a) and
2.10-2.27, 3.27, and 3.62 (4b) for the diastereotopic ethylene
protons.
The coordination of the phosphoramidite pendant sub-
stituent to the metal center of 5a and 5b is mainly supported
by the 31P{1H} NMR spectra, which show singlets at 114 (5a)
and 169 (5b) ppm. The first of them is displaced by 36 ppm
toward higher field with regard to 3a, while the second one
appears displaced by 19 ppm toward lower field with regard
to 3b. These chemical shifts agree well with those previously
reported for osmium-11d and ruthenium-phosphoramidite19
derivatives. The 1H NMR spectra also reflect the rigidity of
the CH2-CH2 chain. Thus, similarly to the 1H NMR spectra
of 4a and 4b, they contain four complex resonances at
2.23-2.30 and 3.05-3.19 (5a) and 2.15-2.22 and
3.09-3.23 (5b) ppm, for the ethylene protons.
(19) Huber, D.; Mezzetti, A. Tetrahedron: Asymmetry 2004, 15, 2193.

2170 Organometallics, Vol. 29, No. 9, 2010
Batuecas et al.
Scheme 2
Table 2. a
insertion of the carbon-carbon double bond of the enol into
the C2-H bond of the aldehyde. In agreement with a direct
participation of the enol in the aldol reaction, its transitory
formation in amounts lower than 10% is observed during the
process.
The osmium complex 4a is surprisingly more efficient than
the ruthenium counterpart 4b. In the presence of the latter,
the yields of the redox isomerizations of the primary alcohols
of this study are in all cases lower than 69%. Several
ruthenium complexes have shown to be active catalysts for
the aldol reaction between aldehydes and allylic alcohols.20
Complex 4b is a new member of this family. In addition to the
redox isomerization of the corresponding primary alcohols,
it effects the aldol-type reactions. After 20 min in the
presence of 2 mol % of 4b, 68% of 2-propen-1-ol is trans-
formed into 3-hydroxy-2-methylpentanal, while only 27% of
the starting alcohol is isomerized (entry 5). Under the same
conditions, 32% of 2-methyl-2-propen-1-ol is converted into
3-hydroxy-2,2,4-trimethylpentanal and 68% of the substrate
isomerizes to 2-methylpropanal (entry 6). In both cases,
the transitory formation of the corresponding enols was also
observed. In the presence of 3-methyl-2-buten-1-ol and
2-methyl-3-phenyl-2-propen-1-ol, complex 4b undergoes de-
activation. 3-Methylbutanal and 2-methyl-3-phenylpropa-
nal can be obtained in only very low yields of 16% and 36%,
respectively (entries 7, 8). 3-Methyl-2-buten-1-ol also under-
goes a position isomerization process of the C-C double
bond to afford 3-methyl-3-buten-1-ol in 31% yield (entry 7).
This is a reaction typically catalyzed by a metal-hydride
intermediate.21
a All reactions were performed in THF-d8 (0.08 M in substrate) at
60 °C in an NMR tube. b Yields referred to starting alcohol. c Turnover
frequencies calculated at 50% of conversion.
are recovered unchanged from their tetrahydrofuran-d8
solutions.
The phosphoramidite complex 5b also leads to mixture of
products. After 65 min, in the presence of 5 mol % of 5b, 41%
of 2-propen-1-ol is isomerized to propanal. However, the
59% of alcohol is transformed into 2-methyl-4-pentenal
according to eq 2 (R = H) (entry 9). A similar reaction
has been observed during the redox isomerization of
several allylic alcohols catalyzed by [Ru(η5-Cp)(PR3)-
(CH3CN)2]PF6. It has been proposed that these products
are a consequence of the oxidative addition of the C-O
bond of the alcohol to the metal center. Thus, the resulting
allyl-M-hydroxy intermediate can generate an allyl-
M-enolate species, which affords the product by C-C
coupling of the allyl and enolate ligands.3e 2-Methyl-2-
propen-1-ol undergoes redox isomerization (38%) and
aldol reaction (68%). The osmium counterpart 5a does
not catalyze any of these reactions, and the substrates
3. Isomerization of Secondary Allylic Alcohols. The os-
mium complex 4a is certainly more efficient for the redox
isomerization of primary allylic alcohols than for the redox
isomerization of secondary allylic alcohols. While the turn-
over frequency calculated at 50% of conversion (TOF50) for
the transformation of 2-propen-1-ol into propanal is 232 h-1
(Table 1, entry 1), the TOF50 for the redox isomerization of
secondary allylic alcohols monosubstituted at the olefin,
such as 1-hepten-3-ol, 1-hexen-3-ol, 1-penten-3-ol, and
R-vinylbenzyl alcohol, into the corresponding ketones
ranges from 33 to 39 h-1 (Table 2, entries 1-4).
The ruthenium counterpart 4b is more efficient than 4a for
the redox isomerization of secondary allylic alcohols, in
contrast to that observed for the primary alcohols. Thus,
the TOF50 values obtained with 4b are in the range 960-
1470 h-1. The isomerization of 2-cyclohexen-1-ol to cyclo-
hexanone with a TOF50 of 1205 h-1 is noteworthy. This
substrate is particularly difficult to isomerize into the ketone.
We note that bis(allyl)-ruthenium(IV) catalyst precursors,
ꢀ
ꢀ
(20) See for example: (a) Uma, R.; Davies, M.; Cresivy, C.; Gree, R.
Tetrahedron Lett. 2001, 42, 3069. (b) Wang, M.; Li, C.-J. Tetrahedron Lett.
2002, 43, 3589. (c) Yang, X.-F.; Wang, M.; Varma, R. S.; Li, C.-J. Org. Lett.
2003, 5, 657. (d) Wang, M.; Yang, X.-F.; Li, C.-J. Eur. J. Org. Chem. 2003,
998. (e) Yang, X.-F.; Wang, M.; Varma, R. S.; Li, C.-J. J. Mol. Catal. A:
Chem. 2004, 214, 147. (f) Bartoszewick, A.; Livendahl, M.; Martín-Matute,
B. Chem.;Eur. J. 2008, 14, 10547.
ꢀ
(21) Chaloner, P. A.; Esteruelas, M. A.; Joo, F.; Oro, L. A. Homo-
geneous Hydrogenation; Kluwer: Dordrecht, The Netherlands, 1994.

Article
Organometallics, Vol. 29, No. 9, 2010 2171
The allyl group coordinates to the metal center in the endo
form, which is preferred for d4 M(η5-C5R5)L2(η3-allyl) com-
plexes23 (L ¼ CO), with the C(9) atom cisoid disposed to the
coordinated pendant amine group and its hydroxy substituent
in syn position with regard to the meso carbon atom C(10). The
C3 skeleton is bonded in an asymmetric fashion. The separation
between the central carbon atom, C(10), and the metal
˚
(2.138(8) A) is shorter than the separation between the metal
˚
and the terminal carbon atoms C(9) (2.215(9) A) and C(11)
˚
(2.157(7) A). The carbon-carbon distances within the allylic
˚
˚
skeleton are 1.385(12) A for C(9)-C(10) and 1.425(10) A for
C(10)-C(11). The angle C(9)-C(10)-C(11) is 113.0(8)°.
The coordination of the pendant amine atom is strong, as in
4a. The separation between the nitrogen atom and the metal,
˚
2.159(6) A, is statistically identical with the Os-N distance in
the latter. The NH hydrogen atom points toward the oxygen of
the hydroxy substituent of the allyl group. The separation
˚
Figure 3. Molecular diagram of complex 6. Selected bond
˚
˚
between these atoms, 2.22 A, is about 0.5 A shorter than the
sum of the van der Waals radii of hydrogen and oxygen
lengths (A) and angles (deg): Os-C(1) 2.241(7); Os-C(2)
2.261(7); Os-C(3) 2.216(8); Os-C(4) 2.180(9); Os-C(5)
2.220(8); Os-C(11) 2.157(7); Os-C(10) 2.138(8); Os-C(9)
2.215(9); Os-N 2.159(6); C(9)-C(10) 1.385(12); C(10)-C(11)
1.425(10); O(1)-H 2.22; N-Os-C(1) 78.5(3); C(9)-Os-C(11)
64.8(3); C(9)-C(10)-C(11) 113.0(8).
˚
˚
(rvdW(H) = 1.20 A; rvdW(O) = 1.40 A), indicating the presence
of an intramolecular N-H O hydrogen bond.24
3 3 3
The interaction appears to stabilize the structure. Although
for this ligand disposition two orientations of the amine are
possible, hydrogen toward oxygen or methyl toward oxygen,
the stereoisomer shown in Figure 3 is also the obtained one
when, at Schlenk tube scale, strongly concentrated tetrahydro-
furan solutions of 4a are treated with 5 equiv of 2-methyl-2-
propen-1-ol at 60 °C for 10 min. By this procedure, complex 6 is
isolated as a yellow solid in 60% yield.
which reach turnover frequencies of 3000 h-1 for the iso-
merization of secondary alcohols monosubstituted at the
olefin, isomerize 2-cyclohexen-1-ol with turnover frequen-
cies lower than 1 h-1 3r
.
The phosphoramidite complex 5b is also an efficient pre-
cursor for the redox isomerization of secondary allylic alco-
hols. However, the obtained TOF50 values, between 20 and
30 h-1, are significantly lower than those for 4b. In the
presence of this precursor, the isomerization of R-vinylbenzyl
alcohol is not clean. After 115 min in the presence of 4 mol %
of 5b, 64% of the alcohol is isomerized, while the rest of
substrate (36%) is transformed into 2-methyl-1,3-diphenyl-4-
penten-1-one according to eq 2 (R = Ph) (Table 2, entry 11).
4. Mechanism of the Redox Isomerizations. The 1H NMR
spectra of the catalytic solutions of 4a show a weak singlet
between -10 and -13 ppm, revealing the presence of a hydride
intermediate during the course of the isomerizations. At
-20 °C, from the solutions containing 2-methyl-2-propen-
1-ol a few yellow crystals suitable for an X-ray diffraction
study were formed. The structure (Figure 3) proves the
formation of the hydroxyallyl complex [OsH(η5-C5,κ-N-CpN)-
{η3-CH2C(CH3)CHOH}]PF6 (6) according to eq 3. 2-Methyl-
propanal formation was observed when solutions of pure 6 in
THF-d8 were allowed to stand at room temperature.
The 1H NMR spectra in dichloromethane-d2 at 253 K of
the crystals and the solid, as well as the 13C{1H} NMR
spectra, are identical and consistent with Figure 3. In agree-
ment with the catalytic solutions, the hydride resonance
appears at -12.20 ppm, whereas the OH signal is observed
at 4.69 ppm. The allyl skeleton displays three resonances at
2.74 and 3.22 (CH2) and 6.91 (CH) ppm. As expected for the
coordination of the nitrogen atom of the amine to the metal
center, the cyclopentadienyl protons give rise to an ABCD
spin system between 4.21 and 6.51 ppm, whereas the
CH2CH2 chain displays four resonances at 2.37, 2.47, 3.58,
and 3.76 ppm. In the 13C{1H} NMR spectrum, the reso-
nances corresponding to the allyl carbon atoms are observed
at 17.4 (C(11)), 78.4 (C(9)), and 93.0 (C(10)) ppm. In
accordance with 4a, the spectrum contains five cyclopenta-
dienyl signals at 68.0, 81.6, 81.7, 92.5, and 122.2 ppm.
A limited number of η3-hydroxyallyl complexes have been
isolated.25 The regioisomer η3-1-hydroxyallyl is particularly
(23) (a) Albers, M. O.; Liles, D. C.; Robinson, D. J.; Shaver, A.;
Singleton, E. Organometallics 1987, 6, 2347. (b) Itoh, K.; Fukahori, T.
J. Organomet. Chem. 1988, 349, 227. (c) Nagashima, H.; Mukai, K.; Shiota,
Y.; Yamaguchi, K.; Ara, K.-I.; Fukahori, T.; Suzuki, H.; Akita, M.; Moro-oka,
Y.; Itoh, K. Organometallics 1990, 9, 799. (d) Hubbard, J. L.; Zoch, C. R.
J. Organomet. Chem. 1995, 487, 65. (e) Mui, H. D.; Brumaghim, J. L.;
Gross, C. L.; Girolami, G. S. Organometallics 1999, 18, 3264. (f) Kondo, H.;
Yamaguchi, Y. Chem. Commun. 2000, 1075. (g) Bi, S.; Ariafard, A.; Jia, G.;
Lin, Z. Organometallics 2005, 24, 680.
The distribution of ligands around the osmium atom of 6 is
consistent with that found in [OsH(η5-Cp)(η3-allyl)(PiPr3)]þ
compounds22 and can be described as a four-legged piano-
stool geometry, where the allyl ligand occupies two cisoid
positions with a C(9)-Os-C(11) angle of 64.8(3)°.
ꢀ
ꢀ
~
(24) (a) Esteruelas, M. A.; Lledos, A.; Olivan, M.; Onate, E.; Tajada,
M. A.; Ujaque, G. Organometallics 2003, 22, 3753. (b) Barrio, P.;
ꢀ
~
ꢁ
Esteruelas, M. A.; Lledos, A.; Onate, E.; Tomas, J. Organometallics 2004,
23, 3008.
(25) (a) Huang, T.-M.; Hsu, R.-H.; Yang, C.-S.; Chen, J.-T.; Lee,
G.-H.; Wang, Y. Organometallics 1994, 13, 3657. (b) Hui, J. W.-S.; Wong,
W.-T. Polyhedron 1996, 15, 541. (c) Pasch, R.; Koelle, U.; Ganter, B.;
Englert, U. Organometallics 1997, 16, 3950. (d) Hsu, R.-H.; Chen, J.-T.; Lee,
G.-H.; Wang, Y. Organometallics 1997, 16, 1159. (e) Casey, C. P.; Nash,
J. R.; Yi, C. S.; Selmeczy, A. D.; Chung, S.; Powell, D. R.; Hayashi, R. K.
J. Am. Chem. Soc. 1998, 120, 722.
ꢀ
ꢀ
ꢀ
(22) (a) Esteruelas, M. A.; Gonzalez, A. I.; Lopez, A. M.; Olivan, M.;
~
ꢀ
Onate, E. Organometallics 2006, 25, 693. (b) Esteruelas, M. A.; Hernandez,
ꢀ
ꢀ
~
Y. A.; Lopez, A. M.; Olivan, M.; Onate, E. Organometallics 2007, 26, 2193.

2172 Organometallics, Vol. 29, No. 9, 2010
Batuecas et al.
Scheme 3
elimination reactions in b4 and b5 are favored by the un-
saturated character of these intermediates.27
The reaction of the enol form present in the catalytic
solution with b5 could be responsible for the formation of
the aldol products. The unsaturated character of this inter-
mediate should favor the Markovnikov insertion of the C-C
double bond of the enol into the metal-hydride bond.
Subsequently, the M-CH2CH2CHO unit of the resulting
intermediate b6 could undergo a position isomerization, via
b7, to afford b8. The latter should give the aldol product by
reductive elimination.
Why is the osmium complex 4a, a catalyst precursor, more
efficient than its ruthenium counterpart, 4b, for the isomeri-
zation of primary alcohols, while the latter is more efficient
than the former for the isomerization of secondary alcohols?
This is because osmium is more reducing than ruthenium and
prefers coordination saturation and redox isomers with more
metal-carbon bonds; that is, ruthenium favors intermedi-
ates b4 and b5 and the steps involving reductive elimination
reactions.
rare. Only two palladium complexes containing this group
have been characterized.26 Complex 6 is the first species of
this type isolated from a catalytic solution and is over-
whelming evidence for mechanism b shown in Figure 1,
which is also consistent with eq 4. In agreement with the
relatively high stability of the hydride-η3-hydroxyallyl inter-
mediates, the reaction shown in eq 4 has an inverse kinetic
isotope effect of 0.36 at 333 K. This is strong evidence
supporting that the migration of the hydride ligand from
the osmium atom to the hydroxyallyl group is the rate-
determining step of the isomerization.
Concluding Remarks
This study shows the preparation and characterization of
new half-sandwich osmium and ruthenium derivatives con-
taining cyclopentadienyl ligands with coordinated amine
and phosphoramidite pendant substituents. Furthermore,
it reveals that the osmium complex [Os(η5-C5,κ-N-CpN)-
(CH3CN)2]PF6 is a more efficient catalyst precursor than
its ruthenium counterpart for the redox isomerization of
primary alcohols to aldehydes, while the latter is more
efficient than the former for the redox isomerization of
secondary allylic alcohols to ketones. Complex [Os(η5-
C5,κ-N-CpN)(CH3CN)2]PF6 is more efficient than its Cp
counterpart [Os(η5-Cp)(CH3CN)3]PF6 for the redox isomeri-
zation of both primary and secondary allylic alcohols.
From the catalytic solutions containing [Os(η5-C5,κ-N-
CpN)(CH3CN)2]PF6 and 2-methyl-2-propen-1-ol, the η3-hy-
droxyallyl complex [OsH(η5-C5,κ-N-CpN){η3-CH2C(CH3)-
CHOH}]PF6 has been isolated and characterized by X-ray
diffraction analysis. This supports a π-allyl-metal-hydride
mechanism. However, some modifications should be made
to the classical proposal since the enol form, the released
product from the metal according to this proposal, is not
detected during clean isomerization processes. The enol is
formed in a transitory manner only when the redox isomeri-
zation vies with an aldol reaction. The pendant amine group
appears to increase the stability of the η3-hydroxyallyl inter-
The pendant amine group appears to favor the formation
of the π-allyl-metal-hydride intermediate, probably as a
consequence of the increase of stability resulting from the
N-H O hydrogen bond. In this context, it should be
3 3 3
mentioned that the Cp counterpart [Os(η5-Cp)(CH3-
CN)3]PF6 is a much less efficient catalyst precursor than
4a. For instance, in the presence of 4 mol % of Cp complex,
2-propen-1-ol gives mixtures of propanal and 3-hydroxy-
2-methylpentanal, whereas, after 12 h, the isomerization of
1-hepten-3-ol to 3-heptanone occurs only in 58% yield.
The cycle b of Figure 1 does not rationalize any of the
results of this study. Thus, it should be modified. The clean
isomerization processes do not show the enol as an inter-
mediate species. However significant concentrations of the
enol form are present in a transitory manner when the
isomerization competes with the aldol reaction. This sug-
gests that the enol tautomerization occurs on the coordina-
tion sphere of the metal. Scheme 3 summarizes a proposal
that allows the rationalization of this fact and the aldol
reactions. Once the η3-hydroxyallyl-metal-hydride key inter-
mediate (b3) is formed, it could evolve into a σ-3-hydroxyal-
lyl-metal-hydride species (b4), which could undergo
reductive elimination to give the enol form, regenerating
the catalyst (b1), or alternatively the enol part of the σ-3-
hydroxyallyl group could tautomerize. In the latter case, a
reductive elimination in the resulting intermediate b5 should
directly lead to the carbonyl compounds. The reductive
mediate by means of a N-H O hydrogen bond.
3 3 3
Experimental Section
Materials and General Methods. The preparation of the metal
complexes was carried out using Schlenk tube techniques under
argon with rigorous exclusion of air. Solvents were dried by the
usual procedures and distilled under argon prior to use or
obtained oxygen- and water-free from an MBraun solvent
purification apparatus. The photochemical reactions were per-
formed in a 200 mL quartz immersion well reactor (RQ 400)
with a 400 W medium-pressure mercury lamp. 1H, 31P{1H}, and
13C{1H} NMR spectra were recorded on either a Varian Gemini
2000, a Bruker ARX 300, a Bruker Avance 300 MHz, a Bruker
~
(27) Esteruelas, M. A.; Lahoz, F. J.; Onate, E.; Oro, L. A.; Sola, E.
J. Am. Chem. Soc. 1996, 118, 89.
(26) Ogoshi, S.; Morita, M.; Kurosawa, H. J. Am. Chem. Soc. 2003,
125, 9020.

Article
Organometallics, Vol. 29, No. 9, 2010 2173
Avance 400 MHz, or a Bruker Avance 500 MHz instrument. 1H
chemical shifts are referenced to residual solvent peaks CD2Cl2
(δ = 5.32 ppm) and CD3CN (δ = 1.94 ppm). 13C{1H} chemical
shifts are referenced to residual solvent peaks CD2Cl2 (δ =
53.8 ppm), CD3CN (δ = 1.39, 118.7 ppm), and CDCl3 (δ =
7.25, 77.0 ppm). An external H3PO4 reference was used for
31P{1H} NMR spectra. Coupling constants, J, are given in hertz.
Spectral assignments were achieved by 1H-1H COSY, 1H{31P},
28.0 (s, C5H4CH2), 32.4 (s, NHCH3), 36.1 [s, CH(CH3)2], 52.3
(s, CH2N), 66.2 (s, Cipso-C5H4), 80.4, 81.5 (both s, CH, C5H4),
84.9, 87.3 (both s, CH-arom, p-cymene), 102.1 (s, CH3Cipso
p-cymene), 113.0 [s, (CH3)2CHCipso, p-cymene]. HRMS
,
(electrospray, m/z): calcd for C18H26NRu [M]þ 358.1108; found
358.1091. IR (ATR, cm-1): ν(NH) 3120 (w), ν(PF6) 822 (s).
Anal. Calcd for C18H26F6NRuP CH2Cl2: C 38.85, H 4.80, N
3
2.38. Found: C 38.96, H 4.46, N 2.44.
13C APT, H-13C HSQC, and H-13C HMBC experiments.
Infrared spectra were recorded on a Spectrum One spectrometer
as neat solids or KBr pellets. High-resolution electrospray mass
spectra were acquired using a MicroTOF-Q hybrid quadrupole
time-of-flight spectrometer (Bruker Daltonics, Bremen,
Germany). MALDI-MS measurements were performed on a
reflex time-of-flying instrument (Bruker Daltonics Microflex
analyzer) equipped with a target micro-SCOUT ion source. C,
H, and N analyses were carried out in a Perkin-Elmer 2400
CHNS/O and a Fisons EA-1108 analyzer. Allyl alcohols were
obtained from commercial suppliers. Alcohol 3-methyl-2-bu-
ten-1-ol-1,1-d2 was prepared by following a previously reported
method.28 Complexes [OsCl2(η6-p-cymene)]2 (1a)10w and [Ru-
Cl2(η6-p-cymene)]2 (1b)29 were prepared according to published
methods. (2,20-Biphenol)PCl was prepared from PCl3 and 2,20-
biphenol by following a previously reported procedure.30
Preparation of [Os(η5-CpN)(η6-p-cymene)]PF6 (2a). THF
(30 mL) was added to a mixture of [OsCl2(η6-p-cymene)]2
(1.00 g, 1.26 mmol) and Li(C5H4CH2CH2NHCH3) (0.409 g,
3.162 mmol) and the mixture stirred for 4 h at rt. The solvent was
then removed under vacuum and the residue extracted with
dichloromethane (15 mL). A solution of KPF6 (466 mg, 2.53
mmol) in acetone (15 mL) was then added to the filtrate and the
mixture stirred for 12 h. The solvent was evaporated to dryness,
the residue extracted with dichloromethane (15 mL), and the
filtrate evaporated to dryness to give a brown oil, which was
washed with diethyl ether (3 ꢀ 10 mL) and dried in vacuo (1.19 g,
2.02 mmol, 80% yield). 1H NMR (300 MHz, CD2Cl2, 298 K):
δ 1.29 [d, 3JH,H = 6.9 Hz, 6 H, CH(CH3)2], 2.20 (s, 3 H, CH3,
p-cymene), 2.45 (s, 3 H, NHCH3), 2.50 [t, 3JH,H = 6.6 Hz, 2 H,
CH2(C5H4)], 2.50 (br s, 1 H, NHCH3), 2.61 [sept, 3JH,H = 6.9
Hz, 1 H, CH(CH3)2], 2.71 (t, 3JH,H = 6.6 Hz, 2 H, CH2N), 5.48,
5.60 (both br s, 2 H, C5H4), 6.06 (4 H, CH-arom, p-cymene).
13C{1H} NMR (75.45 MHz, CD2Cl2, 298 K): δ 20.0 (s, CH3, p-
cymene), 23.5 [s, CH(CH3)2], 28.6 (s, C5H4CH2), 32.5 [s, CH-
(CH3)2], 36.3 (s, NHCH3), 53.0 (s, CH2N), 75.8, 76.5 (both s,
CH, C5H4), 78.0, 78.2 (both s, CH-arom, p-cymene), 93.2
(s, -CH3Cipso, p-cymene), 98.1 (s, Cipso-C5H4), 104.1 [s,
(CH3)2CHCipso, p-cymene]. HRMS (electrospray, m/z): calcd
for C18H26NOs [M]þ 448.1675; found 448.1684. IR (ATR,
cm-1): ν(NH) 3119 (w), ν(PF6) 819 (s). Anal. Calcd for
Preparation of [Os(η5-CpP)(η6-p-cymene)]PF6 (3a). A cold
solution (0 °C) of [Os(η5-CpN)(η6-p-cymene)]PF6 (0.5 g, 1.0
mmol) in dichloromethane (8 mL) was added to a stirred
suspension of (2,20-biphenol)PCl (254 mg, 1.01 mmol) and
piperidinomethyl polystyrene (579 mg, 2.02 mmol) in dichloro-
methane (8 mL) at 0 °C. The reaction mixture was stirred for
12 h at room temperature and then filtered through a glass frit.
The filtrate was evaporated to dryness and the residue extracted
with CH3CN. After removal of the solvent, the residue was
washed with diethyl ether (3 ꢀ 10 mL) and dried in vacuo to yield
1
1
1
a pale brown solid (0.511 g, 0.63 mmol, 75% yield). H NMR
3
(300 MHz, CD2Cl2, 298 K): δ 1.16 [d, JH,H = 6.7 Hz, 6 H,
CH(CH3)2], 2.29 (s, 3 H, CH3, p-cymene), 2.39 (t, 3JH,H = 6.6
Hz, 2 H, CH2C5H4), 2.50 (d, 3JP,H = 8.1 Hz, 3 H, NCH3), 2.59
[sept, 3JH,H = 6.6 Hz, 1 H, CH(CH3)2], 3.11 (dt, 3JH,P = 11.0,
3JH,H = 6.6 Hz, 2 H, CH2N), 5.40-5.60 (4 H, C5H4), 5.90-6.20
(4 H, CH-arom, p-cymene), 7.18 (ddd, 3JH,H = 7.6 Hz, 4JH,H
=
=
3
1.3 Hz, JH,P = 1.0 Hz, 2 H, CH-arom), 7.31 (dddd, JH,H
4
3JH,H = 7.6 Hz, JH,H = 1.3 Hz, JH,P = 0.7 Hz, 2 H, p-CH-
arom), 7.40 (ddd, 3JH,H = 3JH,H = 7.6 Hz, 4JH,H = 1.8 Hz, 2 H,
CH-arom), 7.50 (dd, 3JH,H = 7.6 Hz, 4JH,H = 1.8 Hz, 2 H, CH-
arom). 13C{1H} NMR (75.45 MHz, CD2Cl2, 298 K): δ 20.1 (s,
3
CH3, p-cymene), 23.6 [s, CH(CH3)2], 27.4 (d, JC,P = 2.6 Hz,
CH2C5H4), 32.5 [s, CH(CH3)2], 33.0 (d, JC,P = 16.8 Hz,
2
2
NCH3), 50.0 (d, JC,P = 24.0 Hz, CH2N), 75.8, 78.2 (both s,
CH-arom, p-cymene), 76.6, 77.9 (both s, CH, C5H4), 93.2
(s, CH3Cipso, p-cymene), 96.7 (s, Cipso-C5H4), 104.2 [s,
(CH3)2CHCipso, p-cymene], 122.5, 125.3, 130.0, 130.2 (all s,
3
CH-arom), 131.3 (d, JC,P = 3.0 Hz, Cipso-arom), 151.8 (d,
2JC,P = 5.0 Hz, COP-arom). 31P{1H} NMR (121.479 MHz,
CD3CN, 298 K): δ 149.8 (s). HRMS (electrospray, m/z): calcd
for C30H33NO2OsP [M]þ 662.1860; found 662.1906. Anal.
Calcd for C30H33F6NO2OsP2 0.5C4H10O: C 45.60, H 4.54, N
3
1.66. Found: C 45.69, H 4.12, N 1.71.
Preparation of [Ru(η5-CpP)(η6-p-cymene)]PF6 (3b). Complex
3b was prepared from [Ru(η5-CpN)(η6-p-cymene)]PF6 (0.5 g,
1.0 mmol), (2,20-biphenol)PCl (299 mg, 1.2 mmol), and piper-
idinomethyl polystyrene (686 mg, 2.4 mmol) in dichloro-
methane at 0 °C following an identical procedure to that
described for the synthesis of [Os(η5-CpP)(η6-p-cymene)]PF6
(3a). A pale brown solid was obtained (0.487 g, 0.68 mmol,
1
C18H26F6NOsP CH2Cl2: C 33.73, H 4.17, N 2.07. Found: C
3
68% yield). H NMR (300 MHz, CD3CN, 298 K): δ 1.19 [d,
3JH,H = 6.9 Hz, 6 H, CH(CH3)2], 2.22 (s, 3 H, CH3, p-cymene), 2.42
(t, 3JH,H = 7.0 Hz, 2 H, CH2C5H4), 2.55 (d, 3JP,H = 7.3 Hz, 3 H,
NCH3), 2.64 [sept, JH,H = 6.9 Hz, 1 H, CH(CH3)2], 3.16 (dt,
34.01, H 4.06, N 2.13.
Preparation of [Ru(η5-CpN)(η6-p-cymene)]PF6 (2b). Complex
2b was synthesized from [RuCl2(η6-p-cymene)]2 (1.00 g, 1.63
mmol) and Li(C5H4CH2CH2NHCH3) (0.528 g, 4.075 mmol)
following an identical procedure to that described for the
synthesis of [Os(η5-CpN)(η6-p-cymene)]PF6 (2a). Yield: 81%
3
3JP,H = 11.2, 3JH,H = 7.0 Hz, 2 H, CH2N), 5.13-5.23 (4 H, C5H4),
3
5.90-5.97 (4 H, CH-arom, p-cymene), 7.18 (ddd, JH,H = 7.6,
4JH,H = 1.3, JH,P = 1.0 Hz, 2 H, CH-arom), 7.30 (dddd, 3JH,H
=
1
3JH,H = 7.6, 4JH,H = 1.3, JH,P = 0.7 Hz, 2 H, p-CH-arom), 7.41
(ddd, 3JH,H = 3JH,H = 7.6, 4JH,H = 1.8 Hz, 2 H, CH-arom), 7.52
(dd, 3JH,H = 7.6, 4JH,H = 1.8 Hz, 2 H, CH-arom). 13C{1H} NMR
(75.45 MHz, CD3CN, 298 K): δ 19.7 (s, CH3, p-cymene), 23.5 [s,
(CH3)2CH],27.2(d,3JC,P =3.0Hz,CH2C5H4),32.5(s,NCH3),32.6
[s, CH(CH3)2], 50.1 (d, 2JC,P = 28.6 Hz, CH2N), 80.9, 82.0 (both s,
(1.33 g, 2.65 mmol). H NMR (400 MHz, CD2Cl2, 298 K): δ
1.18 [d, 3JH,H = 7.0 Hz, 6 H, CH(CH3)2], 2.21 (s, 3 H, CH3, p-
cymene), 2.33 (s, 3 H, NHCH3), 2.34 (t, JH,H = 7.1 Hz, 2 H,
3
CH2C5H4), 2.62 [sept, 3JH,H = 7.0 Hz, 1 H, CH(CH3)2], 2.64 (t,
3JH,H = 7.1 Hz, 2 H, CH2N), 4.5 (s, 1 H, NHCH3), 5.08, 5.17
(both br s, 2 H, C5H4), 5.92 (AB spin system, Δν = 8.70, JAB
=
6.34, 4 H, CH-arom, p-cymene). 13C{1H} NMR (75.45 MHz,
CD2Cl2, 298 K): δ 19.9 (s, CH3, p-cymene), 23.6 [s, CH(CH3)2],
CH, C5H4), 85.2, 87.6 (both s, CH-arom, p-cymene), 101.2 (s, Cipso-
C5H4), 102.1 (s, CH3Cipso, p-cymene), 113.0 [s, (CH3)2CHCipso, p-
cymene], 122.8, 125.8, 130.5, 130.7 (all s, CH-arom), 131.6 (s, Cipso
-
2
arom), 152.1 (d, JC,P = 4.8 Hz, COP-arom). 31P{1H} NMR
(28) Vassilikogiannakis, G.; Chronakis, N.; Orfanopoulos, M. J. Am.
Chem. Soc. 1998, 120, 9911.
(29) Bennett, M. A.; Smith, A. K. J. Chem. Soc., Dalton Trans. 1974,
233.
(30) Bartels, B.; Garcıa-Yebra, C.; Rominger, F.; Helmchen, G. Eur.
(121.479 MHz, CD3CN, 298 K): δ 148.2 (s). HRMS (electrospray,
m/z): calcd for C30H33NO2PRu [M]þ 572.1295; found 572.1327.
Anal. Calcd for C30H33F6NO2P2Ru: C 50.28, H 4.64, N 1.95. Found:
C 49.94, H 4.99, N 2.03.
J. Inorg. Chem. 2002, 2569.

2174 Organometallics, Vol. 29, No. 9, 2010
Batuecas et al.
2
Preparation of [Os(η5-C5,K-N-CpN)(CH3CN)2]PF6 (4a). An
acetonitrile (200 mL) solution of [Os(η5-CpN)(η6-p-cymene)]PF6
(1.0 g, 1.69 mmol) and biphenyl (2.42 g, 15.73 mmol) was placed
in a photochemical reactor and irradiated with a 400 W med-
ium-pressure mercury lamp for 6 h at -5 °C. After removal of
the solvent, the residue was chromatographed on neutral alu-
minum oxide (activity V) with a mixture of CH3CN/Et2O
(85:15) as eluent. The resulting yellow solution was then evapo-
rated to dryness and the residue washed with diethyl ether (3 ꢀ
10 mL) and dried in vacuo to yield a yellow microcrystalline solid
(401 mg, 0.74 mmol, 44% yield). 1H NMR (300 MHz, CD2Cl2,
298 K): δ 2.03 (m, 1 H, -CH2-), 2.21 (m, 1 H, -CH2-), 2.56,
151.5 (d, JC,P = 10.7 Hz, COP-arom). 31P{1H} NMR (121.479
MHz, CD2Cl2, 298 K): δ 114.4 (s). HRMS (electrospray, m/z):
calcd for C22H22N2O2OsP [M - CH3CN]þ 569.1029; found
569.1046; calcd for C20H19NO2OsP [M - 2(CH3CN)]þ 528.0763;
found 528.0780. IR (ATR, cm-1): ν(NC) 2280 (w), ν(PF6) 834 (s).
Anal. Calcd for C24H25F6N3O2OsP2: C 38.25, H 3.34, N 5.58.
Found: C 38.73, H 3.20, N 5.75.
Preparation of [Ru(η5-C5,K-P-CpP)(CH3CN)2]PF6 (5b). An
acetonitrile (200 mL) solution of [Ru(η5-CpP)(η6-p-cyme-
ne)]PF6 (300 mg, 0.419 mmol) was placed in a photochemical
reactor and irradiated with a 400 W medium-pressure mercury
lamp for 6 h at -5 °C. Complex 5b was isolated and purified
following an identical procedure to that described for [Os(η5-
C5,κ-P-CpP)(CH3CN)2]PF6 (5a) and obtained as a white solid
(111 mg, 0.167 mmol, 40% yield). 1H NMR (300 MHz, CD2Cl2,
298 K): δ 2.08 (s, 6 H, NCCH3), 2.15-2.22 (2 H, CH2C5H4), 2.58
3
2.58 (both s, 3 H, NCCH3), 2.72 (d, JH,H = 6.1 Hz, 3 H,
NHCH3), 3.24 (m, 1 H, -CH2-), 3.87 (m, 1 H, -CH2-), 4.10,
4.22, 4.74, 4.78 (ABCD system, all br s, 1 H, C5H4), 5.34 (br s,
1 H, NHCH3). 13C{1H} NMR (75.45 MHz, CD2Cl2, 298 K): δ
4.02, 4.18 (both s, NCCH3), 27.1 (s, CH2C5H4), 41.5 (s,
NHCH3), 52.1, 58.7, 60.0, 68.3 (all s, CH, C5H4), 72.1 (s,
-CH2N), 96.6 (s, Cipso-C5H4), 121.6, 122.8 (both s, NCCH3).
HRMS (electrospray, m/z): calcd for C10H15N2Os [M -
CH3CN]þ 355.0845; found 355.0871; calcd for C8H12NOs [M
- 2CH3CN]þ 314.0579; found 314.0586. IR (ATR, cm-1):
ν(NH) 3293 (w), ν(NC) 2273 (w), ν(PF6) 825 (s). Anal. Calcd
for C12H18F6N3OsP: C 26.72, H 3.36, N 7.79. Found: C 26.63, H
3.55, N 7.80.
3
(d, JP,H = 6.0 Hz, 3 H, NCH3), 3.09-3.23 (2 H, CH2N),
4.31-4.37 (2 H, C5H4), 5.18-5.24 (2 H, C5H4), 7.22 (ddd,
3JH,H = 7.6, 4JH,H = 1.0, JH,P = 1.1 Hz, 2 H, CH-arom), 7.37
(dddd, 3JH,H = 3JH,H =7.6, 4JH,H =1.0, JP,H = 1.0 Hz, 2 H, CH-
arom), 7.48 (ddd, 3JH,H = 3JH,H = 7.6, 4JH,H = 1.7 Hz, 2 H, CH-
arom), 7.60 (dd, 3JH,H = 7.6, 4JH,H = 1.7 Hz, 2 H, CH-arom).
13C{1H} NMR (75.45 MHz, CD2Cl2, 298 K): δ 4.3 (s, NCCH3),
2
25.1 (s, CH2C5H4), 36.7 (d, JC,P = 5.6 Hz, NCH3), 55.1 (d,
2JC,P = 27.8 Hz, CH2N), 71.5 (s, CH, C5H4), 85.6 (d, JC,P = 9.1
Hz, CH, C5H4), 94.5(s, Cipso-C5H4), 122.8 (d, 4JC,P = 3.0 Hz, CH-
arom), 126.0 (s, CH-arom), 127.7 (s, NCCH3), 130.1 (s, CH-
Preparation of [Ru(η5-C5,K-N-CpN)(CH3CN)2]PF6 (4b). An
acetonitrile (200 mL) solution of [Ru(η5-CpN)(η6-p-cyme-
ne)]PF6 (665 mg, 1.32 mmol) was placed in a photochemical
reactor and irradiated with a 400 W medium-pressure mercury
lamp for 6 h at -5 °C. Complex 4b was isolated and purified
following an identical procedure to that described for [Os(η5-
C5,κ-N-CpN)(CH3CN)2]PF6 (4a) and obtained as a yellow solid
(594 mg, 0.55 mmol, 42% yield). 1H NMR (300 MHz, CD2Cl2,
298 K): δ 2.10-2.27 (2 H, CH2), 2.39 (s, 6 H, NCCH3), 2.46 (d,
3JH,H = 6.5 Hz, 3 H, NHCH3), 3.27 (m, 1 H, CH2), 3.62 (m, 1 H,
CH2), 3.75 (br s, 1 H, NHCH3), 3.85, 3.96, 4.15, 4.30 (ABCD
system, all br s, 1 H, C5H4). 13C{1H} NMR (75.45 MHz,
CD2Cl2, 298 K): δ 4.20, 4.25 (both s, NCCH3), 27.7 (s,
CH2C5H4), 41.1 (s, NHCH3), 67.7 (s, CH2N), 57.4, 62.9, 67.0,
74.6 (all s, CH, C5H4), 102.5 (s, Cipso-C5H4), 125.9, 126.6 (both s,
NCCH3). HRMS (electrospray, m/z): calcd for C10H15N2Ru [M
- CH3CN]þ 265.0276; found 265.0252; calcd for C8H12NRu [M
- 2CH3CN]þ 224.0010; found 223.9977. IR (ATR, cm-1):
ν(NH) 3299 (w), ν(NC) 2276 (w), ν(PF6) 831 (s). Anal. Calcd
for C12H18F6N3PRu: C 32.01, H 4.03, N 9.33. Found: C 32.57,
H 3.95, N 9.09.
arom), 130.5 (s, CH-arom), 130.6 (s, Cipso-arom), 151,4(d, 2JC,P
=
10.6 Hz, COP-arom). 31P{1H} NMR (121.479 MHz, CD2Cl2, 298
K): δ 168.9 (s). HRMS (electrospray, m/z): calcd for C22H22N2O2-
PRu [M - CH3CN]þ 479.0463; found 479.0497; calcd for
C20H19NO2PRu [M - 2(CH3CN)]þ 438.0197; found 438.0232.
IR (ATR, cm-1): ν(NC) 2284 (w), ν(PF6) 832 (s). Anal. Calcd for
C24H25F6N3O2P2Ru: C 43.38, H 3.79, N 6.32. Found: C 43.60, H
3.66, N 6.30.
Preparation of [OsH(η5-C5,K-N-CpN){η3-CH2C(CH3)CH-
(OH)}]PF6 (6). A solution of [Os(η5-C5,κ-N-CpN)(CH3CN)2]PF6
(100 mg, 0.185 mmol) and 2-methyl-2-propen-1-ol (78 μL, 0.926
mmol) in THF (3 mL) was stirred for 10 min at 60 °C. The solvent
was then removed al 0 °C and the residue obtained washed with
diethyl ether (3 ꢀ 3 mL) and dried under vacuum to give a light
brown solid (61 mg, 0.115 mmol, 62% yield). 1H NMR (400 MHz,
CD2Cl2, 253 K): δ -12.20 (s, 1 H, Os-H), 2.37, 2.47 (both m, 1 H,
CH2C5H4), 2.61 [s, 3 H, CH2C(CH3)CH(OH)], 2.74 [s, 1 H,
CH2C(CH3)CH(OH)], 2.86 (d, JH,H = 5.0 Hz, 3 H, NHCH3),
3.22 [s, 1 H, CH2C(CH3)CH(OH)], 3.58, 3.76 (both m, 1 H,
-CH2N), 4.19 (br s, 1 H, NHCH3), 4.21, 5.20, 6.27, 6.51
(ABCD system, all br s, 1 H, C5H4), 4.69 [s, 1 H, CH2C(CH3)CH-
(OH)], 6.91 [s, 1 H, CH2C(CH3)CH(OH)]. 13C{1H} NMR (125.75
MHz, CD2Cl2, 253 K): δ 16.3 [s, CH2C(CH3)CH(OH)], 17.4 [s,
CH2C(CH3)CH(OH)], 24.6 (s, CH2C5H4), 52.7 (s, NHCH3), 68.0
(s, CH, C5H4), 74.3 (s, -CH2N), 78.4 [s, CH2C(CH3)CH(OH)],
81.6, 81.7 (both s, CH, C5H4), 92.5 (s, CH, C5H4), 93.0 [s, CH2C-
(CH3)CH(OH)], 122.2 (s, Cipso-C5H4). MS (MALDI-TOF): m/z
386 (100), [M þ H]þ. IR (KBr, cm-1): ν(OsH) 2079 (w), ν(PF6)
842 (s). Anal. Calcd for C12H19F6NOOsP: C 27.27, H 3.62, N 2.65.
Found: C 27.79, H 3.44, N 2.77.
Typical Procedure for Catalytic Isomerization of Allylic Alco-
hols. The required amount of catalyst and THF-d8 (0.5 mL) as
solvent were placed in an NMR tube. Then, the corresponding
allylic alcohol (0.4 mmol) was added to the solution, and the
course of the reactions was monitored by 1H NMR at 60 °C.
Determination of the Kinetic Isotope Effect (KIE). The iso-
merizations of 3-methyl-2-buten-1-ol and 3-methyl-2-buten-1-
ol-1,1-d2 were performed by following the typical procedure
described above and followed by 1H NMR spectroscopy in
THF-d8 at 333 K and constant concentrations of the osmium
catalyst 4a (0.032 M). The decrease of the intensity (I) of a
chosen signal corresponding to the substrate, related to an
internal patron, vs the time (min) fits an exponential decay
Preparation of [Os(η5-C5,K-P-CpP)(CH3CN)2]PF6 (5a). An
acetonitrile (200 mL) solution of [Os(η5-CpP)(η6-p-cymene)]PF6
(300 mg, 0.372 mmol) and biphenyl (533 mg, 3.46 mmol) was
placed in a photochemical reactor and irradiated with a 400 W
medium-pressure mercury lamp for 6 h at -5 °C. After removal
of the solvent, the residue was chromatographed on neutral
aluminum oxide (activity V) with a mixture of CH3CN/Et2O
(85:15) as eluent. The resulting yellow solution was then evapo-
rated to dryness and the residue washed with diethyl ether (3 ꢀ
10 mL) and dried under vacuum to yield a white solid (112 mg,
0.149 mmol, 40% yield). 1H NMR (300 MHz, CD2Cl2, 298 K): δ
2.23-2.30 (2 H, CH2C5H4), 2.36 (d, JH,P = 1.6 Hz, 6 H,
3
NCCH3), 2.56 (d, JP,H = 6.4 Hz, 3 H, NCH3), 3.05-3.19
(2 H, CH2N), 4.68-4.70 (2 H, C5H4), 5.33-5.36 (2 H, C5H4), 7.26
(ddd, 3JH,H = 7.8, 4JH,H = 1.3, JH,P = 1.3 Hz, 2 H, CH-arom),
7.37 (dddd, 3JH,H = 7.8, 3JH,H = 7.8, 4JH,H = 1.3, JH,P = 1.3 Hz, 2
H, CH-arom), 7.48 (ddd, 3JH,H = 3JH,H = 7.6, 4JH,H = 1.7 Hz,
2 H, CH-arom), 7.60 (dd, 3JH,H = 7.6 Hz, 4JH,H = 1.7 Hz, 2 H,
CH-arom). 13C{1H} NMR (75.45 MHz, CD2Cl2, 298 K): δ 4.6 (s,
NCCH3), 24.9 (d, 2JC,P = 1.8 Hz, CH2C5H4), 36.7 (d, 2JC,P = 4.3
Hz, NCH3), 55.8 (d, 2JC,P = 23.6 Hz, CH2N), 66.1 (s, CH, C5H4),
83.7 (d, JC,P = 9.7 Hz, CH, C5H4), 92.3 (s, Cipso-C5H4), 122.8 (d,
4JC,P = 3.0 Hz, CH-arom), 122.9 (s, NCCH3), 125.9 (s, CH-arom),
130.0 (s, CH-arom), 130.5 (s, CH-arom), 130.6 (s, Cipso-arom),

Article
Organometallics, Vol. 29, No. 9, 2010 2175
function. Ln(Io/I) (where Io represents the first measured in-
tensity value) vs time fits a linear function from which kobsH for
3-methyl-2-buten-1-ol and kobsD for 3-methyl-2-buten-1-ol-1,1-
d2 can be obtained. The kobsH/kobsD gives a KIE value of 0.36.
Structural Analysis of Complexes 4a and 6. X-ray data were
collected on a Bruker Smart APEX CCD diffractometer
equipped with a normal focus, 2.4 kW sealed tube source (Mo
T = 150(2) K, μ = 7.891 mm-1; 17 316 measured reflections (2θ:
3-58°, ω scans 0.3°), 2163 unique (Rint = 0.0317); min./max.
transmn factors 0.451/0.570. Final agreement factors were R1 =
0.0361 (2013 observed reflections, I > 2σ(I)) and wR2 = 0.0938;
data/restraints/parameters 2163/18/135; GoF = 1.086. Largest
3
˚
peak and hole: 1.617 and -1.420 e/A .
Crystal data for 6: C12H20NO2Os PF6 OC4H8, Mw 601.56,
irregular block, yellow (0.08 ꢀ 0.06 ꢀ 0.02), orthorhombic, space
3
3
˚
radiation, λ = 0.71073 A) operating at 50 kV and 30 (4a)/40 (6)
˚
˚
˚
mA. Data were collected over the complete sphere by a combi-
nation of four sets. Each frame exposure time was 10 s (4a)/20 s
(6), covering 0.3° in ω. Data were corrected for absorption by
using a multiscan method applied with the SADABS program.31
The structures were solved by the Patterson method. Refine-
ment of both complexes was performed by full-matrix least-
squares on F2 with SHELXL97,32 including isotropic and sub-
sequently anisotropic displacement parameters. For 4a, the
pendant amine group of the Cp ligand and the PF6 anion were
observed disordered about a plane of symmetry. All the highest
electronic residuals were observed in close proximity to the
metal centers and make no chemical sense.
group Pna21, a = 12.497(2) A, b = 19.794(4) A, c = 8.1791(15) A,
V = 2023.2(7) A , Z = 4, Dcalc = 1.975 g cm-3, F(000) = 1168,
3
˚
T = 100(2) K, μ = 6.446 mm-1; 18 640 measured reflections (2θ:
3-58°,ωscans 0.3°), 4917 unique (Rint = 0.0668); min./max. transmn
factors 0.583/0.882. Final agreement factors were R1 = 0.0433 (4055
observed reflections, I > 2σ(I)) and wR2 = 0.0781; data/restraints/
parameters 4917/2/257; GoF = 1.041. Largest peak and hole: 1.086
3
˚
and -2.281 e/A . Absolute structure parameter was 0.000(11).
Acknowledgment. Financial support from the Spanish
MICINN (Projects CTQ2008-00810 and Consolider Ingenio
2010 CDS2007-00006) and the DGA (E35) is acknowledged.
C.G.-Y. thanks the Spanish MEC and the University of
Crystal data for 4a: C12H18N3Os PF6, Mw 539.46, irregular
block, yellow (0.12 ꢀ 0.08 ꢀ 0.08), orthorhombic, space group
3
ꢀ
Zaragoza for funding through the “Ramon y Cajal” pro-
˚
˚
˚
Pbcm, a = 7.2245(19) A, b = 13.747(4) A, c = 16.602(4) A,
gram. M.B. thanks the Spanish MICINN for a pre-
doctoral fellowship.
V = 1648.8(8) A , Z = 4, Dcalc = 2.173 g cm-3, F(000) = 1024,
3
˚
(31) Blessing, R. H. Acta Crystallogr. 1995, A51, 33. SADABS: Area-
detector absorption correction; Bruker-AXS: Madison, WI, 1996.
(32) SHELXTL Package v. 6.10; Bruker-AXS: Madison, WI, 2000.
Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112.
Supporting Information Available: CIF files giving crystal
data for compounds 4a and 6. This material is available free of
charge via the Internet at http://pubs.acs.org.