C-C formation and C-O cleavage reactions on hemilabile arene-phosphine ligands in route to η5-Cyclohexadienyl iridium compounds

Article abstract of DOI:10.1021/om800402n

Complexes of the type [Ir{η⁵-3-(CH₃COCH ₂)C₆H₅OCH₂CH₂Pt-Bu ₂-k-P}(alkene)] (alkene = C₂H₄, 4, C ₃H₆, 5) were prepared by nucleophilic addition of acetone enolate to the ansa π-arene/phosphine-type compounds [Ir(alkene)(η⁶-C₆H₅OCH₂CH ₂Pt-Bu₂-k-P)] [BF₄] (alkene = C ₂H₄,1, C₃H₆, 2) where the arene-phosphine is acting as a formal eight-electron-donor chelate ligand. On the other hand, the related [Ir{η⁵-3-(C₆H ₅C=C)C₆H₅OCH₂CH₂Pt- Bu₂-/t-P}(C₂H₄)] complex (6) was obtained by addition of phenylacetylide to compound 1, but the reaction was not fully completed. Compounds 4 and 5 react with methanol with a C-O bond cleavage process, producing the vinylphosphine complexes [Ir(η⁵-C ₆H⁵O)(alkene)(t-Bu₂PCH=CH₂)] (alkene = C₂H₄, 7, C₃H₆, 8). Compounds 7 and 8 are also obtained by treatment of 1 and 2, respectively, with a basic solution in methanol. The vinyl group in 7 adds methanol to render an ether phosphine, which coordinates in a chelate form, and the final compound isolated was [Ir(OC₆H₅)(C₂H₄)(t-Bu ₂PCH₂CH₂OMe-k²-O,P)] (9). In addition, the molecular structures of complexes 4 and 7 have been determined by X-ray diffraction methods.

Full text of DOI:10.1021/om800402n

Organometallics 2008, 27, 4229–4237
4229
C-C Formation and C-O Cleavage Reactions on Hemilabile
Arene-Phosphine Ligands in Route to η5-Cyclohexadienyl Iridium
Compounds§
M. Victoria Jime´nez,* I. Idalia Rangel-Salas,† Fernando J. Lahoz, and Luis A. Oro*
Departamento de Qu´ımica Inorga´nica, Instituto UniVersitario de Cata´lisis Homoge´nea, Instituto de
Ciencia de Materiales de Arago´n, UniVersidad de Zaragoza-CSIC, 50009-Zaragoza, Spain
ReceiVed May 6, 2008
Complexes of the type [Ir{η5-3-(CH3COCH2)C6H5OCH2CH2Pt-Bu2-k-P}(alkene)] (alkene ) C2H4, 4,
C3H6, 5) were prepared by nucleophilic addition of acetone enolate to the “ansa” π-arene/phosphine-
type compounds [Ir(alkene)(η6-C6H5OCH2CH2Pt-Bu2-k-P)][BF4] (alkene ) C2H4, 1, C3H6, 2) where the
arene-phosphine is acting as a formal eight-electron-donor chelate ligand. On the other hand, the related
[Ir{η5-3-(C6H5CtC)C6H5OCH2CH2Pt-Bu2-k-P}(C2H4)] complex (6) was obtained by addition of phe-
nylacetylide to compound 1, but the reaction was not fully completed. Compounds 4 and 5 react with
methanol with a C-O bond cleavage process, producing the vinylphosphine complexes [Ir(η5-
C6H5O)(alkene)(t-Bu2PCHdCH2)] (alkene ) C2H4, 7, C3H6, 8). Compounds 7 and 8 are also obtained
by treatment of 1 and 2, respectively, with a basic solution in methanol. The vinyl group in 7 adds
methanol to render an ether phosphine, which coordinates in a chelate form, and the final compound
isolated was [Ir(OC6H5)(C2H4)(t-Bu2PCH2CH2OMe-k2-O,P)] (9). In addition, the molecular structures of
complexes 4 and 7 have been determined by X-ray diffraction methods.
hemilabile character.5 It is noticeable that η6-arene/free arene
exchange reactions have been studied in detail by Mirkin6 with
the phosphine PhO(CH2)2PPh2. Werner5c has found that unsat-
urated monomeric species such as [MCl(PR3)2] (M ) Rh, Ir)
are accessible both with Pi-Pr3 and with the aryl-functionalized
phosphines i-Pr2P(CH2)n(aryl) and t-Bu2P(CH2)n(aryl) (n ) 2
or 3), both related in terms of size with Pi-Pr3. However,
interesting differences in reactivity were observed with these
aryl-functionalized phosphines compared with the monodentate
Pi-Pr3, as is the case, for instance, of the reversible C-H
activation of the aryl moiety,7,8 the stabilization of a cis-rhodium
dicarbonyl [RhCl(t-Bu2P(CH2)2C6H3-2,6-Me2)(CO)2],9 or the
formation of a dinuclear rhodium(III) complex built up by two
14-electron units.10
Introduction
Functionalized phosphines have been intensively studied,1 as
they could behave as hemilabile ligands during catalysis, either
providing easily accessible coordination vacancies or protecting
the active catalytic site, with a potentially dynamic “on and off”
chelating effect for the metal complex. Hybrid P,O-2 and P,N-
based ligands3 have been the most investigated since P usually
binds strongly to the metal center, whereas the other donor atom
(O or N) is generally only weakly bonded.
Half-sandwich metal-arene complexes are an important and
widely used class of organometallic compounds, which exhibit
a diverse range of coordination chemistry and show considerable
potential as precursors for catalytic organic transformations.4
To stabilize otherwise elusive or coordinatively unsaturated
species, recent work on half-sandwich metal-arene complexes
has mainly concentrated on arene-tethered ligands, the arene-
tethered phosphine with a flexible linkage being the most
popular. Thus, much attention has been paid to ligands such as
R2P(CH2)nXC6H4R (n ) 1, 2; X ) CH2, O), which could behave
as either two-electron or (2+6)-electron donors, thus having a
(4) See for example: (a) Melchart, M.; Habtemariam, A.; Novakova,
O.; Moggach, S. A.; Fabbiani, F. P. A.; Parsons, S.; Brabec, V.; Sadler,
P. J. Inorg. Chem. 2007, 46, 8950–8962. (b) Orian, L.; van Stralen, J. N. P.;
Bickelhaupt, F. M. Organometallics 2007, 26, 3816–3830. (c) Dann, S. E.;
Durran, S. E.; Elsegood, M. R. J.; Smith, M. B.; Staniland, P. M.; Talib,
S.; Dale, S. H. J. Organomet. Chem. 2006, 691, 4829–4842. (d) Werner,
H. Organometallics 2005, 24, 1036–1049. (e) Kleinschmidt, R.; Griebenow,
Y.; Fink, G. J. Mol. Catal. A: Chem. 2000, 157, 83–90. (f) Carmona, D.;
Vega, C.; Lahoz, F. J.; Atencio, R.; Oro, L. A.; Lamata, M. P.; Viguri, F.;
San Jose´, E. Organometallics 2000, 19, 2273–2280.
(5) (a) Chaplin, A. B.; Dyson, P. J. Organometallics 2007, 26, 2447–
2455. (b) Umezawa-Vizzini, K.; Lee, T. R. Organometallics 2004, 23, 1448–
1452. (c) Werner, H. Dalton Trans. 2003, 3829–3837.
(6) (a) Singewald, E. T.; Shi, X.; Mirkin, C. A.; Schofer, S. J.; Stern,
C. L. Organometallics 1996, 15, 3062–3069. (b) Singewald, E. T.; Mirkin,
C. A.; Stern, C. L. Angew Chem., Int. Ed. Engl. 1995, 34, 1624–1626.
(7) Canepa, G.; Brandt, C. D.; Werner, H. Organometallics 2001, 20,
604–606.
§ Dedicated to Heinrich Nöth on the occasion of his 80th birthday.
* Corresponding authors. E-mail: oro@unizar.es; vjimenez@unizar.es.
† Present address: Divisio´n Acade´mica de Ciencias Ba´sicas, Universidad
Jua´rez Auto´noma de Tabasco, Cunduaca´n, Tab., 86690, Me´xico.
(1) (a) Chen, G.; Lam, W. H.; Fok, W. S.; Lee, H. W.; Kwong, F. Y.
Chem. Asian J. 2007, 2, 306–313. (b) Chikkali, S.; Gudat, D.; Niemeyer,
M. Chem. Commun. 2007, 981–983. (c) Grotjahn, D. B.; Gong, Y.;
Zakharov, Y. G. L.; Golen, J. A.; Rheingold, A. L. J. Am. Chem. Soc. 2006,
128, 438–453. (d) Moxham, G. L.; Randell-Sly, H. E.; Brayshaw, S. K.;
Woodward, R. L.; Weller, A. S.; Willis, M. C. Angew. Chem., Int. Ed.
2006, 45, 7618–7622. (e) Braunstein, P. Chem. ReV. 2006, 106, 134–159.
(2) (a) Braunstein, P.; Naud, F. Angew. Chem., Int. Ed. 2001, 40, 680–
699. (b) Braunstein, P.; Knorr, M.; Stern, C. Coord. Chem. ReV. 1998, 178-
180, 903–965. (c) Bader, A.; Lindner, E. Coord. Chem. ReV. 1991, 108,
27–110.
(8) Canepa, G.; Sola, E.; Mart´ın, M.; Lahoz, F. J.; Oro, L. A.; Werner,
H. Organometallics 2003, 22, 2151–2160.
(9) Canepa, G.; Brandt, C. D.; Werner, H. Organometallics 2004, 23,
1140–1152.
(3) Espinet, P.; Soulantica, K. Coord. Chem. ReV. 1999, 193-195, 499–
556.
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124, 9666–9667.
10.1021/om800402n CCC: $40.75
2008 American Chemical Society
Publication on Web 07/31/2008

4230 Organometallics, Vol. 27, No. 16, 2008
Jime´nez et al.
Scheme 1
compared to a possible C-O bond formed through the nucleo-
philic addition of methoxide (MeO-) to the arene.15
Compounds 4 and 5 do not behave as conductors in acetone
and have been fully characterized by elemental analysis, mass
spectrometry, and multinuclear NMR spectroscopy. In addition,
the molecular structure of complex 4 has been determined by
X-ray diffraction methods and confirms the regioselective meta
attack of the nucleophilic addition. The 2-oxo-propyl fragment
1
was clearly identified in the H NMR spectrum by a complex
resonance characteristic of the methylenic protons at δ 1.68 (4)
and 1.85 (5) ppm as the AB part of an ABX system (X ) H3
of the alkoxy-η5-cyclohexadienyl fragment). The carbonyl group
was observed at 1710 cm-1, ν(CdO) stretching, in the IR
spectrum and at δ 204.49 ppm in the 13C{1H} NMR. The
alkoxy-η5-cyclohexadienyl fragment showed a characteristic set
In spite of several aryloxy-tethered bis-phosphines having
found applications in the design of metallomacrocycles,11 less
attention has been paid to the reactivity of metal complexes
containing aryloxy-tethered phosphines of the type R2P-
(CH2)n-OC6H4R.6,8,12 Their particular reactivity concerns the
ortho-selective functionalization of phenols,13 as the presence
of the oxygen atom can promote the activation of the aryl
group, providing potentially novel reactivity.
In this paper, we report the reactivity of cationic Ir(I) and
Ir(III) complexes, [Ir(alkene)(η6-C6H5O(CH2)2Pt-Bu2-k-P)][BF4]
(alkene ) C2H4, C3H6) and [IrH2(η6-C6H5O(CH2)2Pt-Bu2-k-
P)][BF4],8 containing the phosphine t-Bu2P(CH2)2(OC6H5).14
The aryloxy-alkylphosphine in these complexes is coordinated
in an “ansa” π-arene/phosphine fashion, acting as a formal eight-
electron-donor ligand. In general, the reactivity toward nucleo-
philes gives rise to new neutral alkoxy-η5-cyclohexadienyl
phosphine iridium compounds resulting from nucleophilic
addition to the arene ring. Interestingly, along with the C-C
coupling reactions, where the whole phenoxy-tethered phosphine
remains coordinated to the iridium, a C-O bond cleavage has
been observed in the ligand to form oxo-η5-cyclohexa-
dienyl-vinylphosphine iridium complexes.
1
of five resonances in the H NMR16 for the ring very much
high-field shifted compared to those of the starting complexes
1 and 2. Full assignment of the proton and carbon resonances
of the new ligand was achieved by a combination of the 1H-1H
COSY and correlation 1H-13C HSQC NMR spectra (Figure 1,
compound 4). Interestingly, the H3 resonance was observed as
a complex pattern resulting from the coupling to the two
methylenic protons of the 2-oxo-propyl fragment, the two
adjacent CH protons (H2 and H4), and the phosphorus atom.
Similarly, the C4 resonance was observed as a doublet around
35 ppm in the 13C{1H} NMR, exhibiting a large coupling
constant (JC4-P ≈ 28 Hz), in agreement with the relative transoid
disposition to the Pt-Bu2 fragment observed in the molecular
structure (Figure 2).
Coordination to a metal imparts significant electrophilic
character to a coordinated cyclic π-hydrocarbon. Its reaction
with nucleophiles could include multiple possibilities as single
or double addition to the coordinated ring, substitution of a ring
substituent, deprotonation of the coordinated ring or of the side
chain, ligand substitution, or a single electron transfer.17 In
addition, when olefins are coordinated simultaneously together
with a cyclic π-hydrocarbon, the nucleophilic attack takes place
preferably at the alkene,18 although this is not a general rule as
in [Ru(C6H6)(PMe3)2(C2H4)]2+, where another PR3 (R ) Me,
i-Pr, Ph, OMe) added attacks the coordinated ethylene, but hard
bases such as LiMe, NaMeO, and LiMe lead to nucleophilic
addition to the arene.19
Results and Discussion
Reaction of Iridium(I) Phenoxy-Phosphine Derivatives
[Ir(alkene)(η6-C6H5O(CH2)2Pt-Bu2-k-P)][BF4] (1, 2) with
Nucleophiles. The alkene Ir(I) complexes [Ir(C2H4)(η6-
C6H5O(CH2)2Pt-Bu2-k-P)][BF4](1)and[Ir(C3H6)(η6-C6H5O(CH2)2Pt-
Bu2-k-P)][BF4] (2), containing the “ansa” π-arene/phosphine
ligand, were prepared by reaction of [IrH2(η6-C6H5O(CH2)2Pt-
Bu2-k-P)][BF4] (3) with ethene or propene.8
Reaction of the complexes 1 and 2 with sodium methoxide
in acetone gave the neutral complexes [Ir{η5-3-(CH3COCH2)-
C6H5O(CH2)2Pt-Bu2-k-P}(C2H4)] (4) and [Ir{η5-3-(CH3COCH2)-
C6H5O(CH2)2Pt-Bu2-k-P}(C3H6)] (5), which were isolated as
pale yellow solids in good yields. The formation of these
complexes results from the selective nucleophilic attack of
acetone enolate (CH3-CO-CH2-) at the meta position of the
phenyl ring, resulting in the formation of a new C-C bond
(Scheme 1). It is noticeable that only the addition of acetone
enolate (generated in the reaction medium) was observed, in
accordance with the superior stability of the new C-C bond
Concerning the observed regioselectivity in the nucleophilic
attack to a η6-phenol ring, Amouri and Harman have described
the ortho and para selective addition to cathionic oxo-η5-
cyclohexadienyl complexes of iridium(III)13c,20 and η2-pheno-
(15) Addition of heteronucleophiles usually led to equilibria, reversible
reactions, or reactions at the metal center. (a) Le Bras, J.; Rager, M. N.;
Besace, Y.; Amouri, H.; Vaissermann, J. Organometallics 1997, 16, 1765–
1771. (b) McDaniel, K. F. In ComprehensiVe Organometallic Chemistry;
Abel, E. W., Stone, F. G. A., Wilkinson, G., Eds.; Pergamon: Oxford, U.K.,
1995, Vol 6, Chapter 4.
(16) Nucleophilic additions to coordinated arenes have been extensively
studied and are directly related to the electron-withdrawing ability of the
metal center; in fact ketone enolates readily added to a [Cp*Rh(arene)2+
]
complex: Fish, R. H.; Kim, H. S.; Fong, R. H.; Adams, R. D. Organome-
tallics 1990, 9, 1327–1329.
(17) Pike, R. D.; Sweigart, D. A. Coord. Chem. ReV. 1999, 187, 183–
222.
(18) (a) Halpin, W. A.; Williams, J. C.; Hanna, T.; Sweigart, D. A. J. Am.
Chem. Soc. 1989, 111, 376–378. (b) Davies, S. J. Organotransition Metal
Chemistry: Applications to Organic Synthesis; Organic Chemistry Series;
Pergamon Press: Oxford, England, 1982; Vol. 2, Chapter 4.
(19) Werner, H.; Werner, R. Chem. Ber. 1985, 118, 4543–4552.
(20) (a) Amouri, H.; Le Bras, J. Acc. Chem. Res. 2002, 35, 501–510.
(b) Le Bras, J.; Amouri, H.; Vaisermann, J. Inorg. Chem. 1998, 37, 5056–
5060. (c) Le Bras, J.; Amouri, H.; Vaisermann, J. J. Organomet. Chem.
1998, 567, 57–63.
(11) Kuwabara, J.; Ovchinnikov, M. V.; Stern, C. L.; Mirkin, C. A.
Organometallics 2008, 27, 789–792, and references therein.
(12) (a) Jung, S.; Ilg, K.; Brandt, C. D.; Wolf, J.; Werner, H. J. Chem.
Soc., Dalton Trans. 2002, 318–327. (b) Henig, G.; Schulz, M.; Windmuller,
B.; Werner, H. Dalton Trans. 2003, 441–448.
(13) (a) Bedford, R. B.; Coles, S. J.; Hursthouse, M. B.; Limmert, M. E.
Angew. Chem., Int. Ed. 2003, 42, 112–114. (b) Oi, S.; Watanabe, S.; Fukita,
S.; Inoue, Y. Tetrahedron Lett. 2003, 44, 8665–8668. (c) Amouri, H.; Le
Bras, J.; Vaisermann, J. Organometallics 1998, 17, 5850–5857.
(14) Werner, H.; Canepa, I. K.; Wolf, J. Organometallics 2000, 19,
4756–4766.

C-C Formation and C-O CleaVage Reactions
Organometallics, Vol. 27, No. 16, 2008 4231
1
1
Figure 1. H/13C HSQC NMR spectrum for compound 4 showing the characteristic H pattern for the alkoxy-cyclohexadienyl fragment
and, in particular, the high-field shift of the protons, especially for H4.
of ligands. The most interesting structural feature of 4 concerns
the meta carbon atom C(3) of the alkoxy-η5-cyclohexadienyl
ring; the Ir-C(3) separation, 2.799(4) Å, is remarkably longer
than the rest of the Ir-C distances (2.155-2.297(4) Å), and it
could not be considered as a bond distance. The five Ir-bonded
carbon atoms (C(1), C(2), C(4), C(5), and C(6)) maintain a
roughly coplanar disposition, making a significant dihedral angle
of 43.9(3)° with the plane defined by C(2), C(3), and C(4). These
structural parameters are clearly indicative of a η5-coordination
and are comparable with other related oxo-cyclohexadienyl
complexes.23 Additionally, the C-C bond distances within the
six-membered ring also reveal the different nature of the C-C
bonds to C(3) and, consequently, the referred ring η5-coordina-
tion; while the C(2)-C(3) and C(3)-C(4) bond distances are
typical of single C-C bonds (mean 1.516(4) Å)sanalogous,
for instance, to C(3)-C(7) or C(7)-C(8) bond lengths (mean
1.519(4) Å)sthe remaining C-C separations are clearly shorter,
in the usual range of aromatic metal-coordinated bond distances
(1.387-1.442(6) Å). As a whole, the Cromer and Pople
parameters characterized the η5-cyclohexadienyl ring conforma-
Figure 2. Molecular structure of complex 4 (hydrogen atoms are
represented only for the olefinic ligand and for the asymmetric C(3)
atom).
tion as a clear, highly bent envelope (θ ) 57.6(5), φ )
125.3(6)°, and Q ) 0.473(4) Å).24
Reaction of compound 1 with other nucleophiles such as
losmium(II),21 respectively. In general, it has been found that
methyllithium or butyllithium also gave addition products.
the selectivity of the nucleophilic attack on substituted arene
However, in contrast with the precedent cases, the reactions
metal complexes is influenced by the electronic effect of the
were unselective and produced a complicated mixture of
substituent on the arene.18b,22 Electron-donating groups such
compounds (1H NMR evidence). Interestingly, the nucleophilic
as -OMe or -NR2 direct meta addition, in contrast to electron
addition of lithium phenylacetylide in acetone cleanly proceeds
withdrawing substituents, such as chloro, that induce mainly
to give the compound [Ir{η5-3-(C6H5C’C)C6H5O(CH2)2Pt-Bu2-
ortho addition. Thus, the regioselective meta addition is in good
k-P}(C2H4)] (6), which is in equilibrium with 1 (Scheme 2).
agreement with the expected electron-donating character of the
Using a moderate excess of LiCtCPh, an approximately 1:1
alkoxy substituent in the arene.
mixture of both compounds was obtained. Attempts to isolate
Good quality crystals for an X-ray diffraction experiment
pure 6 from the reaction mixture were unsuccessful, and the
were obtained from low concentrated solutions of 4 in diethyl
compound has been characterized in solution.
ether. Bond distances and angles are given in Table 1.
The 1H NMR of 6 shows the characteristic set of resonances
Coordination angles around the metal center, considering
for the alkoxy-η5-cyclohexadienyl fragment that confirms the
midpoints of multiply bonded ligands (η5-ring and η2-ethylene),
nucleophilic addition of phenylacetylide at the meta position
reveal an ideal, slightly distorted trigonal-planar environment
on the phenoxy ring. The resonance for the H3 proton is
observed at δ 3.14 ppm and is masked by those of methylenic
(21) (a) Kopach, M. E.; Harman, D. J. Am. Chem. Soc. 1994, 11, 6–
6581. (b) Kolis, S. P.; Kopach, M. E.; Liu, R.; Harman, D. W. J. Org.
Chem. 1997, 62, 130–136.
(23) (a) Lee, S. G.; Kim, J. A.; Chung, Y. K.; Yoo, T-S.; Kim, N-J.;
Shin, W.; Kim, J.; Kim, K. Organometallics 1995, 14, 1023–1029. (b)
Auffrant, A.; Prim, D.; Rose-Munch, F.; Rose, E.; Schouteeten, S.;
Vaissemann, J. Organometallics 2003, 23, 1898–1913. (c) Le Bras, J.;
Amouri, H.; Vaissermann, J. Organometallics 1996, 15, 5706–5712.
(24) Cromer, D.; Pople, J. A. J. Am. Chem. Soc. 1975, 97, 1354–1358.
(22) (a) Auffrant, A.; Prim, D.; Rose-Munch, F.; Rose, E.; Vaissermann,
J. Organometallics 2002, 21, 3500–3502. (b) Collman, J. P.; Hegedus, L. S.;
Norton, J. R.; Finke, R. G. Principles and Applications of Organotransition
Metal Chemistry, 2nd ed.; University Science: Mill Valley, CA, 1987;
Chapter 20.

4232 Organometallics, Vol. 27, No. 16, 2008
Jime´nez et al.
Table 1. Selected Bond Distances (Å) and Angles (deg) for Complexes 4 and 7
4
7
4
7
Ir-P
2.3188(10)
2.253(4)
2.297(4)
2.799(4)
2.155(4)
2.206(4)
2.273(4)
1.770(2)
2.105(5)
2.097(4)
1.854(4)
1.900(4)
1.910(4)
2.2834(7)
2.492(3)
2.343(3)
2.266(3)
2.299(3)
2.231 (3)
2.216(3)
1.8090(12)
2.103 (3)
2.103 (3)
1.820(3)
1.894(3)
1.897(3)
O(1)-C(1)
O(1)-C(13)
O(2)-C(8)
C(1)-C(2)
C(1)-C(6)
C(2)-C(3)
C(3)-C(4)
C(3)-C(7)
C(4)-C(5)
C(5)-C(6)
C(7)-C(8)
C(10)-C(11)
C(12)-C(13)
1.397(5)
1.431(5)
1.216(5)
1.387(5)
1.442(6)
1.530(6)
1.502(6)
1.532(6)
1.424(7)
1.418(6)
1.506(6)
1.437(7)
1.525(6)
1.267(3)
Ir/C(1)a
Ir-C(2)
Ir/C(3)a
Ir-C(4)
Ir-C(5)
Ir-C(6)
Ir-Gb
1.430(4)
1.452(4)
1.414(4)
1.410(4)
Ir-C(10)
Ir-C(11)
P-C(12)
P-C(14)
P-C(18)
1.397(4)
1.415(4)
1.425(4)
1.308(4)
P-Ir-Gb
124.00(7)
100.73(11)
135.27(12)
111.01(14)
117.97(13)
115.81(13)
99.13(18)
102.36(19)
108.19(18)
118.0(3)
133.39(4)
91.61(7)
O(1)-C(1)-C(2)
O(1)-C(1)-C(6)
C(2)-C(1)-C(6)
C(1)-C(2)-C(3)
C(2)-C(3)-C(4)
C(2)-C(3)-C(7)
C(4)-C(3)-C(7)
C(3)-C(4)-C(5)
C(4)-C(5)-C(6)
C(1)-C(6)-C(5)
P-C(12)-C(13)
117.2(4)
121.0(4)
121.8(4)
118.2(4)
101.2(3)
114.5(4)
114.9(3)
119.5(4)
118.3(4)
116.4(4)
118.2(3)
123.9(2)
122.2(3)
113.4(2)
121.1(3)
122.3(3)
P-Ir-Mb
G-Ir-Mb
134.81(7)
113.50(9)
113.61(9)
114.41(9)
98.58(12)
104.05(13)
111.23(12)
Ir-P-C(12)
Ir-P-C(14)
Ir-P-C(18)
C(12)-P-C(14)
C(12)-P-C(18)
C(14)-P-C(18)
C(1)-O(1)-C(13)
117.8(3)
119.8(3)
123.0(3)
130.5(2)
a These distances are considered bond or interaction distances (see discussion). b G represents the centroid of the η5-dienyl ligands; M that of the
olefinic double bond C(10)-C(11).
Scheme 2
Scheme 3
protons, although the coupling with H2, and H4 was clearly
evidenced in the 1H-1H COSY spectrum. The ethylene ligand
is seen as a very broad signal centered at δ 2.47 ppm. The CR
and Cꢀ of the methylenic groups were observed at δ 69.11 and
81.44 ppm, respectively, in the 13C{1H} NMR spectrum. In
addition, the MALDI-TOF mass spectrum showed an ion at m/z
559.1, which corresponds to the loss of the ethylene ligand.
All these spectroscopic data seem to suggest that the molecular
structure of 6 is analogous to that of 4.
Scheme 4
C-C or C-O Bond Cleavage Reactions on the Com-
plexes [Ir{η5-3-(CH3COCH2)C6H5O(CH2)2Pt-Bu2-k-P}(alk-
ene)](4, 5).Thereactionof[Ir{η5-3-(CH3COCH2)C6H5O(CH2)2Pt-
+
Bu2-k-P}(C2H4)] (4) with electrophiles, such as H+ or CH3
,
results in the formation of either ethyl methyl ketone or
isopropenyl methyl ether as a consequence of the alkylation of
the keto and enol tautomers, respectively.26 In our case, as
isopropenyl methyl ether is the only organic compound detected
by 1H NMR, the Me+ should selectively attack the oxygen atom
of the 2-oxo-propyl group.
Unexpectedly, the alkoxy-η5-cyclohexadienyl compounds
[Ir{η5-3-(CH3COCH2)C6H5O(CH2)2Pt-Bu2-k-P}(alkene)] (4, 5)
slowly convert into new species in methanol. The monitoring
of the reactions by 31P{1H} NMR evidenced a gradual decrease
in the intensity of the resonances at δ 5.85 and 4.70 ppm,
corresponding to compounds 4 and 5, respectively, as new
resulted in the elimination of the 2-oxo-propyl fragment (Scheme
3). Thus, addition of a stoichiometric amount of methyl triflate
or triflic acid to solutions of compound 4 in dichloromethane
allowed the quantitative recovery of η6-arene starting material
1 as the triflate salt. The reaction pathway should involve the
direct electrophilic attack of Me+/H+ to the 2-oxo-propyl
fragment, as isopropenyl methyl ether, CH2dC(CH3)(O-CH3),
1
and acetone were detected by both GC-MS and H NMR.
Alkylations of enolate with triflates are among the most useful
carbon-carbon bond formation reactions.25 It is known that the
reaction of the deprotonated form of acetone with bromomethane
(25) Pellerite, M. J.; Brauman, J. I. J. Am. Chem. Soc. 1983, 105, 2672–
2680.
(26) Bates, R. B.; Taylor, S. R. J. Org. Chem. 1993, 58, 4469–4470.

C-C Formation and C-O CleaVage Reactions
Organometallics, Vol. 27, No. 16, 2008 4233
in the 13C{1H} NMR spectra at δ 166.43 (7) and 166.19 ppm
(8), values that are characteristic for the noncoordination of the
CdO group. In addition, the infrared spectra of both complexes
showed the expected ν(CdO) absorption at 1625 and 1630
cm-1, respectively, in accordance with the ν(CdO) vibrations
observed in deprotonated phenol derivatives.23,29 Finally, the
vinyl group of the phosphine ligand was observed as a set of
three multiplets in the range 5.8-6.0 ppm, with the expected
JHP coupling constants (12-30 Hz).
The formation of complexes 7 and 8 is a consequence of the
methanol-induced C-C and C-O bond cleavage reactions in
the parent complexes [Ir{η5-3-(CH3COCH2)C6H5O(CH2)2Pt-
Bu2-k-P}(alkene)] (4, 5) that result in the elimination of the
2-oxo-propyl fragment, the degradation of the “ansa” π-arene/
phosphine ligand, and the formation of a new vinylphosphine
group.
Figure 3. Molecular structure of complex 7 showing the labeling
scheme used (hydrogens are shown only for the coordinated olefin
and for the OH group of the phenol crystallization molecule).
As the 2-oxo-propyl group is easily lost by reaction with
electrophiles (Me+ or H+), the reaction is probably driven by
the electrophilic attack of the alcohol-liberated proton to the
oxygen atom of the 2-oxo-propyl group, resulting in the
elimination of acetone and the restoration of the η6-coordination
mode of the “ansa” π-arene/phosphine ligand. However, the
presence of the methoxide ion could induce proton abstraction
on the CR atom of the ligand side-chain, leading to the
unexpected breaking of the alkyl C-O bond and the concerted
formation of the new CdC bond. The formation of the final
complexes requires the further tautomerization of the probably
formed η6-phenoxide ligand into the oxo-η5-cyclohexadienyl
ligand. This proposal is strongly supported by the observation
that the “ansa” π-arene/phosphine complexes 1 and 2 react with
potassium hydroxide or potassium tert-butoxide in methanol to
give directly compounds 7 and 8, which were isolated in
moderate yield. Related MeO bond cleavage through a hydroly-
sis process has been observed in a metalated crown ether
complex of Ir(III).30
downfield-shifted resonances became visible at δ 32.02 and
31.04 ppm corresponding to the new species. From these
solutions, complexes [Ir(η5-C6H5O)(C2H4)(t-Bu2PCHdCH2)] (7)
and [Ir(η5-C6H5O)(C3H6)(t-Bu2PCHdCH2)] (8) were obtained
(Scheme 4) in moderate yield. The complexes have been fully
characterized by elemental analysis, mass spectrometry, and
multinuclear NMR spectroscopy. The presence of oxo-η5-
cyclohexadienyl and vinylphosphine ligands in the complexes
has been further confirmed by an X-ray diffraction study on
complex 7.
Single crystals of 7 suitable for X-ray studies were grown
from acetone solutions. Its molecular structure is depicted in
Figure 3, and bond distances and angles are given in Table 1.
As described for 4, the determined geometric parameters confirm
the oxo-η5-cyclohexadienyl bonding mode, although the struc-
tural modifications of the ketonic carbon atom (C(1)) from an
ideal η6-coordination are not as intense as those observed in 4.
Thus, the Ir-C(1) separation, 2.492(3) Å, is only slightly longer
than the remaining Ir-C bond distances, 2.216-2.343(3) Å;
the interplanar angle between the five coplanar Ir-bonded
carbons and the ketonic plane is 14.9(2)°, significantly smaller
than the value observed in 4 (43.9(3)°); and the intra-ring C-C
bond distances do not show serious differences between the
formally single bonds to C(1) (mean 1.441(4) Å) and those of
the aromatic Ir-coordinated C-C bonds (range 1.397-1.415(4)
Å). The ketonic character of the C-O link is evidenced by the
bond distance, 1.267(3) Å, which is quite similar to the bond
lengths described in δ- or γ-lactams.27 The breaking of the
alkoxy C-O bond and formation of the unsaturated vinylphos-
phine substituent is also manifested from the structural analysis
(C12-C(13) 1.308(4) Å).
The process outlined above is further complicated by the
formation of phenol in the reaction media (NMR evidence),
which most likely results from the protonation of the η6-
phenoxide/oxo-η5-cyclohexadienyl ligands by the solvent and
that is probably responsible for the moderate yield of the
reactions. In fact, crystals of complex 7 were obtained as the
phenol solvate in the same way as found in related late transition
metal complexes containing oxo-η5-cyclohexadienyl ligands.31
In addition, complexes of iridium(III) of formula [Cp*Ir(oxo-
η5-cyclohexadienyl)][BF4] have been obtained by Amouri13c,20
by deprotonation of the corresponding phenol derivatives.
The oxo-η5-cyclohexadienyl ligand in complexes 7 and 8 is
not the only reactive site, as the vinyl group of the
t-Bu2P(CHdCH2) ligand smoothly undergoes the addition of
MeOH under the experimental conditions, leading to its
transformation. Interestingly, the controlled treatment of solu-
tions of complex 7 in toluene with methanol resulted in the
formation of the compound [Ir(OC6H5)(C2H4)(t-Bu2P(CH2)2OMe-
k2-O,P)] (9), which was isolated as a brown solid in moderate
yield. Compound 9 contains the methoxiethyldi-tert-butylphos-
phine32 ligand, which results from the anti-Markovnikoff
The Ir-C separation observed for the ketonic carbon, 2.492(3)
Å, compares well with other related transition metal complexes
where a cyclohexadienyl ligand is described to be linked to a
metal in a η5-coordination mode (distances range 2.337-2.666
Å).28 As usual, both η5-dienyl ligands in 4 and 7 maintain a
planar disposition almost perpendicular to the metal-ring
centroid vector (γ-angle 9.4(1)° in 4 and 8.9(1)° in 7).
The oxo-η5-cyclohexadienyl ligand in complexes 7 and 8 was
1
observed in the H NMR spectra as a set of three and five
(29) Snelgrove, J. L.; Conrad, J. C.; Yap, G. P. A.; Fogg, D. E. Inorg.
Chim. Acta 2003, 345, 268–278.
(30) Amouri, H.; Vaissermann, J.; Rager, M. N.; Besace, Y. Inorg. Chem.
1999, 38, 1211–1215.
resonances (4.7-6.2 ppm), respectively, as expected from the
lack of symmetry of the latter. The ketonic group was observed
(31) (a) Abbur-Rashid, K.; Fedorkiw, T.; Lough, A. J.; Morris, R. H.
Organometallics 2004, 23, 86. (b) Dahlenburg, L.; Hock, N. J. Organomet.
Chem. 1985, 284, 129.
(27) Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen,
A. G.; Taylor, R. J. Chem. Soc., Perkin Trans. 2 1987, S1–S19.
(28) Allen, F. H. Acta Crystallogr. 2002, B58, 380–388.
(32) Dombek, B. D. J. Org. Chem. 1978, 43, 3408–3409.

4234 Organometallics, Vol. 27, No. 16, 2008
Jime´nez et al.
Scheme 6. Formation of Compound 10 in Acetone at
Scheme 5. Proposed Mechanism for the Formation of
Compound 9
-60 °C
addition of MeOH to give the intermediate complex [Ir(η5-
C6H5O)(C2H4)(t-Bu2P(CH2)2OMe-k-P)], which has been ob-
served by 1H NMR (δ 4.20, 5.27, and 5.42 ppm). The oxo-η5-
cyclohexadienyl ligand tautomerizes to a k-O-phenoxide ligand,
facilitating the k2-O,P mode of coordination of the methoxi-
ethyldi-tert-butylphosphine ligand in compound [Ir(OC6H5)(C2H4)-
(t-Bu2P(CH2)2OMe-k2-O,P)] (9) (Scheme 5).
addition of MeOH to the vinyl group of the coordinated
vinylphosphine ligand in 7 (Scheme 5).
Reactions of the Iridium(III) Phenoxy-Phosphine Deriva-
tive [IrH2(η6-C6H5O(CH2)2Pt-Bu2-k-P)][BF4] (3) with Nu-
cleophiles. The related dihydride Ir(III) complex, [IrH2(η6-
C6H5O(CH2)2Pt-Bu2-k-P)][BF4] (3), was prepared as previously
described8 by smooth reaction of molecular hydrogen with the
chelate complex [Ir(C8H12)(C6H5O(CH2)2Pt-Bu2-k2-O,P)][BF4].
In general, this compound is more reactive than the iridium(I)
complexes 1 and 2, although the reactions with nucleophiles
usually resulted in complex mixtures of products. However, the
resulting product from the addition of potassium pyrazolate has
been cleanly obtained and characterized in solution at low
temperature.
The characterization of 9 as a square-planar phenoxyirid-
ium(I)33 complex was fairly straightforward by NMR spectros-
copy. The presence of the k-O-phenoxide ligand was inferred
by the set of resonances in the ranges δ 6.89-7.20 ppm and δ
1
111.74-118.23 ppm observed in the H and 13C{1H} NMR
spectra, respectively. The ethylene ligand displayed two mul-
1
tiplets at δ 1.60 and 2.05 ppm in the H NMR spectrum, as in
precedent complexes. On the other hand, the 31P{1H} NMR
showed a single resonance at δ 46.09 ppm, which is also
indicative of a k2-O,P mode of coordination for the methoxi-
ethyldi-tert-butylphosphine ligand, as it has been contrasted with
the spectroscopic data of related k2-O,P-coordinated ether-
functionalized phosphine ligands.12,34 Although both methylene
groups of the methoxyethyl fragment were observed as a doublet
of triplets at δ 3.24 (CH2O) and 1.51 (CH2P), the observed JPH
coupling constant is larger for the former. This fact has already
been noticed in phenoxyethyldi-tert-butylphosphine complexes
coordinated in a k2-O,P mode.8
The addition of an equimolecular amount of potassium
pyrazolate to an acetone solution of complex 3 at 200 K afforded
a pale yellow solution that contains a unique compound, as
evidenced by the resonance at δ 39.27 ppm in the 31P{1H} NMR
spectrum. The compound is stable below 213 K and can be
maintained in solution for several hours, but on raising the
temperature above 233 K, it quickly decomposes.
Vinylphosphines play an important role in organophosphorus
chemistry both as intermediates for the preparation of poly-
phosphines and as ligands in organometallic catalysis.35 The
base-catalyzed addition of alcohols to vinylphosphine oxide to
form alkoxyethylphosphine oxides is known.36 Although the
coordination chemistry of several vinylphosphine ligands has
been studied,37 the effect of the phosphine complexation on the
reactivity of the olefinic double bond has not been extensively
studied. Noteworthy, Schmidbaur38 has demonstrated that
uncoordinated vinylidene groups in a gold vinylidenebis(diphe-
nylphosphine) complex become strongly activated for the
addition of methanol to form methoxiethanodiphenylphosphine
through diphosphine-metal coordination. In the same way, the
coordination of the t-Bu2P(CHdCH2) ligand to iridium results
in the activation of the uncoordinated vinyl fragment for the
The new compound exhibits two doublets of doublets for the
hydride ligands in the H NMR spectrum at δ -11.25 and
1
-17.10 ppm, with coupling constants JHP and JHH that indicate
a mutual cis position.39 The most important characteristic of
this compound is the loss of aromaticity of the phenoxide
fragment, as inferred from both 1H and 13C{1H} NMR spectra.
The five phenoxide signals are identified from its coupling
1
scheme deduced from the H/1H COSY spectrum. The pyra-
zolate is observed at the expected positions, the H5 proton is
close to pyrazolate signals at δ 6.15 ppm, H2 and H6 are shifted
ca. 1 ppm to high field at δ 5.20 and 5.31 ppm, and shifted to
higher fields are H4 and H3 at 3.69 and 3.87 ppm, respectively.
Their carbon atoms and those belonging to the pyrazolate ligand
1
are assigned from the H/13C HSQC correlated spectrum (see
Experimental Section). The proposed formula [IrH2{η5-
(pz)C6H5O(CH2)2Pt-Bu2-k-P}] (10) is based on the spectroscopic
data similarity with those of compound 4, and there is no doubt
that no enolate is coordinated to the arene because no signals
for that fragment were found in either the 1H or 13C{1H} NMR.
Thus, compound 10 results from the selective nucleophilic attack
of the pyrazolate to the 3-position of the arene to form an
alkoxy-η5-cyclohexadienyl ligand (Scheme 6).
(33) Ladipo, F. T.; Kooti, M.; Merota, J. S. Inorg. Chem. 1993, 32,
1681–1688.
(34) Lindner, E.; Wang, O.; Mayer, H. A.; Bader, A. J. Organomet.
Chem. 1993, 458, 229–232.
(35) Julienne, D.; Lohier, J. F.; Delacroix, O.; Gaumont, A. C. J. Org.
Chem. 2007, 72, 2247–2250.
(36) Pietrusiewicz, K. M.; Zablocka, M. Phosphorus Sulfur Relat. Elem.
1988, 40, 47–51.
(37) Hall, D. I.; Ling, J. H.; Nyholm, R. S. Metal complexes of chelating
olefin-group V ligands In Structure and Bonding; Springer: Berlin, 1973;
Vol. 15, Chapter 20, pp 3-51.
(38) Schmidbaur, H.; Herr, R.; Mu¨ller, G.; Riede, J. Organometallics
1985, 4, 1208–1213.
(39) Jime´nez, M. V.; Sola, E.; Lo´pez, J. A.; Lahoz, F. J.; Oro, L. A.
Chem.-Eur. J. 1998, 4, 1398–1410.

C-C Formation and C-O CleaVage Reactions
Organometallics, Vol. 27, No. 16, 2008 4235
JBX ) 6.2, 2H, CH2CO), 2.90 (m br, 4H, C2H4), 3.36 (ddddd, JHH
) 6.2, 6.2, 5.6, 5.6, JHP ) 1.2, 1H, H3), 3.50 (m 1H, CH2-Cꢀ),
3.78 (m, 1H, CH2-Cꢀ), 4.30 (ddd, JHH ) 5.6, 1.8, JHP ) 1.2, 1H,
H2), 4.98 (ddd, JHH ) 5.6, 5.6, JHP ) 0.8, 1H, H5), 5.97 (ddd, JHH
) 5.6, 1.8, JHP ) 1.2, 1H, H6). 31P{1H} NMR (161 MHz, C6D6,
298 K): δ 5.85 (s). 13C{1H} NMR (75 MHz, C6D6, 298 K): δ 15.65
(d, JCP ) 21.6, CH2-CR), 22.45 (s, CH2CO), 29.50 (d, JCP ) 3.8,
PCCH3), 29.95 (d, JCP ) 4.7, PCCH3), 30.31 (CO CH3), 34.79 (C2),
35.19 (d, JCP ) 16.6, PCCH3), 36.08 (d, JCP ) 28.3, C4), 37.33 (d,
Conclusions
We have described the reactivity with nucleophiles of the
“ansa” π-arene/phosphine complexes [Ir(alkene)(η6-C6H5O-
(CH2)2Pt-Bu2-k-P)][BF4] (1, 2) and [IrH2(η6-C6H5O(CH2)2Pt-
Bu2-k-P)][BF4] (3), where the phosphine is a formal eight-
electron-donor chelate ligand. Regioselective nucleophilic ad-
ditiontotheareneisobservedwhenacetoneenolate,phenylacetylide,
or pyrazolate are reacted with complexes 1-3 in acetone solvent.
However, the starting materials 1 and 2 reacted with bases in
methanol solution, giving rise to C-O bond splitting and
formation of oxo-η5-cyclohexadienyl vinylphosphine com-
pounds. For the π-arene/phosphine complexes mentioned above,
the arene is activated for nucleophilic addition through iridium
coordination, and in determined conditions C-C bond formation
is reached, but the presence of the oxygen in the backbone
flexible arm is not innocent, and in basic methanol medium
C-O bond breaking occurs. Coordination of the vinylphosphine
to the iridium center can also induce methanol addition to the
unsaturated bond.
JCP ) 16.3, PCCH3), 37.52 (d, JCP ) 5.9, C3), 59.53 (d, JCP
10.0, CO CH2), 67.29 (s, CH2-Cꢀ), 71.81 (C6), 84.94 (d, JCP
)
)
1.0, C5), 121.20 (C1), 204.49 (CO). Anal. Calcd (%) for C21H36IrO2P
(543.7094): C 46.39, H 6.67. Found C 46.42, H 6.71. MS (MALDI-
TOF, DCTB matrix, CH2Cl2): m/z 515.4 [M - C2H4]+.
Preparation of [Ir{η5-3-(CH3COCH2)C6H5O(CH2)2Pt-Bu2-k-
P}(C3H6)] (5). The compound was prepared following the procedure
described for 4 but starting from the propene complex [Ir(C3H6)(η6-
C6H5O(CH2)2Pt-Bu2-k-P)] (2) (0.34 mmol). Complex 5 was isolated
as a pale yellow solid. Yield: 135 mg (62%). IR (Nujol, cm-1):
1
1711 (s) ν(CdO), 1585 (m) ν(CdC). H NMR (acetone-d6, 298
K): δ 1.15 (d, JHP ) 12.0, 9H, PCCH3), 1.20 (d, JHH ) 6.1, 3H,
dCHCH3), 1.24 (d, JHP ) 12.0, 9H, PCCH3), 1.45 (m, 2H,
CH2-CR), 1.85 (AB part of a ABX spin system, δA ) 1.87, δB )
Experimental Section
1.85, JAB ) 7.6, JAX ) JBX ) 3.8, 2H, CH2CO), 2.10 (dd, JHH
)
Scientific Equipment. Elemental analyses were carried out in a
Perkin-Elmer 2400 CHNS/O analyzer. Infrared spectra were
recorded on a FT-Perkin-Elmer Spectrum One spectrophotometer
using Nujol mulls between polyethylene sheets. NMR spectra were
recorded on Bruker Avance 300 MHz and Bruker Avance 400 MHz
spectrometers. 1H (300.1276 MHz, 400.1625 MHz) and 13C
(75.4792 MHz, 100.6127 MHz) NMR chemical shifts are reported
in ppm relative to tetramethylsilane and referenced to partially
deuterated solvent resonances. Coupling constants (J) are given in
hertz. Spectral assignments were achieved by a combination of
1H-1H COSY, NOESY, 1H{31P}, 13C DEPT, and 1H-13C HSQC
experiments. MALDI-TOF mass spectra were obtained on a Bruker
MICROFLEX spectrometer using DCTB (trans-2-[3-(4-tert-bu-
tylphenyl)-2-methyl-2-propenylidene]malononitrile) as matrix.40
Electrospray mass spectra (ESI-MS) were recorded on a Bruker
MicroTof-Q using sodium formiate as reference. Conductivities
were measured in ca. 5 × 10-4 M acetone solutions of the
complexes using a Philips PW 9501/01 conductimeter.
Synthesis. All experiments were carried out under an argon
atmosphere using Schlenk techniques, and the solvents were distilled
immediately prior to use from the appropriate drying agents.
Oxygen-free solvents were employed throughout. CDCl3 and
CD2Cl2 was dried using activated molecular sieves, C6D6 was dried
using Na/K, and acetone-d6 and methanol-d4 (<0.02% D2O) were
purchased from Euriso-top and used as received. Complexes 1-3
were prepared following published methods.8 The numbering
scheme corresponds to that shown in the structures of compounds
4 and 7 depicted in Figures 2 and 3, respectively.
5.9, 5.2, 1H, H4), 2.28 (dd, JHH ) 11.7, 1.4, 1H, dCH2), 2.31 (s,
3H, COCH3), 2.60 (ddd, JHP ) 3.5, JHH ) 8.0, 1.4, 1H, dCH2),
2.67 (ddq, JHH ) 11.7, 8.0, 6.1, 1H, dCHCH3), 3.24 (ddddd, JHH
) 5.2, 5.2, 3.8, 3.8, JHP ) 1.2, 1H, H3), 3.96 (dd, JHH ) 5.2, 1.8,
1H, H2), 4.21 (m, 1H, CH2-Cꢀ), 3.84 (m, 1H, CH2-Cꢀ), 4.87 (dd,
JHH ) 5.9, 5.2, 1H, H5), 6.29 (dd, JHH ) 5.9, 1.2, 1H, H6). 31P{1H}
NMR (acetone-d6, 298 K): δ 4.70 (s). 13C{1H} NMR (acetone-d6,
298 K): δ 16.76 (d, JCP ) 25.1, CH2-CR), 19.9 (dCH CH3), 20.84
(dCHCH3), 28.4 (dCH2), 30.31 (s, COCH3), 29.02 (d, JCP ) 4.3,
PCCH3), 30.89 (d, JCP ) 4.0, PCCH3), 35.43 (d, JCP ) 27.2, C4),
36.39 (d, JCP ) 16.1, PCCH3), 36.47 (C2), 37.32 (d, JCP ) 5.3,
C2), 38.84 (d, JCP ) 18.1, PCCH3), 60.42 (d, JCP ) 10.0, COCH2),
67.64 (CH2-Cꢀ), 70.80 (C6), 87.62 (C5), 209.96 (CO). Anal. Calcd
(%) for C22H38IrO2P (557.7363): C 47.38, H 6.87. Found: C 47.62,
H 6.50. MS (MALDI-TOF, DCTB matrix, CH2Cl2): m/z 515.4 [M
- C3H6]+.
Reaction of [Ir(C2H4)(η6-C6H5O(CH2)2Pt-Bu2-k-P)][BF4] (1)
with LiCtC-Ph. A suspension of 1 (20 mg, 0.035 mmol) in
acetone-d6 (0.5 mL) was treated with lithium phenylacetylide (5.4
mg, 0.05 mmol) to give a yellow solution. The 1H NMR spectrum
evidenced the formation of compound [Ir{η5-3-(C6H5CtC)C6H5O-
(CH2)2Pt-Bu2-k-P}(C2H4)] (6), which is in equilibrium with 1.
Spectroscopic data for 6: 1H NMR (acetone-d6, 298 K): δ 1.0 (m,
1H, CH2-CR), 1.10 (m, 1H, H4), 1.15 (d, JHP ) 8.7, 9H, PCCH3),
1.17 (d, JHP ) 8.6, 9H, PCCH3), 1.40 (m, 1H, CH2-CR), 2.47 (m
br, 4H, C2H4), 3.14 (masked, 1H, H3), 3.90 (m 1H, CH2-Cꢀ), 4.03
(dd, JHH ) 7.1, JHP ) 1.0, 1H, H2), 4.21 (m, 1H, CH2-Cꢀ), 5.18
(dd, JHH ) 7.1, 5.8, 1H, H5), 6.30 (ddd, JHH ) 7.1, 1.0, JHP ) 1.0,
1H, H6). 31P{1H} NMR (acetone-d6, 298 K): δ 7.04 (s). 13C{1H}
NMR (acetone-d6, 298 K): δ 16.14 (d, JCP ) 22.4, CH2-CR), 29.18
(PCCH3), 30.40 (d, JCP ) 4.5, PCCH3), 34.91 (C2), 35.79 (d, JCP
) 17.1, PCCH3), 36.22 (d, JCP ) 28.3, C4), 38.05 (d, JCP ) 5.9,
C3), 38.25 (d, JCP ) 17.4, PCCH3), 68.01 (s, CH2-Cꢀ), 69.11
(CtC-Ph), 81.44 (CtC-Ph), 85.42 (C6), 115.30 (C5), 128.69
(CH), 129.05 (CH), 130.06 (C), 131.99 (CH), 138.68 (C). MS
(MALDI-TOF, DCTB matrix, acetone-d6): m/z 559.1 [M - C2H4]+.
Preparation of [Ir{η5-3-(CH3COCH2)C6H5O(CH2)2Pt-Bu2-k-P}-
(C2H4)] (4). A solution of 1 (200 mg, 0.35 mmol) in acetone (10
mL) was treated with sodium methoxide (22 mg, 0.40 mmol). After
12 h of stirring, the solvent was pumped off and the residue
extracted with diethyl ether. The resulting pale yellow solution was
filtered, concentrated to ca. 0.5 mL, and treated with pentane. A
light yellow solid precipitated and was filtered, washed twice with
2 mL portions of pentane, and dried in vacuo. Yield: 135 mg (71%).
IR (Nujol, cm-1): 1710 (s) ν(CdO), 1587 (w) ν(CdC). 1H NMR
(C6D6, 298 K): δ 0.73 (m, 2H, CH2-CR), 1.10 (d, JHP ) 11.8, 9H,
PCCH3), 1.10 (d, JHP ) 11.6, 9H, PCCH3), 1.20 (ddd, JHH ) 5.6,
5.6, JHP ) 1.2, 1H, H4), 1.54 (s, 3H, COCH3), 1.68 (AB part of a
Reaction of [Ir{η5-3-(CH3COCH2)C6H5O(CH2)2Pt-Bu2-k-P}-
2H4)] (4) with Methyltriflate. A solution of 4 (15 mg, 0.027
(C
mmol) in 0.5 mL of CD2Cl2 placed in a 5 mm NMR tube was
treated with 3.12 µL of CH3CF3SO3 (0.027 mmol). The initial signal
at δ 5.65 ppm in the 31P NMR corresponding to 4 was completely
transformed in 30 min into a new signal at δ 6.96 ppm assigned to
[Ir(C2H4)(η6-C6H5O(CH2)2Pt-Bu2-k-P)]+ (1). Analysis of the solu-
ABX spin system, ABX, δA ) 1.73, δB ) 1.63, JAB ) 15.2, JAX
)
(40) Ulmer, L.; Mattay, J.; Torres-Garc´ıa, H. G.; Luftmann, H. Eur. J.
Mass Spectrom 2000, 6, 49–52.

4236 Organometallics, Vol. 27, No. 16, 2008
Jime´nez et al.
1
tion mixture by H NMR showed the quantitative formation of 1
(C6D6, 298 K): δ 46.09 (s). 13C{1H} NMR (C6D6, 298 K): δ 17.94
(CH2-CR, CH2dCH2), 27.27 (d, JCP ) 3.0, PCCH3), 27.79 (d, JCP
1
and 2-methoxypropene: H NMR (acetone-d6, 298 K): δ 3.85 (s,
2H, dCH2), 3.52 (s, 3H, OCH3), 1.82 (s, 3H, CH3). GC-MS
) 3.8, PCCH3), 27.91 (d, JCP ) 28.6, PCCH3), 32.24 (d, JCP )
(CD2Cl2): m/z 72 [M]+.
27.5, PCCH3), 52.34 (OCH3), 62.03 (CH2-Cꢀ), 111.74, 113.26,
118.23 (CH-PhO), not seen (C1). Anal. Calcd (%) for C19H34IrO2P
(517.6715): C 44.08, H 6.62. Found: C 43.78, H 5.98.
Preparation of [IrH2{η5-3-(pz)-C6H5O(CH2)2Pt-Bu2-k-P}]
(10). A solution of [IrH2(η6-C6H5O(CH2)2Pt-Bu2-k-P)][BF4] (3)
(40 mg, 0.073 mmol) in acetone-d6 (0.5 mL) was treated with
Reaction of [Ir{η5-3-(CH3COCH2)C6H5O(CH2)2Pt-Bu2-k-
P}(C2H4)] (4) with Triflic Acid. Compound 4 (0.027 mmol) was
reacted with HCF3SO3 in CD2Cl2 and the reaction monitored by
1
NMR. Analysis of the solution mixture by H NMR and GC-MS
showed the formation of 1 and acetone.
Preparation of [Ir(η5-C6H5O)(C2H4)(t-Bu2PCHdCH2)] (7).
Method A: A suspension of 4 (100 mg, 0.18 mmol) in methanol
(10 mL) was stirred for 8 h, the solvent was evacuated, and the
residue was treated with pentane, washed with pentane, and dried
in vacuo. Yield: 64 mg (72%). Method B: A solution of 1 (200
mg, 0.35 mmol) in acetone (10 mL) was treated with potassium
hydroxide in methanol (1 mmol). After 2 h of stirring, the solvent
was pumped off and the residue treated with diethyl ether. The
resulting brown solution was filtered, concentrated to ca. 0.5 mL,
and treated with pentane. A light yellow solid precipitated, which
was filtered, washed twice with 2 mL portions of pentane, and dried
in vacuo. Yield: 64 mg (38%). IR (Nujol mull, cm-1): 1625 (m)
ν(CdO), 1540 (m) ν(CdC). 1H NMR (acetone-d6, 298 K): δ 1.30
(d, JHP ) 13.3, 18H, PCCH3), 1.41 (m, 2H, endo-H CH2dCH2),
2.16 (m, 2H, exo-H CH2dCH2), 4.95 (d, JHH ) 6.7, 2H, H2), 5.75
(t, JHH ) 5.4, 1H, H4), 5.82 (dd, JHP ) 12.0, JHH ) 4.0, 1H, dCH2),
potassium pyrazolate (7.7 mg, 0.073 mmol) at -78 °C and then
13
allowed to warm up to -60 °C. 1H and
C{1H} NMR
evidenced the formation of compound 10. Spectroscopic data:
1H NMR (acetone-d6, 213 K): -17.10 (dd, JHP ) 18.9, JHH
)
7.4, 1H, Ir-H), -11.25 (dd, JHP ) 21.4, JHH ) 7.4, 1H, Ir-H),
1.13 (d, JHP ) 13.3, 9H, PCCH3), 1.26 (d, JHP ) 12.6, 9H,
PCCH3), 1.46 (m, 2H, CH2-CR), 3.69 (m, 1H, H4), 3.87 (d, JHH
) 6.2, 1H, H3), 4.10 (m 1H, CH2-Cꢀ), 4.24 (m, 1H, CH2-Cꢀ),
5.20 (dd, JHH ) 5.6, 5.6, 1H, H2), 5.31 (m, 1H, H6), 6.14 (m,
1H, Pz-H4), 6.15 (m, 1H, H5), 7.34 (d, JHH ) 1.0, 1H, Pz-H5),
7.40 (d, JHH ) 1.0, 1H, Pz-H3). 31P{1H} NMR (acetone-d6, 213
K): δ 39.27 (s). 13C{1H} NMR (acetone-d6, 213 K): δ 13.01 (d,
JCP ) 26.3, CH2-CR), 28.60 (PCCH3), 29.48 (d, JCP ) 4.5,
PCCH3), 34.56 (d, JCP ) 26.8, PCCH3), 35.47 (d, JCP ) 28.5,
PCCH3), 35.67 (d, JCP ) 28.3, C4), 41.98 (C3), 60.62 (d, JCP
)
3.8 Hz, C2), 69.07 (C5), 69.79 (CH2-Cꢀ), 90.87 (C6), 104.84,
126.31 (CH-Pz), 130.49 (C1), 137.99 (CH-Pz).
5.83 (dd, JHP ) 10.9, JHH ) 11.3, 1H, dCH2), 6.08 (ddd, JHP
)
X-ray Structural Determination of Compounds 4 and 7.
Crystals of complex 4 suitable for the X-ray diffraction
experiment were obtained by slow evaporation of diethyl ether
from a concentrated solution at room temperature in the drybox.
Suitable crystals of 7 were obtained by slow diffusion of diethyl
ether into a concentrated solution of the compound in acetone
at 0 °C. Both sets of intensity data were collected at low
temperature (100(2) K) on a CCD Bruker SMART APEX
diffractometer with graphite-monochromated Mo KR radiation
(λ ) 0.71073 Å) by using ω rotations (0.3°). Instrument and
crystal stability were evaluated by measuring equivalent reflec-
tions at different times; no significant decay was observed. Data
were corrected for Lorentz and polarization effects, and a
semiempirical absorption correction was applied.41 The structure
was solved by Patterson and difference Fourier methods.42
Anisotropic displacement parameters were applied for all non-
hydrogen atoms. Hydrogen atoms were found in subsequent
difference Fourier maps and included as free isotropic atoms.
Refinements were carried out by full-matrix least-squares on F2
(SHELXL-97).41 The highest residuals in both structures were
found in the proximity of metal centers and have no chemical
sense.
Crystal data for compound 4: C21H36IrO2P, M ) 543.67; crystal
size 0.252 × 0.247 × 0.041 mm3; monoclinic, P21/n; a )
13.1600(8) Å, b ) 8.4206(5) Å, c ) 19.5860(12) Å; ꢀ )
105.4520(10)°; Z ) 4; V ) 2092.0(2) Å3; Dc ) 1.726 g/cm3; µ )
6.470 mm-1, minimum and maximum transmission factors 0.262
and 0.775; 2θmax ) 55.4°; 13 531 reflections collected, 4946 unique
[R(int) ) 0.0339]; number of data/restrains/parameters 4946/0/370;
final GoF 1.048, R1 ) 0.0301 [4427 reflns I > 2σ(I)], wR2 ) 0.0706
for all data.
30.8, JHH ) 11.3, JHH ) 4.0, 1H, dCH), 6.20 (dd, JHH ) 6.7, 5.4,
2H, H3). 31P{1H} NMR (acetone-d6, 298 K): δ 32.02 (s). 13C{1H}
NMR (acetone-d6, 298 K): δ 17.94 (br, CH2dCH2), 30.27 (d, JCP
) 3.6, PCCH3), 37.93 (d, JCP ) 26.5, PCCH3), 80.10 (C2), 81.15
(C4), 97.37 (C3), 124.65 (d, JCP ) 39.8, PCHdCH2), 130.03
(PCHdCH2), 166.43(CO C1). Anal. Calcd (%) for C18H30IrOP
(485.6294): C 44.52, H 6.23. Found: C 44.58, H 6.29.
Preparation of [Ir(η5-C6H5O)(C3H6)(t-Bu2PCHdCH2)] (8).
Method A: The compound was prepared from [Ir{η5-3-
(CH3COCH2)C6H5O(CH2)2Pt-Bu2-k-P}(C3H6)] (5) following the
procedure described for compound 7 and isolated as a pale
yellow solid. Yield: 76 mg (45%). IR (Nujol mull, cm-1): 1630
1
(m) ν(CdO), 1545 (m) ν(CdC). H NMR (acetone-d6, 298 K):
δ 1.29 (d, JHP ) 13.2, 9H, PCCH3), 1.32 (d, JHP ) 13.2, 9H,
PCCH3), 1.56 (d, JHP ) 6.0, 9H, dCHCH3), 1.59 (dd, JHH
)
13.2, 1.5, 1H, dCH2), 1.90 (ddd, JHH ) 9.6, JHH ) JHP ) 1.5,
1H, dCH2), 2.10 (m, 1H, dCHCH3), 4.71 (d, JHH ) 6.9, 1H,
H2 or H6), 5.35 (d, JHH ) 6.9, 1H, H2 or H6), 5.74 (t, JHH ) 5.7,
1H, H4), 5.83 (dd, JHP ) 12.0, JHH ) 2.7, 1H, dCH2), 5.86 (dd,
JHP ) 14.1, JHH ) 11.4, 1H, dCH2), 6.07 (dd, JHH ) 6.9, 5.7,
1H, H3 or H5), 6.11 (ddd, JHP ) 33.0, JHH ) 11.4, JHH ) 2.7,
1H, dCH), 6.18 (dd, JHH ) 6.9, 5.7, 1H, H3 or H5). 31P{1H}
NMR (C6D6, 298 K): δ 31.43 (s). 13C{1H} NMR (C6D6, 298
K): δ 14.23 (dCH CH3), 21.64 (dCH2), 22.68 (dCHCH3), 29.78
(d, JCP ) 4.0, PCCH3), 30.39 (PCCH3), 37.61 (d, JCP ) 27.1,
PCCH3), 38.15 (d, JCP ) 26.3, PCCH3), 77.53 (C2), 83.45 (C4),
98.02 (C3), 124.00 (d, JCP ) 35.8, PCHdCH2), 129.19
(PCHdCH2), 166.19 (s, CO, C1). Anal. Calcd (%) for C19H32IrOP
(499.6562): C 45.67, H 6.45. Found: C 45.58, H 6.36.
Preparation of [Ir(OC6H5)(C2H4)(t-Bu2P(CH2)2OMe-k2-O,P)]
(9). A solution of 7 (100 mg, 0.21 mmol) in toluene (5 mL) was
treated with methanol (20 µL, 0.49 mmol). After 2 h of stirring,
the solvent was pumped off and the residue treated with hexane at
0 °C. The resulting brown solid was washed with hexane, filtered,
and dried in vacuo. Yield: 66 mg (61%). IR (Nujol mull, cm-1):
1060 (m) ν(CsO), 1580 (m) ν(CdC). 1H NMR (C6D6, 298 K): δ
1.10 (d, JHP ) 13.2, 18H, PCCH3), 1.51 (dt, JHP ) 6.1, JHH ) 6.1,
2H, CH2-CR), 1.60 (m, 2H, endo-H CH2dCH2), 2.05 (m, 2H,
Crystal data for compound 7: C18H30IrOP · C6H6O, M )
579.72; crystal size 0.299 × 0.247 × 0.089 mm3; monoclinic, P21/
n; a ) 7.9252(6) Å, b ) 29.893(2) Å, c ) 9.7153(7) Å; ꢀ )
102.441(1)°; Z ) 4; V ) 2247.6(3) Å3; Dc ) 1.713 g/cm3; µ )
(41) SAINT+ Software for CCD difractometers; Bruker AXS: Madison,
WI, 2000. (b) Sheldrick, G. M. SADABS Program for Correction of Area
Detector Data V. 2.03; University of Go¨ttingen: Go¨ttingen, Germany, 2001.
(42) SHELXTL Package V. 6.10; Bruker AXS: Madison, WI, 2000.
Sheldrick G. M. SHELXS-86 and SHELXL-97; University of Go¨ttingen:
Go¨ttingen, Germany, 1997.
exo-H CH2dCH2), 3.07 (s, 3H, MeO), 3.24 (dt, JHP ) 12.0, JHH
6.1, 2H, CH2-Cꢀ), 6.89 (t, JHH ) 7.7, 1H, PhO), 7.04 (dd, JHH
)
)
7.7, 7.6, 2H, PhO), 7.20 (d, JHH ) 7.6, 1H, PhO). 31P{1H} NMR

C-C Formation and C-O CleaVage Reactions
Organometallics, Vol. 27, No. 16, 2008 4237
6.028 mm-1, minimum and maximum transmission factors 0.197
and 0.585; 2θmax ) 54.1°; 26 188 reflections collected, 4933 unique
[R(int) ) 0.0320]; number of data/restrains/parameters 4933/0/397;
final GoF 1.100, R1 ) 0.0190 [4629 reflns I > 2σ(I)], wR2 ) 0.0437
for all data.
03973/BQU) and CONACYT-Me´xico for a postdoctoral
fellowship to I.I.R. are gratefully acknowledged.
Supporting Information Available: X-ray crystallographic
information files containing full details of the structural analysis
of complexes 4 and 7. This material is available free of charge via
the Internet at http://pubs.acs.org.
Acknowledgment. The financial support from Ministerio
de Educacio´n y Ciencia (MEC/FEDER) (Project CTQ2006-
OM800402N