Reaction of the Iridacyclopentadiene TpMe2Ir (C (R) C (R) C (R) C

Margarita Paneque,*,† Manuel L. Poveda,*,† Nuria Rendón,† and Kurt Mereiter‡. Instituto de InVestigaciones Quımicas and Departamento de Quı...
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Organometallics 2009, 28, 172–180

Reaction of the Iridacyclopentadiene TpMe2Ir(C(R)dC(R)C(R)dC(R))(H2O) (R ) CO2Me) with Alkynes Margarita Paneque,*,† Manuel L. Poveda,*,† Nuria Rendo´n,† and Kurt Mereiter‡ Instituto de InVestigaciones Quı´micas and Departamento de Quı´mica Inorga´nica, Consejo Superior de InVestigaciones Cientı´ficas (CSIC) and UniVersidad de SeVilla, AVenida Ame´rico Vespucio 49, Isla de la Cartuja, 41092 SeVilla, Spain, and Department of Chemistry, Vienna UniVersity of Technology, Getreidemarkt 9/164SC, A-1060 Vienna, Austria ReceiVed February 8, 2008

The iridacyclopentadiene derivative TpMe2Ir(C(R)dC(R)C(R)dC(R))(H2O) (1) (TpMe2 ) hydrotris(3,5-dimethylpyrazolyl)borate, R ) CO2Me) reacts with an excess of MeCtCMe with formation of the iridacycloheptatriene TpMe2Ir(C(Me)dC(Me)C(R)dC(R)C(R)dC(R))(H2O) (3) and the first metallabicyclo[3,2,0]heptatriene TpMe2Ir(dC(Me)C(Me)dC(R)C(R)C(R)dC(R))(H2O) (4). Both species are involved in the equilibrium 3 h 4 + H2O, which has been studied as a function of temperature. By contrast, PhCtCPh gives only a compound related to 4, namely, the species TpMe2Ir(dC(Ph)C(Ph)dC(R)C(R)C(R)dC(R))(H2O) (5), which does not react with water. Complex 1 incorporates two molecules of terminal alkynes such as HCtCPh and HCtCCH2CH2OH with formation of complex chelating alkenyl-allylic structures, and the same is true for Me3SiCtCPh and Me3SiCtCSiMe3, where the SiMe3 groups are replaced by hydrogen atoms under the reaction conditions. In all these cases the two alkynes are added consecutively into one of the Ir-C bonds of 1. Finally, the reaction of 1 with HCtCCO2Me gives a fully substituted cyclopentadiene with two of the substituents being metalated by the iridium center and in this case the two Ir-C bonds of 1 are cleaved in the process. All the new compounds have been characterized by microanalysis, IR and NMR spectroscopies, and in some cases by X-ray diffraction analysis. Introduction 1

In two recent theoretical papers about the well-known process of cyclotrimerization of alkynes catalyzed by transition metal species,2 it has been found that a metallabicyclo[3.2.0]heptatriene (A), the result of the internal coupling of the metallacyclopentadiene-alkyne complex B (eq 1), may be implicated as an active intermediate. Species A then undergoes

(this can be formulated as a saturated bis(carbene) species depending on the system1a), i.e., the expected product of the insertion of the alkyne into a M-C bond of B, which eventually experiences reductive elimination to give a benzenoid nucleus. In a recent paper3 we have shown that the iridacyclopentadiene TpMe2Ir(C(R)dC(R)C(R)dC(R))(H2O) (1)4 (TpMe2 ) hydrotris(3,5-dimethylpyrazolyl)borate, R ) CO2Me) reacts with dimethyl acetylendicarboxylate (MeO2CCtCCO2Me, DMAD) to give the iridacycloheptatriene TpMe2Ir(C(R)dC(R)C-

a structural opening to an unsaturated metallacycloheptatriene * To whom correspondence should be addressed. E-mail: paneque@ iiq.csic.es. † Universidad de Sevilla and Consejo Superior de Investigaciones Cientı´ficas. ‡ Vienna University of Technology. (1) (a) Kirchner, K.; Calhorda, M. J.; Schmid, R.; Veiros, L. F. J. Am. Chem. Soc. 2003, 125, 11721. (b) Yamamoto, Y.; Arakawa, T.; Ogawa, R.; Itoh, K. J. Am. Chem. Soc. 2003, 125, 12143. (2) (a) Collman, J. P.; Hegedus, L. S.; Norton, J. R.; Finke, R. G. Principles and Applications of Organotransition Metal Chemistry; University Science Books: Mill Valley, CA, 1987. (b) Kezuka, S.; Tanaka, S.; Ohe, T.; Nakaya, Y.; Takeuchi, R. J. Org. Chem. 2006, 71, 543. (c) Saito, S.; Yamamoto, Y. Chem. ReV. 2000, 100, 2901. (d) Grotjahn, D. B. In ComprehensiVe Organometallic Chemistry II; Abel, E. W., Stone, F. G. A., Wilkinson, G., Eds.; Pergamon: Oxford, 1995; Vol. 12,Chapter 7.3. (e) Cadierno, V.; Garcı´a-Garrido, S. E.; Gimeno, J. J. Am. Chem. Soc. 2006, 128, 15094. (f) Kakeya, M.; Fujihara, T.; Kasaya, T.; Nagasawa, A. Organometallics 2006, 25, 4131, and reference 1.

(R)dC(R)C(R))(H2O) (2) (eq 2). Surprisingly, and as described in the present contribution, the first example of a transition metal derivative with structure A is obtained when complex 1 is treated with 2-butyne (MeCtCMe). In addition, the reactivity of 1 with other alkynes such as PhCtCPh, Me3SiCtCSiMe3, HCtCPh, HCtCCH2CH2OH, and Me3SiCtCPh, HCtCCO2Me is also reported herein. Part of this work has been the subject of a preliminary communication.5

Results and Discussion Reaction of 1 with 2-Butyne. When TpMe2Ir(C(R)dC(R)C(R)dC(R))(H2O) (1) is treated with an excess of MeCtCMe, (3) Paneque, M.; Posadas, C. M.; Poveda, M. L.; Rendo´n, N.; Santos, ´ lvarez, E.; Salazar, V.; Mereiter, K.; On˜ate, E. Organometallics L. L.; A 2007, 26, 3403. ´ lvarez, E.; Paneque, M.; Posadas, C. M.; Poveda, M. L.; Rendo´n, (4) A N.; Mereiter, K. Chem.-Eur. J. 2007, 13, 5160. (5) Paneque, M.; Poveda, M. L.; Rendo´n, N.; Mereiter, K. J. Am. Chem. Soc. 2004, 126, 1610.

10.1021/om8001153 CCC: $40.75  2009 American Chemical Society Publication on Web 12/02/2008

Reaction of an Iridacyclopentadiene

Organometallics, Vol. 28, No. 1, 2009 173

in C6H12 at 90 °C, a mixture of the complexes 3 and 4 (whose proportion depends on the water concentration in the reaction media) is obtained in very high yield (eq 3).

Figure 1. X-ray structure of complex 3 (30% displacement ellipsoids, hydrogen atoms omitted for clarity except for the water molecule H2O(1w)).

3 is a yellow crystalline solid whose structure is related to that presented for 2 (see Introduction); that is, it is an iridacycloheptatriene that is formally formed by the insertion of MeCtCMe into one of the Ir-C bonds of 1. Complex 3 has been fully characterized by microanalysis, IR and NMR spectroscopies, and X-ray diffraction analysis. As expected, it exhibits NMR features quite similar to those found for 23 and will not be described in any detail here (see Experimental Section). Figure 1 shows a view of the molecular structure of complex 3, while Tables 1 and 2 collect the crystal data and the relevant bond lengths and angles, respectively. As can be observed, the metallacycle features a boat structure with the central double CdC bond pointing to the metal center, while the water ligand is hydrogen bonded to O(56) of the CO2Me substituent at C(52), this carbon being the one bonded to the -C(Me)dC(Me)- moiety (Figure 1; a second hydrogen bond is donated intermolecularly to O(65), not shown). The two Ir-C(sp2) bond distances exhibit similar and normal values (2.03 Å av),3,4,6 while, as expected, the Ir-N(pyrazolyl) bond length trans to the hard H2O ligand (2.03 Å) is shorter than the other two (2.14 Å av).3,4 The other compound formed in eq 3 is complex 4, a green crystalline solid that represents the first example of metallabicyclo[3.2.0]heptatriene structure mentioned in the Introduction. Its 13 C{1H} NMR spectrum features resonances at 275.1 and 20.5 ppm, which are assigned to the carbenic functionality and to the sp3 carbon directly bonded to the iridium, respectively, while in the long-range 1H-13C HETCOR spectrum the cross-peaks found between the Me protons, derived from the added alkyne, and the carbenic carbon are in accord with the depicted structure. The conclusions of these spectroscopic solution studies find (6) Ilg, K.; Paneque, M.; Poveda, M. L.; Rendo´n, N.; Santos, L. L.; Carmona, E.; Mereiter, K. Organometallics 2006, 25, 2230.

additional support in the solid state structure deduced from the X-ray diffraction study carried out for complex 4 (Figure 2 and Tables 1 and 3). The bond distances Ir-C(42) (1.91 Å), Ir-C(63) (2.03 Å), and Ir-C(53) (2.14 Å) are in the range expected for Ir-carbene,6 Ir-alkenyl, and Ir-alkyl functionalities,3,4,6 although the latter bond is somewhat longer than normal Ir-C(sp3) bonds, probably due to ring strain. The C-Ir-C bite angles are 66.0° and 81.8° for the four- and fivememberedmetallacycles,respectively,andfinally,theIr-N(pyrazolyl) bond length of the one trans to the carbene (2.25 Å) is longer than the other two (2.16 Å each). As already commented on, there is no precedent for the structure presented by complex 4 in transition metal chemistry, except for a related silicon compound stabilized by very bulky substituents.7 A tungsten complex with a similar bicyclic skeleton, but with a more complicated bonding pattern, can also be found in the literature.8 It is also worth mentioning that the parent pure organic compound [3.2.0]hepta-1,3,6-triene is not known but has been implicated in a number of chemical reactions as a highly unstable intermediate.9 Interestingly compounds 3 and 4 easily interconvert into each other. Thus, when 3 is dissolved in dry C6D6, the solution turns green, and, on the other hand, 4 gives solutions in acetone-d6 that become yellow when a little water is added. In both cases the interconversion is confirmed by 1H NMR spectroscopy. A quantitative study of the 3 h 4 + H2O equilibrium has been carried out with D2O (0.6 M in acetone-d6) in the temperature range 40-70 °C, and the results are shown in graphic form in Figure 3 (∆H ) 6.5 kcal · mol-1, ∆S ) 19.1 cal · mol-1 · K-1). Scheme 1 shows the proposed mechanism for the 3 h 4 + H2O interconversion. Complex 3 loses the water ligand to give C (we prefer to formulate this intermediate as an unsaturated 16 e- species rather than a 18 e- bis(carbene)1a), which then (7) Kon, Y.; Ogasawara, J.; Sakamoto, K.; Kabuto, C.; Kira, M. J. Am. Chem. Soc. 2003, 125, 9310. (8) (a) Agh-Atabay, N. M.; Davidson, J. L.; Douglas, G.; Muir, K. W. J. Chem. Soc., Chem. Commun. 1989, 549. For a somewhat related iridacyclobutene resulting from a carbene insertion into a iridacyclopentadiene, see: (b) O’Connor, J. M.; Pu, L.; Woolard, S.; Chadha, R. K. J. Am. Chem. Soc. 1990, 112, 6731. (9) (a) Breslow, R.; Washburn, W.; Bergman, R. G. J. Am. Chem. Soc. 1969, 91, 196. (b) Billups, W. E.; Saini, R. K.; Litosh, V. A.; Alemany, L. B.; Wilson, W. K.; Wiberg, K. B. J. Org. Chem. 2002, 67, 4436. (c) Bajorek, T.; Werstink, N. H. Can. J. Chem. 2005, 83, 1352.

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Table 1. Crystal Data and Data Collection and Refinement Details for 3 · CHCl3, 4 · CH2Cl2, 8 · solv, and 11 · 2CH2Cl2 formula mol wt color, habit symmetry, space group a, Å b, Å c, Å R, deg β, deg γ, deg V, Å3 Z Dcalcd, g cm-3 µ, mm-1 θ range, deg temp, K no. of data collected no. of unique data no. of params/restraints R1d (F2 > 2σ(F2)) wR2e (all data) diff Fourier peaks min./max., e Å-3

3 · CHCl3

4 · CH2Cl2a

8 · solvb

11 · 2CH2Cl2c

C31H42BIrN6O9 · CHCl3 965.08 yellow prism orthorhombic, P212121 14.5281(8) 16.3834(9) 17.0149(9) 90 90 90 4049.9(4) 4 1.583 3.550 2.4-30 173(2) 58 618 11 754 (Rint ) 0.062) 488/5 0.0321 0.0712 -0.81/1.86

C31H40BIrN6O8 · CH2Cl2 912.63 green prism triclinic, P1j 11.0348(6) 12.5531(7) 14.0159(8) 88.743(1) 75.343(1) 87.515(1) 1876.4(2) 2 1.615 3.755 2.20-30 298(2) 28 299 10 85 (Rint ) 0.023) 441/0 0.0246 0.0650 -0.43/0.86

C43H46BIrN6O8 977.87 yellow prism monoclinic, C2/c 39.850(2) 11.0782(6) 21.2993(12) 90 108.718(1) 90 8905.5(9) 8 1.459 3.055 2.24-30 173(2) 65 632 12 906 (Rint ) 0.030) 573/283 0.0308 0.0738 -1.91/3.57

C35H42BIrN6O12 · 2CH2Cl2 1111.61 yellow fragment triclinic, P1j 11.225(2) 13.849(3) 16.314(3) 80.248(4) 76.248(4) 70.208(4) 2306.8(7) 2 1.600 3.189 2.58-25 173(2) 20 763 8093 (Rint ) 0.061) 540/205 0.0779 0.1454 -1.67/1.46

a Solvent disordered and squeezed with the program PLATON (Spek, A. L., 2006) but contained in chemical formula and quantities thereof. b Solvent (essentially petroleum ether) disordered and squeezed with the program PLATON, but not contained in chemical formula and quantities thereof. c Solvent content idealized. d R1(F) ) ∑|Fo| - |Fc|/∑|Fo|. e wR2(F2) ) {∑[w(Fo2 - Fc2)2]/∑[(w(Fo2)2]}1/2.

Table 2. Selected Bond Lengths (Å) and Angles (deg) for 3 · CHCl3

Table 3. Selected Bond Lengths (Å) and Angles (deg) for 4 · CH2Cl2

Ir-N(12) Ir-N(22) Ir-N(32) Ir-C(42) Ir-C(63) Ir-O(1W)

2.135(3) 2.149(3) 2.030(3) 2.040(4) 2.022(4) 2.135(3)

C(42)-C(43) C(43)-C(52) C(52)-C(53) C(53)-C(62) C(62)-C(63)

1.361(5) 1.470(5) 1.343(5) 1.490(5) 1.358(5)

Ir-N(12) Ir-N(22) Ir-N(32) Ir-C(42) Ir-C(53) Ir-C(63)

2.163(2) 2.245(2) 2.155(2) 1.905(3) 2.136(2) 2.025(2)

C(42)-C(43) C(43)-C(52) C(52)-C(53) C(53)-C(62) C(62)-C(63)

1.438(4) 1.348(4) 1.506(4) 1.524(3) 1.337(3)

N(12)-Ir-N(22) N(12)-Ir-N(32) N(12)-Ir-C(42) N(12)-Ir-C(63) N(12)-Ir-O(1W) N(22)-Ir-N(32) N(22)-Ir-C(42) N(22)-Ir-C(63)

84.4(1) 88.5(1) 91.6(2) 176.2(2) 86.6(1) 91.5(1) 175.9(2) 91.9(2)

N(22)-Ir-O(1W) N(32)-Ir-C(42) N(32)-Ir-C(63) N(32)-Ir-O(1W) C(42)-Ir-C(63) C(42)-Ir-O(1W) C(63)-Ir-O(1W)

85.3(1) 88.1(2) 91.5(1) 174.4(1) 92.2(2) 94.8(1) 93.2(1)

N(12)-Ir-N(22) N(12)-Ir-N(32) N(12)-Ir-C(42) N(12)-Ir-C(53) N(12)-Ir-C(63) N(22)-Ir-N(32) N(22)-Ir-C(42) N(22)-Ir-C(53)

85.4(1) 87.5(1) 89.6(1) 104.8(1) 168.4(1) 83.1(1) 175.0(1) 99.8(1)

N(22)-Ir-C(63) N(32)-Ir-C(42) N(32)-Ir-C(53) N(32)-Ir-C(63) C(42)-Ir-C(53) C(42)-Ir-C(63) C(53)-Ir-C(63)

89.0(1) 96.4(1) 167.5(1) 102.0(1) 81.8(1) 95.9(1) 66.0(1)

Figure 3. ∆G versus T for the 3 h 4 + H2O equilibrium.

Figure 2. X-ray structure of complex 4 (30% displacement ellipsoids, hydrogen atoms omitted for clarity).

in which a -C(Me)dC(Me)- unit is on the four-membered iridacycle, and this may be due, at least partially, to the stabilization that a donor substituent, like the methyl group, confers to the electrophilic carbene.10 In fact the iridacycloheptatriene 2,3 mentioned in the Introduction, in which all the substituents are CO2Me, does not give a compound related to 4

experiences ring contraction by regioselective attack of a C(CO2Me) sp2 carbon to the iridium to afford compound 4. There is no evidence for the formation of an isomeric species

(10) (a) Carmona, E.; Paneque, M.; Poveda, M. L. Dalton Trans. 2003, 4022. (b) Carmona, E.; Paneque, M.; Santos, L. L.; Salazar, V. Coord. Chem. ReV. 2005, 294, 1729.

Reaction of an Iridacyclopentadiene Scheme 1

(under molecular sieves, in C6D6, at 60 °C, 48 h) even though that the water ligand is labile under these conditions.3 Finally and with respect to the formation of 3 and 4 from 1 and MeCtCMe, the experimental data obtained are not sufficient to decide which species is formed in the first place, as this reaction is slower than the 3 h 4 + H2O equilibrium. As expected,3,4 complex 4 reacts with other Lewis bases such as NCMe and CO with formation of the stable adducts 3 · L (eq 4). Compound 3, in a typical reaction of this kind of iridacycloheptatrienes,3 is cleanly oxidized by tBuOOH to give the ketoester 5 (eq 5). The spectroscopic data of 3 · L are similar to those obtained for 3 and will not be commented on, while for 5 the 13C{1H} NMR spectrum exhibits resonances at 209.1 and 77.5 ppm, assigned to the keto group bonded to Ir and to the quaternary aliphatic carbon, respectively.

Reaction of Complex 1 with PhCtCPh. Complex 1 reacts with an excess of PhCtCPh to give the brown compound 6 in g80% spectroscopic yield (eq 6). Its spectroscopic characteristics indicate that it is related to the already described bicyclic 4 and furthermore that the PhCtCPh molecule has been incorporated into the five-membered iridacycle. Complex 6 has no tendency to react with water, and it is recovered unaltered upon heating, in different solvents, at 90 °C with an excess of added H2O.

Organometallics, Vol. 28, No. 1, 2009 175 Scheme 2

Reaction of Complex 1 with Me3SiCtCSiMe3. When a solution of 1 in C6H12 is heated (90 °C, 12 h) in the presence of an excess of Me3SiCtCSiMe3 (BTMSA), the chelating alkenyl-allylic species 7 is formed in ca. 75% spectroscopic yield (eq 7).

As can be observed, two alkyne moieties have been incorporated into one of the Ir-C bonds of 1 in the form of a 1,2,3η3-butadienyl ligand11 in such a way that all the SiMe3 groups have been replaced, probably due to hydrolysis, by hydrogen atoms. In recent work carried out in this laboratory we have reported4 on compounds related to 7 but with normal allyl termini, i.e., without the dCH2 substituent, and some years ago we also synthesized some 1,2,3-η3-butadienyl Ir(III) complexes containing the TpMe2 ligand.12 Therefore the NMR spectroscopic characterization of 7 was straightforward, and the relevant data are collected in the Experimental Section. For the formation of 7 we propose the mechanism shown in Scheme 2. First, the water molecule is displaced by a molecule of BTMSA, to give D, in which the alkyne has isomerized to a vinylidene ligand,13 a process that has been observed in the reaction of TpMe2Ir(Ph)2(N2) with BTMSA.6 Then, a migratory (11) Brisdon, B. J.; Walton, R. A. Polyhedron 1995, 14, 1259. (12) Boutry, O.; Poveda, M. L.; Carmona, E. J. Organomet. Chem. 1997, 528, 143. (13) (a) Werner, H. J. Organomet. Chem. 1994, 475, 45. (b) Werner, H.; Baum, M.; Schneider, D.; Windmueller, B. Organometallics 1994, 13, 1089. (c) Werner, H.; Lass, R. W.; Gevert, O.; Wolf, J. Organometallics 1997, 16, 4077. (d) Jime´nez, M. V.; Sola, E.; Lahoz, F. J.; Oro, L. A. Organometallics 2005, 24, 2722. (e) Bustelo, E.; Carbo´, J. J.; Lledo´s, A.; Mereiter, K.; Puerta, M. C.; Valerga, P. J. Am. Chem. Soc. 2003, 125, 3311. (f) De Angelis, F.; Sgamellotti, A.; Re, N. Dalton Trans. 2004, 3225.

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Figure 4. X-ray structure of complex 8 (30% displacement ellipsoids, hydrogen atoms omitted for clarity). Table 4. Selected Bond Lengths (Å) and Angles (deg) for 8 · solv Ir-N(12) Ir-N(22) Ir-N(32) Ir-C(41) Ir-C(42) Ir-C(51) Ir-C(62) C(41)-C(42)

2.137(2) 2.087(2) 2.245(2) 2.111(3) 2.144(3) 2.286(3) 2.016(3) 1.439(3)

C(41)-C(51) C(41)-C(72) C(51)-C(52) C(52)-C(73) C(62)-C(63) C(63)-C(72) C(72)-C(73)

1.410(3) 1.531(4) 1.482(4) 1.348(4) 1.346(4) 1.530(4) 1.531(3)

N(12)-Ir-N(22) N(12)-Ir-N(32) N(12)-Ir-C(41) N(12)-Ir-C(42) N(12)-Ir-C(51) N(12)-Ir-C(62) N(22)-Ir-N(32) N(22)-Ir-C(41) N(22)-Ir-C(42) N(22)-Ir-C(51) N(22)-Ir-C(62)

89.9(1) 83.1(1) 134.6(1) 174.1(1) 104.5(1) 90.4(1) 84.8(1) 132.5(1) 95.8(1) 164.0(1) 88.6(1)

N(32)-Ir-C(41) N(32)-Ir-C(42) N(32)-Ir-C(51) N(32)-Ir-C(62) C(41)-Ir-C(42) C(41)-Ir-C(51) C(41)-Ir-C(62) C(42)-Ir-C(51) C(42)-Ir-C(62) C(51)-Ir-C(62)

111.7(1) 98.9(1) 90.0(1) 170.7(1) 39.5(1) 37.1(1) 77.6(1) 70.0(1) 88.3(1) 98.1(1)

insertion reaction into an Ir-C bond of the metallacycle14 furnishes intermediate E, where the whole process is repeated to end up with species G. Finally, bond reorganization of the latter intermediate gives complex 7 (R′ ) H). Although it is clear that all the SiMe3 groups are replaced by hydrogen atoms in the formation of 7, it is not known when and how this occurs, but according to the literature, it probably takes place in the alkyne to vinylidene isomerization.13 Reaction of Complex 1 with HCtCPh and Me3SiCtCPh. Complex 1 reacts with an excess of HCtCPh, under the experimental conditions depicted in eq 8, with formation of a mixture of compounds, with one of them, compound 8, clearly predominating (60% spectroscopic yield). 8 can be isolated by chromatography on silica gel, and its structural complexity has been ascertained by X-ray diffraction studies (Figure 4 and Tables 1 and 4). As can be observed, complex 8 is another chelating alkenylallylic species, in this case bicyclic, in which the allyl ligand has been formed by the coupling of two HCtCPh molecules, with concomitant incorporation into the metallacycle 1. The Ph (14) (a) Chin, C. S.; Lee, H. Chem.-Eur. J. 2004, 10, 4518. (b) Clark, G. R.; Johns, P. M.; Roper, W. R.; Wright, L. J. Organometallics 2006, 25, 1771. (c) O’Connor, J. M.; Hiibner, K.; Merwin, R.; Gantzel, P. K.; Fong, B. S.; Adams, M.; Rheingold, A. L. J. Am. Chem. Soc. 1997, 119, 3631.

substituent of the allyl is positioned anti with respect to the C(R) group that is bonded to the central carbon of the η3-allyl moiety, and it has been found that it is slowly rotating in solution, at room temperature, on the NMR time scale. In the 13 C{1H} NMR spectrum, the carbon nuclei of the allylic ligand resonate at 39.0 (CHPh), 116.6 (Cq), and 60.5 (CH) ppm, respectively, while the aliphatic quaternary carbon, C(R), appears at δ 72.1. With respect to the solid state structure, the Ir-C(62) bond length of 2.02 Å corresponds well for an Ir-C(sp2) single bond,6 while the distances of the metal to the carbon atoms of the η3-allyl moiety are 2.11 Å (central) and 2.14 and 2.29 Å (termini), unexceptional for this kind of ligand.4 Scheme 3 shows a plausible, but highly speculative, mechanism for the formation of 8. First, a molecule of alkyne regioselectively inserts into an Ir-C bond of 1 with formation of the unsaturated metallacycloheptatriene H. This species does not stabilize by addition of water or ring contraction (see the case of MeCtCMe or PhCtCPh) but reacts with another equivalent of HCtCPh to give intermediate I via alkyne to vinylidene isomerization13e,13f and regioselective migratory insertion of this ligand into the Ir-C(H)d bond. Finally, a ring contraction process will form the allyl ligand present in 8. Interestingly, when the reaction of 1 with an excess of Me3SiCtCPh is carried out under conditions similar to those employed for the synthesis of 8, an isomer of this species, the chelating alkenyl-allyl 9 (eq 9), is obtained in ca. 60% isolated yield. They differ only in the stereochemistry of the CHPh terminus of the allyl moiety, and this is reflected by the similarity of the NMR data obtained for both complexes. For the case of 9 the cisoid disposition of the two hydrogen substituents of the allyl is clearly revealed by the NOESY spectrum (see Experimental Section). It is proposed that formation of 9 follows a

mechanism almost identical to that already advanced for 8 (Scheme 3) but with the SiMe3 substituent forcing the different stereochemical outcome, perhaps at the formation stage of the intermediate related to I. Once again the SiMe3 groups have been replaced by hydrogen atoms despite the “neutral” reaction conditions. Reaction of Complex 1 with HCtCCH2CH2OH and HCtCCO2Me. In the first case, complex 10, an analogue of 8, is obtained in ca. 60% isolated yield (eq 10), despite the different nature of the substituents on the alkyne, CH2CH2OH and Ph, respectively. Complex 10 has been fully characterized by NMR spectroscopy, and the corresponding data obtained are collected in the Experimental Section. Finally, the reaction of 1 with an excess of HCtCCO2Me, in C6H12 at 90 °C, furnishes compound 11, in ca. 50% isolated yield, whose molecular complexity has been revealed by X-ray diffraction analysis (eq 11). As can be observed, two molecules

Reaction of an Iridacyclopentadiene

Organometallics, Vol. 28, No. 1, 2009 177 Scheme 3

of the alkyne have been incorporated into complex 1 with formation of a fully substituted cyclopentadiene with two of the substituents being metalated by iridium. The NMR data obtained for 11 are in accord with the structure found in the solid state, and thus the carbon nuclei bonded to Ir resonate at 150.7 (sp2) and 8.1 (sp3) ppm in the 13C{1H} NMR spectrum, while the sp3 carbon of the cyclopentadiene ring appears at δ 94.1. Figure 5 shows a view of a molecule of 11, while structure data are contained in Tables 1 and 5. One of the three Ir-N(pyrazolyl) bond distances of 11, specifically that trans to

the coordinated oxygen atom, is significantly shorter (2.02 Å) than the other two (2.15 Å av). The Ir-C(sp3) and Ir-C(sp2) bond lengths are 2.17 and 1.99 Å, respectively, typical values of these kinds of bonds.3,4,6 Due to the complex structure of 11, it is not appropriate to propose a mechanism for its formation, although it is clear that the two alkyne molecules have not been incorporated consecutively into one of the Ir-C bonds of 1, but instead one each into the two initially existing Ir-C bonds.

Conclusions The reaction of iridacyclopentadiene TpMe2Ir(C(R)dC(R)C(R)dC(R))(H2O) (1) (R ) CO2Me) with an excess of MeCtCMe has allowed the synthesis of the first metallabicyclo[3.2.0]heptatriene, a kind of structure recently invoked in the transition metal mediated catalytic cyclotrimerization of alkynes. This species readily reacts with Lewis bases, with formation of iridacycloheptatrienes, and for the case of H2O, this process is reversible. A related bicyclic compound is obtained when 1 reacts with PhCtCPh, and as in the case of MeCtCMe, the entering alkyne is incorporated into the five-membered part of the bicyclic structure. By contrast, two molecules of alkyne add to 1 when the alkyne is of the terminal type or if it has SiMe3 substituents (to be interchanged by hydrogens in the course of the reaction), giving complicated structures with a highly substituted η3-allyl ligand in most cases.

Experimental Section General Procedures. Microanalyses were by the Microanalytical Service of the Instituto de Investigaciones Quı´micas (Sevilla, Spain). In our hands, compounds 6, 9, and 10 could not be purified satisfactorily. The presence of crystallization solvent in the remaining compounds was authenticated by NMR. Infrared spectra were obtained with a Bruker Vector 22 spectrometer. The NMR instruments were Bruker DRX-500, DRX-400, and DPX-300

Figure 5. X-ray structure of complex 11 (30% displacement ellipsoids, hydrogen atoms omitted for clarity). spectrometers. Spectra were referenced to external SiMe4 (δ 0 ppm) using the residual protio solvent peaks as internal standards (1H NMR experiments) or the characteristic resonances of the solvent nuclei (13C NMR experiments). Spectral assignments were made by means of routine one- and two-dimensional NMR experiments where appropriate. All manipulations were performed under dry, oxygen-free dinitrogen, following conventional Schlenk techniques. The metallacyclopentadiene TpMe2Ir(C(R)dC(R)C(R)dC(R))(H2O) (1) was obtained as reported previously.4 Compounds 3 and 4. To a suspension of 1 in C6H12 (0.6 g, 0.76 mmol; 8 mL) MeCtCMe (6 mL of a 0.5 M solution in C6H12, 3 mmol) was added, and the mixture was stirred at 90 °C for 12 h. Thereafter the green solution was taken to dryness and formation of compounds 3 and 4 (80% spectroscopic yield) was ascertained by 1H NMR. A pure mixture of 3 and 4 was isolated by column chromatography (silica gel), using a 1:1 mixture of hexane/Et2O as eluent (64% yield). Upon crystallization from pentane/CH2Cl2 (1:1) at -20 °C, the mixture of yellow (compound 3) and green

178 Organometallics, Vol. 28, No. 1, 2009

Paneque et al.

Table 5. Selected Bond Lengths (Å) and Angles (deg) for 11 · 2CH2Cl2 Ir-N(12) Ir-N(22) Ir-N(32) Ir-O(45) Ir-C(61) Ir-C(72) C(42)-C(43)

2.023(10) 2.105(10) 2.199(10) 2.112(8) 1.991(12) 2.172(12) 1.471(16)

C(42)-C(61) C(42)-C(71) C(43)-C(53) C(52)-C(53) C(52)-C(71) C(61)-C(62) C(71)-C(72)

1.634(16) 1.510(16) 1.339(17) 1.452(16) 1.392(16) 1.290(14) 1.453(15)

N(12)-Ir-N(22) N(12)-Ir-N(32) N(12)-Ir-O(45) N(12)-Ir-C(61) N(12)-Ir-C(72) N(22)-Ir-N(32) N(22)-Ir-O(45) N(22)-Ir-C(61)

89.6(4) 91.3(4) 174.9(4) 93.9(4) 90.6(5) 81.5(4) 93.5(4) 94.0(5)

N(22)-Ir-C(72) N(32)-Ir-O(45) N(32)-Ir-C(61) N(32)-Ir-C(72) O(45)-Ir-C(61) O(45)-Ir-C(72) C(61)-Ir-C(72)

175.9(5) 93.1(4) 173.1(5) 102.6(4) 81.9(4) 86.0(4) 81.9(5)

crystals (compound 4) obtained was decanted from the mother liquor and dried in vacuo. 3 and 4 were carefully separated by hand to obtain pure samples of both compounds.

3: 1H NMR (CD3COCD3, 25 °C): δ 5.74, 5.71, 5.67 (s, 1 H each, 3 CHpz), 3.82, 3.54, 3.47, 2.89 (s, 3 H each, 4 CO2Me), 2.36, 2.33, 2.31, 2.08, 1.97, 1.96 (s, 3 H each, 6 Mepz), 1.90 (s, 3 H, Me2), 1.17 (s, 3 H, Me1). 13C{1H} NMR (CD3COCD3, 25 °C): δ 178.1, 175.0, 169.6, 166.0 (CO2Me), 161.3, 147.6, 132.7, 126.2 (CCO2Me), 154.6, 153.3, 151.0, 145.0, 144.4, 143.4 (Cqpz), 146.9, 125.9 (CMe), 107.8, 107.3, 106.9 (CHpz), 53.1, 52.1, 51.6, 50.3 (CO2Me), 29.2 (Me1), 17.3 (Me2), 16.4, 15.4, 13.3, 12.6, 12.4, 12.3 (Mepz). IR (Nujol): ν(OH) 3333 cm-1. Anal. Calcd for C31H42BN6O9Ir · 0.5CH2Cl2: C, 42.6; H, 4.8; N, 9.5. Found: C, 42.7; H, 4.7; N, 9.6. 4: 1H NMR (CDCl3, 25 °C): δ 5.81, 5.67, 5.63 (s, 1 H each, 3 CHpz), 3.86, 3.71, 3.49, 3.34 (s, 3 H each, 4 CO2Me), 2.57 (s, 3 H, Me2), 2.46, 2.44, 2.42, 2.37, 1.80, 1.68 (s, 3 H each, 6 Mepz), 1.04 (s, 3 H, Me1). 13C{1H} NMR (CDCl3, 25 °C): δ 275.1 (C1), 173.6, 172.2, 167.7, 163.0 (CO2Me), 165.1, 162.1 (C2 and C3), 154.8, 151.9, 149.3, 143.8, 143.5 (1:1:1:1:2, Cqpz), 141.3, 135.4 (C5 and C6), 109.4, 107.7, 106.3 (CHpz), 51.9, 51.2, 51.1, 50.8 (CO2Me), 45.1 (Me1), 20.4 (C4), 15.0, 14.2, 14.0, 13.2, 12.8, 12.7 (Mepz), 13.9 (Me2). Anal. Calcd for C31H40BN6O8Ir · CH2Cl2: C, 42.1; H, 4.6; N, 9.5. Found: C, 42.9; H, 4.7; N, 9.5. Compound 3 · CO. A solution of 4 in C6H12 (0.05 g, 0.06 mmol; 3 mL) was placed in a Fischer-Porter vessel, and the stirred mixture was heated under 2 atm of CO at 90 °C for 12 h. Thereafter, the pale yellow solution was taken to dryness, and quantitative conversion into 3 · CO was ascertained by 1H NMR. It was crystallized (pale yellow crystals) from its concentrated solutions in hexane/CH2Cl2 (1:1) upon cooling at -20 °C. Alternatively, this compound can be prepared from 3 or from a mixture of 3 and 4, following the method described above.

1 H NMR (CDCl3, 25 °C): δ 5.81, 5.78, 5.77 (s, 1 H each, 3 CHpz), 3.86, 3.68, 3.63, 3.09 (s, 3 H each, 4 CO2Me), 2.36, 2.34, 2.27, 2.19, 2.16 (s, 2:1:1:1:1, 6 Mepz), 1.89 (s, 3 H, Me2), 1.39 (s, 3 H, Me1). 13C{1H} NMR (CDCl3, 25 °C): δ 173.6, 170.4, 167.3, 165.6 (CO2Me), 165.3 (CO), 153.1, 152.6, 151.1, 144.3, 143.3 (1: 1:1:2:1, Cqpz), 152.1, 145.4, 135.9, 126.6 (CCO2Me), 141.8, 131.1 (CMe), 107.5, 106.9, 106.7 (CHpz), 52.1, 51.9, 51.8, 50.7 (CO2Me), 28.2 (Me1), 16.9 (Me2), 15.7, 14.3, 13.6, 13.0, 12.6, 12.5 (Mepz). IR (Nujol): ν(CO) 2046 cm-1. Anal. Calcd for C32H40BN6IrO9 · CH2Cl2: C, 43.5; H, 4.7; N, 9.4. Found: C, 44.0; H, 4.6; N, 9.6. Compound 3 · NCMe. A solution of 4 in CH3CN (0.05 g, 0.06 mmol; 3 mL) was stirred at room temperature for 12 h. Thereafter the yellow solution was taken to dryness and quantitative conversion into 3 · NCMe was ascertained by 1H NMR. This compound was purified by crystallization (yellow crystals) from hexane/CH2Cl2 (1:1) at -20 °C. Alternatively, 3 · NCMe can be prepared from 3 or from a mixture of 3 and 4, following the method described above.

1 H NMR (CDCl3, 25 °C): δ 5.76, 5.72, 5.67 (s, 1 H each, 3 CHpz), 3.85, 3.64, 3.61, 3.05 (s, 3 H each, 4 CO2Me), 2.37 (s, 3 H, NCMe), 2.35, 2.34, 2.22, 2.13, 2.09 (s, 2:1:1:1:1, 6 Mepz), 1.89 (s, 3 H, Me2), 1.26 (s, 3 H, Me1). 13C{1H} NMR (CDCl3, 25 °C): δ 176.9, 172.8, 169.7, 165.9 (CO2Me), 153.8 (1 CCO2Me + 1 Cqpz), 151.8, 150.3, 144.0, 143.7, 142.8 (Cqpz), 150.0, 133.1, 123.5 (CCO2Me), 145.9, 128.3 (CMe), 120.7 (MeCN), 107.2, 106.8, 106.6 (CHpz), 52.0, 51.9, 51.7, 50.6 (CO2Me), 29.5 (Me1), 17.4 (Me2), 16.3, 14.1, 13.6, 13.0, 12.8, 12.7 (Mepz), 4.6 (MeCN). Anal. Calcd for C33H43BN7O8Ir · 0.5CH2Cl2: C, 44.2; H, 4.8; N, 10.8. Found: C, 43.7; H, 4.8; N, 10.8. Compound 5. To a solution of 4 in CH2Cl2 (0.02 g, 0.024 mmol; 3 mL) was added an excess of tBuOOH (∼0.05 mL, 0.53 mmol) and the mixture stirred at room temperature for 12 h. Thereafter the red solution was taken to dryness and the residue subjected to several cycles of adding Et2O and evaporation in vacuo to eliminate the excess peroxide. Quantitative conversion into 5 was ascertained by 1H NMR. Alternatively, 5 can be prepared from 3 or from a mixture of 3 and 4, following the method described above.

H NMR (CDCl3, 25 °C): δ 5.80, 5.69, 5.67 (s, 1 H each, 3 CHpz), 3.95, 3.83, 3.64, 3.23 (s, 3 H each, 4 CO2Me), 2.45, 2.34, 1.94, 1.65, 1.61 (s, 1:2:1:1:1, 6 Mepz), 1.96 (s, 3 H, Me2), 1.52 (s, 3 H, Me1). 13C{1H} NMR (CDCl3, 25 °C): δ 209.1 (C1), 173.9, 171.5, 166.0, 164.9 (CO2Me), 154.1, 152.1, 151.2, 144.2, 143.5 (1:1:1:1:2, Cqpz), 150.5, 114.9 (CMe), 160.8, 127.2 (CCO2Me), 107.1, 106.9, 106.8 (CHpz), 77.5 (C2), 53.4, 52.3, 52.1, 50.8 (CO2Me), 24.2 (Me1), 16.5 (Me2), 16.1, 13.6, 13.3, 12.7, 12.6, 12.1 (6 Mepz). Anal. Calcd for C31H40BN6O9Ir · 0.5CH2Cl2: C, 42.7; H, 4.6; N, 9.5. Found: C, 42.5; H, 4.8; N, 9.4. Compound 6. To a suspension of 1 in cyclohexane (0.6 g, 0.76 mmol; 8 mL) was added PhCtCPh (3.03 mmol, 0.540 g) and the resulting mixture stirred at 90 °C for 12 h. Thereafter the dark brown 1

Reaction of an Iridacyclopentadiene solution was dried under vacuum, and the 1H NMR spectrum of the residue revealed that 6 had been formed in 80% spectroscopic yield.

1 H NMR (CDCl3, 25 °C): δ 7.96, 7.45, 7.31, 7.24, 6.87, 6.45 (d, t, t, t, t, d, 2:1:2:2:1:2, 10 CHar), 5.75, 5.65, 5.34 (s, 1 H each, 3 CHpz), 3.56, 3.54, 3.30, 3.14 (s, 3 H each, 4 CO2Me), 2.54, 2.45, 2.39, 2.38, 2.11, 1.06 (s, 3 H each, 6 Mepz). 13C{1H} NMR (CDCl3, 25 °C): δ 241.0 (C1), 186.7 (C2), 174.3, 171.8, 168.1, 162.6 (CO2Me), 166.0 (C3), 157.7, 140.4 (Cqar), 154.0, 153.8, 151.2, 144.0, 143.6, 143.3 (Cqpz), 140.2, 136.8 (C5 and C6), 129.0, 128.5, 127.4, 127.3, 127.2, 121.6 (1:2:2:2:2:1, CHar), 109.4, 108.3, 105.8 (CHpz), 51.7, 51.2, 51.0, 50.4 (CO2Me), 26.0 (C4), 15.8, 15.0, 13.2, 13.0, 12.9, 12.8 (Mepz). Compound 7. To a suspension of 1 in cyclohexane (0.05 g, 0.063 mmol; 5 mL) was added Me3SiCtCSiMe3 (28.6 µL, 0.126 mmol) and the suspension stirred at 120 °C for 24 h. After that, the solvent was removed under reduced pressure, and formation of compound 7 (∼75% spectroscopic yield) was ascertained by 1H NMR. This compound was purified by column chromatography on silica gel using hexane/Et2O (1:1 f 1:3) mixtures as eluent (yellow microcrystalline solid). Yield: 58%. Rf ) 0.12 [silica gel, hexane/Et2O (1:3)].

H NMR (CDCl3, 25 °C): δ 5.89, 5.86, 5.49 (s, 1 H each, 3 CHpz), 5.31, 4.52 (d, 1 H each, 2JHH ) 1.6 Hz, C4H2), 4.41, 3.54 (d, 1 H each, 2JHH ) 1.6 Hz, C1H2), 3.89, 3.77, 3.43, 2.82 (s, 3 H each, 4 CO2Me), 2.43, 2.27, 2.15, 1.82 (s, 2:2:1:1, 6 Mepz). 13C{1H} NMR (CDCl3, 25 °C): δ 173.2, 169.0, 167.1, 164.5 (CO2Me), 153.1, 152.4, 150.6, 144.4, 143.3, 143.3 (Cqpz), 147.1, 141.1, 131.8, 116.4 (CCO2Me), 141.9 (C3), 108.7, 106.6, 106.3 (CHpz), 100.3 (C4, 1JCH ) 160 Hz), 86.1 (C2), 52.8, 52.4, 51.9, 50.8 (CO2Me), 27.5 (C1, 1 JCH ) 160 Hz), 15.8, 15.4, 14.1, 12.9, 12.7, 12.6 (Mepz). Anal. Calcd for C31H38BN6O8Ir · 0.5CH2Cl2: C, 43.6; H, 4.5; N, 9.6. Found: C, 43.8; H, 4.8; N, 9.3. Compound 8. 1 was suspended in cyclohexane (0.4 g, 0.506 mmol; 8 mL), and PhCtCH (0.22 mL, 2.02 mmol) was added. The mixture was stirred at 90 °C for 12 h, and then the solvent was removed under reduced pressure. Formation of compound 8 (60% spectroscopic yield) was determined by 1H NMR, and the crude product was purified by column chromatography on silica gel using a mixture of hexane/Et2O (1:1) as eluent (pale yellow crystals). Yield: 32%. 1

H NMR (CDCl3, 25 °C): δ 7.41 (m, 2 H, 2 CHar(Ph2)), 7.23 (m, 3 H, 3 CHar(Ph2)), 7.02 (t, 2 H, 2 CHar(Ph1)), 6.89 (br s, 3 H, 3 CHar(Ph1)), 6.37 (s, 1 H, C1H), 6.22 (s, 1 H, C3H), 5.95, 5.66, 1

Organometallics, Vol. 28, No. 1, 2009 179 5.29 (s, 1 H each, 3 CHpz), 3.97, 3.67, 3.59, 3.04 (s, 3 H each, 4 CO2Me), 2.50, 2.41, 2.38, 2.34, 1.59, 0.83 (s, 3 H each, 6 Mepz). 13 C{1H} NMR (CDCl3, 25 °C): δ 172.0, 171.2, 166.6, 164.9 (CO2Me), 155.2, 155.1, 151.9, 144.3, 143.7, 143.2 (Cqpz), 151.8 (CPh2), 145.3, 142.3, 125.1 (CCO2Me), 141.5 (Cqar(Ph1)), 135.0 (Cqar(Ph2)), 130.0 (br, o, o′-CHar(Ph1)), 128.9 (o, o′-CHar(Ph2)), 128.7 (p-CHar(Ph2)), 128.2, 128.0 (m, m′-CHar(Ph1) and m, m′-CHar(Ph2) respectively), 126.1 (p-CHar(Ph1)), 116.6 (C2), 108.8, 108.3, 106.8 (CHpz), 72.1 (C4), 60.5 (C3, 1JCH ) 171 Hz,), 52.8, 51.7, 51.4, 50.7 (CO2Me), 39.0 (C1, 1JCH ) 151 Hz), 16.9, 13.7, 13.5, 13.1, 12.9 (1:1:1:1:2, Mepz). Anal. Calcd for C43H46BN6O8Ir · 0.5CH2Cl2: C, 51.2; H, 4.6; N, 8.2. Found: C, 51.3; H, 4.7; N, 7.8. Compound 9. 1 was suspended in cyclohexane (0.1 g, 0.126 mmol; 4 mL), and PhCtCSiMe3 (99.1 µL, 0.504 mmol) was added. The resulting mixture was stirred at 90 °C for 12 h, and the solvent was removed under vacuum. 1H NMR monitoring of the crude of the reaction showed formation of compound 9 in 80% spectroscopic yield. This complex was purified by column chromatography on silica gel using a mixture of hexane/Et2O (1:1) as eluent. Yield: 58%.

1 H NMR (CDCl3, 25 °C): δ 7.59 (br d, 2 H, 2 CHar(Ph1)), 7.26 (m, 3 H, 3 CHar(Ph1)), 6.91 (t, 1 H, 1 CHar(Ph2)), 6.78 (t, 2 H, 2 CHar(Ph2)), 6.74 (s, 1 H, C3H), 6.47 (d, 2 H, 2 CHar(Ph2)), 5.90 (s, 1 H, C1H), 5.62, 5.60, 5.55 (s, 1 H each, 3 CHpz), 3.86, 3.82, 3.43, 2.77 (s, 3 H each, 4 CO2Me), 2.47, 2.43, 2.42, 2.12, 1.61, 1.07 (s, 3 H each, 6 Mepz). 13C{1H} NMR (CDCl3, 25 °C): δ 172.8, 168.9, 167.4, 163.9 (CO2Me), 154.8, 154.6, 152.0, 143.9, 143.7, 143.7 (Cqpz), 144.0 (CPh2), 143.0, 135.3, 127.7 (CCO2Me), 140.3 (Cqar(Ph1)), 137.1 (Cqar(Ph2)), 130.1 (o, o′-CHar(Ph1)), 129.1 (m, m′CHar(Ph1)), 127.4, 127.3 (o, o′, m, m′-CHar(Ph2)), 126.8 (pCHar(Ph1)), 125.8 (p-CHar(Ph2)), 118.0 (C3, 1JCH ) 154 Hz), 116.0 (C2), 109.6, 106.7, 106.4 (CHpz), 87.5 (C4), 53.0, 52.6, 52.0, 50.8 (CO2Me), 52.2 (C1, 1JCH ) 158 Hz), 15.0, 14.4, 13.5, 13.1, 12.9, 12.8 (Mepz). Compound 10. To a suspension of 1 in cyclohexane (0.1 g, 0.126 mmol; 8 mL) was added HCtCCH2CH2OH (28.7 µL, 0.379 mmol), and the mixture was stirred at 90 °C for 12 h. Thereafter the solvent was removed under reduced pressure, and the formation of compound 10 in ∼85% spectroscopic yield was determined by 1H NMR. This complex was purified by column chromatography on silica gel using Et2O f Et2O/AcOEt (1:1) as eluent. Yield: 56%.

Rf ) 0.39 [silica gel, Et2O/AcOEt (1:3)]. 1H NMR (CDCl3, 25 °C): δ 6.20 (s, 1 H, C3H), 5.82, 5.76, 5.64 (s, 1 H each, 3 CHpz), 5.03 (dd, 1 H, 3JHH ) 11.2, 4 Hz, C1H), 3.90, 3.80, (m, 1 H each, CCH2CH2OH), 3.84, 3.65, 3.57, 3.01 (s, 3 H each, 4 CO2Me), 3.75, 3.60 (m, 1 H each, C1CH2CH2OH), 3.24, 2.65 (ddd, dt, 1 H each, 3 JHH ) 14.9, 9.5, 4.9 Hz; 2JHH ) 13.5, 3JHH 5.2 Hz, CCH2CH2OH), 2.38, 2.37, 2.32, 2.29, 2.25, 1.65 (s, 3 H each, 6 Mepz), 1.65, 1.55

180 Organometallics, Vol. 28, No. 1, 2009 (m, 1 H each, C1CH2CH2OH). Signals of the OH groups have not been located. 13C{1H} NMR (CDCl3, 25 °C): δ 172.6, 171.9, 166.9, 165.3 (CO2Me), 158.1 (CCH2CH2OH), 154.6, 153.8, 149.7, 144.4, 144.2, 143.2 (Cqpz), 144.5, 142.9, 127.0 (CCO2Me), 116.8 (C2), 110.2, 108.2, 106.6 (CHpz), 71.3 (C4), 63.3 (C1CH2CH2OH, 1JCH ) 141 Hz), 61.7 (CCH2CH2OH, 1JCH ) 145 Hz), 58.2 (C3, 1JCH ) 168 Hz), 53.4, 51.5, 51.4, 50.6 (CO2Me), 40.6 (C1, 1JCH ) 147 Hz), 34.5 (C1CH2CH2OH, 1JCH ) 126 Hz), 33.6 (CCH2CH2OH, 1 JCH ) 128 Hz), 17.0, 16.4, 15.2, 13.3, 12.8, 12.7 (Mepz). IR (Nujol): ν (OH) 3439 (br) cm-1. Compound 11. To a suspension of 1 in cyclohexane (0.1 g, 0.126 mmol; 8 mL) was added HCtCCO2Me (22.5 µL, 0.253 mmol), and the mixture was stirred at 90 °C for 12 h. The solvent was removed under reduced pressure, and 1H NMR monitoring of the crude of the reaction showed formation of complex 11 in ∼85% spectroscopic yield. 11 was purified by crystallization from a pentane/CH2Cl2 (1:1) mixture at -20 °C (bright yellow crystals). Yield: 54%.

Paneque et al. (solv ) essentially petroleum ether), and 11 · 2CH2Cl2 were collected on a Bruker Smart APEX CCD area detector diffractometer using graphite-monochromated Mo KR radiation (λ ) 0.71073 Å) and 0.3° ω-scan frames covering complete spheres of the reciprocal space with θmax ) 25-30°. After data integration with the program SAINT+ corrections for absorption, λ/2 effects, and crystal decay were applied with the program SADABS.15 The structures were solved by direct methods, expanded by Fourier syntheses, and refined on F2 with the program suite SHELX97.16 All non-hydrogen atoms were refined anisotropically using DELU restraints for the Uij of 8 · solv and 11 · 2CH2Cl2. Most H atoms were placed in calculated positions and thereafter treated as riding. A torsional parameter was refined for each pyrazole-bound methyl group. The water molecule in 3 · CHCl3 was idealized and refined as a rigid group. The disordered solvents in 4 · CH2Cl2 and 8 · solv were squeezed with the program PLATON, and modest orientation disorder of one COOMe group in 4 · CH2Cl2 and a phenyl ring in 8 · solv was taken into account.17 Crystal data and experimental details are given in Table 1, the molecular structures of the Ir complexes are shown in Figures 1, 2, 4, and 5, and selected geometric data are reported in Tables 2-5.

Acknowledgment. Financial support from the Spanish Ministerio de Ciencia e Innovacio´n (MICINN) (projects CTQ2007-62814andCONSOLIDER-INGENIO2010,CSD2007006, FEDER support, and HU2003-039) and from the Junta de Andalucı´a is gratefully acknowledged. N.R. thanks the MEC and the CSIC for research grants. 1 H NMR (CDCl3, 25 °C): δ 5.92 (s, 1 H, C1H), 5.82, 5.69, 5.61 (s, 1 H each, 3 CHpz), 5.59 (s, 1 H, C5H), 4.05, 3.95, 3.76, 3.70, 3.47, 2.50 (s, 3 H each, 6 CO2Me), 2.45, 2.39, 2.34, 2.19, 1.98, 1.92 (s, 3 H each, 6 Mepz). 13C{1H} NMR (CDCl3, 25 °C): δ 183.3, 168.6, 165.4, 162.6, 161.5 (2:1:1:1:1, CO2Me), 181.2 (C4), 151.3, 128.9 (CCO2Me), 150.7 (C2), 152.4, 150.3, 144.5, 143.2, 142.1 (2: 1:1:1:1, Cqpz), 123.0 (C1, 1JCH ) 157 Hz), 108.3, 107.7, 106.5 (CHpz), 94.1 (C3), 57.2, 52.6, 52.1, 51.8, 51.3, 50.4 (CO2Me), 14.4, 13.0, 13.0, 12.7, 12.3 (1:1:1:2:1, Mepz), 8.1 (C5, 1JCH ) 139 Hz). Anal. Calcd for C35H42BN6O12Ir · 0.5CH2Cl2: C, 43.3; H, 4.4; N, 8.5. Found: C, 43.8; H, 4.2; N, 8.4. X-ray Structure Determination. X-ray data of complexes 3, 4, 8, and 11 in the form of the solvates 3 · CHCl3, 4 · CH2Cl2, 8 · solv

Supporting Information Available: Complete crystallographic data and technical details in CIF format for complexes 3, 4, 8, and 11. This material is available free of charge via the Internet at http://pubs.acs.org. OM8001153 (15) Bruker programs: SMART, version 5.629; SAINT+, version 6.45; SADABS, version 2.10; SHELXTL, version 6.14; Bruker AXS Inc.: Madison, WI, 2003. (16) Sheldrick, G. M. SHELX97: Program System for Crystal Structure Determination; University of Go¨ttingen: Go¨ttingen, Germany, 1997. (17) Spek, A. L. PLATON: A Multipurpose Crystallographic Tool; University of Utrecht: Utrecht, The Netherlands, 2006.