Anti-Markovnikov 1,3-CH Addition of Allenes to Allenes: A

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Anti-Markovnikov 1,3-CH Addition of Allenes to Allenes: A Straightforward Method To Prepare Osmium−Dienylcarbene Complexes Ruth Castro-Rodrigo, Miguel A. Esteruelas,* Ana M. López, and Enrique Oñate Departamento de Quı ́mica Inorgánica-Instituto de Sı ́ntesis Quı ́mica y Catálisis Homogénea (ISQCH), Universidad de Zaragoza-CSIC, 50009 Zaragoza, Spain S Supporting Information *

ABSTRACT: One of the acetone molecules of the solvento complex [OsTp(κ 1 -OCMe 2 ) 2 (P i Pr 3 )]BF 4 (1; Tp = hydridotris(1-pyrazolyl)borate) is displaced by cyclohexylallene to give [OsTp(η 2 -CH 2 CCHCy)(κ 1 -OCMe 2 )(PiPr3)]BF4 (2). Treatment of 2 with a second molecule of cyclohexylallene leads to an 80:20 mixture of the conjugated (Z,Z)-osmahexatriene [OsTp{CH-(Z)-C(CH2Cy)CH[η2-(Z)CHCHCy]}(PiPr3)]BF4 (3) and the (Z,Z)-dienylcarbene [OsTp{CH-(Z)-C[CH2-η2-(Z)-CHCHCy]CHCy}(PiPr3)]BF4 (4), as a result of an anti-Markovnikov 1,3-C−H addition of the coordinated allene of 2 to the CH2C double bond of the second allene molecule. In fluorobenzene at 85 °C, 3 evolves into the hydride-(E,E)-dienylcarbyne [OsHTp{C-(E)C(CH2Cy)CH[(E)-CHCHCy]}(PiPr3)]BF4 (5), whereas 4 isomerizes into the (E,Z)-dienylcarbene [OsTp{CH-(E)C[CH2-η2-(Z)-CHCHCy]CHCy}(PiPr3)]BF4 (6). Complex 2 also reacts with ethyl carboxylateallene. In dichloromethane at room temperature, the reaction gives [OsTp{CH-(Z)-C[CH2-η2-(Z)-CHCHCO2Et]CHCy}(PiPr3)]BF4 (7), which isomerizes into [OsTp{CH-(E)-C[CH2-η2-(Z)-CHCHCO2Et]CHCy}(PiPr3)]BF4 (8) in fluorobenzene at 85 °C. Treatment of 7 with NaOMe yields OsTp{(E)-CHC[CHC(CH2)4CH2]CH2-η2-(Z)-CHCHCO2Et)(PiPr3) (9). The addition of HBF4·OEt2 to 9 gives 8.

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Chart 1

INTRODUCTION C−H bond activation and C−C coupling reactions are the base of a myriad of chemical transformations involving hydrocarbons. Alkynes, alkenes, and conjugated dienes have been widely employed as unsaturated substrates.1 Allenes, which are 1,2dienes possessing two perpendicular π orbitals, have received less attention than the other three classes of π components. For a long period of time, they were viewed as highly unstable. However, over the past decade, allenes have developed from almost a rarity to be an established member of the tools utilized in modern organic synthetic chemistry, in particular for reactions promoted by transition metals.2 Stoichiometric organometallic reactions are the only real support of the mechanistic proposals for the allene catalytic reactions promoted by metals. The coordination of one of the carbon−carbon double bonds to the metal center produces the activation of the substrate, which can then undergo several reactions, including C−C couplings by insertion into M−R bonds,3 oxidative couplings with other unsaturated substrates,4 and homodimerizations.5 The latter on a single metal center affords exounsaturated metallacyclopentanes of the types I−III (Chart 1). We have recently discovered that gem-disubstituted allenes can undergo a metal-promoted double C−H bond activation to afford alkenylcarbyne derivatives. Thus, the π-allene complexes OsCl2(η2-CH2CCRMe)(PiPr3)2 evolve at 353 K, in toluene, into the hydride−alkenylcarbyne derivatives OsHCl2(CCHCRMe)(PiPr3)2 (R = Me, SiMe3).6 One of © 2012 American Chemical Society

the hydrogen atoms of the coordinated CH2 group migrates to the central carbon atom, while the other one goes to the metal center (eq 1). After some months, we proved that not only the

Received: December 22, 2011 Published: February 28, 2012 1991

dx.doi.org/10.1021/om201272q | Organometallics 2012, 31, 1991−2000

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OsCl2(PiPr3)2 metal fragment but also the [OsTp(PiPr3)]+ (Tp = hydridotris(1-pyrazolyl)borate) moiety promotes the reaction (eq 2).7 DFT calculations on the bis(phosphine) system6 suggest that the reactions shown in eqs 1 and 2 are initiated by a 1,2hydrogen shift from the coordinated CH2 group of the allene to the osmium atom. The shift gives the osmacyclopropene intermediate A (Scheme 1), which affords the 16-valence-electron Scheme 1

Figure 1. Molecular diagram of the cation of 2. Selected bond lengths (Å) and angles (deg): Os−P = 2.3802(18), Os−N(1) = 2.142(5), Os−N(3) = 2.099(5), Os−N(5) = 2.126(6), Os−O = 2.133(4), Os−C(1) = 2.180(7), Os−C(2) = 2.115(7), C(1)−C(2) = 1.382(9), C(2)−C(3) = 1.317(9), C(3)−C(4) = 1.515(8); N(1)−Os−C(1) = 162.6(2), N(1)−Os−C(2) = 158.1(2), N(3)−Os−O = 166.35(18), N(5)−Os−P = 177.00(16), Os−C(2)−C(3) = 136.8(5), C(1)− C(2)−C(3) = 149.3(7), C(2)−C(3)−C(4) = 127.3(7). Displacement ellipsoids are given at the 50% probability level.

alkenylcarbene B as a consequence of the migration of the hydride ligand from the metal center to the central carbon atom of the organic substrate. Finally, intermediate B evolves into the hydride−alkenylcarbyne complexes by a 1,2-hydrogen shift from the carbene carbon atom to the metal center.8 We have now observed with monosubstituted allenes that intermediate A can be trapped by other monosubstituted allene to generate novel dienylcarbenes, including osmahexatrienes. This paper reports unprecendented homo- and cross-couplings of allenes which, in contrast to those previously reported, lead to dienylcarbene complexes.

2.126(6) (Os−N(5)), and 2.142(5) Å (Os−N(1)) are consistent with the trans influence of the monodentate ligands increasing in the sequence acetone < PiPr3 ≤ allene. The Os−allene coordination exhibits Os−C(1) and Os−C(2) bond lengths of 2.180(7) and 2.115(7) Å, respectively, which agree well with those found in the complexes [Os(η5-C5H5){η2-CH2C C(Me)SiMe3}(PiPr3)]PF6 (2.173(11) and 2.077(9) Å),7 OsCl2(η2-CH2CCMe2)(PiPr3)2 (2.156(7) and 2.044(6) Å),6 OsCl{C(Me)CHCMe3}(η2-CH2CCHCMe3)(PPh3)2 (2.122(2) and 2.044(2) Å),9 OsCl2{CPh(η2-CHC CHPh)}(PPh3)2 (2.167(11) and 2.067(11) Å),10 and [Os(η5C5H5){CPh(η2-CHCCHPh)}(PiPr3)]BF4 (2.185(11) and 2.015(16) Å),11 while they lie on the lower part of the range reported for the metal−olefin distances in osmium− olefin compounds (between 2.07 and 2.28 Å)12 and are

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RESULTS AND DISCUSSION 1. Homocoupling of Cyclohexylallene. Treatment at room temperature of fluorobenzene solutions of the bis(solvento) complex [OsTp(κ1-OCMe2)2(PiPr3)]BF4 (1) with 1.0 equiv of cyclohexylallene for 15 min leads to [OsTp(η2CH2CCHCy)(κ1-OCMe2)(PiPr3)]BF4 (2) as a result of the displacement of one of the acetone molecules by the less sterically hindered carbon−carbon double bond of the allene. Complex 2 is isolated as a yellow solid in 82% yield, according to eq 3.

significantly shorter than those reported for OsCl{C(Me) CHC(O)OEt}(η2-CH2CCHCO2Et)(PPh3)2 (2.405(3) and 2.416(3) Å).9 The C(1)−C(2) distance of 1.382(9) Å, which is about 0.06 Å longer than the C(2)−C(3) bond length (1.317(9) Å), also lies on the lower part of the range reported for transition-metal olefin complexes (between 1.340 and 1.445 Å).13 The angles C(1)−C(2)−C(3) and Os−C(2)−C(3) are 149.3(7) and 136.8(5)°, respectively. The 1H, 13C{1H}, and 31P{1H} NMR spectra of 2 in acetone at room temperature are consistent with the structure shown in Figure 1. The 1H NMR spectrum shows the CH2 resonances of the coordinated hydrocarbon at 3.03 and 4.80 ppm, whereas the CH signal is observed at 5.04 ppm. In the 13C{1H} NMR spectrum the allene resonances appear at 166.7 (C), 117.1 (CH), and 33.4 ppm (CH2). The 31P{1H} NMR spectrum contains a singlet at −22.2 ppm, shifted about 18 ppm toward higher field with regard to that of 1. The allene ligand of 2 couples a second molecule of cyclohexylallene in dichloromethane at room temperature (eq 4). The reaction affords the conjugated osmahexatriene [OsTp{ CH-(Z)-C(CH2Cy)CH[η2-(Z)-CHCHCy]}(PiPr3)]BF4 (3; 80%) along with the minor dienylcarbene product

Figure 1 gives a view of the cation of 2. The structure proves that the allene is coordinated to the metal center as an η2 ligand through the sterically less hindered C(1)−C(2) double bond, with the cyclohexyl substituent disposed away from the osmium atom. The distribution of ligands around the metal center can be described as a distorted octahedron with the coordinating nitrogen atoms of the Tp ligand in fac sites. The metal coordination sphere is completed by the phosphine ligand disposed trans to N(5) (P−Os−N(5) = 177.00(16)°), the acetone molecule disposed trans to N(3) (O−Os−N(3) = 166.35(18)°), and the C(1)−C(2) double bond of the allene disposed trans to N(1). The central carbon atom of the allene (C(2)) points to the acetone ligand, while the terminal unsubstituted carbon atom C(1) is directed toward the nitrogen atom N(3). The Os−N bond lengths of 2.099(5) (Os−N(3)), 1992


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In agreement with the presence of a double bond between C(2) and C(3), the separation between these atoms is 1.370(15) Å. The C(1)−C(2) and C(3)−C(4) bond lengths of 1.469(14) and 1.443(14) Å, respectively, are consistent with C(sp2)−C(sp2) single bonds. The 1H and 13C{1H} NMR spectra of 3, in dichloromethaned2, at room temperature also support the formation of the osmahexatriene moiety. In the 1H NMR spectrum the characteristic C(1)H, C(3)H, C(4)H, and C(5)H resonances appear at 17.51, 9.26, 5.29, and 5.05 ppm, respectively, whereas in the 13C{1H} spectrum the C(1), C(2), C(3), C(4), and C(5) resonances are observed at 286.4, 179.5, 161.3, 82.1, and 93.8 ppm, respectively. The minor product complex 4 was fully characterized by 1H, 1 H{31P}, 1H−1H COSY, 13C APT, 1H−13C HSQC, 1H−13C HMBC, and 31P{1H} NMR experiments, in dichloromethane at room temperature. In the 1H NMR spectrum, the most noticeable feature is the presence of two signals at 4.27 and 3.55 ppm, corresponding to the CH2 group situated between the olefinic units, in addition to the C(sp2)H resonances at 18.50, 7.01, 6.90, and 4.96 ppm. In the 13C{1H} NMR spectrum, the OsC resonance appears at 270.0 ppm, whereas those due to the coordinated C−C double bond are observed at 70.4 and 86.4 ppm, shifted 110 and 48 ppm toward higher field with regard to the signals corresponding to the free olefinic group (δ 180.8 and 134.8). The carbon atom between the olefinic units displays a singlet at 34.8 ppm. Conjugated metallahexatrienes are rare,15 in particular those of osmium.8e,16 In most cases, they have been prepared via metallacyclopentatriene intermediates containing α substituents with C−H bonds, which undergo a 1,2-hydrogen shift to afford the butadienylcarbene structure.15c−h,16 In contrast to this, the formation of 3 can be rationalized trough intermediate A′ (Scheme 2), analogous to A in Scheme 1. The insertion of the

[OsTp{CH-(Z)-C[CH 2 -η 2 -(Z)-CHCHCy]CHCy}(PiPr3)]BF4 (4; 20%). Figure 2 gives a view of the cation of the green salt 3. The structure proves the formation of the conjugated osmahexatriene

Figure 2. Molecular diagram of the cation of 3. Selected bond lengths (Å) and angles (deg): Os−P(1) = 2.436(3), Os−N(1) = 2.162(8), Os−N(3) = 2.130(9), Os−N(5) = 2.231(9), Os−C(1) = 1.876(12), Os−C(4) = 2.220(9), Os−C(5) = 2.211(11), C(1)−C(2) = 1.469(14), C(2)−C(3) = 1.370(15), C(3)−C(4) = 1.443(14), C(4)−C(5) = 1.409(14); N(1)−Os−P(1) = 166.3(2), N(3)−Os− C(4) = 158.8(4), N(3)−Os−C(5) = 162.8(4), N(5)−Os−C(1) = 168.9(4), Os−C(1)−C(2) = 125.9(9), C(1)−C(2)−C(3) = 109.5(10), C(2)−C(3)−C(4) = 117.3(10), C(3)−C(4)−C(5) = 127.5(10). Displacement ellipsoids are given at the 50% probability level.

Scheme 2

moiety, which is a result of the coupling of the central carbon atom of an allene with the terminal atom of the other allene. In addition, two hydrogen migrations take place from the terminal CH2 groups. One of the hydrogen atoms goes to the substituted carbon atom of an allene, and the other one goes to the central carbon atom of the another allene. As a consequence of the formation of the new C−C bond and the hydrogen migrations, the resulting organic skeleton binds the metal center through the C(sp2) carbon atom C(1) and the C(4)−C(5) double bond. Thus, the polyhedron around the osmium atom can be described as a distorted octahedron, similar to that of 2, with the phosphine trans to N(1) (P(1)−Os−N(1) = 166.3(2)°), C(1) trans to N(5) (C(1)−Os−N(5) = 168.9(4)°), and the C(4)−C(5) bond trans to N(3). The coordination of the tridentate ligand is asymmetric, as expected, with Os−N bond lengths of 2.130(9) (Os−N(3)), 2.162(8) (Os−N(1)), and 2.231(9) Å (Os−N(5)). The Os−C(1) bond length of 1.876(12) Å supports a metal− carbon double bond formulation.8c,f,g,12k,14 The C(4)−C(5) double bond coordinates to the osmium atom in a symmetrical fashion with statistically identical Os−C bond lengths of 2.220(9) (Os−C(4)) and 2.211(11) Å (Os−C(5)), which compare well with the Os−allene distances in 2. The C(4)− C(5) bond length of 1.409(14) Å is statistically identical with the length of the coordinated C−C bond of the allene of 2.

unsubstituted double bond of the second cyclohexylallene molecule into the Os−C(sp2) single bond of the osmacyclopropene should initially give a hydride−osmacyclopentene species, with the unsaturated metallacycle containing two exocyclic carbon−carbon double bonds. Thus, the subsequent reductive elimination of the H−Os−alkenyl moiety of C could afford the minor product 4. The latter should evolve into the main product, complex 3, through the dissociation of the coordinated CHCHCy double bond, which allows a C−H bond activation reaction on the CH2 group between the olefinic 1993


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Scheme 3

(CHCy) and 6.36 and 6.35 ppm (CH). The value of the H−H coupling constant, 15 Hz, strongly supports the E stereochemistry at this double bond. The vinylic hydrogen atom at the central olefinic unit of both rotamers gives at 7.36 ppm a doublet with a H−H coupling constant of 11.4 Hz. In this case, the E stereochemistry at the double bond was inferred from the 1 H NOESY spectrum, which contains cross-peaks between this resonance and those corresponding to the CHCy hydrogen atom. In the 13C{1H} NMR spectrum, the OsC carbon atom displays at 288.8 and 284.8 ppm doublets with a C−P coupling constant of 13 Hz, whereas the C(sp2) resonances due to the dienyl substituent appear between 158 and 124 ppm as singlets. The 31P{1H} NMR shows at 30.4 and 29.3 ppm two singlets in a 1:1 intensity ratio. The (E,Z)-dienylcarbene complex 6 was characterized by X-ray diffraction analysis. Figure 3 gives a view of the cation of the salt. The structure proves the E stereochemistry at the conjugated C(2)−C(3) double bond. The coordination polyhedron around the osmium atom can be described as a distorted octahedron, similar to that of its isomer complex 3, with the C(1) carbon atom and the C(11)−C(12) double bond of the hydrocarbon bonded to the metal center. The Os−C(1) bond length of 1.923(4) Å compares well with that of 3 and supports an Os−C(1) double bond. The coordination of the C(11)−C(12) bond is asymmetrical with Os−C(11) and Os− C(12) bond lengths of 2.234(4) and 2.285(4) Å, respectively, and a C(11)−C(12) distance of 1.385(6) Å. In agreement with the presence of a double bond between C(2) and C(3), the separation between these atoms is 1.362(6) Å. The 1H and 13C{1H} NMR spectra of 6 in dichloromethaned2 at room temperature are consistent with the structure shown in Figure 3. In the 1H NMR spectrum the C(sp2)H resonances appear at 17.61 (C(1)H), 7.11 (C(3)H), 6.92 (C(11)H), and 4.92 ppm (C(12)H), whereas the CH2 signals are observed at 4.26 and 3.55 ppm. The 13C{1H} NMR spectrum shows the C(1) resonance at 280.9 ppm. The signals due to the free olefinic carbon atoms C(2) and C(3) are observed at 182.8 and 144.9 ppm, respectively, while those corresponding to the coordinated C(11) and C(12) atoms appear at 71.6 and 86.8 ppm.

units. The activation should lead to the hydride−osmacyclobutene intermediate D, which would yield E by migratory Markovnikov insertion of the conjugated carbon−carbon double bond into the Os−H bond. The release of the generated C−C double bond and the coordination again of CHCHCy should finally afford 3. The isomerization of 4 into 3 is certainly a 1,3-hydrogen shift, which takes place via the metal center (vide infra). 2. Dissociation of the Coordinated C−C Double Bond of 3. Osmium is more reducing than ruthenium and prefers coordination saturation and redox isomers with more metal− carbon bonds.8 As a consequence of this, in contrast to ruthenium, the coordinatively unsaturated osmium carbene complexes containing α-hydrogen atoms are unstable and undergo α-elimination reactions to afford hydride−carbyne derivatives.8c,f,h,12g,14f,17 In agreement with this and with a marked trend of 3 to dissociate the coordinated C(4)−C(5) double bond, the warming of the fluorobenzene solutions of this compound, at 85 °C for 36 h, yields the hydride−(E,E)dienylcarbyne [OsHTp{C-(E)-C(CH2Cy)CH[(E)-CH CHCy]}(PiPr3)]BF4 (5) as a result of the dissociation of the coordinated C(4)−C(5) double bond of 3, the Z−E isomerization of both C(4)−C(5) and C(2)−C(3) double bonds, and an α-hydrogen migration from C(1) to the metal center.18 Under the same conditions, the conjugated carbon−carbon double bond of 4 undergoes Z−E isomerization and the (E,Z)dienylcarbene product [OsTp{CH-(E)-C[CH2-η2-(Z)-CH CHCy]CHCy}(PiPr3)]BF4 (6) is formed. As a consequence of both processes the 80:20 equilibrium mixtures of 3 and 4 evolve into 88:12 equilibrium mixtures of 5 and 6, in fluorobenzene, at 85 °C (Scheme 3). The 1H, 13C{1H}, and 31P{1H} NMR spectra of 5 reveal that, in dichloromethane at room temperature, it exists as a mixture of the two possible rotamers resulting from a hindered rotation of the dienyl substituent around the C(sp)−C(sp2) bond of the dienylcarbyne ligand. Thus, in agreement with the presence of a hydride ligand in the complex, the 1H NMR spectrum shows two doublets at −6.73 and −6.84 ppm with an H−P coupling constant of 19.8 Hz. The vinylic hydrogen atoms of the terminal olefinic group displays four signals at 6.66 and 6.64 1994


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5.34 ppm. The 13C{1H} NMR spectrum shows the OsC resonance at 273.6 ppm as a doublet with a C−P coupling constant of 9 Hz. The resonances due to the coordinated olefinic atoms are observed as singlets at 76.0 and 62.5 ppm, shifted to significantly higher field with regard to that of the resonances corresponding to the carbon atoms of the free olefinic bond (δ 182.0, 138.8). The warming of fluorobenzene solutions of the (Z,Z)dienylcarbene 7 at 85 °C for 24 h exclusively produces the Z−E isomerization of the CCHCy double bond conjugated with the carbene moiety, in accordance with our initial hypothesis. The resulting (E,Z)-dienylcarbene [OsTp{CH-(E)-C[CH2η2-(Z)-CHCHCO2Et]CHCy}(PiPr3)]BF4 (8) isomer was isolated as a green solid in 91% yield (Scheme 4). Scheme 4 Figure 3. Molecular diagram of the cation of 6. Selected bond lengths (Å) and angles (deg): Os−P = 2.4488(11), Os−N(1) = 2.212(3), Os− N(3) = 2.145(3), Os−N(5) = 2.122(3), Os−C(1) = 1.923(4), Os− C(11) = 2.234(4), Os−C(12) = 2.285(4), C(1)−C(2) = 1.432(6), C(2)−C(3) = 1.362(6), C(2)−C(10) = 1.494(6), C(10)−C(11) = 1.507(6), C(11)−C(12) = 1.385(6); N(1)−Os−C(1) = 169.67(15), N(3)−Os−P = 169.43(9), N(5)−Os−C(11) = 160.67(14), N(5)− Os−C(12) = 161.70(14), Os−C(1)−C(2) = 125.0(3), C(1)−C(2)− C(3) = 121.8(4), C(1)−C(2)−C(10) = 112.2(3), C(2)−C(10)− C(11) = 108.0(3), C(10)−C(11)−C(12) = 127.3(4). Displacement ellipsoids are given at the 50% probability level.

3. Cross-Coupling between Cyclohexylallene and Ethyl Carboxylateallene. The formation of the conjugated osmahexatriene 3 takes place via 4, by insertion of an external allene into the Os−C(sp2) single bond of the osmacyclopropene intermediate A′ (Scheme 2). We reasoned that, according to the Dewar−Chatt−Duncanson model, an electron-withdrawing substituent (such as an ester group) at the coordinated double bond should increase the strength of the metal−olefin interaction. This could prevent its dissociation and therefore the formation of the conjugated osmahexatriene. Furthermore, the selective formation of a related species of 4 should also allows us to investigate the Z−E isomerization of the CHCHCy double bond conjugated with the carbene moiety. Therefore, we carried out the reaction of 2 with ethyl carboxylateallene. Treatment of a dichloromethane solution of 2 with 1.2 equiv of ethyl carboxylateallene for 12 h, at room temperature, selectively leads to [OsTp{CH-(Z)-C[CH2-η2-(Z)-CH CHCO2Et]CHCy}(PiPr3)]BF4 (7), as expected according to Scheme 2. The formation of any conjugated osmahexatriene was not detected. Complex 7 was isolated as a green solid in 88% yield (eq 5).

Complex 8 was characterized by X-ray diffraction analysis. Figure 4 shows a view of the cation of the salt. The structure proves the cross-coupling of the allenes, the coordination of the activated double bond, and the E stereochemistry at the C(2)− C(3) double bond. The coordination polyhedron around the osmium atom can be described as a distorted octahedron similar to that of 6, with the C(1) carbon atom and the C(11)− C(12) double bond of the dienylcarbene ligand bonded to the metal center. The Os−C(1) bond length of 1.916(6) Å is statistically identical with that of 6. As in the latter, the coordination of the C(11)−C(12) double bond is asymmetrical with Os−C(11) and Os−C(12) distances of 2.256(5) and 2.213(5) Å, respectively, and a C(11)−C(12) bond length of 1.377(8) Å. In agreement with the presence of a double bond between C(2) and C(3), the separation between these atoms is 1.358(8) Å. The 1H and 13C{1H} NMR spectra of 8 are consistent with the structure shown in Figure 4 and agree well with those of 6. In the 1H NMR spectrum, the C(sp2)H resonances of the dienylcarbene ligand are observed at 16.99 (C(1)H), 7.09 (C(3)H), 6.90 (C(11)H), and 5.31 ppm (C(12)H), whereas the C(10)H2 signals appear at 4.73 and 4.42 ppm. The 13C{1H} NMR spectrum shows the C(1) resonance at 284.2 ppm. The signals due to the free olefinic carbon atoms C(2) and C(3) are observed at 183.6 and 148.3 ppm, respectively, while those due to the coordinated C(11) and C(12) atoms appear at 76.6 and 62.3 ppm. The saturated character of 7 prevents that the Z−E isomerization of its CCHCy double bond, to afford 8, takes place

The 1H and 13C{1H} NMR spectra of this compound in dichloromethane-d2, at room temperature, agree well with those of 4. In the 1H NMR spectrum the resonances due to the CH2 group situated between the carbon−carbon double bonds appear at 4.91 and 4.46 ppm, whereas the C(sp2)H resonances of the dienylcarbene unit are observed at 17.82, 6.93, 6.87, and 1995


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CHCO2Et}(PiPr3) (9 in Scheme 4), as a result of the deprotonation of the cyclohexyl CδH proton of the conjugated alkenylcarbene moiety of 7. Although the deprotonation is quantitative, complex 9 was isolated as a light brown solid in 41% yield due to its high solubility in common organic solvents. As expected, the addition of 1.2 equiv of HBF4·OEt2 to a diethyl ether solution of 9 produced the instantaneous precipitation of 8. The 1H and 13C{1H} NMR spectra of 9 in benzene-d6 at room temperature strongly support the trienyl nature of the Cdonor ligand. The 1H NMR spectrum, in addition to CH2 signals at 4.93 and 4.13 ppm, shows four olefinic resonances at 8.00, 6.29, 5.99, and 4.99 ppm assigned to OsCH, CγH, and the hydrogen atoms of the coordinated double bond, respectively, whereas the 13C{1H} NMR spectrum contains six C(sp2) resonances at 155.6 (OsC), 152.3 (Cβ), 130.7 (Cδ), 128.3 (Cγ), and 62.6 and 47.0 ppm (Os-η2-olefin).

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Figure 4. Molecular diagram of the cation of 8. Selected bond lengths (Å) and angles (deg): Os−P = 2.4442(16), Os−N(1) = 2.124(4), Os−N(3) = 2.213(4), Os−N(5) = 2.148(4), Os−C(1) = 1.916(6), Os−C(11) = 2.256(5), Os−C(12) = 2.213(5), C(1)−C(2) = 1.433(7), C(2)−C(3) = 1.358(8), C(2)−C(10) = 1.499(7), C(10)− C(11) = 1.519(8), C(11)−C(12) = 1.377(8); N(1)−Os−C(11) = 159.98(19), N(1)−Os−C(12) = 162.29(19), N(3)−Os−C(1) = 169.5(2), N(5)−Os−P = 170.99(11), Os−C(1)−C(2) = 125.4(4), C(1)−C(2)−C(3) = 120.2(5), C(1)−C(2)−C(10) = 112.8(5), C(2)−C(10)−C(11) = 108.0(4), C(10)−C(11)−C(12) = 127.9(5). Displacement ellipsoids are given at the 50% probability level.

CONCLUDING REMARKS This paper shows the discovery of a new type of metalpromoted reaction between unsaturated hydrocarbons: the anti-Markovnikov 1,3-addition of the H−CHC unit of an allene to the CH2C double bond of other allene. These novel reactions afford dienylcarbene organic fragments, which are stabilized by coordination to a metal center. The addition takes place via hydride−metallacyclopropene intermediates of the type H−MCH−CCHR, which are generated on M(η2CH2CCHR) species by a 1,2-hydrogen shift from the coordinated CH2 group of the allene to the metal center.6 The formation of the dienylcarbene organic fragments involves the insertion of the CH2C double bond of an external allene into the M−C(sp2) single bond of the metallacyclopropene intermediate, to afford 3,5-disubstituted metallacyclopentenes with two exocyclic carbon−carbon double bonds, followed by H−M−C reductive elimination. In summary, we report a new type of coupling between allenes, which takes place through novel reactions of these substrates. Both the new coupling and the novel elemental reactions should have a significant influence on the mechanistic proposals of the reactions involving such hydrocarbons and inspire new and original synthetic procedures in organic synthesis.

through the metal center. On the other hand, CδH hydrogen atoms of conjugated alkenylcarbene ligands are fairly acidic.8e,19 According to this, it seems reasonable to think that the isomerizations of 4 and 7 into 6 and 8, respectively, proceed via trienyl intermediates of the type OsTp{CHC[CH C(CH 2 ) 4 CH2 ]CH2 -η 2 -(Z)-CHCHR}(P i Pr3 ) (R = Cy, CO2Et) generated by dissociation of the cyclohexyl CδH proton of the conjugated alkenylcarbene moieties of 4 and 7. Thus, rotation around the Cβ−Cγ single bond of the conjugated dienyl moiety of these intermediates, followed by the addition of the dissociated H+ to the Cδ cyclohexyl carbon atom of the new rotamers, could afford the most stable isomers (Scheme 5).

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Scheme 5

EXPERIMENTAL SECTION

General Methods and Instrumentation. All reactions were carried out under argon with rigorous exclusion of air using Schlenk tube or glovebox techniques. Solvents were dried by the usual procedures and distilled under argon prior to use or obtained oxygenand water-free from an MBraun solvent purification apparatus. All reagents, with the exception of NaBArF4 (BArF4 = tetrakis(3,5bis(trifluoromethyl)phenyl)borate), which was prepared as previously reported,20 were obtained from commercial sources and used without further purification. The starting material [OsTp(κ1-OCMe2)2(PiPr3)]BF4 (1) was prepared according to the published method.21 1H, 31 1 P{ H}, and 13C{1H} NMR spectra were recorded on a Varian Gemini 2000, a Bruker ARX 300, a Bruker Avance 300 MHz, a Bruker Avance 400 MHz, or a Bruker Avance 500 MHz instrument. Chemical shifts (expressed in parts per million) are referenced to residual solvent peaks (1H, 13C{1H}) or external H3PO4 (31P{1H}). Coupling constants, J, are given in hertz. Spectral assignments were achieved by 1H−1H COSY, 1 H{31P}, 13C APT, 1H−13C HSQC, 1H−13C HMBC, and 1H NOESY experiments. Infrared spectra were recorded on a Spectrum One spectrometer as neat solids. C, H, and N analyses were carried out with a Perkin-Elmer 2400 CHNS/O analyzer. High-resolution electrospray mass spectra were acquired using a MicroTOF-Q hybrid quadrupole time-of-flight spectrometer (Bruker Daltonics, Bremen, Germany).

In agreement with this, we have observed that the treatment of tetrahydrofuran solutions of 7 with 1.9 equiv of NaOMe, at room temperature, for 1 h leads to the trienyl species OsTp{(E)-CHC[CHC(CH 2) 4 CH2 ]CH2 -η 2 -(Z)-CH 1996


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Article

Preparation of [OsTp(η2-CH2CCHCy)(κ1-OCMe2)(PiPr3)]BF4 (2). An orange solution of 1 (305 mg, 0.40 mmol) in 7 mL of fluorobenzene was treated with cyclohexylallene (58 μL, 0.40 mmol). After 15 min, the resulting yellowish solution was filtered through Celite and the solvent was evaporated. The foamy residue was washed with pentane (3 × 5 mL) and dried in vacuo. Yellow solid. Yield: 270 mg (82%). Anal. Calcd for C30H51B2F4N6OOsP: C, 43.38; H, 6.19; N, 10.12. Found: C, 43.36; H, 5.96; N, 10.20. HRMS (electrospray, m/z): calcd for C27H45BN6OsP [M − C3H6O]+ 687.3151, found 687.3155. IR (ATR, cm−1): ν(BH) 2487 (w), ν(CC) 1648 (m), ν(BF4) 1046 (s). 1H NMR (400 MHz, CD3COCD3, 298 K): 8.40 (d, 1H, Tp), 8.33 (d, 1H, Tp), 8.22 (d, 1H, Tp), 8.07 (d, 1H, Tp), 8.03 (d, 1H, Tp), 7.66 (d, 1H, Tp), 6.68 (t, 1H, Tp), 6.51 (t, 1H, Tp), 6.39 (t, 1H, Tp), 5.04 (m, 1H, CH), 4.80 (m, 1H, =CH2), 3.03 (m, 1H, CH2), 2.86 (m, 3H, PCH), 2.57 (m, 1H, CHCy), 2.21 (s, 6H, OC(CH3)2), 2.06 (m, 2H, Cy), 1.90 (m, 2H, Cy), 1.79 (m, 1H, Cy), 1.44 (m, 5H, Cy), 1.39 (dd, JH−P = 11.6, JH−H = 7.2, 9H, PCHCH3), 1.26 (dd, JH−P = 13.2, JH−H = 7.2, 9H, PCHCH3); all coupling constans for the pyrazolyl proton resonances were about 2 Hz. 31P{1H} NMR (161.98 MHz, CD3COCD3, 298 K): −22.2 (s). 13C{1H} NMR (100.63 MHz, CD3COCD3, 298 K): 207.1 (s, OC(CH3)2), 166.7 (C), 151.6, 146.9, 139.6, 139.4, 138.8, 138.2 (all s, Tp), 117.1 (s, =CH), 109.6, 109.2 (both s, Tp), 108.2 (d, JC−P = 2, Tp), 45.8 (s, CHCy), 35.2, 35.1 (both s, Cy), 33.4 (s, =CH2), 31.2 (s, OC(CH3)2), 28.0, 28.0, 28.0 (all s, Cy), 27.7 (d, JC−P = 25, PCH), 21.7 (s, PCHCH3), 21.6 (d, JC−P = 3, PCHCH3).

Preparation of BArF4 Salts of 3 and 4. NaBArF4 (578 mg, 0.65 mmol) was added to a mixture of 3 and 4 (277 mg, 0.31 mmol). Acetone (10 mL) was added, and the solution was stirred for 2 h. The solvent was then evaporated, followed by the addition of dichloromethane (5 mL) and filtration through Celite of the resulting suspension. CH2Cl2 was removed under reduced pressure, and the obtained green oil was washed with a 1:5 mixture of diethyl ether and pentane in a dry CO2/iPrOH bath and vacuum-dried. Green solid. Yield: 373 mg (72%). 31P and 1H NMR data were identical with those reported for 3 and 4, except for the additional 1H signals of BArF4−. Anal. Calcd for C68H71B2F24N6OsP: C, 48.87; H, 4.28; N, 5.03. Found: C, 48.99; H, 4.07; N, 4.98. Crystals of the BArF4 salt of 3, suitable for X-ray diffraction analysis, were obtained by slow diffusion of pentane into a concentrated solution of 3 and 4 in dichloromethane at −20 °C. Isomerization of 3 and 4 into [OsHTp{C-(E)-C(CH2Cy) CH-[(E)-CHCHCy]}(PiPr3)]BF4 (5a,b) and [OsTp{CH-(E)-C[CH2-η2-(Z)-CHCHCy]CHCy}(PiPr3)]BF4 (6).22 A mixture of 3 and 4 in a 80:20 molar ratio (80 mg, mmol) was dissolved in fluorobenzene (8 mL) and heated at 85 °C in a Schlenk flask equipped with a Teflon stopcock for 36 h. The solvent was evaporated and the residue washed with pentane (3 × 8 mL) to afford a reddish solid that was vacuum-dried. The obtained solid contained a mixture of 5a,b and 6 in a 44:44:12 molar ratio. Yield: 61 mg (76%). HRMS (electrospray, m/z): calcd for C36H59BN6OsP [M]+ 809.4249, found 809.4281. IR (ATR, cm−1): ν(BH) 2492 (w), ν(OsH) 2109 (w), ν(BF4) 1047 (s). Selected spectroscopic data for 5a,b are as follows. 1H NMR (400 MHz, CD2Cl2, 298 K): 7.36 (d, JH−H = 11.4, 2H, both H4), 6.66 and 6.64 (both d, JH−H = 15.0, 1H each, H6), 6.36 and 6.35 (both dd, JH−H = 15.0, JH−H = 11.4, 1H each, H5), 2.23 (m, 4H, both H3), −6.73 and −6.84 (both d, JH−P = 19.8, 1H each, OsH). 31P{1H} NMR (121.49 MHz, CD2Cl2, 298 K): 30.4 (s) and 29.3 (s). 13C{1H} NMR (75.48 MHz, CD2Cl2, 298 K): 288.8 and 284.8 (both d, JC−P = 13, C1), 157.3 and 155.9 (both s, C6), 152.2 (s, C4), 146.7 (s, C2), 125.0 and 124.6 (both s, C5), 33.4 and 33.3 (both s, C3). Selected spectroscopic data for 6 are as follows. 1H NMR (400 MHz, CD2Cl2, 298 K): 17.61 (d, JH−P = 2.0, 1H, H1), 7.11 (dd, JH−H = 10.4, JH−H = 1.6, 1H, H3), 6.92 (m, 1H, H11), 4.92 (dd, JH−H = 9.6, JH−H = 9.6, 1H, H12), 4.26 (dd, JH−H = 16.4, JH−H = 6.0, 1H, H10), 3.55 (ddd, JH−H = 16.4, JH−H = 9.6, JH−H = 1.6, 1H, H10). 31P{1H} NMR (121.49 MHz, CD2Cl2, 298 K): −13.1 (s). 13C{1H} NMR (75.48 MHz, CD2Cl2, 298 K): 280.9 (d, JC−P = 7, C1), 182.8 (s, C2), 144.9 (s, C3), 86.8 (s, C12), 71.6 (s, C11), 30.3 (s, C10).

Preparation of [OsTp{CH-(Z)-C(CH2Cy)CH[η2-(Z)-CH CHCy]}(PiPr3)]BF4 (3) and [OsTp{CH-(Z)-C[CH2-η2-(Z)-CH CHCy]CHCy}(PiPr3)]BF4 (4). Cyclohexylallene (44 μL, 0.30 mmol) was added to a solution of 2 (210 mg, 0.25 mmol) in 5 mL of dichloromethane. After some minutes the solution turned green. The mixture was stirred overnight and then filtered through Celite. The solvent was evaporated, affording a dark green oil that was washed with pentane (3 × 5 mL) and vacuum-dried. Green solid. Yield: 172 mg (77%). HRMS (electrospray, m/z): calcd for C36H59BN6OsP [M]+ 809.4249, found 809.4244. IR (ATR, cm−1): ν(BH) 2500 (w), ν(C C) 1615 (m), ν(BF4) 1054 (s). The NMR spectra of the obtained solid showed the presence of 3 and 4 in a 80:20 molar ratio. Spectroscopic data for 3 are as follows. 1H NMR (400 MHz, CD2Cl2, 298 K): 17.51 (dd, JH−P < 1, JH−H < 1, 1H, H1), 9.26 (dd, JH−H < 1, JH−H < 1, 1H, H3), 8.07 (d, 1H, Tp), 8.04 (d, 1H, Tp), 8.01 (d, 1H, Tp), 7.92 (d, 1H, Tp), 7.58 (d, 1H, Tp), 6.62 (t, 1H, Tp), 6.53 (t, 1H, Tp), 6.41 (d, 1H, Tp), 6.02 (t, 1H, Tp), 5.29 (dd, JH−H = 10.4, JH−H = 9.8, 1H, H5), 5.05 (ddd, JH−H = 9.8, JH−P = 5.6, JH−H < 1, 1H, H4), 2.79 (AB part of an ABM (M = H) spin system, Δν = 23.6, JA−B = 14.1, JA−M = JB−M = 6.8, 2H, H12), 2.21 (m, 3H, PCH), 1.8−0.8 (m, 19H, Cy), 1.01 (dd, JH−P = 13.0, JH−H = 7.0, 9H, PCHCH3), 0.89 (m, 9H, PCHCH3), 0.31 (m, 1H, CH2Cy), 0.05 (m, 1H, CH2Cy), −1.07 (broad d, JH−H = 12.8, 1H, CH2Cy); all coupling constants for the pyrazolyl proton resonances were about 2 Hz. 31P{1H} NMR (161.98 MHz, CD2Cl2, 298 K): −9.8 (s). 13C{1H} NMR (75.48 MHz, CD2Cl2, 298 K): 286.4 (d, JC−P = 8, C1), 179.5 (s, C2), 161.3 (s, C3), 145.6, 144.0, 143.5, 138.6, 138.3, 137.0, 108.4, 108.2, 106.8 (all s, Tp), 93.8 (s, C5), 82.1 (s, C4), 40.8 (s, CHCy), 40.3 (s, C12), 39.3 (s, CH2Cy), 38.6 (s, CHCy), 33.6, 30.6, 27.6, 26.7, 26.5, 26.4, 26.1, 26.0 (all s, CH2Cy), 25.3 (d, JC−P = 25, PCH), 19.2 (s, PCHCH3), 18.7 (s, PCHCH3). Selected spectroscopic data for 4 are as follows. 1H NMR (500 MHz, CD2Cl2, 298 K): 18.50 (d, JH−P = 2.0, 1H, H1), 7.01 (m, 1H, H4), 6.90 (dd, JH−H = 10.5, JH−H = 1.6, 1H, H12), 4.96 (dd, JH−H = 9.5, JH−H = 9.5, 1H, H5), 4.27 (dd, JH−H = 16.0, JH−H = 6.0, 1H, H3), 3.55 (ddd, JH−H = 16.0, JH−H = 10.5, JH−H = 1.6, 1H, H3). 31 1 P{ H} NMR (161.98 MHz, CD2Cl2, 298 K): −12.9 (s). 13C{1H} NMR (125.78 MHz, CD2Cl2, 298 K): 270.0 (d, JC−P = 10, C1), 180.8 (s, C2), 134.8 (s, C12), 86.4 (s, C5), 70.4 (s, C4), 34.8 (s, C3).

Preparation of BArF4 Salts of 5 and 6. A mixture of the BArF4 salts of 3 and 4 (300 mg, 0.18 mmol) was dissolved in 5 mL of fluorobenzene and heated at 85 °C for 2 days in a Schlenk flask equipped with a Teflon stopcock. After this time, the solvent was evaporated and the obtained reddish oil was washed with pentane (3 × 5 mL) in a dry CO2/iPrOH bath and dried in vacuo. Reddish solid. Yield: 201 mg (67%). 31P and 1H NMR data were identical with those reported for 5 and 6, except for the additional 1H signals of BArF4−. Green crystals of 6 suitable for X-ray diffraction analysis were obtained 1997


Organometallics

Article

resonances were about 2 Hz. 31P{1H} NMR (161.98 MHz, CD2Cl2, 298 K): −10.4 (s). 13C{1H} NMR (100.63 MHz, CD2Cl2, 298 K): 284.2 (d, JC−P = 8, C1), 183.6 (s, C2), 172.3 (s, CO), 148.3 (s, C3), 146.9, 144.2, 144.1, 138.1, 138.0, 136.6, 108.1, 107.6, 106.5 (all s, Tp), 76.7 (s, C11), 62.3 (s, C12), 60.2 (s, CH2CH3), 42.4 (s, CHCy), 30.1 (s, C10), 29.4, 29.4, 26.0 (all s, CH2Cy), 25.6 (d, JC−P = 24, PCH), 25.3, 25.2 (both s, CH2Cy), 19.1 (d, JC−P = 3, PCHCH3), 18.9 (s, PCHCH3), 13.4 (s, CH2CH3).

from a dichloromethane−pentane solution of the 5−6 equilibrium mixture. Preparation of [OsTp{CH-(Z)-C[CH 2 -η 2 -(Z)-CH CHCO2Et]CHCy}(PiPr3)]BF4 (7). Ethyl carboxylateallene (42 μL, 0.36 mmol) was added to a solution of 2 (270 mg, 0.33 mmol) in 5 mL of dichloromethane. After some minutes the solution changed from yellow to green. The mixture was stirred overnight and then filtered through Celite. The solvent was evaporated, and the green oily residue was washed with pentane (3 × 8 mL) and vacuum-dried, affording a green solid. Yield: 257 mg (88%). Anal. Calcd for C33H53B2F4N6O2OsP: C, 44.68; H, 6.03; N, 9.48. Found: C, 44.16; H, 6.38; N, 9.46. HRMS (electrospray, m/z): calcd for C33H53BN6O2OsP [M]+ 799.3677, found 799.3693. IR (ATR, cm−1): ν(BH) 2509 (w), ν(CO) 1702 (m), ν(C−O) 1217 (m), ν(BF4) 1047 (s). 1H NMR (300 MHz, CD2Cl2, 298 K): 17.82 (d, JH−P = 2.1, 1H, H1), 8.24 (d, 1H, Tp), 8.08 (d, 1H, Tp), 8.00 (d, 1H, Tp), 7.91 (d, 1H, Tp), 7.53 (d, 1H, Tp), 6.93 (m, 1H, H5), 6.87 (dd, JH−H = 11.4, JH−H = 1.8, 1H, H3), 6.60 (t, 1H, Tp), 6.58 (t, 1H, Tp), 6.48 (d, 1H, Tp), 5.98 (t, 1H, Tp), 5.34 (JH−H = 9.0, 1H, H6), 4.91 (ddd, JH−H = 16.2, JH−H = 9.6, JH−H = 1.8, 1H, H4), 4.46 (dd, JH−H = 16.2, JH−H = 7.1, 1H, H4), 3.30 (AB part of an ABM3 (M = H) spin system, Δν = 88, JA−B = 10.8, JA−M = 7.2, JB−M = 7.2, 2H, CO2CH2CH3), 2.60 (m, 1H, CHCy), 2.33 (m, 3H, PCH), 1.81−1.19 (m, 10H, CH2Cy), 1.13 (dd, JH−P = 12.9, JH−H = 6.9, 9H, PCHCH3), 0.87 (dd, JH−P = 14.0, JH−H = 6.9, 9H, PCHCH3), 0.43 (M3 part of an ABM3 spin system, JA−M = 7.2, JB−M = 7.2, 3H, COOCH2CH3); all coupling constants for the pyrazolyl proton resonances were about 2 Hz. 31P{1H} NMR (161.98 MHz, CD2Cl2, 298 K): −10.4 (s). 13C{1H} NMR (100.63 MHz, CD2Cl2, 298 K): 273.6 (d, JC−P = 9, C1), 182.0 (s, C2), 172.0 (s, CO), 147.0, 144.3, 144.1 (all s, Tp), 138.8 (s, C3), 138.1, 138.0, 136.6, 108.3, 107.7, 106.7 (all s, Tp), 76.0 (s, C5), 62.5 (s, C6), 60.2 (s, CH2CH3), 42.3 (s, CHCy), 34.5 (s, C4), 30.8, 30.6, 25.8 (all s, CH2Cy), 25.6 (d, JC−P = 25, PCH), 25.0, 24.9 (both s, CH2Cy), 19.1 (d, JC−P = 3, PCHCH3), 19.0 (s, PCHCH3), 13.4 (s, CH2CH3).

Preparation of OsTp{(E)-CHC[CHC(CH2)4CH2]CH2-η2-(Z)CHCHCO2Et}(PiPr3) (9). THF (6 mL) was added to a mixture of 7 (183 mg, 0.21 mmol) and NaOMe (22.3 mg, 0.41 mmol). The solution changed gradually from green to brown. After 1 h the solvent was removed under reduced pressure. Diethyl ether was added, and the mixture was filtered through Celite. The solvent was evaporated, and pentane (2 mL) was added to afford a solution that was cooled overnight to afford a solid which was separated by decantation via cannula at 203 K and vacuum-dried. Light brown solid. Yield: 68 mg (41%). Anal. Calcd for C33H52BN6O2OsP: C, 49.74; H, 6.58; N, 10.55. Found: C, 50.07; H, 6.22; N, 10.81. HRMS (electrospray, m/z): calcd for C33H52BN6O2OsP [M]+ 798.3599, found 798.3655. IR (ATR, cm−1): ν(BH) 2466 (w), ν(CO) 1706 (m), ν(C−O) 1211 (m). 1H NMR (400 MHz, C6D6, 298 K): 8.12 (d, 1H, Tp), 8.09 (d, 1H, Tp), 8.00 (s, 1H, H1), 7.63 (d, 1H, Tp), 7.53 (d, 1H, Tp), 7.48 (d, 1H, Tp), 7.20 (d, 1H, Tp), 6.29 (s, 1H, H3), 6.11 (t, 1H, Tp), 5.99 (m, 1H, H5), 5.92 (t, 1H, Tp), 5.69 (t, 1H, Tp), 4.93 (dd, JH−H = 15.2, JH−H = 8.2, 1H, H4), 4.49 (d, JH−H = 8.8, 1H, H6), 4.13 (dd, JH−H = 15.2, JH−H = 7.6, 1H, H4), 3.50 (AB part of an ABM3 (M = H) spin system, Δν = 37, JA−B = 10.8, JA−M = 7.2, JB−M = 7.2, 2H, CO2CH2CH3), 2.72 (m, 2H, CH2Cy), 2.30 (m, 2H, CH2Cy), 2.15 (m, 3H, PCH), 1.64 (m, 4H, CH2Cy), 1.52 (m, 2H, CH2Cy), 0.94 (dd, JH−P = 11.2, JH−H = 7.2, 9H, PCHCH3), 0.87 (dd, JH−P = 11.2, JH−H = 7.2, 9H, PCHCH3), 0.41 (M3 part of an ABM3 spin system, JA−M = 7.2, JB−M = 7.2, 3H, CO2CH2CH3); all coupling constants for the pyrazolyl proton resonances were about 2 Hz. 31P{1H} NMR (161.98 MHz, C6D6, 298 K): −21.3 (s). 13C{1H} NMR (125.78 MHz, C6D6, 298 K): 174.5 (s, CO2), 155.6 (d, JC−P = 6, C1), 152.3 (s, C2), 146.7, 145.8, 143.4, 135.5, 135.2, 133.8 (all s, Tp), 130.7 (s, CCy), 128.3 (s, C3), 105.9, 104.9, 104.8 (all s, Tp), 62.6 (s, C5), 58.3 (s, CO2CH2CH3), 47.0 (s, C6), 39.4 (s, C4), 39.0, 30.8, 29.8, 29.1, 27.6 (all s, CH2Cy), 25.4 (d, JC−P = 26, PCH), 19.9 (s, PCHCH3), 19.5 (s, PCHCH3), 13.7 (s, CO2CH2CH3).

Preparation of [OsTp{CH-(E)-C[CH 2 -η 2 -(Z)-CH CHCO2Et]CHCy}(PiPr3)]BF4 (8). Method a. A solution of 7 (240 mg, 0.27 mmol) in 10 mL of fluorobenzene was heated at 80 °C for 24 h in a Schlenk flask equipped with a Teflon stopcock. After this time the solvent was removed by evaporation and the residue washed with pentane (3 × 8 mL) and vacuum-dried. Green solid. Yield: 219 mg (91%). Method b. A solution of 9 (55 mg, 0.069 mmol) in diethyl ether (5 mL) was treated with HBF4·Et2O (11.3 μL, 0.083 mmol). Immediately a green solid appeared, which was separated by decantation, washed with pentane (3 × 5 mL), and dried in vacuo. Yield: 39 mg (64%). Anal. Calcd for C33H53B2F4N6O2OsP: C, 44.68; H, 6.03; N, 9.48. Found: C, 44.79; H, 6.31; N, 9.11. HRMS (electrospray, m/z): calcd for C33H53BN6O2OsP [M]+ 799.3677, found 799.3684. IR (ATR, cm−1): ν(BH) 2496 (w), ν(CO) 1710 (m), ν(C−O) 1210 (m), ν(BF4) 1048 (s). 1H NMR (400 MHz, CD2Cl2, 298 K): 16.99 (d, JH−P = 1.6, 1H, H1), 8.25 (d, 1H, Tp), 8.08 (d, 1H, Tp), 8.00 (d, 1H, Tp), 7.89 (d, 1H, Tp), 7.53 (d, 1H, Tp), 7.09 (dd, JH−H = 10.0, JH−H = 2.0, H3), 6.90 (m, 1H, H11), 6.58 (t, 1H, Tp), 6.56 (t, 1H, Tp), 6.43 (d, 1H, Tp), 5.96 (t, 1H, Tp), 5.31 (d, JH−H = 8.8, 1H, H12), 4.73 (ddd, JH−H = 16.6, JH−H = 9.0, JH−H =2.0, 1H, H10), 4.42 (dd, JH−H = 16.6, JH−H = 6.6, 1H, H10), 3.29 (AB part of an ABM3 (M = H) spin system, Δν = 128, JA−B = 10.8, JA−M = 7.2, JB−M = 7.2, 2H, CO2CH2CH3), 2.33 (m, 3H, PCH), 2.23 (m, 1H, CHCy), 1.91−1.23 (m, 10H, CH2Cy), 1.13 (dd, JH−P = 12.8, JH−H = 7.2, 9H, PCHCH3), 0.86 (dd, JH−P = 12.8, JH−H = 7.2, 9H, PCHCH3), 0.43 (M3 part of an ABM3 spin system, JA−M = 7.2, JB−M = 7.2, 3H, COOCH2CH3); all coupling constants for the pyrazolyl proton

Structural Analysis of Complexes 2, 3, 6, and 8. X-ray data were collected on Bruker Smart APEX (2, 3) and Bruker Smart APEX 2 diffractometers (6, 8) equipped with a normal or fine focus, respectively, and a 2.4 kW sealed tube source (Mo radiation, λ = 0.710 73 Å). Data were collected over the complete sphere. Data were corrected for absorption by using a multiscan method applied with the SADABS program.23 The structures were solved by direct methods. Refinement of complexes was performed by full-matrix least squares on F2 with SHELXL97,24 including isotropic and subsequently anisotropic displacement parameters for nondisordered atoms. Some ArF groups of the BArF anions of 3 and 6, the solvents of crystallization CH2Cl2 (3) and pentane (6), and two isopropyl groups of the 1998


Organometallics

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phosphine ligand of 8 were observed to be disordered. These disordered atoms were refined isotropically with restrained geometry. Crystal Data for 2: C30H51BN6OOsP(BF4) Mw 830.56, irregular block, yellow (0.14 × 0.10 × 0.06 mm), orthorhombic, space group P212121, a = 12.7365(17) Å, b = 13.2256(17) Å, c = 20.124(3) Å, V = 3389.8(8) Å3, Z = 4, Dcalcd = 1.627 g cm−3, F(000) = 1672, T = 100(2) K, μ = 3.865 mm−1, 37 723 measured reflections (2θ = 3−58°, ω scans 0.3°), 8256 unique reflections (Rint = 0.1070); minimum/maximum transmission factors 0.540/0.801, final agreement factors R1 = 0.0436 (6901 observed reflections, I > 2σ(I)) and wR2 = 0.0828, Flack parameter 0.001(8), 8256/0/427 data/restraints/parameters, GOF = 0.998, largest peak and hole 1.705 and −1.399 e Å−3. Crystal Data for 3: C36H59BN6OsP(C32H12BF24)·0.35CH2Cl2, Mw 1701.16, irregular block, green (0.16 × 0.10 × 0.04 mm), monoclinic, space group P21/c, a = 13.2854(13) Å, b = 20.752(2) Å, c = 28.060(3) Å, β = 91.6720(10)°, V = 7733.0(13) Å3, Z = 4, Dcalcd = 1.461 g cm−3, F(000) = 3411, T = 173(2) K, μ = 1.794 mm−1, 53 818 measured reflections (2θ = 3−58°, ω scans 0.3°), 15 173 unique reflections (Rint = 0.1114); minimum/maximum transmission factors 0.676/0.862, final agreement factors R1 = 0.0861 (9485 observed reflections, I > 2σ(I)) and wR2 = 0.2311, 15 173/84/855 data/restraints/parameters, GOF = 1.045, largest peak and hole 1.635 and −1.632 e Å−3. Crystal Data for 6: C36H59BN6OsP(C32H12BF24)·C5H12, Mw 1743.24, irregular block, green (0.16 × 0.07 × 0.06 mm), triclinic, space group P1̅, a = 13.397(2) Å, b = 16.445(3) Å, c = 18.943(3) Å, α = 93.825(2)°, β = 108.678(2)°, γ = 104.976(2)°, V = 3768.1(10) Å3, Z = 2, Dcalcd = 1.536 g cm−3, F(000) = 1760, T = 100(2) K, μ = 1.819 mm−1, 40 766 measured reflections (2θ = 3−58°, ω scans 0.3°), 18 897 unique reflections (Rint = 0.0335), minimum/maximum transmission factors 0.699/0.862, final agreement factors R1 = 0.0448 (15 887 observed reflections, I > 2σ(I)) and wR2 = 0.1251, 18 897/ 31/958 data/restraints/parameters, GOF = 1.093, largest peak and hole 4.595 and −1.322 e Å−3. Crystal Data for 8: C33H53BN6O2OsP(BF4), Mw 884.60, irregular block, blue (0.18 × 0.13 × 0.04 mm), monoclinic, space group P21/n, a = 12.2995(16) Å, b = 16.471(2) Å, c = 18.697(2) Å, β = 99.903(2)°, V = 3731.3(8) Å3, Z = 4, Dcalcd = 1.575 g cm−3, F(000) = 1784, T = 100(2) K, μ = 3.519 mm−1, 27 092 measured reflections (2θ = 3−58°, ω scans 0.3°), 10 333 unique reflections (Rint = 0.0631), minimum/ maximum transmission factors 0.672/0.862, final agreement factors R1 = 0.0433 (6510 observed reflections, I > 2σ(I)) and wR2 = 0.1063, 10 333/16/461 data/restraints/parameters, GOF = 1.019, largest peak and hole 1.886 and −2.105 e Å−3.

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ASSOCIATED CONTENT

S Supporting Information *

CIF files giving positional and displacement parameters, crystallographic data, and bond lengths and angles of compounds 2, 3, 6, and 8. This material is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS Financial support from the Spanish MICINN (Projects CTQ2011-23459 and Consolider Ingenio 2010 (CSD200700006)), the Diputación General de Aragón (E35), and the European Social Fund (FEDER) is acknowledged.

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REFERENCES

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