Reactions of Half-Sandwich Ethene Complexes of Rhodium(I

Article pubs.acs.org/Organometallics

Reactions of Half-Sandwich Ethene Complexes of Rhodium(I) toward Iodoperfluorocarbons: Perfluoro-alkylation or -arylation of Coordinated Ethene versus Oxidative Addition† Juan Gil-Rubio,* Juan Guerrero-Leal, María Blaya, and José Vicente Grupo de Química Organometálica, Departamento de Química Inorgánica, Facultad de Química, Universidad de Murcia, E-30071 Murcia, Spain

Delia Bautista SAI, Universidad de Murcia, E-30071 Murcia, Spain

Peter G. Jones Institut für Anorganische und Analytische Chemie, Technische Universität Braunschweig, Postfach 3329, 38023 Braunschweig, Germany S Supporting Information *

ABSTRACT: Perfluoroalkylation or perfluoroarylation of coordinated ethene takes place when complexes [Rh(η5-Cp*)(η2-C2H4)2] or [Rh(η5-Cp*)(η2-C2H4)(PR3)] react with IRF, to give complexes [Rh(η5-Cp*)(CH2CH2RF)(μ-I)]2 (RF = CF(CF3)2 (1a), CF(CF3)CF2CF3 (1b), or C(CF3)3 (1c)) and [(η5-Cp*)IRh(μ-I)2Rh(η5-Cp*)(CH2CH2RF)] (2a−c), or [Rh(η5-Cp*)(CH2CH2RF)I(PR3)] (R = Me, RF = CF(CF3)2 (3a), C(CF3)3 (3c), C6F5 (3d); R = Ph, RF = CF(CF3)2 (3a′), CF2C6F5 (3e′)), respectively. Bridge splitting reactions of 1a, 1b, or 1c with phosphines afford complexes [Rh(η5-Cp*)(CH2CH2RF)I(PR3)] (3a, 3a′, 3c; RF = CF(CF3)2, R = iPr (3a″); RF = CF(CF3)CF2CF3, R = Me (3b), Ph (3b′)). In contrast, oxidative addition dominates over addition to ethene in the reactions of [Rh(η5-Cp*)(η2-C2H4)(PMe3)] with IRF (RF = CF2C6F5, nC3F7, nC4F9, CFCF2) and in the reaction of [Rh(η5-Cp)(η2-C2H4)(PMe3)] with InC4F9, affording complexes of the type [Rh(η5-C5R5)(RF)I(PMe3)] (4e−h and 5, respectively). The reaction of [Rh(η5-Cp*)(η2-C2H4)(PR3)] with ICF(CF3)CF2CF3 gives a mixture of cis- and trans-octafluoro-2butene as the main fluoroorganic reaction product. Evidence for the intermediacy of RF− anions in these reactions has been obtained. 3a′ reacts with AgOTf (OTf = O3SCF3) and XyNC or CO to give complexes [Rh(η5-Cp*){CH2CH2CF(CF3)2}(CNXy)(PPh3)]OTf (6) or [Rh(η5-Cp*){C(O)CH2CH2CF(CF3)2}(CO)(PPh3)]OTf (7), respectively. Complex [Rh(η5-Cp*)I(py)(PMe3)]BF4 (8) was obtained either by reaction of (1) [Rh(η5-Cp*)(η2-C2H4)(PMe3)] with [I(py)2]BF4 or (2) [Rh(η5-Cp*)I2(PMe3)] with AgBF4 and py. The crystal structures of 1a, 1b, 3c, 4g, 7, and 8 have been determined.

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INTRODUCTION Despite the notable advances recently made in the field of metal-catalyzed perfluoroalkylation of organic substrates,1−3 processes involving perfluoroalkyl metal complexes as intermediates remain a challenge, because of the reluctance of these complexes to undergo typical C−C bond formation reactions, such as reductive elimination or insertion of unsaturated molecules into the M−C bond.4−10 Alternatively, some metal complexes are effective initiators of free radical perfluoroalkylations,11−16 but the selectivity of these reactions is difficult to control.11,13,17 In this context, the direct perfluoroalkylation of a substrate coordinated to a metal is of potential interest,18 since it provides a way to the selective formation of C− perfluoroalkyl bonds avoiding the intermediacy of stable metal perfluoroalkyls. © 2011 American Chemical Society

Perfluoroiodocarbons usually react with complexes of the type [M(η5-C5R5)L2] (M = Co, Rh or Ir; R = H or Me; L = CO or PF3) by oxidative addition to give complexes [M(η5-C5R5)I(RF)L], where RF is a perfluorinated alkyl, aryl, or benzyl group.19−31 However, reactions involving perfluoroalkylation of ligands have been observed in a few cases (Scheme 1). For instance, clean perfluoroalkylation at the η5-Cp ring was observed in the reactions of [M(η5-Cp)(PMe3)2] (M = Co or Rh) with InC3F7 or ICF(CF3)2,24,29,30 whereas mixtures of products resulting from perfluoroalkylation at the metal, CO, or η5-Cp ligands were formed in the reactions of [M(η5-Cp)(PMe3)(CO)] Special Issue: Fluorine in Organometallic Chemistry Received: October 10, 2011 Published: November 29, 2011 1287

dx.doi.org/10.1021/om2009588 | Organometallics 2012, 31, 1287−1299

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the Rh−C bond44−46 occurred to afford an unusual highly fluorinated acyl derivative.

Scheme 1

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RESULTS AND DISCUSSION Reactions of [Rh(η5-Cp*)(η2-C2H4)2] with Perfluoroiodocarbons. [Rh(η 5 -Cp*)(η 2 -C 2 H 4 ) 2 ] reacts with IR F (Scheme 2) to give mainly ethene and complexes [Rh(η5Scheme 2

(M = Rh or Ir) with the same perfluoroalkyl iodides.32 Very recently, the perfluoroalkylation of a CO ligand in the reaction between [Ir(η5-Cp*)(CO)2] and perfluorocyclohexyl bromide has been reported.33 Although complexes [Rh(η5-C5R5)(η2-C2H4)L] (R = H or Me; L = phosphine or C2H4)34−37 have been known for a long time, reports of their reactivity toward perfluoroalkyl iodides or bromides are scarce. Thus, [Rh(η5-Cp)(η2-C2H4)2] was reported to react with ICF3 or InC3F7 to give the oxidative addition products [Rh(η5-Cp)(CF3)(μ-I)]2 or [Rh(η5-Cp)I(nC3F7)(η2-C2H4)],38 respectively. In contrast, [Rh(η5-C5Me5)(η2-C2H4)2] does not react with ICF2C6F5.39 The reactions of [Rh(η5-Cp)(η2-C2H4)(PPh3)] with InC3F7 or BrCF2CF2Br also proceed by oxidative addition, yielding compounds [Rh(η5-Cp)(RF)X(PPh3)] (X = I, RF = nC3F7; X = Br, RF = CF2CF2Br), but the analogous reaction with ICF3 affords [Rh(η5-Cp)I2(PPh3)] as the only isolated product.40 Oxidative addition of perfluoroalkyl iodides to the related complex [Rh(Tp)(η2-C2H4)2] (Tp = tris(pyrazolyl)borate) has also been described.41 Therefore, we decided to improve and extend the knowledge of the reactivity of complexes of the type [Rh(η5-C5R5)(η2-C2H4)L] (R = H, Me; L = PR3, C2H4) toward iodoperfluorocarbons. Interestingly, these reactions proceed in most cases by perfluoroalkylation of the coordinated ethene, rather than by oxidative addition. As far as we are aware, perfluoroalkylation of coordinated ethene has been reported only in the reaction of complexes [M(η5-Cp)2(η2-C2H4)] (M = Mo or W) with IC(CF3)3 to give [M(η5Cp)2{CH2CH2C(CF3)3}].42,43 We also report the reactivity toward XyNC or CO of one of the products obtained by perfluoroalkylation of the coordinated ethene. Whereas in the first case a ligand substitution reaction took place, in the second the insertion of a CO molecule into

Cp*)(CH2CH2RF)(μ-I)]2 (RF = CF(CF3)2 (1a), CF(CF3)CF2CF3 (1b), C(CF3)3 (1c)). Compounds 1a and 1b were isolated as crystalline red solids containing small amounts (10%) of [(η5-Cp*)IRh(μ-I)2Rh(η5-Cp*)(CH2CH2RF)] (2a, 2b, respectively). In the case of 1c, a greater amount of the mixed iodide-bridged complex (2c), HC(CF3)3, and small amounts of unidentified compounds were also formed. The identity of complexes 1 was established on the basis of (1) their 1H and 19F NMR data, (2) the characterization of the products of their reactions with various phosphines (see below), and (3) the X-ray structures of 1a and 1b. In addition, the elemental analyses of samples of 1a or 1b containing 10% (determined by 1H NMR) of 2a or 2b, respectively, agree with the calculated values, supporting the formulation of both components. Complex 1a or 1b decomposes in solution at room temperature over several days to give mainly 2a or 2b, together with minor quantities of [Rh(η5-Cp*)I(μ-I)]2 and other products that could not be identified. Hence, the presence of small amounts of 2a or 2b could be attributed to decomposition of 1a or 1b during the reaction time. In contrast, the larger amounts of 2c and other products detected in the reaction of [Rh(η5-Cp*)(η2-C2H4)2] with IC(CF3)3 cannot be attributed solely to decomposition of 1c and are 1288


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In 1b, because of the presence of two chiral centers (at the perfluoro-sec-butyl groups), two diastereomers are possible: the racemic pair (with RR or SS configuration) and the meso diastereomer (with RS configuration). However, in the single crystal used for the X-ray structure determination only the meso isomer was present. Indeed, the molecule of 1b is centrosymmetric, whereas in 1a both CH2CH2CF(CF3)2 groups point to the same side of the molecule (as viewed down the Rh−Rh axis) and the bond distances and angles are slightly different for both metal fragments. In the 1H NMR spectra of 1a−c the methylene protons appear as second-order multiplets around 3 ppm. The 19F NMR spectrum of 1a displays a doublet and a multiplet, corresponding to the CF3 and CF groups, respectively. The CF(CF3)CF2CF3 group of 1b gives five signals, corresponding to the CF, the diastereotopic CF2 fluorines, and the CF3 groups. The identity of complexes 2 in their mixtures with 1 was established on the basis of their 1H and 19F NMR signals. Thus, the 1H spectra show signals corresponding to two different η5-Cp* groups and a complex multiplet around 3 ppm for the methylene protons, and the 19F spectra display a set of signals at chemical shift values very close to those of 1. Although two diastereomers are expected for 1b, only one set of signals was observed in its 1H and 19F NMR spectra, even at low temperature and in a high-field spectrometer (−80 °C, 600 MHz). As the selective formation of one diastereomer of 1b is unlikely, this could be the result of both isomers having almost identical 1H and 19F NMR spectra.51 NMR measurements on samples of 1a or 1b (containing small amounts of 2a or 2b, respectively) treated with 1 equiv of [Rh(η5-Cp*)I(μ-I)]2 revealed that compounds 1, 2, and [Rh(η5-Cp*)I(μ-I)]2 are in equilibrium, whereby complexes 2 are the major components. This process is slow on the NMR time scale at room temperature, but at about 80 °C the Cp* signals of the three compounds coalesce into a unique signal in the 1H NMR spectrum (D8-toluene). This could be explained by an exchange process involving cleavage and restoration of the iodide bridges with combination of the resulting fragments. [Rh(η5-Cp*)(η2-C2H4)2] reacted neither in C6D6 solution with InC4F9, IC6F5, or ICFCF2 at room temperature nor on heating at 50 °C (InC4F9) or at 60 °C (IC6F5 or ICFCF2) for several hours. Heating at higher temperatures led to mixtures of products that were not identified. In agreement with previously reported results, the reaction of [Rh(η5-Cp*)(η2-C2H4)2] and ICF2C6F5 was sluggish, and, after 21 h at room temperature, most starting material remained unreacted.39 Bridge-Cleavage Reactions. The reactions of the mixtures of complexes 1 + 2 with PMe3, PPh3, or PiPr3 led to mononuclear complexes of the type [Rh(η 5 -Cp*)(CH2CH2RF)I(PR3)] (RF = CF(CF3)2, R = Me (3a), Ph (3a′), iPr (3a″); RF = CF(CF3)CF2CF3, R = Me (3b), Ph (3b′); RF = C(CF3)3, R = Me (3c); Scheme 2), which were isolated with 50−82% yields after separation of the byproducts [Rh(η5Cp*)I2(PR3)] by crystallization or chromatography. Complexes 3b and 3b′ were isolated as mixtures of two diastereomers arising from the presence of two stereogenic centers in the molecule, one at the perfluoro-sec-butyl group and another at the Rh atom. The diastereomeric ratios were close to unity (1:1 and 1:1.1, respectively). This implies a negligible influence of the configuration of the perfluoro-sec-butyl group on the side of the attack of the phosphine to the metal, which is in turn attributable to the long distance between the stereogenic carbon atom and the metal.

probably formed through an alternative reaction path (see Mechanistic Studies). The crystal structures of 1a and 1b (Figures 1 and 2) show the presence of iodo-bridged dimers with the pairs of η5-Cp*

Figure 1. Molecular structure of 1a (50% thermal ellipsoids). Selected bond lengths (Å) and angles (deg): Rh(1)−CNT1 (CNT1 = centroid of C1−5) 1.8250(19), Rh(1)−C(11) 2.111(4), Rh(1)−I(1) 2.7198(4), Rh(1)−I(2) 2.7077(4), Rh(2)−CNT2 (CNT2 = centroid of C21−25) 1.8300(18), Rh(2)−C(31) 2.108(4), Rh(2)−I(1) 2.7100(4), Rh(2)−I(2) 2.6987(4), I(1)−Rh(1)−I(2) 87.229(11), C(11)−Rh(1)−I(1) 87.19(10), C(11)−Rh(1)−I(2) 88.35(10), C(31)−Rh(2)−I(2) 87.94(11), C(31)−Rh(2)−I(1) 85.90(10).

Figure 2. Molecular structure of 1b (50% thermal ellipsoids). Selected bond lengths (Å) and angles (deg): Rh(1)−CNT1 (CNT1 = centroid of C1−5) 1.820(3), Rh(1)−C(11) 2.111(6), Rh(1)−I(1) 2.7060(6), Rh(1)−I(1A) 2.7134(6), C(11)−Rh(1)−I(1) 89.44(17), C(11)− Rh(1)−I(1A) 88.87(17), I(1)−Rh(1)−I(1A) 86.513(18), Rh(1)− I(1)−Rh(1A) 93.487(18).

and C2H4RF ligands necessarily mutually trans. This arrangement is usually adopted by halide-bridged pentamethylcyclopentadienyl complexes of Rh or Ir in order to reduce steric hindrance.39,47−50 For the same reason, the CH2CH2RF chains are extended away from the metal. Bond distances and angles in the coordination sphere are very similar for both complexes. 1289


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Reactions of [Rh(η5-Cp*)(η2-C2H4)(PR3)] (R = Me or Ph) with Perfluoroiodocarbons. The reactions between in situ generated [Rh(η5-Cp*)(η2-C2H4)(PR3)] and IRF (Scheme 3

products were tentatively identified in the reaction mixtures. Significant amounts of HRF were also formed in the reactions leading to 4g and 4h. The reaction of [Rh(η5-Cp)(η2-C2H4)(PMe3)] with InC4F9 (Scheme 4) gave [Rh(η5-Cp)(nC4F9)I(PMe3)] (5), which was

Scheme 3

Scheme 4

isolated and characterized. In contrast, the reactions of the same complex with ICF(CF3)2, IC6F5, or ICFCF2 led to intractable mixtures containing large amounts of [Rh(η5-Cp)I2(PMe3)]. The obtained complexes gave the expected signals in their NMR spectra. Because of the presence of a stereogenic center at the metal, the four methylene protons of complexes 3 appear inequivalent in their 1H NMR spectra. For the same reason, two signals are observed for the CF3 groups of 3a, 3a′, and 3a″ and for the CF2 fluorines of 3b and 3b′. The 31P{1H} spectra of complexes 3 showed a doublet as a consequence of the coupling with 103Rh. In contrast, the oxidative addition complexes gave doublets of multiplets (4g and 5) or a doublet of doublets (4h) because of the coupling of 31P with 103Rh and with the 19F nuclei of the rhodium-bound nC4F9 or CFCF2 groups, respectively. The signals of 3b and 3b′ were duplicated because of the presence of two diastereomers (see above). The crystal structures of 3c and 4g were determined by single-crystal X-ray diffraction (Figures 3 and 4). In both

and Table 1) led, in general, to mixtures containing the ethene perfluoroalkylation or perfluoroarylation products (3), the oxidative addition products (4), complexes [Rh(η5-Cp*)I2(PR3)] (R = Me or Ph), and other products that could not be separated and identified. The nature of the main reaction product depends on R and RF. Thus, addition to ethene prevails in the reactions of [Rh(η5-Cp*)(η2-C2H4)(PMe3)] with ICF(CF3)2, IC(CF3)3, or IC6F5 and in the reactions of [Rh(η5-Cp*)(η2-C2H4)(PPh3)] with ICF(CF3)2 or ICF2C6F5 to give complexes 3a, 3c, 3d, 3a′, and 3e′ (Scheme 3), respectively, which were isolated in 12−80% yields (Table 1). The corresponding oxidative addition products were not detected in these reactions except for ICF2C6F5, where a minor amount was tentatively identified in the NMR spectra of the reaction mixture. In contrast, oxidative addition is dominant for the reactions of [Rh(η5-Cp*)(η2-C2H4)(PMe3)] with ICF2C6F5, InC3F7, and InC4F9, which gave the previously reported [Rh(η5-Cp*)(RF)I(PMe3)] (RF = CF2C6F5 (4e)22 or n C3F7 (4f)21) and the new compound [Rh(η5-Cp*)(nC4F9)I(PMe3)] (4g). Complexes 4e and 4g were isolated, but 4f was identified in the reaction mixture by comparison of its NMR signals with those reported. Finally, the reaction of [Rh(η5Cp*)(η2-C2H4)(PMe3)] with ICFCF2 gave [Rh(η5-Cp*)I2(PMe3)] as the main product, and the oxidative addition product 4h was isolated in low yield by chromatography. In the reactions leading to 4e−h, only minor amounts of the corresponding ethene perfluoro(alkylation or vinylation) Table 1. Composition (%) of the Mixture of Products of the Reaction [Rh(η5-Cp*)(η2-C2H4)(PR3)] + IRFa RF

R

attack on ethene

oxidative addition

[Rh(η5-Cp*) I2(PR3)]

CF(CF3)2 CF(CF3)2 C(CF3)3 C6F5 CF2C6F5 CF2C6F5 n C3 F 7 n C4 F 9 CFCF2

Me Ph Me Me Me Ph Me Me Me

51 (3a) 91 (3a′) 100 (3c) 57 (3d) 0 40 (3e′) ≤7b ≤5b ≤7b

0 0 0 0 64 (4e) ≤10b 40 (4f) 40 (4g) 19 (4h)

5 5 0 4 15 31 27 24 40

Figure 3. Molecular structure of 3c (50% thermal ellipsoids). Selected bond lengths (Å) and angles (deg): Rh(1)−CNT (CNT = centroid of C1−5) 1.8789(16), Rh(1)−C(11) 2.120(3), Rh(1)−P(1) 2.2594(9), Rh(1)−I(1) 2.6989(4), C(11)−Rh(1)−P(1) 85.31(10), C(11)− Rh(1)−I(1) 96.26(9), P(1)−Rh(1)−I(1) 89.02(3).

molecules, the fluorinated alkyl group is extended away from the metal in order to reduce steric repulsions with the η5-Cp* and PMe3 ligands. The Rh−CH2 distance in 3c (2.120(3) Å) is not significantly different from those of 1a (2.111(4) and 2.108(4) Å) or 1b (2.111(6) Å). The terminal Rh−I bond of

a

Estimated by integration of the 31P{1H} NMR spectrum of the reaction mixture (error ±5%). bTentatively identified in the NMR spectra of the mixture. 1290


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Information) also indicated the presence of the anions H2F3−, HF2−, and SiF62−, the latter probably being produced by F− attack on the NMR tube glass (see below).53−55 Reactions of 3a′ with AgOTf and XyNC or CO. The reaction of 3a′ with AgOTf and XyNC gave the cationic derivative [Rh(η5-Cp*){CH2CH2CF(CF3)2}(PPh3)(CNXy)]OTf (6) (Scheme 6). In contrast, the analogous reaction of Scheme 6

Figure 4. Molecular structure of 4g (50% thermal ellipsoids). Selected bond lengths (Å) and angles (deg): Rh(1)−CNT (CNT = centroid of C1−5) 1.8872(8), Rh(1)−P(1) 2.2967(5), Rh(1)−I(1) 2.68611(19), Rh(1)−C(11) 2.0716(19), P(1)−Rh(1)−I(1) 88.673(13), C(11)− Rh(1)−I(1) 89.71(5), C(11)−Rh(1)−P(1) 92.48(5), F(1)−C(11)− Rh(1) 108.80(11), F(2)−C(11)−Rh(1) 116.91(12), F(2)−C(11)− F(1) 103.06(14).

3c (Rh−I: 2.6989(4) Å) is slightly shorter than the bridging Rh−I bonds of 1a and 1b (Rh−I: 2.6987(4)−2.7198(4) Å). The Rh−CNT (CNT = centroid of the η5-Cp* ring) distance is longer in 3c (1.8789(16) Å) and 4g (1.8872(8) Å) than in 1a (1.8250(19) and 1.8300(18) Å) or 1b (1.820(3) Å), suggesting that the steric repulsions between the η5-Cp* and PMe3 ligands could be responsible for these differences. The Rh−CNT, Rh−P, and Rh−C bond distances of 4g are not significantly different from the values reported for [Rh(η5-Cp*)Cl(nC3F7)(PMe3)].52 The reaction of [Rh(η5-Cp*)(η2-C2H4)(PR3)] with ICF(CF3)CF2CF3 (Scheme 5) deserves special consideration, since Scheme 5

3a′ with CO led to complex [Rh(η5-Cp*){CH2CH2CF(CF3)2}(PPh3)(CO)]OTf (7), which resulted from insertion of a molecule of CO into the Rh−CH2 bond and coordination of another CO molecule to the metal. Compounds 6 and 7 gave the expected signals in their NMR spectra. The IR spectrum of the isonitrile complex 6 showed a band at 2133 cm−1 corresponding to the ν(CN) mode. The IR spectra of the carbonyl complex 7 displayed a band at 2043 cm−1 corresponding to the ν(CO) mode and another at 1682 cm−1 corresponding to the ν(CO) mode. The crystal structure of 7 was determined by single-crystal X-ray diffraction (Figure 5). The Rh−Ccarbonyl and CO

no oxidative addition product and only traces of the ethene perfluoroalkylation product were detected in the NMR spectra of the reaction mixture (C6D6). Instead, the main reaction products were cis-octafluoro-2-butene, trans-octafluoro-2butene, [Rh(η5-Cp*)I2(PMe3)], and a crystalline red precipitate. The ESI-MS spectrum of this precipitate indicated that it was a salt of the cation [Rh(η5 -Cp*)I(PMe 3) 2]+, which was confirmed by comparing its 1H and 31P{1H} NMR spectra with those of the reported [Rh(η5-Cp*)I(PMe3)2]PF6.37 In addition, the 1H and 19F NMR spectra of the salt (see Experimental Section and Figure S1 of the Supporting

Figure 5. Molecular structure of 7 (50% thermal ellipsoids). Selected bond lengths (Å) and angles (deg): Rh(1)−CNT (CNT = centroid of C1−5) 1.9096(13), Rh(1)−C(11) 1.898(3), Rh(1)−C(12) 2.083(3), Rh(1)−P(1) 2.3380(7), C(11)−O(1) 1.130(4), C(12)−O(2) 1.200(4), C(11)−Rh(1)−C(12) 95.00(12), C(11)−Rh(1)−P(1) 91.99(9), C(12)−Rh(1)−P(1) 87.15(8). 1291


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distances (1.898(3) and 1.130(4) Å) fall in the range of values found for Rh(III) carbonyl complexes containing the η5-Cp* ligand (1.800−2.041 and 1.040−1.149 Å, respectively).56 The Rh−Cacyl distance (2.083(3) Å) is slightly longer than those observed in other Rh(III) acyl complexes containing the η5-Cp* ligand (2.010−2.071 Å). Mechanistic Studies. It is interesting to trace a parallelism between the reactions observed and the reaction of [Rh(η5-Cp*)(η2-C2H4)(PMe3)] with MeI, which led to [Rh(η5-Cp*)(η2-C2H4)(Me)(PMe3)]I through nucleophilic attack of the metal center at the positively charged carbon atom.37 Substitution of the coordinated ethene by iodide finally gives [Rh(η5-Cp*)I(Me)(PMe3)]. The iodine-bound carbon of a perfluoroalkyl iodide also bears a high positive charge, but it is sterically and electrostatically shielded from nucleophilic attack by the negatively charged fluorine substituents, especially in secondary and tertiary perfluoroalkyl iodides.57,58 In addition, the electron-withdrawing character of the perfluoroalkyl group makes the iodine atom electrophilic, allowing nucleophilic attack and subsequent release of a perfluoroalkyl anion.57−60 Such anions have been trapped by Hughes and co-workers in the reactions of Rh(I),29 Mo(II),42,43 W(II),42,43 or Pt(II)61 complexes with perfluoroalkyl iodides. In a benchmark study,42 the same authors reported that the ethene complexes [M(η5-Cp)2(η2-C2H4)] (M = Mo or W) react with IC(CF3)3 to give [M(η5-Cp)2I{CH2CH2C(CF3)3}] via nucleophilic attack of the metal at the iodine, followed by addition of the generated C(CF3)3− anion to the coordinated ethene.42,43 Alternatively, the possibility of a radical mechanism should be considered, since perfluoroalkyl iodides are able to react with electron donors by single electron transfer to give I− and an RF· radical.11,62 Considering these precedents, we attempted to find experimental evidence for the intermediacy of RF· radicals or RF− anions in the ethene perfluoroalkylation reactions. As D8-toluene is expected to react with free RF· radicals to give a D7-benzyl radical and DRF,61 some representative reactions were conducted in this solvent. However, no DRF was detected by NMR spectroscopy in any experiment. As perfluoroalkyl radicals easily add to olefins,11,63,64 the reactions between [Rh(η5-Cp*)(η2-C2H4)(PMe3)] and ICF(CF3)2 were performed in the presence of a 4-fold excess of norbornene. However, the outcome of the reaction was not appreciably altered, and no significant amounts of norbornene perfluoroalkylation products were detected. In addition, the reactions of [Rh(η5-Cp*)(η2-C2H4)(PMe3)] or [Rh(η5-Cp*)(η2-C2H4)2] with ICF(CF3)2 were carried out in the presence of the radical trap (2,2,6,6-tetramethylpiperidin1-yl)oxyl (TEMPO), using C6D6 as solvent. While in the first case the result of the reaction was essentially the same as in the absence of the radical trap, in the second case most of the starting materials remained unreacted after 16 h. As no radicaltrapping products were detected, the reaction inhibition is tentatively attributed to competitive formation of a halogenbonded adduct between TEMPO and the perfluoroalkyl iodide.60 The formation of this adduct did not compete effectively with the rapid reaction between complex [Rh(η5-Cp*)(η2-C2H4)(PMe3)] and ICF(CF3)2. We also attempted to trap radical or carbanionic intermediates by carrying out the reactions in the presence of CH3OD as previously reported.29,42,61,65 In these experiments, RF· radicals should preferentially cleave the weaker C−H bond66 to give HRF, whereas RF− anions should abstract a D+ cation to give DRF. Thus, the reactions of [Rh(η5-Cp*)(η2-C2H4)(PMe3)] with ICF(CF3)2 (in D8-toluene), IC(CF3)3

(in D8-toluene), or IC6F5 (in C6D6) were dramatically affected by the presence of CH3OD (1.5−2.5 equiv). Under these conditions, the formation of complex 3a, 3c, or 3d was inhibited or severely reduced, DRF being the main fluoroorganic product. Moreover, significant amounts of DC(CF3)3 or DC6F5 were detected when the reactions between [Rh(η5-Cp*)(η2-C2H4)(PMe3)] and IC(CF3)3 or IC6F5 were run in C6D6 saturated with D2O. Minor amounts of HRF were also detected in all these experiments, even in the absence of CH3OD, which might be attributed to carbanion protonation by residual water or to the contribution of a minor reaction pathway involving perfluoroalkyl radicals.67 The reactions of [Rh(η 5-Cp*)(η2-C2H4)2] with ICF(CF3)2 or ICF(CF3)CF2CF3 in C6D6 were not significantly affected when they were carried out in the presence of CH3OD or in D2O-saturated solvent. In contrast, the analogous reactions involving IC(CF3)3 gave considerable amounts of DC(CF3)3. Evidence for both radical and anions was obtained in the reaction of [Rh(η5-Cp*)(η2-C2H4)(PMe3)] with InC4F9 in C6D6. Thus, the formation of the oxidative addition product 4g was partially inhibited by carrying out the reaction in the presence of norbornene or TEMPO (2 equiv), and significant amounts of DnC4F9 were observed by carrying it out in the presence of CH3OD (2.5 equiv). This suggests that, in this case, both ionic and radical pathways should contribute significantly to the overall reaction mechanism. Finally, the detection of cis- and trans-octafluoro-2-butene in the reaction of [Rh(η5-Cp*)(η2-C2H4)(PMe3)] with ICF(CF3)CF2CF3 is evidence for the generation of the CF3CF2(CF3)CF− anion, which decomposes by elimination of F− to give the alkenes. The released fluoride anion could trap a proton from residual moisture or react with glass to form the HnFn+1− and SiF62− anions of the isolated salt. No perfluoroalkenes were detected in other reaction mixtures examined by 19F NMR spectroscopy. On the basis of these results, we propose (Scheme 7) that ethene perfluoro(alkylation or arylation) could occur by Scheme 7

nucleophilic attack of the metal on the iodine atom to generate the ionic intermediate A, which could undergo addition of the RF− anion on the coordinated ethene to give complexes 3. When L = C2H4, dinuclear species 1 could be formed by loss of ethene and dimerization, although evidence for the formation of RF− anions was found only in the case of 1c. Compounds [Rh(η5-Cp*)I2(PR3)] and other unidentified byproducts observed in the reactions of [Rh(η5-Cp*)(η2-C2H4)(PMe3)] with IRF could result from the evolution of intermediate A after the dissociation of the ion pair and the destruction of the 1292


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perfluoroalkyl anion by decomposition or by reaction with another molecule. In particular, protonation by residual water would give HRF, which was observed in the reactions leading to 4g or 4h. A similar process could explain the formation of HC(CF3)3 and 2c in the reaction of [Rh(η5-Cp*)(η2-C2H4)2] with IC(CF3)3. Finally, we tried to prepare a salt containing the cation of intermediate A by reaction of [Rh(η5-Cp*)(η2-C2H4)(PMe3)] with the iodinating agent [I(py)2]BF4. However, substitution of ethene by pyridine (py) took place in addition to iodination, to give [Rh(η5-Cp*)I(py)(PMe3)]BF4 (8), which was also obtained by reaction of [Rh(η5-Cp*)I2(PMe3)] with AgBF4 and pyridine. The crystal structure of 8 was determined by single-crystal X-ray diffraction (Figure 6).

EXPERIMENTAL SECTION

General Considerations. Complexes [Rh(η5-Cp*)(η2-C2H4)2]34 and [Rh(η5-Cp)(η2-C2H4)(PMe3)]35 were prepared as previously reported. Solutions of complexes [Rh(η5-Cp*)(η2-C2H4)(PR3)] (R = Me,37 Ph68) were prepared by heating a solution of [Rh(η5-Cp*)(η2-C2H4)2] and PMe3 or PPh3 at 120 °C in a Carius tube for 24 or 3.5 h, respectively. Other reagents were obtained from commercial sources and used without further purification: PMe3 (1 M solution in toluene), IC6F5, InC4F9, InC3F7, ICF2C6F5, [I(py)2]BF4 (Aldrich), ICF(CF3)2 (Acros Organics), ICFCF2 (ABCR). The reactions were carried out under an N2 atmosphere using standard Schlenk techniques. Test reactions were performed in screw-cap NMR tubes equipped with a PTFE-covered rubber septum. Toluene and n-pentane were degassed and dried using a Pure Solv MD-5 solvent purification system from Innovative Technology, Inc. D8-Toluene was deoxygenated by four freeze−pump−thaw cycles, and C6D6 was distilled over CaH2. Both solvents were stored under nitrogen over 4 Å molecular sieves. Infrared spectra were recorded in the range 4000−200 cm−1 on a Perkin-Elmer 16F PC FT-IR spectrometer with Nujol mulls between polyethylene sheets. C, H, N, S analyses were carried out with Carlo Erba 1108 and LECO CHS-932 microanalyzers. NMR spectra were measured on Bruker Avance 200, 300, and 400 instruments. 1H chemical shifts were referenced to residual C6D5H (7.15 ppm), C6D5CD2H (2.09 ppm), CHDCl2 (5.29 ppm), or CHCl3 (7.26 ppm). 13 C{1H} spectra were referenced to C6D6 (128.0 ppm), CDCl3 (77.0 ppm), or CD2Cl2 (53.8 ppm). 19F or 31P{1H} NMR spectra were referenced to external CFCl3 or H3PO4 (0 ppm). The temperature values in NMR experiments were not corrected. ESI-MS and HR-MS spectra were measured on Agilent 5973 and 6620 spectrometers, respectively. A solution of NH4(HCO2) (5 mM) and HCO2H (1%) in MeOH/H2O (75:25) was used as mobile phase unless otherwise stated. Melting points were determined on a Reichert apparatus in an air atmosphere. [Rh(η5-Cp*){CH2CH2CF(CF3)2}(μ-I)]2 (1a) and [(η5-Cp*)IRh(μ-I)2Rh(η5-Cp*){CH2CH2CF(CF3)2}] (2a). ICF(CF3)2 (100 μL, 0.70 mmol) was added to a solution of [Rh(η5-Cp*)(η2-C2H4)2] (186 mg, 0.63 mmol) in n-pentane (3 mL). After stirring for 18 h at room temperature a red, microcrystalline solid precipitated, which was filtered, washed with n-pentane (2 mL), and dried under vacuum (270 mg, 76%). Mp: 258−261 °C (dec). The isolated product contained 10% of [(η5-Cp*)IRh(μ-I)2Rh(η5-Cp*){CH2CH2CF(CF3)2}] as determined by integration of the 1H NMR spectrum. Anal. Calcd for (C30H38F14I2Rh2)0.9(C25H34F7I3Rh2)0.1: C, 31.72; H, 3.39. Found: C, 31.68; H, 3.66. 1a: 1H NMR (300.1 MHz, CDCl3): δ 2.85−2.58 (m, 8 H, CH2), 1.67 (s, 30 H, C5Me5); (300.1 MHz, C6D6) δ 3.15−2.90 (m, 8 H, CH2), 1.37 (s, 30 H, C5Me5). 13C{1H} NMR (75.5 MHz, CD2Cl2): δ 122.0 (dq, 1 JCF = 288.6 Hz, 2JCF = 28.7 Hz, CF3), 95.2 (d, 1JRhC = 6.6 Hz, C5Me5), 38.1 (d, 2JFC = 20.8 Hz, CH2CF), 9.5 (s, C5Me5), 5.9 (d, 1JRhC = 24.9 Hz, RhCH2). The signal corresponding to the CF carbon was not observed. 19 F NMR (282.4 MHz, C6D6): δ −74.6 (d, 3JFF = 7.6 Hz, 6 F, CF3), −181.7 (m, 1 F, CF). X-ray quality single crystals were obtained as deuterobenzene monosolvate by slow evaporation of a C6D6 solution. 2a: 1H NMR (300.1 MHz, C6D6): δ 3.03−2.88 (m, 4 H, CH2), 1.53 (s, 15 H, C5Me5), 1.46 (s, 15 H, C5Me5). 19F NMR (282.4 MHz, C6D6): δ −74.5 (d, 3JFF = 7.5 Hz, 6 F, CF3), −180.2 (m, 1 F, CF). [Rh(η5-Cp*){CH2CH2CF(CF3)CF2CF3}(μ-I)]2 (1b) and [(η5-Cp*)IRh(μ-I)2Rh(η5-Cp*){CH2CH2CF(CF3)CF2CF3}] (2b). These were prepared in the same way as 1a + 2a, starting from [Rh(η5-Cp*)(η2-C2H4)2] (48 mg, 0.16 mmol) and ICF(CF3)CF2CF3 (28 μL, 0.16 mmol) in n-pentane (3 mL). After stirring for 18 h, the reaction mixture was stored at 4 °C for 3 days to give a red, crystalline solid. The mother liquor was removed with a pipet in a ice−water bath, and the solid was washed with cold (0 °C) n-pentane (3 × 1.5 mL) and dried under vacuum (68 mg, 68%). Mp: 140 °C (dec). The isolated product contained 10% of [(η 5 -Cp*)IRh(μ-I) 2 Rh(η 5 -Cp*){CH2CH2CF(CF3)CF2CF3}] as determined by integration of the 1H NMR spectrum. Anal. Calcd for (C32H38F18I2Rh2)0.9(C26H34F9I3Rh2)0.1: C, 31.11; H, 3.13. Found: C, 31.06; H, 3.08. 1b: 1H NMR (400.9 MHz, C6D6): δ 3.19−2.93 (m, 8 H, CH2), 1.39 (s, 30 H, C5Me5). 13C{1H}

Figure 6. Molecular structure (30% thermal ellipsoids) of the cation of the salt [Rh(η5-Cp*)I(C6H5N)(PMe3)]BF4 (8). Selected bond lengths (Å) and angles (deg): Rh−CNT (CNT = centroid of C1− 5) 1.825, Rh−N(11) 2.1271(19), Rh−P 2.3160(7), Rh−I 2.6989(2), N(11)−Rh−I 91.80(5), P−Rh−I 87.64(2), N(11)−Rh−P 90.66(6).

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Article

CONCLUDING REMARKS

Selective ethene perfluoroalkylation takes place in the reaction of [Rh(η5-Cp*)(η 2-C 2H4 )2 ] with secondary or tertiary perfluoroalkyl iodides. In contrast, the course of the reactions of [Rh(η5-Cp*)(η2-C2H4)(PMe3)] with perfluorinated iodides depends on the fluoroorganic iodide used. Thus, ICF(CF3)2, IC(CF3)3, and IC6F5 selectively attack at the ethene, while the reactions with primary perfluoroalkyl iodides and ICF2C6F5 are less selective and proceed preferentially through oxidative addition. Attack at the ethene also prevails in the reaction of [Rh(η5-Cp*)(η2-C2H4)(PPh3)] with ICF(CF3)2 or ICF2C6F5. Evidence for the intermediacy of RF− anions in the ethene perfluoroalkylation or perfluoroarylation reactions points to a mechanism where a cationic Rh(III) intermediate is formed by the nucleophilic attack of the metal center at the iodine atom of the perfluororganic iodide. The reported reactions are rare examples of perfluoroalkylation or perfluoroarylation of a coordinated alkene and represent a first step toward nonradical rhodium-catalyzed perfluoroalkylation of olefins avoiding the formation of perfluoroalkyl metal intermediates. Studies aimed at the development of a rhodiummediated or -catalyzed olefin perfluoroalkylation reaction are in progress. 1293


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Article

NMR (100.8 MHz, CD2Cl2): δ 126.6−109.3 (several m, CFn), 95.2 (d, 1JRhC = 6.5 Hz, C5Me5), 38.6 (d, 2JFC = 21.6 Hz, RhCH2CH2), 9.5 (s, C5Me5), 6.2 (d, 1JRhC = 24.6 Hz, RhCH2). 19F NMR (188.3 MHz, C6D6): δ −72.1 (br s, 3 F, CFCF3), −79.7 (dq, 4JFF = 5JFF = 5.1 Hz, 3 F, CF2CF3), −120.6 (m, 2 F, CF2), −180.9 (br m, 1 F, CF). (+)ESIMS: m/z 731 ([Rh2(C5Me5)2I2H]+), 857 ([Rh2(C5Me5)2I3]+), 977 ([Rh2(C5Me5)2I2(CH2CH2C4F9)]+). X-ray quality single crystals were obtained from an n-hexane solution at 4 °C. 2b: 1H NMR (400.9 MHz, C6D6): δ 3.08−2.91 (m, 4 H, CH2), 1.53 (s, 15 H, C5Me5), 1.48 (s, 15 H, C5Me5). 19F NMR (188.3 MHz, C6D6): δ −72.3 (br s, 3 F, CFCF3), −79.7 (m, 3 F, CF2CF3), −120.5 (m, 2 F, CF2), −180.1 (br m, 1 F, CF). [Rh(η5-Cp*){CH2CH2C(CF3)3}(μ-I)]2 (1c) and [(η5-Cp*)IRh(μ-I)2Rh(η5-Cp*){CH2CH2C(CF3)3}] (2c). These were prepared in the same way as 1a + 2a, starting from [Rh(η5-Cp*)(η2-C2H4)2] (111 mg, 0.38 mmol) and IC(CF3)3 (185, mg, 0.53 mmol) in n-pentane (4 mL). The reaction mixture was evaporated to dryness to give a dark red residue containing 1c, a similar number of equivalents of 2c, and several unidentified minor products (the integration of the 1H NMR spectrum was not accurate because of signal overlap). Attempts to isolate 1c by crystallization or column chromatography led to mixtures containing both products. 1c: 1H NMR (200.1 MHz, C6D6): δ 3.25 (m, 4 H, CH2), 2.97 (m, 4 H, CH2), 1.38 (s, 30 H, C5Me5). 19F NMR (188.3 MHz, C6D6): δ −64.5 (s). 2c: 1H NMR (200.1 MHz, C6D6): δ 3.16− 2.90 (m, 4 H, CH2), 1.52 (s, 15 H, C5Me5), 1.49 (s, 15 H, C5Me5). 19F NMR (188.3 MHz, C6D6): δ −64.7 (s). [Rh(η5-Cp*){CH2CH2CF(CF3)2}I(PMe3)] (3a). Method A. A mixture of [Rh(η5-Cp*)(η2-C2H4)2] (147 mg, 0.50 mmol) and PMe3 (0.60 mmol) was heated in toluene (5 mL) at 120 °C for 24 h in a Carius tube. The resulting solution of [Rh(η5-Cp*)(η2-C2H4)(PMe3)] was cooled at room temperature, and then ICF(CF3)2 (74 μL, 0.50 mmol) was added. A color change from yellow to dark red took place immediately. After stirring for 40 min, the volatiles were removed under vacuum. The residue was extracted with Et2O (15 mL), and the extract was chromatographed on a silica gel column using CH2Cl2 as eluent. The collected fraction (Rf = 0.8) was evaporated to dryness to give an orange, crystalline solid (151 mg, 47%). Method B. ICF(CF3)2 (100 μL, 0.70 mmol) was added to a solution of [Rh(η5-Cp*)(η2-C2H4)2] (200 mg, 0.68 mmol) in npentane (5 mL), and the mixture was stirred for 15 h. The dark red suspension was evaporated to dryness under vacuum, and the residue was dissolved in THF (5 mL). PMe3 (0.74 mmol) was added to the solution, and the mixture was stirred for 3 h. Then, the volatiles were removed under vacuum, and the resulting residue was purified by chromatography as mentioned above (215 mg, 50%). Mp: 91−93 °C. Anal. Calcd for C18H28F7IPRh: C, 33.88; H, 4.42. Found: C, 34.02; H, 4.74. 1H NMR (400.9 MHz, C6D6): δ 3.03 (m, 1 H, Rh−CH2−CH2), 2.26 (m, 1 H, Rh−CH2−CH2), 1.70 (m, 1 H, Rh−CH2−CH2), 1.50 (m, 1 H, Rh−CH2−CH2), 1.46 (d, 4JPH = 2.9 Hz, 15 H, C5Me5), 1.15 (dd, 2JPH = 9.8 Hz, 3JRhH = 0.6 Hz, 9 H, PMe3). 13C{1H} NMR (100.8 MHz, C6D6): δ 122.2 (dq, 1JCF = 287.0 Hz, 2JCF = 29.0 Hz, CF3), 98.2 (dd, 1JRhC = 5.0 Hz, 2JPC = 3.5 Hz, C5Me5), 38.1 (dd, 2JFC = 20.7 Hz, 3 JPC = 4.8 Hz, CH2CF), 17.1 (d, 1JPC = 32.3 Hz, PMe3), 9.7 (s, C5Me5), −0.6 (dd, 1JRhC = 26.0 Hz, 2JPC = 14.9 Hz, Rh−CH2−CH2). The signal corresponding to the CF carbon was not observed. 19F NMR (188.3 MHz, C6D6): δ −74.7 (dq, 3JFF = 4JFF = 8.3 Hz, 3 F, CF3), −75.4 (dq, 3 JFF = 4JFF = 8.3 Hz, 3 F, CF3), −182.0 (m, 1 F, CF). 31P{1H} NMR (162.3 MHz, C6D6): δ 2.8 (d, 1JRhP = 156.4 Hz). [Rh(η5-Cp*){CH2CH2CF(CF3)2}I(PPh3)] (3a′). Method A. [Rh(η5-Cp*)(η2-C2H4)(PPh3)] was generated in situ by heating a solution of [Rh(η5-Cp*)(η2-C2H4)2] (151 mg, 0.51 mmol) and PPh3 (162 mg, 0.62 mmol) in toluene (5 mL) at 120 °C for 3.5 h in a Carius tube. After cooling to room temperature, ICF(CF3)2 (80 μL, 0.55 mmol) was added to the resulting yellow solution, which changed color to dark red. After stirring for 40 min, the volatiles were removed under vacuum. The residue was extracted with Et2O, and the extract was chromatographed on a silica gel column using Et2O/n-hexane (1:1) as eluent. The collected orange fraction (Rf = 0.6) was evaporated to dryness to give an orange, crystalline solid (205 mg, 49%).

Method B. A solution of 1a + 2a (101 mg, 0.086 mmol of 1a) and PPh3 (52 mg, 0.20 mmol) in THF (5 mL) was stirred for 5 h. The volatiles were removed under vacuum, and the resulting residue was purified by column chromatography (see above) to give an orange, crystalline solid (122 mg, 86%). Mp: 145−148 °C. Anal. Calcd for C33H34F7IPRh: C, 48.08; H, 4.16. Found: C, 48.18; H, 4.24. 1H NMR (400.9 MHz, C6D6): δ 7.72 (br m, 6 H, H2 of Ph), 6.99 (m, 9 H, H3 and H4 of Ph), 3.52 (m, 1 H, Rh−CH2−CH2), 2.38 (m, 1 H, Rh− CH2−CH2), 2.08 (m, 1 H, Rh−CH2−CH2), 1.92 (m, 1 H, Rh−CH2− CH2), 1.32 (d, 4JPH = 2.8 Hz, 15 H, C5Me5). 13C{1H} NMR (75.5 MHz, CDCl3, 50 °C): δ 134.9 (br s, C2 of Ph), 133.0 (d, 1JPC = 44.2 Hz, C1 of Ph), 130.1 (s, C4 of Ph), 127.9 (d, 3JPC = 9.9 Hz, C3 of Ph), 121.5 (dq, 1 JCF = 286.1 Hz, 2JCF = 28.6 Hz, CF3), 99.8 (dd, 1JRhC = 4.6 Hz, 2JPC = 3.3 Hz, C5Me5), 38.8 (d, 2JFC = 20.4 Hz, Rh−CH2−CH2), 9.3 (s, C5Me5), 1.6 (dd, 1JRhC = 25.0 Hz, 2JPC = 13.4 Hz, Rh−CH2−CH2). At room temperature the aromatic region of the spectrum is more complex because of slow rotation of the phosphine ligand on the NMR time scale.69 The signal corresponding to the CF carbon was not observed. 19 F NMR (188.3 MHz, C6D6): δ −74.1 (dq, 3JFF = 4JFF = 8.5 Hz, 3 F, CF3), −76.1 (dq, 3JFF = 4JFF = 8.5 Hz, 3 F, CF3), −182.4 (m, 1 F, CF). 31 1 P{ H} NMR (81.0 MHz, C6D6): δ 41.6 (d, 1JRhP = 161.2 Hz). [Rh(η5-Cp*){CH2CH2CF(CF3)2}I(PiPr3)] (3a″). PiPr3 (35 μL, 0.18 mmol) was added to a solution of 1a + 2a (85 mg, 0.072 mmol of 1a) in CH2Cl2 (5 mL). The resulting solution was stirred for 13 h at room temperature and evaporated to dryness. The residue was extracted with n-pentane (15 mL), and the extract was filtered through Celite, concentrated to ca. 2 mL, and stored at −32 °C for 4 h to give orange crystals, which were washed with cold n-pentane (−30 °C, 3 × 1 mL) and dried under vacuum (80 mg, 77%). Mp: 95−97 °C. Anal. Calcd for C24H40F7IPRh: C, 39.91; H, 5.58. Found: C, 39.70; H, 5.60. 1H NMR (300.1 MHz, C6D6): δ 3.65 (m, 1 H, Rh−CH2−CH2), 2.35− 2.18 (m, 4 H, Rh−CH2−CH2 + PCH), 2.08 (m, 1 H, Rh−CH2− CH2), 1.54−1.42 (m, 1 H, Rh−CH2−CH2), 1.46 (d, 4JPH = 2.3 Hz, 15 H, C5Me5), 1.12 (dd, 2JPH = 12.8 Hz, 3JHH = 7.3 Hz, 3 H, CHMe), 1.04 (dd, 2JPH = 12.6 Hz, 3JHH = 7.2 Hz, 3 H, CHMe). 13C{1H} NMR (100.8 MHz, C6D6): δ 122.2 (dq, 1JCF = 283.2 Hz, 2JCF = 29.7 Hz, CF3), 99.8 (dd, 1JRhC = 4.4 Hz, 2JPC = 2.8 Hz, C5Me5), 39.5 (d, 2JFC = 20.5 Hz, Rh−CH2−CH2), 27.9 (d, 1JPC = 18.7 Hz, PCH), 21.0 (br s, CHMe), 20.5 (d, 2JPC = 1.1 Hz, CHMe), 10.2 (s, C5Me5), −5.0 (dd, 1 JRhC = 26.4 Hz, 2JPC = 14.7 Hz, Rh−CH2−CH2). The signal corresponding to the CF carbon was not observed. 19F NMR (188.3 MHz, C6D6): δ −73.9 (dq, 3JFF = 4JFF = 8.5 Hz, 3 F, CF3), −76.0 (dq, 3JFF = 4 JFF = 8.9 Hz, 3 F, CF3), −182.8 (m, 1 F, CF). 31P{1H} NMR (81.0 MHz, C6D6): δ 42.9 (d, 1JRhP = 153.0 Hz). [Rh(η5-Cp*){CH2CH2CF(CF3)CF2CF3}I(PMe3)] (3b). A solution of [Rh(η5-Cp*)(η2-C2H4)2] (70 mg, 0.24 mmol) in n-pentane (4 mL) was treated with ICF(CF3)CF2CF3 (40 μL, 0.24 mmol) at room temperature. After stirring for 20 h at room temperature, PMe3 (0.24 mmol) was added. The solution was stirred at room temperature for 2 h and evaporated to dryness under vacuum. The residue was extracted with n-pentane (15 mL). The extract was filtered, concentrated under vacuum to ca. 2 mL, and stored at −32 °C for 24 h to give orange crystals, which were washed with cold n-pentane (3 × 1 mL) and dried under vacuum (87 mg, 53%). Mp: 100−102 °C. Anal. Calcd for C19H28F9IPRh: C, 33.16; H, 4.10. Found: C, 33.19; H, 3.97. 1H NMR (300.1 MHz, CDCl3): δ 2.59 (m, 1 H, Rh−CH2−CH2), 2.08 (m, 1 H, Rh−CH2−CH2), 1.78 (d, 4JPH = 2.8 Hz, 15 H, C5Me5), 1.57 (m, 1 H, Rh−CH2−CH2), 1.54 (d, 2JPH = 9.8 Hz, 9 H, PMe3), 1.33 (m, 1 H, Rh−CH2−CH2); (300.1 MHz, C6D6) δ 3.10 (m, 1 H, Rh−CH2− CH2), 2.30 (m, 1 H, Rh−CH2−CH2), 1.73 (m, 1 H, Rh−CH2−CH2), 1.50 (m, 1 H, Rh−CH2−CH2), 1.44 (d, 4JPH = 2.9 Hz, 15 H, C5Me5), 1.114 (dd, 2JPH = 9.8 Hz, 3JRhH = 0.7 Hz, 9 H, PMe3), 1.111 (dd, 2JPH = 9.8 Hz, 3JRhH = 0.7 Hz, 9 H, PMe3). 13C{1H} NMR (75.5 MHz, CDCl3): δ 127.5−108.1 (several m, CFn), 98.6 (dd, 1JRhC = 3.2 Hz, 2 JPC = 1.5 Hz, C5Me5), 98.5 (dd, 1JRhC = 3.2 Hz, 2JPC = 1.5 Hz, C5Me5), 37.7 (d, 2JFC = 24.0 Hz, Rh−CH2−CH2), 37.4 (d, 2JFC = 25.0 Hz, Rh− CH2−CH2), 17.5 (dd, 1JPC = 32.4 Hz, 2JRhC = 0.7 Hz, PMe3), 17.4 (dd, 1 JPC = 32.5 Hz, 2JRhC = 0.6 Hz, PMe3), 10.01 (s, C5Me5), 10.00 (s, C5Me5), 0.2 (dd, 1JRhC = 25.6 Hz, 2JPC = 14.7 Hz, Rh−CH2−CH2). 1294


Organometallics

Article

F NMR (282.4 MHz, C6D6): δ −72.0 (s, 3 F, CF3CF, isomer A), −72.7 (s, 3 F, CF3CF, isomer B), −79.5 (s, 3 F, CF3CF2, isomer A), −79.7 (s, 3 F, CF3CF2, isomer B), −120.2 (AB doublet of multiplets, 2 JFF = 292.6 Hz, 1 F, CF2, isomer A), −120.3 (m, 2 F, CF2, isomer B), −121.5 (AB doublet of multiplets, 2JFF = 293.7 Hz, 1 F, CF2, isomer A), −180.8 (m, 1 F, CF, isomer A), −181.3 (m, 1 F, CF, isomer B). 31 1 P{ H} NMR (162.3 MHz, C6D6): δ 2.4 (d, 1JRhP = 156.8 Hz), 2.2 (d, 1 JRhP = 156.8 Hz). (+)ESI-MS: m/z 347, 441 ([Rh(η5-Cp*)I(PMe3)]+), 533, 711 ([M + Na]+); exact mass calcd for C19H28F9INaPRh 710.9777, found 710.9778, Δ = 0.14 ppm. [Rh(η5-Cp*){CH2CH2CF(CF3)CF2CF3}I(PPh3)] (3b′). PPh3 (19 mg, 0.072 mmol) was added to a solution of 1b + 2b (43 mg, 0.034 mmol of 1b) in CH2Cl2 (5 mL). The mixture was stirred for 20 h and evaporated to dryness under vacuum. The residue was extracted with n-pentane (5 mL). The extract was filtered, concentrated to ca. 1 mL, and stored at −32 °C for 24 h. The orange-red crystals that formed were separated from the mother liquor and washed twice with 1 mL portions of cold n-pentane (46 mg, 77%). Mp: 131−133 °C. Anal. Calcd for C34H34F9IPRh: C, 46.70; H, 3.92. Found: C, 46.62; H, 3.44. 1 H NMR (300.1 MHz, C6D6): δ 7.73 (br m, 6 H, Ph), 7.00 (br m, 9 H, Ph), 3.56 (m, 1 H, Rh−CH2−CH2), 2.44 (m, 1 H, Rh−CH2−CH2), 2.16−1.87 (m, 2 H, Rh−CH2−CH2), 1.33 (s, 15 H, C5Me5), 1.32 (d, 15 H, C5Me5); (400.9 MHz, CDCl3) δ 7.65−7.34 (br m, 15 H, Ph), 2.94 (m, 1 H, Rh−CH2−CH2), 2.07 (m, 1 H, Rh−CH2−CH2), 1.76− 1.65 (m, 2 H, Rh−CH2−CH2), 1.51 (d, 4JPH = 2.8 Hz, 15 H, C5Me5), 1.49 (d, 4JPH = 2.8 Hz, 15 H, C5Me5). 13C{1H} NMR (100.8 MHz, C6D6): δ 137.5−132.5 (several br m, Ph), 130.1 (s, Ph), 127.9 (d, JPC = 9.4 Hz, Ph), 126−108 (several overlapping m, CFn), 99.7 (m, C5Me5), 95.5−92.4 (m, CFn), 39.5 (d, 2JFC = 20.9 Hz, Rh−CH2− CH2), 39.0 (d, 2JFC = 21.2 Hz, Rh−CH2−CH2), 9.4 (s, C5Me5), 9.3 (s, C5Me5), 2.5 (dd, 1JRhC = 24.9 Hz, 2JPC = 13.0 Hz, Rh−CH2−CH2), 2.4 (dd, 1JRhC = 24.6 Hz, 2JPC = 13.0 Hz, Rh−CH2−CH2). 19F NMR (188.3 MHz, C6D6): δ −72.5 (m, 3 F, CFCF3, isomer A), −74.4 (m, 3 F, CFCF3, isomer B), −80.1 (dq, 5JFF = 4.6 Hz, 4JFF = 9.0 Hz, 3 F, CF2CF3, isomer A), −80.8 (dq, 5JFF = 5.8 Hz, 4JFF = 10.3 Hz, 3 F, CF2CF3, isomer B), −120.3 (dq, 3JFF = 6.7 Hz, 4JFF = 9.2 Hz, 2 F, CF2, isomer B), −121.4 (dqd, 1JFF = 292.2 Hz, 3JFF = 6.9 Hz, 4JFF = 11.5 Hz, 1 F, CF2, isomer A), −123.2 (dqd, 1JFF = 292.1 Hz, 3JFF = 6.2 Hz, 4 JFF = 9.2 Hz, 1 F, CF2, isomer A), −182.0 (m, 1 F, CF, isomers A and B). 31P{1H} NMR (162.3 MHz, CDCl3): δ 40.5 (d, 1JRhP = 161.8 Hz), 40.0 (d, 1JRhP = 162.1 Hz). (+)ESI-MS: m/z 499 ([Rh(C5Me4CH2)(PPh3)]+), 557, 627 ([Rh(η5-Cp*)I(PPh3)]+), 897 ([M + Na]+), 995 ([Rh 2 (η 5 -Cp*) 2 I 2 (C 2 H 4 C 4 F 9 )(H 2 O)] + ); exact mass calcd for C34H34F9INaPRh 897.0246, found 897.0253, Δ = 0.8 ppm. [Rh(η5-Cp*){CH2CH2C(CF3)3}I(PMe3)] (3c). Method A. This was prepared in the same way as 3a starting from [Rh(η5-Cp*)(η2-C2H4)2] (122 mg, 0.41 mmol), PMe3 (0.45 mmol), and IC(CF3)3 (150 mg, 0.43 mmol). The volatiles were removed under vacuum, and the residue was extracted with n-pentane (25 mL). Evaporation of the solvent gave an orange solid (230 mg, 80%). Method B. IC(CF3)3 (185 mg, 0.52 mmol) was added to a solution of [Rh(η5-Cp*)(η2-C2H4)2] (111 mg, 0.38 mmol) in n-pentane (4 mL). After stirring for 20 h at room temperature, the solvent was removed under vacuum, and the dark red residue was dissolved in toluene (5 mL). Then PMe3 (0.37 mmol) was added, and the solution was stirred for 3 h. The volatiles were removed under vacuum, and the residue was extracted with n-pentane (40 mL). The extract was evaporated to dryness, and the residue was chromatographed on a silica gel column, eluting with Et2O/n-hexane (1:1). The collected fraction (Rf = 0.5) was evaporated to dryness to give an orange solid (135 mg, 52%). X-ray quality single crystals were obtained by slow evaporation of an n-hexane solution. Mp: 135−137 °C. Anal. Calcd for C19H28F9IPRh: C, 33.16; H, 4.10. Found: C, 33.22; H, 4.16. 1H NMR (400.9 MHz, C6D6): δ 3.23 (m, 1 H, Rh−CH2−CH2), 2.30 (m, 1 H, Rh−CH2−CH2), 1.76−1.65 (m, 2 H, Rh−CH2−CH2), 1.45 (d, 4JPH = 3.0 Hz, 15 H, C5Me5), 1.11 (dd, 2JPH = 9.9 Hz, 3JRhH = 0.9 Hz, 9 H, PMe3). 13C{1H} NMR (75.5 MHz, CD2Cl2): δ 122.7 (qm, 1JCF = 287.6 Hz, CF3), 98.8 (dd, 1JRhC = 4.8 Hz, 2JPC = 3.2 Hz, C5Me5), 60.7 (decaplet, 2JCF = 24.2 Hz, CCF3), 36.6 (d, JPC or RhC = 3.6 Hz, Rh−

CH2−CH2), 17.5 (dd, 1JPC = 32.5 Hz, 2JRhC = 0.5 Hz, PMe3), 10.1 (d, 2 JRhC = 1.1 Hz, C5Me5), 1.6 (dd, 1JRhC = 25.6 Hz, 2JPC = 14.4 Hz, Rh− CH2−CH2). 19F NMR (188.3 MHz, C6D6): δ −65.0 (s). 31P{1H} NMR (121.4 MHz, C6D6): δ 2.6 (d, 1JRhP = 156.4 Hz). (+)ESI-MS: m/z 347, 441 ([Rh(η5-Cp*)I(PMe3)]+), 706 ([M + NH4]+); exact mass calcd for C19H32NF9IPRh 706.0223, found 706.0223. [Rh(η5-Cp*)(CH2CH2C6F5)I(PMe3)] (3d). This was prepared from [Rh(η5-Cp*)(η2-C2H4)2] (128 mg, 0.44 mmol), PMe3 (0.44 mmol), and IC6F5 (59 μL, 0.44 mmol) in a similar way to 3a (method A). Column chromatography (silica gel) using Et2O/n-hexane (3:1) as eluent gave an orange fraction (Rf = 0.87), which was evaporated to dryness to give an orange oil (130 mg, 47%). Crystalline 3d was obtained by slow diffusion of n-hexane into a C6D6 solution. Mp: 148−151 °C. Anal. Calcd for C21H28F5IPRh: C, 39.64; H, 4.44. Found: C, 39.60; H, 4.60. 1H NMR (400.9 MHz, C6D6): δ 2.84 (m, 1 H, Rh− CH2−CH2), 2.38 (m, 1 H, Rh−CH2−CH2), 1.96 (m, 1 H, Rh−CH2− CH2), 1.62 (m, 1 H, Rh−CH2−CH2), 1.58 (d, 4JPH = 2.7 Hz, 15 H, C5Me5), 1.28 (dd, 2JPH = 9.8 Hz, 3JRhH = 0.6 Hz, 9 H, PMe3). 13C{1H} NMR (75.5 MHz, C6D6): δ 144.7 (dm, 1JCF = 242.2 Hz, C2 of C6F5), 139.1 (dm, 1JCF = 248.9 Hz, C4 of C6F5), 137.7 (dm, 1JCF = 250.5 Hz, C3 of C6F5), 119.9 (tm, 2JCF = 19.5 Hz, C1 of C6F5), 98.3 (dd, 1JRhC = 4.5 Hz, 2JPC = 3.5 Hz, C5Me5), 30.1 (d, JPC or RhC = 5.7 Hz, RhCH2CH2), 17.4 (d, 1JPC = 32.1 Hz, PMe3), 13.6 (dd, 1JRhC = 25.3 Hz, 2JPC = 14.6 Hz, Rh−CH2−CH2), 10.0 (s, C5Me5). 19F NMR (188.3 MHz, C6D6): δ −146.3 (m, 2 F, F2), −160.5 (m, 1 F, F4), −163.3 (m, 2 F, F3). 31 1 P{ H} NMR (81.0 MHz, C6D6): δ 3.9 (d, 1JRhP = 159.5 Hz). (+)ESIMS (MeCOMe): m/z 194 ([C6F5−C2H3]+), 237 ([Rh(C5Me4CH2)]+), 365 ([Rh(η5-Cp*)I]+), 441 ([Rh(η5-Cp*)I(PMe3)]+), 636 (M+). [Rh(η5-Cp*)(CH2CH2CF2C6F5)I(PPh3)] (3e′). This was prepared from [Rh(η5-Cp*)(η2-C2H4)2] (100 mg, 0.34 mmol), PPh3 (90 mg, 0.34 mmol), and ICF2C6F5 (54 μL, 0.34 mmol) in a similar way to 3a′ (method A). After 15 h the resulting suspension was filtered. The precipitate was identified as [Rh(η5-Cp*)I2(PPh3)] by NMR spectroscopy (see below). The filtrate was purified by column chromatography (silica gel) using Et2O/n-hexane (1:1) as eluent. The orange fraction (Rf = 0.7) was evaporated to dryness to give an orange solid (37 mg, 12%). Yellow-orange crystals were obtained from Et2O/n-pentane at −32 °C. Mp: 141−143 °C. Anal. Calcd for C37H34F7IPRh: C, 50.94; H, 3.93. Found: C, 50.53; H, 3.57. 1H NMR (300.1 MHz, CDCl3): δ 7.65−7.10 (br m, 15 H, Ph), 2.92 (m, 1 H, Rh−CH2−CH2), 2.07 (m, 1 H, Rh−CH2−CH2), 1.59 (m, 1 H, Rh− CH2−CH2), 1.28 (m, 1 H, Rh−CH2−CH2), 1.51 (d, 4JPH = 2.8 Hz, 15 H, C5Me5). 13C{1H} NMR (75.5 MHz, CDCl3): δ 137.6−131.8 (br m, Ph), 129.8 (br s, Ph), 127.7 (br s, Ph), 99.6 (dd, 1JRhC = 4.6 Hz, 2JPC = 3.1 Hz, C5Me5), 47.4 (t, 2JFC = 21.6 Hz, Rh−CH2−CH2), 9.3 (s, C5Me5), 3.1 (ddd, 1JRhC = 24.8 Hz, 2JPC = 13.4 Hz, 3JFC = 2.6 Hz, Rh− CH2−CH2). The signals of the CF2C6F5 carbons could not be assigned because of their low intensity and overlap with phenylic signals. 19F NMR (188.3 MHz, CDCl3): δ −84.6 (dm, 2JFF = 255.3 Hz, 1 F, CF2), −95.4 (dm, 2JFF = 257.6 Hz, 1 F, CF2), −140.6 (m, 2 F, F2 of C6F5), −152.9 (t, 1 F, 2JFF = 21.1 Hz, F4 of C6F5), −161.9 (m, 2 F, F3 of C6F5). 31P{1H} NMR (81.0 MHz, CDCl3): δ 41.6 (d, 1JRhP = 161.8 Hz). (+)ESI-MS: m/z 496, 499 ([Rh(C5Me4CH2)(PPh3)]+), 537, 565, 627 ([Rh(η 5 -Cp*)I(PMe 3 )] + ), 721, 745 ([Rh(η 5 -Cp*)(C2H4CF2C6F5)(PMe3)]+), 911 ([M + K]+); exact mass calcd for C37H34F7IKPRh 911.0023, found 911.0000, Δ = 2.5 ppm. [Rh(η5Cp*)I2(PPh3)]: 1H NMR (300.1 MHz, CDCl3): δ 7.82−7.20 (several br m, 15 H, Ph), 1.76 (d, 3JRhH = 3.3 Hz, 15 H, C5Me5). 31P{1H} NMR (121.5 MHz, CDCl3): δ 27.8 (d, 1JRhP = 148.7 Hz). These data are in agreement with those of a sample prepared by a reported method.69,70 [Rh(η5-Cp*)(CF2C6F5)I(PMe3)] (4e). This was prepared from [Rh(η5-Cp*)(η2-C2H4)2] (137 mg, 0.47 mmol), PMe3 (0.56 mmol), and ICF2C6F5 (76 μL, 0.48 mmol) in a similar way to 3a (method A). Column chromatography (silica gel) using Et2O/n-hexane (3:1) as eluent gave an orange fraction (Rf = 0.6), which was evaporated to dryness to give an orange solid (165 mg, 47%). The 1H, 19F, and 31P{1H} NMR data of this compound agreed with those previously reported.22 Reaction of [Rh(η5-Cp*)(η2-C2H4)(PMe3)] with InC3F7. PMe3 (0.054 mmol) was added to a solution of [Rh(η5-Cp*)(η2-C2H4)2] (16 mg, 0.054 mmol) in C6D6 (0.5 mL) in an NMR tube. The tube

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Organometallics

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13.8 (very br s, 1 H, Fn+1Hn−), 1.94 (t, 4JPH = 3.2 Hz, 15 H, C5Me5), 1.76 (m, 9 H, PMe3); (−90 °C) δ 16.2 (br t, 1JFH = 121 Hz, HF2−), 13.7 (br d, 1JFH = 352 Hz, H2F3−), 1.83 (br s, C5Me5), 1.64 (br s, 9 H, PMe3). 19F NMR (282.4 MHz, CD2Cl2, 21 °C): δ −128.2 (very br s, SiF62−), −165.4 (very br s, Fn+1Hn−); (−90 °C) δ −128.5 (br s, SiF62−), −146.6 (br t, 1JFH = 131.5 Hz, [FHFHF]−), −149.5 (br d, 1JFH = 123.6 Hz, [FHF]−), −174.3 (br dd, 1JFH = 350.0 Hz, 2JFF = 130.9 Hz, [FHFHF]−). 31P{1H} NMR (81.0 MHz, CD2Cl2): δ 1.2 (d, 1JRhP = 131.9 Hz). (+)ESI-MS: m/z 517 ([Rh(η5-Cp*)I(PMe3)2]+); exact mass calcd for C16H33IP2Rh 517.0152, found 517.0171, Δ = 3.7 ppm. [Rh(η5-Cp)(nC4F9)I(PMe3)] (5). A solution of [Rh(η5-Cp)(η2-C2H4)(PMe3)] (290 mg, 1.07 mmol) in n-pentane (10 mL) was treated with InC4F9 (0.19 mL, 1.08 mmol). The mixture was stirred for 10 min. An orange solid precipitated, which was filtered, washed with n-pentane (2 × 10 mL), and dried under vacuum (302 mg, 48%). Mp: 196− 198 °C. Anal. Calcd for C12H14F9IPRh: C, 24.43; H, 2.39. Found: C, 24.31; H, 2.44. 1H NMR (200.1 MHz, CDCl3): δ 5.52 (d, 2JRhH = 1.5 Hz, 5 H, C5H5), 1.81 (d, 2JPH = 11.4 Hz, 9 H, PMe3). 13C{1H} NMR (100.8 MHz, C6D6): δ 135.3 (m, CF2), 117.9 (qt, 1JFC = 288.1 Hz, 2 JFC = 34.1 Hz, CF3), 114.9−106.1 (two overlapped multiplets, 2 CF2), 90.4 (s, C5H5), 21.0 (d, 1JPC = 35.6 Hz, PMe3). 19F NMR (188.3 MHz, CDCl3): δ −54.8 (AB d, 2JFF = 254.2 Hz, 1 F, CαFA), −66.5 (AB d, 2 JFF = 257.0 Hz, 1 F, CαFB), −81.7 (br s, 3 F, CF3), −110.0 (AB d, 2JFF = 281.9 Hz, 1 F, CβFA), −111.8 (AB d, 2JFF = 279.6 Hz, 1 F, CβFB), −125.7 (m, 2 F, CγF2). 31P{1H} NMR (81.0 MHz, C6D6): δ 9.8 (dddd, 1JRhP = 146.0 Hz, JPF = 21.9, 9.5, and 6.4 Hz). [Rh(η5-Cp*){CH2CH2CF(CF3)2}(CNXy)(PPh3)](OTf) (6). AgOTf (36 mg, 0.14 mmol) was added to a solution of 3a′ (116 mg, 0.14 mmol) in THF (9 mL). The mixture was stirred for 2 h at room temperature and evaporated to dryness. The residue was stirred with CH2Cl2 (9 mL), and the suspension was filtered. XyNC (19 mg, 0.14 mmol) was added to the resulting orange solution. After stirring for 5 h at room temperature, the resulting light orange solution was evaporated to dryness. The residue was washed with Et2O (3 × 5 mL) and dried under vacuum to give 5 as a yellowish-brown solid (106 mg, 87%). Anal. Calcd for C43H43F10NO3PRhS: C, 52.82; H, 4.43; N, 1.43; S, 3.28. Found: C, 52.53; H, 4.50; N, 1.51; S, 3.24. IR (Nujol, cm−1): ν(CN) 2133. 1H NMR (400.9 MHz, CD2Cl2): δ 7.59 (m, 3 H, H4 of Ph), 7.51 (m, 6 H, H3 of Ph), 7.31 (m, 7 H, H2 of Ph and H4 of Xy), 7.17 (d, 3JHH = 7.6 Hz, 2 H, H3 of Xy), 2.37−2.22 (m, 2 H, CH2CF), 2.18 (s, 6 H, Me of Xy), 1.80−1.57 (m, 2 H, RhCH2), 1.67 (d, 4JPH = 2.9 Hz, 15 H, C5Me5). 13C{1H} NMR (100.8 MHz, CDCl3): δ 151.7 (dd, 1JRhC = 72.1 Hz, 2JPC = 25.2 Hz, CN), 135.2 (s, C2 of Xy), 133.3 (d, 2JPC = 9.7 Hz, C2 or C3 of Ph), 132.1 (s, C4 of Ph), 130.4 (s, C4 of Xy), 129.3 (br d, 2JPC = 48.2 Hz, C1 of Ph), 129.3 (d, 2JPC = 10.5 Hz, C3 or C2 of Ph), 128.8 (s, C3 of Xy), 126.5 (s, C− N), 120.81 (qd, 1JFC = 286.6 Hz, 2JFC = 28.2 Hz, CF3), 120.74 (qd, 1 JFC = 286.7 Hz, 2JFC = 28.1 Hz, CF3), 104.9 (d, 1JRhC = 2.1 Hz, 2JPC = 3.9 Hz, C5Me5), 91.0 (d of septuplets, 1JFC = 201.7 Hz, 2JFC = 31.0 Hz, CF), 35.3 (d, 2JFC = 21.5 Hz, CH2CF), 18.8 (s, MeAr), 9.3 (s, C5Me5), 4.8 (dd, 1JRhC = 23.4 Hz, 2JPC = 9.4 Hz, RhCH2). 19F NMR (188.3 MHz, CDCl3): δ −75.4 (dq, 3JFF = 4JFF = 8.6 Hz, CF3CF), −76.9 (dq, 3 JFF = 4JFF = 8.6 Hz, CF3CF), −79.0 (s, OTf), −184.9 (m, CF). 31 1 P{ H} NMR (81.0 MHz, CDCl3): δ 43.5 (d, 1JRhP = 131.0 Hz). (+)ESI-MS: m/z 828 (M+); exact mass calcd for C42H43F7NPRh 828.2071, found 828.2087, Δ = 1.9 ppm. [Rh(η5-Cp*){C(O)CH2CH2CF(CF3)2}(CO)(PPh3)]OTf (7). AgOTf (32 mg, 0.12 mmol) was added to a solution of 3a′ (100 mg, 0.12 mmol) in THF (10 mL), and the mixture was stirred at room temperature for 2 h and evaporated to dryness. The residue was extracted with CH2Cl2 (8 mL), and the extract was filtered. CO was bubbled through the extract for 3 min. Then, the reaction tube was closed and the solution was stirred for 48 h at room temperature. A small amount of black precipitate was removed by filtration, and the filtrate was evaporated to dryness to give a dark yellow solid, which was washed with n-pentane (3 × 3 mL) to give crude 7 (73 mg, 69%). Yellow, analytically pure crystals were obtained by liquid diffusion of n-pentane into a CH2Cl2 solution. Mp: 144−146 °C. Anal. Calcd for C36H34F10O5PRhS: C, 47.91; H, 3.80; S, 3.55. Found: C, 48.23; H, 3.79; S, 3.35. IR (Nujol, cm−1): ν(CO) 2043 (CO), 1682 (CO).

was closed and heated at 120 °C for 20 h. Then, it was cooled to room temperature, and InC3F7 (8 μL, 0.054 mmol) was added. After 24 h, 1 H, 19F, and 31P{1H} NMR spectra of the resulting dark red-brown solution were measured. [Rh(η5-Cp*)(nC3F7)I(PMe3)] (4f)21 and [Rh(η5-Cp*)I2(PMe3)] 69,70 were the main reaction products, accounting respectively for 40% and 27% of the mixture (the ratio is based on the integration of the 31P{1H} NMR spectra of the mixture). Their NMR data were in agreement with those previously reported. 4f: 1 H NMR (300.1 MHz, C6D6) δ 1.50 (d, 3JRhH = 3.3 Hz, 15 H, C5Me5), 1.24 (d, 2JPH = 10.6 Hz, 9 H, PMe3). 19F NMR (282.4 MHz, C6D6): δ −66.1 (AB d, 2JFF = 272.4 Hz, 1 F, RhCF2), −68.7 (AB d, 2JFF = 269.3 Hz, 1 F, RhCF2), −78.5 (t, 3JFF = 11.3 Hz, 3 F, CF3), −113.3 (AB d, 2JFF = 279.7 Hz, 1 F, CF2CF3), −114.9 (AB d, 2JFF = 279.1 Hz, 1 F, CF2CF3). 31 1 P{ H} NMR (121.5 MHz, C6D6): δ 2.7 (dm, 1JRhP = 150.7 Hz). [Rh(η5-Cp*)I2(PMe3)]: 1H NMR (300.1 MHz, C6D6): δ 1.58 (d, 3 JRhH = 3.4 Hz, 15 H, C5Me5), 1.48 (d, 2JPH = 10.1 Hz, 9 H, PMe3). 31 1 P{ H} NMR (121.5 MHz, C6D6): δ −2.0 (d, 1JRhP = 138.2 Hz). [Rh(η 5-Cp*)( nC4F9)I(PMe3)] (4g). This was prepared from [Rh(η5-Cp*)(η2-C2H4)2] (150 mg, 0.51 mmol), PMe3 (0.61 mmol), and InC4F9 (90 μL, 0.51 mmol) in a similar way to 3a (method A). Column chromatography (silica gel) using Et2O as eluent gave an orange fraction (Rf = 0.95), which was evaporated to dryness to give an orange oil (40 mg, 12%). X-ray quality single crystals were obtained by slow evaporation of a toluene solution. Mp: 153−156 °C. Anal. Calcd for C17H24F9IPRh: C, 30.93; H, 3.66. Found: C, 31.01; H, 3.36. 1H NMR (400.9 MHz, C6D6): δ 1.49 (d, 4JPH = 2.8 Hz, 15 H, C5Me5), 1.23 (d, 2JPH = 10.5 Hz, 9 H, PMe3). 13C{1H} NMR (75.5 MHz, C6D6): δ 101.5 (dd, 1JRhC = 4.5 Hz, 2JPC = 2.9 Hz, C5Me5), 19.0 (d, 1 JPC = 33.3 Hz, PMe3), 10.4 (s, C5Me5). The signals corresponding to the carbons of the nC4F9 group were not observed. 19F NMR (188.3 MHz, C6D6): δ −66.2 (AB d, 2JFF = 272.1 Hz, 1 F, RhCF2), −68.3 (AB d, 2JFF = 273.0 Hz, 1 F, RhCF2), −80.8 (s, 3 F, CF3), −110.3 (AB d, 2 JFF = 285.4 Hz, 1 F, CβF2), −111.7 (AB d, 2JFF = 285.4 Hz, 1 F, CβF2), −124.6 (m, 2 F, CγF2). 31P{1H} NMR (81.0 MHz, C6D6): δ 2.7 (dm, 1 JRhP = 150.5 Hz). [Rh(η5-Cp*)(CFCF2)I(PMe3)] (4h). This was prepared from [Rh(η5-Cp*)(η2-C2H4)2] (157 mg, 0.53 mmol), PMe3 (0.64 mmol), and ICFCF2 (53 μL, 0.56 mmol) in a similar way to 3a (method A). Column chromatography (silica gel) using Et2O/n-hexane (3:1) as eluent gave an orange fraction (Rf = 0.6), which was evaporated to dryness to give an orange solid (40 mg, 14%). Mp: 132−135 °C. Anal. Calcd for C15H24F3IPRh: C, 34.51; H, 4.63. Found: C, 34.21; H, 4.68. 1 H NMR (300.1 MHz, C6D6): δ 1.53 (d, 4JPH = 2.9 Hz, 15 H, C5Me5), 1.30 (d, 2JPH = 10.8 Hz, 9 H, PMe3). 13C{1H} NMR (75.5 MHz, C6D6): δ 160.2 (ddd, 1JCF = 311.7 and 259.8 Hz, 2JCF = 47.4 Hz, CF CF2), 100.1 (dd, 1JRhC = 4.5 Hz, 2JPC = 3.0 Hz, C5Me5), 18.3 (d, 1JPC = 34.3 Hz, PMe3), 10.0 (s, C5Me5). The signal corresponding to the CFCF2 carbon was not observed. 19F NMR (282.4 MHz, C6D6): δ −90.4 (dd, 2JFF = 93.9 Hz, 3JFF cis = 38.8 Hz, RhCCF trans to Rh), −121.9 (dd, 2JFF = 93.7 Hz, 3JFF trans = 109.4 Hz, RhCCF cis to Rh), −140.4 (ddt, 3JFF trans = 110.3 Hz, 3JFF cis = 3JPF = 36.9 Hz, 2JRhF = 15.0 Hz, RhCFC). 31P{1H} NMR (81.0 MHz, C6D6): δ 6.0 (dd, 1JRhP = 140.8 Hz, 3JPF = 39.9 Hz). Reaction of [Rh(η5-Cp*)(η2-C2H4)(PMe3)] with ICF(CF3)CF2CF3. PMe3 (0.07 mmol) was added to a solution of [Rh(η5Cp*)(η2-C2H4)2] (21 mg, 0.071 mmol) in C6D6 (0.5 mL) in an NMR tube. The tube was closed and heated at 120 °C until the conversion of the starting complex into [Rh(η5-Cp*)(η2-C2H4)(PMe3)] was complete according to the 1H and 31P{1H} NMR spectra (24 h). Then, ICF(CF3)CF2CF3 was added (12 μL, 0.073 mmol). A fast color change from yellow to dark red was observed. After 24 h at room temperature, a crystalline orange-red solid precipitated. After measuring NMR spectra, the solution was removed and the solid was washed with toluene (3 × 0.5 mL) and Et2O (3 × 1 mL) and dried under vacuum. In the 19F NMR spectrum of the solution, the main signals corresponded to trans- and cis-octafluoro-2-butene:71 19F NMR (188.3 MHz, C6D6): δ (trans isomer) −69.1 (m, 6 F, CF3), −159.8 (m, 2 F, CF); (cis isomer) −66.7 (m, 6 F, CF3), −141.6 (m, 2 F, CF). Data of the solid: 1H NMR (300.1 MHz, CD2Cl2, 21 °C): δ 1296


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Table 2. Crystallographic Data formula cryst size (mm3) cryst syst space group a (Å) b (Å) c (Å) α (deg) β (deg) γ (deg) V (Å3) Z ρcalcd (g cm−3) F000 μ (mm−1) transmns θ range (deg) reflns collected Rint data/restraints/params GOF R1a wR2b largest diff peak, hole (e Å−3)

1a·C6D6

1b

3c

4g

7

8

C36H38D6F14I2Rh2 0.20 × 0.15 × 0.04 triclinic P1̅ 12.4747(4) 13.3277(5) 15.0019(5) 70.372(2) 66.215(2) 66.821(2) 2051.06(12) 2 1.956 1164 2.399 0.9101−0.6175 1.52−28.24 23 839 0.0256 9196/12/493 1.057 0.0355 0.0781 1.049, −0.862

C32H38F18I2Rh2 0.17 × 0.11 × 0.10 monoclinic P21/n 14.6027(14) 8.1396(8) 16.9438(16) 90 103.877(2) 90 1955.2(3) 2 2.080 1176 2.533 0.7858−0.5468 2.11−25.68 19 522 0.0492 3703/0/249 1.092 0.0433 0.1081 2.951, −0.745

C19H28F9IPRh 0.18 × 0.12 × 0.08 monoclinic P21/c 17.4942(15) 10.7840(9) 13.5254(12) 90 107.105(2) 90 2438.8(4) 4 1.874 1344 2.104 0.8497−0.6499 2.25−28.61 16 032 0.0254 5737/0/288 1.192 0.0371 0.0739 0.921, −0.464

C17H24F9IPRh 0.26 × 0.18 × 0.04 monoclinic P21/c 9.4279(4) 13.1022(5) 18.0704(7) 90 99.886(2) 90 2199.02(15) 4 1.994 1280 2.329 0.9126−0.6541 1.93−28.09 24 816 0.0223 5074/0/270 1.038 0.0190 0.0462 0.574, −0.450

C36H34F10O5PRhS 0.21 × 0.19 × 0.08 monoclinic P21/c 16.6976(11) 13.5697(9) 16.8812(11) 90 103.331(2) 90 3721.9(4) 4 1.611 1824 0.650 0.9499−0.8049 1.95−28.74 58 112 0.0280 9096/13/485 1.064 0.0470 0.1149 1.280, −1.318

C18H29BF4INPRh 0.4 × 0.3 × 0.2 monoclinic P21/c 8.1288(3) 21.5156(6) 12.9148(4) 90 95.866(3) 90 2246.92(13) 4 1.794 1192 2.24 1.000−0.842 2.52−31.0 101 180 0.037 7156/0/252 1.11 0.0296 0.0699 2.48, −1.13

R1 = ∑||Fo| − |Fc||/∑|Fo| for reflections with I > 2σ(I). bwR2 = [∑[w(Fo2 − Fc2)2]/∑[w(Fo2)2]0.5 for all reflections; w−1 = σ2(F2) + (aP)2 + bP, where P = (2Fc2 + Fo2)/3 and a and b are constants set by the program.

a

H, 4.98; N, 2.28. 1H NMR (400.9 MHz, CD2Cl2): δ 8.86 (br m, 2 H, H2 of py), 7.97 (m, 1 H, H4 of py), 7.55 (m, 2 H, H3 of py), 1.75 (d, 4 JPH = 3.4 Hz, 15 H, C5Me5), 1.66 (dd, 2JPH = 10.7 Hz, 3JRhH = 0.5 Hz, 9 H, PMe3). 13C{1H} NMR (100.8 MHz, CD2Cl2): δ 156.9 (br s, C2 of py), 139.9 (s, C4 of py), 127.9 (s, C3 of py), 100.9 (dd, 1JRhC = 6.2 Hz, 2JPC = 2.6 Hz, C5Me5), 16.9 (d, 1JPC = 33.9 Hz, PMe3), 10.2 (s, C5Me5). 19F NMR (188.3 MHz, CD2Cl2): δ −152.7 (s, 10BF4), −152.6 (s, 11BF4). 31P{1H} NMR (100.8 MHz, CD2Cl2): δ 2.0 (d, 1JRhP = 137.7 Hz). Anion Trapping Experiments. Typical Procedure. Complex [Rh(η5-Cp*)(η2-C2H4)(PMe3)] was generated in situ by heating [Rh(η5-Cp*)(η2-C2H4)2] (15 mg, 0.051 mmol) and PMe3 (55 μL of a 1 M toluene solution, 0.055 mmol) in C6D6 or D8-toluene (0.5 mL) at 120 °C for 24 h in an NMR tube. Then, CH3OD and IRF were consecutively added. After 1 h, the NMR spectra of the dark red solution were measured. The NMR data of the detected species (DRF or HRF; RF = CF(CF3)2,65,72 C(CF3)3,72,73 nC4F9,71,72 and C6F574) are given in the Supporting Information. X-ray Crystallography. Complexes 1a, 1b, 3c, 4g, and 7 were measured on a Bruker Smart APEX, and 8 was measured on an Oxford Diffraction Xcalibur S diffractometer. Data were collected using monochromated Mo Kα radiation in ω-scan mode at 100 K. Absorption corrections were applied on the basis of multiscans (Program SADABS for complexes 1a, 1b, 3c, 4g, and 7 and CrysAlis RED for 8). All structures were refined anisotropically on F2. The methyl groups were refined using rigid groups (AFIX 137), and the other hydrogens were refined using a riding model. Special features and exceptions: For complex 1a, two CF3 groups are disordered over two positions; for complex 7, all the CF3 groups are disordered over two positions.

H NMR (200.1 MHz, CDCl3): δ 7.64−7.52 (m, 9 H, H3 and H4 of Ph), 7.43−7.34 (m, 6 H, H2 of Ph), 2.93−2.76 (m, 1 H, CH2), 2.46− 2.29 (m, 1 H, CH2), 2.18−1.99 (m, 1 H, CH2), 1.78−1.64 (m, 1 H, CH2), 1.72 (d, 4JPH = 3.2 Hz, 15 H, C5Me5). 13C{1H} NMR (75.5 MHz, CDCl3): δ 229.5 (dd, 1JRhC = 27.1 Hz, 2JPC = 9.5 Hz, CO), 190.0 (dd, 1JRhC = 76.2, 2JPC = 20.1, CO), 133.4 (br d, JPC = 9.9 Hz, C2 of Ph), 132.7 (d, JPC = 2.2 Hz, C4 of Ph), 129.7 (d, JPC = 11.1 Hz, C3 of Ph), 120.7 (qd, 1JFC = 286.8 Hz, 2JFC = 27.9 Hz, CF3), 109.6 (dd, 1JRhC = 3.5 Hz, 2JPC = 1.2 Hz, C5Me5), 90.8 (d of septuplets, 1 JFC = 204.0 Hz, 2JFC = 32.2 Hz, CF), 54.7 (s, CH2), 24.3 (d, 2JFC = 20.7 Hz, CH2CF), 9.6 (s, C5Me5). The signal of the C1 of Ph could not be located. 19F NMR (282.4 MHz, CDCl3): δ −76.9 (m, CF3CF), −78.6 (s, OTf), −185.9 (m, CF). 31P{1H} NMR (81.1 MHz, CDCl3): δ 31.6 (d, 1JRhP = 136.9 Hz). (+)ESI-MS: m/z 725 ([Rh(η5-Cp*)(PPh3)(COCH 2 CH 2 C 3 F 7 )] + ), 753 ([Rh(η 5 -Cp*)(PPh 3 )(COCH 2 CH2C3F7)]+); exact mass calcd for M+ (C35H34O2PF7Rh) 753.1234; found 753.1243 (Δ = 1.2 ppm). [Rh(η5-Cp*)I(py)(PMe 3)](BF 4) (8). Method A. A solution of [Rh(η5-Cp*)(η2-C2H4)2] (154 mg, 0.52 mmol) and PMe3 (0.52 mmol) in toluene (4 mL) was stirred at 120 °C for 24 h in a Carius tube. The resulting solution of [Rh(η5-Cp*)(η2-C2H4)(PMe3)] was cooled to room temperature, and [I(py)2](BF4) (195 mg, 0.52 mmol) was added. The mixture was vigorously stirred for 24 h. An orange solid precipitated, which was decanted, washed with Et2O (3 × 5 mL), and dried under vacuum (202 mg, 64%). Method B. AgBF4 (72 mg, 0.37 mmol) was added to a solution of [Rh(η5-Cp*)I2(PMe3)] (208 mg, 0.37 mmol) in THF (10 mL) After stirring for 30 min in the dark, pyridine (30 μL, 0.37 mmol) was added. The suspension was stirred for 30 min more and then evaporated to dryness. The residue was extracted with CH2Cl2 (10 mL). The suspension was filtered, and the filtrate was evaporated to dryness under vacuum. On addition of Et2O (15 mL), an orange solid precipitated, which was filtered, washed with n-pentane (5 mL), and dried under vacuum (133 mg, 60%). X-ray quality single crystals were obtained by liquid diffusion (CH2Cl2/n-hexane). Mp: 218−220 °C. Anal. Calcd for C18H29BF4INPRh: C, 35.62; H, 4.82; N, 2.31. Found: C, 35.78; 1

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ASSOCIATED CONTENT S Supporting Information * Variable-temperature 1H and 19F NMR spectra of [Rh(η5-Cp*)I(PMe3)2]Fn+1Hn. NMR data of the DRF or HRF species detected in the anion trapping experiments. Crystallographic information in 1297


Organometallics

Article

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AUTHOR INFORMATION Corresponding Author *E-mail: [email protected], http://www.um.es/gqo/. ACKNOWLEDGMENTS We thank the Spanish Ministerio de Ciencia e Innovación (grant CTQ2007-60808/BQU, with FEDER support) and Fundación Séneca (grants 02992/PI/05 and 04539/GERM/06) for financial support.

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DEDICATION Dedicated to Prof. Juan Forniés on the occasion of his retirement.

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