(Cycloheptadienyl)diphenylphosphine: A Versatile Hybrid Ligand

Article pubs.acs.org/Organometallics

(Cycloheptadienyl)diphenylphosphine: A Versatile Hybrid Ligand† Alexandre Massard, Vincent Rampazzi, Arnaud Perrier, Ewen Bodio, Michel Picquet, Philippe Richard, Jean-Cyrille Hierso, and Pierre Le Gendre* Institut de Chimie Moléculaire de l’Université de Bourgogne, ICMUB-UMR CNRS 6302, Université de Bourgogne, 9 avenue Alain Savary, BP 47870, 21078 Dijon Cedex, France S Supporting Information *

ABSTRACT: (3,5-Cycloheptadienyl)diphenylphosphine is easily synthesized from the reaction of diphenylphosphine with 1,3,5-cycloheptatriene. This new phosphine-diene has been coordinated as a monodentate P ligand with Pt, Pd, Au, Ni, and Ru; as a bidentate (P, olefin) ligand with Pt and Pd; and as a tridentate (P, diene) ligand with Rh. Fluxional properties of several complexes have been studied via NMR experiments and theoretical consideration.

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INTRODUCTION In recent years, the synthesis of mixed P-olefin ligands, including chiral ones, has generated increasing interest.1,2 Indeed, these ligands can lead to stable, but nonetheless highly active, catalytic systems thanks to the combination of properties of the two electronically different binding sites in a single ligand framework: the σ-donor strength of a phosphorus center with the good π-accepting capability of an olefin. Thus, the olefin, which can readily and reversibly dissociate from the active metal center, is able to open a coordination site, to stabilize reactive intermediates and to facilitate a catalytic step.3,4 The presence of the CC double bond in the immediate vicinity of the transition metal may also create an asymmetric environment.5 (Tropylidenyl)phosphines 1 and 2 (Figure 1) have emerged as

drastically different from that of related (tropylidenyl)phosphines 1 and 2. Herein, we present and compare the coordination chemistry of this new hybrid ligand toward groups 8, 9, and 10 transition metals and gold as a coinage metal.

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RESULTS AND DISCUSSION (3,5-Cycloheptadienyl)diphenylphosphine 3 has been obtained in several grams scale via the one-step n-BuLi-mediated hydrophosphination of 1,3,5-cycloheptatriene with diphenylphosphine. This phosphine is an easy to handle non-air-sensitive solid and is soluble in most of the common organic solvents, such as toluene, ether, THF, dichloromethane, and methanol. The phosphinediene 3 was reacted with miscellaneous metal-containing precursors, including platinum, palladium, gold, nickel, ruthenium, or rhodium compounds. Three different coordination modes of 3 were observed depending on the metal/phosphine stoichiometry and on the nature of the precursor used: a monodentate fashion (κP-coordination), a bidentate fashion (κP:η2-coordination), and a tridentate fashion (κP:η4-coordination). κP-Coordination of 3 in Pd, Pt, Ni, Ru, and Au Complexes. The reaction of [PtCl2(cod)] with 3 in a molar ratio of 1:2 afforded the complex [PtCl2{P(C7H9)Ph2}2] 4 as an offwhite powder (97%) after evaporation of cyclooctadiene (Scheme 1). The ESI mass spectrum of 4 shows the expected parent ion and fragmentation pattern. The complex displays a single resonance in the 31P{1H} NMR spectrum downfield-shifted with respect to the (cycloheptadienyl)phosphine (δP = 14.7 ppm vs −4.7 ppm for 3) with platinum satellites separated by a coupling constant 1J(195Pt−P) of 3690 Hz, which indicates the presence of the chlorine atoms trans to the phosphorus ones and thus the cis geometry.9 The 1H NMR spectra of 4 and of the (cycloheptadienyl)phosphine are very similar, showing one broad and complex signal for the four protons of the dienyl

Figure 1. Tropylidenyl and cycloheptadienyl phosphines.

one of the most fruitful ligands of this class, allowing the synthesis of a wide range of transition-metal complexes.6,7 These phosphines generally behave as chelating ligands in which the phosphorus atom and the central CC bond of the tropylidenyl ring, the latter adopting a boatlike conformation, serve as preferred binding sites. As a part of our ongoing program on the hydrophosphination reaction, we recently described the synthesis of the (3,5-cycloheptadienyl)diphenylphosphine 3.8 In view of the conformational flexibility of the cycloheptadienyl ring and of the relative position of the two double bonds in regard to the phosphorus atom, we felt that the coordination chemistry of this new ligand should be diversified and © 2012 American Chemical Society

Received: October 17, 2011 Published: January 20, 2012 947

dx.doi.org/10.1021/om200999n | Organometallics 2012, 31, 947−958

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Table 1. Different κP Complexes Synthesizeda

Scheme 1. Synthesis of Platinum and Palladium Complexes 4 and 5

system centered at δ = 5.75 ppm, which is consistent with the κP-coordination of 3. A crystallization of the complex by diffusion of pentane in dichloromethane allowed us to obtain single crystals suitable for X-ray diffraction analysis (Figure 2).

a

Conditions: (cycloheptadienyl)phosphine (3), metal salt, CH2Cl2, 20 °C.

with [NiBr2(dme)] led to the bis(phosphine) complex 7 in excellent yield (entry 2). The compound was silent for 1 H NMR, suggesting a paramagnetic tetrahedral Ni(II) complex and gives in the 31P NMR at 190 K a broad singlet at 20.8 ppm. The ESI mass spectrum of 7 shows the expected parent ion and fragmentation pattern. Equimolar reaction of [AuCl(tht)] with 3 provided complex 8 in very good yield, whereas a similar reaction with [Ru(η6-C10H16)Cl]2 led to complex 9 (entries 3 and 4). In both cases, the spectroscopic data show the κP-coordination of 3 with a pendant cycloheptadienyl ring. The 31P NMR spectra of 8 and 9 show a singlet at δ = 41.9 and 22.7 ppm, respectively. The olefinic protons of the cycloheptadienyl moiety in the 1H NMR spectra of 8 and 9 resonate as a broadened multiplet more complex than the analogous signal in 3 or in complexes 4, 5, and 6. We cannot undertake a meaningful analysis of this difference, but simply note that the coordination of the (cycloheptadienyl)phosphine 3 to Au or Ru destroys the fortuitous isochrony of the olefinic protons. κP:η2-Coordination of 3 in Pt and Pd Complexes. With the aim to involve the cycloheptadienyl ring in the coordination sphere of the metal, we next reacted 1 equiv of [PtCl2(cod)] with only 1 equiv of 3 (Scheme 2). Interestingly, no trace of 4

Figure 2. Crystal structure of 4 (ORTEP plot, 30% probability ellipsoids). Dichloromethane solvent molecule omitted for clarity. Selected distances (Å) and angles (deg): Pt−P1 2.254(2), Pt−P2 2.272(3), Pt−Cl1 2.350(2), Pt−Cl2 2.360(2), C3−C4 1.323(18), C4−C5 1.473(19), C5−C6 1.333(17), C22−C23 1.35(2), C23−C24 1.40(2), C24−C25 1.312(19); P1−Pt−P2 98.21(9), P1−Pt−Cl1 91.31(9), P2−Pt−Cl1 170.42(9), P1−Pt−Cl2 176.26(9), P2−Pt− Cl2 84.09(9), Cl1−Pt−Cl2 86.35(9), C3−C4−C5−C6 21(2), C22− C23−C24−C25 21(3).

The crystal structure of 4 shows a square-planar environment around the Pt center. The angles P2−Pt−P1 (98.20(9)°) and Cl1−Pt−Cl2 (86.34(9)°) are significantly distorted from the ideal 90° due to the steric hindrance of the phosphine groups. The Pt−P bond lengths [Pt−P1 2.254(2) Å and Pt−P2 2.272(3) Å] range in classical values.10 The cycloheptadienyl ring adopts a half-chair-like conformation with the diphenylphosphino group in an exo position as in the phosphine 3. The palladium analogue [PdCl2{P(C7H9)Ph2}2] (5) was synthesized following the same way (Scheme 1). This complex was quantitatively obtained (98%) as a yellow powder. The ESI mass spectrum of 5 shows the expected parent ion and fragmentation pattern. The 1H NMR spectrum of 5 is comparable to the one of 4, giving evidence of the κP-coordination of 3. The reaction of 2 equiv of 3 with [Pd(η3-C4H7)Cl]2 gave complex 6 in good yield (Table 1, entry 1). Both 1H and 13C NMR of 6 show the expected loss of symmetry of the methallyl ligand, when compared to the dimeric precursor.11 Hence, the 1 H NMR leads to four separate signals for the allylic anti and syn protons (Δδ 1Hanti = 0.96 ppm and Δδ 1Hsyn = 1.44 ppm), whereas two different chemical shifts are found in the 13C NMR spectrum for the methylenic carbons cis and trans to the phosphorus atom at δ = 59.5 and 78.2 ppm, respectively. Moving up in the periodic table, the reaction of 2 equiv of 3

Scheme 2. Synthesis of Platinum Complex 10 and Palladium Complex 12

was observed in this case. The expected complex 10 was formed in 30 min in very good yield and was isolated as an offwhite solid. The 31P{1H} NMR spectrum of 10 displays one peak at 33.3 ppm with platinum satellites (1J(195Pt−P) = 3459 Hz). This coupling constant indicates the presence of one chlorine atom trans to the phosphorus one.9 The 1H NMR signal of the olefinic protons, which resonates as a broad multiplet centered 948


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Figure 3. Partial 1H NMR spectra of 4 (a) and 10 (b), signals corresponding to the dienic system.

Figure 4. (a) Crystal structure of 10 (ORTEP plot, 30% probability ellipsoids). Selected distances (Å) and angles (deg) (Ct is the C1C2 centroid): Pt−P 2.2305(10), Pt−Cl1 2.3609(10), Pt−Cl2 2.3228(11), Pt−C1 2.187(4), Pt−C2 2.170(4), Pt−Ct 2.064(3), C1−C2 1.394(5), C6− C7 1.336(6), C1−C7 1.475(5); Cl1−Pt−Cl2 90.85(4), Cl2−Pt−P 89.91(4), Ct−Pt−P 89.56(8), Ct−Pt−Cl1 89.98(8). (b) Overlay structures of 10 and of the free (cycloheptadienyl)phosphine 3 (in red; the P atom of the nonbonded ligand is located in the exo position).

at δ = 5.72 ppm in 4, is now split into four multiplets centered at δ = 5.31, 5.40, 5.86, and 6.18 ppm (Figure 3). Two of these signals at δ = 5.31 and 5.86 ppm have satellites with 2 195 J( Pt−H) = 68 and 73 Hz and can thus be assigned to the olefinic protons of the coordinated olefin. The signal at δ = 5.86 ppm appears as a pseudotriplet and can be attributed to the proton farthest away from the P atom (Hδ). In COSY experiment, Hδ shows two cross peaks with the other olefinic protons, whereas the proton (Hγ) giving the signal at δ = 5.31 ppm is connected to only one (see the Supporting Information). The remaining two signals at δ = 5.40 and 6.18 ppm can be attributed to the protons of noncoordinated olefin, the most upfield-shifted signal being due to the second Hδ, as attested by the COSY spectrum of 10. These data unequivocally demonstrate that the (cycloheptadienyl)phosphine chelates the Pt atom in solution, the binding sites being the phosphorus atom and one of the two olefins. The nature of complex 10 was further confirmed from the ESI mass spectrum. Noteworthy, an analogue complex 11, bearing methyl groups instead of chlorides, was synthesized from [PtMe2(cod)] in moderate yield (48%).

A slow diffusion of heptane in a dichloromethane solution of 10 afforded yellow needles suitable for a crystallographic structure determination of this complex. The platinum atom occupies the center of a square-planar arrangement defined by the phosphorus atom, the centroid of one of the two CC double bonds and the two chlorine atoms (Figure 4a). The conformational flexibility of the ligand allows the phosphorus atom to lie in an endo position of the cycloheptadienyl ring, thus forming a Pt chelate. The flip of the ligand to the endo conformation does not affect significantly the shape of the cycloheptadienyl ring, as it can be seen in the overlay structures of 10 and of the free ligand (the best overlay fit between the two rings leads to a residual rms distance between equivalent atoms equal to 7.8 × 10−2 Å, Figure 4b). Expectedly, the coordinated C1C2 bond distances (1.394(5) Å) are slightly elongated when compared with that of the free ligand or to the noncoordinated CC bond of the cycle (1.336(6) Å). The Pt−C(olefin) bond and Pt−P bond distances (Pt−C1, 2.187(4) Å; Pt−C2, 2.170(4) Å; Pt−P, 2.2305(10) Å) are in the ranges of those observed for related complexes.12 The difference in the Pt−Cl bond lengths (Pt−Cl1, 2.3609(10) Å vs 949


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raised back, the 1H NMR spectrum again exhibits two broad signals. The NMR behavior of 12 is consistent with the coordination of one of the two olefins to the Pd center with an accompanying dynamic exchange process. A low-energy activation barrier ΔG⧧ = 12.15 ± 0.06 or 12.0 ± 0.3 kcal·mol−1 can be estimated using the coalescence temperature Tc = 264 or 270 K and the respective maximum peak separation in the slow-exchange limit Δν190 K = 216 or 474 Hz, depending on the spin systems taken into account (see the Supporting Information).13,14 It is worth noting that, upon heating until 393 K, there is no sign of such a dynamic exchange in the case of the platinum complex. The coordination shifts Δδ = (δcomplex − δfree ligand) observed for the olefinic carbons of 10 (mean Δ̅ δ = −40.1 ppm) and of 12 (Δ̅ δ = −21.1 ppm) in the corresponding 13C NMR spectra indicate a higher degree of back-donation from the Pt center to the CC unit and may partly account for a more rigid Pt structure.5 At this stage, a range of related questions arise about the relative stability of the 16-electron complexes (κP:η2-coordination) versus 18-electron complexes (κP:η4-coordination), about the mechanism of the dynamic exchange process, and on the difference in the dynamic behaviors of the Pd and Pt complexes. Simple orbital interaction considerations may first clarify the electronic environment at the pseudo-square-planar complexes 10 and 12. For the 16-electron system, in which the metal is bonded to only one double bond, the σ-donor interaction occurs mainly with the φ2 orbital of the dienyl π system, whereas the π interaction takes place between a filled dπ metal orbital with the empty φ3 orbital, giving rise to a net back-donation stabilization effect (Figure 7). Differently, in the 18-electron system, it is the occupied φ1 orbital that is involved in the stabilizing σ-donation system for symmetrical reasons. The second occupied φ2 orbital interacts then with a filled dπ metal orbital. This 4-electron/2-orbital π interaction leads to a net repulsive polarization effect. Consequently, a higher energy is expected for the 18-electron species and such a complex would rather be an intermediate, or a transition state, in the dynamic exchange process of the two olefins connecting the two 16-electron complexes. DFT calculations confirm that these 18-electron structures are transition states and give a ΔG⧧ (298 K) for the Pd transition state A⧧ equal to 10.5 kcal·mol−1 and a substantially higher value of 20.1 kcal·mol−1 for the Pt TS (Figure 8). A dissociative mechanism has been also considered for the dynamic exchange process in both complexes (10 and 12). It involves the decoordination of the olefin that generates low-coordinate complexes that relax to T-shaped geometries with both chloride atoms in the trans position (B in Figure 8).15 As expected, these 14-electron intermediates lie higher in energy than the 16-electron complexes with a ΔG (298 K) equal to 10.9 kcal·mol−1 for the Pd complex and 18.9 kcal·mol−1 for the Pt one. These energy values give a good indication of the difference in the metal−olefin bond strength.16,17 Although the energy values involved in the dissociative and associative processes seem rather similar, they refer to two different types of entities, an intermediate B for the dissociative process and a transition state A⧧ for the associative route. Despite that we did not determine the transition states for this dissociative process, it is clear that the associative mechanism requires less energy and thus takes preference over the dissociative one, with the energy of its transition state lying in the range of one of the intermediates in this dissociative mechanism.18 Concerning the difference in the dynamic behavior of both complexes, DFT calculations of the

Pt−Cl2, 2.3228(11) Å) reflects the stronger trans influence of the phosphorus atom as compared to the olefin. The same synthetic way was applied to the formation of [{(η2-C7H9)PPh2-κP}PdCl2] (12) (Scheme 2). The complex was obtained in 16 h in excellent yield. The 31P NMR spectrum of 12 displays one singlet at δ = 57.4 ppm, attesting the coordination of the phosphorus atom to the Pd center. The 1 H NMR spectrum of 12 appears much simpler than the spectrum of 10 acquired under similar conditions (solvent, temperature, and NMR field). It displays only two broad signals at δ = 5.91 and 6.48 ppm in the chemical shift area of the dienic system (instead of four signals for 10) with identical relative intensities and one multiplet between 2.80 and 2.90 ppm (instead of four signals split from 2.25 to 3.46 ppm for 10). All these data are consistent with a symmetric chelate structure. Single crystals of 12 suitable for X-ray diffraction analysis were obtained by recrystallization in acetonitrile at −18 °C. Surprisingly, the solid-state structures of 12 and 10 are very

Figure 5. Crystal structure of 12 (ORTEP plot, 30% probability ellipsoids). Selected distances (Å) and angles (deg) (Ct is the C1C2 centroid): Pd−P 2.2334(5), Pd−Cl1 2.3659(5), Pt−Cl2 2.3240(6), Pd−C1 2.233(2), Pd−C2 2.219(2), Pd−Ct 2.1164(16), C1−C2 1.382(3), C6−C7 1.339(3), C1−C7 1.467(3); Cl1−Pd−Cl2 92.89(2), Cl2−Pd−P 87.99(2), Ct−Pd−P 89.26(4), Ct−Pd−Cl1 90.35(4).

similar (Figure 5). The geometry around the Pd is squareplanar with the (cycloheptadienyl)phosphine ligand coordinated in a bidentate mode. Remarkably, switching from Pt to Pd does not cause significant changes in the metal−phosphorus and metal−chlorine distances (Pd−P, 2.2334(5) Å; Pd−Cl1, 2.3659(5) Å; and Pd−Cl2, 2.3240(6) Å). Conversely, while coordinated CC bond lengths are similar in both complexes, the Pd−C1 and Pd−C2 distances (2.233(2) and 2.219(2) Å, respectively) are longer than those observed in the Pt complex 10. These data suggest a stronger metal−olefin interaction in the platinum complex. Because the ability of the (cycloheptadienyl)phosphine to adopt a bidentate coordination mode in the solid state was thus established, it appeared clearly that the environment around the Pd should be asymmetric. Nevertheless, as already mentioned, NMR data collected at room temperature are consistent with a symmetric chelate structure. To elucidate this apparent discrepancy, we measured 1H NMR spectra of 12 at lower temperatures. By decreasing the temperature, a decoalescence phenomenon was observed (Figure 6). At 190 K, the two broad signals of the olefinic protons are split into four signals consistent with the solid-state conformation. The VT-NMR shows a reversible behavior, since, when the temperature is 950


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Figure 6. (a) Dynamic exchange of the two olefin environments. (b) 1H NMR spectra of 12 at selected temperatures (CD2Cl2, 600.13 MHz).

Figure 7. Top view of the 16-electron and of the 18-electron complexes as well as a schematic representation of the dienyl π system.

κP:η4-Coordination of 3 in Rh Complexes. [Rh(cod)2]BF4 was reacted with an equimolar quantity of 3 and furnished complex 13 in good yield (Scheme 3). The 31P{1H} NMR spectrum of 13 reveals a doublet at δ = 78.6 ppm with a rhodium coupling constant of 151 Hz, consistent with the coordination of the phosphorus atom to the rhodium center. The 1H NMR spectrum of 13 shows two signals at δ = 4.03 and 6.47 ppm due to the olefinic protons of the (cycloheptadienyl)phosphine, which provides evidence of the η4-coordination of the cycloheptadienyl moiety.20 The variable-temperature NMR experiment did not reveal significant changes and led to the conclusion that the structure of 13 is rigid in solution at the NMR time scale. As shown in Figure 9, the X-ray structure reveals a tridentate coordination of the (cycloheptadienyl)diphenylphosphine. The structure was solved in the noncentrosymmetric group Pc with the result that two independent complexes are present in the asymmetric unit as well as two BF4− counteranions and two

Figure 8. (A⧧) Transition state of the Pd complex in square-planar geometry calculated at the DFT level. (B) Tricoordinated Pd complex in T-shaped geometry calculated at the DFT level (same geometries are obtained in the Pt series).

activation barriers in the associative mechanism give a lower energy level for the Pd vs Pt complexes (Δ(ΔG⧧) = 9.6 kcal·mol−1). These results account for the higher fluxionality of the Pd complex and can be related to the higher lability of olefinic ligands generally observed for Pd−alkene complexes.19 951


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Scheme 3. Synthesis of Rhodium Complex 13

The addition of a second equivalent of the hybrid ligand 3 to 13 led to the formation of the bis[(cycloheptadienyl)diphenylphosphine] cationic Rh complex 14 in good yield (Scheme 4). The 31P{1H} NMR spectrum of 14 shows a doublet at δ = 66.8 ppm with a rhodium coupling constant of 143 Hz. The 1H NMR spectrum of complex 14 shows only two sharp signals at δ = 4.29 and 5.32 ppm for the olefinic protons. These data are consistent with the coordination of each (cycloheptadienyl)phosphine ligand to the rhodium center in a symmetric chelating fashion. Because the tridentate coordination of both ligands would lead to a 20-electron Rh(I) species, which is rather less than likely, this apparent symmetry can more probably be achieved under dynamical conditions (Figure 10). The fluxional properties of 14 were probed by a variabletemperature 31P{1H} NMR experiment in CD2Cl2 from 300 K down to 165 K (Figure 10, upper traces). At 218 K, the signal is broad and merges almost with the baseline. At 214 K, two broad resonances appear and become clearly visible at 190 K at δ = 56.9 and 80.1 ppm, which indicates that the metal is chelated in a different manner by the two (cycloheptadienyl)phosphines. Down to 165 K, the two broad signals give rise to sharp doublets centered at δ = 56.5 and 79.0 ppm with typical rhodium coupling constants of 151 and 134 Hz, respectively. It is noteworthy that the 31P−31P coupling is not observed at low temperature, although it might be expected to be seen. The dynamic properties of 14 in solution could be explained by a slippage of the diene moiety on the Rh center, as described for the Pd complex 12, but extended to both cycloheptadienyl rings at a concerted tempo (Figure 10). By comparing selected experimental 31P{1H} NMR spectra from this coalescence phenomenon with computer simulated ones (Figure 10, lower traces), on the basis of an interchange in the coordination mode of the two noncoupled phosphines, exchange rates (k) can be calculated for each temperature. A standard Eyring plot of ln(k/T) against 1/T gives the following thermodynamic values at 298 K: ΔS⧧ = 1.0 ± 2.7 cal·K−1·mol−1, ΔH⧧ = 8.8 ± 0.6 kcal·mol−1, and ΔG⧧ = ΔH⧧ − TΔS⧧ = 8.5 ± 1.0 kcal·mol−1 (see the Supporting Information).22 The low activation barrier is consistent with the observed dynamic behavior of 14, and the value of the entropy (equal to zero within the uncertainty) is consistent with the above-described concerted slippage of the diene moieties on the Rh center in which the transition state does not exhibit any loss or gain of degrees of freedom. A diffraction study on a single crystal of 14 confirmed the two different coordination modes (κP:η2, κP:η4) of ligand 3 within the same metal complex (Figure 11a). The structure of 14 is very similar to the one of 13, but with two of the basal positions of the square-planar pyramid around the rhodium atom being occupied by the phosphorus atom and one olefin of

Figure 9. Crystal structure of the cation complex 13 (ORTEP plot, 30% probability ellipsoids). Only one molecule is represented; dichlomethane solvent molecules and the BF4− counteranion are omitted for clarity. Selected distances (Å) and angles (deg) (Ctnm represents the centroid of the Cn−Cm bond): Rh1−P1 2.3435(13), Rh1−C1 2.251(5), Rh1−C2 2.220(6), Rh1−C5 2.244(5), Rh1−C6 2.247(4), Rh1−C11 2.183(5), Rh1−C12 2.184(6), Rh1−C13 2.185(6), Rh1−C14 2.192(5), C11−C12 1.408(8), C12−C13 1.425(9), C13−C14 1.428(7), Rh1−Ct12 2.126(4), Rh1−Ct56 2.139(4), Rh1−Ct1112 2.067(4), Rh1−Ct1314 2.069(4); Ct12− Rh1−Ct56 84.63(14), Ct12−Rh1−P1 110.09(15), Ct12−Rh1− Ct1112 150.49(16), Ct12−Rh1−Ct1314 100.09(15), Ct56−Rh1− Ct1314 146.01(15), Ct56−Rh1−Ct1112 97.44(15), Ct56−Rh1−P1 113.46(11), Ct1112−Rh1−P1 96.11(12), Ct1112−Rh1−Ct1314 62.51(15), Ct1314−Rh1−P1 96.61(12).

dichloromethane solvent molecules. Nevertheless, due to a pseudoinversion center, both molecules have almost identical geometrical parameters. The best overlay fit between the two molecules leads to a residual rms distance between equivalent atoms (excluding the phenyl groups) equal only to 0.048 Å. For the sake of clarity, the geometrical parameters are given for only one molecule. The geometry around the rhodium center is a distorted square-based pyramid with P atom deviating from the ideal apical position. The basal positions are occupied by the two olefins of the cyclooctadiene ligand and the dienyl part of the hybrid ligand. As expected, the bond lengths C11−C12, C12−C13, and C13−C14 (1.408(8), 1.425(9), and 1.428(7) Å, respectively) of the coordinated cycloheptadienyl ring are similar and range between those of single and double bonds found in the (cycloheptadienyl)phosphine 3. The flexibility of the cycloheptadienyl ring in the endo chairlike conformation allows minimizing the steric congestion in complex 13, as attested by the normal Rh−P (2.3435(13) Å) and Rh−C(olefin) bond lengths (mean: 2.186(6) Å).21 952


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Scheme 4. Synthesis of Rhodium Complex 14

Figure 10. Dynamic exchange of the two phosphorus environments. Upper traces: 31P{1H} NMR spectra of 14 at selected absolute temperatures T (CD2Cl2, 242.92 MHz). Lower traces: computer-simulated spectra using gNMR (calculated exchange rates k shown in parentheses if given).

observed in the Pd and Pt complexes (10 and 12, respectively). The η2-coordinated cycloheptadienyl ring displays distinct C C−CC bond lengths (C22−C23 1.397(2) Å, C23−C24

the bidentate (cycloheptadienyl)phosphine in place of the cyclooctadiene ligand (Figure 11b). Ligand 3 in its bidentate coordination mode adopts a conformation comparable to that 953


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Figure 11. (a) Crystal structure of the cationic complex 14 (ORTEP plot, 30% probability ellipsoids). H atoms, dichloromethane solvent molecules, and the BF4− counteranion are omitted for clarity. Selected distances (Å) and angles (deg) (Ctnm represents the centroid of the Cn−Cm bond): Rh−P1 2.3449(4), Rh−P2 2.3398(4), Rh−C3 2.2152(16), Rh−C4 2.1880(16), Rh−C5 2.1866(16), Rh−C6 2.2111(16), Rh−C22 2.2165(16), Rh− C23 2.2703(16), Rh−Ct34 2.0826(12), Rh−Ct56 2.0807(12), Rh−Ct2223 2.1320(12), C3−C4 1.428(3), C4−C5 1.412(3), C5−C6 1.423(2), C22−C23 1.397(2), C23−C24 1.469(2), C24−C25 1.333(3); Ct34−Rh−Ct56 62.20(5), Ct34−Rh−P1 96.95(4), Ct34−Rh−P2 143.10(4), Ct34− Rh−Ct2223 94.63, Ct56−Rh−P1 94.66(4), Ct56−Rh−P2 97.40(4), Ct56−Rh−Ct2223 143.61(5), Ct2223−Rh−P1 116.94, Ct2223−Rh−P2 85.02(3), P1−Rh−P2 116.105(14). (b) Overlay structures of 13 and 14 (in red). on a Bruker micrOTOF-Q ESI-MS. 1H (300.13, 500.13, or 600.13 MHz), 13C (75.5, 125.8, or 150.9 MHz), and 31P (121.5, 202.5, or 242.9 MHz) NMR spectra were recorded on a Bruker 300 Avance, a Bruker 500 Avance DRX spectrometer, or on a Bruker 600 Avance II spectrometer. Chemical shifts are quoted in parts per million (δ) relative to TMS (1H), using the residual protonated solvent as an internal standard, or external 85% H3PO4 (31P). Coupling constants are reported in hertz. Synthetic Procedures. (3,5-Cycloheptadienyl)diphenylphosphine (3). In a Schlenk tube, an n-BuLi solution (0.19 mmol, 1.6 M in hexanes) was added to a solution of diphenylphosphine (1.25 mmol) in freshly distilled toluene (2 mL). The solution was stirred for 30 min at room temperature, and then 3,5-cycloheptatriene (3.75 mmol) was added. The reaction mixture was stirred until full consumption of diphenylphosphine (monitored by GC), around 18 h at 70 °C. The reaction was then quenched with a small amount of water, and MgSO4 was added. The mixture was filtered, and the filtrate was evaporated under reduced pressure. The obtained slurry was triturated with pentane to afford a white solid. The solid was dissolved in a small amount of dichloromethane and crystallized by diffusion of pentane (316 mg, 91%). 1H NMR (CDCl3, 300.13 MHz, 298 K): δ (ppm) 2.23−2.48 (m, 4H, cycloheptadiene CH2), 2.71−2.81 (m, 1H, cycloheptadiene CH), 5.79−5.89 (m, 4H, cycloheptadiene CH), 7.32−7.37 (m, 6H, Ph), 7.49−7.55 (m, 4H, Ph). 13C NMR (CDCl3, 75.47 MHz, 298 K): δ (ppm) 34.3 (d, 2JC−P = 18.1 Hz, cycloheptadiene CH2), 34.7 (d, 1JC−P = 11.0 Hz, cycloheptadiene CH), 126.0 (s, cycloheptadiene CH), 128.5 (d, 2JP−C = 7.1 Hz, Ph Cortho), 129.0 (s, cycloheptadiene CH), 132.8 (d, 4JC−P = 13.8 Hz, Ph Cpara), 133.6 (d, 3JC−P = 19.3 Hz, Cmeta), 137.3 (d, 1JC−P = 14.4 Hz, Ph Cipso). 31 1 P{ H} NMR (CDCl3, 202.45 MHz, 298 K): δ (ppm) −4.7 (s). cis-Bis{(3,5-cycloheptadienyl)diphenylphosphine}PtCl2 (4). 3 (83 mg, 0.30 mmol, 2.5 equiv) was dissolved in 2 mL of dichloromethane. This solution was cannulated over 5 min to a solution of [PtCl2(cod)] (45 mg, 0.12 mmol, 1 equiv) in 2 mL of dichloromethane. When the addition was completed, the solution was stirred for 18 h at room temperature. The solution was then evaporated under reduced pressure and triturated with pentane to afford a white solid. The solid was dissolved in dichloromethane and crystallized by diffusion of pentane (96 mg, 97%). 1H NMR (CD2Cl2, 300.13 MHz, 298 K): δ (ppm) 1.98 (m, 4H, cycloheptadiene CH2), 2.72 (m, 4H, cycloheptadiene CH2), 3.23 (m, 2H, cycloheptadiene CH), 5.72 (m, 8H, cycloheptadiene CH), 7.22−7.32 (m, 12H, Ph), 7.39−7.47 (m, 8H, Ph). 13C NMR (CD2Cl2, 75.47 MHz, 298 K): δ (ppm) 34.6 (s, cycloheptadiene CH2), 35.9 (d, 1JC−P = 40.7 Hz, cycloheptadiene CH), 125.7 (s, cycloheptadiene CH), 127.6 (d, 1JP−C = 56.6 Hz, Ph Cipso),

1.469(2) Å, C24−C25 1.333(3) Å), whereas these distances in its tridentate counterpart are nearly the same (C3−C4 1.428(3) Å, C4−C5 1.412(3) Å, C5−C6 1.423(2) Å). Both Rh−P bond distances are similar and fall in the usual range (Rh−P1 2.3449(4) Å, Rh−P2 2.3398(4) Å).

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CONCLUSION The coordination chemistry of (3,5-cycloheptadienyl)diphenylphosphine 3 toward groups 8, 9, and 10 transition metals and gold as a coinage metal has been studied. This hybrid ligand is conformationally flexible and can thus behave as a mono-, bi-, or tridentate ligand, depending on metals and experimental conditions. Illustrative coordination complexes have been prepared and fully characterized. The structure of a Pd(II) complex containing the bidentate (cycloheptadienyl)phosphine was found to be fluxional in solution, as illustrated by its NMR dynamic behavior. This NMR behavior is consistent with the coordination of one of the two olefins to the palladium center with an accompanying dynamic exchange process. DFT calculations gave insight into this mechanism and account for the relative stability of the 16-electron complexes (κP:η2coordination) versus the 18-electron complexes (κP:η4coordination) and of the lower fluxionality of the parent platinum complex. A fluxional Rh(I) complex bearing two (cycloheptadienyl)phosphine ligands in a bi- and tridentate fashion has also been described. The rhodium center is then surrounded by two phosphines and four olefins, which should considerably improve the stability of low oxidation states.23 All these observations and the variety of complexes described herein make this type of phosphine-diene promising for organometallic chemistry and catalysis.

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EXPERIMENTAL SECTION

All reactions were carried out under an atmosphere of purified argon using vacuum line techniques. Solvents were dried and distilled under argon before use. All other reagents were commercially available and used as received. All the analyses were performed at the “Plateforme d’Analyses Chimiques et de Synthèse Moléculaire de l’Université de Bourgogne”. The identity and purity (≥95%) of the complexes were unambiguously established using high-resolution mass spectrometry and multinuclear NMR. The exact mass of the complexes was obtained 954


Organometallics

Article

75.47 MHz, 298 K): δ (ppm) 33.4 (d, 2JC−P = 6.6 Hz, cycloheptadiene CH2), 36.0 (d, 1JC−P = 35.7 Hz, cycloheptadiene CH), 126.8 (s, cycloheptadiene CH), 128.7 (d, 1JC−P = 57.9 Hz, Ph Cipso), 129.5 (d, 2JC−P = 11.4 Hz, Ph Cortho), 130.9 (d, 3JC−P = 19.0 Hz, cycloheptadiene CH), 132.3 (d, 4JC−P = 2.6 Hz, Ph Cpara), 134.0 (d, 3JC−P = 12.8 Hz, Ph Cmeta). 31P{1H} NMR (CDCl3, 121.49 MHz, 298 K): δ (ppm) 41.9. HR-MS (ESIpos, methanol/dichloromethane; m/z): calcd C19H19PAuClNa+ [M + Na]+ 533.04907. Found 533.04706. {(3,5-Cycloheptadienyl)diphenylphosphine}(2,7dimethyloctadienediyl)RuCl2 (9). 3 (111 mg, 0.4 mmol, 2.2 equiv) was dissolved in 2 mL of dichloromethane. This solution was cannulated over 5 min to a solution of [Ru(η6-C10H16)Cl]2 (112 mg, 0.18 mmol, 1 equiv) in 2 mL of dichloromethane (dichloro-bis-μchloro-bis[(1−3η:6−8η)-2,7-dimethyloctadienediyl]diruthenium(II) is commercially available, but we preferred synthesizing it according to Salzer and co-workers’ method).24 When the addition was completed, the solution was stirred for 15 min, evaporated under reduced pressure, and triturated with pentane to afford a yellow solid. The solid was rinsed with pentane (200 mg, 94%). 1H NMR (CDCl3, 600.13 MHz, 298 K): δ (ppm) 1.72 (m, 1H, CH2), 1.97 (m, 1H, CH2), 2.15 (s, 6H, CH3), 2.58 (m, 2H, CH2), 3.11−3.20 (m, 2H, CH2), 3.35 (m, 2H, CH2), 3.39 (m, 1H, cycloheptadiene CH), 3.42 (d, 2JH−H = 3.3 Hz, 2H, allyl CH), 4.51 (d, 2JH−H = 9.2 Hz, 2H, allyl CH), 5.20 (m, 2H, allyl CH), 5.79−5.92 (m, 4H, cycloheptadiene CH), 7.34− 7.43 (m, 6H, Ph), 7.74 (t, 3JH−H = 8.6 Hz, 2H, Ph), 7.83 (t, 3JH−H = 8.6 Hz, 2H, Ph). 31P{1H} NMR (CDCl3, 242.97 MHz, 298 K): δ (ppm) 22.7. HR-MS (ESIpos, acetonitrile/dichloromethane; m/z): calcd C29H35PRuCl+ [M − Cl]+ 551.12029. Found 551.12082. {(η2-3,5-Cycloheptadienyl)diphenylphosphine-κP}PtCl2 (10). 3 (49 mg, 0.18 mmol, 1.2 equiv) was dissolved in 2 mL of dichloromethane. This solution was cannulated over 5 min to a solution of [PtCl2(cod)] (53 mg, 0.14 mmol, 1 equiv) in 3 mL of dichloromethane. When the addition was completed, the solution was stirred for 30 min at room temperature. The solution was then evaporated under reduced pressure and triturated with pentane to afford an off-white solid. The solid was dissolved in dichloromethane and crystallized by diffusion of heptane to afford yellow needles (70 mg, 92%). 1H NMR (CDCl3, 300.13 MHz, 298 K): δ (ppm) 2.25−2.34 (m, 1H, cycloheptadiene CH2), 2.55 (dd, 2JH−H = 16.3 Hz, 3JH−P = 45.7 Hz, 1H, cycloheptadiene CH2), 2.74−3.13 (m, 1H, cycloheptadiene CH2), 3.23− 3.46 (m, 1H, cycloheptadiene CH2), 3.44 (m, 1H, cycloheptadiene CH), 5.31 (m, +dm, 2JH−Pt195 = 72.5 Hz, 1H, cycloheptadiene CH), 5.40 (m, 1H, cycloheptadiene CH), 5.86 (t, +dt, 3JH−P = 8.1 Hz, 2 JH−Pt195 = 67.7 Hz, 1H, cycloheptadiene CH), 6.18 (m, 1H, cycloheptadiene CH), 7.40−7.60 (m, 6H, Ph), 7.75−7.90 (m, 4H, Ph). 13C NMR (CDCl3, 75.47 MHz, 298 K): δ (ppm) 35.0 (s, cycloheptadiene CH2), 38.1 (d, 2JC−P = 6.1 Hz, cycloheptadiene CH2), 38.1 (d, 1JC−P = 36.8 Hz, cycloheptadiene CH), 83.0 (s, +d, 1JC−Pt195 = 126.1 Hz, cycloheptadiene CH), 90.8 (d, 2JC−P = 7.2 Hz, cycloheptadiene CH), 122.9 (d, 1JC−P = 62.6 Hz, Ph Cipso), 128.1 (d, 1JC−P = 63.3 Hz, Ph Cipso), 128.8 (d, 2JC−P = 11.2 Hz, Ph Cortho), 128.9 (s, cycloheptadiene CH), 129.0 (d, 2JC−P = 11.2 Hz, Ph Cortho), 132.0 (d, 4JC−P = 2.9 Hz, Ph Cpara), 132.7 (d, 4JC−P = 2.8 Hz, Ph Cpara), 133.1 (d, 3JC−P = 9.1 Hz, Ph Cmeta), 133.4 (d, 3JC−P = 4.0 Hz, cycloheptadiene CH), 135.4 (d, 3JC−P = 10.9 Hz, Ph Cmeta). 31P{1H} NMR (CDCl3, 121.49 MHz, 298 K): δ (ppm) 33.3 (s, +d, 1JP−Pt195 = 3458.8 Hz). HR-MS (ESIpos, methanol/dichloromethane; m/z): calcd C19H19ClPPt+ [M − Cl]+ 508.05552. Found 508.05788. {(η2-3,5-Cycloheptadienyl)diphenylphosphine-κP}PtMe2 (11). 3 (106 mg, 0.37 mmol, 1 equiv) was dissolved in 3 mL of dichloromethane. This solution was cannulated over 5 min to a solution of [PtMe2(cod)] (124 mg, 0.37 mmol, 1 equiv) in 2 mL of dichloromethane. When the addition was completed, the solution was stirred for 30 min at room temperature. The solution was then evaporated under reduced pressure and triturated with pentane to afford an offwhite solid. The solid was dissolved in dichloromethane and precipitated by diffusion of pentane (90 mg, 48%). 1H NMR (CD2Cl2, 300.13 MHz, 298 K): δ (ppm) 0.47 (d, +dd, 3JH−P = 7.5 Hz, 2JH−Pt195 = 65.6 Hz, 3H, CH3), 1.00 (d, +dd, 3JH−P = 7.1 Hz, 2JH−Pt195 = 87.3 Hz, 3H, CH3), 2.30−2.71 (br s, 4H, cycloheptadiene CH2), 3.44−3.52 (m, 1H,

128.5 (t, 2JC−P = 5.3 Hz, Ph Cortho), 131.4 (s, Ph Cpara), 132.1 (t, 3JC−P = 8.3 Hz, cycloheptadiene CH), 134.0 (t, 3JC−P = 4.5 Hz, Ph Cmeta). 31P{1H} NMR (CD2Cl2, 121.49 MHz, 298 K): δ (ppm) 14.2 (s, +d, 1JP−Pt195 = 3681.1 Hz). Several attempts at high-resolution mass spectrometry failed to give a signal for C38H38P2PtCl+, but an exchange between one chloride and one methoxy group has been observed. HR-MS (ESI po s , methanol/dichloromethane; m/z): calcd C39H41O1P2Pt+ [M − 2Cl + OMe]+ 782.22749. Found 782.22839. cis-Bis{(3,5-cycloheptadienyl)diphenylphosphine}PdCl2 (5). 3 (170 mg, 0.61 mmol, 2 equiv) was dissolved in 3 mL of dichloromethane. This solution was cannulated over 5 min to a solution of PdCl2 (54 mg, 0.30 mmol, 1 equiv) in 2 mL of dichloromethane. When the addition was completed, the solution was stirred for 18 h at room temperature. The solution was then filtered over Celite, evaporated under reduced pressure, and triturated with pentane to afford a yellow solid. The solid was rinsed with pentane (220 mg, 98%). 1H NMR (CDCl3, 300.13 MHz, 298 K): δ (ppm) 1.98 (m, 4H, cycloheptadiene CH2), 2.83 (m, 4H, cycloheptadiene CH2), 3.45 (m, 2H, cycloheptadiene CH), 5.79 (m, 8H, cycloheptadiene CH), 7.41−7.50 (m, 12H, Ph), 7.60−7.66 (m, 8H, Ph). 13C NMR (CDCl3, 75.47 MHz, 298 K): δ (ppm) 31.0 (t, 2JP−C = 12.0 Hz, cycloheptadiene CH), 33.5 (s, cycloheptadiene CH2), 125.6 (s, cycloheptadiene CH), 127.9 (t, 1JC−P = 21.5 Hz, Ph Cipso), 128.3 (t, 2JC−P = 4.9 Hz, Ph Cortho), 130.6 (s, Ph Cpara), 132.4 (t, 3JC−P = 8.3 Hz, cycloheptadiene CH), 134.2 (t, 3JC−P = 5.7 Hz, Ph Cmeta). 31P{1H} NMR (CDCl3, 121.49 MHz, 298 K): δ (ppm) 28.7. HR-MS (ESIpos, methanol/ dichloromethane; m/z): calcd C38H38P2ClPd+ [M − Cl]+ 697.11666. Found 697.12201. {(3,5-Cycloheptadienyl)diphenylphosphine}(2-methylallyl)PdCl (6). 3 (181 mg, 0.65 mmol, 2 equiv) was dissolved in 2 mL of dichloromethane. This solution was cannulated over 5 min to a solution of [Pd(η3-C4H8)Cl]2 (115 mg, 0.33 mmol, 1 equiv) in 3 mL of dichloromethane. When the addition was completed, the solution was stirred for 30 min, evaporated under reduced pressure, and triturated with hexane to afford a yellow solid. The solid was rinsed with hexane (250 mg, 81%). 1H NMR (CDCl3, 300.13 MHz, 298 K): δ (ppm) 1.89 (s, 3H, CH3), 2.23−2.35 (m, 2H, cycloheptadiene CH2), 2.53 (m, 1H, allyl CHanti), 2.67−2.75 (m, 2H, cycloheptadiene CH2), 3.01 (m, 1H, allyl CHsyn), 3.11−3.19 (m, 1H, cycloheptadiene CH), 3.49 (d, 1JH−H = 9.8 Hz, allyl CHanti), 4.45 (d, 1JH−H = 6.1 Hz, allyl CHsyn), 5.81 (m, 4H, cycloheptadiene CH), 7.40−7.44 (m, 6H, Ph), 7.59−764 (m, 4H, Ph). 13C NMR (CDCl3, 75.47 MHz, 298 K): δ (ppm) 23.4 (s, allyl CH3), 33.6 (d, 2JC−P = 4.6 Hz, cycloheptadiene CH2), 33.8 (d, 1JC−P = 19.6 Hz, cycloheptadiene CH), 59.5 (s, allyl CH2), 78.2 (s, allyl CH2), 125.8 (s, cycloheptadiene CH), 128.7 (d, 2JC−P = 9.6 Hz, Ph Cortho), 130.5 (d, 4JC−P = 2.2 Hz, Ph Cpara), 131.5 (d, 1JC−P = 36.7 Hz, Ph Cipso), 132.3 (s, cycloheptadiene CH), 133.3 (d, 3JC−P = 11.5 Hz, Ph Cmeta). 31P{1H} NMR (CDCl3, 121.49 MHz, 298 K): δ (ppm) 31.9. HR-MS (ESIpos, methanol/dichloromethane; m/z): calcd C23H26PPd+ [M − Cl]+ 439.08106. Found 439.08415. Bis{(3,5-cycloheptadienyl)diphenylphosphine}NiBr2 (7). 3 (50 mg, 0.18 mmol, 2.2 equiv) was dissolved in 2 mL of dichloromethane. This solution was cannulated to a solution of [NiBr2(dme)] (25 mg, 0.08 mmol, 1 equiv) in 2 mL of dichloromethane. The solution quickly turned to green and was stirred for 30 min at room temperature. The solution was then evaporated under reduced pressure and triturated with pentane to afford a brown solid (60 mg, 95%). 31P{1H} NMR (CD2Cl2, 242.97 MHz, 190 K): δ (ppm) 20.8 (br s). HR-MS (ESIpos, methanol/dichloromethane; m/z): calcd C38H38BrP2Ni+ 695.0959. Found 695.0963. {(3,5-Cycloheptadienyl)diphenylphosphine}AuCl (8). 3 (54 mg, 0.19 mmol, 1.1 equiv) was dissolved in 2 mL of dichloromethane. This solution was cannulated to a solution of [AuCl(tht)] (56 mg, 0.17 mmol, 1 equiv) in 2 mL of dichloromethane. The solution was stirred for 1 h at room temperature. The solution was then evaporated under reduced pressure and triturated with pentane to afford a white solid (82 mg, 95%). 1H NMR (CDCl3, 300.13 MHz, 298 K): δ (ppm) 2.33−2.61 (m, 4H, cycloheptadiene CH2), 3.03−3.15 (m, 1H, cycloheptadiene CH), 5.74−5.89 (m, 4H, cycloheptadiene CH), 7.43−7.56 (m, 6H, Ph), 7.72−7.70 (m, 4H, Ph). 13C NMR (CDCl3, 955


Organometallics

Article

Table 2. Crystal and Structure Refinement Data for 4, 10, 12, 13, and 14 compounds empirical formula fw temperature (K) cryst syst space group a (Å) b (Å) c (Å) α (deg) β (deg) γ (deg) volume (Å3) Z ρcalc (g/cm3) μ (mm−1) size (mm3) F(000) λ θ Range (°) index ranges

reflns collected Rint reflections with I ≥ 2σ(I) data/restraints/param final R indices [I ≥ 2σ(I)] R indices (all data) goodness-of-fitc on F2 Flack param abs correction max and min trans Δρ (e Å−3) CCDC deposition no.

4

10

12

13

14

C38H38Cl2P2Pt, CH2Cl2 907.53 115(2) orthorhombic P212121 10.4161(2) 16.7564(4) 21.2276(6) 90 90 90 3704.99(15) 4 1.627 4.190 0.12 × 0.05 × 0.05 1800 0.71073 1.91−27.46 h: −13; 13 k: −21; 21 l: −27; 27 8341 0.059 7752 8341/1/399 R1a = 0.0557 wR2b = 0.1116 R1a = 0.0637 wR2b = 0.1179 1.129 0.082(11)

C19H19Cl2PPt 544.30 115(2) orthorhombic Pna21 8.2954(3) 14.9017(5) 14.3336(5) 90 90 90 1771.86(11) 4 2.040 8.307 0.20 × 0.15 × 0.07 1040 0.71073 2.06−27.51 h: −10; 10 k: −19; 19 l: −18; 10 15978 0.031 3200 3238/3/215 R1a = 0.0167 wR2b = 0.0421 R1a = 0.0172 wR2b = 0.0425 1.112 0.000(6) semiempirical 0.46 and 0.25 0.73 and −1.33 834837

C19H19Cl2PPd 455.61 115(2) orthorhombic Pna21 8.2534(3) 14.8778(5) 14.3698(5) 90 90 90 1764.50(11) 4 1.715 1.441 0.25 × 0.20 × 0.12 912 0.71073 2.88−27.47 h: −10; 10 k: −19; 19 l: −18; 18 12765 0.038 3777 3814/3/215 R1a = 0.0169 wR2b = 0.0395 R1a = 0.0173 wR2b = 0.0399 1.081 0.563(18) semiempirical 0.81 and 0.73 0.24 and −0.32 834838

C27H31PRh, CHCl3, BF4 695.58 115(2) monoclinic Pc 15.4399(7) 10.7640(4) 22.4708(8) 90 129.564(2) 90 2879.0(2) 4 1.605 0.971 0.25 × 0.20 × 0.15 1408 0.71073 1.71−27.58 h: −19; 20 k: −13; 9 l: −29; 29 22354 0.036 11004 11612/18/734 R1a = 0.0370 wR2b = 0.0786 R1a = 0.0404 wR2b = 0.0812 1.073 0.46(3) semiempirical 0.84 and 0.78 0.77 and −0.63 834839

C38H38P2Rh, CHCl3, BF4 865.71 115(2) monoclinic C2/c 34.3066(8) 11.7956(3) 18.6351(4) 90 105.3250(10) 90 7272.9(3) 8 1.581 0.828 0.25 × 0.20 × 0.10 3520 0.71073 2.56−27.59 h: −44; 44 k: −15; 13 l: −24; 24 15076 0.013 7828 8321/6/469 R1a = 0.0248 wR2b = 0.0552 R1a = 0.0272 wR2b = 0.0566 1.067

2.02 and −0.93 834836

0.79 and −0.57 834840

R1 = ∑(∥Fo| − |Fc∥)/∑|Fo|. bwR2 = [∑w(Fo2 − Fc2)2/∑[w(Fo2)2]1/2, where w = 1/[σ2(Fo2 + (0.00P)2 + 50.87P] for 4, w = 1/[σ2(Fo2 + (0.021P)2 + 2.00P] for 10, w = 1/[σ2(Fo2 + (0.00P)2 + 1.51P] for 12, w = 1/[σ2(Fo2 + (0.00P)2 + 7.91P] for 13, and w = 1/[σ2(Fo2 + (0.01P)2 + 17.66P] for 14, where P = (max(Fo2,0) + 2*Fc2)/3. cS = [∑w(Fo2 − Fc2)2/(n − p)]1/2 (n = number of reflections, p = number of parameters). a

(br s, 2H, cycloheptadiene CH), 6.48 (br s, 2H, cycloheptadiene CH), 7.49−7.52 (m, 4H, Ph), 7.59−7.62 (m, 2H, Ph), 7.86−7.90 (m, 4H, Ph). 1 H NMR (CD2Cl2, 600.13 MHz, 190 K): δ (ppm) 2.14 (d, 2JH−H = 19.7 Hz, 1H, cycloheptadiene CH2), 2.78 (pseudo t, 2JH−H ≈ 3JC−P ≈ 23.5 Hz, 1H, cycloheptadiene CH2), 2.93 (dd, 2JH−H = 16.9 Hz, 3JH−P = 55.0 Hz, 1H, cycloheptadiene CH2), 3.44 (br m, 1H, cycloheptadiene CH2), 3.58 (br s, 1H, cycloheptadiene CH), 5.47 (br s, 1H, cycloheptadiene CH), 6.20 (br s, 1H, cycloheptadiene CH), 6.26 (br s, 1H, cycloheptadiene CH), 6.56 (br s, 1H, cycloheptadiene CH), 7.46 (br s, 4H, Ph), 7.58 (br s, 2H, Ph), 7.74 (br s, 4H, Ph). 13C NMR (CD2Cl2, 125.76 MHz, 298 K): δ (ppm) 36.2 (bs, cycloheptadiene CH2), 41.0 (d, 1JC−P = 29.4 Hz, cycloheptadiene CH), 126.2 (d, 1JC−P = 42.7 Hz, Ph Cipso), 128.8 (d, 2JC−P = 11.3 Hz, Ph Cortho), 132.5 (d, 4JC−P = 2.5 Hz, Ph Cpara), 134.2 (d, 3JC−P = 8.8 Hz, Ph Cmeta), (cycloheptadiene CH not observed). 13C NMR (CD2Cl2, 150.92 MHz, 190 K): δ (ppm) 34.6 (s, cycloheptadiene CH2), 37.6 (d, 2JC−P = 4.0 Hz, cycloheptadiene CH2), 39.4 (d, 1JC−P = 29.0 Hz, cycloheptadiene CH), 101.7 (s, cycloheptadiene CH), 110.1 (d, 2JC−P = 6.9 Hz, cycloheptadiene CH), 123.2 (d, 1JC−P = 56.6 Hz, Ph Cipso), 126.7 (s, cycloheptadiene CH), 127.6 (d, 1JC−P = 56.0 Hz, Ph Cipso), 128.3 (d, 2JC−P = 10.8 Hz, Ph Cortho), 128.4 (d, 2JC−P = 11.6 Hz, Ph Cortho), 132.1

cycloheptadiene CH), 4.08 (br s, 2H, cycloheptadiene CH), 6.11 (br s, 2H, cycloheptadiene CH), 7.44 (m, 6H, Ph), 7.64−7.71 (m, 4H, Ph). 13 C NMR (CD2Cl2, 75.47 MHz, 298 K): δ (ppm) 0.3 (d, +dd, 2JC−P = 5.8 Hz, 1JC−Pt195 = 748.2 Hz, CH3), 8.1 (d, +dd, 3JC−P = 109.5 Hz, 1 JC−Pt195 = 624.0 Hz, CH3), 35.7 (br s, cycloheptadiene CH2), 39.3 (d, 1JC−P = 26.3 Hz, cycloheptadiene CH), 87.1 (br s, cycloheptadiene CH), 97.1 (br s, cycloheptadiene CH), 127.8−137.0 (m, Ph). 31P{1H} NMR (CDCl3, 121.49 MHz, 298 K): δ (ppm) 42.9 (s, +d, 1JP−Pt195 = 1894.0 Hz). HR-MS (ESIpos, methanol/dichloromethane; m/z): calcd C20H22PPt+ [M − CH3]+ 488.11014. Found 488.11130. {(η2-3,5-Cycloheptadienyl)diphenylphosphine-κP}PdCl2 (12). 3 (54 mg, 0.19 mmol, 1 equiv) was dissolved in 3 mL of dichloromethane. This solution was cannulated over 5 min to a solution of [PdCl2(cod)] (56 mg, 0.19 mmol, 1 equiv) in 1 mL of dichloromethane. When the addition was completed, the solution was stirred for 16 h at room temperature. The solution was then evaporated under reduced pressure and triturated with pentane to afford a yellow solid. The solid was dissolved in dichloromethane and precipitated by diffusion of pentane. The collected mass was 81 mg (92%). 1H NMR (CD2Cl2, 600.13 MHz, 298 K): δ (ppm) 2.80−2.90 (br m, 4H, cycloheptadiene CH 2), 3.55 (m, 1H, cycloheptadiene CH), 5.91 956


Organometallics

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(s, Ph Cpara), 132.4 (s, Ph Cpara), 132.6 (d, 3JC−P = 8.3 Hz, Ph Cmeta), 134.9 (d, 3JC−P = 10.4 Hz, Ph Cmeta), 137.1 (s, cycloheptadiene CH). 31 1 P{ H} NMR (CD2Cl2, 242.97 MHz, 298 K): δ (ppm) 57.4. HR-MS (ESIpos, acetonitrile/dichloromethane; m/z): calcd C19H19Cl2PPdNa+ [M + Na]+ 476.95285. Found 476.95533. [(1,5-Cyclooctadiene){(η4-3,5-cycloheptadienyl)diphenylphosphine-κP}Rh][BF4] (13). 3 (117 mg, 0.42 mmol, 1 equiv) was dissolved in 2 mL of dichloromethane. This solution was cannulated over 5 min to a solution of freshly prepared [Rh(cod)2]BF4 (170 mg, 0.42 mmol, 1 equiv) in 2 mL of dichloromethane. When the addition was completed, the solution was stirred for 90 min at room temperature. The solution was then concentrated, and the product was precipitated by addition of diethyl ether to afford a pale yellow powder (193 mg, 80%). 1H NMR (CD2Cl2, 600.13 MHz, 298 K): δ (ppm) 1.11 (dd, 2JH−H = 14.3 Hz, 3JH−P = 60.3 Hz, 2H, cycloheptadiene CH2), 2.29 (m, 2H, cycloheptadiene CH2), 2.39 (m, 2H, COD CH2), 2.52 (m, 2H, COD CH2), 3.24 (m, 1H, cycloheptadiene CH), 4.03 (br s, 2H, cycloheptadiene CH), 4.41 (br s, 4H, COD CH), 6.47 (br s, 2H, cycloheptadiene CH), 7.50 (m, 4H, Ph), 7.61 (m, 6H, Ph). 13C NMR (CD2Cl2, 75.47 MHz, 298 K): δ (ppm) 29.8 (d, 2JC−P = 14.1 Hz, cycloheptadiene CH2), 32.0 (d, 2JC−Rh = 2.1 Hz, COD CH2), 54.5 (d, 1JC−P = 33.2 Hz, cycloheptadiene CH), 77.0 (dd, 2JC−P = 9.0 Hz, 1JC−Rh = 3.3 Hz, cycloheptadiene CH), 93.2 (d, 1JC−Rh = 6.4 Hz, COD CH), 102.1 (s, cycloheptadiene CH), 129.9 (d, 2JC−P = 9.3 Hz, Ph Cortho), 130.3 (dd, 1JC−P = 30.4 Hz, 2JC−Rh = 1.8 Hz, Ph Cipso), 131.9 (d, 4JC−P = 2.4 Hz, Ph Cpara), 132.9 (d, 3JC−P = 9.7 Hz, Ph Cmeta). 31 1 P{ H} NMR (CDCl3, 121.49 MHz, 298 K): δ (ppm) 78.6 (d, 1JP−Rh = 150.6 Hz). HR-MS (ESIpos, methanol/dichloromethane; m/z): calcd C27H31PRh+ [M]+ 489.12129. Found 489.12302. [{(η 4 -3,5-Cycloheptadienyl)diphenylphosphine-κP}{(η 2 -3,5cycloheptadienyl)diphenylphosphine-κP}Rh][BF4] (14). 3 (33 mg, 0.12 mmol, 1 equiv) was dissolved in 1 mL of dichloromethane. This solution was cannulated over 5 min to a solution of 13 (69 mg, 0.12 mmol, 1 equiv) in 1 mL of dichloromethane. The initially yellow solution turned to orange, and the solution was stirred overnight at room temperature. The solution was then concentrated, and the product was precipitated by addition of pentane to afford an orange powder (79 mg, 88%). 1H NMR (CDCl3, 600.13 MHz, 298 K): δ (ppm) 1.83 (dd, 2JH−H = 15.0 Hz, 3JH−P = 50.4 Hz, 4H, cycloheptadiene CH2), 2.27 (m, 4H, cycloheptadiene CH2), 3.21 (m, 2H, cycloheptadiene CH), 4.29 (m, 4H, cycloheptadiene CH), 5.32 (m, 4H, cycloheptadiene CH), 7.35 (m, 8H, Ph), 7.45−7.51 (m, 12H, Ph). 13 C NMR (CD2Cl2, 125.76 MHz, 298 K): δ (ppm) 33.8 (d, 2JC−P = 10.1 Hz, cycloheptadiene CH2), 49.5 (d, 1JC−P = 31.4 Hz, cycloheptadiene CH), 94.5 (m, cycloheptadiene CH), 100.4 (m, cycloheptadiene CH), 129.1 (d, 2JC−P = 8.8 Hz, Ph Cortho), 131.3 (d, 1JC−P = 35.2 Hz, Ph Cipso), 131.5 (s, Ph Cpara), 132.9 (d, 3JC−P = 10.1 Hz, Ph Cmeta). 31P{1H} NMR (CD2Cl2, 242.97 MHz, 298 K): δ (ppm) 66.8 (d, 1JP−Rh = 143.2 Hz). 31P{1H} NMR (CD2Cl2, 242.97 MHz, 165 K): δ (ppm) 56.5 (d, 1JP−Rh = 133.8 Hz), 79.0 (d, 1JP−Rh = 151.1 Hz). HR-MS (ESIpos, methanol/dichloromethane; m/z): calcd C38H38P2Rh+ [M]+ 659.14983. Found 659.14929. X-ray Crystallography Procedures. X-ray Analysis of Compounds 4, 10, 12, 13, and 14. Intensity data were collected on a Bruker-Nonius APEX II diffractometer equipped with an Oxford Cryosystem low-temperature device operating at 115 K. The structures were solved by direct methods (SIR92)25 and refined with full-matrix least-squares methods based on F2 (SHELXL-97)26 with the aid of the WINGX program.27 Compound 4 was solved in the P212121 space group. Except for the solvent, all non-hydrogen atoms were refined with anisotropic thermal parameters. Hydrogen atoms were included in their calculated positions and refined with a riding model. The CH2Cl2 solvent molecule is badly disordered and was modeled as a rigid group over three positions using an overall isotropic temperature factor. Compounds 10 and 12 were solved in the Pna21 space group. All non-hydrogen atoms were refined with anisotropic thermal parameters. Except for the two hydrogen atoms belonging to the coordinated double bond, which were refined using just a restraint on the C−H distance, all other hydrogen atoms were included in their calculated positions and refined with a riding model. Compound 13

was solved in the Pc noncentrosymmetric group. If two independent complexes present in the asymmetric unit seem to be related by an inversion center, this is not the case of the solvent, and a refinement of the structure in the P21/c space group, at the cost of a disordered solvent, results in numbers of non-positive definite thermal parameters and in worse R values (R1 = 0.17 and wR2 = 0.42). The noncentrosymmetric group was then favored. All non-hydrogen atoms were refined with anisotropic thermal parameters. Except for hydrogen atoms belonging to the coordinated double bonds, which were refined using just a restraint on the C−H distance, all other hydrogen atoms were included in their calculated positions and refined with a riding model. Compound 14 was refined in the C2/c space group. All non-hydrogen atoms were refined with anisotropic thermal parameters. Except for hydrogen atoms belonging to the coordinated double bonds, which were refined using just a restraint on the C−H distance, all other hydrogen atoms were included in their calculated positions and refined with a riding model. Crystallographic data are reported in Table 2. Theoretical Calculations. Calculations were performed using Jaguar v. 5.528 at the DFT B3LYP/6-31G** level using the LANL2DZ effective core basis set for the metals. The transition structures were first located by a scan of the surface using a pertinent internal coordinate and then by the quadratic synchronous transit method (QST). The frequencies were checked, and the visualization of the mode with a negative eigenvalue clearly corresponds to the expected atomic displacements. DFT calculations were performed using HPC resources from DSI-CCUB (Université de Bourgogne).

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ASSOCIATED CONTENT

S Supporting Information *

Spectroscopic data, estimation of thermodynamic data, geometries of DFT molecular structures, and CIF files. 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]. Fax: +33-380396098.

ACKNOWLEDGMENTS We thank the Conseil Régional de Bourgogne (PARI IME SMT08 program), the Ministère de l’Enseignement Supérieur et de la Recherche, and the Centre National de la Recherche Scientifique (CNRS, CP2D program “Chimie et Procédés pour le Développement Durable″) for financial support. We thank Miss Marie-José Penouilh and Dr. Fanny Chaux for mass spectrometry analyses.

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DEDICATION Dedicated to Doctor Christian Bruneau on the occasion of his 60th birthday. †

REFERENCES

(1) For examples of P-olefin ligands, see: (a) Moret, S.; Dallanegra, R.; Chaplin, A. B.; Douglas, T. M.; Hiney, R. M.; Weller, A. S. Inorg. Chim. Acta 2010, 363, 574−580. (b) Kaddouri, H.; Vicente, V.; Ouali, A.; Ouazzani, F.; Taillefer, M. Angew. Chem., Int. Ed. 2009, 48, 333− 336. (c) Lewis, J. C.; Berman, A. M.; Bergman, R. G.; Ellman, J. A. J. Am. Chem. Soc. 2008, 130, 2493−2500. (d) Douglas, T. M.; Notre, J. L.; Brayshaw, S. K.; Frost, C. G.; Weller, A. S. Chem. Commun. 2006, 3408−3410. (e) Mora, G.; Van Zutphen, S.; Thoumazet, C.; Le Goff, X. F.; Ricard, L.; Grützmacher, H.; Le Floch, P. Organometallics 2006, 25, 5528−5532. (f) Bassetti, M.; Alvarez, P.; Gimeno, J.; Lastra, E. Organometallics 2004, 23, 5127−5134. (g) Yin, J.; Rainka, M. P.; Zhang, X.-X.; Buchwald, S. L. J. Am. Chem. Soc. 2002, 124, 1162−1163. (h) Barthel-Rosa, L. P.; Maitra, K.; Nelson, J. H. Inorg. Chem. 1998, 37,

957


Organometallics

Article

633−639. (i) Christ, M. L.; Sabo-Etienne, S.; Chaudret, B. Organometallics 1995, 14, 1082−1084. (j) Wermer, P. H.; Dobson, C. B.; Dobson, G. R. J. Organomet. Chem. 1986, 311, C47−C50. (k) Clark, P. W.; Curtis, J. L. S.; Garrou, P. E.; Hartwell, G. E. Can. J. Chem. 1974, 52, 1714−1719. (l) Interrante, L. V.; Bennett, M. A.; Nyholm, R. S. Inorg. Chem. 1966, 5, 2212−2217. (2) For examples of chiral P-olefin ligands, see: (a) Shintani, R.; Narui, R.; Tsutsumi, Y.; Hayashi, S.; Hayashi, T. Chem. Commun. 2011, 47, 6123−6125. (b) Cao, Z.; Liu, Y.; Liu, Z.; Feng, X.; Zhuang, M.; Du, H. Org. Lett. 2011, 13, 2164−2167. (c) Drinkel, E.; Briceño, A.; Dorta, R.; Dorta, R. Organometallics 2010, 29, 2503−2514. (d) Grugel, H.; Minuth, T.; Boysen, M. M. K. Synthesis 2010, 3248− 3258. (e) Liu, Z.; Du, H. Org. Lett. 2010, 12, 3054−3057. (f) Minuth, T.; Boysen, M. M. K. Org. Lett. 2009, 11, 4212−4215. (g) Štěpnička, P.; Lamac, M.; Císarová, I. J. Organomet. Chem. 2008, 693, 446−456. (h) Pregosin, P. S. Chem. Commun. 2008, 4875−4884. (i) Mariz, R.; Briceño, A.; Dorta, R.; Dorta, R. Organometallics 2008, 27, 6605− 6613. (j) Duan, W.-L.; Iwamura, H.; Shintani, R.; Hayashi, T. J. Am. Chem. Soc. 2007, 129, 2130−2138. (k) Defieber, C.; Ariger, M. A.; Moriel, P.; Carreira, E. M. Angew. Chem., Int. Ed. 2007, 46, 3139−3143. (l) Stemmler, R. T.; Bolm, C. Synlett 2007, 1365−1370. (m) Piras, E.; Läng, F.; Rüegger, H.; Stein, D.; Wörle, M.; Grützmacher, H. Chem. Eur. J. 2006, 12, 5849−5858. (n) Kasák, P.; Arion, V. B.; Widhalm, M. Tetrahedron: Asymmetry 2006, 17, 3084−3090. (o) Shintani, R.; Duan, W.-L.; Nagano, T.; Okada, A.; Hayashi, T. Angew. Chem., Int. Ed. 2005, 44, 4611−4614. (3) Johnson, J. B.; Rovis, T. Angew. Chem., Int. Ed. 2008, 47, 840− 871. (4) For a general review on hemilability, see: Braunstein, P.; Naud, F. Angew. Chem., Int. Ed. 2001, 40, 680−699. (5) Defieber, C.; Grützmacher, H.; Carreira, E. M. Angew. Chem., Int. Ed. 2008, 47, 4482−4502. (6) (a) Herberhold, M.; Schmalz, T.; Milius, W.; Wrackmeyer, B. Inorg. Chim. Acta 2003, 352, 51−60. (b) Herberhold, M.; Schmalz, T.; Milius, W.; Wrackmeyer, B. Inorg. Chim. Acta 2002, 334, 10−16. (c) Herberhold, M.; Schmalz, T.; Milius, W.; Wrackmeyer, B. J. Organomet. Chem. 2002, 641, 173−184. (d) Herberhold, M.; Schmalz, T.; Milius, W.; Wrackmeyer, B. Z. Anorg. Allg. Chem. 2002, 628, 437−445. (e) Herberhold, M.; Bauer, K.; Milius, W. J. Organomet. Chem. 1997, 545−546, 267−275. (7) (a) Fischbach, U.; Rüegger, H.; Grützmacher, H. Eur. J. Inorg. Chem. 2007, 2654−2667. (b) Thoumazet, C.; Ricard, L.; Grutzmacher, H.; Le Floch, P. Chem. Commun. 2005, 1592−1594. (c) Maire, P.; Deblon, S.; Breher, F.; Geier, J.; Böhler, C.; Rüegger, H.; Schönberg, H.; Grützmacher, H. Chem.Eur. J. 2004, 10, 4198−4205. (d) Mlakar, M.; Boulmaâz, S.; Schönberg, H.; Grützmacher, H. Electroanalysis 2003, 15, 1043−1053. (e) Deblon, S.; Liesum, L.; Harmer, J.; Schönberg, H.; Schweiger, A.; Grützmacher, H. Chem.Eur. J. 2002, 8, 601−611. (f) Deblon, S.; Ruegger, H.; Schonberg, H.; Loss, S.; Gramlich, V.; Grutzmacher, H. New J. Chem. 2001, 25, 83−92. (g) Thomaier, J.; Boulmaaz, S.; Schonberg, H.; Ruegger, H.; Currao, A.; Grutzmacher, H.; Hillebrecht, H.; Pritzkow, H. New J. Chem. 1998, 22, 947−958. (h) Boulmaaz, S.; Loss, S.; Schonberg, H.; Deblon, S.; Worle, M.; Nesper, R.; Grutzmacher, H.; Mlakar, M. Chem. Commun. 1998, 2623−2624. (8) Perrier, A.; Comte, V.; Moïse, C.; Richard, P.; Le Gendre, P. Eur. J. Org. Chem. 2010, 1562−1568. (9) The value of the coupling constant 1JP−Pt depends on the nature of the other ligands coordinated to the Pt center and notably on the nature of the ligand trans to the P atom. 1JP−Pt > 3000 Hz values are generally observed for trans-[P-PtXY-Cl] complexes, whereas lower coupling constants (1JP−Pt < 3000 Hz) are reported for trans-[P-PtXY-P] and trans[P-PtXY-olefin] complexes; see, for example: (a) Rigamonti, L.; Forni, A.; Manassero, M.; Manassero, C.; Pasini, A. Inorg. Chem. 2010, 49, 123−135. (b) Roger, J.; Mom, S.; Beaupérin, M.; Royer, S.; Meunier, P.; Ivanov, V. V.; Doucet, H.; Hierso, J.-C. ChemCatChem 2010, 2, 296− 305. (c) Feducia, J. A.; Gagné, M. R. J. Am. Chem. Soc. 2008, 130, 592−599.

(10) Khairul, W. M.; Fox, M. A.; Zaitseva, N. N.; Gaudio, M.; Yufit, D. S.; Skelton, B. W.; White, A. H.; Howard, J. A. K.; Bruce, M. I.; Low, P. J. Dalton Trans. 2009, 610−620. (11) (a) Grabulosa, A.; Muller, G.; Ordinas, J. I.; Mezzetti, A.; Maestro, M. Á .; Font-Bardia, M.; Solans, X. Organometallics 2005, 24, 4961−4973. (b) Godleski, S. A.; Gundlach, K. B.; Ho, H. Y. Organometallics 1984, 3, 21−28. (12) Wrackmeyer, B.; Ullmann, B.; Kempe, R.; Herberhold, M. Z. Anorg. Allg. Chem. 2005, 631, 2629−2634. (13) Despite our efforts, we were not able to get satisfactory computer simulated spectra and thus to determine the thermodynamic values from a Eyring plot. (14) The expanded (k = 2) uncertainties on ΔG⧧ are computed by propagation of estimated uncertainties on temperatures and frequencies. (15) For T-shaped Pd complexes,see: Stambuli, J. P.; Incarvito, C. D.; Bühl, M.; Hartwig, J. F. J. Am. Chem. Soc. 2004, 126, 1184−1194. (16) According to theoretical calculations, bond strengths for the square-planar group X ethylene complexes are found to be Ni(II) < Pd(II) < Pt(II): Strömberg, S.; Svensson, M.; Zetterberg, K. Organometallics 1997, 16, 3165−3168. (17) Forniés, J.; Martín, A.; Martín, L. F.; Menjón, B. Organometallics 2005, 24, 3539−3546. (18) Similar fluxional properties have been described by Wrackmeyer and Herberhold for related tri(tropylidenyl)phosphine palladium complexes. In their case, they also favored a concerted exchange of the cycloheptatrienyl rings over a dissociative mechanism; see refs 6a and 6c. (19) Nyholm, R. S. Pure Appl. Chem. 1971, 27, 127−144. (20) The reaction of (2,4,6-cycloheptatrienyl)phosphine with M(CO)3L3 gives {(η4-norcaradiene)P(C7H7)2-κP}M(CO)3 complexes (M = Cr, Mo, W): Herberhold, M.; Bauer, K.; Milius, W. J. Organomet. Chem. 1997, 545−546, 267−276. (21) Orpen, A. G.; Brammer, L.; Allen, F. H.; Kennard, O.; Watson, D. G.; Taylor, R. J. Chem. Soc., Dalton Trans. 1989, S1−S89. (22) The 95% level uncertainty is estimated from the least-squares fit for 7 degrees of freedom. (23) The parent tropylidenyldiphenylphosphine allowed the synthesis of stable rhodium(0) and rhodium(−1) complexes; see refs 7e and 7f. (24) Bauer, A.; Englert, U.; Geyser, S.; Podewils, F.; Salzer, A. Organometallics 2000, 19, 5471−5476. (25) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A. J. Appl. Crystallogr. 1993, 26, 343−350. (26) Sheldrick, G. M. SHELXL-97; Institüt für Anorganische Chemie der Universität: Göttingen, Germany, 1998. (27) Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837−838. (28) Jaguar 5.5; Schrodinger, LLC: Portland, OR, 2003.

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