Article pubs.acs.org/Organometallics
Light-Driven Methyl Exchange Reactions in Square-Planar Palladium(II) and Platinum(II) Complexes Allan R. Petersen, Russell A. Taylor, Inmaculada Vicente-Hernández, Jasmin Heinzer, Andrew J. P. White, and George J. P. Britovsek* Department of Chemistry, Imperial College London, Exhibition Road, London SW7 2AZ, U.K. S Supporting Information *
ABSTRACT: Square-planar palladium(II) and platinum(II) methyl complexes with terpyridine and 6,6″-diamino terpyridine ligands undergo methyl exchange reactions upon exposure to light. The halflife of the methyl exchange reactions correlates with the relative Pd−C and Pt−C bond strengths. No exchange between methyl and phenyl groups is observed, probably due to the stronger Pt−C bond in the platinum phenyl complex. A mechanism is proposed whereby a dinuclear intermediate is generated upon irradiation that has a weakened M−C bond in the excited state, resulting in the observed methyl exchange reactions.
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INTRODUCTION The exchange of alkyl groups between organometallic complexes is a fundamental process in organometallic reactivity. The strength of the transition-metal−carbon bond can vary considerably and depends on the metal, the oxidation state, and the alkyl group to some degree.1−3 The self-exchange of alkyl groups is common in dialkyl zinc reagents,4,5 but alkyl exchange can also occur between two different metals: for example, the chain transfer to aluminum reaction between zirconium and aluminum, resulting in chain growth termination in olefin polymerization catalysis.6 Cross-coupling reactions, catalyzed by late transition metals, involve transmetalation of carbonbased ligands between palladium and other metals such as tin and copper.7 We have shown that catalyzed chain growth can occur on zinc, which involves extremely rapid reversible alkyl exchange between two metals such as iron and zinc.8−10 In a different context, methyl exchange reactions between palladium centers have been investigated as a potential pathway for methane homologation to ethane.11 Alkyl exchange reactions between late-transition-metal complexes have been known since the 1970s. Initially, methyl for halogen exchange reactions were observed for palladium(II), platinum(II), gold(I), and gold(III) complexes, whereby a dinuclear methyl- and chloro-bridged intermediate of type A was proposed (see Figure 1).12−15 Methyl scrambling was reported between [Pd(CH 3 ) 2 (PMePh 2 ) 2 ] and [Pd(CD3)2(PMePh2)2], and a methyl-bridged dinuclear species of type B, formed upon dissociation of one of the phosphane ligands, was proposed as an intermediate in these scrambling reactions.16 Exchange of aryl groups in palladium(II) complexes was reported to occur with retention of configuration, and a dinuclear intermediate of type C was proposed.17 Methyl transfer reactions between mononuclear Pt(II) and Pt(IV) complexes have been known for some time, but these reactions are generally slow.13,18−21 For example, alkyl exchange occurs between cis-[Pt(CD3)2(PMe2Ph)2] and [Pt© 2014 American Chemical Society
Figure 1. Proposed intermediates for exchange reactions between square-planar complexes.
(NO3)2(CH3)2(PMe2Ph)2] and in this case either a binuclear intermediate of type A or an intermediate featuring a Pt−Pt bond was proposed.18 Methyl-for-ethyl exchange reactions were reported in oxidative addition studies of ethyl iodide with [Pt(CH3)2(bipy)].22 Recently, related d8−d10 transmetalations between Pt−Cu and Pt−Au systems have been reported and a methyl-bridged Pt−Cu complex could be isolated.23,24 Puddephatt and co-workers reported that [Pt(CH3)2(bipy)] undergoes rapid methyl exchange with [Pt(CD3)2(bipy)] and that this reaction is catalyzed by the oxidant AgBF4.25 In 2009, methyl scrambling was observed between [Pt(CH3)2(bipy)] and [Pt(CD3)2(bipy)] in the presence of CuOTf, but surprisingly not with AgOTf.26 A mechanism whereby a oneelectron oxidation results in small amounts of a Pt(III) intermediate that disproportionates to give a Pt(IV) trimethyl and a Pt(II) monomethyl complex was proposed.27 The Pt(IV) complex subsequently exchanges methyl groups with the starting complex.18 In a recent report, oxidation of a dinuclear Pd(II) methyl complex resulted in a dinuclear Pd(III) methyl Received: January 16, 2014 Published: March 13, 2014 1453
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Figure 2. Chemical shift versus 1/T for the methyl signal in [Pt(CH3)(1)](SbF6) in CD3CN over the temperature range from 233 to 343 K.
the linear relationship of δ ∝ T reported previously for [Pt(CH3)(terpy)]Cl in D2O (10 mM), which was observed within the temperature range 295−335 K and which may have been too narrow to observe the nonlinear behavior seen here.40 The 195Pt satellites broaden at lower temperatures due to chemical shift anisotropy. Furthermore, the NH2 protons are observed as a single broad resonance at room temperature but as two distinct peaks for the exo and endo protons at temperatures below 253 K. Restricted rotation around the C−N bond leads to coalescence at 263 K, and an activation barrier of ΔG⧧ ≈ 12 kcal/mol was calculated for this process. The 195Pt NMR resonance for [Pt(CH3)(1)](SbF6) was observed at −2600 ppm, significantly lower than for [Pt(CH3)(terpy)](SbF6), which was observed at −3230 ppm (cf. −3200 ppm for [Pt(CH3)(terpy)](BPh4)),41 but still within the range of −2500 and −3200 ppm typically seen for terpyridine Pt(II) complexes.42 The labeled complex [Pt(CD3)(1)](SbF6) was prepared from [PtI(CD3)(SMe2)2], which was obtained directly from cis-/trans-[PtCl2(SMe2)2] with CD3Li·LiI in diethyl ether. The 2H NMR spectrum in acetone shows a CD3 signal at 1.29 ppm as a broad signal with unresolved 195Pt satellites. The solid-state structure of [Pt(CH3)(1)](SbF6) shows a distorted-square-planar coordination geometry (see Figure 3). The steric interactions of the amino substituents with the Pt− Me group lead to a significant distortion of the square plane, with the methyl carbon lying ca. 0.53 Å out of the N3Pt plane. This distortion is also seen in the N1−Pt−Me angle, which at 167.31(14)° is significantly bent compared to the analogous angle of 179.0(3)° in [Pt(CH3)(terpy)](BPh4).41 The Pt−Me distance is also affected by this repulsion, measuring 2.070(4) Å for [Pt(CH3)(1)](SbF6), which is slightly longer than for [Pt(CH3)(terpy)](BPh4) (2.039(6) Å). The cations in [Pt(CH3)(1)](SbF6) pack in a head-to-tail fashion across two independent centers of symmetry to form an extended stack along the crystallographic a axis direction (see Figure 4). The central N(1) pyridyl ring in one cation overlays the outer N(8)based ring in the next cation across one center of symmetry (centroid···centroid and mean interplanar separations of ca. 3.98 and 3.33 Å, rings inclined by ca. 2°, interaction a in Figure 4), while also overlaying the outer N(15)-based ring in another cation across the other center of symmetry (centroid···centroid and mean interplanar separations of ca. 3.71 and 3.38 Å, rings inclined by ca. 6°, interaction b). The interaction across the first center of symmetry is supplemented by a further contact between the N(8)-based ring in the first cation and the N(15) ring in the Ci-related counterpart (centroid···centroid and mean
complex, which was followed by methyl exchange to give a Pd(II) and a Pd(IV) dimethyl complex.28 In some cases where alkyl exchange reactions have been observed, indications (often as footnotes) regarding the influence of light on alkyl scrambling reactions have been reported: for example, Mayer, Sanford, and co-workers reported that methyl scrambling occurs between [Pd(CH 3 ) 2 ( t Bu 2 bipy )] and [Pd(CD3)2(tBu2bipy)] in the presence of light.29 During our investigations on bipy and terpy platinum and palladium complexes,30−32 we discovered that certain terpy methyl complexes undergo alkyl exchange reactions upon exposure to light. The interaction of light with Pd(II) and Pt(II) terpyridine complexes and their luminescent properties have been known for some time,33−35 and the photochemistry and photophysics of these complexes have received considerable interest in recent years.36−38 However, to the best of our knowledge, the light-driven exchange of alkyl ligands with these types of complexes has not been studied. Here we show that, upon exposure to sunlight or UV light, methyl exchange reactions readily occur between different terpyridine Pt(II) complexes and also between Pt(II) and Pd(II) methyl complexes. A mechanism for the methyl exchange reactions is proposed, which takes into account the previously reported observations and the influence of light seen here and which may be more general for light-driven ligand exchange reactions in square-planar metal complexes.
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RESULTS AND DISCUSSION The complex [Pt(CH3)(1)](SbF6) (see Figure 2) was prepared by combining the ligand 6,6′-diaminoterpyridine (1) with [PtCl(CH3)(SMe2)2] and AgSbF6.32 The 1H NMR spectrum shows the methyl signal at δ 1.45 ppm (2JH−Pt = 72 Hz) in d6acetone at 298 K and at 1.37 ppm (2JH−Pt = 70 Hz) in d3acetonitrile at 298 K. These chemical shift values are highly concentration and temperature dependent due to aggregation of the complexes in solution (vide infra). The VT-1H NMR analysis of [Pt(CH3)(1)](SbF6) in CD3CN (14 mM) is shown in Figure S5 (Supporting Information). A change in chemical shift of the Pt−CH3 signal from 1.03 to 1.54 ppm is observed over the temperature range from 233 to 343 K (effectively a concentration range from 15.4 to 13.2 mM due to the change in density)39 with a negative inversely proportional relationship between the chemical shift and temperature: δ ∝ −1/T (R2 = 0.999, see Figure 2 and also Figures S6 and S7 (Supporting Information)). Thus, at lower temperature, the chemical shift decreases due to increased shielding, probably as a result of aggregation of the complexes in solution. This contrasts with 1454
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Figure 5. Structure of the cation present in the crystal of [Pt(C6H5)(1)](SbF6) (50% probability ellipsoids). Selected bond lengths (Å) and angles (deg): Pt−N(1) 2.010(3), Pt−N(15) 2.083(3), Pt−N(8) 2.082(3), Pt−C(21) 2.043(4); N(1)−Pt−N(8) 79.33(13), N(8)−Pt−N(15) 159.27(13), N(1)−Pt−N(15) 79.94(13), C(21)− Pt−N(8) 100.12(14), N(1)−Pt−C(21) 178.56(14), C(21)−Pt− N(15) 100.60(14).
Figure 3. Structure of the cation present in the crystal of [Pt(CH3)(1)](SbF6) (50% probability ellipsoids). Selected bond lengths (Å) and angles (deg): Pt−N(1) 1.991(3), Pt−N(15) 2.048(3), Pt−N(8) 2.059(3), Pt−C(21) 2.070(4); N(1)−Pt−N(8) 79.96(12), N(8)−Pt−N(15) 159.25(12), N(1)−Pt−N(15) 79.60(13), N(8)−Pt−C(21) 101.64(15), N(1)−Pt−C(21) 167.31(14), N(15)−Pt−C(21) 99.08(15).
out of the N3Pt plane and a pyrN−Pt−C(Ph) angle of 178.55(14)°. As a result, the phenyl ring is orientated approximately orthogonally (ca. 81°) to the coordination plane, similar to that seen in related terpyridine platinum phenyl complexes.43,44 Also in this case, in the solid state the cations of [Pt(C6H5)(1)](SbF6) pack in a head-to-tail fashion via π···π interactions across two independent centers of symmetry to form an extended stack of cations along the crystallographic a axis direction (see Figure 6). The central N(1)-based pyridine ring in one cation links to the outer N(8) ring in a Ci-related counterpart (centroid···centroid and mean interplanar separations of ca. 3.63 and 3.32 Å, rings inclined by ca. 3°, interaction a in Figure 6), and also to the outer N(15) ring in another cation across the other center of symmetry (centroid···centroid
Figure 4. Stacking arrangement in the solid state observed for complex [Pt(CH3)(1)](SbF6). The π···π interactions have the following respective centroid···centroid and mean interplanar separations (Å): (a) 3.98, 3.33; (b) 3.71, 3.38; (c) 3.94, 3.38. The shortest Pt···Pt distance is 4.91 Å.
interplanar separations of ca. 3.94 and 3.38 Å, rings inclined by ca. 7°, interaction c). Attempts to prepare the phenyl complex [Pt(C6H5)(1)]Cl from [Pt(C 6 H 5 )Cl(1,5-COD)] and 1 in DCM were unsuccessful, and only starting materials were recovered. [Pt(C6H5)(1)]Cl can be synthesized by reacting equimolar amounts of trans-[Pt(C6H5)Cl(SMe2)2] and 1 in DCM. [Pt(C6H5)(1)](SbF6) was prepared by a metathesis reaction of [Pt(C6H5)(1)]Cl and AgSbF6 in MeOH (see Figures S3a and S3b, Supporting Information). Unlike [Pt(CH3)(1)](SbF6), in [Pt(C6H5)(1)](SbF6) (Figure 5) the N3PtC plane is essentially flat, the ipso carbon C(21) lying only ca. 0.05 Å
Figure 6. Stacking arrangement in the solid state for [Pt(C6H5)(1)](SbF6). The π···π stacking interactions have the following respective centroid···centroid and mean interplanar separations (Å): (a) 3.63, 3.32; (b) 3.54, 3.44. The shortest Pt···Pt distance is 5.73 Å. 1455
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and mean interplanar separations of ca. 3.54 and 3.44 Å, rings inclined by ca. 3°, interaction b). The exchange of the chloride anion of complex [Pd(CH3)(1)]Cl, prepared from [PdCl(CH3)(1,5-COD)] and 1, for SbF6− gave repeatedly impure products, and an alternative route was developed, inspired by previous work on [Pt(CH3)(1,5-COD)((CH3)2CO)](PF6).45,46 [PdCl(CH3)(1,5-COD)] was reacted with AgSbF6 in acetone to give a solution of [Pd(CH3)(1,5-COD)((CH3)2CO)](SbF6), followed by addition of 1 to give [Pd(CH3)(1)](SbF6) cleanly. The reaction times were kept short (15 min), as [Pd(CH3)(1,5-COD)((CH3)2CO)](SbF6) can be unstable in solution. It is worth noting that the 1H NMR signals for the three hydrogens of the central pyridine ring combine into one singlet at 8.30 ppm (see Figure S4, Supporting Information). UV−Vis Spectroscopy. The UV/vis spectra of [Pt(CH3)(1)](SbF6) and [Pt(C6H5)(1)](SbF6) in acetonitrile (Figure 7)
Figure 8. UV/vis spectra of [Pd(CH3)(1)](SbF6) (orange) and [Pd(CH3)(terpy)](SbF6) (yellow) in CH3CN at 298 K.
Figure 7. UV/vis spectra of [Pt(CH3)(1)](SbF6) (red) and [Pt(C6H5)(1)](SbF6) (blue) in CH3CN at 298 K.
are rather similar, because they are dominated by the charge transfer bands due to the 6,6′-diaminoterpy ligand, resulting in strong absorptions (ε ≈ 7000−10000 M−1cm−1) in the 350− 450 nm region. The spectra are complicated due to multiple transitions in this region, notably IL (π → π*) and MLCT (dz2 → pz for monomeric or dσ*→pσ for dimeric complexes; vide infra).47 It is worth noting that the spectra in Figure 7 are distinctly different from that for the nonsubstituted terpyridine complex [Pt(CH3)(terpy)](SbF6), where the absorptions in the 350−450 nm region are much less intense (ε ≈ 1000 M−1 cm−1).32 A similar observation is made for palladium, where strong absorptions are seen in the 350−450 nm region for [Pd(CH3)(1)](SbF6), which are absent for the nonsubstituted complex [Pd(CH3)(terpy)](SbF6) (see Figure 8). Methyl Exchange Reactions. A mixture of equimolar amounts of [Pt(CD3)(1)](SbF6) and [Pt(CH3)(terpy)](SbF6) in CD3CN was exposed to UV irradiation (365 nm, 100 W) at room temperature in 5 min intervals. The exchange reaction shown in eq 1 was monitored by 1H NMR spectroscopy, and the ratio versus time plot in Figure 9 shows the decay of [Pt(CH3)(terpy)](SbF6) and the increase of [Pt(CH3)(1)](SbF6). The half-life for this methyl exchange under these conditions was approximately 17 min. It should be noted that, in the absence of light, no methyl exchange reaction is observed. In another experiment, a mixture of the two complexes [Pt(CD3)(1)](SbF6) and [Pd(CH3)(1)](SbF6) in an approximately 1:1 ratio in CD3CN was exposed to UV light (365 nm,
Figure 9. Methyl exchange between [Pt(CD3)(1)](SbF6) and [Pt(CH3)(terpy)](SbF6) upon exposure to UV light at 5 min intervals (see eq 1). The ratios between [Pt(CH3)(1)](SbF6) and [Pt(CH3)(terpy)](SbF6) have been determined by 1H NMR spectroscopy.
100 W), and the exchange reaction as shown in eq 2 was monitored by 1H NMR spectroscopy (see Figures S8 and S9, Supporting Information). The half-life of the methyl exchange reaction was determined as 11 min under these conditions, 1456
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significantly faster than the exchange between the two platinum complexes in eq 1. Pt−C bonds are approximately 8 kcal/mol stronger than Pd−C bonds,21,48 and the faster exchange process in eq 2 is most likely a result of the weaker Pd−C bond in this case. Furthermore, in eq 1, the Pt−C bond in [Pt(CH3)(terpy)](SbF6) is likely to be stronger due to the absence of amino substituents. The reaction can also be followed by 2H NMR spectroscopy. For example, a solution of [Pt(CD3)(1)](SbF6) in normal acetone shows a signal at 1.29 ppm for [Pt(CD3)(1)](SbF6) and another signal at 0.70 ppm slowly appears for the [Pd(CD3)(1)](SbF6) complex upon irradiation by sunlight (see Figure 10). No methyl−phenyl exchange reaction was observed between the phenyl complex [Pt(C6H5)(1)](SbF6) and [Pt(CH3)(terpy)](SbF6) or [Pd(CH3)(1)](SbF6) after irradiation (365 nm, 100 W) at room temperature for up to 190 min. The Pt−C bond strength for platinum(II) phenyl complexes is approximately 50 kcal/mol, whereas the BDE for a platinum(II)− methyl bond is significantly smaller: approximately 36 kcal/mol and about 8 kcal/mol less for a palladium(II)−methyl bond.21,48−50 In [Pt(CH3)(1)](SbF6), the steric hindrance caused by the NH2 substituents weakens the Pt−C bond, as can be seen from the Npyr−Pt−C angles, which are 178.55(14) and 167.31(14)° for complexes [Pt(C6H5)(1)](SbF6) and [Pt(CH3)(1)](SbF6), respectively. We therefore propose that exchange of the phenyl ligand is inhibited due to the stronger Pt−C bond in this case, although a possible influence of steric factors cannot be excluded at this stage. Proposed Mechanism for the Methyl Exchange Processes. Square-planar palladium(II) and platinum(II) complexes, as well as other d8 metal complexes, are wellknown to form weakly associated dimers or extended aggregates in the solid state and in solution, due to a combination of attractive M···M and π···π interactions.28,47,51−54 These interactions have also been observed in terpyridine palladium(II) and platinum(II) complexes.35,40−42,55−57 For example, π···π interactions are seen in the solid-state structures of complexes [Pt(CH3)(1)](SbF6) and [Pt(C6H5)(1)](SbF6) (see Figures 4 and 6), whereas a
Figure 10. 2H NMR spectra of a mixture of [Pt(CD3)(1)](SbF6) and [Pd(CH3)(1)](SbF6) in acetone (denoted s), before (top) and after (bottom) exposure to sunlight.
Pt···Pt interaction was observed in [Pt(OOCH3)(1)]SbF6 (Pt···Pt separation 3.20 Å).32 Electronic excitation of the dimeric, loosely associated [M··· M] complexes results in the formation of excited dinuclear triplet state complexes 3[M−M]*.52,53,58 The excitation of these complexes is akin to the formal removal of electrons from the HOMO by electrochemical methods, which is known to result in a stepwise oxidation from M(II)···M(II) to M(III)− M(III) complexes for palladium(II) and platinum(II)28,54,59 or from M(I)···M(I) to M(II)−M(II) complexes in the case of rhodium and iridium.60 The result in each case is an oxidized dinuclear complex with a strong metal−metal bond. In addition to the charge transfer excited states, d−d excited states may be thermally accessible from these excited states.57,61 The presence of an accessible d−d excited state results in population of the strongly antibonding dx2−y2 orbital, which will cause a weakening of the metal−ligand bonds in the excited state, including the metal−carbon bond. This destabilization of the complex would explain the facile methyl exchange reaction between the terpyridine palladium(II) and platinum(II) complexes seen here upon exposure to UV light. Taking all these observations together, we propose the following mechanism for the light-driven alkyl exchange reactions in square-planar terpyridine palladium(II) and platinum(II) complexes, depicted for the exchange reaction between [Pt(CD3)(1)](SbF6) and [Pd(CH3)(1)](SbF6) in Scheme 1. Exposure of the dimeric, loosely associated [M···M] terpyridine complexes to UV light results in excited dinuclear triplet state complexes 3[M−M]* with a metal−metal bond. The d−d excited state results in a weakening of the metal− ligand bonding due to occupation of the antibonding dx2−y2 orbital, which facilitates the intramolecular methyl exchange reaction, before the complex relaxes back to the ground state. Radiative decay of the excited triplet state resulting in 1457
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Square-planar palladium and platinum complexes aggregate in the solid state and in solution, and irradiation results in an excited triplet state with a M−M bond. A mechanism is proposed whereby a weakening of the M−C bond due to the occupation of the antibonding dx2−y2 orbital in the excited state is believed to be responsible for the observed methyl exchange reactions in these complexes. Further investigations are underway to establish the scope of these alkyl exchange reactions for other alkyl substituents and for different metal complexes.
Scheme 1. Proposed Mechanism for the Light-Driven Methyl Exchange Reaction between Square-Planar Palladium(II) and Platinum(II) Complexes
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EXPERIMENTAL SECTION
All moisture- and dioxygen-sensitive compounds were prepared using standard vacuum line, Schlenk, or cannula techniques. A standard nitrogen-filled glovebox was used for any subsequent manipulation and storage of these compounds. NMR spectra were recorded using Bruker DRX 400 MHz, AV 400 MHz, and AV 500 MHz spectrometers. The 1 H NMR and 13C NMR chemical shifts were referenced to the residual protio impurity and 13C signal of the deuterated solvent, respectively. The 2H NMR chemical shifts were referenced to the residual deuterio impurity of the protonated solvent. The 19F NMR chemical shifts were referenced to CFCl3. 195Pt chemical shifts were determined by 1 H/195Pt HMBC spectroscopy and referenced to K2PtCl6 in D2O. J values are given in Hz. Mass spectra were recorded using either a Micromass AutoSpec Premier spectrometer or a Waters LCT Premier spectrometer. Elemental analyses were carried out by the Science and Technical Support Unit at London Metropolitan University. UV/vis spectra were recorded using a Perkin-Elmer Lambda 20 spectrometer. All spectra were recorded at 298 K unless otherwise stated. Solvents and Reagents. Diethyl ether and THF were dried by prolonged reflux, under a nitrogen atmosphere, over sodium metal with a benzophenone ketyl indicator and distilled freshly prior to use. DCM and acetonitrile were treated in a similar manner, but using calcium hydride as the drying agent. Toluene and pentane were dried by passing through a column, packed with commercially available Q-5 reagent (13% CuO on alumina) and activated alumina (pellets, 3 mm), under a stream of nitrogen. Acetone was dried over B2O3 and distilled under nitrogen.70 All solvents were thoroughly deoxygenated before use. The following compounds were prepared according to literature procedures: [Pt(C6H5)Cl(1,5-COD)],71 [Pt(CH3)(1)]Cl and [Pt(CH3)(terpy)](SbF6),32 [PdCl(CH3)(1,5-COD)],72 trans-[PtCl(CH3)(SMe2)2],73 and cis/trans-[PtCl2(SMe2)2],.73,74 All other chemicals were obtained commercially and used as received. trans-[Pt(C6H5)Cl(SMe2)2]. SMe2 (0.9 mL, 12.25 mmol) was added to a stirred suspension of [Pt(C6H5)Cl(1,5-COD)] (0.074 g, 0.18 mmol) in dry methanol (10 mL). The resulting colorless solution was stirred overnight. The solution was then reduced to a minimum volume and the residue redissolved in dry methanol (10 mL) before it was again reduced in volume. The off-white product was dried in vacuo. Yield: 0.049 g (63%). The analytical data were consistent with previously reported data.75−77 1H NMR (400 MHz, CDCl3): δ 7.32 (dd, 3JPtH = 22.2, J = 1.1, 8.0, 2H, o-C6H5), 6.99 (t, J = 7.2, 2H, mC6H5), 6.92 (t, J = 7.2, 1H, p-C6H5), 2.34 (s, +d, 3JPtH = 57.1, 12H, SMe2). trans-[PtI(CD3)(SMe2)2]. Methyl-d3-lithium solution (1.92 mL, 0.96 mmol, 0.5 M CD3Li·LiI in diethyl ether) was added dropwise to a suspension of cis-/trans-[PtCl2(SMe2)2] (0.150 g, 0.38 mmol) in dry diethyl ether (20 mL) at 0 °C. The suspension was stirred for 15 min before saturated NH4Cl(aq) (5 mL) was added followed by deionized water (10 mL). The two phases were separated, and the organic phase was washed with distilled water (2 × 10 mL). The combined aqueous phase was washed with diethyl ether (2 × 10 mL). The combined organic phase was dried over MgSO4, filtered, and reduced to a minimum volume, yielding a brown solid. Yield: 0.139 g (78%). 1H NMR (500 MHz, CDCl3): δ 2.62 (s, +d, 3JPtH = 55.2, 12H, SMe2). 2H NMR (61 MHz, CHCl3): δ 0.69 (s, +d, 2JPtD = 11.4, PtCD3). 13C[1H] NMR (125 MHz, CDCl3): δ 25.0 (s, +d, 2JPtC = 16.7, SMe2). MS
luminescence is also possible and has indeed been observed for terpyridine Pt(II) methyl and phenyl complexes43,55 and also for complex [Pt(CH3)(1)](SbF6).32 The proposed mechanism resembles the dinuclear mechanism proposed in several recent studies which involve the use of chemical oxidants with squareplanar metal complexes, for example using Cl2,62 PhICl2, PhI(OAc) 2 , 63 (PhIAr)(BF 4 ), 64 PhI(CCSiMe 3 )(OTf), 65 RSSR,66 and (C6H4CMe2O)ICF3,67 and on several occasions dinuclear M(III)−M(III) intermediates have been isolated and structurally characterized.63,65,68,69 The difference here is that formal oxidation to the dinuclear M(III)−M(III) intermediate is light-driven, rather than induced by a chemical oxidant. The methyl exchange reactions seen here between squareplanar d8 metal complexes are probably related to the transmetalation reactions between d8 and d10 metal complexes reported in recent years.23,24 No light is required in the latter case, as metal−metal bonding occurs readily in the ground state between the d8 metal complex and the electrophilic d10 metal complex. A bimetallic methyl-bridged Pt(II)−Cu(I) intermediate has been isolated, which supports the formulation of a dimethyl-bridged intermediate as proposed in Scheme 1,23 although a stepwise methyl transfer via a [Me2M−M] intermediate cannot be excluded at this stage.
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CONCLUSIONS In the present study, we have prepared a series of palladium(II) and platinum(II) methyl and phenyl complexes containing terpyridine and 6,6′-diaminoterpyridine ligands. A systematic investigation into the methyl exchange reactions in these square-planar platinum(II) and palladium(II) methyl complexes has been carried out. The methyl exchange reactions are driven by light, either sunlight or UV light, and occur with a half-life of 17 min at room temperature in the case of [Pt(CD3)(1)](SbF6) and [Pt(CH3)(terpy)](SbF6) upon exposure to UV light (365 nm, 100 W). Under similar conditions, the exchange reaction is faster (half-life of 11 min) between [Pt(CD3)(1)](SbF6) and the palladium complex [Pd(CH3)(1)](SbF6), most likely due to the weaker Pd−C bond. No methyl−phenyl exchange has been observed for these complexes, probably due to the stronger M−C bond in the case of the phenyl platinum complex [Pt(C6H5)(1)](SbF6). 1458
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(+LSIMS, m/z (%)): 337 (10) [(M − I)+], 318 (20) [(M − I − CD3)2+]. [Pt(CH3)(1)](SbF6). To a mixture of [Pt(CH3)(1)]Cl (84.3 mg, 0.1657 mmol) and AgSbF6 (56.7 mg, 0.1650 mmol) was added 20 mL of dry methanol. The resulting yellow suspension was stirred overnight in the dark. All volatiles were removed from the suspension, and 10 mL of dry acetone was added to the remaining solid. The bright yellow acetone solution was removed by filtration, and the residual insoluble products were washed twice with 10 mL of acetone. Upon removal of all volatiles from the combined acetone fractions, a yellow solid remained. Crystals suitable for X-ray diffraction analysis were obtained by slow diffusion from an acetone solution, layered over dichloromethane. Yield: 76.5 mg (65%). 1H NMR ((CD3)2CO, 298 K): 1.45 (s, 3H, 2JPtH = 72.3, PtMe), 6.76 (br, 4H NH2), 7.00 (dd, 2H, J = 1.2, 8.6, Ar-H), 7.46 (dd, 2H, J = 1.2, 7.3, Ar-H), 7.74 (dd, 2H, J = 7.3, 8.5, Ar-H), 8.11 (d, 2H, J = 8.0, Ar-H), 8.25 (dd, 1H, J = 7.5, 8.6 Hz, ArH). 1H NMR (CD3CN, 298K): 8.01 (t, J = 8.1, 1H, H4′), 7.74 (d, J = 8.1, 2H, H3′,5′), 7.56 (dd, J = 1.2, 7.4, 2H, H4,4″), 7.14 (dd, J = 1.1, 7.3, 2H, H3,3″), 6.76 (dd, J = 1.2, 8.5 Hz, 2H, H5,5″), 6.01 (s, 4H, NH2) 1.37 (s, 3H, J = 69.6, Pt-Me). 13C{1H} NMR ((CD3)2CO): −22.6 (Pt-C), 113.7 115.7, 112.6, 139.1, 139.2, 153.1, 156.3, 162.0. 19F NMR ((CD3)2CO): −123.4 (superposition of a sextet due to 121SbF6− (1JF121Sb = 1946) and an octet due to 123SbF6− (1JF123Sb = 1069 Hz). IR (Nujol, cm−1): 3501 (νN−H), 3394 (νN−H), 1637, 1603, 1562, 1498, 1406, 1292, 1277, 1186, 1151, 1002, 792, 663. MS (+ESI, m/z (%)): 475 (100) [(M + 2H)+]. MS (−ESI, m/z (%)): 235 (100) [121SbF6−], 237 (70) [123SbF6−]. Anal. Calcd for C16H16F6N5PtSb: C, 27.10; H, 2.27; N, 9.88. Found: C, 27.25; H, 2.32; N, 9.94. Crystal data for [Pt(CH3)(1)](SbF6): [C16H16N5Pt](SbF6), Mr = 709.18, triclinic, P1̅ (No. 2), a = 7.5946(3) Å, b = 11.1946(8) Å, c = 12.3542(2) Å, α = 71.412(11)°, β = 72.151(7)°, γ = 80.680(5)°, V = 945.22(8) Å3, Z = 2, Dc = 2.492 g cm−3, μ(Mo Kα) = 8.891 mm−1, T = 173 K, orange needles, Oxford Diffraction Xcalibur 3 diffractometer; 5969 independent measured reflections (Rint = 0.0185), F2 refinement,78 R1(obsd) = 0.0254, wR2(all) = 0.0625, 5454 independent observed absorption-corrected reflections (|Fo| > 4σ(|Fo|), 2θmax = 64°), 279 parameters. CCDC 976849. [Pt(CD3)(1)](SbF6). trans-[PtI(CD3)(SMe2)2] (0.105 g, 0.23 mmol) and AgSbF6 (0.078 g, 0.23 mmol) were dissolved in dry acetone (10 mL), and the suspension was stirred, covered in aluminum foil, for 30 min. The suspension was filtered into another Schlenk flask containing 6,6″-diamino-2,2′:6′,2″-terpyridine (0.059 g, 0.23 mmol). The residue was washed with dry acetone (5 mL). The washings were combined with the initial acetone solution, yielding an orange suspension. The suspension was stirred overnight. The suspension was filtered and the residue washed with dry acetone (5 mL). The resultant orange acetone solution was reduced to a minimum volume, yielding an orange solid. The product was dissolved in a minimum amount of dry acetone, precipitated with dry ether, and filtered. The product was washed with dry diethyl ether (2 × 5 mL) and dry DCM (2 × 5 mL) and dried under vacuum, giving a pale yellow solid. Yield: 0.119 g (74%). 1H NMR (400 MHz, CD3CN): δ 7.99 (t, J = 8.1, 1H, H4′), 7.72 (d, J = 8.1, 2H, H3′, H5′), 7.55 (dd, J = 7.5, 8.4, 2H, H4, H4″), 7.12 (dd, J = 0.7, 7.1, 2H, H3, H3″), 6.75 (dd, J = 0.8, 8.6, 2H, H5, H5″), 6.00 (s, 4H, NH2). 2H NMR (77 MHz, CH3CN): δ 1.35 (s, PtCD3). 13C[1H] NMR (100 MHz, CD3CN): δ 162.5, 156.9, 153.7, 139.9, 139.7, 123.2, 116.4, 114.5. 19F NMR (470 MHz, CD3CN): δ −123.9 (superposition of a sextet due to 121SbF6− and an octet due to 123SbF6−). MS (+LSIMS, m/z (%)): 476 (100) [(M − SbF6)+], 458 (50) [(M − CD3 − SbF6)+]. MS (−LSIMS, m/z (%)): 237 (70) [123SbF6−], 235 (100) [121SbF6−]. Anal. Calcd for C16H13D3N5F6PtSb: C, 26.97; H, 1.84; N, 9.83. Found: C, 27.15; H, 1.87; N, 9.88. [Pt(C6H5)(1)]Cl. trans-[Pt(C6H5)(Cl)(SMe2)2] (0.092 g, 0.21 mmol) and 6,6″-diamino-2,2′:6′,2″-terpyridine (1; 0.056 g, 0.21 mmol) were mixed in DCM (15 mL). The resultant yellow solution was stirred for 4 days. The suspension was filtered, washed with diethyl ether (2 × 5 mL), and dried in vacuo, giving a bright yellow solid. Yield: 0.050 g (41%). 1H NMR (400 MHz, CD3OD): δ 8.26 (dd, J = 7.1, 9.0, 1H, H4′), 8.18 (d, J = 7.5, 2H, H3′, H5′), 7.89 (dd, J = 1.2, 7.7, 2H, o-C6H5), 7.67 (dd, J = 7.4, 8.6, 2H, H4, H4″), 7.47 (dd, J =
1.2, 7.3, 2H, H3, H3″), 7.30 (t, J = 7.6, 2H, m-C6H5), 7.10 (t, J = 7.4, 1H, p-C6H5), 6.63 (dd, J = 1.0, 8.6, 2H, H5, H5″). 13C{1H} NMR (125 MHz, CD3OD): δ 164.7, 157.2, 155.4, 141.7, 141.2, 139.9, 138.8, 131.2, 127.0, 123.2, 117.9, 114.6. MS (+FAB, m/z (%)): 537 (30) [(M − Cl)+], 459 (20) [(M − C6H5 − Cl)+]. Anal. Calcd for C21H18N5ClPt: C, 44.18; H, 3.18; N, 12.27. Found: C, 44.27; H, 3.10; N, 12.19. [Pt(C6H5)(1)](SbF6). [Pt(C6H5)(1)]Cl (0.045 g, 0.08 mmol) and AgSbF6 (0.027 g, 0.08 mmol) were mixed in dry methanol (15 mL). The flask was wrapped in aluminum foil and the solution stirred overnight. The resultant orange suspension was reduced to a minimum volume. The residue was extracted with dry acetone (10 mL) and filtered into a new Schlenk flask. The gray residue left behind was washed with dry acetone (2 × 10 mL). The washings were combined with the initial acetone extraction, and the resultant clear yellow solution was reduced to a minimum volume, giving a bright orange solid. Yield: 0.042 g (69%). Crystals suitable for X-ray analysis were grown from an acetone solution layered with hexane. 1H NMR (400 MHz, d6-acetone): δ 8.46 (dd, J = 6.8, 9.3, 1H, H4′), 8.43 − 8.34 (m, 2H, H3′, H5′), 7.91 (dd, J = 1.3, 7.8, 2H, o-C6H5), 7.83 (dd, J = 7.5, 8.3, 2H, H4, H4″), 7.68 (dd, J = 1.1, 7.3, 2H, H3, H3″), 7.32 (t, J = 7.6, 2H, m-C6H5), 7.10 (t, J = 7.4, 1H, p-C6H5), 6.83 (dd, J = 1.2, 8.7, 2H, H5, H5″), 6.32 (s, 4H, NH2). 13C{1H} NMR (100 MHz, d6acetone): δ 164.2, 156.8, 154.9, 141.4, 141.3, 140.1, 138.4, 131.0 (1JPtC = 47.5), 126.8, 123.3, 117.9, 114.8. 19F NMR (376 MHz, d6-acetone): δ −122.5 (superposition of a sextet due to 121SbF6− and an octet due to 123SbF6−). MS (+LSIMS, m/z (%)): 535 (10) [(M − SbF6)+], 457 (5) [(M − C6H5 − H − SbF6)+]. MS (−LSIMS, m/z (%)): 237 (70) [123SbF6−], 235 (100) [121SbF6−]. Anal. Calcd for C21H18N5F6PtSb: C, 32.70; H, 2.35; N, 9.08. Found: C, 32.78; H, 2.40; N, 9.01. Crystal data for [Pt(C6H5)(1)](SbF6): [C21H18N5Pt](SbF6)·C3H6O, M = 829.32, triclinic, P1̅ (No. 2), a = 8.5949(3) Å, b = 10.6819(3) Å, c = 15.9071(5) Å, α = 76.754(2)°, β = 75.232(3)°, γ = 70.253(3)°, V = 1312.64(8) Å3, Z = 2, Dc = 2.098 g cm−3, μ(Cu Kα) = 18.624 mm−1, T = 173 K, pale yellow platy needles, Oxford Diffraction Xcalibur PX Ultra diffractometer; 5039 independent measured reflections (Rint = 0.0308), F2 refinement,78 R1(obs) = 0.0263, wR2(all) = 0.0709, 4831 independent observed absorption-corrected reflections (|Fo| > 4σ(|Fo|), 2θmax = 143°), 381 parameters. CCDC 976850. [Pd(CH3)(terpy)](SbF6). [Pd(CH3)(terpy)]Cl (110 mg, 0.28 mmol) and AgSbF6 (97 mg, 0.28 mmol) were mixed in 30 mL of dry acetonitrile. The suspension was stirred overnight in the dark. Then it was filtered, the volume was reduced to approximately 2 mL, and 30 mL of dry diethyl ether was added. The solid was filtered and washed with 3 × 5 mL of Et2O and subsequently dried under vacuum. Yield: 150 mg (90%). 1H NMR (400 MHz, (CD3)2CO): δ 0.56 (s, 3H, Me), 7.92 (m, 2 H, CH), 8.45 (td, 2 H, CH, 3JHH = 8, 4JHH = 1.6), 8.52 (m, 1 H, CH), 8.62 (m, 4H, CH), 8.76 (m, 2 H, CH). 13C{1H} NMR (500 MHz (CD3)2CO): δ 5.82 (CH3), 124.32 (CH), 125.73 (CH), 129.25 (CH), 142.11 (CH), 142.52 (CH), 152.46 (C), 152.58 (CH), 159.52 (C). FAB (M): [M+] 354, [M+ − Me] 339. Anal. Calcd for C16H14N3F6PdSb: C, 32.55; H, 2.39; N, 7.12. Found: C, 31.98; H, 1.97; N, 6.98. [Pd(CH3)(1)](SbF6). [PdCl(CH3)(1,5-COD)] (0.037 g, 0.14 mmol) and AgSbF6 (0.048 g, 0.14 mmol) were mixed in dry acetone (10 mL), and the suspension was stirred, covered in aluminum foil, for 15 min. The suspension was filtered into another Schlenk flask containing a solution of 6,6″-diamino-2,2′:6′,2″-terpyridine (0.037 g, 0.14 mmol) in dry acetone (5 mL). The residue was washed with dry acetone (10 mL). The washings were combined with the initial acetone solution, giving a yellow solution. The solution was stirred for 15 min and then reduced to a minimum volume, giving a yellow solid. The solid was washed with dry DCM (5 mL) and dried under vacuum, giving a pale yellow solid. Yield: 0.042 g (49%). 1H NMR (400 MHz, d6-acetone): δ 8.30 (s, 3H, H3′, H4′, H5′), 7.82 (dd, J = 7.4, 8.5, 2H, H4, H4″), 7.65 (dd, J = 1.2, 7.3, 2H, H5, H5″), 7.07 (dd, J = 1.0, 8.7, 2H, H3, H3″), 6.55 (s, 4H, NH2), 1.07 (s, 3H, PdCH3). 13C{1H} NMR (100 MHz, d6-acetone): δ 162.3, 156.1, 153.6, 141.1, 140.4, 122.9, 116.1, 113.7, −11.7 (PdCH3). 19F NMR (376 MHz, d6acetone): δ −122.2 (superposition of a sextet due to 121SbF6− and an 1459
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octet due to 123SbF6−). MS (+LSIMS, m/z (%)): 384 (50) [(M − SbF6)+], 371 (70) [(M − CH3 − SbF6)+]. MS (−LSIMS, m/z (%)): 237 (70) [123SbF6−], 235 (100) [121SbF6−]. Anal. Calcd for C16H16N5F6PdSb: C, 30.97; H, 2.60; N, 11.29. Found: C, 31.07; H, 2.50; N, 11.17. Alkyl Exchange Reactions. The general procedure is given, exemplified for the reaction between [Pt(CD3)(1)](SbF6) and [Pd(CH3)(1)](SbF6). A solution of [Pt(CD3)(1)](SbF6) (4.7 mg, 6.60 μmol) and [Pd(CH3)(1)](SbF6) (4.7 mg, 7.57 μmol) in CD3CN (0.572 mL) in a normal glass NMR tube was irradiated with UV light (365 nm, 100 W). After set time intervals, a 1H NMR spectrum was taken until no further changes occurred and equilibrium was reached. The constant Ke = [PtCD3][PdCH3]/[PtCH3][PdCD3] was determined as 1.3 at equilibrium, due to the slightly larger amount of Pd complex used in this case.
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(15) Arnold, D. P.; Bennett, M. A.; McLaughlin, G. M.; Robertson, G. B.; Whittaker, M. J. J. Chem. Soc., Chem. Commun. 1983, 32. (16) Ozawa, F.; Ito, T.; Nakamura, Y.; Yamamoto, A. Bull. Chem. Soc. Jpn. 1981, 54, 1868. (17) Casado, A. L.; Casares, J. A.; Espinet, P. Organometallics 1997, 16, 5730. (18) Puddephatt, R. J.; Thompson, P. J. J. Organomet. Chem. 1979, 166, 251. (19) Aye, K.-T.; Vittal, J. J.; Puddephatt, R. J. J. Chem. Soc., Dalton Trans. 1993, 1835. (20) Ling, S. M. M.; Payne, N. C.; Puddephatt, R. J. Organometallics 1985, 4, 1546. (21) Aye, K.-T.; Canty, A. J.; Crespo, M.; Puddephatt, R. J.; Scott, J. D.; Watson, A. A. Organometallics 1989, 8, 1518. (22) Nabavizadeh, S. M.; Habibzadeh, S.; Rashidi, M.; Puddephatt, R. J. Organometallics 2010, 29, 6359. (23) Moret, M.-E.; Serra, D.; Bach, A.; Chen, P. Angew. Chem., Int. Ed. 2010, 49, 2873. (24) Serra, D.; Moret, M.-E.; Chen, P. J. Am. Chem. Soc. 2011, 133, 8914. (25) Arsenault, G. J.; Anderson, C. M.; Puddephatt, R. J. Organometallics 1988, 7, 2094. (26) Moret, M.-E.; Chen, P. J. Am. Chem. Soc. 2009, 131, 5675. (27) Johansson, L.; Ryan, O. B.; Romming, C.; Tilset, M. Organometallics 1998, 17, 3957. (28) Luo, J.; Khusnutdinova, J. R.; Rath, N. P.; Mirica, L. M. Chem. Commun. 2012, 48, 1532. (29) Lanci, M. P.; Remy, M. S.; Kaminsky, W.; Mayer, J. M.; Sanford, M. S. J. Am. Chem. Soc. 2009, 131, 15618. (30) Britovsek, G. J. P.; Taylor, R. A.; Sunley, G. J.; Law, D. J.; White, A. J. P. Organometallics 2006, 25, 2074. (31) Taylor, R. A.; Law, D. J.; Sunley, G. J.; White, A. J. P.; Britovsek, G. J. P. Chem. Commun. 2008, 2800. (32) Taylor, R. A.; Law, D. J.; Sunley, G. J.; White, A. J. P.; Britovsek, G. J. P. Angew. Chem., Int. Ed. 2009, 48, 5900. (33) Yip, H.-K.; Cheng, L.-K.; Cheung, K.-K.; Che, C.-M. J. Chem. Soc., Dalton Trans. 1993, 2933. (34) Crites, D. K.; Cunningham, C. T.; McMillin, D. R. Inorg. Chim. Acta 1998, 273, 346. (35) Lai, S.-W.; Chan, M. C. W.; Cheung, K.-K.; Che, C.-M. Inorg. Chem. 1999, 38, 4262. (36) McMillin, D. R.; Moore, J. J. Coord. Chem. Rev. 2002, 229, 113. (37) Williams, J. A. G. Top. Curr. Chem. 2007, 281, 205. (38) Wong, K. M.-C.; Yam, V. W.-W. Coord. Chem. Rev. 2007, 251, 2477. (39) Kratze, H.; Müller, S. J. Chem. Thermodyn. 1985, 17, 151. (40) Arena, G.; Monsú Scolaro, L.; Pasternack, R. F.; Romeo, R. Inorg. Chem. 1995, 34, 2994. (41) Romeo, R.; Scolaro, L. M.; Plutino, M. R.; Albinati, A. J. Organomet. Chem. 2000, 593−594, 403. (42) Cummings, S. D. Coord. Chem. Rev. 2009, 253, 449. (43) Lazzaro, D. P.; Fanwick, P. E.; McMillin, D. R. Inorg. Chem. 2012, 51, 10474. (44) Jude, H.; Krause Bauer, J. A.; Connick, W. B. J. Am. Chem. Soc. 2003, 125, 3446. (45) Clark, H. C.; Adediran Mesubi, M. J. Organomet. Chem. 1981, 215, 131. (46) Klein, A.; Klinkhammer, K.-W.; Scheiring, T. J. Organomet. Chem. 1999, 592, 128. (47) Houlding, V. H.; Miskowski, V. M. Coord. Chem. Rev. 1991, 111, 145. (48) Ananikov, V. P.; Musaev, D. G.; Morokuma, K. Organometallics 2005, 24, 715. (49) Hackett, M.; Whitesides, G. M. J. Am. Chem. Soc. 1988, 110, 1449. (50) Hill, G. S.; Puddephatt, R. J. Organometallics 1998, 17, 1478. (51) Bailey, J. A.; Hill, M. G.; Marsh, R. E.; Miskowski, V. M.; Schaefer, W. P.; Gray, H. B. Inorg. Chem. 1995, 34, 4591.
ASSOCIATED CONTENT
S Supporting Information *
Text, figures, and CIF files giving X-ray crystallographic data for [Pt(CH3)(1)](SbF6) and [Pt(C6H5)(1)](SbF6) and experimental details and characterization data for all complexes. This material is available free of charge via the Internet at http:// pubs.acs.org.
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AUTHOR INFORMATION
Corresponding Author
*G.J.P.B.: e-mail,
[email protected]; tel, +44-(0)2075945863; fax, +44-(0)20-75945804. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS We are grateful to the EPSRC and BP for a CASE Award to R.A.T. We thank Johnson Matthey for a generous loan of palladium and platinum salts. Prof. Allan Canty, University of Tasmania, is thanked for very helpful discussions.
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REFERENCES
(1) Rabinovich, I. B.; Nistratov, V. P.; Telnoy, V. I.; Sheiman, M. S. Thermochemical and Thermodynamic Properties of Organometallic Compounds; Begell House: New York, 1999. (2) Martinho Simões, J. A.; Beauchamp, J. L. Chem. Rev. 1990, 90, 629. (3) Bryndza, H. E.; Fong, L. K.; Paciello, R. A.; Tam, W.; Bercaw, J. E. J. Am. Chem. Soc. 1987, 109, 1444. (4) Nehl, H.; Scheidt, W. R. J. Organomet. Chem. 1985, 289, 1. (5) Henold, K.; Soulati, J.; Oliver, J. P. J. Am. Chem. Soc. 1969, 91, 3171. (6) Bochmann, M.; Lancaster, S. J. J. Organomet. Chem. 1995, 497, 55. (7) Metal-Catalysed Cross Coupling Reactions, 2nd ed.; de Meijere, A., Diederich, F., Eds.; Wiley-VCH: Weinheim, Germany, 2004. (8) Britovsek, G. J. P.; Cohen, S. A.; Gibson, V. C.; Maddox, P. J.; van Meurs, M. Angew. Chem., Int. Ed. 2002, 41, 489. (9) Britovsek, G. J. P.; Cohen, S. A.; Gibson, V. C.; van Meurs, M. J. Am. Chem. Soc. 2004, 126, 10701. (10) van Meurs, M.; Britovsek, G. J. P.; Gibson, V. C.; Cohen, S. A. J. Am. Chem. Soc. 2005, 127, 9913. (11) Remy, M. S.; Cundari, T. R.; Sanford, M. S. Organometallics 2010, 29, 1522. (12) Visser, J. P.; Jager, W. W.; Masters, C. Recl. Trav. Chim. Pays-Bas 1975, 94, 70. (13) Puddephatt, R. J.; Thompson, P. J. J. Chem. Soc., Dalton Trans. 1975, 1810. (14) Puddephatt, R. J.; Thompson, P. J. J. Chem. Soc., Dalton Trans. 1977, 1219. 1460
dx.doi.org/10.1021/om500048t | Organometallics 2014, 33, 1453−1461
Organometallics
Article
(52) Bercaw, J. E.; Durrell, A. C.; Gray, H. B.; Green, J. C.; Hazari, N.; Labinger, J. A.; Winkler, J. R. Inorg. Chem. 2010, 49, 1801. (53) Smith, D. C.; Gray, H. B. Chem. Soc. Rev. 1990, 100, 169. (54) Marino, N.; Fazen, C. H.; Blakemore, J. D.; Incarvito, C. D.; Hazari, N.; Doyle, R. P. Inorg. Chem. 2011, 50, 2507. (55) Arena, G.; Calogero, G.; Campagna, S.; Monsú Scolaro, L.; Ricevuto, V.; Romeo, R. Inorg. Chem. 1998, 37, 2763. (56) Zhang, H.-X.; Kato, M.; Sasaki, Y.; Ohba, T.; Ito, H.; Kobayashi, A.; Chang, H.-C.; Uosaki, K. Dalton Trans. 2012, 41, 11497. (57) McGuire, R., Jr.; McGuire, M. C.; McMillin, D. R. Coord. Chem. Rev. 2010, 254, 2574. (58) Miskowski, V. M.; Rice, S. F.; Gray, H. B.; Dallinger, R. F.; Milder, S. J.; Hill, M. G.; Exstrom, C. L.; Mann, K. R. Inorg. Chem. 1994, 33, 2799. (59) Bercaw, J. E.; Durrell, A. C.; Gray, H. B.; Green, J. C.; Hazari, N.; Labinger, J. A.; Winkler, J. R. Inorg. Chem. 2010, 49, 1801. (60) Hill, M. G.; Mann, K. R. Catal. Lett. 1991, 11, 341. (61) Williams, J. A. G. Top. Curr. Chem. 2007, 281, 205. (62) Bandoli, G.; Caputo, P. A.; Intini, F. P.; Sivo, M.; Natile, G. J. Am. Chem. Soc. 1997, 119, 10370. (63) Powers, D. C.; Ritter, T. Nat. Chem. 2009, 1, 302. (64) Deprez, N. R.; Sanford, M. S. J. Am. Chem. Soc. 2009, 131, 11234. (65) Canty, A. J.; Gardiner, M. G.; Jones, R. C.; Rodemann, T.; Sharma, M. J. Am. Chem. Soc. 2009, 131, 7236. (66) Bonnington, K. J.; Jennings, M. C.; Puddephatt, R. J. Organometallics 2008, 27, 6521. (67) Ye, Y.; Ball, N. D.; Kampf, J. W.; Sanford, M. S. J. Am. Chem. Soc. 2010, 132, 14682. (68) Mirica, L. M.; Khusnutdinova, J. R. Coord. Chem. Rev. 2013, 257, 299. (69) Powers, D. C.; Lee, E.; Ariafard, A.; Sanford, M. S.; Yates, B. F.; Canty, A. J.; Ritter, T. J. Am. Chem. Soc. 2012, 134, 12002. (70) Burfield, D. R.; Smithers, R. H. J. Org. Chem. 1978, 43, 3966. (71) Shekhar, S.; Hartwig, J. F. J. Am. Chem. Soc. 2004, 126, 13016. (72) Rülke, R. E.; Ernsting, J. M.; Spek, A. L.; Elsevier, C. J.; van Leeuwen, P. W. N. M.; Vrieze, K. Inorg. Chem. 1993, 32, 5769. (73) Kukushkin, V. Y. Inorg. Synth. 1998, 32, 141. (74) Moret, M.-E.; Chen, P. Organometallics 2007, 26, 1523. (75) Hadj-Bagheri, N.; Puddephatt, R. J. Polyhedron 1988, 7, 2695. (76) Kukushkin, V. Y.; Lövqvist, K.; Norén, B.; Oskarsson, Å.; Elding, L. I. Phosphorus, Sulfur Silicon Relat. Elem. 1992, 73, 253. (77) Kapoor, P.; Kukushkin, V. Y.; Lövqvist, K.; Oskarsson, Å. J. Organomet. Chem. 1996, 517, 71. (78) SHELXTL; Bruker AXS, Madison, WI. SHELX-97: Sheldrick, G. M. Acta Crystallogr., Sect. A 2008, A64, 112. SHELX-2013; http:// shelx.uni-ac.gwdg.de/SHELX/index.php.
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