Synthesis and Structure of Platinum Bis(phospholane) Complexes Pt

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Synthesis and Structure of Platinum Bis(phospholane) Complexes Pt(diphos*)(R)(X), Catalyst Precursors for Asymmetric Phosphine Alkylation Marites A. Guino-o,† Andrew H. Zureick,† Natalia F. Blank,†,‡ Brian J. Anderson,† Timothy W. Chapp,† Youngmin Kim,† David S. Glueck,*,† and Arnold L. Rheingold§ †

6128 Burke Laboratory, Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, United States Department of Chemistry, Norwich University, Northfield, Vermont 05663, United States § Department of Chemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093, United States ‡

S Supporting Information *

ABSTRACT: The complexes Pt((R,R)-Me-DuPhos)(Ph)(Cl) (1) and Pt((R,R)i-Pr-DuPhos)(Ph)(Cl) (2) have been used as catalyst precursors in Pt-catalyzed asymmetric alkylation of secondary phosphines. To investigate structure− reactivity−selectivity relationships in these reactions, analogous complexes with different bis(phospholane) ligands and/or Pt-hydrocarbyl groups were prepared. Treatment of Pt(COD)(R)(Cl) (R = Me, Ph) with BPE or DuPhos ligands gave Pt((R,R)-Me-BPE)(Me)(Cl) (3), Pt((R,R)-Ph-BPE)(Me)(Cl) (5), Pt((R,R)-PhBPE)(Ph)(Cl) (6), and Pt((R,R)-i-Pr-DuPhos)(Me)(Cl) (7). However, treatment of Pt(COD)(Me)(Cl) with (R,R)-Me-FerroLANE gave a mixture of products, which were converted upon heating to Pt((R,R)-Me-FerroLANE)(Me)(Cl) (8). A related mixture formed from Pt(COD)(Ph)(Cl) precipitated trans-[Pt((R,R)-MeFerroLANE)(Ph)(Cl)]n (9T), which on treatment with AgOTf followed by LiCl gave cis-Pt((R,R)-Me-FerroLANE)(Ph)(Cl) (9) as the major product. The reaction of Pt(COD)(Ph)(Cl) with (R,R)-Me-BPE gave the dinuclear dication [(Pt((R,R)-MeBPE)(Ph))2(μ-(R,R)-Me-BPE))][Cl]2 (10) instead of the expected Pt((R,R)-Me-BPE)(Ph)(Cl) (4). The iodide Pt((R,R)-MeBPE)(Ph)(I) (11) was formed from Pt(COD)(Ph)(I) and BPE but decomposed readily. Treatment of Pt(COD)X2 with (R,R)Me-BPE gave Pt((R,R)-Me-BPE)X2 (X = Cl (12), I (13)). Reaction of Pt(COD)Ph2 with (R,R)-Me-BPE gave Pt((R,R)-MeBPE)Ph2 (14), which was protonated with HCl to yield 4. Treatment of Pt((R,R)-Me-DuPhos)Cl2 with excess (9-phenanthryl) magnesium bromide gave Pt((R,R)-Me-DuPhos)(9-phenanthryl)(Br) (15), while a similar reaction with excess (6-methoxy-2naphthyl)magnesium bromide gave Pt((R,R)-Me-DuPhos)Ar2 (16). Complexes 3, 4, 6−10, and 12−14 were structurally characterized by X-ray crystallography. Structure−reactivity−selectivity relationships in this series of Pt catalyst precursors were investigated in the catalytic alkylation of the bis(secondary phosphine) PhHP(CH2)3PHPh with benzyl bromide.

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INTRODUCTION

varied hydrocarbyl groups would probe the effects of this component.

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We recently developed the Pt catalyst precursors Pt((R,R)-MeDuPhos)(Ph)(Cl) and Pt((R,R)-i-Pr-DuPhos)(Ph)(Cl) (1 and 2, Chart 1) 1 for asymmetric alkylation of secondary phosphines2 and used them for synthesis of an enantiomerically pure DiPAMP analogue,3 in enantioselective tandem alkylation/arylation of primary phosphines to yield 1-phosphaacenaphthenes,4 and in studies of catalyst and substrate control in alkylation of bis(secondary phosphines).5 The modular design of these catalyst precursors enabled variation of the diphosphine and Pt-hydrocarbyl moieties for investigation of structure−reactivity−selectivity relationships, which might lead to more active and selective catalysts.3 Because earlier studies had shown that tightly binding chelate diphosphines were required to avoid displacement by the phosphine substrates and products,2,3 we planned to prepare related complexes using bis(phospholano)ethane (BPE) and bis(phospholano)ferrocene (FerroLANE) ligands, structural analogues of DuPhos (Chart 1). Similarly, synthesis of Pt complexes with © 2012 American Chemical Society

RESULTS AND DISCUSSION Synthesis of the Bis(phospholane) Complexes Pt(diphos*)(R)(Cl). Treatment of Pt(COD)(R)(Cl) (COD = cyclooctadiene; R = Ph, Me) with commercially available bis(phospholanes) gave the complexes Pt((R,R)-Me-BPE)(Me)(Cl) (3), Pt((R,R)-Ph-BPE)(R)(Cl) (R = Me (5), Ph (6)), and Pt((R,R)-i-Pr-DuPhos)(Me)(Cl) (7) (Scheme 1, top). These syntheses were straightforward, like the previously reported preparations6 of the DuPhos complexes 1, 2, and Pt((R,R)-Me-DuPhos)(Me)(Cl).7 In contrast, the reaction of Pt(COD)(Me)(Cl) with (R,R)Me-FerroLANE gave mixtures which contained the expected product 8 and several other Pt complexes, whose 31P NMR spectra showed singlets with JPt−P ≈ 3000 Hz, consistent with Received: July 25, 2012 Published: September 19, 2012 6900

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mixture for several days in toluene at 63 °C resulted in clean conversion to cis-Me-FerroLANE complex 8, which was isolated in high yield. Treatment of Pt(COD)(Ph)(Cl) with (R,R)-Me-FerroLANE in THF gave a similar mixture, from which a complex of composition [Pt((R,R)-Me-FerroLANE)(Ph)(Cl)]n (9T) precipitated. Its 31P NMR spectrum (δ 31.4, JPt−P = 2936 Hz, CDCl3) showed it contained trans phosphines. 9T did not dissolve in nitromethane and was sparingly soluble in acetone, acetonitrile, and DMSO but gave a nonconducting solution in CHCl3 and was even slightly soluble in toluene, suggesting it was neutral monomeric A or, more likely, the less strained Aframe complex B, not a salt such as C or D (Scheme 1, right). In contrast to the results for the Pt-Me analogue 8, heating a mixture containing 9T, cis-Pt((R,R)-Me-FerroLANE)(Ph)(Cl) (9), and other unidentified Pt-Ph complexes did not lead to isomerization. However, treatment of 9T with AgOTf induced rapid isomerization to what is presumably cis-Pt((R,R)-MeFerroLANE)(Ph)(OTf) (31P{1H} NMR (CDCl3): δ 29.7 (d, J = 14, JPt−P = 1681 Hz; 29.2 (d, J = 14, JPt−P = 4332 Hz)). Addition of excess LiCl to this intermediate gave 9 as the major product (Scheme 1, right). Although we could not obtain pure bulk samples of 9, it was identified by spectroscopy and X-ray crystallography (see below for details). Treatment of Pt(COD)(Ph)(Cl) with (R,R)-Me-BPE did not yield the expected product, Pt((R,R)-Me-BPE)(Ph)(Cl) (4); instead, the dinuclear dication [(Pt((R,R)-Me-BPE)(Ph))2(μ-(R,R)-Me-BPE))][Cl]2 (10, Scheme 1, top left), in which Me-BPE bridges the two Pt centers,11 was formed.12 Using the iodide precursor Pt(COD)(Ph)(I) gave Pt((R,R)Me-BPE)(Ph)(I) (11, Scheme 1, left), which could be characterized spectroscopically but decomposed in solution and on attempted recrystallization.13

Chart 1. Modular Pt(bis(phospholane))(R)(X) Catalyst Precursors for Asymmetric Phosphine Alkylation

trans phosphines (Scheme 1, right).8 These intermediates may contain trans and/or bridging (R,R)-Me-FerroLANE in structures such as A−D, by analogy to related observations in the formation of Pt(dppm)(Me)(Cl) (dppm = Ph2PCH2PPh2) 9 and Pd(dRpf)(Me)(Cl) (dRpf = 1,1′dialkylphosphinoferrocene; R = t-Bu, i-Pr, Et).10 Heating this

Scheme 1. Synthesis of the Platinum Bis(phospholane) Catalyst Precursors Pt(diphos*)(R)(Cl) (3−9 and 11) and Related Complexesa

a Treatment of Pt(COD)(R)(X) (center) with a bis(phospholane) ligand was intended to yield Pt(diphos*)(R)(X) (3−9 and 11). Syntheses of 3 and 5−7 were straightforward, but 8 and 9 were initially formed as components of mixtures, which might include complexes A−D. Attempts to prepare 4 directly gave dinuclear 10; therefore, it was prepared via 14 instead.

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Table 1. 31P NMR Data for Pt(diphos*)(R)(X) Complexesa

Complex 4 could be prepared by an alternative indirect route (Scheme 1, bottom left). Reaction of Pt(COD)X2 with (R,R)Me-BPE gave Pt((R,R)-Me-BPE)X2 (X = Cl (12), I (13)). Arylation of 13 using 2 equiv of AgOTf in methanol, followed by treatment with NaBPh4,14 or reaction of Pt(COD)Ph2 with (R,R)-Me-BPE, gave Pt((R,R)-Me-BPE)Ph2 (14). The latter approach was preferred, since the NaBPh4 route gave product mixtures and the arylation stoichiometry could not be controlled to give monophenyl complex 4. Similarly, attempted monoarylation of dichloride 12 using PhMgBr with or without added ZnCl2 gave the target Pt((R,R)-Me-BPE)(Ph)(Cl) (4) in a mixture of other products. Instead, protonation of 14 with HCl, generated from acetyl chloride and methanol,15 gave 4 as the major product in mixtures which, depending on the stoichiometry, also contained dichloride 12, unreacted starting material 14, and other Pt complexes (Scheme 1, left). Although sparingly soluble 12 could be separated, attempts to remove 14 and purify 4 resulted in partial decomposition to unidentified Pt complexes. Although we could not obtain pure bulk samples of 4, it was characterized spectroscopically and by X-ray crystallography (see below). Synthesis of the Aryl Complexes Pt((R,R)-MeDuPhos)(Ar)(X) (X = Br, Ar). Treatment of Pt((R,R)-MeDuPhos)Cl2 with commercially available aryl Grignard reagents led to substitution of one or more chlorides, depending on the structure of the aryl group. (9-Phenanthryl)magnesium bromide gave Pt((R,R)-Me-DuPhos)(9-phenanthryl)(Br) (15) (Scheme 2) as a mixture of two atropisomers resulting from

complex (no.) Pt((R,R)-Me-BPE)(Me)(Cl) (3) Pt((R,R)-Me-BPE)(Ph)(Cl) (4) Pt((R,R)-Ph-BPE)(Me)(Cl) (5) Pt((R,R)-Ph-BPE)(Ph)(Cl) (6) Pt((R,R)-i-Pr-DuPhos)(Me) (Cl) (7) Pt((R,R)-Me-FerroLANE) (Me)(Cl) (8) Pt((R,R)-Me-FerroLANE) (Ph)(Cl) (9) trans-[Pt((R,R)-MeFerroLANE)(Ph)(Cl)]n (9T)b [(Pt((R,R)-Me-BPE)(Ph))2 (μ-(R,R)-Me-BPE)][Cl]2 (10)c Pt((R,R)-Me-BPE)(Ph)(I) (11) Pt((R,R)-Me-BPE)Ph2 (14) Pt((R,R)-Me-DuPhos)(9phenanthryl)(Br) (15)d Pt((R,R)-Me-DuPhos)(6MeO-2-naphthyl)2 (16)

JPt−P1

δ(P2) (trans to X)

JPt−P2

JPP

1707

64.9

4045

2

66.8

1598

59.6

3885

3

69.7

1645

59.2

4168

73.9

1712

64.8

4256

64.3

1734

50.2

4119

2

36.6

1767

31.8

4244

11

28.1

1622

28.7

4236

15

31.4

2936

59.8

1606

64.5

2498

8

67.7

1635

60.0

3964

4

60.3 66.8

1636 1680

58.2

3929

6

66.0 60.3

1709 1687

56.0

3951

6

δ(P1) (trans to R) 73.6

a Solvent: CDCl3 for 3, 5−7, 9, 9T, 15, and 16, C6D6 for 4, 8, and 14, and CD2Cl2 for 10 and 11. δ values are given in ppm and coupling constants in Hz; 31P NMR external chemical shift standard: 85% H3PO4. bTrans complex; only one 31P NMR peak. cIn CD2Cl2; the μBPE signal appeared at δ 30.3 (JPt−P = 2596). JPP(P2-μ-BPE) = 341 Hz, JPP(P1-μ-BPE) = 15 Hz). dTwo atropisomers.

Scheme 2. Synthesis of Pt(Me-DuPhos) Aryl Complexes ([Pt] = Pt((R,R)-Me-DuPhos))

restricted rotation about the Pt−C bond.16 An excess of the less hindered (6-methoxy-2-naphthyl)magnesium bromide gave diaryl complex 16. An attempt to prepare an aryl halide complex, analogous to 15, using 1 equiv of 6-methoxy-2naphthyl Grignard reagent per platinum still gave diaryl 16. Unfortunately, treatment of 16 with 1 equiv of HCl, generated from acetyl chloride and methanol,15 resulted in protonation of both aryl groups and formation of Pt((R,R)-Me-DuPhos)Cl2. Spectroscopic and Structural Characterization of the Bis(phospholane) Complexes. The new complexes Pt(diphos*)(R)(X) were characterized by spectroscopy and elemental analyses. They showed the expected AX 31P NMR patterns, with typical JPt−P values for the phosphorus nuclei trans to halide (about 4100 Hz) and a hydrocarbyl group (about 1700 Hz, Table 1). The crystal structures of complexes 3, 4, 6−10, and 14 are shown in Figures 1−8; see Table 2 and the Supporting Information for crystallographic details. The structures of the dihalide complexes Pt((R,R)-Me-BPE)X2 (12 and 13, Figures

Figure 1. ORTEP diagram of Pt((R,R)-Me-BPE)(Me)(Cl) (3).

S1 and S2) closely resembled those of analogous DuPhos complexes (see the Supporting Information for details).17 The structural parameters in these approximately squareplanar complexes were rather insensitive to the structure of the 6902

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Figure 2. ORTEP diagram of Pt((R,R)-Me-BPE)(Ph)(Cl) (4). Figure 4. ORTEP diagram of one of the three independent molecules of Pt((R,R)-i-Pr-DuPhos)(Me)(Cl) (7) in the unit cell.

Figure 3. ORTEP diagram of Pt((R,R)-Ph-BPE)(Ph)(Cl)·CHCl3 (6·CHCl3). The solvent molecule is not shown.

bis(phospholane) ligands, but data for several analogues showed consistent trends. For example, comparison of the Pt−P bond lengths in Pt-Ph and Pt-Me complexes of Me-BPE, Me-DuPhos, and Me-FerroLANE showed the trans influence order Ph > Me, although the effect was small.18 Switching from Me-BPE to Ph-BPE in Pt(BPE)(Ph)(Cl) complexes 4 and 6 resulted in slightly longer Pt−C, Pt−P, and Pt−Cl bonds, presumably due to the increased steric bulk of Ph-BPE. Otherwise, the most striking structural variation was evident in Me-FerroLANE complexes 8 and 9, in which the bite angles of 101−102° were much larger than those in the DuPhos and BPE complexes (bite angles 86−88°). The chelate Pt(Me-BPE) geometry in dication 10·3CH2Cl2 was similar to that of the

Figure 5. ORTEP diagram of Pt((R,R)-Me-FerroLANE)(Me)(Cl) (8). A 75/25 disorder in the Pt-Me and Cl groups is not shown.

other derivatives, despite replacement of the halide with a μBPE donor. Structure−Reactivity−Selectivity Relationships in Catalytic Asymmetric Phosphine Alkylation. The new catalyst precursors were tested in the known asymmetric alkylation of the bis(secondary phosphine) PhHP(CH2)3PHPh (17) with benzyl bromide (Scheme 3).2a,3 The product 18 is potentially useful as a DiPAMP analogue with an unusual three-carbon linker,19 and the catalytic reaction is challenging, since both 6903

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Figure 6. ORTEP diagram of Pt((R,R)-Me-FerroLANE)(Ph)(Cl) (9).

Figure 8. ORTEP diagram of Pt((R,R)-Me-BPE)Ph2 (14; one of the four independent molecules). Selected average bond lengths (Å) and angles (deg): Pt−P = 2.2871(19), Pt−C = 2.089(8); P−Pt−P = 85.36(7), C−Pt−C = 87.8(3), P−Pt−C(trans) = 178.0(2), P−Pt− C(cis) = 93.4(2).

was expected for complex 2, because, as a result of the absolute configuration conventions, (R,R)-Me-DuPhos and (R,R)-i-PrDuPhos have opposite configurations.1 Similarly, (R,R)-Ph-BPE and (R,R)-Me-BPE have opposite configurations, and their Pt(Ph)(Cl) complexes led to opposite enantiomers of 18. In general, replacing the Pt-Ph group with Pt-Me led to large decreases in selectivity, as observed previously.3 The low selectivity observed with FerroLANE complexes 8, 9, and 9T likely arose from displacement of this ligand from Pt; free MeFerroLANE was observed in the reaction mixtures by 31P NMR spectroscopy.

Figure 7. ORTEP diagram of the cation in [(Pt((R,R)-MeBPE)(Ph))2(μ-(R,R)-Me-BPE))][Cl]2·3CH2Cl2 (10·3CH2Cl2). Solvent molecules are not shown. Selected bond lengths (Å) and angles (deg): Pt(1)−C(15) = 2.058(6), Pt(1)−P(1) = 2.2902(16), Pt(1)− P(2) = 2.3214(15), Pt(1)−P(3) = 2.3383(15), Pt(2)−C(55) = 2.095(6), Pt(2)−P(4) = 2.2848(15), Pt(2)−P(5) = 2.3262(16), Pt(2)−P(6) = 2.3299(16); C(15)−Pt(1)−P(1) = 87.17(16), C(15)− Pt(1)−P(2) = 169.15(17), P(1)−Pt(1)−P(2) = 83.62(6), C(15)− Pt(1)−P(3) = 88.39(16), P(1)−Pt(1)−P(3) = 172.57(5), P(2)− Pt(1)−P(3) = 101.35(5), C(55)−Pt(2)−P(4) = 86.81(17), C(55)− Pt(2)−P(5) = 169.35(18), P(4)−Pt(2)−P(5) = 83.87(6), C(55)− Pt(2)−P(6) = 88.37(17), P(4)−Pt(2)−P(6) = 173.59(6), P(5)− Pt(2)−P(6) = 101.30(6).

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CONCLUSION

Preparation of the title bis(phospholane) complexes Pt(diphos*)(R)(Cl) was not as simple as anticipated from previous work with DuPhos complexes. The increased flexibility of the BPE and FerroLANE linkers presumably was responsible for complications such as the formation of BPE-bridged dication 10 and trans-coordinated intermediates, including 9T, in the synthesis of Me-FerroLANE complexes 8 and 9. Although the complexes were structurally very similar, the selectivities of these catalyst precursors in a test asymmetric phosphine alkylation were remarkably different, being much higher for the original catalyst Pt(Me-DuPhos)(Ph)(Cl) and emphasizing the importance of both the phospholane methyl substituents and the Pt-aryl group. As in earlier work,1 we hypothesize that Me-DuPhos is superior to Me-BPE because of its increased rigidity, while the more flexible Me-FerroLANE led to reduced selectivity, apparently because it was readily displaced from platinum. We plan to explore the generality of these structure−selectivity relationships with the new catalyst precursors in other asymmetric processes for P−C bond formation.

substrate 17 and product 18 might chelate to platinum and displace the chiral bis(phospholane) ligand. The reaction may be screened conveniently using 31P NMR spectroscopy because the rac and meso isomers of 18 have different chemical shifts.3 All the catalyst precursors described above promoted this reaction, which occurred in minutes in THF at room temperature using the base NaOSiMe3. Marked effects of precatalyst structure on the diastereoselectivity and enantioselectivity were observed (Table 3). The original catalyst precursor, Pt((R,R)-Me-DuPhos)(Ph)(Cl) (1), was found to be the most selective, followed by its closest structural analogues Me-BPE complex 4 and Ptphenanthryl complex 15, which share the same phospholane methyl substituents and contain Pt-aryl groups. Dication 10 gave selectivity similar to that of 4, consistent with dissociation of the bridging Me-BPE ligand during catalysis. These complexes preferentially formed the same enantiomer of 18, while all other precursors gave the opposite enantiomer.20 This 6904

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Table 2. Selected Bond Lengths (Å) and Angles (deg) for Pt(diphos*)(R)(Cl) Complexes

Pt−C Pt−X Pt−P (trans to R) Pt−P (trans to X) P−Pt−P C−Pt−X P−Pt−C (trans) P−Pt−X (trans) P−Pt−C (cis) P−Pt−X (cis) a

Pt((R,R)-MeBPE)(Me) (Cl) (3)

Pt((R,R)-MeDuPhos)(Me) (Cl)a

Pt((R,R)-i-PrDuPhos)(Me) (Cl) (7)b

Pt((R,R)-MeFerroLANE) (Me)(Cl) (8)

Pt((R,R)-MeFerroLANE) (Ph)(Cl) (9)

Pt((R,R)-Ph-BPE) (Ph)(Cl)·CHCl3 (6·CHCl3)

Pt((R,R)-MeBPE)(Ph) (Cl) (4)

Pt((R,R)-MeDuPhos)(Ph) (Cl)c

2.165(5) 2.3784(15) 2.2724(14)

2.264(13) 2.347(9) 2.223(5)

2.114(11) 2.360(3) 2.226(3)

2.1676(10) 2.3335(8) 2.3019(9)

2.066(8) 2.3792(17) 2.3534(19)

2.072(5) 2.4150(18) 2.3125(18)

2.061(3) 2.3789(8) 2.2833(9)

2.074(3) 2.3721(7) 2.2774(7)

2.1953(14)

2.205(5)

2.265(3)

2.2464(9)

2.2239(19)

2.2043(18)

2.1953(9)

2.2012(7)

86.66(5) 89.54(14) 178.72(14)

88.2(2) 93.9(12) 172.0(4)

88.43(9) 85.6(4) 174.2(3)

101.84(3) 84.5(2) 171.7(2)

101.04(6) 85.7(2) 171.5(2)

86.20(5) 90.16(13) 173.22(13)

86.35(3) 89.95(9) 176.58(10)

86.99(3) 89.47(8) 170.79(9)

176.02(5)

177.4(4)

173.38(10)

170.04(4)

172.76(6)

172.43(4)

176.47(3)

175.22(2)

92.44(14) 91.42(5)

96.0(4) 90.3(4)

92.7(4) 93.86(11)

86.4(2) 87.31(4)

87.4(2) 85.88(6)

91.65(13) 92.80(5)

93.57(9) 90.16(3)

93.67(8) 90.50(3)

Reference 24. bAverage for three independent molecules in the unit cell. cReference 25.

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Scheme 3. Pt-Catalyzed Asymmetric Alkylation of Bis(secondary phosphine) 17

General Experimental Details. Unless otherwise noted, all reactions and manipulations were performed in dry glassware under a nitrogen atmosphere at ambient temperature in a drybox or using standard Schlenk techniques. Petroleum ether (bp 38−53 °C), CH2Cl2, ether, THF, and toluene were dried over alumina columns similar to those described by Grubbs.21 NMR spectra were recorded by using a Varian 300 or 500 MHz spectrometer. 1H or 13C NMR chemical shifts are reported vs Me4Si and were determined by reference to the residual 1H or 13C solvent peaks. 31P NMR chemical shifts are reported vs H3PO4 (85%) used as an external reference. Coupling constants are reported in Hz, as absolute values. Unless indicated, peaks in NMR spectra are singlets. Quantitative Technologies Inc. provided elemental analyses. Mass spectrometry was performed at the University of Illinois. Unless otherwise noted, reagents were from commercial suppliers. The complexes Pt(COD)Cl2,22 Pt(COD)I2, Pt(COD)(Me)(Cl), Pt(COD)Ph2, Pt(COD)(Ph)(Cl), and Pt(COD)(Ph)(I),15 Pt((R,R)-Me-Duphos)(Ph)(Cl) (1) and Pt((R,R)-i-Pr-Duphos)(Ph)(Cl) (2),6 Pt((R,R)-Me-Duphos)(Me)(Cl),7 Pt((R,R)-Me-Duphos)Cl2,17a and [(S)-C6H4CH(Me)NMe2PdCl]223 were made by the literature methods. Pt((R,R)-Me-BPE)(Me)(Cl) (3). A solution of (R,R)-Me-BPE (50 mg, 0.21 mmol, 1 equiv) in 1 mL of CH2Cl2 was added to a solution of Pt(COD)(Me)(Cl) (73 mg, 0.21 mmol, 1 equiv) in 1 mL of CH2Cl2 at −78 °C. After it was stirred for 30 min at −78 °C, the mixture started to become cloudy. The cold bath was removed and, while still cold, the solvent was removed in vacuo, resulting in a sticky white precipitate. The solid was washed twice with petroleum ether (∼3 mL each), and the residual solid was dried under vacuum. 31P NMR analysis showed a mixture of the desired product and an impurity, the dinuclear dication [(Pt((R,R)-Me-BPE)(Me))2(μ-(R,R)-Me-BPE)][Cl]2, identified by 31P{1H} NMR spectroscopy (CDCl3) in analogy to the isolated Pt-Ph complex 10 (see below): δ 71.0 (dd, J = 8, 350, JPt−P = 2480), 68.4 (dd, J = 8, 16, JPt−P = 1725), 45.45 (dm, J = 350, JPt−P = 2520). The solid was dissolved in THF (∼3 mL), and the solution was filtered. Slow evaporation of the filtrate gave clear colorless blocks (68 mg (65%), pure by NMR spectroscopy). Anal. Calcd for C15H31ClP2Pt: C, 35.75; H, 6.20. Found: C, 35.92; H, 6.09. HRMS (ESI): m/z calcd for C15H31P2Pt (M − Cl)+ 468.1561, found m/z 468.1560. 31P{1H} NMR (CDCl3): δ 73.6 (d, J = 2, JPt−P = 1707), 64.9 (d, J = 2, JPt−P = 4045). 1H NMR (CDCl3): δ 3.03−2.97 (m, 1H), 2.82−2.75 (m, 1H), 2.29−2.08 (m, 6H), 1.76−1.60 (m, 4H), 1.56−1.41 (m, 4H), 1.40 (dd, J = 7, 17, 3H), 1.23 (dd, J = 7, 18, 3H), 1.18 (dd, J = 7, 15, 3H), 1.15 (dd, J = 7, 15, 3H), 0.54 (dd, J = 3, 7, JPt−H = 54, 3H). 13C{1H} NMR (CDCl3): δ 38.1 (d, J = 24, CH), 36.8 (d, J = 38, CH), 36.3 (dd, J = 2, CH2), 36.1 (d, J = 3, CH2), 35.3 (d, J = 2, CH2), 32.5 (d, J = 38, CH), 32.2 (d, J = 24, CH), 26.9 (dd, J = 34,

Table 3. Selectivity of Pt-Catalyzed Alkylation of Bis(secondary phosphine) 17 (Scheme 3)a entry 1 2 3 4 5 6 7 8 9 10 11 12 13

cat. precursor

yield, %

drb

erc

53 44 26 52

4.2 2.8 1.0 2.0 2.4

68:1 1:10 1:1.3 15.5:1 15.8:1

62 53 35 58 61 78 64

1.1 1.1 1.1 1.2 1.1 1.2 0.8

1:2.0 1:2.0 1:1.7 1:1.6 1:1.2 NDf NDg

42

2.6

13.6:1

d

Pt((R,R)-Me-DuPhos)(Ph)(Cl) (1) Pt((R,R)-i-Pr-DuPhos)(Ph)(Cl) (2) Pt((R,R)-Me-BPE)(Me)(Cl) (3) Pt((R,R)-Me-BPE)(Ph)(Cl) (4) [(Pt((R,R)-Me-BPE)(Ph))2(μ-(R,R)-MeBPE))][Cl]2 (10)e Pt((R,R)-Ph-BPE)(Me)(Cl) (5) Pt((R,R)-Ph-BPE)(Ph)(Cl) (6) Pt((R,R)-Me-DuPhos)(Me)(Cl) Pt((R,R)-i-Pr-DuPhos)(Me)(Cl) (7) Pt((R,R)-Me-FerroLANE)(Me)(Cl) (8) Pt((R,R)-Me-FerroLANE)(Ph)(Cl) (9) trans-[Pt((R,R)-Me-FerroLANE)(Ph) (Cl)]n (9T) Pt((R,R)-Me-DuPhos)(9-phenanthryl) (Br) (15)

EXPERIMENTAL SECTION

a

Conditions: 10 mol % of Pt catalyst, 2 equiv of PhCH2Br, 2 equiv of NaOSiMe3 in THF. Isolated yields are reported. The reactions proceeded in high yield according to 31P NMR monitoring; the modest isolated yields are due to the small scale. The diastereomeric ratio in the crude product mixture matched that observed for the isolated products. See the Experimental Section for details bdr = rac:meso ratio. cCatalyst precursors 1, 4, and 15 preferentially formed one enantiomer of 18, and the other catalyst precursors favored the other enantiomer. The absolute configuration of 18 has not been determined.20 dData from duplicate experiments in ref 26; see also ref 3. e4.5% catalyst loading. fND = not determined gNote that the low solubility of 9T in THF was anomalous in this series of catalyst precursors, but we tried to carry out the catalytic reaction under similar conditions.

6905

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Organometallics

Article

18, CH2), 21.7 (dd, J = 24, 6, CH2), 19.3−19.2 (m, CH2 and Me), 14.4 (Me), 13.9 (Me), 5.9 (dd, J = 7, 96, Pt-Me). Pt((R,R)-Ph-BPE)(Me)(Cl) (5). A solution of (R,R)-Ph-BPE (50 mg, 0.10 mmol, 1 equiv) in 1 mL of CH2Cl2 was added to a solution of Pt(COD)(Me)(Cl) (35 mg, 0.10 mmol, 1 equiv) in 1 mL of CH2Cl2 at room temperature. After the mixture was stirred for 30 min, the solvent was removed in vacuo, resulting in a yellowish precipitate. The solid was washed twice with petroleum ether (∼3 mL each), and the remaining solid was dried under vacuum. Colorless blocks (56 mg, 76% yield) were obtained after recrystallization from CH2Cl2 layered with MeOH at −30 °C. Anal. Calcd for C35H39ClP2Pt: C, 55.89; H, 5.23. Found: C, 55.80; H, 5.42. HRMS (ESI): m/z calcd for C35H39P2Pt (M − Cl)+ 716.2178, found m/z 716.2203. 31P{1H} NMR (CDCl3): δ 73.9 (JPt−P = 1712), 64.8 (JPt−P = 4256). 1H NMR (CDCl3): δ 7.58−7.56 (m, 2H), 7.32− 7.08 (m, 14H), 6.94−6.93 (m, 2H), 6.87−6.85 (m, 2H), 4.53−4.47 (m, 1H), 4.10−3.99 (m, 1H), 3.31−3.17 (m, 2H), 2.55−2.24 (m, 5H), 2.17−2.00 (m, 1H), 1.29−1.24 (m, 1H), 1.15−0.99 (m, 2H), 0.95− 0.84 (m, 2H), 0.72−0.61 (m, 1H), 0.60−0.47 (dd, JP−H = 8, 3, JPt−H = 50, 3H). 13C{1H} NMR (CDCl3): δ 139.0 (d, J = 5), 137.9, 137.3 (d, J = 5), 135.4 (d, J = 5), 129.5 (d, J = 6), 128.8 (d, J = 2), 128.6 (d, J = 2), 128.35, 128.31 (d, J = 2), 128.2 (d, J = 6), 128.0 (d, J = 4), 127.3 (d, J = 4), 127.0 (d, J = 2), 126.7 (d, J = 2), 126.4 (d, J = 3), 52.0 (d, J = 19, CH), 48.8 (d, J = 33, CH), 43.7 (CH), 43.5 (d, J = 19, CH), 36.9 (d, J = 19, CH2), 33.6 (d, J = 19, CH2), 32.8 (CH2), 30.6 (CH2), 29.2 (dd, J = 17, 34, CH2), 23.5 (dd, J = 6, 23, CH2), 5.0 (dd, J = 7, 98, PtCH3). Pt((R,R)-Ph-BPE)(Ph)(Cl) (6). A solution of (R,R)-Ph-BPE (50 mg, 0.01 mmol, 1 equiv) in 1 mL of CH2Cl2 was added to a solution of Pt(COD)(Ph)(Cl) (41 mg, 0.01 mmol, 1 equiv) in 1 mL of CH2Cl2. The reaction mixture was stirred at room temperature for 30 min. All volatiles were removed in vacuo, giving a sticky white solid, which was washed twice with petroleum ether (∼3 mL each). The solution was decanted, and the residue was dried in vacuo, yielding a white solid. Recrystallization from CH2Cl2 or CHCl3 layered with petroleum ether gave colorless blocks (75 mg, 93% yield). Anal. Calcd for C40H41ClP2Pt: C, 59.00; H, 5.08. Found: C, 58.79; H, 4.97. HRMS: m/z calcd for C40H41ClP2PtNa (M + Na)+ 837.1921, found m/z 837.1925. 31P{1H} NMR (CDCl3): δ 69.7 (JPt−P = 1645), 59.2 (JPt−P = 4168). 1H NMR (CDCl3): δ 7.75−7.73 (m, 2H), 7.42− 7.38 (m, 3H), 7.32−7.29 (m, 3H), 7.27−7.15 (m, 8H), 7.09−7.06 (m, 6H), 6.92−6.89 (m, 1H), 6.83−6.81 (m, 2H), 4.75−4.69 (m, 1H), 4.11−3.99 (m, 1H), 3.28−3.18 (m, 2H), 2.61−2.47 (m, 2H), 2.38− 2.28 (m, 1H), 2.15−1.97 (m, 3H), 1.95−1.86 (m, 1H), 1.71−1.61 (m, 1H), 1.18−1.06 (m, 2H), 0.95−0.74 (m, 2H). 13C{1H} NMR (CDCl3): δ 159.5 (d, J = 8, Ar), 158.6 (Ar), 139.1 (d, J = 4, Ar), 137.3−137.1 (overlapping m, Ar), 137.2 (Ar), 137.1 (d, J = 5, Ar), 136.6 (d, J = 5, Ar), 129.8 (d, J = 6, Ar), 128.9 (d, J = 2, Ar), 128.7 (d, J = 2, Ar), 128.5 (d, J = 1, Ar), 128.3 (d, J = 1, Ar), 128.13 (d, J = 9, Ar), 128.12 (Ar), 127.7 (d, J = 8, Ar), 127.6 (d, J = 4, Ar), 126.97 (d, J = 2, Ar), 126.94 (d, J = 2, Ar), 126.55 (d, J = 3, Ar), 126.48 (d, J = 3, Ar), 52.1 (d, J = 21, CH), 48.9 (d, J = 35, CH), 42.4 (d, J = 19, CH), 41.5 (d, J = 31, CH), 36.6 (d, J = 6, CH2), 33.2 (CH2), 31.9 (d, J = 6, CH2), 30.7 (CH2), 29.5 (dd, J = 16, 33, CH2), 23.5 (dd, J = 5, 20, CH2). Pt((R,R)-i-Pr-DuPhos)(Me)(Cl) (7). A solution of (R,R)-i-PrDuPhos (50 mg, 0.12 mmol, 1 equiv) in 1 mL of CH2Cl2 was added to a solution of Pt(COD)(Me)(Cl) (42 mg, 0.12 mmol, 1 equiv) in 1 mL of CH2Cl2 at room temperature. After the mixture was stirred for 30 min, the solvent was removed in vacuo, giving an offwhite solid. The solid was washed twice with petroleum ether (∼3 mL each) and then dried under vacuum. Recrystallization by vapor diffusion of ether into a CH2Cl2 solution at −30 °C gave colorless blocks (70 mg, 89% yield). Anal. Calcd for C27H47ClP2Pt: C, 48.83; H, 7.13. Found: C, 48.65; H, 7.10. 31P{1H} NMR (CDCl3): δ 64.3 (d, J = 2, JPt−P = 1734), 50.2 (d, J = 2, JPt−P = 4119). 1H NMR (CDCl3): δ 7.76−7.73 (m, 1H), 7.70−7.69 (m, 1H), 7.54−7.51 (m, 2H), 2.98−2.92 (m, 1H), 2.70− 2.63 (m, 1H), 2.53−2.16 (m, 7H), 2.08−1.98 (m, 1H), 1.86−1.67 (m, 2H), 1.66−1.51 (m, 2H), 1.34−1.23 (m, 1H), 1.19−1.10 (m, 1H),

1.07 (d, J = 7, 3H), 1.02 (d, J = 7, 3H), 0.93 (dd, J = 7, 10, 3H), 0.90− 0.84 (m, 3H), 0.79 (d, J = 7, 3H), 0.75 (d, J = 7, 3H), 0.72 (d, J = 7, 3H), 0.70 (d, J = 7, 3H), 0.69 (overlapping dm, J = 7, 3H, Pt-Me). 13 C{1H} NMR (C6D6): δ 133.5 (d, J = 13, Ar), 132.6 (dd, J = 3, 14, Ar), 130.5 (m, Ar), 54.3 (d, J = 22, CH), 53.4 (d, J = 37, CH), 49.4 (d, J = 34, CH), 48.1 (d, J = 23, CH), 31.4 (d, J = 4, CH2), 31.3 (CH2), 30.5 (d, J = 4, CH2), 30.4 (d, J = 5, CH), 29.8 (d, J = 8, CH), 28.3 (d, J = 15, CH), 25.6 (d, J = 7, CH3), 25.4 (d, J = 6, CH3), 24.8 (d, J = 6, CH3), 24.6 (d, J = 6, CH3), 21.6 (d, J = 9, CH3), 21.2 (d, J = 10, CH3), 21.0 (d, J = 8, CH3), 20.8 (d, J = 6, CH3), 6.2 (dd, J = 6, 105, Pt-CH3). The quaternary aryl signals were not observed. Pt((R,R)-Me-FerroLANE)(Me)(Cl) (8). A bright red solution of (R,R)-Me-FerroLANE (200 mg, 0.48 mmol) in 3 mL of THF was added to a yellow solution of Pt(COD)(Me)(Cl) (171 mg, 0.48 mmol) in 3.5 mL of THF, giving a reddish orange solution, which was stirred for 1 h. The solvent was removed under vacuum, leaving a reddish orange solid, which was washed with two 5 mL aliquots of pentane and dried under vacuum. The 31P{1H} NMR spectrum (C6D6) showed signals due to product 8 (ca. 50%, δ 36.6 (d, J = 11, JPt−P = 1767), 31.7 (d, J = 11, JPt−P = 4245)) as well as several unidentified signals at δ 36.1 (JPt−P = 2943), 34.0 (m, JPt−P = 2975, broad Pt satellites), and 32.6 (JPt−P = 3002). The solid was dissolved in 12 mL of toluene, and the solution was heated for 6 days at 63 °C in an oil bath. 31P{1H} NMR analysis (toluene) showed that all of these intermediates were converted to 8 after heating. The solvent was pumped off, giving 296 mg of orange solid (85% yield). Vapor diffusion of pentane into a toluene solution at −20 °C gave orange Xray-quality crystals. Elemental analysis was performed on orange crystals grown by vapor diffusion of pentane into a THF solution. NMR spectra were obtained on a sample recrystallized by layering pentane onto a concentrated THF solution, left at −20 °C for 1 week. Anal. Calcd for C23H37ClP2FePt: C, 41.84; H, 5.35. Found: C, 42.26; H, 5.21. HRMS (ESI): m/z calcd for C23H37ClP2FePt (M − Cl)+ 623.1990, found m/z 623.1199. 31P{1H} NMR (C6D6): δ 36.6 (d, JPt−P = 1767, J = 11), 31.8 (d, JPt−P = 4244, J = 11). 1H NMR (C6D6): δ 4.28−4.24 (m, 2H, CpH), 4.10−4.06 (m, 2H, CpH), 3.98 (br, 2H, CpH), 3.96−3.91 (m, CH2, 1H), 3.65 (br, 1H, CpH), 3.59 (br, 1H, CpH), 2.67−2.57 (m, 1H, CH), 2.41−2.23 (m, 2H, CH), 2.03−1.94 (m, 1H, CH), 1.90−1.84 (m, 1H, CH2), 1.80 (dd, JP−H = 18, JH−H = 7, 3H, CH3), 1.77−1.68 (m, 1H, CH2), 1.45−1.40 (m, 1H, CH2), 1.39 (dd, JP−H = 19, JH−H = 8, 3H, CH3), 1.32 (dd, JP−H = 7, 4, JPt−H = 60, 3H, Pt-CH3), 1.20−0.99 (m, 4H, CH2), 0.95 (dd, JP−H = 18, JH−H = 7, 3H, CH3), 0.71 (dd, JP−H = 15, JH−H = 7, 3H, CH3). 13C{1H} NMR (C6D6): δ 76.7 (d, J = 15, Cp), 75.3 (d, J = 17, Cp), 74.2 (d, J = 8, Cp), 74.0 (d, J = 8, Cp), 73.2 (d, J = 3, JPt−C = 32, broad Pt satellites, Cp), 72.9 (Cp), 72.3 (quat-Cp, overlapping neighboring peaks), 72.2 (d, J = 3, Cp), 72.0 (d, J = 5, Cp), 70.5 (d, J = 30, quat-Cp), 37.3 (CH2), 36.3 (d, J = 3, JPt−C = 22, CH2), 35.8 (d, J = 1, JPt−C = 14, CH2), 35.3 (d, J = 29, JPt−C = 15, CH), 34.6 (d, J = 27, JPt−C = 16, CH), 34.2 (d, J = 3, JPt−C = 57, CH2), 33.3 (d, J = 40, JPt−C = 44, CH), 33.0 (d, J = 41, JPt−C = 65, CH), 22.2 (d, J = 7, JPt−C = 55, CH3), 21.3 (d, J = 10, JPt−C = 25, CH3), 15.0 (CH3), 14.3 (CH3), 8.7 (dd, J = 98, 9, JPt−C = 480, Pt-CH3). trans-[Pt((R,R)-Me-FerroLANE)(Ph)(Cl)]n (9T). A bright red solution of (R,R)-Me-FerroLANE (100 mg, 0.24 mmol, 1 equiv) in 5 mL of THF was added in two aliquots to a beige solution of Pt(COD)(Ph)(Cl) (100 mg, 0.24 mmol, 1 equiv) in 5 mL of THF, giving a reddish orange solution. The mixture was stirred for 1 h, and a milky orange slurry formed. The slurry was filtered over a frit, giving an orange solid and an orange filtrate. The 31P{1H} NMR spectrum (THF) of the filtrate showed signals due to cis product 9 (ca. 40%, δ 28.7 (d, J = 14, JPt−P = 4236), 28.1 (d, J = 15, JPt−P = 1622)) as well as several unidentified signals at δ 31.0, 30.7, 30.6 (ca. 50%, JPt−P = 2942), 30.4, 29.2, and 27.3. The 31P{1H} NMR spectrum (toluene) of the orange solid showed only one peak due to 9T (δ 31.2, JPt−P = 2927). The orange solid was washed with two 5 mL aliquots of pentane and then dried under vacuum, leaving 122 mg of orange solid (70% yield). This material was sparingly soluble in most solvents but could be recrystallized from chloroform/pentane by vapor diffusion to give a chloroform adduct, identified by elemental analysis. The amount of 6906

dx.doi.org/10.1021/om300704e | Organometallics 2012, 31, 6900−6910

Organometallics

Article

cocrystallized chloroform could not readily be determined by 1H NMR integration because of the low solubility of 9T. Anal. Calcd for C28H37ClP2FePt: C, 46.58; H, 5.17. Anal. Calcd for C28H37ClP2FePt·CHCl3: C, 41.40; H, 4.55. Found: C, 41.96; H, 4.45. HRMS (ESI): m/z calcd for C28H37P2FePt (M − Cl)+ 686.1368, found m/z 686.1377. 31P{1H} NMR (CDCl3): δ 31.4 (broad Pt satellites, JPt−P = 2936). 1H NMR (CDCl3): δ 7.41 (d, J = 7, 2H, Ar), 6.85 (t, J = 7, 2H, Ar), 6.73 (t, J = 7, 1H, Ar), 4.90 (4H, CpH), 4.78 (2H, CpH), 4.68 (2H, CpH), 2.86 (br, 2H, CH), 2.16 (br, 4H, CH2), 1.96 (br, 2H, CH), 1.73 (dd, JP−H = 17, JH−H = 9, 6H, Me), 1.59−1.50 (m, 4H, CH2), 0.23 (dd, JP−H = 13, JH−H = 7, 6H, Me). 13C{1H} NMR (CDCl3): δ 138.8 (Ph), 135.2 (quat, Pt−C(Ph)), 127.8 (Ph), 121.9 (Ph), 77.0 (m, quat Cp, overlapping CDCl3 peak), 74.2 (t, J = 22, Cp), 72.8 (Cp), 72.7 (Cp), 38.3 (t, J = 18, CH), 34.2 (CH2), 34.0 (CH2), 31.5 (t, J = 18, CH), 20.2 (br, CH3), 13.7 (CH3). The initial orange filtrate was pumped down under vacuum, leaving an orange oily solid, which was washed with two 5 mL aliquots of pentane. The solid was dried under vacuum, leaving 40 mg of solid as a mixture of products (23% yield). No effective conversion or separation of 9 and 9T was possible by heating (see 8) or extraction. Vapor diffusion of pentane into a THF solution gave a supernatant slightly further enriched in 9, but the desired isomer could not be isolated in pure form by this method. Orange X-ray-quality crystals of 9 were grown over 1 week from the pentane solution used to wash the orange oily solid. Pt((R,R)-Me-FerroLANE)(Ph)(Cl) (9). A solution of 5 mg of 9T (0.007 mmol, 1 equiv) and 2 mg of AgOTf (0.007 mmol, 1 equiv) in 1.5 mL of CDCl3 was stirred for 30 min, filtered through Celite to give a bright yellow filtrate, treated with 1 mg of LiCl (0.023 mmol, 3.4 equiv), and filtered through Celite again. The resulting solution gave a clean 31P{1H} NMR (CDCl3) spectrum consistent with 9. On a 50 mg Pt scale, a byproduct 31P{1H} NMR signal was observed at δ 40.5 (CHCl3), but using 40 mg of 9T (0.055 mmol, 1 equiv), 13 mg of AgOTf (0.050 mmol, 0.9 equiv), and 5 mg of LiCl (0.12 mol, 2.1 equiv) gave 28 mg (70% yield) of a yellow-orange solid (ca. 95% 9, 5% byproduct), which could not be obtained analytically pure. Treatment of 30 mg of the soluble fraction obtained in the synthesis of 9T (see above) with 1 equiv of AgOTf gave ca. 50% 9 and ca. 50% of the δ 40.5 byproduct. HRMS (ESI): m/z calcd for C28H37P2FePt (M − Cl)+ 686.1368, found m/z 686.1373. 31P{1H} NMR (C6D6): δ 29.2 (d, J = 15, JPt−P = 4242), 28.7 (d, J = 15, JPt−P =1639). 1H NMR (C6D6): δ 7.89−7.69 (m, 2H, Ar), 7.25 (br, 2H, Ar), 7.03 (t, J = 7, 1H, Ar), 4.41 (br, 1H, CpH), 4.35 (br, 1H, CpH), 4.19 (br, 2H, CpH), 4.04 (br, 1H, CpH), 4.03 (br, 1H, CpH), 3.86−3.79 (m, 1H, CH), 3.78 (br, 1H, CpH), 3.64 (br, 1H, CpH), 2.54−2.44 (m, 1H, CH), 2.43−2.33 (m, 1H, CH), 2.04−1.99 (m, 1H, CH), 1.95 (dd, JH−H = 7, JP−H = 17, 3H, Me), 1.91−1.67 (m, 4H, CH2), 1.69 (dd, JH−H = 7, JP−H = 19, 3H, Me), 1.15−1.01 (m, 2H, CH2), 0.96 (dd, JH−H = 7, JP−H = 14, 3H, Me), 0.95−0.81 (m, 2H, CH2), 0.55 (dd, JH−H = 7, JP−H = 16, 3H, Me). 13 C{1H} NMR (C6D6): δ 158.7 (dd, J = 9, 115, quat, Pt−C(Ph)), 136.4 (Ph), 128.0 (Ph, overlapping C6D6 peaks), 123.4 (Ph), 77.1 (dd, J = 3, 17, Cp), 74.3 (d, J = 7, Cp), 74.1 (d, J = 15, Cp), 73.9 (d, J = 9, Cp), 73.2 (d, J = 2, Cp), 72.7 (Cp), 72.4 (dd, J = 7, 51, quat Cp), 72.4 (d, J = 4, Cp), 71.8 (d, J = 3, Cp), 69.1 (dd, J = 1, 31, quat Cp), 37.2 (CH2), 35.9 (d, J = 3, CH2), 35.7 (br, CH2), 35.1 (d, J = 10, CH), 34.8 (d, J = 19, CH), 34.6 (d, J = 25, CH), 34.5 (dd, J = 2, 42, CH), 33.6 (d, J = 3, CH2), 22.1 (d, J = 7, Me), 20.4 (d, J = 10, Me), 15.0 (Me), 13.9 (Me). [(Pt((R,R)-Me-BPE)(Ph))2(μ-(R,R)-Me-BPE))][Cl]2 (10). A solution of Pt(COD)(Ph)(Cl) (86 mg, 0.21 mmol, in 1 mL of CH2Cl2) was added to a solution of (R,R)-Me-BPE (50 mg, 0.21 mmol, in 1 mL of CH2Cl2). The reaction mixture was stirred at either room temperature or −78 °C for 15−30 min (the results were the same at both temperatures). All volatiles were removed in vacuo, giving an off-white solid, which was washed twice with petroleum ether (3 mL). The residue was dissolved in 1 mL of CH2Cl2, layered with THF, and cooled to −30 °C. Thin needles crystallized overnight (70 mg, 25% yield, pure by NMR spectroscopy).

The same batch of crystals was used for elemental analysis and crystal structure determination. Three equivalents of CH2Cl2 per dinuclear Pt complex was observed in the crystal structure, and the elemental analysis results are most consistent with loss of some of these solvent molecules. Anal. Calcd for C54H94Cl2P6Pt2: C, 46.65; H, 6.82. Calcd for C54H94Cl2P6Pt2·1.5CH2Cl2: C, 43.92; H, 6.44. Found: C, 44.10; H, 7.01. 31P{1H} NMR (CD2Cl2): δ 64.5 (dd, J = 7, 341, JPt−P = 2498), 59.8 (dd, J = 8, 15, JPt−P = 1606), 30.3 (dm, J = 333, JPt−P = 2596). 1H NMR (CD2Cl2): δ 7.28−7.01 (m, 10H), 2.54−1.68 (m, 36H), 1.58−0.90 (m, 48H). 13C{1H} NMR (CD2Cl2): δ 137.9, 136.2, 130.5, 129.4, 124.3, 40.8 (CH), 40.4 (CH), 38.8 (d, J = 28, CH), 37.6 (CH2), 37.4 (CH2), 36.6 (CH2), 36.4 (CH2), 35.9 (d, J = 22, CH), 35.0 (CH2), 33.8 (CH), 31.0 (d, J = 20, CH), 23.1 (CH2), 22.2 (CH2), 20.4 (CH3), 19.7 (d, J = 7, CH3), 19.2 (d, J = 4, CH3), 14.8 (CH3), 14.1 (CH3), 13.7 (CH3). Pt((R,R)-Me-BPE)(Ph)(I) (11). A pale beige solution of Pt(COD)(Ph)(I) (98 mg, 0.19 mmol) in 1.5 mL of CH2Cl2 was cooled to −78 °C. A clear solution of (R,R)-Me-BPE (50 mg, 0.19 mmol) in 1.5 mL of CH2Cl2 was added dropwise, and the reaction mixture was stirred for 24 h, with gradual warming to room temperature. The solvent was pumped off, giving an opaque solid, which was washed with two 5 mL aliquots of pentane, giving a white solid. The solvent was again pumped off, giving 126 mg of white solid (99% yield). However, 31P NMR (CD2Cl2) showed unidentified impurities at δ 62.1 (m), 59.8 (m), 37.0 (m), 30.5 (m), and 28.9 (m), and the crude sample contained ca. 95% of the major product. Additional impurities (31P{1H} NMR δ 74.2 and 1H NMR δ 1.18 (dd, JHH = 7, JP−H = 16)) were consistent with Pt((R,R)-Me-BPE)I2 (13; see below). Vapor diffusion of pentane into a THF solution gave long white needles, but growth of all of the listed impurities was observed by 31P{1H} NMR. The preparation was reproduced on the same scale once in the dark and again using THF in place of CH2Cl2. In both cases, significantly more of the impurities (31P NMR δ 37.0−28.9) were observed. Pt((R,R)-Me-BPE)(Ph)(I) was ca. 85% of the mixture. Because the compound decomposed upon attempted recrystallization, analytically pure material could not be obtained. HRMS (ESI): m/z calcd for C20H33P2Pt (M − I)+ 530.1705, found m/z 530.1708. 31P{1H} NMR (CD2Cl2): δ 67.7 (d, J = 4, JPt−P = 1635), 60.0 (d, J = 4, JPt−P = 3964). 1H NMR (C6D6): δ 7.88−7.75 (m, 2H, Ar), 7.25 (td, J = 7, 1, 2H, Ar), 7.02 (t, J = 7, 1H, Ar), 3.21−3.12 (m, 1H), 2.52−2.41 (m, 1H), 1.89−1.58 (m, 5H), 1.44 (dd, JP−H = 18, JH−H = 6, 3H, Me), 1.40−1.22 (m, 3H), 1.09 (dd, JP−H = 18, JH−H = 7, 3H, Me), 1.06−0.92 (m, 3H), 0.90−0.80 (m, 1H), 0.85 (dd, JP−H = 14, JH−H = 7, 3H, Me), 0.80−0.70 (m, 2H), 0.77 (dd, JP−H = 15, JH−H = 7, 3H, Me). 13C{1H} NMR (C6D6): δ 164.5 (dd, J = 119, 9, quat, Pt-Ph), 138.0 (br, JPt−C = 24, Ar), 137.5 (apparent t, J = 2, JPt−C = 37, Ar), 121.7 (JPt−C = 12, Ar), 38.0 (d, J = 26, CH), 36.4 (d, J = 37, CH), 36.2 (d, J = 3, CH2), 36.1 (CH2), 35.1 (br d, J = 4, CH2), 34.3 (d, J = 2, JPt−C = 50, broad Pt satellites), 30.9 (d, J = 26), 30.2 (dd, J = 47, 2), 26.6 (dd, J = 34, 18, CH2), 20.6 (dd, J = 23, 6, CH2), 19.5 (Me), 19.3 (Me), 14.0 (d, J = 1, Me), 13.3 (d, J = 1, Me). Pt((R,R)-Me-BPE)Cl2 (12). A clear solution of (R,R)-Me-BPE (100 mg, 0.387 mmol) in 1.5 mL of CH2Cl2 was added to a stirred white slurry of Pt(COD)Cl2 (145 mg, 0.387 mmol) in 1 mL of CH2Cl2. The resulting pale yellow slurry gave a bright yellow homogeneous solution. After it was stirred for 35 min, the solution became a yellow slurry again. The solvent was removed under vacuum, leaving a pale yellow solid, which was washed with two 5 mL aliquots of pentane and dried under vacuum to give 198 mg of pale yellow solid (98% yield). Vapor diffusion of pentane into a CH2Cl2 solution at −20 °C gave white crystals, which were used for elemental analysis. Anal. Calcd for C14H28Cl2P2Pt: C, 32.07; H, 5.38. Found: C, 31.83; H, 5.27. HRMS (ESI): m/z calcd for C14H28P2Pt (M − Cl)+ 488.1003, found 488.0996. 31P{1H} NMR (CD2Cl2): δ 74.1 (JPt−P = 3517). 1H NMR (CD2Cl2): δ 3.34−3.22 (m, 2H), 2.32−2.09 (m, 6H), 1.82−1.62 (m, 8H), 1.42 (dd, JH−H = 7, JP−H = 18, 6H, Me), 1.21 (dd, JH−H = 7, JP−H = 16, 6H, Me). 13C{1H} NMR (CD2Cl2): δ 37.9 (d, JP−C = 38, JPt−C = 34, CH), 35.7 (d, JP−C = 4, CH2), 35.4 (d, JP−C = 2, JPt−C = 38, CH2), 33.6 (d, JP−C = 37, JPt−C = 37, CH), 24.7 (dd, JPt−C = 122, JP−C = 7, 34, CH2), 18.8 (d, JP−C = 3, JPt−C = 37, Me), 13.6 (Me). 6907

dx.doi.org/10.1021/om300704e | Organometallics 2012, 31, 6900−6910

Organometallics

Article

Pt((R,R)-Me-BPE)I2 (13). A clear solution of (R,R)-Me-BPE (100 mg, 0.388 mmol) in 1.5 mL of CH2Cl2 was added dropwise to a yellow solution of Pt(COD)I2 (216 mg, 0.388 mmol) in 5 mL of CH2Cl2 at −78 °C. The reaction mixture was stirred for 16 h, as the cold bath was warmed. No color change was immediately observed. After gradual warming to room temperature, the mixture became an orange slurry. After the solvent was pumped off, the orange solid was washed with two 5 mL aliquots of pentane and redissolved in 3 mL of CH2Cl2. The solvent was again pumped off, giving 265 mg of an orange solid (97% yield). Orange crystals were grown from very slow evaporation of a CH2Cl2 solution and were used for elemental analysis and X-ray crystallography. Note that when this reaction was done at room temperature, an unidentified impurity (31P NMR δ 73.0) was also formed. Anal. Calcd for C14H28I2P2Pt: C, 23.78; H, 3.99. Found: C, 24.19; H, 4.03. HRMS: m/z calcd for C14H28P2Pt (M − I)+ 580.0359, found 580.0353. 31P{1H} NMR (CH2Cl2): δ 74.5 (JPt−P = 3263). 1H NMR (CD2Cl2): δ 3.90−3.83 (m, 2H), 2.30−2.14 (m, 8H), 1.97−1.90 (m, 2H), 1.72−1.48 (m, 4H), 1.38 (dd, JH−H = 7, JP−H = 19, 6H, Me), 1.20 (dd, JH−H = 7, JP−H = 16, 6H, Me). 13C{1H} NMR (CD2Cl2): δ 38.3 (d, JP−C = 35, JPt−C = 36, CH), 36.4 (d, JP−C = 38, JPt−C = 39, CH), 35.9 (broad, CH2), 35.8 (broad, JPt−C = 36, CH2), 25.1 (dd, JP−C = 9, 32, CH2), 19.3 (broad, JPt−C = 39, Me), 13.8 (Me). Pt((R,R)-Me-BPE)Ph2 (14). A clear solution of (R,R)-Me-BPE (36 mg, 0.14 mmol) in 2.5 mL of THF was added quickly to a golden brown solution of Pt(COD)Ph2 (64 mg, 0.14 mmol) in 1.5 mL of THF. The solution was stirred for 1 h, and the solvent was pumped off, giving a white solid, which was washed with two 4-mL aliquots of cold pentane and dried again under vacuum, giving 85 mg of white solid (99% yield). Vapor diffusion of pentane into a THF solution gave opaque white crystals, which were used for X-ray crystallography. Anal. Calcd for C26H38P2Pt: C, 51.39; H, 6.30. Found: C, 51.42; H, 5.74. HRMS (ESI): m/z calcd for C26H38P2Pt 607.2097, found m/z 607.2096. 31P{1H} NMR (C6D6): δ 60.3 (JPt−P = 1636). 1H NMR (C6D6): δ 7.79 (app t, JPt−H = 59, J = 6, 4H, Ar(ortho)), 7.25 (td, JP−H = 2, JH−H = 8, 4H, Ar), 6.94 (t, J = 7, 2H, Ar), 2.52 (m, JH−H = 6, 2H, CH), 1.56−1.39 (m, 6H), 1.32−1.24 (m, 1H), 1.20 (dd, JP−H = 17, JH−H = 7, 6H, CH3), 1.10−0.94 (m, 3H), 0.90 (dd, JP−H = 14, JH−H = 7, 6H, CH3), 0.88−0.74 (m, 4H). 13C{1H} NMR (C6D6): δ 164.7 (dd, J = 110, 9, quat, Pt−C), 137.5 (t, J = 2, JPt−C = 36, Ph), 127.8 (d, J = 27, JPt−C = 60, Ph), 121.8 (Ph), 37.8 (d, J = 27, JPt−C = 26, CH), 35.5 (d, J = 2, CH2), 35.3 (JPt−C = 22, CH2), 28.9 (dd, JPt−C = 27, J = 25, 2, CH), 23.8 (dd, J = 23, 15, JPt−C = 26, CH2), 19.5 (d, J = 9, JPt−C = 32, Me), 13.9 (Me). Pt((R,R)-Me-BPE)(Ph)(Cl) (4). Pt((R,R)-Me-BPE)Ph2 (14; 110 mg, 0.18 mmol) was dissolved in 5 mL of a 3:2 mixture of CH2Cl2 and MeOH. With stirring, 12.8 μL (0.18 mmol, 1 equiv) of acetyl chloride was added, and the solution was stirred for 30 min. The 31P{1H} NMR spectrum (CH2Cl2/MeOH) of the solution showed signals due to 4 (ca. 70%) as well as impurities at δ 73.0 (Pt((R,R)-Me-BPE)Cl2 (12), ca. 25%), 64.5, and 60.7. Concentration of the solution caused white solid to precipitate, and the slurry was filtered over a frit to give 12 mg of white solid 12. The filtrate was pumped down under vacuum, leaving an oily white solid. Extraction of the solid with 5 mL of toluene left behind most residual 12, giving 78 mg of 4 (81% yield). Vapor diffusion of pentane into a toluene solution gave white X-ray-quality crystals, but the 31P{1H} NMR spectrum of the sample still showed minor impurities (ca. 5%) at δ 64.5 and 60.7. Analytically pure material could not be obtained, and slow decomposition occurred on attempted recrystallization. HRMS (ESI): m/z calcd for C20H33P2Pt (M − Cl)+ 530.1705, found m/z 530.1696. 31P{1H} NMR (C6D6): δ 66.8 (d, J = 4, JPt−P = 1598), 59.6 (d, J = 4, JPt−P = 3885). 1H NMR (C6D6): δ 7.83 (app td, J = 7, 1, JPt−H = 39, 2H), 7.28 (app td, J = 10, 1, 2H), 7.04 (t, J = 7, 1H), 3.21−3.14 (m, 1H), 2.52−2.45 (m, 1H), 1.86−1.52 (m, 4H), 1.44 (dd, J = 18, 7, 3H, Me), 1.46−1.13 (m, 4H), 1.07 (dd, J = 18, 7, 3H, Me), 0.96−0.84 (m, 3H), 0.81 (dd, J = 14, 7, 3H, Me), 0.73 (dd, J = 15, 7, 3H, Me), 0.78−0.74 (m, 2H), 0.66−0.62 (m, 1H). 13C{1H} NMR (C6D6): δ 138.0 (br, JPt−C = 24, Ar), 127.9 (d, J = 7, overlapping C6D6 signals, Ar), 123.2 (Ar), 38.1 (d, J = 26, CH), 36.5 (d, J = 37, CH),

36.1 (broad, 2 CH2), 35.0 (d, J = 4, CH2), 34.3 (CH2), 30.8 (d, J = 26, CH), 30.1 (d, J = 36, CH), 26.6 (dd, J = 34, 17, P-CH2), 20.6 (dd, J = 22, 7, P-CH2), 19.4 (Me), 19.3 (Me), 14.0 (Me), 13.3 (Me). The Pt− C(Ph) quaternary carbon signal was not observed. Pt((R,R)-Me-Duphos)(9-phenanthryl)(Br) (15). Under N2, a slurry of Pt((R,R)-Me-Duphos)Cl2 (150 mg, 0.26 mmol) in 20 mL of dry toluene was cooled to 0 °C and (9-phenanthryl)magnesium bromide (1.57 mL of a 0.5 M solution in THF, 0.8 mmol, 3 equiv) was added dropwise. The resulting yellow slurry was stirred at 0 °C for 1 h and then was slowly warmed to room temperature before heating to 50 °C for 1 h. The solid dissolved, resulting in a pale yellow solution, and the reaction was determined to be complete by 31P NMR spectroscopy. The mixture was then cooled to 0 °C, 5 mL of water was added, and the mixture was slowly warmed to room temperature. Water (50 mL) and CH2Cl2 (50 mL) were added, and the layers were separated. The aqueous layer was extracted with CH2Cl2 (2 × 25 mL), and the organic layers were combined, dried with MgSO4, and concentrated by rotary evaporation to give an orange oil. Ether (20 mL) was added, and the resulting yellow slurry was filtered to give the product (77 mg, 42%), a pale yellow powder, as a mixture of two rotamers. HRMS: m/z calcd for C32H37P2Pt (M − Br)+ m/z 678.2019, found 678.2015. Anal. Calcd for C32H37BrP2Pt: C, 50.67; H, 4.92. Found: C, 49.97; H, 4.42. 31P{1H} NMR (CDCl3, two rotamers, A:B = 1.6:1 ratio): δ 66.8 (d, J = 6, JPt−P = 1680, A), 66.0 (d, J = 6, JPt−P = 1709, B), 58.2 (d, J = 6, JPt−P = 3929, A), 56.0 (d, J = 6, JPt−P = 3951, B). 1H NMR (CDCl3): δ 8.74−8.66 (m, 4H, Ar), 8.64−8.61 (m, 2H, Ar), 8.10 (d, J = 8, JPt−H = 45, 1H of 1 rotamer (A or B), Ar), 7.82−7.74 (m, 5H, Ar), 7.65−7.57 (m, 6H, Ar), 7.52−7.45 (m, 8H, Ar), 3.77− 3.71 (m, 2H), 3.62−3.52 (m, 2H), 2.93−2.82 (m, 2H), 2.68−2.16 (m, 9H), 2.10−2.00 (m, 1H), 1.88−1.73 (m, 4H), 1.68 (dd, J = 18, 7, B, Me), 1.59 (dd, J = 18, 7, A, Me), 1.53 (dd, J = 18, 7, B, Me), 1.49− 1.37 (m, 2H), 1.04 (dd, J = 15, 7, A, Me), 1.04 (dd, J = 15, 7, B, Me), 0.95 (dd, J = 16, 7, A, Me), 0.86 (dd, J = 16, 7, B, Me), 0.77 (dd, J = 18, 7, A, Me), 0.70−0.65 (m, JPt−H = 39, 2H). 13C{1H} NMR (CDCl3): δ 160.7 (dd, J = 117, 8, A, Ar), 160.3 (dd, J = 117, 7, B, Ar), 144.7 (dd, J = 48, 37, Ar), 143.8 (dd, J = 48, 38, Ar), 142.6 (dd, J = 36, 26, Ar), 142.4 (dd, J = 36, 25, Ar), 141.7 (d, J = 4, A, Ar), 140.9 (d, J = 4, B, Ar), 136.5 (d, J = 2, JPt−C = 50, A, Ar), 134.8 (d, J = 1, B, Ar), 133.6 (d, J = 8, Ar), 133.4 (d, J = 8, Ar), 133.1 (d, J = 5, Ar), 133.0 (d, J = 4, Ar), 132.6 (d, J = 2, Ar), 132.5 (d, J = 3, Ar), 132.4 (dd, J = 15, 4, Ar), 132.1 (dd, J = 15, 4, Ar), 131.7 (d, J = 6, Ar), 131.6−131.3 (m, overlapping peaks, 4Ar), 131.3 (d, J = 6, Ar), 128.9 (A, Ar), 128.6 (B, Ar), 127.39 (Ar), 127.37 (Ar), 125.9 (Ar), 125.6 (Ar), 125.0 (Ar), 124.9 (Ar), 124.6 (Ar), 124.2 (Ar), 124.0 (Ar), 122.6 (Ar), 122.5 (Ar), 122.4 (Ar), 122.1 (Ar), 43.3 (d, J = 39), 42.4 (d, J = 29), 41.7 (d, J = 28), 40.4 (d, J = 38), 37.6, 37.5, 37.2 (d, J = 3), 36.8 (d, J = 4), 36.5, 36.3, 36.0, 35.5−35.4 (m), 35.34, 35.30, 35.2, 35.0, 33.1 (d, J = 37), 17.3 (d, J = 8), 17.1 (d, J = 8), 16.7 (d, J = 5), 16.2 (d, J = 5), 14.6 (d, J = 2), 14.59−14.55 (m), 13.8 (d, J = 1). Pt((R,R)-Me-DuPhos)Ar2 (Ar = 6-Methoxy-2-naphthyl, 16). Under N2, a slurry of Pt((R,R)-Me-Duphos)Cl2 (376 mg, 0.66 mmol) and 20 mL of dry THF was cooled to 0 °C before (6-methoxy-2naphthyl)magnesium bromide (3.9 mL of a 0.5 M solution in THF, 1.97 mmol, 3 equiv) was added via syringe. The resulting pale yellow slurry was slowly warmed to room temperature, stirred for 1 h, and then warmed to 50 °C and stirred for 2 h, after which the reaction was determined to be complete by 31P NMR spectroscopy. Water (10 mL) was added slowly, followed by a saturated NaHCO3 solution (40 mL) and 50 mL of CH2Cl2, and the layers were separated. The aqueous layer was extracted with 2 × 20 mL of CH2Cl2, and the organic layers were combined, dried with MgSO4, and concentrated by rotary evaporation to give a yellow oil. The oil was dissolved in 2 mL of CH2Cl2, layered with 10 mL of ether, and stored at 0 °C overnight. The next morning the solution was decanted from the product, which was dried in vacuo to yield 110 mg of white crystals. The supernatant was pumped down in vacuo to give a white solid, which was washed with ether (3 × 2 mL) to give 420 mg of a white solid (overall yield 530 mg, 98%). 6908

dx.doi.org/10.1021/om300704e | Organometallics 2012, 31, 6900−6910

Organometallics

Article

Anal. Calcd for C40H46O2P2Pt: C, 58.89; H, 5.68. Found: C, 57.34; H, 5.27. HRMS: calcd for C40H46O2P2Pt (M+) m/z 815.2621, found 815.2620. 31P{1H} NMR (CDCl3): δ 60.3 (JPt−P = 1687). 1H NMR (CDCl3): δ 7.85 (d, J = 6.5, JPt−H = 60, 2H, Ar), 7.74−7.61 (m, 4H, Ar), 7.55−7.51 (m, 4H, Ar), 7.34 (d, J = 8, 2H, Ar), 6.96−6.94 (m, 4H, Ar), 3.84 (6H, OMe), 3.19−3.14 (br m, 2H), 2.68−2.60 (m, 2H), 2.09−2.00 (m, 2H), 1.90−1.79 (m, 2H), 1.58 (qd, J = 12, 5, 2H), 1.23 (dd, J = 17, 7, 6H, Me), 0.97 (dd, J = 14, 7, 6H, Me), 0.80−0.71 (br m, 2H). 13C{1H} NMR (CDCl3): δ 159.2 (dd, J = 113, 9, q, Pt−Ar), 155.3 (Ar), 145.6 (apparent t, J = 35, Ar), 138.0 (JPt−C = 35, Ar), 134.1 (t, J = 2, JPt−C = 22, Ar), 133.2 (d, J = 15, JPt−C = 14, Ar), 131.1 (Ar), 130.6 (br, Ar), 130.5 (d, J = 6, Ar), 128.4 (Ar), 124.2−124.1 (br m, JPt−C = 53, Ar), 116.5 (Ar), 105.7 (Ar), 55.4 (OMe), 41.3 (d, J = 29, JPt−C = 27), 37.0 (JPt−C = 20), 36.0 (d, J = 3), 32.3 (d, J = 28, JPt−C = 27), 16.9 (d, J = 10, JPt−C = 19), 14.8. Catalyst Screening in Alkylation of 1,3-Bis(phenylphosphino)propane with Benzyl Bromide (Scheme 3): General Procedure. A solution of 1,3-bis(phenylphosphino)propane (26 mg, 0.1 mmol) in 0.1 mL of THF was added to a slurry of NaOSiMe3 (22.4 mg, 0.2 mmol) in 0.2 mL of THF. The mixture was added to a solution of the Pt catalyst precursor (0.01 mmol, 10 mol % per bis(phosphine)) in 0.1 mL of THF. The reaction mixture was transferred to an NMR tube equipped with a septum. Benzyl bromide (34 mg, 24 μL, 0.2 mmol) was added via microliter syringe, and the reaction mixture was monitored by 31P NMR spectroscopy. After completion of the reaction (ca. 10 min) the catalyst and sodium bromide were removed from the mixture on a silica column (10 cm height, 0.5 cm diameter), using ca. 20 mL of 9/1 pentane/THF as an eluent (∼20 mL). The solvent was removed in vacuo to give tertiary bis(phosphine) 18, which was dissolved in 0.5 mL of C6D6 and added to solid [(S)-C6H4CH(Me)NMe2PdCl]2 (1 equiv). Integration of the 31 P NMR signals of the resulting diastereomers gave the dr and er values shown in Table 3. The dr values measured for the isolated phosphine product were consistent with those observed directly by 31P NMR analysis of the crude reaction mixtures.3 Only this latter method was used for reactions catalyzed by precursors 9 and 9T, in which free FerroLANE was observed. 31P{1H} NMR (C6D6): δ 34.9 (meso-18), 32.7 (rac-18), 31.3 (meso-18), 28.3 (rac-18). Catalyst precursors 1, 4, and 15 preferentially formed the enantiomer of rac-18 which gave rise to the δ 28.3 peak, and the other catalyst precursors favored the other enantiomer (δ 32.7 signal).

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10138. See also: Marinho, V. R.; Ramalho, J. P. P.; Rodrigues, A. I.; Burke, A. J. Eur. J. Org. Chem. 2010, 1593. (2) (a) Scriban, C.; Glueck, D. S. J. Am. Chem. Soc. 2006, 128, 2788− 2789. (b) Scriban, C.; Glueck, D. S.; Golen, J. A.; Rheingold, A. L. Organometallics 2007, 26, 1788−1800; 2007, 26, 5124 (addition/ correction). (c) Glueck, D. S. Synlett 2007, 2627−2634. (d) Glueck, D. S. Coord. Chem. Rev. 2008, 252, 2171−2179; 2011, 255, 356 (erratum). (e) Related Ru catalysts were developed independently; see: Chan, V. S.; Stewart, I. C.; Bergman, R. G.; Toste, F. D. J. Am. Chem. Soc. 2006, 128, 2786−2787. Chan, V. S.; Chiu, M.; Bergman, R. G.; Toste, F. D. J. Am. Chem. Soc. 2009, 131, 6021−6032. (3) Anderson, B. J.; Glueck, D. S.; DiPasquale, A. G.; Rheingold, A. L. Organometallics 2008, 27, 4992−5001; 2009, 28, 386 (addition/ correction). (4) Anderson, B. J.; Guino-o, M. A.; Glueck, D. S.; Golen, J. A.; DiPasquale, A. G.; Liable-Sands, L. M.; Rheingold, A. L. Org. Lett. 2008, 10, 4425−4428. (5) (a) Chapp, T. W.; Glueck, D. S.; Golen, J. A.; Moore, C. E.; Rheingold, A. L. Organometallics 2010, 29, 378−388. (b) Chapp, T. W.; Schoenfeld, A. J.; Glueck, D. S. Organometallics 2010, 29, 2465− 2473. (6) (a) Synthesis of 1: Brunker, T. J.; Blank, N. F.; Moncarz, J. R.; Scriban, C.; Anderson, B. J.; Glueck, D. S.; Zakharov, L. N.; Golen, J. A.; Sommer, R. D.; Incarvito, C. D.; Rheingold, A. L. Organometallics 2005, 24, 2730−2746. (b) Synthesis of 2: Scriban, C.; Glueck, D. S.; DiPasquale, A. G.; Rheingold, A. L. Organometallics 2006, 25, 5435− 5448. (7) Scriban, C.; Wicht, D. K.; Glueck, D. S.; Zakharov, L. N.; Golen, J. A.; Rheingold, A. L. Organometallics 2006, 25, 3370−3378. (8) Pregosin, P. S.; Kunz, R. W. 31P and 13C NMR of Transition Metal Phosphine Complexes; Springer-Verlag: New York, 1979. (9) Cooper, S. J.; Brown, M. P.; Puddephatt, R. J. Inorg. Chem. 1981, 20, 1374−1377. (10) Zuideveld, M. A.; Swennenhuis, B. H. G.; Boele, M. D. K.; Guari, Y.; van Strijdonck, G. P. F.; Reek, J. N. H.; Kamer, P. C. J.; Goubitz, K.; Fraanje, J.; Lutz, M.; Spek, A. L.; van Leeuwen, P. W. N. M. Dalton Trans. 2002, 2308−2317. (11) For related μ-diphosphine Pd complexes, see: Zhuravel, M. A.; Glueck, D. S.; Incarvito, C. D.; Rheingold, A. L. Organometallics 1999, 18, 4673−4676. We are not aware of other μ-BPE complexes, but a byproduct whose 31P NMR spectrum resembled that of 10 was observed in the formation of Pt((R,R)-Me-BPE)(Me)(Cl) (3); see the Experimental Section. (12) Related reactions of electron-rich bis(alkylphosphino)ethanes with Pt(COD)(Ph)(X) precursors gave the expected products. Pt(dcpe)(Ph)(Cl) (dcpe = Cy2PCH2CH2PCy2, Cy = cyclohexyl): Hackett, M.; Ibers, J. A.; Whitesides, G. M. J. Am. Chem. Soc. 1988, 110, 1436−1448. Pt(depe)(Ph)(Br) (depe = Et2PCH2CH2PEt2): Clarke, M. L.; Heydt, M. Organometallics 2005, 24, 6475−6478. An unidentified impurity was reported in the depe reaction, but it reacted with more Pt(COD)(Ph)(Br). (13) Decomposition of related Pd aryl iodide complexes has been observed. See: (a) Moncarz, J. R.; Laritcheva, N. F.; Glueck, D. S. J. Am. Chem. Soc. 2002, 124, 13356−13357. (b) Reference 6a. (c) Tschoerner, M.; Pregosin, P. S.; Albinati, A. Organometallics 1999, 18, 670−678. (14) Siegmann, K.; Pregosin, P. S.; Venanzi, L. M. Organometallics 1989, 8, 2659−2664. (15) Clark, H. C.; Manzer, L. E. J. Organomet. Chem. 1973, 59, 411− 428. (16) (a) Brown, J. M.; Perez-Torrente, J. J.; Alcock, N. W. Organometallics 1995, 14, 1195−1203. (b) Moncarz, J. R.; Brunker, T. J.; Jewett, J. C.; Orchowski, M.; Glueck, D. S.; Sommer, R. D.; Lam, K.-C.; Incarvito, C. D.; Concolino, T. E.; Ceccarelli, C.; Zakharov, L. N.; Rheingold, A. L. Organometallics 2003, 22, 3205−3221. (17) (a) Wicht, D. K.; Zhuravel, M. A.; Gregush, R. V.; Glueck, D. S.; Guzei, I. A.; Liable-Sands, L. M.; Rheingold, A. L. Organometallics 1998, 17, 1412−1419. (b) Reference 6b.

S Supporting Information *

Text, tables, figures, and CIF files giving additional experimental information, details of the X-ray crystallographic studies, and NMR spectra. This material is available free of charge via the Internet at http://pubs.acs.org. Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We thank the National Science Foundation for support, the Department of Education for GAANN fellowships for B.J.A. and T.W.C., and Dartmouth College for Lemal and Zabriskie Undergraduate Research Fellowships and a James O. Freedman Presidential Scholarship to A.H.Z. N.F.B. thanks Norwich University for sabbatical leave support.

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REFERENCES

(1) Despite the identical R,R labels, (R,R)-Me-Duphos and (R,R)-iPr-Duphos have opposite stereochemistry: Burk, M. J.; Feaster, J. E.; Nugent, W. A.; Harlow, R. L. J. Am. Chem. Soc. 1993, 115, 10125− 6909

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Organometallics

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(18) Appleton, T. G.; Clark, H. C.; Manzer, L. E. Coord. Chem. Rev. 1973, 10, 335−422. (19) (a) Johnson, C. R.; Imamoto, T. J. Org. Chem. 1987, 52, 2170− 2174. (b) Imamoto, T.; Crepy, K. V. L; Katagiri, K. Tetrahedron: Asymmetry 2004, 15, 2213. (20) We have not yet been able to determine the absolute configuration of bis(phosphine) 18, but it will be investigated in future studies of the mechanism and stereochemistry of the Ptcatalyzed alkylation. (21) Pangborn, A. B.; Giardello, M. A.; Grubbs, R. H.; Rosen, R. K.; Timmers, F. J. Organometallics 1996, 15, 1518−1520. (22) McDermott, J. X.; White, J. F.; Whitesides, G. M. J. Am. Chem. Soc. 1976, 98, 6521−6528. (23) Tani, K.; Brown, L. D.; Ahmed, J.; Ibers, J. A.; Nakamura, A.; Otsuka, S.; Yokota, M. J. Am. Chem. Soc. 1977, 99, 7876−7886. (24) Scriban, C.; Wicht, D. K.; Glueck, D. S.; Zakharov, L. N.; Golen, J. A.; Rheingold, A. L. Organometallics 2006, 25, 3370−3378. (25) Brunker, T. J.; Blank, N. F.; Moncarz, J. R.; Scriban, C.; Anderson, B. J.; Glueck, D. S.; Zakharov, L. N.; Golen, J. A.; Sommer, R. D.; Incarvito, C. D.; Rheingold, A. L. Organometallics 2005, 24, 2730−2746. (26) Anderson, B. J. Ph.D. Thesis, Dartmouth College, 2008.

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