Asymmetric Synthesis of P-Stereogenic Homo- and Heterobimetallic

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Asymmetric Synthesis of P-Stereogenic Homo- and Heterobimetallic Complexes via Selective Monoinsertion of Dialkynylphosphine into the Pd-C Bond of a Palladacycle Shuli Chen, Sumod A. Pullarkat, Yongxin Li, and Pak-Hing Leung* Division of Chemistry & Biological Chemistry, School of Physical & Mathematical Sciences, Nanyang Technological University, Singapore 637371

bS Supporting Information ABSTRACT: Subsequent to their coordination onto chiral cyclopalladated/platinated [1-(dimethylamino)ethyl]naphthalene templates, a series of asymmetric monoinsertions of the carbon-carbon triple bond of dialkynylphosphines into the Pd-C bond of chiral R-methyl N,N-dimethyl benzylamine palladacycles have been demonstrated. These insertion reactions exhibited high regioselectivity and moderate stereoselectivity under mild conditions, and a variety of chiral homo- or heterobimetallic complexes incorporating a newly generated P-stereogenic center were formed. In some instances, the monoinsertion product would subsequently undergo a series of transformations during their purification via column chromatography or upon stirring them with H2O to generate a zwitterionic complex incorporating an additional four-membered ring system with a newly generated C-stereogenic center. The coordination chemistry and the absolute stereochemistry of the monoinsertion products and the transformation products were determined by single-crystal X-ray crystallographic analysis.

’ INTRODUCTION It has been well established that orthopalladated complexes exhibit high reactivity toward a large variety of unsaturated molecules, such as carbon monoxide,1 allenes,2 alkenes,1d,3 alkynes,1c,d,4 isocyanides,1a,d,5 and acyl halides6 via insertion of these unsaturated molecules into the Pd-C bond of the orthopalladated complexes. As depalladation of the organometallic complexes resulting from such insertion reactions could provide useful heterocyclic compounds that would be otherwise hard to achieve by conventional organic synthetic methodologies, this protocol therefore has attracted great interest in organic synthesis.4a,7 Being one of the representative insertion reactions, insertion of alkynes into the Pd-C bond of orthopalladated complexes can yield substituted olefins with a high degree of regio- and stereocontrol.8 Depending on the electronic and steric properties of the alkyne substrate as well as the coordination environment around the metal center and the reaction conditions, multiple insertion of alkynes into the Pd-C bond of orthopalladated complexes could also take place and in some cases wherein the insertion products after sequential mono-, di-, and tri-insertion of alkynes can be isolated.7e,8,9 More recently, simultaneous synthesis and characterization of enlarged palladacycles resulting from insertion of one, two, or three molecules of alkynes per palladium atom into the Pd-C bond of orthopalladated complexes has also r 2011 American Chemical Society

been reported.10 However, in some cases, the product obtained via monoinsertion of a single alkyne would be very difficult to isolate since the second and third alkyne moiety inserts sequentially into the Pd-C bond.4a,11 Over the past few years, our group has successfully applied chiral cyclometalated-amine complexes as efficient chiral auxiliaries to promote asymmetric Diels-Alder reactions,12 asymmetric hydroamination reactions,13 asymmetric hydroarsination reactions,14 and asymmetric hydrophosphination reactions15 to synthesize a series of chiral phosphine substrates. We have recently also reported the insertion of dialkynylphosphines into the PdC bond of orthopalladated benzylamine activated by a ruthenium complex.16 However, the control of the selectivity in the reaction in that reaction scenario was not satisfactory. In continuation of our investigations into the application of chiral cyclometalatedamine complexes for asymmetric transformations, we herein illustrate the efficiency of these chiral cyclopalladated and cycloplatinated complexes in promoting a series of asymmetric selective monoinsertions of coordinated di(1-propynyl)phenylphosphine into the Pd-C bond of an orthopalladated N, N-dimethyl benzylamine with high regioselectivity to provide a Received: November 15, 2010 Published: February 17, 2011 1530

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Scheme 1

Table 1. Selected Bond Distances (Å) and Angles (deg) of Complex (Rc)-3 Pd(1)-C(2) Pd(1)-N(1)

Figure 1. Molecular structure of complex (Rc)-3.

variety of homo- and heterobimetallic complexes. To the best of our knowledge, reports on an insertion reaction involving a phosphinoalkyne into a Pd-C bond leading to the generation of a P-chiral framework is rare if not nonexistent.

’ RESULTS AND DISCUSSION Preparation of Precursor Complexes (Rc)-3 and (Rc)-4. As illustrated in Scheme 1, the synthesis of the chiral phosphine complex (Rc)-3 was easily achieved by treatment of the prochiral di(1-propynyl)phenylphosphine, PhP(CtCMe)2, with 0.5 equiv of the dimeric palladium(II) complex (Rc)-1 in dichloromethane for 2 h at room temperature. Due to the unique electronic directing effects originating from the π-accepting aromatic carbon and the σ-donating nitrogen donor of the orthopalladated N,N-dimethyl naphthylamine ring, the monodentate phosphine ligand split the chloride bridge in (Rc)-1 and regioselectively coordinated to the orthopalladated N,N-dimethyl naphthylamine complex in the position trans to the naphthylamine-N donor atom to form the monomeric chloro complex (Rc)-3.17 The 31 1 P{ H} NMR spectrum of the crude product in CDCl3 exhibited a sharp singlet at δ -20.5. The complex (Rc)-3 was recrystallized from dichloromethane-hexane as yellow crystals in 84% yield. The single-crystal X-ray structural analysis of the complex (Rc)-3 confirmed the formation of the expected monomeric chloro complex (Figure 1). The geometry at palladium is slightly distorted square planar (torsion angle 3.95°) with bond angles in the range 81.1(1)-93.6(1)° and 172.9(1)-174.5(1)°. Selected bond distances and angles for (Rc)-3 are given in Table 1. Using a similar procedure to that employed for the preparation of the palladium complex (Rc)-3, the platinum analogue (Rc)-4 was also prepared by treatment of the di(1-propynyl)phenylphosphine with 0.5 equiv of the dimeric platinum(II) complexes

2.021(3) 2.128(3)

C(18)-C(19) C(2)-Pd(1)-N(1)

1.173(5) 81.2(1)

Pd(1)-P(1)

2.229(1)

C(2)-Pd(1)-P(1)

93.6(1)

Pd(1)-Cl(1)

2.371(1)

N(1)-Pd(1)-P(1)

174.5(1)

P(1)-C(15)

1.757(3)

C(2)-Pd(1)-Cl(1)

172.9(1)

P(1)-C(18)

1.759(3)

N(1)-Pd(1)-Cl(1)

92.8(1)

P(1)-C(21)

1.818(3)

P(1)-Pd(1)-Cl(1)

92.6(1)

C(15)-C(16)

1.175(4)

(Rc)-2 in CH2Cl2 (Scheme 1). The 31P{1H} NMR spectrum of the crude products in CDCl3 exhibited a sharp singlet at δ -39.5 (1JP-Pt = 4505 Hz). The complex (Rc)-4 was then recrystallized from dichloromethane-hexane as pale yellow crystals in 87% yield. Insertion Reaction of the Dialkynylphosphine-Bearing Orthoplatinated N,N-Dimethyl Naphthylamine Complex. The insertion reaction between the orthoplatinated N,N-dimethyl naphthylamine complex (Rc)-4 and 0.5 equiv of orthopalladated N,N-dimethyl benzylamine dimer (Rc)-5 was carried out at room temperature in dichloromethane. This reaction was monitored using 31P{1H} NMR spectroscopy and was found to be complete in 36 h. The 31P{1H} NMR spectrum of the crude reaction mixture in CDCl3 exhibited two sharp singlets at δ 38.2 (1JP-Pt = 4047 Hz) and δ -35.9 (1JP-Pt = 3983 Hz) with relative intensities of 2:1, respectively, indicating the formation of two distinct stereoisomeric products (Scheme 2). The crude diastereomeric reaction mixture can be efficiently separated by silica gel column chromatography and crystallized from acetonehexane to give complex (Rc,Sp,Rc)-6 and complex (Rc,Rp,Rc)-6 as light yellow crystals in 23% and 19% yields, respectively. According to the single-crystal X-ray structural analysis data obtained, the phosphorus resonance signal at δ -38.2 is assigned to the major product, complex (Rc,Sp,Rc)-6, while the signal at δ -35.9 is assigned to the minor product, complex (Rc,Rp,Rc)-6. The single-crystal X-ray diffraction studies of the complex (Rc, Sp,Rc)-6 confirmed that the desired insertion product has indeed been generated. As shown in Figure 2, one of the original carbon-carbon triple bonds in the dialkynylphosphine, bond C(18)-C(19), has been inserted into the palladium-carbon bond, Pd(1)-C(30), of the original cyclopalladated complex (Rc)-5, forming a new carbon-carbon bond between C(19) and C(30), together with the formation a new metal-carbon bond between Pd(1) and C(18). The ring expansion induced by the insertion of one carbon-carbon triple bond of the dialkynylphosphine into the palladium-carbon bond of cyclopalladated complex (Rc)-5 led to the formation of a new seven-membered 1531

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Scheme 2

Figure 2. Molecular structure of complex (Rc,Sp,Rc)-6.

ring. Furthermore, the platinum and palladium centers are now bridged by a Cl atom to give a new five-membered bimetallic heterocycle in which the phosphorus donor atom is coordinated regioselectively at the position trans to the naphthylamine-N

donor atom of the original cycloplatinated complex (Rc)-4. A new stereogenic center at phosphorus was thus generated, which adopts the S absolute configuration. The absolute configurations of the two stereocenters at C(11) and C(24) remained unchanged. 1532


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This insertion reaction is highly regioselective since the methyl group of the dialkynylphosphine was located exclusively at the position next to the previously metalated carbon atom of the orthopalladated N,N-dimethyl benzylamine. The geometries at the platinum and palladium centers are distorted square planar with bond angles at Pt(1) in the ranges 79.7(2)-97.9(2)° and 174.9(2)-176.2 (1)°, while those at Pd(1) are in the ranges 84.7(2)-94.9(2)° and 169.8(2)-173.1(1)°. The C(18)-C(19) bond distance in (Rc,Sp,Rc)-6 [1.335(7) Å] clearly indicates that it is a CdC bond. Table 2 shows selected bond distances and angles of complex (Rc,Sp,Rc)-6. The molecular structure and absolute stereochemistry of the minor product, complex (Rc,Rp,Rc)-6, was also established by X-ray crystallography (Figure 3). Similar to the formation of the major product, complex (Rc,Sp,Rc)-6, after insertion of one of the CtC bonds in the dialkynylphosphine into the palladiumcarbon bond of the cyclopalladated complex (Rc)-5, an enlarged seven-membered ring was formed together with the formation of a new five-membered bimetallic heterocycle in which the phosphorus donor atom is coordinated regioselectively at the position trans to the naphthylamine-N donor atom. The newly generated stereocenter at phosphorus adopts the R absolute configuration. As was observed in (Rc,Sp,Rc)-6, the absolute

configurations of the two stereocenters at C(11) and C(24) remained unchanged. The geometry at platinum and palladium centers are distorted square planar with bond angles at Pt(1) in the ranges 81.7(5)-97.9(4)° and 174.7(4)-179.4(3)°, while those at Pd(1) are in the ranges 83.4(4)-92.6(5)° and 171.5(2)174.3(2)°. Table 3 shows selected bond distances and angles of complex (Rc,Rp,Rc)-6. Interestingly, while the two insertion complexes were being separated by column chromatography, the 31P{1H} NMR spectrum of the eluted fractions showed an additional phosphorus resonance signal at δ -2.3. Subsequently, it was established that this new phosphorus signal always appeared when the complex (Rc,Sp,Rc)-6 was passed through a silica gel column. The signal at δ -2.3 was eventually confirmed as the unexpected chiral product (Rc,Sp,Rc,Rc)-7 after it had been recrystallized from diethyl ether-acetonitrile as light yellow crystals in 3% yield. It should be noted that complex (Rc,Sp,Rc,Rc)-7 is a bimetallic zwitterionic complex with a positive charge at platinum and a negative charge at palladium. It is proposed that complex (Rc,Sp, Rc)-6 underwent a series of transformations while passing through the column to give the transformed product (Rc,Sp,Rc, Rc)-7. As shown in Scheme 3, these transformations included a nucleophilic attack by water present in the eluents toward the

Table 2. Selected Bond Distances (Å) and Angles (deg) of Complex (Rc,Sp,Rc)-6

Table 3. Selected Bond Distances (Å) and Angles (deg) of Complex (Rc,Rp,Rc)-6

Pt(1)-C(2)

2.009(5)

C(2)-Pt(1)-N(1)

79.7(2)

Pt(1)-C(2)

1.994(12)

C(2)-Pt(1)-N(1)

81.7(5)

Pt(1)-N(1)

2.132(4)

C(2)-Pt(1)-P(1)

97.9(2)

Pt(1)-N(1)

2.143(9)

C(2)-Pt(1)-P(1)

97.9(4)

Pt(1)-P(1)

2.220(1)

N(1)-Pt(1)-P(1)

176.2(1)

Pt(1)-P(1)

2.224(2)

N(1)-Pt(1)-P(1)

179.4(3)

Pt(1)-Cl(2)

2.418(1)

C(2)-Pt(1)-Cl(2)

174.9(2)

Pt(1)-Cl(1)

2.432(3)

C(2)-Pt(1)-Cl(1)

174.7(4)

Pd(1)-C(18)

2.008(5)

N(1)-Pt(1)-Cl(2)

95.2(1)

Pd(1)-C(18)

2.007(6)

N(1)-Pt(1)-Cl(1)

93.2(3)

Pd(1)-N(2) Pd(1)-Cl(2)

2.115(5) 2.364(2)

P(1)-Pt(1)-Cl(2) C(18)-Pd(1)-N(2)

87.2(2) 94.9(2)

Pd(1)-N(2) Pd(1)-Cl(3)

2.117(10) 2.421(2)

P(1)-Pt(1)-Cl(1) C(18)-Pd(1)-N(2)

87.1(1) 92.6(5)

Pd(1)-Cl(1)

2.437(2)

C(18)-Pd(1)-Cl(1)

169.8(2)

Pd(1)-Cl(1)

2.348(3)

C(18)-Pd(1)-Cl(1)

83.4(4)

P(1)-C(15)

1.767(6)

N(2)-Pd(1)-Cl(1)

91.0(1)

P(1)-C(15)

1.776(13)

N(2)-Pd(1)-Cl(1)

174.3(2)

P(1)-C(18)

1.819(5)

N(2)-Pd(1)-Cl(2)

173.1(1)

P(1)-C(18)

1.809(9)

N(2)-Pd(1)-Cl(3)

94.1(2)

C(15)-C(16)

1.172(8)

C(18)-Pd(1)-Cl(2)

84.7(2)

C(15)-C(16)

1.187(16)

C(18)-Pd(1)-Cl(3)

171.5(2)

C(18)-C(19)

1.335(7)

Cl(1)-Pd(1)-Cl(2)

90.4(1)

C(18)-C(19)

1.330(12)

Cl(1)-Pd(1)-Cl(3)

90.2(1)

Figure 3. Molecular structure of complex (Rc,Rp,Rc)-6. 1533


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intact carbon-carbon triple bond of the dialkynylphosphine, leading to the generation of a methyl ketone,18 followed by a chloride bridge splitting step and subsequent coordination of O to the Pt center as well as the concomitant formation of a new C-Pd bond. On the basis of these considerations, complex (Rc, Sp,Rc)-6 was directly treated with H2O in acetone and was found to be transformed to (Rc,Sp,Rc,Rc)-7 completely in 70% isolated yield after two day’s stirring. The complex (Rc,Sp,Rc,Rc)-7 crystallized as two independent molecules in the same unit cell. The pair of molecules has the same molecular connectivity and differs only slightly in their bond distances and bond angles. For clarity, only one molecule is depicted in Figure 4. The X-ray structural analysis of complex (Rc,Sp,Rc,Rc)-7 revealed that the remaining carbon-carbon triple bond of the monoinsertion product (Rc,Sp,Rc)-6, C(15)C(16), took part in a series of transformations to ultimately form a new five-membered platinum chelate via the carbonyl oxygen O(1) and the P(1), and the absolute configuration at P(1) has not been affected after the formation of the new ring and remained as S. In addition, a new metal-carbon bond was formed between Table 4. Selected Bond Distances (Å) and Angles (deg) of Complex (Rc,Sp,Rp,Rc)-7 Pt(1)-C(2)

1.983(6)

C(2)-Pt(1)-O(1)

172.6(3)

Pt(1)-N(1)

2.140(6)

N(1)-Pt(1)-O(1)

94.7(2)

Pt(1)-O(1)

2.117(5)

C(2)-Pt(1)-P(1)

101.3(2)

Pt(1)-P(1)

2.217(2)

N(1)-Pt(1)-P(1)

174.6(2)

Pd(1)-C(18)

2.001(6)

O(1)-Pt(1)-P(1)

83.2(1)

Pd(1)-C(15)

2.131(7)

C(18)-Pd(1)-C(15)

75.0(2)

Pd(1)-N(2) Pd(1)-Cl(1)

2.180(6) 2.409(2)

C(18)-Pd(1)-N(2) C(15)-Pd(1)-N(2)

96.0(2) 167.3(2)

C(15)-C(16)

1.429(9)

C(18)-Pd(1)-Cl(1)

171.9(2)

C(18)-C(19)

1.326(9)

C(15)-Pd(1)-Cl(1)

97.2(2)

O(1)-C(16)

1.280(8)

N(2)-Pd(1)-Cl(1)

92.1(2)

C(2)-Pt(1)-N(1)

81.2(2)

C(16)-O(1)-Pt(1)

117.8(4)

Pd (1) and C(15) that resulted in the formation of a new fourmembered metallic heterocycle incorporating Pd(1), C(18), P(1), and C(15). Consequently, a new stereocenter at C(15) was also generated that adopts the R absolute configuration. The absolute configurations at C(11) and C(27) stereocenters were retained throughout these transformations. Interestingly, unlike complex (Rc,Sp,Rc)-6, the minor product (Rc,Rp,Rc)-6 did not undergo these transformations while passing through a silica gel column under similar conditions. However, when complex (Rc,Rp,Rc)-6 was treated with water in acetone for several days, the 31P{1H} NMR spectrum showed a new phosphorus resonance signal at δ -3.0, which was later confirmed to be the analogous zwitterionic complex (Rc,Rp,Rc,Sc)-7. However, this transformation is much slower than that of the major product and took one month to complete. Complex (Rc, Rp,Rc,Sc)-7 was recrystallized from benzene and pentane as light yellow crystals. The ORTEP from the X-ray structural analysis of complex (Rc,Rp,Rc,Sc)-7 is shown in Figure 5. Similar to the formation of complex (Rc,Sp,Rc,Rc)-7, apart from the newly formed five-membered platinum chelate via the carbonyl oxygen O(1) and the P(1), and four-membered metallic heterocycle consisting of Pd(1), C(18), P(1), and C(15), the absolute configurations at P, C(11), and C(27) remained unchanged, while the newly formed stereogenic center at C(15) adopts the R absolute configuration. It needs to be mentioned that in the above insertion reaction involving the orthopalladated N,N-dimethyl benzylamine dimer (Rc)-5, the newly formed phosphorus stereogenic center of the major product adopts the S absolute configuration, while that of the minor product adopts the R absolute configuration. Additionally, transformed complex (Rc,Rc,Sp,Rc)-7 was never observed in the original crude reaction mixture, but it always coexisted with another insertion product, complex (Rc,Sp,Rc)-6, during the purification process via silica gel column. In order to investigate the origin of the stereoselectivity of the insertion reaction and establish that the transformation from complex (Rc, Sp,Rc)-6 to complex (Rc,Rc,Sp,Rc)-7 is a general phenomenon,

Scheme 3

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Figure 4. Molecular structure of complex (Rc,Sp,Rc,Rc)-7.

Figure 5. Molecular structure of complex (Rc,Rp,Rc,Sc)-7.

one more insertion reaction of a dialkynylphosphine coordinated to the orthoplatinated N,N-dimethyl naphthylamine template (Rc)-4 with the orthoplladated N,N-dimethyl benzylamine dimer (Sc)-8 was conducted in dichloromethane at room temperature. The insertion reaction between complex (Rc)-4 and the dimeric palladium(II) complex (Sc)-8 was found to be complete in 24 h, and the 31P{1H} NMR spectrum of the crude reaction mixture in CDCl3 exhibited two sharp singlets at δ -9.3 (1JP-Pt = 4203 Hz) and δ -28.6 (1JP-Pt = 4046 Hz) with relative intensities of 2:1, which were subsequently separated efficiently by silica gel column chromatography (Scheme 4). The newly generated stereogenic phosphorus of the major product complex (Rc,Rp,Sc)-9, however, is the R absolute configuration and not S as was observed in the major product of the insertion reaction involving complex (Rc)-4 and dimeric palladium(II) complex (Rc)-5. As expected, a transformed zwitterionic product, complex (Rc,Rp, Sc,Sc)-10, which exhibited a sharp singlet at δ -7.1 (1JP-Pt = 3883 Hz), was again always observed during the purification process, and it was later confirmed that this transformed product

always coexisted with the major product, complex (Rc,Rp,Sc)-9, when it was passed through a silica gel column (Scheme 4). As in the previous instance, it was later found that the transformed product (Rc,Rp,Sc,Sc)-10 can also be obtained directly from complex (Rc,Rp,Sc)-9 upon stirring for 5 days with H2O in acetone. Similar to the insertion reaction between complex (Rc)-4 and dimeric palladium(II) complex (Rc)-5, the minor product (Rc,Sp,Sc)-9 did not undergo the transformations while passing through the silica gel column. However, when complex (Rc,Sp,Sc)-9 was treated with water in acetone for 10 days, it transformed completely into the zwitterionic product, complex (Rc,Sp,Sc,Rc)-10 (Scheme 5). Complexes (Rc,Rp,Sc)-7, (Rc,Rp,Sc, Sc)-10, and (Rc,Sp,Sc,Rc)-10 were recrystallized from dichloromethane-hexane or benzene-pentane as light yellow crystals. Unfortunately, single crystals of the minor product complex (Rc, Sp,Sc)-9 suitable for X-ray structure analysis could not be obtained despite many attempts to crystallize it using a wide variety of solvent systems. The single-crystal X-ray crystallographic study confirmed the expected structures of complexes (Rc,Rp,Sc)-9, (Rc,Rp,Sc,Sc)-10, 1535


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Scheme 4

and (Rc,Sp,Sc,Rc)-10 (Figures 6, 7, 8). As shown in Figure 6, similar to the formation of the monoinsertion products, complex (Rc,Rp,Rc)-6 and complex (Rc,Sp,Rc)-6, an enlarged seven-membered ring with the methyl group located next to the phenyl group of the orthopalladated N,N-dimethyl benzylamine has been formed accompanied by the formation of two new bonds, Pd(1)-C(18) and C(19)-C(30), via the monoinsertion of dialkylphosphine into the Pd(1)-C(30) bond of the complex (Sc)-8. Meanwhile, the platinum and palladium centers are bridged by Cl(1) to give a new five-membered bimetallic heterocycle with a newly generated R-phosphorus center. The absolute configurations of the two stereocenters at C(11) and C(24) remained unchanged as expected. Table 6 shows selected bond distances and angles of complex (Rc,Rp,Sc)-9. The zwitterionic complex (Rc,Rp,Sc,Sc)-10 crystallized as two independent molecules in the same unit cell. The pair of independent molecules have the same molecular connectivity and differ slightly only in the bond distances and bond angles. For clarity, only one molecule is depicted in Figure 7. The X-ray structure analysis of complex (Rc,Rp,Sc,Sc)-10 revealed that the remaining alkynyl carbon-carbon triple bond in the monoinsertion product, complex (Rc,Rp,Sc)-9, C(15)-C(16), also underwent a series of transformations to generate a five-membered platinum chelate via the carbonyl oxygen O(1) and the P(1) with the absolute configuration at the P(1) center remaining

unchanged. In addition, a new bond was also generated between Pd(1) and C(15) that resulted in a new four-membered metallic heterocycle with the generation of a new chiral S-carbon stereocenter at C(15). The geometries at both platinum and palladium centers are slightly distorted square planar with bond angles at Pt(1) recorded in the ranges 81.9(2)-92.3(2)° and 174.1(2)174.7(2)°, while those at Pd(1) are found to be 74.8(3)97.2(2)° and 165.3(2)-171.7(2)°. Table 7 shows selected bond distances and angles of complex (Rc,Rp,Sc,Sc)-10. As depicted in Figure 8, the zwitterionic complex (Rc,Sp,Sc,Rc)-10 has similar molecular connectivity to that of the complex (Rc,Rp,Sc,Sc)-10 except that the absolute configuration at the P(1) stereogenic center adopts S in the newly formed five-membered Pt(1)O(1)-C(16)-C(15)-P(1) chelate and the newly generated carbon stereocenter adopts the R absolute configuration in the four-membered metallic heterocycle formed by C(15), P(1), Pd(1), and C(18). Table 8 shows selected bond distances and angles of complex (Rc,Sp,Sc,Rc)-10. Based on the observation that the absolute configuration of the P-stereocenter remained unchanged after the transformation from the monoinsertion product to the transformed zwitterionic product, the absolute configuration of the P-stereocenter in the minor monoinsertion product, complex (Rc,Sp,Sc)-9, should adopt the S absolute configuration, as it can transform to the zwitterionic product (Rc,Sp,Sc,Rc)-10. 1536


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Scheme 5

Figure 6. Molecular structure of complex (Rc,Rp,Sc)-9.

Insertion Reaction of the Dialkynylphosphine-Bearing Orthopalladated N,N-Dimethyl Naphthylamine Complex.

In order to study the subtle metal template effects arising from the presence of hetero metal centers toward the reactivity and selectivity of the insertion of the dialkynylphosphine into the Pd-C bond of the cyclopalladated N,N-dimethyl benzylamine dimer, orthoplatinated N,N-dimethyl naphthylamine template (Rc)-4 was replaced by orthopalladated N,N-dimethyl naphthylamine complex (R c)-3 and subsequently yielded insertion products with dimeric palladium(II) complexes (R c)-5 and (S c)-8 separately. These insertion reactions were carried out in dichloromethane at room temperature and monitored by 31 1 P{ H} NMR spectroscopy. As illustrated in Scheme 5, the insertion reaction between complex (Rc)-3 and 0.5 equiv of dimeric palladium(II) complex (Rc)-5 was found to be complete in 3 days, and prior to isolation the 31P{1H} NMR spectrum of the crude reaction mixture in CDCl3 exhibited two sharp singlets at δ -16.4 and -16.9 with

relative intensities of 1:2.5. The major and minor monoinsertion products, complexes (Rc,Sp,Rc)-11 and (Rc,Rp,Rc)-11, could be separated by silica gel column chromatography and crystallized from acetone-hexane as yellow crystals in 30% and 22% yields, respectively. It is noteworthy that the newly formed phosphorus stereogenic centers of the major and minor products adopt S and R absolute configurations, respectively, which is in accordance with the insertion reaction between complex (Rc)-4 and dimeric palladium(II) dimer (Rc)-5. Similar to the analogous insertion reaction between complexes (Rc)-4 and (Rc)-5, the transformed bimetallic zwitterionic complex (Rc,Sp,Rc,Rc)-12 was also formed while the two insertion complexes were being separated by column chromatography. When complex (Rc,Sp,Rc)-11 was treated directly with H2O in acetone for one week, it transformed to complex (Rc,Sp,Rc,Rc)-12 completely. The minor monoinsertion product, however, did not generate the transformed product either by passing through a silica gel column or on stirring with H2O for a prolonged period. 1537


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Figure 7. Molecular structure of complex (Rc,Rp,Sc,Sc)-10.

Figure 8. Molecular structure of complex (Rc,Sp,Sc,Rc)-10.

The analogous insertion reactions of dialkynylphosphinebearing orthopalladated N,N-dimethyl naphthylamine template with the dimeric palladium(II) complex (Sc)-8 was found to complete in 3 days (Scheme 6). The 31P{1H} NMR spectrum of the crude reaction mixture in CDCl3 exhibited a major sharp singlet at δ 8.7 together with several trace minor resonance signals. The product from the reaction involving dimer (Sc)-8 and the major product was eventually confirmed as the monoinsertion product complex (Rc,Rp,Sc)-13 and could be crystallized from acetone-hexane as yellow crystals. The newly formed phosphorus stereogenic center of the major product in this insertion reactions is also in accordance with the analogous insertion reactions involving orthoplatinated N,N-dimethyl naphthylamine template (Rc)-4. Similar to the analogous insertion reaction mentioned earlier, a transformed zwitterionic complex (Rc,Rp,Sc,Sc)-14 was also obtained by treating complex (Rc,Rp,Sc)-13 with H2O in acetone for 10 days.

The molecular structure and absolute stereochemistry of the monoinsertion products, complexes (Rc,Sp,Rc)-11, (Rc,Rp,Rc)-11, and (Rc,Rp,Sc)-13, have been established by X-ray crystallography. As shown in the ORTEP of complex (Rc,Sp,Rc)-11, Figure 9, an enlarged seven-membered ring was formed via the insertion of the bond C(18)-C(19), one of the carbon-carbon triple bonds of the dialkynylphosphine, into the Pd(2)-C(30) bond of complex (Rc)-5 with the methyl group adjacent to the phenyl ring of (Rc)-5, together with the formation of a new Pd(1)Cl(2)-Pd(2)-C(18)-P(1) five-membered homobimetallic ring bridged by Cl in which the phosphorus donor atom is coordinated regioselectively in the position trans to the naphthylamine-N donor atom. The absolute configuration of the newly generated stereogenic center at P adopts an S absolute configuration, while the absolute configurations of the two stereocenters at C(11) and C(24) remained unchanged. The geometry at 1538


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Table 5. Selected Bond Distances (Å) and Angles (deg) of Complex (Rc,Rp,Rc,Sc)-7

Table 8. Selected Bond Distances (Å) and Angles (deg) of Complex (Rc,Sp,Sc,Rc)-10

Pt(1)-C(2)

1.989(4)

C(2)-Pt(1)-O(1)

174.9(2)

Pt(1)-C(2)

1.992(5)

C(2)-Pt(1)-O(1)

173.6(2)

Pt(1)-N(1)

2.138(4)

N(1)-Pt(1)-O(1)

93.7(1)

Pt(1)-N(1)

2.143(4)

N(1)-Pt(1)-O(1)

94.2(1)

Pt(1)-O(1)

2.118(3)

C(2)-Pt(1)-P(1)

101.5(2)

Pt(1)-O(1)

2.127(3)

C(2)-Pt(1)-P(1)

102.2(1)

Pt(1)-P(1)

2.216(1)

N(1)-Pt(1)-P(1)

176.6(1)

Pt(1)-P(1)

2.218(1)

N(1)-Pt(1)-P(1)

169.5(1)

Pd(1)-C(18)

1.990(4)

O(1)-Pt(1)-P(1)

83.6(1)

Pd(1)-C(18)

2.001(5)

O(1)-Pt(1)-P(1)

83.2(1)

Pd(1)-C(15)

2.146(4)

C(18)-Pd(1)-C(15)

77.2(2)

Pd(1)-C(15)

2.150(4)

C(18)-Pd(1)-C(15)

77.4(2)

Pd(1)-N(2)

2.137(4)

C(18)-Pd(1)-N(2)

96.5(2)

Pd(1)-N(2)

2.139(4)

C(18)-Pd(1)-N(2)

96.8(2)

Pd(1)-Cl(1) C(15)-C(16)

2.418(1) 1.432(7)

C(15)-Pd(1)-N(2) C(18)-Pd(1)-Cl(1)

168.2(2) 168.7(1)

Pd(1)-Cl(1) C(15)-C(16)

2.412(1) 1.429(7)

C(15)-Pd(1)-N(2) C(18)-Pd(1)-Cl(1)

169.6(2) 167.3(1)

C(18)-C(19)

1.349(6)

C(15)-Pd(1)-Cl(1)

95.4(1)

C(18)-C(19)

1.344(7)

C(15)-Pd(1)-Cl(1)

95.0(1)

O(1)-C(16)

1.268(6)

N(2)-Pd(1)-Cl(1)

92.1(1)

O(1)-C(16)

1.283(7)

N(2)-Pd(1)-Cl(1)

92.18(11)

C(2)-Pt(1)-N(1)

81.2(2)

C(16)-O(1)-Pt(1)

118.6(3)

C(2)-Pt(1)-N(1)

81.3(2)

C(16)-O(1)-Pt(1)

118.1(3)

Table 6. Selected Bond Distances (Å) and Angles (deg) of Complex (Rc,Rp,Sc)-9 Pt(1)-C(2)

1.992(5)

C(2)-Pt(1)-P(1)

97.8(2)

Pt(1)-N(1)

2.130(5)

N(1)-Pt(1)-P(1)

174.3(2)

Pt(1)-P(1)

2.207(2)

C(2)-Pt(1)-Cl(1)

174.4(2)

Pt(1)-Cl(1)

2.411(1)

N(1)-Pt(1)-Cl(1)

95.3(1)

Pd(1)-C(18)

1.990(6)

P(1)-Pt(1)-Cl(1)

87.1(1)

Pd(1)-N(2)

2.093(5)

C(18)-Pd(1)-N(2)

94.5(2)

Pd(1)-Cl(1)

2.358(1)

C(18)-Pd(1)-Cl(1)

85.2(2)

Pd(1)-Cl(2) C(15)-C(16)

2.416(2) 1.187(9)

N(2)-Pd(1)-Cl(1) C(18)-Pd(1)-Cl(2)

176.3(1) 169.3(2)

C(18)-C(19)

1.345(8)

N(2)-Pd(1)-Cl(2)

92.3(1)

C(2)-Pt(1)-N(1)

80.2(2)

Cl(1)-Pd(1)-Cl(2)

88.6(1)

Table 7. Selected Bond Distances (Å) and Angles (deg) of Complex (Rc,Rp,Sc,Sc)-10 Pt(1)-C(2)

1.984(7)

C(2)-Pt(1)-O(1)

174.1(2)

Pt(1)-N(1)

2.120(5)

N(1)-Pt(1)-O(1)

92.3(2)

Pt(1)-O(1)

2.147(5)

C(2)-Pt(1)-P(1)

102.0(2)

Pt(1)-P(1)

2.223(2)

N(1)-Pt(1)-P(1)

174.7(2)

Pd(1)-C(18)

1.975(7)

O(1)-Pt(1)-P(1)

83.7(1)

Pd(1)-N(2)

2.173(6)

C(18)-Pd(1)-N(2)

94.1(3)

Pd(1)-C(15)

2.153(7)

C(18)-Pd(1)-C(15)

74.8(3)

Pd(1)-Cl(1) O(1)-C(16)

2.420(2) 1.259(8)

N(2)-Pd(1)-Cl(1) C(18)-Pd(1)-Cl(1)

93.4(2) 171.7(2)

C(15)-C(16)

1.444(9)

N(2)-Pd(1)-Cl(1)

93.4(2)

C(18)-C(19)

1.333(9)

C(15)-Pd(1)-Cl(1)

97.2(2)

C(2)-Pt(1)-N(1)

81.9(2)

C(16)-O(1)-Pt(1)

116.7(4)

both palladium centers is distorted square planar. Table 9 shows selected bond distances and angles of complex (Rc,Sp,Rc)-11. The X-ray structures of complexes (Rc,Rp,Rc)-11 and (Rc,Rp,Sc)13 are shown in Figures 10 and 12, respectively. Similar to the structure of complex (Rc,Sp,Rc)-11, they all have a newly generated enlarged seven-membered ring and a five-membered homobimetallic ring bridged by Cl via the insertion of one of the carbon-carbon triple bonds of the dialkynylphosphine into the Pd-C bond of the dimeric complex (Rc)-5 or (Sc)-8. The geometry at each palladium center is distorted square planar. Selected bond distances and angles of complexes (Rc,Rp,Rc)-11 and (Rc,Rp,Sc)-13 are shown in Tables 10 and 12, respectively. It should be noted that the dipalladium complex (Rc,Sp,Rc)-11 and

its heterobimetallic analogue complex (Rc,Sp,Rc)-6 are isostructural. Similarly, complexes (Rc,Rp,Rc)-11 and (Rc,Rp,Rc)-6 as well as complexes (Rc,Rp,Sc)-13 and (Rc,Rp,Sc)-9 are isostructural. As shown in Figures 11 and 13, the X-ray structural analysis of the dipalladium zwitterionic complexes (Rc,Sp,Rc,Rc)-12 and (Rc, Rp,Sc,Sc)-14 revealed that the absolute configurations of the P- and C-stereogenic centers were the same as complexes (Rc,Sp,Rc)-11 and (Rc,Rp,Sc)-13, respectively, while the newly formed stereogenic carbon centers accompanying the formation of the four-membered metallic heterocycle adopt R and S, respectively. The geometry at each palladium center is distorted square planar. Tables 11 and 13 show selected bond distances and angles of complexes (Rc,Sp,Rc,Rc)-12 and (Rc,Rp,Sc,Sc)-14, respectively. It is noteworthy that the dipalladium zwitterionic complex (Rc,Sp,Rc,Rc)-12 and its heterobimetallic analogue (Rc, Sp,Rc,Rc)-7 are isostructural, while the dipalladium zwitterionic complex (Rc,Rp,Sc,Sc)-14 and its heterobimetallic analogue (Rc, Rp,Sc,Sc)-10 are isostructural. Chemo-, Regio-, and Stereoselectivity Considerations. It should be noted that the above-mentioned insertion reactions proceed via an intermolecular pathway. This is evident from the fact that the dialkynylphosphine was coordinated onto the chiral orthometalated N,N-dimethyl naphthylamine template prior to the insertion of the carbon-carbon triple bond into the Pd-C bond of the N,N-dimethyl benzylamine palladacycle instead of insertion into the M-C bond of the original naphthylamine complex bearing the dialkynylphosphine moiety. Due to the fact that only one carbon-carbon triple bond of the dialkynylphosphine was inserted into the Pd-C bond of the N,N-dimethyl benzylamine palladacycle, the current insertion reactions are chemically selective in the activation of the CtC moieties toward insertion. It has been generally accepted that the insertion reaction of alkynes involves the η2-coordination of the alkyne to the metal center followed by the migratory insertion of CtC into the metal-carbon bond of the palladacycles.19 As illustrated in Scheme 6, upon coordination to the chiral cyclometalated template, the CtC bond of dialkynylphosphine coordinates in the η2 mode to the Pd center of the orthopalladated N,Ndimethyl benzylamine to form a four-coordinated complex via a chloro bridge-splitting reaction on the orthopalladated N, N-dimethyl benzylamine template.4d,19 Since the CtC unit is not symmetric, the η2-coordination step may proceed via two different pathways: pathway A or B (Scheme 6). The steric repulsion arising from the phenyl group of the orthopalladated N, N-dimethyl benzylamine and the naphthyl ring of the orthometalated N,N-dimethyl naphthylamine in pathway A is higher than 1539


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Scheme 6

Figure 9. Molecular structure of complex (Rc,Sp,Rc)-11.

that of the phenyl group of the orthopalladated N,N-dimethyl benzylamine and the Me group of the coordinated dialkynylphosphine in pathway B. Furthermore, in pathway B it is easier for

the Cl atom on the M center to donate a lone pair of electrons to the Pd center of the orthopalladated N,N-dimethyl benzylamine. It is clear that pathway B, with the methyl group located close to 1540


Organometallics

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the phenyl group of the orthopalladated N,N-dimethyl benzylamine, is sterically and electronically much more favorable than pathway A, in which the methyl group takes the position adjacent to the Cl atom. Therefore, the subsequent insertion of the CtC moiety of dialkynylphosphines bearing a chiral cyclometalated template into the Pd-C bond of the orthopalladated N,Ndimethyl benzylamine proceeds with excellent regioselectivity to form a seven-membered ring with the methyl group invariably located adjacent to the phenyl group of the orthopalladated N,Ndimethyl benzylamine, while the lone pair on Cl in the chiral cyclometalated template is donated to the Pd center of the orthopalladated N,N-dimethyl benzylamine to generate a fivemembered bimetallic homo- or heterocycle. In the current insertion reactions, when orthometalated N,Ndimethyl naphthylamine complex (Rc)-3/(Rc)-4 was employed to carry out insertion reactions with the complex (Rc)-5, the absolute configuration at the newly generated stereogenic phosphorus center of the major product always adopted an S absolute configuration, and that of the minor product was R. It has been well established that the chiral naphthylamine chelate ring in (Rc)-1/(Rc)-2 is locked into the static δ conformation both in the solid state and in solution with the methyl substituent on the stereogenic carbon invariably taking up the axial position above the PdCN ring (Scheme 8).20 On the basis of the absolute chirality of the phosphorus center and the absolute conformation of the Pt/Pd-Cl-Pd-P five-membered bimetallic ring, the

above insertion reaction may generate up to four stereoisomeric products. As shown in Scheme 7, isomers A and B have the same λ absolute conformation of the five-membered bimetallic ring, but differ in their absolute configuration at the newly generated stereogenic phosphorus center in that the absolute configuration of the phosphorus center in isomer A is R, while in isomer B it is S. Similarly, isomers C and D are conformers with the same δ absolute conformation of the five-membered bimetallic ring but different absolute configuration at the newly formed phosphorus centers. A correlation between the X-ray crystallography data of the current insertion reaction products and a Dreiding model study indicates that isomers C and D are sterically unfavorable due to the steric repulsion arising from the axial C-methyl group of the orthometalated N,N-dimethyl naphthylamine complex (Rc)-3/(Rc)-4 with the C-methyl group of complex (Rc)-5. Therefore isomers A and B with λ absolute conformation of the five-membered bimetallic ring could be deduced to be the favorable products. On the other hand, in isomers A and B, steric repulsion also exists between the vinylic methyl group and the alkynylphosphine located below the PdCN ring. Taking into account the X-ray crystallography data of the insertion reaction products together with a Dreiding model study, it is evident that the Ph group of the alkynylphosphine prefers to occupy the position above the ring to attain the least steric repulsion. Therefore, isomer B with the S-phosphorus stereogenic center is sterically more favorable than isomer A. As a result, isomers B

Table 9. Selected Bond Distances (Å) and Angles (deg) of Complex (Rc,Sp,Rc)-11

Table 10. Selected Bond Distances (Å) and Angles (deg) of Complex (Rc,Rp,Rc)-11

Pd(1)-C(2)

1.996(2)

N(1)-Pd(1)-P(1)

175.1(1)

Pd(1)-C(2)

1.980(16)

N(1)-Pd(1)-P(1)

177.8(4)

Pd(1)-N(1)

2.128(2)

C(2)-Pd(1)-Cl(2)

176.9(1)

Pd(1)-N(1)

2.121(12)

C(2)-Pd(1)-Cl(1)

174.5(4)

Pd(1)-P(1)

2.238(1)

N(1)-Pd(1)-Cl(2)

96.1(1)

Pd(1)-P(1)

2.245(4)

N(1)-Pd(1)-Cl(1)

93.5(4)

Pd(1)-Cl(2)

2.417(1)

P(1)-Pd(1)-Cl(2)

87.4(2)

Pd(1)-Cl(1)

2.425(4)

P(1)-Pd(1)-Cl(1)

88.3(1)

Pd(2)-C(18)

2.000(2)

C(18)-Pd(2)-N(2)

95.3(1)

Pd(2)-C(18)

2.009(12)

C(18)-Pd(2)-N(2)

93.3(5)

Pd(2)-N(2)

2.119(2)

C(18)-Pd(2)-Cl(2)

84.8(1)

Pd(2)-N(2)

2.129(12)

C(18)-Pd(2)-Cl(1)

83.2(5)

Pd(2)-Cl(2)

2.356(1)

N(2)-Pd(2)-Cl(2)

172.4(1)

Pd(2)-Cl(1)

2.344(4)

N(2)-Pd(2)-Cl(1)

173.4(3)

Pd(2)-Cl(3) C(18)-C(19)

2.441(1) 1.345(3)

C(18)-Pd(2)-Cl(3) N(2)-Pd(2)-Cl(3)

169.2(1) 90.5(1)

Pd(2)-Cl(2) C(18)-C(19)

2.460(3) 1.327(19)

C(18)-Pd(2)-Cl(2) N(2)-Pd(2)-Cl(2)

171.9(4) 94.1(3)

C(2)-Pd(1)-N(1)

81.0(1)

Cl(2)-Pd(2)-Cl(3)

90.7(2)

C(2)-Pd(1)-N(1)

81.0(5)

Cl(1)-Pd(2)-Cl(2)

89.8(1)

C(2)-Pd(1)-P(1)

95.5(1)

Pd(2)-Cl(2)-Pd(1)

82.8 (2)

C(2)-Pd(1)-P(1)

97.1(4)

Pd(2)-Cl(1)-Pd(1)

83.2(1)

Figure 10. Molecular structure of complex (Rc,Rp,Rc)-11. 1541


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and A should be the major and minor products, respectively, of the insertion reaction between complexes (Rc)-3/(Rc)-4 and (Rc)-5. This is confirmed by the X-ray crystallographic analysis where isomer B represents complexes (Rc,Sp,Rc)-6 and (Rc,Sp, Rc)-11, while complexes (Rc,Rp,Rc)-6 and (Rc,Rp,Rc)-11 are represented by isomer A. Figures 14, 15, 16, and 17 are sectional ORTEP drawings of complexes (Rc,Sp,Rc)-6, (Rc,Sp,Rc)-11, (Rc, Rp,Rc)-6, and (Rc,Rp,Rc)-11, respectively, corresponding to isomers A and B. For clarity only the atoms included in isomers A and B are shown. Table 11. Selected Bond Distances (Å) and Angles (deg) of Complex (Rc,Rp,Rc,Rc)-12 Pd(1)-C(2)

1.977(4)

C(2)-Pd(1)-O(1)

173.1(1)

Pd(1)-N(1)

2.136(3)

N(1)-Pd(1)-O(1)

96.2(1)

Pd(1)-O(1)

2.135(3)

C(2)-Pd(1)-P(1)

99.5(1)

Pd(1)-P(1)

2.232(1)

N(1)-Pd(1)-P(1)

174.8(1)

Pd(2)-C(18) Pd(2)-C(15)

2.000(4) 2.135(4)

O(1)-Pd(1)-P(1) C(18)-Pd(2)-C(15)

83.3(1) 75.3(1)

Pd(2)-N(2)

2.171(3)

C(18)-Pd(2)-N(2)

95.6(1)

Pd(2)-Cl(1)

2.406(1)

C(15)-Pd(2)-N(2)

167.5(1)

C(15)-C(16)

1.442(5)

C(18)-Pd(2)-Cl(1)

172.1(1)

C(18)-C(19)

1.329(5)

C(15)-Pd(2)-Cl(1)

97.1(1)

O(1)-C(16)

1.265(5)

N(2)-Pd(2)-Cl(1)

92.2(1)

C(2)-Pd(1)-N(1)

81.5(1)

C(16)-O(1)-Pd(1)

117.5(2)

Table 12. Selected Bond Distances (Å) and Angles (deg) of Complex (Rc,Rp,Sc)-13 Pd(1)-C(2)

1.991(5)

N(1)-Pd(1)-P(1)

173.5(1)

Pd(1)-N(1) Pd(1)-P(1)

2.134(4) 2.229(1)

C(2)-Pd(1)-Cl(1) N(1)-Pd(1)-Cl(1)

174.7(1) 95.8(1)

Pd(1)-Cl(1)

2.413(1)

P(1)-Pd(1)-Cl(1)

87.4(1)

Pd(2)-C(18)

2.000(5)

C(18)-Pd(2)-N(2)

93.9(2)

Pd(2)-N(2)

2.109(4)

C(18)-Pd(2)-Cl(1)

85.3(1)

Pd(2)-Cl(1)

2.359(1)

N(2)-Pd(2)-Cl(1)

176.8(1)

Pd(2)-Cl(2)

2.415(1)

C(18)-Pd(2)-Cl(2)

170.5(1)

C(18)-C(19)

1.355(7)

N(2)-Pd(2)-Cl(2)

93.3(1)

C(2)-Pd(1)-N(1) C(2)-Pd(1)-P(1)

81.4(2) 95.9(1)

Cl(1)-Pd(2)-Cl(2) Pd(2)-Cl(1)-Pd(1)

87.8(1) 108.0(1)

However, in the insertion reactions involving orthometalated naphthylamine complex (Rc)-3/(Rc)-4 and dimeric palladium(II) complex (Sc)-8, the major product contained one newly formed stereogenic phosphorus center with the R-absolute configuration, while the absolute configuration of the newly generated stereogenic phosphorus center in the minor product adopted an S configuration. Similar to the insertion reactions involving dimeric palladium(II) complex (Rc)-5, this insertion reaction may also generate four possible stereoisomeric products (Scheme 8). As shown in Scheme 8, owing to the steric repulsion arising from the axial C-methyl group of the orthometalated N,Ndimethyl naphthylamine complex (Rc)-3/(Rc)-4 with the C-methyl group of the dimeric palladium(II) complex (Sc)-8, isomers E and F with λ absolute conformation are sterically unfavorable, while isomers G and H with δ absolute conformation should be the favorable products. This is confirmed by the X-ray crystallographic analysis where isomer G is represented by complexes (Rc,Rp,Sc)-9 and (Rc,Rp,Sc)-13. Figures 18 and 19 are sectional ORTEP drawings of complexes (Rc,Rp,Sc)-9 and (Rc, Rp,Sc)-13, respectively, corresponding to the isomer G. For clarity only the atoms included in isomer G are shown.

’ CONCLUSIONS In conclusion, a series of asymmetric selective monoinsertions of dialkynylphosphine ligands into Pd-C bonds of chiral N,Ndimethyl benzylamine palladacycles have been demonstrated under mild conditions. In this study, cyclopalladated and cycloplatinated complexes containing an N,N-dimethyl naphthylamine system have been shown to control the regio- and stereoselectivity of the insertion reaction to give a variety of homo- or heterobimetallic complexes bearing a newly formed P-stereogenic center with high regioselectivity and moderate stereoselectivity. The remaining CtC of the monoinsertion product would undergo a series of transformations to generate a zwitterionic complex containing a new four-membered ring with a newly generated C-stereogenic center, while the absolute configuration at P remained unchanged. We are currently exploring ways to improve the selectivity of the insertion reaction and extend it to other cyclometalated systems and alkyne substrates. Catalytic applications of the insertion products and the zwitterionic systems are also being investigated.

Figure 11. Molecular structure of complex (Rc,Sp,Rc,Rc)-12. 1542


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Figure 12. Molecular structure of complex (Rc,Rp,Sc)-13.

Table 13. Selected Bond Distances (Å) and Angles (deg) of Complex (Rc,Rp,Sc,Sc)-14

Figure 13. Molecular structure of complex (Rc,Rp,Sc,Sc)-14.

’ EXPERIMENTAL SECTION Reactions involving air-sensitive compounds were performed under a positive pressure of purified nitrogen. NMR spectra were recorded at 25 °C on Bruker ACF 300 and AMX500 spectrometers. Optical rotations were measured on the specified solution in a 1 dm cell at 25 °C with a Perkin-Elmer 341 polarimetrer. Melting points were determined on a B€uchi melting point B-540. Elemental analyses were performed by the Elemental Analysis Laboratory of the Department of Chemistry at the National University of Singapore. The dimeric complexes (Rc)-5 and (Sc)-8,21 dimeric complex (Rc)-1,22,23 and dimeric complex (Rc)-224 were prepared according to standard literature methods. The di(1-propynyl)phenylphosphine was prepared by the revised literature methods.25 Synthesis of Complexes (Rc)-3 and (Rc)-4. To a solution of di(1-propynyl)phenylphosphine (1.06 g, 5.69 mmol) in dichloromethane was added complex (Rc)-1 (1.94 g, 2.85 mmol), and the reaction mixture was then left to stir for 2 h at room temperature. Upon completion, the solvent was removed and slow addition of hexane to the crude reaction mixture in dichloromethane gave complex (Rc)-3 as yellow crystals: mp 225-227 °C; [R]D -130 (c 0.5, CH2Cl2); 2.49 g (84% yield). Anal. Calcd for C26H27ClNPdP: C, 59.3; H, 5.2; N, 2.7. Found: C, 59.7; H, 5.4; N, 2.5. 31P{1H} NMR (CDCl3, 121 MHz): δ 20.5(s). 1H NMR (CDCl3, 300 MHz): δ 1.97 (d, 3H, JHH = 6.4 Hz,

Pd(1)-C(2)

1.971(6)

C(2)-Pd(1)-O(1)

176.1(2)

Pd(1)-N(1)

2.120(4)

N(1)-Pd(1)-O(1)

94.1(2)

Pd(1)-O(1)

2.138(4)

C(2)-Pd(1)-P(1)

99.8(2)

Pd(1)-P(1) Pd(2)-C(18)

2.234(1) 1.991(5)

N(1)-Pd(1)-P(1) O(1)-Pd(1)-P(1)

175.6(2) 84.1(1)

Pd(2)-N(2)

2.153(5)

C(18)-Pd(2)-N(2)

96.6(2)

Pd(2)-C(15)

2.130(5)

C(18)-Pd(2)-C(15)

75.5(2)

Pd(2)-Cl(1)

2.428(1)

C(15)-Pd(2)-N(2)

171.7(2)

O(1)-C(16)

1.254(7)

C(18)-Pd(2)-Cl(1)

170.0(2)

C(15)-C(16)

1.434(8)

N(2)-Pd(2)-Cl(1)

92.4(1)

C(18)-C(19)

1.350(7)

C(15)-Pd(2)-Cl(1)

95.4(1)

C(2)-Pd(1)-N(1)

82.0(2)

C(16)-O(1)-Pd(1)

116.9(4)

CHMe), 2.01(d, 3H, JPH = 3.2 Hz, tCMe), 2.1(d, 3H, JPH = 3.6 Hz, tCMe), 2.71(d, 3H, JPH = 2.0 Hz, NMe), 2.96 (d, 3H, JPH = 4.0 Hz, NMe), 4.4 (qn, 1H, JHH = JPH = 6.4 Hz, CHMe), 7.27-7.44 (m, 11H, aromatics). 13C NMR (CDCl3, 100 MHz): δ 5.7 (d, 1C, JPC = 2.5 Hz, tCMe), 5.8 (d, 1C, JPC = 2.6 Hz, tCMe), 23.8 (s, 1C, CHMe), 48.6 (d, 1C, JPC = 2.3 Hz, NMe), 51.5 (d, 1C, JPC = 3.5 Hz, NMe), 70.3 (d, 1C, JPC = 114.6 Hz, PCtC), 70.4 (d, 1C, JPC = 114.0 Hz, PCtC), 73.2 (d, 1C, JPC = 3.7 Hz, CHMe), 106.5 (d, 1C, JPC = 18.7 Hz, PCtC), 106.8 (d, 1C, JPC = 18.7 Hz, PCtC), 123.4-150.5 (m, 16C, Ar). Using a similar procedure to the preparation of complex (Rc)-3, complex (Rc)-4 was synthesized. Complex (Rc)-4 was crystallized from hexane-dichloromethane as light yellow crystals: 2.8 g (87% yield); mp 153-155 °C; [R]D -64 (c 0.5, CH2Cl2). Anal. Calcd for C26H27ClNPtP: C, 50.8; H, 4.4; N, 2.3. Found: C, 50.7; H, 4.4; N, 2.2. 31P{1H} NMR (CDCl3, 121 MHz): δ -39.5 (s, JPt-P = 4505 Hz, 1P). 1H NMR (CDCl3, 300 MHz): δ 1.92 (d, 3H, JHH = 6.4 Hz, CHMe), 2.04 (d, 3H, JPH = 3.6 Hz, tCMe), 2.13 (d, 3H, JPH = 3.6 Hz, tCMe), 2.79 (d, 3H, JPH = 2.3 Hz, JPtH = 29.3 Hz, NMe), 2.96 (d, 3H, JPH = 3.9 Hz, JPtH = 22.1 Hz, NMe), 4.55 (qn, 1H, JHH = JPH = 6.9 Hz, CHMe), 7.24-8.13 (m, 11H, aromatics). 13C NMR (CDCl3, 100 MHz): δ 5.5 (d, 1C, JPC = 2.9 Hz, tCMe), 5.6 (d, 1C, JPC = 2.9 Hz, tCMe), 22.6 (s, 1C, CHMe), 48.5 (d, 1C, JPC = 1.7 Hz, NMe), 52.2 (d, 1C, JPC = 3.8 Hz, NMe), 69.2 (d, 1C, JPC = 132.4 Hz, PCtC), 69.3 (d, 1C, JPC = 132.8 Hz, PCtC), 74.5 (d, 1C, JPC = 3.6 Hz, CHMe), 105.4 (d, 1C, JPC = 10.2 Hz, PCtC), 105.6 (d, 1C, JPC = 10.3 Hz, PCtC), 123.2-147.6 (m, 16C, Ar).

Synthesis of Complexes (Rc,Sp,,Rc)-6, (Rc,Rp,,Rc)-6, (Rc,Sp, Rc,Rc)-7, and (Rc,Rc,Rc,Sc)-7. Complex (Rc)-4 (0.50 g, 0.81 mmol) was dissolved in dichloromethane (100 mL). This solution then was treated with dimeric complex (Rc)-5 (0.24 g, 0.41 mmol). The mixture was stirred 1543


Organometallics

ARTICLE

Scheme 7

Scheme 8

at room temperature for 36 h. Upon completion, the solvent was removed to give a dark brown residue, which was purified by column chromatography (hexane-acetone, 6:1) to give the products as light yellow solids. Complex (Rc,Sp,Rc)-6 was crystallized from hexane-acetone as light yellow crystals: 0.17 g (23% yield); mp 212-214 °C (dec); [R]D þ208

(c 0.3, CH2Cl2). Anal. Calcd for C36H41Cl2N2PPdPt: C, 47.8; H, 4.6; N, 3.1. Found: C, 47.5; H, 4.5; N, 2.9. 31P{1H} NMR (CDCl3, 121 MHz): δ -38.2 (s, JPt-P = 4074 Hz, 1P). 1H NMR (CDCl3, 300 MHz): δ 1.03 (d, 3H, JHH = 6.8 Hz, CHMe0 ), 2.03 (s, 3H, NMe0 ), 2.17 (d, 3H, JPH = 2.8 Hz, dCMe), 2.20 (d, 3H, JHH = 5.6 Hz, CHMe), 2.52 (s, 3H, NMe0 ), 2.72 (d, 1544


Organometallics

Figure 14

Figure 15 3H, JPH = 2.0 Hz, NMe), 2.78 (d, 3H, JPH = 2.0 Hz, tCMe), 3.29 (d, 3H, NMe, JPH = 3.2 Hz), 3.56 (q, 1H, JHH = 6.8 Hz, CH0 Me), 4.58 (qn, 1H, JHH = JPH = 6.4 Hz, CHMe), 7.13-8.23 (m, 15H, aromatics). 13C NMR (CDCl3, 100 MHz): δ 6.0 (d, 1C, JPC = 2.0 Hz, tCMe), 8.7 (S, 1C, C0 HMe0 ), 22.9 (s, 1C, dCMe), 23.3 (d, 1C, JPC = 9.3 Hz, CHMe), 42.5 (s, 1C, NMe0 ), 49.9 (s, 1C, NMe0 ), 50.0 (s, 1C, NMe), 53.1 (d, 1C, JPC = 3.2 Hz, NMe), 62.1 (s, 1C, C0 HMe0 ), 70.7 (d, 1C, JPC = 73.1 Hz, PCtC), 73.7 (d, 1C, JPC = 3.6 Hz, CHMe), 106.3 (d, 1C, JPC = 11.0 Hz, PCtC), 123.2-148.0 (m, 24C, Ar and CdC). Complex (Rc,Rp,Rc)-6 was crystallized from hexane-acetone as light yellow crystals: 0.14 g (19% yield); mp 178-180 °C (dec); [R]D þ140 (c 0.5, CH2Cl2). Anal. Calcd for C36H41Cl2N2PPdPt: C, 47.8; H, 4.6; N, 3.1. Found: C, 47.6; H, 5.1; N, 3.1. 31P{1H} NMR (CDCl3, 121 MHz): δ -35.9 (s, JPt-P = 3983 Hz, 1P). 1H NMR (CDCl3, 300 MHz): δ 1.33 (d, 3H, JHH = 7.2 Hz, CHMe0 ), 1.59 (d, 3H, JPH = 2.4 Hz, =CMe), 2.05(d, 3H, JHH = 3.6 Hz, CHMe), 2.22 (d, 3H, JPH = 6.4 Hz, tCMe),

ARTICLE

Figure 16

Figure 17 2.59 (brs, 3H, NMe), 2.73(s, 3H, NMe0 ), 3.24 (s, 3H, NMe0 ), 3.36 (d, 3H, JPH = 3.6 Hz, NMe), 4.25 (q, 1H, JHH = 6.8 Hz, CH0 Me), 4.50 (qn, 1H, JHH = 6.8 Hz, JPH = 6.4 Hz, CHMe), 7.32-8.19 (m, 15H, aromatics). 13 C NMR (CDCl3, 100 MHz): δ 5.4 (d, 1C, JPC = 2.4 Hz, tCMe), 8.9 (S, 1C, C0 HMe0 ), 22.9 (s, 1C, dCMe), 23.6 (d, 1C, JPC = 10.1 Hz, CHMe), 42.2 (s, 1C, NMe0 ), 50.1 (s, 1C, NMe0 ), 50.4 (s, 1C, NMe), 53.3 (d, 1C, JPC = 3.4 Hz, NMe), 62.5 (s, 1C, C0 HMe0 ), 69.3 (d, 1C, JPC = 109.6 Hz, PCtC), 73.5 (d, 1C, JPC = 3.6 Hz, CHMe), 105.0 (d, 1C, JPC = 15.0 Hz, PCtC), 123.2-147.9 (m, 24C, Ar and CdC). Complex (Rc,Sp,Rc,Rc)-7 was crystallized from acetonitrile-diethyl ether as light yellow crystals: 0.02 g (3% yield); mp 208-210 °C (dec); [R]D þ67.0 (c 0.3, CH2Cl2). Anal. Calcd for C36H42ClN2OPPdPt: C, 48.7; H, 4.8; N, 3.2. Found: C, 48.4; H, 4.8; N, 3.6. 31P{1H} NMR (CDCl3, 121 MHz): δ -2.3 (s, JPt-P = 3872 Hz, 1P). 1H NMR (CDCl3, 300 MHz): δ 1.17 (d, 3H, JHH = 7.2 Hz, CHMe0 ), 1.92 (d, 3H, JHH = 1.6 Hz, CHMe), 1.95(d, 3H, JPH = 6.8 Hz, dCMe), 2.27 (d, 3H, JPH = 2.0 Hz, OdCMe), 2.49 (s, 3H, NMe0 ), 2.56 (s, 1H, PCH), 3.06 (d, 3H, JPH = 1.6 Hz, 1545


Organometallics

ARTICLE

Complex (Rc,Rp,Rc,Sc)-7 was prepared following a similar procedure to that for the preparation of complex (Rc,Sp,Rc,Rc)-7 and via stirring with H2O in acetone for one month and crystallizing from benzenepentane as light yellow crystals: 0.010 g (49% yield); mp 208-210 °C (dec); [R]D -33.3 (c 0.5, CH2Cl2). Anal. Calcd for C36H42ClN2OPPdPt: C, 48.7; H, 4.8; N, 3.2. Found: C, 48.5; H, 4.7; N, 3.5. 31P{1H} NMR (CDCl3, 121 MHz): δ -3.0 (s, JPt-P = 3838.7 Hz, 1P). 1H NMR (CDCl3, 300 MHz): δ 1.56 (d, 3H, JHH = 6.6 Hz, CHMe0 ), 1.94 (d, 3H, JHH = 7.8 Hz, CHMe), 1.96 (d, 3H, JPH = 1.5 Hz, dCMe), 2.34 (d, 3H, JPH = 1.3 Hz, OdCMe), 2.63 (s, 3H, NMe0 ), 2.86 (s, 3H, NMe0 ), 2.90 (s, 1H, PCH), 3.06 (s, 3H, NMe), 3.16 (q, 1H, JHH = 6.7 Hz, CH0 Me), 3.26 (d, 3H, NMe, JPH = 2.9 Hz), 4.81 (qn, 1H, JHH = 6.3, JPH = 5.9 Hz, CHMe), 7.00-7.77 (m, 15H, aromatics). 13C NMR (CDCl3, 100 MHz): δ 18.6 (S, 1C, C0 HMe0 ), 22.5 (d, 1C, JPC = 46.0 Hz, PCH), 22.9 (s, 1C, dCMe), 26.8 (d, 1C, JPC = 13.2 Hz, CHMe), 30.5 (d, 1C, JPC = 7.6 Hz, COMe), 46.5 (s, 1C, NMe0 ), 50.0 (s, 1C, NMe), 51.0 (s, 1C, NMe0 ), 52.9 (d, 1C, JPC = 3.4 Hz, NMe), 72.2 (d, 1C, JPC = 3.1 Hz, CHMe), 75.1 (s, 1C, C0 HMe0 ), 114.6 (d, 1C, JPC = 19.0 Hz, PCd), 122.9-148.9 (m, 23C, Ar and dCMe), 225.5 (d, 1C, JPC = 6.0 Hz, COMe).

Synthesis of Complexes (Rc,Rp,Sc)-9, (Rc,Sp,Sc)-9, (Rc,Rp,Sc, Sc)-10, and (Rc,Sp,Sc,Rc)-10. Complex (Rc)-4 (0.50 g, 0.81 mmol) Figure 18

Figure 19 NMe), 3.09 (s, 3H, NMe0 ), 3.31 (d, 3H, NMe, JPH = 2.8 Hz), 4.05 (q, 1H, JHH = 6.4 Hz, CH0 Me), 4.84 (qn, 1H, JHH = JPH = 6.4 Hz, CHMe), 7.12-8.01 (m, 15H, aromatics). 13C NMR (CDCl3, 100 MHz): δ 10.6 (S, 1C, C0 HMe0 ), 21.5 (d, 1C, JPC = 46.0 Hz, PCH), 22.9 (s, 1C, dCMe), 26.2 (d, 1C, JPC = 12.3 Hz, CHMe), 30.2 (d, 1C, JPC = 7.8 Hz, COMe), 39.2 (s, 1C, NMe0 ), 46.9 (s, 1C, NMe), 48.8 (s, 1C, NMe0 ), 52.8 (s, 1C, NMe), 62.7 (s, 1C, C0 HMe0 ), 71.9 (s, 1C, CHMe), 118.2 (d, 1C, JPC = 19.5 Hz, PCd), 122.7-148.9 (m, 23C, Ar and dCMe), 226.1 (d, 1C, JPC = 5.8 Hz, COMe). Complex (Rc,Sp,Rc,Rc)-7 can also be prepared by stirring complex (Rc,Sp,Rc)-6 (0.021 g, 0.023 mmol) with H2O (1 mL) in 10 mL of acetone for two days at room temperature. Acetone was removed through rotatory evaporation followed by extraction with dichloromethane (2 10 mL) and drying over MgSO4. Subsequent purification by silica gel chromatography (hexane-acetone, 8:1) followed by crystallization gave complex (Rc,Sp,Rc,Rc)-7 in 70% isolated yield (0.014 g).

was dissolved in dichloromethane (100 mL). This solution then was treated with dimeric palladium(II) complex (Sc)-8 (0.24 g, 0.41 mmol). The mixture was stirred at room temperature for 24 h. Upon completion, the solvent was removed to give a dark brown residue, which was purified by column chromatography (hexane-acetone, 6:1) to give the products as light yellow solids. Complex (Rc,Rp,Sc)-9 was crystallized from hexanedichloromethane as light yellow crystals: 0.23 g (31% yield); mp 197199 °C (dec); [R]D -77 (c 0.3, CH2Cl2). Anal. Calcd for C36H41Cl2N2PPdPt: C,47.7; H, 4.6; N, 3.1. Found: C, 47.5; H, 5.0; N, 3.1. 31P{1H} NMR (CDCl3, 121 MHz): δ -9.3 (s, JPt-P = 4203 Hz, 1P). 1H NMR (CDCl3, 300 MHz): δ 1.19 (d, 3H, JHH = 6.8 Hz, CHMe0 ), 1.81 (s, 3H, NMe0 ),1.88 (d, 3H, JHH = 6.0 Hz, CHMe), 1.97 (d, 3H, JPH = 3.6 Hz, dCMe), 2.45 (s, 3H, NMe0 ), 2.63 (d, 3H, JPH = 1.6 Hz, CMe), 2.84 (s, 3H, NMe, JPH = 2.0 Hz), 3.13 (d, 3H, NMe, JPH = 2.8 Hz), 4.09 (q, 1H, JHH = 6.8 Hz, CH0 Me), 4.53 (qn, 1H, JHH = 6.4 Hz, JPH = 6.8 Hz, CHMe), 7.32-8.19 (m, 15H, aromatics). 13C NMR (CDCl3, 100 MHz): δ 5.6 (d, 1C, JPC = 2.2 Hz, tCMe), 9.4 (S, 1C, C0 HMe0 ), 22.6 (s, 1C, dCMe), 23.3 (d, 1C, JPC = 12.1 Hz, CHMe), 42.5 (s, 1C, NMe0 ), 48.3 (s, 1C, NMe0 ), 48.5 (d, 1C, JPC = 2.3 Hz, NMe), 52.7 (d, 1C, JPC = 3.2 Hz, NMe), 63.4 (s, 1C, C0 HMe0 ), 71.1 (d, 1C, JPC = 89.4 Hz, PCtC), 73.4 (d, 1C, JPC = 3.4 Hz, CHMe), 106.9 (d, 1C, JPC = 11.5 Hz, PCtC), 123.0-147.6 (m, 24C, Ar and CdC). Complex (Rc,Sp,Sc)-9 was a light yellow solid: 0.12 g (16% yield); mp 210-211 °C (dec); [R]D -160 (c 0.5, CH2Cl2). Anal. Calcd for C36H41Cl2N2PPdPt: C,47.7; H, 4.6; N, 3.1. Found: C, 47.6; H, 4.9; N, 3.2. 31 1 P{ H} NMR (CDCl3, 121 MHz): δ -28.6 (s, JPt-P = 4046 Hz, 1P). 1 H NMR (CDCl3, 300 MHz): δ 1.44 (d, 3H, JHH = 7.1 Hz, CHMe0 ), 1.59 (d, 3H, JPH = 1.9 Hz, dCMe), 1.69 (d, 3H, JHH = 6.3 Hz, CHMe), 2.31 (d, 3H, 4JPH = 3.5 Hz, tCMe), 2.76 (s, 3H, NMe), 3.11 (s, 6H, NMe0 Me0 ), 3.34 (s, 3H, NMe), 4.39 (q, 1H, JHH = 7.1 Hz, CH0 Me), 4.5 (qn, 1H, JHH = JPH = 6.5 Hz, CHMe), 7.31-8.08 (m, 15H, aromatics). 13C NMR (CDCl3, 100 MHz): δ 5.7 (d, 1C, JPC = 2.3 Hz, tCMe), 9.1 (S, 1C, C0 HMe0 ), 22.5 (s, 1C, dCMe), 23.3 (d, 1C, JPC = 9.9 Hz, CHMe), 42.3 (s, 1C, NMe 0 ), 43.5 (s, 1C, NMe0 ), 48.5 (d, 1C, J PC = 2.0 Hz, NMe), 50.5 (s, 1C, NMe), 62.7 (s, 1C, C0 HMe0 ), 70.6 (d, 1C, JPC = 109.6 Hz, PCtC), 72.8 (d, 1C, JPC = 3.6 Hz, CHMe), 105.5 (d, 1C, JPC = 14.4 Hz, PCtC), 123.2-148.0 (m, 24C, Ar and CdC). Complex (Rc,Rp,Sc,Sc)-10 was crystallized from hexane-dichloromethane as light yellow crystals: 0.015 g (2% yield); mp 180-182 °C (dec); [R]D -26 (c 0.2, CH2Cl2). Anal. Calcd for C36H42ClN2OPPdPt: C, 48.7; H, 4.8; N, 3.2. Found: C, 48.9; H, 4.8; N, 3.2. 31P{1H} NMR (CDCl3, 121 MHz): δ -7.2 (s, JPt-P = 3887 Hz, 1P). 1H NMR (CDCl3, 300 1546


Organometallics

ARTICLE

Table 14. Crystallographic Data for Complexes (Rc)-3, (Rc,Sp,Rc)-6, (Rc,Rp,Rc)-6, and (Rc,Sp,Rc,Rc)-7 (Rc)-3

(Rc,Sp,Rc)-6

(Rc,Sp,Rc,Rc)-7

formula

C26H27ClNPPd

C39H47Cl2N2OPPdPt

C39.50H50Cl2N2O0.50PPdPt

C39H46.50ClN3.50OPPdPt

fw

526.31

963.15

964.18

948.21

space group

P2(1)2(1)2(1)

P2(1)2(1)2(1)

P2(1)

P1

cryst syst

orthorhombic

orthorhombic

monoclinic

triclinic

a/Å

12.6734(5)

11.8696(5)

11.9361(7)

9.9179(4)

b/Å

12.7251(5)

14.7315(6)

15.1004(9)

11.8461(6)

c/Å

15.6035(7)

22.5613(10)

12.6209(8)

18.4656(10)

R/deg β/deg

90 90

90 90

90 97.846(2)

76.381(3) 81.483(3)

γ/deg

90

90

90

65.363(2)

V/Å3

3730.0(10)

3945.0(3)

2253.5(2)

1913.49(16)

Z

4

4

2

2

T/K

295(2)

295(2)

173(2)

173(2)

Fcalcd/g cm-3

1.389

1.622

1.421

1.646

λ/Å

0.71073

0.71073

0.71073

0.71073

μ/mm-1 F(000)

0.919 1072

4.205 1904

3.680 956

4.267 938

Flack param

0.00(2)

0.001(4)

-0.049(9)

0.004(3)

R1 (obsd data)a

0.0326

0.0310

0.0549

0.0347

wR2 (obsd data)b

0.0710

0.0624

0.1435

0.0738

)

R1 = ∑ Fo|- |Fc /∑|Fo|. b wR2 = )

a

(Rc,Sp,Rc)-6

√ {∑[w(Fo2 - Fc2)2]/∑[w(Fo2)2]}, w-1 = σ2(Fo2) þ (aP)2 þ bP.

MHz): δ 1.25 (d, 3H, JHH = 6.8 Hz, CHMe0 ), 1.88 (d, 3H, JHH = 6.4 Hz, CHMe), 1.95 (d, 3H, JPH = 1.6 Hz, dCMe), 2.32 (d, 3H, JPH = 1.6 Hz, OdCMe), 2.53 (s, 3H, NMe0 ), 2.83 (s, 1H, PCH), 3.02 (d, 3H, JPH = 1.6 Hz, NMe), 3.08 (s, 3H, NMe0 ), 3.27 (d, 3H, NMe, JPH = 2.8 Hz), 4.31 (q, 1H, JHH = 7.2 Hz, CH0 Me), 4.79 (qn, 1H, JHH = JPH = 6.8 Hz, CHMe), 7.19-7.78 (m, 15H, aromatics). 13C NMR (CDCl3, 100 MHz): δ 10.5 (S, 1C, C0 HMe0 ), 21.4 (d, 1C, JPC = 45.8 Hz, PCH), 22.7 (s, 1C, dCMe), 24.7 (d, 1C, JPC = 11.9 Hz, CHMe), 30.1 (d, 1C, JPC = 11.9 Hz, COMe), 39.1 (s, 1C, NMe0 ), 46.3 (s, 1C, NMe), 49.3 (s, 1C, NMe0 ), 52.7 (d, 1C, JPC = 2.8 Hz, NMe), 63.0 (s, 1C, C0 HMe0 ), 72.1 (d, 1C, JPC = 2.8 Hz, CHMe), 121.4 (d, 1C, JPC = 19.5 Hz, PCd), 122.8-148.9 (m, 23C, Ar and dCMe), 225.6 (d, 1C, JPC = 6.0 Hz, COMe). Complexes (Rc,Rp,Sc,Sc)-10 and (Rc,Sp,Sc,Rc)-10 can also be prepared via stirring complexes (Rc,Rp,Sc)-9 and (Rc,Sp,Sc)-9 with H2O in acetone separately. Complex (Rc,Sp,Sc,Rc)-10 was crystallized from benzene-pentane as light yellow crystals: 0.011 g (45% yield); mp 194-195 °C (dec); [R]D þ76.5 (c 0.5, CH2Cl2). Anal. Calcd for C36H42ClN2OPPdPt: C, 48.7; H, 4.8; N, 3.2. Found: C, 48.8; H, 4.7; N, 3.2. 31P{1H} NMR (CDCl3, 121 MHz): δ -1.7 (s, JPt-P = 3820.5 Hz, 1P). 1H NMR (CDCl3, 300 MHz): δ 1.12 (d, 3H, JHH = 6.6 Hz, CHMe0 ), 1.97 (d, 3H, JHH = 7.5 Hz, CHMe), 1.98 (s, 3H, dCMe), 2.30 (s, 3H, OdCMe), 2.56 (s, 3H, NMe0 ), 2.68 (s, 1H, PCH), 2.87 (s, 3H, NMe), 3.03 (s, 3H, NMe0 ), 3.06 (q, 1H, JHH = 7.9 Hz, CH0 Me), 3.30 (d, 3H, NMe, JPH = 2.2 Hz), 4.83 (qn, 1H, JHH = 4.7, JPH = 6.0 Hz, CHMe), 6.89-8.06 (m, 15H, aromatics). 13C NMR (CDCl3, 100 MHz): δ 17.5 (S, 1C, C0 HMe0 ), 22.3 (d, 1C, JPC = 45.6 Hz, PCH), 23.0 (s, 1C, dCMe), 27.5 (d, 1C, JPC = 13.7 Hz, CHMe), 30.4 (d, 1C, JPC = 7.4 Hz, COMe), 47.1 (s, 1C, NMe0 ), 50.2 (s, 1C, NMe), 50.8 (s, 1C, NMe0 ), 52.8 (d, 1C, JPC = 3.4 Hz, NMe), 72.1 (d, 1C, JPC = 2.8 Hz, CHMe), 75.0 (s, 1C, C0 HMe0 ), 112.0 (d, 1C, JPC = 20.7 Hz, PCd), 122.8-148.8 (m, 23C, Ar and dCMe), 225.8 (d, 1C, JPC = 5.7 Hz, COMe).

Synthesis of Complex (Rc,Sp,Rc)-11, (Rc,Rp,Rc)-11, and (Rc, Sp,Rc,Rc)-12. Complex (Rc)-3 (0.28 g, 0.47 mmol) was added to a solution of complex (Rc)-5 (0.50 g, 0.95 mmol) in dichloromethane (100 mL). The mixture was stirred at room temperature for 3 days.

Upon completion, the solvent was removed to give a dark brown residue, which was purified by column chromatography (hexane-acetone, 3:2) give the products as yellow solids. Complex (Rc,Sp,Rc)-11 was crystallized from acetone-hexane to give yellow crystals: 0.23 g (30% yield); mp 195-196 °C (dec); [R]D þ112 (c 0.5, CH2Cl2). Anal. Calcd for C36H41Cl2N2PPd2: C, 53.0; H, 5.0; N, 3.4. Found: C, 52.8; H, 4.7; N, 3.2. 31P{1H} NMR (CDCl3, 121 MHz): δ -16.9 (s, 1P). 1H NMR (CDCl3, 300 MHz): δ 1.05 (d, 3H, JHH = 7.0 Hz, CHMe0 ), 2.08 (s, 3H, NMe0 ), 2.19 (d, 3H, JPH = 3.3 Hz, dCMe), 2.27 (d, 3H, JHH = 6.3 Hz, CHMe), 2.54 (s, 3H, NMe0 ), 2.67 (d, 3H, 4JPH = 1.7 Hz, tCMe), 2.75 (d, 3H, NMe, JPH = 2.1 Hz), 3.07 (d, 3H, NMe, JPH = 3.8 Hz), 3.60 (q, 1H, JHH = 7.0 Hz, CH0 Me), 4.35 (qn, 1H, JHH = JPH = 6.3 Hz, CHMe), 7.18-8.20 (m, 15H, aromatics). 13C NMR (CDCl3, 100 MHz): δ 6.0 (d, 1C, JPC = 1.8 Hz, tCMe), 8.8 (S, 1C, C0 HMe0 ), 23.5 (d, 1C, JPC = 9.4 Hz, CHMe), 24.2 (s, 1C, dCMe), 42.4 (s, 1C, NMe0 ), 49.7 (S, 1C, NMe0 ), 49.8 (s, 1C, NMe), 52.2 (d, 1C, JPC = 2.9 Hz, NMe), 62.2 (s, 1C, C0 HMe0 ), 71.2 (d, 1C, JPC = 56.2 Hz, PCtC), 72.5 (d, 1C, JPC = 3.5 Hz, CHMe), 107.6 (d, 1C, JPC = 7.9 Hz, PCtC), 123.5-149.5 (m, 24C, Ar and CdC). Complex (Rc,Rp,Rc)-11 was crystallized from acetonehexane to give yellow crystals: 0.17 g (22% yield); mp 203-205 °C (dec); [R]D þ164 (c 0.5, CH2Cl2). Anal. Calcd for C36H41Cl2N2PPd2: C, 53.0; H, 5.0; N, 3.4. Found: C, 52.8; H, 4.6; N, 3.1. 31P{1H}NMR (CDCl3, 121 MHz): δ -16.4 (s, 1P). 1H NMR (CDCl3, 300 MHz): δ 1.36 (d, 3H, JHH = 7.0 Hz, CHMe0 ), 1.67 (d, 3H, JPH = 1.7 Hz, =CMe), 2.04 (d, 3H, JHH = 3.5 Hz, CHMe), 2.34 (d, 3H, 4JPH = 6.3 Hz, tCMe), 2.56 (s, 3H, NMe), 2.78 (s, 3H, NMe0 ), 3.16 (d, 3H, NMe, JPH = 4.0 Hz), 3.27 (s, 3H, NMe0 ), 4.26-4.32 (m, 2H, CHMe and CH0 Me), 7.28-8.26 (m, 15H, aromatics). 13C NMR (CDCl3, 100 MHz): δ 5.6 (d, 1C, JPC = 2.2 Hz, tCMe), 8.9 (S, 1C, C0 HMe0 ), 23.6 (d, 1C, JPC = 9.9 Hz, CHMe), 24.4 (s, 1C, dCMe), 42.2 (s, 1C, NMe0 ), 49.8 (S, 1C, NMe), 50.3 (s, 1C, NMe0 ), 52.3 (d, 1C, JPC = 3.1 Hz, NMe), 62.4 (s, 1C, C0 HMe0 ), 70.9 (d, 1C, JPC = 94.2 Hz, PCtC), 72.4 (d, 1C, JPC = 3.6 Hz, CHMe), 105.9 (d, 1C, JPC = 11.7 Hz, PCtC), 122.4-149.4 (m, 24C, Ar and CdC). Complex (Rc,Sp,Rc,Rc)-12 was crystallized from acetonitrile as light yellow crystals: 0.023 g (3% yield); mp 197 °C (dec); [R]D -100 (c 0.5, CH2Cl2). Anal. Calcd for C36H42ClN2OPPd2: C, 54.2; H, 5.3; N, 3.5. 1547


Organometallics

ARTICLE

Table 15. Crystallographic Data for Complexes (Rc,Rp,Rc,Sc)-7, (Rc,Rp,Sc)-9, (Rc,Rp,Sc,Sc)-10, and (Rc,Sp,Sc,Rc)-10 (Rc,Rp,Rc,Sc)-7

(Rc,Rp,Sc,Sc)-10

(Rc,Sp,Sc,Rc)-10

formula

C42H48ClN2OPPdPt

C37H43Cl4N2PPdPt

C36.50H43Cl2N2OPPdPt

C42H48ClN2OPPdPt

fw

964.73

989.99

929.09

964.73

space group

P2(1)

P2(1)2(1)2(1)

P2(1)2(1)2(1)

P2(1)

cryst syst

monoclinic

orthorhombic

orthorhombic

monoclinic

a/Å

9.4113(3)

12.3661(17)

10.4219(3)

9.7661(4)

b/Å

19.0850(6)

16.004(3)

16.0129(5)

19.0720(7)

c/Å

11.0368(3)

18.848(3)

42.5362(15)

10.6031(4)

R/deg β/deg

90 105.7810(10)

90 90

90 90

90 103.175(2)

γ/deg

90

90

90

90

V/Å3

1907.65(10)

3730.0(10)

7098.6(4)

1922.94(13)

Z

2

4

8

2

T/K

103(2)

103(2)

103(2)

103(2)

Fcalcd/g cm-3

1.680

1.763

1.739

1.666

λ/Å

0.71073

0.71073

0.71073

0.71073

μ/mm-1 F(000)

4.281 956

4.587 1944

4.671 3656

4.247 956

Flack param

-0.009(3)

0.006(5)

0.027(4)

0.005(4)

R1 (obsd data)a

0.0360

0.0413

0.047

0.0205

wR2 (obsd data)b

0.0753

0.1005

0.1011

0.0498

)

R1 = ∑ Fo|-|Fc /∑|Fo|. b wR2 = )

a

(Rc,Rp,Sc)-9


Table 16. Crystallographic Data for Complexes (Rc,Sp,Rc)-11, (Rc,Rp,Rc)-11 (Rc,Sp,Rc,Rc)-12, (Rc,Rp,Sc)-13, and (Rc,Rp,Sc,Sc)-14 (Rc,Rp,Rc)-11

(Rc,Sp,Rc,Rc)-12

(Rc,Rp,Sc)-13

(Rc,Rp,Sc,Sc)-14

formula

C39H47Cl2N2OPPd2

C36H49Cl2N2O3.50PPd2

C38.84H46.34Cl1.31N3.34OPPd2

C39H47Cl2N2OPPd2

C36.50H43Cl2N2OPPd2

fw

874.46

880.44

866.36

874.46

840.40

space group

P2(1)2(1)2(1)

C2

P1

P2(1)2(1)2(1)

P2(1)2(1)2(1)

cryst syst a/Å

orthorhombic 12.3412(4)

monoclinic 23.9174(17)

triclinic 9.9213(3)



b/Å

15.0175(5)

14.8830(11)

11.8390(4)

16.1640(6)

16.178(3)

c/Å

19.9738(6)

11.7442(9)

18.3636(6)

19.0600(7)

42.663(8)

R/deg

90

90

76.468(2)

90

90

β/deg

90

116.069(4)

81.334(2)

90

90

γ/deg

90

90

65.2880(10)

90

90

V/Å3

3701.8(2)

3755.2(5)

1901.62(11)

3843.5(3)

7215(2)

Z T/K

4 103(2)

4 103(2)

2 103(2)

4 103(2)

8 295(2)

Fcalcd/g cm-3

1.569

1.557

1.513

1.511

1.547

λ/Å

0.71073

0.71073

0.71073

0.71073

0.71073

μ/mm-1

1.192

1.181

1.114

1.148

1.220

F(000)

1776

1792

880

1776

3400

Flack param

-0.021(14)

-0.07(7)

-0.027(14)

-0.02(3)

0.01(2)

R1 (obsd data)a

0.0317

0.0672

0.0328

0.0367

0.0497

wR2 (obsd data)b

0.0668

0.1461

0.0729

0.1066

0.0938

)

R1 = ∑ Fo|-|Fc /∑|Fo|. b wR2 = )

a

(Rc,Sp,Rc)-11


Found: C, 53.9; H, 5.1; N, 3.3. 31P{1H} NMR (CDCl3, 121 MHz): δ 15.9 (s, 1P). 1H NMR (CDCl3, 300 MHz): δ 1.19 (d, 3H, JHH = 7.0 Hz, CHMe0 ), 1.97 (d, 3H, JHH = 1.4 Hz, CHMe), 2.02 (d, 3H, JPH = 6.3 Hz, dCMe), 2.26 (d, 3H, JPH = 0.9 Hz, OdCMe), 2.52 (s, 1H, PCH), 2.53 (s, 3H, NMe0 ), 3.06 (s, 3H, NMe0 ), 3.10 (d, 3H, JPH = 2.7 Hz, NMe), 3.12 (s, 3H, NMe), 4.08 (q, 1H, JHH = 7.0 Hz, CH0 Me), 4.58 (qn, 1H, JHH = 6.3, JPH = 6.0 Hz, CHMe), 7.21-8.02 (m, 15H, aromatics). 13C NMR

(CDCl3, 100 MHz): δ 10.7 (S, 1C, C0 HMe0 ), 20.3 (d, 1C, JPC = 39.2 Hz, PCH), 24.2 (s, 1C, dCMe), 26.3 (d, 1C, JPC = 12.3 Hz, CHMe), 30.7 (d, 1C, JPC = 8.5 Hz, COMe), 39.2 (s, 1C, NMe0 ), 46.6 (s, 1C, NMe), 48.9 (s, 1C, NMe0 ), 51.8 (d, 1C, JPC = 2.4 Hz, NMe), 62.8 (s, 1C, C0 HMe0 ), 70.8 (d, 1C, JPC = 2.9 Hz, CHMe), 120.4 (d, 1C, JPC = 5.9 Hz, PCd), 123.0-150.2 (m, 23C, Ar and dCMe), 225.5 (d, 1C, JPC = 7.2 Hz, COMe). 1548


Organometallics Complex (Rc,Sp,Rc,Rc)-12 can also be prepared through stirring complex (Rc,Sp,Rc)-11 with H2O in acetone for 7 days in 40% isolated yield.

Synthesis of Complexes (Rc,Rp,Sc)-13 and (Rc,Rp,Sc,Sc)14. Complex (Rc)-3 (0.28 g, 0.47 mmol) was added to the solution of complex (Sc)-8 (0.50 g, 0.95 mmol) in dichloromethane (100 mL). The mixture was stirred at room temperature for 3 days. Upon completion, the solvent was removed to give a dark brown residue, which was purified by column chromatography (hexane-acetone, 5:1) to give the products as yellow solids. Complex (Rc,Rp,Sc)-13 was crystallized from hexane-acetone as yellow crystals: 0.22 g (28% yield); mp 198-200 °C (dec); [R]D -61 (c 0.3, CH2Cl2). Anal. Calcd for C36H41Cl2N2PPd2: C, 52.9; H, 5.1; N, 3.4. Found: C, 52.9; H, 5.5; N, 3.4. 31P{1H} NMR (CDCl3, 121 MHz): δ 8.7 (s). 1H NMR (CDCl3, 300 MHz): δ 1.22 (d, 3H, JHH = 7.2 Hz, CHMe0 ), 1.58 (d, 3H, JPH = 2.0 Hz, dCMe), 1.90 (br s, 3H, tCMe), 1.97 (d, 3H, JHH = 2.0 Hz, CHMe), 2.47 (s, 3H, NMe0 ), 2.59 (d, 3H, JPH = 1.6 Hz, NMe), 2.76 (s, 3H, NMe0 ), 2.90 (d, 3H, JPH = 2.8 Hz, NMe),4.1 (q, 1H, JHH = 20.5 Hz, CH0 Me), 4.3 (qn, 1H, JHH = JPH = 12.8 Hz,CHMe), 7.24-8.84 (m, 15H, aromatics). 13C NMR (CDCl3, 100 MHz): δ 5.7 (d, 1C, JPC = 2.1 Hz, tCMe), 9.5 (S, 1C, C0 HMe0 ), 23.81 (s, 1C, dCMe), 23.84 (d, 1C, JPC = 13.8 Hz, CHMe), 42.5 (s, 1C, NMe0 ), 48.3 (d, 1C, JPC = 2.1 Hz, NMe), 48.5 (s, 1C, NMe0 ), 51.5 (d, 1C, JPC = 2.8 Hz, NMe), 63.9 (s, 1C, C0 HMe0 ), 72.1 (d, 1C, JPC = 75.1 Hz, PCtC), 72.2 (d, 1C, JPC = 3.4 Hz, CHMe), 107.6 (d, 1C, JPC = 8.2 Hz, PCtC), 123.2-150.4 (m, 24C, Ar and CdC). Complex (Rc,Rp,Sc,Sc)-14 was crystallized from hexane-acetone as yellow crystals: 0.027 g (4% yield); mp 202-204 °C (dec); [R]D þ50 (c 0.2, CH2Cl2). Anal. Calcd for C36H42ClN2OPPd2: C, 54.2; H, 5.3; N, 3.5. Found: C, 53.8; H, 5.1; N, 3.4. 31P{1H} NMR (CDCl3, 121 MHz): δ 10.9. 1H NMR (CDCl3, 300 MHz): δ 1.26 (d, 3H, JHH = 6.8 Hz, CHMe0 ), 1.85 (d, 3H, JHH = 1.6 Hz, CHMe), 1.99 (d, 3H, JPH = 6.4 Hz, dCMe), 2.27 (d, 3H, JPH = 1.2 Hz, OdCMe), 2.54 (s, 3H, NMe0 ), 2.74 (d, 1H, JPH = 4.0 Hz, PCH), 2.97 (brs, 3H, NMe), 3.03 (d, 3H, NMe, JPH = 3.2 Hz), 3.07 (s, 3H, NMe0 ), 4.35 (q, 1H, JHH = 7.2 Hz, CH0 Me), 4.79 (qn, 1H, JHH = JPH = 5.6 Hz, CHMe), 7.21-7.80 (m, 15H, aromatics). 13C NMR (CDCl3, 100 MHz): δ 10.6 (S, 1C, C0 HMe0 ), 20.4 (d, 1C, JPC = 38.6 Hz, PCH), 23.8 (s, 1C, dCMe), 24.6 (d, 1C, JPC = 12.1 Hz, CHMe), 30.5 (d, 1C, JPC = 8.4 Hz, COMe), 39.0 (s, 1C, NMe0 ), 46.1 (s, 1C, NMe), 49.2 (s, 1C, NMe0 ), 51.6 (d, 1C, JPC = 3.2 Hz, NMe), 63.1 (s, 1C, C0 HMe0 ), 70.9 (d, 1C, JPC = 2.8 Hz, CHMe), 123.0-150.3 (m, 24C, Ar and CdC), 224.5 (d, 1C, JPC = 7.5 Hz, COMe). Complex (Rc,Rp,Sc,Sc)-14 can also be prepared through stirring complex (Rc,Rp,Sc)-13 with H2O in acetone for 10 days in 43% isolated yield.

Crystal Structure Determination of (Rc)-3, (Rc,Rp,Rc)-6, (Rc, Sp,Rc)-6, (Rc,Rp,Rc, Sc)-7, (Rc,Sp,Rc,Rc)-7, (Rc,Rp,Sc)-9, (Rc,Rp,Sc, Sc)-10, (Rc,Sp,Sc,Rc)-10, (Rc,Rp,Rc)-11, (Rc,Sp,Rc)-11, (Rc,Sp,Rc, Rc)-12, (Rc,Rp,Sc)-13, and (Rc,Sp,Sc,Sc)-14. X-ray crystallographic data for all these complexes are given in Tables 14, 15, and 16. Diffraction data were collected on a SMART CCD diffractometer with graphic-monochromated Mo KR radiation. For all the complexes, SADABS absorption corrections were applied. All non-hydrogen atoms were refined anisotropically. Hydrogen atoms were introduced at fixed distance from carbon atoms and were assigned fixed thermal parameters. The absolute configurations of all chiral complexes were determined unambiguously using the Flack parameter.26

’ ASSOCIATED CONTENT

bS

Supporting Information. For complexes (Rc)-3, (Rc,Rp, Rc)-6, (Rc,Sp,Rc)-6, (Rc,Rp,Rc,Sc)-7, (Rc,Sp,Rc,Rc)-7, (Rc,Rp,Sc)-9, (Rc,Rp,Sc,Sc)-10, (Rc,Sp,Sc,Rc)-10, (Rc,Rp,Rc)-11, (Rc,Sp,Rc)-11, (Rc,Sp,Rc,Rc)-12, (Rc,Rp,Sc)-13, and (Rc,Sp,Sc,Sc)-14 tables of crystal data, data collection, solution and refinement, final

ARTICLE

positional parameters, bond distances and angles, thermal parameters of non-hydrogen atoms, and calculated hydrogen parameters. This material is available free of charge via the Internet at http://pubs.acs.org.

’ AUTHOR INFORMATION Corresponding Author

*E-mail; [email protected].

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Asymmetric Synthesis of P-Stereogenic Homo- and Heterobimetallic

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