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Norbornadiene as a Building Block for the Synthesis of Linked Benzazocinones and Benzazocinium Salts through Tetranuclear Carbopalladated Intermediates José Antonio García-López,† Roberto Frutos-Pedreño,† Delia Bautista,‡ Isabel Saura-Llamas,*,† and José Vicente*,† †

Grupo de Química Organometálica, Departamento de Química Inorgánica, Facultad de Química, Universidad de Murcia, 30100 Murcia, Spain ‡ SAI, Universidad de Murcia, 30100 Murcia, Spain S Supporting Information *

ABSTRACT: The six-membered C,N-palladacycle [Pd(C,NC6H4CH2CMe2NH2-2)(μ-Cl)]2 (A) derived from phentermine reacts with norbornadiene to give a di- or tetranuclear complex arising from the double insertion of the same molecule of the strained alkene into one or two distinct Pd−aryl bonds. The tetranuclear complex has been characterized by X-ray diffraction studies and exhibits a very unusual cisoid geometry in both the disposition of the C,N-chelate ligands and the position of the palladium centers. The newly formed Pd−alkyl bonds are still reactive toward the insertion of unsaturated molecules, and the tetranuclear complex reacts with CO or isocyanides to give double benzazocinones or benzazocinium salts with a cisoid geometry, after depalladation of the corresponding organometallic intermediates which have been isolated in some cases. When the related palladacycles derived from phenethylamine or Nmethylphenethylamine are used as starting materials, polymeric compounds are obtained, from which double benzazocinones or benzazocinium salts with a transoid geometry are obtained after CO or RNC insertion and subsequent depalladation. The presence of substituents on the α-carbon atom of the chelated amine influences the regiochemistry of the double carbopalladation of the norbornadiene.

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INTRODUCTION

The rigid structure of 2-norbornene and its derivatives, such as norbornadiene, which hampers the otherwise facile β-hydride elimination from the carbopalladated intermediates, has made possible the isolation and characterization of the organometallic species arising from their insertions into the Pd−C bond of a range of metallic complexes,9 contributing to a better understanding and design of the aforementioned processes. For instance, organometallic derivatives resulting from the insertion of 2-norbornene or norbornadiene into Pd−alkyl,10,11 Pd−aryl,12−14 Pd−acyl,7,15−17 and Pd−iminoacyl bonds18 have been prepared and fully characterized. Our research group reported the insertion of 2-norbornene into the Pd−C bond of six-membered palladacycles to give extended eight-membered palladacycles.13,14 The resulting Pd− Cnorbornyl bond was still reactive toward the insertion of other unsaturated molecules such as CO and RNC.13,14 We thought that the extension of this chemistry to the related norbornadiene system could give rise to new organometallic and organic structures with interesting structural features. The

The unique structure and singular chemical behavior of 2norbornene and its derivatives have boosted their use in the last few decades in both organic synthesis and materials science. For instance, the Pd-catalyzed/norbornene-mediated reaction, known as the Catellani reaction,1 has proven to be a tremendously versatile tool for the dual functionalization of the ipso and ortho positions of iodoarenes, leading to highly substituted aromatic rings through the formation of several C− C or C−heteroatom bonds in a straightforward manner.2 The auxiliary ligand role played by norbornene in these cascade transformations relies on its ability to insert reversibly into the Pd−Caryl bond.1,3 Norbornene has also been successfully polymerized4 and copolymerized with other alkenes5 or CO6 to produce materials with interesting mechanical and optical properties (high glass transition temperatures, high optical transparency, low dielectric constant, and low birefringence). These copolymerizations are proposed to proceed via alternating migratory insertion reactions of the two different unsaturated species into the Pd−C bond (i.e., CO and alkenes to give polyketones).7,8 © XXXX American Chemical Society

Received: October 17, 2016

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DOI: 10.1021/acs.organomet.6b00795 Organometallics XXXX, XXX, XXX−XXX

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Organometallics carbopalladation of norbornadiene could serve as a good model to study the double functionalization of the norbornene-like structure and, furthermore, to disclose some of the factors governing the regiochemistry of this process.

Chart 1. Isomers Arising from Insertion of Norbornadiene into the Pd−C Bond of Six-Membered Palladacycles

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RESULTS AND DISCUSSION Synthesis and Structure of Eight-Membered Palladacycles Derived from Phentermine. The ortho-metalated complex [Pd(C,N-C6H4CH2CMe2NH2-2)(μ-Cl)]2 (A)19 reacted with 2 equiv of norbornadiene (NBD, C7H8; molar ratio Pd/NBD 1/1) in CH2Cl2 at room temperature, to give the dimeric complex [Pd{C,N-CH(C5H6)CHC6H4(CH2CMe2NH2)-2}(μ-Cl)]2 (1a; Scheme 1), which

is the normal geometry observed in the insertion of norbornene or norbornadiene into Pd−C bonds.7,12,13,16,17,20 The hydrogen atoms of the remaining double bond of the bicyclic moiety appeared as a complex system centered at 6.20 ppm. The IR spectrum of complex 2a showed the ν(CN) stretching frequency at 2162 cm−1, very close to those of related complexes.13 The crystal structure of complex 2a·0.5CH2Cl2 was solved by X-ray diffraction studies (Figure 1). The palladium atom was in

Scheme 1. Insertion of Norbornadiene into the Pd−C Bond of the Six-Membered Palladacycle A

Figure 1. X-ray thermal ellipsoid plot of the complex 2a·0.5CH2Cl2 (50% probability) along with the labeling scheme. The solvent molecule and the hydrogen atoms bonded to carbon have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Pd(1)−N(1) = 2.092(2), Pd(1)−Cl(1) = 2.4459(6), Pd(1)−C(11) = 1.921(2), Pd(1)−C(12) = 2.051(2), C(12)−C(13) = 1.582(3), C(17)−C(18) = 1.335(4); N(1)−Pd(1)−Cl(1) = 90.09(6), Cl(1)− Pd(1)−C(11) = 88.50(7), C(11)−Pd(1)−C(12) = 94.40(9), C(12)− Pd(1)−N(1) = 86.98(8), Pd(1)−C(11)−N(2) = 172.9(2), C(11)− N(2)−C(22) = 170.5(2).

a slightly distorted square planar environment, with a mean deviation of the Pd(II) coordination plane of 0.059 Å and a dihedral angle of 6.5° between the planes N(1)−Pd(1)−C(12) and Cl(1)−Pd(1)−C(11). The chelated ligand formed an eight-membered metallacycle, with a boat−chair conformation.21 The structure arises from the expected syn-exo addition of NBD (Chart 1). The discrete molecules are associated through N−H···Cl hydrogen bonds, giving dimers (details, including symmetry operations, are given in the Supporting Information). The inserted bicyclic unit of complex 1a retained one double bond, and thus, it could react with another 1 equiv of the palladacycle A to undergo a second insertion reaction. Indeed, the complex 1a reacted with 1 equiv of dimer A (molar ratio Pd/Pd 1/1) to give the tetranuclear complex 3a in good yields (81%; Scheme 1). In the NMR spectra of 3a only one-fourth of

contained an eight-membered palladacycle arising from the insertion of one molecule of the alkene into the Pd−C bond. Complex 1a was insoluble in CH2Cl2, CHCl3, acetone, and DMSO, which precluded its characterization by 1H and 13C NMR. Nevertheless, its elemental analysis and reactivity were in agreement with the structure depicted in Scheme 1. Complex 1a reacted with 2 equiv of 2,6-dimethylphenyl isocyanide (XyNC; molar ratio Pd/XyNC 1/1) to afford the corresponding mononuclear complex 2a (Scheme 1), which was soluble in the common organic solvents. The 1H NMR spectrum of complex 2a indicated the nonequivalence of the NH2 and CH2 protons and CMe2 methyl groups of the eightmembered palladacycle. The syn addition of the Pd−C bond to the exo face of the olefin (Chart 1) can be easily distinguished by the coupling constant between Hα and Hβ (3JHH = 8.4 Hz), the hydrogen atoms of the inserted former double bond.17 This B


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Organometallics

Reactions of Tetranuclear Complex 3a with 2,6Dimethylphenyl Isocyanide (XyNC). The tetranuclear complex 3a reacted with 4 equiv of XyNC (ratio Pd/XyNC 1/1) to give the dinuclear complex 4a-Xy (Scheme 2),

the molecule is observed: that is, the four aryl rings are equivalent as well as both norbornadienyl bridging units and, within each unit, both halves of the inserted moiety. Therefore, in solution, the complex must have a C2v symmetry, indicating that the addition of the second palladium center occurred cis to the first and that both C,N-chelate groups are also in a cisoid disposition. This was corroborated by the molecular structure in the solid state of complex 3a (vide infra). To the best of our knowledge, only four examples of the insertion of the two double bonds present in the same norbornadiene molecule into two different Pd−C(O)Me bonds have been described, and in all cases, the resulting dinuclear complexes exhibited a transoid geometry for the palladium centers.11,16 The tetranuclear complex 3a was also obtained by reacting palladacycle A with 1 equiv of NBD (molar ratio Pd/NBD 1/ 0.5). The asymmetric unit of the crystal structure of complex 3a· CH3COCH3 contains two independent molecules of 3a and two acetone solvent molecules (Figure 2). The molecular

Scheme 2. Reactions of 3a with XyNC

insoluble in the reaction medium, along with a complicated mixture of other products. Among them, it was possible to identify the bis-iminoacyl complex 5a, containing one inserted and one coordinated isocyanide per palladium center. Although complex 4a-Xy was insoluble in all the common organic solvents, which prevented us from measuring its NMR spectra, its elemental analysis was in agreement with the structure depicted in Scheme 2. In addition, the IR spectra of 4a-Xy displayed one strong absorption at 2167 cm−1, which could be assigned to ν(CN) of the coordinated isocyanide. Finally, supporting the proposed structure, complex 4a-Xy reacted with 2 equiv of XyNC (ratio Pd/XyNC 1/1) to afford complex 5a in good yield (80%). The bis-iminoacyl complex 5a was also obtained (71%; Scheme 2) when the reaction of 3a and XyNC was carried out in a 1/8 molar ratio (ratio Pd/XyNC 1/2). The 1H and 13C NMR spectra of complex 5a are in agreement with the proposed structure. In solution, the molecule presents Cs symmetry, with a mirror plane that contains the carbon atom of the methylene bridge and both bridgehead carbons of the norbornadienyl moiety. The methinic protons on the bridgehead carbon atoms resonate separately at 2.59 and 3.56 ppm, indicating their different chemical environments and proving that both palladacycles adopted a mutually cisoid disposition. The 1H NMR spectrum of 5a also revealed the nonequivalence of the hydrogen atoms of the NH2 and CH2 groups, as well as the Me groups of the CMe2 moiety of the eight-membered palladacycle. The prevented rotation around the Xy−N bond of the inserted

Figure 2. X-ray thermal ellipsoid plot of one (molecule 1) of the two independent molecules of the complex 3a·CH3COCH3 (50% probability) along with the labeling scheme. The solvent molecule and the hydrogen atoms bonded to carbon have been omitted for clarity. Selected bond lengths (Å) and angles (deg) for both independent molecules present in the asymmetric unit (molecules 1 and 2) are given in the Supporting Information.

structure can be described as two dinuclear palladium subunits “(C−N)Pd(μ-Cl)2Pd(C−N)” held together by two norbornadienyl moieties. Each palladium atom adopts a distorted or very distorted square planar geometry (mean deviation of the planes Pd(1)−N(1)−C(11)−Cl(1A or B)−Cl(1C or D) are in the range 0.056−0.133 Å), with the distortion most noticeable in the Cltrans to N−Pd−C(11) angles, with an average value of 97.6°. The cisoid arrangement of the C,N-cyclopalladated ligands is confirmed unambiguously and reflected in the geometry of the Pd2Cl2 bridges. Each chlorine atom of the Pd2Cl2 unit is trans either to two carbon atoms (Cl(lA) and Cl(1D)) or to two nitrogen atoms (Cl(1B) and Cl(1C)). In the molecule, the average length of the Pd−Cl bonds trans to carbon is 2.54 Å, and the average length of the Pd−Cl bonds trans to nitrogen is 2.35 Å, with a difference of ca. 0.19 Å. These distinct values result from the different trans influences of the aryl carbon and nitrogen atoms of the chelate amino ligand. The Pd−Pd distances are over 3 Å, indicating the absence of a bonding interaction. C


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Organometallics

or 8 equiv of tBuNC. Attempts to prepare a double-iminoacyl complex analogous to 5a containing tBuNC were unsuccesful, probably due to the high steric hindrance of the tBu substituent (see below). The formation of complex 7a occurred even when the reaction of 3a with 4 equiv of tBuNC was carried out at 0 °C. That is, the insertion of the coordinated tBuNC took place at 0 °C, even when a 1/1 Pd/RNC ratio was used, whereas with XyNC at room temperature the coordinated complex could be isolated in a better yield. This was a surprising result because, due to electronic factors,24,30,31 XyNC normally inserts more quickly than tBuNC. Very likely, the steric hindrance at the two Pd(II) centers, bridged by the norbornadienyl unit and bearing one coordinated tBuNC each of them, is responsible for this behavior. A similar steric hindrance at the Pd(II) centers avoided the formation of the double-coordinated/doubleinserted iminoacyl derivative containing tBuNC, analogous to 5a. The 1H and 13C NMR spectra of complexes 4a-Bu and 7a are in agreement with the proposed structures. The 1H NMR spectrum of 4a-Bu showed signals corresponding to only one type of palladacycle, one tBu group (δ 1.46 ppm), and two distinct bridgehead methinic protons for the norbornadienyl unit, accounting for a Cs-symmetric structure in solution. For complex 7a, the 1H NMR spectrum showed the presence of two different palladacycles and three tBu resonances (δ 1.58, 1.45, and 1.07 ppm), indicating the presence of two coordinated and one inserted isocyanide. The amidinium salt 6a-Bu was prepared by the reaction of the tetranuclear palladacycle 3a with 6 equiv of tBuNC in refluxing CHCl3 (Pd/isocyanide ratio 1/3, Scheme 3). According to the accepted mechanism for the synthesis of amidines through the insertion of isocyanides into the Pd−C bond, the formation of 6a-Bu requires that both palladium centers undergo the insertion process. However, only complex 7a can be obtained from 3a, even when 8 equiv of tBuNC was used: that is, both palladium centers cannot support simultaneously one inserted and one coordinated tert-butyl isocyanide. A plausible mechanism for the synthesis of amidinium salt 6a-Bu involves (after coordination of the isocyanide) two sequential insertion/decomposition steps: that is, (1) insertion of tBuNC into one Pd−C bond (to give complex 7a), (2) depalladation of this center, releasing the steric hindrance (intermediate I; Scheme 4), (3) insertion of a second t BuNC unit into the remaining Pd−C bond (intermediate II; Scheme 4), and finally, (4) a second depalladation, rendering the double-amidinium salt. In order to obtain more information about the formation of intermediate I, we carried out the reaction between 3a and 6 equiv of tBuNC in refluxing CHCl3 in the presence of AgOTf. Under these conditions, derivative 8a was obtained (Scheme 3), which apparently resulted from the C−C reductive coupling of a cyano-palladium(II) complex that could have formed after the dealkylation of the coordinated t BuNC ligand in intermediate I (Scheme 4). There are numerous examples of t BuNC ligand dealkylation reactions, which happen to be relatively easy in cationic complexes.31,32 Moreover, we have found similar results in the decomposition of cationic alkenyl complexes of Pd(II) containing coordinated tBuNC.33 Decomposition of complex 7a was also studied under different conditions. In CDCl3 solution at room temperature or on heating to 60 °C, decomposition of 7a afforded Pd(0) and very complicated mixtures from which no components could be

isocyanide fragment, due to steric hindrance, also makes the two Me groups nonequivalent, as well as the meta and ortho positions of the inserted xylyl ring (1H NMR, Me 1.16 and 1.94 ppm; m-H 6.62 and 6.70 ppm; 13C NMR, Me 16.9 and 19.3 ppm, o-CH 124.9, 129.5 ppm, m-CH 127.2, 127.8 ppm). For complexes 4a-Xy and 5a, we propose that the coordinated isocyanides are located in positions cis to the aryl groups because this is the normal behavior for arylalkylamine palladacycles,13,22−25 and this is in agreement with the well-established transphobia between C-/C-donor ligands.26 When the iminoacyl complex 5a was treated with AgOTf (AgCF3SO3) and heated in CHCl3, the double-amidinium salt 6a-Xy was obtained (69% yield; Scheme 2), along with metallic palladium and AgCl. We had previously used a similar synthetic route to prepare 2-aminoisoindolinium, 3,4-dihydroisoquinolinium, hexahydro-3-benzo[d]azocinium, and 10-membered amidinium salts derived from 5-,23 6-,24,27 8-,13,25,28 and 10membered C,N-palladacycles.29 Reactions of Tetranuclear Complex 3a with tBuNC. The reaction of 3a and tBuNC in a 1/4 molar ratio (Pd/tBuNC 1/1) afforded a mixture of the coordination complex 4a-Bu, complex 7a, which contained two coordinated and one inserted t BuNC moiety, and traces of the starting tetranuclear palladacycle (Scheme 3). Complex 7a was independently prepared in excellent yield (89%) from the reaction of 3a with 6 Scheme 3. Reactions of 3a with tBuNC

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Organometallics Scheme 4. Decomposition of Complex 7a

Figure 3. X-ray thermal ellipsoid plot of IA (50% probability) along with the labeling scheme. The hydrogen atoms bonded to carbon have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Pd(1)−C(11) = 1.936(4), Pd(1)−C(12) = 2.060(4), Pd(1)−N(1) = 2.101(3), Pd(1)−Cl(1) = 2.4457(11), N(1′)−C(11′) = 1.291(6), N(2′)−C(11′) = 1.350(6), N(1′)−C(8′) = 1.456(6), N(2′)−C(17′) = 1.507(10); C(11)−Pd(1)−C(12) = 92.74(17), C(12)−Pd(1)− N(1) = 87.93(14), C(11)−Pd(1)−Cl(1) = 89.54(13), N(1)−Pd(1)− Cl(1) = 89.55(10), C(8′)−N(1′)−C(11′) = 128.8(4), N(1′)− C(11′)−C(12′) = 125.5(4), N(1′)−C(11′)−N(2′) = 119.2(4), C(12′)−C(11′)−N(2′) = 115.3(4), C(11′)−N(2)−C(17″) = 119.6(6).

identified. However, when complex 7a was treated with AgOTf and the resulting mixture was refluxed in CHCl3, after separation of the formed AgCl, an appreciable amount of compound 8a was formed (as determined by the 1H NMR spectrum of the mixture) along with other unidentified compounds. In an attempt to get single crystals of 7a, n-pentane was added dropwise into a solution of 7a in CH2Cl2 (or CHCl3), in a small vial. After slow solvent diffusion during a 48 h period, decomposition to Pd(0) was observed and a few brown crystals could be extracted from the vial.34 An X-ray diffraction study showed them to correspond to IA, the amidine derived from intermediate I (Scheme 4 and Figure 3). We have previously observed that decomposition of palladacycles containing one coordinated isocyanide can afford Pd(0) and the free amidine or the amidinium salt, depending on the reaction conditions and the acidic character of the NH groups.24 The crystal structure of complex IA showed a norbornadienyl moiety bridging an eight-membered palladacycle and a benzazocine ring. The palladium center is in a very distorted square planar environment (mean deviation of the plane Pd(1)−N(1)−C(11)−C(12)−Cl(1) 0.103 Å) and forms part of an eight-membered palladacycle that adopts a twist-boat− chair conformation. In the benzazocine ring, which presents a twist-boat conformation, the Nexocyclic−C (N(1′)−C(11′) = 1.291(6) Å) and Nendocyclic−C (C(11′)−N(2′) = 1.350(6) Å) bond lengths are quite different, although there must be some electronic delocalization because the (Me2)C−N−C−N− C(tBu) moiety is almost planar (mean deviation of the plane C(12′)−C(11′)−N(1′)−N(2′)−C(17″) 0.023 Å). The 1H NMR of these crystals supported the proposed structure, the most noticeable signals being those corresponding to the tBu groups (δ 1.47 and 0.86 ppm). The absence of resonances corresponding to the NH proton above 7.7 ppm

was also remarkable, because the double-amidinium salt 6a-Bu displayed in its 1H NMR spectrum one singlet at 8.38 ppm attributable to one of the two NH groups. Additionally, the crystal structure of the compound 6a-Bu (see the Supporting Information) has also been determined by X-ray diffraction studies, and it shows a fused eight-membered azacycle with a twist-boat conformation. The four groups at the tetrasubstituted norbornadienyl unit are in an exo disposition, as expected. Reaction of Tetranuclear Complex 3a with CO. Complex 3a reacts with CO at room temperature, in the presence of AgOTf and Na2CO3, to afford Pd(0) and the corresponding tetrahydrobenzazocinone 9a in good yield (80%; Scheme 5). The formation of this lactam can be explained according to the generally accepted mechanism for the insertion of CO into the Pd−C bond of palladacycles: that is, (1) coordination of CO to the metal center, (2) migratory Scheme 5. Reactions of 3a with CO

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Organometallics insertion of the organyl group to the coordinated CO, and (3) depalladation of the acyl complex through a C−N coupling.35 The AgOTf is used to remove the chloro ligand, generating a cationic palladacycle that facilitates the insertion process of CO into the Pd−C bond and the decomposition of the resulting complex.24,33 In the overall process, lactam 9a is synthesized from palladacycle A, through a sequential insertion of norbornadiene and CO into the Pd−C bond of two metallacycles. The organic derivative 9a has been characterized by IR and NMR spectroscopy and high-resolution mass spectrometry. The NMR data support the structures of the compound shown in Scheme 5. In solution, the molecule has Cs symmetry and only half of the molecule is observed in its NMR spectra. The most noticeable signals are (1) one singlet at 4.94 ppm in the 1 H NMR spectrum, corresponding to the NH proton, and (2) one singlet at 173.1 ppm in the 13C NMR spectrum, corresponding to the CO group. The 1H NMR spectra of complex 9a also showed the diastereotopic nature of the NH2 and CH2 protons and the CMe2 methyl groups. The crystal structure of compound 9a·CHCl3 was solved by X-ray diffraction studies (see the Supporting Information) and showed two fused eight-membered azacycles with a twist-boat (TB) conformation, bridged by a norbornadienyl unit. The four substituents at this norbornadienyl unit are in exo positions with respect to the methylene bridge of the bicyclic system. There are two independent molecules of 9a·CHCl3 in the asymmetric unit. The molecules are connected through hydrogen bonds, giving zigzag chains (see the Supporting Information). Synthesis and Structure of Eight-Membered Palladacycles Derived from N-Methylphenethylamine and Phenethylamine. The reaction of NBD with other sixmembered palladacycles was also carried out. When the orthometalated complex [Pd(C,N-C6H4CH2CH2NHMe-2)(μ-Cl)]2 (B) was treated with 1 equiv of norbornadiene (molar ratio Pd/ NBD 2/1) in acetone at room temperature for 6 h, the offwhite solid X precipitated out of the reaction medium. The 1H NMR (DMSO-d6) of this solid showed very broad signals that could not be assigned, although its reactivity indicated that the cyclometalated polymeric complex 3b should be present (Scheme 6). Addition of XyNC to a suspension of solid X in acetone afforded a red solution, which slowly evolved to a dark suspension, from which complex 5b could be isolated. Likewise, treatment of X in CH2Cl2 with AgOTf, Na2CO3, and CO rendered Pd(0) and the lactam 9b (Scheme 6), which was isolated pure in low yield (16%). The analysis of the 1H NMR spectra (CDCl3) of the crude reaction mixture arising from the reaction of palladacycle B, norbornadiene, AgOTf, and CO showed that 9b was the main component. No significant amounts of any other compounds containing the arylalkylamine were detected by 1H NMR. However, the presence of the corresponding cisoid isomer of lactam 9b in the crude cannot be discarded (the fraction of the crude product that was not soluble in CDCl3 was also insoluble in any other common organic solvents), although its isolation and characterization were not possible. In the 1H NMR spectra of 5b and 9b there was only one resonance for both the bridgehead methinic protons (5b, δ 3.22 ppm; 9b, δ 3.20 ppm), indicating that both compounds had C2 symmetry in solution: that is, both emerged from a complex in which the addition of the second palladium center to the norbornadiene occurred trans to the first (polymeric species

Scheme 6. Synthesis and Reactivity of Derivatives Containing Norbornadiene and N-Methylphenethylamine or Phenethylamine

3b; Scheme 6). The C2 symmetry of 5b was corroborated by its molecular structure in the solid state (Figure 4). The crystal structure of complex 5b (Figure 4) shows a dinuclear complex, with a norbornadienyl unit bridging two nine-membered palladacycles that adopt a mutually transoid disposition. Each palladium center is coordinated to a chloro

Figure 4. X-ray thermal ellipsoid plot of the compound 5b·Et2O (50% probability) along with the labeling scheme. The solvent molecule and the hydrogen atoms bonded to carbon have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Pd(1)−Cl(1) = 2.4287(5), Pd(1)−C(10) = 1.940(2), Pd(1)−C(11) = 2.007(2), Pd(1)−N(1) = 2.1179(18), Pd(1′)−Cl(1′) = 2.4129(5), Pd(1′)− C(10′) = 1.920(2), Pd(1′)−C(11′) = 2.0095(19), Pd(1′)−N(1′) = 2.0916(18); N(1)−Pd(1)−Cl(1) = 91.79(5), Cl(1)−Pd(1)−C(10) = 87.31(6), C(10)−Pd(1)−C(11) = 91.60(8), C(11)−Pd(1)−N(1) = 89.18(7), N(1′)−Pd(1′)−Cl(1′) = 90.61(5), Cl(1′)−Pd(1′)−C(10′) = 89.85(6), C(10′)−Pd(1′)−C(11′) = 90.64(8), C(11′)−Pd(1′)− N(1′) = 89.18(7). F


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Organometallics ligand, the NH2 group of the chelate amine, the terminal carbon of an isocyanide ligand, and the carbon atom of an inserted isocyanide, in a distorted square planar geometry (mean deviations from the planes: Pd(1)−Cl(1)−N(1)− C(10)−C(11), 0.037 Å; Pd(1′)−Cl(1′)−N(1′)−C(10′)− C(11′), 0.061 Å). Both palladium coordination planes form an angle of 76.2°. Again, the four substituents at carbons C(12), C(13), C(12′), and C(13′) are in exo positions with respect to the methylene bridge of the bicyclic system. The different dispositions of the bridged metallacycles (cisoid vs transoid) depending on the nature of the starting six-membered palladacycle moved us to try the phenethylamine derivative C (Scheme 6), which had no substituents either on the nitrogen or on the α-carbon atoms. When the orthometalated complex [Pd(C,N-C6H4CH2CH2NH2-2)(μ-Cl)]2 (C) was treated with 1 equiv of norbornadiene (molar ratio Pd/NBD 2/1) in CH2Cl2 at room temperature for 8 h, and the resulting mixture was heated at 50 °C under a CO atmosphere, the lactam 9c was obtained (isolated, 33%; Scheme 6), along with palladium(0) and some unidentified products. Similarly to what happened to 9b, the 1H NMR spectra of 9c exhibited only one resonance for both bridgehead methinic protons (δ 3.19 ppm), indicating that both palladium centers are in a transoid disposition. The generation of traces of the cisoid lactam 9c cannot be ruled out, although it could not be detected in the 1H NMR spectrum of the crude reaction mixture carried out in DMSO-d6. It was tempting to attribute the cisoid vs transoid disposition of both palladacycles to steric effects. However, the orthometalated ring with less steric hindrance (phenethylamine) afforded the same transoid form as the ortho-metalated ring containing a secondary amine (N-methylphenethylamine), which seems to be also the preferred geometry according to the other examples reported in the literature. We have no explanation for the unusual behavior of the phentermine, although the presence of two methyl substituents on the α-C atom may not be completely innocent, affecting slightly the ring conformation and influencing the capability of the chloro ligands to effectively establish the halogeno bridges in one or the other disposition.

C6H4(CH2CR2NHR′-2)(μ-Cl)]2 (R = Me, R′ = H, A; R = H, R′ = H, B; R = H, R′ = Me, C) were prepared as previously reported.19,36 All other reagents were obtained from commercial sources and used as received. Unless otherwise stated, NMR spectra were recorded in CDCl3 on Bruker Avance 300 and 400 spectrometers at 298 K. Chemical shifts are referenced to internal TMS. Signals in the 1H and 13C NMR spectra of all complexes were assigned with the help of APT, HMQC, and HMBC techniques. Inserted and coordinated XyNC (2,6dimethylphenyl isocyanide) are denoted XyNCi and XyNCc, respectively, and the 1,2-C6H4 arylene group is denoted Ar. Melting points were determined on a Reichert apparatus and are uncorrected. Conductivities were measured with a Crison Micro CM2200 conductimeter. Elemental analyses were carried out with a Carlo Erba 1106 microanalyzer. Infrared spectra were recorded in the range 4000−200 cm−1 on a PerkinElmer Spectrum 100 spectrophotometer, using Nujol mulls between polyethylene sheets. High-resolution ESI mass spectra were recorded on an Agilent 6220 Accurate-Mass TOF LC/MS instrument. Chart 2 gives the numbering schemes for the new palladacycles and the organic derivatives.

CONCLUSION In conclusion, we have studied the double-carbopalladation reactions of norbonadiene through the addition of two C−Pd bonds to the strained diene. The relative regiochemistry of this double carbopalladation proved sensitive to the substitution pattern of the C,N-chelated arylalkylamine. The Cnorbornyl−Pd group could be further functionalized by means of RNC insertion to give interesting norbornadienyl-linked expanded palladacycles, depending on the steric hindrance of the isocyanide substituent. Depalladation of the iminoacyl derivatives or the acyl analogues arising from CO insertion afforded fused heterocycles such as double-amidine or benzazocinone derivatives. Additionally, these stoichiometric reactions resemble the basic steps of some copolymerization processes and may serve as models for reactions where the norbornadiene scaffold is involved.

Synthesis of [Pd{C,N-CH(C5H6)CHC6H4(CH2CMe2NH2)-2}(μCl)]2 (1a). Norbornadiene (nor; 120 μL, 1.18 mmol) was added to a solution of palladacycle A19 (300 mg, 0.52 mmol) in CH2Cl2 (10 mL). The mixture was stirred for 1 h, and the resulting suspension was filtered. The solid was washed with CH2Cl2 (2 mL) and Et2O (10 mL) and air-dried to give complex 1a as a yellow solid. Yield: 276 mg, 0.361 mmol, 70%. Anal. Calcd for C34H44Cl2N2Pd2 (764.48): C, 53.42; H, 5.80; N, 3.66. Found: C, 53.41; H, 5.73; N, 3.88. Dec pt: 207 °C. IR (cm−1): ν(NH), 3212 w. Complex 1a was insoluble in CH2Cl2, CHCl3, acetone, and DMSO, which prevented us from measuring its NMR spectra. Synthesis of [Pd{C,N-CH(C5H6)CHC6H4(CH2CMe2NH2)-2}Cl(CNXy)] (2a). XyNC (55 mg, 0.419 mmol) was added to a suspension of 1a (150 mg, 0.198 mmol) in CH2Cl2 (10 mL). The mixture was stirred for 15 min, and the resulting solution was filtered through a plug of Celite. The filtrate was concentrated to ca. 1 mL, and Et2O (20 mL) was added. The suspension was filtered, and the solid was washed with Et2O (2 × 5 mL) and air-dried to give 2a as a yellow solid. Yield: 133 mg, 0.259 mmol, 65%. Anal. Calcd for C26H31ClN2Pd (513.411): C, 60.82; H, 6.09; N, 5.46. Found: C, 60.67; H, 6.19; N, 5.71. Dec pt: 164 °C. IR (cm−1): ν(NH), 3198 w; ν(CN), 2162 vs. 1H NMR (400.9 MHz): δ 7.34 (d, 1 H, H6, 3JHH = 7.6 Hz), 7.25 (td, 1 H, H5, 4 JHH = 2.0, 3JHH = 7.6 Hz), 7.21−7.15 (m, 3 H, H3 + H4 + p-H of Xy), 7.05 (d, 2 H, m-H, Xy, 3JHH = 8.0 Hz), 6.22 (dd, 1 H, CHC, 4JHH = 2.8, 3JHH = 5.6 Hz), 6.17 (dd, 1 H, CHC, 4JHH = 3.2, 3JHH = 5.6 Hz),

Chart 2. Numbering Schemes for the New Palladium(II) Complexes and the Organic Derivatives

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EXPERIMENTAL SECTION

General Considerations, Materials, and Instrumentation. Unless otherwise noted, all preparations were carried out at room temperature under atmospheric conditions. Synthesis-grade solvents were obtained from commercial sources. The palladacycles [Pd(C,NG


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Organometallics

mL) was added. The suspension was filtered, and the solid was washed with Et2O (3 × 3 mL) and vacuum-dried to give 4a-Bu·1.5H2O as a beige solid. Yield: 39 mg, 0.045 mmol, 19%. Anal. Calcd for C37H54Cl2N4Pd2·1.5H2O (865.63): C, 51.34; H, 6.64; N, 6.47. Found: C, 51.17; H, 6.59; N, 6.32. Dec pt: > 180 °C. IR (cm−1): ν(OH), 3620 w; ν(NH), 3400 br, 3279 w, 3196 w; ν(CN), 2193 s. 1 H NMR (400.9 MHz): δ 7.47 (br d, 1 H, H6, 3JHH = 7.6 Hz), 7.24 (m, 1 H, H5), 7.17 (m, 2 H, H3 + H4), 3.15−2.92 (m, 4.5 H, 2 H of NH2 + Hα + 0.5 of CH-nor + 1 H of CH2Ar), 2.93 (br d, 1 H, Hβ, 3JHH = 8.4 Hz), 2.58 (br d, 1 H, CH2Ar, 2JHH = 14.4 Hz), 2.48−2.46 (m, 1.5 H, 0.5 H of CH-nor + 1 H of CH2-nor), 1.64 (s, 3 H, CMe2), 1.60 (s, 1.5 H, H2O), 1.54 (s, 3 H, CMe2), 1.46 (s, 9 H, tBu). Because of the symmetry of 4a-Bu in solution, its 1H NMR spectrum only shows the signals corresponding to half of the molecule. 13C{1H} NMR (100.8 MHz): δ 146.5 (s, C1), 135.5 (s, C2), 133.0 (s, CH, C3), 126.5 (s, CH, C5), 125.0 (s, C4), 123.5 (s, C6), 58.8 (s, CH, nor), 57.5 (s, CMe3), 56.3 (s, CMe2), 53.3 (s, CHα), 51.4 (s, CHβ), 47.6 (s, CH, nor) 43.9 (s, CH2Ar), 36.1 (s, Me, CMe2), 35.1 (s, CH2, nor), 30.3 (s, Me, tBu), 28.8 (s, Me, CMe2). The 13C resonance corresponding to the CN group was not observed. Synthesis of 5a. Method A. XyNC (117 mg, 0.89 mmol) was added to a solution of 3a·4H2O (149 mg, 0.105 mmol) in CH2Cl2 (12 mL). The mixture was stirred for 1 h and filtered through a plug of Celite. The filtrate was concentrated to ca. 3 mL, and Et2O (30 mL) was added. The suspension was filtered, and the solid was washed with Et2O (3 × 3 mL) and vacuum-dried to give 5a as a yellow solid. Yield: 176 mg, 0.15 mmol, 71%. Method B. XyNC (22 mg, 0.168 mmol) was added to a suspension of complex 4a-Xy·H2O (73 mg, 0.077 mmol) in CH2Cl2 (20 mL), and the mixture was stirred for 1 h. The yellow filtrate was concentrated to ca. 3 mL, and Et2O (30 mL) was added. The resulting suspension was filtered, and the solid was washed with Et2O (3 × 3 mL) and vacuumdried to give 5a as a pale yellow solid. Yield: 74 mg, 0.062 mmol, 80%. Anal. Calcd for C63H72Cl2N6Pd2 (1197.05): C, 63.21; H, 6.06; N, 7.02. Found: C, 63.18; H, 5.87; N, 6.88. Dec pt: 206 °C. IR (cm−1): ν(NH), 3243 m, 3205 w; ν(CN), 2168 vs; ν(CN), 1689 m, 1674 m, 1636 m. 1H NMR (400.9 MHz, DMSO-d6): δ 7.51 (br d, 1 H, H6, 3JHH = 8.0 Hz), 7.29 (br d, 1 H, H3, 3JHH = 7.2 Hz), 7.20−7.09 (m, 3 H, H4 + H5 + p-H, XyNCc), 7.05 (br d, 2 H, m-H, XyNCc, 3JHH = 7.6 Hz), 6.70 (m, 2 H, m-H, XyNCi), 6.62 (m, 1 H, p-H, XyNCi), 4.39 (d, 1 H, Hβ, 3 JHH = 9.2 Hz), 3.87 (m, 1 H, NH2), 3.82 (d, 1 H, Hα, 3JHH = 9.6 Hz), 3.56 (br s, 0.5 H, CH, nor), 3.44 (d, 1 H, CH2Ar, 2JHH = 14.0 Hz), 2.92 (br s, 1 H, CH2, nor), 2.74 (d, 1 H, CH2Ar, 2JHH = 14.4 Hz), 2.59 (br s, 0.5 H, CH, nor), 2.11 (s, 6 H, Me, XyNCc), 1.94 (s, 3 H, Me, XyNCi), 1.68 (s, 3 H, Me, CMe2), 1.49 (s, 3 H, Me, CMe2), 1.16 (s, 3 H, Me, XyNCi). Because of the symmetry of the complex in solution, its 1H NMR spectrum only shows the signals corresponding to half of the molecule. 13C{1H} NMR (75.4 MHz, DMSO-d6): δ 149.1 (s, i-C, XyNCi), 143.3 (s, C1), 135.4 (s, C2), 134.5 (s, o-C, XyNCc), 131.0 (s, CH, C3), 129.5 (s, CH, C4), 128.1 (s, CH, C6), 127.8 (s, m-CH, XyNCi+c), 127.2 (s, m-CH, XyNCi), 126.6 (s, CH, C5), 125.9 (s, o-C, XyNCi), 125.6 (s, i-C, XyNCc), 125.4 (s, p-CH, XyNCc), 124.9 (s, o-C, XyNCi), 122.1 (s, p-CH, XyNCi), 63.0 (s, CHβ), 55.3 (s, CMe2), 51.1 (s, CH, nor), 51.0 (s, CHα), 49.4 (s, CH, nor), 43.0 (s, CH2Ar), 37.4 (s, CH2, nor), 35.7 (s, Me, CMe2), 29.8 (s, Me, CMe2), 19.3 (s, Me, XyNCi), 18.2 (s, Me, XyNCc), 16.9 (s, Me, XyNCi). The 13C resonances corresponding to the CN and CN groups were not observed. Synthesis of 5b. Norbornadiene (36.8 μL, 0.36 mmol) was added to a solution of palladacycle B (200 mg, 0.36 mmol) in acetone (30 mL), and the mixture was stirred for 6 h. Then, XyNC (191 mg, 1.46 mmol) and acetone (5 mL) were added. The new mixture was stirred for 17 h and filtered. The filtrate was concentrated to ca. 5 mL, and Et2O (20 mL) was slowly added. The suspension was filtered, and the solid was washed with Et2O (3 × 3 mL) and vacuum-dried to give crude 5b. Crude 5b was recrystallized twice from acetone/Et2O (1/1) to give analytically pure 5b as a beige solid. Yield: 59 mg, 0.05 mmol, 14%. Anal. Calcd for C61H68Cl2N6Pd2 (1169.00): C, 62.68; H, 5.86; N, 7.19. Found: C, 62.53; H, 5.93; N, 7.31. Dec pt: 230 °C. IR (cm−1): ν(NH), 3289 w; ν(CN), 2177 vs; ν(CN), 1628 s. 1H NMR

3.36 (br d, 1 H, NH2, 2JHH = 10.8 Hz), 3.17 (br s, 1 H, CH, nor), 3.09 (br s, 1 H, CH, nor), 2.86 (d, 1 H, CH2Ar, 2JHH = 14.4 Hz), 2.73 (d, 1 H, Hβ, 3JHH = 8.4 Hz), 2.63 (dd, 1 H, CH2Ar, 4JHH = 1.6, 2JHH = 14.4 Hz), 2.37 (m, partially obscured by the resonance of Me, 2 H, Hα + 1 H of CH2−nor), 2.35 (s, 6 H, Me, Xy), 1.92 (br d, 1 H, NH2, 2JHH = 10.8 Hz), 1.70 (br d, 1 H, CH2, nor, 2JHH = 8.0 Hz), 1.49 (s, 3 H, CMe2), 1.46 (s, 3 H, CMe2). 13C{1H} NMR (100.8 MHz): δ 145.9 (s, C1), 138.0 (s, CHC), 137.3 (s, CHC), 135.6 (s, C2), 135.4 (s, oC, Xy), 132.4 (s, CH, C3), 129.1 (s, p-CH, Xy), 127.8 (s, m-CH, Xy), 127.1 (s, CH, C5), 125.0 (s, CH, C4), 124.3 (s, CH, C6), 55.4 (s, CMe2), 52.7 (s, CH, nor), 49.0 (s, CHα), 47.2 (s, CH, nor), 46.9 (s, CH2, nor), 44.1 (s, CH2Ar), 43.1 (s, CHβ), 36.2 (s, Me, CMe2), 28.1 (s, Me, CMe2), 18.8 (s, Me, Xy). The 13C resonances corresponding to CN and i-C of XyNC were not observed. Single crystals of 2a·0.5CH2Cl2 suitable for an X-ray diffraction study were obtained by slow diffusion of n-pentane into a solution of 2a in CH2Cl2. Synthesis of 3a·4H2O. Method A. Norbornadiene (56 μL, 0.551 mmol) was added to a solution of palladacycle A (320 mg, 0.551 mmol) in CH2Cl2 (15 mL). The mixture was stirred for 4 h and then filtered through a plug of Celite. The orange filtrate was concentrated to ca. 1 mL, and Et2O (20 mL) was added. The suspension was filtered, and the solid was washed with Et2O (2 × 2 mL) and vacuumdried to give the complex 3a·4H2O as a pale orange solid. Yield: 333 mg, 0.235 mmol, 85%. Method B. Palladacycle A (84 mg, 0.145 mmol) was added to a suspension of complex 1a (110 mg, 0.144 mmol) in CH2Cl2 (15 mL), and the mixture was stirred for 24 h. The resulting clear orange solution was filtered through a plug of Celite. The filtrate was concentrated to ca. 1 mL, and Et2O (20 mL) was added. The resulting suspension was filtered, and the solid was washed with Et2O (2 × 2 mL) and air-dried to give 3a·4H2O as a pale orange solid. Yield: 166 mg, 0.117 mmol, 81%. Anal. Calcd for C54H72Cl4N4Pd4·4H2O (1416.729): C, 45.78; H, 5.69; N, 3.95. Found: C, 45.65; H, 5.38; N, 3.84. Dec pt: 180 °C. IR (cm−1): ν(NH), 3494 br, 3294 w, 3230 w. 1 H NMR (400.9 MHz): δ 7.48 (br d, 1 H, H6, 3JHH = 7.6 Hz), 7.22 (td, 1 H, H5, 4JHH = 1.2, 3JHH = 7.2 Hz), 7.08 (br t, 1 H, H4, 3JHH = 7.2 Hz), 7.02 (dd, 1 H, H3, 4JHH = 0.8, 3JHH = 7.2 Hz), 3.18 (br s, 1 H, NH2), 2.69 (br s, 1 H, both CH of nor), 2.67 (d, one peak of the doublet was overlapped with the signal of CH-nor, 1 H, CH2Ar), 2.57 (d, 1 H, CH2Ar, 2JHH = 14.0 Hz), 2.49 (d, one peak of the doublet was overlapped with the signal of the CH2-nor, 1 H, Hβ, 3JHH = 8.4 Hz), 2.46 (s, 1 H, CH2, nor), 2.27 (d, 1 H, Hα, 3JHH = 8.8 Hz), 1.83 (br d, 1 H, NH2, 2JHH = 10.8 Hz), 1.59 (s, 2 H, H2O), 1.45 (s, 3 H, Me), 1.24 (s, 3 H, Me). Because of the symmetry of 3a in solution, its 1H NMR spectrum only shows the signals corresponding to one-fourth of the molecule. 13C{1H} NMR (100.8 MHz): δ 143.9 (s, C1), 134.5 (s, C2), 132.1 (s, CH, C3), 127.3 (s, CH, C5), 125.2 (s, CH, C6), 124.7 (s, CH, C4), 57.4 (s, CH, nor), 55.0 (s, CMe2), 51.8 (s, CHβ), 47.5 (s, CH, nor), 47.4 (s, CHα), 44.1 (s, CH2Ar), 36.8 (s, CH2, nor), 36.0 (s, Me), 27.8 (s, Me). Single crystals of 3a·CH3COCH3 suitable for an X-ray diffraction study were obtained by slow diffusion of Et2O into a solution of 3a· 4H2O in acetone. Synthesis of 4a-Xy·H2O. XyNC (67.9 mg, 0.52 mmol) was added to a solution of 3a·4H2O (174 mg, 0.123 mmol) in CH2Cl2 (20 mL). The mixture was stirred for 1 min and filtered through a plug of Celite. The filtrate was stirred for 2 h and the solvent partially removed to ca. 10 mL. The suspension was filtered, and the solid was washed with CH2Cl2 (3 × 3 mL) and vacuum-dried to give the complex 4a-Xy·H2O as a colorless solid. Yield: 89 mg, 0.093 mmol, 38%. Anal. Calcd for C45H54Cl2N4Pd2·H2O (952.71): C, 56.73; H, 5.92; N, 5.88. Found: C, 56.91; H, 5.89; N, 6.00. Dec pt: 207−211 °C. IR (cm−1): ν(OH), 3633 w; ν(NH), 3424 br, 3203 w; ν(CN), 2167 s. Complex 4a-Xy· H2O was insoluble in CH2Cl2, CHCl3, acetone, and DMSO, which prevented us from measuring its NMR spectra. Synthesis of 4a-Bu·1.5H2O. tBuNC (56 μL, 0.496 mmol) was added to a solution of 3a·4H2O (167 mg, 0.118 mmol) in CH2Cl2 (20 mL) at 0 °C. The mixture was stirred for 15 min and filtered through a plug of Celite. The filtrate was concentrated to ca. 2 mL, and Et2O (20 H


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Organometallics (400.9 MHz): δ 7.60 (m, 1 H, H6), 7.25 (m, 3 H, H3 + H4 + H5), 7.15 (t, 1 H, p-H, XyNCc, 3JHH = 7.6 Hz), 6.99 (d, 1 H, m-H, XyNCi, 3 JHH = 7.2 Hz), 6.93 (d, 2 H, m-H, XyNCc, 3JHH = 7.6 Hz), 6.81 (t, 1 H, p-H, XyNCi, 3JHH = 7.6 Hz), 6.73 (d, 1 H, m-H, XyNCi, 3JHH = 7.2 Hz), 4.54 (d, 1 H, Hβ, 3JHH = 10.0 Hz), 3.96 (m, 1 H, CH2Ar), 3.79 (m, 1 H, CH2N), 3.66 (d, 1 H, Hα, 3JHH = 10.0 Hz), 3.22 (s, 1 H, CH, nor), 2.87 (br s, 1 H, CH2, nor), 2.74 (m, 2 H, 1 H of CH2Ar + 1 H of CH2N), 2.31 (s, 3 H, Me, XyNCi), 2.10 (s, 6 H, Me, XyNCc), 2.01 (s, 3 H, Me, NMe), 0.87 (s, 3 H, Me, XyNCi). Because of the symmetry of the complex in solution, its 1H NMR spectrum only shows the signals corresponding to half of the molecule. 13C{1H} NMR (75.4 MHz): δ 188.0 (s, CN), 147.5 (s, i-C, XyNCi), 142.5 (s, C1), 136.3 (s, C2), 135.8 (s, o-C, XyNCc), 129.6 (s, p-CH, XyNCc), 129.3 (s, mCH, XyNCi), 128.4 (s, CH, C6), 127.9 (s, m-CH, XyNCc), 127.7 (s, C3 + C5 + m-CH of XyNCi), 127.4 (s, CH, C4), 126.5 (s, o-C, XyNCi), 125.8 (s, i-C, XyNCc), 123.2 (s, p-CH, XyNCi), 70.1 (s, CHβ), 55.5 (s, CH2N), 51.9 (s, CHα), 49.4 (s, CH, nor), 40.2 (s, Me, NMe), 37.9 (s, CH2, nor), 30.6 (s, CH2Ar), 20.1 (s, Me, XyNCi), 18.4 (s, Me, XyNCc), 16.0 (s, Me, XyNCi). The 13C resonance corresponding to CN was not observed. Single crystals of 5b·Et2O suitable for an X-ray diffraction study were obtained by slow diffusion of Et2O into a solution of 5b in CHCl3. Synthesis of 6a-Xy. AgOTf (58 mg, 0.226 mmol) was added to a suspension of 5a (133 mg, 0.111 mmol) in acetone (20 mL). The mixture was stirred for 1 h and filtered through a plug of Celite. The solvent was removed from the filtrate, CHCl3 (20 mL) was added to the residue, and the mixture was stirred at 60 °C for 24 h and then cooled to room temperature. The black suspension was filtered through a plug of anhydrous MgSO4, and the solvent was removed from the filtrate. The residue was purified by flash chromatography on silica gel, using acetone as eluent. The acetone solution was collected, and the solvent was removed to give an orange residue. CHCl3 (40 mL) and active carbon (35 mg) were added, and the mixture was stirred for 30 min and filtered through a plug of MgSO4. The filtrate was concentrated to ca. 3 mL, and n-pentane (50 mL) was added. The suspension was filtered, and the solid was washed with n-pentane (3 × 3 mL) and vacuum-dried to give 6a-Xy as a pale yellow solid. Yield: 47 mg, 0.05 mmol, 45%. Anal. Calcd for C47H54F6N4O6S2 (949.09): C, 59.48; H, 5.73; N, 5.90. Found: C, 59.31; H, 5.90; N, 6.14. Mp: 230 °C. ΛM (Ω−1 cm2 mol−1): 129 (5.82 × 10−4 M in acetone). IR (cm−1): ν(NH), 3331 m, 3222 br; ν (CN), 1615 s. ESI-HRMS: exact mass calcd for C45H53N4, 649.4265 [(M − H)+]; found, 649.4251. 1H NMR (400.9 MHz): δ 9.65 (br s, 1 H, NH), 7.57 (br d, 1 H, H7, 3JHH = 7.6 Hz), 7.37 (br t, 1 H, H8, 3JHH = 7.2 Hz), 7.30 (br t, overlapped with the resonance of the CHCl3 present in the CDCl3, 1 H, H9, 3JHH = 7.2 Hz), 7.21−7.13 (m, 3 H, H10 + m-H and p-H of Xy), 6.97 (br d, 1 H, m-H, Xy, 3JHH = 7.2 Hz), 5.26 (br s, 1 H, NH), 4.61 (d, 1 H, H6, 3JHH = 10.4 Hz), 4.45 (d, 1 H, H5, 3JHH = 10.4 Hz), 4.10 (d, 1 H, CH2Ar, 2 JHH = 14.8 Hz), 3.74 (br s, 0.5 H, CH, nor), 3.65 (br s, 0.5 H, CH, nor), 2.75 (d, partially obscured by the resonance of CH2-nor, 1 H, CH2Ar, 2JHH = 15.2 Hz), 2.73 (br s, partially obscured by the resonance of CH2Ar, 1 H, CH2, nor), 2.19 (s, 3 H, Me, Xy), 1.85 (s, 3 H, Me, CMe2), 1.20 (s, 3 H, Me, Xy), 1.19 (s, 3 H, Me, CMe2). Because of the symmetry of 6a-Xy in solution, its 1H NMR spectrum only shows the signals corresponding to half of the molecule. 13C{1H} NMR (75.4 MHz): δ 166.2 (s, CN), 138.0 (s, C6a), 136.6 (s, C10a), 135.6 (s, o-C, Xy), 135.4 (s, o-C, Xy), 130.6 (s, CH, C10 or pH of Xy), 130.5 (s, CH, C10 or p-H of Xy), 129.7 (s, m-CH, Xy), 129.6 (s, m-CH, Xy), 128.5 (s, i-C, Xy), 128.0 (s, CH, C8), 127.7 (s, CH, C9), 125.1 (s, CH, C7), 58.0 (s, CMe2), 51.1 (s, CH, C5), 47.6 (s, CH, C6), 44.1 (s, CH, nor), 42.2 (s, CH, nor), 41.8 (s, CH2Ar), 40.1 (s, CH2, nor), 31.1 (s, Me, CMe2), 28.8 (s, Me, CMe2), 17.4 (s, Me, Xy), 16.2 (s, Me, Xy). Synthesis of 6a-Bu·2H2O. tBuNC (139.1 μL, 1.231 mmol) was added to a solution of 3a·4H2O (207 mg, 0.146 mmol) in CHCl3 (35 mL). The mixture was stirred at 65 °C for 24 h and filtered through a plug of Celite. The solvent was removed from the filtrate, and the residue was purified by column chromatography on silica gel, using an acetone/CH2Cl2 mixture as eluent to remove the impurities and then a

5/1 CH2Cl2/MeOH mixture as eluent (Rf = 0.4). The compound 6aBu·2H2O was isolated as a colorless solid after evaporation of the solvents. Yield: 77 mg, 0.116 mmol, 40%. Anal. Calcd for C37H54Cl2N4·2H2O (661.80): C, 67.15; H, 8.83; N, 8.47. Found: C, 67.31; H, 8.66; N, 8.38. Dec pt: 278−280 °C. ΛM (Ω−1 cm2 mol−1): 47 (5.41 × 10−4 M in acetone). IR (cm−1): ν(NH), 3250 br; ν(CN), 1616 s. ESI-HRMS: exact mass calcd for C37H53N4, 553.4265 [(M − H)+]; found, 553.4271. 1H NMR (400.9 MHz): δ 8.38 (br s, 1 H, NH), 7.35 (br d, 1 H, H7, 3JHH = 7.6 Hz), 7.26 (td, 1 H, H8, 4JHH = 1.2, 3JHH = 7.6 Hz), 7.19 (td, 1 H, H9, 4JHH = 1.2, 3JHH = 7.2 Hz), 7.14 (dd, 1 H, H10, 4JHH = 1.2, 3JHH = 7.2 Hz), 5.40 (br s, 1 H, NH), 4.93 (d, 1 H, H6, 3JHH = 10.0 Hz), 4.75 (br s, 0.5 H, CH, nor), 4.58 (d, 1 H, CH2Ar, 2JHH = 14.8 Hz), 4.36 (d, 1 H, H5, 3JHH = 10.0 Hz), 3.26 (br s, 0.5 H, CH, nor), 2.67 (d, 1 H, CH2Ar, 2JHH = 14.4 Hz), 2.36 (br s, 1 H, CH2, nor), 2.04 (s, 3 H, Me, CMe2), 1.92 (br s, 2 H, H2O), 1.49 (s, 3 H, Me, CMe2), 1.14 (s, 9 H, Me, tBu). Because of the symmetry of 6a-Bu in solution, its 1H NMR spectrum only shows the signals corresponding to half of the molecule. 13C{1H} NMR (100.8 MHz): δ 166.0 (CN), 139.2 (s, C6a), 137.3 (s, C10a), 130.0 (s, CH, C10), 127.2 (s, CH, C8), 126.9 (s, CH, C9), 124.6 (s, CH, C7), 58.7 (s, CMe2), 54.5 (s, CMe3), 51.2 (s, CH, C6), 47.9 (s, CH, C5), 44.0 (s, CH, nor), 41.73 (s, CH2Ar), 41.67 (s, CH, nor), 40.4 (s, CH2, nor), 32.0 (s, Me, CMe2), 29.5 (s, Me, CMe2), 28.5 (s, Me, tBu). Single crystals of 6a-Bu·CHCl3·3H2O suitable for an X-ray diffraction study were obtained by slow diffusion of Et2O into a solution of 6a-Bu·2H2O in CHCl3. Synthesis of 7a·2H2O. tBuNC (96 μL, 0.847 mmol) was added dropwise to a stirred solution of complex 3a·4H2O (200 mg, 0.141 mmol) in CH2Cl2 (15 mL) at 0 °C, and the mixture was further stirred for 1 h at 0 °C. The pale yellow solution was concentrated to ca. 2 mL, and Et2O (15 mL) was added. The resulting suspension was filtered, and the solid was washed with Et2O (2 × 5 mL) and air-dried to give a first crop of the complex 7a·2H2O as a pale yellow solid (195 mg, 0.203 mmol). The filtrate was concentrated to ca. 3 mL, and n-pentane (15 mL) was added. The suspension was filtered, and the solid was washed with n-pentane (2 × 5 mL) and air-dried to give a second crop of the complex 7a·2H2O as a pale yellow solid (45 mg, 0.047 mmol). Yield: 240 mg, 0.251 mmol, 89%. Anal. Calcd for C42H63Cl2N5Pd2· 2H2O (957.760): C, 52.67; H, 7.05; N, 7.31. Found: C, 52.85; H, 7.08; N, 7.42. Dec pt: 161 °C. IR (cm−1): ν(OH), 3436 br m; ν(NH), 3312 w, 3202 w; ν(CN), 2193 s; ν(CN), 1656 m. 1H NMR (400.9 MHz): δ 7.47−7.41 (m, 2 H, C6H4), 7.29−7.7 (m, 6 H, C6H4), 4.11 (d, 1 H, CH, nor, 3JHH = 9.2 Hz) 3.40−3.32 (m, 3 H, 1 H of NH2 + 1 H of CH2Ar + 1 H of CH-nor), 3.17 (d, 1 H, CH2, nor, 2JHH = 8.8 Hz), 2.98−2.91 (m, 3 H, 1 H of NH2 + 1 H of CH2Ar + 1 H of CHnor), 2.82 (s, 1 H, CH, nor), 2.70−2.57 (m, 3 H, 1 H of NH2 + 1 H of CH2Ar + 1 H of CH2Ar), 2.38 (s, 1 H, CH, nor), 2.27 (d, 1 H, CH2, nor, 2JHH = 9.2 Hz), 1.95 (d, 1 H, NH2, 2JHH = 10.8 Hz), 1.90 (s, 3 H, Me, CMe2), 1.84 (d, 1 H, NH2, 2JHH = 10.4 Hz), 1.76 (s, 4 H, H2O), 1.62 (s, 3 H, CMe2), 1.58 (s, 9 H, Me, tBu), 1.57 (s, 3 H, Me, CMe2), 1.45 (s, 9 H, Me, tBu), 1.41 (s, 3 H, Me, CMe2), 1.07 (s, 9 H, Me, t Bu). 13C{1H} NMR (100.8 MHz): δ 169.6 (s, CN), 146.2 (s, C, C6H4), 144.0 (s, C, C6H4), 134.8 (s, C, C6H4), 133.5 (s, C, C6H4), 132.7 (s, CH, C6H4), 128.8 (s, CH, C6H4), 127.6 (s, CH, C6H4), 126.8 (s, CH, C6H4), 126.3 (s, CH, C6H4), 125.3 (s, CH, C6H4), 125.2 (s, CH, C6H4), 123.9 (s, CH, C6H4), 65.4 (s, CH, nor), 57.7 (s, CMe2), 55.5 (s, CMe3), 55.0 (s, CH, nor), 54.9 (s, CMe2), 52.3 (s, CH, nor), 52.2 (s, CH, nor), 51.5 (s, CH, nor), 46.5 (s, CH, nor), 44.2 (s, CH2Ar), 42.1 (s, CH2Ar), 36.4 (s, Me, CMe2), 35.7 (s, Me, CMe2), 34.6 (s, CH2, nor), 33.4 (s, Me, CMe2), 31.1 (s, Me, tBu), 30.5 (s, Me, t Bu), 29.9 (s, Me, tBu), 28.0 (s, Me, CMe2). The 13C resonances corresponding to the CN of coordinated tBuNC groups and to the CMe3 of two tBu groups were not observed. Synthesis of 8a. tBuNC (111 mg, 1.250 mmol) was added to a suspension of 3a·4H2O (208.3 mg, 0.147 mmol) in acetone (20 mL), and the resulting yellow solution was stirred for 5 min. AgOTf (159.2 mg, 0.620 mmol) was added, the mixture was stirred for 30 min, and the solvent was removed. CHCl3 (30 mL) was added to the black residue, and the mixture was refluxed for 24 h. The solvent was removed, the residue was extracted with acetone (7 × 5 mL), and the I


Article

Organometallics

mixture was heated at 50 °C under a CO atmosphere (1 bar) for 24 h. Formation of metallic palladium was observed. The resulting black suspension was filtered through a plug of Celite, and the solvent was removed from the filtrate. The residue was chromatographed on silica gel, using an 8/1 EtOAc/MeOH mixture as eluent (Rf = 0.7−0.8). The compound 9b was isolated as a pale yellow solid after evaporation of the solvents and recrystallization from CH2Cl2 (1 mL)/Et2O (20 mL). Yield: 27 mg, 0.065 mmol, 16%. Dec pt: > 180 °C. IR (cm−1): ν(CO) 1634 s. ESI-HRMS: exact mass calcd for C27H31N2O2, 415.2380 [(M + H)+]; found, 415.2388. 1H NMR (400.9 MHz): δ 7.51 (br d, 1 H, H7, 3 JHH = 7.6 Hz), 7.24 (td, partially obscured by the resonance of the CHCl3 present in the CDCl3, 1 H, H8, 4JHH = 1.2, 3JHH = 7.6 Hz), 7.13 (td, 1 H, H9, 4JHH = 1.2, 3JHH = 7.6 Hz,), 7.08 (td, 1 H, H10, 4JHH = 1.2, 3JHH = 7.6 Hz), 4.25 (ddd, 1 H, CH2N, 3JHH = 6.8, 3JHH = 10.0, 2 JHH = 15.6 Hz), 3.37−3.24 (m, 4 H, H5 + H6 + 1 H of CH2N + 1 H of CH2Ar), 3.20 (br s, 1 H, CH, nor), 3.08−2.99 (m, 1 H, CH2Ar), 2.53 (s, 3 H, Me), 2.37 (s, 1 H, CH2, nor). Because of the symmetry of 9b in solution, its 1H NMR spectrum only shows the signals corresponding to half of the molecule. 13C{1H} NMR (100.8 MHz): δ 173.0 (s, CO), 139.6 (s, C6a), 135.8 (s, C10a), 130.8 (s, CH, C10), 127.5 (s, CH, C8), 126.69 (s, CH, C9), 126.66 (s, CH, C7), 53.1 (s, CH, C5), 49.0 (s, CH, C6), 46.2 (s, CH2N), 42.8 (s, CH, nor), 36.1 (s, CH2, nor), 34.7 (s, Me), 32.8 (s, CH2Ar). Synthesis of 9c. Norbornadiene (32.2 μL, 0.317 mmol) was added to a suspension of palladacycle C (166 mg, 0.317 mmol) in CH2Cl2 (40 mL), and the mixture was stirred for 8 h in a Carius tube. Na2CO3 (67 mg, 0.632 mmol) was added, and the resulting mixture was heated at 50 °C under a CO atmosphere (1 bar) for 17 h. Formation of metallic palladium was observed. The resulting black suspension was filtered through a plug of Celite, and the solvent was removed from the filtrate. Acetone (5 mL) and n-pentane (30 mL) were added to the yellow residue, and the mixture was stirred for 10 min. The suspension was filtered, and the solid was washed with n-pentane (3 × 5 mL) and vacuum-dried to give crude 9c as a pale yellow solid. Yield: 41 mg, 0.106 mmol, 33%. Crude 9c was recrystallized from CH2Cl2/npentane to give pure an analytically pure sample of 9c as a pale yellow solid (27 mg, 0.070 mmol; recrystallization yield 66%). Dec pt: >245 °C. IR (cm−1): ν(NH) 3241 w, 3217 w, 3141 w; ν(CO) 1656 s. ESIHRMS: exact mass calcd for C25H27N2O2, 387.2067 [(M + H)+]; found, 387.2061. 1H NMR (400.9 MHz): δ 7.47 (br d, 1 H, H7, 3JHH = 7.6 Hz), 7.24 (br t, partially obscured by the resonance of the CHCl3 present in the CDCl3, 1 H, H8, 3JHH = 7.6 Hz), 7.17 (br t, 1 H, H9, 4 JHH = 1.2, 3JHH = 7.6 Hz), 7.06 (br d, 1 H, H10, 3JHH = 7.2 Hz), 5.26 (m, 1 H, NH), 3.82−3.74 (m, 1 H, CH2N), 3.48−3.04 (m, 4 H, H5 + H6 + 1 H of CH2N + 1 H of CH2Ar), 3.19 (br s, 1 H, CH, nor), 2.95− 2.88 (m, 1 H, CH2Ar), 2.36 (s, 1 H, CH2, nor). Because of the symmetry of 9c in solution, its 1H NMR spectrum only shows the signals corresponding to half of the molecule. 13C{1H} NMR (100.8 MHz): δ 174.9 (s, CO), 139.8 (s, C6a), 136.2 (s, C10a), 130.1 (s, CH, C10), 127.4 (s, CH, C8), 126.9 (s, CH, C9), 125.8 (s, CH, C7), 52.6 (s, CH, C5), 48.6 (s, CH, C6), 42.7 (s, CH, nor), 38.9 (s, CH2N), 36.2 (s, CH2, nor), 32.5 (s, CH2Ar). Single-Crystal X-ray Structure Determinations. Relevant crystallographic data, details of the refinements, a complete set of Cartesian coordinates and details (including symmetry operators) of hydrogen bonds, and CIF files for compounds 2a·0.5CH2Cl2, 3a· CH3COCH3, 5b·Et2O, 6a-Bu·CHCl3·3H2O, IA, and 9a·CHCl3 (CCDC 1510226−15110231) are given in the Supporting Information. Data Collection. Crystals suitable for X-ray diffraction were mounted in inert oil on a glass fiber and transferred to a Bruker SMART (2a·0.5CH2Cl2, 9a·CHCl3) or a Bruker D8 QUEST diffractometer (3a·CH3COCH3, 5b·Et2O, 6a-Bu·CHCl3·3H2O, IA). Data were recorded at 100(2) K, using graphite-monochromated Mo Kα radiation (λ = 0.71073 Å) and ω-scan (2a·0.5CH2Cl2, 5b·Et2O, 9a· CHCl3) or ω- and ϕ-scan (3a·CH3COCH3, 6a-Bu·CHCl3·3H2O, IA) mode. Multiscan absorption corrections were applied for all complexes. Structure Solution and Refinements. Crystal structures were solved by direct methods, and all non-hydrogen atoms were refined

combined extracts were filtered through a plug of Celite. The filtrate was concentrated to ca. 4 mL, and Et2O (20 mL) was added. The suspension was filtered, and the solid was washed with Et2O (3 × 3 mL) and vacuum-dried to give 8a as a pale gray solid. Yield: 114 mg, 0.143 mmol, 49%. Anal. Calcd for C35H46N4F6S2O6 (796.90): C, 52.75; H, 5.82; N, 7.03; S, 8.05. Found: C, 52.56; H, 5.77; N, 7.06; S, 7.86. Mp: 270 °C (dec). ΛM (Ω−1 cm2 mol−1): 124 (5.33 × 10−4 M in acetone). IR (cm−1): ν(NH), 3421 w, 3365 m; ν(CN), 2245 w; ν(CN), 1615 s. ESI-HRMS: exact mass calcd for C33H45N4, 497.3644 [(M − H)+]; found, 497.3656. 1H NMR (400.9 MHz, DMSO-d6): δ 7.81 (br s, 3 H, NH3), 7.67 (br d, 1 H, H′7, 3JHH = 7.6 Hz), 7.56 (br d, 1 H, H7, 3JHH = 7.2 Hz), 7.39−7.25 (m, 6 H, H8 + H8′ + H9 + H9′ + H10 + H10′), 7.00 (s, 1 H, NH), 6.26 (s, 1 H, NH), 3.82 (m, 2 H, H6 + H6′), 3.53−3.48 (m, 3 H, H5 + H5′ + 1 H of CH2), 3.41 (br s, 1 H, CH, nor), 3.26 (br s, 1 H, CH, nor), 2.97 (d, 1 H, CH′2Ar, 2JHH = 14.0 Hz), 2.85 (d, 1 H, CH′2Ar, 2JHH = 14.4 Hz), 2.80 (d, 1 H, CH2Ar, 2JHH = 14.4 Hz), 2.19, 2.10 (AB system, 2 H, CH2, nor, 2JAB = 11.6 Hz), 1.69 (s, 3 H, Me, CMe2), 1.54 (s, 3 H, Me, CMe2), 1.27 (s, 3 H, Me, CMe′2), 1.25 (s, 3 H, Me, CMe′2), 0.92 (s, 9 H, Me, tBu). 13C{1H} NMR (75.4 MHz, DMSO-d6): δ 163.7 (s, C N), 139.8 (s, C6a′), 138.6 (s, C6a), 135.8 (s, C10a), 134.2 (s, C10a′), 131.6 (s, CH, C10′), 130.3 (s, CH, C10), 127.5 (s, CH, C8 or C8′), 127.3 (s, CH, C8 or C8′), 127.1 (s, CH, C9), 127.0 (s, CH, C9′), 126.7 (s, CH, C7′), 124.8 (s, CH, C7), 119.5 (s, CN), 57.7 (s, CMe2), 55.4 (s, CMe3), 54.6 (s, C′Me2), 50.4 (s, CH, C6), 48.5 (s, CH, C5), 46.8 (s, CH, C5′), 45.4 (s, CH, nor), 42.6 (s, CH, nor), 41.8 (s, CH2Ar), 40.8 (s, CH′2Ar), 38.5 (s, CH, C6′), 37.6 (s, CH2, nor), 29.5 (s, Me, CMe2), 28.6 (s, Me, CMe2), 27.6 (s, Me, tBu), 25.5 (s, Me, CMe′2), 25.2 (s, Me, CMe′2). Synthesis of 9a. AgOTf (168 mg, 0.654 mmol) was added to a solution of 3a·4H2O (218 mg, 0.154 mmol) in CH2Cl2 (20 mL) in a Carius tube, and the mixture was stirred for 3 h. Na2CO3 (140 mg, 1.321 mmol) was added, and the resulting suspension was stirred under a CO atmosphere (1.2 bar) for 20 h. Formation of metallic palladium was observed. The suspension was filtered through a plug of Celite, and the solvent was removed from the filtrate. Acetone (3 mL) was added to the residue, the mixture was stirred for 5 min, and npentane (15 mL) was added. The resulting brown suspension was filtered, and the solid was washed with CH2Cl2 (6 × 5 mL). The solvent was removed from the combined filtrates, and the residue was purified by column chromatography on silica gel, using a 6/1 EtOAc/ MeOH mixture as eluent (Rf = 0.7). The compound 9a was isolated as a colorless solid after evaporation of the solvent. Yield: 109 mg, 0.246 mmol, 80%. Mp: >300 °C. ESI-HRMS: exact mass calcd for C29H35N2O2, 443.2693 [(M + H)+]; found, 443.2692. IR (cm−1): ν(NH) 3385 w, 3209 br; ν(CO) 1655 s, 1643 s. 1H NMR (300.1 MHz): δ 7.45 (br d, 1 H, H7, 3JHH = 7.5 Hz), 7.27 (td, partially obscured by the resonance of the CHCl3 present in the CDCl3, 1 H, H8, 4JHH = 1.5, 3JHH = 7.5 Hz), 7.19 (td, 1 H, H9, 4JHH = 1.2, 3JHH = 7.5 Hz), 7.09 (dd, 1 H, H10, 4JHH = 1.2, 3JHH = 7.2 Hz,), 4.94 (br s, 1 H, NH), 3.50 (d, 1 H, H6, 3JHH = 11.7 Hz), 3.46 (d, partially overlapped with the resonance of H6, 1 H, CH2Ar, 2JHH = 14.4 Hz), 3.27 (br s, 0.5 H, CH, nor), 3.22 (br s, 0.5 H, CH, nor), 3.00 (d, 1 H, H5, 3JHH = 10.5 Hz), 2.67 (d, 1 H, CH2Ar, 2JHH = 14.1 Hz), 2.33 (br s, 1 H, CH2, nor), 1.60 (s, 3 H, Me), 1.28 (s, 3 H, Me). Because of the symmetry of the complex in solution, its 1H NMR spectrum only shows the signals corresponding to half of the molecule. 13C{1H} NMR (75.4 MHz): δ 173.1 (s, CO), 140.1 (s, C6a), 136.4 (s, C10a), 129.4 (s, CH, C10), 127.4 (s, CH, C8), 126.3 (s, CH, C9), 125.1 (s, CH, C7), 52.3 (s, CMe2), 51.7 (s, CH, C5), 51.6 (s, CH, C6), 45.8 (s, CH, nor), 44.0 (s, CH2Ar), 40.9 (s, CH, nor), 37.2 (s, CH2, nor), 31.2 (s, Me), 30.3 (s, Me). Single crystals of 9a·CHCl3 suitable for an X-ray diffraction study were obtained by slow diffusion of n-pentane into a solution of 9a in CHCl3. Synthesis of 9b. Norbornadiene (40.9 μL, 0.402 mmol) was added to a solution of palladacycle B (221.8 mg, 0.402 mmol) in CH2Cl2 (35 mL), and the mixture was stirred for 24 h in a Carius tube. AgOTf (207 mg, 0.806 mmol) was added, and the suspension was stirred for 3 h. Na2CO3 (86 mg, 0.811 mmol) was then added and the J


Organometallics

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anisotropically on F2 using the program SHELXL-2014/7.37 Hydrogen atoms were refined as follows: complexes 2a·0.5CH2Cl2 and 5b·Et2O, NH2 or NH free with SADI, methyl rigid group, all others riding; complexes 3a·CH3COCH3 and IA, NH2 and/or NH free with DFIX, ordered methyls rigid group, all others riding; compound 6a-Bu· CHCl3·3H2O, NH and H2O free with DFIX, methyls rigid group, all others riding; compound 9a·CHCl3, NH free, methyls rigid group, all others riding. Special Features. For 2a·0.5CH2Cl2, an ill-defined region of residual electron density over an inversion center was interpreted as half of a dichloromethane molecule. For 3a·CH3COCH3, one chloride is disordered over two positions, with a ca. 90/10 occupancy distribution; the minor chloride part was refined as isotropic. Three carbon atoms of one of the aryl rings were disordered over two positions with a ca. 63/37 occupancy distribution; all of these atoms were refined as isotropic. One NH2CMe2 moiety is disordered over two positions, with a ca. 56/44 occupancy distribution; all these atoms were refined as isotropic. A region of residual electron density could not be interpreted in terms of realistic solvent molecules, even allowing for possible disorder. For this reason the program SQUEEZE, which is part of the PLATON system,38 was employed to remove mathematically the effects of the solvent. Standard deviations of refined parameters should be interpreted with caution. The void volume per cell was 1415 Å3 with a void electron count per cell of 427. This additional solvent was not taken into account when derived parameters such as the formula weight were calculated, because the nature of the solvent was uncertain. For IA, the two tBu groups are disordered over two positions, with ca. 56/44 and 53/46 occupancy distributions; these carbon atoms were refined as isotropic. A region of residual electron density could not be interpreted in terms of realistic solvent molecules, even allowing for possible disorder. For this reason the program SQUEEZE, which is part of the PLATON system,38 was employed to remove mathematically the effects of the solvent. Standard deviations of refined parameters should be interpreted with caution. The void volume per cell was 2665.2 Å3 with a void electron count per cell of 431. This additional solvent was not taken into account when derived parameters such as the formula weight were calculated, because the nature of the solvent was uncertain. For 9a· CHCl3, one of the two chloroform molecules is badly disordered over two positions, with a ca. 67/33 occupancy distribution. The carbon atoms of both parts were refined as isotropic.

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ACKNOWLEDGMENTS We thank the Spanish Ministerio de Economiá y Competitividad (grant CTQ2015-69568-P) and Fundación Séneca (grant 19890/GERM/15) for financial support.

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REFERENCES

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.organomet.6b00795. 1

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Article

H and 13C-APT NMR spectra of compounds 9a−c, crystallographic data, and details of hydrogen bonds (including symmetry operators) (PDF) Crystallographic data for compounds 2a·0.5CH2Cl2, 3a· CH3COCH3, 5b·Et2O, 6a-Bu·CHCl3·3H2O, 9a·CHCl3 and IA. (CIF)

AUTHOR INFORMATION

Corresponding Authors

*E-mail for I.S.-L.: [email protected]. *E-mail for J.V.: [email protected]. ORCID

Isabel Saura-Llamas: 0000-0001-8335-6747 Notes

The authors declare no competing financial interest. K


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