Synthesis and Structures of Cyclopropanedicarboxylate Gallium

Article pubs.acs.org/Organometallics

Synthesis and Structures of Cyclopropanedicarboxylate Gallium Complexes Roman A. Novikov,†,‡ Konstantin V. Potapov,†,§ Daniil N. Chistikov,†,§ Anna V. Tarasova,† Michail S. Grigoriev,∥ Vladimir P. Timofeev,‡ and Yury V. Tomilov*,† †

N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky prosp., 119991 Moscow, Russian Federation ‡ V. A. Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, 32 Vavilov st., 119991 Moscow, Russian Federation § Lomonosov Moscow State University, Faculty of Chemistry, 1-3 Leninskiye Gory, 119991 Moscow, Russian Federation ∥ Radiochemistry Department, A. N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, 40 Obruchev st., 117342 Moscow, Russian Federation S Supporting Information *

ABSTRACT: A series of novel gallium dimethylmalonate and cyclopropane-1,1-dicarboxylate complexes have been synthesized using gallium halides as Lewis acids. The structure and properties of the resulting complexes as well as the mechanisms of reactions involved have been studied. Some complexes have ionic structures and consist of ligand-bound Ga cations and tetrahalogallate anions. The structures of gallium complexes were studied by multinuclear NMR spectroscopy, including that on 71Ga nuclei. Furthermore, X-ray diffraction analysis was carried out for the six complexes. Dimethyl cyclopropanedicarboxylate was considered as the simplest analogue of donor− acceptor cyclopropanes. It is a convenient model for studying such cyclopropanes, while the complexes obtained are analogues of intermediates in their reactions catalyzed by Lewis acids. In particular, elongation of the C−CH2 bond in the cyclopropane ring and activation of the latter by gallium halides have been shown experimentally. The data obtained are a new step in studies on this very interesting and promising class of substrates.

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a σ bond in the cyclopropane ring occurs, resulting in its opening with generation of a 1,3-dipolar intermediate, which then undergoes subsequent reactions (Scheme 1).1 A vast majority of information on the mechanisms of these reactions was obtained from indirect data using computational methods, isotopic tracers, and optically active cyclopropanes.1 Recently, we were the first to detect and characterize tin, titanium, and gallium DAC complexes with Lewis acids and studied their reactivity and structures by a number of methods, including X-ray diffraction analysis.3a These were the first experimental data on the characterization of intermediates in DAC reactions. In continuation of these studies, we synthesized and studied new gallium complexes of nonsubstituted cyclopropanedicarboxylate, the simplest DAC analogue, using its reactions with gallium halides. This approach seems quite promising, because lately gallium compounds have been widely used as catalysts and reagents in various DAC reactions in order to construct carbo- and heterocyclic compounds (Scheme 2).3 Studies of gallium complexes that are intermediates in DAC reactions

INTRODUCTION Donor−acceptor cyclopropanes (cyclopropanes with donor and acceptor substituents in vicinal positions, DAC) are now popular as sources of 1,3-dipoles that are generated from them on treatment with Lewis acids.1,2 The capability of donor− acceptor cyclopropanes to undergo [2 + 3]-, [3 + 3]-, and [3 + 4]-dipolar cycloaddition with various substrates is now used to build five-, six-, and seven-membered carbo- and heterocycles (Scheme 1); these reactions can be performed enantioselectively, which makes them very attractive for application in organic synthesis.1,2 Aryl, sometimes alkyl, alkoxy, and amino groups are used as electron-donating substituents in cyclopropanes, whereas carbonyl, alkoxycarbonyl, and cyano groups are used mainly as electron-withdrawing substituents. Tin(II) triflates and rareearth-element triflates as well as chloroalanes are the most popular Lewis acids; gallium and indium compounds are less common.1,2 Since DACs are widely used in contemporary organic synthesis, it is important to study the mechanisms of their reactions. Presumably, a complex of the Lewis acid with the donor−acceptor cyclopropane is first formed due to coordination to the electron-accepting group. As a result, polarization of © XXXX American Chemical Society

Received: May 14, 2015

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DOI: 10.1021/acs.organomet.5b00399 Organometallics XXXX, XXX, XXX−XXX

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Organometallics Scheme 1. Donor−Acceptor Cyclopropanes (DAC) in Modern Organic Synthesis

Scheme 2. Ga Compounds in DAC Chemistry

system, these reactions have not been studied to date. Reactions of the malonyl anion and anions of 1,3-dicarbonyl compounds with gallium compounds were studied.4 However, systems of this kind were of little use for the DAC model. Dimethyl malonate (1) readily and quickly reacts with gallium trichloride in dichloromethane solution even at room temperature. The reaction almost quantitatively gives gallium complex 2a, having rather a complex structure (Scheme 3). Owing to poor solubility, it is gradually deposited as a colorless powder or crystals, depending on the synthesis conditions. What is more, this complex has low stability in air and readily undergoes hydrolysis; thus, it always has to be handled in a dry

allow one not only to attain a better understanding of the mechanisms of these reactions and learn to control them but also to use them to control DAC reactivity. Gallium complexes with ligands containing a cyclopropane ring have not been known before.

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RESULTS AND DISCUSSION Complexes of Dimethyl Malonate with GaCl3 and GaBr3. At first, we studied the reaction of dimethyl malonate with GaCl3 and GaBr3 as a simplified model of reactions of gallium halides with two geminal ester groups. An analysis of the literature showed that, despite the simplicity of the reacting B


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Organometallics Scheme 3. Complexes of Dimethyl Malonate with GaCl3 and GaBr3

GaCl3 in a 1/1 ratio. Since the coordination sphere of gallium in the monomeric complex is not saturated, it is quite probable that in fact it has a dimeric structure or is in equilibrium with it (the monomer−dimer equilibrium for similar gallium complexes was shown by us previously3a by diffusion-ordered NMR spectroscopy (DOSY)). Complex 3a is highly unstable and is very quickly converted to stable ionic complex 2a by transligandation with modification of the stoichiometric composition and release of the free ligand (Scheme 3). The conversion of complex 3a takes about 10 min at room temperature or just a few seconds at elevated temperatures. The conversion is accompanied by simultaneous crystallization of the final complex, and the process itself occurs in complex 3a without a solvent. Therefore, the conversion of 3a to 2a is strongly accelerated by intense stirring due to faster diffusion. In addition to the very short lifetime of complex 3a, it is unstable in air and readily undergoes hydrolysis. These phenomena complicate the study of this compound. Still, the data of 1H, 13C, 71Ga, and 35Cl NMR spectra obtained after mixing the reagents represent its structure well and are quite similar to the data for analogous complexes that we obtained previously.3a Complexes of dimethyl malonate with gallium trichloride have very characteristic 71Ga NMR spectra which, along with Xray diffraction analysis, provide the main method to study these complexes (Figures 2 and 3). The 71Ga atom manifests high sensitivity, and the 71Ga chemical shift is very sensitive to the environment, which makes it possible to determine the number of different types of gallium atoms in a compound being studied and their coordination spheres.6 The main problem lies in the large width of 71Ga lines, but this can be partially solved by deconvolution to separate the overlapping signals. The 71Ga NMR spectrum of complex 3a contains one rather narrow signal with δ +248 corresponding to gallium trichloride coordinated with two oxygen atoms.3a,6 On transition to complex 2a, the signal in the 71Ga NMR spectrum shifts downfield to δ +256 due to the formation of tetrachlorogallate anions, and a second weaker signal appears at δ +189, which corresponds to Ga3+ cations coordinated with three dimethyl malonate molecules. Since complex 2a is not soluble in any solvent without decomposition, solid-state gallium spectra were recorded for it. However, this fact did not preclude the interpretation of these spectra. Thus, the solid-state 71Ga NMR spectrum of complex 2a contains two signals of different types of gallium that strongly overlap but can be easily separated by deconvolution (Figure 3).

argon environment. Complex 2a is almost insoluble in lowpolar organic solvents, whereas in polar solvents it decomposes with abstraction of the original molecule of dimethyl malonate (1). It proved impossible to grow a single crystal of this complex by recrystallization due to its low solubility. Therefore, we had to prepare it during a synthesis of the complex itself under thoroughly chosen conditions. In this case, we succeeded in growing colorless monoclinic crystals of complex 2a up to several millimeters in size. According to X-ray diffraction data, complex 2a is an ionic compound that crystallizes as a solvate with dichloromethane (Figure 1). This complex consists of the tripositive cation

Figure 1. ORTEP diagram of 2a, with thermal ellipsoids given at the 50% probability level.

[Ga(L)3]3+, in which gallium has an octahedral environment, and three tetrahedral tetrachlorogallate anions. Thus, far, complexes of this kind have not been reported in the literature.5 A detailed study of the reaction of dimethyl malonate with gallium trichloride showed that the process occurs in a more complex manner and a few more intermediates are formed before the formation of the final complex 2a (Scheme 3). In fact, upon addition of GaCl3 to a solution of dimethyl malonate in dichloromethane, complex 3a is first deposited as a thick oil. This complex is an adduct of dimethyl malonate with C


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Organometallics

Figure 2. 71Ga NMR spectra of dimethyl malonate−GaCl3 complexes.

of both complexes were also characterized by 1H, and 81Br NMR spectra.

13

C,

71

Ga,

Figure 3. Solid-state 71Ga NMR spectra of complex 2a: (black) experimental spectrum; (pink) simulated spectrum after deconvolution into two components shown in blue; (orange) difference between the experimental and calculated spectra. Figure 4. ORTEP diagram of the cationic part of 2b, with thermal ellipsoids given at the 50% probability level.

Furthermore, gallium NMR spectra allowed us to monitor the course of the reaction. In fact, the spectra recorded during crystallization with conversion of complex 3a to complex 2a strongly differed from the spectra of the starting and final compounds. The 71Ga signal in the spectra was much broader and had an irregular shape. This corresponded to some number of strongly overlapping signals. Thus, at this time, the reaction mixture contained a few intermediate gallium complexes, which corresponded on the one hand to sequential replacement of chloride ions with dimethyl malonate molecules in the coordination sphere of a Ga atom and on the other hand to formation of GaCl4− anions (Figure 2). Gallium tribromide reacts with dimethyl malonate similarly to gallium trichloride to give similar complexes. However, owing to the even higher lability and hydrolytic instability of gallium bromide complexes, it was even more difficult to work with them. Mixing the reagents first resulted in liquid complex 3b, which crystallized with time to give complex 2b. The time required for conversion of complexes 3a,b to 2a,b is nearly the same. According to X-ray diffraction analysis, complex 2b has an ionic structure similar to that of 2a and also crystallizes as a solvate with dichloromethane (Figures 4 and 5). The structures

Figure 5. ORTEP diagram of 2b·CH2Cl2, with thermal ellipsoids given at the 50% probability level. D


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Organometallics Scheme 4. Complexes of Dimethyl Cyclopropane-1,1-dicarboxylate with GaCl3

has a chemical shift of δ +254, which is equal to that for complex 2a and corresponds to tetrachlorogallate anion. The other signal with smaller intensity and greater width has a chemical shift of δ +228 and corresponds to the Ga3+ cation coordinated with three molecules of cyclopropane 5. This downfield shift is stronger than that for complex 2a, as expected due to electron density donation by the cyclopropane ring. The 71 Ga NMR spectra of the initial complex 6a contain one rather narrow signal at δ +245 corresponding to GaCl3 coordinated with two oxygen atoms (Figure 7).

Complexes of Dimethyl Cyclopropane-1,1-dicarboxylate with GaCl3. After studying the reaction of dimethyl malonate with GaCl3 in detail, we started a more detailed study of the reaction of the latter with dimethyl cyclopropane-1,1dicarboxylate (5). As we have shown previously,3a cyclopropane 5 reacts with GaCl3 to give complex 6a as a thick oil. However, unlike 3a, this complex was found to be more stable and did not change for a long time (more then 1−2 weeks) at room temperature under an inert atmosphere. Still, we found that drying of complex 6a under high vacuum resulted in its crystallization to give a new ionic complex 7a (Scheme 4), which proved to be similar to complex 2a: i.e., under these conditions complex 6a loses traces of dichloromethane and a molecule of cyclopropanedicarboxylate 5 to give gallium complex 7a as a flocculent white powder nearly insoluble in dichloromethane. Complex 7a is stable for a long time under an inert atmosphere but quickly undergoes hydrolysis in air. The structure of this complex was proven by solid-state NMR spectroscopy on 71Ga nuclei by analogy with the corresponding dimethyl malonate complex (Figure 6). Like complex 2a, complex 7a contains a gallium cation coordinated with three cyclopropanedicarboxylate molecules, as well as three tetrahedral tetrachlorogallate anions. The solid-state 71Ga NMR spectra of compound 7a contain two strongly overlapping broad signals of gallium atoms that are easily separated by deconvolution. The most intense signal

Figure 7. 71Ga NMR spectra of cyclopropanedicarboxylate 5−GaCl3 complexes.

Complexes of Dimethyl Cyclopropane-1,1-dicarboxylate with GaBr3. A similar chain of transformations was also observed in the reaction of cyclopropanedicarboxylate 5 with gallium bromide (Scheme 5). As with GaCl3, an oil-like complex 6b is formed initially. However, unlike the case for 6a, it proved to be less stable and easily underwent further transformations. In fact, immediately after cyclopropane 5 and GaBr3 were mixed, a thick colorless oil settled out. The compound identified in the solution corresponded to complex 6b and/or its dimer, while the oily part was a mixture of nearly equal amounts of complexes 6b and 8b, the structures of which were determined using 1H, 13C, 71Ga, and 81Br NMR spectroscopy. It is clear that complex 8b, which has an ionic structure and consists of singly charged [GaL2Br2]+ cations with two coordinated cyclopropanedicarboxylate molecules and GaBr4− anions, is a product of subsequent trans-ligandation of the original complex 6b, and it may not be ruled out that both complexes can be in equilibrium with each other (Scheme 5). The 71Ga NMR spectrum of complex 6b contains rather a

Figure 6. Solid-state 71Ga NMR spectra of complex 7a: (black) experimental spectrum; (pink) simulated spectrum after deconvolution into two components shown in blue; (orange) difference between the experimental and calculated spectra. E


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Organometallics Scheme 5. Complexes of Dimethyl Cyclopropane-1,1-dicarboxylate with GaBr3

Figure 8. 71Ga NMR spectra of cyclopropanedicarboxylate 5−GaBr3 complexes: (black) experimental spectra; (crimson) computed spectra after deconvolution, with the components shown in blue; (orange) difference between the experimental and computed spectra.

narrow signal of gallium at δ +65 (Figure 8). The spectrum of complex 8b contains a broader signal at δ +68, which actually includes signals from two types of Ga atoms. The downfield shift by several ppm corresponds to coordination of gallium with the second cyclopropanedicarboxylate molecule and formation of a tetrabromogallate anion (see Complexes of

Dimethyl Malonate with GaCl3 and GaBr3 for the chloride analogues). When complexes 6b and 8b are kept under an inert atmosphere for a few days, a crystalline product is gradually formed. Though it is highly sensitive to moisture, we succeeded in obtaining a single crystal of this complex and performed its X-ray diffraction study, which showed that it is ionic complex F


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Organometallics 7b, structurally identical with chloride complex 7a (Figures 9 and 10).

Figure 11. ORTEP diagram of the cationic part of 9b, with thermal ellipsoids given at 50% probability level.

Figure 9. ORTEP diagram of the cationic part of 7b, with thermal ellipsoids given at the 50% probability level.

Furthermore, both oxygen atoms collected three more gallium atoms with their tetrahedral environment from bromine atoms into a cluster to create a four-membered Ga2O2 ring. Like the other complexes that we studied, compound 9b crystallized as a solvate with dichloromethane (Figure 12).

Figure 10. ORTEP diagram of molecule 7b, with thermal ellipsoids given at the 50% probability level.

Figure 12. ORTEP diagram of the molecule 9b·CH2Cl2, with thermal ellipsoids given at the 50% probability level.

On the other hand, if minor contact of complex 8b with atmospheric moisture is provided before it is converted to the final complex 7b, it is partially hydrolyzed to give the new complex 9b, which crystallizes as colorless small monoclinic crystals, which we also managed to study by X-ray diffraction analysis. In this case, it was most important to find an optimum time of contact with air, since overly long exposure of the complex to air resulted in its complete and irreversible hydrolysis. The structure of complex 9b was quite unexpected (Figure 11). The central gallium atom coordinated with two cyclopropanedicarboxylate molecules retained a hexacoordinated environment, but both bromine atoms were replaced by oxygen atoms from water molecules: i.e., the most hydrolytically unstable Ga−Br bonds were the first to be hydrolyzed.

Complexes of Dimethyl Cyclopropane-1,1-dicarboxylate with Ga2Cl4. Unlike GaCl3, cyclopropanedicarboxylate 5 reacts with Ga2Cl4 in a different manner. The latter has an ionic structure in the crystal and is composed of Ga(I) and tetrachlorogallate anions; thus, there are two different types of gallium atoms, one of which is in a low oxidation state. The reaction of Ga2Cl4 with cyclopropane 5 involves disproportionation of monovalent gallium atoms to give Ga(0), which eventually precipitates as a gray powder, and Ga(III), which participates in coordination with cyclopropane 5 and chloride anions. According to 1H, 13C, 71Ga, and 35Cl NMR spectra, the reaction initially gave a mixture of soluble gallium complexes with variable compositions whose structures could not be determined. G


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Organometallics

moisture (Scheme 6), similarly to the formation of bromide complex 9b. The intermediate complex 8a itself is apparently quite specific. First, it cannot be obtained directly from complex 6a by analogy with 6b, since chloride complex 6a is quite stable and does not undergo reactions of this kind. Second, it is surprising that these reactions do not give the stable complex 7a, and in general, unlike the case for 8b, the complex was found to be fairly well soluble in CH2Cl2. Owing to partial evaporation of the solvent from the reaction mixture, yet another gallium complex precipitated after 1−2 more weeks as small colorless monoclinic crystals. Its structure as a solvate with dichloromethane, which was determined by Xray diffraction analysis, corresponded to ionic complex 10 (Scheme 6 and Figures 14 and 15) formed by the [Ga4(L)4(OMe)2Cl4]2+ cation and GaCl4− anions: i.e., its structure incorporated six gallium atoms of three different types. It is interesting to note that the structure of complex 10 includes four coordinated fragments of cyclopropanedicarboxylate molecules, in which one of the carboxylate groups was reduced to a hydroxymethyl group (apparently, by monovalent gallium), while the two methylate anions released in this process took part in coordination to two gallium atoms as bridging ligands to form a four-membered Ga2O2 ring. Complexes 9a and 10 can be separated by fractional crystallization or by mechanical separation of crystals that have different shapes. Both compounds are stable for a long

However, in about 1 week, a gallium complex crystallized from the reaction mixture as colorless monoclinic crystals, which according to XDR data corresponded to a solvate of chloride complex 9a with dichloromethane (Figure 13). On the

Figure 13. ORTEP diagram of molecule 9a, with thermal ellipsoids given at the 50% probability level.

basis of these data, it may be believed that complex 9a is formed from complex 8a due to partial hydrolysis with traces of

Scheme 6. Reactions of Dimethyl Cyclopropanedicarboxylate 5 with Ga2Cl4

H


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spectroscopy and XRD. Some of the complexes obtained have an ionic structure, and some are neutral compounds (Figure 16).

Figure 16. Ga complexes of dimethyl malonate and dimethyl cyclopropane-1,1-dicarboxylate.

In all complexes of dimethyl cyclopropane-1,1-dicarboxylate, the cyclopropane ring is retained and the gallium atom is coordinated with two ester groups. Due to coordination and conjugation effects, the C−CH2 bond of the cyclopropane ring is elongated, as follows from XRD data for complexes 7b and 9a,b. In addition, though this elongation is not very strong, it is still rather noticeable and quite characteristic (Table 1).

Figure 14. ORTEP diagram of the cationic part of 10, with thermal ellipsoids given at the 50% probability level.

Table 1. Comparison of C−CH2 Bond Lengths in the Cyclopropane Ring in Ga Complexes 7b, 9a,b, 10, and Cyclopropane-1,1-dicarboxylic Acid (11)7 According to Xray Diffraction Data C−CH2 bond length (A)

a

complex

individual

average

11 7b 9a 9b 10

1.531; 1.535; 1.531; 1.540a 1.55; 1.55; 1.54; 1.55; 1.54; 1.57 1.540; 1.555 1.55; 1.56 1.52; 1.53; 1.51; 1.53

1.534 1.55 1.548 1.555 1.523

A cell contains two crystallographically independent molecules.

The most significant bond elongation should be observed for complexes 6, but they are liquids; thus, an XRD study cannot be performed for them. However, a considerable elongation of the C−CH2 bond can be indirectly inferred from the strong downfield shifts of signals in the 1H and 13C NMR spectra.3a Elongation of C−CH2 bonds indicates that the cyclopropane ring is activated due to coordination with the gallium atom that serves as a Lewis acid. It is interesting to note that elongation of C−CH2 bonds in the cyclopropane ring does not occur in complex 10, where one of the two ester groups is reduced to CH2OH: i.e., activation of the cyclopropane ring requires two geminal ester groups for better coordination and conjugation. Some of the gallium complexes that we obtained have quite complex structures, indicating how complex the real structures of the intermediates and mechanisms of many DAC reactions are, how little we know about them, and how important it is to continue studies in this direction. Many complexes crystallize as solvates with dichloromethane; hence, the solvate shell consisting of solvent molecules is very important in real processes involving DACs catalyzed by gallium compounds and it should also be taken into consideration and studied.

Figure 15. ORTEP diagram of complex 10·2CH2Cl2, with thermal ellipsoids given at the 50% probability level.

time under an inert atmosphere but decompose very quickly in air. It should be noted that we failed to detect complexes of cyclopropane 5 with gallium atoms in low oxidation states, i.e., Ga(I) or Ga(II); all gallium in low oxidation states underwent disproportionation or oxidation to Ga(III). This fact is easily and unambiguously confirmed by 71Ga NMR spectroscopy: Ga in low oxidation states has a strong negative chemical shift at δ from −500 to −700, whereas the chemical shift of coordinated Ga(III) is about δ +250,6 as we observed in the detected Ga complexes. The gray precipitates of metallic Ga(0) were also analyzed by 71Ga NMR spectroscopy (broad signal at about +4500 ppm). Ga Complexes of Dimethyl Cyclopropane-1,1-dicarboxylate: Overview. As a result, we obtained a set of new gallium complexes that are formed in reactions of gallium halides with dimethyl malonate and dimethyl cyclopropanedicarboxylate considered as the simplest DAC analogue. Their structures and properties were studied by multinuclear NMR I


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mg, 1.52 mmol) in dry CH2Cl2 (3 mL) at room temperature. The mixture was stirred at room temperature for 15 s. Complex 3a (∼95%) was isolated as a thick heavy oil. This complex is very unstable, and at room temperature it completely transformed into complex 2a in just 10 min with crystallization. Therefore, complex 3a could not be isolated in pure form. To study the structure of complex 3a, the reaction was carried out in an NMR tube on loading 0.3 mmol of both starting reagents in dry CD2Cl2 (0.5 mL); the necessary NMR experiments were acquired immediately after the synthesis of the complex. 1 H NMR (400.1 MHz, neat): δ 4.9 (s, 8H, CH2 + 2OCH3, W1/2 = 60 Hz). 13C NMR (100.6 MHz, neat): δ 41.7 (br s, CH2), 64.5 (br s, 2OCH3), 181.7 (br s, 2COO). 71Ga NMR (122.0 MHz, neat): δ +248 (s, W1/2 = 4000 Hz). 35Cl NMR (39.2 MHz, neat): δ +243 (s, W1/2 = 6000 Hz). We failed to obtain other physicochemical data due to the high instability of the complex. Complex [CH2(CO2Me)2]3Ga3+·[GaCl4]3− (2a). Method A. Solid GaCl3 (357 mg, 2.03 mmol) was added in one portion under an argon atmosphere with stirring to a solution of dimethyl malonate (1; 200 mg, 1.52 mmol) in dry CH2Cl2 (3 mL) at room temperature. The reaction mixture was stirred for 30 min and then evaporated in vacuo. The complex 2a (555 mg, 99%) was obtained as a colorless fine crystalline powder with mp 157−167 °C dec. Complex 2a has poor stability in air. Method B. Solid GaCl3 (357 mg, 2.03 mmol) was added in one portion under an argon atmosphere with stirring to a solution of dimethyl malonate (1; 200 mg, 1.52 mmol) in dry CH2Cl2 (3 mL) at room temperature. The complex 3a was isolated as a thick heavy oil which quickly crystallized into the target complex 2a. The reaction mixture was stirred at room temperature for 15 min. The precipitate was filtered on a Schott filter, washed with CH2Cl2 (2 × 1 mL), and dried in vacuo. The complex obtained (467 mg, 84%) is similar to complex 2a prepared above. Method C. Solid GaCl3 (357 mg, 2.03 mmol) was added in one portion under an argon atmosphere with stirring to a solution of dimethyl malonate (1; 200 mg, 1.52 mmol) in dry CH2Cl2 (3 mL) at 40 °C, and the reaction mixture was stirred for 1 min. The target complex 2a immediately precipitated as a white fine crystalline powder, which was filtered on a Schott filter, washed with CH2Cl2 (2 × 1 mL), and dried in vacuo. The complex obtained (450 mg, 82%) is similar to complex 2a prepared above. Data for complex 2a·CH2Cl2 is as follows. Anal. Calcd for C16H26Cl14O12Ga4: C, 16.21; H, 2.21. Found: C, 16.33; H, 2.24. IR (KBr): ν 2962, 1737 br (CO), 1617, 1444, 1358, 1304, 1197, 1130 cm−1. 1H NMR (400.1 MHz, solid state): δ 5.4 (s, W1/2 = 8500 Hz). 13 C NMR (100.6 MHz, solid state): δ 59.2 (s, CH2, W1/2 = 800 Hz), 65 (s, 2OCH3, W1/2 = 3000 Hz), 185 (s, 2COO, W1/2 = 4000 Hz). 71 Ga NMR (122.0 MHz, solid state): δ +189.2 (s, 1Ga, Ga3+, W1/2 = 8000 Hz), +257.6 (s, 3Ga, GaCl4−, W1/2 = 9000 Hz). EI/MS (m/z, %): 273 (1), 214 (1), 176 (4), 141 (17), 132 (5), 119 (2), 101 (100), 84 (51), 74 (64), 69 (18), 59 (95), 42 (55), 29 (69). X-ray diffraction data for a single crystal of 2a·CH2Cl2: CCDC 1024005, orthorhombic crystal, 100 K, a = 13.8249(10) Å, b = 14.8020(11) Å, c = 20.4605(15) Å, α = 90°, β = 90°, γ = 90°, V = 4186.96 Å3, dcalc = 1.881 g cm−3, space group P212121. Selected bond lengths (Å): Ga(1)−O(1) 1.963; O(1)−C(1) 1.233; C(1)−C(2) 1.503; C(1)−O(3) 1.281; Ga(2)−Cl(1) 2.158. Selected angles (deg): O(1)−Ga(1)−O(2) 90.7; O(2)−Ga(1)−O(5) 179.1; Ga(1)−O(1)− C(1) 126.7; O(1)−C(1)−C(2) 123.5; C(1)−C(2)−C(3) 114.7; O(3)−C(1)−C(2) 113.2; Cl(1)−Ga(2)−Cl(2) 108.44. Complex CH2(CO2Me)2·GaBr3 (3b). Solid GaBr3 (200 mg, 0.65 mmol) was added in one portion under an argon atmosphere with stirring to a solution of dimethyl malonate (1; 85 mg, 0.65 mmol) in dry CH2Cl2 (3 mL) at room temperature. The mixture was stirred at room temperature for 5−10 s until complete dissolution of gallium bromide. Complex 3b (∼95%) was isolated as a thick heavy oil, which was very unstable and at room temperature almost completely transformed into complex 2b in just 1−2 min with crystallization. Therefore, complex 3b could not be isolated in pure form. To study the structure of complex 3b, the reaction was carried out in NMR tube

CONCLUSION We have synthesized a series of novel gallium dimethylmalonate and cyclopropane-1,1-dicarboxylate complexes based on gallium halides. The structures and properties of the resulting complexes have been studied. It has been shown that some complexes have ionic structures and consist of ligand-bound Ga cations and tetrahalogallate anions. The mechanisms of the reactions have been studied in detail. The structures of gallium complexes have been studied by multinuclear NMR spectroscopy, including that on 71Ga nuclei. Furthermore, X-ray diffraction analysis has been carried out for six complexes. An elongation of the C−CH2 bond in the cyclopropane ring and its activation by gallium halides have been shown experimentally.

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EXPERIMENTAL SECTION

General Experimental Details. All reagents and solvents used were commercial grade chemicals (>99.5%) and were used without additional purification. All operations with gallium halides and its complexes were carried out under a dry argon atmosphere. 1H and 13C NMR spectra were recorded on a 400 MHz (400.1 and 100.6 MHz, respectively) and 300 MHz spectrometers (300.1 and 75.5 MHz, respectively) in CD2Cl2 and CDCl3 containing 0.05% Me4Si as the internal standard. 35Cl, 71Ga, and 81Br NMR spectra were recorded on a 400 MHz spectrometer (39.2, 122.0, and 108.0 MHz, respectively) in CD2Cl2 and CDCl3; the standards were NaCl, Ga(NO3)3, and NaBr solutions in water, respectively. Monitoring of the reactions in NMR tubes were made in CD2Cl2 solution containing 0.05% Me4Si as the internal standard. Solid-state 1H, 13C, and 71Ga NMR spectra were recorded on a 400 MHz spectrometer (400.1, 100.6, and 122.0 MHz, respectively) on liquid BBI and QNP probes without MAS. Measurements of the diffusion coefficients were performed using 2D 1 H DOSY NMR spectroscopy (diffusion ordered spectroscopy) in CD2Cl2 solutions and without solvent on a 300 MHz spectrometer (300.1 MHz for 1H). A BPP-LED pulse sequence was used with Δ = 100−1500 ms and Te = 5 ms. The DOSY spectra were processed by monoexponential fitting and the SCORE algorithm using Bruker TopSpin and DOSYToolbox software.8 The MestreNova software was used for 71Ga NMR spectra deconvolution and line fitting. IR spectra were obtained on a FT-IR spectrometer in CHCl3 solution (1%). Mass spectra were recorded using electron impact ionization (EI, 70 eV, direct inlet probe). High-resolution mass spectra were obtained using simultaneous electrospray ionization (ESI). The elemental compositions were determined on a PerkinElmer Series II 2400 CHN Analyzer. X-ray crystallographic data for complexes 2a,b, 7b, 9a,b and 10 were obtained on a “Bruker 1K SMART CCD” diffractometer (Mo Kα radiation) at 100 K. The starting arrays of measured intensities were processed using the APEX2 program.9 The structure was solved by direct methods and refined by full-matrix least squares in the anisotropic approximation for non-hydrogen atoms on F2hkl. Hydrogen atoms were placed in geometrically calculated positions. NMR Spectra of Starting Materials. Dimethyl malonate (1): 1H NMR (400.1 MHz, CD2Cl2) δ 3.37 (s, 2H, CH2), 3.72 (s, 6H, 2OCH3); 13C NMR (100.6 MHz, CD2Cl2) δ 42.7 (CH2), 53.9 (2OCH3), 168.5 (2COO). Dimethyl cyclopropanedicarboxylate (5): 1H NMR (400.1 MHz, CD2Cl2) δ 1.45 (s, 2H, 2CH2), 3.74 (s, 6H, 2OCH3); 13C NMR (100.6 MHz, CD2Cl2) δ 16.4 (2CH2), 27.8 (C), 52.4 (2OCH3), 170.0 (2COO). GaCl3: 71Ga NMR (122.0 MHz, CD2Cl2) δ +221 (s, W1/2 = 12000 Hz); 35Cl NMR (39.2 MHz, CD2Cl2) δ +235 (s, W1/2 = 6700 Hz). GaBr3: 71Ga NMR (122.0 MHz, CD2Cl2) δ +38.9 (s, W1/2 = 14500 Hz). Ga2Cl4: 71Ga NMR (122.0 MHz, solid state) δ −609.0 (s, 1Ga, Ga(I)+, W1/2 = 2000 Hz), +222.9 (m, 1Ga, Ga(III)Cl4−, W0 = 40000 Hz); 35Cl NMR (39.2 MHz, solid state) δ +223 (s, W1/2 = 6000 Hz). Complex CH2(CO2Me)2·GaCl3 (3a). Solid GaCl3 (266 mg, 1.52 mmol, 1.0 equiv) was added in one portion under an argon atmosphere with stirring to a solution of dimethyl malonate (1; 200 J


Article

Organometallics

1306, 1228, 1197, 1131 cm−1. 1H NMR (400.1 MHz, solid state): δ 8.1 (s, 10H, 2CH2 + 2OCH3, W1/2 = 14000 Hz). 13C NMR (100.6 MHz, solid state): δ 25 (s, C, W1/2 = 10000 Hz), 48 (s, 2CH2, W1/2 = 10000 Hz), 69 (s, 2OCH3, W1/2 = 5000 Hz), 185 (s, 2COO, W1/2 = 25000 Hz). 71Ga NMR (122.0 MHz, solid state): δ +228.9 (s, 1Ga, Ga3+, W1/2 = 7500 Hz), +255.2 (s, 3Ga, GaCl4−, W1/2 = 5200 Hz). EI/ MS (m/z, %): 311 (1), 283 (6), 225 (2), 176 (4), 158 (5), 141 (25), 127 (66), 113 (17), 100 (43), 85 (23), 69 (100), 59 (98), 39 (99), 29 (100). Reaction of Dimethyl Cyclopropanedicarboxylate 5 with GaBr3. Method A (Synthetic Procedure). Solid GaBr3 (309 mg, 1.0 mmol) was added in one portion under an argon atmosphere with stirring to a solution of cyclopropane 5 (158 mg, 1.0 mmol) in dry CH2Cl2 (3.5 mL) at room temperature, and the reaction mixture was stirred at room temperature for 1 min until complete dissolution of gallium bromide. As a result a thick heavy oil settled in precipitate. The composition of the solution and oily precipitate was analyzed by NMR spectroscopy without separation. The solution contains only complex 6b, but its concentration is low. The oily precipitate is a mixture of the two gallium complexes 6b and 8b in about an equimolar ratio. Attempts to isolate the compounds failed due to their low stability and easy hydrolyzation in air. Therefore, the obtained complexes were used in further synthesis without isolation. Method B (NMR Studies). Solid GaBr3 (56 mg, 0.18 mmol) was added in one portion under an argon atmosphere to a solution of cyclopropane 5 (28 mg, 0.18 mmol) in dry CD2Cl2 (0.5 mL) at room temperature with vigorous shaking in an NMR tube. The necessary NMR experiments were acquired after the mixing of reagents. Complex (CH2)2C(CO2Me)2·GaBr3 (6b). 1H NMR (400.1 MHz, CD2Cl2): δ 2.3−4.8 (br m, CH2 + OCH3). 1H NMR (400.1 MHz, oily mixture of complexes 6b and 8b without solvent): δ 3.0−6.1 (br m, CH2 + OCH3). 71Ga NMR (122.0 MHz, CD2Cl2): δ +64.8 (s, W1/2 = 850 Hz). 71Ga NMR (122.0 MHz, oily mixture of complexes 6b and 8b without solvent): δ +65.1 (s, W1/2 = 1200 Hz). We failed to obtain other physicochemical data due to the high instability of the complex and its very easy hydrolyzation in air. Complex [(CH2)2C(CO2Me)2]2GaBr2+·[GaBr4]− (8b). 1H NMR (400.1 MHz, oily mixture of complexes 6b and 8b without solvent): δ 3.5−6.3 (br m, CH2 + OCH3). 71Ga NMR (122.0 MHz, oily mixture of complexes 6b and 8b without solvent): δ +68.7 (s, 2Ga, GaBr2+ and GaBr4−, W1/2 = 2400 Hz). We failed to obtain other physicochemical data due to the high instability of the complex and its very easy hydrolyzation in air. Mixture of Complexes 6b and 8b (∼1:1). 1H NMR (400.1 MHz, neat): δ 3.2−4.7 (br m, CH2), 4.7−6.3 (br m, OCH3). 13C NMR (100.6 MHz, neat): δ 28.4−39.9 (br m, CH2 and C), 53.2−67.2 (br m, OCH3), 179.1−186.0 (br m, COO). 71Ga NMR (122.0 MHz, neat): δ +65.1 (s, 6b, W1/2 = 1200 Hz), +68.7 (s, 2Ga, GaBr2+ and GaBr4−, 8b, W1/2 = 2400 Hz). We failed to obtain other physicochemical data due to the high instability of the complex and its very easy hydrolyzation in air. Complex [(CH2)2C(CO2Me)2]2GaO2(GaBr2)(GaBr3)2 (9b). The reaction mixture from method A (mixture of complexes 6b and 8b) without preliminary separation was kept at room temperature with partial access of air over 1−2 days. Herewith the gallium complexes were partially hydrolyzed and the oil precipitate crystallized into complex 9b (∼40%) as almost colorless monoclinic crystals. The structure of this complex was established by X-ray diffraction analysis. Complex 9b has low stability and decomposes even under an inert atmosphere over several days. X-ray diffraction data for a single crystal of 9b·CH2Cl2: CCDC 1044998, monoclinic crystals, 100 K, a = 15.6176(13) Å, b = 13.6696(9) Å, c = 17.6101(14) Å, α = 90°, β = 104.382(2)°, γ = 90°, V = 3641.7 Å3, dcalc = 2.465 g cm−3, space group C2/c. Selected bond lengths (Å): Ga(1)−O(1) 1.904; Ga(1)−O(2) 1.992; Ga(1)−O(3) 1.980; Ga(2)−O(1) 1.868; Ga(3)−O(1) 1.831; Ga(2)−Br(1) 2.287; Ga(3)−Br(2) 2.324; Ga(3)−Br(3) 2.314; Ga(3)−Br(4) 2.326; C(1)− O(2) 1.230; C(2)−O(3) 1.234; C(1)−C(5) 1.47; C(2)−C(5) 1.47; C(5)−C(6) 1.56; C(5)−C(7) 1.55; C(6)−C(7) 1.47. Selected angles (deg): Br(2)−Ga(3)−O(1) 106.1; Br(2)−Ga(3)−Br(3) 111.22;

on loading 0.15 mmol of both starting reagents in 0.5 mL of dry CD2Cl2; the necessary NMR experiments were acquired immediately after the synthesis of the complex. 1 H NMR (400.1 MHz, neat): δ 4.3 (s, 2H, CH2, W1/2 = 480 Hz), 6.5 (s, 6H, 2OCH3, W1/2 = 360 Hz). 71Ga NMR (122.0 MHz, neat): δ +66.3 (s, W1/2 = 2600 Hz). We failed to obtain other physicochemical data due to the high instability of the complex. Complex [CH2(CO2Me)2]3Ga3+·[GaBr4]3− (2b). Method A (Synthetic Procedure). Solid GaBr3 (250 mg, 0.81 mmol was added in one portion under an argon atmosphere with stirring to a solution of dimethyl malonate (1; 80 mg, 0.61 mmol) in dry CH2Cl2 (3 mL) at room temperature, and the mixture was stirred at same temperature for 10 s until complete dissolution of gallium bromide. The complex 3b was isolated as a thick heavy oil; after 1 min it started to crystallize as the target complex 2b, and crystallization was complete within 5 min. Complex 2b was obtained as colorless rhombic crystals up to several millimeters in size. These crystals were used for X-ray analysis and establishment of the structure of the complex. Complex 2b is quite stable under an inert atmosphere but is very easily hydrolyzed in air. Method B (NMR Studies). Solid GaBr3 (56 mg, 0.18 mmol) was added in one portion under an argon atmosphere to a solution of dimethyl malonate 1 (24 mg, 0.18 mmol) in dry CD2Cl2 (0.5 mL) at room temperature with vigorous shaking in an NMR tube. The necessary NMR experiments were acquired after the mixing of reagents. Data for complex 2b·CH2Cl2 are as follows. 1H NMR (400.1 MHz, solid state): δ 5.8 (s, W1/2 = 600 Hz). 71Ga NMR (122.0 MHz, solid state): δ +63.9 (s, 3Ga, GaBr4−, W1/2 = 2500 Hz), + 121 (s, 1Ga, Ga3+, W1/2 = 18500 Hz). 81Br NMR (108.0 MHz, solid state): δ −320 (s, 12Br, 3GaBr4−, W1/2 = 19000 Hz). X-ray diffraction data for a single crystal of 2b·CH2Cl2: CCDC 1044995, orthorhombic crystal, 100 K, a = 13.9506(6) Å, b = 15.3484(6) Å, c = 20.9664(10) Å, α = 90°, β = 90°, γ = 90°, V = 4489.31 Å3, dcalc = 2.543 g cm−3, space group P212121. Selected bond lengths (Å): Ga(4)−O(11) 1.93; O(11)−C(12) 1.25; C(11)−C(12) 1.44; C(12)−O(12) 1.39; Ga(1)−Br(11) 2.326. Selected angles (deg): O(11)−Ga(4)−O(13) 91.0; O(11)−Ga(4)−O(21) 177.8; Ga(4)−O(11)−C(12) 125; O(11)−C(12)−C(11) 128; C(12)− C(11)−C(13) 120; O(12)−C(12)−C(11) 113; Br(11)−Ga(1)− Br(12) 111.7. We failed to obtain other physicochemical data due to the very easy hydrolyzation of this complex in air. Complex (CH2)2C(CO2Me)2·GaCl3 (6a). Solid GaCl3 (222 mg, 1.26 mmol) was added in one portion under an argon atmosphere with stirring to a solution of cyclopropane 5 (200 mg, 1.26 mmol) in dry CH2Cl2 (2.5 mL), and the mixture was kept at room temperature for 15 min without stirring. Complex 6a was isolated as a thick heavy oil which was separated by decantation. The complex 6a obtained by this method (420 mg, 99%) is nearly pure according to NMR data. Complex 6a is stable under an inert atmosphere but is easily hydrolyzed in air. Anal. Calcd for C7H10Cl3GaO4: C, 25.16; H, 3.02. Found: C, 24.59; H, 3.07. IR (KBr): ν 3009, 2957, 2855, 1739 br (CO), 1615, 1444, 1364, 1229, 1197, 1132 cm−1. 1H NMR (400.1 MHz, CD2Cl2): δ 2.65 (s, 4H, 2CH2, W1/2 = 75 Hz), 4.1 (s, 6H, 2OCH3, W1/2 = 60 Hz). 71Ga NMR (122.0 MHz, CD2Cl2): δ 252 (s, W1/2 = 2300 Hz). 1H NMR (400.1 MHz, neat): δ 3.7 (s, 4H, 2CH2, W1/2 = 400 Hz), 5.1 (s, 6H, 2OCH3, W1/2 = 400 Hz). 13C NMR (100.6 MHz, neat): δ 30.5 (br s, C), 35.7 (br s, 2CH2), 62.4 (br s, 2OCH3), 183.4 (br s, 2COO). 71Ga NMR (122.0 MHz, neat): δ 252 (s, W1/2 = 2300 Hz). MS (m/z, %): 176 (17, 69Ga35Cl237Cl+ and 71Ga35Cl3+), 158 (3, C7H10O4+), 141 (76, 69 Ga35Cl37Cl+ and 71Ga35Cl2+), 127 (41, C7H10O4 − OMe+), 106 (11, 69 Ga37Cl+ and 71Ga35Cl+), 100 (21, C7H10O4 − CO2Me + H+), 59 (50), 59 (51), 50 (100), 44 (79), 36 (55), 29 (48). Complex [(CH2)2C(CO2Me)2]3Ga3+·[GaCl4]3− (7a). Liquid complex 6a (300 mg, 0.90 mmol) was dried under high vacuum (0.01 mbar) over 2 h for removal of traces of methylene chloride and formed cyclopropanedicarboxylate 5. As a result, the complex 7a (252 mg, 96%) was obtained as a white fluffy powder, easily hydrolyzed in air. Anal. Calcd for C21H30Cl12O12Ga4: C, 21.38; H, 2.54. Found: C, 21.40; H, 2.55. IR (KBr): ν 2958, 1739 br (CO), 1616, 1444, 1363, K


Article

Organometallics Ga(3)−O(1)−Ga(2) 130.0; Ga(3)−O(1)−Ga(1) 133.1; O(1)− Ga(2)−Br(1) 113.0; Br(1)−Ga(2)−Br(1) 118.97; Ga(2)−O(1)− Ga(1) 96.4; O(1)−Ga(1)−O(2) 95.5; O(1)−Ga(1)−O(3) 96.2; O(2)−Ga(1)−O(3) 86.8. We failed to obtain other physicochemical data due to the high instability of the complex and its very easy hydrolyzation in air. Complex [(CH2)2C(CO2Me)2]3Ga3+·[GaBr4]3− (7b). The reaction mixture from method A (mixture of complexes 6b and 8b) without preliminary separation was kept at room temperature under an argon atmosphere without access of moisture traces over 2−3 days. Herewith the oil precipitate crystallized into complex 7b (∼50−60%) as almost colorless tetragonal crystals. The structure of this complex was established by X-ray diffraction analysis. The necessary condition for the formation of complex 7b requires a complete absence of moisture traces. Complex 7b has low stability and decomposes even under an inert atmosphere over several days. X-ray diffraction data for single crystal of 7b: CCDC 1044996, tetragonal crystals, 100 K, a = 25.1557(3) Å, b = 25.1557(3) Å, c = 14.7095(4) Å, α = 90°, β = 90°, γ = 90°, V = 9308.31 Å3, dcalc = 2.444 g cm−3, space group P42/n. Selected bond lengths (Å): Ga(1)−O(11) 1.926; Ga(1)−O(13) 1.938; O(11)−C(11) 1.24; C(11)−C(15) 1.46; C(15)−C(16) 1.55; C(15)−C(17) 1.55; C(16)−C(17) 1.45; Ga(2)− Br(1) 2.306. Selected angles (deg): O(11)−Ga(1)−O(33) 98.7; O(11)−Ga(1)−O(13) 89.3; O(11)−Ga(1)−O(23) 175.9; Ga(1)− O(11)−C(11) 130.4; O(11)−C(11)−C(15) 125.5; Br(1)−Ga(2)− Br(1) 113.12. We failed to obtain other physicochemical data due tothe high instability of the complex and its very easy hydrolyzation in air. Reaction of Dimethyl Cyclopropanedicarboxylate 5 with Ga2Cl4. Solid Ga2Cl4 (267 mg, 0.95 mmol) was added in one portion under an argon atmosphere with stirring to a solution of cyclopropane 5 (200 mg, 1.26 mmol) in dry CH2Cl2 (3 mL) at room temperature, and the reaction mixture was stirred for 15 min until complete dissolution of gallium chloride. As a result the metallic gallium precipitated as a gray powder, which was filtered on a Schott filter under an argon atmosphere. The obtained solution was analyzed by NMR spectroscopy. It contains a mixture of gallium complexes; the main gallium complex is the complex 8a. Attempts to isolate it failed due to its low stability. This solution was left to crystallize at room temperature for several weeks, with partial evaporation of the solvent. After 1 week the complex 9a (∼30−40%) crystallized from the solution as monoclinic colorless crystals with sizes up to 2 mm. Two weeks later upon evaporation of most of the methylene chloride the complex 10 (∼5−10%) crystallized from the solution as small wellfaceted colorless monoclinic crystals. The structures of both complexes were established by X-ray analysis. Complexes 9a and 10 can be separated using fractional crystallization or mechanical separation of the crystals having various shapes. Both complexes very easily and quickly hydrolyzed in air. Complex [(CH2)2C(CO2Me)2]2GaCl2+·[GaCl4]− (8a). 1H NMR (400.1 MHz, CH2Cl2): δ 2.25−2.9 (br m, 4H, 2CH2), 3.6−4.4 (br m, 6H, 2OCH3). 71Ga NMR (122.0 MHz, CH2Cl2): δ +250 (s, 1Ga, GaCl2+, W1/2 = 1600 Hz), + 252 (s, 1Ga, GaCl4−, W1/2 = 4800 Hz). We failed to obtain other physicochemical data due to the low stability of the complex and the impossibility of its isolation in pure form. Complex [(CH2)2C(CO2Me)2]2GaO2(GaCl2)(GaCl3)2 (9a). X-ray diffraction data for single crystal of 9a·CH2Cl2: CCDC 1044997, monoclinic crystals, 100 K, a = 15.1696(4) Å, b = 13.4325(3) Å, c = 17.4348(4) Å, α = 90°, β = 103.5240(10)°, γ = 90°, V = 3454.11 Å3, dcalc = 1.915 g cm−3, space group C2/c. Selected bond lengths (Å): Ga(1)−O(1) 1.897; Ga(1)−O(2) 1.980; Ga(1)−O(3) 1.977; Ga(2)− O(1) 1.860; Ga(3)−O(1) 1.822; Ga(2)−Cl(1) 2.1403; Ga(3)−Cl(2) 2.1737; Ga(3)−Cl(3) 2.1622; Ga(3)−Cl(4) 2.1684; C(1)−O(2) 1.241; C(2)−O(3) 1.230; C(1)−C(5) 1.472; C(2)−C(5) 1.465; C(5)−C(6) 1.555; C(5)−C(7) 1.540; C(6)−C(7) 1.461. Selected angles (deg): Cl(2)−Ga(3)−O(1) 106.21; Cl(2)−Ga(3)−Cl(3) 110.35; Ga(3)−O(1)−Ga(2) 130.87; Ga(3)−O(1)−Ga(1) 132.45; O(1)−Ga(2)−Cl(1) 112.27; Cl(1)−Ga(2)−Cl(1) 117.47; Ga(2)− O(1)−Ga(1) 96.41; O(1)−Ga(1)−O(2) 94.95; O(1)−Ga(1)−O(3) 96.57; O(2)−Ga(1)−O(3) 86.83. We failed to obtain other

physicochemical data due to the low stability of the complex and its easy hydrolyzation in air. Complex {[(CH 2 ) 2 C(CO 2 Me) (CH 2 O)] 4 Ga 2 (OMe) 2 (GaCl 2 ) 2 } 2+ · {GaCl4}2− (10). X-ray diffraction data for a single crystal of 10· 2CH2Cl2: CCDC 1044999, monoclinic crystals, 100 K, a = 10.1397(3) Å, b = 19.5202(8) Å, c = 14.3428(6) Å, α = 90°, β = 91.3460(10)°, γ = 90°, V = 2838.07 Å3, dcalc = 1.863 g cm−3, space group P21/n. Selected bond lengths (Å): Ga(1)−Cl(1) 2.168; Ga(1)−Cl(2) 2.131; Ga(1)− O(1) 1.878; Ga(1)−O(4) 1.881; Ga(2)−O(1) 1.952; Ga(2)−O(4) 1.947; Ga(2)−O(2) 1.976; Ga(2)−O(5) 1.974; Ga(2)−O(7) 1.941; Ga(3)−Cl(3) 2.161; Ga(3)−Cl(4) 2.155; Ga(3)−Cl(5) 2.166; Ga(3)−Cl(6) 2.226; O(1)−C(1) 1.446; O(2)−C(2) 1.25; C(1)− C(4) 1.50; C(2)−C(4) 1.46; C(4)−C(5) 1.52; C(4)−C(6) 1.53; C(5)−C(6) 1.47. Selected angles (deg): Cl(1)−Ga(1)−Cl(2) 114.06; Cl(1)−Ga(1)−O(1) 104.2; O(1)−Ga(1)−O(4) 105.4; Ga(1)− O(1)−Ga(2) 119.0; O(1)−Ga(2)−O(2) 89.6; O(1)−Ga(2)−O(7) 93.9; O(7)−Ga(2)−O(7) 79.3; Ga(2)−O(7)−Ga(2) 100.7; Cl(3)− Ga(3)−Cl(4) 113.8. We failed to obtain other physicochemical data due to the poor stability of the complex and its easy hydrolyzation in air.

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ASSOCIATED CONTENT

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AUTHOR INFORMATION

S Supporting Information *

Copies of , and a text file of all computed molecule Cartesian coordinates in a format for convenient visualization of complexes 2a, 2b, 7b, 9a, 9b and 10 are listed in Online Supporting Information. The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.organomet.5b00399. NMR spectra for all new compounds and crystallographic data and refinement parameters for all crystal structures (PDF) Crystallographic data for 2a (CIF) Crystallographic data for 2b (CIF) Crystallographic data for 7b (CIF) Crystallographic data for 9a (CIF) Crystallographic data for 9b (CIF) Crystallographic data for 10 (CIF) Computed molecule Cartesian coordinates for 2a (XYZ) Computed molecule Cartesian coordinates for 2b (XYZ) Computed molecule Cartesian coordinates for 7b (XYZ) Computed molecule Cartesian coordinates for 9a (XYZ) Computed molecule Cartesian coordinates for 9b (XYZ) Computed molecule Cartesian coordinates for 10 (XYZ)

Corresponding Author

*Y.V.T.: tel/fax, +7 499 135 6390; e-mail, [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported financially by the Russian Scientific Fund (Grant 14-13-01054). REFERENCES

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