Reactivity of NCN-Chelated (NCN= C6H3-2, 6-(CH2NMe2) 2

Article pubs.acs.org/Organometallics

Reactivity of NCN-Chelated (NCN = C6H3-2,6-(CH2NMe2)2) Antimony(III) and Bismuth(III) Oxides toward Oxides of Arsenic Tomás ̌ Svoboda,† Roman Jambor,† Aleš Růzǐ čka,† Robert Jirásko,‡ Antonín Lyčka,§ Frank De Proft,∥ and Libor Dostál*,† †

Department of General and Inorganic Chemistry and ‡Department of Analytical Chemistry, Faculty of Chemical Technology, University of Pardubice, Studentská 573, Pardubice 53210, Czech Republic § Research Institute for Organic Syntheses, Rybitví 296, CZ-533 54 Pardubice, Czech Republic ∥ Eenheid Algemene Chemie (ALGC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050 Brussels, Belgium S Supporting Information *

ABSTRACT: Organoantimony(III) and organobismuth(III) oxides (LMO) 2 (where L is the NCN-chelating ligand C 6 H 3 -2,6(CH2NMe2)2 and M = Sb (1), Bi (2)) reacted smoothly with arsenic oxides As2O5 and As2O3 to form the molecular oxides [(LM)3(AsO4)2] and [(LM)2(As2O5)] (where M = Sb (3, 5), Bi (4, 6)). All compounds were characterized by electrospray ionization (ESI) mass spectrometry, nuclear magnetic resonance (NMR) spectroscopy, and, in the case of 5 and 6, single-crystal X-ray diffraction (XRD) analyses. Compound 3 formed two conformational isomers in a benzene or chloroform solution, as confirmed by 1H and 13C NMR spectroscopy. As in the case of 3, 5 also formed conformational isomers in a benzene solution, whereas the bismuth analogue 6 was unstable in solution. The stabilities of the three possible conformers of 5 were studied by density functional theory (DFT) calculations.

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known, and their structures have been established by singlecrystal X-ray diffraction (XRD) analyses, but these examples include only organic derivatives of arsenic acids such as arsinates.6 However, to the best of our knowledge, related organometallic antimony or bismuth complexes with inorganic oxides of arsenic (i.e., complexes containing purely inorganic AsMO cores) are unknown. As a part of our ongoing interest in the chemistry of main-group organometallic oxides, we report here a study dealing with reactions of intramolecularly coordinated oxides 1 and 2 with As2O5 and As2O3. Our aim in this study is the preparation of well-defined mixed Sb/As and Bi/As oxido compounds.7 We found that the treatment of 1 and 2 with an appropriate amount of As2O5 in a tetrahydrofuran (THF) solution yielded the desired compounds [(LM)3(AsO4)2] (where M = Sb (3), Bi (4)) as white solids in good yields (Scheme 1). The identities of both compounds were confirmed by elemental analysis and ESI mass spectrometry (Figure S1, Supporting Information). The molecular structure of 4 could not be determined by the single-crystal XRD technique; further, in the case of 3, the result of the crystal structure determination revealed only a disordered structure (Figure S2). The 1H NMR spectrum of 3

he chemistry of heterobimetallic oxides is currently being extensively studied, not only because of their interesting or unique structural features, but also with regard to their potential uses in catalysis or material sciences. Syntheses of well-defined and soluble heterobimetallic oxides often require the presence of various ancillary ligands. Among these ligands, β-diketiminate ligands hold a special position and have been shown to be useful cadidates in the preparation of a wide range of heterobimetallic oxides that combine both transition metals and main-group elements.1 In such compounds, the central atom is held in the ligand’s cavity by the effective interaction of the central atom with two nitrogen atoms, and it is further shielded by pendant bulky aryl substituents. The potential of formally bidentate NC-chelating ligands to stabilize various mixed main-group-element compounds has also been demonstrated as well.2 In an extension of this approach, but now using tridentate NCN ligands instead of bidentate NC ligands, we recently reported on the syntheses of molecular organoantimony3 and organobismuth4 oxides (LMO)2 (where M = Sb (1), Bi (2) and L = C6H3-2,6-(CH2NMe2)2), in which the central M2O2 ring is stabilized by the help of two pincer-type ligands and the central atoms are tightly bound by the NCN donor sets. It hence has been demonstrated that these oxides may be used as precursors for the preparation of mixed phosphorus−antimony (bismuth)−oxido compounds.5 Analogous heavier congeners, i.e., organometallic compounds containing an As−O−M linkage (where M = Sb, Bi) are © 2012 American Chemical Society

Received: October 24, 2011 Published: February 16, 2012 1725

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spectrometry. The molecular structures of both compounds were unambiguously determined with the help of single-crystal XRD (Figure 1A,B). The molecular structures of 5 and 6 are closely related and are therefore described together. A unit of As2O3 was incorporated into the dimeric structures of starting oxides 1 and 2, resulting in the observed central M2As2O5 cores (where M = Sb, Bi). The As−O bonding distances varied between 1.738(3) and 1.804(2) Å for 5 and between 1.733(6) and 1.818(7) Å for 6, values that approximated the covalent radius sum ∑cov(As,O) of 1.84 Å.9 The observed range of values for the Sb−O bond distances (2.019(2)−2.049(2) Å) and for the Bi−O bond distances (2.136(7)−2.183(6) Å) similarly approximated the covalent radius sums ∑cov(Sb,O) and ∑cov(Bi,O) of 2.02 and 2.14 Å,9 respectively. The central antimony (5) and bismuth (6) atoms were connected via two nearly equivalent O−As−O bridges (bonding angles of 98.08(10) and 102.67(12)° for 5 and 98.0(3) and 102.2(3)° for 6), and the arsenic atoms As1 and As2 were connected by an additional oxygen bridge (As−O−As bonding angle of 123.95(11)° for 5 and 126.4(3)° for 6). This additional bridge divided the central girdle into two six-membered rings MAs2O3 (Figure 1C). Interestingly, whereas one of these rings adopted a chairlike conformation, the second ring adopted a boatlike structure. These different conformations are most probably the best variants possible as a result of the minimization of the steric repulsion between the lone pairs of electrons of the central atoms and between both pincer ligands. The ligands (L) are therefore mutually oriented with a head-to-tail disposition (where the head corresponds to the ligand arms and the tail corresponds to the phenyl ring of L (Figure 1C); for the possible formation of other conformers see further discussion below and Figure 2). The Sb−N interatomic distances in 5 (range 2.638(4)−2.694(3) Å) and Bi−N in 6 (range 2.680(8)− 2.781(7) Å) indicate the presence of intramolecular N→M interactions, and the N−Sb−N and N−Bi−N bonding angles, ranging from 117.78(9) to 119.27(9)° in 5 and 6, establish the cis coordination of donor nitrogen atoms. As a result of these additional interactions, the coordination polyhedron around each of the central antimony and bismuth atoms may be described as a strongly distorted tetragonal pyramid with the ipso carbon atom of the ligand L in an apical position and the basal plane formed by two nitrogen and two oxygen atoms (Figure 1). On the basis of the molecular structure of 5, the existence of three different conformers seems to be possible, and these isomers can be formed by a simple flipping of the pincer ligands in the molecular structure of 5 (Figure 2). Of these three isomers, the head-to-tail isomer is as determined in the solid state (Figures 1 and 2A). A second possible isomer is a head-tohead conformer, in which both phenyl rings of the ligands are oriented outside the central inorganic core (Figure 2B). The third isomer would then contain both phenyl rings of the ligands directed into the central core of the compound, as illustrated in Figure 2C. The 1H NMR spectrum of 5 is relatively complex and is built up of two sets of signals (Figure S5).10 In one set, the observation of two AX patterns for the NCH2 groups and two signals for the N(CH3)2 groups, together with two sets of aromatic signals in a measured approximate mutual integral ratio of 1:1, indicates the presence of two nonequivalently bonded pincer ligands in the structure. This finding is consistent with the head-to-tail isomer as determined in the solid state (Figures 1 and 2A) in which the two ligands are

Scheme 1

exhibits two sets of signals, suggesting the possible formation of two conformational isomers in solution, similar to those for the recently reported phosphate [(LSb)3(PO4)2] (Figure S3).5c One set of signals consists of a sharp AX pattern from the CH2N groups and corresponds to the propeller-like symmetric structure 3-sym, in which all three ligands (L) are equivalent (Figure S3). The other set consists of three AX patterns, corresponding to three nonequivalent CH2N groups in a mutual 1:1:1 integral ratio, thus indicating the presence of the less symmetrical compound 3-asym (Figure S3). The ratio of these two isomers is strongly solvent dependent: the use of CDCl3 and C6D6 resulted in 3-sym:3-asym ratios of 1:1.65 and 1:0.3, respectively, as determined by the integration of the 1H NMR spectra. A similar result has been reported for conformers of [(LSb)3(PO4)2],5c for which the ratios 1:0.91 and 1:0.2 were observed in CDCl3 and C6D6, respectively. When these values are compared, the preference for the asymmetric isomer in the case of 3 is evident. This preference could be ascribed to the presence of the larger arsenic atom in the axial bridging position, which might be favorable for accommodation of the three ligands in an asymmetric conformation. Similar results and conclusions, supported by theoretical considerations, have been reported for group 15 cryptands; these also reflect a dependence of conformational isomer ratios on the bridging atom used.8 The variabletemperature 1H NMR spectra of 3 suggest that formation of both isomers in solution is a dynamic process. Thus, heating of the sample to 330 K in CDCl3 or C6D6 resulted in a strong broadening of all signals, and although no coalescence was observed due to the temperature limits of the respective solvents, it is highly probable that a rapid exchange between both conformers will take place at higher temperatures. Similar results were obtained in the case of 5 (vide infra). The 1H NMR spectrum of 4 in C6D6 revealed only one AX pattern for the CH2N groups and two broader signals for the NMe2 groups (Figure S4); only one set of signals was obtained in the corresponding 13C NMR spectrum of 4. These observations indicate that no conformers were formed in benzene solutions of 4 at ambient temperature, as had been similarly concluded for the phosphorus congener [(LBi)3(PO4)2].5c The reaction of 1 or 2 in a THF solution with an appropriate amount of As2O3 led to the formation of the compounds [(LSb)2(As2O5)] (5) and [(LBi)2(As2O5)] (6) as white solids in good yields (Scheme 1). The identity of both compounds was confirmed by elemental analysis and electrospray mass 1726

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Figure 1. continued 118.2(3), As(2)−O(2)−Bi(1) = 135.1(4), As(2)−O(4)−Bi(2) = 125.7(3), O(1)−Bi(1)−O(2) = 87.9(3), O(3)−Bi(2)−O(4) = 82.2(2), N(1)−Bi(1)−N(2) = 118.0(2), N(3)−Sb(2)−N(4) = 118.1(2).

situated in nonequivalent positions. In addition, there is a second set of signals, consisting of one AX pattern for the NCH2 groups and one signal for the N(CH3)2 moieties (integral intensity of 0.24 in comparison with the first set of signals). This observation indicates the presence of a symmetrical conformer with identically bonded pincer ligands. It is possible to tentatively assign this set of signals to the symmetrical head-to-head isomer (Figure 2B); in this case, a massive steric repulsion among the phenyl rings and the ligand arms would tend to exclude the third conformer, which is illustrated in Figure 2C. Furthermore, this third structure would give rise to two sets of signals for two nonequivalent ligands in the 1H NMR spectrum, similar to the signals observed for the head-to-tail isomer, contrary to observation. Similarly, two sets of signals, ascribable to the head-to-tail and head-to-head isomers, are observed in the 13C NMR spectrum of 5 (Figure S8). This presumption of the formation of two conformers was verified by density functional theory (DFT) studies (vide infra). All these observations therefore point to the formation of conformational isomers in a solution of 5, similar to those observed for 3 (vide supra) and its phosphorus analogue [(LSb)3(PO4)2].5c Furthermore, the molecular phosphite [(LSb)2(P(O)2(H)(O))2],5b which contains a Sb2O4P2 central ring system similar to that of Sb2O4As2 in 5, has been reported to exist formally as a head-to-head isomer in the solid state, providing a precedent for the formation of the various isomers in this type of system. For 5, a mutual exchange between the two conformers exists as a reversible process, as evidenced by variable-temperature 1H NMR studies (Figure S6). Thus, heating of a sample in CDCl3 to 330 K resulted in the observation of only one set of broadened signals, indicating rapid fluxional behavior of 5 at this temperature. Unfortunately, similar solution studies on 6 were hampered in part by the low solubility of 6 after isolation and the instability of 6 in CDCl3, in which it decomposes to other undefined products. The 1H NMR spectra obtained for 6 were rather complicated and broad, and so the NMR results for 6 were inconclusive. DFT geometry optimizations were performed in order to gain better insight into the formation of possible conformational isomers of 5. In the first step, 5 was optimized starting from the crystallographically determined molecular structure (Figure 2A). Overall good agreement of the computed geometrical parameters with the experimental values was found, as can be seen by comparing the computed selected geometrical parameters with the selected experimental ones in Figure 1. Next, two different conformers of 5 were constructed (Figure 2B,C), followed by a subsequent geometry optimization. In the case of the third conformer (Figure 2C) geometry optimization resulted in a reorientation of the ligands to give the head-to-tail conformer of 5 (Figure 2A), as observed in the solid state, confirming that this third conformer was most probably not present experimentally. In contrast, in the case of the head-to-head isomer of 5 (Figure 2B), the optimization of the geometry (also given in the Supporting Information) confirmed this second equilibrium structure (Figure 2B), with an energy of only 11.7 kcal mol−1 above that of the head-to-tail

Figure 1. ORTEP plots of compounds 5 (A) and 6 (B) showing 50% probability displacement ellipsoids and the atom-numbering scheme (hydrogen atoms and the dichloromethane solvent molecule for both compounds are omitted for clarity) and a view of the central core of 5 and 6 (C). Selected bond lengths (Å) and angles (deg) (computed values for compound 5 are given in parentheses): 5, As(1)−O(1) = 1.748(2) (1.764), As(1)−O(3) = 1.791(2) (1.803), As(1)−O(4) = 1.743(2) (1.783), As(2)−O(2) = 1.739(2) (1.764), As(2)−O(3) = 1.804(2) (1.803), As(2)−O(5) = 1.738(3) (1.783), Sb(1)−O(1) = 2.049(2) (2.059), Sb(1)−O(2) = 2.041(2) (2.059), Sb(1)−N(1) = 2.638(4) (2.701), Sb(1)−N(2) = 2.694(3) (2.701), Sb(1)−C(1) = 2.153(4) (2.178), Sb(2)−O(4) = 2.019(2) (2.037), Sb(2)−O(5) = 2.030(2) (2.037), Sb(2)−N(3) = 2.667(3) (2.725), Sb(2)−N(4) = 2.645(3) (2.725), Sb(2)−C(13) = 2.151(3) (2.181), O(1)−As(1)− O(4) = 98.09(10) (99.1), O(2)−As(2)−O(5) = 102.67(12) (99.1), As(1)−O(3)−As(2) = 123.95(11) (128.2), As(1)−O(1)−Sb(1) = 122.05(11) (128.6), As(1)−O(4)−Sb(2) = 136.98(11) (138.5), As(2)−O(2)−Sb(1) = 130.46(13) (128.6), As(2)−O(5)−Sb(2) = 137.10(19) (138.4), O(1)−Sb(1)−O(2) = 84.65(10) (86.7), O(4)− Sb(2)−O(5) = 88.06(11) (90.3), N(1)−Sb(1)−N(2) = 117.78(9) (119.0), N(3)−Sb(2)−N(4) = 119.27(9) (117.7); 6, As(1)−O(1) = 1.750(6), As(1)−O(3) = 1.733(6), As(1)−O(5) = 1.789(6), As(2)− O(2) = 1.738(8), As(2)−O(4) = 1.734(6), As(2)−O(5) = 1.818(7), Bi(1)−O(1) = 2.136(7), Bi(1)−O(2) = 2.145(2), Bi(1)−N(1) = 2.751(7), Bi(1)−N(2) = 2.680(8), Bi(1)−C(1) = 2.232(8), Bi(2)− O(3) = 2.183(6), Bi(2)−O(4) = 2.161(6), Bi(2)−N(3) = 2.690(9), Bi(2)−N(4) = 2.740(8), Bi(2)−C(13) = 2.225(9), O(1)−As(1)− O(3) = 98.0(3), O(2)−As(2)−O(4) = 102.2(3), As(1)−O(5)−As(2) = 126.4(3), As(1)−O(1)−Bi(1) = 134.5(3), As(1)−O(3)−Bi(2) = 1727

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Figure 2. Representation of possible conformers of 5. (CH3)2N), 2.90 (very broad signals of (CH3)2N), 2.67 and 5.13 (AX pattern, prochiral CH2N), 6.77 (m, Ar-H-3−5). 1H NMR (C6D6, 400.13 MHz): minor isomer (3-asym) δ 1.40 (very broad signals of (CH3)2N), 2.90 (very broad signals of (CH3)2N), 2.43 and 4.36, 2.61 and 4.80, 2.90, and 5.26 (three AX pattern, three prochiral CH2N,), 6.77 (m, Ar-H-3−5). 1H NMR (CDCl3, 400.13 MHz): δ minor isomer (3-sym) 1.92 (very broad signals of (CH3)2N), 2.49 (very broad signals of (CH3)2N), 2.83 and 4.73 (AX pattern, prochiral CH2N), 6.80−7.27 (m, Ar-H-3−5). 1H NMR (CDCl3, 400.13 MHz): major isomer (3asym) δ 1.92 (very broad signals of (CH3)2N), 2.49 (very broad signals of (CH3)2N), 2.41 and 3.85, 2.55 and 4.12, 2.92, and 4.93 (three AX pattern, three prochiral CH2N), 6.80−7.27 (m, Ar-H-3−5). 13C NMR (CDCl3, 100.63 MHz): minor isomer (3-sym) δ 42.4 and 45.6 (broad s, (CH3)2N), 63.8 (s, CH2N), 125.9 (s, Ar-C-3,5), 128.9 (Ar-C-4), 148.7 (s, Ar-C-2,6), 157.7 (s, Ar-C-1). 13C NMR (CDCl3, 100.63 MHz): major isomer (3-asym) δ 42.4 and 45.6 (broad s, (CH3)2N), 63.3, 63.4, 63.7 (three s, CH2N), 126.0, 126.2, 126.3, (three s, Ar-C3,5), 128.2 128.5, 128.8 (three s, Ar-C-4), 147.9, 148.0, 148.1 (three s, Ar-C-2,6), 157.3, 157.5, 158.3 (three s, Ar-C-1). Synthesis of Compound 4. The procedure was analogous to that described for 3 above. The reaction in THF (20 mL) of compound 2 (0.45 g, 0.54 mmol) with As2O5 (0.124 g, 0.54 mmol) gave compound 4 (yield 0.54 g, 94%). For 4: mp 255 °C dec. Anal. Calcd for C36H57As2O8N6Bi3: C, 29.2; H, 3.9. Found: C, 29.1; H, 4.1. Positiveion ESI-MS: m/z 1517 [M + K]+; m/z 1501 [M + Na]+; m/z 1481 [M + H + H2]+; m/z 1355 [(LBiO)3AsO2]+; m/z 939 [(LBiO)2AsO2]+, 100%. MS/MS of 1481: m/z 939 [(LBiO)2AsO2]+. 1H NMR (C6D6, 400.13 MHz): δ 1.35 (broad s, 6H, N(CH3)2), 3.06 (broad s, 6H, N(CH3)2), 2.95 and 5.27 (AX pattern, 4H, prochiral CH2N), 6.87 (t, 1H, Ar-H-4), 7.15 (d, 2H, Ar-H-3,5). 13C NMR (C6D6, 100.63 MHz) δ 42.2 (broad s, N(CH3)2), 47.5 (broad s, N(CH3)2), 67.0 (s, CH2N), 128.6 (s, Ar-C-3,5), 128.7 (s, Ar-C-4), 154.6 (s, Ar-C-2,6), 217.8 (s, ArC-1). Synthesis of Compound 5. The procedure was analogous to that described for 3 above. The reaction in THF (10 mL) of compound 1 (0.82 g, 1.24 mmol) with As2O3 (0.25 g, 1.24 mmol) gave compound 5 (yield 0.96 g, 90%). For 5: mp 277−279 °C dec. Anal. Calcd for C24H38As2O5N4Sb2: C, 33.7; H, 4.5. Found: C, 33.9; H, 4.7. Positiveion ESI-MS: m/z 893 [M + K]+; m/z 877 [M + Na]+; m/z 855 [M + H]+; m/z 747 [(LSbO)2AsO]+, 100%; m/z 329 [LSbOH]+. MS/MS of 855: m/z 747 [(LSbO)2AsO]+; m/z 329 [LSbOH]+. All masses are related to the 121Sb isotope. 1H NMR (CDCl3, 400.13 MHz): for both isomers of 5 δ 1.91, 2.19, and 2.24 (s, (CH3)2N), 2.98 and 4.72, 2.79

conformer of 5 (Figure 2A). This DFT work clearly proved the possibility of formation of these two conformers (Figures 2A,B) in a solution of 5. In conclusion, we have demonstrated the versatility of intramolecularly bonded antimony and bismuth oxides 1 and 2 for the preparation of molecular heterobimetallic As−Sb and As−Bi oxides. Each of the antimony−arsenic oxides 3 and 5 forms two conformers in solution via simple flipping of the pincer ligands, as shown by NMR spectroscopy and DFT studies.

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EXPERIMENTAL SECTION

General Procedures. The 1H and 13C NMR spectra were recorded on a Bruker 400 spectrometer, using a 5 mm tunable broad-band probe. Appropriate chemical shifts in the 1H and 13C NMR spectra were related to the residual signals of the solvents (CDCl3, δ(1H) 7.27 ppm and δ(13C) 77.23 ppm; C6D6, δ(1H) 7.16 ppm and δ(13C) 128.39 ppm). Positive-ion electrospray ionization (ESI) mass spectra were measured on an Esquire 3000 ion trap analyzer (Bruker Daltonics, Bremen, Germany) in the range m/z 50− 1600. Samples were dissolved in acetonitrile and analyzed by direct infusion at a flow rate of 5 μL/min. The ion-source temperature was 300 °C, the tuning parameter compound stability was 100%, and the flow rate and the pressure of nitrogen were 4 L/min and 10 psi, respectively. Starting compounds 1 and 2 were prepared according to literature procedures.3,4 As2O3 and As2O5 were obtained from commercial suppliers and used as delivered. Synthesis of Compound 3. A solution of 1 (0.65 g, 0.99 mmol) in THF (20 mL) was added to a stirred suspension of As2O5 (0.23 g, 0.99 mmol) in THF (10 mL) at room temperature. The reaction mixture turned into a clear solution within 12 h. The volume of the solution was reduced to ca. 5 mL under vacuum, and addition of pentane (15 mL) to this solution resulted in precipitation of a white powder, which was collected by filtration and washed with an additional 10 mL of pentane. The white powder was dried in vacuo and characterized as 3 (yield 0.84 g, 95%). For 3: mp >300 °C. Anal. Calcd for C36H57As2O8N6Sb3: C, 35.5; H, 4.7. Found: C, 35.7; H, 5.0. Positive-ion ESI-MS: m/z 1215 [M + H] + ; m/z 1091 [(LSbO)3AsO2]+, 100%; m/z 763 [(LSbO)2AsO2]+. MS/MS of 1215: m/z 763 [(LSbO)2AsO2]+ (see Figure S1). 1H NMR (C6D6, 400.13 MHz): major isomer (3-sym) δ 1.40 (very broad signals of 1728

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Organometallics

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(b) Mandal, S. K.; Roesky, H. W. Acc. Chem. Res. 2010, 43, 248. (c) Roesky, H. W. Z. Anorg. Allg. Chem. 2010, 636, 2192. (2) For example see: (a) Beckmann, J.; Jurkschat, K. Coord. Chem. Rev. 2001, 215, 267. (b) Beckmann, J.; Jurkschat, K.; Pieper, N.; Schurmann, M. Chem. Commun. 1999, 1095. (3) Dostál, L.; Jambor, R.; Růzǐ čka, A.; Erben, M.; Jirásko, R.; Č ernošková, Z.; Holeček, J. Organometallics 2009, 28, 2633. (4) Fridrichová, A.; Svoboda, T.; Jambor, R.; Padělková, Z.; Růzǐ čka, A.; Erben, M.; Jirásko, R.; Dostál, L. Organometallics 2009, 28, 5522. (5) (a) Svoboda, T.; Jambor, R.; Růzǐ čka, A.; Padělková, Z.; Erben, M.; Jirásko, R.; Dostál, L. Eur. J. Inorg. Chem. 2010, 1663. (b) Svoboda, T.; Jambor, R.; Růzǐ čka, A.; Padělková, Z.; Erben, M.; Dostál, L. Eur. J. Inorg. Chem. 2010, 5222. (c) Svoboda, T.; Dostál, L.; Jambor, R.; Růzǐ čka, A.; Jirásko, R.; Lyčka, A. Inorg. Chem. 2011, 50, 6411. (6) (a) Gibbons, M. N.; Sowerby, D. B. J. Chem. Soc., Dalton Trans. 1997, 2785. (b) Amburose, C. V.; Singh, A. K.; Jha, N. K.; Sharma, P.; Cabrera, A.; Espinoza-Perez, G. J. Organomet. Chem. 1999, 572, 87. (7) The reactions between oxides 1 and 2 and corresponding heavier group 15 oxides Sb2O3 and Bi2O3 were attempted under similar conditions, but no reaction was observed; forcing reaction conditions resulted in the destruction of the organometallic part of the compounds or elimination of free ligand L. (8) (a) Cangelosi, V. M.; Zakharov, L. N.; Johnson, D. W. Angew. Chem., Int. Ed. 2010, 49, 1248. (b) Cangelosi, V. M.; Carter, T. G.; Crossland, J. L.; Zakharov, L. N.; Johnson, D. W. Inorg. Chem. 2010, 49, 1248. (9) (a) Pyykkö, P.; Atsumi, M. Chem. Eur. J. 2009, 15, 186. (b) Pyykkö , P.; Atsumi, M. Chem.Eur. J. 2009, 15, 12770. (c) Pyykkö, P.; Riedel, S.; Patzschke, M. Chem. Eur. J. 2005, 11, 3511. (10) The 1H NMR spectra are identical regardless of whether single crystals or the isolated powder bulk sample was used for analysis. The 1 H NMR spectrum is also concentration independent. (11) Zhao, Y.; Truhlar, D. G. Theor. Chem. Acc. 2008, 120, 215. (12) Hydrogen and first row: Kendall, R. A.; Dunning, T. H.; Harrison, R. J. J. Chem. Phys. 1992, 96, 6796. Second row: Woon, D. E.; Dunning, T. H. J. Chem. Phys. 1993, 98, 1358. Third row: Wilson, A. K.; Woon, D. E.; Peterson, K. A.; Dunning, T. H. Jr. J. Chem. Phys. 1999, 110, 7667. (13) Peterson, K. A. J. Chem. Phys. 2003, 119, 11099. (14) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J. A., Jr.; Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam, N. J.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, Ö .; Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J. Gaussian 09, Revision B.01; Gaussian, Inc., Wallingford, CT, 2009.

and 4.57, 2.93, and 4.75 (three AX pattern, three prochiral CH2N), 6.93, 6.99, 7.09 (dd, Ar-H-3−5), 7.06, 7.14, 7.15 (dd, Ar-H-4). 13C NMR (CDCl3, 100.63 MHz): both isomers of 5 δ 43.9 (broad s, N(CH3)2), 63.5, 63.6, 64.0 (s, CH2N) 125.4, 125.9, 126.3 (s, Ar-C3,5), 128.1, 128.2, 128.6 (s, Ar-C-4), 147.8, 148.1, 148.3 (s, Ar-C-2,6), 156.2, 157.1, 157.4 (s, Ar-C-1). Synthesis of Compound 6. The procedure was analogous to that described for 3 above. The reaction in THF (10 mL) of compound 2 (0.74 g, 0.89 mmol) with As2O3 (0.18 g, 0.89 mmol) gave compound 6 (yield 0.8 g, 87%). For 6: mp 235−237 °C dec. Anal. Calcd for C24H38As2O5N4Bi2: C, 28.0; H, 3.7. Found: C, 28.1; H, 3.9. Positiveion ESI-MS: m/z 1339 [(LBiO)3AsO]+; m/z 1121 [(LBiO)2AsO + As2O3]+; m/z 1031 [M + H]+; m/z 923 [(LBiO)2AsO]+, 100%. MS/ MS of 1031: m/z 923 [(LBiO)2AsO]+; m/z 417 [LBiOH]+. Crystallographic Data. Data for 5: C24H38As2N4O5Sb2·CH2Cl2, Mr = 940.85, triclinic, P1̅, colorless plate, a = 10.2410(8) Å, b = 10.3480(6) Å, c = 18.2559(9) Å, α = 88.854(5)°, β = 88.549(6)°, γ = 62.660(5)°, V = 1717.9(2) Å3, Z = 2, T = 150(1) K, 36 813 total reflections, 7827 independent reflections (Rint = 0.051), R1 (obsd data) = 0.034, wR2 (all data) = 0.056, CCDC 833631. Data for 6: C24H38As2N4O5Bi2·CH2Cl2, Mr = 1115.31, triclinic, P1̅, colorless block, a = 10.2801(6) Å, b = 10.3930(4) Å, c = 18.4839(14) Å, α = 89.888(5)°, β = 88.760(6)°, γ = 61.948(4)°, V = 1742.35(18) Å3, Z = 2, T = 150(1) K, 33 621 total reflections, 7907 independent reflections (Rint = 0.057), R1 (obsd data) = 0.042, wR2 (all data) = 0.096, CCDC 833632. Computations. All structures were optimized at the MO6-2X11/ cc-pVDZ12 level of theory (cc-pVDZ-PP13 on Sb), which uses a ccpVDZ like basis set for the valence region, together with a small-core relativistic pseudopotential; the Cartesian coordinates of the resulting gas-phase optimized geometries can be found in the Supporting Information. All computations were performed using the Gaussian 09 program.14

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ASSOCIATED CONTENT

S Supporting Information *

Figures, tables, and CIF files giving the central core of the molecular structure of compound 3, MS and NMR spectra of the compounds studied, all crystal data and structure refinement details, atomic coordinates, anisotropic displacement parameters, and geometric data for compounds 5 and 6, together with details of the calculated conformers of 5. This material is available free of charge via the Internet at http:// pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Fax: +420 466037068. Tel: +420 466037163. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We thank the Grant Agency of the Czech Republic (project P106/10/0443) and the Ministry of Education of the Czech Republic (project MSM0021627501) for financial support. R.J. acknowledges the support of grant project No. MSM0021627502 sponsored by the Ministry of Education, Youth and Sports of the Czech Republic. F.D.P. wishes to acknowledge the Research Foundation-Flanders (FWO) and the Vrije Universiteit Brussel (VUB) for continuous support to this research group.

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REFERENCES

(1) For reviews in the field see: (a) Sarish, S. P.; Nembenna, S.; Nagendran, S.; Roesky, H. W. Acc. Chem. Res. 2011, 44, 157. 1729

dx.doi.org/10.1021/om201025d | Organometallics 2012, 31, 1725−1729