Organic Amides as Suitable Precursors to Stabilize Stannylenes

Article pubs.acs.org/Organometallics

Organic Amides as Suitable Precursors to Stabilize Stannylenes Lucía Á lvarez-Rodríguez, Javier A. Cabeza,* Pablo García-Á lvarez,* and Diego Polo Departamento de Química Orgánica e Inorgánica-IUQOEM, Universidad de Oviedo-CSIC, E-33071 Oviedo, Spain S Supporting Information *

ABSTRACT: This contribution demonstrates that deprotonated amides (amidates) can be used to stabilize stannylenes. Thus, the dimeric stannylene [Sn2{μ-tBuNC(O)tBu}2Cl2] (1) was obtained by treating Li{tBuNC(O)tBu} with 1 equiv of SnCl2. Chloride exchange reactions of 1 with Li{tBuNC(O)tBu} and Li(HMDS) (HMDS = N(SiMe3)2) lowered aggregation, affording the monomeric tetra- and tricoordinated tin(II) derivatives [Sn{tBuNC(O)tBu}2] (2) and [Sn{tBuNC(O)tBu}(HMDS)] (3), respectively. Alternatively, 3 can be prepared by direct deprotonation of the amide with Sn(HMDS)2. Compounds 1−3 are stannylenes that contain an unprecedented SnNCO four-membered ring.

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INTRODUCTION Heavier carbene analogues [MR2; M = Si, Ge, Sn, or Pb; R = anionic group], also known as group-14 metalenes, are species of fundamental interest in main group chemistry.1,2 They are very reactive molecules that, as a result of their marked dual Lewis acid−base character3 and their versatility (they can easily be electronically and sterically tuned because R can virtually be any anionic group), display a unique and rich derivative chemistry, which is currently being extensively studied.2 A particular family of group-14 metalenes are those of general formula [M(RD)X], where RD is an anionic fragment bearing a donor group (D) that forms an intramolecular donor−acceptor adduct with the metalene atom, thus acting as an anionic chelate, and X is a halogen atom. The chemistry of these species has undergone an exponential growth in the past few years, in comparison with that of the more classical MR2 molecules,4,5 because they are less electrophilic and bulkier (hence, more stable6) than classical MR2 molecules, and can be easily tuned by exchanging the halogen with other anionic group.7 Among the large library of known [M(RD)X] molecules, the most studied ones are those containing an N,N-chelate as the RD fragment (e.g., β-diketiminate, amidinate, or guanidinate), which have been proven useful as ligands for transition-metal complexes, activation of small molecules and inert bonds, insertion into organic and inorganic σ-bonds, addition to unsaturated substrates, participation in redox processes, precursors to other metalenes, etc.2 This rich derivative chemistry is a consequence of their easy preparation and the great variety of modifications allowed by their RD moieties.8 [M(RD)X] molecules equipped with an N,O-chelate as the RD group, [M(N∼O)X], are also known;9−14 however, their derivative chemistry has yet been scarcely developed, the hitherto reported investigations being mostly devoted to the synthesis and characterization of the examples shown in Figure 1. As far as we are aware, among all hitherto known [M(N∼O)X] molecules, those containing four-membered MNCO rings have not yet been reported. © XXXX American Chemical Society

Figure 1. Hitherto known [M(N∼O)X] metalenes (references in parentheses).

In this work, aimed at opening new avenues for the chemistry of group-14 metalenes containing N,O-chelates as RD fragments, we describe the use of simple amides as suitable (they can be easily deprotonated to furnish amidates15) and versatile (they can be easily prepared from different substrates through different routes16) precursors to a new generation of [M(N∼O)X] metalenes in which N∼O = amidate. We chose N-tert-butyl-2,2-dimethylpropionamide as the starting amide because the large volume of its tBu groups might stabilize the target metalene molecules. Received: May 27, 2013

A

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some chlorostannylenes in the solid state.18 Within the amidate backbone, the C−N and C−O bond distances (C1−N1 1.280(7) Å; C1−O1 1.345(7) Å) lie in the range of normal C(sp2)N and C(sp2)−O bonds,19 indicating that the amidate negative charge is mostly localized on the oxygen atom. The tin atoms are in a very distorted trigonal bipyramidal ligand arrangement, with the electron lone pair, the chlorine, and the covalently bonded O atom in equatorial positions (relevant bond angles are given in the caption of Figure 2). This distortion can be attributed to the planar Sn2O2 ring and not to the planarity and rigidity of the N∼O amidate fragments, since the structurally related [Sn2(μ-Me2NCH2CH2O)2Cl2]9c and [Sn2(μ-2-Me2NCH2C6H4O)2Cl2]13a complexes contain more flexible and non planar N∼O fragments chelating the tin atoms. Further chloride exchange reactions of 1 with Li{tBuNC(O)tBu} (A) and Li(HMDS) afforded the mononuclear derivatives [Sn{tBuNC(O)tBu}2] (2) and [Sn{tBuNC(O)tBu)(HMDS)] (3), respectively (Scheme 1). Alternatively, compound 2 was also prepared by treating Li{tBuNC(O)tBu} with 0.5 equiv of SnCl2, while direct deprotonation of the amide with 1 equiv of Sn(HMDS)2 proved to be the best method to prepare 3. However, reacting 2 equiv of the amide with Sn(HMDS)2, even after prolonged reaction times and/or high temperatures, did not lead to compound 2 (a mixture of 3 and Sn(HMDS)2 was always recovered from the reaction solutions). The molecular structure of 2 could not be determined in the solid state. However, taking into account the structures of other homoleptic [Sn(N∼O)2] stannylenes20 and that only one set of signals for both amidate fragments is observed in the 1H and 13 C NMR of 2, its structure in solution is most likely monomeric, being the tin atom N,O-chelated by two symmetry related amidate units. The structure of 3 was determined by XRD (Figure 3). It is a monomeric compound in which the tin atom is placed inside a

RESULTS AND DISCUSSION The lithium amidate Li{tBuNC(O)tBu} (A) was prepared by deprotonating its parent amide with tBuLi in diethyl ether. Further reaction of A with 1 equiv of SnCl2 in the same solvent quantitatively afforded [Sn2{μ-tBuNC(O)tBu}2Cl2] (1) and LiCl (Scheme 1), as evidenced by 1H and 7Li NMR analyses of the crude reaction solution. Scheme 1

Figure 2 shows that 1 is a centrosymmetric dimer in which each tin atom is bonded to the N and O atoms of the amidate

Figure 2. XRD molecular structure of compound 1. Hydrogen atoms have been omitted for clarity. Selected bond lengths (Å) and angles (deg): C1−N1 1.280(7), C1−O1 1.345(7), Sn1−N1 2.281(4), Sn1− O1 2.179(4), Sn1−Cl1 2.436(2), Sn1−O1a 2.524(5), N1−C1−O1 112.2(5), C2−C1−N1 135.2(5), C2−C1−O1 112.5(4), N1−Sn1−O1 58.5(2), N1−Sn1−O1a 126.5(1), N1−Sn1−Cl1 86.5(1), O1−Sn1− Cl1 91.6(1), O1a−Sn1−Cl1 85.5(1), O1−Sn1−O1a 69.0(2), Sn1− O1−Sn1a 111.1(2).

Figure 3. XRD molecular structure of 3. Hydrogen atoms have been omitted for clarity. Selected bond lengths (Å) and angles (deg): C1− N1 1.303(3), C1−O1 1.314(3), Sn1−N1 2.277(2), Sn1−O1 2.177(2), Sn1−N2 2.118(2), N1−C1−O1 112.8(2), C2−C1−N1 133.4(2), C2−C1−O1 113.8(2), N1−Sn1−O1 58.56(6), N1−Sn1−N2 99.56(7), O1−Sn1−N2 97.86(6).

ligand, to the Cl atom, and to the other [Sn{NtBuC(O)tBu}Cl] subunit via an O → Sn dative bond. In the resulting Sn2O2 four-membered planar ring, the lengths of the covalent O−Sn bonds (Sn1−O1 2.179(4) Å) are substantially shorter than those of the dative O → Sn bonds (Sn1−O1a 2.524(5) Å). This feature has also been reported for related [Sn(N∼O)Cl] metalenes, such as [Sn2(μ-Me2NCH2CH2O)2Cl2]9c and [Sn2(μ-2-Me2NCH2C6H4O)2Cl2].13a However, the more classical nonintramoleculary donor-stabilized tin(II) alkoxo complexes [Sn2(μ-OtBu)2X2] (X = Cl,17a,b HMDS,17c OSiPh317d) contain symmetrical alkoxy bridges. Intermolecular Sn···Cl contacts are absent in 1, although they have been observed in

distorted tetrahedron defined by the electron lone pair, the N and O atoms of the amidate ligand, and the N atom of the HMDS group. This distortion is mostly caused by the small bite angle of the amidate ligand, N1−Sn1−O1 58.56(6)°. In the crystal lattice, 3 is packed forming dimers via long intermolecular Sn···O contacts (∼3.11 Å). Although these contacts are shorter than the sum of the van der Waals radii of Sn and O (3.69 Å),21 they are much longer than those observed in 1 or in the dimers [Sn2(μ-Me2NCH2CH2O)2Cl2]9c and [Sn2(μ-2-Me2NCH2C6H4O)2Cl2].13a The bulkiness of the HMDS and amidate groups may be regarded as responsible for the monomeric structure of 3, as the related complex B

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[Sn2(μ-Me2NCH2CH2O)2(HMDS)2],22 which contains a sterically more alleviated 2-(N,N-dimethylamino)ethanolate fragment chelating the tin atom, displays a dimeric structure analogous to that of 1. The amidate C−N and C−O bond distances are ∼0.02 Å longer and ∼0.04 Å shorter, respectively, than those observed in 1, revealing a higher degree of electron delocalization. This can be attributed to the absence of short intermolecular O → Sn contacts in 3. The solution 1H- and 13C-NMR spectra of 1−3 are very similar (specially the 13C data), reflecting that the amidate fragments are little affected by the structural differences of each complex. However, the δ(119Sn) chemical shifts, −281.1 ppm for 1, −147.8 ppm for 2, and 41.8 ppm for 3, are clearly dependent on the environment of the tin atom. It is noteworthy that the complexes of the analogous series [Sn2(μ-2Me 2 NCH 2 C 6H 4 O) 2 Cl 2 ], [Sn(2-Me 2NCH2 C 6 H 4 O) 2 ], and [Sn(2-Me2NCH2C6H4O)2(HMDS)], where the tin atoms are chelated by an aminophenolato ligand, show 119Sn chemical shifts at considerably higher field than those of 1−3 (∼200 ppm),13a which can be attributed to the lower donating capabilities of the amidate fragment.

analysis were obtained from a concentrated toluene solution of 1 kept at −20 °C. Anal. Calcd for C18H36Cl2N2O2Sn2 (620.82): C, 34.82; H, 5.85; N, 4.51. Found: C, 35.02; H, 5.99; N, 4.39. 1H NMR (400.1 MHz, 293 K, C6D6): δ 1.34 (s, 18 H, 2 C(CH3)3), 1.23 (s, 18 H, 2 C(CH3)3). 13C{1H} NMR (100.6 MHz, 298 K, C6D6): δ 180.6 (2 C(O)C(CH3)3), 52.4 (2 C(CH3)3), 40.4 (2 C(CH3)3), 32.4 (2 C(CH3)3), 29.7 (2 C(CH3)3). 119Sn{1H} NMR (149.2 MHz, 298 K, C6D6): δ −281.1. [Sn{tBuNC(O)tBu}2] (2). Method a: tBuLi (2.6 mL, 4.4 mmol, 1.7 M in pentane) was dropwise added to a solution of N-tert-butyl-2,2dimethylpropionamide (630 mg, 4.0 mmol) in diethyl ether (10 mL) at 0 °C. The resulting jellylike colorless suspension was allowed to warm up to room temperature and then stirred for 2 h. The addition of solid SnCl2 (748 mg, 4 mmol) led to a pale yellow suspension that was stirred overnight. Freshly prepared lithium N-tert-butyl-2,2dimethylpropionamidate (4.0 mmol) was added, and the resulting mixture was stirred overnight. The solvent was removed under reduced pressure, and the solid residue was extracted into hexane/ toluene 1:1 (2 × 20 mL) to remove the released LiCl. Solvent removal of the extracts allowed the isolation of 2 as a white solid (1.052 g, 61%). Method b: tBuLi (3.9 mL, 6.6 mmol, 1.7 M in pentane) was dropwise added to a solution of N-tert-butyl-2,2-dimethylpropionamide (945 mg, 6.0 mmol) in diethyl ether (10 mL) at 0 °C. The resulting jellylike colorless suspension was allowed to warm up to room temperature and then stirred for 2 h. Solid SnCl2 (569 mg, 3 mmol) was added to give a pale yellow suspension that was allowed to stir overnight. The solvent was removed under reduced pressure and the solid residue was extracted into hexane/toluene 1:1 (2 × 20 mL) to remove the released LiCl. Solvent removal of the extracts allowed the isolation of 2 as a white solid (0.882 g, 68%). Anal. Calcd for C18H36N2O2Sn (431.20): C, 50.14; H, 8.42; N, 6.50. Found: C, 50.36; H, 8.53; N, 6.37. 1H NMR (400.5 MHz, 293 K, C6D6, ppm): δ 1.38 (s, 18 H, 2 C(CH3)3), 1.27 (s, 18 H, 2 C(CH3)3). 13C{1H} NMR (100.7 MHz, 298 K, C6D6, ppm): δ 180.6 (2 C(O)C(CH3)3), 52.5 (2 C(CH3)3), 40.4 (2 C(CH3)3), 32.3 (2 C(CH3)3), 29.7 (2 C(CH3)3). 119 Sn{1H} NMR (149.2 MHz, 298 K, C6D6, ppm): δ −147.8. [Sn{tBuNC(O)tBu)(HMDS)] (3). Method a: tBuLi (2.6 mL, 4.4 mmol, 1.7 M in pentane) was dropwise added to a solution of N-tertbutyl-2,2-dimethylpropionamide (630 mg, 4.0 mmol) in diethyl ether (10 mL) at 0 °C. The resulting jellylike colorless suspension was allowed to warm up to room temperature and then stirred for 2 h. The addition of solid SnCl2 (748 mg, 4.0 mmol) led to a pale yellow suspension that was allowed to stir overnight. Li(HMDS) (4 mL, 4.0 mmol, 1.0 M in hexanes) was added, and the resulting mixture was stirred overnight. The solvent was removed under reduced pressure and the solid residue was extracted into hexane/toluene 1:1 (2 × 20 mL) to remove the released LiCl. Solvent removal from the extracts allowed the isolation of 3 as a white solid (0.922 g, 53%). Method b: Sn(HMDS)2 (2.8 mL, 2.6 mmol, 0.94 M in toluene) was added to a solution of N-tert-butyl-2,2-dimethylpropionamide (409 mg, 2.6 mmol) in diethyl ether (10 mL) at room temperature. The resulting orange solution was stirred overnight, affording an almost colorless solution. Solvent removal and further vacuum-drying of the resulting solid residue overnight to eliminate the released H(HMDS) allowed the isolation of 3 as a white solid (1.06 g, 94%). Crystals suitable for Xray analysis were obtained from a concentrated toluene solution of 3 kept at −20 °C. Anal. Calcd for C15H36N2OSi2Sn (435.34): C, 41.38; H, 8.34; N, 6.44. Found: C, 41.50; H, 8.52; N, 6.58. 1H NMR (300.1 MHz, 293 K, C6D6, ppm): δ 1.19 (s, 18 H, 2 C(CH3)3), 0.38 (s, 18 H, HMDS). 13C{1H} NMR (75.5 MHz, 298 K, C6D6, ppm): δ 182.5 (C(O)C(CH3)3), 53.0 (C(CH3)3), 41.3 (C(CH3)3), 33.0 (C(CH3)3), 29.1 (C(CH3)3), 6.2 (2 Si(CH3)3, HMDS). 119Sn{1H} NMR (149.2 MHz, 298 K, C6D6, ppm): δ 41.8. X-ray Diffraction Analysis. Crystals of 1 and 3 were analyzed by X-ray diffraction. A selection of crystal, measurement, and refinement data is given in Table 1. Diffraction data were collected on an Oxford Diffraction Xcalibur Onyx Nova single crystal diffractometer. Empirical absorption corrections were applied using XABS224 (for 1) and the SCALE3 ABSPACK algorithm as implemented in CrysAlisPro RED25 (for 3). The structures were solved using the program SIR-97.26

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CONCLUDING REMARKS N-tert-Butyl-2,2-dimethyl-propionamidate has been identified as a good ligand for stabilizing tin(II) derivatives. It has allowed the synthesis of the first group-14 metalenes containing a simple amidate fragment (compounds 1−3), which unprecedentedly have the metal atom involved in a four-membered MNCO ring. Considering (a) the great interest of low-valent heavy maingroup reagents in modern chemistry, (b) the easy preparation and deprotonation or simple amides, and (c) the great variety of electronic and steric modifications allowed by the amide and terminal X groups, these results represent the starting point of a new generation of versatile group-14 metalenes. Currently, we are working to extend this methodology using other amides and other group-14 atoms.

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EXPERIMENTAL SECTION

General Procedures. Solvents were dried over sodium diphenyl ketyl and distilled under argon before use. The reactions were carried out under argon, using Schlenk-vacuum line techniques. N-tert-Butyl2,2-dimethylpropionamide HNtBuC(O)tBu23 and Sn(HMDS)25a,c were prepared following published procedures. All remaining reagents were purchased from commercial sources. All reaction products were vacuum-dried for several hours prior to being weighed and analyzed. NMR spectra were run on Bruker DPX-300 or Bruker AV-400 instruments, using as standards: a residual protic solvent resonance for 1 H [δ(C6HD5) = 7.16 ppm], a solvent resonance for 13C [δ(C6D6) = 128.1 ppm], and an external reference of SnMe4 [δ = 0.0 ppm] in CDCl3 for 119Sn. Microanalyses were obtained from the University of Oviedo Microanalytical Service. [Sn2{μ-NtBuC(O)tBu}2Cl2] (1). tBuLi (2.6 mL, 4.4 mmol, 1.7 M in pentane) was dropwise added to a solution of N-tert-butyl-2,2dimethylpropionamide (630 mg, 4.0 mmol) in diethyl ether (10 mL) at 0 °C. The resulting jellylike colorless suspension was allowed to warm up to room temperature and then stirred for 2 h. Addition of solid SnCl2 (748 mg, 4.0 mmol) led to a pale yellow suspension that was stirred overnight. The solvent was removed under reduced pressure, and the solid residue was extracted into hexane (2 × 10 mL) to remove the accompanying LiCl. Solvent removal allowed the isolation of 1 as a white solid (0.298 g, 24%). The low isolated yield of 1 is due to its low solubility in hexane. Performing the extraction with more polar solvents (such as toluene) did not effectively separate 1 from LiCl (as evidenced by 7Li NMR). Crystals suitable for X-ray C

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the Group-14 Metals. In Metal Amide Chemistry; Wiley-VCH: Weinheim, Germany, 2008; Chapter 9. (2) For recent reviews on the chemistry of MR2 species, see, for example: (a) Blom, B.; Stoelzel, M.; Driess, M. Chem. Eur. J. 2013, 19, 40. (b) Mandal, S. K.; Roesky, H. W. Acc. Chem. Res. 2012, 45, 298. (c) Yao, S.; Xiong, Y.; Driess, M. Organometallics 2011, 30, 1748. (d) Asay, M.; Jones, C.; Driess, M. Chem. Rev. 2011, 111, 354. (e) Kira, M. Chem. Commun. 2010, 46, 2893. (f) Mandal, S. K.; Roesky, H. W. Chem. Commun. 2010, 46, 6016. (g) Mizuhata, Y.; Sasamori, T.; Tokitoh, N. Chem. Rev. 2009, 109, 3479. (h) Nagendran, S.; Roesky, H. W. Organometallics 2008, 27, 457. (3) In their singlet ground state, MR2 molecules are equipped with both a nucleophilic (lone pair of electrons) and electrophilic (vacant p orbital) reactive site at the metalene atom. This dual Lewis acid−base character is markedly higher than that of their carbene relatives. (4) For representative examples of heavier N-heterocyclic carbene analogues, see (a) Schuefler, C. D.; Zuckerman, C. D. J. Am. Chem. Soc. 1974, 96, 7160. (b) Veith, M. Angew. Chem., Int. Ed. 1975, 14, 263. (c) Pfeiffer, J.; Maringgele, W.; Noltemeyer, M.; Meller, A. Chem. Ber. 1989, 122, 245. (d) Herrmann, W. A.; Denk, M.; Behm, J.; Scherer, W.; Klingan, F.-R.; Bock, H.; Solouki, B.; Wagner, M. Angew. Chem., Int. Ed. 1992, 31, 1485. (e) Denk, M.; Lennon, R.; Hayashi, R.; West, R.; Belyakov, A. V.; Verne, H. P.; Haaland, A.; Wagner, M.; Metzler, N. J. Am. Chem. Soc. 1994, 116, 2691. (f) Gans-Eichler, T.; Gudat, D.; Nieger, M. Angew. Chem., Int. Ed. 2002, 41, 1888. (g) Charmant, J. P. H.; Haddow, M. F.; Hahn, F. E.; Heitmann, D.; Fröhlich, R.; Mansell, S. M.; Russell, C. A.; Wass, D. F. Dalton Trans. 2008, 6055. (5) For representative examples of Lappertś type metalenes, see (a) Harris, D. H.; Lappert, M. F. J. Chem. Soc., Chem. Comm. 1974, 895. (b) Davidson, P. J.; Harris, D. H.; Lappert, M. F. J. Chem. Soc., Dalton. Trans. 1976, 2268. (c) Lappert, M. F.; Power, P. P.; Slade, M. J.; Hedberg, L.; Hedberg, K.; Schomaker, V. J. Chem. Soc., Chem. Comm. 1979, 369. (d) Reference 1b. (6) The internal donor−acceptor adduct in [M(RD)X] molecules diminishes the electrophilic character of the metalene atom and provides and a greater steric protection (at least a three-coordinate M atom is formed). (7) See, for example, (a) Reference 2f. (b) Sen, S. S.; Kritzler-Kosch, M. P.; Nagendran, S.; Roesky, H. W.; Beck, T.; Pal, A.; Herbst-Irmer, R. Eur. J. Inorg. Chem. 2010, 5304. (c) Akkari, A.; Byrne, J. J.; Saur, I.; Rima, G.; Gornitzka, H.; Barrau, J. J. Organomet. Chem. 2001, 622, 190. (d) Dias, H. V. R.; Wang, Z. J. Am. Chem. Soc. 1997, 119, 4650. (8) β-Diketiminates and amidinates can be synthesized, for example, by condensation of β-diketones with amines followed by deprotonation and by addition of organolithium reagents to carbodiimides, respectively. (9) (a) Aysin, R. R.; Leites, L. A.; Bukalov, S. S.; Khrustalev, V. N.; Borisova, I. V.; Zemlyanskii, N. N.; Smirnov, A. Y.; Nechaev, M. S. Russ. Chem. Bull. 2011, 60, 69. (b) Khrustalev, V. N.; Portnyagin, I. A.; Zemlyansky, N. N.; Borisova, I. V.; Ustynyuk, Y. A.; Antipin, M. Y. J. Organomet. Chem. 2005, 690, 1056. (c) Khrustalev, V. N.; Zemlyansky, N. N.; Borisova, I. V.; Kuznetsova, M. G.; Krut’ko, E. B.; Antipin, M. Y. Russ. Chem. Bull. 2007, 56, 267. (d) Zemlyansky, N. N.; Borisova, I. V.; Khrustalev, V. N.; Antipin, M. Y.; Ustynyuk, Y. A.; Nechaev, M. S.; Lunin, V. V. Organometallics 2003, 22, 5441. (e) Sienkiewicz, A. V.; Kokozay, V. N. Polyhedron 1994, 13, 1439. (f) Kokozay, V.; Sienkiewicz, A. J. Coord. Chem. 1994, 31, 1. (g) Kokozei, V. N.; Polyakov, V. R.; Simonov, Y. A. Zh. Neorg. Khim. 1992, 37, 1810. (h) Driess, M.; Dona, N.; Merza, K. Dalton Trans. 2004, 3176. (10) (a) Yoneda, A.; Ohfuchi, S.; Hoshimoto, A.; Kitamura, C. Kenkyu Hokoku Himeji Kogyo Daigaku Kogakubu (Jpn.) 2002, 54, 60. (b) Uddin, M. J.; Islam, S.; Islam, M. A.; Begum, F.; Haider, S. Z. J. Bangladesh Chem. Soc. 1995, 8, 7. (c) Umapathy, P.; Badrinarayanan, S.; Sinha, A. P. B. J. Electron Spectrosc. 1983, 28, 261. (d) Bhide, S. N.; Umapathy, P.; Gupta, M. P.; Sen, D. N. J. Inorg. Nucl. Chem. 1978, 40, 1003. (e) Bhide, S. N.; Umapathy, P.; Sen, D. N. J. Indian Chem. Soc. 1977, 54, 851. (f) Doskey, M. A.; Curran, C. Inorg. Chim. Acta 1969, 3, 169. (g) Morrison, J. S.; Haendler, H. M. J. Inorg. Nucl. Chem. 1967,

Table 1. Crystal, Measurement, and Refinement Data for the Compounds Studied by X-ray Diffraction formula fw crystal system space group a, Å b, Å c, Å α, β, γ, deg V, Å3 Z F(000) Dcalcd, g cm−3 μ (Cu Kα), mm−1 crystal size, mm T, K θ range, deg min/max h, k, l no. collected reflns no. unique reflns no. reflns with I > 2σ(I) no. parameters/ restraints GOF on F2 R1 (on F, I > 2σ(I)) wR2 (on F2, all data) min/max Δρ, e Å−3

1

3

C18H36Cl2N2O2Sn2 620.81 orthorhombic Pbca 13.7979(2) 10.8846(1) 16.5218(2) 90, 90, 90 2481.32(5) 4 1238 1.662 18.099 0.60 × 0.35 × 0.28 123(2) 5.83−69.40 0/16, 0/13, 0/19 2320 2268 1980

C15H36N2OSi2Sn 435.33 monoclinic P21/n 8.9906(1) 14.6286(2) 16.6861(2) 90, 96.069(1), 90 2182.25(5) 4 904 1.325 10.368 0.28 × 0.14 × 0.11 123(2) 4.03−67.25 −10/10, −17/17, −19/19 13359 3911 3695

126/0

202/0

1.096 0.079 0.218 −3.434/3.457

1.038 0.022 0.058 −0.651/0.485

Isotropic and full matrix anisotropic least-squares refinements were carried out using SHELXL.27 All non-H atoms were refined anisotropically. The molecular plots were made with the PLATON program package.28 The WINGX program system29 was used throughout the structure determinations. CCDC deposition numbers: 941297 (1) and 941298 (3).

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ASSOCIATED CONTENT

S Supporting Information *

ORTEP drawings of 1 and 3, NMR spectra of 1−3, and crystallographic data in CIF format. 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] (J.A.C.); [email protected] (P.G.-A.). Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work has been supported by the Spanish MICINN (Projects CTQ2010-14933 and DELACIERVA-09-05) and the European Union (FEDER Grants and Marie Curie Action FP72010-RG-268329). D.P. is also grateful to MICINN for an FPI fellowship.

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REFERENCES

(1) (a) Lee, V. Y.; Sekiguchi, A. Organometallic Compounds of Low Coordinate Si, Ge, Sn and Pb: From Phantom Species to Stable Compounds; Wiley-VCH: Chichester, U.K., 2010. (b) Lappert, M. F.; Protchenko, A.; Power, P.; Seeber, A. Subvalent Amides of Silicon and D

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Organometallics

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dx.doi.org/10.1021/om400476c | Organometallics XXXX, XXX, XXX−XXX