Article pubs.acs.org/IC
Novel Stannatrane N(CH2CMe2O)2(CMe2CH2O)SnO-t-Bu and Related Oligonuclear Tin(IV) Oxoclusters. Two Isomers in One Crystal Britta Glowacki,† Michael Lutter,† Dieter Schollmeyer,‡ Wolf Hiller,† and Klaus Jurkschat*,† †
Fakultät für Chemie und Chemische Biologie, Technische Universität Dortmund, 44221 Dortmund, Germany Institut für Organische Chemie, Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany
‡
S Supporting Information *
ABSTRACT: The syntheses of the alkanolamine N(CH2CMe2OH)2(CMe2CH2OH) (1), of the stannatrane N(CH2CMe2O)2(CMe2CH2O)SnO-t-Bu (2), and of the trinuclear tin oxocluster 3 consisting of the two isomers [(μ3-O)(O-t-Bu){Sn(OCH2CMe2)(OCMe2CH2)2N}3] (3a) and [(μ3-O)(μ3-O-t-Bu){Sn(OCH2CMe2)(OCMe2CH2)2N}3] (3b) as well as the isolation of a few crystals of the hexanuclear tin oxocluster [LSnOSn(OH) 3 LSnOH] 2 [L = N(CH2CMe2O)2(CMe2CH2O)] (4) are reported. The compounds were characterized by 1H, 13C, 15N, and 119Sn (1−3) nuclear magnetic resonance and infrared spectroscopy, electrospray ionization mass spectrometry, and single-crystal X-ray diffraction analysis (1−4). A graph set analysis was performed for compound 1. The relative energies of 3a and 3b were estimated by density functional theory calculations that show that the energy differences are small.
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INTRODUCTION Tricyclic metal and metalloid derivatives of trialkanolamines are called metallatranes.1 They are characterized by their cage structure, including right- or left-handed (Δ and Λ) propellertype geometry and an intramolecular N → M (M = metal or metalloid) coordination. Among the metallatranes, the stannatranes N(CH2CH2X)3SnR (X = O; R = alkyl or aryl)2−5 and related derivatives for which X = S,3b NMe,2 CH2,3d−h and N{CH2C(O)X}3SnR (X = O or NMe)3c,i became very popular to the extent that, as result of the particular reactivity of the Sn−R bond,3j−m the so-called tricarbastannatranes N(CH2CH2CH2)3SnR are used for the manufacturing of the drug carbapenem.3n−p Less investigated have been inorganic stannatranes N(CH2CH 2O)3SnX (X = halogen, alkoxide, thiolate, or carboxylate) lacking any Sn−C bond.2,6−13 An interesting aspect of the latter class of stannatranes is the fact that their hydrolysis might be controlled in such a way that intermediates along the path to the final product tin dioxide, SnO2, can be isolated. In this context, we reported the two trinuclear tin oxoclusters [(μ3-O)(μ3-O-t-Bu){Sn(OCH2CH2)(OCMe2CH2)2N}3] (A) and [(μ3-O)(2,6-Me2C6H3-O){Sn(OCH2CH2)(OCMe2CH2)2N}3] (B).13 In the solid state, these clusters differ by the position of the alkoxide substituents RO− (R = t-Bu or 2,6-Me2C6H3) with respect to the μ3-Obridging oxygen atom. Cluster A was trans-configurated and cluster B cis. Notably, in the 119Sn nuclear magnetic resonance (NMR) spectrum of cluster A, we noticed, in addition to the single resonance belonging to the three equal tin atoms, three © XXXX American Chemical Society
minor but equally intense resonances that were tentatively assigned to the cis isomer. However, this was not proven unambiguously. In recent years, a variety of symmetric as well as unsymmetrical trialkanolamines have been synthesized. Representative examples are N(CH2CMe2OH)3, N(CH2CMe2OH)2(CH 2 CH 2 OH), N(CH 2 CMe 2 OH)(CH 2 CH 2 OH) 2 , 14 N(CH2CHMeOH)2(CH2CH2OH),15 N(CHMeCH 2OH)3 ,16 and N(CH2CMe2OH)2(CH2CH2CH2OH).13 Also mentioned in the literature was N(CH2CMe2OH)2(CMe2CH2OH).17,18 However, to the best of our knowledge, this compound was not characterized by any spectroscopic method. As a continuation of our systematic studies of alkanolamine derivatives of tin11,13,19 and motivated by the excellent delayed action catalytic activity for polyurethane formation20,21 of selected representatives, we report herein the syntheses and complete characterization of the alkanolamine N(CH 2 CMe 2 OH) 2 (CMe 2 CH 2 OH), the stannatrane N(CH2CMe2O)2(CMe2CH2O)SnO-t-Bu, and related tri- and hexanuclear tin oxoclusters. In the case of the trinuclear tin oxocluster, both isomers crystallized in one unit cell, thus convincingly supporting the interpretation, as mentioned above, of the 119Sn NMR spectrum of cluster A. Received: June 13, 2016
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DOI: 10.1021/acs.inorgchem.6b01429 Inorg. Chem. XXXX, XXX, XXX−XXX
Article
Inorganic Chemistry
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colorless single crystalline material: mp 183 °C; 1H NMR (600.29 MHz, C6D6, 295 K) δ 3.42 [s, J(1H−117Sn) = 78.1 Hz, J(1H−119Sn) = 81.8 Hz, 2H, CH2O], 2.43 and 1.84 [AB, JAB(1H−1H) = 8.1, 16.5, and 15.4 Hz, 4H, NCH2], 1.66 [s, J(1H−117/119Sn) = 31.5 Hz, 9H, OC(CH3)3], 1.25 and 1.14 [s, 6H each, C(CH3)2O], 0.71 [s, 3H, NC(CH3)2]; 13C{1H} NMR (150.94 MHz, C6D6, 295 K) δ 72.7 [s, J(13C−117/119Sn) = 40.1 Hz, OC(CH3)3], 69.9 [s, J(13C−117/119Sn) = 16.5 Hz, CH2O], 68.1 [s, J(13C−117/119Sn) = 19.8 Hz, C(CH3)2O], 62.2 [s, J(13C−117Sn) = 56.1 Hz, J(13C−119Sn) = 58.3 Hz, NC(CH3)2], 61.6 [s, J(13C−117/119Sn) = 51.7 Hz, NCH2], 34.1 [s, J(13C−117/119Sn) = 28.1 Hz, OC(CH3)3], 33.9 [s, J(13C−117/119Sn) = 34.8 Hz, C(CH3)2O], 23.1 [s, NC(CH3)2] (assignment of the resonances supported by 1H−1H COSY, 1H−13C HMBC, and 1H−13C HSQC NMR experiments); 119Sn{1H} NMR (223.85 MHz, C6D6, 295 K) δ −317 (s); 1H−15N HMBC NMR (600.20, 60.83 MHz, C6D6, 295 K) δ(15N) 43.5 (referenced to NH3), −338.3 (referenced to CH3NO2); MS (ESI+) m/z 391.2 [2 − O-t-Bu + MeCN]+, 422.2 [LSnOH + 3H2O + H]+ [L = N(CH2CMe2O)2(CMe2CH2O)3−], 511.2 (not assigned), 583.4 [2 − O-t-Bu + LH3]+, 737.3 [LSnOSnL + Na]+, 753.3 [LSnOSnL + K]+, 930.6 [LSnLHSnL + H]+, 1062.5 [3 − O-t-Bu]+, 1449.8 [2·LSnOSnL + Na]+, 1465.9 [2·LSnOSnL + K]+; MS (ESI−) m/z 438.2 [LSnOH + 2H2O + Cl]−. Anal. Calcd for 2: C, 45.5; H, 7.9; N, 3.3. Found: C, 44.7; H, 7.8; N, 3.3. The difference between C(calcd) and C(found) might be the result of partial hydrolysis during the measurement. Synthesis of Compound 3 Consisting of (μ3-Oxido)(tertbutoxido)-tris(2,8,9-trioxa-5-aza-3,3,7,7,11,11-hexamethyl-1stannatricyclo[3.3.3.0 1,5 ]undecane) [(μ 3 -O)(O-t-Bu){Sn(OCH2CMe2)(OCMe2CH2)2N}3] (3a) and (μ3-Oxido)(μ3-tert-butoxido)-tris(2,8,9-trioxa-5-aza-3,3,7,7,11,11-hexamethyl-1stannatricyclo[3.3.3.0 1,5 ]undecane) [(μ 3 -O)(μ 3 -O-t-Bu){Sn(OCH2CMe2)(OCMe2CH2)2N}3] (3b). A solution of 2 (1.67 g, 4.00 mmol) in toluene was stored at −20 °C in a Schlenk flask that had not been closed properly. Within several weeks, water had diffused into the flask, causing formation of the tin oxocluster 3·C7H8 (0.4 g, 0.41 mmol, 10%) as colorless blocks: mp 185 °C; 1H NMR (400.25 MHz, C6D6, 298 K) δ 7.13−7.00 (complex pattern, 5H, CHaromatics), 3.91− 3.56 (complex pattern, 6H, CH2O), 2.89−2.57 and 2.04−1.98 (complex pattern, 12H, NCH2), 2.11 (s, 3H, C6H5CH3) 1.94−0.71 [complex pattern, 63H, OC(CH3)3, C(CH3)2O, and NC(CH3)2]; 13 C{1H} NMR (100.64 MHz, C6D6, 298 K) δ 138.2 (Ci), 129.7 (Co), 128.2 (Cm) 126.0 (Cp), 74.8 [OC(CH3)3], 68.5 (CH2O), 67.4 and 66.8 [C(CH3)2O], 64.3 and 61.6 [s, NC(CH3)2], 60.9 (s, NCH2), 35.0, 34.8 and 34.2 [OC(CH3)3], 31.8 and 31.7 [C(CH3)2O], 27.4 and 22.7 [NC(CH3)2] (assignment of 13C resonances based on analogy with compound 2); 119Sn{1H} NMR (223.85 MHz, C6D6, 295 K) δ −526, −616, −633, −682; 1H−15N HMBC NMR (600.20, 60.83 MHz, C6D6, 295 K) δ (15N) 44.3, 45.3, and 45.8 (referenced to NH3), −337.5, −336.5, and −336.0 (referenced to CH3NO2); MS (ESI+) m/ z 1062.5 [3 − O-t-Bu]+; MS (ESI−) m/z 438.2 [2 + OH]−. Anal. Calcd for 3·C7H8: C, 45.2; H, 7.3; N, 3.6. Found: C, 44.7; H, 7.3; N, 3.3. Isolation of [LSnOSn(OH)3LSnOH]2 [L = N(CH2CMe2O)2(CMe2CH2O)] (4). A NMR tube containing a solution of compound 3·C7H8 (approximately 40 mg) in C6D6 was stored for ∼2 months in the fume hood. The formation of approximately five colorless crystals was noticed, of which three were isolated. Singlecrystal X-ray diffraction analysis revealed these to be compound 4· 2C6D6: mp 267−294 °C dec. Computational Details. The density functional theory (DFT) calculations were performed with Gaussian0922 by using the hybrid functional B3LYP,23 the pure BP6824 functional, and the wB97xD25 functional. The latter includes dispersive interactions. The split valence basis set def2-TZVP26 was used for the tin atom and contains the effective core potentials of tin. For all other atoms, the Pople basis set 6-31g(d)27a−h was employed. After geometry optimization, stationary points were verified by frequency analysis (no imaginary frequencies for local minima). For the calculations including toluene as the solvent, the IEFPCM solvent model was used.27i−n
EXPERIMENTAL SECTION
General Aspects. All solvents were dried and purified by standard procedures. All reactions were performed under an atmosphere of dry argon using Schlenk techniques. Bruker Avance III HD 400 MHz, Bruker Avance III HD 500 MHz (with a Prodigy probehead), Bruker Avance III HD 600 MHz (with a Cryo probehead), and Agilent DD2 500 MHz spectrometers were used to obtain 1H, 13C, and 119Sn NMR spectra as well as the twodimensional (2D) spectra. 1H, 13C, 15N, and 119Sn NMR chemical shifts are given in parts per million and were referenced to Me4Si (1H and 13C) and Me4Sn (119Sn). The 1H−15N HMBC NMR measurements were referred to NH3 (15N) and CH3NO2 (15N) (IUPAC) standards. The C6D6 used for the NMR samples was dried over sodium, and the samples were prepared under inert conditions. Melting points are uncorrected and were measured on a Büchi MP560 device. The electrospray ionization mass spectra were recorded on a Thermoquest-Finnigan instrument using MeOH, CH2Cl2, or MeCN as the mobile phase. The samples were introduced as solutions via a syringe pump operating at a rate of 0.5 μL/min. The capillary voltage was 4.5 kV, while the cone skimmer voltage varied between 50 and 250 kV. Identification of the expected ions was assisted by comparison of experimental and calculated isotope distribution patterns. The m/z values reported correspond to those of the most intense peak in the corresponding isotope pattern. For the high-resolution mass measurement, an LTQ Orbitrap (Fourier transformation mass spectrometer) coupled to an Accela HPLC System (consisting of Accela pump, an Accela autosampler, and an Accela PDA detector) from Thermo Electron was used. The eluents were eluent A (0.1% formic acid) and eluent B (0.1% formic acid in acetonitrile), isocratic 50% A/50% B. The samples were introduced into MeCN via a syringe pump (injection volume of 5 μL). The flow rate was 250 μL/min, and the samples were scanned over the wavelength range of 200−600 nm. Electrospray ionization was conducted at a source voltage of 3.8 kV, a capillary voltage of 41 V, a capillary temperature of 275 °C, and a tube lens voltage of 140 V. The scanned mass range was m/z 150−2000, and the resolution was set to 60000. Elemental analyses were performed on a LECO-CHNS932 analyzer under noninert conditions. The infrared spectra were recorded with a PerkinElmar Two (ATR) spectrometer under noninert conditions. Synthesis of Bis(2-dimethyl-2-hydroxypropyl)(1-dimethyl-2hydroxypropyl)amine, N(CH2CMe2OH)2(CMe2CH2OH) (1). A mixture of 2-amino-2-methylpropan-1-ol (10.00 g, 112.20 mmol) and isobutylenoxide (48.54 g, 673.17 mmol) was stirred in a Teflonsealed glass vessel and heated at 120 °C for 15 days. The volatiles were removed under reduced pressure, and the residue was distilled by fractionated vacuum distillation (10−3 mbar, 140 °C). Compound 1 was obtained as a colorless oil (2.84 g, 12.12 mmol, 11%) that crystallized upon standing at room temperature. Single crystals were obtained from an isohexane solution: mp 92 °C; 1H NMR (400.25 MHz, CDCl3, 298 K) δ 4.35 (s br, 3H, OH), 3.20 (s, 2H, CH2OH), 2.55 (s, 4H, NCH2), 1.18 [s, 12H, C(CH3)2)OH], 0.83 [s, 6H, NC(CH3)2]; 13C{1H} NMR (125.77 MHz, C6D6, 298 K) δ 70.9 (s, CH2OH), 69.8 [s, C(CH3)2OH], 65.1 (s, NHCH2), 60.1 [s, NC(CH3)2], 29.8 [s, C(CH3)2OH], 22.9 [NHC(CH3)2]; 1H−15N HMBC NMR (600.20, 60.83 MHz C6D6, 295 K) δ (15N) 45.5 (referenced to NH3), −336.3 (referenced to CH3NO2); IR spectroscopy ν(OH) 3336.3, 3292.0 cm−1; MS (ESI+) m/z 234.2 [1 + H]+; MS (ESI−) m/z 232.1 [1 − H]−, 252.1 [1 + F]−, 286.1 [1 + Cl]−; HRMS (ESI+) calcd m/z 234.20637 [1 + H]+, 256.18831 [1 + Na]+, found m/z 234.20691 [1 + H]+, 256.18876 [1 + Na]+. Synthesis of 1-tert-Butoxido-(2,8,9-trioxa-5-aza3,3,7,7,11,11-hexamethyl-1-stannatricyclo[3.3.3.0 1 , 5 ]undecane) (2). To a stirred solution of tin(IV)-tetra-tert-butoxide (7.93 g, 19.28 mmol, 1.5 equiv) in dry toluene (150 mL) was added within a period of 10 min at room temperature a solution of 1 (3.00 g, 12.86 mmol) in dry toluene (20 mL). The t-BuOH formed was removed by azeotropic distillation followed by evaporation of the toluene under reduced pressure. The residue was recrystallized from toluene at 4 °C, giving compound 2 (3.42 g, 8.16 mmol, 63%) as a B
DOI: 10.1021/acs.inorgchem.6b01429 Inorg. Chem. XXXX, XXX, XXX−XXX
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Inorganic Chemistry Scheme 1. Synthesis of Amino Alcohol 1 and Stannatrane 2
Figure 1. Molecular structure of compound 1 (asymmetric unit, ORTEP presentation at 30% probability of the depicted atoms and atom numbering scheme).
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Crystallography. Intensity data were collected on a Stoe IPDS 2T instrument using Mo Kα radiation at 193 K with an Oxford Cryostream (compound 1) and an XcaliburS CCD diffractometer (Oxford Diffraction) using Mo Kα radiation at 173 K (compounds 2− 4). The structures were determined with direct methods using SIR2004 (compound 1) and SHELXS-2014/728 (compounds 2 and 3), and refinements were conducted against F2 by using SHELXL-2014/ 7.28 The C−H hydrogen atoms were positioned with idealized geometry and refined using a riding model. All non-hydrogen atoms were refined using anisotropic displacement parameters. The data obtained by the measurement of one crystal of compound 1 were treated in the refinement procedure as a two-component twin. Applying the TwinRotMat option in PLATON29 revealed a twin law (BASF 0.68195). To improve the main part of the structure, the severely disordered electron densities of noncoordinating solvent molecules of compound 3 were modeled by the SQUEEZE routine of PLATON.30 The molecular structure of compound 4 was refined as a twocomponent inversion twin (BASF 0.45487). The OH protons were not located on the difference Fourier map. CCDC-1483888 (1), CCDC-1483889 (2), CCDC-1483890 (3), and CCDC-1496144 (4) contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac. uk/data_request/cif. For decimal rounding of numerical parameters and su values, the rules of IUCr have been employed.31 All figures were generated using ORTEP32 or Diamond33 visualization software.
RESULTS AND DISCUSSION
The aminoalcohol bis(2-dimethyl-2-hydroxypropyl)(1-dimethyl-2-hydroxypropyl)amine, N(CH2CMe2OH)2(CMe2CH2OH) (1), was prepared by the reaction of 2-amino-2-methylpropan1-ol with an excess of 1,1-dimethyloxirane (Scheme 1). Compound 1 is a colorless oil, which slowly crystallizes at room temperature. It is hygroscopic and shows good solubility in common organic solvents, such as diethyl ether, tetrahydrofuran, chloroform, dichloromethane, and hot toluene. Single crystals of 1 were obtained from its solution in isohexane. The molecular structure of compound 1, as determined by singlecrystal X-ray diffraction analysis, is shown in Figure 1. Alkanolamine 1 crystallizes in space group P1̅ with four crystallographic independent molecules in the asymmetric unit of the unit cell (Z = 2). Selected interatomic distances and angles involving the hydrogen bonds are listed in Table 1. The equivalent 2-hydroxy-2-methylpropyl chains (CH2CMe2OH) form intramolecular hydrogen bonds [d(D··· A): O(11A)−H(11A)···O(17A), 2.587(3) Å; O(11B)−H(11B)···O(17B), 2.610(4) Å; O(11C)−H(11C)···O(17C), 2.582(4) Å; O(11D)−H(11D)···O(17D), 2.603(3) Å], giving an eight-membered ring. The 1-hydroxy-2-methylpropyl chain (CMe2CH2OH) is involved in intermolecular hydrogen bonds with O···O distances varying between 2.674(4) and 2.679(4) Å. As result of this, an infinite chain of molecules of 1 is formed. Twelve types of hydrogen bonds were identified (Table 2) and analyzed by graph set analysis.34 The unitary motif N1 contains four finite patterns (D), for hydrogen bond types b, e, h, and k: N1 = D, four hydrogen-bonded patterns (S), for hydrogen bond C
DOI: 10.1021/acs.inorgchem.6b01429 Inorg. Chem. XXXX, XXX, XXX−XXX
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Inorganic Chemistry Table 1. Selected Interatomic Distances (angstroms) and Angles (degrees) of the Hydrogen Bonds in Ligand 1 D−H···A
d(D···A)
