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Feb 17, 2019 - Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario N9B 3P4, Canada ...... Neil Burford: 0000-0002-7698-3...
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Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX

Halogen and Sulfur Oxidation of Germanium and Tin Dications Riccardo Suter,*,† Ala’aeddeen Swidan,‡ Charles L. B. Macdonald,‡ Neil Burford,*,† and Michael J. Ferguson§ †

Department of Chemistry, University of Victoria, Victoria, British Columbia V8W 3 V6, Canada Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario N9B 3P4, Canada § X-ray Crystallography Laboratory, Department of Chemistry, University of Alberta, Edmonton, AB T6G 2G2, Canada ‡

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ABSTRACT: Herein we present the oxidation of base-stabilized tetrelII dications [LM][OTf]2 [L = BIMEt3 = tris(1-ethyl-benzoimidazol-2-ylmethyl)amine and M = Ge, Sn] with PCl5, SeCl4, Br2, and I2 to access dicationic dihalides [LMX2][OTf]2. The addition of oxygen-rich donor molecules (picoline N-oxide, OPEt3) to dications [LM][OTf]2 yielded donor−acceptor complexes bearing a tetrel(II) dication adjacent to a pnictogen(V) moiety. The addition of elemental sulfur to [LGe][OTf]2 yielded [(LGeS)2][OTf]4 containing a dimeric tetracation.

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In addition, the oxidation of [(BIMEt3)Ge]2+ with elemental sulfur results in an unusual dimeric tetracation.

INTRODUCTION Germylenes (R2Ge) and stannylenes (R2Sn)1 undergo oxidative addition with perfluorinated pyridines,2 halides,3 inorganic acids,4 and other protic substrates,5 implicating these species as potential catalytic sites by analogy with transition metals.6 The germanium center in [(NacNac)Ge] was oxidized with N2O to form a ligand-stabilized GeO,7 and accordingly, germanone R2GeO (R = 1,1,3,3,5,5,7,7-octaethyl-s-hydrindacen-4-yl) was accessed by the oxidation of the germylene with Me3NO.8 A similar oxidation is reported for [LGe] (L = N-heterocyclic carbene) with heavier chalcogens (S, Se, and Te),9 and in general, germylenes react with elemental chalcogens to form four-membered inorganic rings.10 An array of dicationic germanium and tin centers have been established within neutral ligand scaffolds,11 some of which are observed to undergo oxidation reactions, despite the low-lying HOMO. A water complex of Ge2+ has been reported that can be interpreted as a protonated base-stabilized GeO unit.12 The accessibility of the HOMO in cationic [LGe]2+ is evident in trinuclear pentacation complex [LGe → Ag ← GeL]5+ [L = 2,7-bis(2-pyridyl)-3,6-diazaocta-2,6-diene].13 Substituted tris((benzoimidazol-2-yl)methyl)amines (BIMX3) have been used in the coordination chemistry of main group elements and transition metals because of the multidentate character of the ligand.14 We have recently demonstrated that BIMEt3 [tris(1ethyl-benzoimidazol-2-ylmethyl)amine] is an oxidatively inert ligand that enables the fluorination of nonmetal centers to their maximum oxidation state.15 We now report the general halogenation of [(BIMEt3)M]2+ for M = Ge and Sn to access derivatives of [(BIMEt3)MX2]2+ and provide a facile approach to expanding the rare examples of generic formula [LMX2]2+.16 © XXXX American Chemical Society

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RESULTS AND DISCUSSION Reactions of [(BIMEt3)Ge][OTf]2 with SeCl4, Br2, or I2 in MeCN give light-yellow to red solutions and exhibit 1H NMR spectra that are consistent with that of [(BIMEt3)GeF2][OTf]2,16a implicating the formation of the corresponding dihalide bistriflate salts. Similar results are observed for reactions of [(BIMEt3)Sn][OTf]2 with PCl5, Br2, or I2 in dichloromethane (Scheme 1). Crystals suitable for X-ray diffraction analysis unambiguously identified three of the products as [(BIMEt3)MX2][OTf]2 with X = Cl, Br, I and M = Sn, Ge (Figure 1). For M = Sn, the reactions were followed by 119Sn NMR spectroscopy made possible by the distinct chemical shifts for the derivatives with X = Cl (119Sn δ = −478.9 ppm), X = Br (119Sn δ = −750.4 ppm), and X = I (119Sn δ = −1507.1 ppm) due to the heavy atom effect.17 The chemical shift for X = F (119Sn δ = −556.2 ppm) is inconsistent with the trend of the heavier halides. Derivatives of [(BIMEt3)SnX2][OTf]2·(MeCN)2 crystallize in triclinic space groups P1̅ for X = I and P1 for X = Br. There are no close interactions between the triflate anions and the tin center, which are octahedrally coordinated by three benzoimidazole nitrogens centers, the apex nitrogen, and the two halide substituents. The tin halide bond that is trans to the amine nitrogen center is significantly shorter than that trans to the imine nitrogen center. Similar features are observed for Received: February 17, 2019

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DOI: 10.1021/acs.inorgchem.9b00419 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry Scheme 1. Synthesis for Derivatives of [LMX2][OTf]2

−571.1). In contrast, reactions of triethylphosphine oxide with derivatives of [(BIMEt3)M][OTf]2 (M = Sn, Ge) were shown by 31P NMR spectroscopy to result in quantitative formation of the corresponding complexes (M = Sn, δ = 68.4 (s) and M = Ge, δ = 72.1 (s) ppm). This is a significant shift to higher frequency compared to the free phosphine oxide, 48.3 ppm, and clearly indicates the formation of a donor−acceptor complex. The absence of redox processes for electron-deficient tin(II) halides with phosphine oxide or pyridine N-oxide donors was stated earlier with SnX2 (X = F, Cl).19 The chelating ligand (2-mercaptopyridine-N-oxide) forms stable complexes with Sn(II) and Ge(II) without oxidation of the metal center, likely hindered by the greater ring strain in the five-membered heterocycle upon oxidation.20 Single crystals grown from either DCM or MeCN solutions layered with diethyl ether yielded the solid-state structures that are consistent with that derived from the NMR data. [(BIMEt3)(OPEt3)Sn][OTf]2 crystallizes in the P1̅ space group with two independent cations in the asymmetric unit. The sterically demanding OPEt3 donor imposes a slight distortion of the benzoimidazole arm, resulting in a relatively longer adjacent Sn−N bond (2.657(3) and 2.589(3) Å). Similarly, the Sn−N bond para to OPEt3 is long (2.459 and 2.465(3) Å) compared to those in [(BIMEt3)Sn][OTf]2 (2.395(4), 2.375(4), and 2.263(4)).15c Both Sn···OTf interactions are at the limit of the range of VdW interactions (3.580(3) and 3.341(3) Å). Derivatives of [(BIMEt3)M(OPic)][OTf]2 crystallize in space groups P21/n (M = Ge) and P1̅ (M = Sn). As expected from the 1H NMR data, the presence of picoline N-oxide imposes a distortion on one of the benzoimidazole groups out of the coordination sphere, resulting in a tridentate BIMEt3. The other benzoimidazole groups are closer, with short Ge−N bonds (2.0489(19) and 2.0645(19) Å). The Ge−O bond (2.1062(17) Å) is long, effecting a short N−O bond (1.354(3) Å) and suggesting significant charge delocalization over the Ge−O−N unit. The existence of the stereochemically active lone pair in both complexes and the long M−O bond indicate a Ge(II) center rather than a Ge(IV) oxide. Although the oxidation of [(BIMEt3)Ge]2+ with oxo donors did not yield germanium oxides, sulfide [(BIMEt3)GeS]2+ was targeted through the addition of sulfur, in a minimum amount of DCM, to a solution of [(BIMEt3)Ge][OTf]2 in MeCN. On standing at room temperature for 16 h, crystals formed and were identified as dimeric salt [{(BIMEt3)GeS}2][OTf]4 (Figure 3). The compound is only sparingly soluble in MeCN, and NMR spectroscopic analysis in DMSO-d6 was precluded by slow decomposition as evidenced by signals corresponding to the free ligand. In the solid state, the four Ge−S bonds are similar in length (2.3312(9), 2.2017(8) Å) and are significantly longer than that in the neutral germanethione in Tbt(Tip)GeS (2.049(3) Å)21 and are compared to typical Ge−S single bonds in neutral [(LGeS)2] dimers with L = (DippN)2Si(iPr)2 (Ge S 2.1992(3),

Scheme 2. Attempted Oxidation Reactions with Picoline NOxide and Coordination to Triethylphosphine Oxide

Scheme 3. Reaction of [(BIMEt3)Ge][OTf]2 with S8

[(BIMEt3)GeCl2][OTf]2, which crystallizes in monoclinic space group P21/n. (For selected bond distances, see Table 1.) The abstraction of fluoride substituents from [(BIMEt3)GeF2][OTf]2 was studied earlier and yielded the triflate salt [(BIMEt3)GeF][OTf]3.15a The abstraction of the fourth fluoride was not possible even at elevated temperatures. Similarly, attempts to abstract the residual halides in [(BIMEt3)GeCl2][OTf]2 with TMSOTf or AgOTf were not successful. Electron-rich germanium(II) species or phosphenium (R2P+) cations react with organic oxidizing agents such as pyridine N-oxide or trimethyl amine N-oxide to form the parent oxides.7,8,18 The addition of picoline N-oxide resulted also in the formation of donor−acceptor complexes as evidenced by the characteristic picoline 1H NMR resonances. The para-methyl group in picoline N-oxide is a useful indicator of the electron-donating properties of the pyridine substituent, and it is shifted to significantly higher frequency (1H δ = 2.51 ppm) in the germanium complex compared to that in the tin salt (1H δ = 2.23 ppm), suggesting a higher electron deficiency at the germanium center. This is due to a fluxional binding in solution, as evidenced by the broad signal for the N−CH2−Ar groups in the 1H NMR spectrum at 4.93 ppm (s, CH2, 6H). This equilibrium is implicit in the solid-state structure, where one of the benzoimidazole groups is dissociated (Figure 2). The singlet resonance in the 119Sn NMR spectrum of the analogous tin salt was observed at δ = −651.1 ppm, which is similar to that for [(BIMEt3)Sn][OTf]2 (δ = −628.7 ppm) and significantly different from that for [(BIMEt3)Sn][OTf]4 (δ = B

DOI: 10.1021/acs.inorgchem.9b00419 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry

Figure 1. Structure of the cations in (a) [(BIMEt3)GeCl2][OTf]2, (b) [(BIMEt3)SnBr2][OTf]2·MeCN2, and (c) [(BIMEt3)SnI2][OTf]2·MeCN2. Thermal ellipsoids are shown at the 50% probability level. Hydrogen atoms, solvent molecules, and weakly coordinating anions are omitted for clarity. Interatomic distances and angles are summarized in Table 1.

and are best described as the two occupied p orbitals at sulfur. Both the LUMO and LUMO+1 are localized on the Ge2S2 unit and are best described as the s orbitals on germanium, which interact with the nitrogen atoms and the empty p orbitals on sulfur in an antibonding manner. NBO analysis of [{(BIMMe3)GeS}2]4+ reveals a positive charge on the germanium atoms (+1.63) and a negative charge on the sulfur atoms (−0.66). Each BIMMe3 ligand therefore carries +1.03 charge. The Wiberg bond indices for the Ge−S interactions are 0.866 and 0.697, which coincide with the long bonds observed in the solid state. The imidazole N−Ge interactions (0.398) are significantly stronger than that of the amine (0.221). While a S−S (0.125) interaction is evident, the bond index for Ge− Ge (0.028) is negligible. Chart 1 offers a selection of the many viable Lewis drawings for the Ge2S2 core of [{(BIMMe3)GeS}2]4+, which can be considered to be isoelectronic to the Sb 4 core of [(PMe3 ) 4 Sb] 4+ (A compares with F).25 The core of [{(BIMMe3)GeS}2]4+ is also isoelectronic with the dimers of the neutral tetrel/pnictogen rings such as (RCP)2,26 (RC As)2,27 (NacNac-GeP)2,28 and (PhC(NtBu)2SiP)2 (B).29 However, the calculations imply that resonance structures C and D are the most substantive contributors. The closest electronic and structural comparison is with neutral aluminum sulfide dimer G [RAl(μ-S)]2 (known for RC(SiMe3)330 or Mes*31). Resonance structure E with two cationic charges on each BIMEt3 ligand results in a neutral Ge2S2 ring comparable to that in [(MesGeS)2] (H).32

Table 1. Bond Distances (Angstroms) and Angles (Degrees) for [{(BIMEt3)GeS}2][OTf]4 [{(BIMEt3)GeS}2]4+ CCDC Ge N

Ge N1 Ge S S OTf S−Ge−S Ge−S−Ge Ge···Ge S···S

1847486 2.027(3) 2.020(3) 2.020(3) 2.194(3) 2.3312(9) 2.2017(9) 3.513 3.729 92.843 87.157 3.126 3.284

2.2577(3) Å) or L = (Ph3SiN)2Si(iPr)2 (Ge S 2.2197(5), 2.2484(5) Å),22 L = MeN{(CH2CH2N(C6F5)}2 (Ge S 2.2062(17), Ge S 2.2875(18) Å),23 or L = 1,8-(iPrN)2C10H6 (2.2230(9) and 2.2457(9) Å).24 Structure optimization at the B3lyp/TZVP level of theory, using a simplified ligand scaffold (BIMMe3) yielded the gasphase structure of [{(BIMMe3)GeS}2]4+ with similar but slightly longer alternating Ge−S bonds (2.259 and 2.388 Å, Figure 4). The highest occupied molecular orbitals (HOMO to HOMO-11) are exclusively ligand-centered, and only HOMO12 and HOMO-13 are centered on the heterocycle (Figure 3) C

DOI: 10.1021/acs.inorgchem.9b00419 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry

Figure 2. Solid-state structure of the cations in (a) [(BIMEt3)GeOPic][OTf]2, (b) [(BIMEt3)Sn(OPEt3)][OTf]2, and (c) [(BIMEt3)Sn(OPEt3)][OTf]2·Et2O. Thermal ellipsoids are shown at the 50% probability level. Hydrogen atoms, solvent molecules, and triflate anions are omitted for clarity. For weakly interacting triflate anions, only the coordinating oxygen atoms are shown. Interatomic distances and angles are summarized in Table 1.

Figure 3. Structure of the cation in [{(BIMEt3)GeS}2][OTf]4. Thermal ellipsoids are shown at the 50% probability level. Hydrogen atoms, solvent molecules, and noncoordinating anions are omitted for clarity. Interatomic distances and angles are summarized in Table 2.

Figure 4. Selected molecular orbitals of [{BIMMe3)SGe}2]4+ at the B3lyp/TZVP level of theory.

Structure optimization of [(BIMMe3)GeS]2+ in the gas phase (b3lyp/TZVP) suggests a C3v cage structure with a terminal GeS bond. The monomer is energetically favored (ΔG = −544.0 kJ/mol and ΔH = −484.4 kJ/mol) over the dimer, indicating that packing effects and additional π−π interactions are responsible for the observed solid-state structure. However, attempts to isolate [(BIMEt3)(L)GeS][OTf]2 with an additional donor was not successful, yielding dimeric [{(BIMEt3)GeS}2][OTf]4.

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CONCLUSIONS We have introduced the BIMEt3 ligand scaffold as a versatile and redox inert ligand for the stabilization of various tetrel(IV) complexes. In this context, we were able to show that even with an overall positive charge of +2, salts of type [(BIMEt3)E][OTf]2 are prone to oxidation with PCl5, SeCl4, Br2, and I2. The oxidation reaction with sulfur yielded D

DOI: 10.1021/acs.inorgchem.9b00419 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry

Table 2. Select Bond Distances (Angstroms) and Angles (Degrees) for [LMX2]2+ Salts (L = BIMEt3; X = Cl, Br, I) and [LML′]2+ Salts (L′ = OPic, OPEt3) [LGeCl2]2+

[LSnBr2]2+

[LSnI2]2+

CCDC M−N

1847488 1.993(2) 1.965(2) 1.981(2)

1847489 2.167(3) 2.177(3) 2.183(3)

M−N1

2.147(2)

M−X

2.1707(7) 2.2464(8)

1847487 2.144(5) 2.145(5) 2.161(5) 2.146(5)a 2.152(5)a 2.168(5)a 2.330(4) 2.331(4)a 2.4732(6) 2.5442(7) 2.4778(7)a 2.5308(7)a

[LGe(OPic)]2+

[LSn(OPic)]2+

[LSn(OPEt3)]2+

1843707 2.0489(19) 2.0645(19)

1844125 2.360(3) 2.368(4) 2.383(4)

2.356(3)

2.3896(18)

2.623(4)

2.6783(3) 2.7675(3)

Ge−O 2.1062(17)

Sn−O 2.335(3)

1843706 2.330(2) 2.465(3) 2.657(3) 2.322(3)a 2.459(3)a 2.589(3)a 2.523(3) 2.540(3)a Sn−O 2.269(2) Sn−O 2.287(3)a

E−O

N−O 1.354(3)

N−O 1.342(5)

M−OTf

3.552(3) 3.043(3)

3.563(3)

P−O 1.510(2) P−O 1.509(3)a 3.580(3) 3.341(3)

a

Values correspond to the second cation in the unit cell. and then rapidly cooled under a stream of cold N2 of the lowtemperature apparatus (Oxford Cryostream) attached to the diffractometer. The data were then collected using the APEXII (Bruker AXS) software suite on a Bruker Photon 100 CMOS diffractometer using a graphite monochromator with Mo Kα (λ = 0.71073 Å). For each sample, data were collected at low temperature. APEXII software was used for data reductions, and SADABS (Bruker AXS) was used for absorption corrections (multiscan; semiempirical from equivalents). XPREP was used to determine the space group, and the structures were solved and refined using the SHELX33 software suite as implemented in the WinGX34 or OLEX235 program suites. Validation of the structures was conducted using PLATON.36 All quantum chemical calculations were carried out using Gaussian 16.37 Synthesis of [(BIMEt3)GeCl2][OTf]2. [(BIMEt3)Ge][OTf]2 (0.1 mmol, 91 mg) was dissolved in 3 mL of MeCN, and SeCl4 (0.1 mmol, 22 mg) was added as a solid, causing the reaction mixture to turn red. After 5 min, a red precipitate was formed which dissolved over the course of 1 h, forming a light-yellow solution with minor amounts of a colorless precipitate. The clear solution was then filtered through glass filter paper and was layered with 4 mL of diethyl ether and placed in a freezer at −35 °C for 72 h. Colorless crystals were isolated from the solution. Yield: 76 mg (81%) of composition C32H33F6Cl2GeN7O6S2, MW = 933.3 g/mol, MP = 248 °C (dec.) EA [calcd]: C, 41.18; H, 3.56; N, 10.51. EA [found]: C, 41.27; H, 3.57; N, 10.41. 1H NMR (300 MHz, MeCN-d3) δ = 9.04 (d, J = 8.6 Hz, 1H), 8.41−8.53 (m, 2H, CHarom), 7.72−7.84 (m, 2H, CHarom), 7.44−7.66 (m, 7H, CHarom), 5.75 (d, J = 17.1 Hz, 2H, CH2), 5.54 (d, J = 17.1 Hz, 2H, CH2), 5.18 (s, 2H, CH2), 4.43 (m, 4H, CH2), 4.01 (q, J = 7.4 Hz, 2H), 1.51 (t, J = 7.3 Hz, 6H), 1.27 (t, J = 7.4 Hz, 3H). 19F{1H} NMR (283 MHz, CD3CN) δ = −79.3 (OTf). 13C{1H} NMR (75.5 MHz CD3CN) δ = 148.0 (s), 146.4 (s), 134.5 (s), 134.1 (s), 132.4 (s), 132.0 (s) 126.2 (s), 125.91 (s), 125.85 (s), 116.0 (s), 112.6 (s), 112.0 (s), 57.0 (s), 56.5 (s), 40.7 (s), 40.3 (s), 13.4 (s), 12.2 (s). Synthesis of [(BIMEt3)GeBr2][OTf]2. A Schlenk flask was charged in a glovebox with [(BIMEt3)Ge][OTf]2 (0.2 mmol, 182 mg) and 5 mL of MeCN. The reaction vessel was then connected to a Schlenk line, and bromine (0.4 mmol, 64 mg) was added, yielding a lightyellow solution. The mixture was stirred for 30 min at room temperature. The volatiles were removed, and the solid residue was washed with diethyl ether (2 mL) and was dried again under reduced pressure, yielding 186 mg (91%) of a colorless powder with composition C32H33Br2F6N7O6S2Ge·MeCN. MW = 1063.6 g/mol, MP = 234 °C (dec.). EA [calcd]: C, 38.41; H, 3.41; N, 10.54. EA

Chart 1. Selected Resonance Structures (A−E) for [{(BIMMe3)GeS}2]4+ and Isoelectronic Analogues (F−H)

unprecedented tetracationic dimer [{(BIMEt3)GeS}2]4+, with a Ge2S2 ring that is surprisingly stable toward other neutral donor ligands. The use of such complexes as active species for the activation of polarized bonds is under investigation.

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EXPERIMENTAL SECTION

General Considerations. All air- and moisture-sensitive manipulations were carried out using standard vacuum line Schlenk techniques or in a MBraun Labmaster inert atmosphere drybox containing an atmosphere of purified nitrogen. THF-d8, CD2Cl2, and C6D6 were purchased from Sigma-Aldrich. CD2Cl2 was dried over CaH2 and distilled, and THF-d8 and C6D6 were distilled over potassium. All glassware was stored in a 170 °C oven for several hours and was degassed prior to use. Solvents were distilled over the appropriate drying agent. Anhydrous-grade MeCN was obtained from Sigma-Aldrich and used without distillation but stored over 3 Å molecular sieves. Solvents were additionally tested using a ketyl test to guarantee oxygen- and moisture-free conditions. TMSOTf (99%) was distilled before use. [(BIMEt3)Ge][OTf]215a and [(BIMEt3)Sn][OTf]215c were synthesized following literature procedures. NMR tubes were charged and sealed inside the glovebox. 1H NMR spectra were recorded on Bruker spectrometers operating at 300 MHz, 13C NMR spectra, at 76 MHz, 31P NMR spectra, at 121.6 MHz, 19 F NMR spectra, at 282.5 MHz, and 119Sn NMR spectra, at 134 MHz. All 1H and 13C NMR chemical shifts are reported relative to SiMe4 using the 1H (residual) and 13C chemical shifts of the solvent as a secondary standard. Elemental analysis was performed at the University of Windsor Mass Spectrometry Service Laboratory using a PerkinElmer 2400 combustion CHN analyzer. Crystals for investigation were covered in Paratone, mounted into a goniometer head, E

DOI: 10.1021/acs.inorgchem.9b00419 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry

= −79.3 (OTf). 13C{1H} NMR (75.5 MHz CD3CN) δ = 148.3 (s), 135.7 (s), 134.6 (s), 127.6 (s), 127.5 (s), 127.0 (s), 126.9 (s), 117.6 (s), 116.7 (s), 113.9 (s), 113.2 (s), 56.7 (s), 55.3 (s), 41.8 (s), 41.3 (s), 14.8 (s), 13.6 (s). 119Sn{1H} NMR (134 MHz CD3CN) δ = −750.4 (s). Synthesis of [(BIMEt3)SnI2][OTf]2. [(BIMEt3)Sn][OTf]2 (0.1 mmol, 97 mg) was dissolved in 3 mL of MeCN, and iodine (0.1 mmol, 25 mg) was added as a solid, yielding a dark-yellow solution. From the reaction mixture, crystals (suitable for single-crystal X-ray diffraction analysis) have grown directly over the course of several hours. The mother liquor was decanted and was layered with 4 mL of diethyl ether and placed in the freezer at −35 °C for 72 h. The solution was again decanted, the light-yellow solid was washed with diethyl ether, and the remaining volatiles were removed under reduced pressure. The result was a combined yield of 112 mg (99%) with composition C32H33F6I2N7O5S2Sn. MW = 1146.3 g/mol and MP = 142 °C (dec.). EA [calcd]: C, 33.53; H, 2.90; N, 8.55. EA [found]: C, 31.87; H, 2.69; N, 7.82. The constant low values likely result from traces of potentially formed [I3]−. 1H NMR (300 MHz, MeCN-d3) δ = 9.28 (d, J = 8.3 Hz, 1H), 8.53−8.70 (m, 2H), 7.73−7.93 (m, 2H), 7.54−7.70 (m, 7H), 5.43 (d, J = 17.1 Hz, 4H), 5.34 (d, J = 17.1 Hz, 4H), 5.04 (s, 2H), 4.47 (q, J = 7.2 Hz, 4H), 4.06 (q, J = 7.3 Hz, 2H), 1.54 (t, J = 7.3 Hz, 6H), 1.29 (t, J = 7.2 Hz, 3H). 19F{1H} NMR (283 MHz, CD3CN) δ = −79.32 (OTf). 13C{1H} NMR, not soluble enough to get reliable data. 119Sn{1H} NMR (134 MHz CD3CN) δ = −1507.1 (s) Synthesis of [(BIMEt3)(OPEt3)Ge][OTf]2. [(BIMEt3)Ge][OTf]2 (0.1 mmol, 91 mg) was suspended in 3 mL of DCM, and OPEt3 (0.1 mmol, 14 mg) was added as a solid, yielding a clear, colorless solution. The reaction mixture was layered with 4 mL of diethyl ether and placed in the freezer at −35 °C for 72 h. The colorless precipitate was filtered off and washed with diethyl ether. The solid was dried under reduced pressure to yield 68 mg of a colorless solid. The mother liquor was concentrated and layered again with diethyl ether and then placed in the freezer for another 72 h. The precipitate was filtered off and dried under reduced pressure, with a combined yield of 84 mg (84%) with composition C38H48F6GeN7O7PS2. MW = 996.6 g/mol and MP = 150 °C (melt/dec.). EA [calcd]: C, 45.80; H, 4.86; N, 9.84. EA [found]: 45.55; H, 4.69; N, 9.66. 1H NMR (300 MHz, MeCN-d3) δ = 7.87 (s, 3H), 7.57 (s, 3H), 7.38 (s, 6H), 4.92 (s, 6H), 4.24 (q, J = 7.13 Hz, 6H), 1.8−2.2 (m, 6H, overlaps with MeCN signal), 1.34 (t, J = 7.3 Hz, 9H), 0.9−1.25 (m, 9H). 19F{1H} NMR (283 MHz, CD3CN) δ = −79.3 (s). 31P{1H} NMR (121.5 MHz, CDCl3) δ = 72.1 (s). 13C{1H} NMR (75.5 MHz CD3CN) δ = 151.9 (s), 137.1 (s), 134.1 (s), 124.2 (s), 123.9 (s), 111.1 (s), 53.4 (s), 39.5 (s), 18.3 (s), 17.4 (s), 13.5 (s), 4.6 (d, J = 5.1 Hz). Synthesis of [(BIMEt3)(OPEt3)Sn][OTf]2. [(BIMEt3)Sn][OTf]2 (0.1 mmol, 97 mg) was dissolved in 3 mL of DCM, and OPEt3 (0.1 mmol, 14 mg) was added as a solid, yielding a clear, colorless solution. The reaction mixture was stirred at room temperature for 30 min. It was then layered with 4 mL of diethyl ether and placed in the freezer at −35 °C for 72 h. The colorless precipitate was filtered off and washed with diethyl ether. The residue was dried under reduced pressure to yield 81 mg (75%) of a colorless solid with composition C38H48F6N7O7PS2Sn·DCM0.5. MW = 1085.1 g/mol and MP = 101 °C (melt/dec.). EA [calcd]: C, 42.62; H, 4.55; N, 9.04. EA [found]: C, 42.47; H, 4.28; N, 9.14. 1H NMR (300 MHz, MeCN-d3) δ = 7.9−8.0 (m, 3H), 7.5−7.6 (m, 3H), 7.25−7.45 (m, 6H), 4.85 (s, 6H), 4.24 (q, J = 7.3 Hz, 6H), 1.57 (dq, JPH = 11.9, JHH = 7.7 Hz, 6H), 1.35 (t, J = 7.3 Hz, 9H), 0.67 (dt, JHH = 7.7, JPH = 17.4 Hz, 9H). 19F{1H} NMR (283 MHz, CD3CN) δ = −79.3 (s). 31P{1H} NMR (121.5 MHz, CDCl3) δ = 68.4 (s). 13C{1H} NMR (75.5 MHz CD3CN) δ = 151.4 (s), 137.1 (s), 134.4 (s), 124.1 (s), 123.9 (s), 116.3 (s), 111.2 (s), 55.8 (s), 39.2 (s), 18.2 (s), 17.4 (s), 13.7 (s), 4.2 (d, J = 4.7 Hz). Synthesis of [(BIMEt3)(OPic)Ge][OTf]2. [(BIMEt3)Ge][OTf]2 (0.1 mmol, 91 mg) was suspended in 3 mL of DCM, and picolineN-oxide (0.15 mmol, 16 mg) was added as a solid, yielding a clear, colorless solution. The reaction mixture was layered with 4 mL of diethyl ether and placed in the freezer at −35 °C for 72 h. The precipitate was filtered off and washed with diethyl ether. The residue

[found.]: C, 38.48; H, 3.35; N, 10.97. 1H NMR (300 MHz, MeCNd3) δ = 9.29 (d, J = 8.7 Hz, 1H), 8.26−8.41 (m, 2H), 7.73−7.88 (m, 2H), 7.39−7.68 (m, 7H), 5.65 (s, 4H), 5.23 (s, 2H), 4.45 (dq, J = 1.0, 7.4 Hz, 4H), 4.03 (q, J = 7.4 Hz, 2H), 1.52 (t, J = 7.3 Hz, 6H), 1.27 (t, J = 7.4 Hz, 3H). 19F{1H} NMR (283 MHz, CD3CN) δ = −79.26 (OTf). 13C{1H} NMR (75.5 MHz CD3CN) δ = 148.1 (s), 146.1 (s), 134.5 (s), 134.1 (s), 132.5 (s), 131.9 (s), 126.1 (s), 126.0 (s), 125.9 (s), 125.7 (s), 116.2 (s), 112.5 (s), 112.0 (s), 56.5 (s), 56.1 (s), 40.6 (s), 40.3 (s), 13.5 (s), 12.2 (s). Synthesis of [(BIMEt3)GeI2][OTf]2. [(BIMEt3)Ge][OTf]2 (0.1 mmol, 91 mg) was dissolved in 2 mL of MeCN, and I2 (0.1 mmol, 25 mg) was added as a solid yielding a dark-red solution. After stirring at room temperature for 30 min, the reaction mixture was filtered through Celite and the filtrate was layered with 6 mL of diethyl ether and was placed in the freezer at −35 °C for 72 h. A yellow microcrystalline solid precipitated, which was collected by decanting the supernatant. The solid was washed with diethyl ether and dried under reduced pressure, yielding 112 mg (96%) of a yellow microcrystalline solid with composition C35H41F6GeI2N7O6S2. MW = 1160.3 g/mol and MP = 212 °C (dec.). EA [calcd]: C, 36.23; H, 3.56; N, 8.45. EA [found]: C, 35.77; H, 3.20; N, 9.08. The constant low values likely result from traces of potentially formed [I3]−. 1H NMR (300 MHz, MeCN-d3) δ = 9.24 (d, J = 8.3 Hz, 1H), 8.59 (dd, J = 4.4, 4.5 Hz, 2H), 7.70−7.91 (m, 2H, CHarom), 7.33−7.70 (m, 7H, CHarom), 5.54 (s, CH2, 4H), 5.10 (s, CH2, 2H), 4.45 (q, J = 7.4 Hz, 4H), 4.06 (q, J = 7.1 Hz, 2H), 1.51 (t, J = 7.3 Hz, 6H), 1.26 (t, J = 7.2 Hz, 3H). 19F{1H} NMR (283 MHz, CD3CN) δ = −79.25 (OTf). 13 C{1H} NMR (75.5 MHz CD3CN) δ = 150.0 (s), 147.3 (s), 135.3 (s), 135.1 (s), 134.2 (s), 126.8 (s), 126.7 (s), 126.2 (s), 126.0 (s), 117.2 (s), 116.3 (s), 113.2 (s), 112.5 (s), 55.3 (s), 55.4 (s), 41.0 (s), 40.6 (s), 14.3 (s), 13.1 (s). Synthesis of [(BIMEt 3 )SnCl2 ][OTf] 2 . [(BIMEt 3)Sn][OTf]2 (0.124 mmol, 120 mg) was suspended in 5 mL of DCM, and PCl5 (0.124 mmol, 26 mg) was added as a solid to the reaction mixture. Stirring for 30 min yielded a light-yellow solution. The solution was concentrated to 3 mL and was layered with diethyl ether (4 mL) and placed in the freezer at −35 °C for 72 h. The supernatant was decanted off, and the colorless crystals (suitable for X-ray diffraction analysis) were washed with diethyl ether, and the volatiles were removed under reduced pressure, yielding 120 mg (95%) of a colorless solid with composition C32H33Cl2F6N7O6S2Sn·MeCN1. MW = 1020.4 g/mol and MP = 262 °C (dec.). EA [calcd]: C, 40.02; H, 3.56; N, 10.98. EA [found]: C, 40.22; H, 3.50; N, 11.35. 1H NMR (300 MHz, MeCN-d3) δ = 8.72 (s, 1H, CHarom), 8.19 (s, 2H, CHarom), 8.80 (s, 2H, CHarom), 7.56 (s, 7H, CHarom), 5.80 (d, JHH = 16.6 Hz, 2H, CH2), 5.36 (d, JHH = 16.6 Hz, 2H, CH2), 5.13 (s, 2H, CH2), 4.45 (s, 4H, CH2), 4.06 (s, 2H, CH2), 1.51 (s, 6H, CH3), 1.28 (s, 3H, CH3). (There are no resolved multiplets because of severe line broadening.) 19F{1H} NMR (283 MHz, CD3CN) δ = −79.3 (OTf). 13 C{1H} NMR (75.5 MHz CD3CN) δ = 147.5 (s), 134.4 (s), 133.7 (s), 126.4 (s), 126.3 (s), 125.9 (s), 116.4 (s), 115.3(s), 112.7 (s), 111.9 (s), 57.0 (s), 55.9 (s), 40.6 (s), 40.2 (s), 13.5 (s), 12.4 (s). 119 Sn{1H} NMR (134 MHz CD3CN) δ = −478.9 (s). Synthesis of [(BIMEt3)SnBr2][OTf]2. A Schlenk flask was charged with [(BIMEt3)Sn][OTf]2 (0.25 mmol, 227 mg) and 2 mL of MeCN in a glovebox and was then connected to a Schlenk line. Bromine (0.5 mmol, 80 mg) was added, and the mixture was stirred for 30 min at room temperature, yielding a light-yellow solution. The volatiles were removed and the solid was extracted with DCM (4 mL) and filtered over a glass filter. The volatiles were again removed under reduced pressure, yielding 242 mg (91%) of a colorless solid with composition C32H33Br2F6N7O6S2Sn. Single crystals suitable for single-crystal X-ray diffraction analysis were grown from a saturated acetonitrile solution layered with diethyl ether. MW = 1068.3 g/mol and MP = 238 °C (dec.). EA [calcd]: C, 35.98; H, 3.11; N, 9.18. EA [found]: C, 35.72; H, 2.98; N, 9.04. 1H NMR (300 MHz, MeCN-d3) δ = 8.93 (d, J = 8.3 Hz, 1H), 8.26−8.41 (m, 2H), 7.73−7.88 (m, 2H), 7.39−7.68 (m, 7H), 5.39 (d, J = 17.4, 2H), 5.69 (d, J = 17.4, 2H), 5.11 (s, 2H), 4.44 (dq, J = 3.2, 7.3 Hz, 4H), 4.05 (q, J = 7.2 Hz, 2H), 1.51 (t, J = 7.3 Hz, 6H), 1.26 (t, J = 7.2 Hz, 3H). 19F{1H} NMR (283 MHz, CD3CN) δ F

DOI: 10.1021/acs.inorgchem.9b00419 Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry

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was dried under reduced pressure to yield 82 mg (85%) of a colorless solid with composition C38H40F6GeN8O7S2. MW = 971.5 g/mol and MP = 126 °C (dec.). EA [calcd]: C, 46.98; H, 4.15; N, 11.53. EA [found]: C, 47.09; H, 4.01; N, 11.28. 1H NMR (300 MHz, MeCNd3) δ = 8.43 (d, J = 6.7 Hz, CHarom, 2H), 8.13 (d, J = 7.7 Hz, CHarom, 3H), 7.64 (d, J = 7.7 Hz, CHarom, 3H), 7.60 (d, J = 6.7 Hz, CHarom, 2H), 7.41 (pseudoquint, J = 7.6 Hz, CHarom, 6H), 4.93 (s, CH2, 6H), 4.29 (q, J = 7.3 Hz, CH2 6H), 2.51 (s, CH3, 3H), 1.37 (t, J = 7.3 Hz, CH3, 9H). 19F{1H} NMR (283 MHz, CD3CN) δ = −79.32 (OTf). 13 C{1H} NMR (75.5 MHz CD3CN) δ = 151.7 (s), 149.6 (s), 139.1.2 (s), 137.7 (s), 134.2 (s), 128.2 (s), 124.2 (s), 124.0 (s), 117.8 (s), 111.0 (s), 52.3 (s), 39.5 (s), 19.8 (s), 13.5 (s). Synthesis of [(BIMEt3)(O-Pic)Sn][OTf]2. [Sn(BIMEt3)][OTf]2 (0.1 mmol, 97 mg) was dissolved in 3 mL of DCM, and picoline-Noxide (0.12 mmol, 13 mg) was added as a solid, yielding a clear, colorless solution. The reaction mixture was layered with 4 mL of diethyl ether and placed in the freezer at −35 °C for 72 h. The crystalline precipitate was filtered off and washed with ether. The residue was dried under reduced pressure to yield 80 mg (78%) of a colorless solid with composition C38H40F6N8O7S2Sn. MW = 1017.6 g/mol and MP = 198 °C (dec.). EA [calcd]: C, 44.85; H, 3.96; N, 11.01. EA [found]: C, 44.60; H, 3.75; N, 10.90. 1H NMR (300 MHz, MeCN-d3) δ = 7.90 (d, J = 7.18 Hz, CH, 2H), 7.77 (m, CH, 2H), 7.59 (d, J = 7.15 Hz, CH, 3H), 7.35 (m, CH, 6H), 7.08 (m, CH, 2H), 4.89 (s, CH2, 6H), 4.26 (q, J = 7.28 Hz, 6H), 2.19 (s, CH3, 3H), 1.38 (t, J = 7.28, CH3, 9H). 19F{1H} NMR (283 MHz, CD3CN) δ = −79.32 (OTf). 13C{1H} NMR (75.5 MHz CD3CN) δ = 151.8 (s), 146.2 (s), 138.2 (s), 137.3 (s), 134.5 (s), 127.3 (s), 124.1 (s), 123.8 (s), 116.6 (s), 111.1 (s), 54.8 (s), 39.2 (s), 19.2 (s), 13.6 (s). 119 Sn{1H} NMR (134 MHz CD3CN) δ = −651.1 (s) Synthesis of [{(BIMEt3)GeS}2][OTf]4. Elemental sulfur (4 mg, 0.1 mmol) was dissolved in 3 mL of DCM and was added dropwise to a solution of [Ge(BIMEt3)][OTf]2 (0.1 mmol, 91 mg) in 4 mL of MeCN. The reaction mixture was stirred for 16 h at room temperature. The mixture was concentrated to half its volume and layered with diethyl ether (4 mL) and placed in the freezer. The solution was decanted off, and the colorless solid was washed with DCM and diethyl ether. Drying under reduced pressure yielded 40 mg of product. The mother liquor was again concentrated and layered with ether to isolate another 46 mg of product. The total yield was 86 mg (92%) of composition C32H33F6GeN7O6S3. MW = 895.1 g/mol and MP = 232 °C (dec.). EA [calcd]: C, 42.97; H, 3.72; N, 10.96. EA [found.]: C, 42.36; H, 3.71; N, 10.64. 1H NMR (300 MHz, DMSOd6) δ = 8.51 (d, J = 8.4 Hz, 1H), 7.89 (d, J = 8.3 Hz, 2H), 7.64 (d, J = 8.3 Hz, 1H), 7.49 (t, J = 7.8 Hz, 1H), 7.39 (t, J = 7.6 Hz, 4H), 7.00 (t, J = 7.7 Hz, 2H), 6.84 (t, J = 7.8 Hz, 2H), 5.85 (dd, J = 17.2, 42.2 Hz, 4H), 5.14 (s, CH2, 2H) 4.46 (q, J = 7.6 Hz, 4H), 3.89 (q, J = 7.3, Hz, 2H), 1.58 (t, J = 7.3 Hz, 6H), 1.07 (t, J = 7.3 Hz, 3H). 19F{1H} NMR (283 MHz, DMSO-d6) δ = −77.7 (OTf). 13C{1H} NMR (75.5 MHz, DMSO-d6) δ = 148.6 (s), 146.3 (s), 133.7 (s), 133.3 (s), 132.0 (s), 131.8 (s), 125.5 (s), 125.2 (s), 124.9 (s), 124.8 (s), 124.4 (s), 114.3 (s), 112.4 (s), 55.0 (s), 54.7 (s), 14.7 (s), 13.6 (s).

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AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected]. Fax: +1 250 721 7147. Tel: +1 250 721 7150. ORCID

Charles L. B. Macdonald: 0000-0002-0574-1524 Neil Burford: 0000-0002-7698-390X Michael J. Ferguson: 0000-0002-5221-4401 Author Contributions

R.S. performed the major experiments and drafted and reviewed the manuscript. A.S. and M.J.F. performed singlecrystal X-ray diffraction measurements and contributed to the analysis of the data. A.S. ran the elemental analysis on the isolated compounds. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The work was supported by the University of Victoria, the University of Windsor, and the Natural Sciences and Engineering Research Council of Canada (NSERC, 2498092013, CLBM; 1304596-2016, NB). This research was enabled in part by support provided by WestGrid, Compute Canada (www.computecanada.ca) and Gaussian 16. Yuqiao Zhou from the University of Alberta is thanked for his assistance regarding X-ray crystallography.

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REFERENCES

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S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.9b00419. Calculation details and spectra (PDF) Accession Codes

CCDC 1843706, 1843707, 1844125 and 1847486−1847489 contain the supplementary crystallographic data for this article. The data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/ structures. G

DOI: 10.1021/acs.inorgchem.9b00419 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry

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DOI: 10.1021/acs.inorgchem.9b00419 Inorg. Chem. XXXX, XXX, XXX−XXX