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Main group metal halide complexes with sterically hindered thioureas XVI: The synthesis, characterization, and crystal structures of two new complexes of 1,3-dimethyl-2(3H)-imidazolethione with indium trihalides
Inorganica Chimica Acta 285 (1999) 217±222
Main group metal halide complexes with sterically hindered thioureas XVI: The synthesis, characterization, and crystal structures of two new complexes of 1,3-dimethyl-2(3H)-imidazolethione with indium trihalides Daniel J. Williamsa,*, Vicky L.H. Bevilacquaa, Peter A. Morsona, Kelly J. Dennisona, William T. Penningtonb, George L. Schimekb, Donald VanDerveerc, John S. Krugerc, Nancy T. Kawaid a
Department of Chemistry, Kennesaw State University, Kennesaw, GA 30144-5591, USA b Department of Chemistry, Clemson University, Clemson, SC 29634-1905, USA c School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332-0400, USA d Bruker Optics, Billerica, MA 01821, USA Received 31 March 1998; received in revised form 25 May 1998; accepted 1 July 1998
Abstract In an attempt to make complexes analogous to the bis-dmit adducts of Group 15 trihalides [dmit 1,3-dimethyl-2(3H)-imidazolethione], two new trihalide complexes of In(III) were synthesized and characterized. The crystal and molecular structures for both of these compounds showed a distorted trigonal bipyramidal con®guration with the thiones and one halide occupying equatorial positions and the two remaining halides arranged in a near-linear X±In±X axial grouping (X Cl, Br). This stands in contrast to the dimeric distorted octahedral structures observed for BiCl3(dmit)2 and SbCl3(dmit)2. The far-infrared and laser-Raman spectra as well as solution state proton and solid state 13 C NMR spectra are reported. # 1999 Elsevier Science S.A. All rights reserved. Keywords: Indium(III) halide complexes; Thiourea complexes; Crystal structures
1. Introduction The stereoactivity of the lone pair of electrons in AX6E main group complexes (A central metal, X two electron donor, E lone pair) has been a puzzlement to many researchers ever since the introduction of valence shell electron pair repulsion theory (VSEPR) as a model for prediction of structure [1]. A recent paper by GarciaMontvalo et al. reported the structures of octahedral complexes of In(III) made with the same ligands which had been used for analogous Bi(III) complexes [2]. The study correlated the hard±soft acid±base nature of the donor site with lone pair stereoactivity as predicted by Wynne [3] and sought to understand the nature and degree of distortions in both types of complexes that could be attributed to the
*Corresponding author. Tel.: +1-770-423-6159; fax: +1-770-423-6744.
presence or absence of the lone pair in the coordination sphere. Two of our previous papers reported structures of MCl3(dmit)2 where M Sb, Bi and dmit 1,3-dimethyl2(3H)-imidazolethione (Fig. 1) [4,5]. Both structures could be described as distorted octahedra achieved through coordination with a neighboring molecule. There was no clear evidence of lone pair stereoactivity in either structure. Nevertheless, in light of Garcia-Montvalo's study, further understanding of the nature of the octahedral distortions noted with the Group 15 trihalide dmit adducts may be achievable if the analogous Group 13 compounds could be investigated, and if the adducts were isostructural. Since no dmit adduct of any of the Group 13 trihalide has ever been reported or characterized, this study reports the successful synthesis and characterization of InX3(dmit)2 where X Cl, Br. Additionally, the X-ray crystallographic structures as well as new spectroscopic data including solid state 13 C nuclear magnetic resonance data (MAS-NMR) are reported.
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2.2.3. Dmit Proton NMR () 3.48 (s, 3H, methyl), 6.82 (s, 2H, ring ole®nic). Solution 13 C NMR (ppm): 35.7 (methyl); 119.0 (ring ole®nic); 164.2 (thiocarbonyl). 13 C (MAS-NMR) (ppm): 36.5 (methyl); 117.3 (ring ole®nic); 161.0 (thiocarbonyl). Fig. 1. 1,3-dimethyl-2(3H)-imidazolethione (dmit).
2. Experimental 2.1. General All chemicals were reagent grade and used as commercially obtained without further puri®cation. Spectroscopic grade CD3CN (Aldrich) was used as solvent to obtain the proton and 13 C nuclear magnetic resonance (NMR) data. Dmit was prepared using methods reported in the literature [6]. Carbon, hydrogen, and nitrogen analyses were done by Atlantic Microlabs. Melting points (uncorrected) were taken in capillary tubes on a BuÈchi SMP-20 melting point apparatus. 2.2. Synthesis 2.2.1. Bis[1,3-dimethyl-2(3H)-imidazolethione] trichloroindium(III) A mixture of 1.35 g (4.60 mmol) InCl34H2O (Aldrich) and 1.60 g dmit (12.5 mmol) were mixed in 50 ml hot CH3CN to which enough absolute ethanol had been added to dissolve all solids. The solution was then boiled down to about half volume and allowed to cool. White crystals were obtained in about 90% yield. M.p. 237±2388C. Anal. Calc. for C10H16Cl3InN4S2: C, 25.15; H, 3.38; Cl, 24.04; N, 11.73. Found: C, 25.37; H, 3.39; Cl, 23.77; N, 11.72%. Proton NMR (): 3.66 (s, 3H, methyl), 7.07 (s, 2H, ring ole®nic). Solution 13 C NMR (ppm): 36.6 (methyl); 121.4 (ring ole®nic); not observed (thiocarbonyl). 13 C (MAS-NMR) (ppm): 37.5 (methyl); 123.3 (ring ole®nic); 147.8 (thiocarbonyl). Crystallographic-grade crystals were grown from slow evaporative cooling of CH3CN. 2.2.2. Bis[1,3-dimethyl-2(3H)-imidazolethione] tribromoindium(III) The same procedure was used as described above using InBr3 (Alfa) and dmit. White crystals were obtained in about 50% yield. M.p. 228±2298C. Anal. Calc. for C10H16Br3InN4S2: C, 19.66; H, 2.64; Br, 39.24; N, 9.17. Found: C, 19.77; H, 2.62; Br, 39.20; N, 9.26%. Proton NMR (): 3.67 (s, 3H, methyl), 7.10 (s, 2H, ring ole®nic). Solution 13 C NMR (ppm): 36.8 (methyl); 121.5 (ring ole®nic); not observed (thiocarbonyl). 13 C (MAS-NMR) (ppm): 37.9 (methyl); 122.1 (ring ole®nic); 148.2 (thiocarbonyl). The recrystallization solvent was water.
2.3. Crystallography 2.3.1. InCl3(dmit)2 Intensity data were measured with graphite-monochroÊ ) at 22 18C by mated Mo Ka radiation ( 0.71073 A using !/2 scans (2max 508) on a Rigaku AFC7R diffractometer. An empirical absorption correction based on azimuthal scans of several moderately intense re¯ections was applied to the data ( 1.92 mmÿ1; transmission coef®cients: 0.95±1.00), as were Lorentz and polarization corrections. The intensities of three check re¯ections measured periodically throughout data collection ¯uctuated by only 1%, indicating crystal and electronic stability. The structures were solved by direct methods and re®ned by using full-matrix least-squares techniques. All non-hydrogen atoms were re®ned anisotropically; hydrogen atoms Ê ) with a were placed in optimized positions (dC±H 0.96 A 2 Ê re®ned group thermal parameter (U 0.103(8) A ). As the compound crystallizes in the acentric space group P21212, re®nement was carried out for both enantiomers of the crystal. This re®nement was based on two inequivalent octants of data and (h, k, l; 1433 observed data (I > 3(I)) gave residuals of: R 0.0216, Rw 0.0221, GOF 1.57. The ®nal re®nement was based on the model which gave signi®cantly better residual values. Structure solution, re®nement and the calculation of derived results were performed with the SHELXTL [7] package of computer programs. Neutral atom scattering factors were those of Cromer and Waber [8], and the real and imaginary anomalous dispersion corrections were those of Cromer [9]. Relevant crystallographic data are given in Table 1, and the selected bond distances and angles are shown in Table 2. Fig. 2 shows the ORTEP drawing at the 50% probability level. 2.3.2. InBr3(dmit)2 Data collection was carried out using a Siemens SMART CCD diffractometer at 170 K. Preliminary cell constants were obtained from 60 narrow frames (frame width 0.38 in (!) data. Final cell parameters were obtained by global re®nement of re¯ections obtained from integration of all the frame data. A total of 1271 frames of intensity data were collected with a frame width of 0.38 in ! and a counting time of 30 s per frame at a crystal-to-detector distance of 4.911 cm. The double-pass method of scanning was used to exclude any noise. The collected frames were integrated using the preliminary cell-orientation matrix. Empirical absorption corrections were applied ( 7.752 mmÿ1; transmission coef®cients: 0.210 to 0.127) [10]. The integra-
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Table 1 Crystallographic data for InCl3(dmit)2 (1) and InBr3(dmit)2 (2) Empirical formula Formula weight Color, habit Crystal size (mm) Temperature (K) Ê) Wavelength (A Crystal system Space group Unit cell dimensions Ê) a (A Ê) b (A Ê) c (A (8) Ê 3) Volume (A Z Density (calculated) (Mg mÿ3) F(000) Diffractometer Cell parameter collection Absorption coefficient (mmÿ1) Range for data collection (8) Goodness-of-fit Final R indices R Rw Extinction coefficient Ê ÿ3) Largest difference peak, hole (e A
C10H16Cl3InN2S4 (1) 477.56 colorless, parallelepiped 0.12 0.12 0.14 295(1) 0.71073 orthorhombic P21212
C10H16Br3InN2S4 (2) 610.94 colorless, parallelepiped 0.41 0.44 0.31 173(2) 0.71073 monoclinic P2/n
10.134(1) 10.891(1) 8.415(1) 928.8(1) 2 1.708 472 Rigaku AFC-7R 24 (22.52 < 2 < 28.67) 1.92 2.50±25.00 GOF1 1.57 (1.86)a
14.9853(3) 8.3123(1) 15.2930(3) 91.964(1) 1903.8(1) 4 2.131 1160 Siemens SMART CCD See text 7.75 1.87±28.76 1.21
0.0216 (0.0256)a 0.0221 (0.0262)a 0.0011 0.21, ÿ0.23
0.0320 0.0805 0.0016 1.07, ÿ0.85
a
Values in parentheses refer to the incorrect enantiomer. E.s.d.s given in parentheses.
Table 2 Ê ) and angles (8) for InCl3(dmit)2 Coordination sphere bond distances (A Distances In(1)±Cl(1) In(1)±S(1) Angles Cl(1)±In(1)±Cl(2) Cl(2)±In(1)±S(1) Cl(1)±In(1)±S(1a) In(1)±S(1)±C(1)
2.505 (1) 2.516 (1) 98.2 110.2 81.6 105.5
(1) (1) (1) (2)
In(1)±Cl(2)
Cl(1)±In(1)±S(1) Cl(1)±In(1)±Cl(1a) S(1)±In(1)±S(1a)
2.402 (2)
92.8 (1) 163.5 (1) 139.7 (1)
Atoms labeled with a lower-case character were generated by the following symmetry operation: (a) 1 ÿ x, 1 ÿ y, z. E.s.d.s given in parentheses.
tion process yielded a total of 11632 re¯ections of which 4467 were independent re¯ections. The ®rst 50 frames of data were recollected at the end of data collection (13.5 h total data collection time) to monitor crystal decay. No crystal decay was observed for this data set. The non-H atoms were re®ned anisotropically to convergence. The H atoms were treated using an appropriate riding model. Relevant crystallographic data are given in Table 1, and the selected bond distances and angles are shown in Table 3. Fig. 3 shows the ORTEP structure at the 50% probability level. 2.4. Solution studies Proton NMR spectra were recorded with a Varian Gemini 300 MHz spectrometer and proton decoupled 13 C spectra were collected on a Bruker AVANCE DPX 300 MHz instrument. Chemical shifts are reported in ppm () relative to tetramethylsilane. Key: s-singlet, d-doublet, m-multiplet. 2.5. Solid state spectra
Fig. 2. ORTEP drawing of InCl3(dmit)2. Thermal ellipsoids are drawn at the 50% probability level.
Laser Raman spectra were collected on neat solids in non¯uorescing glass vials or capillary tubes on a Bruker Model RFS 100/S Fourier transform (FT) spectrophotometer, and far-infrared (FIR) spectra were collected in mineral oil mulls (Nujol) between polyethylene plates with a Bruker Model IFS66V FTIR spectrophotometer. Only the peaks
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D.J. Williams et al. / Inorganica Chimica Acta 285 (1999) 217±222
Table 3 Ê ) and angles (8) for InBr3(dmit)2 Coordination sphere bond distances (A Distances In(1)±Br(1) In(2)±Br(3) In(1)±S(1) Angles Br(1)±In(1)±Br(2) Br(3)±In(2)±Br(4) Br(2)±In(1)±S(1) Br(4)±In(2)±S(2) Br(1)±In(1)±S(1A) Br(3)±In(2)±S(2) In(1)±S(1)±C(1)
2.680 (1) 2.670 (1) 2.528 (2)
98.2 99.3 110.4 108.9 81.5 81.1 104.9
(1) (1) (1) (1) (1) (1) (2)
In(1)±Br(2) In(2)±Br(4) In(2)±S(2)
Br(1)±In(1)±S(1) Br(3)±In(2)±S(2B) Br(1)±In(1)±Br(1A) Br(3)±In(2)±Br(3B) S(1)±In(1)±S(1A) S(2)±In(2)±S(2B) In(2)±S(2)±C(6)
2.547 (1) 2.563 (1) 2.529 (2)
92.3 92.9 162.2 161.4 139.2 142.2 103.2
(1) (1) (1) (1) (1) (1) (2)
Atoms labeled with an upper-case character were generated by the following symmetry operation: (A) ÿx 1/2, y, ÿz ÿ 1/2; (B) ÿx 1/2, y, ÿz 1/2. E.s.d.s given in parentheses.
Fig. 3. ORTEP drawing of one of the two unique molecules in the asymmetric unit for InBr3(dmit)2. Thermal ellipsoids are drawn at the 50% probability level.
within the range of primary interest (viz. up to 500 cmÿ1) are reported. All values are in cmÿ1 (2). The spectral results with assignments are reported below in Table 4. Solid state 13 C NMR (MAS-NMR) spectra were collected on a Bruker AVANCE DPX 300 MHz instrument ®tted with solid state probe. Chemical shifts are reported in ppm () relative to tetramethylsilane. The solid state and solution state (CD3CN) spectra for dmit are reported above.
The resultant stoichiometries of the InX3(dmit)2 complexes appeared promising for a comparative structural study with the Group 15 analogs cited above, but the results of the crystal structures revealed a different picture altogether. No form of polymerization was noted; both indium compounds are strictly monomeric. Thus, these two complexes proved unhelpful in assessing lone pair effects for the Group 15 analogs. Nevertheless, since there are so few InX3 thiourea-type complexes reported in the literature, they do provide useful structural information especially when coupled with solid state vibrational data as discussed below. 3.1. Crystallographic data As seen in Figs. 2 and 3, both complexes display a distorted trigonal bipyramidal geometry around the indium with the thione ligands occupying equatorial positions along with one of the halide atoms. The remaining two halogens occupy the axial positions in a near linear X±In±X arrangement. The largest angular deviations from the ideal trigonal bipyramidal con®guration is observed for both complexes in the S±In±S angles, which average around 1398. There is strikingly similar angular modes of distortion in both complexes which may be due to dmit steric bulk and packing constraints. Ê in The average In±Cl bond distance of 2.544(5) A InCl3(tu)3 is slightly longer than the observed axial In±Cl Ê ) in InCl3(dmit)2 as is the In±S bond distance (2.505(1) A Ê [11] as compared to average distance of 2.593(5) A Ê 2.516(1) A. The tribromide complex actually shows two independent complexes, each on a two-fold axis. Although there are small difference in In±Br bond lengths and angles (Table 3), they are not structurally signi®cant. Fig. 3 shows one of the two independent molecules. Average ligand bond angles and distances calculated from both structures are displayed in Fig. 4. These values are in agreement with those noted in other dmit structural studies [4,5]. 3.2. Spectroscopy Proton NMR spectra show the normal down®eld shifts observed upon complexation as do the solution state 13 C
3. Results and discussion Additions of three-fold molar excesses of dmit to solutions of InX3 (X Cl, Br) give rise to the formation of two new bis adducts. In contrast, the only other structural study reported for an indium thiourea-type complex gave a tris adduct, InCl3(tu)3, under similar conditions (tu thiourea) [11]. The sterically hindered nature of dmit is the most likely explanation for the limited degree of substitution in the valence shell of indium despite the molar excess ligand.
Ê ) and angles (8) computed from Fig. 4. Average dmit bond distances (A both structures. E.s.d.s given in parentheses.
D.J. Williams et al. / Inorganica Chimica Acta 285 (1999) 217±222
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Table 4 Far-infrared (FIR) and laser Raman spectra InCl3(dmit)2 FIR 503 483 332 325
(m) (m) (m) (m)
300 (s,br) 295 (m,sh)
252 (s,br)
InBr3(dmit)2 Raman
FIR
Raman
503 (m) 484 (w)
501 (m) 482 (s) 331 (m)
501 (m) 483 (m)
dmit dmit dmit
318 (m) 300 (w)
dmit dmit (In±Cl)eq
321 (m) 299 (m) 294 (m) 255 (m) 237 (s)
226 (m) 200 (vw)
298 (m)
277 (vw) 270 (vw) 252 (m)
128 (m) 112 (m) 100 (s) 89 (m)
252 (w)
224 (m) 200 (s)
asym(Cl±In±Cl) (In±S) sym(Cl±In±Cl) (In±Br)eq (In±Cl) asym(Br±In±Br) sym(Br±In±Br)
155 (m)
(In±Br) (In±Br)
231 (s,br) 224 203 199 183
(m,sh) (m) (m) (vs)
137 (m) 128 (m) 112 (m)
Assignments
132 (vw) 108 100 93 88
(m) (m) (m) (m)
117 (m) 108 (m) 90 (m)
Key: s strong; m medium; w weak; sh shoulder; v very.
spectra. Thiocarbonyl carbons were not observable in solution state 13 C spectra despite repeated attempts with extended scan times. Low solubility is the most likely explanation. However, recorded MAS-NMR 13 C spectra and solution state spectra correlate very closely in the shifts which are observed. Sometimes solid and solution state data are not directly comparable because of solid state anisotropy with respect to chemical shifts [12], but this does not appear to be the case in this instance. It is interesting to compare the solution state and solid state spectra of free dmit with those recorded for the InX3 complexes. The general trends in the 13 C spectra are ®rst, a down®eld shift of the ole®nic carbons due to increased ring aromaticity in the complexes relative to the free ligand, and secondly, a concomitant increase in shielding for the thiocarbonyl carbon due to reduced bond order. These trends are noted in the solid state spectrum and in part in the solution state spectra as explained above. Similar trends are seen in the 13 C solution spectra for other dmit complexes and derivatives [13]. This is the ®rst literature report of solid state 13 C NMR spectra for dmit and dmit-based complexes. In many of our previous papers, we provided examples of solid state vibrational data coupled with X-ray data as an important tool for structure determination in the absence of crystallographic data [14±16]. One particularly important vibrational marker in these types of compounds is the linear
X±M±X group. Solid state vibrational data are summarized in Table 4, and assignments are made based on frequency and relative intensity. The predominant feature in the observed spectra is the pattern characteristic of linear X± M±X groups. The lower frequency symmetric band predominates the Raman spectrum while the higher frequency asymmetric band is a main feature of the FIR. Additionally, the equatorial In±X stretch is observed at a frequency higher than those observed for the linear grouping. Assignments are based, in part, on those made for the analogous SbX3(dmit)2 complexes (X Cl, Br) which also have linear X±M±X moieties [4,14]. 4. Supplementary material Supplemental crystallographic data sets for both structures are available through the Cambridge Structural Database. Acknowledgements We would like to thank the Wilcom Foundation of Marietta, GA and the Georgia Institute of Technology Faculty Development Fund for partial support of this research. We also gratefully acknowledge the National
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Science Foundation for the purchase of the NMR equipment at Georgia Tech (BIR 9306392) and at Kennesaw State (DUE 9452027). References [1] J.E. Huheey, E.A. Keiter, R.L. Keiter, Inorganic Chemistry, 4th ed., Harper Collins College Publishers, New York, 1993, pp. 214±215. [2] V. Garcia-Montvalo, R. Cea-Olivares, D.J. Williams, G. EspinozaPerez, Inorg. Chem. 35 (1996) 3948. [3] K.J. Wynne, J. Chem. Ed. 50 (1973) 328. [4] B. Rubin, F.R. Hedrich, W.K. Dean, D.J. Williams, A. Viehbeck, Inorg. Chem. 20 (1981) 4434. [5] D.J. Williams, B. Rubin, J. Epstein, W.K. Dean, A. Viehbeck, Cryst. Struct. Commun. 11 (1982) 1. [6] B.L. Benac, E.M. Burgess, A.J. Arduengo, Org. Synth. 64 (1985) 92.
[7] G.M. Sheldrick, SHELXTL, Crystallographic Computing System, Nicolet Instruments Division, Madison, WI, 1986. [8] D.T. Cromer, J.T. Waber, International Tables for X-ray Crystallography, Vol. IV, Table 2.2B, Kynoch Press, Birmingham, UK, 1974. [9] D.T Cromer, International Tables for X-ray Crystallography, Vol. IV, Table 2.3.1, Kynoch Press, Birmingham UK, 1974. [10] R.H. Blessing, Acta Crystallogr., Sect. A 51 (1995) 33. [11] M.A. Malyarik, A.B. Ilyukhin, S.P. Petrosynants, Y.A. Buslaev, Russ. J. Inorg. Chem. 37 (1992) 763. [12] R.K. Harris, Nuclear Magnetic Resonance Spectroscopy, Longman Scientific and Technical, London, 1986, p. 153. [13] D.J. Williams, T.A. Ly, J.W. Mudge, D. VanDerveer, R.L. Jones, Inorg. Chim. Acta 214 (1994) 133. [14] D.J. Williams, A. Viehbeck, Inorg. Chem. 18 (1979) 1823. [15] K.J. Wynne, P.S. Pearson, Inorg. Chem. 10 (1972) 2735. [16] D.J. Williams, D. VanDerveer, B.R. Crouse, R.R. Raye, T.R. Carter, K.S. Hagen, M. Brewer, Main Group Chem. 2 (1997) 61.
Main group metal halide complexes with sterically hindered thioureas XVI: The synthesis, characterization, and crystal structures of two new complexes of 1,3-dimethyl-2(3H)-imidazolethione with indium trihalides Daniel J. Williamsa,*, Vicky L.H. Bevilacquaa, Peter A. Morsona, Kelly J. Dennisona, William T. Penningtonb, George L. Schimekb, Donald VanDerveerc, John S. Krugerc, Nancy T. Kawaid a
Department of Chemistry, Kennesaw State University, Kennesaw, GA 30144-5591, USA b Department of Chemistry, Clemson University, Clemson, SC 29634-1905, USA c School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332-0400, USA d Bruker Optics, Billerica, MA 01821, USA Received 31 March 1998; received in revised form 25 May 1998; accepted 1 July 1998
Abstract In an attempt to make complexes analogous to the bis-dmit adducts of Group 15 trihalides [dmit 1,3-dimethyl-2(3H)-imidazolethione], two new trihalide complexes of In(III) were synthesized and characterized. The crystal and molecular structures for both of these compounds showed a distorted trigonal bipyramidal con®guration with the thiones and one halide occupying equatorial positions and the two remaining halides arranged in a near-linear X±In±X axial grouping (X Cl, Br). This stands in contrast to the dimeric distorted octahedral structures observed for BiCl3(dmit)2 and SbCl3(dmit)2. The far-infrared and laser-Raman spectra as well as solution state proton and solid state 13 C NMR spectra are reported. # 1999 Elsevier Science S.A. All rights reserved. Keywords: Indium(III) halide complexes; Thiourea complexes; Crystal structures
1. Introduction The stereoactivity of the lone pair of electrons in AX6E main group complexes (A central metal, X two electron donor, E lone pair) has been a puzzlement to many researchers ever since the introduction of valence shell electron pair repulsion theory (VSEPR) as a model for prediction of structure [1]. A recent paper by GarciaMontvalo et al. reported the structures of octahedral complexes of In(III) made with the same ligands which had been used for analogous Bi(III) complexes [2]. The study correlated the hard±soft acid±base nature of the donor site with lone pair stereoactivity as predicted by Wynne [3] and sought to understand the nature and degree of distortions in both types of complexes that could be attributed to the
*Corresponding author. Tel.: +1-770-423-6159; fax: +1-770-423-6744.
presence or absence of the lone pair in the coordination sphere. Two of our previous papers reported structures of MCl3(dmit)2 where M Sb, Bi and dmit 1,3-dimethyl2(3H)-imidazolethione (Fig. 1) [4,5]. Both structures could be described as distorted octahedra achieved through coordination with a neighboring molecule. There was no clear evidence of lone pair stereoactivity in either structure. Nevertheless, in light of Garcia-Montvalo's study, further understanding of the nature of the octahedral distortions noted with the Group 15 trihalide dmit adducts may be achievable if the analogous Group 13 compounds could be investigated, and if the adducts were isostructural. Since no dmit adduct of any of the Group 13 trihalide has ever been reported or characterized, this study reports the successful synthesis and characterization of InX3(dmit)2 where X Cl, Br. Additionally, the X-ray crystallographic structures as well as new spectroscopic data including solid state 13 C nuclear magnetic resonance data (MAS-NMR) are reported.
0020-1693/99/$ ± see front matter # 1999 Elsevier Science S.A. All rights reserved. PII: S0020-1693(98)00334-X
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2.2.3. Dmit Proton NMR () 3.48 (s, 3H, methyl), 6.82 (s, 2H, ring ole®nic). Solution 13 C NMR (ppm): 35.7 (methyl); 119.0 (ring ole®nic); 164.2 (thiocarbonyl). 13 C (MAS-NMR) (ppm): 36.5 (methyl); 117.3 (ring ole®nic); 161.0 (thiocarbonyl). Fig. 1. 1,3-dimethyl-2(3H)-imidazolethione (dmit).
2. Experimental 2.1. General All chemicals were reagent grade and used as commercially obtained without further puri®cation. Spectroscopic grade CD3CN (Aldrich) was used as solvent to obtain the proton and 13 C nuclear magnetic resonance (NMR) data. Dmit was prepared using methods reported in the literature [6]. Carbon, hydrogen, and nitrogen analyses were done by Atlantic Microlabs. Melting points (uncorrected) were taken in capillary tubes on a BuÈchi SMP-20 melting point apparatus. 2.2. Synthesis 2.2.1. Bis[1,3-dimethyl-2(3H)-imidazolethione] trichloroindium(III) A mixture of 1.35 g (4.60 mmol) InCl34H2O (Aldrich) and 1.60 g dmit (12.5 mmol) were mixed in 50 ml hot CH3CN to which enough absolute ethanol had been added to dissolve all solids. The solution was then boiled down to about half volume and allowed to cool. White crystals were obtained in about 90% yield. M.p. 237±2388C. Anal. Calc. for C10H16Cl3InN4S2: C, 25.15; H, 3.38; Cl, 24.04; N, 11.73. Found: C, 25.37; H, 3.39; Cl, 23.77; N, 11.72%. Proton NMR (): 3.66 (s, 3H, methyl), 7.07 (s, 2H, ring ole®nic). Solution 13 C NMR (ppm): 36.6 (methyl); 121.4 (ring ole®nic); not observed (thiocarbonyl). 13 C (MAS-NMR) (ppm): 37.5 (methyl); 123.3 (ring ole®nic); 147.8 (thiocarbonyl). Crystallographic-grade crystals were grown from slow evaporative cooling of CH3CN. 2.2.2. Bis[1,3-dimethyl-2(3H)-imidazolethione] tribromoindium(III) The same procedure was used as described above using InBr3 (Alfa) and dmit. White crystals were obtained in about 50% yield. M.p. 228±2298C. Anal. Calc. for C10H16Br3InN4S2: C, 19.66; H, 2.64; Br, 39.24; N, 9.17. Found: C, 19.77; H, 2.62; Br, 39.20; N, 9.26%. Proton NMR (): 3.67 (s, 3H, methyl), 7.10 (s, 2H, ring ole®nic). Solution 13 C NMR (ppm): 36.8 (methyl); 121.5 (ring ole®nic); not observed (thiocarbonyl). 13 C (MAS-NMR) (ppm): 37.9 (methyl); 122.1 (ring ole®nic); 148.2 (thiocarbonyl). The recrystallization solvent was water.
2.3. Crystallography 2.3.1. InCl3(dmit)2 Intensity data were measured with graphite-monochroÊ ) at 22 18C by mated Mo Ka radiation ( 0.71073 A using !/2 scans (2max 508) on a Rigaku AFC7R diffractometer. An empirical absorption correction based on azimuthal scans of several moderately intense re¯ections was applied to the data ( 1.92 mmÿ1; transmission coef®cients: 0.95±1.00), as were Lorentz and polarization corrections. The intensities of three check re¯ections measured periodically throughout data collection ¯uctuated by only 1%, indicating crystal and electronic stability. The structures were solved by direct methods and re®ned by using full-matrix least-squares techniques. All non-hydrogen atoms were re®ned anisotropically; hydrogen atoms Ê ) with a were placed in optimized positions (dC±H 0.96 A 2 Ê re®ned group thermal parameter (U 0.103(8) A ). As the compound crystallizes in the acentric space group P21212, re®nement was carried out for both enantiomers of the crystal. This re®nement was based on two inequivalent octants of data and (h, k, l; 1433 observed data (I > 3(I)) gave residuals of: R 0.0216, Rw 0.0221, GOF 1.57. The ®nal re®nement was based on the model which gave signi®cantly better residual values. Structure solution, re®nement and the calculation of derived results were performed with the SHELXTL [7] package of computer programs. Neutral atom scattering factors were those of Cromer and Waber [8], and the real and imaginary anomalous dispersion corrections were those of Cromer [9]. Relevant crystallographic data are given in Table 1, and the selected bond distances and angles are shown in Table 2. Fig. 2 shows the ORTEP drawing at the 50% probability level. 2.3.2. InBr3(dmit)2 Data collection was carried out using a Siemens SMART CCD diffractometer at 170 K. Preliminary cell constants were obtained from 60 narrow frames (frame width 0.38 in (!) data. Final cell parameters were obtained by global re®nement of re¯ections obtained from integration of all the frame data. A total of 1271 frames of intensity data were collected with a frame width of 0.38 in ! and a counting time of 30 s per frame at a crystal-to-detector distance of 4.911 cm. The double-pass method of scanning was used to exclude any noise. The collected frames were integrated using the preliminary cell-orientation matrix. Empirical absorption corrections were applied ( 7.752 mmÿ1; transmission coef®cients: 0.210 to 0.127) [10]. The integra-
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Table 1 Crystallographic data for InCl3(dmit)2 (1) and InBr3(dmit)2 (2) Empirical formula Formula weight Color, habit Crystal size (mm) Temperature (K) Ê) Wavelength (A Crystal system Space group Unit cell dimensions Ê) a (A Ê) b (A Ê) c (A (8) Ê 3) Volume (A Z Density (calculated) (Mg mÿ3) F(000) Diffractometer Cell parameter collection Absorption coefficient (mmÿ1) Range for data collection (8) Goodness-of-fit Final R indices R Rw Extinction coefficient Ê ÿ3) Largest difference peak, hole (e A
C10H16Cl3InN2S4 (1) 477.56 colorless, parallelepiped 0.12 0.12 0.14 295(1) 0.71073 orthorhombic P21212
C10H16Br3InN2S4 (2) 610.94 colorless, parallelepiped 0.41 0.44 0.31 173(2) 0.71073 monoclinic P2/n
10.134(1) 10.891(1) 8.415(1) 928.8(1) 2 1.708 472 Rigaku AFC-7R 24 (22.52 < 2 < 28.67) 1.92 2.50±25.00 GOF1 1.57 (1.86)a
14.9853(3) 8.3123(1) 15.2930(3) 91.964(1) 1903.8(1) 4 2.131 1160 Siemens SMART CCD See text 7.75 1.87±28.76 1.21
0.0216 (0.0256)a 0.0221 (0.0262)a 0.0011 0.21, ÿ0.23
0.0320 0.0805 0.0016 1.07, ÿ0.85
a
Values in parentheses refer to the incorrect enantiomer. E.s.d.s given in parentheses.
Table 2 Ê ) and angles (8) for InCl3(dmit)2 Coordination sphere bond distances (A Distances In(1)±Cl(1) In(1)±S(1) Angles Cl(1)±In(1)±Cl(2) Cl(2)±In(1)±S(1) Cl(1)±In(1)±S(1a) In(1)±S(1)±C(1)
2.505 (1) 2.516 (1) 98.2 110.2 81.6 105.5
(1) (1) (1) (2)
In(1)±Cl(2)
Cl(1)±In(1)±S(1) Cl(1)±In(1)±Cl(1a) S(1)±In(1)±S(1a)
2.402 (2)
92.8 (1) 163.5 (1) 139.7 (1)
Atoms labeled with a lower-case character were generated by the following symmetry operation: (a) 1 ÿ x, 1 ÿ y, z. E.s.d.s given in parentheses.
tion process yielded a total of 11632 re¯ections of which 4467 were independent re¯ections. The ®rst 50 frames of data were recollected at the end of data collection (13.5 h total data collection time) to monitor crystal decay. No crystal decay was observed for this data set. The non-H atoms were re®ned anisotropically to convergence. The H atoms were treated using an appropriate riding model. Relevant crystallographic data are given in Table 1, and the selected bond distances and angles are shown in Table 3. Fig. 3 shows the ORTEP structure at the 50% probability level. 2.4. Solution studies Proton NMR spectra were recorded with a Varian Gemini 300 MHz spectrometer and proton decoupled 13 C spectra were collected on a Bruker AVANCE DPX 300 MHz instrument. Chemical shifts are reported in ppm () relative to tetramethylsilane. Key: s-singlet, d-doublet, m-multiplet. 2.5. Solid state spectra
Fig. 2. ORTEP drawing of InCl3(dmit)2. Thermal ellipsoids are drawn at the 50% probability level.
Laser Raman spectra were collected on neat solids in non¯uorescing glass vials or capillary tubes on a Bruker Model RFS 100/S Fourier transform (FT) spectrophotometer, and far-infrared (FIR) spectra were collected in mineral oil mulls (Nujol) between polyethylene plates with a Bruker Model IFS66V FTIR spectrophotometer. Only the peaks
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Table 3 Ê ) and angles (8) for InBr3(dmit)2 Coordination sphere bond distances (A Distances In(1)±Br(1) In(2)±Br(3) In(1)±S(1) Angles Br(1)±In(1)±Br(2) Br(3)±In(2)±Br(4) Br(2)±In(1)±S(1) Br(4)±In(2)±S(2) Br(1)±In(1)±S(1A) Br(3)±In(2)±S(2) In(1)±S(1)±C(1)
2.680 (1) 2.670 (1) 2.528 (2)
98.2 99.3 110.4 108.9 81.5 81.1 104.9
(1) (1) (1) (1) (1) (1) (2)
In(1)±Br(2) In(2)±Br(4) In(2)±S(2)
Br(1)±In(1)±S(1) Br(3)±In(2)±S(2B) Br(1)±In(1)±Br(1A) Br(3)±In(2)±Br(3B) S(1)±In(1)±S(1A) S(2)±In(2)±S(2B) In(2)±S(2)±C(6)
2.547 (1) 2.563 (1) 2.529 (2)
92.3 92.9 162.2 161.4 139.2 142.2 103.2
(1) (1) (1) (1) (1) (1) (2)
Atoms labeled with an upper-case character were generated by the following symmetry operation: (A) ÿx 1/2, y, ÿz ÿ 1/2; (B) ÿx 1/2, y, ÿz 1/2. E.s.d.s given in parentheses.
Fig. 3. ORTEP drawing of one of the two unique molecules in the asymmetric unit for InBr3(dmit)2. Thermal ellipsoids are drawn at the 50% probability level.
within the range of primary interest (viz. up to 500 cmÿ1) are reported. All values are in cmÿ1 (2). The spectral results with assignments are reported below in Table 4. Solid state 13 C NMR (MAS-NMR) spectra were collected on a Bruker AVANCE DPX 300 MHz instrument ®tted with solid state probe. Chemical shifts are reported in ppm () relative to tetramethylsilane. The solid state and solution state (CD3CN) spectra for dmit are reported above.
The resultant stoichiometries of the InX3(dmit)2 complexes appeared promising for a comparative structural study with the Group 15 analogs cited above, but the results of the crystal structures revealed a different picture altogether. No form of polymerization was noted; both indium compounds are strictly monomeric. Thus, these two complexes proved unhelpful in assessing lone pair effects for the Group 15 analogs. Nevertheless, since there are so few InX3 thiourea-type complexes reported in the literature, they do provide useful structural information especially when coupled with solid state vibrational data as discussed below. 3.1. Crystallographic data As seen in Figs. 2 and 3, both complexes display a distorted trigonal bipyramidal geometry around the indium with the thione ligands occupying equatorial positions along with one of the halide atoms. The remaining two halogens occupy the axial positions in a near linear X±In±X arrangement. The largest angular deviations from the ideal trigonal bipyramidal con®guration is observed for both complexes in the S±In±S angles, which average around 1398. There is strikingly similar angular modes of distortion in both complexes which may be due to dmit steric bulk and packing constraints. Ê in The average In±Cl bond distance of 2.544(5) A InCl3(tu)3 is slightly longer than the observed axial In±Cl Ê ) in InCl3(dmit)2 as is the In±S bond distance (2.505(1) A Ê [11] as compared to average distance of 2.593(5) A Ê 2.516(1) A. The tribromide complex actually shows two independent complexes, each on a two-fold axis. Although there are small difference in In±Br bond lengths and angles (Table 3), they are not structurally signi®cant. Fig. 3 shows one of the two independent molecules. Average ligand bond angles and distances calculated from both structures are displayed in Fig. 4. These values are in agreement with those noted in other dmit structural studies [4,5]. 3.2. Spectroscopy Proton NMR spectra show the normal down®eld shifts observed upon complexation as do the solution state 13 C
3. Results and discussion Additions of three-fold molar excesses of dmit to solutions of InX3 (X Cl, Br) give rise to the formation of two new bis adducts. In contrast, the only other structural study reported for an indium thiourea-type complex gave a tris adduct, InCl3(tu)3, under similar conditions (tu thiourea) [11]. The sterically hindered nature of dmit is the most likely explanation for the limited degree of substitution in the valence shell of indium despite the molar excess ligand.
Ê ) and angles (8) computed from Fig. 4. Average dmit bond distances (A both structures. E.s.d.s given in parentheses.
D.J. Williams et al. / Inorganica Chimica Acta 285 (1999) 217±222
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Table 4 Far-infrared (FIR) and laser Raman spectra InCl3(dmit)2 FIR 503 483 332 325
(m) (m) (m) (m)
300 (s,br) 295 (m,sh)
252 (s,br)
InBr3(dmit)2 Raman
FIR
Raman
503 (m) 484 (w)
501 (m) 482 (s) 331 (m)
501 (m) 483 (m)
dmit dmit dmit
318 (m) 300 (w)
dmit dmit (In±Cl)eq
321 (m) 299 (m) 294 (m) 255 (m) 237 (s)
226 (m) 200 (vw)
298 (m)
277 (vw) 270 (vw) 252 (m)
128 (m) 112 (m) 100 (s) 89 (m)
252 (w)
224 (m) 200 (s)
asym(Cl±In±Cl) (In±S) sym(Cl±In±Cl) (In±Br)eq (In±Cl) asym(Br±In±Br) sym(Br±In±Br)
155 (m)
(In±Br) (In±Br)
231 (s,br) 224 203 199 183
(m,sh) (m) (m) (vs)
137 (m) 128 (m) 112 (m)
Assignments
132 (vw) 108 100 93 88
(m) (m) (m) (m)
117 (m) 108 (m) 90 (m)
Key: s strong; m medium; w weak; sh shoulder; v very.
spectra. Thiocarbonyl carbons were not observable in solution state 13 C spectra despite repeated attempts with extended scan times. Low solubility is the most likely explanation. However, recorded MAS-NMR 13 C spectra and solution state spectra correlate very closely in the shifts which are observed. Sometimes solid and solution state data are not directly comparable because of solid state anisotropy with respect to chemical shifts [12], but this does not appear to be the case in this instance. It is interesting to compare the solution state and solid state spectra of free dmit with those recorded for the InX3 complexes. The general trends in the 13 C spectra are ®rst, a down®eld shift of the ole®nic carbons due to increased ring aromaticity in the complexes relative to the free ligand, and secondly, a concomitant increase in shielding for the thiocarbonyl carbon due to reduced bond order. These trends are noted in the solid state spectrum and in part in the solution state spectra as explained above. Similar trends are seen in the 13 C solution spectra for other dmit complexes and derivatives [13]. This is the ®rst literature report of solid state 13 C NMR spectra for dmit and dmit-based complexes. In many of our previous papers, we provided examples of solid state vibrational data coupled with X-ray data as an important tool for structure determination in the absence of crystallographic data [14±16]. One particularly important vibrational marker in these types of compounds is the linear
X±M±X group. Solid state vibrational data are summarized in Table 4, and assignments are made based on frequency and relative intensity. The predominant feature in the observed spectra is the pattern characteristic of linear X± M±X groups. The lower frequency symmetric band predominates the Raman spectrum while the higher frequency asymmetric band is a main feature of the FIR. Additionally, the equatorial In±X stretch is observed at a frequency higher than those observed for the linear grouping. Assignments are based, in part, on those made for the analogous SbX3(dmit)2 complexes (X Cl, Br) which also have linear X±M±X moieties [4,14]. 4. Supplementary material Supplemental crystallographic data sets for both structures are available through the Cambridge Structural Database. Acknowledgements We would like to thank the Wilcom Foundation of Marietta, GA and the Georgia Institute of Technology Faculty Development Fund for partial support of this research. We also gratefully acknowledge the National
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Science Foundation for the purchase of the NMR equipment at Georgia Tech (BIR 9306392) and at Kennesaw State (DUE 9452027). References [1] J.E. Huheey, E.A. Keiter, R.L. Keiter, Inorganic Chemistry, 4th ed., Harper Collins College Publishers, New York, 1993, pp. 214±215. [2] V. Garcia-Montvalo, R. Cea-Olivares, D.J. Williams, G. EspinozaPerez, Inorg. Chem. 35 (1996) 3948. [3] K.J. Wynne, J. Chem. Ed. 50 (1973) 328. [4] B. Rubin, F.R. Hedrich, W.K. Dean, D.J. Williams, A. Viehbeck, Inorg. Chem. 20 (1981) 4434. [5] D.J. Williams, B. Rubin, J. Epstein, W.K. Dean, A. Viehbeck, Cryst. Struct. Commun. 11 (1982) 1. [6] B.L. Benac, E.M. Burgess, A.J. Arduengo, Org. Synth. 64 (1985) 92.
[7] G.M. Sheldrick, SHELXTL, Crystallographic Computing System, Nicolet Instruments Division, Madison, WI, 1986. [8] D.T. Cromer, J.T. Waber, International Tables for X-ray Crystallography, Vol. IV, Table 2.2B, Kynoch Press, Birmingham, UK, 1974. [9] D.T Cromer, International Tables for X-ray Crystallography, Vol. IV, Table 2.3.1, Kynoch Press, Birmingham UK, 1974. [10] R.H. Blessing, Acta Crystallogr., Sect. A 51 (1995) 33. [11] M.A. Malyarik, A.B. Ilyukhin, S.P. Petrosynants, Y.A. Buslaev, Russ. J. Inorg. Chem. 37 (1992) 763. [12] R.K. Harris, Nuclear Magnetic Resonance Spectroscopy, Longman Scientific and Technical, London, 1986, p. 153. [13] D.J. Williams, T.A. Ly, J.W. Mudge, D. VanDerveer, R.L. Jones, Inorg. Chim. Acta 214 (1994) 133. [14] D.J. Williams, A. Viehbeck, Inorg. Chem. 18 (1979) 1823. [15] K.J. Wynne, P.S. Pearson, Inorg. Chem. 10 (1972) 2735. [16] D.J. Williams, D. VanDerveer, B.R. Crouse, R.R. Raye, T.R. Carter, K.S. Hagen, M. Brewer, Main Group Chem. 2 (1997) 61.