Preparation and characterization of six-coordinate titanium(IV) monothiocarbamate complexes. X-ray crystal structure of Dichlorobis(N,N-dimethylcarbamothioato-O,S)titanium(IV)

Accepted Manuscript Preparation and Characterization of Six-Coordinate Titanium(IV) Monothiocarbamate Complexes. X-ray Crystal Structure of Dichlorobis(N,N-dimethylcarbamothioato-O,S)titanium(IV) Stephen L. Hawthorne, Heikyung Chun, Robert C. Fay PII: DOI: Reference:

S0020-1693(18)31581-0 https://doi.org/10.1016/j.ica.2018.11.017 ICA 18632

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Inorganica Chimica Acta

Received Date: Revised Date: Accepted Date:

12 October 2018 11 November 2018 14 November 2018

Please cite this article as: S.L. Hawthorne, H. Chun, R.C. Fay, Preparation and Characterization of Six-Coordinate Titanium(IV) Monothiocarbamate Complexes. X-ray Crystal Structure of Dichlorobis(N,Ndimethylcarbamothioato-O,S)titanium(IV), Inorganica Chimica Acta (2018), doi: https://doi.org/10.1016/j.ica. 2018.11.017

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Preparation and Characterization of Six-Coordinate Titanium(IV) Monothiocarbamate Complexes. X-ray Crystal Structure of Dichlorobis(N,N-dimethylcarbamothioato-O,S)titanium(IV) Stephen L. Hawthorne, Heikyung Chun, and Robert C. Faya Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, NY, 14853, USA ––––– aCorresponding author: [email protected]; above postal address Declarations of Interest: none Graphical Abstract

Ti(Me2mtc)2Cl2 (Me2mtc = N,N-dimethylmonothiocarbamate) has a distorted octahedral structure in which the Ti(IV) atom is bonded to two cis Cl atoms and two planar, bidentate monothiocarbamate ligands. The complex exists (unexpectedly) as the C2 stereoisomer that has S atoms in trans positions. Keywords: Titanium; N,N-dialkylmonothiocarbamate ligand; X-ray crystal structure; C2 stereoisomer; Trans sulfur atoms Abstract Six-coordinate titanium(IV) N,N-dialkylmonothiocarbamate complexes Ti(R2mtc)2Cl2 (R = Me, Et, i-Pr, or i-Bu) have been prepared in excellent yield by

2 reaction of titanium(IV) chloride with stoichiometric amounts of sodium N,Ndialkylmonothiocarbamates in dichloromethane or benzene. The complexes were characterized by conductance measurements and by infrared and 1H NMR spectroscopy. The x-ray crystal structure of Ti(Me2mtc)2Cl2 was determined in order to establish the location of the sulfur atoms, which are generally cis in monothiocarbamate and monothio--diketonate complexes. Ti(Me2mtc)2Cl2 has a distorted octahedral structure in which the Ti(IV) atom is bonded to two cis Cl atoms and two planar, bidentate monothiocarbamate ligands. The complex exists (unexpectedly) as the C2 stereoisomer that has S atoms in trans positions. 1. Introduction Previous papers from this laboratory have described the structure and stereochemistry of eight-coordinate dodecahedral titanium(IV) and zirconium(IV) N,Ndialkymonothiocarbamate complexes, M(R2mtc)4 (M = Ti or Zr; R = Me or Et) [1], [2]. These complexes have a structure in which all four S atoms are clustered in all-cis positions on one side of the molecule with all four O atoms on the other side. These structures violate Orgel’s rule, which predicts that the S and O atoms should sort between the dodecahedral A and B sites [3]. Similarly, the analogous seven-coordinate pentagonal bipyramidal titanium(IV) complexes, Ti(R2mtc)3Cl (R = Me or Et), have a structure in which all three S atoms are clustered on one side of the molecule in all-cis positions on one triangular face of the coordination polyhedron [4]. This paper reports preparation and characterization of the corresponding sixcoordinate N,N-dialkymonothiocarbamate complexes, Ti(R2mtc)2Cl2 1 (R = Me, Et, i-Pr, or i-Bu), and the x-ray crystal structure of Ti(Me2mtc)2Cl2. This structure was determined

3

1 (R = Me, Et, i-Pr, or i-Bu) In order to discover whether the clustering of S atoms found in the seven- and eightcoordinate complexes persists in the six-coordinate compounds. 2. Experimental Sodium N,N-dialkylmonothiocarbamates, Na(R2mtc) (R = Me, Et, i-Pr, or i-Bu), were prepared as described previously [1], [4]. Titanium(IV) chloride (Matheson Coleman and Bell) was used as purchased without further purification. Solvents were dried by refluxing for at least 24 h over calcium hydride and were distilled immediately before use. Syntheses and subsequent handling of the compounds were conducted under anhydrous conditions in a dry nitrogen atmosphere. 2.1 Synthesis of Compounds 2.1.1 Preparation of Dichlorobis(N,N-dimethylcarbamothioato-O,S)titanium(IV), Ti(Me2mtc)2Cl2 Titanium(IV) chloride (1.93 mL, 17.6 mmol) was added with rapid stirring to a suspension of Na(Me2mtc) (4.45 g, 35.0 mmol) in dichloromethane (150 mL). The mixture was refluxed for 5 h, then filtered, and the precipitate washed with three 15-mL portions of dichloromethane. Reduction of the combined filtrate and washings to ~60 mL followed by addition of ~180 mL of hexane afforded dark red crystals, which were dried

4 in vacuo for 23 h; yield 5.36 g (94%); mp 149–175 C dec, lit [5] 150–152 C dec. Anal. Calcd for Ti(C3H6NOS)2Cl2: C, 22.03; H, 3.70; Cl, 21.68; N, 8.56; Ti, 14.64. Found: C, 21.86; H, 3.80; Cl, 21.75; N, 8.58; Ti, 14.36. 2.1.2 Preparation of Dichlorobis(N,N-diethylcarbamothioato-O,S)titanium(IV), Ti(Et2mtc)2Cl2 This complex was prepared by reaction of titanium(IV) chloride (4.1 mL, 37 mmol) with Na(Et2mtc) (11.58 g, 74.6 mmol) in dichloromethane (100 mL) using a procedure similar to that for preparation of Ti(Me2mtc)2Cl2. The yield of red-orange crystals was 12.76 g (90%); mp 77–95 C dec, lit [5] 137–140 C dec. Anal. Calcd for Ti(C5H10NOS)2Cl2: C, 31.34; H, 5.26; Cl, 18.50; N, 7.31; S, 16.73; Ti, 12.50. Found: C, 31.18; H, 5.32; Cl, 18.43; N, 7.31; S, 16.54; Ti, 12.58. 2.1.3 Preparation of Dichlorobis(N,N-diisopropylcarbamothioato-O,S)titanium(IV), Ti(iPr2mtc)2Cl2 This complex was prepared by reaction of titanium(IV) chloride (0.99 mL, 9.0 mmol) with Na(i-Pr2mtc) (3.30 g, 18.0 mmol) in benzene (150 mL). The resulting redorange powder was dried in vacuo at 100 C for 25 h to remove benzene of crystallization; yield 3.46 g (88%); mp 141–158 C dec. Anal. Calcd for Ti(C7H14NOS)2Cl2: C, 38.28; H, 6.42; Cl, 16.14; N, 6.38; Ti, 10.90. Found: C, 38.25; H, 6.62; Cl, 15.87; N, 6.18; Ti, 10.96. 2.1.4 Preparation of Dichlorobis(N,N-diisobutylcarbamothioato-O,S)titanium(IV), Ti(iBu2mtc)2Cl2

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This complex was prepared from titanium(IV) chloride (2.0 mL, 18 mmol) and Na(i-Bu2mtc) (7.94 g, 37.9 mmol) in dichloromethane (100 mL). The yield of large red crystals was 6.24 g (70%); mp 126–132 C dec. Anal. Calcd for Ti(C9H18NOS)2Cl2: C, 43.64; H, 7.32; Cl, 14.31; N, 5.65; S, 12.94; Ti, 9.67. Found: C, 43.64; H, 7.47; Cl, 14.73; N, 5,60; S, 12.79; Ti, 9.49. 2.2 Physical Measurements Conductance measurements were made, and infrared and proton NMR spectra were recorded as described previously [4]. Variable-temperature 1H NMR spectra of Ti(Me2mtc)2Cl2 in dichloromethane solution (–94 to 29 C) and in diphenylmethane solution (62 to 109 C) were recorded on a Bruker HX-90 spectrometer, which was locked on the solvent methylene resonance. Temperatures were determined with a copper-constantan thermocouple immersed in either dichloromethane or silicone oil in an NMR sample tube. 2.3 X-ray Crystallography Several well-formed crystals of Ti(Me2mtc)2Cl2 obtained from dichloromethanehexane were sealed in Lindemann glass capillaries under an atmosphere of dry nitrogen. A dark red, rectangular prism (0.55  0.25  0.20 mm) mounted along the long axis was used for data collection. Crystal data: Ti(SOCN(CH3)2)2Cl2, MW 327.07, triclinic, space group P1 or P1, a = 12.415 (9) Å, b = 12.589 (8) Å, c = 8.945 (5) Å,  = 92.50 (5),  = 90.01 (5),  = 105.88 (5), V = 1343.3 Å3, Z = 4, c = 1.617 g/cm3, m = 1.60 g/cm3. The unit cell parameters were determined at 20 C from the least-squares

6 refinement of the setting angles for 15 reflections (15.0 < 2 < 19.5) centered on a Syntex P21 diffractometer with graphite-monochromatized Mo K𝛼 radiation ( = 0.71069 Å). The observed density was measured by flotation in a solution of hexane and iodomethane. Intensity data were collected with a Syntex P21 diffractometer (Mo K𝛼 radiation) using the –2 scan mode with variable scan speeds of 2.0 to 29.3/min. The range of each scan extended from 1.0 below the calculated position of the K1 reflection to 1.0 above the calculated position of the K2 reflection. The intensities of three standard reflections, monitored every 100 reflections, remained constant throughout data collection. A total of 3527 unique reflections having 2 < 45 was scanned. Based on the dimensions of the crystal and a linear absorption coefficient of 1.33 mm–1, an absorption correction was considered unnecessary; the maximum error resulting from neglect of an absorption correction was estimated to be <8% in any intensity and <4% in any structure amplitude. The intensity data were reduced to a set of relative squared amplitudes, Fo 2, by application of standard Lorentz and polarization factors. Those 3284 reflections having Fo > 2.0F, where F is defined elsewhere [6], were retained as “observed” for the structure analysis. The structure was solved and refined successfully on the assumption that the space group is P1. Therefore, there are two molecules of Ti(Me2mtc)2Cl2 per asymmetric unit. The positions of the two independent Ti atoms and the four independent Cl atoms were located by direct methods using the MULTAN program. The remaining non-hydrogen atoms were found in the first Fourier map, and after several cycles of least-squares refinement, all 24 hydrogen atoms were located in a subsequent

7 difference Fourier map. Hydrogen atom positions were adjusted assuming a C–H bond length of 1.0 Å and regular tetrahedral geometry for the methyl groups. Each H atom was assigned an isotropic thermal parameter 1.0 Å2 larger than that of the adjacent C atom. Hydrogen atoms were included in subsequent least-squares calculations but were not refined. The structure was refined by full-matrix least squares using anisotropic thermal parameters for all non-hydrogen atoms and empirical weights, w = (F)–2, obtained from counting statistics. Because of the limited capacity of the least-squares program, the positional and anisotropic thermal parameters of 10 of the 30 atoms were varied in successive cycles. In the final cycles of refinement, thermal parameters of all 30 atoms and then positional parameters of all 30 atoms were varied in successive cycles. The quantity minimized in the least-squares calculations was w( Fo – Fc )2. Upon convergence, the residuals R1 =  Fo  – Fc /  Fo  and R2 = [w( Fo  – Fc )2 / w Fo 2]1/2 were 0.039 and 0.054, respectively. In the final cycles of refinement, no parameter shifted by more than 0.27 (the average was 0.02) of its estimated standard deviation. A final difference Fourier showed no anomalous features; the strongest peak (0.40 e/Å3) was near the position of one Cl atom. Scattering factors for Ti, Cl, S, O, N, and C were taken from Cromer and Mann [7]. Anomalous dispersion corrections, real and imaginary, for Ti, Cl, and S were

8 obtained from Cromer [8]. Calculations were performed on Prime 400 and IBM 370/168 computers using programs listed in a previous paper [2]. 3. Results and Discussion 3.1 Preparation and Characterization Six-coordinate titanium(IV) N,N-dialkylmonothiocarbamate complexes Ti(R2mtc)2Cl2 (R = Me, Et, i-Pr, or i-Bu) have been prepared in excellent yield by reaction of titanium(IV) chloride with stoichiometric amounts of sodium N,Ndialkylmonothiocarbamates in dichloromethane or benzene. TiCl4 + 2 Na(SOCNR2)  Ti(SOCNR2)2Cl2 + 2 NaCl The complexes were obtained in excellent purity as judged by satisfactory elemental analysis and 1H NMR spectra (Table 1). The Ti(R2mtc)2Cl2 complexes are soluble in polar organic solvents, such as dichloromethane and chloroform, less soluble in benzene, and essentially insoluble in saturated hydrocarbons. They are thermally stable but are hydrolyzed rapidly when exposed to air; they show evidence of hydrolysis within minutes in the solid state, and almost instantaneously in solution. As expected, these complexes behave as nonelectrolytes in dichloromethane solution; molar conductances of ~10–3 M solutions are <0.10 ohm–1 cm2 mol–1. 3.2 Vibrational Spectra Infrared frequencies for the Ti(R2mtc)2Cl2 complexes are listed in Table 2. The IR spectra closely resemble spectra of the seven-coordinate Ti(R2mtc)3Cl and eight-

9 coordinate Ti(R2mtc)4 complexes and indicate that the Ti(R2mtc)2Cl2 complexes contain bidentate monothiocarbamate ligands. The vibrational frequencies exhibit a clear dependence on the coordination number of the Ti atom. The very strong, broad band at 1535–1581 cm–1 in the Ti(R2mtc)2Cl2 complexes, assigned to the coupled (C. . .O) and C. . .N) stretching vibration [9], shifts to higher frequency by some 22–38 cm–1 as the coordination number of Ti decreases from eight to seven to six. Similarly, (Ti–O) at 560–588 cm–1, (Ti–Cl) (369–397 cm–1), and (Ti–S) (344–366 cm–1) occur at higher frequencies in the six-coordinate Ti(R2mtc)2Cl2 complexes than in the corresponding seven- and eight-coordinate complexes. These observations are consistent with the stronger metal–ligand bonds expected for the complexes of lower coordination number. 3.3 X-ray Structure of Dichlorobis(N,N-dimethylcarbamothioato-O,S)titanium(IV), Ti(Me2mtc)2Cl2 The molecular structure of Ti(Me2mtc)2Cl2 is depicted in Figure 1. Bond lengths, polyhedral edge lengths, and bond angles within the TiCl2O2S2 coordination groups are presented in Table 3, and bond lengths and bond angles in the monothiocarbamate ligands are given in Table 4. Both crystallographically independent molecules in the asymmetric unit have the same distorted octahedral structure in which the Cl atoms and bidentate monothiocarbamate ligands are bonded to the six-coordinate Ti(IV) atom. Averaged dimensions of the TiCl2O2S2 coordination groups and the monothiocarbamate ligands in the two crystallographically independent molecules are essentially identical (Tables 3 and 4).

10 Comparison of the metal–ligand bond lengths in Ti(Me2mtc)2Cl2 with corresponding values for Ti(Me2mtc)3Cl and Ti(Me2mtc)4 reveals a systematic shortening of the Ti–Cl, Ti–O, and Ti–S bonds as the coordination number of Ti deceases from eight to seven to six: Ti–Cl in Ti(Me2mtc)2Cl2 (av 2.264 Å) is 0.066 Å shorter than Ti–Cl in Ti(Et2mtc)3Cl (2.330 Å); Ti–O (av 2.013 Å) is 0.068 Å less than in Ti(Et2mtc)3Cl (av 2.081 Å) and 0.076 Å less than in Ti(Et2mtc)4 (av 2.089 Å); Ti–S (av 2.441 Å) is 0.040 Å less than in Ti(Et2mtc)3Cl (av 2.481 Å) and 0.130 Å less than in Ti(Et2mtc)4 (av 2.571 Å). These trends match the trends in vibrational frequencies (Section 3.2) and are consistent with stronger metal–ligand bonds as the coordination number of Ti decreases. The bidentate monothiocarbamate ligands in Ti(Me2mtc)2Cl2 are planar. The mean deviation of the 24 atoms of the four crystallogaphically independent ligands from their respective SOCNC2 mean planes is 0.011 Å; the maximum deviation is 0.023 Å. Distortion of the TiCl2O2S2 coordination group from regular octahedral geometry arises because the small bite (av S . . . O, 2.539 Å) of the monothiocarbamate ligand is unable to span a 90 bond angle at the Ti atom; the averaged S–Ti–O bite angle is 68.8. The two monothiocarbamate ligands are rotated in opposite directions within the nearly perpendicular TiS1O1Cl2 and TiS2O2Cl1 planes so as to locate the Ti–S bonds ~12 off the vertical axis perpendicular to the ruffled equatorial plane defined by Ti, Cl1, Cl2, O1, and O2 (Figure 1). The most interesting aspect of the structure is the trans arrangement of the sulfur atoms. The Ti(Me2mtc)2Cl2 molecule exists in the solid state as the octahedral C2 stereoisomer that has Cl atoms in cis positions and S atoms in trans positions. A cis

11 arrangement of halogen atoms in dihalobis(bidentate ligand) complexes is common, but the trans arrangement of the two S atoms was unexpected in view of the clustering of S atoms in all-cis positions in eight-coordinate M(R2mtc)4 (M = Ti or Zr; R = Me or Et) [1], [2] and seven-coordinate Ti(R2mtc)3Cl (R = Me or Et) [4]. Complexes that contain two monothiocarbamate ligands are uncommon, but two of known structure, bis(cyclomethylenethiocarbamato)bis(pyrrolidine)cobalt(II), Co[SCN(C4H8)]2(NC4H9)2, and [R2NH2][UO2(R2mtc)2(OR’)] (R,R’ = alkyl), have the S atoms in cis positions [10]. A cis arrangement of S atoms is also characteristic of monothio--diketonate complexes. Six-coordinate M(RCSCHCOR’)3 complexes exist as the octahedral facial isomer in which all three S atoms are clustered on one triangular face of the octahedron [11]–[25], and four-coordinate square planar M(RCSCHCOR’)2 complexes exist as the cis isomer [18]–[32]. The preference for cis stereochemistry has been rationalized in terms of weakly attractive S . . . S non-bonded interactions [11], [28a], [29] or has been attributed to metal d  sulfur d bonding [25], [33]. We have ruled out attractive S . . . S interactions in the case of the eight-coordinate monothiocarbamate complexes and have suggested instead that the all-cis stereoisomer might be stabilized by a trans influence of the S atoms [2]. Since the metal–sulfur bonds are more nearly perpendicular in cis isomers than in trans isomers, M–S  bonding would indeed tend to stabilize cis isomers, but in the case of do Ti(IV) complexes the  bonding would have to be sulfur p  metal d Because all the monothiocarbamate and monothio--diketonate complexes known to us have a cis arrangement of S atoms, the observed structure of Ti(Me2mtc)2Cl2 having trans S atoms seems remarkable and remains unexplained.

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3.4 Proton NMR Spectra Comparison of 1H NMR chemical shift data for the Ti(R2mtc)2Cl2 complexes (Table 1) with data for the corresponding Ti(R2mtc)3Cl and Ti(R2mtc)4 complexes [1], [4] reveals that the various alkyl group resonances generally move to lower magnetic field as the coordination number of Ti decreases from eight to seven to six. This observation is also consistent with stronger metal–ligand bonds as the coordination number of Ti decreases; decreasing the coordination number results in a shift of electron density from the ligands toward the Ti atom, thus deshielding the alkyl protons. The NMR spectra exhibit two N-alkyl resonances owing to hindered rotation about the C. . .N partial double bond in the planar monothiocarbamate ligands. Variable temperature spectra of Ti(Me2mtc)2Cl2 in dichloromethane (–94 to 29 C) exhibit two methyl resonances down to about –30 C, below which the two peaks are too broad to be resolved. The broadening is presumably due to solvent viscosity since S-methyl-N,Ndimethylmonothiocarbamate exhibits similar line broadening at the same temperatures. The two methyl resonances for Ti(Me2mtc)2Cl2 are consistent with the C2 stereoisomer found in the solid state, but the presence of additional isomers in solution could be obscured by the line broadening. At higher temperatures in diphenylmethane solution, rotation about the C. . .N bond causes the two methyl resonances to broaden and coalesce at about 109 C. Severe thermal decomposition precluded a total line shape analysis, but a rate constant for the bond rotation process of 15 s–1 at 109 C could be estimated from the relation kc = /2 [34], where  = 6.57 Hz is the frequency difference between the two

13 resonances. The corresponding free energy barrier is 21 kcal/mol, essentially the same value estimated for C. . .N bond rotation in Ti(Me2mtc)3Cl. Acknowledgments The support of this research by the National Science Foundation (Grants MPS7424297 and CHE-7620300) is gratefully acknowledged. We thank Professors J.L. Hoard and R.E. Hughes for access to the diffractometer. Supplementary Data Supplementary crystallographic data including tables of structure factors, atomic fractional coordinates, thermal parameters, and mean plane calculations have been deposited at the Cambridge Crystallographic Data Center, CCDC deposition number 1856822.

14 References [1] S.L. Hawthorne, A.H. Bruder, R.C. Fay, Inorg. Chem. 17 (1978), 2114. [2] W.L. Steffen, R.C. Fay, Inorg. Chem. 17 (1978), 2120. [3] L.E. Orgel, J. Inorg. Nucl. Chem. 14 (1960), 136. [4] S.L. Hawthorne, R.C. Fay, J. Am. Chem. Soc. 101 (1979), 5268. [5] V.D. Gupta, V.K. Gupta, Indian J. Chem. 22A (1983), 250. [6] L.J. Radonovich, A. Bloom, and J.L. Hoard, J. Am. Chem. Soc. 94 (1972), 2073. [7] D.T. Cromer, J.B. Mann, Acta Crystallogr. Sect. A 24 (1968), 321. [8] D.T. Cromer, Acta Crystallogr. Sect. A 18 (1965), 17. [9] B.J. McCormick, B.P. Stormer, Inorg. Chem. 11 (1972), 729. [10] B.J. McCormick, R. Bereman, C. Baird, Coord. Chem. Rev. 54 (1984), 99. [11] R.H. Holm, D.H. Gerlach, J.G. Gordon, II, M.C. McNamee, J. Am. Chem. Soc. 90 (1968), 4184. [12] J. Ollis, M. Das, V.J. James, S.E. Livingstone, K. Nimgirawath, Cryst. Struct. Commun. 4 (1976), 679. [13] B.F. Hoskins, C.D. Pannan, Inorg. Nucl. Chem. Lett. 11 (1975), 409. [14] M. Das, D.T. Haworth, J. Inorg. Nucl. Chem. 43 (1981), 2317. [15] M. Das, D.T. Haworth, J. Inorg. Nucl. Chem. 43 (1981), 3015. [16] D.T. Haworth, J. Beery, M. Das, J. Fluorine Chem. 20 (1982), 599. [17] L.W. Tari, G.A. Stern, J.B. Westmore, A.S. Secco, Acta Crystallogr., Sect. C Cryst. Struct. Commun. C46 (1990), 197. [18] G.A. Stern, J.B. Westmore, Canad. J. Chem. 77 (1999), 1734, and references therein.

15 [19] S.E. Livingstone, J. Organomet. Chem. 239 (1982), 143. [20] M. Das, D.T. Haworth, Transition Met. Chem. 21 (1996), 442. [21] D.T. Haworth, M. Das, Synth. React. Inorg. Met.-Org. Chem. 26 (1996), 169. [22] M. Das, S.E. Livingstone, S.W. Fillipczuk, J.W. Hayes, D.V. Radford, J. Chem. Soc. Dalton Trans. (1974), 1409. [23] M. Das, D.T. Haworth, J. Inorg. Nucl. Chem. 43 (1981), 515. [24] M. Das, Inorg. Chim. Acta 36 (1979), 79. [25] D.T. Haworth. D.L. Maas, M. Das, J. Inorg. Nucl. Chem. 43 (1981), 1807. [26] J. Sieler, P. Thomas, E. Uhlemann, E. Hohne, Z. Anorg. Allg. Chem. 380 (1971), 160. [27] L. Kutschabsky, L. Beyer, Z. Chem. 11 (1971), 30. [28] (a) J. Coetzer, J.C.A. Boeyens, J. Cryst. Mol. Struct. 1 (1971), 277; (b) L. E. Pope, J.C.A. Boeyens, Acta Crystallogr., Sect. B 32 (1976), 1599. [29] O. Siiman, D.D. Titus, C.D. Cowman, J. Fresco, H.B. Gray, J. Am. Chem. Soc. 96 (1974), 2353. [30] E.S. Shugam, I.M. Shkol’nikova, S.E. Livingstone, Zh. Strukt. Khim. 8 (1967), 550. [31] D.C. Craig, M. Das, S.E. Livingstone, N.C. Stephenson, Cryst. Struct. Commun. 3 (1974), 283. [32] D.W. Bennett, T.A. Siddiquee, D.T. Haworth, M. Das, J. Chem. Crystallogr. 34 (2004), 865. [33] D.P. Craig, A. Macoll, R.S. Nyholm, L.E. Orgel, L.E. Sutton, J. Chem. Soc. (1954), 332. [34] H.S. Gutowsky, C.H. Holm, J. Chem. Phys. 25 (1956), 1228.

16

Figure 1. A model in perspective of the Ti(Me2mtc)2Cl2 molecule.

17 Table 1 Proton chemical shifta and coupling constantb data for Ti(R2mtc)2Cl2 complexes ––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– Compound

CH

CH2

CH3

J

––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– Ti(Me2mtc)2Cl2

–3.20, –3.17

Ti(Et2mtc)2Cl2

–3.61,–3.55

Ti(i-Pr2mtc)2Cl2

–4.41,–3.76

Ti(i-Bu2mtc)2Cl2

–2.05

–3.39, –3.30

–1.24, –1.22

7.3, 7.2c

–1.42, –1.25

7.0, 6.8c

–0.92, –0.89

7.5, 7.3, 6.6, 6.5d

––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– aIn

ppm (0.01) relative to an internal reference of tetramethylsilane (1% by

volume) at 34 C in CDCl3. bIn Hz (0.2) at 34 C in CDCl3. cThe first coupling constant refers to the downfield methyl resonance; the second refers to the upfield methyl resonance. dThe coupling constants are given in the order: J(CH3–CH) for the downfield methyl resonance, J(CH3–CH) for the upfield methyl resonance, J(CH2–CH) for the downfield methylene resonance, and J(CH2–CH) for the upfield methylene resonance.

18 Table 2 Characteristic infrared bands for Ti(R2mtc)2Cl2 complexes (cm–1)a ––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– Compound

(C. . .O), C. . .N)

(C. . .S)

(Ti–O)

(Ti–S)

(Ti–Cl)

Other bandsb

––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– Ti(Me2mtc)2Cl2

1581 vs, b

930 m

572 s

352 s, b

379 sh

1418 m, 1399 m 1335 m, 1306 m 1236 m, 1133 s 1057 w, 973 w 703 s, 654 m 480 m, 416 s

Ti(Et2mtc)2Cl2

1552 vs, b

948 m

572 s

351 s

374 s

1345 m, 1325 m 1297 m, 1264 s 1197 m, 1136 m 1100 m, 1080 m 880 s, 787 w 679 s, 665 w 522 m, 471 m 399 s

Ti(i-Pr2mtc)2Cl2

1535 vs, b

920 m

588 m 576 s

366 s

397 s

1355 s, 1303 s 1295 s, 1203 m 1163 m, 1148 m 1139 m, 1121 m 1036 s, 881 m 839 s, 675 m 635 m, 539 m 518 m

Ti(i-Bu2mtc)2Cl2

1545 vs, b

920 m

578 m 560 s

344 s

369 s

1439 s, 1389 m 1346 m, 1282 m 1245 s, 1189 m 1172 w, 1146 s 1128 w, 1095 m 939 m, 889 w 816 m, 739 s 671 m, 663 m 486 m, 429 w 408 m, 397 m ––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– aAs Nujol mulls between CsI plates. b2000–250 cm–1 region. Table 3

19 Bond Distances, Polyhedral Edge Lengths, and Bond Angles in the Coordination Group of Ti(Me2mtc)2Cl2a –––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– Length, Å Angle, deg –––––––––––––––––––––––––––––– ––––––––––––––––––––––––––––– Atoms Molecule 1 Molecule 2 Avb Atoms Molecule 1 Molecule 2 Avb –––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– Ti–Cl1 2.257 (3) 2.283 (2) Cl1–Ti–O2 157.4 (1) 157.9 (1)  2.264 (2,12,19)  158.0 (1,3,6) Ti–Cl2 2.268 (2) 2.246 (2) Cl2–TI–O1 158.2 (1) 158.3 (1) Ti–S1

2.440 (2)

2.424 (2)

Ti–S2

2.439 (3)

2.459 (2)

Ti–O1

2.017 (3)

2.021 (3)

Ti–O2

2.010 (2)

2.003 (3)

Cl1. . .Cl2 3.343 (3)

3.348 (3)

Cl1. . .S1 3.740 (4)

3.779 (3)

Cl2. . .S2

3.808 (3)

3.784 (3)

Cl2–Ti–S2

Cl1. . .S2 3.282 (2)

3.337 (3)

Cl1–Ti–S2

88.6 (1)

Cl2. . .S1

3.324 (2)

3.288 (3)

Cl2–Ti–S1

89.7 (1)

Cl1. . .O1 3.137 (3)

3.098 (3)

Cl1–Ti–O1

94.3 (1)

Cl2. . .O2

3.023 (3)

3.058 (3)

Cl2–Ti–O2

89.7 (1)

S1. . .O1c 2.541 (3)

2.534 (3)

S1–Ti–O1

68.8 (1)

S2. . .O2c 2.541 (3)

2.540 (3)

S2–Ti–O2

68.9 (1)

S1. . .O2 3.334 (3)

3.254 (3)

S1–Ti–O2

96.5 (1)

S2. . .O1 3.214 (3)

3.279 (3)

S2–Ti–O1

91.8 (1)

94.1 (1)  94.0 (1,13,25) 93.6 (1)

O1. . .O2 2.821 (4)

2.822 (4) 2.822 (3,1,1)

O1–Ti–O2

88.9 (1)

89.0 (1) 89.0 (1,1,1)

 2.441 (2,10,18)

S1–Ti–S2

156.4 (2) 156.0 (1) 156.2 (2,2,2)

 2.013 (3,6,10) 3.346 (3,3,3)  3.778 (3,19,38)

 3.308 (3,23,29)

 3.079 (3,39,58)

 2.539 (3,3,5)

 3.270 (3,36,64)

Cl1–Ti–Cl2 Cl1–Ti–S1

95.3 (1)

95.3 (1)

95.3 (1,0,0)

105.5 (1) 106.8 (1)  106.8 (1,7,13) 108.0 (1) 107.0 (1) 89.4 (1)  89.3 (1,3,7) 89.4 (1) 91.9 (1)  92.0 (1,12,23) 91.9 (1) 68.8 (1)  68.8 (1,1,3) 68.5 (1)

20 aNumbers

in parentheses are estimated standard deviations in the last significant figure. bThe

numbers in parentheses following each averaged value are the root-mean-square estimated standard deviation for an individual datum and the mean and maximum deviation from the average value. cThe “bite” of the ligand.

21 Table 4 Bond Lengths (Å) and Bond Angles (deg) in the N,N-Dimethylmonothiocarbamate Ligandsa –––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– Molecule 1 Molecule 2 –––––––––––––––––– –––––––––––––––––– Bond Ligand 1 Ligand 2 Ligand 1 Ligand 2 Avb –––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– (a) Bond Lengths S. . .Oc

2.541 (3)

2.541 (3)

2.534 (3)

2.540(3)

2.539 (3,3,5)

C–S

1.737 (4)

1.733 (3)

1.729 (4)

1.733 (4)

1.733 (4,2,4)

C–O

1.283 (4)

1.292 (4)

1.282 (4)

1.288 (4)

1.286 (4,4,6)

C–N

1.310 (4)

1.311 (4)

1.312 (4)

1.308 (4)

1.310 (4,1,2)

C1–N

1.473 (5)

1.459 (5)

1.463 (5)

1.466 (5)

C2–N

1.451 (5)

1.465 (5)

1.462 (5)

1.453 (5)



1.462 (5,5,11)

(b) Bond Angles S–C–O

113.7 (2)

113.5 (2)

113.8 (3)

113.6 (2)

113.7 (2,1,2)

C–S–Ti

75.2 (1)

75.3 (1)

75.6 (1)

74.8 (1)

75.2 (1,2,4)

C–O–Ti

102.3 (2)

102.1 (2)

101.7 (2)

102.8 (2)

102.2 (2,3,6)

S–C–N

124.9 (3)

125.4 (2)

124.9 (2)

125.4 (3)

125.2 (3,3,3)

O–C–N

121.3 (3)

121.1 (3)

121.3 (3)

121.0 (3)

121.2 (3,1,2)

C1–N–C

121.0 (3)

120.7 (3)

121.3 (3)

119.9 (3)

C2–N–C

122.3 (3)

121.6 (3)

121.4 (3)

122.9 (3)

C1–N–C2

116.7 (3)

117.7 (3)

117.3 (3)

117.2 (3)

aNumbers



121.4 (3,7,15) 117.2 (3,3,5)

in parentheses are estimated standard deviations in the last significant figure. bThe

numbers in parentheses following each averaged value are the root-mean-square estimated standard deviation for an individual datum and the mean and maximum deviation from the average value. cThe “bite” of the ligand.

Highlights I don’t know what is being requested here. A summarizing statement of the main points of our work is the Abstract, repeated below:

22 Six-coordinate titanium(IV) N,N-dialkylmonothiocarbamate complexes Ti(R2mtc)2Cl2 (R = Me, Et, i-Pr, or i-Bu) have been prepared in excellent yield by reaction of titanium(IV) chloride with stoichiometric amounts of sodium N,N-dialkylmonothiocarbamates in dichloromethane or benzene. The complexes were characterized by conductance measurements and by infrared and 1H NMR spectroscopy. The x-ray crystal structure of Ti(Me2mtc)2Cl2 was determined in order to establish the location of the sulfur atoms, which are generally cis in monothiocarbamate and monothio-diketonate complexes. Ti(Me2mtc)2Cl2 has a distorted octahedral structure in which the Ti(IV) atom is bonded to two cis Cl atoms and two planar, bidentate monothiocarbamate ligands. The complex exists (unexpectedly) as the C2 stereoisomer that has S atoms in trans positions.

Graphical Abstract

Graphical Abstract Synopsis Ti(Me2mtc)2Cl2 (Me2mtc = N,N-dimethylmonothiocarbamate) has a distorted octahedral structure in which the Ti(IV) atom is bonded to two cis Cl atoms and two planar, bidentate monothiocarbamate ligands. The complex exists (unexpectedly) as the C2 stereoisomer that has S atoms in trans positions.