Experimental and Theoretical Investigations of Tellurium(IV

Article pubs.acs.org/Organometallics

Experimental and Theoretical Investigations of Tellurium(IV) Methanediides and Their Insertion Products with Sulfur and Iodine Ramalingam Thirumoorthi, Tristram Chivers,* and Ignacio Vargas-Baca* Department of Chemistry, University of Calgary, 2500 University Drive N.W., Calgary, AB, Canada, T2N 1N4, and Department of Chemistry and Chemical Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada, L8S 4M1 S Supporting Information *

ABSTRACT: The reactions of Li2[C(Ph2PS)2] with tellurium tetrahalides in a 1:1 molar ratio in toluene afford the complexes {TeX2[C(Ph2PS)2]}2 (7a, X = Cl; 7b, X = Br; 7c, X = I). These complexes dimerize through halide bridges in the solid state, and the tridentate ligand is S,C,Scoordinated to the tellurium center with a Te−C bond length of 2.024(3), 2.030(6), and 2.045(8) Å, respectively. In the case of TeBr4, small amounts of the complex TeX2[SC(Ph2PS)2] (8b, X = Br) were isolated and shown by X-ray analysis to be the result of formal sulfur insertion into the Te−C bond of 7b. Complex 8b and the corresponding dichloride and diiodide, 8a (X = Cl) and 8c (X = I), may be prepared in good yields by the metathetical reactions of Li2[SC(Ph2PS)2] with TeX4 in toluene. The complex TeI2[(I2)C(Ph2PS)2] (9) was isolated as a minor product from the reaction of Li2[C(Ph2PS)2] and TeI4 and identified by X-ray crystallography. Complex 9 is constructed from the insertion of an iodine atom of an I2 molecule into the Te−C bond of 7c, resulting in a T-shaped geometry at that iodine atom and an almost linear Te−I−I unit with an elongated I−I bond; the C−I bond length is typical for a C(sp3)−I bond. DFT calculations supplemented with Hirshfeld charge analysis, Boys−Foster localization of molecular orbitals, and evaluation of the electron localization functions indicate that in these species the ligand engages predominantly in σ bonding through the lone pairs on the carbon and sulfur atoms. The latter atoms participate in three-center interactions with tellurium. The bonds between the heavy elements and carbon are strongly polarized, and the character of the latter atom ranges from sp2 to sp3.

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INTRODUCTION The coordination chemistry of the PCP-bridged sulfur-centered ligand [C(Ph2PS)2]2− (1) has been studied extensively since the discovery of a convenient route to the dilithium derivative of this methanediide by Le Floch and co-workers in 2004.1 The dianion 1 engages in strong metal−carbon interactions with a variety of transition metals,2 scandium,3 lanthanides,4 and actinides.5 DFT calculations indicate that the metal−carbon bond in these monomeric S,C,S-coordinated complexes is highly polar with low double-bond character for both early and late transition metals;1a,2a,c the carbon lone pairs are stabilized by negative hyperconjugation into σ* P−C and P−S antibonding orbitals.6 By contrast, the metal−carbon bonds in scandium, samarium, thulium, and uranium complexes exhibit significant multiple-bond character.3−5 It has been proposed that the alkylidene-like reactivity of the carbene-type ligand in samarium complexes of 1 and the related imino ligand [C(Ph2PNSiMe3)2]2− 7obscures the distinction between Fischer and Schrock carbenes.6b,8 The formation of carbenoid species, stabilized by incorporation of lithium halides, upon mild oxidation of Li2(1)9,10 provides a distinctive indication of the carboncentered reactivity of the dianion 1 in comparison with the chalcogen-based dimerization observed for oxidation of analogous dichalcogen PNP-bridged anions.11−13 With the exception of Li21,1 the synthesis and structures of main group metal and metalloid complexes of 1 have attracted attention only in the past couple of years, and an understanding © 2012 American Chemical Society

of the nature of the metal−carbon bonding in these s- and pblock complexes is still being developed. The homoleptic magnesium complex [Mg{C(PPh2S)2}(THF)]214 (2) and the heteroleptic group 13 derivatives [MCl{C(PPh2S)2}]2 (3a, M = Al; 3b, M = Ga; 3c, M = In)14 adopt similar dimeric structures in which two metal−methanediide monomers are linked headto-tail via the sulfur atoms. The divalent group 14 complexes [M{μ2-C(PPh2S)2}]2 (M = Sn, Pb) are also dimeric, but, in this case, the methanediide ligands bridge two metal centers with either one (M = Sn) or two of the sulfur donor atoms (4, M = Pb) coordinated to the metal.15 The homoleptic germanium(IV) complex [Ge{C(PPh2S)2}2] (5) is a monomer in which the two ligands are C,S-bonded to the metal center and one of the thiophosphinoyl groups of each ligand remains uncoordinated.13 On the basis of DFT calculations and a topological analysis of the electron densities in 5 it was concluded that the Ge−C bond order in 5 is “between a single and double bond”.16 In a preliminary communication we described the synthesis and structures of [MCl{C(PPh2S)2}]2 (6a, M = Sb; 6b, M = Bi), the first group 15 complexes of 1, which form dimers through weak M···S interactions in the solid state.17 DFT calculations revealed novel features of the S,C,S-bonding of 1 to the metal center in these complexes, which embody a polar M−C single bond and a three-center two-electron S−M−S bond; the lone Received: October 3, 2011 Published: January 5, 2012 627

dx.doi.org/10.1021/om200925k | Organometallics 2012, 31, 627−636

Organometallics

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(7b), and 32.4 (7c). The 125Te NMR spectra are comprised of 1:2:1 triplets with chemical shifts in the range 955−985 ppm. We were unable to obtain the 13C NMR chemical shifts for the PCP carbon or the ipso carbon of the phenyl groups. In addition to 7b, the reaction of Li21 with TeBr4 produces small amounts of red crystals, which were isolated and identified as the sulfur-insertion product [TeBr2{SC(PPh2S)2}] (8b) by single-crystal X-ray analysis.19 Complex 8b is presumably formed by the formal insertion of a sulfur atom into the Te−C bond of 7b. Leung and co-workers have shown that the dimeric lead(II) complex 4 undergoes sulfur insertion into the Pb−C bond upon reaction with elemental sulfur in toluene at ambient temperature to give the monomeric complex Pb[SC(PPh2S)2] in low yield (14%).15 Our attempts to prepare 8b from the reaction of 7b with elemental sulfur in a similar manner yielded a mixture of products from which pure 8b could not be isolated. However, the direct synthesis of the series of tellurium(IV) dihalide complexes [TeX2{SC(PPh2S)2}] (8a, X = Cl; 8b, X = Br; 8c, X = I) via metathesis of TeX4 with the known reagent Li2[SC(PPh2S)2]20 was subsequently developed (vide inf ra). X-ray Structures of 7a−c. Single crystals of 7a, 7b, and 7c were grown by slow diffusion of hexane into solutions of these complexes in dichloromethane. The compounds are isostructural and crystallize in a monoclinic (7a and 7b) or orthorhombic (7c) crystal system with space groups P21/n and Pbca, respectively. The diiodide 7c cocrystallized with one dichloromethane molecule. The three complexes adopt a similar dimeric structure, which is exemplified by the thermal ellipsoid plot of the dichloride 7a shown in Figure 1. The monomeric units are

pairs on the carbon and pnictogen are essentially noninteracting.17

In this context we sought to expand our understanding of bonding in heavy p-block metalloid complexes of 1 by comparing the structures of tellurium(IV) complexes of 1 with those of the group 15 complexes 6a,b. To this end we describe here (a) the synthesis and structures of the heteroleptic complexes [TeX2{C(PPh2S)2}]2 (7a, X = Cl; 7b, X = Br; 7c, X = I), (b) the structure of 8b formed by insertion of sulfur into the Te−C bond of 7b, (c) the synthesis of the series [TeX2{SC(PPh2S)2}] (8a, X = Cl; 8b, X = Br; 8c, X = I) via metathesis, and (d) the formation and structure of [TeI2{(I2)C(PPh2S)2}] (9), the novel product of I2-insertion into the Te−C bond of 7c. The bonding trends in the series of tellurium(IV) methanediides 7a−c are analyzed by means of DFT calculations, which are also employed to elucidate the nature of the bonding in the insertion products 8b and 9.

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RESULTS AND DISCUSSION Reactions of Li21 with TeX4 (X = Cl, Br, I). The reaction of the Li2[C(Ph2PS)2] with tellurium tetrahalides in a 1:1 molar ratio in toluene gave a complicated mixture on the basis of 31P NMR spectra of the crude product from which the expected metathetical products [TeX2{C(PPh2S)2}]2 (7a, X = Cl; 7b, X = Br; 7c, X = I) were isolated as yellow (7a and 7b) or red (7c) crystals in 27−28% yields after extraction with dichloromethane followed by recrystallization from dichloromethane− hexane. The solid-state structures of 7a−c were determined by single-crystal X-ray analysis (vide inf ra). Complexes 7a−c can be handled in air for short periods of time; however, the neutral ligand H2C(PPh2S)2 is slowly produced in THF solutions,18 and it is also a significant component of the mixture of products formed in these reactions. In CD2Cl2 solution these complexes exhibit a single resonance in the 31P NMR spectra flanked by 125Te satellites with 2J(31P,125Te) in the range 135−143 Hz; the change in halide ligands does not influence the chemical shifts significantly: δ31P = 31.9 (7a), 32.2

Figure 1. View of 7a showing the atomic numbering scheme and thermal ellipsoids at 30% probability. Hydrogen atoms of phenyl groups have been omitted for clarity.

comprised of a bicyclic system made up of a central Te−C bond bridged by two Ph2PS groups. The five-coordinate Te atom is in a highly distorted square-pyramidal environment with the two halides and two S atoms in the basal plane and the carbon atom at the apex. Alternatively, the Te atom is in a distorted T-shaped geometry if the Te−S interactions are disregarded. The monomeric units are held together by weak, secondary tellurium−halide interactions [d(Te···X′) = 3.3308(8) (7a), 3.4206(8) (7b), and 3.5880(8) (7c)], which are ca. 0.5 Å 628


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ca. 0.10 Å and the average P−S distances (av 2.0292(11); 2.034(3); 2.032(4) Å) are longer by ca. 0.09 Å when compared with those in the parent molecule, CH2(PPh2S)2,26 indicating electron delocalization, as inferred previously for other p-block element complexes.14,17 The P1−C25−P2 bond angles of 144− 145° for 7a−c are similar to those found in the group 15 complexes 6a,b.17 X-ray Structure of 8b and Direct Synthesis of [TeX2{SC(PPh2S)2}] (8a, X = Cl; 8b, X = Br; 8c, X = I). The minor product isolated as red crystals from the reaction of Li21 with TeBr4 (vide supra) was identified by an X-ray structural determination as [TeBr2{SC(PPh2S)2}] (8b) (see Figure 2);

shorter than the sum of the van der Waals radii for Te and the halogen X.21 Selected structural parameters for 7a−c are summarized in Table 1. The geometry at the carbon atom is planar (359.7−359.8°) Table 1. Selected Bond Lengths (Å) and Angles (deg.) for 7a−c X = Cl (7a) Te1−C25 Te1−X1 Te1−X2 Te1···X1′ Te1−S1 Te1−S2 P1−S1 P2−S2 P1−C25 P2−C25 C25−Te1−X1 C25−Te1−X2 C25−Te1−S1 X1−Te1−S1 C25−Te1−S2 X1−Te1−S2 S1−Te1−S2 P1−S1−Te1 P2−S2−Te1 C25−P1−S1 C25−P2−S2 P2−C25−P1 P2−C25−Te1 P1−C25−Te1 X2−Te1−S1 X2−Te1−S2 X1−Te1−X2

2.024(3) 2.6192(7) 2.5329(8) 3.3308(8) 2.6590(8) 2.6421(8) 2.023(1) 2.036(1) 1.723(3) 1.726(3) 94.27(8) 95.03(8) 74.43(8) 87.67(2) 74.41(8) 92.85(3) 147.79(2) 79.56(3) 79.39(3) 98.55(10) 98.83(10) 144.57(18) 107.22(14) 107.92(14) 92.25(3) 92.38(3) 170.28(3)

X = Br (7b)

X = I (7c)

2.030(6) 2.7984(8) 2.6965(8) 3.4206(8) 2.629(2) 2.662(2) 2.041(3) 2.027(2) 1.729(7) 1.721(7) 95.06(17) 95.64(17) 74.7(2) 93.70(4) 73.3(2) 87.17(4) 147.89(6) 79.63(8) 79.59(8) 98.6(2) 98.5(2) 144.8(4) 108.0(3) 106.9(3) 92.46(4) 92.60(4) 168.76(3)

2.045(8) 3.0488(8) 2.9262(8) 3.5880(8) 2.602(3) 2.707(2) 2.042(3) 2.021(4) 1.722(9) 1.727(9) 98.2(3) 96.9(3) 74.3(3) 91.88(6) 72.6(6) 89.47(6) 146.71(8) 80.73(10) 79.42(10) 97.7(3) 99.3(3) 144.1(5) 108.5(5) 107.2(4) 91.40(6) 95.87(6) 164.86(3)

Figure 2. View of 8b showing the atomic numbering scheme and thermal ellipsoids at 30% probability. The dichloromethane molecules and hydrogen atoms of phenyl groups have been omitted for clarity.

selected structural parameters are summarized in Table 2. The C−S bond length in 8b (1.732(11) Å) is slightly shorter than that in the lead(II) complex [PbS{C(PPh2S)2}] (1.801(8) Å).15 The geometry around the tellurium atom is square pyramidal [the sum of bond angles for the TeS2Br2 basal plane is 359.5(1)o] with the third sulfur atom at the apex. The Te−S bond length in the axial position is shorter by ca. 0.15 Å than the average Te−S bond length in the basal plane.27 The geometry of the tricoordinate carbon has changed from planar (359.7o) in 7b to pyramidal (340.7(6)°) in 8b, and the P−Ccarbene bond distance is increased by ca. 2%.

for all three complexes. The Te−C25 bond lengths are 2.024(3) (7a), 2.030(6) (7b), and 2.045(8) Å (7c), indicating only a minor influence of the change in electronegativity of the halide ligands. These distances are intermediate between typical Te−C single- and double-bond lengths of 2.142 and 1.937 Å, respectively,22 perhaps suggesting some multiple-bond character. They are also shorter than those in tellurium(IV) complexes with Te−Caryl single bonds and a similar coordination environment, e.g., TeCl2[(C6H4OCH3)(Ph2P(S)NP(S)( iPr)2] (2.147(11) Å), 2 3 TeBr 2 [(C 6 H 4 OCH 3 )(S 2 P(OMe) 2 )] (2.127(8) Å),24 and PhTeI2(S2CNEt2) (av 2.142(6) Å), respectively;25the average Te−X bond lengths for 7a−c are somewhat longer (by 0.03−0.10 Å) than those in the aforementioned complexes.23−25 As expected, there is a significant difference between the bridging and terminal Te−X bond lengths (0.086, 0.102, and 0.123 Å for 7a, 7b, and 7c, respectively). Importantly, the Te−S bond lengths (2.6506(8) (7a), 2.6458(19) (7b), and 2.6545(3) Å (7c)) in the monomeric units are significantly longer than the sum of the covalent radii of tellurium and sulfur (2.41 Å).22 However, this elongation is less marked in the Te(IV) complexes 7a−c (ca. 10%) than in the group 15 complexes 6a,b (12−13%).17 The tridentate S(P)C(P)S ligand in 7a−c exists in an almost planar conformation; the largest deviations are observed for P1 (0.0901 Å), P2 (0.0937 Å), and P2 (0.0563 Å) in 7a, 7b, and 7c, respectively. The average P−Ccarbene bond distances in 7a−c are shorter by

Table 2. Selected Bond Lengths (Å) and Angles (deg.) for 8b Te1−S1 Te1−S2 Te1−S3 Te1−Br1 Te1−Br2 S3−Te1−Br1 S3−Te1−Br2 Br1−Te1−Br2 S3−Te1−S2 Br1−Te1−S2 Br2−Te1−S2 S3−Te1−S1 Br1−Te1−S1

2.697(3) 2.666(3) 2.529(3) 2.635(1) 2.646(1) 90.88(7) 92.56(7) 89.79(5) 82.91(9) 173.32(8) 88.05(7) 82.98(9) 91.26(8)

P1−S1 P2−S2 C25−S3 P1−C25 P2−C25 Br2−Te1−S1 S2−Te1−S1 P1−C25−P2 P1−C25−S3 P2−C25−S3 P1−S1−Te1 P2−S2−Te1 C25−S3−Te1

2.047(4) 2.051(4) 1.732(11) 1.758(11) 1.766(10) 175.43(8) 90.42(10) 122.0 (6) 109.5(6) 109.2(6) 99.61(14) 99.84(13) 99.0(3)

In the light of the identification of 8b we synthesized the series of compounds [TeX2{SC(PPh2S)2}] (8a, X = Cl; 8b, X = Br; 8c, X = I) by employing the reaction of the known reagent 629


Organometallics

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Li2[SC(PPh2S)2]20 with TeX4 in a 1:1 molar ratio in toluene. The products were obtained as brownish-yellow (8a and 8b) or red (8c) solids in 35−45% yields after extraction with dichloromethane followed by recrystallization from dichloromethane− hexane. The derivatives 8b and 8c are more sensitive toward moisture than 8a, and a pure sample of 8c could not be obtained A single resonance was observed in the 31P NMR spectra in CD2Cl2 at δ 70.8 (8a) and 72.1 (8b) flanked by 125Te satellites with 2J(31P,125Te) = 71 and 68 Hz, respectively. The 125Te NMR resonances for 8a and 8b are centered at 1159 and 1090 ppm, respectively, and in the case of 8a a well-resolved 1:2:1 triplet was observed [2J(31P,125Te = 71 Hz)]. Solutions of 8b in THF also showed a minor resonance for H2C(Ph2PS)2, which increased with time, but this was not observed for solutions of 8a. Formation and X-ray Structure of [TeI2{(I2)C(PPh2S)2}] (9). The reaction of Li21 with TeI4 produced a few red crystals of a byproduct, which were separated manually from crystals of the major product 7c that was obtained by hexane diffusion into a benzene solution. A single-crystal X-ray analysis identified this minor product as [TeI2{(I2)C(PPh2S)2}] (9) (see Figure 3). Compound 9 is formally the result of the insertion of

is a sterically bulky aryl group. The central I atom in 9 features a T-shaped geometry. In this respect the only structurally characterized organo-iodine compound with a hypervalent I−I bond is the o-nitrodiphenyliodonium iodide,29 which features distances I−I 3.1802(2) Å, Cax−I 2.175(3) Å, and Ceq−I 2.109(3) Å and bond angles I−I−Cax 176.83(8)° and Ceq−I−I 86.66(9)°. Our attempts to generate 9 by the direct reaction of I2 and 7c in CH2Cl2 or toluene were unsuccessful. This may be due to the formation of a 1:1 adduct between I2 and 7c, cf. Me2TeI4.30 Selected structural parameters for 9 are given in Table 3. The I−I bond distance of 2.8829(14) Å in 9 is almost 6% longer Table 3. Selected Bond Lengths (Å) and Angles (deg.) for 9 Te1−S1 Te1−S2 Te1−I1 Te1−I2 Te1−I3 I3−C25 S1−Te1−I1 S1−Te1−I2 S2−Te1−I1 S2−Te1−I2 S1−Te1−S2 I1−Te1−I2 S1−Te1−I3 I1−Te1−I3 I2−Te1−I3

2.655(4) 2.929(3) 2.787(1) 2.906(1) 3.028(1) 2.177(1) 89.31(8) 177.80(9) 172.51(7) 92.61(7) 85.24(10) 92.87(4) 88.90(8) 90.35(4) 91.40(4)

I3−I4 S1−P1 S2−P2 P1−C25 P2−C25 C25−I3−I4 C25−I3−Te1 I4−I3−Te1 P1−S1−Te1 P2−S2−Te1 P1−C25−P2 P1−C25−I3 P2−C25−I3

2.883(1) 2.016(5) 1.983(5) 1.833(13) 1.840(13) 90.3(3) 83.1(3) 173.35(5) 101.77(16) 100.19(15) 121.6(7) 109.6(6) 108.9(5)

than that in the iodine molecule (2.715(6) Å)31 in the solid state. The bond angle Te1−I3−I4 is 173.35(5)°, cf. Te−I−I = 173.34 (2)° and d(I−I) = 2.8446(6) Å in (2,4,6-iPr3C6H2)2TeI224 In contrast to the structure of 8b, the bond distances in the basal plane of the square pyramid in 9 are markedly asymmetrical; the Te−I and Te−S bond lengths differ by 0.12 and 0.27 Å, respectively. The structures of 8b and 9 also differ in that the axial Te−I bond in 9 is shorter by ca. 0.18 Å than the mean Te−I bond distance in the basal plane, whereas the converse is true for the Te−S bonds in 8b. The C−I bond length of 2.177(11) Å in 9 is in the range 2.14−2.21 Å found for typical C(sp3)−I bonds, cf. 2.05−2.09 Å for C(sp2)−I bonds.32 It is also comparable to the value of 2.147(3) Å found for the dimeric lithium complex of the anion [IC(PPh2S)2]−,10 but significantly longer than the distance of 2.104(3) Å reported for a carbene−iodine adduct.33 Computational Analysis of Bonding. GGA DFT (PW91) calculations were carried out in order to investigate bonding in these systems. Unless otherwise noted, there was in general a very good agreement between the optimized and experimental structures. As is the case for most systems that feature a combination of several heavy elements and pendant conjugated organic groups, the molecular orbitals initially obtained from geometry optimizations were considerably delocalized over the molecules, hampering straightforward interpretation. In order to examine the bonding between the chalcogen and the ligands, the electronic structures were probed by the calculation of Hirschfeld charges,34 Nalewajski− Mrozek bond orders,35 the electron localization function,36 and the Boys−Foster method of orbital localization.37 The most significant calculated atomic charges and bond orders are compiled in Tables 5 and 6, respectively.

Figure 3. View of 9 showing the atomic numbering scheme and thermal ellipsoids at 30% probability. Hydrogen atoms of phenyl groups have been omitted for clarity.

one iodine atom of an I2 molecule into the Te−C bond of 7c, a process that is, to our knowledge, unprecedented. The addition of I2 to diaryl tellurides Ar2Te produces two structural isomers of Ar2TeI2 (A and B in Scheme 1). Isomer A adopts the Scheme 1

expected bisphenoidal (ψ-trigonal bipyramidal) arrangement with four-coordinate tellurium, while isomer B involves a trigonalplanar geometry for the three-coordinate tellurium center with an almost linear Te−I−I unit;28 the latter is observed when Ar 630


Organometallics

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Table 4. Crystallographic Data for 7a−c, 8b, and 9 empirical formula fw temperature (K) cryst syst space group a (Å), α (deg) b (Å), β (deg) c (Å), γ (deg) Volume (Å3) Z calcd density (mg/m3) absorp coeff (mm−1) F(000) cryst size (mm3) θ range (deg) limiting indices reflns collected/ unique completeness to θ max. and min. transmn refinement method data/restraints/ parameters goodness-of-fit on F2 R1, wR2 [I > 2σ(I)] R1, wR2 (all data) largest diff peak and hole (e Å−3)

7a

7b

C25H20TeCl2P2S2 644.97 173(2) monoclinic P21/n 11.6080(3), 90 19.2180(4), 110.1750(10) 12.3350(3), 90 2582.89(11) 4 1.659

C25H20Br2P2S2Te 733.89 173(2) monoclinic P21/n 11.9410(3), 90 19.5420(3), 111.3521(13) 12.2900(6), 90 2671.03(15) 4 1.825

C26H22Cl2I2 P2S2Te 912.80 173(2) orthorhombic Pbca 13.1740(4), 90 21.1720(6), 90 22.3250(4) Å, 90 6226.9(3) 8 1.947

7c

C27H24Br2Cl4P2S3Te 935.80 173(2) triclinic P1̅ 11.4370(5), 76.170(3) 12.5610(7), 72.742(3) 12.9940(8), 70.952(3) 1664.02(16) 2 1.868

C25H20I4P2S2Te 1081.67 173(2) monoclinic P21/n 10.1720(20), 90.00 16.4910(33), 101.990(30) 18.2070(36), 90.00 2987.53 4 2.405

1.657

4.394

3.363

3.920

5.391

1272 0.19 × 0.16 × 0.14 2.75 to 27.49 −15 ≤ h ≤ 15, −22 ≤ k ≤ 24, −15 ≤ l ≤ 16 9829/5718 [R(int) = 0.0245] 96.7% 0.8012 and 0.7436

1416 0.02 × 0.01 × 0.01 2.74 to 25.00 −14 ≤ h ≤ 14, −23 ≤ k ≤ 23, −14 ≤ l ≤ 13 17 433/4688 [R(int)= 0.0988] 99.7% 0.9173 and 0.9574

3456 0.20 × 0.11 × 0.07 1.9 to 27.50 −16 ≤ h ≤ 16, −26 ≤ k ≤ 26, −27 ≤ l ≤ 27 11 273/6061 [R(int) =0.0559] 99.1% 0.7987 and 0.5528

908 0.40 × 0.30 × 0.10 2.21 to 25.00 −13 ≤ h ≤ 13, −14 ≤ k ≤ 14, −15 ≤ l ≤ 15 11 118/5827 [R(int) =0.0775] 99.4% 0.3031 and 0.6952

1984 0.20 × 0.18 × 0.14 2.29 to 25.00 −12 ≤ h ≤ 12, −19 ≤ k ≤ 19, −21 ≤ l ≤ 21 9853/5193 [R(int) = 0.0526] 98.8% 0.5191 and 0.4119

full-matrix least-squares on F2 5718/0/289 4688/0/289

6061/0/316

5827/0/346

5193/0/307

0.982

1.065

1.038

1.109

1.109

0.0317, 0.0959

0.0487, 0.0810

0.0575, 0.1525

0.0763, 0.1389

0.0638, 0.1318

0.0362, 0.1019 0.449 and −0.356

0.0733, 0.0905 0.677 and −0.616

0.0802, 0.1729 0.966 and −0.843

0.1163, 0.1593 1.567 and −1.591

0.0845, 0.1460 1.661 and −2.006

Table 5. Calculated Hirshfeld Charges for Selected Atoms in 7(a−c), 8b, and 9

8b

9

Table 6. Calculated Bond Orders for Selected Atom Pairs in 7(a−c), 8b, and 9

atom

7a

7b

7c

8b

9

atom pair

7a

7b

7c

8b

9

Te1 X1 X1 S1 S2 P1 P2 C25 S3 I3 I4

0.44 −0.31 −0.31 −0.12 −0.12 0.29 0.29 −0.26

0.42 −0.30 −0.30 −0.12 −0.12 0.29 0.29 −0.26

0.38 −0.28 −0.28 −0.12 −0.12 0.29 0.29 −0.26

0.36 −0.21 −0.21 −0.17 −0.18 0.28 0.28 −0.22 0.00

0.23 −0.18 −0.18 −0.17 −0.17 0.27 0.27 −0.22

Te1−X1 Te1−X2 Te1−S1 Te1−S2 Te1−C25 Te1−S3 Te1−I Te1−(I3)−I4 P1−C25 P1−C25 S1−P1 S2−P2 C25−S3 C25−I3 I3−I4 S1−(Te1)−S2 X1−(Te1)−X2 S1−(Te1)−X2 S2−(Te1)−X1

0.78 0.77 0.53 0.53 1.02

0.74 0.74 0.53 0.53 1.03

0.70 0.70 0.54 0.54 1.04

0.88 0.88 0.46 0.46

0.93 0.88 0.48 0.40

0.33 −0.21

TeX2[C(Ph2PS)2] (7a−c). Bonding in this structural family is best conceptualized as a donor−acceptor interaction between the fragments [C(Ph2PS)2]2− and [:TeX2]2+. There are two available orbitals in the nearly linear chalcogen fragment (A and B in Scheme 2). The ligand is in principle able to engage in σ donation through lone pairs on the sulfur and the central carbon atoms (C in Scheme 2). The second carbon-centered lone pair of electrons is available only for π interaction (D in Scheme 2). In all three compounds the Te1−C25 bond order (average 1.03) clearly corresponds to a single bond, which is highly polarized in view of the atomic charges (cf. the charges of C25 and the halogen atoms X). A three-center interaction is

0.68

1.10 1.10 1.18 1.18

1.10 1.10 1.18 1.18

1.09 1.09 1.18 1.18

0.99 0.99 1.24 1.24 1.53

0.27 0.37 1.03 1.03 1.22 1.27 1.08 0.58

0.22 0.33

0.22 0.38

0.23 0.44 0.26 0.26

0.27 0.30

denoted by half-integer Te1−S bond orders as well as a small fractional S1−(Te1)−S2 bond order, i.e., the value calculated between the sulfur atoms across tellurium. Similar Te1−Cl and Cl1−(Te)−Cl2 bond orders are observed. Delocalization through 631


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composition of the equivalent localized orbitals, are comparable to those previously calculated for the pnictogen derivatives [MX{C(PPh2S)2}] (M = Sb, Bi),17 the main difference being the lack of one Cl atom in the [MCl]2+ fragment. [TeX2{SC(PPh2S)2}] (8b). The preceding analysis for the 7a−c family provides a useful point of comparison to 8b and 9. In the case of the product of formal sulfur insertion into the Te−C bond, 8b, most of the calculated atomic charges and bond orders closely follow the corresponding parameters in 7a−c. The small changes in atomic charges are consistent with the neutral character of the inserted S3 atom. The bond orders reflect the presence of additional bonds and differences in the coordination sphere of tellurium. As the S1 and S2 atoms sit opposite Br2 and Br1, the corresponding Te−Br, Te−S, and Br−(Te)−S fractional bond orders are consistent with threecenter interactions. While the Te1−S3 bond order is just under 0.7, the S3−C25 bond order indicates a substantial doublebond character; this is consistent with the composition of the πC−S localized molecular orbital (Figure 6). However, the ELF shape (Figure 7) indicates that the corresponding π electron pair is strongly polarized toward carbon. This observation is consistent with the retention of negative charge on C25. In this instance the tellurium three-center interactions are also translated into pairs of σ orbitals. In view of the somewhat unexpected absence of charge on S3, supplementary calculations were carried out for the [SC(Ph2PS)2]2− fragment, using the atom positions observed in 8b. Such calculations placed most of the dianion charge on S1 and S2 (−0.42 each), S3 (−0.34), and C25 (−0.25); these values indicate that a significant reorganization of electron density occurs upon attachment of the [:TeBr2]2+ moiety. [TeI2{(I2)C(PPh2S)2}] (9). This compound was the only case in which there were disagreements between the experimental and optimized structures, other than changes in the orientation of the aromatic rings. The most significant differences were located within the TeS2I4 group of atoms, up to 15.5° in dihedral (C1−P1−S1−Te1) and up to 10.4° in bond (C25− I3−I4) angles. Such deviations are likely the result of packing forces on the conformation of the molecule; the distortion energy was estimated as 18 kJ/mol on the basis of the optimization of a model in which the S1, S2, Te1, I1, and C25 atoms were fixed at their experimental positions. There are many structural parallels between 9 and 8b; this also translates into similar values of atomic charges and bond orders. The C25−I3 bond order corresponds to a single bond, while the Te1−I3, I3−I4 and Te1−(I3)-I4 bond orders typify a three-center interaction, and the positive charge of I3 is characteristic of a hypervalent atom. The localized molecular orbitals (Figure 8) are also consistent with an AX3E2 iodine atom. The apparent sp3 character of C25 in 9 is consistent with a prominent lobe of the ELF (Figure 9). This feature does suggest that the canonical form in Scheme 3 is a major contributor to the bonding in this molecule. In support of this interpretation, the optimized structure of the hypothetically protonated species [TeX2{S(CH)(PPh2S)2}]+ displayed almost no changes in molecular dimensions with respect to 9.

Scheme 2

the structure is evident in the P−S bond orders (1.18 throughout the family). Although the P−C25 bond orders are just 1.1, the stabilizing effect of conjugation through the P atoms is palpable in the localized orbital with πTe−C character (Figure 4).38 In this

Figure 4. Selected localized orbitals of 7a.

respect the major orbital interactions are clearly identified in the composition of the other localized orbitals in Figure 4. We note that the Boys−Foster method decomposes the three-center S−Te−S interactions into pairs of σTe−S orbitals. Similarly, two σTe−Cl localized orbitals are obtained from the Cl1−Te1−Cl2 interaction. Given the modest degree of conjugation, the pair of π electrons on C25 retains a significant local character, which can be recognized in the shape of the electron localization function around that atom; a section of the ELF is illustrated for 7a in Figure 5. The orientation of the lone pair on tellurium,

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CONCLUSIONS The metathetical reactions of Li21 with tellurium tetrahalides give the expected heteroleptic complexes 1TeX2 (X = Cl, Br, I) in modest yields. The dianionic ligand 1 is S,C,S-coordinated to tellurium in these complexes. Theoretical calculations indicate a polarized Te−C single bond with a significant negative charge on carbon together with a two-electron three-center S−Te−S

Figure 5. Contour plot of the electron localization function in the Cl1−Te1−Cl2−C25 plane of 7a.

opposite the Te1−C25 bond, is also apparent in the plot. The values of bond order and atomic charge, as well as the overall 632


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Figure 6. Selected localized orbitals of 8b. and Ph2Te2 (δ 422 ppm) (125Te). Elemental analyses were performed by the Analytical Services Laboratory, Department of Chemistry, University of Calgary. General Synthesis of {TeX2[C(PPh2S)2]}2 [X = Cl (7a); Br (7b); I (7c)]. A yellow solution of Li2[C(PPh2S)2] (0.670 mmol) in toluene was slowly transferred by cannula to a flask containing solid TeX4 (0.180 g (X = Cl), 0.299 g (X = Br), 0.425 g (X = I); 0.670 mmol)). The mixture was kept at −78 °C for 15 min, and then it was allowed to reach ambient temperature and stirred for 16 h. A brown, insoluble solid was separated from the mixture by filtration, which was dried under vacuum, and the 31P NMR spectrum of this crude product was recorded. The brown solid was extracted with dichloromethane and filtered to remove lithium halides. The recrystallized product was obtained by hexane diffusion into a dichloromethane solution. In the data given below, 31P NMR chemical shifts for the crude products are given first followed by yields, elemental analyses, and NMR data for the recrystallized products. The 1H NMR spectra for 7a−c showed broad bands for phenyl resonances at 7.59−7.53 (m, 12H) and 7.34− 7.29 (m, 8H). {TeCl2[C(PPh2S)2]}2 (7a). Yield: 0.120 g (28%). Mp: 89−90 °C (dec). 31P{1H} NMR (162 MHz, C4D8O, 25 °C): δ 23.0 (d, J = 13 Hz), 28.7, 32.5, 35.8 (d, J = 13 Hz), 39.3, 66.7, 75.6. Anal. Found: C, 45.63; H, 3.17. Calcd for C25H20P2S2TeCl2: C, 46.55; H, 3.12. 13 C{1H}NMR (101 MHz, CD2Cl2, 25 °C): δ 129.6 (t, m-Ph, 3JP−C = 6.0 Hz), 132.9 (t, o-Ph, 2JP−C = 6.0 Hz), 133.7 (p-Ph). 31P{1H} NMR (162 MHz, CD2Cl2, 25 °C): δ 31.9 (s, 2J{31P, 125Te} = 143 Hz). 125Te NMR (126.4 MHz, CD2Cl2, 25 °C): δ 954 (t, 2J{31P, 125Te} = 143 Hz). {TeBr2[C(PPh2S)2]}2 (7b). Yield: 0.132 g (27%). Mp: 122−123 °C (dec). 31P{1H} NMR (162 MHz, C4D8O, 25 °C): δ 29.0, 32.5, 45.0, 68.0, 73.6. Anal. Found: C, 41.00; H, 2.48. Calcd for C25H20P2S2TeBr2: C, 40.91; H, 2.75. 13C{1H}NMR (101 MHz, CD2Cl2, 25 °C): δ 129.7 (t, m-Ph, 3JP−C = 6.0 Hz), 133.0 (t, o-Ph, 2JP−C = 6.0 Hz), 133.8 (p-Ph). 31P{1H} NMR (162 MHz, CD2Cl2, 25 °C): δ 32.2 (s, 2J{31P, 125 Te} = 140 Hz). 125Te NMR (126.4 MHz, CD2Cl2, 25 °C): δ 972 (t, 2J{31P, 125Te} = 141 Hz). Orange crystals of 8b were separated manually from the recrystallized sample of 7b under a microscope. {TeI2[C(PPh2S)2]}2 (7c). Yield: 0.149 g (27%). Higher yields of pure 7c were obtained by reducing the reaction time to 6 h, after which the red solid was removed by filtration and treated with dichloromethane (20 mL) followed by evaporation to give 7c (0.278 g, 50%). Mp: 160− 161 °C (dec). 31P{1H} NMR (162 MHz, C4D8O, 25 °C): δ 29.3, 32.5, 48.0, 69.6, 70.9. 13C{1H} NMR (101 MHz, CD2Cl2, 25 °C): δ 129.6 (t, m-Ph, 3JP−C = 7.0 Hz), 133.2 (t, o-Ph, 2JP−C = 7.0 Hz), 133.8 (p-Ph). 31P{1H} NMR (162 MHz, CD2Cl2, 25 °C): δ 32.4 (s, 2J {31P, 125 Te} = 135 Hz). 125Te NMR (126.4 MHz, CD2Cl2, 25 °C): δ 984 (m, br). Found: C, 35.94; H, 2.43. Anal. Calcd for C25H20P2S2TeI2: C, 36.27; H, 2.44. A few brown crystals of TeI2[C(I2)(PPh2S)2] (9) were separated manually from the red crystals of 7c obtained by hexane diffusion into a benzene solution. General Synthesis of TeX2[C(S)(PPh2S)2] [X = Cl (8a); Br (8b); I (8c)]. One equivalent of sulfur (0.021 g, 0.670 mmol) was added to a

Figure 7. Contour plot of the electron localization function in the Te1−S3−C25 plane of 8b.

bonding arrangement. Although the lability of the Te−C bond in these complexes is indicated by the structural characterization of minor products that formally involve the insertion of sulfur and I2 into this bond, it has not been possible to prepare these complexes by direct reactions of 1TeX2 with these reagents. However, the sulfur insertion products are obtained in fair yields via metathetical reactions of TeX4 and Li2[SC(Ph2PS)2]. The C−S bond in the insertion product TeBr2[SC(Ph2PS)2] has a substantial π-component, and interestingly, the negative charge on carbon is retained and the inserted sulfur atom is essentially neutral. The iodine insertion product [TeI2{(I2)C(PPh2S)2}] is a rare example of an organoiodine compound with a hypervalent I−I bond. The structural parameters supported by theoretical calculations are consistent with a C(sp3)−I single bond that incorporates a negatively charged carbon atom and a hypervalent Te−I−I arrangement with a positively charged central iodine atom.

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EXPERIMENTAL SECTION

General Procedures. All reactions and manipulations of reagents and products were carried out under an argon atmosphere using standard Schlenk techniques. Solvents were dried over and distilled from CaH2 (CH2Cl2) and Na/benzophenone (toluene, Et2O, and THF). MeLi (Aldrich, 1.6 M in Et2O), CH2(PPh2)2 and TeBr4 (Aldrich Chemical Co.), and TeCl4 and TeI4 (Alfa Aesar Chemicals) were commercial samples that were used without further purification. Bis(diphenylthiophosphino)methane was synthesized from CH2(PPh2)2 and elemental sulfur according to the reported procedure.4a The reagent Li2[C(PPh2S)2] (Li21) was obtained by treatment of CH2(PPh2S)2 with two equivalents of MeLi as a yellow turbid solution by following the protocol described in the literature.1a 1 H, 13C, 31P{1H}, and 125Te{1H} NMR spectra were recorded on Bruker 400 NMR spectrometers. Chemical shifts are reported in ppm relative to external standards: (CH3)4Si (1H and 13C), 85% H3PO4 (31P), 633


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Figure 8. Selected localized orbitals of 9. Te−S and Te−I(3) bonds are omitted.

Scheme 3

Figure 9. Contour plot of the electron localization function in the Te1−I3−C25 plane of 9. (p-Ph), 134.0 (m, o-Ph). 31P{1H} NMR (162 MHz, CD2Cl2, 25 °C): δ 70.8 (s, 2J{31P, 125Te} = 71 Hz). 125Te NMR (126.4 MHz, CD2Cl2, 25 °C): δ 1159 (t, 2J{31P, 125Te} = 71 Hz). TeBr2[C(S)(PPh2S)2] (8b). Yield: 0.229 g (45%). Mp: 177−178 °C (dec). Anal. Found: C, 39.78; H, 2.59. Calcd for C25H20P2S2TeBr2: C, 39.20; H, 2.63. 31P{1H} NMR (162 MHz, C4D8O, 25 °C): δ 32.5, 68.1. 13C{1H} NMR (101 MHz, C4D8O, 25 °C): δ 129.6 (m, m-Ph), 133.3 (p-Ph), 133.8 (m, o-Ph). 31P{1H} NMR (162 MHz, CD2Cl2, 25 °C): δ 72.1 (s, 2J{31P, 125Te} = 68 Hz). 125Te NMR (126.4 MHz, CD2Cl2, 25 °C): δ 1090 (m, br). TeI2[C(S)(PPh2S)2] (8c). Yield: 0.202 g (35%). 31P{1H} NMR (162 MHz, CD2Cl2, 25 °C): δ 58.7, 72.0. 31P{1H} NMR (162 MHz, C4D8O, 25 °C): δ 32.5, 69.6. 13C{1H} NMR (101 MHz, C4D8O, 25 °C): δ 129.5 (m, m-Ph), 133.2 (p-Ph), 133.5 (m, o-Ph). Despite numerous attempts, we were unable to obtain an analytically pure sample of 8c that was free from H2C(PPh2S)2.

toluene solution of Li2[C(PPh2S)2] (0.670 mmol) at −78 °C. After 15 min the mixture was allowed to reach room temperature and then stirred for a further 2 h. This solution was cooled to −78 °C, and then solid TeX4 (0.180 g (X = Cl), 0.299 g (X = Br), 0.425 g (X = I); 0.670 mmol) was added. After 15 min, the mixture was allowed to reach ambient temperature and then stirred for a further 4 h. A brownish-yellow (8a, 8b) or red (8c) solid was separated by filtration of the above mixture. This residue was treated with dichloromethane and filtered to remove lithium halides. Pure samples (8a, 8b, and 8c) were obtained as yellow, orange, and red crystals, respectively, by hexane diffusion into a dichloromethane solution. TeCl2[C(S)(PPh2S)2] (8a). Yield: 0.198 g (44%). Mp: 159−160 °C (dec). Anal. Found: C, 44.10; H, 2.82. Calcd for C25H20P2S2TeCl2: C, 44.35; H, 2.98. 31P{1H} NMR (162 MHz, C4D8O, 25 °C): δ 66.6. 13 C{1H} NMR (101 MHz, C4D8O, 25 °C): δ 129.6 (m, m-Ph), 133.2 634


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X-ray Crystallography. Crystallographic data for 7a−c, 8b, and 9 are given in Table 4. Data were collected with a Nonius Kappa CCD diffractometer with use of monochromated Mo Kα radiation (λ = 0.71073 Å) at −100 °C. The structures were solved by direct methods using the program SHELXS-9739 and refined with SHELXL-9740 and by full-matrix least-squares with anisotropic thermal parameters for the non-hydrogen atoms. Hydrogen atoms were included in calculated positions and were refined by riding model. In the structure of 8b, one of the chlorine atoms in the dichloromethane solvent molecule was disordered over two positions (0.65:0.35) in the final refinement.

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(11) (a) Chivers, I.; Eisler, D. J.; Ritch, J. S.; Tuononen, H. M. Angew. Chem., Int. Ed. 2005, 44, 4953. (b) Ritch, J. S.; Chivers, I.; Eisler, D. J.; Tuononen, H. M. Chem.Eur. J. 2007, 13, 4643. (12) (a) Robertson, S. D.; Chivers, T.; Tuononen, H. M. Inorg. Chem. 2008, 47, 10634. (b) Robertson, S. D.; Chivers, T.; Tuononen, H. M. Inorg. Chem. 2009, 48, 6755. (13) Chivers, T.; Ritch, J. S.; Robertson, S. D.; Konu, J.; Tuononen, H. M. Acc. Chem. Res. 2010, 43, 1053. (14) Leung, W.-P.; Wan, C.-L.; Mak, T. C. W. Organometallics 2010, 19, 1622. (15) Leung, W.-P.; Wan, C.-L.; Kan, K.-W.; Mak, T. C. W. Organometallics 2010, 19, 814. (16) Foo, C.; Lau, K.-C.; Yang, Y-F; So, C.-W. Chem. Commun. 2009, 6816. (17) Thirumoorthi, R.; Chivers, T.; Vargas-Baca. Dalton Trans. 2011, 40, 8086. (18) The resonance for H2C(PPh2S)2 appears at either δ31P = 32.5 or 35.0 in d8-THF in the presence or absence of lithium halides, respectively, and δ31P = 34.9 in CD2Cl2. (19) Very recently, low yields of a related uranium(IV) complex [(1) U{SC(PPh2S)2}(pyr)] were obtained by mild thermolysis of the solvated homoleptic complex [(1)2U(THF)2] in pyridine.5a (20) Konu, J.; Chivers, T.; Tuononen, H. M. Chem.Eur. J. 2010, 16, 12977. (21) Alcock, N. W. Adv. Inorg. Chem. Radiochem. 1972, 15, 1. (22) Pauling, L. The Nature of The Chemical Bond, 3rd ed.; Cornell University Press: Ithaca, NY, 1960; p 224. (23) Birdsall, D. J.; Novosad, J.; Slawin, A. M. Z.; Woollins, J. D. J. Chem. Soc., Dalton Trans. 2000, 435. (24) Chadha, R. K.; Drake, J. E.; McManus, N. T.; Quinian, B. A.; Sarkar, A. B. Organometallics 1987, 6, 813. (25) Husebye, S.; Kudis, S.; Lindeman, S. V.; Strauch, P. Acta Crystallogr. 1995, C51, 1870. (26) Carmalt, C. J.; Cowley, A. H.; Decken, A.; Lawson, Y. G.; Norman, N. C. Acta Crystallogr. 1996, 52C, 931. (27) In common with other metal complexes of the dianions [EC(Ph2PE)2]2− (E = S, Se), the (C)S−Te distance is substantially shorter than the mean (P)S−Te bond length in 8b. (a) Konu, J.; Chivers, T. Chem. Commun. 2010, 46, 1431. (b) Risto, M.; Chivers, T.; Konu, J. Dalton Trans. 2011, 40, 8238. (28) (a) Laur, P. H.; Saberi-Niaki, S. M.; Scheiter, M.; Hu, C.; Englert, U.; Wang, Y.; Fleischhauer, J. Phosphorus, Sulfur, Silicon 2005, 180, 1035. (b) Faoro, E.; den Oliveira, G. M.; Lang, E. S.; Pereira, C. B. J. Organomet. Chem. 2010, 695, 1480. (29) Nikiforov, V. A.; Karavan, V. S.; Miltsov, S. A.; Selivanov, S. I.; Kolehmainen, E.; Wegelius, E.; Nissinen, M. ARKIVOC 2003, 4, 191. The original structure was reported as the salt [2-NO2C6H4-I-IC6H5]+I− neglecting the I−I bond. Revised distances and angles weremeasured from the data deposited at the Cambridge CrystallographicData Centre, reference code enigen. (30) Pritzkow, H. Inorg. Chem. 1979, 18, 311. (31) Bolhuis, F. V.; Koster, P. B.; Migchelsen, T. Acta Crystallogr. 1967, 23, 90. (32) Trotter, J. The Chemistry of the Carbon-Halogen Bond, Part 1; John Wiley & Sons Ltd.: New York, 1973; pp 49−62. (33) Kuhn, N.; Kratz, T.; Henkel, G. J. Chem. Soc., Chem. Commun. 1993, 1778. (34) (a) Hirshfeld, F. L. Theor. Chim. Acta 1977, 44, 129. (b) Wiberg, K. B.; Rablen, P. R. J. Comput. Chem. 1993, 14, 1504. (35) (a) Michalak, A.; De Kock, R. L.; Ziegler, T. J. Phys. Chem. A 2008, 112, 7256. (b) Nalewajski, R. F.; Mrozek, J. Int. J. Quantum Chem. 1994, 51, 187. (c) Nalewajski, R. F.; Mrozek, J. Int. J. Quantum Chem. 1997, 61, 589. (d) Nalewajski, R. F.; Mrozek, J.; Michalak, A. Pol. J. Chem. 1998, 72, 1779. (e) Nalewajski, R. F.; Mrozek, J.; Mazur, G. Can. J. Chem. 1996, 74, 1121. (36) Becke, A. D.; Edgecombe, K. E. J. Chem. Phys. 1990, 92, 5397. (37) (a) Edmiston, C.; Rudenberg, K. Rev. Mod. Phys. 1963, 35, 457. (b) Foster, J. M.; Boys, S. F. Rev. Mod. Phys. 1960, 32, 300. (c) von Niessen, W. J. Chem. Phys. 1972, 56, 4290.

ASSOCIATED CONTENT

S Supporting Information *

Tables of crystal data, atomic positions and displacement parameters, and bond lengths and bond angles in CIF format and computational details. This information is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Phone: 403-220-5741. Fax: 403289-9488. E-mail: [email protected]. Fax: 905522-2509. Phone: 905-525-9140, ext. 23497.

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ACKNOWLEDGMENTS Financial support from the Natural Sciences and Engineering Research Council of Canada is gratefully acknowledged. This work was made possible by the facilities of the Shared Hierarchical Academic Research Computing Network (SHARCNET: www. sharcnet.ca) and Compute/Calcul Canada.

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REFERENCES

(1) (a) Cantat, T.; Mézailles, N.; Ricard, L.; Jean, Y.; Le Floch, P. Angew. Chem., Int. Ed. 2004, 43, 6382. (b) Cantat, T.; Ricard, L.; Jean, Y.; Le Floch, P.; Mézailles, N. Organometallics 2006, 25, 4965. (2) (a) Heuclin, H.; Cantat, T.; Le Goff, X. F.; Le Floch, P.; Mézailles, N. Eur. J. Inorg. Chem. 2011, 2540. (b) Cantat, T.; Ricard, L.; Mézailles, N.; Le Floch, P. Organometallics 2006, 25, 6030. (c) Cantat, T.; Demange, M.; Mézailles, N.; Ricard, L.; Jean, Y.; Le Floch, P. Organometallics 2005, 24, 4838. (3) Fustier, M.; Le Goff, X. F.; Le Floch, P.; Mézailles, N. J. Am. Chem. Soc. 2010, 132, 13108. (4) (a) Cantat, T.; Jaroschik, F.; Ricard, L.; Le Floch, P.; Nief, F.; Mézailles, N. Organometallics 2006, 25, 1329. (b) Cantat, T.; Jaroschik, F.; Nief, F.; Ricard, L.; Mézailles, N.; Le Floch, P. Chem. Commun. 2005, 5178. (5) (a) Tourneux, J.-C.; Berthet.; Cantat, T.; J-C; Thuéry, P.; Mézailles, N.; Le Floch, P.; Ephritikhine, M. Organometallics 2011, 30, 2957. (b) Tourneux, J.-C.; Berthet.; Cantat, T.; J-C; Thuéry, P.; Mézailles, N.; Ephritikhine, M. J. Am. Chem. Soc. 2011, 133, 6162. (c) Tourneux, J.-C.; Berthet, J-C; Thuéry, P.; Mézailles, N.; Le Floch, P.; Ephritikhine, M. Dalton Trans. 2010, 39, 2494. (d) Cantat, T.; Arliguie, T.; Noël, A.; Thuéry, P.; Ephritikhine, M.; Le Floch, P.; Mézailles, N. J. Am. Chem. Soc. 2009, 131, 963. (6) (a) Cantat, T.; Mézailles, N.; Auffrant, A.; Le Floch, P. Dalton Trans. 2008, 1957. (b) For a recent review of group 1−4 andf-element complexes of 1 and related imino ligands, see: Liddle, S. T.; Miles, D. P.; Wooles, A. J. Chem. Soc. Rev. 2011, 40, 2164. (7) Mills, D. P.; Soutar, L.; Lewis, W.; Blake, A. J.; Liddle, S. T. J. Am. Chem. Soc. 2010, 132, 14379. (8) Mindiola, D. J.; Scott, J. Nat. Chem. 2011, 3, 15. (9) Cantat, T.; Jacques, X.; Ricard, L.; Le Goff, X. F.; Mézailles., N.; Le Floch, P. Angew. Chem., Int. Ed. 2007, 46, 5947. (10) Konu, J.; Chivers, T. Chem. Commun. 2008, 4995. 635


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(38) The combination of the px orbital of Te with the out-of-phase σ orbitals of the Cl atoms has the appropriate symmetry, orientation, energy, and overlap to be mixed with the pz orbital of the carbon atom. It is this orbital interaction that the Boys−Foster localization method reports as the π(Te−C) localized orbital. (39) Sheldrick, G. M. SHELXS-97, Program for Crystal Structure Determination; University of Göttingen: Göttingen, 1997. (40) Sheldrick, G. M. SHELXL-97, Program for Crystal Structure Refinement; University of Göttingen: Göttingen, 1997.

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Experimental and Theoretical Investigations of Tellurium(IV

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