Trigonal Bipyramidal M₂Ch₃^2- (M = Sn, Pb; Ch = S, Se, Te) and TlMTe₃^3- Anions:  Multinuclear Magnetic Resonance, Raman Spectroscopic, and Theoretical Studies, and the X-ray Crystal Structures of (2,2,2-crypt-K⁺)₃TlPbTe₃^3-·2en and (2,2,2-crypt-K⁺)₂Pb₂Ch₃^2-·0.5en (Ch = S, Se)

Abstract

The series of group 14 metal trigonal bipyramidal anions has been extended to the mixed group 13/group 14 metal TlMTe(3)(3)(-) anions (M = Sn, Pb), obtained by the reaction of Tl(2)M(2)Te(3) and K(2)Te in en or in en/ethylamine mixtures and a stoichiometric excess of 2,2,2-crypt with respect to K(+). The thallium anions were characterized in solution by (119)Sn, (205)Tl, (207)Pb, and (125)Te NMR spectroscopy. The small magnitudes of the relativistically corrected reduced coupling constants, (1)(K(M)(-)(Ch))(RC) and (1)(K(Tl)(-)(Ch))(RC), observed for the previously reported M(2)Ch(3)(2)(-) (Ch = Se, Te) and the TlMTe(3)(3)(-) anions are consistent with predominantly p-bonded cages, and this observation is supported by local and nonlocal density functional theory (DFT) calculations. Theory indicates M-M and Tl-M interactions of high s character corresponding to Mayer bond orders of 0.13-0.32. The (K(M)(-)(M))(RC) and (K(Tl)(-)(M))(RC) couplings are unusually large compared to those of the butterfly-shaped Tl(2)Ch(2)(2)(-) anions and likely arise from higher M-M and Tl-M bond orders, a larger number of coupling pathways, and smaller M-Ch-M and M-Ch-Tl bond angles. The TlPbTe(3)(3)(-) anion has also been structurally characterized by X-ray crystallography in (2,2,2-crypt-K(+))(3)TlPbTe(3)(3)(-).2en [monoclinic system, space group P2(1)/c, Z = 4, a = 15.256(5) Å, b = 26.087(9) Å, c = 20.984(8) Å, and beta = 93.03(3) degrees ] along with Pb(2)Ch(3)(2)(-) (Ch = S, Se) in (2,2,2-crypt-K(+))(2)Pb(2)Ch(3)(2)(-).0.5en [Pb(2)S(3)(2)(-): triclinic system, space group P&onemacr;, Z = 2, a = 10.189(2) Å, b = 11.329(2) Å, c = 23.194(4) Å, alpha = 95.439(14) degrees, beta = 92.562(14) degrees, and gamma = 90.549(14) degrees; Pb(2)Se(3)(2)(-): triclinic system, space group P&onemacr;, Z = 2, a = 10.187(2) Å, b = 11.403(2) Å, c = 23.360(6) Å, alpha = 95.26(2) degrees, beta = 92.17(2) degrees, and gamma = 90.89(2) degrees ]. Density functional theory calculations show that the experimental structures for the M(2)Ch(3)(2)(-) and TlPbTe(3)(3)(-) anions are true minima and reproduce the experimental bond distances and angles. The vibrational frequencies determined by DFT calculations are in good agreement with those determined by Raman spectroscopy and have been used in their assignment.

Syntheses, Vibrational Spectra, and Theoretical Studies of the Adamantanoid Sn4Ch104- (Ch = Se, Te) Anions: X-ray Crystal Structures of [18-Crown-6-K]4[Sn4Se10]·5en and [18-Crown-6-K]4[Sn4Te10]·3en·2THF

“…We have previously shown that density functional theory 39-43 can be used to calculate the geometries and the vibrational frequencies of classically bonded anions of the heavy main group elements. 44,45 In the present study, DFT calculations provide fully optimized geometries and definitive vibrational assignments for the Sn 4 Ch 10 4-(Ch ) Se, Te) anions. The calculated geometries (Table 4) are in good agreement with the experimental ones (Table 2) and reproduce experimental trends, with the Sn-Ch t bonds ∼0.1 Å shorter than the SnCh b bonds.…”

Bautechnik aktuell 3/2015

“…Compound 1 crystallizes in the monoclinic space group P 2 1 / c with 4 formula units per unit cell. The bond lengths and angles within the trigonal bipyramidal [Pb 2 Se 3 ] 2– anion are similar to those in [K([2.2.2]crypt)] 2 [Pb 2 Se 3 ]10 (values given in parenthesis): Pb–Pb 3.2194(6) Å [cf. 3.2260(8) Å], Pb–Se 2.7366(14)–2.7842(12) Å [cf.…”

“… Reaction pathways for the oligomerization of en , as reported10 or observed herein (see Figure S1 and Table S2, Supporting Information). …”

“…The crystallographically determined structures of according chalcogenidometalate anions reported in the literature can be summarized within a few lines: For thallium containing compounds, one knows the butterfly‐like anions [Tl 2 Ch 2 ] 2– (Ch = Se, Te),4,5 a distorted and {TlSe}‐capped heterocuban‐derived anion [Tl 5 Se 5 ] 3– ,6 [Tl 4 Se 8 ] 4– , which comprises edge‐sharing [TlSe 4 ] tetrahedra,7 [Tl 3 Se 15 ] 3– with (Se 4 ) 2– ligands bound to a [Tl 3 Se 3 ] unit,8 the tetranuclear Tl 3+ polyselenide [Tl 4 Se 16 ] 4– ,9 and finally the related, though ternary, trigonal bipyramidal [TlPbTe 3 ] 3– anion 10. The list of selenido‐ and telluridoplumbates additionally contains the trigonal bipyramidal [Pb 2 Ch 3 ] 2– anions,10–13 trigonal pyramidal [PbTe 3 ] 4– ,14 [Pb(Se 4 ) 2 ] 2– with two (Se 4 ) 2– tetraselenide ligands,15 and tetrahedral [PbSe 4 ] 4– 16. For Bi compounds, only the trigonal bipyramid [BiCh 3 ] 3– anions (Ch = Se, Te)17 and [(S 7 ) 2 Bi(S 6 )Bi(S 7 ) 2 ] 4– 18 have been known so far.…”

“…This way, we were able to obtain solutions of the [Pb 2 Ch 3 ] 2– anions (Ch = Se, Te)10 in high abundance and purity, and to isolate single‐crystals of [K(18‐crown‐6)] 2 [Pb 2 Se 3 ] · en ( 1 ) and [K(18‐crown‐6) 2 ][Pb 2 Te 3 ] · en 20. A corresponding reduction of “Bi 2 Te 3 · Te” yielded the telluridobismuthate [K 2 (18‐crown‐6) 2 ( en )K( en ) 2 ][BiTe 3 ] ( 2 ).…”