Vibrational Spectra and Crystal Structures of Tris- and Tetrakis(ethylenethiourea)copper(I) Systems

Abstract

A room-temperature redetermination of the crystal structure of [Cu(SC(NHCH2)2)3]2 (SOs) has been carried out. The original determination, recorded in communication format in space group Ic, Z = 4, seemingly with the full formula as the asymmetric unit, is a t variance with our findings which describe the structure in space group R3c, a 12.741(7), c 35.59(1) A (hexagonal setting), Z = 6, with one-third of each of two independent cations, each lying on a threefold axis, comprising the asymmetric unit. The sulfate ion also lies on a threefold axis in proximity to only one of the two cations, the S-0 axial bond approaching the copper atom normal to the planar CuS3 array [Cu-S, 0 2.269(2), 2.834(8) A]; in the other cation, unperturbed by any sulfate approach, Cu-S is appreciably shorter [2.246(2) A]. R was 0.029 for 905 'observed' reflections. A redetermination of the structure of tetrakis(ethylenethiourea)copper(~) nitrate is also recorded; crystals are triclinic, Pi, a 13.211(2), b 11.2167(4), c 7.566(3) A, a: 81.93(2), / 3 78.35(3), y 87.22(1)', 2 = 2, R being 0.031 for 3861 independent 'observed' reflections. The copper environment is quasi-tetrahedral, Cu-S ranging between 2.3322(9) and 2.3658(12) A, and S-Cu-S 98.76(3)-117.83(3)'.The vibrational (far-infrared and Raman) spectra are recorded for these CuS, systems, and discussed and assigned in the light of the structural results.

Structural and Spectroscopic Studies of [M((x)tu)4]+ Systems (M = Cu, Ag; (x)tu = (substituted) Thiourea)

“…All ligands except one, have an intracation NH···S interaction. The [Cu(etu) 4 ] ϩ cation has also been structurally characterized (in the nitrate salt) in refs. [4,5] [11].…”

“…The results of the single crystal X-ray structure determination on the 1 : 4 AgNO 3 : etu adduct show it to be a monohydrate of that formulation, the complex being ionic [Ag(etu) 4 ](NO 3 ) · H 2 O. The complex is not isotypic with its copper(I) counterpart, which is anhydrous [4]; four formula units, devoid of crystallographic symmetry, comprise the asymmetric unit of the structure, the components of all cations being similarly aligned within the unit cell ( Fig. 1(b)), www.zaac.wiley-vch.de the planes of two of the ligands within each cation lying quasi-parallel to the ac face and the other pair quasi-parallel to the bc face.…”

“…Deviations of the silver atoms from the associated ligand planes are also erratic, those for cation 1 all being 0.23(2) Å or less, while for cation 2, all are greater than 1.06(2) Å . The mean AgϪS distance (2.59(4) Å ) may be compared with the value of 2.336 (11) [7], but in the sulfate, one of the two cations is unperturbed by anion approaches and disposed on a crystallographic 3-axis, having a quasi-trigonal planar metal atom environment with AgϪS 2.4680(6) Å , SϪAgϪS 119.811(2)° [7], the isotypic copper(I) counterpart having CuϪS 2.246(2) Å , SϪCuϪS 120.00(7)° [4].…”

“…A considerable and diverse array of complexes of simple copper(I) salts with (substituted-) thiourea ligands ('(x)tu') has been structurally characterized, the many stoichiometries defined with simple ligands, 1 : n (n ϭ 1, 2, 2 1 / 2 , 3, 4), 4 : n (n ϭ 6, 7,9,10,11,12), and 6 : 14, as summarized in Table 1 of a parallel publication [1], masking an even more diverse array of mononuclear, oligonuclear and polynuclear forms. The ionic [Cu(xtu) 4 ] ϩ array has been defined for salts of [SiF 6 ] 2Ϫ (with tu) [2,3], NO 3 Ϫ (with 'etu' ϭ 'ethylenethiourea', SC(NHCH 2 ) 2 [4,5], and (interestingly) Cl Ϫ (with 'phtu' ϭ PhNHCSNH 2 ) [6]. The range of complexes defined with silver(I) is much less extensive, defined in diverse forms for n ϭ 1, 1 1 / 2 , 2, 3 stoichiometries, as summarized in further parallel publications [7,8], with no example seemingly characterized for the [Ag((x)tu) 4 ] ϩ parent of the series, although the existence of the nitrate salt with the etu ligand was claimed in an early study [9].…”

“…The ionic [Cu(xtu) 4 ] ϩ array has been defined for salts of [SiF 6 ] 2Ϫ (with tu) [2,3], NO 3 Ϫ (with 'etu' ϭ 'ethylenethiourea', SC(NHCH 2 ) 2 [4,5], and (interestingly) Cl Ϫ (with 'phtu' ϭ PhNHCSNH 2 ) [6]. The range of complexes defined with silver(I) is much less extensive, defined in diverse forms for n ϭ 1, 1 1 / 2 , 2, 3 stoichiometries, as summarized in further parallel publications [7,8], with no example seemingly characterized for the [Ag((x)tu) 4 ] ϩ parent of the series, although the existence of the nitrate salt with the etu ligand was claimed in an early study [9]. Accordingly, we sought to reproduce the synthesis of AgNO 3 : etu (1 : 4) and to confirm it structurally and characterize the cation spectroscopically; as the data on the salts of [Cu(xtu) 4 ] ϩ with 'hard' anions are old, we have, in parallel, redetermined the in the far-IR spectra of these compounds are assigned to ν(MS) modes, and the frequencies are compared with those predicted by previously established correlations between ν(MS) and the MϪS bond length d(MS) for copper or silver complexes with tu or etu ligands.…”