Tetrachloro- and Tetrabromoarsonium(V) Cations:  Raman and ⁷⁵As, ¹⁹F NMR Spectroscopic Characterization and X-ray Crystal Structures of [AsCl₄][As(OTeF₅)₆] and [AsBr₄][AsF(OTeF₅)₅]

Abstract

The salts [AsX4][As(OTeF5)6] and [AsBr4][AsF(OTeF5)5] (X = Cl, Br) have been prepared by oxidation of AsX3 with XOTeF5 in the presence of the OTeF5 acceptors As(OTeF5)5 and AsF(OTeF5)4. The mixed salts [AsCl4][Sb(OTeF5)6-nCl(n-2)] and [AsCl4][Sb(OTeF5)6-nCl(n)] (n > or = 2) have also been prepared. The AsBr4+ cation has been fully structurally characterized for the first time in SO2ClF solution by 75As NMR spectroscopy and in the solid state by a single-crystal X-ray diffraction study of [AsBr4][AsF(OTeFs)5]: P1, a = 9.778(4) A, b = 17.731(7) A, c = 18.870(8) A, alpha = 103.53(4)degrees, beta = 103.53(4) degrees, gamma = 105.10(4) degrees, V = 2915(2) A3, Z = 4, and R1 = 0.0368 at -183 degrees C. The crystal structure determination and solution 75As NMR study of the related [AsCl4][As(OTeF5)6] salt have also been carried out: [AsCl4][As(OTeF5)6], R3, a = 9.8741(14) A, c = 55.301(11) A, V= 4669(1) A3, Z = 6, and R1 = 0.0438 at -123 degrees C; and R3, a = 19.688(3) A, c = 55.264(11) A, V= 18552(5) A3, Z = 24, and R1 = 0.1341 at -183 degrees C. The crystal structure of the As(OTeF5)6- salt reveals weaker interactions between the anion and cation than in the previously known AsF6- salt. The AsF(OTeF5)5- anion is reported for the first time and is also weakly coordinating with respect to the AsBr4+ cation. Both cations are undistorted tetrahedra with bond lengths of 2.041(5)-2.056(3) A for AsCl4+ and 2.225(2)-2.236(2) A for AsBr4+. The Raman spectra are consistent with undistorted AsX4+ tetrahedra and have been assigned under Td point symmetry. The 35Cl/37Cl isotope shifts have been observed and assigned for AsCl4+, and the geometrical parameters and vibrational frequencies of all known and presently unknown PnX4+ (Pn = P, As, Sb, Bi; X = F, Cl, Br, I) cations have been calculated using density functional theory methods.

PX4+, P2X5+, and P5X2+ (X=Br, I) Salts of the Superweak Al(OR)4 Anion [R=C(CF3)3]

“…In contrast, earlier calculations [18,36] on the PX 4 cations gave an overestimation of the PÀX bond lengths of about 0.05 ä. Also the difficult to model [4] P 2 X 5 geometries with an experimental d(P À P) of 2.22(1) to 2.246(3) ä were reproduced by MP2 to within 0.02 ä, while BP86 and B3LYP optimizations overestimated the PÀP distance by 0.10 to 0.19 ä.…”

“…the I-P-I (Br-P-Br) bond angles range from 109.2(1) to 109.6(1)8 (109.3(1) to 109.9(1)8)) and are stabilized by four sets of symmetry-equivalent weak X À F contacts at 3.140(4), 3.439(4), and 3.520(4) ä (1 a) or 3.252(5), 3.333(5), and 3.343(5) ä (1 b), which are shorter than the sum of the F and X van der Waals radii of 3.60 (I) or 3.40 ä (Br) (Figure 1). In contrast to AsCl 4 , [18] no EÀF contacts (E P, As) below 4.276 (1 a) or 4.047 ä (1 b) were observed.…”

Mixed Chloride/Azide Complexes of Arsenic and Antimony

“…The strong coordination of the very strong Lewis base pyridine at the arsenic centre weakens the AsϪCl bond. This lengthens the AsϪCl bond, which is significantly longer than it is in the cationic species AsCl 4 ϩ [2.042 (3)Ϫ2.0545(9) Å ] [1,23] or binary AsCl 3 [2.17(2) Å ]. [24] The calculations show a coordinative bond (2.459 Å ) between the arsenic atom and the nitrogen atom of the pyridine ring, which is weaker in the gas phase compared to the solid state [2.158(3) Å ].…”

Synthesis, Characterization, Crystal Structure and hybrid DFT Computation of the Chlorooxoarsenate(III), [NMe4]2[As4O2Cl10]·2 CH3CN

“…The [11,12] or in AsC13 (2.17(2) Ä) [13]. Similar bond lengths can only be found in the [AsCIö]-anion (2.187(4) -2.245(2) Ä) [14] or in the Lewis acidbase adduct ASCI3 • NMe3 (2.18(1) A) [15] in which the donation of the lone pair of the nitrogen atom to the arsenic center weakens the As-Cl bonds.…”