Room Temperature Syntheses of AuF6- and PtF6- Salts, Ag+AuF6-, Ag2+PtF62-, and Ag2+PdF62-, and an Estimate for E(MF6-) [M = Pt, Pd

Abstract

Solutions of AuF4- or PtF62- salts, prepared from the metals at ∼20 °C, in liquid anhydrous hydrogen fluoride (aHF), made basic with alkali fluorides, are further oxidized by photodissociated F2 (visible or near-UV light) to give AuF6- or PtF6- salts, including O2+AuF6- (with O2 in the F2). Similar photochemical oxidation of PdF62- salts does not occur. This new synthetic approach has provided LiAuF6 and LiPtF6 for the first time, each of which has the LiSbF6 type (R3̄) structure with (hexagonal cell): LiAuF6, a = 4.9953(9) Å, c = 13.704(3) Å, V/Z = 98.71(6) Å3; LiPtF6, a = 5.0236(7) Å, c = 13.623(2) Å, V/Z = 99.25(5) Å3. Interaction of AuF6- with Ag+ gives Ag+AuF6- (R3̄, a = 5.283(3) Å, c = 15.053(6) Å, V/Z = 121.3(2) Å3), whereas PtF62- or PdF62- stabilize Ag2+ as Ag2+Pt(Pd)F62- (R3̄; AgPtF6: a = 5.049(8) Å, c = 14.46(2) Å, V/Z = 106.4(5) Å3; and AgPdF6, a = 5.00(4) Å, c = 14.6(2) Å, V/Z = 105(3) Å3). New cubic modifications (probable space group Ia3) have been found for AgMF6 (M, a value, Å): Ru, 9.653(10); Os, 9.7318(9); Ir, 9.704(2). The preference for Ag2+Pt(Pd)F62- over Ag+Pt(Pd)F6- is attributed to a second electron affinity of Pt(Pd)F6, E(Pt(Pd)F6-)> 60 kcal mol-1.