Oxidizing Elemental Platinum with Oleum under Harsh Conditions: The Unique Tris(disulfato)platinate(IV) [Pt(S₂O₇)₃]²⁻ Anion

Abstract

For the first time, direct oxidation of elemental platinum by a mineral acid to its tetravalent state was observed in course of the reaction of platinum with oleum (65 % SO3) in the presence of barium carbonate. The reaction has been carried out in torch-sealed glass ampoules at 160 °C and gave yellow single crystals of Ba[Pt(S2O7)3](H2SO4)0.5(H2S O7)0.5 (triclinic, P1, Z=2, a=992.05(2), b=1069.07(3), c=1114.22(3) pm, α=69.49(7), β=72.96(2), γ=72.93(1)°, V=1033.95(5) Å(3)). The structure of Ba[Pt(S2O7)3](H2SO4)0.5(H2S2O7)0.5 exhibits the unique tris-(disulfato)-platinate anion [Pt(S2O7)3](2-) with three chelating disulfate groups coordinated to the platinum atom. Charge balance is achieved by the Ba(2+) ions, which are coordinated by (S2O7)(2-) groups from the platinate complex and by disordered sulfuric acids and disulfuric acid molecules. Thermal decomposition of the bulk material revealed elemental platinum and barium sulfate as decomposition residual.

Palladium(IV) in an Oxoanionic Environment: The XeF2 Assisted Synthesis of [Pd(S2O7)3]2−

“…From the quantum chemical calculations also the expected vibrational frequencies could be extracted so that an assignment of (13) the bands observed in both IR and Raman spectrum were possible ( Figure S4, Table S9 2À type complexes most of the normal modes are complex combination vibrations. [13,14] The thermal decomposition of K 2 [Pd(S 2 O 7 ) 3 ] is a threestep process ( Figure S5, Table S10) and leads finally to a mixture of K 2 SO 4 and elemental palladium. Note that the last step of the degradation can be clearly attributed to the decomposition of PdO.…”

“…[10] It is worth mentioning that also the divalent palladium compounds display fascinating structures and the [12] Under special conditions we were also able to prepare tetravalent platinum compounds, for example, the complex nitrate (NO) 2 2À which forms in SO 3 -rich oleum. [13] In 2À type complexes for the metals (M) germanium, tin, titanium, and even for silicon, representing a rarely seen example of octahedral Si IV coordination with inorganic oxo-ligands. [14] With respect to these findings we argued that this type of complex should also be a suitable candidate for the stabilization of tetravalent palladium.…”

Oxidizing Rhodium with Sulfuric Acid: The Sulfates Rh2(SO4)3 and Rh2(SO4)3·2H2O

“…All of the reactions that we performed analogous to the procedure applied for palladium have led nearly exclusively to trivalent platinum sulfates, which are structurally marked by the presence of a metal–metal bonded [Pt 2 ] 6+ dumbbell . The only exception is the Pt IV complex [Pt(S 2 O 7 ) 3 ] 2– with three chelating disulfate ions surrounding the metal . As a consequence of our findings for palladium and platinum we recently started to extend our investigations on the remaining platinum metals, i.e.…”

Pd4+ in oxoanionischer Umgebung: Die XeF2‐unterstützte Synthese von [Pd(S2O7)3]2−

“…Stattdessen führen Reaktionen mit H 2 SO 4 und/oder SO 3 nahezu immer zu Pt III ‐Sulfaten, in denen [Pt 2 ]‐Hanteln vorliegen, die von chelatisierenden Sulfatgruppen koordiniert werden . Unter bestimmten Bedingungen ist es uns sogar gelungen, vierwertige Platinverbindungen, beispielsweise in Form des komplexen Nitrats (NO) 2 [Pt(NO 3 ) 6 ] aus Reaktionen mit N 2 O 5 und des Tris(disulfato)platinat‐Anions [Pt(S 2 O 7 ) 3 ] 2− , das sich aus SO 3 ‐reichem Oleum gewinnen lässt, zu stabilisieren . In diesem [Pt(S 2 O 7 ) 3 ] 2− ‐Anion wird das Platinatom von drei chelatisierenden S 2 O 7 2− ‐Anionen oktaedrisch koordiniert.…”

“…Aus den quantenchemischen Berechnungen konnten außerdem die zu erwartenden Schwingungsfrequenzen erhalten werden, sodass eine Zuordnung der beobachteten Schwingungen im IR‐ und Raman‐Spektrum möglich wurde (Abbildung S4, Tabelle S9). Wie zuvor für andere Komplexe des [M(S 2 O 7 ) 3 ] 2− ‐Typs diskutiert, entsprechen die meisten Normalmoden komplexen Kombinationsschwingungen …”