Hexacarbonyldiplatinum(I). Synthesis, Spectroscopy, and Density Functional Calculation of the First Homoleptic, Dinuclear Platinum(I) Carbonyl Cation, [{Pt(CO)₃}₂]²⁺, Formed in Concentrated Sulfuric Acid

Abstract

The dissolution of PtO2 in concentrated H2SO4 under an atmosphere of CO results in the formation of hexacarbonyldiplatinum(I), [{Pt(CO)3}2]2+ (1), the first homoleptic, dinuclear, cationic platinum carbonyl complex, of which a prolonged evacuation leads to reversible disproportionation to give cis-[Pt(CO)2]2+ (solv) (2) and Pt(0). 1 has been completely characterized by NMR (13C and 195Pt), IR, Raman, and EXAFS spectroscopy. The structure of 1 is rigid on the NMR time scale at room temperature. NMR: δ(13CA) 166.3, δ(13CB) 158.7, δ(195Pt) −211.0 ppm; 1 J(Pt−CA) = 1281.5 Hz, 1 J(Pt−CB) = 1595.7 Hz, 1 J(Pt−Pt‘) = 550.9 Hz. The strongly polarized, sharp Raman band at 165 cm-1 (ρ = ca. 0.25) indicates the presence of a direct Pt−Pt bond. The IR and Raman spectra in the CO stretching region are entirely consistent with the presence of only terminal CO's on a nonbridged Pt−Pt bond with D 2 d symmetry. ν(CO)IR: 2174 (E), 2187 (B 2), and 2218 cm-1 (B 2); ν(CO)Raman: 2173 (E), 2194 (B 2), 2219 (B 2), 2209 (A 1) and 2233 cm-1 (A 1). EXAFS measurements show that the Pt−Pt bond is 2.718 Å and the mean length of the Pt−C bonds is 1.960 Å. The geometric optimization for 1 by a density functional calculation at the B3LYP level of theory predicts that the dinuclear cation contains two essentially planar tricarbonyl platinum(I) units that are linked via a Pt−Pt bond about which they are twisted by exactly 90.0° with respect to each other.

Syntheses of [Pt6(CO)8(SnCl2)(SnCl3)4]4–and [Pt6(CO)8(SnCl2)(SnCl3)2(PPh3)2]2–Platinum–Carbonyl Clusters Decorated by SnIIFragments

“…The 13 C NMR spectrum of 1 ‐ 13 CO (Figure ) shows two resonances in the CO region at δ C = 181.9 (2 t‐CO, 1 J Pt–C = 2470 Hz) and 192.5 ppm (4 t‐CO, 1 J Pt‐C = 2420 Hz) in a ratio of 1:2, in accord with the solid‐state structure, which contains six terminal carbonyl ligands in two different environments. The 1 J Pt‐C coupling constants are in keeping with those usually found for terminal CO ligands in Pt compounds . Owing to the poor resolution of the spectrum, it was not possible to resolve smaller coupling constants.…”

“…Interestingly, both resonances of the µ‐CO ligands show two different 1 J Pt‐C coupling constants, a larger one (1082 and 1004 Hz for the two resonances) and a smaller one (494 and 409 Hz). This indicates asymmetric coordination of µ‐CO to the two Pt atoms, as previously found in analogous polynuclear Pt–carbonyl compounds, and in agreement with the solid‐state structure of 3 (see next section). Thus, the larger 1 J Pt‐C values correspond to shorter Pt–C bonds (1.973–2.026 Å), and the smaller one to longer bonds (2.164–2.192 Å).…”

Preparation and Crystal Structure of Copper(I) Carbonyl Hydrogensulfate, obtained by Carbonylation in Sulphuric AcidDedicated to Professor Joachim Strähle on the Occasion of his 65th Birthday

“…The carbonyl derivative [Cu(SO 4 H)(CO)] is the first example of a structurally characterized hydrogensulfatocarbonyl derivative of copper. It belongs to the family of noble-metal carbonyl complexes studied in solution by Souma and co-workers [2,14,16]. This paper has pointed out that carbonyl groups are compatible with the hydrogensulfato ligand.…”

Ag[Fe(CO)5]2+: A Bare Silver Complex with Fe(CO)5 as a Ligand

“…[1,2] Metal carbonyls can be easily reduced, yielding anionic carbonyl metalates such as [Fe(CO) 4 ] 2À or [Co(CO) 4 ] À . [3,4] Oxidation gives the much rarer homoleptic metal carbonyl cations, including [Ir(CO) 6 ] 3+ , [5] [M(CO) 6 ] 2+ (M = Fe, Ru, Os), [6,7] [M(CO) 6 ] + (M = Mn, Tc, Re), [8] [Pd 2 (CO) 6 ] 2+ , [9] [M(CO) 4 ] 2+ (M = Pd, Pt), [10,11] [Rh(CO) 4 ] + , [12] [Co(CO) 5 ] + , [13] [Au(CO) 2 ] + , [14] [Hg y (CO) 2 ] 2+ (y = 1,2), [15] and also unstable [Ag(CO) x ] + (x = 1,2) or [Cu(CO) x ] + (x = 1-4). [16][17][18] The interest in those arises from their relative scarceness, interesting electronic structure, and their potent catalytic activity.…”