Hexacarbonyldiplatinum(I). Synthesis, spectroscopy, and density functionalcalculation of the first homoleptic, dinuclear platinum(I) carbonyl cation, [{Pt(CO)(3)}(2)](2+), formed in concentrated sulfuric acid
Q. Xu et al., Hexacarbonyldiplatinum(I). Synthesis, spectroscopy, and density functionalcalculation of the first homoleptic, dinuclear platinum(I) carbonyl cation, [{Pt(CO)(3)}(2)](2+), formed in concentrated sulfuric acid, J AM CHEM S, 122(29), 2000, pp. 6862-6870
The dissolution of PtO2 in concentrated H2SO4 under an atmosphere of CO res
ults 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 character
ized by NMR (C-13 and Pt-195), IR, Raman, and EXAFS spectroscopy. The struc
ture of 1 is rigid on the NMR time scale at room temperature. NMR: delta(C-
13(A)) 166.3, delta(C-13(B)) 158.7, delta(Pt-195) -211.0 ppm; (1)J(Pt-C-A)
= 1281.5 Hz, (1)J(Pt-C-B) 1595.7 Hz, (1)J(Pt-Pt') = 550.9 Hz. The strongly
polarized, sharp Raman band at 165 cm(-1) (rho ca. 0.25) indicates the pres
ence 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-2d symmetry. v(CO)(IR): 2174 (E), 2187 (B-2),
and 2218 cm(-1) (B-2); v(CO)Raman: 2173 (E), 2194 (B-2), 2219 (B-2)r 2209
(A(1)) and 2233 cm(-1) (A(1)). EXAFS measurements show that the Pt-Pt bond
is 2.718 Angstrom and the mean length of the Pt-C bonds is 1.960 Angstrom.
The geometric optimization for 1 by a density functional calculation at the
B3LYP level of theory predicts that the dinuclear cation contains two esse
ntially planar tricarbonyl platinum(I) units that are linked via a Pt-Pt bo
nd about which they are twisted by exactly 90.0 degrees with respect to eac
h other.