Ambidentate dimethyl sulfoxide coordination in protonated dimethyl sulfoxide, (CH3)2SO-H+, and in dichlorobis(dimethyl sulfoxide) palladium(II) and platinum(II) solid solvates, by vibrational and sulfur K-edge X-ray absorption spectroscopy

• The protonated dimethyl sulfoxide cation (CH3)2SO-H+ formed in concentrated hydrochloric acid displays a new low energy feature in its sulfur K-edge X-ray absorption near edge structure (XANES) spectrum. Density Functional Theory – Transition Potential (DFT-TP) calculations reveal that the energy of the transition S(1s)  LUMO, which has antibonding *(S-O) character, has decreased about 0.8 eV. Normal coordinate force field analyses of the vibrational spectra show that the SO stretching force constant of the oxygen-coordinated (CH3)2SO-H+ species has decreased to 3.73 N cm-1 from 4.72 N cm-1 in neat liquid dimethyl sulfoxide. The effects of sulfur coordination on the ambidentate dimethyl sulfoxide molecule were investigated for the trans-Pd((CH3)2SO)2Cl2 and cis-Pt((CH3)2SO)2Cl2 complexes with square planar coordination of the chlorine and sulfur atoms. The XANES spectra again showed shifts toward low energy of the transition S(1s)  LUMO, now with antibonding *(M-Cl, M-S) character, with a larger shift for M = Pt than Pd. DFT-TP calculations indicated that the differences between the XANES spectra of the geometrical isomers of the M((CH3)2SO)2Cl2 complexes are expected to be too small to allow experimental distinction. The vibrational spectra of the palladium(II) and platinum(II) complexes were recorded and complete assignments of the fundamentals were achieved. Even though the M-S bond distances are quite similar the high covalency especially of the Pt-S bonds induces significant increases in the S-O stretching force constants, 6.79 and 7.18 N cm-1, respectively.

Ämnesord

NATURVETENSKAP  -- Kemi -- Oorganisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Inorganic Chemistry (hsv//eng)

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Coordination chemistry

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