SCALED HARTREE-FOCK FORCE-FIELD CALCULATIONS FOR ORGANOTHALLIUM COMPOUNDS - NORMAL-MODE ANALYSIS FOR TLCH3, TL(CH3)2+, TL(CH3)3, TL(CH3)2BR, AND TL(CH3)4-

Abstract

In a recent paper we presented Hartree-Fock (HF) calculations for aliphatic organothallium compounds. The diagonal HF force constants obtained from a Fletcher-Powell geometry optimization are now used for a normal-mode analysis of TlCH,, Tl(CH,),+, T1(CH3),, T1(CHJ2Br, and Tl(CH3)c. In order to calculate frequencies comparable to experimental values, the HF force field has been scaled by using scaling factors obtained from experimental infrared and Raman measurements on T1(CH3)2+ and TlBr. The vibrational spectra of Tl(CH3)2+ were remeasured (infrared and Raman) in order to obtain an accurate force field. Predictions are made for the vibrational spectrum of the as yet undetected TlCH, molecule. Experimental infrared and Raman results for T1(CH3), compare reasonably well with our calculated frequencies (ex- perimental v,,(Tl-C) = 450 cm-', v,,(Tl-C) = 465 cm-l, v,,(C-H) = 2917 cm-l, v,,(C-H) = 3020 cm-l; scaled HF u,,(Tl-C) = 488 cm-', v,,(Tl-C) = 514 cm-', vSp(C-H) = 2892 cm-l, Y, (C-H) = 2999 cm-l). Relativistic and correlation effects are analyzed for the vibrational frequencies ~ f i l ( C H , ) ~ +