Calculations and analysis of 55Mn nuclear quadrupole coupling for asymmetric top acyl methyl manganese pentacarbonyl

Highlights: • Revised data analysis for rotational and quadrupole parameters favor the dihapto isomer. • The data and calculations agree better for the dihapto form than for the agnostic form. • The calculated energy for the dihapto form is 3350 cm⁻¹ lower in energy than the agostic form. Revised assignments of the measured transitions for the asymmetric top acyl isomers of methyl manganese pentacarbonyl are presented, along with a corresponding fit to determine rotational and quadrupole coupling constants. New assignments for measured transitions give a better fit to the spectrum and better agreement between experimental and calculated quadrupole coupling strengths. The best agreements were obtained for B3LYP and M11 DFT calculations with triple and quadruple-zeta basis sets. Experimental molecular parameters from the new analysis are: A = 840.0843(52), B = 774.2861(17), C = 625.6528(13). D_J = 0.000212(21). D_JK = 0.00488(18), 1.5χ_aa = −46.96(11), 0.25(χ_bb - χ_cc) = -13.44(3) MHz.