An additive treatment of 115In nuclear quadrupole coupling constants for organoindium compounds

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Using previously measured 119Sn IV and 115In III e 2 Qq values, we use the additivity model to rationalize and calculate 115In e 2 Qq values for In III in a variety of coordination environments. A semiquantitative estimate of In III e 2 Qq values (in MHz) may be obtained by multiplying the 1 2 s 2Qq value (in mm sec −1) for the isostructural Sn IV compound by 310. Absolute partial quadrupole coupling constants ( pqcc) have been derived for the first time for linear ( sp hybridized metal) and trigonal planar ( sp 2 hybridized metal) species. The ratios of the pqcc values ( pqcc) Me tet:( pqcc) Me tba: ( pqcc) Me oct is 1.23:1.09:1. These are in good agreement with the corresponding 119Sn partial quadrupole splitting ( pqs) values. The relative pqce values for ligands in two to six coordination are in qualitative agreement with those expected from a simple molecular orbital approach. The pqcc parameters are used to calculate the expected e 2 Qq values for a number of methylindium species in four, five, and six coordination. These calculations should be very useful for structural elucidation. For the associated compounds MeInBr 2 and EtInI 2, these calculations suggest highly associated structures with In having a coordination number of greater than four. For the six coordinate Me 2In moieties, the trend in e 2 Qq with C-In-C angle is reproduced qualitatively by a simple distortion calculation.