The effect of fluorination in trimethylamine: gas-phase structures of CF3N(CH3)2 and (CF3)2NCH3

Article abstract of DOI:10.1016/0022-2860(94)08308-8

The molecular structures of CF3N(CH3)2 and (CF3)2NCH3 have been determined by gas electron diffraction.The following skeletal parameters (r_a distances and <α angles) have been obtained for CF3N(CH3)2:C-F=135.1(4) pm, N-C_H=148.1(10) pm, N-C_F=138.3(16) pm, C_HNC_H=113.0(27) ^o, C_HNC_F=111.9(9) ^o; (CF3)2NCH3:C-F=133.3(3) pm, N-C_H=147.8(13) pm, N-C_F=142.0(8) pm, C_HNC_F=116.8(13) ^o, C_FNC_F=117.8(11) ^o.C_H and C_F are the methyl and trifluoromethyl carbon atoms, respectively.Experimental uncertainties are 3? values and include possible systematic errors.The most surprising result is the large difference between the N-C_H and N-C_F bond lengths of about 10 and 6 pm in these compounds.All nitrogen bond angles increase concomitantly with increasing number of CF3 groups.An attempt is made to rationalize the observed structural trends.