Modified Schomaker-Stevenson Rule

A modified Schomaker-Stevenson rule for the prediction of single bond distances between p-block elements... 

The molecular structures of the fluorinated methanes have been accurately determined by rotational spectroscopy (Table 9). The C-H bmid distances all fall in the narrow range from 108.4 to 109.1 pm. The C-F bond distance in CH3F is indistinguishable from the value predicted by the modified Schomaker-Stevenson rule, 138.2 pm, but decreases monotonically with increasing number of F atoms to 131.5 pm in 03 4. 

The dative N Al bond in (CH3)3NA1(CH3)3, 210 pm, is 20 pm longer than the Al-N bond in crystalline AIN and 28 pm longer than the normal covalent N-Al bond distance predicted by the modified Schomaker-Stevenson (MSS) rule see Sect. 6. The dative P—>A1 bond in (CH3)3PA1(CH3)3 is about 23 pm longer than the covalent bond distance predicted by the MSS rule. 

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