text: Of academic interest, SO acts like a Lewis acid towards the alkyl ligand. The pathway for the insertion of SO into metal alkyl bond begins with attack of the alkyl nucleophile on the sulfur centre in SO.  The "insertion" proceed the sulfur dioxide between the metal and the alkyl ligand leads to the O, O-sulphinate. Alternatively an O-sulphinate can arise.  Both of these intermediates commonly convert to an S-sulphinate.  S-sulphinate has sulfur&ndash;oxygen stretching frequencies from 1250–1000 cm and 1100–1000 cm.  The O, O-sulphinate and O-sulphinate are difficult to distinguish as they have stretching frequencies from 1085–1050 cm and 1000–820 cm or lower. The pathway involving the O, O 'sulphinate can generally be ruled out if the original metal complex fulfilled the 18-electron rule because the two metal&ndash;oxygen bonds would exceed the 18 electron rule.  
  The pathway by which SO inserts into a square planar alkyl complexes involves the formation of an adduct.  Thereafter, the alkyl ligand migrates to the SO.