This is a bit late, but if you react a Grignard with an electrophilic source of NO2 +, you will wind up with a mixture of products (-NO2, -ONO). You could concieveably do a Friedels-Crafts type nitration (so named by Olah), with a lewis acid catalyst like AlCl3 or TiCl4 and NO2Cl. That's some nasty stuff, though.