Novel N-formyl hydroxylamine compounds of formula I: wherein R1 is hydrogen, alkyl, heteroaryl, heterocycloalkyl, aryl, heteroaryl or cycloalkyl; R3 is hydrogen, halogen or alkoxy; R4 is pyridazinyl; n is 0 to 3; and wherein one or more of the ring nitrogen heteroatoms of said pyridazinyl is optionally oxidized and their derivatives are disclosed. These N-formyl hydroxylamine compounds inhibit peptidyl deformylase (PDF), an enzyme present in prokaryotes. The compounds are useful as antimicrobials and antibiotics. The compounds of the invention display selective inhibition of peptidyl deformylase versus other metalloproteinases such as MMPs. Methods of preparation and use of the compounds are also disclosed.