Herbicidal diacyl derivatives of propylene diamine

Novel herbicidal compounds are provided having the formula (I) wherein one of R1a and R1b is a methyl, hydroxymethyl or monohalomethyl group and the other is hydrogen; R2 is a group R3-(X1)m- where X1 is a methylene, oxy or thio linkage, m is 0 or 1, and R3 is a substituted phenyl group of formula where RA2 is a hydrogen, halogen or methyl group and RA3 is a halogen or halomethyl group; and R4 is an alpha-halo- or alpha,alpha-dihalo-(C1-3)alkyl group or a group having the formula -(X2)n-R5 where X2 is a methylene, oxy or thio linkage, n is 0 or 1, and R5 is an optionally substituted five-member or six-member aromatic or heterocyclic ring.