The reaction of PhCH(2)Mn(CO)(5) with several tertiary amines such as 8-methylquinoline, N,N-dimethyl-1-naphthylamine, or mono- and disubstituted N,N-dimethylbenzylamiile derivatives, in refluxing n-hexane, affords the corresponding neutral C,N-cyclometalated Mn(I) compounds of stoichiometry Mn(C-N)(CO)(4), 1-8 (C-N = cyclometalated ligand), in good yields. These new compounds have been characterized by their IR and H-1 and C-13{H-1} NMR spectra. The crystal structure of Mn(C6H2(OCH3)(2)-4,6-CH(2)NMe(2)-2)(CO)(4), 4 (monoclinic, P2(1)/n; a = 13.644 (4) Angstrom, b = 9.153 (3) Angstrom, c = 14.432 (4) Angstrom, beta = 115.57 (2)degrees, Z = 4), shows:the N,N-dimethylbenzylamine derivative to be coordinated as a chelating ligand and that the distance between the oxygen atom of the ortho OMe group and the carbon atom of one carbonyl group is shorter than the sum of their van der Waals radii. The orientation in the cyclometalation of benzylamine derivatives, when two possibilities exist, tends to avoid the steric interaction between the R groups ortho to the Mn-C bond and a CO unit. : However, when this R group is OMe, the latter compound isomerizes so that the interaction between the O atom of the methoxy unit and the C atom of the CO can take place.