In order to study the properties of sulfur coordinated transition metal centers, [Mo(NO)(Cl)(dttd)] (1) (dttd 2- = 2,3,8,9-dibenzo-1,4,7,10-tetrathiadecane(2 -)) was synthesized. It shows no reaction with AgPF 6 , but it reacts very rapidly even at low temperatures with liquid ammonia and dialkylamines HNR 2 (HNMe 2 , HNEt 2 ) yielding the corresponding amidocomplexes [Mo(NO)(NR 2 )(dttd)] (R = H 4, Me 2, Et 3). For these reactions an associative mechanism is suggested. X-ray structure analyses of [Mo(NO)(Cl)(dttd)] (1) and [Mo(NO)(NMe 2 )(dttd)] (2) show the Mo centers to be coordinated pseudo-octahedrally by two trans thiolato S, two cis thioether S atoms and the two cis coligands NO and Cl or NO and NMe: , respectively. Both dialkylamido complexes (R = Me 2, Et 3) show no coalescence of the two N(alkyl) signals in the 1 H NMR spectra up to 140 °C, the NH-Signals of 4 coalesce at 70 ± 5 °C (⊿G* = 73 ± 1.5 kJ mol -1 ). The amido ligands act as σ - π four electron donor ligands such that the Mo center obtains a formal 18 electron configuration and the Mo-NR 2 bond represents a Mo = N double bond. This follows from the short Mo-N distance (192.4(8) pm) and the planarity of the N(alkyl) atom of 2 as well as the stability of the Mo - NR 2 bond (R = H, M e, Et) with respect to rotation. Since sterical effects can be excluded, the high rotation barriers must be due to exclusively electronic effects.