The isocyanate complexes [Nb(q-C,H,SiMe,),(RNCO)CI] (R = Ph 2, But 3, Pr" 4, Pr' 5) have been prepared from the reaction of [Nb(q-C,H,SiMe,),Ci] 1 with the appropriate ligands. Treatment of 1 with the corresponding amines NH,R afforded the imido complexes [Nb(q-C,H,SiMe,),(=NR)CI] ( R = Ph 6, But 7 , Pr" 8 or Pr' 9) which can also be prepared by thermal treatment of the corresponding isocyanate complexes 2-5. All complexss have been characterised in solution by both 'H and 13C N M R spectroscopy. Complex 1 crystallises in the monoclinic space group P2,lc showin and p = 103.22(3)". It has a binuclear structure with two almost symmetrical chloride bridges, giving a closed-shell, 18-electron configuration. Complex 6 crystallises in the monoclinic space group P2Jn with Z = 4, a = 7.343(2), b = 16.880(3), c = 20.227(4) A and p = 96.41 (2)". The structure shows a value of 165.1 (2)" for the Nb-N-C angle and an Nb-N bond distance of 1.792(2) A, intermediate between that expected for double and triple bonds.