The metallacycles [Cl3MS2N3]2(M = Mo, W) 1a and 2a have been obtained from reactions of S4N4with Mo2Cl10and WCl6, respectively, and from S3N3Cl3with the hexacarbonyls M(CO)6. The adducts Cl3MS2N3· CH3CN 1b and 2b are formed with acetonitrile, and the salts [Ph4As+][Cl4MS2N3-] 1c and 2c with addition of Ph4AsCl. Reactions of Mo2Cl10and WCl6, respectively, with related S -N com pounds lead predominantly to 1a and 2a; Mo2Cl10reacts with S3N2Cl2to give 1a , and with [Me3SiN]2S to give [Cl3MoN]x, while WCl6yields Cl4WNSCl with S3N2Cl2, and 2a with [Me3SiN]2S. [Cl3MoN ]xdoes not react with S4N4, but [Cl3WN]xforms 2a. Reactions of VCl4and VOCl3with [Me3SiN]2S give [Cl2V S2N3]x, 3. 2c has also been obtained by the reaction of [Ph4As+][Cl5WNSCL-] with [Me3SiN]2S. The oxidation states of the metal atoms are +6 for 1a-c and 2a-c, and +5 for 3, respectively; as determined by 51V and 95Mo NMR spectroscopy and magnetic susceptibility measurements. The UV/VIS spectra of 1b , 1c , 2b, c and 3 are discussed. The electrical conductivity of 3 is reported.