Synthesis and Characterization of Tungsten Alkenyl−Carbyne and Alkenyl−Ketenyl Complexes Containing Dithio Ligands. X-ray Crystal Structure and MO Analyses of [(dppe){κ3(S,C,S)-S2CPCy3}W⋮CCHC(CH2)3CH2][BF4]

The reaction = 1,2-bis(diphenylphosphino)ethane; n = 1 ( 1a ), 4 ( 1b )) with S 2 CPCy 3 in methanol for 10 min affords = 1 ( 2a ), 4 ( 2b )). Similarly, the = 1 ( 3a ), 4 ( 3b )) have been prepared by the reaction with [NBu 4 ][S 2 P(OEt) 2 ]. When 1a and 1b are reacted with S 2 CPCy 3 in methanol for 24 h, the = 1 ( 4a ), 4 ( 4b )) are formed. Moreover, when 1a and 1b are reacted with NaS 2 CNR 2 (R = Me, Et), the formed (R = Me, n = 1 ( 5a ), 4 ( 5b ); R = Et, n = 1 ( 5c ), 4 ( 5d )) subsequent to the coupling between the carbyne group and carbon monoxide. IR and 1 H, 31 P, and 13 C NMR data are reported for all of the species. The molecular structure of compound 4a, determined by X-ray diffraction methods, shows that the S 2 CPCy 3 ligand is bound to the metal in a pseudoallylic κ 3 ( S,C,S) fashion. The metal coordination is completed by the W⋮C triple bond of the alkenyl−carbyne group and by two additional W−P bonds. Since the metal center in 4a is formally a deficient 16-electron species and since the synthetic route has clearly indicated that an additional CO ligand is preferentially rejected by the metal, a reasonable interpretation of the bonding has been sought by means of EHMO calculations. Not only has the coexistence between the dithiocarboxylate and the carbyne ligands been elucidated, but also the strength of the W−S bonds is accounted for in comparison with the weaker W−S bonds observed in other saturated W complexes containing a κ 3 ( S,C,S) dithio ligand. Finally, qualitative theoretical considerations are presented for the different behavior of the dithiocarbamate ligand.