Organometallic complexes containing thiosemicarbazone and related ligands. Part II(1). η3-allyl dicarbonyl complexes of molybdenum(II) with attached thiosemicarbazone ligands

π-Complexes of Chromium, Molybdenum and Tungsten, Excluding those of Cyclopentadienyls and Arenes

“…Protonation of [MoX(r| 2 -MeC=CMe) 2 (r| -L)] (X = Br or Cl; L = Cp or indenyl) yields the Ti 2 -vinylalkyne species (77) which, as shown in Scheme 1 2 reacts with phosphorus-donor ligands to give the t| 4 (5e)-butadienyl complex (78); T| 4 -vinylallene, (79), and r| 4 -diene products are formed reversibly fro m (78). 2 3 1 * 2 3 2 Early work on t| 4 (5e)-butadienyl complexes demonstrated that HBF 4 protonation of [W(S 2 CNEt 2 ) 2 (T| 2 -PhCsCPh) 2 ] affords (80). The structures of (80) and (78) represent the two extremes of bonding description for the T| 4 (5e)-butadienyl ligand; crystallographic studies reveal that in (80) there is a marked asymmetry in the tungsten-C-2 and tungsten-C-4 distances 233 but a corresponding asymmetry is not observed for (78) (X = Br, PR 3 = PMe 3 , L = indenyl; 231 X = Br, PR 3 = P(OMe) 3 (81), crystallographically characterized for R 1 = Me, R 2 = CO 2 Me, in which the carbene carbon C-l is orientated trans to the Cp ligand; subsequent conversion to supine (exo) butadienyl products such as (82), in which C-l is orientated trans to F 3 CC^CCF 3 , occurs on increase o f temperature.…”