Syntheses and Structures of trans-bis(Alkenylacetylide) Ruthenium Complexes

A series of ruthenium alkenylacetylide complexes trans-[Ru{C equivalent to CC(=CH2)R}Cl(dppe)(2)] (R=Ph (1 a), (C)C4H3S(1 b), 4-MeS-C6H4 (1 c), 3,3-dimethyl-2,3-dihydrobenzo[b]thiophene (DMBT) (1 d)) or trans-[Ru{C equivalent to C-(C)C6H9}Cl(dppe)(2)] (1 e) were allowed to react with the corresponding propargylic alcohol HC equivalent to CC(Me)R(OH) (R=Ph (A), (C)C4H3S (B), 4-MeS-C6H4 (C), DMBT (D) or HC equivalent to C-(C)C6H10(OH) (E) in the presence of TlBF4 and DBU to presumably give alkenylacetylide/allenylidene intermediates trans-[Ru{C equivalent to CC(=CH2)R}{C=C=C(Me)}(dppe)(2)]PF6 ([2]PF6). These complexes were not isolated but deprotonated to give the isolable bis(alkenylacetylide) complexes trans-[Ru{C equivalent to CC(=CH2)R}(2)(dppe)(2)] (R=Ph (3 a), (C)C4H3S (3 b), 4-MeS-C6H4 (3 c), DMBT (3 d)) and trans-[Ru{C equivalent to C-(C)C6H9}(2)(dppe)(2)] (3 e). Analogous reactions of trans-[Ru(CH3)(2)(dmpe)(2)], featuring the more electron-donating 1,2-bis(dimethylphosphino)ethane (dmpe) ancillary ligands, with the propargylic alcohols A or C and NH4PF6 in methanol allowed isolation of the intermediate mixed alkenylacetylide/allenylidene complexes trans-[Ru{C equivalent to CC(=CH2)R}{C=C=C(Me)}(dmpe)(2)]PF6 (R=Ph ([4 a]PF6), 4-MeS-C6H4 ([4 c]PF6). Deprotonation of [4 a]PF6 or [4 c]PF6 gave the symmetric bis(alkenylacetylide) complexes trans-[Ru{C equivalent to CC(=CH2)R}(2)(dmpe)(2)] (R=Ph (5 a), 4-MeS-C6H4 (5 c)), the first of their kind containing the dmpe ancillary ligand sphere. Attempts to isolate bis(allenylidene) complexes [Ru{C=C=C(Me)R}(2)(PP)(2)](2+) (PP=dppe, dmpe) from treatment of the bis(alkenylacetylide) species 3 or 5 with HBF4 . Et2O were ultimately unsuccessful.