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

Abstract A series of ruthenium alkenylacetylide complexes trans‐ [Ru{C≡CC(=CH 2 )R}Cl(dppe) 2 ] (R=Ph ( 1 a ), c C 4 H 3 S ( 1 b ), 4‐MeS‐C 6 H 4 ( 1 c ), 3,3‐dimethyl‐2,3‐dihydrobenzo[ b ]thiophene (DMBT) ( 1 d )) or trans‐ [Ru{C≡C‐ c C 6 H 9 }Cl(dppe) 2 ] ( 1 e ) were allowed to react with the corresponding propargylic alcohol HC≡CC(Me)R(OH) (R=Ph ( A ), c C 4 H 3 S ( B ), 4‐MeS‐C 6 H 4 ( C ), DMBT ( D ) or HC≡C‐ c C 6 H 10 (OH) ( E ) in the presence of TlBF 4 and DBU to presumably give alkenylacetylide/allenylidene intermediates trans‐ [Ru{C≡CC(=CH 2 )R}{C=C=C(Me)}(dppe) 2 ]PF 6 ([ 2 ]PF 6 ). These complexes were not isolated but deprotonated to give the isolable bis(alkenylacetylide) complexes trans‐ [Ru{C≡CC(=CH 2 )R} 2 (dppe) 2 ] (R=Ph ( 3 a ), c C 4 H 3 S ( 3 b ), 4‐MeS‐C 6 H 4 ( 3 c ), DMBT ( 3 d )) and trans‐ [Ru{C≡C‐ c C 6 H 9 } 2 (dppe) 2 ] ( 3 e ). Analogous reactions of trans‐ [Ru(CH 3 ) 2 (dmpe) 2 ], featuring the more electron‐donating 1,2‐bis(dimethylphosphino)ethane (dmpe) ancillary ligands, with the propargylic alcohols A or C and NH 4 PF 6 in methanol allowed isolation of the intermediate mixed alkenylacetylide/allenylidene complexes trans‐ [Ru{C≡CC(=CH 2 )R}{C=C=C(Me)}(dmpe) 2 ]PF 6 (R=Ph ([ 4 a ]PF 6 ), 4‐MeS‐C 6 H 4 ([ 4 c ]PF 6 ). Deprotonation of [ 4 a ]PF 6 or [ 4 c ]PF 6 gave the symmetric bis(alkenylacetylide) complexes trans‐ [Ru{C≡CC(=CH 2 )R} 2 (dmpe) 2 ] (R=Ph ( 5 a ), 4‐MeS‐C 6 H 4 ( 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 HBF 4 ⋅ Et 2 O were ultimately unsuccessful.