The Pentynoate Ligand as a Building Block for Multimetallic Systems

The complexes [RuRCl(CO)(BTD)(PPh 3 ) 2 ] (R = CH=CH t Bu, CH=CHC 6 H 4 Me‐4, CH=CHC 5 H 4 FeC 5 H 5 ; BTD = 2,1,3‐benzothiadiazole) and [Ru{C(C≡CPh)=CHPh}(CO)(PPh 3 ) 2 ] reacted with pentynoic acid to yield the same complex, [RuCl(O 2 CCH 2 CH 2 C≡CH)(CO)(PPh 3 ) 2 ], through cleavage of the vinyl ligand. In contrast, the products [RuR(O 2 CCH 2 CH 2 C≡CH)(CO)(PPh 3 ) 2 ] were formed when NaO 2 CCH 2 CH 2 C≡CH was used. An osmium example, [Os(CH=CHC 6 H 4 Me‐4)(O 2 CCH 2 CH 2 C≡CH)(CO)(PPh 3 ) 2 ], was also prepared from treatment of [Os(CH=CHC 6 H 4 Me‐4)Cl(CO)(BTD)(PPh 3 ) 2 ] with NaO 2 CCH 2 CH 2 C≡CH. Coupling of the pendant alkyne in [RuCl(O 2 CCH 2 CH 2 C≡CH)(CO)(PPh 3 ) 2 ] to yield the homodimetallic complex [{RuCl(O 2 CCH 2 CH 2 C≡C)(CO)(PPh 3 ) 2 } 2 ] was achieved by using [PdCl 2 (PPh 3 ) 2 ], CuI and NEt 3 . The reactivity of the alkyne unit was further exploited by the metallation of the alkyne with ClAu(PR 3 ) (R = Ph, Cy) and Co 2 (CO) 8 to yield the multimetallic species [Ru(CH=CHC 6 H 4 Me‐4)(O 2 CCH 2 CH 2 C≡CAuPR 3 )(CO)(PPh 3 ) 2 ] and [Ru(CH=CHC 6 H 4 Me‐4)(O 2 CCH 2 CH 2 CC{Co 2 (CO) 6 }H)(CO)(PPh 3 ) 2 ]. The structures of the complexes [Ru(CH=CHC 6 H 4 Me‐4)(O 2 CCH 2 CH 2 C≡CH)(CO)(PPh 3 ) 2 ] and [Ru(CH=CH t Bu)(O 2 CCH 2 CH 2 C≡CH)(CO)(PPh 3 ) 2 ] were determined crystallographically.