Syntheses and Structures of trans-bis(Alkenylacetylide) Ruthenium Complexes |
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| Authors: | Michael R. Hall Prof. Stephen A. Moggach Prof. Paul J. Low |
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| Affiliation: | School of Molecular Sciences, University of Western Australia, 35 Stirling Highway, Crawley, 6009 Western Australia, Australia |
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| Abstract: | A series of ruthenium alkenylacetylide complexes trans-[Ru{C≡CC(=CH2)R}Cl(dppe)2] (R=Ph ( 1 a ), cC4H3S ( 1 b ), 4-MeS-C6H4 ( 1 c ), 3,3-dimethyl-2,3-dihydrobenzo[b]thiophene (DMBT) ( 1 d )) or trans-[Ru{C≡C-cC6H9}Cl(dppe)2] ( 1 e ) were allowed to react with the corresponding propargylic alcohol HC≡CC(Me)R(OH) (R=Ph ( A ), cC4H3S ( B ), 4-MeS-C6H4 ( C ), DMBT ( D ) or HC≡C-cC6H10(OH) ( E ) in the presence of TlBF4 and DBU to presumably give alkenylacetylide/allenylidene intermediates trans-[Ru{C≡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≡CC(=CH2)R}2(dppe)2] (R=Ph ( 3 a ), cC4H3S ( 3 b ), 4-MeS-C6H4 ( 3 c ), DMBT ( 3 d )) and trans-[Ru{C≡C-cC6H9}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≡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≡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. |
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| Keywords: | acetylide allenylidene cumulene helical molecular orbitals Ruthenium |
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