| Autor: |
Biswas M; Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai-400076, India. lahiri@chem.iitb.ac.in., Dey S; Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai-400076, India. lahiri@chem.iitb.ac.in., Dhara S; Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai-400076, India. lahiri@chem.iitb.ac.in., Panda S; Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai-400076, India. lahiri@chem.iitb.ac.in., Lahiri GK; Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai-400076, India. lahiri@chem.iitb.ac.in. |
| Abstrakt: |
This article addresses the impact of metal-ligand redox cooperativity on the functionalisation of coordinated ligands. It demonstrates the structure-reactivity correlation of bis(aldimine) derived bis-bidentate L (Py-CHN-(CH 2 ) n -NCH-Py, with n = 2 (L1), 3 (L2), 4 (L3)) as a function of the conformation ( syn / anti ) of its alkylene linker as well as the overall structural form ( cis / trans ) of (acac) 2 Ru II (μ-L)Ru II (acac) 2 complex moieties (1-5) possessing an electron-rich acetylacetonate (acac) co-ligand. A systematic variation of the bridging alkylene unit of L in Ru II /Ru II -derived 1-5 led to the following reactivity/redox events, which were validated through structural, spectroscopic, electrochemical and theoretical evaluations: (i) Cyclisation of the ethylene linked ( syn conformation) bis-aldimine unit of L1 via C-C coupling yielded pyrazine bridged (acac) 2 Ru II (μ-L1')Ru II (acac) 2 , 1a, while the corresponding anti -form (ethylene linker) of the metal-bound L1 in 2 ((acac) 2 Ru II (μ-L1)Ru II (acac) 2 ) led to oxygenation at the ligand backbone (bis-aldimine (L) → bis(carboxamido) (L'')) via O 2 activation to generate Ru III Ru III -derived (acac) 2 Ru III (μ-L1'' 2- )Ru III (acac) 2 (2a). (ii) Consequently, propylene and butylene linked L2 and L3 bridged between two {Ru(acac) 2 } units in 3 and 4/5 underwent oxygenation of L to L'' to yield diruthenium(III) complexes 3a and 4a/5a, respectively. (iii) In contrast, analogous L bridged oxidised [(acac) 2 Ru III (μ-L)Ru III (acac) 2 ](ClO 4 ) 2 ([2](ClO 4 ) 2 -[5](ClO 4 ) 2 ) and [{(PPh 3 ) 2 (CO)(H)Ru II } 2 (μ-L)](ClO 4 ) 2 ([6](ClO 4 ) 2 -[8](ClO 4 ) 2 ) involving electron poor co-ligands failed to undergo the oxygenation of L irrespective of its n value, reemphasising the effective role of redox interplay between Ru II and L particularly in the presence of an electron-rich acac co-ligand in the functionalisation of the latter in 1a-5a. |
