1477587-01-1Relevant academic research and scientific papers
Controlled interaction of benzaldehyde thiosemicarbazones with palladium: Formation of bis-complexes with cis-geometry and organopalladium complexes, and their catalytic application in C-C and C-N coupling
Dutta, Jayita,Bhattacharya, Samaresh
, p. 10707 - 10721 (2013)
Reaction of a 1 : 1 mixture of 4-R-benzaldehyde thiosemicarbazone (R = OCH3, CH3, H, Cl and NO2) and 2-picolinic acid with an equivalent quantity of Na2[PdCl4] in ethanolic medium, under relatively mild reflux, affords a group of complexes of type [Pd(NS-R)2] as the major product and another family of complexes of type [{Pd(CNS-R)}n] as the minor product (where NS-R and CNS-R denote the N,S- and C,N,S-coordinated thiosemicarbazone, respectively). The [{Pd(CNS-R)}n] complexes are conveniently obtained in good yields from similar reactions carried out under prolonged reflux. The sulfur-bridge in the [{Pd(CNS-R)}n] complexes undergoes facile cleavage upon their reaction with triphenylphosphine to yield complexes of type [Pd(CNS-R)(PPh 3)]. Crystal structures of [Pd(NS-OCH3)2], [Pd(NS-CH3)2], [Pd(NS-Cl)2], [Pd(CNS-CH 3)(PPh3)], [Pd(CNS-H)(PPh3)] and [Pd(CNS-Cl)(PPh3)] have been determined. In the [Pd(NS-R) 2] complexes the thiosemicarbazones are coordinated to the metal center, via dissociation of the acidic proton, as monoanionic bidentate N,S-donors forming five-membered chelate rings, while in the [Pd(CNS-R)(PPh 3)] complexes they are coordinated to palladium, via dissociation of the acidic proton and activation of an ortho C-H bond, as dianionic tridentate C,N,S-donors forming two adjacent five-membered chelate rings. The [Pd(NS-R)2] and [Pd(CNS-R)(PPh3)] complexes show characteristic 1H NMR signals, and in dichloromethane solution they all display intense absorptions in the visible and ultraviolet regions. The [Pd(NS-R)2] and [Pd(CNS-R)(PPh3)] complexes have shown notable efficiency in catalyzing C-C and C-N coupling reactions. The Royal Society of Chemistry 2013.
