Mechanistic Studies on the Formation of η²-Diphosphine (η⁶-p-cymene)ruthenium(II) Compounds

Abstract

A new range of pendent diphosphine (η 6 -p-cymene)ruthenium(II) complexes, [RuCl(PPh 3 )(η 1 -(P-P))-(η 6 -p-cymene)]PF 6 (P-P ) dppm, cis-PPh 2 CHCHPPh 2 (dppv), dppe, dppp, dppf), have been prepared by substitution of the labile acetonitrile ligand in [RuCl(CH 3 CN)(PPh 3 )(η 6 -p-cymene)]PF 6 . The formation of chelate complexes, [RuCl(η 2 -(P-P))(η 6 -p-cymene)] + , from these pendent phosphine complexes and from the related neutral complexes, [RuCl 2 (η 1 -(P-P))(η 6 -p-cymene)] (P-P ) dppm, dppv), has been investigated, including determination of activation enthalpies (∆H q ) and entropies (∆S q ). A concerted substitution mechanism is proposed for the latter complexes, in which methanol plays an important role in the ring-closing process by formation of hydrogen bonds with the chloride ligands. This proposal is supported by volumes of activation (∆V q ) determined by variable-pressure UV-visible spectroscopy. In contrast, a dissociative mechanism is proposed for the series of cationic pendent phosphine complexes, which generally require higher temperatures to effect ring closure. Secondary reaction pathways can be observed in some cases and are discussed in terms of differences between the phosphine complexes and supplemented by investigations using electrospray ionization mass spectrometry (ESI-MS). The X-ray structures of [RuCl(PPh 3 )(η 1 -(P-P))(η 6 -p-cymene)]PF 6 (P-P ) dppm, dppv, dppp) and [RuCl(η 2 -dppv)-(η 6 -p-cymene)]PF 6 are also reported.

Ruthenium diphosphine complexes as an efficient hydroamination catalyst

“…1 and 2, respectively. The structures of two complexes are similar to previously reported ruthenium(II) complexes of diphosphines [36][37][38][39]. Single crystal structure of 1 confirmed the four-coordinate geometry with two chlorine ion and cymene ligand which is connected through p-electrons of l 6 -cymene and one phosphor of dppm ligand in the complex.…”

Cytotoxicity of Ru(II) piano–stool complexes with chloroquine and chelating ligands against breast and lung tumor cells: Interactions with DNA and BSA

“…All the 1D and 2D NMR experiments ( 1 H, 13 was used as an internal reference for the 15 N dimension in the 1 H-15 N gHMBC experiment.…”

Hydrolysis study of the bifunctional antitumour compound RAPTA-C, [Ru(η6-p-cymene)Cl2(pta)]

“…g 4 ? g 6 , implicated in catalytic processes [47] and characterised in substitution reactions (also involving electrostriction) and hydrogen bonding of the chloride to the reaction solvent [48], could be involved in the hydrolysis process. Fig.…”