Synthesis, characterization, and reactivity of half-sandwich Ru(II) complexes containing phosphine, arsine, stibine, and bismutine ligands

The synthesis and some reactions of the Ru(II) and Ru(IV) half-sandwich complexes [RuCp(EPh₃)(CH₃CN)₂]⁺ (E=P, As, Sb, Bi) and [RuCp(EPh₃)(η³-C₃H₅)Br]⁺ have been investigated. The chemistry of this class of compounds is characterized by a competitive coordination of EPh₃ either via a RuE or a η⁶-arene bond, where the latter is favored when the former is weaker, that is in going down the series. Thus in the case of Bi, the starting material [RuCp(CH₃CN)₃]⁺ does not react with BiPh₃ to give [RuCp(BiPh₃)(CH₃CN)₂]⁺ but instead gives only the η⁶-arene species [RuCp(η⁶-PhBiPh₂)]⁺ and [(RuCp)₂(μ-η⁶,η⁶-Ph₂BiPh)]²⁺. Similarly, the EPh₃ ligand can be replaced by an aromatic solvent or an arene substrate. Thus, the catalytic performance of [RuCp(EPh₃)(CH₃CN)₂]⁺ for the isomerization of allyl-phenyl ethers to the corresponding 1-propenyl ethers is best with E=P, while the conversion drops significantly using the As and Sb derivatives. By the same token, only [RuCp(PPh₃)(CH₃CN)₂]⁺ is stable in a non-aromatic solvent, whereas both [RuCp(AsPh₃)(CH₃CN)₂]⁺ and [RuCp(SbPh₃)(CH₃CN)₂]⁺ rearrange upon warming to [RuCp(η⁶-PhEPh₂)]⁺ and related compounds. In addition, the potential of [RuCp(EPh₃)(CH₃CN)₂]⁺ as precatalysts for the transfer hydrogenation of acetophenone and cyclohexanone has been investigated. Again aromatic substrates are clearly less suited than non-aromatic ones due to facile η⁶-arene coordination leading to catalyst's deactivation.     

THERMOCHEMISTRY OF HETEROATOMIC COMPOUNDS,XX. THEORETICAL CALCULATIONS OF THE VAPORIZATION ENTHALPIES OF ALKYLARSINES,STIBINES, AND BISMUTHINES

The vaporization enthalpies (ΔH _vap ) of 26 primary, secondary, and tertiary alkylarsines, stibines, and bismuthines were calculated using the Trouton and Wadso equations and the first-order topological solvation index, ¹ χ ^S . The contributions to vaporization enthalpy for ─AsH ₂ (16.6 ± 0.2), > AsH (16.7 ± 0.1) groups and As(III)-atom in R ₃ As (13.7 ± 1.0), ─SbH ₂ (22.0 ± [2.0]), > SbH (19.0 ± [2.0]) groups and Sb(III)-atom in R ₃ Sb (12.7 ± 3.5), ─BiH ₂ (26.3 ± [2.2]), > BiH (24.3 ± [2.2]) groups and Bi(III)-atom in R ₃ Bi (16.2 ± 3.1 kJ mol^?1 ) were calculated.