Self-Assembled, Highly Positively Charged, Allyl-Pd Crowns: Cavity-Pocket-Driven Interactions of Fluoroanions

A series of dodecanuclear highly positively charged homo- and heterometallamacrocycles [{Pd(η³ -2-Me-C₃ H₄ )}₆ (4-PPh₂ py)₁₂ {M₂ (tpbz)}₃ ]¹⁸⁺ (M=Pd, Pt; tpbz=1,2,4,5-tetrakis(diphenylphosphanyl)benzene were synthesized by the quantitative self-assembly of {Pd(η³ -2-Me-C₃ H₄ )}⁺ , {M₂ (tpbz)}⁴⁺ and 4-PPh₂ py moieties in 2:1:4 molar ratio. The cationic assemblies were obtained as salts of different fluorinated anions with diverse sizes and electronic properties, namely BF₄ ^- , PF₆ ^- , SbF₆ ^- and CF₃ SO₃ ^- . The new crown-like metallamacrocycles showed remarkable differences in their NMR spectra due to the presence of the different counteranions. On the basis of the observed variations, the metallacycles have been tested as catalytic precursors in allylic alkylation reactions. The anion-dependent activity and selectivity has been analysed and compared with that of the corresponding monometallic allylic corners [Pd(η³ -2-Me-C₃ H₄ )(4-PPh₂ py)₂ ]X (X=BF₄ ^- , PF₆ ^- , SbF₆ ^- , CF₃ SO₃ ^- ). DFT calculations have been employed in order to help to the interpretation of the experimental data and to model the anion-crown interactions.