P,C-Chelation versus P,P-coordination of unsymmetrical phosphorus ylides in palladacyclopropa[60]fullerene complexes; synthetic, spectroscopic, and theoretical studies

Abstract

The new palladacyclopropa[60]fullerene complexes incorporating α-keto stabilized phosphorus ylides were synthesized in a three-component reaction of the unsymmetrical phosphorus ylides [Ph₂P(CH₂)_nPPh₂C(H)C(O)C₆H₄-m-R] (n = 1, R = Br, NO₂, (Y¹, Y²); n = 2, R = Br, NO₂, (Y³, Y⁴)), C₆₀ and Pd(dba)₂ (dba = dibenzylideneacetone). The obtained novel P,C-chelated [(η²-C₆₀)Pd(κ²-Y¹)] (1) and [(η²-C₆₀)Pd(κ²-Y²)] (2) complexes and P,P-coordinated [(η²-C₆₀)Pd(Y³)₂] (3) and [(η²-C₆₀)Pd(Y⁴)₂] (4) complexes were characterized successfully by IR, UV-Vis, ESI-MS and NMR (¹H, ¹³C and ³¹P) spectroscopic methods. Complexes 1–4 are rare examples of palladacyclopropa[60]fullerene complexes with phosphorus ylide ligands. Spectroscopic results revealed that none of possible side products including P,P-coordinated [(η²-C₆₀)Pd(Y¹)₂] and [(η²-C₆₀)Pd(Y²)₂] complexes and also P,C-chelated [(η²-C₆₀)Pd(κ²-Y³)] and [(η²-C₆₀)Pd(κ²-Y⁴)] complexes are formed. The EDA analysis indicated that in all the above complexes the metal–ligand bonds are mostly electrostatic in nature.