Phosphorus guiding palladium: [4 + 4] metallomacrocyclic PdII complex and self-assembly of heterometallic PdII/ZnII grid-type complex

Abstract

The reaction of heteroditopic ligand 1 featuring a hard pyridine–hydrazone–pyrimidine (N,N,N) site and a softer pyrimidine–hydrazone–phosphane (N,N,P) pocket with [Pd(CH₃CN)₄](OTf)₂ in different metal-to-ligand ratios (M : L) gave the homobimetallic Pd^II complex [Pd₂(1)(CH₃CN)₂](OTf)₄ (2, M : L ratio 2 : 1), the [4 + 4] metallomacrocyclic Pd^II complex [Pd(1)]₄(OTf)₈ (3, M : L ratio 1 : 1) and the monometallic complex [Pd(1)₂](OTf)₂ (4, M : L ratio 1 : 2). The soft N,N,P pocket preferably coordinates Pd^II, while the harder N,N,N coordination site selectively binds Zn^II forming the homoleptic meridional “corner” complexes [Zn(1)₂](OTf)₂ (5) and [Pd₂Zn(1)₂](OTf)₆ (6). The distinctive coordination behavior of ligand 1 is highlighted by the self-assembly of the heterometallic Pd^II/Zn^II grid-type complex [Pd₂Zn₂(1)₂](OTf)₈ (7) in a one-pot reaction. Complexes 2–7 were characterized by mass spectrometry, UV/Vis and NMR spectroscopy including DOSY NMR, and single-crystal X-ray diffraction studies were performed for 2–4 and 7.