Zirconium(IV) tris(phosphinoamide) complexes as a tripodal-type metalloligand: A route to Zr-M (M = Cu, Mo, Pt) heterodimetallic complexes

Treatment of ZrCl₄ with 3 equiv. of Li(PPh₂NR) (R = tBu, iPr) gives tris(phosphinoamide)zirconium complexes, (PPh ₂NR)₃-ZrCl [R = tBu (1a), iPr (1b)], in high yield. Crystal structures of 1a,b show that three phosphorus atoms are coordinated to the zirconium center in the solid state, whereas variable temperature NMR studies indicate a reversible coordination/dissociation process of three phosphorus atoms in the solution state. Reaction of 1a,b with CuCl give rise to the formation of Zr-Cu heterodimetallic complexes, ClCu(Ph₂PNR) ₃-ZrCl [R = tBu (2a), iPr (2b)]. The molecular structures of 2a,b show that the Cu atom adopts a pseudotetrahedral coordination geometry with tripodal phosphorus moieties and a chlorine atom, whereas the ligand arrangement around the Zr atom is trigonal bipyramidal with the linear Cl-Zr-Cu axis at the apical site. A Zr-Mo heterodimetallic complex, (CO)₃-Mo(Ph ₂PNiPr)₃ZrCl (3), is synthesized from 1b and Mo(CO) ₃-(CH₃CN)₃, in which the ligands around the Mo center are arranged octahedrally, and three phosphorus moieties are coordinated in the fac-P₃ fashion. The reaction of 1b with a square planar Pt^II precursor, such as (COD)PtCl₂, is unique and gives (κ²-Ph₂PNiPr)Pt(Ph₂PNiPr) ₂ZrCl₃ (4), which is the first example of a Zr-Pt zwitterionic heterodimetallic complex. The reaction involves intramolecular migration of two chlorine atoms from Pt to Zr as well as that of a Ph ₂PNiPr moiety from Zr to Pt.