Four-Coordinate, Trigonal Pyramidal Pt(II) and Pd(II) Complexes

We report herein the characterization of electrophilic, trigonal bipyramidal {[SiP3R]Pt(L)}+ cations ([SiP3R] = [(2-R2PC6H4)3Si]; R = Ph, iPr) that feature weakly coordinated ligands including CH2Cl2, Et2O, toluene, and H2. A cationic toluene adduct that shows a close platinum aryl C−H σ-contact is perhaps most noteworthy in this context. For the isopropyl-substituted ligand, [SiP3iPr], it has proven possible to exclude the fifth axial donor to afford the rigorously four-coordinate, trigonal pyramidal (TP) complex {[SiP3iPr]Pt}+. An isostructural TP palladium complex {[SiP3iPr]Pd}+ is also accessible. Prototypical four-coordinate d8 platinum and palladium complexes are square planar. The TP d8 cations described herein are hence geometrically distinct.