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

We report herein the characterization of electrophilic, trigonal bipyramidal {[SiP_3^R]Pt(L)}+ cations ([SiP_3 ^R] ) [(2-R_2PC_6H_4)_3Si]; R ) Ph, ^iPr) that feature weakly coordinated ligands including CH_2Cl_2, Et_2O, toluene, and H_2. 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, [SiP_3^(iPr)], it has proven possible to exclude the fifth axial donor to afford the rigorously four-coordinate, trigonal pyramidal (TP) complex {[SiP_3^(iPr)]Pt}^+. An isostructural TP palladium complex {[SiP_3^(iPr)]Pd}^+ is also accessible. Prototypical four-coordinate d^8 platinum and palladium complexes are square planar. The TP d^8 cations described herein are hence geometrically distinct.