True and masked three-coordinate T-shaped platinum(II) intermediates

Abstract

SummaryAlthough four-coordinate square-planar geometries, with a formally 16-electron counting, are absolutely dominant in isolated Pt(II) complexes, three-coordinate, 14-electron Pt(II) complexes are believed to be key intermediates in a number of platinum-mediated organometallic transformations. Although very few authenticated three-coordinate Pt(II) complexes have been characterized, a much larger number of complexes can be described as operationally three-coordinate in a kinetic sense. In these compounds, which we have called masked T-shaped complexes, the fourth position is occupied by a very weak ligand (agostic bond, solvent molecule or counteranion), which can be easily displaced. This review summarizes the structural features of the true and masked T-shaped Pt(II) complexes reported so far and describes synthetic strategies employed for their formation. Moreover, recent experimental and theoretical reports are analyzed, which suggest the involvement of such intermediates in reaction mechanisms, particularly C–H bond-activation processes.

Taming the Cationic Beast: Novel Developments in the Synthesis and Application of Weakly Coordinating Anions

“…[388] Ther emoval of au nivalent residue from as quare-planar platinum(II) complex to introduce aW CA represents an ideal method for the formation of (masked) Tshaped complexes. [388] Ther emoval of au nivalent residue from as quare-planar platinum(II) complex to introduce aW CA represents an ideal method for the formation of (masked) Tshaped complexes.…”

“…In platinum catalysis,t hree-coordinate T-shaped, 14electron complexes are thought to be key intermediates for fundamental reactions including b-hydride elimination, olefin insertion reactions,and in the Shilov-type systems for hydrocarbon CÀHbond activations and this area has been reviewed in detail. [388] Ther emoval of au nivalent residue from as quare-planar platinum(II) complex to introduce aW CA represents an ideal method for the formation of (masked) Tshaped complexes.…”

Synthesis and Reactivity of a Neutral, Three‐Coordinate Platinum(II) Complex Featuring Terminal Amido Ligation

“…Although the conversion of stable four-coordinate (square-planar), 16-electron complexes into highly reactive three-coordinate, [2] 14-electron species is ac ommonly invoked mechanistic paradigm in platinum chemistry, [3] isolable three-coordinate Pt II complexes have proven elusive. [4] Indeed, the coordination chemistry of d 8 species of Pt II is almost exclusively dominated by square-planar species. Notwithstanding the utility of "operationally" three-coordinate Pt II compounds,s uch as those featuring aw eak agostic interaction occupying the fourth coordination site, [5] the structural characterization of genuine three-coordinate Pt II species is limited to reports by the groups of Braunschweig [6] and Conejero/Lledós.…”

“…[4] Although the apparently Y-shaped neutral Pt II complex [(IPr)Pt-(SiMe 2 Ph) 2 ]( C)w as also described, [8] subsequent analysis suggests that this complex can be more appropriately viewed as aplatinum(0) s-disilane species (Scheme 1). [9] By comparison, isolable three-coordinate,f ormally 14 electron Pt II complexes featuring terminal amido ligation have not been reported previously,o wing in part to the considerable synthetic challenges associated with the preparation of monomeric (nonbridging) species of this type.…”

“…[4] Indeed, the coordination chemistry of d 8 species of Pt II is almost exclusively dominated by square-planar species. Notwithstanding the utility of "operationally" three-coordinate Pt II compounds,s uch as those featuring aw eak agostic interaction occupying the fourth coordination site, [5] the structural characterization of genuine three-coordinate Pt II species is limited to reports by the groups of Braunschweig [6] and Conejero/Lledós.…”