Synthesis, Solid-State Structure, and Electronic Nature of a Phosphinine-Stabilizedtriangulo Palladium Cluster

Abstract

The reaction of Pd(OAc) 2 with an excess of 2,4,6-triphenylphosphinine results in the formation of a red dimeric Pd 0 complex of unknown structure. Treatment of this complex with PEt 3 affords a novel green triangulo Pd 3 cluster that is stabilized by three phosphinine and three PEt 3 ligands. An X-ray structural analysis shows that the phosphinine ligands serve as bridges between two Pd atoms. Quantummechanical calculations of a model compound reproduce the experimental geometry of the real complex adequately and also illuminate the bonding properties. Specifically, the interaction energy between each phosphinine ligand and the Pd 3 core amounts to 42.2 kcal mol À1 and involves both s and p orbitals.

Using “click” chemistry to access a new class of tripodal P3-ligand containing PC bonds

“…At this stage we cannot be certain what the nature of the bonding within the Pt 2 (m-P) fragments of 7 is, but it is of note that this bridging mode is comparable to that exhibited by the phosphabenzene ligand, PC 5 Ph 3 -2,4,6 (TPPB), in the palladium(0) trimer, [{(Et 3 P)Pd(m-TPPB)} 3 ]. 19 In that case, computational studies suggested that both s-and low lying porbitals at phosphorus are involved in bridging its short Pd-Pd bonds.…”

2,4,6‐Triarylphosphinines versus 2,4,6‐Triarylpyridines: An Investigation of the Differences in Reactivity between Structurally Related Aromatic Phosphorus and Nitrogen Heterocycles

“…Reetz et al. described the treatment of 2,4,6‐triphenylphosphinine ( 1 ) with Pd(OAc) 2 in toluene at −78 °C 22. The authors postulated the oxidation of excess 1 by Pd II under formation of the polymeric Pd 0 species [Pd( 1 ) 2 ] n , rather than the formation of a CH activated product (Scheme ).…”

“… Postulated pathway by Reetz et al 22. for the formation of polymeric species [Pd( 1 ) 2 ] n starting from 2,4,6‐triphenylphosphinine ( 1 ) and Pd(OAc) 2 .…”

Modulation of Benzene or Naphthalene Binding to Palladium Cluster Sites by the Backside‐Ligand Effect

“…The different electronic effects of the backside COT and benzene ligands exerting on [Pd 3 L 3 ] 2+ is reflected by the distinct geometries of the Pd 3 core in A and B ; that is, pseudo‐ C 3 v symmetry in A (a nearly equilateral Pd 3 triangle; PdPd=2.79 Å, 2.79 Å, 2.82 Å); C 2 v symmetry in B (a distorted isosceles Pd 3 triangle; PdPd=2.77 Å, 2.77 Å, 2.68 Å; Figure 2 a,b). 19 MO analysis suggested that this geometrical difference of the Pd 3 core is related to the difference of the π‐electron number of the backside ligand: The highest occupied molecular orbital (HOMO) and the next‐HOMO of A are essentially degenerated as a result of the MO interactions between the degenerated e′ orbitals of the pseudo‐ C 3 v symmetric [Pd 3 L 3 ] fragment5c, 20 and the in‐phase combination of the COT‐benzene ligand orbitals (Figure 2 c). When two 6π benzene ligands are the sandwich ligands, where the sum of the ligand π‐electrons (12 e) are two less than that of the COT‐benzene ligand system (14 e), these degenerated orbitals are each half‐occupied, and hence the structure is subjected to Jahn–Teller distortion as found in B .…”