Synthesis and structure of .pi.-phosphinacetylene complexes of zerovalent palladium and platinum

Abstract

Preliminary results from this laboratory suggest that in other thermal reactions of hydrocarbons, diradicals may be resting points on the side of a hill leading to the transition state.

Dinuclear palladium(ii) compounds with bridging cyclometalated phosphines. Synthesis, crystal structure and electrochemical study

“…In most of these compounds the palladium atoms are quite separated and synergic interaction between the two metal centers might only be possible in one case, 20 with three bridging ligands. Palladium complexes with ligands spanning a P-C bridging coordination mode are usually restricted to those ligands with the carbon atom being part of the p system: olefin, 21 acetylene 22 or arene. 23 The typical paddle wheel structure (type B in Scheme 1), common for other transition metals, is only observed in a limited number of palladium(II) compounds.…”

Synthesis and Reactivity of σ-Alkynyl/P-Bonded Phosphinoalkyne Platinum Complexes toward cis-[M(C6F5)2(thf)2] (M = Pt, Pd)

“…Phosphinoalkynes and acetylides have been widely used in the formation of organometallic complexes containing two or more transition metals. Phosphinoalkynes (PPh 2 C⋮CR) are potentially difunctional ligands with the capacity to coordinate as simple phosphines or disubstituted acetylenes or to simultaneously use the phosphorus lone pair and the acetylenic π-orbitals in a polydentate bonding mode . Although all three of these possibilities have been observed, it seems that the coordinating ability of PPh 2 C⋮CR is usually dominated by the phosphine donor sites, especially for complexes of metals in their normal oxidation states.…”

“…Although all three of these possibilities have been observed, it seems that the coordinating ability of PPh 2 C⋮CR is usually dominated by the phosphine donor sites, especially for complexes of metals in their normal oxidation states. The participation of the acetylenic triple bonds in coordination seems to require a low-valent metal site with a high affinity for alkyne π-electrons. , These bonding situations are well represented by the low-valent dinuclear complexes [Fe 2 (μ-η 3 -PPh 2 C⋮CPh) 2 (CO) 6 ],3c [Ni 2 (μ-η 3 -PPh 2 C⋮CBu t ) 2 (CO) 2 ],3f [M 2 (μ-η 3 -PPh 2 C⋮CPh) 2 (PPh 3 ) 2 ] (M = Pt, Pd) 3g (Scheme , A ), and [Fe 2 (μ-η 3 -PPh 2 C⋮ CBu t )(CO) 8 ] 3d (Scheme , B ), in which the PPh 2 C⋮CR groups act as four-electron bridging ligands ( P , η 2 ) and by the tetranuclear [Co 4 (μ 3 -η 3 -PPh 2 C⋮CR) 2 (CO) 10 ] 3a and trinuclear [Ni 2 Cp 2 (μ 3 -η 3 -PPh 2 C⋮CPh)Ni(CO) 3 ] 2b derivatives in which the ligands behave as six-electron donors ( P , η 2 :η 2 , Scheme , C ). In this context, we have recently shown that the reaction of cis -[MCl 2 (PPh 2 C⋮CPh) 2 ] (M = Pt, Pd) with cis -[Pt(C 6 F 5 ) 2 (thf) 2 ] gives the unusual dinuclear derivatives [(C 6 F 5 ) 2 Pt(μ-Cl)(μ-η 3 -PPh 2 C⋮CPh)MCl(PPh 2 C⋮CPh)] 4 (Scheme , D ) containing a diphenyl(phenylethynyl)phosphine acting as a bridging ligand (μ- P :η 2 ) between two Pt(II) centers.…”

Electrochemical chiral recognition by microparticle coatings of Pd complexes with bridging cyclometalated phosphines

“…This is the case of some dinuclear palladium(II) complexes containing two bridging ligands and two cyclometalated units with the ligand having a chelating coordination mode [15]. The availability of high oxidation states of palladium and the possibility of modulating the reactivity of the complexes via synergic interaction between the metal centres can be considered as relevant factors with regard to the use of such compounds in catalysis [16], so that different dinuclear palladium compounds with bridging ligands have been synthesized [17][18][19][20][21][22][23][24][25].…”