Factors influencing the formation of cis and trans isomers in long-chain bis(phosphine) complexes of platinum(II)

Abstract

The square-planar platinum(II) complexes of a series of bis(diphenylphosphine)alkanes have been synthesized and characterized by infrared and phosphorus-31 NMR spectroscopy, elemental analysis, and vapor-phase osmometry. Cis complexes are formed when the complex precursor is potassium tetrachloroplatinate(II), while the corresponding trans complexes are preferred when the starting material is Zeise's salt. An unusual trans-bonded complex with dpe has also been isolated. The trans isomers revert to their cis analogues in the presence of heat or excess bis(phosphine). The cis dimers are the most stable isomers for the majority of the cis complexes. The preferred ring sizes for the cis chelated monomers are 14-and 19-membered chelate rings. The amount of trans monomer increases with increasing chain length and reaches a maximum with a chelate ring size of 15 members and can be correlated directly with ring contributions to the chemical shift-thus ring contributions in trans monomeric complexes can be used as a measure of ring strain for these ligands. Large flexible chelate rings (19 members or above) appear to be unstable in the trans configuration.

Electron‐Transfer Studies of trans‐Platinum Bis(acetylide) Complexes

“…On the other hand, the presence of two hydrogen atoms at α positions to the phosphorus atom for the n-butyl groups may also generate steric strain, which would result in an increase of the C-P-C angle. Both effects are in accordance with the experimentally observed 1 [59] As observed for selenides 5a-5d, the 195 Pt-31 P coupling constants increase, as expected, with an increasing number of ferrocenyl units (vide supra, Exp. Section).…”

1,2‐Bis‐N‐[2′‐(diphenylphosphanyl)benzoyl]diaminobenzene, a New Chelating Ligand with Versatile Coordination Properties

“…[9] In general, the stability of the trans monomer increases with increasing chain length and reaches a maximum for a metallacycle containing 15 ring members. [10] Herein, we report the synthesis of a new diphosphane ligand containing an ortho-phenylene spacer group for the synthesis of trans-dicoordinate as well as cis-tetracoordinate square-planar palladium() and platinum() complexes.…”

sp Carbon Chains Surrounded by sp3 Carbon Double Helices: A Class of Molecules that are Accessible by Self-Assembly and Models for “Insulated” Molecular-Scale Devices We thank the Deutsche Forschungsgemeinschaft (SFB 583), Johnson Matthey PMC (platinum loan), the Spanish Ministerio de Educación y Ciencia, and the Fulbright Commission (Fellowships, J.M.M.-A.) for support, and Dr. A. M. Arif for assistance with the analysis of one crystal structure.

“…Several monoplatinum complexes of macrocyclic diphosphanes have also been observed to oligomerize. [17] A second-generation approach with two new design elements was investigated. First, the p-tolyl ligands on platinum were replaced with pentafluorophenyl (C 6 F 5 ) ligands.…”