| Sumario: | A series of sterically demanding aryl phosphine ligands (L) bearing terphenyl substituents, PRAr′ (R = hydrocarbyl, Ar′ = 2,6-diarylphenyl radical) has been prepared and characterized. The stability of these ligands towards oxidation in the air has been tested, and theoretical and experimental studies aimed to provide information on their electronic and steric properties have been performed. Treatment of the metal dimers [MCl(COD)](M = Rh, Ir; COD = 1,5-cyclooctadiene) with ligands PMeAr(L1) and PMeAr(L5), in a 1:1 metal:ligand ratio, afforded the expected square-planar 16-electron complexes [MCl(COD)(PMeAr)] and [MCl(COD)(PMeAr)], respectively. These compounds were readily converted into the corresponding dicarbonyl derivatives, [MCl(CO)(PMeAr)] and [MCl(CO)(PMeAr)], respectively. While the expected κ-P coordination mode of the PRAr′ ligands is found for these rhodium and iridium species, the mononuclear Pt(II) derivative obtained by reaction of PtClwith PMeArhas composition [PtCl(PMeAr)], and exhibits a bidentate κ-P, η-arene coordination mode involving one of the ipso carbon atoms of a flanking terphenyl aryl ring. The corresponding carbonyl compound [PtCl(CO)(PMeAr)], was generated under a CO atmosphere and exhibits κ-P coordination mode.
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