Selective cleavage by acids of one metal-carbon σ-bond of a bis(ortho-platinated) triarylphosphane: A³¹P NMR trans-influence series based on the unit Pt(κ²-C₆H ₃-5-Me-2-PPh₂)(PPh₂-4-tol)

Supporting information for this article is available on the WWW under http://www.eurjic.org or from the author. Treatment of the bis(chelate) complex cis-[Pt(κ²-C₆H₃-5-Me-2-PPh ₂)₂] (1) with strong acids causes selective cleavage of one of the metal-aryl bonds to give cis-[PtX(κ²-C ₆H₃-5-Me-2-PPh₂)(PPh₂-4-tol)] [X = Cl (2), Br (3), I (4), ONO₂ (5) and OCOCF₃ (6)], from which a series of neutral and cationic derivatives can be derived by metathetical reactions. The complexes 2 and 6 rearrange spontaneously to the corresponding trans isomers, this reaction being promoted by CO. The J(Pt-P) values for the phosphorus atom of the four-membered ring can be ordered to establish a trans-influence series of anionic ligands X and neutral ligands L, which correlates well with, but is more extensive than, that based earlier on PtMe(dppe) complexes. Single-crystal X-ray structural analysis of trans-[Pt(κ¹-OCOCF₃)(κ²-C ₆H₃-5-Me-2-PPh₂)(PPh₂-4-tol)] (trans-6), cis-[PtX(κ²-C₆H₃-5-Me-2- PPh₂)(PPh₂-4-tol)] [X = Cl (2), CN (11), Me (43) and C₆F₅ (45)], and [Pt(κ²-C ₆H₃-5-Me-2-PPh₂)(PPh₂-4-tol) ₂]BF₂ (34) show these complexes to have distorted square-planar geometry. The Pt-P distances to the phosphorus atom of the four-membered ring in 2, 11, 43 and 45 broadly follow the trend of J(Pt-P) values, Cl^- being placed near the bottom and Me^- near the top of the trans-influence series, but the corresponding Pt-P distance in 34 is out of line. The Pt-P distances to PPh₂-4-tol cis to X or L tend to decrease with increasing trans-influence of X or L, in agreement with previous indications of a ligand cis-influence that runs opposite to the trans-influence.