cis-to-trans Isomerization Promoted by Pyridine as a Crucial Step for the Selective Preparation of trans-Pt(SAr)(Cl)(PAr‘3)2

Tuning diastereoisomerism in platinum(ii) phosphino- and aminothiolato hydrido complexes

Tuning between the cis and trans Pt(ii) based complexes bearing phosphinothiolato and aminothiolato ligands.

Cooperation between cis and trans influences in cis-Pt(II)(PPh(3))(2) complexes: structural, spectroscopic, and computational studies

The relevance of cis and trans influences of some anionic ligands X and Y in cis-[PtX(2)(PPh(3))(2)] and cis-[PtXY(PPh(3))(2)] complexes have been studied by the X-ray crystal structures of several derivatives (X(2) = (AcO)(2) (3), (NO(3))(2) (5), Br(2) (7), I(2) (11); and XY = Cl(AcO) (2), Cl(NO(3)) (4), and Cl(NO(2)) (13)), density functional theory (DFT) calculations, and one bond Pt-P coupling constants, (1)J(PtP). The latter have allowed an evaluation of the relative magnitude of both influences. It is concluded that such influences act in a cooperative way and that the cis influence is not irrelevant when rationalizing the (1)J(PtP) values, as well as the experimental Pt-P bond distances. On the contrary, in the optimized geometries, evaluated through B3LYP/def2-SVP calculations, the cis influence was not observed, except for compounds ClPh (21), Ph(2) (22), and, to a lesser extent, Cl(NO(2)) (13) and (NO(2))(2) (14). A natural bond order analysis on the optimized structures, however, has shown how the cis influence can be related to the s-character of the Pt hybrid orbital involved in the Pt-P bonds and the net atomic charge on Pt. We have also found that in the X-ray structures of cis-[PtX(2)(PPh(3))(2)] complexes the two Pt-X and the two Pt-P bond lengths are different each other and are related to the conformation of the phosphine groups, rather than to the crystal packing, since this feature is observed also in the optimized geometries.

Proton-Induced Cis−Trans Conversion of a Platinum(II) Center Coordinated by l-Cysteinatocobalt(III) Metalloligands

Treatment of LambdaL-[Co(L-cys-N,S)(en)2]+ (l-H2cys = L-cysteine) with [PtCl4]2- in water, followed by the addition of acid, gave an S-bridged CoIII2PtII trinuclear complex ([1]4+), which was reversibly converted to its deprotonated complex ([2]2+) in an aqueous solution. While [1]4+ formed only a trans isomer, [2]2+ existed as a mixture of trans and cis isomers. The selective formation of a cis isomer was achieved by treatment of [1]4+ or [2]2+ with phthalic acid in water, which afforded a unique CoIII4PtII2 hexanuclear complex ([3]4+). Complex [3]4+ was reverted back to [1]4+ by treatment with aqueous HCl, accompanied by the complete cis-to-trans conversion.