Cis and Trans Isomers of Pt(SiHAr2)2(PR3)2(R = Me, Et) in the Solid State and in Solutions

This is the authors' abstract. We don't add key points for this paper.

trans-Pt(SiHPh 2 ) 2 (PMe 3 ) 2 ( 1 ) is prepared from the reaction of H 2 SiPh 2 with cis-PtEt 2 (PMe 3 ) 2 and is characterized by X-ray crystallography. Dissolution of 1 in THF-d 8 or CD 2 Cl 2 causes its isomerization into cis-Pt(SiHPh 2 ) 2 (PMe 3 ) 2, which is equilibrated to 1 in the solutions. Temperature-dependent 1 H NMR spectra of a mixture of the isomers provided thermodynamic parameters for the trans to cis isomerization, ΔH° = 5.7(3) kJ mol -1 and ΔS° = 6.7(7) J mol -1 K -1 in CD 2 Cl 2 and ΔH° = 3.8(2) kJ mol -1 and ΔS° = 3.5(6) J mol -1 K -1 at 298 K in THF-d 8, respectively. The reactions of H 2 SiAr 2 with Pt(PEt 3 ) 4 give cis-Pt(SiHAr 2 ) 2 (PEt 3 ) 2 ( 2, Ar = C 6 H 5; 3, Ar = C 6 H 4 F-p), which are considerably more stable than the trans isomers in CD 2 Cl 2 (ca. 96:4 in an equilibrated CD 2 Cl 2 solution of Pt(SiHPh 2 ) 2 (PEt 3 ) 2 at room temperature).