Synthesis and Structures of Zeise‐type Complexes with Vinylsilane Ligands and Quantum Chemical Analysis of the Platinum–Vinylsilane Bonding

Zeise‐type complexes with vinylsilanes as π‐ligands [K(18C6)][PtCl3(η2‐CH2=CHX)] (X = SiMe3, 4; SiPh3, 5; Si(OMe)3, 6; 18C6 = 18‐crown‐6) and [K(18C6)]2[(PtCl3)2{η2,η2‐(CH2=CHSiMe2)2O}] (7) have been prepared by the reaction of [K(18C6)]2[Pt2Cl6] (3) with the appropriate vinylsilanes. The identities of the complexes have been confirmed by NMR spectroscopy as well as for 4, 5 and (PPh4)[PtCl3{η2‐CH2=CHSi(OMe)3}] (6′) also by single‐crystal X‐ray diffraction measurements. DFT calculations exhibited, that the coordination induced C=C bond lengthenings and the pyramidalization angles of the olefins in the vinylsilane complexes [PtCl3(η2‐CH2=CHX)]− (X = SiMe3, 4c; SiPh3, 5c; Si(OMe)3, 6c) are the same as in Zeise's anion [PtCl3(η2‐CH2=CH2)]− (8c) while the amount of the π back‐donation in the vinylsilane complexes 4c–6c is higher than that in the ethylene complex 8c.