title: Investigations of the Nature of Zn(II) -Si(II) Bonds.
abstract: A series of zinc(II) silylenes was prepared by using the silylene {PhC(NtBu)2 }(C5 Me5 )Si. Whereas reaction of the silylene with ZnX2 (X=Cl, I) gave the halide-bridged dimers [{PhC(NtBu)2 }(C5 Me5 )SiZnX(μ-X)]2 , with ZnR2 (R=Ph, Et, C6 F5 ) as reagent the monomers [{PhC(NtBu)2 }(C5 Me5 )SiZnR2 ] were obtained. The stability of the complexes and the Zn-Si bond lengths clearly depend on the substitution pattern of the zinc atom. Electron-withdrawing groups stabilize these adducts, whereas electron-donating groups destabilize them. This could be rationalized by quantum chemical calculations. Two different bonding modes in these molecules were identified, which are responsible for the differences in reactivity: 1) strong polar Zn-Si single bonds with short Zn-Si distances, Zn-Si force constants close to that of a classical single bond, and strong binding energy (ca. 2.39 Å, 1.33 mdyn Å(-1) , and 200 kJ mol(-1) ), which suggest an ion pair consisting of a silyl cation with a Zn-Si single bond; 2) relatively weak donor-acceptor Zn-Si bonds with long Zn-Si distances, low Zn-Si force constants, and weak binding energy (ca. 2.49 Å, 0.89 mdyn Å(-1) , and 115 kJ mol(-1) ), which can be interpreted as a silylene-zinc adduct.
authors.affiliation: Institute of Inorganic Chemistry, Karlsruhe Institute of Technology (KIT), Engesserstrasse 15, 76131, Karlsruhe, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Schäfer
authors.affiliation: Institute of Inorganic Chemistry, Karlsruhe Institute of Technology (KIT), Engesserstrasse 15, 76131, Karlsruhe, Germany. ralf.koeppe@kit.edu.
authors.forename: Ralf
authors.initials: R
authors.lastname: Köppe
authors.affiliation: Institute of Inorganic Chemistry, Karlsruhe Institute of Technology (KIT), Engesserstrasse 15, 76131, Karlsruhe, Germany. roesky@kit.edu.
authors.forename: Peter W
authors.initials: PW
authors.lastname: Roesky
keywords: amidinate ligands; density functional calculations; silicon; silylenes; zinc