Investigations of the Nature of ZnII−SiII Bonds. Issue 21 (13th April 2016)

• Record Type: Journal Article
• Authors: Schäfer, Sebastian; Köppe, Ralf; Roesky, Peter W.
• Is Part Of: Chemistry. Volume 22:Issue 21(2016)
• Page Start: 7127
• Page End: 7133
• Publication Date: 2016-04-13
• Subjects: amidinate ligands -- density functional calculations -- silicon -- silylenes -- zinc; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201505001
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: A series of zinc(II) silylenes was prepared by using the silylene {PhC(N t Bu)2 }(C5 Me5 )Si. Whereas reaction of the silylene with ZnX2 (X=Cl, I) gave the halide‐bridged dimers [{PhC(N t Bu)2 }(C5 Me5 )SiZnX(μ‐X)]2, with ZnR2 (R=Ph, Et, C6 F5 ) as reagent the monomers [{PhC(N t Bu)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. Abstract : One bond, two modes : Zinc(II) silylenes were prepared from ZnX2 (X=Cl, I) or ZnR2 (R=Ph, Et, C6 F5 ) and the silylene {PhC(N t Bu)2 }(C5 Me5 )Si (L ). Two different bonding modes were identified in the Zn−Si II complexes (see figure): 1) ion pairs consisting of a silyl cation with a Zn−Si single bond (e.g., [L Zn(C6 F5 )2 ]) and 2) relatively weak donor–acceptor Zn−Si bonds, which can be interpreted as silylene–zinc adducts (e.g., [L ZnEt2 ]).