Square Planar Coordination of Silver in a η⁴‐Cyclobutadiene‐(η⁵‐C₅H₅)ReBr₂ Complex Framework

Abstract

Halide addition and abstraction experiments with the cationic rhenacyclopentatriene [(η5‐C5H5){ReC4(SBn)4}Br]BF4 and the side‐on cyclobutadiene complexes [(η5‐C5H5)(η4‐C4Ph4)ReX2] (X = Br, I), respectively, are described. Reversible interconversion of both coordination modes of the metal bonded C4R4 moiety depending on the presence or absence of the second bromide ligand is demonstrated for the sulfide derivative. However, formation of the [(η5‐C5H5)(ReC4Ph4)X]+ congener by halide abstraction at [(η5‐C5H5)(η4‐C4Ph4)ReX2] turned out to be impossible. Instead, formation of silver halide complexes with the halide bridging rhenium and silver under retention of the metalorganic scaffold are observed. Governed by the phenyl substituent framework a square‐planar coordination environment about the Ag cation is adopted for X = Br. Changing X = Br by X = I led to the formation of a heptanuclear complex with di‐ and three‐coordinate silver ions.