A Five‐Coordinate Compound with Inverted Ligand Field: An Unprecedented Geometry for Silver(III)

By using suitable synthetic procedures, we have first isolated the square‐planar organosilver(III) compounds [PPh4][trans‐(CF3)2AgX2] [X=Cl (1 a), Br (2 a)]. The geometry and stereochemistry of the chloro‐derivative 1 a have been unambiguously established by single‐crystal X‐ray diffraction (SC‐XRD) methods. Following our calculations on the relative stability of the cis‐/trans‐[(CF3)2AgX2]− couples (X=F, Cl, Br, I), the experimentally obtained compounds 1 a and 2 a appear to be kinetically favored stereoisomers. They display some tendency to associate an additional X− ligand affording rare five‐coordinate AgIII species [(CF3)2AgX3]2−. Interestingly, compound [PPh4]2[(CF3)2AgBr3] (3) has been identified by SC‐XRD methods as the first AgIII derivative with trigonal symmetry in general and trigonal bipyramidal geometry in particular. This unusual five‐coordinate species also exhibits inverted ligand field.