Intramolecular Metal-Fluorocarbon Coordination, C-F Bond Activation and Lanthanoid-Fluoride Clusters with Tethered Polyfluorophenylamide Ligands

Metalation of either N,N-diethyl- or N,N-dimethyl-N'-2,3,5,6-tetrafluorophenylethane-1,2-diamines (HL 1a, 1b respectively) with [M{N(SiMe3)(2)}] (M=Na, K) or [Yb{N(SiMe3)(2)}(2)(thf)(2)] yielded the metalamido compounds [Na(L)) (2a), [K(L)] (3a) and [Yb(L)(2)(thf)(2)] (4a, 4b). The Yb complexes were also synthesised by redox transmetalation/ligand exchange from Yb, Hg(C6F5)(2) and HL in THF or 4a from a reaction of 3a with YbI2 in THE In the presence of N,N,N',N'-tetramethyl-1,2-ethanediamine (TMEDA) the complexes 2a and 3a yielded [Na(L)(2)Na(tmeda)] (5a) and [K-2(L)(2)(tmeda)(2)] (6a), respectively, as crystalline compounds, whilst crystallisation of 4a from DME gave [Yb(L)(2)(dme)] (7a). Their structures have chelating metal-amide and NR2 donors and additional intramolecular M-F-C connectivity with relatively short bond lengths (Na-F 2.65-3.00 angstrom; K-F 2.70-3.00 angstrom; Yb-F 2.56 angstrom). The Yb complexes undergo C-F activation in solution forming [Yb-4(L)(6)F-6] (8a, 8b). The connectivity of [Yb-4(L)(6)F-6], as shown by the X-ray structures, comprised a circular Yb-4(mu-F)(4) periphery with two opposing Yb centres having either one L ligand and a Yb-2(mu-F)(2) bridge or two L ligands. Each polyfluorophenylamide exhibits additional intramolecular Yb-F-C coordination from one of the ortho-F atoms resulting in seven or eight coordinate Yb centres. An attempt to synthesise 4a by redox transmetalation/ligand exchange using Hg(C=-CPh)(2) as the mercury reagent gave [Yb-4(O)(2)(L)(4)(-cPh)(4)(thf)(2)]center dot THF (9a center dot THF), most likely as a result of oxidation of the initially formed product.