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Intramolecular Metal–Fluorocarbon Coordination, CF Bond Activation and Lanthanoid–Fluoride Clusters with Tethered Polyfluorophenylamide Ligands
Author(s) -
Deacon Glen B.,
Forsyth Craig M.,
Junk Peter C.,
Wang Jun
Publication year - 2009
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200802294
Subject(s) - chemistry , intramolecular force , ligand (biochemistry) , amide , trimethylsilyl , lanthanide , metal , medicinal chemistry , transmetalation , chelation , metalation , stereochemistry , crystallography , inorganic chemistry , organic chemistry , catalysis , ion , biochemistry , receptor
Activating CF bonds : Strong metal–fluorocarbon coordination in complexes of electropositive metals (e.g., Na, K, Yb) with chelating polyfluorophenyl‐substituted amide ligands is a precursor to CF bond activation and fluoride abstraction when M=Yb II , giving heteroleptic Yb III fluoride clusters (see scheme).Metalation of either N , N ‐diethyl‐ or N , N ‐dimethyl‐ N ′‐2,3,5,6‐tetrafluorophenylethane‐1,2‐diamines (HL 1 a , 1 b respectively) with [M{N(SiMe 3 ) 2 }] (M=Na, K) or [Yb{N(SiMe 3 ) 2 } 2 (thf) 2 ] yielded the metal–amido compounds [Na(L)] ( 2 a ), [K(L)] ( 3 a ) and [Yb(L) 2 (thf) 2 ] ( 4 a , 4 b ). The Yb complexes were also synthesised by redox transmetalation/ligand exchange from Yb, Hg(C 6 F 5 ) 2 and HL in THF or 4 a from a reaction of 3 a with YbI 2 in THF. In the presence of N , N , N ′, N ′‐ tetramethyl‐1,2‐ethanediamine (TMEDA) the complexes 2 a and 3 a yielded [Na(L) 2 Na(tmeda)] ( 5 a ) and [K 2 (L) 2 (tmeda) 2 ] ( 6 a ), respectively, as crystalline compounds, whilst crystallisation of 4 a from DME gave [Yb(L) 2 (dme)] ( 7 a ). Their structures have chelating metal–amide and NR 2 donors and additional intramolecular M‐F‐C connectivity with relatively short bond lengths (NaF 2.65–3.00 Å; KF 2.70–3.00 Å; YbF 2.56 Å). The Yb complexes undergo CF activation in solution forming [Yb 4 (L) 6 F 6 ] ( 8 a , 8 b ). The connectivity of [Yb 4 (L) 6 F 6 ], as shown by the X‐ray structures, comprised a circular Yb 4 (μ‐F) 4 periphery with two opposing Yb centres having either one L ligand and a Yb 2 (μ‐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 4 a by redox transmetalation/ligand exchange using Hg(CCPh) 2 as the mercury reagent gave [Yb 4 (O) 2 (L) 4 (CCPh) 4 (thf) 2 ] ⋅ THF ( 9 a⋅ THF), most likely as a result of oxidation of the initially formed product.