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Rapid and complete fluorination of the complexes [MCl 3 (L)] (L ¼ Me 3-tacn, BzMe 2-tacn, M ¼ Al, Ga, In) occurs at room temperature via reaction of a MeCN solution of the complex with 3 mol equiv. of KF in water. The Ga and In complexes are also readily fluorinated using R 4 NF (R ¼ Me or n Bu) in MeCN solution, whereas no reaction occurs with the Al species under these conditions. The distorted octahedral fac-trifluoride coordination at M is confirmed in solution by multinuclear (19 F, 27 Al, 71 Ga and 115 In) NMR spectroscopic studies, leading to sharp resonances with 19 F-71 Ga and 19 F-115 In couplings evident. The [MF 3 (L)] are extremely stable in aqueous solution and at low pH; they crystallise as tetrahydrates, [MF 3 (Me 3-tacn)]$4H 2 O, with extended H-bonding networks formed through both F/H-O and O/H-O contacts. [InF 3 (BzMe 2-tacn)]$1.2H 2 O also shows intermolecular F/H-O hydrogen bonding contacts. The prospects for developing this coordination chemistry further to take advantage of the high metal-fluoride bond energies to enable rapid, late-stage fluorination of large macromolecules under mild conditions for PET imaging applications in nuclear medicine are discussed. This work also demonstrates that F-18 radiolabelling to form [F-18] [GaF 3 (BzMe 2-tacn)] is effected readily at room temperature in aqueous MeCN over 30-60 min on addition of 2.99 mol equiv. of [ 19 F]-KF aq and 0.4 mL [ 18 F]-KF aq (100-500 MBq) to [GaCl 3 (BzMe 2-tacn)] with ca. 30% incorporation. Recent efforts towards boron-based agents for F-18 capture include the work of Perrin, 6 Gabbaï 7 and Tsien. 8 Recently McBride and others have reported the use of Al-F complexes based upon functionalised bis-carboxylate derivatives of 1,4,7-triazacyclononane for F-18 imaging (Scheme 1). Incorporation of F-18 via formation of M-F bonds with biologically relevant ligand scaffolds provides an exciting alternative to C-F based PET agents. 9 McBride et al. have also used the formation of Al-F bonds to label a wide range of biomolecules rapidly in a single step. 9 However, the need for elevated temperatures (100 C) for uorination in this 'one-pot'

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