Synthesis and co-ordination chemistry of the macrocycle 1,4,7-triisopropyl-1,4,7-triazacyclononane

The bulky tridentate macrocycle 1,4,7-triisopropyl-1,4,7-triazacyclononane (L) has been prepared and its co-ordination chemistry investigated. Reaction of L with [M(CO)6] in refluxing mesitylene affords airstable [ML(CO)3](M = Cr 1, Mo 2 or W 3) in excellent yields. Oxidation of complexes 1 and 2 with SOCl2 in CCl4 yields [MLCl3](M = Cr 4 or Mo 5) whereas [MLBr3](M = Cr 6 or Mo 7) were obtained by using bromine as oxidant in CHCl3. Exhaustive oxidative decarbonylation of 2 in semi-concentrated nitric acid affords colourless [MoLO3]·3H2O 8 which reacts with phenyl isocyanate in dry toluene yielding [MoLO3]·(PhNH)2CO 9. In dry MeCN the ligand reacts with VCl3 to give [VLCl3]10 which undergoes ligand substitution in water in the presence of NaSCN to give [VL(NCS)3]11. When this reaction was carried out in the presence of oxygen [VOL(NCS)2]12 was obtained. The molecular structures of 2, 8 and 9 have been established by single-crystal X-ray analysis.