Preparation and characterization of the kinetic and thermodynamic isomers of dinuclear molybdenum and tungsten complexes with metal–metal triple bonds supported by p-tert-butylcalix[4]arene anions†
Abstract
The reaction between M2(NMe2)6 and <2 equiv. of p-tert-butylcalix[4]arene (H4L) in hydrocarbon solvents leads to (H2NMe2)2[M2(µ,η2,η2-L)2] 1 (M = Mo, W), which isomerizes to the unbridged isomers (H2NMe2)2[M2(η4-L)2] 2 upon heating in refluxing pyridine (L = quadruply deprotonated calix[4]arene); related complexes M2(η4-HL)2 3 (M = Mo, W) are prepared from reactions involving M2(OBut)6 and H4L, and these react with HNMe2 to give 2 (M = Mo and W) while [NH2Me2][W2(η4-L)(η4-HL)] 4 can be obtained by the reaction between 2 and 3 (M = W) in a 1:1 ratio.