Ion pair catalysis of tungstate and molybdate

A complex of formula (I), comprising an organic cation (A) and an inorganic anion (B):

• wherein:
• each R1 independently represents C1-3 alkyl-aryl or C1-3 alkyl-Heta, which aryl or Heta groups are unsubstituted or are substituted by from one to five R3 substituents;
• each R2 independently represents aryl, which group is unsubstituted or substituted by from one to five R4 substituents;
• Heta represents a 4- to 14-membered heterocyclic group containing one or more heteroatoms selected from O, S and N, which heterocyclic group comprises one, two or three rings;
• each R3 and R4 independently represents halo, branched or unbranched C1-6 alkyl, branched or unbranched C2-6 alkenyl, branched or unbranched C2-6 alkynyl;
• C3-6 cycloalkyl, aryl or OR5;
• R5 represents H, branched or unbranched C1-6 alkyl, branched or unbranched C2-6 alkenyl, branched or unbranched C2-6 alkynyl, C3-6 cycloalkyl or aryl,
• wherein alkyl, alkenyl, alkynyl, cycloalkyl, and aryl, when present in R3, R4, and R5, are optionally substituted by one or more halogen atoms.