A compound, e.g. a diamine ligand, represented by the following general formula (1): (Formula (1)) wherein each * represents an asymmetric carbon atom; X represents a group selected from one of an ester (e.g. a t-butyl ester); a thioester; an amide; a heterocyclic moiety (e.g. a five-membered heterocyclic ring) comprising one or more of O, S, Se, and/or P (e.g. a furan, a tetrahydrofuran, a thiophene, an isoxazole, a bromo-furan, or a thiazole); a moiety (e.g. a five-membered heterocyclic ring) comprising a nitrogen atom, wherein the nitrogen atom is protected with a protecting group containing an electron-withdrawing group, preferably the protecting group is selected from one of a carbamate protecting group, an amide protecting group, an aryl sulphonamide protecting group, or an alkyl sulphonamide protecting group; and optionally X may additionally comprise a solid support, e.g. a polymeric or a silica particle; Y represents or is CtT'T'' where 't' is 0 or 1 and when 't' is 1 T' and T'' may individually represent a substituent, e.g. if t is 1, T' and/or T'' may each be hydrogen or deuterium atom, or a halogen atom; for example, Y may represent a carbon atom comprising two further substituents; Z represents a hydrogen atom or a deuterium atom; R1 represents an alkyl group (e.g. a functionalised alkyl group) preferably having between 1 to 100 carbon atoms, for example, between 1 to 30 carbon atoms (e.g. 1 to 20 carbon atoms, or 1 to 10 carbon atoms), a halogenated alkyl group preferably having between 1 to 100 carbon atoms (e.g. CF3), for example, between 1 to 30 carbon atoms (e.g. 1 to 20 carbon atoms, or 1 to 10 carbon atoms), an aryl group preferably having between 5 to 100 carbon atoms, e.g. 6 to 30 carbon atoms and optionally having one or more substituents selected from alkyl groups preferably having 1 to 100 carbon atoms, e.g. 1 to 10 carbon atoms, halogenated alkyl groups preferably having 1 to 100 carbon atoms, e.g. 1 to 10 carbon atoms, and/or halogen atoms; or R1 represents a solid support, e.g. a silica particle or a polymeric particle; R2 and R3 each independently represent a group selected from alkyl groups preferably having between 1 to 100 carbon atoms, for example 1 to 20 carbon atoms (e.g. 1 to 10 carbon atoms), aryl groups (e.g. phenyl groups), and cycloalkyl groups preferably having 3 to 8 carbon atoms, the aryl group or phenyl group optionally having one or more substituents selected from alkyl groups preferably having between 1 to 100 carbon atoms, e.g. between 1 to 20 carbon atoms (e.g. 1 to 10 carbon atoms), alkoxy groups preferably having between 1 to 100 carbon atoms, for example, between 1 to 20 carbon atoms (e.g. 1 to 10 carbon atoms), and halogen atoms, and each hydrogen atom of the cycloalkyl groups being optionally replaced by an alkyl group preferably having between 1 to 100 carbon atoms, e.g. 1 to 20 carbon atoms (e.g. 1 to 10 carbon atoms), or R1 represents a polyethylene glycol (PEG) moiety having the formula C2nH4n+2On+1 wherein n is an integer between 1 and 100; or R2 and R3 form a ring together with carbon atoms to which R2 and R3 are bonded; R4 represents a hydrogen atom or a deuterium atom.