The invention relates to all compounds of the formula (I) or (II) in which: L is a neutral ligand; X, X′ are anionic ligands; R1 and R2 are, separately, a hydrogen, a C1-C6 alkyl, a C1-C6 perhalogenoalkyl, a aldehyde, a ketone, an ester, a nitrile, an aryl, a pyridinium alkyl, an optionally substituted C5 or C6 pyridinium alkyl, perhalogenoalkyl or cyclohexyl, a Cnh2NY radical 10 with n between 1 and 6 and y an i8onic marker, or a radical having the formula: wherein R1 can be a radical of formula (Ibis) when the compound has formula (I) or of formula (IIbis) when the compound has formula (II), R3 is a C1-C6 alkyl, or a C5 or C6 cycloalkyl or a C5 or C6 aryl; R0, R4, R5, R6, R7, R8, R9, R10, R11, are, separately, a hydrogen, C1-C6 alkyl, a C1-C6 perhalogenoalkyl, or a C5 or C6 aryl; wherein R9, R10, R11 can be a heterocycle; X1 is anion. R1 and R2 can form, with the N and the C to which they are attached, a heterocycle.