A simple synthesis of group 2 anthracenides and their use as reducing agents for polypnictogen ligand complexes.

By using an improved synthetic pathway, the anthracenides of the group 2 metals Ca, Sr, and Ba are straightforwardly accessible for subsequent organometallic syntheses. These highly reactive compounds are slightly soluble in tetrahydrofuran and can be used as synthons for group 2 metal transfer due to the lability of the anthracene substituent. These features were used to explore their reactivity towards the polyphosphorus ligand complexes [CpFe(η-P)] (Cp = C(CH)) and [CpFe(η-(1-CH-2-PPh-P))], respectively. The resulting products, [CpFe(μ-η-P)Mg(thf)] 0.5 thf (thf = tetrahydrofuran) and [{CpFe(μ-η-(1-CH-2-PPh-P))}Mg(thf)]·3 thf, are first examples of molecular magnesium-containing polypnictogenide transition metal complexes without stabilization by N-donor ligands that are soluble in organic N-donor-free solvents. The P ligand in the latter complex is the first example of a 2,2'-diphosphanyl-substituted decaphosphadihydrofulvalen-shaped structural motif (2,2'-bis(diphenylphosphanyl)-1,1'-dimethyl-3,3'-bipentaphosphole). The complexes [CpFe(μ-η-P)Sr(thf)]·2 thf and [Cp*Fe(μ-η-(1-CH-2-PPh-P))Sr(thf)]·2 thf represent the first examples of molecular polypnictogen compounds of strontium that are stable in organic solvents.