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

Abstract

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 [Cp*Fe(η5-P5)] (Cp* = C5(CH3)5) and [Cp*Fe(η3:1-(1-CH3-2-PPh2-P5))], respectively. The resulting products, [Cp*Fe(μ-η4:2:1-P5)Mg(thf)3] 0.5 thf (thf = tetrahydrofuran) and [{Cp*Fe(μ-η2:2:1-(1-CH3-2-PPh2-P5))}2Mg(thf)2]·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 P12 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 [Cp*Fe(μ3-η4:4:1-P5)Sr(thf)4]2·2 thf and [Cp*Fe(μ3-η2:1:1:1:1-(1-CH3-2-PPh2-P5))Sr(thf)3]2·2 thf represent the first examples of molecular polypnictogen compounds of strontium that are stable in organic solvents.