Phosphido-bis(borane) complexes of the alkaline earth metals

The reaction between two equivalents of {(Me3Si)(2)CH}(Ph)PH(BH3) (1) and Bu2Mg, followed by two equivalents of BH3 center dot SMe2, gives the corresponding phosphido-bis(borane) complex, which may be crystallised as two distinct chemical species: the complex [{(Me3Si)(2)CH}(Ph)P(BH3)(2)](2)Mg(THF)(4)center dot THF (2a), and two different THF solvates (1 : 1 and 1 : 2) of the solvent-separated ion triples [{(Me3Si)(2)CH}(Ph)P(BH3)(2)](2)[Mg(THF)(6)]center dot THF (2b) and [{(Me3Si)(2)CH}(Ph)P(BH3)(2)](2)[Mg(THF)(6)]center dot 2THF (2c). Similar reactions between two equivalents of 1 and either (4-tBuC(6)H(4)CH(2))(2)Ca(THF)(4) or [(Me3Si)(2)CH](2)Sr(THF)(2), followed by two equivalents of BH3 center dot SMe2, give the heavier alkali metal complexes [{(Me3Si)(2)CH}(Ph)P(BH3)(2)](2)M(THF)(4) [M = Ca (3), Sr (4)]. Surprisingly, compounds 2a, 3 and 4 adopt almost identical structures in the solid state, which differ only in the geometrical arrangement of the phosphido-bis(borane) ligands and the hapticity of the borane groups.

Automated summary

This study synthesized and characterized a series of phosphido-bis(borane) complexes, which showed almost identical structures in the solid state, with differences only in the arrangement of phosphido-bis(borane) ligands and the hapticity of the borane groups.