Novel organo-magnesium compounds and their use

Organo-magnesium compounds obtainable by reacting compounds of formula (I) with compounds of formula (II)

• wherein
• R1 each independently of the other residue R1 present in the compound of formula (I) denotes alkyl which is either not or once substituted by phenyl and
• R2 each independently of the other residue R2 present in the compound of formula (II) denotes alkyl which is either not or once substituted either by optionally substituted phenyl or N(R3)2, or denotes optionally substituted phenyl or denotes Si(R3)3, wherein in the aforementioned formulae R3 is alkyl or optionally substituted phenyl.