The reactions of organomagnesium akoxides EtMgOR (R= Me, Et) with dialkynyl magnesium complexes Mg(CoCR¢F) (R¢F= tBu, SiMe3) give a series of the tetranuclear magnesium complexes [Mg4(OR)2Et2(CoCR¢F)4(THF)4] (R= Me, Et; R¢F= tBu, SiMe3). The reactions of diethyl magnesium complexes MgEt2 with alkynes HCoCR (R= tBu, SiMe3) give two different kinds magnesium complexes. One kind is [Mg4(OEt)2-Et2(CoCR)4(THF)4] (R= tBu, SiMe3); another kind is [Mg4O(CoCR)6(THF)4] (R= tBu, SiMe3). Besides, the reaction of diisopropylamide magnesium complex Mg(NiPr2)2 with alkyne HCoCtBu give first example including two different kind bridge ligands trinuclear magnesium complex Mg3(NiPr2)2(CoCtBu)4(THF)2.