A number of barium 1,2,4-diazaphospholide (dp(-)) complexes have been prepared by protonolysis of barium bis[bis(trimethylsilyl)]amide (Ba[N(SiMe3)(2)](2)(THF)(2)) and the corresponding 1,2,4-diazaphospholes, The bis(3,5-diphenyl-1,2,4-diazaphospholide)-tetrakis(tetrahydrofuran)barium [eta(2)(N,N-3,5-Ph(2)dP)(2)Ba(THF)(4)] (1) and bis(3,5-diphenyl-1,2,4-diazaphospholide)-tetrakis(dimethylsulfoxide)bari um [eta(2)(NM-3,5-Ph2dP)(2)Ba(DMSO)(4)] (2) were prepared by the reactions of Ba[N(SiMe3)(2)](2)(THF)(2) and 3,5-diphenyl-1,2,4-diazaphosphole (H[3,5-Ph(2)dp]) in tetrahydrofuran (THF) or dimethylsulfoxide (MO), respectively, while the bis(3,5-disubstituted-1,2,4-diazaphospholide)-(18-crown-6) barium complexes [trans-eta(2)(N,M-dP)(2)Ba(18-crown-6)] (3), [Cis-eta(2) (N,N)-tBu(2)dp)(2)Ba(18-crown-6)] (4), (trans-eta(2)(N,N)-tBu(2)dp)(2)Ba(18-crown-6)] (5), [cis-eta(2)(N,N-Ph(2)dp)(2)Ba(18-crown-6)] (6), and [trans-eta(2)(N,N-Ph(2)dP)(2)Ba(18-crown-6)] (7) were synthesized by the reaction of Ba[N(SiMe3)(2)](2)(THF)(2) and the corresponding 1,2,4-diazaphospholes in the presence of 18-crown-6 in THF or DMSO. Complexes 1, 2, 3, 4, and 7 have been structurally characterized. Complex 4 is the first structurally characterized barium complex in which the two organic ligands are located on the same side of 18-crown-6 (cis conformation). The P-31{H-1} NMR spectra suggested a partial dissociation of the barium 1,2,4-diazaphospholides 2, 4, and 7 into the corresponding ion associated complexes in solutions.