The molecular structures of four different crown ether adducts of CsP(H)(t)Bu(3)Mes and CsP(H)Dmp ((t)Bu(3)Mes = 2,4,6-tri-tert-butylphenyl; Dmp = 2,6-dimesitylphenyl) are reported featuring monomeric or triple-decker-type structures in the solid state. The crown ether adducts 1, 2, and 4 are prepared in good yields using different stoichiometries CsP(H)R/18-crown-6 followed by crystallization of the corresponding cesium phosphide derivative from toluene at -30 degrees C. 1 crystallizes from toluene as the crown ether adduct [CsP(H)(t)Bu(3)Mes](18-crown-6) . 0.5 toluene (1 . 0.5 toluene) in the monoclinic space group P2(1)/c. Crystal data for 1 . 0.5 toluene at 243 K:a = 22.919(4) Angstrom; b = 17.184(3) Angstrom; c = 21.307(6) Angstrom; beta = 111.79(2)degrees; V = 7697(4) Angstrom(3); Z = 8; D-calcd = 1.247 g/cm(3); R1 = 4.89%. 2 crystallizes from toluene in the presence of excess crown ether as the adduct [CsP(H)Dmp](18-crown-6) (2) in the orthorhombic space group P2(1)2(1)2(1). Crystal data for 2 at 173 K: a = 13.8223(2) Angstrom; b = 14.6926(2) Angstrom; c = 18.6259(2) Angstrom; V = 3782.60(8) Angstrom(3); Z = 4; D-calcd = 1.304 g cm(-3); R1 = 3.97%. Using deuterated benzene instead of toluene as the recrystallization solvent, 2 crystallizes as the benzene solvate [CsP(H)Dmp](18-crown-6)(eta(2)-C6D6) . benzene (3 . benzene) in the orthorhombic space group Pccn (No. 56). Crystal data for 3 at 173 K: a = 20.1567(4) Angstrom; b = 25.8617(5) Angstrom; c = 17.3173(4) Angstrom; V = 9027.3(5) Angstrom(3); Z = 8; D-calcd = 1.340 g cm(-3); R1 = 9.34%. 4 crystallizes from toluene using a 2:1 stoichiometry [CsP(H)Dmp: 18-crown-6] as the crown ether adduct [CsP(H)Dmp](2)(18-crown-6) . toluene (4 . toluene) in the triclinic space group P (1) over bar. Crystal data for 4 . toluene at 198 K: a = 11.2885(2) Angstrom; b = 11.6675(2) Angstrom; c = 14.5247(2) Angstrom; alpha = 66.5752(3)degrees; beta = 71.1301(7)degrees; gamma = 88.0975(8)degrees; V = 1650.96(6) Angstrom(3); Z = 1, D-calcd = 1.321 g/cm(3), R1 = 4.29%. 1 . 0.5 toluene, 2, and 3 . benzene represent first examples of monomeric cesium phosphide species, while the solid state structure of 4 . toluene features a triple-decker-type arrangement.