A silicophosphonate bearing four hydroxyl groups, [RSi(OH){OP(O)(H)(OH)}](2)O (2; R = (2,6-(Pr2C6H3)-Pr-i)N(SiMe3)), has been isolated from the reaction between RSi(OH)(3) and [EtNPCl](3), In contrast, the reaction between the sodium salt of substituted phenols and [EtNPCl](3) yields [EtNP(OAr)](3) [Ar = -(C6H3Pr2)-Pr-i-2,6 (3), -C6H2Me3-2,4,6 (4), -C6H3Me2-2,6 (5), -C10H7-1 (6), and -(C6H4Bu)-Bu-i-4 (7)]. The cis isomers 3a-7a preferentially crystallize out from the cis/trans isomeric mixture. Single-crystal X-ray diffraction studies carried out for 3a, 4a, and 5a reveal that the P3N3 ring adopts a flattened-chair conformation with the aryloxy substituent on all three phosphorus atoms occupying the axial position. Oxidation of the cis isomers 3 and 5 by H2O2, sulfur, and selenium yields the trichalcogenides [EtNP(E)((OC6H3Pr2)-Pr-i-2,6)](3) (E = O (8), S (10), Se (12)) and [EtNP(E)(OC6H3Me2-2,6)](3) (E = O (9), S (11), Se (13)). The reaction leading to the formation of the triselenide 12 also produces small quantities of the diselenide [Et3N3P3(OR)(3)Se-2] (R = -(C6H3Pr2)-Pr-i-2,6) (14). The P3N3 ring in these lambda(5)-phosphazanes is highly distorted and resembles more of a twist-boat conformation. The DFT calculations on model systems [HNP(S)(OMe)](3) (15) and [HNP(Se)(OMe)](3) (16) indicate five low-lying unique conformers A-E. The chair conformer with a triaxial-OMe group is identified as the lowest-energy conformer in both cases.