The　hydrothermal　reaction　of　V2O5,　NiCl2.　6H(2)O,　ethylenediamine　and　H2O　in　the　mole　ratio　1:1:4.9:120　at　150　degrees　C　for　55　h　produced　violet　prismatic　crystals　of　Ni(en)(3)(VO3)(2).　The　crystal　of　the　title　compound　is　hexagonal　P6(1),　a　=　8.986(1),　c　=　34.031(2)　Angstrom,　V=　2379.8(5)　Angstrom(3),　Z　=　6,　D-calc　=　1.829　g　cm(-3)　and　R　=　0.0609　for　1406　observed　reflections.　The　structure　of　Ni(en)(3)(VO3)(2)　consists　of　spiral　anion　(VO3)(infinity)　chains　formed　by　corner-sharing　VO4　tetrahedra　with　Ni(en)(3)(2+)　complex　cations　occupying　the　interchain　positions,　where　there　are　electrostatic　interactions　and　hydrogen　bonds　between　the　anion　chain　and　the　complex　cation.　The　title　compound　is　the　first　example　of　a　vanadium　compound,　in　which　the　repeat　unit　of　the　chain　is　12-nuclear　corner-sharing　tetrahedra,　V12O36.　The　magnetic　susceptibility　of　the　title　compound　has　been　studied.　(C)　2000　Elsevier　Science　S.A.　All　rights　reserved.