Two　new　metavanadates,　Cu(tn)2(VO3)2　(tn　=　1,3-diaminopropane)　and　Ni(NH3)2(VO3)2,　have　been　prepared　under　hydrothermal　conditions　and　their　single-crystal　structures　determined　by　X-ray　diffraction.　Both　structures　consist　of　corner-sharing　VO4　tetrahedral　chains　with　complex　cations　occupying　the　interchain　positions.　While　there　dominantly　exist　electrostatic　interactions　between　the　Cu(tn)2/2+　fragments　and　the　vanadium　oxide　chains　in　Cu(tn)2(VO3)2,　the　Ni(NH3)2/2+　moieties　in　the　Ni(NH3)2(VO3)2　bridge,　the　vanadium　oxide　chains　into　a　three-dimensional　framework　structure　by　Ni-O　covalent　interactions.　The　magnetic　properties　were　measured　in　the　temperature　ranging　from　4　to　275　K.　It　is　shown　that　Cu(tn)2(VO3)2　possesses　well-separated　Cu2+　centers　and　that　the　magnetic　behavior　of　Ni(NH3)2(VO3)2　can　be　explained　based　on　a　one-dimensional　Ising　model.　©　2000　Elsevier　Science　B.V.