Can not detect Item inside the chest

I cant detect the items inside the chest here is the command:
/testforblock 691 18 -317 chest 4 {Items:[

{id:minecraft:diamond,Slot:0b,Count:2b}

]}
here is the error dysplay the command block:
[20:11:07] El análisis de la dataTag falló: Expected '}' but got ':' at: {Items:[{id:minecraft:<--[HERE]