apparently there is no data tag support on level events configuration.
Support for stuff like these is useful.

give @p chest[container=[{slot:0,item:{id:"minecraft:iron_pickaxe",count:1}},{slot:1,item:{id:"minecraft:iron_axe",count:1}},{slot:2,item:{id:"minecraft:iron_hoe",count:1}},{slot:3,item:{id:"minecraft:iron_shovel",count:1}},{slot:4,item:{id:"minecraft:iron_helmet",count:1}},{slot:5,item:{id:"minecraft:iron_chestplate",count:1}},{slot:6,item:{id:"minecraft:iron_leggings",count:1}},{slot:7,item:{id:"minecraft:iron_boots",count:1}},{slot:8,item:{id:"minecraft:shield",count:1}}]] 1

Nevermind, it works. I forgot about character escapes

Happy you found a solution ^ ^