You can remove quotes with stringr::str_remove_all()
library(stringr)
reproducibile_users_invite <-c("{\"firstName\":\"Emmanuel\",\"surname\":\"Emmanuel2\",\"email\":\"Emmanuel@email.com\",\"userCredentials\":{\"username\":\"EEmmanuel2\",\"userRoles\":[{\"id\":\"cBCK2qrYxyv\"}],\"catDimensionConstraints\":[{\"id\":\"MnQamDMlY87\"}]},\"organisationUnits\":[{\"id\":\"LndFoMpqBfp\"}],\"dataViewOrganisationUnits\":[{\"id\":\"LndFoMpqBfp\"}],\"userGroups\":[{\"id\":\"MA3AsjoPf3o\"}]}",
"{\"firstName\":\"Grant\",\"surname\":\"Grant2\",\"email\":\"Grant@email.com\",\"userCredentials\":{\"username\":\"GGrant2\",\"userRoles\":[{\"id\":\"cBCK2qrYxyv\"}],\"catDimensionConstraints\":[{\"id\":\"MnQamDMlY87\"}]},\"organisationUnits\":[{\"id\":\"LndFoMpqBfp\"}],\"dataViewOrganisationUnits\":[{\"id\":\"LndFoMpqBfp\"}],\"userGroups\":[{\"id\":\"MA3AsjoPf3o\"}]}",
"{\"firstName\":\"Patience\",\"surname\":\"Patience2\",\"email\":\"Patience@email.com\",\"userCredentials\":{\"username\":\"PPatience2\",\"userRoles\":[{\"id\":\"cBCK2qrYxyv\"}],\"catDimensionConstraints\":[{\"id\":\"MnQamDMlY87\"}]},\"organisationUnits\":[{\"id\":\"LndFoMpqBfp\"}],\"dataViewOrganisationUnits\":[{\"id\":\"LndFoMpqBfp\"}],\"userGroups\":[{\"id\":\"MA3AsjoPf3o\"}]}",
"{\"firstName\":\"Thomas\",\"surname\":\"Thomas2\",\"email\":\"Thomas@email.com\",\"userCredentials\":{\"username\":\"TThomas2\",\"userRoles\":[{\"id\":\"cBCK2qrYxyv\"}],\"catDimensionConstraints\":[{\"id\":\"MnQamDMlY87\"}]},\"organisationUnits\":[{\"id\":\"LndFoMpqBfp\"}],\"dataViewOrganisationUnits\":[{\"id\":\"LndFoMpqBfp\"}],\"userGroups\":[{\"id\":\"MA3AsjoPf3o\"}]}",
"{\"firstName\":\"Andrew\",\"surname\":\"Andrew2\",\"email\":\"Andrew@email.com\",\"userCredentials\":{\"username\":\"AAndrew2\",\"userRoles\":[{\"id\":\"cBCK2qrYxyv\"}],\"catDimensionConstraints\":[{\"id\":\"MnQamDMlY87\"}]},\"organisationUnits\":[{\"id\":\"nDd4i6SPeth\"}],\"dataViewOrganisationUnits\":[{\"id\":\"nDd4i6SPeth\"}],\"userGroups\":[{\"id\":\"MA3AsjoPf3o\"}]}",
"{\"firstName\":\"Nicholas\",\"surname\":\"Nicholas2\",\"email\":\"Nicholas@email.com\",\"userCredentials\":{\"username\":\"NNicholas2\",\"userRoles\":[{\"id\":\"cBCK2qrYxyv\"}],\"catDimensionConstraints\":[{\"id\":\"MnQamDMlY87\"}]},\"organisationUnits\":[{\"id\":\"nDd4i6SPeth\"}],\"dataViewOrganisationUnits\":[{\"id\":\"nDd4i6SPeth\"}],\"userGroups\":[{\"id\":\"MA3AsjoPf3o\"}]}"
)
str_remove_all(reproducibile_users_invite, '"')
#> [1] "{firstName:Emmanuel,surname:Emmanuel2,email:Emmanuel@email.com,userCredentials:{username:EEmmanuel2,userRoles:[{id:cBCK2qrYxyv}],catDimensionConstraints:[{id:MnQamDMlY87}]},organisationUnits:[{id:LndFoMpqBfp}],dataViewOrganisationUnits:[{id:LndFoMpqBfp}],userGroups:[{id:MA3AsjoPf3o}]}"
#> [2] "{firstName:Grant,surname:Grant2,email:Grant@email.com,userCredentials:{username:GGrant2,userRoles:[{id:cBCK2qrYxyv}],catDimensionConstraints:[{id:MnQamDMlY87}]},organisationUnits:[{id:LndFoMpqBfp}],dataViewOrganisationUnits:[{id:LndFoMpqBfp}],userGroups:[{id:MA3AsjoPf3o}]}"
#> [3] "{firstName:Patience,surname:Patience2,email:Patience@email.com,userCredentials:{username:PPatience2,userRoles:[{id:cBCK2qrYxyv}],catDimensionConstraints:[{id:MnQamDMlY87}]},organisationUnits:[{id:LndFoMpqBfp}],dataViewOrganisationUnits:[{id:LndFoMpqBfp}],userGroups:[{id:MA3AsjoPf3o}]}"
#> [4] "{firstName:Thomas,surname:Thomas2,email:Thomas@email.com,userCredentials:{username:TThomas2,userRoles:[{id:cBCK2qrYxyv}],catDimensionConstraints:[{id:MnQamDMlY87}]},organisationUnits:[{id:LndFoMpqBfp}],dataViewOrganisationUnits:[{id:LndFoMpqBfp}],userGroups:[{id:MA3AsjoPf3o}]}"
#> [5] "{firstName:Andrew,surname:Andrew2,email:Andrew@email.com,userCredentials:{username:AAndrew2,userRoles:[{id:cBCK2qrYxyv}],catDimensionConstraints:[{id:MnQamDMlY87}]},organisationUnits:[{id:nDd4i6SPeth}],dataViewOrganisationUnits:[{id:nDd4i6SPeth}],userGroups:[{id:MA3AsjoPf3o}]}"
#> [6] "{firstName:Nicholas,surname:Nicholas2,email:Nicholas@email.com,userCredentials:{username:NNicholas2,userRoles:[{id:cBCK2qrYxyv}],catDimensionConstraints:[{id:MnQamDMlY87}]},organisationUnits:[{id:nDd4i6SPeth}],dataViewOrganisationUnits:[{id:nDd4i6SPeth}],userGroups:[{id:MA3AsjoPf3o}]}"