Add AD Groups to Sharepoint Online Group using CSOM

I have the following situation:



The hole point is to add both the users and the groups from AD to Sharepoint. I got adding the users to work using the following code:

    User adUser = ctx.Web.EnsureUser(ad.LogOnName);
    ctx.Load(gc, x => x.Users);

Where the LogOnName is the User Principal Name of the user. When adding the groups as LogOnName is used the group name.

Any suggestions where I am mistaken wehn adding the groups?