I would guess you purchase a static single domain certificate which only covers the domain name and not subdomain.
Sadly, www. is a sub by certificate standards.
If that is the case I see 3 moves you could make.
1. Purchase another certificate for the www. that you never plan on using and make a redirect. (Waste of cash, forget I even mentioned it. Unless you plan on using www.name_domain.com to host content one day.
2. Leave your name_domain.com as it is, create a new website in your IIS name it www.Redirect_domain.com. In your basic bindings settings assign the common IP (SSL/Non SSL) using port 80 http: www.name_domain.com. Save it.
In the HTTP Redirect make your permanent redirect to exact destination of name_domain.com (or relative if you are migrating for SEO reasons.)
3. Leave both on the one binding www.name_domain.com port 80 http and the name_domain.com on SSL port 443.
Now you'll have to work with a local redirect from any.name_domain.com to name_domain.com this can be done with your web.config.
My personal experience (The second option is best 2) is to take a few minutes and create a new IIS website for the www.name_domain.com and do the redirect to the https://name_domain.com
But this is only true if you're planning on 301 redirects from www.name_domain.com.
Your settings my be SSL "All Unassigned" if you have any issues with routing in your IIS bindings.