What social networks provide corporate intranet accounts for business?

Question

Social media

And are there any convenient services at all that allow you to create your own corporate social network with access control by groups, personal messages and a general feed like Facebook, Vkontakte, Google+, etc.?
In groups, it should also be convenient to download and view various materials (documents, photos, videos, links). And it is convenient to manage these groups and all accesses.
PS Do not offer Bitrix24 - there, in my opinion, there is a very unusable interface for this task, and too many clicks need to be done to work with at least a dozen groups and a dozen posts in the feed. And it should be really convenient and fast for a large number of groups and employees (from hundreds to several thousand).

Answer 1

What's wrong with a closed group in VK?