This is Clematis Henryi. I have just ordered one to grow over an arbor.
In my experience, these are tricky plants and slow to establish themselves. When they are unhappy, there's not a damn thing you can do about it. When they are happy on a sunny fence, they are great. They supposedly like their feet cool, shaded, and mulched.
I've tried everything but, like people, they just go their own way and follow their own path, whether it leads to heaven, hell, or Paramus.
I also like Sweet Autumn Clematis, which is a tougher, more forgiving variety.