ok, sorry I found out what to do. Just for those wanting to know.
1. Select the paragraph style of the TOC
2. Click on tabs
3. Add a right-justify tab
4. Define "." as leader
5. Click OK
6. Click on the Spacer next to the TOC Headline to get to the tab position and you will see InDesign creates automatically the dots.... This last point was the riddle.
I wonder why InDesign doesn't offer Standardized TOC formats as simple as for instance Word...
However, tks Jimoblak for the support!!!! ;-)