We're trying to follow the old Chisholm prep from 1981 (http://dx.doi.org/10.1021%2Fic50220a049) and are getting super low yields.  Any words of advice?

Ta(NMe₂)₅ + 2 TMSCl --> [TaCl₂(NMe₂)₃]₂ + 2 TMSNMe₂