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

we're being quite rigorous with technique;  I saw the student set up the reaction.  Vac transfer of the TMSCl was fine.  We got product, but only about 10% yield.  Lots of stuff remaining in solution.  We are using a slight excess of TMSCl, but perhaps we need more?

thanks in advance, any lurkers out there,

Adam