What does it mean in a Ni(II)complex if the HNMR spectrum appears unbroadened and unshifted & what does this tell you about the coordination geometry?
If the proton spectrum is unbroadened and not shifted out of the ~0-10ppm range, then I would have to say it is a diamagnetic compound.

It could be low spin square planar.  Tetrahedral and octahedral d8 cannot be diamagnetic.



Image source: http://upload.wikimedia.org/wikipedia/commons/a/a6/Chem507f09sqvstet2.png

Could also be two nickel atoms in the complex that are antiferromagnetically
coupled for a net spin of zero.