  The complete set of structural parameters of the new series of compounds
NiNb$_{2-x}$V$_x$O$_6$ ($0\leq x \leq 2$) with the unusual columbite-type
structure is presented here. In the samples containing vanadium, this
crystalline structure was stabilized by synthesis in conditions of high
pressure and high temperature. Here we report here the first Raman spectrum for
the NiV$_2$O$_6$-\textsl{Pbcn} polymorph and extend the list of the previously
observed modes for the NiNb$_2$O$_6$. The evolution of the vibrational Raman
spectrum produced when the vanadium is substituted for niobium along the series
is also presented and discussed. This evolution is interpreted by taking into
account the changes in the local structural environment of the niobium/vanadium
atoms and its influence over the nickel-oxygen bonds around them. The presence
of vanadium atoms favors an increase of the symmetry in the arrangement of
oxygen atoms around the nickel-ones; in counterpart, the vanadium is in an
octahedral environment which is more distorted than that of the niobium.
Because of these apparently subtle differences, the homogeneous distribution of
vanadium in the solid solution NiNb$_{2-x}$V$_x$O$_6$ is not possible.
