What kind of isomerism does Ni(PPh3)2Cl2 have and what is their IUPAC name?
A metal phosphine complex, dichlorobis(triphenylphosphine)nickel(II) exists in two isomeric forms (blue and red) based on how you prepared it (Wikipedia). The blue isomer, which is paramagnetic can be prepared by treating hydrated nickel chloride ($\ce{NiCl2.6H2O}$) with triphenylphosphine in alcohols or glacial acetic acid. When allowed to crystallize from chlorinated solvents (e.g., dicloroethane (Ref.1), dicloromethane (Ref.2)), the tetrahedral isomer converts to the square planar red isomer, which is trans and diamagnetic:



References:


Benedetto Corain, Bruno Longato, Roberto Angeletti, Giovanni Valle, “trans-[Dichlorobis(triphenylphosphine)nickel(II)]•$\ce{(C2H4Cl2)2}$: a clathrate of the allogon of venanzi's tetrahedral complex,” Inorganica Chimica Acta 1985, 104(1), 15–18 (https://doi.org/10.1016/S0020-1693(00)83780-9).
A. S. Batsanov,  J. A. K. Howard, “trans-Di­chloro­bis­(tri­phenyl­phosphine)­nickel(II) bis­(di­chloro­methane) solvate: redetermination at $\pu{120 K}$,” Acta Cryst. 2001, E57, m308–m309 (https://doi.org/10.1107/S1600536801008741).