NbCl(dimethoxyethane) has received significant attention as a reagent for reductive coupling of carbonyls and imines. It is sold as a 1,2-dimethoxyethane complex. Nb(III) adducts are also known for 1,4-dioxane and diethyl ether.
Niobium(III) chloride forms a series of compounds with the formula NbClL with Nb=Nb double bond. With tertiary phosphines and arsines, the complexes are edge-share bioctahedra, e.g., NbCl(PPhMe). 
Thioethers form adducts with one bridging thioether (RS).  These face-sharing bioctahedra have the formula NbX(RS) (X = Cl, Br).