Review of crystallographic and molecular structures of complexes formed between N,N'-dialkyloxamides, N,N'-dialkyldithio-oxamides, N,N'-dialkylmalonamides, N,N'-dialkyldithiomalonamides, N,N'-dialkylsuccinamides, and toluene, 3,4-dithiol with Group VB and Group IV metal halides