1,1′-Bis(N,N-dimethylamino)ferrocene,1,1′-bis(N,N-dimethylamino) cobaltocenium hexafluorophosphate and 1,1′-bis(N,N-dimethylamino)titanocene dichloride. Crystal structure of 1,1′-bis(N,N-dimethylamino)titanocene dichloride