Niobate(8-), bis(mu12-(orthosilicato(4-)-O:O:O:O':O':O':O'':O'':O'':O''':O''':O'''))heneicosa-mu-oxobis(pentadeca-mu-oxononaoxononatungstate)hexa-, octahydrogen, compd. with N,N-dimethylmethanamine (1:8)