Diaqua(7,l5-dihydro-7,9,13,15-tetramethylpyrido[2',1',6':12,13,14][1,2,4,7,9,10,13]heptaazacyclopentadeca[3,4,5,6,7,8-aklmn][1,10]phenanthroline)cobalt(II) bis(tetrafluoroborate) [Co(H2O)2(tdmmb)][BF4]2