Nickel(II) complexes of novel ligands containing a tetraazabicyclononane ring: synthesis and structures of [3,7-bis(2-aminoethyl)-1,3,5,7-tetraazabicyclo[3.3.1]nonane]nickel(II) perchlorate and (8-methyl-1,3,6,8,10,13,15-heptaazatricyclo[13.1.1.113,15]octadecane)nickel(II) perchlorate