(3as.3'as.7as)-1.1'.3.3'-tetrabenzyl-2.2-dibromo-3a.3'a.4.4'.5.5'.6.6'.7.7'.7a.7'a-dodecahydro-2.2'-spirobi[cyclohexa[d]1.3-diaza-2-nickelacyclopentane]