Crystal Structure of a Supramolecular Complex Built up from Molybdenum(II) Trifluoroacetate and Copper(II) Schiff-Base Components, [{CuL t-Bu } 2 {Mo 2 (O 2 CCF 3 ) 4 } 3 (H 2 O) 2 ] n , H 2 L t-Bu = 2,3-bis((5- tert -butyl-2-hydroxybenzylidene)amino)-2,3-butenedinitrile