Copper(I) Complexes of a Flexible Bis-phospholane Ligand: Route to Paddle-Wheel- and Box-Type Macrocycles

Two bis-phospholane copper­(I) metallamacrocycles were selectively synthesized starting from the same two building blocks, namely, ligand 1 and [Cu­(NCCH₃)₄]­BF₄. Reaction conditions (ligand:metal (L:M) ratio and dilution) can be tuned to obtain either a paddle-wheel- (2, L:M = 3:2) or box-type complex (3, L:M = 8:4). Their structures were unequivocally determined by X-ray crystallography. The solution ³¹P­{¹H} NMR spectrum of complex 2 consists of a broad signal, as is common for such complexes, whereas complex 3 shows splitting of the ³¹P­{¹H} NMR signal into a pseudoquartet due to ^63,65Cu–³¹P coupling, a rare occurrence exhibited only by highly symmetrical copper­(I) phosphine complexes.