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(NCCH)]BF. 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 P{H} NMR spectrum of complex 2 consists of a broad signal, as is common for such complexes, whereas complex 3 shows splitting of the P{H} NMR signal into a pseudoquartet due to Cu-P coupling, a rare occurrence exhibited only by highly symmetrical copper(I) phosphine complexes.