Fixation and Release of Intact E4 Tetrahedra (E = P, As)

By the reaction of [NacnacCuCH(3)CN] with white phosphorus (P-4) and yellow arsenic (As-4), the stabilization and enclosure of the intact E-4 tetrahedra are realized and the disubstituted complexes [(NacnacCu)(2)(mu,eta(2:2)-E-4)] (1a: E=P, 1b: E=As) are formed. The mono-substituted complex [NacnacCu(eta(2)-P-4)] (2), was detected by the exchange reaction of 1a with P-4 and was only isolated using low-temperature work-up. All products were comprehensively spectroscopically and crystallographically characterized. The bonding situation in the products as intact E-4 units (E=P, As) was confirmed by theory and was experimentally proven by the pyridine promoted release of the bridging E-4 tetrahedra in 1.