6533b871fe1ef96bd12d0f92

RESEARCH PRODUCT

Relaxed but highly compact diansa metallacyclophanes.

subject

description

A series of monoansa [μ-1,1′-PR-3,3′-Co(1,2-C2B9H10)2]− and diansa [8,8′-μ-(1″,2″-benzene)-μ-1,1′-PR-3,3′-Co(1,2-C2B9H9)2]− (R = Ph, tBu) cobaltabisdicarbollidephanes have been synthesized, characterized and studied by NMR, MALDI-TOF-MS, UV-visible spectroscopy, cyclic voltammetry, and DFT calculations. Single crystal X-ray diffraction revealed a highly relaxed structure characterized by the title angle α of 3.8° ([7]−), this being the smallest angle α for a metallacyclophane. In such compounds, the metal-to-phosphorus distance is less than the sum of their van der Waals radii. The availability of a phosphorus lone pair causes an electron delocalization through the metal, as shown by the abnormal 31P NMR chemical shift. Remarkably, the combination of a phosphine donor and a phenyl acceptor moieties causes a synergistic effect that is observed through the different techniques used in this study. The importance of having an available lone pair is demonstrated by the oxidation of phosphorus with hydrogen peroxide, sulfur, and elemental black selenium to produce the corresponding PV compounds. When the electron lone pair is used to form the bond with the corresponding chalcogen atom, the communication between the donor and acceptor moieties on the diansa metallacyclophane is shut down. Spanish Ministerio de Ciencia e Innovacion (CTQ2010-16237), CSIC (I3P grant to P.F.) and the Generalitat de Catalunya 2009/SGR/00279. peer-reviewed