Supramolecular adducts based on weak interactions between the trimeric Lewis acid complex (perfluoro-ortho-phenylene)mercury and polypnictogen complexes

Abstract

Reactions of the trinuclear Lewis acid perfluoro-ortho-phenylene)mercury [(o-HgC₆F₄)₃] (1) with the polypnictogen complex [CpMo(CO)₂(η³-P₃)] (2) containing a cyclo-P₃ ligand and the series of E₂ complexes [{CpMo(CO)₂}₂(μ,η²:η²-E₂)] (E = P(3a), As(3b), Sb(3c), Bi(3d)) are reported. In all cases, the reaction products show very weak interactions between the E_n ligand complexes and the Lewis acid 1, as evidenced by their highly dynamic behaviour in solution and the formation of adducts in the solid state showing Hg⋯E contacts below the respective sum of the van der Waals radii. The complexes 2 (P₃), 3a (P₂) and 3b (As₂) show interactions of only one pnictogen atom with all three Hg atoms of 1. The complex 3c (Sb₂) forms two adducts with 1 showing either a side-on coordination of the Sb₂ dumbbell towards Hg or an end-on coordination of both Sb atoms towards two independent molecules of 1. The Bi₂ complex 3d shows an almost parallel alignment of the Bi₂ dumbbell situated above the center of the planar Lewis acid 1. The arrangements of the E₂ complex series towards 1 are rationalized with the help of electrostatic potential maps obtained by DFT calculations. Finally the structural characterizations of a new modification of the free Sb₂ complex 3c, the Bi₂ complex 3d, the starting material of its preparation [Bi{CpMo(CO)₃}₃] (4) and an unprecedented ‘Cr₄As₅’ cluster 5 are presented.