Inorganic Chemistry, Vol.48, No.15, 7452-7456, 2009
Heterobimetallic Bismuth(III)/Molybdenum(VI) and Antimony(III)/Molybdenum(VI) Calix[5]arene Complexes. Progress toward Modeling the SOHIO Catalyst
The treatment of the monometallic bismuth or antimony complexes [M{(t)BuC5(H)(2)}] (M = Bi, Sb) with 1.5 equiv of MoO2((OBu)-Bu-t)(2) in 1,2-dimethoxyethane (DME) produced soluble Bi-III/Mo-VI and Sb-III/Mo-VI heterometallic calix[5]arene complexes [Bi2Mo4O11{(t)BuC5(H)}(2)] 1 and [Sb2Mo4O11{(t)BuC5(H)}(2)] 2 in 55 and 45% yields, respectively. In solution the H-1 NMR patterns for 1 and 2 are characteristic of a C-s symmetry with three pairs of doublets for the methylene protons and three singlets in a 1:2:2 ratio for the tert-butyl groups. Complex 1 crystallizes in the P (1) over bar space group and consists of a dimeric heterometallic Bi/Mo (1:2 ratio) complex featuring an overall Mo4Bi2O21 oxo cluster. The remarkable oxo-rich core structure of 1 contains Bi(mu-O)Mo, Mo(mu-O)Mo, Mo = O center dot center dot center dot Mo, and Bi-O-Bi interactions that resemble aspects of the proposed SOHIO catalyst active site and the crystal structure of the Bi2Mo2O9 oxide phase.