Issue 30, 2009

Crystal structure of octabromoditechnetate(iii) and a multi-configurational quantum chemical study of the δ→δ* transition in quadruply bonded [M2X8]2− dimers (M = Tc, Re; X = Cl, Br)

Abstract

The technetium(III) compound (n-Bu4N)2[Tc2Br8] was prepared by metathesis of (n-Bu4N)2[Tc2Cl8] with concentrated aqueous HBr in acetone and recrystallized from acetone–diethyl ether solution (2 : 1 v/v). The acetone solvate obtained, (n-Bu4N)2[Tc2Br8]·4[(CH3)2CO] (1), crystallizes in the monoclinic space groupP21/n with a = 13.8959(8) Å, b = 15.2597(9) Å, c = 15.5741(9) Å, β = 109.107(1)°, R1 = 0.028, and Z = 4. The Tc–Tc distance (2.1625(9) Å) and the average Tc–Br distances (2.4734(7) Å) are in excellent agreement with those previously determined by EXAFS spectroscopy. These and other experimental data on quadruply metal–metal bonded group 7 [M2X8]2− dimers (M = Tc, Re; X = Cl, Br) are compared to the results of a set of multi-configurational quantum chemical studies. The calculated molecular structures of the ground states are in very good agreement with the structures determined experimentally. The theory overestimates the δ→δ* transition energies by some 1 000 cm−1, but mimics the trends in δ→δ* energies across the series.

Graphical abstract: Crystal structure of octabromoditechnetate(iii) and a multi-configurational quantum chemical study of the δ→δ* transition in quadruply bonded [M2X8]2− dimers (M = Tc, Re; X = Cl, Br)

Supplementary files

Article information

Article type
Paper
Submitted
02 Feb 2009
Accepted
03 Apr 2009
First published
08 May 2009

Dalton Trans., 2009, 5954-5959

Crystal structure of octabromoditechnetate(III) and a multi-configurational quantum chemical study of the δ→δ* transition in quadruply bonded [M2X8]2− dimers (M = Tc, Re; X = Cl, Br)

F. Poineau, L. Gagliardi, P. M. Forster, A. P. Sattelberger and K. R. Czerwinski, Dalton Trans., 2009, 5954 DOI: 10.1039/B902106J

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