
%0 Journal Article
%A Rossignoli, Monica 
%A Burns, Robert C. 
%A Craig, Donald C. 
%T Photolytic, Pyrolytic and Trimethylamine <emph type="2">N</emph>-Oxide Induced CO Removal from [BiFe<emph type="8">4</emph>(CO)<emph type="8">16</emph>]<emph type="7">3&#x2013;</emph>: Synthesis, X-Ray Crystal Structure and Properties of [N(PPh<emph type="8">3</emph>)<emph type="8">2</emph>]<emph type="8">2</emph>[Bi<emph type="8">2</emph>Fe<emph type="8">5</emph>(CO)<emph type="8">17</emph>]
%J Australian Journal of Chemistry
%D 2001/05/11
%V 53
%N 12
%P 975-982
%K Anionic clusters; photolysis; pyrolysis; bismuth; organotransition metal compounds; group 15 elements; trimethylamine N-oxide.
%R https://doi.org/10.1071/CH00148
%U https://www.publish.csiro.au/paper/CH00148 
%X The formation of anionic-cluster species from compounds containing the &#8216;open&#8217; (i.e. non-cluster) &#91;BiFe4(CO)16&#93;3&#8211; (or &#91;Bi&#123;Fe(CO)4&#125;4&#93;3&#8211;) ion following loss of CO as a result of photolytic, pyrolytic and chemical means has been investigated. Photolysis of salts of the &#91;BiFe4(CO)16&#93;3&#8211; ion in acetonitrile, where the associated cations are &#91;N(PPh3)2&#93;+ or &#91;NEt4&#93;+, produce a range of species including &#91;Bi2Fe5(CO)17&#93;2&#8211;, &#91;Bi2Fe4(CO)9&#93;2&#8211;, &#91;Bi2Fe3(CO)9&#93;2&#8211;, &#91;Fe2(CO)8&#93;2&#8211; and &#91;Fe4(CO)13&#93;2&#8211;, with the distribution of species being cation dependent. The previously unknown &#91;Bi2Fe5(CO)17&#93;2&#8211; ion was obtained as the &#91;N(PPh3)2&#93;+ salt, crystallizing in the triclinic space group P 1, with a 15.851(7), b 17.199(8), c 20.020(8) &#197;, &#945; 114.72(2), &#946; 95.51(3), &#947; 113.01(2)o, Z 2 and V 4338(3) &#197;3. The structure was determined by X-ray diffraction methods to an R of 0.035 (Rw = 0.040) for 6778 independent observed reflections. The anion consists of a central square-based pyramidal &#8216;nido-Bi2&#91;Fe(CO)3&#93;3&#8217; cluster unit, with two external Fe(CO)4 fragments attached to the two trans four-coordinate bismuth atoms located in the base of the pyramid. A thermogravimetric study of &#91;NEt4&#93;3&#91;BiFe4(CO)16&#93; indicated decomposition above 150&#x02DA;C, with an apparent loss of three CO molecules per &#91;BiFe4(CO)16&#93;3&#8211; ion below 160&#x02DA;C. Decomposition was complete by 205&#x02DA;C and also involved pyrolysis of the &#91;NEt4&#93;+ cations. Pyrolysis of solid &#91;NEt4&#93;3&#91;BiFe4(CO)16&#93; at 160&#x02DA;C for several hours under N2 implicated an intermediate species in the Bi/Fe carbonyl anion system, probably &#91;Bi2Fe3(CO)9&#93;2&#8211;, in addition to the &#91;Fe2(CO)8&#93;2&#8211; ion, although the final product obtained was found to be &#91;Bi2Fe4(CO)13&#93;2&#8211;. Reaction of &#91;NEt4&#93;3 &#91;BiFe4(CO)16&#93; with trimethylamine N-oxide in acetonitrile, in an attempt to selectively remove CO by chemical means, lead to the slow formation of &#91;Bi2Fe4(CO)13&#93;2&#8211; and a little &#91;Bi2Fe5(CO)17&#93;2&#8211;, although the &#91;Bi2Fe5(CO)17&#93;2&#8211; was observed to react slowly with (CH3)3NO to give &#91;Bi2Fe4(CO)13&#93;2&#8211; as the major product. Conversion of &#91;Bi2Fe5(CO)17&#93;2&#8211; to &#91;Bi2Fe4(CO)13&#93;2&#8211; is likely initiated through nucleophilic attack at the axial carbon site of a pendant Fe(CO)4 group, according to extended-H&#220;ckel molecular orbital calculations. Calculations also show that there is no instability introduced in having a second pendant Fe(CO)4 attached to the central cluster unit, and the anion can be produced by reaction of &#91;Bi2Fe4(CO)13&#93;2&#8211; with Fe2(CO)9 in tetrahydrofuran, through the addition of an Fe(CO)4 fragment to the three-coordinate bismuth atom in the anion. The other product of the reaction is volatile Fe(CO)5, which is easily separated from the desired product. 
