Manganese butterfly structure

Proposals for the structure of the manganese site in the SI state include cube (18) and "butterfly structures (19), both with bridging /i3-oxos. Three alternative geometries for the cluster, consistent with our results and with distorted versions of the proposed models, are suggested in figure 7. 

Figure 52 shows the structure of [Mn4" (HL33)(L33)(NCS)4], which can also be viewed as either a dimer-of-dimers or a severely distorted butterfly. The links between the two macrocycles are two triply bridging alkoxide donors, one from each macrocycle. The wings of the butterfly have closed to bring the two outer manganese ions quite close to one another an extension of this movement would result in formation of a cubane. 

The results of the XAS and EPR data, combined with knowledge from model complexes, (discussed later) allow for the formulation of structural models of the OEC. Many manganese compounds have been proposed as structural models for the OEC, ranging from butterfly arrangements to adamantanes to cubanes (26, 27,29-34, 50). Most of those proposals, however, are inconsistent with the known structural data for the OEC. Currently the most widely favored model is the dimer of dimers model (Scheme 11), first suggested by Klein,... 

A large fraction of the binuclear mixed chalcogen/carbonyl transition metal complexes of iron and manganese contain the M2E (CO)6 core with the butterfly-type structure (n = 2) or substructure (n — 3, see Section 1.10.3). As an example of a complex with thiolate ligands, the structure of [Fe2(SC3H7)2(CO)6] is shown in... 

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