Hydrazine clusters

Beu TA, Buck U, Siebers JG, Wheatley RJ. A new intermolecular potential for hydrazine clusters structures and spectra. J Chem Phys 2001 106 6795-6805. 

The 2,2 -bipyrazine (bpz)-substituted RU3 cluster monomer 42, dimer 43, and trimer 44 could be accessed by reaction of triruthenium precursor 2 with different amounts of 2,2/-bipyrazine [30]. The trimeric species 44 containing two parent Ru30(0Ac)6(py)2 n m and one derivate Ru30(0Ac)5(py)2II m m units could be directly prepared by reaction of 3.8 equivalents of 2 with 2,2/-bipyrizine. It is also accessible by reaction of dimeric species 43 with 1.8 equivalents of 2. The bpz adopts ri1 (N),(x-r 1 (N),r(1 (N) and p,4-r 1(N),r 1(N),r 1(C),r 2(N,N) bonding modes in 42, 43, and 44, respectively. Reduction of 3+ trimer 44 by addition of aqueous hydrazine allowed isolation of neutral intracluster mixed-valence species 44b containing three Ru 11,111,11 units. Oxidation of 44b with two... 

In contrast with formation of three types of bpz-substituted RU3 cluster species, reactions of 2 with pyq induced isolation of monomer 45 and trimer 46 containing 6>rf/ 6>-metallated pyq depending on the reaction conditions [30]. Reduction of the 3+ trimeric complex 46 by addition of aqueous hydrazine gave neutral species 46a. Oxidation of 46a by addition of two equivalents of ferrocenium hexaflu-orophosphate afforded 2+ intercluster heterovalent complex46b containing two Ru30(0Ac)6(py)2II,III,m and one Ru30(OAc)5(py)2II,m,n moieties. 

We are, however, focussing on using such a unit as a means of introducing possible analogs of intermediates in N2 fixation such as hydrazines, via modification of routes proven for such transformations in simple mononuclear Mo O complexes (81). In addition, synthetic routes to clusters containing more readily replaceable ligands on Mo (such as CO) are currently being explored. 

Using coupled cluster CCSD(T)//B3P86 methods, the Ea values for HERON rearrangement of model hydrazines 215b-d have also been computed to be between 24 and 34 kcalmoU The authors ruled out alternative concerted rearrangements, which were computed to be energetically unfavourable. 

In the case of giant wheel (molybdenum blue) compounds, the general synthetic strategy involves the acidification (pH 1) and reduction of an aqueous molybdate(VI) solution [possible reducing agents iron powder, tin(II) chloride, molybdenum(V) chloride, ascorbic acid, cysteine, hydroxylamine, hypophos-phorous acid, sodium dithionite, or hydrazine sulfate].On the other hand, an icosahedral ball-shaped cluster can be formed in an aqueous Mo(VI)... 

The final aim of this work is to encourage the experimental study of these complexes and understand the importance of the chiral effect of the different monomers within the final clusters as has been shown in the experimental study of hydrazine and lactate clusters. Another report on the different motifs of hydrogen peroxide clusters has also been published that shows similar energetic trends to the ones found in our work, but without considering their implications in the chiral recognition processes [119]. 

The structure of 46b shown in Fig. 2 is a tetramer, which is held together by Li clusters. The Li+ ions are bound to different units (Table VI) Lil connects the two units belonging to the monomer and is bound end-on to N3 and end-on to N2. By being bound side-on to N3a and N4a, the hydrazine unit of the second monomer, the coordination sphere of Lil is saturated. 

Thus, a number of systems of the catalytic and noncatalytic reduction of dinitrogen to hydrazin and ammonia and the successful synthesis of model iron- and iron-molibdenum (vanadium) clusters have been reported. These investigations have formed a basis for subsequent progress in mimicking the nitrogenase reaction. 

Coucouvanis, D., Mosier, P.E. Malinak, S. Laughlin, L. Demadis, K.D. (1995) Catalytic reduction of hydrazine and acetylene to ammonia and ethylene and stoichiometric reduction of CN to ammonia and methane by Fe/M/S clusters (M =Mo, V) with structural features similar to those of the Fe/Mo/S site in nitrogenase, Plant Sci. Biotechnol. Agric. (Nitrogen Fixation Fundamentals and Applications) 27, 137-42. 

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