Heptanuclear compounds

A substantial number of Mo peroxo complexes has been structurally characterized. These complexes all have nearly symmetrically side-on-bound peroxide. Among them are mononuclear, dinuclear, tetranuclear and heptanuclear compounds. The tetranuclear and hep-tanuclear complexes are related to the isopoly molybdates. Structural studies have identified... 

The versatile binding modes of the Cu2+ ion with coordination number from four to six due to Jahn-Teller distortion is one of the important reasons for the diverse structures of the Cu-Ln amino acid complexes. In contrast, other transition metal ions prefer the octahedral mode. For the divalent ions Co2+, Ni2+, and Zn2+, only two distinct structures were observed one is a heptanuclear octahedral [LnM6] cluster compound, and the other is also heptanuclear but with a trigonal-prismatic structure. 

Cr CNNi(tetren) 6](C104)9 is a red-purple solid, soluble in water-acetonitrile mixtures where the undissociated heptanuclear entity can be identified by electrospray ionization mass spectrometry. IR spectroscopy shows the presence of a unique /cn band at 2146 cm of the bridging cyano ligand and an intense band of the perchlorate anion at cr = 1090 cm The IR spectrum of the C-enriched compound prepared from K3[Cr( CN)6] displays a /cn band at 2103 cm The compound crystallizes in a trigonal system, space group R3, with parameters a = b = 15.274 A and c = 41.549 A. The magnetic properties indicate a ferro-... 

Scheme 8.16 Preparation of the trinuclear PtW2 complex 60, and schematic representations of the molecular structures of the pentanuclear PtW2Cu2 and the heptanuclear Pt4W3 compounds 61 and 62, both prepared from 60 as a precursor ([W] = W(CO)2(C5H5), [Cu]=Cu(C5Me5), R = p-Tol)...

The heptanuclear complex [Cu°(tren)]6[Mo (CN)g] (C104)g (204) is characterized by the presence of six noninteracting Cu(ll) ions that surround the central diamagnetic [Mo (CN)g]" fragment [Fig. 45(Z))]. Upon irradiation with blue light (406 15 nm) at lOK, the compound exhibits a gradual increase in magnetic susceptibility that saturates after 10 h of continuous irradiation [Fig. 70(a)]. This effect was explained as a photoinduced electron transfer from Mo(lV) to Cu(ll) ions, which is promoted by the irradiation into the intervalence MMCT band... 

Compound 82, containing a deprotonated bridging A-hydroxyglutarimide, was obtained in an unusual hydroxylamine elimination and cyclization reaction upon reaction of lb with glutaroddiydroxamic acid (132). Even four distinct hydroxamate binding modes were observed in a heptanuclear Ni(ll) complex with 2-(dimethylamino)phenylhydroxamic acid (2-dmAphaH), [Ni7(2-dmAphaH-l)2 (2-dmApha)g(H20)2]S04- I5H2O (133). 

The use of [Mn (salen)(H20)] with the potassium salt of hexacyanomet-allate(III) leads to heptanuclear complexes [27,28]. hi one case, however, a trinuclear FeMn2 complex was isolated by Long and coworkers [27] however, the crystal contains dimeric [Mn(salen)(H20)]2 species, two mononuclear Mn complexes, and one Fe(CN)g molecule. It is interesting to note here that the stoichiometry corresponds to a neutral FeMns compound. The same situation is found for the heptanuclear complex based on hexacyanoferrate that CO crystallizes with one molecule of Fe(CN)g to lead to the FeMna neutral stoichiometry as well [28]. 

Both compounds contain the carbide atom in an octahedral cavity. The hydride cluster is a simple octahedron with three terminal carbonyls on each rhenium atom. The heptanuclear cluster can instead be considered as the same octahedron in which the two hydrides are replaced by a [Re ( 0)3] fragment leading to a monocapped octahedral cluster. Both structures have seven skeletal dectron pairs. 

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