Dinuclear species

Molybdenum(V) compounds generally occur as mononuclear or dinuclear species. Molybdenum pentachloride [10241-05-1] MoCl, formed by combination of the elements, serves as a usebil and reactive starting material (Fig. 1). MoCl has a dinuclear stmcture (Fig. 3) in the soHd state but is mononuclear in the gas phase. In solution or in the soHd state the compound, actually Mo2C1 q (Fig- 3a), is readily hydroly2ed in air to form MoOCl ... 

The different nucleophilicities of 3,5-dimethyl- and 3,5-bis(trifluoromethyl) pyrazoles are shown by their reactions widi lraas-[Rh(CO)Cl(Ph3P)2]. The dimethyl derivative gives die dinuclear species similar to 111. The less nucleophilic fluorine derivative gives 116, where die pyrazole ring is monodentate. The fluoro compound similar to 111 [L2 = (CO)2l may be obtained in the absence... 

ICA(238)179). Further reaction of the l,3-di- o-propyl-derivative with water gives the dinuclear species 24. 

On carbonylation in methylene chloride it undergoes the substitution of the diene ligands, rearrangement, and cis-trans isomerization to yield 64 (97JOM(530) 259). l,r-(l,2-Ethylene)-3,3 -imidazol-2,2 -diylidene and the dimer [(T -cod)Rh (ir-Cl)] form the dinuclear species 65. 

With [RUjfCOlij], dinuclear species 161 emerges (88JCS(D)1437). In contrast, with [Os3(CO) q(AN)J, two isomers, 162 and 163, result (88JOM (353)251). Isomer 162 enters the CO/AN monosubstitution reaction in acetonitrile in the presence of Mc3N0-2H20, the product on subsequent thermolysis forms the hexanuclear complex 164. 

A related dinuclear species 77, recently described, constitutes the first dinuclear gold(I) complex with heterobridged phosphor-1,1 -dithiolato moieties and bis(ylide) bridging ligands [ 102]. It is obtained by reaction between [ AuS2PPh2] and the diylide gold complex 74 (R=Me). No intermolecular Au-Au interaction is observed in 77 but the oxidative addition of chlorine to the product leads to a new complex 78 in which a single bond is formed between the two Au(II) centers (Scheme 26). 

The active catalyst is probably a dinuclear species in which the chiral ligand replaces isopropoxide. 

Complex (51b) was prepared according to Equation (11). The dangling formyl groups can be used for further derivatization (e.g., (517) shown in Figure 16), and (516) serves as a valuable starting material for the synthesis of macrocyclic dinuclear species (compare Section 6.3.4.12).1367... 

Cd thiolates and selenolates tend to form q-S- or q-Se-bridged dinuclear species, even with bulky organic groups, e.g., 2,4,6-tri-t-butylphenyl.317 318 With some ligand combinations, heterocubanes with Cd4S4 core or oligonuclear species derived from heterocubanes are formed.319,320... 

Hydrolysis of ferric solutions is readily induced by addition of base. Initially, at rather acid pH, the purple ferric aqua-ion Fe(H20)63+, upon addition of base undergoes the first deprotonation step (equation 5), which is followed by reversible dimerization (equation 6), giving a yellow solution of mono- and dinuclear species ... 

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