Molybdenum complexes tetranuclear

The lanthanide metals, with their larger coordination numbers, invariably have the ligand coordinated in either a trismonodentate or a tetrakismonodentate fashion (42, 55, 57) (see Figs. 10 and 11). Thus, the ligand apparently tends toward the maximization of its coordinating capacity where circumstances allow, giving rise in many cases to the formation of sheet or cage structures. Limited chain formation was observed in the platinum, palladium, and rhodium complexes described, while the molybdenum complexes described by Hilbers et al. consist of dinuclear and tetranuclear units. 

Molecular examples of trivalent molybdenum are known in mononuclear, dinuclear, and tetranuclear complexes, as illustrated in Figure 5. The hexachloride ion, MoCk (Fig- 5a) is generated by the electrolysis of Mo(VI) in concentrated HCl. Hydrolysis of MoCP in acid gives the hexaaquamolybdenum(III) ion, Mo(H20) g, which is obtainable in solution of poorly coordinating acids, such as triflic acid (17). Several molybdenum(III) organometaUic compounds are known. These contain a single cyclopentadienyl ligand (Cp) attached to Mo (Fig. 5d) (27). 

Furthermore, chemical oxidation of [Mo(CO)6] with organic molecules containing acidic hydrogen gives rise to molybdenum species in the +2, -i-3 and +A oxidation states. Higher oxidation states (r-5 and -i-6) have been observed when halogens directly oxidize [Mo(CO)6], A Mo tetranuclear complex has been obtained when hydrochloric acid reacts with the tri-p-hydroxy-dimolybdenum complex, as shown in Equation 9.2 ... 

A few cluster complexes with fused triangles of molybdenum or tungsten have been reported. They are tetranuclear and hexanuclear cluster complexes, which may be viewed also as having fused incomplete cu-banes of M3E4. 

Mo(Tp )(CO)3(r 3-allyl)] requires higher potentials for a generally irreversible oxidation to proceed. The product of oxidation of [Mo(Tp )(CO)3l] with oxygen was a tetranuclear linear molybde-num(V) complex with terminal metal ions coordinated to Tp ligands and inner molybdenum(V) ions surrounded exclusively by oxygen donors.115... 

An example of the model complexes that point the way to potentially fascinating polymers in the future is given by the tetranuclear species 6.21 [49]. Remarkable square arrays of molybdenum-molybdenum quadruple bonds with oxalate spacers have also been prepared by simple assembly procedures, as illustrated by the formation of the complex Mog(oxalate)4(N-N)g (6.22) (N-N = di(p-methoxyphenyl)forma-midinate) (Fig. 6.11) from [Mo2(N-N)2(NCMe)2] and [oxalate] " [52]. 

Addition of PF3 to Mo2(OBu )e caused exchange of Bu 0 for F with the formation of the fluorine-bridged tetranuclear complex [Mo4()t,-F)4(OBu )8] containing a bisphenoid of molybdenum atoms with two short Mo=Mo (2.26 A) and four long nonbonding... 

Cotton FA, Shang M (1991) The stmcture of the molybdenum tetranuclear cluster complex Mo4Cl8(PEt3)4 how unrecognized disorder previously reduced the quality of the refinement. J Cluster Sci 2 121-129... 

Ryan TR, McCarley RE (1982) Synthesis and characterization of rectangular tetranuclear cluster complexes of molybdenum(II) by condensation of quadruply bonded dimers. Inorg Chem 21 2072-2079... 

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