Bond compounds with complexes containing

REACTIONS OF LOW VALENT METAL COMPOUNDS WITH COMPLEXES CONTAINING METAL—METAL MULTIPLE BONDS. 

The chemistry of technetium is quite complex especially because of its numerous oxidation states (4-7 to -1). In the higher oxidations states (Tc(IV) to Tc(VII)), the metal behaves as a hard Lewis acid and its chemistry is dominated by multiple-bonded oxo ligands. The lower oxidation states ions can be classified as soft metals and will form stable compounds with hgands containing the following donor atoms P, As, S, Se, X (except F ), N, and itt-acceptors such as CO, NO, and isonitriles. 

Similar behavior is observed for calix[4]arene (see Calixarenes) complexes of the type (89). Moreover, the oxygen donor atoms are particularly appropriate for the oxophilic early transition metals. A rich chemistry has been developed with complexes containing zirconium - carbon bonds. In this area, aryne zirconocene compounds can be thermally generated and isolated withont trimethylphosphane additional coordination. Zirconium-bntadiene chemistry has been explored as well and constitutes a source of zircoiuum complexes. 

Since silicon is an analog of carbon in the Periodic System, it is important to survey reactions of Si-H compounds with complexes of metals in low oxidation states. Similar to C-H compounds, derivatives containing Si-H bonds easily react with low-valent metal complexes via oxidative addition mechanism to afford hydridosilyl or silyl compounds. Typical examples of such reactions [70] are shown below. 

The phosphido complex, Th(PPP)4 [143329-04-0], where PPP = P(CH2CH2P(CH2)2)2) has been prepared and fully characterized (35) and represents the first actinide complex containing exclusively metal—phosphoms bonds. The x-ray stmctural analysis indicated 3-3-electron donor phosphides and 1-1-electron phosphide, suggesting that the complex is formally 22-electron. Similar to the amido system, this phosphido compound is also reactive toward insertion reactions, especially with CO, which undergoes a double insertion (35,36). 

Cychc polyarsines undergo a number of reactions with transition metal compounds to form complexes containing both As—As and As—metal bonds. The stmctural chemistry of these complexes has been the subject of a recent review (112). 

The moments of complexes containing NO offer a puzzling problem. The diamagnetism of compounds of iron and ruthenium suggests that Feiv and RuIV form a double bond with NO, making seven bonds in all, which woud lead to /t = 0. But this structure cannot be applied to [Co(NH3)6-NO]Cl2, which has a moment corresponding to a triplet state. Further study of such complexes is needed. 

The reactivity of a remarkable electronically unsaturated tantalum methyli-dene complex, [p-MeCgH4C(NSiMe3)2]2Ta( = CH2)CH3, has been investigated. Electrophilic addition and olefination reactions of the Ta = CH2 functionality were reported. The alkylidene complex participates in group-transfer reactions not observed in sterically similar but electronically saturated analogs. Reactions with substrates containing unsaturated C-X (X = C, N, O) bonds yield [Ta] = X compounds and vinylated organic products. Scheme 117 shows the reaction with pyridine N-oxide, which leads to formation of a tantalum 0x0 complex. ... 

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