Dimetal complexes

Reaction of ButadiynediyI dimetal Complexes with Fc2(CO)9 Formation of Various Complexes with the C4 bridge... 

The interaction of butadiynediyl dimetal complexes [Fp -C -CsC-M, Fp =FeCp (CO)2, M= Fp, Rp, SiMea, Rp= RuCp(CO)2] with diiron nonacarbonyl, Fe2(CO)9, results in the formation of a mixture of products, as is also observed in the case of their interaction with organic acetylenes. Interesting polymetallic complexes, propargylidene-ketene compounds, zwitterionic cluster compounds, and pa-p -propargylidene-cyclobutene compoimds were isolated from the reaction mixtures and successfully characterized. The product distributions were found to be dependent on the metal fragment (M) at the other end of the C4 rod. The results of the reaction are described... 

Tetrakis(carboxylato)dimetal complexes have been prepared from Cr, Cu, Mo, Re, Rh,... 

The rhenium compound 10 is rather unreactive. Carbonylation (100°C, 200 atm) gives Cp Re(CO)3, while treatment with I2 affords Cp Re(CO)2-(I)2. It does not react with ethyne, diazomethane, or phosphines under conditions where other dimetal complexes with multiple MM bonds do so (78). The manganese complex 8, also somewhat unreactive, reacts with phosphites by Mn=Mn cleavage. In the case of P(OEt)3 the two products Cp Mn(CO)2[P(OEt)3] and CpMn(CO)[P(OEt)3]2 form in a 1 1 ratio (51). 

A number of alkynes add across the Co=Co bonds of 4 (223-226). In such cases the addition is followed by an insertion reaction to give dimetal complexes 91 bridged by a —C(=0)—CR=CR— unit. Addition of... 

Since the W(C0)2(O-CsHs) fragment is isolobal with RC5 (23), addition of [w=CC6HifMe-4(C0)2(ti-CsHs)] across the C02 and Rh2 dimetal centres of [Co2(C0)s] and [Rh2(y-CO)2(n-CsMes)2] to give compounds (40) and (41), respectively, has also been successfully accomplished(21). Formation of (40) and (41) in this manner is analogous to the reaction of alkynes with these and other dimetal complexes affording tetrahedrane-type structures with a dicarbadimetalla core. 

Developments in the chemistry of multiply bonded dimetal complexes with bridging phosphine ligands. ... 

In this chapter we have tried to summarize the current status of the chemistry of quadruply bridged dimetal complexes of the group 10 elements. The area is closely related to that involving similar compounds of the group 9 elements and also the doubly bridged di- and polynuclear complexes of platinum and related metals, which are not included here. We have been able to include the latest developments in this subject area. We have not attempted to be comprehensive, and some omissions may have resulted. 

Scheme 5-40. Hexacarbonyl dimetal complexes containing a l,l -ferrocenylene dithiolate bridge.

Dimetal complexes in which an RC=ML moiety formally acts as a four-electron donor to a metal (M ) as in the products 45 are electronically unsaturated species with a cluster-valence-electron (c.v.e.) count of 32. The three-membered rings may be depicted in a number of ways, the most relevant of which are shown below. 

Compound 46a is structurally related to complexes 46b-46e (Fig. 2), which are obtained directly by protonating the combinations of reagents indicated in Scheme 8. In these syntheses (43,47), intermediates analogous to the tetracarbonyl dimetal complexes 45 are clearly implicated, but none were detected. However, complex 46e reacts with PMe3 to yield a product [W2( -CMe)(CO)3(PMe3) f/5-7,8-C2B9H8-10-Et-7,8-Me2KfFCjH5)] in... 

Just as vinylidene-type resonance forms constitute one extreme description for the oxidised forms of alkynyl complexes (Scheme 6.4), cumulenic structures may result from the oxidation of oligoynediyl-bridged dimetal complexes (Schemes 6.5 to 6.8). Interesting examples come from the work of Sato, who... 

As we have noted in a previous section of this chapter, cumulenic resonance forms present one extreme description for dimetal complexes linked by all carbon bridges. They are frequently encountered in some oxidation state (mostly the dioxidised one) and also contribute to intermediate ones between the purely cumulenic and oligoynediyl or the cumulenic- and the alkynyl-bridged dicarbyne forms (see Schemes 6.6-6.8). Purely cumulenic wires are encountered in ot,a)-di- or -tetraferrocenyl substituted cumulenes, but no evidence other than a splitting of the ferrocenyl-based redox waves has been presented to support the presence of electronic interactions between the fer-rocenyl end groups across the cumulenic ligands. Based on the results of ex-... 

Tetrakis(carboxylato)dimetal complexes have been prepared from Cr, Cu, Mo, Re, Rh, Ru, Tc, and W. For leading references, see FA Cotton, RA Walton. Multiple Bonds Between Metal Atoms. New York Wiley, 1982. 

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