Group 8 heterobimetallics complexes

Very few mixed heterobimetallic complexes which contain an alkali metal and a group 14 which are metal not directly bonded to one another have been structurally characterized. Wright and co-workers, in developing a series... 

Asymmetric catalytic addition of dialkylphosphites to a C=0 double bond is a powerful method, and probably the most general and widely applied, for formation of optically active a-hydroxy phosphonates [258], The basic principle of this reaction is shown in Scheme 6.108. Several types of catalyst have been found to be useful. The transition-metal-catalyzed asymmetric hydrophosphonylation using chiral titanium or lanthanoid complexes was developed by several groups [259, 260], The most efficient type of chiral catalyst so far is a heterobimetallic complex consisting... 

Homo- and heterobimetallic complexes of the lanthanides are routinely observed with the large calix[8]arene [191]. However, this extended highly functionalized cavity can also accommodate just one lanthanide ion as shown in [Eu(H6L)(N03XDMF)4] 3DMF (H8L = p-tert-butylcalix[8]arene, Table 13) [192]. Only two adjacent phenolic OH groups were deprotonated according to... 

Attempts to structurally characterize the generated Ln(III)/Al hetero-bimetallic complexes were not successful. Addition of coordinating solvents, such as THF or pyridine, afforded complex mixtures from which only lanthanide(III) chloride donor-adducts crystallized. The presence of reactive ethyl groups was confirmed by the reaction with D20 (generating CH3CH2D) [134], The catalytic relevance of such heterobimetallic complexes was confirmed by the quantitative conversion of a 7500-fold excess of iso-prene into polyisoprene within 5-10 minutes at ambient temperature, after the addition of one equivalent of i-Bu3Al cocatalyst. 

Table 22 Thermodynamic data for the exchange of bridging and terminal methyl groups in Ln/Al heterobimetallic complexes ...

Heterobimetallic Complexes. Monohalide TiIV compounds containing amido,47 alkoxides,48 or tripodal amido49 groups react with many metal carbonyl cationic species to give unsupported heterodinuclear complexes such as 17-A-V. 

A strong dependence on the leaving group is also noted in preparation of Cp(CO)3-MRe(CO)s (M = Mo, W) . These differing product mixtures result from three different mechanisms direct nucleophilic attack [reaction (f)], electron transfer [reaction (g)], and a two-electron transfer [reaction (h)] . Reaction of Fe(CO)4" with Re(CO)sBr gives the heterobimetallic complex ... 

A similar reaction between fr<3ins-Ir(CO)(CH3)(P(p-tolyl)3)2 and CpMofCOfsH gives a heterobimetallic complex with a bridging phosphide group . 

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