Silyl-cobalt compound

Cobalt-magnesium exchange reaction of a silyl-cobalt compound with a Grignard reagent. 

A silyl-cobalt complex is a good precursor for silyllithium and silylmag-nesium compounds (Scheme 2) (9a,h). Evidence for the generation of... 

The investigations described so far indicate that reactions of metal carbonylates in general lead only to the coordination of two metal carbonyl groups to the 1,3,5-trisilacyclohexanes. From the chemistry of silylcobalt compounds it is known that silanes of the type R SiH (n = 1-3) cleave dinuclear Co2(CO)g, producing silyl-cobalt-carbonyl complexes [166, 167, 171]. 

Silicon and germanium hydrides react with cobalt, manganese and rhenium carbonyls affording complexes having a silicon (or germanium)-metal bond. These reactions, described previously for inactive compounds have been used in the synthesis of optically active silyl and germyl-transition metals ... 

By cobalt-lithium exchange, the group of Sekiguchi and coworkers generated several dilithium salts of variously substituted cyclobutadiene dianions . By the reaction of the functionalized acetylenes (e.g. compound 137) with CpCo(CO)2 (136), the corresponding cobalt sandwich complexes, related to compound 138, were obtained (Scheme 50). These can be interconverted into the dilithium salts of the accordant cyclobutadiene dianions (e.g. dilithium compound 139) by reaction with metallic lithium in THF. Bicyclic as well as tricyclic (e.g. dilithium compound 141, starting from cobalt complex 140) silyl substituted systems were generated (Scheme 51) . ... 

These compounds have been obtained indirectly by reactions of silylated acetylenes with metal carbonyls or olefin complexes. Thus, trimethylsilylphenylacetylene reacts with rj5-cyclopentadienylcobalt dicarbonyl, cobaltocene, or rjs-cyclopentadienyl-(l,3-cyclooctadiene) cobalt, in refluxing xylene, to give a mixture of cis- and trans-bis-(trimethylsilyl)cyclobutadiene complexes (R = Me, R = Ph) 68, 127, 137) ... 

While platinum and rhodium are predominantly used as efficient catalysts in the hydrosilylation and cobalt group complexes are used in the reactions of silicon compounds with carbon monooxide, in the last couple of years the chemistry of ruthenium complexes has progressed significantly and plays a crucial role in catalysis of these types of processes (e.g., dehydrogenative silylation, hydrosilylation and silylformylation of alkynes, carbonylation and carbocyclisation of silicon substrates). 

The chemistry of silicon, germanium, and tin transition metal compounds has been the subject of several reviews (12, 180). Optically active silyl ligands have been introduced in a transition metal complex by reaction of chiral functional organosilanes. However chiral silyl ligands containing complexes are limited to a few metal centers we shall discuss in turn iron, cobalt, platinum, and manganese complexes. 

Bromocyclizadon led to the formatitHi of tetracyclic 680 as a single stereoisomer. Kinetic deprotonatitm followed by treatment with methyl iodide furnished derivative 681. Compound 682 was obtained by exchanging the silyl ether with acetate. Again, cobalt(l)-mediated reductive coupling afforded the dimeric diketopiperazine 683. 

In the presence of ruthenium, rhodium and cobalt complexes that initially contain or generate M-H and M-Si bonds, divinylderivatives of silicon compounds undergo de-ethenated silylative polycondensation to yield a mixture of oligomers and cyclic unsaturated siloxanes (silanes, silazanes) according to equation 3. 

Konno reported a detailed study of the reaction of fluorine-containing propargyl acetates under Nicholas conditions with a variety of nucleophiles. Allylstannanes and allylsilanes provided moderate yields of the desired products, while enamines, silyl enol ethers, and silyl ketene acetals furnished the target compounds with excellent efficiency. In one example, cobalt-alkyne complex 25 reacts with silyl ketene acetal 26 in the presence of trimethylsilyl triflate to yield, after cobalt decomplexation, ester 27. ... 

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