Multiple bonding transition metal derivatives

Another possible explanation for enhanced stabilities of perfluoro-alkyltransition metal compounds concerns possible multiple bonding between the metal and the fluorocarbon group 230). Whatever the reason, a large number of fluorocarbon derivatives of the transition metals have now been described, and a study of their synthesis, properties, and reactions constitutes an important new branch of organotransition metal chemistry. Fluoroalkyltransition metal compounds were first described in 1959 J 8), while perfluoroary 1-transition metal derivatives were discovered in 1963 201, 234). Some typical syntheses of fluorocarbon-transition, metal compounds are shown below ... 

Multiple bonds between silicon and other elements comprise a new area with many surprises. Considerable development in methods still remains. Only recently have Si=M (M = transition metal derivatives) been generated. The approach used in the first reported case was based on simple condensation chemistry, similar to that used for the formation of silicon-carbon bonds, and is shown in equation 22. Not surprisingly, the... 

Transition metal-catalyzed hydroboration of carbon-carbon multiple bonds using organoborane derivatives and coupling with alkanes to form linear alkyl-... 

Transition metal-catalyzed hydroboration of carbon-carbon multiple bonds using organoborane derivatives and coupling with alkanes to form linear alkyl-boranes has provided valuable applications in organic synthesis.Titanocene catecholborane complexes recently synthesized and characterized by Hartwig also appear to be the best examples of genuine / -BH a complexes (Figure 13.3). ... 

Several reviews have dealt with the chemistry of transition metal-nitrogen derivatives,255-257 including compounds with metal-nitrogen multiple bonds,258,259 especially those encountered in high oxidation states. 

The reaction of carbonyl sulfide with [M(02)(PPh3)2] (where M = Pd or Pt) has resulted in the first reported examples of transition metal complexes of the monothiocarbonate anion (47 R = O-). Bidentate S—O coordination was concluded from 3IP H NMR analyses of these compounds.184 A short structural review of metal complexes of monothiocarbamate ions (47 R = N(R )R") demonstrates their varied coordination chemistry.185 In complexes of the dialkyl forms the sulfur atom is seen to have considerable mercaptide character , whereas aromatic amine derivatives demonstrate C—S and M—S partial multiple bonding.185,251 A review on the coordination chemistry of these ligands has appeared.186 Additional detail is provided in Chapter 16.4 of this volume. 

The catalytic [2 + 2 + 1]-cycloaddition reaction of two carbon—carbon multiple bonds with carbon monoxide has become a general synthetic method for five-membered cyclic carbonyl compounds. In particular, the Pauson-Khand reaction has been widely investigated and established as a powerful tool to synthesize cyclopentenone derivatives.110 Various kinds of transition metals, such as cobalt, titanium, ruthenium, rhodium, and iridium, are used as a catalyst for the Pauson-Khand reaction. The intramolecular Pauson-Khand reaction of the allyl propargyl ether and amine 91 produces the bicyclic ketones 93, which bear a heterocyclic ring as shown in Scheme 31. The reaction proceeds through formation of the bicyclic metallacyclopentene intermediate 92, which subsequently undergoes insertion of CO to give 93. 

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