Phosphine complexes borates

In 2008, Shibata and co-workers reported a cationic iridium bidentate phosphine complex catalyzed C—H bond alkylation reaction of 2-methy-lacetophenone with alkynes and alkenes (Scheme 5.61). Compared with alkynes, the use of styrenes as acceptors requires the weakly coordinated tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (BARF) as a counteranion of the iridium complex and a higher temperature to achieve good yields. When a norbornene was used as the acceptor, the sole example of an asymmetric ortho C—H bond alkylation product 175 was obtained in 58% yield and 70% ee. 

Thereby, the presence of tertiary monophosphines is critical, because both polymeric (26) and cyclic tetrameric (24 and 25) complexes can be obtained depending on the phosphine added to the reaction mixture. Furthermore, with some of the phosphines rapid decomposition and deposition of metallic silver occurs. In the macrocyclic molecules 24 and 25 a pair of silver atoms is bridged by two bis(l-imidazolyl)borate moieties, with a transannular Ag Ag distance of 8.61 A for 24 and 8.89 A for 25. The conformations of 24 and 25 are... 

Examination of the backbones of the neopentane-based, carbon-anchored TIME and bulky TIME tripodal ligands reveals possible reasons for the lack of 1 1 complex formation with metal centers. A hypothetical complex of TIME would contain three eight-membered rings (Fig. 9, I) with much lower stability than the more commonly observed five, six, or seven-membered rings formed, for instance, by poly(p5irazolyl)borate or poly(phosphine) ligands. In order... 

Hereafter are described the few complexes featuring pendant borane moeities that have been obtained as rearranged- or side-products starting from phosphine-borates. 

All the reactions of the hydrocyanation process are catalyzed by zero-valent nickel phosphine or phosphite complexes. These are used in combination with Lewis acid promoters such as zinc chloride, trialkyl boron compounds, or trialkyl borate ester. The ability of the precatalyst to undergo ligand dissociation... 

The reactions of iridium olefin complexes are not restricted to reactions with phosphines. Amines have also employed in bridge-splitting and substitution reactions with [Ir(COD)Cl]2, especially chelating diamines. The reactions proceed to yield [Ir(COD)N-N]2 compounds. A fertile chemical area involves the irw(pyrazolyl)borate (see Tris(pyrazolyl)borates) family of compounds with the monoethylene and bisethylene complexes serving as reactive entries in this field. ... 

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