Ligands allyl types

Phosphinous amides, based on proline and tetrahydroisoquinoline carboxylic acid, bearing a second donor center (50, Ar=Ph R =H, CH3,Tr, Ph R =H, CH3,Tr, Ph and 51, R =H,Tr R =H,Tr) (Scheme 40) have been developed for use in allylic alkylation and amination of substituted propenyl acetates, yielding the corresponding products in 87-98% (5-94% ee) and 29-97% (14-93% ee) respectively [55, 167]. With bidentate ligands of type 38 where R=(S)-PhMeCH, and with the bis(aminophosphanes) 52 (R=Ph) similar allylic alkylations have been also tested [168,169]. 

Preliminary results suggest that ligands of type 3 are useful for Pd-catalyzed nucleophilic enantioselective substitution of allylic acetates by the sodium salt of dimethyl malonate. 

Reactions proceeding according to scheme (10) also account for the effect of Lewis acids or other electron acceptors on catalysts of the 7i-allylic type. The formation of ionic or charge transfer complexes favours the coordination of the conjugated diene as an s-cis-tf ligand, and hence the formation of cis-1,4 monomeric units, if an anti form is predominant [7]. The formation of an ionic complex is shown below, as an example, for 7i-allylnickel chloride and aluminium trichloride [194]. 

Curtis and Eisenstein355 have made a molecular orbital analysis of the regioselectivity of the addition of nucleophiles to 77-allyl complexes and on the conformation of the 773-allyl ligand in [MoX(CO)2L2(773-allyl)] type complexes. A detailed study of the chirality retention in rearrangements of complexes of the type [MX(CO)2(dppe)(rj3-C3H5)] has been made.356 Studies of the photoelectron spectra,357 electrochemical properties,358 infrared spectroelectrochemistry,359 and fast atom bombardment mass spec-... 

The dithioester complexes of type 418, in which the ligand coordinates as an allylic type, 4e donor, are converted by alkylation to the stabilized, 2e donor dithiocarbenium complexes (419) (256). Addition of CS2, fol-... 

Not all substituted acac type complexes have simple structures. A nonanuclear clusters involving yttrium and the bidentate ligand allyl acetoacetate [MeC(0)CHC(0)0CH2=CH2] has been... 

Thus, the amount of phosphane added can be used to markedly influence the product distribution when 2-substituted methylenecyclopropanes are used as substrates. A possible explanation of this observation might lie in the ability of a strong donor ligand, such as an alkylphosphane, to prevent a hapticity change of the ring-cleaved methylenecyclopropane from 1/ -coordination (allyl-type) to 1/ -coordination (trimethylenemethane-type), which is indispensable for induction of the scrambling reaction. 

The stability of these bismuthonium salts (82) - (85) depends on the nature of the anionic counterpart and of the fourth ligand. The allyl derivatives (84) are too unstable to be isolated. On the other hand, the tetrafluoroborate salts of the derivatives of the three other types of onium compounds are thermally stable. Ligand coupling- type products are formed with more nucleophilic anions, for example during the attempted exchange of anion with bromide or iodide, or during the slow decomposition of a solution of bismuthonium tosylates in chloroform. ... 

Several ligands were used with allyl-type and vinyl-type initiators, such as 1,1,4,7,10,10-hexamethyltriethylenetetramine (HMDETA), NJJyN JJ jN -pentamethyldiethylenetriamine (PMDETA), or compound 7 in Scheme 66. Zeng et al. showed that the combination of initiator 1 in Scheme 66 with BA6TREN or initiator 4 in Scheme 66 with BA6TREN gave the best control of the molar mass for the ATRP of 2-(dimethylamino)ethyl methacrylate. These allylic macromonomers are then able to copolymerize with acrylamide. 

Ruthenium and osmium form clusters containing a bridging ligand of the allyl type bonded to three metal atoms " see scheme (7.69). 

The various 7r-allylic-type ligands which have so far been recognized are shown in the first column of Table IV. At present more 7r-allylic complexes of palladium are known than of the other metals, but the preparation of TT-allylic complexes of other metals is more a matter of time than chemistry in that similar complexes of most of the transition metals should be obtainable. 

H. Werner, N. Mahr, G. Frenking, and V. Jonas, OrganometaUics, 14,619 (1995). Synthetic, Structural, and Theoretical Studies on a Novel Rhodium(I) Complex Containing a ir-Allyl-Type Ylide Ligand. 

It has been established, that the formation of 7i-allyl type of metal-ligand bond is possible with the use of diphosphinemethylene [12] ... 

The intermediate coordination, trihapto of allyl type is also known but rare. It is important, because the shift of M-(r) -Cp) (18e) to M-(T] -Cp) (16e) temporarily liberates a coordination site on the metal, which can allow a catalytic function to operate or an associative ligand substitution to avoid a 20-electron transition state or... 

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