Nucleophilic attack fluxionality

RhCl(cod)(PR3)(hexene)]. The fluxional nature of compounds (5) have been investigated by and NMR spectroscopy/ At room temperature the dangling and coordinated phosphines rapidly exchange positions. Retention of /rh-p above the high-temperature limit confirms this to be an intramolecular process. The iridium complex presumably behaves in the same way, but reaches coalescence at a lower temperature. The processes are probably analogous to ligand replacement by associative nucleophilic attack. 

Cationic phosphine methylplatinum(ii) complexes containing 2,9-dimethyl-l,10-phenanthroline (dmphen) exhibit fluxionality owing to hemilability of the dmphen (26, Scheme 19). Apparently, this is the route involved with some counterions, but others, such as CU, involve nucleophilic attack to form a five-coordinate intermediate, which could rearrange via either a k - or a re -intermediate. One should note that 26 is not planar and the rings make a significant... 

C6H5R)(PF3)3] (R = H, Ph) afforded the highly fluxional agostic diene complex (20), characterised by X-ray diffraction for R = Ph. The nucleophilic attack of hydride on a variety of (Ti<5-arene)chromium tricarbonyl complexes has been studied and the X-ray crystal structure of (21), derived from the reaction with [Cr( n6-dibenzofuran)(CO)3], has been reported . 

Nucleophilic attack to palladium is one of the important reactions that Pd 77 -allylic complexes undergo. Ligand-substitution reactions and metathesis of the auxiliary ligands lead to new TT-allyl complexes, and they are a valuable and common synthetic route for a large number of compounds. These reactions have been collected in Section 8.06.6.2.1. The fluxional behaviour of Pd 77 -allyls often involves nucleophilic attack to palladium, and some examples have been discussed in Section 8.06.6.2.3. 

Complex (2) is fluxional, by NMR techniques. The molecular motion arises from internal nucleophilic attack at Pt by the pendant arm of the potentially tridentate ligand, and /pt p is retained at the high temperature limit, confirming the intramolecular nature of the process. ... 

The solvomercuration of alkenes has been exhaustively studied and is now well understood. The mechanism of this reaction proceeds through two steps coordination of the mercuric ion to the alkene to form a fluxional cationic intermediate and subsequent nucleophilic anti-attack. Charge stabilization of the cationic intermediate constitutes one of the factors dictating the regioselectivity of the reaction (Scheme 11). 

Cationic Si in RaSi is very unfavorable, so nucleophilic displacement of a group at Si never goes by an Sn 1 route, but by attack at Si (Sn2). This can take place with or without inversion because the 5-coordinate intermediate is fluxional by the Berry process (Eq. 10.2). 

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