Organometallic Intramolecular π‐Olefin‐Metal Coordination Compounds

Abstract

In this review article complexes of the type X,M-R are dealt with in which a a-bonded organic ligand R is additionally linked by a n-bond with the metal M. In other words, the complexes contain metallacycles with three and a half, four and a half, five and a half members, etc. Well-known five and a half membered ring systems are those with 4-penteny1, 1,4pentadienyl, norbornyl, norbornenyl, cyclooctenyl, and endo-dicyclopentadienyl ligands. Metallacycles of this size are strain-free and stable. Donor ligands such as amines and phosphanes can displace the coordinated double bond of the n-ligand from the metal. This C=C double bond is lengthened from cu. 133 pm to 136-146 pm by the coordination. 4-Pentenyl Compoundsq3-Allylcobalt complexes readily form the five and a half membered n-coordination compounds 8 by insertion of fluoroolefins into the q3-allyl-cobaltThe observation that q3-allyl(tricarbonyI)cobalt complexes already react at room temperature, whereas the phosphane-and phosphite-complexes react only on heating is explained by the electrophilicity of cobalt being lowered on bonding to the phosphorus ligand. Monophosphane-and monophosphite-substituted products 8 can [*I Dr. 1. Omae Central Research Institute, Teijin Limited Asahigaoka, Hino, Tokyo, 191 (Japan) [*I The C-atoms of the ligands in 7-9,93, 100-103 and in Figure I are not numbered systematically.Angen,. Chem. Int. Ed. Engl. 21 (1982) 889-902 0 Verlag Chemie GmbH, 6940 Weinheim. 1982 0570-0833/82/1212-0889 $02.50/0 = 1,2; m + n = 3 Angew. Chem. In(. Ed. Engl. 21 11982) 889-902 Angew. Chem. Int. Ed. Engl. 21 (1982) 889-902 O M e X -q d -X cd X J OMe

Regiospecific hydride abstraction from metallacycles: conversion of metallacyclopentanes to cationic π-allylic complexes

“…Complex (13) reacts with AgBF4 at room temperature to give immediately (14),' in high yields. By reacting [Rh(qs-C,Me,)(PPh,)I,] with 3-butenylmagnesium bromide the q3-l-rnethylallyl complex (1 5 ) is obtained directly (Scheme 3).…”

Cyclometalation of the platinum metals with nitrogen and alkyl, alkenyl, and benzyl carbon donors

“…152 The chloro ligands in 276 could be exchanged with acetylacetone to generate (87%) 277 in the presence of AgBF4. The X-ray structure of 275 offered interesting insight into the steric factors associated with a fused fourmembered ring; one conclusion is that in square-planar Pt(II) complexes, the amido nitrogens exert a relatively strong trans effect as suggested by the Pt-Cl bond length [2.318 (9) A].152 7r-Complex 278, which exists in solution as an equilibrium mixture of t?3-and ^-butenyl forms, was transformed by isocyanate insertion into the C-metal bond to give imide 279. 7r-Bonding to the 7,5-olefin rather than the a,/3-olefin is favored based on molecular models but not proven.…”

Study of the Evolution of η1-η2-Enylpalladium Complexes When the Palladium-Migration Process Is Blocked

“…When all of the starting material had been consumed, 1a was found to account for 99% of the Pf present (less than 1% left in solution); in addition, 2 (1%) was observed. According to these data, insertion of the less-hindered allylic double bond into the Pd−Pf bond is preferred to form a stable 5.5-membered η 1 -η 2 palladacycle ( 1a ) . The formation of a small amount of 2 can be interpreted via Pd−H elimination−readdition followed by β-Cl elimination (Scheme ).…”