Derivate des Imidazols, XI. (C₈H₁₄N₂)M(CO)₅ (M = Mo, W) ‐ Terminale Koordination eines Olefins in Pentacarbonylmetall‐Komplexen

Abstract

-(CBH14NZ)M(C0)5 (M = Mo, W) -Terminal Coordination of an Olefin in PentacarbonylMetal Complexes* The 2-methylenimidazoline complexes (C8H14N2)M(C0)5 veal the strong donor character of the ylidic ligand in 6. The (M = Mo, W; 6) are obtained from M(C0)6 and 1,3,4,5-tetra-end-on coordination mode of the olefin is demonstrated by methyl-2-methyleneimidazoline (5). Spectroscopic data re-an X-ray structure analysis of 6a.Olefine sind an Ubergangsmetall-Zentren im Regelfall uber beide olefinischen Kohlenstoff-Atome koordiniert (1; ,,side-on") [ Ein Vergleich der I3C-NMR-Daten von 6 mit denen des nichtkoordinierten Liganden 5 [6 = 153.65 (C-2), 40.22 (CH2)][9] zeigt fur das Methylen-Kohlenstoff-Atom rnit 6 = -6.74 (6a) bzw. -2.87 (6b) die erwartete Hochfeldverschiebung sowie fur C-2 (6a: 6 = 163.77; 6b: 6 = 163.42) eine deutliche Koordinationsentschirmung. Im 'H-NMR-Spektrum zeigt sich ein drastischer Koordinationseffekt beziiglich der chemischen Verschiebung der MethylenChem.

Syntheses and Structures of Molybdenum, Tungsten, and Manganese Complexes of a Cyclic Thiourea, [M(CO)5(SC3N2Me4)] (M = Mo, W) and [{CpMn(CO)2}2(μ‐SC3N2Me4)]

“…As a whole, their structures are akin to Kuhn's complex 11. [8] They also resemble that of a methyleneimidazoline complex, [Mo(CO) 5 -(CH 2 =C 3 N 2 Me 4 )], [18] whose ligand, an ylidic olefine, is isoelectronic with 1. The M-S bond lengths are 2.6084(11) Å and 2.6113(11) Å in 3, and 2.6146(14) Å in 4.…”

N‐Heterocyclic Olefin‐Ligated Palladium(II) Complexes as Pre‐Catalysts for Buchwald–Hartwig Aminations

“…Moreover, N‐heterocyclic olefins are considered to be softer σ‐donors than NHCs and might yield stable coordination complexes with the soft Pd 0 centers found during cross‐coupling catalysis. Although the seminal work by Kuhn and co‐workers introduced various NHO⋅M(CO) 5 complexes to the community (M=Cr, Mo, and W), the number of metal complexes comprising NHOs as ligands is still limited, with examples of Au, Ir, and Rh complexes now known . NHOs have also been used to stabilize reactive main‐group environments, and an exciting new direction is their use in organocatalysis …”

The Resurgence of the Highly Ylidic N‐Heterocyclic Olefins as a New Class of Organocatalysts

“…They can also be used as dienophiles in inverse‐electron‐demand Diels–Alder and other cycloaddition reactions . Due to the strong nucleophilicity of the α‐carbon, NHOs are often stronger Lewis bases than their parent NHCs, leading to several applications of NHOs as end‐on ligands in transition metal coordination and catalysis,– as well as stabilization of the metalloid boron and silicon in borenium ions, and silylenes . Very recently, NHOs have elicited great interest among synthetic chemists for their intriguing new roles as organocatalysts in important chemical transformations, such as CO 2 sequestration and polymerization reactions (Figure ) .…”