Mehrfachbindungen zwischen hauptgruppenelementen und übergangsmetallen

N‐Heterocyclic Carbene Complexes of Rhodium and Iridium: Steric Effects on Molecular Conformation

“…The first metal-NHC complexes were reported in 1968 by Wanzlick and Schönherr [4] and by Öfele [5] and the first stable free carbenes were isolated in 1991 by Arduengo et al [6,7] They form strong bonds to metal centers [8][9][10][11][12] and this makes them particularly beneficial in their use as ligands in organometallic catalysts. Contemporary NHC research is both vigorous and diverse; the chemistry of NHC complexes is the frequently the subject of review articles [13][14][15][16][17][18] and metal-NHC complexes of many transition elements have been reported.…”

Synthesis, Characterization and Dynamic Behavior of Mono- and Dinuclear Palladium(II) Carbene Complexes Derived From 1,1′-Methylenebis(4-alkyl-1,2,4-triazolium) Diiodides

“…Although some examples of che-4,5-dihydro-1H-1,2,4-triazole-5-ylidene) [9] and 1,1Ј-methyllate complexes with a trans-configuration are known, they enebis(4-methyl-4,5-dihydro-1H-1,2,4-triazole-5-ylidene)-are rare; normally, bidentate ligands act as bridges when 1,1Ј-methylenebis(3-methyl-4,5-dihydro-1H-imidazole-5-they form palladium(II) complexes with a trans-configura-ylidene)palladium(II) diiodide [5q] have also been reported.…”

Hybrid Ligands with N‐Heterocyclic Carbene and Chiral Phosphaferrocene Components

“…Heating of ligands 4,5 and 13 with [Mo(CO) 6 ] yielded Mo carbonyl complexes 16,18 and 17, respectively. [13] Treatment of 5 with [Mo-A C H T U N G T R E N N U N G (MeCN) 3 D 8 ]THF shows a doublet for the carbene carbon at a typical shift [13] of 189 ppm with a 2 J- 1 H} NMR spectrum, two in the range for coordinated phosphaferrocene units and two in the region expected for the free P-donor. In complex 19, containing meso-5 as ligand, the two P atoms are equivalent, so one singlet is observed in the 31 P{ 1 H} spectrum, while rac-5 affords a C 1 -symmetric complex 19, due to the facial ligand arrangement.…”

“…They have proven to be useful in stereodiscriminating stoichiometric and catalytic reactions, [8] while the number of NHC complexes affording high ee values is still quite limited. [5] Here we report a new type of multidentate hybrid ligand in which a powerful s-donor NHC is functionalized with one (4,13) or two (5,14,15) chiral p-acidic phosphaferrocene groups, giving bidentate PC-or tridentate PCP-ligands. These ligands are believed to be well suited for asymmetric catalysis, because of the closeness of the chiral information to the metal, [8e] the bulky substituents, [5b] and the electronic differentiation, which should be more distinct than in other well investigated PN-ligands.…”