Theoretical Investigation of the<sup>13</sup>C NMR Chemical Shift–NCN Angle Correlation in N‐Heterocyclic Carbenes

Nonnenmacher, Michael; Kunz, Doris

doi:10.1002/9783527636402.ch22

Cited by 2 publications

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“…Proof for formation of a dinuclear complex was finally achieved by X-ray structure analysis of single crystals obtained from a saturated solution of 5 in dichloromethane. In contrast to the chelating coordination behavior of 1,10-phenanthroline, biscarbene 1 shows a bridging coordination to two silver atoms as is found (rarely) with 2,2′-bipyridine ligands . The preferred linear coordination mode of the Ag(I) atoms is completed by a second biscarbene ligand (Figure ).…”

Section: Resultsmentioning

confidence: 53%

“…This relatively small carbene angle indicates a strong s character of the σ orbital at the carbene atoms, similar to that of pyrido-annelated carbenes, and consequently a reduced σ-donor character. Applying the carbene angle–chemical shift relationship, , we expect a relatively high field value for the 13 C NMR carbene signal at around 200 ppm. The distance between the carbene atoms is reduced slightly (2.97 Å), as is the C–C–C angle between the annelated rings (135°).…”

Section: Resultsmentioning

confidence: 99%

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1,10-Phenanthroline Analogue Pyridazine-Based N-Heterocyclic Carbene Ligands

2011

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Synthesis of a planar, π-conjugated pyridazine-based biscarbene is reported. Starting from 3,6-dimethylpyridazine, the bisimidazolium salt 1*2HPF 6 was prepared in a four-step synthesis by chlorination, amination, formylation, and cyclization. The free carbene 1 can be generated in situ by addition of base. Despite the rigid annelated tricycle, the carbene ligand turns out to be highly flexible upon coordination of transition-metal complexes. With silver(I) oxide or copper(I) oxide binuclear carbene complexes with a bridging coordination mode of the ligand are obtained. Transmetalation of both complexes to the respective gold complex is described. The bridging coordination mode of the carbene ligand is similar to that of 2,2′-bipyridine. Reaction of the bisimidazolium salt 1*2HPF 6 with potassium acetate and [RhCl(COD)] 2 leads to a mononuclear rhodium complex with the chelating binding mode of 1, resembling strongly the coordination properties of 1,10-phenanthroline.

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Section: Resultsmentioning

confidence: 53%

Section: Resultsmentioning

confidence: 99%