Nucleophilic Carbenes: An Incredible Renaissance

1,3‐Dialkyl‐ and 1,3‐Diaryl‐3,4,5,6‐tetrahydropyrimidin‐2‐ylidene Rhodium(i) and Palladium(II) Complexes: Synthesis, Structure, and Reactivity

“…The rhodium compounds bromo(cod) [1,3-bis(2-propyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene]rhodium (7), bromo-(cod)(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)rhodium (8) (cod = h 4 -1,5-cyclooctadiene, mesityl = 2,4,6-trimethylphenyl), chloro(cod)(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)rhodium (9), and chloro-(cod)[1,3-bis(2-propyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene]rhodium (10) were prepared by reaction of [{Rh(cod)Cl} 2 ] with lithium tert-butoxide followed by addition of 1,3-dimesityl-3,4,5,6-tetrahydropyrimidinium bromide (3), 1,3-dimesityl-3,4,5,6-tetrahydropyrimidinium tetrafluoroborate (4), 1,3-di-2-propyl-3,4,5,6-tetrahydropyrimidinium bromide (6), and 1,3-di-2-propyl-3,4,5,6-tetrahydropyrimidinium tetrafluoroborate, respectively. Complex 7 crystallizes in the monoclinic space group P2 1 /n, and 8 in the monoclinic space group P2 1 .…”

Unsymmetrical Carbene Homologues: Isolable Pyrido[ b ]‐1,3,2 λ 2 ‐diazasilole, ‐germole and ‐stannole and Quantum‐Chemical Comparison with Unstable Pyrido[ c ] Isomers

“…Like carbenes, [1] most silylenes (silanediyls) are highly reactive, short-lived intermediates which are detected by spectroscopic methods or trapping reactions. [2] A few isolable representatives with higher coordination number were described recently.…”

Synthesis and properties of heteroaromatic carbenes of the imidazole and triazole series and their fused analogues

“…Autotransformations of heterocyclic carbenes, and their aromatic derivatives, were only discovered in the 1990s. [276][277][278] Several of the studies showed that some heterocyclic carbenes become unstable upon heating. 103,168,279 Interestingly, reactions of this type have not been studied until recently.…”