Ylides and ylidions: a comparative study of unusual gas-phase structures

Carbene Complexes of Nonmetals

“…The water-methylene complex, H 2 OϪCH 2 (13), is the simplest oxonium ylide. NeutralizationϪreionization studies of H 2 OϪCH 2 · ϩ in a tandem mass spectrometer indicated that an appreciable fraction of 13 must have survived the microsecond lifetime of the experiment.…”

“…Variable-temperature 13 C and 29 Si NMR spectra of 105 revealed the presence of a dissociative equilibrium in solution; dissociation of 105 into 103 and 104 was nearly complete at ca. 85°C.…”

“…N 155Ϫ159 1.07 [13Ϫ15,18] 147Ϫ150 [c] 1.01 [25] O 171Ϫ183 1.25 [13,17,18,20] P 167Ϫ168 0.89 [12Ϫ14,17,18] 166Ϫ170 [d] 0.91 [23] 170Ϫ173 [c] 0.93 [22] S 164Ϫ168 0.90 [12Ϫ14,17,18] 171Ϫ175 [c] 0.95 [24] I 216Ϫ230 1.00Ϫ1.07 [19] 204Ϫ213 [c] 0.95Ϫ1.00 [26] [a] Computed bond lengths of RnXϪCR 1 R 2 (R, R 1 , R 2 ϭ H, Me) relative to bond lengths of HnXϪCH 3 computed by the same method.…”

“…Binding energies (ylide relative to R n X ϩ R 1 R 2 C:) should be more relevant. Although the computed binding energies depend on the method employed (Table 2), [13,17] the following trends are observed: (a) the order of binding energies is O ഠ I Ͻ N ഠ S Ͻ P; (b) ylides Me n XϪCH 2 are more strongly bound than ylides H n XϪCH 2 ; [17c,17d] (c) for ylides H n XϪCR 1 R 2 , the activation energies for 1,2-H shift are lower than the binding energies. [13,17,20] Such species are, at best, fleeting intermediates in the course of XϪH insertion reactions (H n O 79 MP2A…”

An ab initio study on the insertion reactions of CH [X2II] with NH3, H2O, and HF

“…In each case, the system, following the calculated IRC, goes downhill to the intermediate complex (2a, 2b, or 2c) in the negative direction of the IRC, and to the insertion product (4a, 4b, or 4c) in the positive direction, which further confirms that the intermediate complex exists prior to the transition state in the path of the insertion reaction for each of the three CH reactions. In 1987, Yates et al (13) found, in the HF and MPn potential energy surfaces of the CH2-NH, and CH, OH, systems, two species that could be considered as intermediate complexes in the insertion reactions of CH,('A,) with NH3 and H,O, respectively. In 1991, Sudhakar and Lammertsma (14) reported their theoretical (HF and MPn) studies on singlet nitrene insertion into H 2 0 and HF, and they found the complexes HN-OH, and HN-FH in the insertion reaction paths.…”