Investigations of the Structure and Reactivity of a Stannaketenimine

Abstract

9] Crystal structure analysis of 1: H,SO,, M, =114.08, a = 628.5(3), b = 1420.0(4), c =773.4(3) pm, 2 = 8, V, = 0.6902 nm', space group Pbca, crystal size 0.69 x 0.66 x 0.21 mm', four-circle diffractometer, Mo,. radiation, 912 measured reflections, 713 independent reflections with J > 0, numerical absorption correction, 64 refined parameters, R = 0.047, R, = 0.041. Further details of the crystal structure investigation may be obtained from the Fachinformationszentrum Karlsruhe, Gesellschaft fur wissenschaftlich-technische Information rnbH, D-W-7514 Eggenstein-Leopoldshafen 2 (FRG) on quoting the depository number CSD-55888, the names of the authors, and the journal citation.[13] Compare with the distances given in the legend of Figure 1. Closer inspection shows that the bond S-02 is shorter than S-03, although the former participates in an intermolecular hydrogen bond. This finding should be seen, for example, in connection with the variance of the distances between sulfur atoms and terminal oxygen atoms in trimeric sulfur trioxide.

Synthesis and Properties of the First Stable Silylene–Isocyanide Complexes

“…These properties of 5 c ± e resemble those of the reported stannaketenimine, [18] and indicate sharp contrasts to those of 1-phospha-3-silaallene [19] and 1-phospha-3-germaallene, [20] which reportedly have cumulative-compound character.…”

“…As for the tin analogues of silaketenimines, a stannnaketenimine, [{2,4,6-(CF 3 ) 3 C 6 H 2 } 2 -SnCNMes], has been isolated as a stable compound, and its X-ray structural analysis revealed that it has a bent SnCN structure bearing a pyramidally coordinated tin atom. [18] It has been proposed that the Sn À C bond in the SnCN structure, which was found to be longer than an Sn À C single bond, may be described as a double p-donor ± acceptor interaction. Recently, Escudie ¬ et al have reported the spectroscopic observation of two new species having an > MCE-(M Group 14 element; E Group 15 element) structure, for example, 1-phospha-3-silaallene [Tip(Ph)SiCPMes*] (Tip 2,4,6-(iPr) 3 C 6 H 2 ; Mes* 2,4,6-(tBu) 3 C 6 H 2 ) [19] and 1-phospha-3-germaallene [Mes 2 Ge C PMes*].…”

“…These results clearly indicate that 5 c ± e dissociate into 2 and 3 c ± e in solution and an equilibrium exists between them. Gr¸tzmacher et al have reported [18] that a stannaketenimine dissociates into the corresponding stannylene and isocyanide and that the variable-temperature 117 Sn NMR experiments show a downfield shift with increasing temperature owing to an increase of the ratio of the stannylene in the equilibrium mixture. This result suggests rapid interconversion between the stannaketenimine and the stannylene plus isocyanide.…”

Computational Analysis of n→π* Back-Bonding in Metallylene–Isocyanide Complexes R2MCNR′ (M = Si, Ge, Sn; R =tBu, Ph; R′ = Me,tBu, Ph)

“…The last case to be considered is the stannylene-isocyanide adduct 1 that is to some extent an extreme system as its linear geometry suggests little or no -type interactions. 4 In agreement with this assumption, geometry optimization and subsequent frequency calculation gave ν(CN) = 61 cm 1 . This value is in fact slightly greater than what was observed for any of the systems in the set of model compounds.…”

“…9 In general, metal-mediated coupling and polymerization of unsaturated organic molecules are important industrial processes, 10 and the synthesis of heterocycles resulting from coupling and cycloaddition reactions of isocyanides with other heteroelement unsaturated species is a widely used technique. 11 [4] During our investigations of the chemistry of the adduct 5, it was realized that its ν(CN) stretching band is shifted to slightly lower wave number relative to the analogous stretching frequency of the free isocyanide. 7a This prompted us to investigate the possibility of Ge-C -bonding in 5 i.e.…”