Synthesis, structure, and fluxional behavior of 4-sila-, 4-germa-, and 4-stanna-3a,4,4a,8-tetrahydro-4,4,8,8-tetramethyl-s-indacenes

Abstract

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Electronic Coupling in Mixed‐Valence Dinuclear Ferrocenes and Cobaltocenes with Saturated Bridging Groups

“…These were thoroughly degassed before use by passage of a stream of dinitrogen through the solvent. The following compounds were prepared according to published procedures: [Fe(Cp*)Cl(tmeda)], [17] [Co(Cp*)Cl] 2 , [55] [Li 2 (C 5 H 4 ) 2 CMe 2 ], [56,57] [Li 2 (C 5 H 4 ) 2 SiMe 2 ], [57,58] [Li 2 -(C 5 H 4 ) 2 GeMe 2 ], [57,59] [Li 2 {(C 5 H 4 )Si(Me) 2 } 2 ], [57,60] + .…”

Mechanisms and kinetics of the elementotropic rearrangements of tetrahydro-4,4,8,8-tetramethyl-4,8-disila-sym-indacene

“…4 It is interesting to note that unlike 2, no dynamics caused by elementotropic rearrangements is observed at all for the type 1 silicon derivative. 4 This fact shows that replacement of one of the bridging Si(CH3) 2 groups in molecule 2 by a C(CH3) 2 group results in a sharp increase in the activation barriers to rearrangements, which is likely associated with increasing strains in the five-membered cycle in the type lc and 2e intermediates and in the transition states.…”

“…The 4-sila-, -germa-and -stanna derivatives of (1) have been synthesized and studied in detail previously. 4 In these molecules, possible migrations of the bridging atom of the element are restricted to three sites: C(1)/(7), C(Sa)/(7a), and C(3a)/(4a). In this case, the tin and germanium derivatives exist in solution as equilibrium mixtures of interconverting isomers la and lb (Scheme I).…”

“…The use of 2D exchange ACCORDION NMR spectroscopy and a specially developed procedure for quantitative processing of the spectra 5 made it possible to reveal the mechanisms and to calculate the kinetic and thermodynamic parameters of the rearrangements of compounds 1 (E = Ge, Sn). 4,5 Much more complex elementotropic equilibria occur for tetrahydro -4,4,8,8- obtained in attempting to synthesize the corresponding 6,6-dialkyl-6-elementafulvenes (4). ~--9 However, compounds 4 appeared to be extremely unstable and reactive and dimerize instantly in an individual state 6-1z (Scheme 2).…”

“…It should be noted that despite the efficient synthetic application of compounds of types 1--3, their dynamic stereochemistry has been studied in few works. [3][4][5]14 The molecular dynamics of type 2 disilicon derivatives has been investigated only in one paper 14 dedicated to studying the dynamic behavior of the monoanion 5 obtained by deprotonation of one of the cyclopentadienyl rings of 2. Of special note is the fact that the dynamic stereochemistry of 5 is in essence a simplified model of the rearrangements of 2, since [1,5]-sigmatropic shifts of the silicon atoms in compound 5 are possible only in the one cyclopentadienyl ring that does not undergo deprotonation.…”