Bent angles

Although Lappert et al. reported on the isolation of the purple dialkylplumbylene 65 as early as 1973, its structure has only recently been determined. In the solid state, compound 65 exists as a loosely bonded dimer with a second plumbylene molecule and has a Pb- -Pb separation of 412.9 pm, with trans-bent angles between the PbC2 plane and the Pb- -Pb vector of 34.2°.82... 

The reaction of lead(n) chloride with 2,4,6-triisopropylphenylmagnesium bromide furnished red crystals of compound 84, the first molecule with a short Pb=Pb double bond length of 305.15(3) pm and trans-bent angles of 43.9° and 51.2°.96,96a Compound 84 is stable in the solid state. In solution, it dissociates into the plumbylene molecules 85 that, for example, react with a nucleophilic carbene to furnish the highly labile, zwitterionic adduct 86 (Scheme 2).97... 

In contrast to the C=C double bond of sterically crowded alkenes, in which variations of the bond lengths are small, the Si=Si bond lengths of dis-ilenes vary between 214 and 229 pm. The twist angle r of the two SiR2 planes varies between 0° and 25°. A further peculiarity of the disilenes, not observed in alkenes, is the possibility of trans-bending of the substituents, which is described by the trans-bent angle 0 between the SiR2 planes and the Si=Si vector. The 0 values can reach up to 34°. These differences can be... 

It should be emphasized that the NO+ and NO- character of NO and the linear or bent angle in a nitrosyl complex do not necessarily imply that NO would be released from the complex in the free form NO or as NO+ or NO-. 

II) trans-bent conformation (C2V symmetry) —> a double dative bond (characterized by a trans-bent angle k as defined in Scheme 6). 

A further peculiarity of the disilenes, not observed in the alkenes, is the possibility for /ram-bending of the substituents, which is described by the /ram-bent angle 0 between the R2Si planes and the Si-Si vector. This effect which, especially for double bonds... 

The C-0 bond lengths R(C-O) and the mean amplitudes a of the bent angle distribution were determined from trial-and-error fits of the observed MRMI maps [10], as plotted in Fig. 1.3c. The large values of R(C-O) com-... 

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