Methylene group coordinates

IR spectra of these complexes suggest that the ligands are coordinated by the oxygen atom. The magnetic non-equivalence of the methylene groups due to flanking by the sulphur is influenced seriously by the oxygen coordination to the tin atom. 

A five-membered methanide auracycle [Au(C6F5)2(SPPli2CFl2PPh2)]C104 (25) is described with the monosulfonated dppm, obtained after chlorine elimination of [Au (C6F5)2Cl(SPPh2CH2PPh2)j with a silver salt. After deprotonation of the methylene group (26) and later coordination of additional metal centers affords dinuclear and trinuclear methanide derivatives (27, 28) [210]. 

In cases of complexes bearing an exocyclic double bond directly coordinated to the metal center, the carbons of the double bond usually exhibit coupling with NMR-active metal centers and/or auxiliary ligands.6 14 18 19 The chemical shifts of the quaternary carbon atom vary from 66.976 to 82.2818 ppm, while the methylene group gives rise to signals at 29.16,14 41.91,6 or 51.3418 ppm in the 13C 1H NMR spectra. As one can see, the chemical shift variation is relatively broad and significantly affected by the nature of the metal center. 

Apparently, photo-oxidation processes are dominant during the initial period and lead to the formation of active centers contributing to further cross-linking of macrochains. It can be assumed that methylene groups adjacent to coordination-bound tin atoms are most susceptible to photo-oxidation. 

N-heterocyclic compounds containing six-membered rings (pyridine and analogues) behave as excellent -acceptors and in turn they provide a rather soft site for metal ion coordination. The 7r-excessive five-membered pyrazole is a poorer 7r-acceptor and a better 7r-donor and it acts as relatively hard donor site. Inclusion of six- and five-membered N-heterocycles like pyridine and pyrazole in one ligand system leads to very attractive coordination chemistry with variations of the electronic properties.555 The insertion of a spacer (e.g., methylene groups) between two heterocycles, which breaks any electronic communication, makes the coordination properties even more manifold. 

We consider now the bis(ferrocenyl) molecule in which the two ferrocenyl subunits are separated by a methylene group, namely diferro-cenylmethane. The molecular structure of this molecule is known. The two ferrocenyl subunits occupy two positions of the tetrahedral coordination of the bridging methylene carbon atom. In each ferrocenyl group, the cyclopentadienyl rings assume an eclipsed disposition.28... 

As matters would have it, the mercuricyclization of 36 can advance comparably on both surfaces of the it bond, with the result that 43 and 44 are formed competitively (Scheme 3-7). [31] These diastereomeric products diffracted well and provided the important structural information displayed in Figs. 3-3 and 3-4. [32] In 43, all six heteroatoms are projected equatorially. This is not so for 44 where the axial C-Hg and C-O bonds generated along the reaction coordinate are preserved. The latter phenomenon is made possible because the methylene groups from four tetra-hydrofuran rings are able to remain axially disposed. 

A planar arrangement (297) for a cluster of four Li atoms, consisting of two equilateral triangles, is found by XRD for the solid complex 298. Each Li atom is coordinated to methylene groups of both types (from n-BuLi and the metallated carbosilane) and to N and O atoms of the substituent in the carbosilane. Further characterization of the solid 298 can be made by Li and CP/MAS NMR spectroscopies, and in solution by H, Li, and Si NMR spectroscopies. The combination of both organolithium compounds in 298 is found to form a more effective reagent than each of them alone °. 

CD2CH2CD2 and CH2CD2CH2 diradicals decay at somewhat longer lifetimes, in 183 and 129 fs, respectively. Torsional motions of the terminal methylene groups are obviously critical to the reaction coordinate leading to vibrationally excited cyclopropane-dj products. 

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