C-H- • -S interactions

Figure 12.29. (a) Molecules of 61 are linked into chains via C—H - S interactions and (b) inserted in two perpendicular directions into a lattice of 19. 

Wang, Z., D.S. Gamble, and C.H. Langford (1990). Interaction of atrazine with Laurentian fulvic acid Binding and hydrolysis. Anal. Chim.Acta, 232 181-188. 

B7. Bruckner, H. W., Schreiber, C., and Waxman, S., Interaction of chemotherapeutic agents with methotrexate and 5-fluorouracil and its effect on de nova DNA synthesis. Cancer. Res. 35, 801-806 (1975). 

NMR has proved to be one of the most valuable techniques to obtain information on electron distribution and dynamics [3], as well as on dimensionality and on the role of electron-electron interactions, in organic conductors. Since they contain atoms such as C, H, N, S, and Se, having isotopes with nuclear spin, they have nuclear magnetic moments of the form... 

A.J. Ramirez-Cuesta, P.C.H. Mitchell, S.F. Parker (2001). J. Mol. Catal. A-Chem., 167,217-224. An INS study of the interaction of dihydrogen with the cobalt site of cobalt alumino phosphate catalyst. 

It is evident that the chemical intuition behind the slightly metaphysical discussion whether t2 (14 eV) and ax (23 eV) orbitals in methane are different already before ionization, is the question whether the C 2p—H 1 s interaction is more or less important than C 2 s—H 1 s for the dissociation energy to the five individual atoms. Obviously,... 

A new class of dicyanopyrazinoquinoxaline derivatives were also synthesized and tested for their electronic performance. The mobilities obtained for all the compounds (48c-48h) were very low, ranging from 10 -10 cm V s, but some of the compounds had a very uifique crystal packing arrangement that the authors referred to as a molecular tape structure arising from the C-H N intermolecular interactions. [282]... 

Due to this lack of acidity, the internal carbon often does not activate upon metalation with many transition metals. This results in a novel form of porphyrin metal binding where the internal C-H bond(s) remain intact but lie close to the bound metal. Several metals exhibit this type of bonding, including manganese (25-27), rhodium (25), iron (29), cobalt (30 zinc (57), palladiiun (52), silver (55), cadmium, and mercury (34), The C-H bond can reside very close to the metal ion, often within 2.5 A. As a result of this proximity, this interaction has been referred to as agostic, however, the key measurement that would define the agostic interaction, the C- H coupling constant, has yet to be measured. 

There is evidence of analogous hyperconjugative interaction in F-substituted compounds. In particular, the v(C-H) for methyl fluoride is 16 cm" red-shifted relative to methane (2976 vs. 2992 cm" ). Because hybridization effects imposed by Bent s rule should increase s-character in the C-H bonds and lead to the blue-shift, the experimental red-shift observation indicates the importance of np->-o C-H interactions. Additional fluorine substituents remove most of the red-shift (v(C-H) for CH F and CHFj are 2984 vs. 2990cm" respectively) suggesting the increasing importance of rehybridization (progressive s-character increase in the C-H bond(s)) and, possibly, the importance of Up o C-F interactions that partially neutralize the donor capacity of the fluorine lone pairs. Small blue-shifts are observed for the chloro- and bromoderivatives of methane. 

S.3.3. Intramolecular Coordination of Aliphatic C-H Bonds (Agostic Interactions)... 

C.H. Tseng, S. Somaroo, Y. Sharf, E. Knill, R. Laflamme, T.F. Havel, D.G. Cory, Quantum simulation of a three-body-interaction Hamiltonian on an NMR quanmm computer, Phys. Rev. A 61 (1999) 012302. 

The role of interactions involving organic fluorine like C-H - F-C, C, C-F - F-C (resulted in the formation of different molecular motifs) were observed to be crucial in the crystal packing of these polymorphs in presence of other stronger interactions like N-H - 0=S, C-H "0=S, C-H - Jt. 

Zumzi, A.S. Chiu, C.-H. Lahiri, S.K. Chua, K.M. Kinetics of copper and high Pb/High Sn bilayered Pb-Sn solder interactions. J. Electron. Mater. 1999, 28, 1224. 

Mono-substituted and unsymmetrical di-substituted ureas may be prepared by a modification of Wohler s urea synthesis, salts of primary or secondary amines being used instead of the ammonium salt for interaction with potassium cyanate. Thus when an aqueous solution containing both aniline hydrochloride and potassium cyanate is heated, aniline cyanate is first formed, and then C,HjNH,HCl -h KCNO = C,H6NHj,HCNO -h KCl C,HsNH HCNO = C.H NHCONH, by the usual molecular rearrangement is converted into monophenyburea. 

Phenylstibine [58266-50-5] C H Sb, has been obtained by the reduction of phenyldiio do stihine [68972-61-2] CgH3l2Sb, (73) or phenyldichlorostibine [5035-52-9] 031130.2, (74) with lithium borohydride. It has also been prepared by the hydrolysis or methanolysis of phenylbis(trimethylsilyl)stibine [82363-95-9] C22H23Si2Sb (75). Diphenylstibine [5865-81-6] C22H22Sb, can be prepared by the interaction of diphenylchlorostibine [2629-47-2] C22H2QClSb, with either Hthium borohydride (76) or lithium aluminum hydride (77). It is also formed by hydrolysis or methanolysis of diphenyl (trimethylsilyl)stibine [69561-88-2] C H SbSi (75). Dimesitylstibine [121810-02-4] h.3.s been obtained by the protonation of lithium dimesityl stibide with trimethyl ammonium chloride (78). The x-ray crystal stmcture of this secondary stibine has also been reported. 

Since equatorial attack is roughly antiperiplanar to two C-C bonds of the cyclic ketone, an extended hypothesis of antiperiplanar attack was proposed39. Since the incipient bond is intrinsically electron deficient, the attack of a nucleophile occurs anti to the best electron-donor bond, with the electron-donor order C—S > C —H > C —C > C—N > C—O. The transition state-stabilizing donor- acceptor interactions are assumed to be more important for the stereochemical outcome of nucleophilic addition reactions than the torsional and steric effects suggested by Felkin. 

---