New Ga/N‐based Active Lewis Pairs,Trifunctional Ga–Ga Compounds,Reactions with Cyanamide and Dual Insertion of Isocyanate

Hydrogallation of Me₃Si–C≡C–NR'₂ with R₂Ga–H (R = tBu, CH₂tBu, iBu) yielded Ga/N‐based active Lewis pairs, R₂Ga–C(SiMe₃)=C(H)–NR'₂ ( 7 ). The Ga and N atoms adopt cis‐positions at the C=C bonds and show weak Ga–N interactions. tBu₂GaH and Me₃Si–C≡C–N(C₂H₄)₂NMe afforded under exposure of daylight the trifunctional digallium(II) compound [MeN(C₂H₄)₂N](H)C=C(SiMe₃)Ga(tBu)–Ga(tBu)C(SiMe₃)=C(H)[N(C₂H₄)₂NMe] ( 8 ), which results from elimination of isobutene and H₂ and Ga–Ga bond formation. 8 was selectively obtained from the ynamine and [tBu(H)Ga–Ga(H)tBu]₂[HGatBu₂]₂. 7a (R = tBu; NR'₂ = 2,6‐Me₂NC₅H₈) and H₈C₄N–C≡N afforded the adduct tBu₂Ga‐C(SiMe₃)=C(H)(2,6‐Me₂NC₅H₈) · N≡C–NC₄H₈ ( 11 ) with the nitrile bound to gallium. The analogous ALP with harder Al atoms yielded an adduct of the nitrile dimer or oligomers of the nitrile at room temperature. The reaction of 7a with Ph–N=C=O led to the insertion of two NCO groups into the Ga–C_vinyl bond to yield a GaOCNCN heterocycle with Ga bound to O and N atoms ( 12 ).     

Triphenylantimony(v) Derivatives of 2,2-Disubstituted Benzothiazoline Ligands: Synthetic and Spectroscopic Studies

The reactions of triphenylantimony(v) isopropoxide with 2,2-disubstituted benzothiazolines in a 1:2 molar ratio in refluxing benzene solution yielded the corresponding triphenylantimony(v) derivatives (1–5) of the type Ph₃Sb[SC₆H₄N: C(R)CH₂C(O)R']₂, [Where, R═CH₃, R'═CH₃(1); R═CH₃, R'═C₆H₅(2); R═CH₃, R'═4-CH₃C₆H₄(3); R═CH₃, R'═4-ClC₆H₄(4); and R═CF₃, R'═C₆H₅(5)]. All of these newly synthesized derivatives have been characterized by elemental analyses and molecular weight measurements as well as IR and NMR [¹H and ¹³C] spectral studies. On the basis of spectral data, seven-coordination around central antimony atom has been assigned to these derivatives.     

NEW NONGEMINAL CYCLOPHOSPHAZENES

A series of new nongeminally-substituted cyclic phosphazenes with various substituents has been prepared via deprotonation-substitution reactions at the Me groups of both the cis and trans isomers of [(Me)(Ph)PN] ₃ . Treatment of [(Me)(Ph)PN] ₃ with n-BuLi followed by reaction with organic electrophilic reagents affords a variety of cyclic derivatives, [(RCH ₂ )(Ph)PN] ₃ , [R = Me, Cl, Br, I, (CH ₂ ) ₂ Br, CH ₂ CH═CH ₂ , SR, C(═O)OLi, C(═O)OMe, C(═O)OEt]. The structures of theses cis cyclic phosphazenes, which were obtained by x-ray diffraction, illustrate the basket-like shape of the molecules. Heating the cis and trans isomers of the parent [(Me)(Ph)PN] ₃ produced mixtures of cyclic trimers and tetramers. The latter were isolated and characterized by x-ray crystallography. Nanoparticles of gold and silver were prepared by reduction of metal salts with a reducing agent in the presence of selected trimers.     

Probing long‐range spin–spin coupling constants in 2‐halo‐substituted cyclohexanones and cyclohexanethiones: The role of solvent and stereoelectronic effects

Earlier studies with 2‐bromocyclohexanone demonstrated a measurable long‐range coupling constant (⁴J_H2,H6) for the equatorial conformer, although ⁴J_H2,H4 and ⁴J_H4,H6 were not observed; as a consequence, it is inferred that the carbonyl group plays an important role particularly due to hyperconjugative interactions σ_C2H2→π*_C═O and σ_C6H6→π*_C═O. In the present study, NBO analysis and coupling constant calculations were performed to cyclohexanone and cyclohexanethione alpha substituted with F, Cl, and Br, aiming to evaluate the halogen effect and acceptor character of the π* orbital on the long‐range coupling pathway. The σ_C2H2→π*_C1═Y and σ_C6H6→π*_C1═Y (Y═O and S) hyperconjugative interactions for the equatorial conformer indeed contribute for the ⁴J_H2,H6 transmission mechanism_. Surprisingly, the ⁴J_H2,H6 value is higher for the carbonyl compounds, although the interactions σ_C2H2→π*_C═Y and σ_C6H6→π*_C═Y are more efficient for the thiocarbonyl compounds. Accordingly, the Fermi contact (FC) contribution for the thiocarbonyl compounds decays deeper than in ketones, thus reducing more the ⁴J_H2,H6 values. Moreover, both π_C═S→σ*_C─X and π_C═S→σ*_C─H interactions seem to be stronger in thiocarbonyl than in carbonylic compounds. The implicit solvent effect (DMSO and water) on the coupling constant values was negligible when compared with the gas phase. On the other hand, an explicit solvent effect was found and ⁴J_H2,H6 for the thiocarbonyl compounds appeared to be more sensitive than for the cyclohexanones.     

A photochemical route to ferrocenyl‐substituted ferrapyrrolinone complexes

In the presence of iron pentacarbonyl, photochemical reaction between phenylisocyanate and ferrocenylacetylene results in ferrapyrrolinone complex [Fe₂(CO)₆(μ₂‐η³‐FcC═C(H)C(O)NPh)] ( 1 ) and maleimide 3‐ferrocenyl‐1‐phenyl‐1H ‐pyrrole‐2,5‐dione ( 2 ). Under similar experimental conditions, ferrocenyl−/phenyl‐substituted butadiyne primarily shows the activation of only one C☰C bond and results in ferrapyrrolinone complexes [Fe₂(CO)₆(μ₂‐η³‐FcC═C(C☰CR)C(O)NPh)] ( 3 , R = Fc; 3a , R = Ph), maleimides 3‐ferrocenyl‐1‐phenyl‐4‐(ferrocenylethynyl)‐1H –pyrrole‐2,5‐dione ( 5 ) and 3‐ferrocenyl‐1‐phenyl‐4‐(phenylethynyl)‐1H –pyrrole‐2,5‐dione ( 5a ) and [Fe₂(CO)₆(μ₂‐η³‐FcC═C(R)C(O)NPh)] ( 4 ; R  = 3‐ferrocenyl‐1‐phenyl‐1H ‐pyrrole‐2,5‐dione). Compound 4 consists of ferrapyrrolinone and a maleimide unit, formed by the activation of both C☰C bonds of diferrocenylbutadiyne. Activation of both C☰C bonds in a substituted butadiyne is a rare observation. Formation of the ferrapyrrolinone compounds is an advance over the earlier reported methods which generally use internal alkynes and involve prior synthesis of other clusters.     

13C NMR STUDY OF SUBSTITUENT EFFECTS IN 1,2,4-OXADIAZOLE AND 1,2,4-THIADIAZOLE DERIVATIVES

¹³C chemical shifts of C═N, C═O and C═S carbons of 3,4-disubstituted-1,2,4-oxadiazole-5-ones(thiones) and 3,4-disubstituted-1,2,4-thiadiazole-5-ones have been determined in CDCl₃ solution. Exceptionally good Hammett correlations of ¹³C NMR chemical shifts of these carbons with σ were obtained. The negative ρ values observed (inverse substituent effects) indicate π-polarization of the C═N, C═O and C═S bonds. As expected, the long distance C═O and C═S ¹³C chemical shifts were found less susceptible to substituent-induced electronic changes.     

The first C(O)NHP(O)-based phosphoric triamide structure with an N‒H···π hydrogen bonding: A combination of X-ray crystallography and theoretical study to evaluate the strength of hydrogen bonds

The hydrogen bond pattern of N-(4-methoxybenzoyl)-N′,N″-bis(4-methylbenzyl)-phosphoric triamide, C₂₄H₂₈N₃O₃P, (I), was investigated. In the crystal structure, the molecules are aggregated through N_CP―H···O═P and N_P―H···O═C hydrogen bonds in a one-dimensional arrangement parallel to the c axis (N_CP is the nitrogen atom in the C(O)NHP(O) segment and N_P stands for the two other nitrogen atoms bonded to the P atom). There is also a novel N_P?H···π hydrogen bond in the crystal which extends the aggregation of the molecules to a two-dimensional array parallel to the bc plane. A Cambridge Structural Database (CSD, version 5.37, Feb 2016) analysis shows that the N―H···π hydrogen bond was not observed in any of 156 [RC(O)NH]P(O)[NR¹R² Allen, F. H.; Taylor, R. Chem. Soc. Rev. 2004, 33, 463-475.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]]₂ (R¹ ≠ H, R² = H or ≠ H) phosphoric triamide structures reported so far. The theoretical calculations at the B3LYP/6-311G^** level of theory (DFT, AIM, and NBO) were performed to evaluate the strengths of N_CP―H···O═P, N_P―H···O═C and N_P―H···π hydrogen bonds, considering two-aggregate molecular assemblies containing these hydrogen bonds. The calculations on the title compound suggest that the intermolecular N_CP―H···O═P hydrogen bond is stronger than N_P―H···O═C and N_P―H···π interactions. The hydrogen bond strength was investigated by NBO, topological analysis, geometry calculation, Hirshfeld surface analysis and experimental spectroscopic results, which are in agreement with each other.     

The reaction of perfluoroalkanesulfinates: IV. Perfluoroalkyl radical addition to olefins initiated by single electron oxidation of perfluoroalkanesulfinate

Sodium perfluoroalkanesulfinates [Cl (CF₂)_n SO₂ Na (1), a , n = 4; b , n = 6; c , n = 8] with the reduction potentials about 0.95—1.00V could be oxidized readily with various oxidizing agents such as Mn (OAc)₃ 2H₂O, Ce (SO₄)₂, HgSO₄ and Co₂O₃ to generate perfluoroalkyl radicals which added to the olefins RCH ? CHR' to give two kinds of adducts, namely RCH (R_f) CHXR' (3, X ? H; 4, X ? OAc), with good yields depending upon the solvent system used. Different oxidizing agents showed slight variation on the yields of the adducts. The reaction time could be greatly shortened at higher temperature. Thus, this reaction provides a new way for introducing a perfluoroalkyl group into olefinic compounds.     

Alkylation of salts ofN-(β-hydroxyalkyl)-N′-hydroxydiazeneN-oxides with alkyl halides and dimethyl sulfate

Salts ofN-(β-hydroxyalkyl)-N′-hydroxydiazeneN-oxides, RCH(OH)CH₂N(O)=NO⁻ M⁺ (R=Me, Prⁱ, or Bu^t; and M=Li, Na, K, Ag, NH₄, or Me₄N), were prepared. Their alkylation with alkyl halides R′X (X=Cl, Br, or I) and dimethyl sulfate was studied. Generally, alkylation afforded mixtures ofN-(β-hydroxyalkyl)-N′-alkoxydiazeneN-oxides RCH(OH)CH₂N(O)=NOR′ andO-alkyl-N-(β-hydroxyalkyl)-N-nitrosohydroxylamines RCH(OH)CH₂N(NO)OR′. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1996–2001, October, 1998.     

Kinetics of the liquid-phase oxidation of 2-hydroxycyclohexanone

The kinetics of oxygen uptake in the azobisisobutyronitrile-initiated oxidation of 2-hydroxycy-clohexanone (RCH(OH)C(O)R) at 323 K has been investigated (chlorobenzene solvent, [RCH(OH)C(O)R] = 0.15-1.30 mol/L, initiation rate of w _i = 0.016–0.473 mol L^?1 s^?1). The effective oxidizability parameter k _{p, eff}(2k _t,eff)^?0.5 has been determined by solving the inverse kinetic problem using the entire data array obtained while varying [RCH(OH)C(O)R] and w _i. The rate constants of chain propagation and termination and the equilibrium constant of the addition of the hydroxyperoxyl radical to the ketoalcohol have been derived from the dependence of the oxidizability parameter on the substrate concentration. The rate constant of bimolecular chain initiation has been calculated to be k ₀ = 9.7 × 10^?7 L mol^?1 s^?1. The ratio of the rate constants of quadratic-law peroxyl radical recombination reactions without and with chain termination (k _eff′/k _t,eff′) increases with increasing [RCH(OH)C(O)R], passes through a maximum at a substrate concentration of 0.8 mol/L, and then falls off. It is demonstrated that this effect is due to the variation of the proportions of the hydroperoxyl and organic (1-hydroxy-2-oxocyclohexylperoxyl or 1,2-dihydroxy-1-cyclo-hexylperoxyl) radicals in the reaction medium.