Tatsuo Erabi

Bis(2,6-dimethoxyphenyl) sulfide, selenide and telluride, and their derivatives

Abstract 2,6-Dimethoxyphenyl derivatives of sulfur, selenium, and tellurium, such as ΦEEΦ, Φ 2 E, ΦSeH, [MeΦ 2 E]X (X=MeSO 4 , ClO 4 ), Φ 2 EO ·  x H 2 O, [Φ 2 EOR]ClO 4 , [Φ 2 EOH]ClO 4 (R=Me, Et), Me 2 SnCl 2  · 2Φ 2 EO (E=S, Se) [Φ=2,6-(MeO) 2 C 6 H 3 ; E=S, Se, Te] have been prepared, and their properties compared with common phenyl derivatives. The reaction rates of Φ 2 E with dimethyl sulfate and butyl bromide increased in the order E=S 3 M and Φ 3 M, M=P>As>Sb. These reactivities are parallel with the electrochemical oxidation potentials reported for Ph 2 E and with the first ionization potentials reported for Ph 3 M. The rate of Φ 2 Te was faster than that of Ph 3 P and slightly faster than that of Φ 3 Sb. From the reactivity of [Φ 2 E-Me] + salts with nucleophiles, the E + –Me bond strengths were estimated to increase in the order E=Se 2 EO with dimethyl sulfate increased in the order E=S 2 EO was faster than that of Φ 2 E. The origins of these reactivities and bond strengths are discussed.

TWO-STEP SYNTHESIS OF TRIARYLMETALS (AS, SB, BI) STARTING FROM THE METAL OXIDES AND 2,6-DIMETHOXYBENZENETHIOL

Reported here is a new synthetic method of triarylmetals MAr3 (M = As, Sb, Bi). It is composed of two-step reactions starting from the metal oxides: (1) A reaction of the metal oxide with 2,6-dimethoxybenzenethiol ΦSH [Φ = 2,6-(MeO)2C6H3] in the presence of acid to give the thiolatometals M(SΦ)3, and (2) A reaction of M(SΦ)3 with organolithium reagent LiAr to give MAr3 (Ar = Ph, 4-MeC6H4, 4-Me2NC6H4, Φ). Since ΦSH is odorless and crystalline, most of it can be recovered after the reactions without difficulty for repeated usages. The intermediates M(SΦ)3 are also crystalline and inert against hydrolysis.

1:1 Complexes of dimethyltin dihalides with tris(2,6-dimethoxyphenyl)phosphine oxide, its sulphide, and related compounds

Dimethyltin dihalides Me2SnX2 (X = Cl, Br) only form 1:1 complexes with 2,6-dimethoxyphenylphosphine oxides Φ3PO, PhΦ2PO and Ph2ΦPO (Φ = 2,6-(MeO)2C6H3) even though the ligands are used in excess. 2,6-Dimethoxyphenylphosphine sulphides Φ3PS and PhΦ2PS also form analogous 1:1 complexes, while Ph2ΦPS and Ph3PS do not react. X-Ray crystal structural analysis of Me2SnCl2·OPΦ3 reveals that the tin atom is penta-coordinated in a distorted trigonal bipyramidal arrangement, with a chlorine and two methyl carbon atoms in the equatorial positions and the other chlorine and the Φ3PO oxygen atom in the axial positions.

Tris(2-6-dimethoxephenyl) borane and its adducts

Tris(2,6-dimethoxpphenyl)borane, φ3B(φ = 2,6,-(MeO)2C6H3), an air-stable crystalline compound, formed isolable 1:1 adducts with ammonia and some primary amines but not with tertiary amines, secondary amines, or sec-alkylamines. Some tetraalkylammonium tris(2,6-dimethoxypyenyl)cyanoborates [R4N][φ3BCN] are soluble both in water and in benzene, and the stearyltrimethylammonium salt is soluble even in n-hexane. The freezing point depression measurements for some tetraalkylammonium salts suggested that they are associated in benzene by several molecules.

Oxidation potential of benzylferrocenes and related compounds: effects of the ortho-methoxy substituent in the phenyl group

Oxidation potentials of some ferrocenyl derivatives of type Fc-CHΦOH, FcCΦΦ′OH, FcCH 2 Φ, FcCHΦΦ′ [Fc=Fe(η 5 -C 5 H 5 )(η 5 -C 5 H 4 ); Φ, Φ′=2,4,6-(MeO) 3 C 6 H 2 , 2,6-(MeO) 2 ·C 6 H 3 , 2,5-(MeO) 2 ·C 6 H 3 , 2,4-(MeO) 2 ·C 6 H 3 , 2-MeOC 6 H 4 , 4-MeOC 6 H 4 , C 6 H 5 ] were measured in acetonitrile. All of them exhibited a reversible one-electron oxidation–reduction wave based on the ferrocene–ferrocenium redox couple with a wide range of shift. Compounds having ortho -methoxy groups showed lower redox potentials than those of compounds having para -methoxy groups. The X-ray crystal structure of FcCHΦ 2 a showed that the ortho -methoxy oxygens were situated very close to the central carbon, and there is a possibility that one of the oxygen lone-pairs interacts with the antibonding orbital of CFc σ-bond. Some other possibilities are also discussed.

Stability and reactivity of ferrocenyl(2,4,6-trimethoxyphenyl)carbenium salts

Abstract Ferrocenyl(phenyl)methanols, Fc–CHΦOH [Fc=Fe(η 5 -C 5 H 5 )(η 5 -C 5 H 4 ), Φ a =2,4,6-(MeO) 3 C 6 H 2 ( 1a ); Φ b =2,6-(MeO) 2 C 6 H 3 ( 1b )], were prepared by the reactions of FcCHO with ΦLi. 1a reacted with only a slight excess of perchloric acid or tetrafluoroboric acid even in methanol and in 1 M HCl acid to give dark violet crystals of the carbenium salts, [FcCHΦ a ]X [X=ClO 4 ( 2a ), BF 4 ( 2a′ )]. 1b reacted with these acids in diethylether to give the carbenium salts, [FcCHΦ b ]X [X=ClO 4 ( 2b ), BF 4 ( 2b′ ) (dark red–brown crystals)] in good yields. The p K R + values could be measured in HCl acid for 1a (3.0) and for 1b (1.6). 2a and 2b were labile in hot 2-propanol to give the reduced compounds, FcCH 2 Φ. 1a and 1b reacted with 1,3,5-trimethoxybenzene, Φ a H, in 2-methyl-2-propanol containing only a slight excess of HCl acid to give diphenyl(ferrocenyl)methanes, FcCHΦ a 2 and FcCHΦ a Φ b , respectively. While 1a decomposed in neat 1,3-dimethoxybenzene, Φ b H, in the presence of acid, 1b reacted to give 2,4-dimethoxyphenyl(2,6-dimethoxyphenyl)ferrocenylmethane, FcCHΦ b Φ d [Φ d =2,4-(MeO) 2 C 6 H 3 ]. The 1 H-NMR spectrum of 2a was temperature-dependent and indicated that the free rotations of both Fc and Φ a groups in 2a existed at r.t. but were frozen at −60°C.

Dependence of the rotational barrier of the Ar-group in RArTeX2 on the R-group [Ar = 2,6-(MeO)2C6H3; R = Me, Et, i-Pr; X = Cl, Br, I]

Alkyl(2,6-dimethoxyphenyl)tellurium dihalides, RArTeX2 [Ar = 2,6-(MeO)2C6H3; X = Cl 2a–c, Br 3a–c, I 4a–c; R = Me a, Et b, i-Pr c] were prepared by the reactions of alkyl 2,6-dimethoxyphenyl telluride, RArTe 1, with SOCl2, Br2 or I2, respectively. The rotational barrier ΔG‡ of the Ar-group around the Te–C bond in 2a–c, 3a–c and 4a–c estimated by variable temperature 1H NMR spectra was dependent on the alkyl (R) group as well as on the halogen atoms. It decreased in the order R = Me > Et > i-Pr as well as X = Cl > Br > I. The 125Te resonances of 1 were observed at higher magnetic fields than those of RPhTe, and those of 1a–c, 2a–c, 3a–c and 4a–c shifted to lower magnetic field in the order R = Me > Et > i-Pr. The X-ray crystallographic analyses of 2a–c, 3a, 3b and 4a showed that the geometry around tellurium was pseudo-trigonal bipyramidal with the alkyl group, the Ar group and a lone pair of electrons in the equatorial positions and with two halogen atoms in the apical positions. Whereas each of the Te–C(Ar) bond distances were very similar [2.10 ± 0.01 A], the Te–C(R) bonds of 2a–c were longer than Te–C(Ar) and increased in length in the order R = Me < Et < i-Pr. The C(Ar)–Te–C(R) bond angles also increased in the order R = Me < Et < i-Pr. These molecules were bridged by intermolecular Te⋯X bonding to form dimers or polymers. Based on these results and VSEPR theory, the dependence of the rotational barrier ΔG‡ of the Ar-group in RArTeX2 on the R-group is discussed.

Anodic Oxidation of Bis(2,6-Dimethoxyphenyl)Chalcogenides

Cyclic voltammetric measurements were made for bis(2,6-dimethoxyphenyl)chalcogenides (Φ2X, Φ= 2,6-dimethoxyphenyl, X = S, Se, Te). It is expected that the active species generated at the first oxidation wave are the corresponding cation radicals for Φ2Te and Φ2S, whereas it is the cation for Φ2Se.