“…Selenol/diselenide exchange reactions between RSeH and (RSe) 2 have been previously investigated, e.g., R = CH 2 CH 2 OH 33 and CH 2 CH 2 NH 3 + , , with the conclusion that the deprotonated selenolate, RSe - , is the species responsible for effecting the exchange. − On this basis, a reasonable mechanism for the (seim R* )H/(seim R ) 2 exchange process (where R* is a label to describe the exchange) involves (i) proton transfer from (seim R* )H to one of the nitrogen atoms of (seim R ) 2 to generate [(seim R* )] - and [(seim R ){(seim R )H}] + , followed by (ii) nucleophilic attack by [(seim R* )] - on [(seim R ){(seim R )H}] + to liberate (seim R )H and form (seim R* )(seim R ), as illustrated in Scheme . 3 …”
1-Mesityl-1,3-dihydro-imidazole-2-selone, (seim(Mes))H, may be obtained from 1-mesitylimidazole via (i) deprotonation with Bu(n)Li, (ii) treatment with elemental selenium, and (iii) addition of HCl(aq). Structural characterization of (seim(Mes))H by X-ray diffraction demonstrates that the compound exists as the selone rather than selenol tautomer, a result that is in accord with DFT calculations. Solutions of (seim(Mes))H are oxidized by air to give bis(1-mesitylimidazol-2-yl)diselenide, (seim(Mes))(2). A corresponding investigation of (seim(Me))H demonstrates that, in contrast to a previous report, the selenium analogue of methimazole exists in the selone form with a structure analogous to that of methimazole. (1)H and (77)Se NMR studies demonstrate that the (seim(R)) groups of the selone (seim(R))H and diselenide (seim(R))(2) undergo facile exchange on the NMR time scale.
“…Selenol/diselenide exchange reactions between RSeH and (RSe) 2 have been previously investigated, e.g., R = CH 2 CH 2 OH 33 and CH 2 CH 2 NH 3 + , , with the conclusion that the deprotonated selenolate, RSe - , is the species responsible for effecting the exchange. − On this basis, a reasonable mechanism for the (seim R* )H/(seim R ) 2 exchange process (where R* is a label to describe the exchange) involves (i) proton transfer from (seim R* )H to one of the nitrogen atoms of (seim R ) 2 to generate [(seim R* )] - and [(seim R ){(seim R )H}] + , followed by (ii) nucleophilic attack by [(seim R* )] - on [(seim R ){(seim R )H}] + to liberate (seim R )H and form (seim R* )(seim R ), as illustrated in Scheme . 3 …”
1-Mesityl-1,3-dihydro-imidazole-2-selone, (seim(Mes))H, may be obtained from 1-mesitylimidazole via (i) deprotonation with Bu(n)Li, (ii) treatment with elemental selenium, and (iii) addition of HCl(aq). Structural characterization of (seim(Mes))H by X-ray diffraction demonstrates that the compound exists as the selone rather than selenol tautomer, a result that is in accord with DFT calculations. Solutions of (seim(Mes))H are oxidized by air to give bis(1-mesitylimidazol-2-yl)diselenide, (seim(Mes))(2). A corresponding investigation of (seim(Me))H demonstrates that, in contrast to a previous report, the selenium analogue of methimazole exists in the selone form with a structure analogous to that of methimazole. (1)H and (77)Se NMR studies demonstrate that the (seim(R)) groups of the selone (seim(R))H and diselenide (seim(R))(2) undergo facile exchange on the NMR time scale.
“…Meanwhile, we have recently succeeded in the first isolation of stable hydrido(selenolato) platinum(II) complex cis -(Ph 3 P) 2 Pt(H)(SeTrip) using a bulky substituent, the 9-triptycyl group (Trip = 9-triptycyl) . On the basis of this result, we envisioned that the introduction of the 9-triptycyl group onto a germanium atom that should coordinate to a platinum center would be useful for the preparation of novel classes of germyl(hydrido) complexes.…”
The first stable dihydrogermyl(hydrido) platinum(II) complex cis-(Ph3P)2Pt(H)(GeH2Trip) (2) was synthesized by the oxidative addition reaction of an overcrowded trihydrogermane, TripGeH3 (1, Trip = 9-triptycyl), with (Ph3P)2Pt(η2-C2H4) in toluene. The reaction of 1 with (dppe)PtCl2 in the presence of NaBH4 afforded the corresponding hydrido complex (dppe)Pt(H)(GeH2Trip) (3) together with bis(germyl) platinum(II) complex (dppe)Pt(GeH2Trip)2 (4). In addition, the ligand exchange reaction of complex 2 with free Cy2PCH2CH2PCy2 in toluene resulted in the formation of (dcpe)Pt(H)(GeH2Trip) (5) in moderate yield. The structures of complexes 2−5 were fully determined on the basis of their NMR and IR spectra and elemental analyses. Moreover, the low-temperature X-ray crystallography of 2, 3, and 5 revealed that the platinum center has a distorted square-planar environment, probably due to the steric requirement of the cis-coordinated phosphine ligands and the bulky 9-triptycyl group on the germanium atom. Furthermore, the thermal rearrangement of bis(germyl) complex 4 in toluene at 60 °C gave digermyl(hydrido) complex (dppe)Pt(H)[Ge(HTrip)GeH2Trip] (6) in high yield without irreversible reductive elimination of tetrahydrodigermane.
The reaction of [PtH(SeTrip)(PPh 3 ) 2 ] (Trip = 9-triptycyl) (3) with dimethyl acetylenedicarboxylate (DMAD) or methyl propiolate gave hydroselenation syn adducts. The reaction of [PtH(SeTrip)(dppe)] [dppe = 1,2-bis(diphenylphosphanyl)-ethane], which has a stronger phosphane σ-donor ligand than 3, with DMAD gave both syn and anti adducts. The reaction of 3 and DMAD in the presence of PPh 3 yielded no
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