Reactivity of Novel <i>N</i>,<i>N′</i>-Diphosphino-Silanediamine-Based Rhodium(I) Derivatives

The coordination abilities of the novel N,N′-diphosphino-silanediamine ligand of formula SiMe2(NtolPPh2)2 (SiNP, 1) have been investigated toward rhodium, and the derivatives [RhCl(SiNP)]2 (2), [Rh(SiNP)(COD)][BF4] (3), and Rh(acac)(SiNP) (4) have been synthesized. The stability of the dinuclear frame of [RhCl(SiNP)]2 (2) toward incoming nucleophiles has been shown to be dependent on their π-acceptor ability. Indeed, the mononuclear complexes RhCl(SiNP)(L) (L = CO, 5; CNtBu, 6) have been isolated purely and quantitatively upon reaction of 2 with CO and CNtBu, respectively. Otherwise, PPh3 and RhCl(SiNP) equilibrate with Rh(Cl)(SiNP)(PPh3) (7). Carbon electrophiles such as MeI and 3-chloro-1-proprene afforded the oxidation of rhodium(I) to rhodium(III) and the formation of RhCl2(η3-C3H5)(SiNP) (8) and Rh(Me)(I)(SiNP)(acac) (10), respectively. The methyl derivative 10 is thermally stable and does not react either with CO or with CNtBu even in excess. Otherwise, RhCl2(η3-C3H5)(SiNP) (8) is thermally stable but reacts with CO, affording 3-chloro-1-proprene and RhCl(SiNP)(CO) (5). Finally, upon reaction of Rh(acac)(SiNP) (4) and 3-chloro-1-proprene, RhCl(acac)(η1-C3H5)(SiNP) (9a) and [Rh(acac)(η3-C3H5)(SiNP)]Cl (9b) could be detected at 233 K. At higher temperatures, 9a and 9b smoothly decompose, affording the dinuclear derivative [RhCl(SiNP)]2 (2) and the CC coupling product 3-allylpentane-2,4-dione

Reactivity of Novel <i>N</i>,<i>N′</i>-Diphosphino-Silanediamine-Based Rhodium(I) Derivatives

The coordination abilities of the novel N,N′-diphosphino-silanediamine ligand of formula SiMe2(NtolPPh2)2 (SiNP, 1) have been investigated toward rhodium, and the derivatives [RhCl(SiNP)]2 (2), [Rh(SiNP)(COD)][BF4] (3), and Rh(acac)(SiNP) (4) have been synthesized. The stability of the dinuclear frame of [RhCl(SiNP)]2 (2) toward incoming nucleophiles has been shown to be dependent on their π-acceptor ability. Indeed, the mononuclear complexes RhCl(SiNP)(L) (L = CO, 5; CNtBu, 6) have been isolated purely and quantitatively upon reaction of 2 with CO and CNtBu, respectively. Otherwise, PPh3 and RhCl(SiNP) equilibrate with Rh(Cl)(SiNP)(PPh3) (7). Carbon electrophiles such as MeI and 3-chloro-1-proprene afforded the oxidation of rhodium(I) to rhodium(III) and the formation of RhCl2(η3-C3H5)(SiNP) (8) and Rh(Me)(I)(SiNP)(acac) (10), respectively. The methyl derivative 10 is thermally stable and does not react either with CO or with CNtBu even in excess. Otherwise, RhCl2(η3-C3H5)(SiNP) (8) is thermally stable but reacts with CO, affording 3-chloro-1-proprene and RhCl(SiNP)(CO) (5). Finally, upon reaction of Rh(acac)(SiNP) (4) and 3-chloro-1-proprene, RhCl(acac)(η1-C3H5)(SiNP) (9a) and [Rh(acac)(η3-C3H5)(SiNP)]Cl (9b) could be detected at 233 K. At higher temperatures, 9a and 9b smoothly decompose, affording the dinuclear derivative [RhCl(SiNP)]2 (2) and the CC coupling product 3-allylpentane-2,4-dione

The First Nitro-Substituted Heteroscorpionate Ligand

The new dihydridobis(3-nitro-1,2,4-triazolyl)borate ligand, [H2B(tzNO2)2]-, has been synthesized in dimethylacetamide solution, using 3-nitro-1,2,4-triazole and KBH4 through careful temperature control, and characterized as its potassium salt. The zinc(II) and cadmium(II) complexes, {M[H2B(tzNO2)2]Cl(H2O)2}, have been prepared by metathesis of [H2B(tzNO2)2]K with ZnCl2 and CdCl2, respectively. The complexes likely contain a metal core in which the ligand is coordinated to the metal ions in the κ2-N,N‘ or κ4-N,N‘,O,O‘ fashion. A single-crystal structural characterization is reported for the potassium dihydrobis(3-nitro-1,2,4-triazolyl)borate. The potassium salt is polymeric and shows several K···N and K···O interactions

The First Nitro-Substituted Heteroscorpionate Ligand

The new dihydridobis(3-nitro-1,2,4-triazolyl)borate ligand, [H2B(tzNO2)2]-, has been synthesized in dimethylacetamide solution, using 3-nitro-1,2,4-triazole and KBH4 through careful temperature control, and characterized as its potassium salt. The zinc(II) and cadmium(II) complexes, {M[H2B(tzNO2)2]Cl(H2O)2}, have been prepared by metathesis of [H2B(tzNO2)2]K with ZnCl2 and CdCl2, respectively. The complexes likely contain a metal core in which the ligand is coordinated to the metal ions in the κ2-N,N‘ or κ4-N,N‘,O,O‘ fashion. A single-crystal structural characterization is reported for the potassium dihydrobis(3-nitro-1,2,4-triazolyl)borate. The potassium salt is polymeric and shows several K···N and K···O interactions

Single Two-Electron Transfers and Successive One-Electron Transfers in Biferrocenyl−Indacene Isomers

Novel biferrocenyl complexes of s- and as-dihydroindacenes have been prepared and the charge transfer properties of their mono- and dicationic derivatives, selectively generated by one-electron and two-electron oxidation, have been investigated. Mixed-valence cations are generated by chemical oxidation using acetylferricinium as an oxidant agent and monitored in the visible, IR, and near-IR regions. The IT bands in the near-IR spectra are rationalized in the framework of Marcus−Hush theory. The rigid and planar indacene platform bonded to two terminal redox groups displays a redox chemistry that can be switched from single two-electron transfers to two successive one-electron transfers by changing the supporting electrolyte from nBu4NPF6 to nBu4NB(C6F5)4

Single Two-Electron Transfers and Successive One-Electron Transfers in Biferrocenyl−Indacene Isomers

Novel biferrocenyl complexes of s- and as-dihydroindacenes have been prepared and the charge transfer properties of their mono- and dicationic derivatives, selectively generated by one-electron and two-electron oxidation, have been investigated. Mixed-valence cations are generated by chemical oxidation using acetylferricinium as an oxidant agent and monitored in the visible, IR, and near-IR regions. The IT bands in the near-IR spectra are rationalized in the framework of Marcus−Hush theory. The rigid and planar indacene platform bonded to two terminal redox groups displays a redox chemistry that can be switched from single two-electron transfers to two successive one-electron transfers by changing the supporting electrolyte from nBu4NPF6 to nBu4NB(C6F5)4

A Simple Route to Novel Palladium(II) Catalysts with Oxazolin-2-ylidene Ligands

Novel palladium(II) complexes with oxazolin-2-ylidene ligands have been synthesized via direct reaction of palladium acetate and oxazolium salts, prepared in turn by alkylation of oxazole with methyl iodide or benzylic bromides. The resulting complexes have been characterized and used as catalysts in Heck coupling reactions of aryl bromides, where they exhibit remarkable catalytic activity, higher than that of the closely related bis-imidazolin-2-ylidene and bis-benzothiazolin-2-ylidene complexes

A Novel Compound in the Lanthanide(III) DOTA Series. X-ray Crystal and Molecular Structure of the Complex Na[La(DOTA)La(HDOTA)]·10H₂O

A Novel Compound in the Lanthanide(III) DOTA Series. X-ray Crystal and Molecular Structure of the Complex Na[La(DOTA)La(HDOTA)]·10H2

Energetics and Structure of Uranium(VI)–Acetate Complexes in Dimethyl Sulfoxide

The thermodynamics of the complexation between uranium­(VI) and acetate in dimethyl sulfoxide (DMSO) was studied at 298 K in an ionic medium of 0.1 mol dm^–3 tetrabutyl ammonium perchlorate. The results show that the uranyl ion forms three strong successive mononuclear complexes with acetate. The complexes, both enthalpically and entropically stabilized, are significantly more stable in DMSO than in water. This feature can be ascribed to the weak solvation of acetate in DMSO. The thermodynamic parameters for the formation of the uranium­(VI) complexes with acetate in DMSO are compared with those with ethylenediamine in the same solvent. The difference between the two ligand systems reveals that, for the complexation reactions involving charge neutralization, the reorganization of the solvent gives a very important contribution to the overall complexation energetics. The coordination mode of acetate in the uranyl complexes and the changes of the solvation sphere of UO₂²⁺ upon complexation were investigated by FT-IR spectroscopy in DMSO and in acetonitrile/DMSO mixtures. In addition, DFT calculations were performed to provide an accurate description of the complexation at the molecular level. The experimental and calculated results suggest that acetate is solely bidentate to UO₂²⁺ in the 1:1 and 1:3 complexes but mono- and bidentate in the 1:2 complexes. The DFT calculations also indicate that the medium effects must always be taken into account in order to gain accurate information on the complex formation in solution. In fact, the relative stability of the reaction products changes markedly when the DFT calculations are carried out in vacuum or in DMSO solution

A Simple Route to Novel Palladium(II) Catalysts with Oxazolin-2-ylidene Ligands

Novel palladium(II) complexes with oxazolin-2-ylidene ligands have been synthesized via direct reaction of palladium acetate and oxazolium salts, prepared in turn by alkylation of oxazole with methyl iodide or benzylic bromides. The resulting complexes have been characterized and used as catalysts in Heck coupling reactions of aryl bromides, where they exhibit remarkable catalytic activity, higher than that of the closely related bis-imidazolin-2-ylidene and bis-benzothiazolin-2-ylidene complexes