Ti(O<i>i</i>Pr)₄‑Mediated Multicomponent Reactions Involving Triple Additions to Isonitrile Carbon Atoms

Double addition of Grignard reagents to isonitriles was achieved in the presence of stoichiometric amounts of [Ti­(O<i>i</i>Pr)₄]. Functionalized isonitrile components were obtained in situ via lithiation of chiral and achiral 2-oxazolines, and the resulting amidomethyltitanium intermediate further reacted with a range of electrophiles. The established multicomponent procedure gave rise to highly substituted 2-aminomorpholines, acyclic diamino alcohols, and prenylated amino alcohols via straightforward synthetic protocols

Ti(O<i>i</i>Pr)₄‑Mediated Multicomponent Reactions Involving Triple Additions to Isonitrile Carbon Atoms

Double addition of Grignard reagents to isonitriles was achieved in the presence of stoichiometric amounts of [Ti­(O<i>i</i>Pr)₄]. Functionalized isonitrile components were obtained in situ via lithiation of chiral and achiral 2-oxazolines, and the resulting amidomethyltitanium intermediate further reacted with a range of electrophiles. The established multicomponent procedure gave rise to highly substituted 2-aminomorpholines, acyclic diamino alcohols, and prenylated amino alcohols via straightforward synthetic protocols

Iridium Half-Sandwich Complexes with Di- and Tridentate Bis(pyridylimino)isoindolato Ligands: Stoichiometric and Catalytic Reactivity

A series of κ²-(<i>N</i>,<i>N</i>)-coordinated bis­(2-pyridylimino)­isoindolato (BPI) complexes [Cp*Ir­(BPI)­Cl], which possess “three-legged piano-stool” structures, with the iridium atom being coordinated by the Cp* ligand 2 × N and Cl, were prepared via deprotonation of the BPIH ligands with either potassium hydride or LDA and subsequent reaction with [Cp*IrCl₂]₂ in THF. Cationic complexes [Cp*Ir­(BPI)]⁺ containing κ³-(<i>N</i>,<i>N</i>,<i>N</i>)-coordinated BPI ligands were prepared as well as complexes with bidentate-coordinated BPI ligands, where the chloride ligand was substituted by either neutral or anionic ligands. Substitution in the <i>ortho</i>-position of the PBI ligands led to the formation of cycloiridated κ³-(<i>N</i>,<i>N</i>,<i>C</i>) species. Upon substitution of the anionic ligand by triphenylphosphine, a product was obtained with a hitherto unobserved κ²-(<i>N</i>,<i>N</i>) coordination of <i>o</i>Me-BPI to the metal center via the deprotonated nitrogen atom of the isoindole unit and one of the imine nitrogen atoms of the BPI ligand. A series of (<i>para</i>-cymene) osmium half-sandwich complexes with analogous structures and reactivities to their isoelectronic Cp*Ir­(BPI) congeners were also prepared. Finally, it has been demonstrated that both Ir and Os complexes are catalytically active in the transfer hydrogenation of various ketones and imines

Structures, Electronics, and Reactivity of Strained Phosphazane Cages: A Combined Experimental and Computational Study

A series of formamidine-bridged P₂N₂ cages have been prepared. Upon deprotonation, these compounds serve as valuable precursors to hybrid <i>N</i>-heterocyclic carbene ligands, whereas direct metalation gives rearranged dimetallic complexes as a result of cleavage of the formamidine bridge. The latter metal complexes contain an intact cyclophosphazane moiety that coordinates two distinct metal centers in a monodentate and a chelating fashion. A computational study has been carried out to elucidate the bonding within the P₂N₂ framework as well as the reactivity patterns. Natural bond orbital analysis indicates that the cage motif is poorly described by localized Lewis structures and that negative hyperconjugation effects govern the stability of the bicyclic framework. The donor capacity of the cyclophosphazane unit was assessed by inspection of the frontier molecular orbitals, highlighting the fact that π-back-donation from the metal fragments is crucial for effective metal–ligand binding

Iridium Half-Sandwich Complexes with Di- and Tridentate Bis(pyridylimino)isoindolato Ligands: Stoichiometric and Catalytic Reactivity

A series of κ²-(<i>N</i>,<i>N</i>)-coordinated bis­(2-pyridylimino)­isoindolato (BPI) complexes [Cp*Ir­(BPI)­Cl], which possess “three-legged piano-stool” structures, with the iridium atom being coordinated by the Cp* ligand 2 × N and Cl, were prepared via deprotonation of the BPIH ligands with either potassium hydride or LDA and subsequent reaction with [Cp*IrCl₂]₂ in THF. Cationic complexes [Cp*Ir­(BPI)]⁺ containing κ³-(<i>N</i>,<i>N</i>,<i>N</i>)-coordinated BPI ligands were prepared as well as complexes with bidentate-coordinated BPI ligands, where the chloride ligand was substituted by either neutral or anionic ligands. Substitution in the <i>ortho</i>-position of the PBI ligands led to the formation of cycloiridated κ³-(<i>N</i>,<i>N</i>,<i>C</i>) species. Upon substitution of the anionic ligand by triphenylphosphine, a product was obtained with a hitherto unobserved κ²-(<i>N</i>,<i>N</i>) coordination of <i>o</i>Me-BPI to the metal center via the deprotonated nitrogen atom of the isoindole unit and one of the imine nitrogen atoms of the BPI ligand. A series of (<i>para</i>-cymene) osmium half-sandwich complexes with analogous structures and reactivities to their isoelectronic Cp*Ir­(BPI) congeners were also prepared. Finally, it has been demonstrated that both Ir and Os complexes are catalytically active in the transfer hydrogenation of various ketones and imines

Iridium Half-Sandwich Complexes with Di- and Tridentate Bis(pyridylimino)isoindolato Ligands: Stoichiometric and Catalytic Reactivity

A series of κ²-(<i>N</i>,<i>N</i>)-coordinated bis­(2-pyridylimino)­isoindolato (BPI) complexes [Cp*Ir­(BPI)­Cl], which possess “three-legged piano-stool” structures, with the iridium atom being coordinated by the Cp* ligand 2 × N and Cl, were prepared via deprotonation of the BPIH ligands with either potassium hydride or LDA and subsequent reaction with [Cp*IrCl₂]₂ in THF. Cationic complexes [Cp*Ir­(BPI)]⁺ containing κ³-(<i>N</i>,<i>N</i>,<i>N</i>)-coordinated BPI ligands were prepared as well as complexes with bidentate-coordinated BPI ligands, where the chloride ligand was substituted by either neutral or anionic ligands. Substitution in the <i>ortho</i>-position of the PBI ligands led to the formation of cycloiridated κ³-(<i>N</i>,<i>N</i>,<i>C</i>) species. Upon substitution of the anionic ligand by triphenylphosphine, a product was obtained with a hitherto unobserved κ²-(<i>N</i>,<i>N</i>) coordination of <i>o</i>Me-BPI to the metal center via the deprotonated nitrogen atom of the isoindole unit and one of the imine nitrogen atoms of the BPI ligand. A series of (<i>para</i>-cymene) osmium half-sandwich complexes with analogous structures and reactivities to their isoelectronic Cp*Ir­(BPI) congeners were also prepared. Finally, it has been demonstrated that both Ir and Os complexes are catalytically active in the transfer hydrogenation of various ketones and imines