Coordinating Tectons 4: Coordination Chemistry of the 4,5-Diazafluoren-9-yl Moiety as a Metallo-Ligand for Allenylidene Complexes

We describe how the 4,5-diazafluoren-9-yl moiety has been utilized in the construction of multinuclear complexes incorporating a ruthenium­(II) allenylidene functionality. The coordination chemistry of diazafluorenyl-terminated allenylidene complexes is limited by the sensitivity (instability) of the allenylidene moiety under a variety of synthetic conditions. In contrast the κ²-N,N′-coordination of the diazafluorenyl propargylic alcohol (alkynol) to a metal center <i>prior</i> to allenylidene formation provides a facile route toward the synthesis of multinuclear allenylidene coordination complexes. Our synthetic attempts and successes are discussed in combination with spectroscopic and electronic characterization of the latter cases

Coordinating Tectons 4: Coordination Chemistry of the 4,5-Diazafluoren-9-yl Moiety as a Metallo-Ligand for Allenylidene Complexes

We describe how the 4,5-diazafluoren-9-yl moiety has been utilized in the construction of multinuclear complexes incorporating a ruthenium­(II) allenylidene functionality. The coordination chemistry of diazafluorenyl-terminated allenylidene complexes is limited by the sensitivity (instability) of the allenylidene moiety under a variety of synthetic conditions. In contrast the κ²-N,N′-coordination of the diazafluorenyl propargylic alcohol (alkynol) to a metal center <i>prior</i> to allenylidene formation provides a facile route toward the synthesis of multinuclear allenylidene coordination complexes. Our synthetic attempts and successes are discussed in combination with spectroscopic and electronic characterization of the latter cases

Domino Reactions for the Synthesis of Anthrapyran-2-ones and the Total Synthesis of the Natural Product (±)-BE-26554A

A domino alkyne addition/CO insertion/Nu acylation reaction to a series of novel anthrapyran-2-ones in good to excellent yields is described. In addition, an efficient synthetic sequence involving carbonylation, formation of a β-keto-sulfoxide, and cyclization is presented en route to the antibiotic and antitumor compound (±)-BE-26554A

Domino Reactions for the Synthesis of Anthrapyran-2-ones and the Total Synthesis of the Natural Product (±)-BE-26554A

A domino alkyne addition/CO insertion/Nu acylation reaction to a series of novel anthrapyran-2-ones in good to excellent yields is described. In addition, an efficient synthetic sequence involving carbonylation, formation of a β-keto-sulfoxide, and cyclization is presented en route to the antibiotic and antitumor compound (±)-BE-26554A

Coordinating Tectons: Bimetallic Complexes from Bipyridyl Terminated Group 8 Alkynyl Complexes

Bipyridyl appended ruthenium alkynyl complexes have been used to prepare a range of binuclear homometallic ruthenium and heterometallic ruthenium–rhenium complexes. The two metal centers are only weakly coupled, as evinced by IR and UV–vis–near NIR spectroelectrochemical experiments and supported by quantum chemical calculations. The alkynyl complexes of the type [Ru­(CCbpy)­{L_n}] ({L_n} = {(PPh₃)₂Cp}, {(dppe)­Cp*}, {Cl­(dppm)₂}) undergo reversible one-electron oxidations centered largely on the alkynyl ligands, as has been observed previously for closely related complexes. The homometallic binuclear complexes, exemplified by [Ru­(C₂bpy-κ²-<i>N</i>′<i>N</i>-RuClCp)­(PPh₃)₂Cp] undergo two essentially reversible oxidations, the first centered on the (C₂bpy-κ²-<i>N</i>′<i>N</i>-RuClCp) moiety and the second on the Ru­(CCbpy)­(PPh₃)₂Cp fragment, leading to radical cations that can be described as Class II mixed-valence complexes. The heterometallic binuclear complexes [Ru­(C₂bpy-κ²-<i>N</i>′<i>N</i>-ReCl­(CO)₃)­{L_n}] display similar behavior, with initial oxidation on the ruthenium fragment giving rise to a new optical absorption band with Re → Ru­(CCbpy) charge transfer character. The heterometallic complexes also exhibit irreversible reductions associated with the Re hetereocycle moiety

Coordinating Tectons: Bimetallic Complexes from Bipyridyl Terminated Group 8 Alkynyl Complexes

Bipyridyl appended ruthenium alkynyl complexes have been used to prepare a range of binuclear homometallic ruthenium and heterometallic ruthenium–rhenium complexes. The two metal centers are only weakly coupled, as evinced by IR and UV–vis–near NIR spectroelectrochemical experiments and supported by quantum chemical calculations. The alkynyl complexes of the type [Ru­(CCbpy)­{L_n}] ({L_n} = {(PPh₃)₂Cp}, {(dppe)­Cp*}, {Cl­(dppm)₂}) undergo reversible one-electron oxidations centered largely on the alkynyl ligands, as has been observed previously for closely related complexes. The homometallic binuclear complexes, exemplified by [Ru­(C₂bpy-κ²-<i>N</i>′<i>N</i>-RuClCp)­(PPh₃)₂Cp] undergo two essentially reversible oxidations, the first centered on the (C₂bpy-κ²-<i>N</i>′<i>N</i>-RuClCp) moiety and the second on the Ru­(CCbpy)­(PPh₃)₂Cp fragment, leading to radical cations that can be described as Class II mixed-valence complexes. The heterometallic binuclear complexes [Ru­(C₂bpy-κ²-<i>N</i>′<i>N</i>-ReCl­(CO)₃)­{L_n}] display similar behavior, with initial oxidation on the ruthenium fragment giving rise to a new optical absorption band with Re → Ru­(CCbpy) charge transfer character. The heterometallic complexes also exhibit irreversible reductions associated with the Re hetereocycle moiety

Molecular Imprisonment: Host Response to Guest Location, Orientation, and Dynamics in Clathrates of Dianin’s Compound

Single crystal X-ray diffraction data measured at 100 K for Dianin’s compound (DC) and 18 of its clathrates formed with a wide range of guest molecules provide considerable insight into the way the host adjusts to accommodate guest molecules. Detailed information is also obtained regarding the location, orientation, and dynamics of the guests in the host cavity. Although all unit cells are closely similar in size, the host undergoes significant change in response to the imprisonment of its various guests. Enclathration typically results in a larger cell and cavity volume, but for the small molecules methanol, ethanol, and nitromethane the host actually shrinks significantly around the guests in the cavity. In most clathrates, there is evidence of close contacts between atoms in the guest and the phenol −OH group and/or ring of the DC host. The series of clathrates formed by benzene, toluene, and the halobenzenes show the orientation of the benzene ring to be progressively modifed by the increasing size of the substituent atom or group on the ring in a systematic manner that reflects functional group contributions to van der Waals volumes

Coordinating Tectons. Experimental and Computational Infrared Data as Tools To Identify Conformational Isomers and Explore Electronic Structures of 4‑Ethynyl-2,2′-bipyridine Complexes

4-Ethynyl-2,2′-bipyridyl-substituted ruthenium alkynyl complexes have been prepared and used to access a range of binuclear homometallic ruthenium and heterometallic ruthenium–rhenium complexes. These have been characterized by a variety of spectroscopic and single-crystal X-ray diffraction experiments. The IR spectra of a number of these ruthenium alkynyls display multiple ν­(CC) bands in the IR spectra, which are rationalized in terms of putative conformational isomers, whose calculated infrared stretching frequencies are comparable to those obtained experimentally. The mononuclear alkynyl ruthenium complexes undergo reversible one-electron oxidations centered largely on the alkynyl ligands, as inferred from the significant shift in ν­(CC) frequency on oxidation, while the binuclear complex [Ru­{CC-4-bpy-κ²-<i>N</i>,<i>N</i>′-RuClCp}­(dppe)­Cp*]⁺ undergoes initial oxidation at the very electron rich {RuCl­(bpy)­Cp} fragment, causing only a small change in ν­(CC). A combination of IR and UV–vis spectroelectrochemical experiments, supported by quantum chemical calculations on a selected range of conformers, led to the classification of [Ru­{CC-4-bpy-κ²-<i>N</i>,<i>N</i>′-RuClCp}­(dppe)­Cp*]⁺ as a weakly coupled class II mixed-valence compound (<i>H</i>_ab = 306 cm^–1). These results indicate that there is improved electronic communication through the 4-ethynyl-2,2′-bipyridyl ligand in comparison to the analogous 5-ethynyl-2,2′-bipyridyl complexes (<i>H</i>_ab = 17 cm^–1)

Coordinating Tectons. Experimental and Computational Infrared Data as Tools To Identify Conformational Isomers and Explore Electronic Structures of 4‑Ethynyl-2,2′-bipyridine Complexes

4-Ethynyl-2,2′-bipyridyl-substituted ruthenium alkynyl complexes have been prepared and used to access a range of binuclear homometallic ruthenium and heterometallic ruthenium–rhenium complexes. These have been characterized by a variety of spectroscopic and single-crystal X-ray diffraction experiments. The IR spectra of a number of these ruthenium alkynyls display multiple ν­(CC) bands in the IR spectra, which are rationalized in terms of putative conformational isomers, whose calculated infrared stretching frequencies are comparable to those obtained experimentally. The mononuclear alkynyl ruthenium complexes undergo reversible one-electron oxidations centered largely on the alkynyl ligands, as inferred from the significant shift in ν­(CC) frequency on oxidation, while the binuclear complex [Ru­{CC-4-bpy-κ²-<i>N</i>,<i>N</i>′-RuClCp}­(dppe)­Cp*]⁺ undergoes initial oxidation at the very electron rich {RuCl­(bpy)­Cp} fragment, causing only a small change in ν­(CC). A combination of IR and UV–vis spectroelectrochemical experiments, supported by quantum chemical calculations on a selected range of conformers, led to the classification of [Ru­{CC-4-bpy-κ²-<i>N</i>,<i>N</i>′-RuClCp}­(dppe)­Cp*]⁺ as a weakly coupled class II mixed-valence compound (<i>H</i>_ab = 306 cm^–1). These results indicate that there is improved electronic communication through the 4-ethynyl-2,2′-bipyridyl ligand in comparison to the analogous 5-ethynyl-2,2′-bipyridyl complexes (<i>H</i>_ab = 17 cm^–1)