d-d Dative Bonding Between Iron and the Alkaline-Earth Metals Calcium, Strontium, and Barium

Double deprotonation of the diamine 1,1 '-(tBuCH(2)NH)-ferrocene (1-H-2) by alkaline-earth (Ae) or Eu(II)metal reagents gave the complexes1-Ae (Ae=Mg, Ca, Sr, Ba) and1-Eu.1-Mg crystallized as a monomer while the heavier complexes crystallized as dimers. The Fe...Mg distance in1-Mg is too long for a bonding interaction, but short Fe...Ae distances in1-Ca,1-Sr, and1-Ba clearly support intramolecular Fe...Ae bonding. Further evidence for interactions is provided by a tilting of the Cp rings and the related(1)H NMR chemical-shift difference between the Cp alpha and beta protons. While electrochemical studies are complicated by complex decomposition, UV/Vis spectral features of the complexes support Fe -> Ae dative bonding. A comprehensive bonding analysis of all1-Ae complexes shows that the heavier species1-Ca,1-Sr, and1-Ba possess genuine Fe -> Ae bonds which involve vacant d-orbitals of the alkaline-earth atoms and partially filled d-orbitals on Fe. In1-Mg, a weak Fe -> Mg donation into vacant p-orbitals of the Mg atom is observed

Transmetalation from Magnesium–NHCs—Convenient Synthesis of Chelating π-Acidic NHC Complexes

The synthesis of chelating N-heterocyclic carbene (NHC) complexes with considerable π-acceptor properties can be a challenging task. This is due to the dimerization of free carbene ligands, the moisture sensitivity of reaction intermediates or reagents, and challenges associated with the workup procedure. Herein, we report a general route using transmetalation from magnesium−NHCs. Notably, this route gives access to transition-metal complexes in quantitative conversion without the formation of byproducts. It therefore produces transition-metal complexes outperforming the conventional routes based on free or lithium-coordinated carbene, silver complexes, or in situ metalation in dimethyl sulfoxide (DMSO). We therefore propose transmetalation from magnesium−NHCs as a convenient and general route to obtain NHC complexes

Intramolecular Alkene Hydroamination with Hybrid Catalysts Consisting of a Metal Salt and a Neutral Organic Base

Hybrid catalysts consisting of alkaline earth iodides (AeI2) and the Schwesinger base tBuP4 catalyse the intramolecular alkene hydroamination of H2C=CHCH2CR2CH2NH2 [CR2=CPh2, C(CH2)5, CMe2]. Activities decrease along the row: Ca > Sr >> Mg > Ba. Hybrid catalysts consisting of tBuP4 and ZnI2, AlI3, FeCI3 or NaI were found to be fully inactive. Also, the hybrid catalyst tBuP3/CaI2 was not active which means that the base strength of the non‐nucleophilic organic base must be higher than that of tBuP3 (pKa BH+ = 38.6). Combinations of tBuP4 with CaX2 (X = Cl, Br, OiPr, OTf, NTf2) were found to be fully inactive which may in part be explained by poor solubility. The hybrid catalysis method is therefore limited to the combination tBuP4/CaI2 but the iodide ligands may be partially or fully replaced by chiral ligands. Chiral modifications of the hybrid catalysts gave in intramolecular alkene hydroamination ee values up to 33 %

Carbon-Rich Ruthenium Allenylidene Complexes Bearing Heteroscorpionate Ligands

A series of ruthenium allenylidene complexes bearing polyaromatic substituents have been prepared starting from [Ru­(bdmpza)­Cl­(PPh₃)₂] (<b>1</b>) (bdmpza = bis­(3,5-dimethyl­pyrazol-1-yl)­acetato). Reacting <b>1</b> with 1,1-bis­(3,5-di-<i>tert</i>-butyl­phenyl)-1-methoxy-2-propyne results in the formation of two structural isomers of an allenylidene complex [Ru­(bdmpza)­Cl­(CCC­(Ph^<i>t</i>Bu₂)₂)­(PPh₃)] (<b>5A</b>/<b>5B</b>), as well as the related carbonyl complex [Ru­(bdmpza)­Cl­(CO)­(PPh₃)] (<b>4A</b>/<b>4B</b>). Conversion of 9-ethynyl-9-fluorenol leads to the corresponding allenylidene complex [Ru­(bdmpza)­Cl­(CC(FN))­(PPh₃)] (<b>7A</b>/<b>7B</b>) (FN = fluorenyl). Based on anthraquinone, a new synthetic route toward 10-ethynyl-10-hydroxy­anthracen-9-one via the trimethylsilyl-protected propargyl alcohol is described, and subsequent conversion of this compound to the allenylidene complex ([Ru­(bdmpza)­Cl­(CC(AO))­(PPh₃)] (<b>12A</b>/<b>12B</b>) (AO = anthrone) is reported. The synthetic route from 7<i>H</i>-benzo­[<i>no</i>]­tetraphen-7-one to the propargyl alcohol 7-ethynyl-7<i>H</i>-benzo­[<i>no</i>]­tetraphen-7-ol is described, which is followed by the transformation into the allenylidene complex [Ru­(bdmpza)­Cl­(CC(BT))­(PPh₃)] (<b>17A</b>/<b>17B</b>) (BT = benzotetraphene). The molecular structures of <b>4B</b>, <b>7A</b>, <b>7B</b>, <b>12A</b>, <b>12B</b>, <b>13A</b>, and <b>17A</b> have been characterized by single-crystal X-ray crystallography, and these analyses suggest that <b>17A</b> might function as a “metal-tuned organic field effect transistor”. The electrochemical properties of the allenylidene complexes have been studied via cyclic voltammetry, and time-dependent DFT calculations have been conducted to assign weak absorptions in the NIR region to forbidden MLCT transitions

Carbon-Rich Ruthenium Allenylidene Complexes Bearing Heteroscorpionate Ligands

A series of ruthenium allenylidene complexes bearing polyaromatic substituents have been prepared starting from [Ru­(bdmpza)­Cl­(PPh₃)₂] (<b>1</b>) (bdmpza = bis­(3,5-dimethyl­pyrazol-1-yl)­acetato). Reacting <b>1</b> with 1,1-bis­(3,5-di-<i>tert</i>-butyl­phenyl)-1-methoxy-2-propyne results in the formation of two structural isomers of an allenylidene complex [Ru­(bdmpza)­Cl­(CCC­(Ph^<i>t</i>Bu₂)₂)­(PPh₃)] (<b>5A</b>/<b>5B</b>), as well as the related carbonyl complex [Ru­(bdmpza)­Cl­(CO)­(PPh₃)] (<b>4A</b>/<b>4B</b>). Conversion of 9-ethynyl-9-fluorenol leads to the corresponding allenylidene complex [Ru­(bdmpza)­Cl­(CC(FN))­(PPh₃)] (<b>7A</b>/<b>7B</b>) (FN = fluorenyl). Based on anthraquinone, a new synthetic route toward 10-ethynyl-10-hydroxy­anthracen-9-one via the trimethylsilyl-protected propargyl alcohol is described, and subsequent conversion of this compound to the allenylidene complex ([Ru­(bdmpza)­Cl­(CC(AO))­(PPh₃)] (<b>12A</b>/<b>12B</b>) (AO = anthrone) is reported. The synthetic route from 7<i>H</i>-benzo­[<i>no</i>]­tetraphen-7-one to the propargyl alcohol 7-ethynyl-7<i>H</i>-benzo­[<i>no</i>]­tetraphen-7-ol is described, which is followed by the transformation into the allenylidene complex [Ru­(bdmpza)­Cl­(CC(BT))­(PPh₃)] (<b>17A</b>/<b>17B</b>) (BT = benzotetraphene). The molecular structures of <b>4B</b>, <b>7A</b>, <b>7B</b>, <b>12A</b>, <b>12B</b>, <b>13A</b>, and <b>17A</b> have been characterized by single-crystal X-ray crystallography, and these analyses suggest that <b>17A</b> might function as a “metal-tuned organic field effect transistor”. The electrochemical properties of the allenylidene complexes have been studied via cyclic voltammetry, and time-dependent DFT calculations have been conducted to assign weak absorptions in the NIR region to forbidden MLCT transitions

Carbon-Rich Ruthenium Allenylidene Complexes Bearing Heteroscorpionate Ligands

A series of ruthenium allenylidene complexes bearing polyaromatic substituents have been prepared starting from [Ru­(bdmpza)­Cl­(PPh₃)₂] (<b>1</b>) (bdmpza = bis­(3,5-dimethyl­pyrazol-1-yl)­acetato). Reacting <b>1</b> with 1,1-bis­(3,5-di-<i>tert</i>-butyl­phenyl)-1-methoxy-2-propyne results in the formation of two structural isomers of an allenylidene complex [Ru­(bdmpza)­Cl­(CCC­(Ph^<i>t</i>Bu₂)₂)­(PPh₃)] (<b>5A</b>/<b>5B</b>), as well as the related carbonyl complex [Ru­(bdmpza)­Cl­(CO)­(PPh₃)] (<b>4A</b>/<b>4B</b>). Conversion of 9-ethynyl-9-fluorenol leads to the corresponding allenylidene complex [Ru­(bdmpza)­Cl­(CC(FN))­(PPh₃)] (<b>7A</b>/<b>7B</b>) (FN = fluorenyl). Based on anthraquinone, a new synthetic route toward 10-ethynyl-10-hydroxy­anthracen-9-one via the trimethylsilyl-protected propargyl alcohol is described, and subsequent conversion of this compound to the allenylidene complex ([Ru­(bdmpza)­Cl­(CC(AO))­(PPh₃)] (<b>12A</b>/<b>12B</b>) (AO = anthrone) is reported. The synthetic route from 7<i>H</i>-benzo­[<i>no</i>]­tetraphen-7-one to the propargyl alcohol 7-ethynyl-7<i>H</i>-benzo­[<i>no</i>]­tetraphen-7-ol is described, which is followed by the transformation into the allenylidene complex [Ru­(bdmpza)­Cl­(CC(BT))­(PPh₃)] (<b>17A</b>/<b>17B</b>) (BT = benzotetraphene). The molecular structures of <b>4B</b>, <b>7A</b>, <b>7B</b>, <b>12A</b>, <b>12B</b>, <b>13A</b>, and <b>17A</b> have been characterized by single-crystal X-ray crystallography, and these analyses suggest that <b>17A</b> might function as a “metal-tuned organic field effect transistor”. The electrochemical properties of the allenylidene complexes have been studied via cyclic voltammetry, and time-dependent DFT calculations have been conducted to assign weak absorptions in the NIR region to forbidden MLCT transitions