Molybdenum 1,4-Diazabuta-1,3-diene Tricarbonyl Solvento Complexes Revisited: From Solvatochromism to Attractive Ligand–Ligand Interaction

Various complexes of the types [Mo­(DAD)­(CO)₃L] (L = CO, MeCN, MeOH, THF, DMSO, DMF, Me₂CO, EtOAc, THT, Im^H, Im¹, <i>t</i>BuNC, <i>n</i>Bu₃P), (ER₄)­[Mo­(DAD)­(CO)₃X] (ER₄ = NEt₄⁺; X^– = Cl^–, Br^–, I^–, NCS^–, CN^– and ER₄⁺ = PPh₄⁺; X^– = N₃^–), and (ER₄)­[{Mo­(DAD)­(CO)₃}₂(μ-X)] (ER₄⁺ = NEt₄⁺; X^– = CN^–, OAc^– and ER₄⁺ = PPh₄⁺; X^– = N₃^–; DAD = <i>N</i>,<i>N</i>′-bis­(2,6-dimethylphenyl)­butane-2,3-diimine) were prepared by ligand exchange from cycloheptatriene molybdenum tricarbonyl. A total of 19 crystal structures were determined, including unprecedented structural characterization of molybdenum(0) coordination by dimethyl sulfoxide (DMSO), methanol, ethyl acetate (EtOAc), acetone, and <i>N</i>,<i>N</i>-dimethylformamide (DMF). Correlation of ¹³C NMR shifts with the complex geometry suggests a direct ligand–ligand interaction between DAD and O-bonded coligands with CO and SO double bonds, such as EtOAc, Me₂CO, DMF, and DMSO. Unexpectedly, the solvatochromic properties of these tricarbonyl complexes [Mo­(DAD)­(CO)₃L] are unfavorable for the determination of Kamlet–Taft parameters of the corresponding solvent L. Contrastingly, the UV/vis absorption of [Mo­(DAD)­(CO)₄] is strongly correlated with the Kamlet–Taft parameter π*, which is shown for 22 solvents, including seven room temperature ionic liquids

Axial Functionalization of Sterically Hindered Titanium Phthalocyanines

Several axially functionalized, weakly aggregating titanium phthalocyanines (Pc) have been synthesized and characterized. Soluble titanium dichlorido tetrakis-(1,1,4,4-tetramethyl-6,7-tetralino)-porphyrazine [Pc^#TiCl₂] (<b>5</b>) has been prepared by reductive cyclotetramerization of the respective dinitrile precursor in the presence of TiCl₄. <b>5</b> and the analogous oxido compound [Pc^#TiO] (<b>1</b>) are versatile starting materials for the formation of other axially functionalized titanium phthalocyanines such as organoimido (<b>6</b>, <b>7</b>), alkoxido and aryloxido (<b>8</b>, <b>9</b>), peroxido (<b>10</b>), sulfido (<b>12</b>), disulfido (<b>11</b>), selenido (<b>14</b>) or diselenido (<b>13</b>) species. Furthermore the deprotonated ligand salts [Pc^#M₂] (M = Li (<b>2</b>), Na (<b>3</b>), K (<b>4</b>) are described. The reactivity of the titanium compounds was studied in atom group transfer reactions and ethene polymerization. The crystal structures of <b>5</b> and the free ligand Pc^#H₂ are reported. <b>5</b> crystallizes from dichloromethane in the cubic space group <i>Im</i>3̅. The two chlorido ligands exhibit a cis arrangement. The free ligand Pc^#H₂ crystallizes in the trigonal space group <i>R</i>3̅

Axial Functionalization of Sterically Hindered Titanium Phthalocyanines

Several axially functionalized, weakly aggregating titanium phthalocyanines (Pc) have been synthesized and characterized. Soluble titanium dichlorido tetrakis-(1,1,4,4-tetramethyl-6,7-tetralino)-porphyrazine [Pc^#TiCl₂] (<b>5</b>) has been prepared by reductive cyclotetramerization of the respective dinitrile precursor in the presence of TiCl₄. <b>5</b> and the analogous oxido compound [Pc^#TiO] (<b>1</b>) are versatile starting materials for the formation of other axially functionalized titanium phthalocyanines such as organoimido (<b>6</b>, <b>7</b>), alkoxido and aryloxido (<b>8</b>, <b>9</b>), peroxido (<b>10</b>), sulfido (<b>12</b>), disulfido (<b>11</b>), selenido (<b>14</b>) or diselenido (<b>13</b>) species. Furthermore the deprotonated ligand salts [Pc^#M₂] (M = Li (<b>2</b>), Na (<b>3</b>), K (<b>4</b>) are described. The reactivity of the titanium compounds was studied in atom group transfer reactions and ethene polymerization. The crystal structures of <b>5</b> and the free ligand Pc^#H₂ are reported. <b>5</b> crystallizes from dichloromethane in the cubic space group <i>Im</i>3̅. The two chlorido ligands exhibit a cis arrangement. The free ligand Pc^#H₂ crystallizes in the trigonal space group <i>R</i>3̅

Axial Functionalization of Sterically Hindered Titanium Phthalocyanines

Several axially functionalized, weakly aggregating titanium phthalocyanines (Pc) have been synthesized and characterized. Soluble titanium dichlorido tetrakis-(1,1,4,4-tetramethyl-6,7-tetralino)-porphyrazine [Pc^#TiCl₂] (<b>5</b>) has been prepared by reductive cyclotetramerization of the respective dinitrile precursor in the presence of TiCl₄. <b>5</b> and the analogous oxido compound [Pc^#TiO] (<b>1</b>) are versatile starting materials for the formation of other axially functionalized titanium phthalocyanines such as organoimido (<b>6</b>, <b>7</b>), alkoxido and aryloxido (<b>8</b>, <b>9</b>), peroxido (<b>10</b>), sulfido (<b>12</b>), disulfido (<b>11</b>), selenido (<b>14</b>) or diselenido (<b>13</b>) species. Furthermore the deprotonated ligand salts [Pc^#M₂] (M = Li (<b>2</b>), Na (<b>3</b>), K (<b>4</b>) are described. The reactivity of the titanium compounds was studied in atom group transfer reactions and ethene polymerization. The crystal structures of <b>5</b> and the free ligand Pc^#H₂ are reported. <b>5</b> crystallizes from dichloromethane in the cubic space group <i>Im</i>3̅. The two chlorido ligands exhibit a cis arrangement. The free ligand Pc^#H₂ crystallizes in the trigonal space group <i>R</i>3̅

Molybdenum 1,4-Diazabuta-1,3-diene Tricarbonyl Solvento Complexes Revisited: From Solvatochromism to Attractive Ligand–Ligand Interaction

Various complexes of the types [Mo­(DAD)­(CO)₃L] (L = CO, MeCN, MeOH, THF, DMSO, DMF, Me₂CO, EtOAc, THT, Im^H, Im¹, <i>t</i>BuNC, <i>n</i>Bu₃P), (ER₄)­[Mo­(DAD)­(CO)₃X] (ER₄ = NEt₄⁺; X^– = Cl^–, Br^–, I^–, NCS^–, CN^– and ER₄⁺ = PPh₄⁺; X^– = N₃^–), and (ER₄)­[{Mo­(DAD)­(CO)₃}₂(μ-X)] (ER₄⁺ = NEt₄⁺; X^– = CN^–, OAc^– and ER₄⁺ = PPh₄⁺; X^– = N₃^–; DAD = <i>N</i>,<i>N</i>′-bis­(2,6-dimethylphenyl)­butane-2,3-diimine) were prepared by ligand exchange from cycloheptatriene molybdenum tricarbonyl. A total of 19 crystal structures were determined, including unprecedented structural characterization of molybdenum(0) coordination by dimethyl sulfoxide (DMSO), methanol, ethyl acetate (EtOAc), acetone, and <i>N</i>,<i>N</i>-dimethylformamide (DMF). Correlation of ¹³C NMR shifts with the complex geometry suggests a direct ligand–ligand interaction between DAD and O-bonded coligands with CO and SO double bonds, such as EtOAc, Me₂CO, DMF, and DMSO. Unexpectedly, the solvatochromic properties of these tricarbonyl complexes [Mo­(DAD)­(CO)₃L] are unfavorable for the determination of Kamlet–Taft parameters of the corresponding solvent L. Contrastingly, the UV/vis absorption of [Mo­(DAD)­(CO)₄] is strongly correlated with the Kamlet–Taft parameter π*, which is shown for 22 solvents, including seven room temperature ionic liquids

Axial Functionalization of Sterically Hindered Titanium Phthalocyanines

Several axially functionalized, weakly aggregating titanium phthalocyanines (Pc) have been synthesized and characterized. Soluble titanium dichlorido tetrakis-(1,1,4,4-tetramethyl-6,7-tetralino)-porphyrazine [Pc^#TiCl₂] (<b>5</b>) has been prepared by reductive cyclotetramerization of the respective dinitrile precursor in the presence of TiCl₄. <b>5</b> and the analogous oxido compound [Pc^#TiO] (<b>1</b>) are versatile starting materials for the formation of other axially functionalized titanium phthalocyanines such as organoimido (<b>6</b>, <b>7</b>), alkoxido and aryloxido (<b>8</b>, <b>9</b>), peroxido (<b>10</b>), sulfido (<b>12</b>), disulfido (<b>11</b>), selenido (<b>14</b>) or diselenido (<b>13</b>) species. Furthermore the deprotonated ligand salts [Pc^#M₂] (M = Li (<b>2</b>), Na (<b>3</b>), K (<b>4</b>) are described. The reactivity of the titanium compounds was studied in atom group transfer reactions and ethene polymerization. The crystal structures of <b>5</b> and the free ligand Pc^#H₂ are reported. <b>5</b> crystallizes from dichloromethane in the cubic space group <i>Im</i>3̅. The two chlorido ligands exhibit a cis arrangement. The free ligand Pc^#H₂ crystallizes in the trigonal space group <i>R</i>3̅

Soluble Molybdenum(V) Imido Phthalocyanines and Pyrazinoporphyrazines: Crystal Structure, UV–vis and Electron Paramagnetic Resonance Spectroscopic Studies

Soluble alkyl and aryl imido phthalocyanines [Pc^#Mo­(NR)­Cl] (R = <i>t</i>Bu, Mes) with molybdenum­(V) as central metal were prepared and studied by UV–vis and electron paramagnetic resonance (EPR) spectroscopy. As structural analogue to the weakly aggregating, soluble alkyl substituted Pc^# ligand, a new, more electron deficient octaazaphthalocyanine, the pyrazinoporphyrazine ligand Ppz^#, was designed. The respective alkyl and aryl imido complexes [Ppz^#Mo­(NR)­Cl] are the first examples of molybdenum pyrazinoporphyrazines. UV–vis and EPR spectra revealed unexpected differences between the alkyl and the aryl imido complexes, indicating different electronic structures depending on the nature of the axial ligand. The octahedral coordination of the molybdenum atoms by the axial NR and Cl ligands and the equatorial macrocycles could be verified by EPR spectroscopy. This result was also confirmed by the crystal structure of [Pc^#Mo­(NMes)­Cl], which crystallizes from CH₂Cl₂ in the cubic space group <i>Im</i>3̅

A New Synthetic Pathway to the Second and Third Generation of Superbasic Bisphosphazene Proton Sponges: The Run for the Best Chelating Ligand for a Proton

We present the up to now strongest chelating neutral pincer ligand for the simplest electrophile of chemistry, the proton. Two novel bisphosphazene proton sponges, 1,8-bis­(tris­pyrroli­dino­phospha­zenyl)­naphtha­lene (TPPN) and its higher homologue P₂-TPPN, were obtained via a Staudinger reaction and investigated concerning their structural features and basic properties by experimental and computational means. They exhibit experimental p<i>K</i>_BH⁺ values in acetonitrile of 32.3 and 42.1, respectively, exceeding the existing basicitiy record for proton sponges by more than 10 orders of magnitude. We show that Schwesinger’s concept of homologization of phosphazene bases and Alder’s concept of proton chelation in a constrained geometry regime of basic centers can be combined in the design of highly basic nonionic superbases of pincer type

A New Synthetic Pathway to the Second and Third Generation of Superbasic Bisphosphazene Proton Sponges: The Run for the Best Chelating Ligand for a Proton

We present the up to now strongest chelating neutral pincer ligand for the simplest electrophile of chemistry, the proton. Two novel bisphosphazene proton sponges, 1,8-bis­(tris­pyrroli­dino­phospha­zenyl)­naphtha­lene (TPPN) and its higher homologue P₂-TPPN, were obtained via a Staudinger reaction and investigated concerning their structural features and basic properties by experimental and computational means. They exhibit experimental p<i>K</i>_BH⁺ values in acetonitrile of 32.3 and 42.1, respectively, exceeding the existing basicitiy record for proton sponges by more than 10 orders of magnitude. We show that Schwesinger’s concept of homologization of phosphazene bases and Alder’s concept of proton chelation in a constrained geometry regime of basic centers can be combined in the design of highly basic nonionic superbases of pincer type

New Lithium Phosphonium Diylides: A Methylene and a Cyclopentadienyl Moiety as Ylidic Coordination Sites

A set of lithium phosphonium diylides Li­[CH₂-PR₂-Cp^X] (<b>9</b>–<b>12</b>; Cp^X = C₅Me₄, C₅H₃<i>t</i>Bu, R = Ph, Me) is presented. Two of the lithium complexes were characterized by means of single-crystal X-ray analysis, revealing a dimeric head-to-tail arrangement in the solid state. The coordination behavior of <b>9</b>–<b>12</b> in the liquid phase is solvent dependent. These lithium phosphonium diylides exist as contact ion pairs in benzene and as solvent-separated ion pairs in THF solutions. Phosphonium salts [H₃C-PR₂-Cp^XH)]⁺I^– (<b>1</b>–<b>4</b>) are starting materials for the syntheses of the title compounds and exist as mixtures of isomers due to [1,5]-prototropic rearrangements. The dynamic behavior in solution has been investigated. Two different routes allow access to title compounds <b>9</b>–<b>12</b>. Reactions of <b>1</b>–<b>4</b> with 2 equiv of <i>n</i>BuLi give <b>9</b>–<b>12</b> in a one-pot synthesis. In an alternative two-step route, dehydrodehalogenation of <b>1</b>–<b>4</b> with KH gives the corresponding phosphonium ylides <b>5</b>–<b>8</b>. Two of these phosphonium ylides were characterized by single-crystal X-ray analysis. In one case two different conformers were obtained