(2,2-Bipyrid­yl)bis­(η5-penta­methyl­cyclo­penta­dien­yl)strontium(II)

In the title compound, [Sr(C10H15)2(C10H8N2)], the Sr—N distances are 2.624 (3) and 2.676 (3) Å, the Sr⋯Cp ring centroid distances are 2.571 and 2.561 Å and the N—C—C—N torsion angle in the bipyridine ligand is −2.2 (4)°. Inter­estingly, the bipyridine ligand is tilted. The angle between the plane defined by the Sr atom and the two bipyridyl N atoms and the plane defined by the 12 atoms of the bipyridine ligand is 10.7 (1)°

(2,2-Bipyridyl)bis(eta5-1,2,3,4,5-pentamethylcyclopentadienyl)Strontium(II)

In the title compound, the Sr-N distances are 2.624 (3) and 2.676 (3) Angstroms. The Sr-centroid distances are 2.571 and 2.561 Angstroms. The N-C-C-N torsion angle in the bipyridine ligand is 2.2 (4){sup o}. Interestingly, the bipyridine ligand is tilted. The angle between the plane defined by Sr1, N1 and N2 and the plane defined by the 12 atoms of the bipyridine ligand is 10.7{sup o}

5,6-Dimethyl-1,10-phenanthroline

In the title compound, C14H12N2, the N⋯N distance is 2.719 (1) Å. The N—C—C—N torsion angle [0.9 (1)°] is close to the ideal value of 0° as expected. Bond lengths and angles are consistent with those observed for [1,10]phenanthroline and coordinated 5,6 dimeth­yl[1,10]phenanthroline. In the crystal, C—H⋯N hydrogen bonds link the mol­ecules into C(4) chains running parallel to the b axis. Weak π–π inter­actions between benzene and pyridine rings [centroid–centroid distance = 3.5337 (7) Å] and between benzene rings [centroid–centroid distances = 3.6627 (7) and 3.8391 (7)Å] also occur

Transition metal complexes with multidentate phosphorous/nitrogen ligands. Synthesis, characterization and reactivity.

AbstractTransition metal complexes with multidentate phosphorous/nitrogen ligands.Synthesis, characterization and reactivity.BySergio Santiago RozenelDoctor in Philosophy in ChemistryUniversity of California, BerkeleyProfessor John Arnold, ChairChapter 1: Chromium complexes supported by the multidentate monoanionic ligand [N2P2] {H[N2P2] = tBuN(H)SiMe2N(CH2CH2PiPr2)2} are presented, and the activity of these complexes towards ethylene oligomerization/polymerization is examined. The complexes [N2P2]CrCl2 (1) and [N2P2]CrCl (2) polymerized ethylene after activation with MAO. Derivatives of 1 and 2 were synthesized in order to gain insights about the active species in the ethylene oligomerization/polymerization processes. The alkyl complexes [N2P2]CrMe (3), [N2P2]CrCH2SiMe3 (4) and [N2P2]Cr(Cl)CH2SiMe3 (5), the cationic species {[N2P2]CrCl}BF4 (7), {[N2P2]CrCl}BPh4 (8) and {[N2P2]CrCH2SiMe3}BF4 (9), and the Cr(II) complex [N2P2]CrOSO2CF3 (11) were not active ethylene oligomerization/polymerization catalysts in absence of an activator. Reaction of 1 with two equivalents of MeLi led to reduction to 3. However, with one equivalent of MeLi the stable mixed alkyl-halide derivative [N2P2]Cr(Cl)Me (6) was obtained. Reaction of 2 with Red-Al® produced the hydride ([N2P2]Cr)2(ì-H)2 (10), which reacted with CO to produce the Cr(I) complex [N2P2]Cr(CO)2 (12). Reduction of 2 with KC8 in the presence of p-tolyl azide produced the dimeric cis µ-imido ([N2P2]Cr)2(ì-NC7H7)2 (13). A similar reduction in the presence of ethylene resulted in the isolation of the Cr(III) metallacyclohexane compound [N2P2]CrC4H8 (14). Chapter 2: A series of Co, Ni and Cu complexes with the ligand HN(CH2CH2PiPr2)2 (HPNP) has been isolated and their electrochemical behavior investigated by cyclic voltammetry. The nickel complexes [(HPNP¬)NiOTf]OTf and [(HPNP)NiNCCH3](BF4)2 display reversible reductions, as does the related amide derivative (NP2)NiBr. Related copper(I) and cobalt(II) derivatives were isolated and characterized. Addition of piperidine to [(HNP2)NiNCCH3](BF4)2 led to the formation of the new species [(HPNP)Ni(N(H)C(CH3)NC5H10)](BF4)2. Nucleophilic addition of piperidine to acetonitrile to produce HN=C(CH3)NC5H10 was catalyzed by [(HPNP)NiNCCH3](BF4)2. Chapter 3: A series of bimetallic ruthenium complexes [HPNPRu(N2)]2(µ-Cl)2](BF4)2 (2), [(HPNPRu(H2)Cl)2(µ-Cl)2](BF4)2 (3), [(HPNPRu)2(µ-H2NNH2)(µ-Cl)2](BF4)2 (4), [(HPNPRu)2(µ-Cl)2(µ-HNNPh)](BF4)2 (5), [HPNPRu(NH3)(ç2-N2H4)](BF4)Cl (6), [(HNP2Ru)2(µ-Cl)2(µ2-OSO2CF3)]OSO2CF3 (7), [HPNPRu]2(µ-Cl)3]BPh4 (8) and [HPNPRu]2(µ-Cl)3]BF4 (9) were isolated and characterized in the course of reactions aimed at studying the reduction of N2 and hydrazine. Complex 4 produces ammonia catalytically from hydrazine, and complex 2 generates ammonia upon reaction with Cp2Co/HLuBF4. DFT calculations support the idea that the diazene complex formed is more stable than the expected Chatt-type intermediate.Chapter 4: The reduction chemistry of cobalt complexes with the PNP ligand was explored. Reaction of (HPNP)CoCl2 (1) with n-BuLi generated the deprotonated Co(II) product (PNP)CoCl (2), and the Co(I) reduced species (HPNP)CoCl (3). The reaction of complex 2 with KC8 was investigated, where it was found that the products obtained depended upon the inert gas used to carry out the reaction: (PNP)CoN2 (4) under N2, bimetallic complex [(PNP)Co]2 (5) under Ar, and (HPNP)Co(H)3 (8) under H2. Complex 5 reacted with H2 to generate the bimetallic complex [(PNP)CoH]2 (6). With H2, H3SiPh and AgBPh4 complex 3 generated the species (HPNP)CoCl(H)2 (9), (HPNP)CoCl(H)SiH2Ph (10) and [(HPNP)CoCl]BPh4 (11) respectively. DFT calculations were performed to gain insights about the transformations observed

5,6-Dimethyl-1,10-phenanthroline

In the title compound, C14H12N2, the N...N distance is 2.719 (1) Å. The N—C—C—N torsion angle [0.9 (1)°] is close to the ideal value of 0° as expected. Bond lengths and angles are consistent with those observed for [1,10]phenanthroline and coordinated 5,6 dimethyl[1,10]phenanthroline. In the crystal, C—H...N hydrogen bonds link the molecules into C(4) chains running parallel to the b axis. Weak π–π interactions between benzene and pyridine rings [centroid–centroid distance = 3.5337 (7) Å] and between benzene rings [centroid–centroid distances = 3.6627 (7) and 3.8391 (7)Å] also occur

(2,2′-Bipyridyl-κ2N,N′)bis(η5-pentamethylcyclopentadienyl)barium

In the title compound, [Ba(C10H15)2(C10H8N2)], the Ba—N distances are 2.798 (3) and 2.886 (3) Å, and the Cp ring centroid distances to Ba2+ are 2.7291 (7) and 2.7192 (9) Å. The angle between the N atoms in the bypyridine ligand and the metal ion is 56.80 (8)° and the N—C—C—N torsion angle in the bipyridine ligand is 1.7 (4)°. The bipyridine ligand is almost planar, the dihedral angle formed by the intersection of the planes defined by the pyridyl rings being 3.04 (19)°, and the angle between the plane defined by the Ba2+ ion and the two bipyridyl N atoms and the plane defined by the 12 atoms of the bipyridine ligand is 10.2 (3)°. The average Ba—N and Ba—centroid distances are 0.16 and 0.14 Å longer, respectively, than the equivalent distances in the isotypic strontium compound [Kazhdan et al. (2008). Acta Cryst. E64, m1134]. This difference is in accord with the difference between the ionic radii of 0.16 Å suggested by Shannon [Acta Cryst. (1976), A32, 751–767]

Bimetallic Ruthenium PNP Pincer Complex As a Platform to Model Proposed Intermediates in Dinitrogen Reduction to Ammonia

A series of ruthenium complexes was isolated and characterized in the course of reactions aimed at studying the reduction of hydrazine to ammonia in bimetallic systems. The diruthenium complex {[HPNPRu­(N₂)]₂(μ-Cl)₂}­(BF₄)₂ (<b>2</b>) (HPNP = HN­(CH₂CH₂PⁱPr₂)₂) reacted with 1 equiv of hydrazine to generate [(HPNPRu)₂(μ²-H₂NNH₂)­(μ-Cl)₂]­(BF₄)₂ (<b>3</b>) and with an excess of the reagent to form [HPNPRu­(NH₃)­(κ²-N₂H₄)]­(BF₄)Cl (<b>5</b>). When phenylhydrazine was added to <b>2</b>, the diazene species [(HPNPRu)₂(μ²-HNNPh)­(μ-Cl)₂]­(BF₄)₂ (<b>4</b>) was obtained. Treatment of <b>2</b> with H₂ or CO yielded {[HPNPRu­(H₂)]₂(μ-Cl)₂}­(BF₄)₂ (<b>7</b>) and [HPNPRuCl­(CO)₂]­BF₄ (<b>8</b>), respectively. Abstraction of chloride using AgOSO₂CF₃ or AgBPh₄ afforded the species [(HPNPRu)₂(μ²-OSO₂CF₃)­(μ-Cl)₂]­OSO₂CF₃ (<b>9</b>) and [(HPNPRu)₂(μ-Cl)₃]­BPh₄ (<b>10</b>), respectively. Complex <b>3</b> reacted with HCl/H₂O or HCl/Et₂O to produce ammonia stoichiometrically; the complex catalytically disproportionates hydrazine to generate ammonia

Unusual activation of H 2 by reduced cobalt complexes supported by a PNP pincer ligand

International audienc

Unusual activation of H 2 by reduced cobalt complexes supported by a PNP pincer ligand

International audienc

Bimetallic Ruthenium PNP Pincer Complex As a Platform to Model Proposed Intermediates in Dinitrogen Reduction to Ammonia

A series of ruthenium complexes was isolated and characterized in the course of reactions aimed at studying the reduction of hydrazine to ammonia in bimetallic systems. The diruthenium complex {[HPNPRu­(N₂)]₂(μ-Cl)₂}­(BF₄)₂ (<b>2</b>) (HPNP = HN­(CH₂CH₂PⁱPr₂)₂) reacted with 1 equiv of hydrazine to generate [(HPNPRu)₂(μ²-H₂NNH₂)­(μ-Cl)₂]­(BF₄)₂ (<b>3</b>) and with an excess of the reagent to form [HPNPRu­(NH₃)­(κ²-N₂H₄)]­(BF₄)Cl (<b>5</b>). When phenylhydrazine was added to <b>2</b>, the diazene species [(HPNPRu)₂(μ²-HNNPh)­(μ-Cl)₂]­(BF₄)₂ (<b>4</b>) was obtained. Treatment of <b>2</b> with H₂ or CO yielded {[HPNPRu­(H₂)]₂(μ-Cl)₂}­(BF₄)₂ (<b>7</b>) and [HPNPRuCl­(CO)₂]­BF₄ (<b>8</b>), respectively. Abstraction of chloride using AgOSO₂CF₃ or AgBPh₄ afforded the species [(HPNPRu)₂(μ²-OSO₂CF₃)­(μ-Cl)₂]­OSO₂CF₃ (<b>9</b>) and [(HPNPRu)₂(μ-Cl)₃]­BPh₄ (<b>10</b>), respectively. Complex <b>3</b> reacted with HCl/H₂O or HCl/Et₂O to produce ammonia stoichiometrically; the complex catalytically disproportionates hydrazine to generate ammonia