Synthesis and Reactivity of a Transition Metal Complex Containing Exclusively TEMPO Ligands: Ni(η²-TEMPO)₂

The reaction of Ni(COD)2 with two equivalents of the TEMPO radical at 68 °C affords the 16 e– “bow-tie” complex Ni(η2-TEMPO)2, 1, in 78% yield. Compound 1 reacts with tert-butyl isocyanide and phenylacetylene at room temperature to yield the 16 e– distorted square planar nickel complexes Ni(η2-TEMPO)(η1-TEMPO)(CNtBu), 2, and Ni(η2-TEMPO)(η1-TEMPOH)(CCPh), 4, respectively. The facile reactivity of 1 is aided by the transition of the TEMPO ligand from an η2 to η1 binding mode. Complex 4 is an unusual example of hydrogen atom transfer from phenylacetylene to a coordinated TEMPO ligand

Synthesis and Structural Characterization of Ruthenium Carbonyl Cluster Complexes Containing Platinum with a Bulky N‑Heterocyclic Carbene Ligand

The reaction of Ru₃(CO)₁₂ with Pt­(IMes)₂ in benzene solvent at room temperature afforded the monoplatinum–triruthenium cluster complex Ru₃Pt­(IMes)₂(CO)₁₁, <b>1</b>, in 21% yield and the trigonal bipyramidal cluster complex Ru₃Pt₂(IMes)₂(CO)₁₂, <b>2</b>, in 26% yield. The reaction of Ru­(CO)₅ with Pt­(IMes)₂ in benzene solvent at 0 °C yielded two trinuclear cluster complexes, the monoplatinum–diruthenium Ru₂Pt­(IMes)­(CO)₉, <b>3</b>, and the monoruthenium–diplatinum cluster complex RuPt₂(IMes)₂(CO)₆, <b>4</b>. The reaction of <b>2</b> with hydrogen at 80 °C afforded the tetrahydrido–tetraruthenium complex Ru₄(IMes)­(CO)₁₁(μ-H)₄, <b>5</b>, and the dihydrido–diruthenium–diplatinum complex Ru₂Pt₂(IMes)₂(CO)₈(μ-H)₂, <b>6</b>. All six compounds were structurally characterized by single-crystal X-ray diffraction analyses

Synthesis and Reactivity of a Transition Metal Complex Containing Exclusively TEMPO Ligands: Ni(η²-TEMPO)₂

The reaction of Ni(COD)2 with two equivalents of the TEMPO radical at 68 °C affords the 16 e– “bow-tie” complex Ni(η2-TEMPO)2, 1, in 78% yield. Compound 1 reacts with tert-butyl isocyanide and phenylacetylene at room temperature to yield the 16 e– distorted square planar nickel complexes Ni(η2-TEMPO)(η1-TEMPO)(CNtBu), 2, and Ni(η2-TEMPO)(η1-TEMPOH)(CCPh), 4, respectively. The facile reactivity of 1 is aided by the transition of the TEMPO ligand from an η2 to η1 binding mode. Complex 4 is an unusual example of hydrogen atom transfer from phenylacetylene to a coordinated TEMPO ligand

Reversible Inter- and Intramolecular Carbon–Hydrogen Activation, Hydrogen Addition, and Catalysis by the Unsaturated Complex Pt(IPr)(SnBu^t₃)(H)

The complex Pt­(IPr)­(SnBu^t₃)­(H) (<b>1</b>) was obtained from the reaction of Pt­(COD)₂ with Bu^t₃SnH and IPr [IPr = <i>N</i>,<i>N</i>′-bis­(2,6-diisopropylphenyl)­imidazol-2-ylidene]. Complex <b>1</b> undergoes exchange reactions with deuterated solvents (C₆D₆, toluene-<i>d</i>₈, and CD₂Cl₂), where the hydride ligand and the methyl hydrogen atoms on the isopropyl group of the IPr ligand have been replaced by deuterium atoms. Complex <b>1</b> reacts with H₂ gas reversibly at room temperature to yield the complex Pt­(IPr)­(SnBu^t₃)­(H)₃ (<b>2</b>). Complex <b>2</b> also undergoes exchange reactions with deuterated solvents as in <b>1</b> to deuterate the hydride ligands and the methyl hydrogen atoms on the isopropyl group of the IPr ligand. Complex <b>1</b> catalyzes the hydrogenation of styrene to ethylbenzene at room temperature. The reaction of <b>1</b> with 1 equiv of styrene at −20 °C yields the η²-coordinated product Pt­(IPr)­(SnBu^t₃)­(η²-CH₂CHPh)­(H) (<b>3</b>), and with 2 equiv of styrene, it forms Pt­(IPr)­(η²-CH₂CHPh)₂ (<b>4</b>)

Reversible Inter- and Intramolecular Carbon–Hydrogen Activation, Hydrogen Addition, and Catalysis by the Unsaturated Complex Pt(IPr)(SnBu^t₃)(H)

The complex Pt­(IPr)­(SnBu^t₃)­(H) (<b>1</b>) was obtained from the reaction of Pt­(COD)₂ with Bu^t₃SnH and IPr [IPr = <i>N</i>,<i>N</i>′-bis­(2,6-diisopropylphenyl)­imidazol-2-ylidene]. Complex <b>1</b> undergoes exchange reactions with deuterated solvents (C₆D₆, toluene-<i>d</i>₈, and CD₂Cl₂), where the hydride ligand and the methyl hydrogen atoms on the isopropyl group of the IPr ligand have been replaced by deuterium atoms. Complex <b>1</b> reacts with H₂ gas reversibly at room temperature to yield the complex Pt­(IPr)­(SnBu^t₃)­(H)₃ (<b>2</b>). Complex <b>2</b> also undergoes exchange reactions with deuterated solvents as in <b>1</b> to deuterate the hydride ligands and the methyl hydrogen atoms on the isopropyl group of the IPr ligand. Complex <b>1</b> catalyzes the hydrogenation of styrene to ethylbenzene at room temperature. The reaction of <b>1</b> with 1 equiv of styrene at −20 °C yields the η²-coordinated product Pt­(IPr)­(SnBu^t₃)­(η²-CH₂CHPh)­(H) (<b>3</b>), and with 2 equiv of styrene, it forms Pt­(IPr)­(η²-CH₂CHPh)₂ (<b>4</b>)

Reversible Hydrogen Activation by the Pt Complex Pt(Sn^<i>t</i>Bu₃)₂(CN^<i>t</i>Bu)₂

The new platinum complex Pt(SntBu3)2(CNtBu)2(H)2, 1, was obtained in 32% yield from the reaction of Pt(COD)2 with tBu3SnH and CNtBu at room temperature. Compound 1 is a mononuclear 18 electron platinum complex in an octahedral geometry which contains two SntBu3's, two CNtBu's, and two hydride ligands. The two hydride ligands in 1 can be eliminated, both in solution and in the solid state, to yield the 16 electron complex Pt(SntBu3)2(CNtBu)2, 2. Compound 2 reacts with hydrogen at room temperature in solution and in the solid state to regenerate 1

Helical Chiral 2,2′-Bipyridine <i>N-</i> Monoxides as Catalysts in the Enantioselective Propargylation of Aldehydes with Allenyltrichlorosilane

A highly enantioselective synthesis of homopropargylic alcohols is achieved by using the new helical chiral 2,2′-bipyridine N-monoxide catalyst and allenyltrichlorosilane. This method can be further extended to the enantio- and regioselective propargylation of N-acylhydrazones

Facile Activation of Hydrogen by an Unsaturated Platinum−Osmium Cluster Complex

The electronically unsaturated platinum−osmium complex Pt2Os3(CO)10(PtBu3)2, 3, has been obtained from the reaction of Os3(CO)10(NCMe)2 with Pt(PtBu3)2. Compound 3 adds hydrogen at 0 °C to yield the dihydrido complex Pt2Os3(CO)10(PtBu3)2(μ-H)2, 4 (93% yield) within 10 min and subsequently the tetrahydrido complex Pt2Os3(CO)10(PtBu3)2(μ-H)4, 5, in 70% yield within 60 min. Compound 3 contains a trigonal bipyramidal cluster of five metal atoms having the two platinum atoms in the apical sites. With the addition of each equivalent of hydrogen, the trigonal bipyramidal cluster opens by series of Pt−Os bond cleavages that result in sequential shifts of the Pt groups to edges of the Os3 triangle. The hydrogen addition process can be reversed partially at 25 °C by purging solutions of 5 with nitrogen

New High Nuclearity Platinum−Ruthenium Carbonyl Cluster Complexes Containing a Phenylacetylene Ligand: Structures and Properties

Reaction of the mixed-metal carbonyl cluster complex Ru5(CO)15(C)[Pt(PBut3)], 3, with PhC2H yielded the new compound PtRu5(CO)13(PBut3)(μ5-C)(μ3-PhC2H), 4, in 41% yield. Two new bimetallic cluster complexes, Pt2Ru5(CO)13(PBut3)2(μ5-C)(μ3-PhC2H), 5, and Pt3Ru5(CO)13(PBut3)3(μ5-C)(μ3-PhC2H), 6, were subsequently obtained in 44% and 40% yield, respectively, from the reaction of 4 with an excess of Pt(PBut3)2. All products were characterized crystallographically by single-crystal X-ray diffraction techniques. The structure of 4 consists of a square-pyramidal cluster of five ruthenium atoms with a Pt(PBut3) group capping one of the Ru3 triangles. A PhC2H ligand bridges one of the PtRu2 triangles. Compounds 5 and 6 are similar to 4 but have in addition one and two Pt(PBut3) groups bridging one and two edges of the Ru5 square-pyramidal portion of the cluster. Compound 6 was shown to be dynamically active on the 31P NMR time scale by a process that involves an interchange of two of its inequivalent Pt(PBut3) groups

Helical Chiral 2,2′-Bipyridine <i>N-</i> Monoxides as Catalysts in the Enantioselective Propargylation of Aldehydes with Allenyltrichlorosilane

A highly enantioselective synthesis of homopropargylic alcohols is achieved by using the new helical chiral 2,2′-bipyridine N-monoxide catalyst and allenyltrichlorosilane. This method can be further extended to the enantio- and regioselective propargylation of N-acylhydrazones