A Phosphine-ß-diketiminate Nickel(I)-Complex for Small Molecule Activation

A bis(diphenyl)-phosphine functionalized ß-diketimine ligand (PNac-H) was applied for the synthesis of a subvalent Ni(I) complex [PNac-Ni]. Here, the Ni(I) center is stabilized by a tetradentate PNNP-type pocket, forming a square planar coordination sphere. Subsequently, the Ni(I) complex was investigated with regard to its reactivity and the activation of small molecules. The reductive potential of Ni(I) enabled an activation of different substrate classes, such as CH2 X2 (X=Br, I), I2 or Ph2 E2 (E=S, Se). The ligand's design allows a stabilization of the reactive Ni(I) species while at the same time enabling activation processes due to a hemilabile coordination behavior and accessible axial coordination sites. The activation products have been characterized by single crystal X-ray diffraction, NMR and IR spectroscopy as well as elemental analysis.

Metal-Metal (MM) Bond Distances and Bond Orders in Binuclear Metal Complexes of the First Row Transition Metals Titanium Through Zinc

This survey of metal-metal (MM) bond distances in binuclear complexes of the first row 3d-block elements reviews experimental and computational research on a wide range of such systems. The metals surveyed are titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, and zinc, representing the only comprehensive presentation of such results to date. Factors impacting MM bond lengths that are discussed here include (a) the formal MM bond order, (b) size of the metal ion present in the bimetallic core (M₂) ⁿ⁺, (c) the metal oxidation state, (d) effects of ligand basicity, coordination mode and number, and (e) steric effects of bulky ligands. Correlations between experimental and computational findings are examined wherever possible, often yielding good agreement for MM bond lengths. The formal bond order provides a key basis for assessing experimental and computationally derived MM bond lengths. The effects of change in the metal upon MM bond length ranges in binuclear complexes suggest trends for single, double, triple, and quadruple MM bonds which are related to the available information on metal atomic radii. It emerges that while specific factors for a limited range of complexes are found to have their expected impact in many cases, the assessment of the net effect of these factors is challenging. The combination of experimental and computational results leads us to propose for the first time the ranges and "best" estimates for MM bond distances of all types (Ti-Ti through Zn-Zn, single through quintuple).

Complexes of Ni(i): a “rare” oxidation state of growing importance

The synthesis and diverse structures, reactivity (small molecule activation and catalysis) and magnetic properties of Ni(i) complexes are summarized.

Low-temperature N-O bond cleavage and reversible N-P bond formation processes in the reactions of the unsaturated anions [M2(η5-C5H5)2(μ-PCy2)(μ-CO)2]- (M = Mo, W) with the nitrosyl complex [Re(η5-C5H4Me)(CO)2(NO)]+

The unsaturated anion [Mo2Cp2(μ-PCy2)(μ-CO)2](-) (Na(+) salt) reacted rapidly with [ReCp'(CO)2(NO)]BF4 in a dichloromethane solution at 253 K to give the oxo nitride tetracarbonyl complex [Mo2ReCp2Cp'(μ-N)(μ-O)(μ-PCy2)(CO)4] as the major product (Cp = η(5)-C5H5; Cp' = η(5)-C5H4Me). This complex underwent spontaneous decarbonylation at room temperature to give the unsaturated tricarbonyl derivative [Mo2ReCp2Cp'(μ-N)(μ-O)(μ-PCy2)(CO)3], a very dioxygen-sensitive molecule rapidly evolving upon manipulation to give the dioxo nitride dicarbonyl complex [Mo2ReCp2Cp'(μ-N)(μ-O)(μ-PCy2)(O)(CO)2] in modest yield. The latter product was obtained as a mixture of isomers, with the major ones differing in the relative arrangement (cis and trans) of their MoCp moieties [Mo-Mo = 2.7707(8) Å in the cis isomer]. The ditungsten anion [W2Cp2(μ-PCy2)(μ-CO)2](-) (Na(+) salt) also reacted rapidly with [ReCp'(CO)2(NO)]BF4 in a dichloromethane solution at 253 K to give an analogous oxo nitride complex, [W2ReCp2Cp'(μ-N)(μ-O)(μ-PCy2)(CO)4], but instead of releasing CO, this complex undergoes at room temperature a reversible insertion of the nitride ligand into a W-PCy2 bond, to reach an equilibrium with its phosphinoimido-bridged isomer [W2ReCp2Cp'(μ3-N:N:P-NPCy2)(O)(CO)4], which displays a V-shaped metal core [W-W = 3.0564(7) Å; W-Re = 2.9021(6) Å]. Decarbonylation of this mixture in a refluxing toluene solution led to partial degradation and condensation of these heterometallic species, to give [ReCp'(CO)3] and the pentanuclear oxo nitride complex [W4ReCp4Cp'(μ2-N)(μ3-N)(μ-O)(O)(μ-PCy2)2(CO)3], a very air-sensitive molecule displaying both linear and trigonal nitride ligands bound to rather unsaturated ditungsten centers [W-W = 2.7246(6) and 2.7900(6) Å].