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Dicobalt complexes supported by flexible macrocyclic ligands were used to target the generation of the bridging nitrido species [( nPDI2)Co2(μ-N)(PMe3)2]3+ (PDI=2,6-pyridyldiimine; n=2, 3, corresponding to the number of catenated methylene units between imino nitrogen atoms). Depending on the size of the macrocycle and the reaction conditions (solution versus solid-state), the thermolysis of azide precursors yielded bridging phosphinimido [(2PDI2)Co2(μ-NPMe3)(PMe3)2]3+, amido [( nPDI2)Co2(μ-NH2)(PMe3)2]3+ ( n=2, 3), and C−H amination [(3PDI2*-μ-NH)Co2(PMe3)2]3+ products. All results are consistent with the initial formation of [( nPDI2)Co2(μ-N)(PMe3)2]3+, followed by 1) PMe3 attack on the nitride, 2) net hydrogen-atom transfer to form N−H bonds, or 3) C−H amination of the alkyl linker of the nPDI2 ligand. [ABSTRACT FROM AUTHOR]

The complex [(nacnac)Ti(OAr)]2(μ2:η2,η2-P2) ( 1) is formed via reductive decarbonylation of the phosphaethynolate ion −[OCP], which serves as a P atom source. Complex 1 is the first structurally characterized Group 4 transition metal P2 complex and its structure reveals the rhombic Ti2P2 core is essentially planar with short bond lengths suggesting some degree of multiple bonding character between the Ti-P and P-P sites. Computational studies of 1 provide an understanding of the Ti2P2 core as well as the origin of the highly downfield 31P NMR spectroscopic signal. [ABSTRACT FROM AUTHOR]

We report the synthesis of a gallium complex incorporating redox-active pyridyl nitroxide ligands. The (pyNO−)2GaCl complex was prepared in 85% yield via a salt metathesis route and was characterized by 1H and 13C NMR spectroscopies, X-ray diffraction, and theory. UV–Vis absorption spectroscopy and electrochemistry were used to access the optical and electrochemical properties of the complex, respectively. Our discussion focuses primarily on a comparison of the gallium complex to the corresponding aluminum derivative and shows that although the complexes are very similar, small differences in the electronic structure of the complexes can be correlated to the identity of the metal. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of two high-valent vanadium-cyclo-P3 complexes, (nacnac)V(cyclo-P3)(Ntolyl2) (1) and (nacnac)V(cyclo-P3)(OAr) (2), and an inverted sandwich derivative, [(nacnac)V(Ntolyl2)]2(µ2-η³:η²-cyclo-P3) (3), are presented. These novel complexes are prepared by activating white phosphorus (P4) with three-coordinate vanadium(II) precursors. Structural metrics, redox behavior, and DFT electronic structure analysis indicate that a [cyclo-P3]³-ligand is bound to a V(V) center in monomeric species 1 and 2. A salient feature of these new cyclo-P3 complexes is their significantly downfield shifted (by ~300 ppm) 31P NMR resonances, which is highly unusual compared to related complexes such as (Ar[iPr]N)3Mo(cyclo-P3) (4) and other cyclo-P3 complexes that display significantly upfield shifted resonances. This NMR spectroscopic signature was thus far thought to be a diagnostic property for the cyclo-P3 ligand related to its acute endocyclic angle. Using DFT calculations, we scrutinized and conceptualized the origin of the unusual chemical shifts seen in this new class of complexes. Our analysis provides an intuitive rational paradigm for understanding the experimental 31P NMR spectroscopic signature by relating the nuclear magnetic shielding with the electronic structure of the molecule, especially with the characteristics of metal-cyclo-P3 bonding. [ABSTRACT FROM AUTHOR]

The ethylene complex (PNP)Ti(n²-H2C-CH2)(CH2tBu) or (PNP)Ti-CHtBu(CH2tBu) (PNP- = N[2-P(CHMe2)2-4-methylphenyl]2) reacts with H2CPPh3 to form the n²-phosphinoalkylidene (PNP)Ti-CHPPh2(Ph) (1). Compound 1 activates benzene via the transient intermediate [(PNP)Ti=CPPh2] (C). By treatment of (PNP)Ti-CHtBu(OTf) with LiCH2PPh2, 1 or its isotopologue (PNP)Ti-CDPPh2(C6D5) (1-d6) can be produced by an independent route involving intermediate C, which activates benzene or benzene-d6 and dehydrogenates cyclohexane-d12. Addition of MeOTf to 1 results in elimination of benzene concomitant with the formation of the phosphonioalkylidyne complex, [(PNP)Ti=CPPh2Me(OTf) (2). Theoretical studies of 2 suggest a resonance structure having dominant Ti-C triple-bond character with some contribution also from a C-P multiple bond. [ABSTRACT FROM AUTHOR]