Replacement of a Cyclometalated Terdentate Diamino Ligand by a Phosphorus Analogue. Isolation and Crystallographic Characterization of an Intermediate in Aryl C−H Bond Activation in Models of Dendrimer-Bound Organometallic Catalysts

A Cobalt(I) Pincer Complex with an η2‐Caryl−H Agostic Bond: Facile C−H Bond Cleavage through Deprotonation, Radical Abstraction, and Oxidative Addition

“…Theoverall geometry about the cobalt center is best described as distorted trigonal bipyramidal, where the two carbonyl ligands and the agostic h 2 -C aryl -H bond define the equatorial plane and the phosphine moieties the axial positions.T he bond between the ipso-carbon and the Co atom is extremely long (2.2197 (6) + (5)a re substantially shorter:1 .998(2) and 1.953-(2) , respectively.T he H(1) atom (which was located in difference Fourier maps and refined freely) strongly interacts with the cobalt center (1.72(2) ), which was also evident from the 1 HNMR spectrum of 3.I ti sn oteworthy that this hydrogen is severely removed from the aromatic plane by approximately 358 8 (in related Ru, Rh, and Os complexes,this angle is in the range of 14-30 o ). [5,7,10,14] TheC 1 ÀH1 bond length of 1.05(3) i si nt he range observed in X-ray diffraction measurements for unactivated hydrocarbons (for example,1.08 i nC 6 H 6 ).…”

“…Accordingly,t he key complex described here may be viewed as am issing link on the pathway to Rh III hydride complexes (Scheme 1). [7][8][9] Complex 3 exhibits two bands at 1950 and 2009 cm À1 in the IR spectrum for the mutually cis CO ligands,assignable to the symmetric and asymmetric CO stretching frequencies,respectively (compare 1906 and 1963 cm À1 in the more electron-rich complex 1).…”

Structural Investigation in Solution of a Series of Five-Coordinate Bisphosphanylaryl Ruthenium(II) Complexes

“…Interpretation of the 1 H, 13 C and 31 P NMR patterns of 7 was further frustrated by the lack of a detailed assignment of the 1 H and 13 C NMR spectra in complexes where the PCP-type ligand had phenyl groups attached to the phosphorus atoms, [8] mainly those with geometries other than square-planar. [2,3,5,9,10] In particular, a detailed understanding of the binding mode of the HϪPCHP ligand in 7 requires an accurate assignment of the aromatic region of the 1 H and 13 C NMR spectra of related complexes such as 1؊3. Furthermore, these PCP metal complexes have an increasing importance as novel catalysts [8b,8c,11Ϫ13] as well as materials with interesting new physico-chemical properties.…”

Bis(ortho)-Chelated Bis(phosphanyl)aryl Ruthenium(II) Complexes Containing an η1-P-Monodentate or μ-Bridging η1-P,η1-P′ Bonded R−PCHP Arene Ligand, 1-R-3,5-(CH2PPh2)2C6H3 [R = H, Br, or, Si(n-CH2CH2C8F17)3] — Cyclometalation Reaction Intermediates and Potential Catalysts for Use in Fluorinated Biphasic Systems

“…However, some drawbacks have been encountered for R groups containing sensitive functionalities (e.g., when R ϭ SiMe 3 , desilylation can occur). [10,15] Other chlorinated solvents can be used as the reaction medium, such as CH 2 Cl 2 or o-dichlorobenzene. However, 1,2-dichloroethane has been shown to be the best choice in terms of reaction times (typically 1Ϫ2 h), yields, and ease of work-up of the resulting products.…”

“…Only a few cases are known where the ligand is bonded as a neutral (noncyclometalated) RϪPCHP species. Examples of this type of bonding are observed in just a few square-planar d 8 metal complexes, [5Ϫ7] tetrahedral silver compounds, [8] and the octahedral ruthenium species 1 [9] and 2 [10] (Figure 3). …”