The synthesis and structure of [CO(η-C₅Me₅)Et{P(p-tolyl)₃}] cation: a model for the β-elimination transition state

Abstract

Protonation of [Co(q-C5Me5)(C2H4){ P ( p -t ~l y l ) ~) ] affords the ethyl cation [Co(q-C5Me5)Et{ P ( p -t ~l y l ) ~) ] + in which there is a strong three-centre interaction between the metal and a (3-C-H, as indicated by 1H and 13C n.m.r. and by a single crystal X-ray diffraction study of the tetrafluoroborate salt.

Intramolecular Apical C–H···M Interactions in Square‐Planar Nickel(II) Complexes with Dianionic Tridentate Ligands and 2‐Phenylimidazole

“…These delocalisation energies are insignificant compared with those obtained for strong agostic interactions and are comparable with C-H···M hydrogen-bonding interactions. [29,30] The "atoms in molecules" theory [31] has also been used for further probing of the topological properties of the CH···Ni interaction in 1 and 2. The values obtained for the electron densities (ρ b = 0.011 and 0.012 a.u.…”

Yttrium Complexes of the Chelating,C2-Symmetric, Bis(silylamido)biphenyl Ligand [DADMB]2-(={[6,6‘-Me2-(C6H3)2](2,2‘-NSiMe2tBu)2}2-)

“…The 3 J YH coupling constant of 1.9 Hz for the CH 3 protons of the ethyl ligand is very similar to the related value ( 3 J YH = 1.4 Hz) reported for (η 5 -CH 3 C 5 H 4 ) 2 Y(CH 2 CH 3 )(THF), and the 1 J CH coupling constant of 120 Hz is typical for an sp 3 C−H bond. Although β-agostic interactions are often observed in early-transition-metal ethyl complexes, − ,,− their existence cannot be determined on the basis of the (averaged) 1 J CH coupling constant only. The IR spectrum of 7 does not contain evidence for agostic C−H bonds (no low-energy C−H bands were detected).…”

Misassigned C–H⋯Cu agostic interaction in a copper(ii) ephedrine derivative is actually a weak, multicentred hydrogen bond

“…In contrast, we obtained charge differences of 20.058e for [FeP(OMe 3 ) 3 (C 8 H 13 )] + and 20.007e for [Co(g 5 -C 5 Me 5 )PPh 3 Et] both of which are well established cases of an agostic interaction. 16,17 An important distinguishing feature of an agostic interaction is the dative interaction from the s C2H orbital to the low lying empty metal orbital. This interaction is not seen in the case of hydrogen bonding.…”

“…For complex 1, the net s C2H to metal delocalization energy is 1.50 kcal mol 21 ; this value goes up to as much as 56.66 kcal mol 21 for a strongly agostic interaction as in the case of the [Co(g 5 -C 5 Me 5 )PPh 3 Et] complex. 17 The atoms in molecule (AIM) theory 19 may also be used to probe the distinction between agostic and hydrogen bond interactions. Popelier 20 and Coppens 21 have pointed out that for the weaker agostic interactions, it is sometimes difficult to identify the BCP and bond path.…”