1,3-Metal–Carbon Bonding Predicts Rich Chemistry at the Edges of Aromatic Hydrocarbons

Abstract

The existence of a hitherto unrecognized 1,3-metal−carbon bond (1,3-MC bond) in particular types of transitionmetal complexes is proposed using evidence from CCD X-ray structure analysis and DFT calculations. The name "edge complex" is suggested for the molecules, because the metal is coordinated at the V-shaped edges of olefinic and aromatic hydrocarbon moieties. Several edge complexes of group 4 metals have been identified from inspection of CCD data. The 1,3-MC bond is due to a d π −p π interaction between the metal and a β-carbon in the four-membered metallacycle region. The 1,3-MC-bonded metallacycle exhibits significant planar tetracoordinate character of the C β atom. Moreover, the metallacycle possesses a catastrophic ring critical point (rcp) in AIM analysis, where the highest eigenvalue of the rcp exhibits a linear correlation with the M−C β distance. The formation of hitherto unknown 1,3-MC-bonded multinuclear edge complexes of polycyclic aromatic hydrocarbons is predicted. Their electronic properties are attractive for the design of optoelectronic materials.

Productive Alkyne Metathesis with “Canopy Catalysts” Mandates Pseudorotation

“…29 The bond lengths are uneven: whereas the Mo1− C2 bond is only slightly shorter than the Mo1−C3 bond, the difference is more pronounced for C1−C2 versus C1−C3 (Figure 2). 30,31 It is remarkable that the metallacyclobutadiene forms A/B surface in the X-ray structure of 7 even though it is fairly close to the trigonal-bipyramidal rendition C where the tautomers converge (Scheme 1); 18 this peculiar situation may explain why their interconversion in solution is fast even at −90 °C as manifested in the spectra of C 2v symmetry. 32,33 The comparison of 7 with the structure of tungstenacyclobutadiene 5 24 derived from the catalytically incompetent tungsten alkylidyne 3 is also informative, as it allows the effect of the tripodal "canopy" ligand architecture to be assessed (Figure 2).…”

Hypercoordinate β-carbon in Grubbs and Schrock olefin metathesis metallacycles

“…This level of theory is previously used for the study of metallacyclobutadienes and found to yield structural data in good agreement with experimental results. [68][69][70][71] For Ru and W, the def2-TZVPP basis set augmented with effective core potential is used. Vibrational frequency calculation is performed on all optimized structures to verify their minimum energy configuration (zero imaginary frequency).…”

Theoretical Investigation of Promising Molecules for Obtaining Complexes with Planar Tetracoordinate Carbon

“…The electronic approach is that the ptC is placed on aromatic systems, in which the lone electron pair on ptC is delocalized. 29−31 The mechanical strategy is that the ptC atom is confined within a ring or a cage. 20,32−34 In addition to the main group element compounds with ptC, many stable complexes with ptC are also considered to adopt the electronic approach.…”