A π-Stacked Organometallic Propeller: Experimental and Theoretical Studies on Reactivity and Bonding in the π-Arene-Bridged Nickel Triple-Decker [{(η5-Me4EtC5)Ni}2(μ-η3:η3-decacyclene)]

Abstract

Keywords: Sandwich complexes / Nickel / Arenes / EHMO calculations / Cyclopentadienyl ligands Synthesis, structure, reactivity, and theoretical studies of a new type of Ni triple-decker complexes are reported. A prominent feature of its molecular structure is the (η 3 :η 3 )-bis-(enyl) coordination of two [(η 5 -Me 4 EtC 5 )Ni] fragments to the central arene ring of the polycondensed π-perimeter decacyclene. The central arene ring of decacyclene displays a distinct chair conformation with significant tilt angles of 25.5 and 26.1°. The three naphthalene units are twisted in a propeller-like fashion with torsion angles of 16°, 16.6°, and 19°, which is twice the twisting observed for the free decacyclene ligand. According to Extended Hückel Molecular Orbital (EHMO) calculations, a qualitative measure for arene lability in the title compound and a number of related arene-bridged metal complexes can be attributed to a subsequent filling of [ ‡] New address:

Azobenzene-functionalized iridium(iii) triscyclometalated complexes

“…Coordination of the nitrogen atom of an azoaromatic ligand to a metal centre has been a recurring topic for many years. From the early reports that proposed such a coordination mode, 46,47 many X-ray structures have been obtained for cyclometalated azobenzenes, [48][49][50][51][52][53][54] 2-(arylazo)pyridines, [55][56][57][58][59][60] 2,2′-azobis-( pyridine), [61][62][63] As observed frequently in other complexes containing chelating azoaromatics, in the molecular structure of complex [Ir-( ppy) 2 (1)] + the "free" phenyl ring is twisted with respect to the phenyl involved in the chelate ring (the angle between the phenyl planes defined as the torsion angle C33-N4-N5-C37 is 167.3(3)°). This twist produces a rupture in the conjugation within the azobenzene fragment.…”

Triple-decker transition metal complexes bridged by a single carbocyclic ring

“…A shift away from symmetrical (l-g 6 :g 6 ) coordination has been shown to enhance the metal-arene orbital overlap population for late-transition metal arenebridged complexes [87]. Increased metal-arene slippage is thus seen for metals such as cobalt (complexes 26 and 27, g 4 :g 4 binding) and nickel (A, Fig.…”

“…Increased metal-arene slippage is thus seen for metals such as cobalt (complexes 26 and 27, g 4 :g 4 binding) and nickel (A, Fig. 17, g 3 :g 3 binding to the central aromatic ring of decacyclene) [87] compared to vanadium (complex 19, g 6 :g 6 binding). The l-g 6 :g 6 cobalt complex trans-(CpCo) 2 [l-g 6 :g 6 -C 6 (COOMe) 6 ] (22) appears to be an exception, but has not been structurally characterised [75]; it may be that the steric bulk of the middle deck forces a more symmetrical arrangement of the coordinated metal fragments.…”

“…It has been demonstrated by EHMO calculations on l-g 6 :g 6 -and l-g 3 :g 3 -benzene-bridged complexes of V, Co, and Ni that the orbital overlap population between a given metal and an arene ring, which is used as a measure of arene-metal bond stability, decreases as additional electrons are placed in the frontier orbitals [87]. Therefore, an increased metal-arene lability is expected in the triple-decker arene-bridged complexes of the late transition metals (e.g.…”

Reversible Halide‐Modulated Nickel–Nickel Bond Cleavage: Metal–Metal Bonds as Design Elements for Molecular Devices

“…Corroborating this calculated interaction, the crystal structure of 2 shows the C7-C8 and C10-C11 distances to be shorter than the other C-C bonds of the central arene. Bifacial η 3 ,η 3 -bridging of an arene between two metal centers has been previously observed in dinuclear Ni, [10a, 18] Pt, [19] and Co complexes. [20] In contrast, in compound 2 , the arene bridges in η 3 ,η 1 –fashion, probably due to the steric constraints of the triphosphine.…”