A Theoretical Study on Structures, Bonding Energies and Aromaticity of Two New Series of Dinuclear Phosphametallocenes: (η⁵‐P₅)MM′(η⁵‐P₅) and (η⁵‐C₅H₅)MM′(η⁵‐P₅) (M, M′ = Zn, Cd)

Abstract

The equilibrium geometries, the energies, the harmonic vibrational frequencies, and the nucleus independent chemical shifts (NICSs) of the ground state of (η 5 -P 5 )MMЈ(η 5 -P 5 ) and (η 5 -C 5 H 5 )MMЈ(η 5 -P 5 ) (M, MЈ = Zn, Cd) are calculated by the hybrid density functional method B3LYP with LANL2DZ basis sets. The analysis of energy and harmonic frequencies on the equilibrium geometries of both series dinuclear decaand pentaphosphametallocenes shows that all the minima with singlet electronic state have an staggered (9°Յ D (E-M-M-EЈ) Յ 36°) conformation except for the eclipsed CpCd 2 (P 5 ) (C 5v ), and all the D 5h and the D 5d symmetric conformations are transition states while the energy differences between the most stable minimum and the transition states are very small (Յ 0.1 kcal/mol), thus, the rotation of the P 5 ring about M-M bond in all complexes is almost free. The analysis of the NBO, the Laplacian of the electron density, the electrostatic interaction energy, the bonding energy decomposition, and the molecular orbital correlation diagrams for the two series complexes reveals that the properties of all the dinuclear phosphametallocenes investigated are similar to that of the dizinc metallocenes. The M-M (or M-MЈ) bond in the dinuclear phosphametallocenes is a weak σ covalent bond, and the magnitude of bonding energy of the M-M (or M-MЈ) bond correlates with the energy difference between the energy of HOMO in M(η 5 -P 5 ) (or MCp) ( 2 A, C 5v ) frag-

Zinc−Zinc Bonded Zincocene Structures. Synthesis and Characterization of Zn2(η5-C5Me5)2 and Zn2(η5-C5Me4Et)2

“…We have recently communicated the synthesis and structural and electronic properties of Zn 2 (η 5 -C 5 Me 5 ) 2 , 1 , the first stable molecular compound of zinc with a zinc−zinc bond . This report attracted the interest of the scientific community and was followed shortly by a number of theoretical studies dedicated to 1 and also to related species. , Furthermore two new examples of zinc−zinc bonded compounds have been provided. Robinson and co-workers have reported the generation of Zn 2 [HC(CMeNAr) 2 ] 2 (Ar = 2,6-Pr i 2 C 6 H 3 ), with three-coordinate zinc atoms (bidentate β-diketiminate ligands), and very recently Power and co-workers have characterized the zinc−zinc bonded species Zn 2 Ar 2 for ArC 6 H 3 2,6-(C 6 H 3 2,6-Pr i 2 ) 2 , where the Zn 2 2+ unit is supported by monodentate ligands.…”

Metal–Metal and Metal–Ligand Bonds in (η5-C5H5)2M2 (M = Be, Mg, Ca, Ni, Cu, Zn)

“…In addition, the analogous dinuclear metallocenes, such as Zn 2 (η 5 -Cp*) 2 , and the dinuclear cyclopentadienylcobalt carbonyls were investigated. The heterodinuclear metallocenes Cp–Zn–Cd–Cp, (η 5 -P 5 )MM′(η 5 -P 5 ), and (η 5 -C 5 H 5 )MM′(η 5 -P 5 ) (M, M′ = Zn, Cd) have also been studied. It is worth pointing out that compounds containing two main-group-metal atoms instead of transition-metal atoms sandwiched between two cyclopentadienyl groups, such as C 5 H 5 MMC 5 H 5 (M = Be, Mg, Ca) and CpE–MCp (E = B, Al, Ga; M = Li, Na, K), have also aroused interest.…”

Multimetallocenes. A Theoretical Study

“…The crystal structure of decamethyldizincocene reveals a pair of zinc atoms which are sandwiched between two permethylcyclopentadienyl rings (Cp*) in such a way that the Zn−Zn bond is collinear with the C 5 axes of the organic rings. The discovery of the dizincocene, the first dimetallocene, has triggered the interest of several experimental and theoretical groups in finding analogous compounds Cp* 2 M 2 , where M is any metal other than zinc. − Until today the search for stable species with the formula Cp* 2 M 2 has not been successful except for M = Zn. However, there is a related question regarding the change of element M which has not been addressed so far: How many atoms M n can be sandwiched by two Cp* rings, yielding a stable multimetallocene, Cp* 2 M n ?…”