“Bent Bonds” between Bismuth and Carbon Atoms as a Result of CH Activation in MoBi Complexes

Abstract

The reaction of molybdocenedihydride with two equivalents of [Bi(OtBu)(3)] proceeds via alcohol elimination and provides the compound [Cp(2)Mo{Bi(OtBu)(2)}(2)] (1), which contains two Mo--Bi metal bonds, in good yields. If the two reagents are employed in a 1:1 ratio continuative condensation reactions occur. These initially lead to [{Cp(2)Mo}(2){mu-Bi(OtBu)}(2)] (2), which, however, is very unstable in solution and decomposes via additional alcohol elimination: Complex-induced proximity effects facilitate the cleavage of C--H bonds within the cyclopentadienyl ligands by the residual alkoxide ligands, so that spontaneously two further equivalents of alcohol are released, thereby yielding two isomeric compounds 3 and 4 with Cp ligands bridging Mo--Bi metal bonds: The first isomer (3) contains two mu(2)-eta(5):eta(1)-C(5)H(4) ligands, the second isomer (4) contains one bridging mu(3)-eta(5):eta(1):eta(1)-C(5)H(3) ligand. The binding of these ligands to molybdenum and bismuth atoms at the same time is made possible through "bent bonds" between the bismuth and certain carbon centres. These unusual bonding situations were analysed by means of calculations based on density functional theory (DFT), the atoms in molecules (AIM) theory, natural bond order (NBO) considerations and the electron localisation function (ELF). According to the results the bonds can be understood in terms of carbanionic centres interacting with bismuth cations (i.e. closed-shell interactions). The formation of these bonds and the thermodynamics/kinetics involved on going from 2 to 3 and 4 were also studied by theoretical methods, so that the product formation is rationalised. The crystal structures of all four new compounds were determined. These structures but also the properties and mechanisms of formation are discussed against the background of the corresponding results obtained while studying the system [(Me)Cp(2)MoH(2)]/[Bi(OtBu)(3)].

Synthesis, structure and reactivity of complexes containing a transition metal–bismuth bond

“…The Bi-C bonds are surprising in that they are bent out of the plane of the cyclopentadienyl rings by approximately 40 • , suggesting a non-linear overlap between Bi and C orbitals. A theoretical investigation into this system showed the two isomeric products to be close in energy, with the unsymmetrical isomer slightly favoured [77]. The calculated Wiberg bond index between the bismuth and carbon centres suggests a relatively strong interaction, with natural bond order analyses indicating 2c-2e bonds polarised towards carbon.…”

“…Early research into bismuth-molybdenum species showed that the reaction of BrBiMe 2 and the sodium molybdate Na[Cp(CO) 3 Mo] did not result in the expected dimethyl derivative but instead in twofold substituted [{Cp(CO) 3 Both the bimetallic and trimetallic species exist for molybdenum, and are in fact in equilibrium in solution meaning that stoichiometric control is essential for high-yielding synthesis of either target [77][78][79]. The concentration of BiCl 3 is the controllable factor, its addition resulting in redistribution reactions in solution, in accordance with the equilibria.…”

f-Element-metal bond chemistry

“…Complex 19 contains two doubly deprotonated cyclopentadienyl ligands, η 5 -μ 4 -C 5 H 4 , deprotonated in the 1,2-positions. Such selective multiple deprotonations of cyclopentadiene are rare and have been observed in group 8 and ferrocene compounds but only in the form of 1,3-deprotonations (Clegg et al 2001, Andrikopoulos et al 2004, Roggan et al 2005 . DFT calculations on the Lu-Re bond in 19 revealed 81 % of the population as Re character and 8 % belonging to each of the Lu atoms.…”

Molecular Lanthanoid–Transition‐Metal Cluster through CH Bond Activation by Polar Metal–Metal Bonds

“…Upon cooling to 253 K signal separation occurs and for the CH 2 group (typical) geminal [18] The here observed selective 1,2-bis-deprotonation of one Cp ring of a metallocene is unusual. [19] The three Lu ions of the central structural element form an approximately equilateral triangle with two sides being bridged by C 2 Re triangles.…”