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“Bent Bonds” between Bismuth and Carbon Atoms as a Result of CH Activation in MoBi Complexes
Author(s) -
Roggan Stefan,
Schnakenburg Gregor,
Limberg Christian,
Sandhöfner Steffen,
Pritzkow Hans,
Ziemer Burkhard
Publication year - 2004
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200400836
Subject(s) - chemistry , natural bond orbital , bismuth , crystallography , atoms in molecules , alkoxide , density functional theory , molecule , metal , ligand (biochemistry) , computational chemistry , stereochemistry , catalysis , organic chemistry , biochemistry , receptor
The reaction of molybdocenedihydride with two equivalents of [Bi(O t Bu) 3 ] proceeds via alcohol elimination and provides the compound [Cp 2 Mo{Bi(O t Bu) 2 } 2 ] ( 1 ), which contains two MoBi 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 {μ‐Bi(O t Bu)} 2 ] ( 2 ), which, however, is very unstable in solution and decomposes via additional alcohol elimination: Complex‐induced proximity effects facilitate the cleavage of CH 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 MoBi metal bonds: The first isomer ( 3 ) contains two μ 2 ‐η 5 :η 1 ‐C 5 H 4 ligands, the second isomer ( 4 ) contains one bridging μ 3 ‐η 5 :η 1 :η 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(O t Bu) 3 ].