Comparison of Side‐On and End‐On Coordination of E₂ Ligands in Complexes [W(CO)₅E₂] (E=N, P, As, Sb, Bi, Si⁻, Ge⁻, Sn⁻, Pb⁻)

Abstract

Complexes of W(CO)(5) with neutral diatomic pnictogen ligands N(2), P(2), As(2), Sb(2), and Bi(2) and anionic Group 14 ligands Si(2) (2-), Ge(2) (2-), Sn(2) (2-), and Pb(2) (2-) coordinated in both side-on and end-on fashion have been optimized by using density functional theory at the BP86 level with valence sets of TZP quality. The calculated bond energies have been used to compare the preferential binding modes of each respective ligand. The results were interpreted by analyzing the nature of the interaction between the ligands and the metal fragment using an energy partitioning method. This yields quantitative information regarding the strength of covalent and electrostatic interactions between the metal and ligand, as well as the contributions by orbitals of different symmetry to the covalent bonding. Results show that all the ligands studied bind preferentially in a side-on coordination mode, with the exception of N(2), which prefers to coordinate in an end-on mode. The preference of the heavier homologues P(2)-Bi(2) for binding in a side-on mode over the end-on mode in the neutral complexes [(CO)(5)WE(2)] comes mainly from the much stronger electrostatic attraction in the former species. The energy difference between the side-on and end-on isomers of the negatively charged complexes with the ligands Si(2) (2-), Ge(2) (2-), Sn(2) (2-), and Pb(2) (2-) is much less and it cannot be ascribed to a particular bonding component.

The Dimethylbismuth Cation: Entry Into Dative Bi−Bi Bonding and Unconventional Methyl Exchange

“…[3,4] Following these pioneering contributions, different types of compounds featuring Bi À Bi multiple bonds have been reported more recently. These include dibismuthenes such as the pivotal TbtBi=BiTbt (B) (Tbt = 2,4,6-[CH-(SiMe 3 ) 2 ] 3 -C 6 H 2 ), [5] Bi 2 units in the coordination sphere of transition metals (as in Bi 2 (W(CO) 5 ) 3 (C)), [6] [K(222-crypt)] 2 -[Bi 2 ] containing naked [Bi 2 ] 2À anions (D), [7] and free Bi 2 (E), which has been generated and analyzed in the gas phase and in noble gas matrices (Figure 1 a). [8] In contrast, compounds featuring unidirectional Bi!Bi donor-acceptor interactions have not been reported to date.…”

Das Dimethylbismut‐Kation: Zugang zu dativen Bi‐Bi‐Bindungen und unkonventionellem Methylaustausch

“…[3,4] In Folge dieser Pionierbeiträge wurden in jüngerer Zeit verschiedene Arten von Verbindungen mit Bi À Bi-Mehrfachbindungen berichtet. Diese beinhalten Dibismutene, wie das wegweisende TbtBi = BiTbt (B) (Tbt = 2,4,6-[CH(SiMe 3 ) 2 ] 3 -C 6 H 2 ), [5] Bi 2 -Einheiten in der Koordinationssphäre von Übergangsmetallen (wie in Bi 2 (W(CO) 5 ) 3 (C)), [6] [K(222-crypt)] 2 [Bi 2 ] mit nackten [Bi 2 ] 2À -Anionen (D), [7] und freies Bi 2 (E), das in der Gasphase und in Edelgasmatrices erzeugt und analysiert wurde (Abbildung 1 a). [8] Im Gegensatz dazu sind Verbindungen mit unidirektionalen Bi!Bi-Donor-Akzeptor-Wechselwirkungen bisher noch nicht beschrieben worden.…”

Infrared Photodissociation Spectroscopy of Heteronuclear Arsenic–Iron Carbonyl Cluster Anions

“…The experimental As–As bond length of 2.372 (5) Å in the As 3 Co­(CO) 3 cluster is 0.068 Å shorter than the experimental value in gaseous As 4 (2.44 Å) . The As–As bonds are significantly shortened when the Co­(CO) 3 groups substituted arsenic atoms in As 4 because the Co­(CO) 3 system is more electronegative and can effectively function as an “electron sink”. ,, The resultant partial charge transfer from the arsenic atoms to the Co­(CO) 3 system decreases the antibonding character between the arsenic atoms and thereby shortens the As–As bond. , In this study, the predicted As–As bond length of 2.412 Å in the As 3 Fe­(CO) 3 – cluster anion is 0.044 Å shorter than that of the As 4 cluster (2.456 Å) calculated at the B3LYP/aug-cc-pVTZ level. As shown in Table , the natural charge of the As 3 group in As 3 Fe­(CO) 3 – is calculated to be 0.29, indicating that the arsenic atoms transfer 0.29 e to the negatively charged Fe­(CO) 3 – group.…”