Structure and bonding of tetrylone complexes [(CO)₄W{E(PPh₃)₂}] (E = C–Pb)

Abstract

Quantum chemical calculations at the BP86 level with various basis sets (SVP, TZVPP, TZ2P+) have been carried out for transition metal complexes of carbodiphosphorane analogues E(PPh₃)₂ with E = C–Pb. The nature of the W(CO)₄–E(PPh₃) bonds was analysed with charge and energy decomposition methods. The equilibrium structures of the tetrylone complexes W(CO)₄–E(PPh₃)₂ possess for E = C, Si, Ge a trigonal bipyramidal coordination at tungsten with the tetrylone ligand occupying an equatorial position. The heavier homologues with E = Sn, Pb exhibit a square pyramidal coordination at tungsten where the tetrylone ligand is at a basal position, while one phenyl group is found trans to the apical CO group which yields a hexacoordinated tungsten complex. The bond dissociation energies for the W(CO)₄–E(PPh₃)₂ bonds are higher than for the W(CO)₅–E(PPh₃)₂ homologues. The bonding analyses of the complexes show that the W–E bonds have a significant contribution from (CO)₄W←E(PPh₃)₂ π-donation. All complexes W(CO)₄–E(PPh₃)₂ are suitable targets for synthesis.

Keywords:

• tetrylones
• bonding analysis
• transition metal complexes
• energy decomposition analysis

Acknowledgements

This work was supported by a grant of the Deutscher Akademischer Austausch Dienst (DAAD). TANN thanks Dr. Ralf Tonner for his support. Excellent service by the Hochschulrechenzentrum of the Philipps-Universität Marburg is gratefully acknowledged. Additional computer time was provided by CSC Frankfurt.

Notes

^aThe values in parentheses give the percentage contribution to the total attractive interactions ΔE _elstat + ΔE _orb.

^bThe values in parentheses give the percentage contribution to the total orbital interactions ΔE _orb.

^cThe values in parentheses were obtained at BP86/def2-TZVPP level.