Molecular orbital calculations on dinitrogen-bridged transition-metal dimers Academic Article uri icon


  • Fenske-Hall molecular orbital calculations on [{Ru(NH3)5}2(N2)]4+, [{(Nb(PH3)2(CH2)(CH3)}2(N2)], [{Zr(C5H5)2(N2)}2(N2)], and [{Re(PH3)4Cl}|MoCl4(OH))N2] are reported. These molecules model μ-N2 dimers in which the N-N bond lengths vary from 1.124 to 1.298 Å. The calculated Mulliken populations of the μ-N21πg orbitals decrease in the order Nb dimer > Zr dimer > Re-Mo dimer > Ru dimer, which is also the order of decreasing bond length as determined by X-ray crystallography. Our calculations suggest that more electrons are donated into the μ-N21πg lirg system in the Nb, Zr, and Re-Mo cases because of the presence of unoccupied d1π orbitals, which are at higher energy than occupied d1π orbitals and stabilize the μ-N21πgMO. These orbitals also allow delocalization of the μ-N21πg lirg electrons, which alleviates charge buildup. Differences between the Nb and Zr dimer M-N and N-N bond strengths are enhanced by synergetσ donation in the Nb dimer. © 1984, American Chemical Society. All rights reserved.

author list (cited authors)

  • Powell, C. B., & Hall, M. B.

citation count

  • 10

publication date

  • December 1984