CIS,TRANS,CIS OR ALL-CIS GEOMETRY IN D(0) OCTAHEDRAL DIOXO COMPLEXES - AN IMOMM STUDY OF THE ROLE OF STERIC EFFECTS

The relative stabilities of two different isomers of d(0) MoO2Cl2L2 sp ecies are examined for two different complexes with the help of the in tegrated molecular orbital molecular mechanics method IMOMM. The exper imentally reported preference of the MoO2Cl2(N,N,N',N'-tetramethylethy lenediamine) complex for the all-cis arrangement and that of the MaO(2 )Cl(2)(N,N'-di-tert-butyl-1, 4-diaza-1,3-butadiene) complex for the ci s,trans,cis arrangement are properly reproduced. The inversion of rela tive stabilities is shown to be associated to the balance between elec tronic and steric contributions, the former favoring the cis,trans,cis arrangement and the latter stabilizing the all-cis form.