ORGANOMETALLIC ANALOGS OF THE CYCLOBUTADIENE DICATION - AN AB-INITIO MO AND DENSITY-FUNCTIONAL STUDY OF THE SYMMETRICAL PLANAR AND PUCKERED[WL(2)(MU-CR)](2) COMPLEXES (L=H, ME, F, OH R=H, F, ME)

Ab initio MO and density functional theory calculations are reported f or tungsten complexes [WL(2)(mu-CR)](2) (L = H, Me, F, OH; R = H, F, M e). The general perception that these complexes are always planar is c ontradicted. The effect of ligand L and substituent R on the puckering of four-membered W2C2 ring are studied. With L = H, the ring puckerin g is in the order of R = F < H < Me. With R = H, the ring puckering is in the order of L = OH approximate to F < Me < H. The puckering of W2 C2 ring depends more on the ligand L than on the substituent R. The an alogous nature of these complexes to cyclobutadiene dications is also discussed.