No abstract

No abstract

crystals that are strictly isomorphous with those of the same isomer of the tantalum analogue.9 In both cases, the two chelate rings have the same ( ) conformation and the molecule is chiral. The two molecular structures have principal dimensions that do not differ significantly at the 3 level. Thus, there are the following differences (esd's in parentheses): M-M, 0.004 (3) Á; M-P, 0.018 (8) A; M-Clb, 0.009 (9) A; M-C1" 0.000 (10) A. While corresponding Nb and Ta molecules of this class have previously been found to have similar dimensions, as in the comparison of 1 and 2 above, this is apparently the first case in which they have been so similar as to be identical within the 3 criterion.Comparison of 1 and 3. These two structures are surprisingly similar in view of the difference between dene and depe as ligands.The two Nb-Nb distances are different in a statistically significant sense, viz., 2.741 (3) A in the depe compound (3) and 2.764 (1) A in the dene compound (1), but in a chemical sense the difference (9) Cotton, F.

No abstract

No abstract