Preparation and Structure of [Mo4(OMe)2(OiPr)10]; Comments on Why [W2(OiPr)6] Dimerizes, Whereas [Mo2(OiPr)6] Does Not

A [MoMo]6⊕ complex is thermodynamically more stable than a corresponding [WW]6⊙ complex! It is assumed that this finding can be attributed to nuclear repulsive effects, which are larger in the case of tungsten than in the case of molybdenum. The structure of the title complex is characterized by two short and two long MoMo distances (2.238(1) and 3.344(1)Å, resp.) and thus by two bisalkoxide-bridged MoMo units. The formation of alkoxide bridges could be an important step in the dimerization of [W2(OiPr)6].