LIGAND SUBSTITUTION AND OXIDATIVE ADDITION REACTIONS OF DIMOLYBDENUM AND DITUNGSTEN (TRIPLE-BONDED METAL) COMPOUNDS (1,2-BENZOQUINONE).

摘要

The systematic development of the chemistry surrounding M(,2)X(,6) (M(TBOND)M) M = Mo, W compounds over the past decade has been primarily addressed by Chisholm and coworkers. Ligand substitution and oxidative-addition are just two of the reaction pathways under investigation. Metathetical reactions of a variety of M(,2)X(,6) (M(TBOND)M) compounds and R(H)NCH(,2)CH(,2)N(H)R', where R = R' = Me or R' = Et, R = Me, or the corresponding dilithium diamide salt, have provi- ded products of formula M(,2)(RNCH(,2)CH(,2)NR')(,3) (M(TBOND)M) where M = Mo, W. Spectroscopic studies of these molecules, which exhibit a near-eclipsed conformation about the metal-metal triple bond, suggest them to be electronically similar to the staggered ethane-like M(,2)X(,6) systems. Investigation of oxidative addition of tetrachloro-1,2-benzo- quinone and 9,10-phenanthrenequinone to M(,2)(OR)(,6) (M(TBOND)M) M = Mo, W, compounds may promote understanding and proof of generality of these oxidative processes. The reaction products have general formula M(,2)((mu)-OR)(,2)(OR)(,4-2x)(OO)(,2+x),(' )M = Mo, W; x = 0, 1 or 2; R = Pr('i), Ne. These metal-metal singly bonded compounds exhibit fluxional ('1)H NMR behavior for x = 1 or 2. For the reaction of tetrachloro-1,2-benzoquinone and Mo(,2)(OBu('t))(,6) the compound (MoO(,2)(OO)py)(,2)O pyH (,2) is formed.(' )The reaction of acetone and W(,2)(OPr('i))(,6)L(,2), where L = HNMe(,2) or py, gives 2,3-dimethyl-2-butene and the tetranuclear cluster W(,4)O(,2)(OPr('i))(,12), which has localized metal-metal triple and single bonds. This reaction probably proceeds via an oxidative-addition type process on the way to providing alkene products of the reductive coupling of the acetone. All of this work has required the use of air sensitive techniques and standard spectroscopic methods.