Theoretical Study of the CO Migratory Insertion Reactions of Pt(Me)(OMe)(dppe) and Ni(Me)(OR)(bpy) (R = Me, O-p-C6H4CN): Comparison of Group 10 Metal−Alkyl, −Alkoxide, and −Aryloxide Bonds

Abstract

We report the results of theoretical mechanistic studies on the alternative migratory insertion reactions of CO with the metal−oxygen and metal−carbon bonds of Pt(Me)(OMe)(dhpe) (dhpe = H2PCH2CH2PH2) and Ni(Me)(OR)(α-diimine) (R = Me, Ph, α-diimine = NHCHCHNH) as models for Pt(Me)(OMe)(dppe) (dppe = Ph2PCH2CH2PPh2) and Ni(Me)(O-p-C6H4CN)(bpy) (bpy = 2,2‘-bipyridyl), respectively. With Pt(Me)(OMe)(dhpe) the methoxycarbonyl product, Pt(Me)(CO2Me)(dhpe), is favored over the acyl alternative, Pt{C(O)Me}(OMe)(dhpe), by 13 kcal/mol. Two alternative pathways for methoxycarbonyl formation were located, both of which are initiated via displacement of a chelate arm to form two isomers of Pt(Me)(OMe)(CO)(η1-H2PCH2CH2PH2) (2a, CO trans to OMe; 2b, CO trans to Me). Subsequent CO migratory insertion into the Pt−OMe bond of 2b yields the methoxycarbonyl product directly. Alternatively, isomerization of 2a to a third isomer, 2c (CO trans to phosphine), can occur, from which CO migratory insertion again produces the metho...