Non-redox Oxy-Insertion via Organometallic Baeyer-Villiger Transformations: A Computational Hammett Study of Platinum(II) Complexes

作者：Figg Travis M^*; Cundari Thomas R; Gunnoe T Brent

来源：Organometallics, 2011, 30(14): 3779-3785.

DOI：10.1021/om200258d

A Hammett analysis of platinum-mediated oxy-insertion into Pt-aryl bonds is performed using DFT calculations. Modeled transformations involve the conversion of cationic Pt(II)-aryl complexes [((X)bpy)Pt(R)(OY)](+) (R = p-X-C(6)H(4); Y = 4-X-pyridine; (X)bpy = 4,4'-X-bpy; X = NO(2), H, NMe(2)) to the corresponding [((X)bpy)Pt(OR)](+) complexes via an organometallic Baeyer-Villiger (BV) pathway. Computational modeling predicts that incorporation of an electron-deficient NO(2) group at the 4-position of pyridine-N-oxide lowers the activation barrier to the organometallic BV transformation. In contrast, computational studies reveal that increasing the donor ability of the migrating aryl group, by placement of NMe(2) at the para position, lowers the activation barrier to the oxy-insertion step. The impact on the calculated activation barrier is greater for variation of the R group than for modification of Y of the oxygen delivery reagent. For the p-NO(2)/p-NMe(2)-substituted aryl migrating groups (R), the Delta Delta G double dagger for X = NMe(2) versus X = NO(2) is 12 kcal/mol, which is three times larger than that calculated for the changes that occur upon substitution of NO(2) and NMe(2) groups (Delta Delta G double dagger approximate to 4 kcal/mol) at the 4-position of the pyridine group. For these Pt(II) complexes with bipyridine (bpy) supporting ligands, the influence of modification of the bpy ligand is calculated to be minimal with Delta Delta G double dagger approximate to 0.4 kcal/mol for the oxy-insertion of bpy ligands substituted at the 4/4' positions with NMe(2) and NO(2) groups. Overall, the predicted activation barriers for oxy-insertion (from the YO adducts [((X)bpy)Pt(R)(OY)](+)) are large and in most cases are >40 kcal/mol, although some calculated Delta G double dagger's are as low as 32 kcal/mol.

• 出版日期2011-7-25