Copper(I) Complexes of Amide Functionalized Bisphosphine: Proximity Enhanced Metal-Ligand Cooperativity and Its Catalytic Advantage in C()-H Bond Activation of Unactivated Cycloalkanes in Dehydrogenative Carboxylation Reactions.

The reactions of amide functionalized bisphosphine, -PhPCHC-(O)N(H)CHPPh- () (BalaHariPhos), with copper salts is described. Treatment of with CuX in a 1:1 molar ratio yielded chelate complexes of the type [CuX{(-PhPCHC(O)N(H)CHPPh-)}-κ] (X = Cl, ; Br, ; and I, ), which on subsequent treatment with KOBu resulted in a dimeric complex [Cu(-PhPCHC(O)(N)CHPPh-)] (). Interestingly, complexes - showed weak N-H···Cu interactions. These weak H-bonding interactions are studied in detail both experimentally and computationally. Also, Cu complexes - were employed in the oxidative dehydrogenative carboxylation (ODC) of unactivated cycloalkanes in the presence of carboxylic acids to form the corresponding allylic esters. Among complexes -, halide-free dimeric Cu complex showed excellent metal-ligand cooperativity in the oxidative dehydrogenative carboxylation (ODC) in the presence of carboxylic acids to form the corresponding allylic esters through C()-H bond activation of unactivated cycloalkanes. Mechanistic details of the catalytic process were established by isolating the precatalyst [Cu{(-PhPCHC(O)(NH)CHPPh-)-κ}(OOCPh)] () and fully characterized by mass spectrometry, NMR data, and single-crystal X-ray analysis. Density functional theory-based calculations further provided a quantitative understanding of the energetics of a series of H atom transfer steps occurring in the catalytic cycle.