How to make weak hydrogen bonds less weak
Abstract
Interionic C–H···O hydrogen bond distances have been investigated in organometallic and inorganic salts showing that the average lengths unequivocally follow the order [(M)C–H]+···[O]-<(M)C–H···O (M=first row transition metal) and [(PPh4)C–H]+···[OM]-<[(PPN)C–H]+···[OM]-<[(BPh4)C–H]-···[OM]+, which is the order of decreasing charge assistance to the weak hydrogen bonds.