Ethylenediamine‐Derived PNNP Bisphosphine: Synthesis and Transition Metal Chemistry

The synthesis of the ethylenediamine‐derived bisphosphine ligand, ( o ‐PPh 2 (C 6 H 4 )C(O)NH(CH 2 )) 2 ( 1 ) (hereafter referred to as PN H N H P), is described via two methods distinct from previously reported procedures. Treatment of ligand 1 with Pd(COD)Cl 2 afforded the trans ‐dichloropalladium complex [PdCl 2 (PN H N H P)‐κ 2 ‐ P,P ] ( 2 ). In contrast, the reaction of 1 with Pd(COD)Cl 2 in the presence of a base led to the formation of the tetradentate cis ‐complex [Pd(PNNP)‐κ 4 ‐ P,N,N,P ] ( 3 ). Similarly, ligand 1 reacted with Pt(COD)Cl 2 to yield the corresponding cis ‐complex [Pt(PNNP)‐κ 4 ‐ P,N,N,P ] ( 4 ). Reaction of 1 with NiCl 2 (DME) in the presence of a base resulted in the formation of [Ni(PNNP)‐κ 4 ‐ P,N,N,P ] ( 5 ). Notably, exposure of the cis ‐palladium complex 3 to HCl gas led to its conversion to the trans ‐complex 2 , while the cis ‐platinum complex 4 remained unaffected. Density functional theory (DFT) calculations confirm that the conversion of 3 to 2 is thermodynamically favorable, with a Gibbs free energy change (ΔG) of −29.7 kcal mol. Furthermore, treatment of ligand 1 with cuprous halides yield [CuX(PN H N H P)‐κ 2 ‐ P,P ] ( 6 : X = Cl; 7 : X = Br; 8 : X = I). Reaction with Cu(NCCH 3 ) 4 BF 4 produced the dinuclear complex [Cu 2 (PN H N H P) 2 ‐κ 4 ‐ P,O,O,P ]BF 4 ( 9 ).