Synthesis and characterization of homologous nickel(II) and palladium(II) complexes with biphosphine monoxide ligands Ph2P(CH2)nP(O)Ph2 (n = 1–3) and pTol2P(CH2)P(O)pTol2

A series of cationic nickel complexes [(η3-methally)Ni(P∧P(O))]SbF6 (1–4) [P∧P(O) = Ph2P(CH2)P(O)Ph2 (dppmO) (1), Ph2P(CH2)2P(O)Ph2 (dppeO) (2), Ph2P(CH2)3P(O)Ph2 (dpppO) (3), pTol2P(CH2)P(O)pTol2 (dtolpmO) (4)] has been synthesized in good yields by treatment of [(η3-methally)NiBr]2 with biphosphine monoxides and AgSbF6. The ligands are coordinated in a bidentate way. Starting from [(η3-all)PdI]2 the cationic complexes [(η3-all)P∧P(O))]Y (8–14). [P∧P(O) = dppmO, dppeO, dpppO, dtolpmO;Y = BF4, SbF6, CF3SO3, pTolSO3] were synthesized in good yields. The coordination mode of the ligand is dependent on the backbone and the anion, revealing a monodentate coordination with dppmO for stronger coordinating anions. The intermediates [(η3-all)Pd(I)(P∧P(O)-κ1-P)] (5–7) [P∧P(O) = dppmO (5), dppeO (6), dtolpmO (7)] were isolated and characterized. Neutral methyl complexes [(Cl)(Me)Pd(P∧P(O))] (15–18). [P∧P(O) = dppmO (15), dppeO (16), dpppO (17), dtolpmO (18)] can easily be obtained in high yields starting from [(cod)PdCl2]. For dppmO two different routes are presented. The structure of [(Me)(Cl)Pd{;Ph2P(CH2-P(O)Ph2-κ2-P,O};] · CH2Cl2 (15) with the chlorine atom trans to phosphorus was determined by X-ray diffraction.