Bis(diphenylphosphino)methane-Phosphonate Ligands and Their Pd(II), Ni(II) and Cu(I) Complexes. Catalytic Oligomerization of Ethylene

The bis(diphenylphosphino)methane-phosphonate-based (dppm-phosphonate) ligands (Ph2P)2CHP(O)(OR)2 (R = Me, L1; R = Ph, L2) form metal complexes by selective coordination of the diphosphine moiety to Pd(II) and Ni(II) centers. The formation of complexes containing the chelating, deprotonated form of ligand L1 or L2 occurred when basic ligands were present in the precursor complex, such as Me or dmba (on Pd(II)) or acac (on Ni(II)). The Cu(I) complex [CuL1]2(BF4)2 (9) was obtained that is suggested to be dinuclear, each Cu(I) being chelated by a phosphine and a P═O donor and further bound to the phosphine group of another ligand. The crystal structures of the mononuclear complexes [PdCl2{(Ph2P)2CHP(O)(OMe)2-P,P}] (2a), [PdCl2{(Ph2P)2CHP(O)(OPh)2-P,P}] (2b), [Pd{(Ph2P)2CP(O)(OMe)2-P,P}2] (6a) in 6a·2CH2Cl2, [Pd{(Ph2P)2CP(O)(OPh)2-P,P}2] (6b), [Ni{(Ph2P)2CP(O)(OMe)2-P,P}2] (10a) in 10a·4CHCl3, [Ni{(Ph2P)2CP(O)(OPh)2-P,P}2] (10b) in 10b·4CHCl3, [NiCl2{(Ph2P)2CHP(O)(OMe)2-P,P}] (11a) in 11a·CHCl3 and of the din...