Versatile nuclephilic Michael addition to chelated (Ph2P)2Cdouble bond; length as m-dashCH2 (vdpp) in Schiff base cyclometallated palladium(II) compounds: C–C, C–O and C–N bond formation, dinuclear palladacycles and geometrical isomerism

Treatment of the mononuclear complex [Pd{2,4-(MeO2)C6H2C(H)double bond; length as m-dashN(Cy)-C6,N}{(Ph2P)2Cdouble bond; length as m-dashCH2-P,P′}][PF6] (1) with methyl 2-oxocyclopentanecarboxilate, α-acetylbutyrolactone or methyl phenylsulfonylacetate in the presence of anhydrous sodium carbonate yielded the addition products [Pd{2,4-(MeO)2C6H2C(H)double bond; length as m-dashN(Cy)-C6,N}{(Ph2P)2CHCH2C(R1)(R2)-P,P′}][PF6] (R1 = COOCH3, R2 = COCH2CH2CH2, 2; R1 = COCH3, R2 = COOCH2CH2, 3; R1 = COOCH3, R2 = SO2Ph, 4) in high yield. The existence of two chiral carbon atoms in the diphosphine moiety produces the existence of optical isomers. Reaction of 1 with acetone and potassium tert-butoxide afforded complex [Pd{2,4-(Me)2C6H2C(H)double bond; length as m-dashN(Cy)-C6,N}{(Ph2P)2CHCH2CH2COCH3-P,P′}][PF6] (5), via C–C bond formation. Complex 1 reacts in methanol and in ethanol to give the corresponding addition products [Pd{2,4-(MeO)2C6H2C(H)double bond; length as m-dashNCy-C6,N}{(Ph2P)2CHCH2OR-P,P′}][PF6] (R = CH3, 6; R = CH2CH3, 7), via C–O bond formation. Treatment of complex 1 with cyclohexylamine or dimethylhidrazine gives place to [Pd{2,4-(MeO)2C6H2C(H)double bond; length as m-dashN(Cy)-C6,N}{(Ph2P)2CHCH2N(H)R–P,P′}][PF6] (R = C6H11, 8; R = N(CH3)2, 9), via C–N formation. The crystal structure of 7 has been determined by X-ray crystallography and comprises equimolar amounts of the (C16R) and (C16S) enantiomers. Reaction of compound 1 with dl-alanine or dl-metionine and anhydrous sodium carbonate yields [Pd{2,4-(MeO)2C6H2C(H)double bond; length as m-dashN(Cy)-C6,N}{(Ph2P)2CHCH2NHCH(R1)(R2)-P,P′}][PF6] (R1 = CH3, R2 = COOH, 10; R1 = CH2CH2SCH3, R2 = COOH, 11). Treatment of complex 1 with piperazine give rise to the dinuclear compound [{Pd[2,4-(MeO)2C6H2C(H)double bond; length as m-dashN(Cy)-C6,N]}2{(Ph2P)2CHCH2N(CH2CH2)2NCH2CH(PPh2)2-P,P,P′,P′}][PF6]212, in which each N–H bond of the piperazine has been added to the vinylidene bond of one vdpp ligand.