Reactivity of C(sp2)-Pd and C(sp3)-Pd bonded palladacycles with diphosphines. Crystal and molecular structure of the novel A-frame complex [{Pd[2,5-Me2C6H2C(H)double bond; length as m-dashN(2,4,6-Me3C6H2)-C6]}2(μ-Ph2PCH2PPh2)2(μ-Cl)][PF6]

Treatment of the halogen-bridged complexes [Pd{2,5-Me2C6H2C(H)double bond; length as m-dashN(2,4,6-Me3C6H2)-C6,N}(μ-X)]2 (1a, X = Cl; 2a, X = Br) with the tertiary diphosphine Ph2PCH2PPh2 (dppm), regardless of the molar ratio used, gave a mixture of two complexes: [Pd{2,5-Me2C6H2C(H)double bond; length as m-dashN(2,4,6-Me3C6H2)-C6}(μ-Ph2PCH2PPh2)2(μ-X)]2[PF6] (5a, X = Cl; 6a, X = Br), which presents an A-frame structure, and [Pd{2,5-Me2C6H2C(H)double bond; length as m-dashN(2,4,6-Me3C6H2)-C6,N}(Ph2PCH2PPh2-P,P)][PF6], 3a, with the diphosphine as chelating. The mixture could be separated and the corresponding complexes isolated. However, reaction of 1a and 2a with the diphosphine Ph2PC(double bond; length as m-dashCH2)PPh2 (vdpp) exclusively gave the mononuclear complex [Pd{2,5-Me2C6H2C(H)double bond; length as m-dashN(2,4,6-Me3C6H2)-C6,N}{Ph2PC(double bond; length as m-dashCH2)PPh2-P,P}][PF6], 4a, analogous to 3a. Treatment of the halogen-bridged complexes [Pd{1-CH2-2-[HCdouble bond; length as m-dashN(2,4,6-Me3C6H2)]-4-MeC6H3-C,N}(μ-X)]2 (1a′, X = Cl; 2a′, X = Br) with dppm or vdpp in a cyclometallated complex/diphosphine 1:2 M ratio, gave mononuclear complexes with the chelating diphospines [Pd{1-CH2-2-[HCdouble bond; length as m-dashN(2,4,6-Me3C6H2)]-4-MeC6H3-C,N}(Ph2PCH2PPh2-P,P)][PF6], 3a′, and [Pd{1-CH2-2-[HCdouble bond; length as m-dashN(2,4,6-Me3C6H2)]-4-MeC6H3-C,N}{Ph2PC(double bond; length as m-dashCH2)PPh2-P,P}][PF6], 4a′. When the reaction was carried out using a cyclometallated complex/diphosphine 1:1 M ratio the dinuclear complexes [{Pd[1-CH2-2-{HCdouble bond; length as m-dashN(2,4,6-Me3C6H2)}-4-MeC6H3-C,N]}2(μ-X)(μ-Ph2PCH2PPh2)][Cl], (5a′, X = Cl; 7a′, X = Br) and [{Pd[1-CH2-2-{HCdouble bond; length as m-dashN(2,4,6-Me3C6H2)}-4-MeC6H3–C,N]}2(μ-Cl){μ-Ph2PC(double bond; length as m-dashCH2)PPh2}][Cl], 6a′, were obtained. The molecular structures of complexes 3a, 4a, 5a and 6a′ were determined by X-ray single crystal diffraction.