Pd center dot center dot center dot H-C interactions. Preparation and structure of orthometalated tetranuclear complexes of palladium(II) and platinum(II)

The reaction of 2-(1-naphthyl)benzothiazoline with palladium(II) acetate leads to helical mononuclear and orthometalated tetranuclear products. The molecular structures of mononuclear palladium(II) [Pd(H1-nabz)(2)] (1) (H(2)1-nabz = 2-N-(1-naphthylmethylideneamino)benzenethiolate), tetranuclear palladium(II) [Pd-4(1-nabz)(4)] (2) and tetranuclear platinum(II) [Pt-4(1-nabz)(4)] (3) have been determined by single-crystal X-ray diffraction method. Crystal data for complex 1 are as follows: a = 14.208(3) Angstrom, b = 18.227(4) Angstrom, c = 14.398(8) Angstrom; beta = 94.55(3)degrees; V = 3717.0(23) Angstrom(3); space group = P2(1)/n, Z = 4. Crystal data for the complex 2 are as follows: a = b = 15.798(3) Angstrom, c = 23.728(4) Angstrom; V = 5921.7(20) Angstrom(3); space group = I4(1)/a, Z = 16 for the Pd(1-nabz) unit. Crystal data for the complex 3 are as follows: a = b = 15.496(2) Angstrom, c = 24.348(3) Angstrom; V = 5845.3(20) Angstrom(3); space group I4(1)/a, Z = 16 for the Pt(1-nabz) unit. The mononuclear palladium(II) complex reveals short orthohydrogen palladium distances of 2.66(7) and 2.48(7) Angstrom. These short distances and H-1 NMR studies provide a M ... H-C interaction which can be regarded as a three-center four-electron interaction. The molecular structures of 2 and 3 confirm the formation of unusual tetranuclear compounds featuring a rare C,N,S-tridentate ligand derived from orthometalation of pendant side arm. The structural and chemical properties of the mononuclear palladium(II) complex 1 clearly suggest that 1 is a potential intermediate in the formation of the tetranuclear complex 2 by orthometalation reactions.