ThSeCH 2 CH 2 OPh (Th=2-thienyl, C 4 H 3 S-; Ph=phenyl) (2) has been prepared by the reaction of BrCH 2 CH 2 OPh (1) and ThSeLi. The compound was characterized by 1 3 C{ 1 H}- and 7 7 Se-NMR spectroscopy and X-ray crystallography. 2 is monoclinic, space group P2 1 /c, a=10.865(2), b=5.152(1), c=41.996(8) A, β=92.20(3) o . All bond lengths and angles are quite normal as exemplified by the respective Se C(alkyl) and Se C(aryl) bonds of 1.957(6)-1.966(6) and 1.901(7)-1.905(7) A. The lattice is composed of discrete molecules that are joined together by weak hydrogen bonds into a three-dimensional network. Upon treating ThSeCH 2 CH 2 OPh with [PdCl 2 (NCPh) 2 ] and [NiCl 2 (PPh 3 ) 2 ] in benzene, a dinuclear palladium complex [Pd 2 Cl 2 (μ-Cl)(μ-SeTh)(PPh 3 ) 2 ] (3) and a mononuclear complex [PdCl 2 (PPh 3 ) 2 ] (4) were formed together with a precipitation of NiCl 2 . The X-ray quality crystals were recrystallized in CH 2 Cl 2 . 3.2.5CH 2 Cl 2 is monoclinic, space group C2/c, a=32.907(7), b=14.545(3), c=22.433(5) A, β=114.37(3) o and contains a novel asymmetrical arrangement of one bridging chlorido and thienylselenolato ligand. Both palladium atoms show an square-planar coordination. The terminal Pd Cl bond lengths are 2.388(1) and 2.346(1) A with slightly longer distances of 2.418(1) and 2.450(1) A involving the bridging chlorido ligand. The Pd Se distances are 2.4092(9) and 2.4376(7) A.