Genuine Examples of Tetrahedral Tetradentate Sulfide Ligand Bridging Four Pd Atoms: Controlled Formation of [(μ₄-S){(μ₂-X)Pd₂(C^∧N)₂}₂] (X = OH or Cl; HC^∧N = <i>p</i>-C₂H₅OC₆H₄CHNC₆H₄-<i>p</i>-C₂H₅) Complexes

A smooth reaction of [(μ3-S)(μ3-OH)Pd3(C∧N)3] (2) with [(μ2-X)2Pd2(C∧N)2] (2:1; HC∧N = p-C2H5OC6H4CHNC6H4-p-C2H5, X = OH, Cl) provides [(μ4-S){(μ2-OH)Pd2(C∧N)2}2] (3) and [(μ4-S)(μ2-Cl)(μ2-OH)Pd4(C∧N)4] (4). Treatment of 3 with HCl (molar ratio 1:2) leads to the corresponding tetranuclear complex [(μ4-S)(μ2-Cl)2Pd4(C∧N)4] (5). The three complexes contain a (μ4-S)Pd4 core. A density functional theory study of the bonds in 3 supports that the bonding of the S atom can be described in terms of four two-center two-electron S−Pd bonds, in contrast to most other (μ4-S)M4 systems in the literature, where the presence of M−M bonds prevents a bond-localized description of the molecule. The X-ray structures of 2, 3, and 5 are reported.将[(三桥联硫)(三桥联羟基)三钯三(C∧N配体)](2)与[(双桥联X)二钯二(C∧N配体)]以2:1的摩尔比（其中HC∧N为对乙氧基苯亚甲基对乙氧基苯胺：p-C2H5OC6H4CH=NC6H4-p-C2H5，X为羟基、氯原子）进行温和反应，得到[(四桥联硫){(双桥联羟基)二钯二(C∧N配体)}2](3)与[(四桥联硫)(双桥联氯)(双桥联羟基)四钯四(C∧N配体)](4)。以1:2的摩尔比用氯化氢处理3，可得到相应的四核配合物[(四桥联硫)(双桥联氯)₂四钯四(C∧N配体)](5)。上述三种配合物均含有(四桥联硫)Pd₄四核核心。对配合物3中的成键进行密度泛函理论（Density Functional Theory, DFT）研究表明，硫原子的成键可通过四个两中心两电子S-Pd键来描述；这与文献中多数(μ4-S)M4体系不同，这类体系因存在M-M金属键而无法对分子进行定域成键描述。本文报道了配合物2、3和5的X射线单晶衍射结构。