Pushmi‐pullyu with palladium: Although created by σ donation from SnCl2 to a PdII complex, the SnPd bonds in the compounds depicted exhibit formal σ donation in the opposite direction. Computational and spectroscopic data support stannylpalladium (PdISnIII) and palladastanna(IV)ocane (Pd0→SnIV) descriptions over stannylene coordination.

A series of new complexes of a general motif [R2E(μ-N,S)2TM-L] (E: metalloid group 14 element; TM: group 10 metal; R: Cl, Ph, pyS, OH, (N,N,O)-chelating ligands; N,S: 1-methylimidazole-2-thiolate (methimazolyl, mt(-)), pyridine-2-thiolate (pyS(-)); L: PPh3, PCy3, pyS) was synthesised and characterised by single-crystal X-ray diffraction, multi-nuclear NMR spectroscopy ((1)H, (13)C, (31)P, (119)Sn), (119)Sn Mössbauer spectroscopy and quantum chemical calculations. The E-TM bonding situation in these compounds can be described with various resonance structures which comprise E(ii)→TM(ii), E(iii)-TM(i) and E(iv)←TM(0) features. Thus, in these complexes the atoms of the group 14 based ligand sites reveal L-, X- and Z-type ligand characteristics. A systematic comparison between structural and spectroscopic parameters as well as the results from NLMO analyses of structurally related compounds provided information about the differences in the E-TM bonding situation upon alteration of the metal atoms or ligand patterns. Under investigation are the structurally related compounds [Cl2Sn(μ-pyS)2TM-PPh3] (1: TM = Pd; 2: TM = Ni; 3: TM = Pt), [Cl2Ge(μ-pyS)2Pd-PPh3] (4) and, for in silico analysis, [Cl2Si(μ-pyS)2Pd-PPh3] (5), which indicate a pronounced shift of the E-TM bond electron pair towards TM for TM = Pt. Further complexes serve as representatives of these compounds with different bridging ligands {[Cl2Sn(μ-mt)2Pd-PPh3] (8)}, different trans-E-TM-bound ligands {[Cl2Sn(μ-pyS)2Pd-PCy3] (9), [Cl2Sn(μ-pyS)2Pd]4 (10)} and with different substituents at Sn (including penta- and hexacoordinated tin compounds), i.e., [R2Sn(μ-pyS)2Pd-PPh3] with R = Ph (6) and pyS (7), [(O,N,N)Sn(μ-pyS)2Pd-PPh3] (11) and (12) having two different (O,N,N) tridentate ligands, and [(μ-OH)ClSn(μ-pyS)2Pd-PPh3]2 (13). The latter series indicates a shift of the E-TM (= Sn-Pd) bond electron pair towards Pd upon transition from penta- to hexacoordinated tin compounds.

Treatment of the bis(chelate) complex trans-[Pd(κ(2)-2-C6F4PPh2)2] (7) with PMe3 gave trans-[Pd(κC-2-C6F4PPh2)2(PMe3)2] (13) as a mixture of syn- and anti-isomers. Reaction of 13 with CuCl, AgCl, or [AuCl(tht)] (tht = tetrahydrothiophene) gave the heterobinuclear complexes [(Me3P)2Pd(μ-2-C6F4PPh2)2MCl] [M = Cu (14), Ag (15), Au (16)], from which the corresponding salts [(Me3P)2Pd(μ-2-C6F4PPh2)2M]PF6 [M = Cu (17), Ag (18), Au (19)] could be prepared by abstraction of the chloro ligand with TlPF6; 18, as well as its triflato (20) and trifluoroacetato (21) analogues, were also prepared directly from 13 and the appropriate silver salt. Reaction of 13 with [AuCl(PMe3)] gave the zwitterionic complex [(Me3P)PdCl(μ-2-C6F4PPh2)2Au] (24) in which the 2-C6F4PPh2 ligands are in a head-to-head arrangement. In contrast, the analogous reaction with [AuCl(PPh3)] gave [(Ph3P)PdCl(μ-2-C6F4PPh2)2Au] (25) with a head-to-tail ligand arrangement. Single crystal X-ray diffraction studies of complexes 14-21 show short metal-metal separations [2.7707(11)-2.9423(3) Å] suggestive of attractive noncovalent (dispersion) interactions, a conclusion that is supported by theoretical calculations of the electron localization function and the noncovalent interactions descriptor.