Linear Cu Pd , Cu Pd , and Ag Pd Metal Chains Supported by Rigid N,N'-Diphosphanyl N-Heterocyclic Carbene Ligands and Metallophilic Interactions.

Selective copper(I) to palladium(0) transmetallation of P-donors from the rigid N,N'-diphosphanyl-imidazol-2-ylidene C H [NP(tBu) ] (PC P) was observed when known Cu (μ -PC P,κP,κC ,κP) was reacted with [Pd(PPh ) ]. When 1.2 equivalents of [Pd(PPh ) ] was used, the product Cu Pd(μ -PC P,κP,κC ,κP) (2(OTf) ) was obtained, which features a Cu -Cu -Pd chain and appears to be the first linear heterotrinuclear complex with d -d interactions between Pd and Cu . When the Cu precursor was reacted with 3.0 equivalents of [Pd(PPh ) ], the complex CuPd (μ -PC P,κP,κC ,κP) (3(OTf) ) was obtained, which, on the basis of magnetic measurements, DFT calculations, and computed nuclear shieldings, was formulated as containing a Pd -Cu -Pd chain with an electron hole delocalized over the whole cation, including the metal chain. Similarly, selective transmetallation of the P-donors in Ag (μ -PC P,κP,κC ,κP) from silver to palladium (originating from [Pd(PPh ) ]) gave the linear chain Ag Pd(μ -PC P,κP,κC ,κP) (5(OTf) ), which on the basis of NMR spectroscopy comprises an Ag -Ag -Pd metal core. However, X-ray diffraction data collected on various samples of 5(OTf) were modeled with 50:50 metal disorder at the terminal positions, corresponding to a (Ag /Pd )-Ag -(Ag /Pd ) formulation. Upon standing in solution, 5(OTf) transformed to 6(OTf) , the regioisomer of 5(OTf) in which the Pd center has migrated to the central position of an Ag -Pd -Ag chain. Prolonged standing in CH Cl or by reaction with [PtCl (NCMe) ] converts complex 6(OTf) to the Ag /Pd complex Ag PdCl (μ -PC P,κP,κC ,κP) (7(OTf) ). The structural data of 2(OTf) , 3(OTf) , and 7(OTf) establish significant heterometallophilic interactions.