As shown in Figures and, 1 and 2 are two-coordinate Pd(I) complexes featuring linear C(carbene)-Pd-C(aryl) core (180.0 o for 1 and 179.2(1) o for 2). Irrespective their different para-substituents on aryl ligands, 1 and 2 have the bond distances and angles around the C(carbene)-Pd-C(aryl) cores very close to each other. The Pd-C(aryl) bond distances in 1 and 2 are 2.066(4) and 2.055(7) Å, respectively, which locate on the long end of the Pd-C(aryl) bonds of the reported palladium aryl complexes that are mostly known for Pd(II) complexes. The distance of Pd-C(carbene) bonds in 1 and 2 are 2.121(4) and 2.115(7) Å, respectively, which are longer than the Pd-C(carbene) bonds in [(IPr)2Pd] (2.013 Å) and [(IPr)2Pd][PF6] (2.055(7) Å in average). The long Pd-C(carbene) bonds can be attributed to the joint effect of the strong trans-influence of aryl ligand and severe steric repulsion between IPr and the bulky aryl ligands in the aryl complexes. Probably due to steric reason, the imidazole planes of the IPr ligands in 1 and 2 are not co-planar with the central arene planes of their aryl ligands, but form dihedral angles around 41 degree. The dihedral angles are close to those in the homoleptic Pd NHC complexes [(IPr)2Pd][PF6] (46 degree) and [(IPr)2Pd] (39 degree). Complexes 1 and 2 are air-sensitive. Under a dinitrogen atmosphere and at room temperature, their solids and THF solutions, however, can be stored for months without noticeable decomposition. In line with their mononuclear nature, complexes 1 and 2 are paramagnetic. The [Pd(PAd3)2][BAr , and [Pd(IPr)2][PF6] (Table ), implying the location of high spin-density on the Pd centers of 1 and 2. Accordingly, density functional theory (DFT) calculations on 2 at its S = 1/2 state indicated that 85% of the unpaired spin resides on the Pd center (Figure ). Molecular orbital analysis identified an electronic configuration of (4dxz+5p) 2 (4dyz) 2 (dx2-y2+5p) 2 (4dxy) 2 (4dz2+5s) for its Pd center (Figure ), arguing for its Pd(I) nature. It is interesting to note that, despite of the low-valent nature of the Pd(I) complex, the orbital interactions between the Pd center and its aryl and NHC ligands are essentially σ-type in-character (UNO 262). The bond dissociation energy of the Pd-C(aryl) bond in 2 is estimated to be 77 kcal mol -1 based on singlepoint-energy calculations (Figure ), which is much higher than that of the Pd-N(amido) bond in (BINAP)Pd(NHAr Trip ) (F in Figure , 51 kcal mol -1 ) and accounts for the stability of the Pd(I) aryl complex at ambient temperature.