Interestingly, a non-covalent interaction between the Ni and H1 atoms was confirmed in the gas-phase-optimized structure of 3a (level: PBE0/def2-TZVPD//M06L/def2-SVPD for O, F, and Ni; def2-SVP for all other atoms) via a topological analysis of the electron density, which was calculated using the quantum-theory-of-atoms-in-molecule (AIM) method (Figure ). It should also be noted here that the geometric parameters of the solid state structure of 3a confirmed by SC-XRD analysis were closely reproduced in the theoretically calculated gasphase-optimized structure, e.g., the interatomic distances between the Ni and C5 atoms was 3.18 Å in the gas-phase and 3.240(4) Å in the crystalline state. In fact, the Ni•••H1 distance (2.13 Å) and the relatively high electron density ( = 0.026 e rBohr -3 ) as well as the positive value of the Laplacian of the electron density (∇ 2  = +0.061 e rBohr -5 ) at the bond-critical point (BCP) between these atoms, suggests the participation of an agostic Ni•••H interaction. Dissociation of the N-phosphinoyl moiety from the tetrahedral 2a to afford trigonal planar 3a also caused obvious changes in the wavenumbers of the stretching vibration of the CO ligands.