The molecular structures of 2a, 2c, 3a and 3c obtained from SC-XRD analysis are shown in Fig. . In these cases, the C1 and O1 atoms adopt a syn-orientation with respect to the N-P bonds (C1-N2-P-O1 torsion angle: 5.8(2)° in 2a; 8.5(1)° in 2c; 1.3(3)° in 3a; 6.5(2)° in 3c), indicating that the complexation proceeded via the rotation of the N-phosphinoyl group in free 1, wherein the C1 and O1 atoms adopt an anti-orientation (C-N-P-O: 175.9(1)° in 1a; 179.7(2)° in 1c) . The interatomic distances between Ni and O1 suggest the absence of a bonding interaction between these atoms in 3a During the preparation of the aforementioned complexes, we noticed the partial formation of 2c when a solution of 3c was concentrated in vacuo. In fact, stirring the crystalline powder of 3c at rt for 10 h in vacuo (0.3 mmHg) resulted in the formation of 2c in 50% yield (Fig. ). Prolonging the reaction time resulted in a slight improvement in the efficiency of CO desorption from 3c (20 h, 59%). Nevertheless, further desorption was not expected, as the solids adhered to the inner surface of the reaction vessel, limiting the surface area of 3c exposed to the reduced pressure even under stirring conditions (Fig. ). To promote the desorption, we explored the use of a dispersant. Dispersing 3c into tetradecane (C14H30) in the reaction flask (V = 50 mL) resulted in a significant improvement of the desorption, and 2c was obtained in >99% yield after 2 h at rt with concomitant loss of the crystallinity (Fig. ); however, ca. 2 wt% of C14H30 was removed under the applied reaction conditions. Desorption also proceeded quantitatively within 30 minutes when 3c was fully dissolved in 1,3-dimethoxybenzene (DMB), albeit that the partial removal of DMB (ca. 2 wt%) was again inevitable (Fig. ).