roots (1 octet, 48 sextets, 119 quartets, 113 doublets) were then mixed by spin orbit coupling using the restricted active space self-interaction (RASSI) method. The SINGLE_ANISO module was used to decompose the resulting spin-orbit wave functions into the CF Hamiltonian formalism. Diamond was employed for molecular graphics. Gaussian 16 Rev C.01 84 was used to perform density functional theory calculations on 3-Yb and 4-Yb. Hydrogen positions were optimized while freezing all heavier atoms at the crystal structure positions using the PBE density functional with the Stuttgart RSC 1997 ECP for Yb and cc-pDVZ basis set for the ligand atoms. Dispersion interactions were treated using Grimme's D3 dispersion correction. Topological analysis of the total electron density was performed using Multiwfn 3.8, where the electron density at the bond critical point and delocalization indices were calculated to quantify the Yb-P interaction strength.