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The burgeoning interest in 2D black phosphorus (bP) contributes to expand its applications in countless fields. In the present study, 2D bP is used as a support for homogeneously dispersed palladium nanoparticles directly grown on it by a wet chemical process. EELS-STEM analysis evidences a strong interaction between palladium and P atoms of bP nanosheets. A quantitative evaluation of this interaction comes from XAS measurements that find out a very short Pd-P distance of 2.26 {\AA} proving for the first time the existence of an unprecedented Pd-P coordination bond of covalent nature. Additionally, the average Pd-P coordination number of about 1.7 reveals that bP acts as a polydentate phosphine ligand towards the surface Pd atoms of the nanoparticles, thus preventing their agglomeration and inferring structural stability. These unique properties result in a superior performance in the catalytic hydrogenation of chloronitroarenes to chloroaniline, where a higher chemoselectivity in comparison to other heterogeneous catalyst based on palladium has been observed.