R-Aminomethylphosphonic　acid　(R　=　diethyl　and　bis(2-ethylhexyl),　denoted　as　DEAPA　and　2EAPA,　respectively)　was　applied　as　ligands　to　synthesize　a　series　of　aminomethylphosphonic　molybdenum　precursors　(DEAPA-Mo,　2EAPA-Mo,　and　2EAPA-2Mo)　under　moderate　conditions.　Single-crystal　X-ray　diffraction,　X-ray　photoelectron　spectroscopy,　infrared　and　Raman　spectroscopy,　scanning　electron　microscopy,　and　high-resolution　transmission　electron　microscopy　techniques　were　employed　to　analyze　the　samples　before　and　after　sulfidation.　The　samples　were　applied　as　catalyst　precursors　for　slurry-phase　hydrocracking　of　Karamay　atmospheric　residue.　The　effects　of　organic　ligand　chain　length　and　Mo/P　molar　ratio　on　catalytic　performance　were　investigated.　The　results　indicate　that　2EAPA-Mo　exhibits　1.61　wt　%　coke　formation　and　85.5　wt　%　liquid　yields.　As　a　catalyst　precursor,　2EAPA-Mo　disperses　well　in　the　feed　oil　and　upon　in　situ　sulfidation　facilitates　the　formation　of　a　MoS2　phase　that　is　highly　active.　The　superior　performance　is　attributed　to　the　small　particle　size,　short　slab　length,　and　low　layer　stacking　number　of　MoS2　and　the　introduction　of　phosphorus.　©　2019　American　Chemical　Society.