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　MoS　2　phase　that　is　highly　active.　The　superior　performance　is　attributed　to　the　small　particle　size,　short　slab　length,　and　low　layer　stacking　number　of　MoS　2　and　the　introduction　of　phosphorus.　©　2019　American　Chemical　Society.