RESIDUE   HP4      5
CONECT      P1     4 O1   O2   H4   H3  
CONECT      O1     1 P1  
CONECT      O2     1 P1  
CONECT      H4     1 P1  
CONECT      H3     1 P1  
END   
HET    HP4              5
HETSYN     HP4 Hypophosphite
HETNAM     HP4 phosphinate
FORMUL      HP4    H2 O2 P1 1-