Four compounds are reported in this study. Co7Pr17 (10, cP96, P213, a = 13.4147(8) Å, Z = 4), either nonexistent or obscured in the Co/Pr phase diagram, has been obtained from a PrBr3 flux. With 29.2 mol % Co, it is close to Co2Pr5 (28.6 mol % Co, 2, C2Mn5 type of structure, mC28, C2/c, a= 16.5471(7) Å, b = 6.5107(3) Å, c = 7.1067(3) Å, β = 96.230(3)°, Z = 4), existent in the Co/Pr phase diagram, produced by arc-melting of a stoichiometric mixture of the metals. The addition of the reactive metal tin to Co/Pr mixtures yielded two new ternary polar intermetallics, CoSn3Pr1–x(x = 0.04, 11, RuSn3La type, cP40, Pm3̅n, a = 9.587(3) Å, Z = 8) and Co2–xSn7Pr3 (x = 0.78, 12, Ni2–xSn7–yCe3 type, oC24, Cmmm, a = 4.5043(4) Å, b= 27.227(2) Å, c = 4.5444(3) Å, Z = 2). Electronic structure calculations reveal extensive heteroatomic Co–Pr interactions in the binaries with little homoatomic contributions. With tin as the third component in the ternaries, heteroatomic Co–Sn and Sn–Pr bonding interactions are dominant, following the sequence of coordination spheres around Co.