A process to prepare an olefin polymerization procatalyst comprising a Ti 3+ complex, said process comprising: a) forming a delta form MgCl 2 species by combining i) R 2 Mg in a solvent selected from C 5-12 alkanes, and ii) reactive organic chloride or HCl; wherein each R is independently selected from C 2-8 alkyl radicals, and wherein the mole ratio of added Cl and Mg is from about 2.0 to about 3.0; b) adding to said delta form MgCl 2 species prepared in step a) R 1 x AlX 3-x and a tetravalent titanium compound in any order or at the same time, wherein the Al/Ti molar ratio is from about 3 to about 10; or c) adding to said delta form MgCl 2 species prepared in step a), an aluminum alkyl halide of the formula R 1 x AlX 3-x first, a tetravalent titanium compound second, followed by an alkyl aluminum alkoxide of the formula R 4 y AlOR 5 3-y , wherein the Al/Ti molar ratio when measuring Al supplied from R 1 x AlX 3-x only is from about 0.7 to about 2 and the Al/Ti molar ratio when measuring Al supplied from R 4 y AlOR 5 3-y is from about 1 to about 2; and further wherein the Mg/Ti molar ratio is from about 5 to about 10; x is 1 or 2; y is 1 or 2; each R 1 is independently selected from C 1-8 alkyl radicals; the tetravalent titanium compound is selected from TiR 2 X 3 , Ti(OR 3 )X 3 , TiX 4 , and mixtures thereof; each X is independently selected from the halogen radicals; and each R 2 is independently selected from C 1-8 alkyl radicals and benzyl. each R 3 , R 4 and R 5 are independently selected from C 1-8 alkyl radicals. a) forming a delta form MgCl 2 species by combining i) R 2 Mg in a solvent selected from C 5-12 alkanes, and ii) reactive organic chloride or HCl; wherein each R is independently selected from C 2-8 alkyl radicals, and wherein the mole ratio of added Cl and Mg is from about 2.0 to about 3.0; i) R 2 Mg in a solvent selected from C 5-12 alkanes, and ii) reactive organic chloride or HCl; wherein each R is independently selected from C 2-8 alkyl radicals, and wherein the mole ratio of added Cl and Mg is from about 2.0 to about 3.0; b) adding to said delta form MgCl 2 species prepared in step a) R 1 x AlX 3-x and a tetravalent titanium compound in any order or at the same time, wherein the Al/Ti molar ratio is from about 3 to about 10; or c) adding to said delta form MgCl 2 species prepared in step a), an aluminum alkyl halide of the formula R 1 x AlX 3-x first, a tetravalent titanium compound second, followed by an alkyl aluminum alkoxide of the formula R 4 y AlOR 5 3-y , wherein the Al/Ti molar ratio when measuring Al supplied from R 1 x AlX 3-x only is from about 0.7 to about 2 and the Al/Ti molar ratio when measuring Al supplied from R 4 y AlOR 5 3-y is from about 1 to about 2; the Mg/Ti molar ratio is from about 5 to about 10; x is 1 or 2; y is 1 or 2; each R 1 is independently selected from C 1-8 alkyl radicals; the tetravalent titanium compound is selected from TiR 2 X 3 , Ti(OR 3 )X 3 , TiX 4 , and mixtures thereof; each X is independently selected from the halogen radicals; and each R 2 is independently selected from C 1-8 alkyl radicals and benzyl. each R 3 , R 4 and R 5 are independently selected from C 1-8 alkyl radicals. <EOS>