A composition comprising: ingredients comprising (A) a catalytically active reaction product of i) an iron carbonyl compound having general formula (i): Fe a (CO) b , where subscript a is an integer with a value ranging from 1 to 3, subscript b is an integer with a value ranging from 5 to 12; and ii) a silicon containing ligand that coordinates with Fe, where the silicon containing ligand has, per molecule, at least one atom of Si and at least one aliphatically unsaturated group; and (B) an aliphatically unsaturated compound having an average, per molecule, of one or more aliphatically unsaturated organic groups capable of undergoing hydrosilylation reaction; and optionally (C) an SiH functional compound having an average, per molecule, of one or more silicon bonded hydrogen atoms; which is distinct from ingredients (A) and (B); with the proviso that when ingredient (B) lacks a silicon bonded hydrogen atom, then the composition includes ingredient (C); wherein the silicon containing ligand that coordinates with Fe is unit formula: (R 1 R 2 2 Si-R 3 1/2 ) c (R 1 R 2 Si-R 3 2/2 ) d (R 2 Si-R 3 3/2 ) e (Si-R 3 4/2 ) f (R 2 3 Si-R 3 1/2 ) g (R 2 2 SiR 3 2/2 ) h ; where subscript c is 0 or more; subscript d is 0 or more; subscript e is 0 or more; subscript f is 0 or more; with the proviso that ( c + d + e + f ) > 0; subscript g is 0 or more; subscript h is 0 or more; each R 1 is independently an alkynyl group or an alkenyl group; each R 2 is independently an alkyl group, a cycloalkyl group, or an aryl group; and each R 3 is an oxygen atom or an amino group of formula =NH. (A) a catalytically active reaction product of i) an iron carbonyl compound having general formula (i): Fe a (CO) b , where subscript a is an integer with a value ranging from 1 to 3, subscript b is an integer with a value ranging from 5 to 12; and ii) a silicon containing ligand that coordinates with Fe, where the silicon containing ligand has, per molecule, at least one atom of Si and at least one aliphatically unsaturated group; and i) an iron carbonyl compound having general formula (i): Fe a (CO) b , where subscript a is an integer with a value ranging from 1 to 3, subscript b is an integer with a value ranging from 5 to 12; and ii) a silicon containing ligand that coordinates with Fe, where the silicon containing ligand has, per molecule, at least one atom of Si and at least one aliphatically unsaturated group; and (B) an aliphatically unsaturated compound having an average, per molecule, of one or more aliphatically unsaturated organic groups capable of undergoing hydrosilylation reaction; and with the proviso that when ingredient (B) lacks a silicon bonded hydrogen atom, then the composition includes ingredient (C); wherein the silicon containing ligand that coordinates with Fe is unit formula: (R 1 R 2 2 Si-R 3 1/2 ) c (R 1 R 2 Si-R 3 2/2 ) d (R 2 Si-R 3 3/2 ) e (Si-R 3 4/2 ) f (R 2 3 Si-R 3 1/2 ) g (R 2 2 SiR 3 2/2 ) h ; where subscript c is 0 or more; subscript d is 0 or more; subscript e is 0 or more; subscript f is 0 or more; with the proviso that ( c + d + e + f ) > 0; subscript g is 0 or more; subscript h is 0 or more; each R 1 is independently an alkynyl group or an alkenyl group; each R 2 is independently an alkyl group, a cycloalkyl group, or an aryl group; and each R 3 is an oxygen atom or an amino group of formula =NH. <EOS>