A method for preparing a product includes combining starting materials including A) a siloxane oligomer having silicon bonded hydrogen atoms, B) an alkoxysilane having at least one aliphatically unsaturated group capable of undergoing hydrosilylation reaction and C) an iridium complex catalyst. The method can be used to produce a compound of formula (I). This compound can be used in a hydrosilylation reaction with a vinyl-functional polyorganosiloxane. The resulting product includes an ethyltrimethoxysilyl functional polyorganosiloxane useful in condensation reaction curable sealant compositions.