Though all Persons of the Godhead are shown as working together for our salvation, Paul focuses on the unique work of each Person in God. The Father was praised for choosing us and decreeing that we become his children. All of this was done ‘in Christ’ (v4-5), but it is the Father whose work is emphasized. Now Paul (still in prison as he writes these things!) moves his focus from eternity past to historical time, when at the cross Jesus accomplished what the Father planned.
We get a glimpse of this relationship between the Father’s saving work in election and the Son’s saving work at the cross in John’s gospel, as Jesus speaks of the Father giving him some people:
All that the Father gives me will come to me, and whoever comes to me I will never cast out.  For I have come down from heaven, not to do my own will but the will of him who sent me.  And this is the will of him who sent me, that I should lose nothing of all that he has given me, but raise it up on the last day.  For this is the will of my Father, that everyone who looks on the Son and believes in him should have eternal life, and I will raise him up on the last day.” John 6:37-40, ESVJesus says that the Father’s will is that he should lose (fail to save) NONE of those the Father gave him, but raise them up on the last day (save them completely). We also see man’s responsibility in verse 40; the ones God gave Jesus must come to him and believe (and they “will come to me” – v37).
Jesus mentions this group of people God gave him to save again in his high priestly prayer, just before his death:
“Father, the hour has come; glorify your Son that the Son may glorify you,  since you have given him authority over all flesh, to give eternal life to all whom you have given him. … And now, Father, glorify me in your own presence with the glory that I had with you before the world existed.  “I have manifested your name to the people whom you gave me out of the world. Yours they were, and you gave them to me, and they have kept your word.  Now they know that everything that you have given me is from you.  For I have given them the words that you gave me, and they have received them and have come to know in truth that I came from you; and they have believed that you sent me.  I am praying for them. I am not praying for the world but for those whom you have given me, for they are yours. John 17:1b-2, 5-9, ESVWhat a conversation! Jesus is thinking back to the glory he had with the Father before he was born as a Man! And he speaks with the Father about the ones God gave the Son to redeem at the cross.
This is what we see in Ephesians 1. The Father set his love on his people, and gave them to Christ to redeem! Praise God, the Persons of the Godhead work together for our salvation. God is not at conflict with himself. He is One; he is at peace. The Persons of God are in unity. The Father elects us, the Son redeems us, and the Spirit seals us. How glorious this is!