The chief executive officer of the city shall be the chairman of the board of commissioners. He shall preside at all meetings of the board of commissioners, and vote on all questions, as other members of said board but shall have no veto power. The chairman shall sign all deeds, bonds, contracts and other instruments requiring the assent of the city, and shall cause the seal of said city to be affixed thereto by the city clerk. He shall see that all contracts and agreements with the city are faithfully kept, and fully performed, and to that end shall, when directed by the board of commissioners, cause legal proceedings to be commenced and prosecuted in the name of the city, against all persons or corporations failing to fulfill their agreements or contracts, either in whole or in part, and by like authority shall, on behalf of the city, prosecute and defend all actions or suits to which the city may be a part, or in which it may be interested.