DFT investigation of homotrinuclear and heterotrinuclear [Msub class='a-plus-plus'3sub(Phz)sub class='a-plus-plus'2sub],[MM′sub class='a-plus-plus'2sub(Phz)sub class='a-plus-plus'2sub],[Msub class='a-plus-plus'3sub(CO)sub class='a-plus-plus'2sub(Phz)sub class='a-plus-plus'2sub],[MM′sub class='a-plus-plus'2/