Photolysis of Fe 2(CO) 4( μ− η 5, η 5-C 5H 4CH 2C 5H 4) in the presence of phosphines or phosphites results in the formation of simple carbonyl substitution products Fe 2(CO)( μ-CO) 2L( μ− η 5, η 5-C 5H 4CH 2C 5H 4) or Fe 2( μ-CO) 2L 2( μ- η 5, η 5-C 5H 4CH 2C 5H 4). Acetylenes react photochemically with the diiron compound to give vinylketone-bridged derivatives of the form Fe 2(CO)( μ−CO)[ μ− η 1: η 3-RCC(R)CO]( μ− η 5, η 5-C 5H 4CH 2C 5H 4), where R = CH 3O 2C and C 6H 5. Reaction of Ru 2(CO) 4( μ− η 5, η 5-C 5H 4CH 2C 5H 4) with triphenylphosphine under photochemical conditions resulted in loss of two carbon monoxide ligands nad PC insertion by ruthenium to yield Ru 2(CO)( σ-C 6H 5) μ-CO)[ μ-P(C 6H 5) 2]( μ− η 5, η 5-C 5H 4CH 2C 5H 4). Photolysis of Ru 2(CO) 4( μ− η 5, η 5-C 5H 4CH 2C 5H 4) with diphenylacetylene gave the previously reported Ru 2(CO) 2( μ-CO)[ μ− η 1: η 1-(C 6H 5) 2C 2]( μ− η 5, η 5-C 5H 4CH 2C 5 H 4) and an air oxidation product, Ru 2(CO)( μ-CO)[ μ− η 1: η 3-C 6H 5CC(C 6H 5)O]( μ− η 5, η 5-C 5H 4 CH 2C 5H 4). The diphenylacetylene derivative underwent acetylene exchange, but did not undergo exchange with triphenylphosphine. All compounds have been characterized by spectroscopic methods, elemental analysis and/or mass spectroscopy. The molecular structures of two ruthenium compounds were determined by X-ray crystallography. Ru 2(CO)( σ−C 6H 5)( μ-CO)[ μ-P( 6H 5) 2]( μ− η 5, η 5-C 5H 4CH 2 C 5H 4): monoclinic, P2 1 c , a = 13.902(3) A ̊ , b = 13.283(3) A ̊ , c = 14.426(4) A ̊ , β = 101.62(2)°, V = 2609(1) A ̊ 3, z = 4, R(F) = 3.98% . Ru 2(CO)( μ-CO)[ μ− η 1: η 3-C 6H 5C C(C 6H 5)O]( μ− η 5, η 5-C 5H 4CH 2 C 5H 4): orthorhombic, Pccn. a = 15.000(4) A ̊ , b = 15.662(4) A ̊ , c = 19.053(4) A ̊ , V = 4476(2) A ̊ 3 , z = 8, R( F) = 3.05%.