Synthesis and reaction chemistry of [(μ-SeR)(μ-σ,π-Ctriple bond; length of mdashCPh)]Fe2(CO)6

RSeCtriple bond; length of mdashCPh (1a, R = Et; 1b, R = n-Bu; 1c, R = Ph; 1d, R = 2,4,6-Me3C6H2) reacts with equimolar amounts of Fe2(CO)9 (2) to give [(μ-SeR)(μ-σ,π-Ctriple bond; length of mdashCPh)]Fe2(CO)6 (3a, R = Et; 3b, R = n-Bu; 3c, R = Ph; 3d, R = 2,4,6-Me3C6H2).Complexes 3a–3d exist as two isomers, depending on the axial or equatorial position of R at selenium.Addition of P(OiC3H7)3 (4) to 3d affords {(μ-Se-2,4,6-Me3C6H2)[μ-η1-Cdouble bond; length as m-dashCPh(P(OiC3H7)3)]}Fe2(CO)6 (5) along with {(μ-Se-2,4,6-Me3C6H2)[μ-η1:η1-PhCdouble bond; length as m-dashC(P(OiC3H7)3)]}Fe2(CO)6 (6). The solid-state structures of 3d, 5 and 6 were determined by single X-ray structure analysis.In mononuclear 3d the Fe(CO)3 fragments are bridged by a μ-Se-2,4,6-Me3C6H2 and a μ-σ,π-Ctriple bond; length of mdashCPh unit, resulting in an over-all butterfly arrangement.Due to steric reasons, the mesityl group is pointing away from the PhCtriple bond; length of mdashC entity and hence, is located in an equatorial position.Compounds 5 and 6, which co-crystallise in the ratio of 7:93, feature aμ-bridging 2,4,6-Me3C6H2Se unit and either a vinylidenic Cdouble bond; length as m-dashCPh(P(OiC3H7)3) (complex 5) or a olefinic PhCdouble bond; length as m-dashC(P(OiC3H7)3) (complex 6) building block of which the latter entity is part of a diiron cyclobutene ring.