Studies of some carbon compounds of the transition metals. II. The structure of MeC: CMe.H2F2(CO)8

Abstract

The structure of the complex MeCi CMe.H2Fe~(CO)8, isolated from the reaction of but-2-yne with alkaline solutions of iron hydrocarbonyl, has been determined by three-dimensional Fourier methods and refined by least-squares methods. The compound crystallizes in the monoclinic system, space group P2t/c, with four molecules in a unit cell of dimensions a=12.26, b=7.47, c=15-7 A, fl=97.5 °.The structure exhibits a number of novel features which include (i) a four-carbon chain chelated on to one of the iron atoms with which it forms single metal-carbon bonds, (ii) :~-bonds between this four-carbon chain and the second iron atom, (iii) the probability that one of the six Fe-C~O linkages is non-linear (168°). The metal-carbon separations can be classified into three groups of average length 2-13, 1-95 and 1-78 A. The latter is significantly shorter than the single-bond distance (1.95 A) and provides confirmation for the shortening of the metal-CO distance as a result of partial double-bond character. Carbon-oxygen separations correspond either to normal triple-bond carbonyl links (1.14 A) or to phenolic C-OH lengths (1-37 A) in agreement with chemical and spectroscopic evidence. The metal atoms are bonded together with a normal covalent Fe-Fe separation of 2.49 A.

Synthesis, structure and electrochemistry of CO incorporated diruthenium metallacyclic compounds [Ru2(CO)6{μ-η1:η1:η2:η2-1,4-Fc2C5H2O}] and [Ru2(CO)6{μ-η1:η1:η2:η2-1,5-Fc2C5H2O}]

“…Various ferroles have been obtained by reacting acetylenes and iron carbonyl in water [21] or in alkaline solutions [22] and by refluxing a solution of Fe 3 (CO) 12 and alkynes in hydrocarbon solvents [23]. Decomplexation reactions of nickel maleoyl complexes [Ni(bpy){C 2 R 2 (CO) 2 }] [24] and of some acyloxy ferrole complexes [25] have led to isolation of cyclobutendiones, C 2 R 2 (CO) 2 .…”

Olefin and Acetylene Complexes of Transition Metals.

“…The structure of the but-2-yne complex, as determined by Hock and Mills (136,137), is shown diagrammati-forms a five-membered ring with two CO groups and a Fe(CO)3 group, and this diene system is coordinated to another Fe(CO)3 group. By donation of an unshared pair of electrons from the latter iron atom to the former, each achieves an inert gas configuration.…”

A data-intensive re-evaluation of semibridging carbonyl ligands

“…The first structurally characterized SBCO ligand was reported in 1961 by Hock and Mills, 29 who found that one of the putatively terminal CO ligands in diiron complex 1 (Fig. 2a) was anomalously "bent" (∠(Fe-C-O) = 168°) despite the Fe II ⋯CO distance (2.484 Å) being "clearly too long for any simple interaction".…”