Studies of some carbon compounds of the transition metals. I. The crystal structure of dicyclopentadienyldiiron tetracarbonyl

Abstract

Dicyclopentadienyldi-iron tetracarbonyl, Fe2(CO)4(C5:Hs)2, is monoclinic with a = 7-07-4-0.03, b = 12.46~=0.05, c = 7.99+0.04 A, fl = 108 ° 25'±25', Z = 2 and space group t)21/c. The structure has been determined from two-dimensional data estimated visually from Weissenberg photographs taken with Co Ka radiation.

The Nature of Unsupported Uranium–Ruthenium Bonds: A Combined Experimental and Theoretical Study

“…À ion derivatives of 1-4 by salt-elimination strategies failed and gave the known dimeric complex [27] as the sole identifiable decomposition product. Reasoning that in the context of tripodal triamido uranium derivatives the relatively contracted valence orbitals of iron might disfavor uraniummetal bond formation, or that the…”

Formal chromium–chromium triple bonds and bent rings in the binuclear cycloheptatrienylchromium carbonyls (C7H7)2Cr2(CO)n (n=6,5,4,3,2,1,0): A density functional theory study

“…For the iron systems both cis [12] and trans [13][14][15] isomers of (g 5 -C 5 H 5 ) 2 Fe 2 (CO) 2 (l-CO) 2 formal Fe-Fe single bonds, as well as (g 5 -C 5 H 5 ) 2 Fe 2 (l-CO) 3 with a formal r þ 2 2 p Fe@Fe double bond of triplet spin multiplicity, are stable compounds [16][17][18][19], characterized structurally by X-ray diffraction. Furthermore, (g 5 -C 5 H 5 ) 2 Fe 2 (l-CO) 2 , with a formal Fe"Fe triple bond, is a probable intermediate in the pyrolysis of (g 5 -C 5 H 5 ) 2 Fe 2 (CO) 2 (l-CO) 2 to give the tetrahedral Fe 4 cluster [20] (g 5 -C 5 H 5 ) 4 Fe 4 (l 3 -CO) 4 .…”

Structure, Spectroscopy and Photochemistry of the [M(η5-C5H5)(CO)2]2 Complexes (M=Fe, Ru)

“…The X-ray and neutron diffraction studies [7][8][9] showed that I has a centrosymmetric structure in the solid phase with two bridging and two terminal carbonyl groups (trans-bridged form). Low-temperature crystallization made possible isolation of the cis form [10].…”

“…X-ray study of I together with sublimation experiments and low-temperature crystallization led to conclusion that the cis form is thermodynamically less stable [7,10]. 1 H-NMR spectra of I dissolved in C 6 D 6 -CS 2 showed, however, that the cis-bridged isomer is by 4.2 kJ/mol more stable than the trans one, with the energy barrier of transbridged-I´non-bridged-I interconversion of about 54.3 kJ/mol [18].…”

“…The frequencies calculated for all mentioned forms are real, confirming that these are true minima of the energy surface. The cis-non-bridged (cis-nb) form was also optimised; For non-bridged form c [9] d [10] e [12] f [7] this form, however, revealed one imaginary frequency for both I and II, which indicated its transition state character. The cis-nb form was examined because it was postulated earlier as one of the possible isomers of I and II.…”