Experimental charge density study of dicobalt octacarbonyl and comparison with theory

Abstract

The second point demonstrated by the present experiments is that the determination of transitionmetal ordering is not difficult using only powder X-ray diffraction techniques. In the present calculation, the fixed atomic parameters and B factors of V3S 4 were used, because the number of reflections sufficient to measure the accurate intensity was limited to seven, and was thus much less than the number of parameters to be determined. Even so, the reliability of the NOA model can obviously be recognized in the differences in R values (Table 1), and in the match of F o and F c, especially for reflections 002, 101, 202 and 013, the structure factors of which are dominantly contributed to by the difference in the atomic scattering factors allocated to M(1) and M(2). This easy recognition of metal ordering suggests the possibility of investigating the behaviour of metal ordering 'at high temperatures'. This may elucidate the question of whether vacancy ordering and different metal ordering are coupled or are independent, because the in situ X-ray diffraction experiments at high temperature have so far concerned only vacancy ordering (e.g. Nakazawa, Saeki & Nakahira, 1975; Nakazawa, 1979; Wada, 1979a,b). The use of synchrotron-radiation X-rays may be particularly helpful in this context, because of tunability for a given wavelength and the intense flux. AbstractThe structure of dicobalt octacarbonyl, Co2(CO)8, has been redetermined at low temperature. Cell dimensions at 100 K are: a = 6.503 ( theoretical results predicting metal-metal bonding through the bridging ligand, d-Orbital populations derived from the refinement results agree well with theoretical values. The splitting of the 'eg-type' levels is evident when the refinement is performed in a coordinate system fitted to the local pseudo octahedral symmetry.

Electron‐Density Investigation of Metal–Metal Bonding in the Dinuclear “Borylene” Complex [{Cp(CO)2Mn}2(μ‐BtBu)]

“…Interestingly, the CO group charges differ from approximately zero (C5ÀO1 and C7ÀO3) to À0.24 and À0.27 e (C6À O2 and C8ÀO4, respectively). This asymmetry is mirrored in the signals for the Cp and CO ligands in the IR spectrum [18,21] and 3 [20] , at the M-M midpoint for 1 and 2 and at the BCP for 3. 28.0 and 54.7; CO stretch.…”

“…[18] According to the bond descriptors shown in Table 2 the Mn-Mn distance in 1 is shorter and the density at the midpoint accordingly higher than in [Mn 2 (CO) 10 ] (3), which is commonly believed to show a Mn À Mn bond. However, the ratio j V j /G, which classifies bonding by energy density considerations, is the smallest in the series [Mn 2 (CO) 10 ] [20] (3), [Co 2 (CO) 8 ] [18,21] (2), and [{Cp(CO) 2 Mn} 2 (m-BtBu)] (1).…”

Salts of the Cobalt(I) Complexes [Co(CO)5]+ and [Co(CO)2(NO)2]+ and the Lewis Acid–Base Adduct [Co2(CO)7COB(CF3)3]

“…The electron-withdrawing effect of BA C H T U N G T R E N N U N G (CF 3 ) 3 decreases the bond lengths in Co1-C5-Co2 by about 0.1 in comparison to those in Co1-C4-Co2 and leads to a diametrically unsymmetrical carbonyl bridge. The structural differences between [Co 2 (CO) 7 COÀBA C H T U N G T R E N N U N G (CF 3 ) 3 ] and [Co 2 (CO) 8 ] [37] are small and not very significant (Table 2) except for the asymmetric carbonyl bridges. The bond lengths of the terminal …”

Elektronendichteuntersuchung der Metall‐Metall‐Bindung im zweikernigen “Borylen”‐Komplex [{Cp(CO)2Mn}2(μ‐BtBu)]

“…[18] Entsprechend der Bindungsdeskriptoren in Tabelle 2 [18,21] und 3 [20] (am M-M-Mittelpunkt für 1 und 2 und am BCP für 3). Das Vorhandensein einer positiven Ladung am Boratom, wie in DFT-Rechnungen [3] vorhergesagt, wird durch die integrierte Ladung (+ 1.04 e) der QTAM-Analyse aus der experimentellen ED-Verteilung bestätigt.…”