Abstract
The heterometallic chromium-manganese carbonyl nitrosyls CrMn(NO)(CO)n (n = 9, 8) have been investigated by density functional theory. The lowest energy CrMn(NO)(CO)9 structures have unbridged staggered conformations with a ~2.99 Å Cr–Mn single bond similar to the experimental and lowest energy structures of the isoelectronic Mn2(CO)10 and Cr2(NO)2(CO)8. A significantly higher energy CrMn(NO)(CO)9 isomer has a nearly symmetrical bridging nitrosyl group and a very weakly semibridging carbonyl group. The two lowest energy structures of the unsaturated CrMn(NO)(CO)8 have a five-electron donor bridging η2-µ-NO nitrosyl group or a four-electron donor bridging η2-µ-CO group, as well as a Cr–Mn single bond of length ~2.94 Å. The next higher energy CrMn(NO)(CO)8 structure has exclusively terminal CO and NO ligands and a shorter Cr–Mn single bond of ~2.85 Å, suggesting an 18-electron configuration for the manganese atom and a 16-electron configuration for the chromium atom indicated by a vacant coordination site nearly perpendicular to the Cr–Mn bond.
Highlights
The isoelectronic bimetallic molecules Mn2 (CO)10 and Cr2 (NO)2 (CO)8 have been known for some time [1]
CrMn(NO)(CO)8 structure has exclusively terminal CO and NO ligands and a shorter Cr–Mn single bond of ~2.85 Å, suggesting an 18-electron configuration for the manganese atom and a 16-electron configuration for the chromium atom indicated by a vacant coordination site nearly perpendicular to the Cr–Mn bond
Mn2 (CO)10 can be synthesized by the reductive carbonylation of manganese(II)
Summary
The isoelectronic bimetallic molecules Mn2 (CO) and Cr2 (NO) (CO) have been known for some time [1]. Derivatives are known as stable of the metal atoms. Mn Mn formal triple bond distance for Mn2(CO) (Figure 2) [9,10,11,12] Such results are consistent with the theoretical studies on the. 2 n+2 derivatives an unbridgedMn structure with a7 Cr=Cr distance suggesting the energy formal Cr double theunbridged formalthe double bond required to preserve the 18-electron for both chromium atoms. Cr Cr distances suggesting formal triple bonds, again preserving the the chromium atoms. In view of the different types of low-energy structures predicted for isoelectronic unsaturated derivatives, investigation of the intermediate isoelectronic heterobinuclear. 9 derivatives has not yet been reported, n−1 heterobinuclear metal carbonyl anion. 3 ) is has not yet been reported, the heterobinuclear metal carbonyl anion known [15,16,17,18,19]. CrMn(NO)(CO) systems, isoelectronic with the stable Mn2(CO) and Mn2(CO), respectively
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