Binuclear Cobalt Thiocarbonyl Carbonyl Derivatives: Comparison with Homoleptic Binuclear Cobalt Carbonyls

Abstract

Density functional theory studies on Co(2)(CS)(2)(CO)(8) show the structure with two bridging CS groups to be the global minimum. Furthermore, swapping a terminal CO group with a bridging CS group to give a terminal CS group and a bridging CO group increases the energy of the structure by 7 +/- 2 kcal/mol. Thus, unbridged Co(2)(CS)(2)(CO)(8) structures lie at least 11 kcal/mol above the doubly bridged global minimum Co(2)(mu-CS)(2)(CO)(6), unlike Co(2)(CO)(8) where the doubly bridged and unbridged structures are significantly closer in energy. The lowest energy unsaturated Co(2)(CS)(2)(CO)(n) (n = 5, 4, 3) structures are predicted to contain four-electron donor bridging eta(2)-mu-CS groups, unlike the corresponding homoleptic carbonyls Co(2)(CO)(n+2), which contain only two-electron donor carbonyl groups. For example, the three lowest energy Co(2)(CS)(2)(CO)(5) structures contain a single eta(2)-mu-CS group accompanied by a Co-Co distance of approximately 2.7 A, consistent with the single bond required to give both cobalt atoms the favored 18-electron configuration.

Structural changes upon replacing carbonyl groups with thiocarbonyl groups in first row transition metal derivatives: new insights

“…13). 58 This observation alone is an indication that bridging thiocarbonyl groups are more favorable than bridging carbonyl groups, since for the carbonyl analogues doubly bridged Co 2 (m-CO) 2 (CO) 6 The 18-electron rule [38][39][40][41][42] suggests that the unsaturated binuclear cobalt carbonyls Co 2 (CO) 7 and Co 2 (CO) 6 as well as their thiocarbonyl analogues should have formal CoQCo double bonds and formal CoRCo triple bonds, respectively. Our previous theoretical studies 53 predict a Co 2 (CO) 7 structure with a Co-Co single bond between a Co(CO) 4 group with trigonal bipyramidal cobalt coordination and an 18-electron configuration and a Co(CO) 3 group with square planar cobalt coordination and the 16-electron configuration typical for late transition metal square planar derivatives (Fig.…”

“…59 Three low energy structures are found for the corresponding cobalt thiocarbonyl derivative Co 2 (CS) 2 (CO) 5 lying within B1 kcal mol À1 in energy. 58 All three structures have a fourelectron donor bridging Z 2 -m-CS group and differ only in the location of the terminal CS group relative to the central Co 2 (Z 2 -m-CS) unit. The comparison between the lowest energy structures of Co 2 (CO) 7 and Co 2 (CS) 2 (CO) 5 is another example of the preference of binuclear metal thiocarbonyl derivatives to have four-electron donor bridging Z 2 -m-CS groups relative to analogous carbonyl derivatives.…”

Major Difference between the Isoelectronic Fluoroborylene and Carbonyl Ligands: Triply Bridging Fluoroborylene Ligands in Fe3(BF)3(CO)9 Isoelectronic with Fe3(CO)12

“…The greater tendency of a CS group to bridge a pair of metal atoms than a CO group is also predicted by DFT studies of binuclear M 2 (CS) 2 (CO) n derivatives of other first-row transition metals such as manganese, 19 iron, 20 and cobalt. 21 For Fe 3 (CS) 3 (CO) 9 the lowest energy unbridged structure analogous to the lowest energy M 3 (CO) 12 structures (M = Ru, Os) is predicted to lie ∼20 kcal/mol above the doubly CS-bridged global minimum.…”

Binuclear Cyclopentadienylmanganese Carbonyl Thiocarbonyls: Four‐Electron Donor Bridging Thiocarbonyl Groups of Two Types and a Bridging Acetylenedithiolate Ligand

“…To date, these theoretical studies have been restricted to the first row transition metals and to compounds containing only carbonyl and thiocarbonyl groups. In this connection, our theoretical studies on [Fe 2 (CS) 2 (CO) n ], [19] [Co 2 (CS) 2 (CO) n-1 ], [20] and [Cr 2 (CS) 2 -(CO) n+2 ] (n = 7, 6, 5, 4) [21] indicate not only that CS is a preferred bridging ligand to CO but also that four-electron donor CS groups are frequently found in the low energy structures of binuclear derivatives in preference to higher order metal-metal multiple bonds. Moreover, for [Cr 2 -(CS) 2 2 (CO) n ] (n = 3, 2, 1, 0) were included in this study because of the prospects of synthesizing or at least generating them from the stable and readily obtained [17,18] [(η 5 -C 5 H 5 )Mn(CS)(CO) 2 ].…”