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ABSTRACT: B3LYP/DZP(Lanl2dz) study of Fe(CO)n(CE)2 (E = S, Se, Te; n = 4, 3) suggests that the Fe(η(2)-E-C) structures are energetically preferred for singlet Fe(CO)4(C2E2) and triplet Fe(CO)3(C2E2). The tendency for coupling reactions of CE ligands to form C2E2 ligands by carbon-carbon bond formation increases in the sequence S < Se < Te.
Chemical Communications 04/2013; · 6.17 Impact Factor
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ABSTRACT: The chemistry of metal thiocarbonyls is much more limited than that of metal carbonyls because of the instability of CS as a synthetic reagent. In view of the many gaps remaining in experimentally realized metal thiocarbonyl chemistry, theoretical studies using density functional methods have been used to explore the possible future scope of metal thiocarbonyl chemistry. This paper reviews such theoretical studies on binuclear metal carbonyl derivatives of the types M(2)(CS)(2)(CO)(n) and Cp(2)M(2)(CS)(2)(CO)(n) (Cp = η(5)-C(5)H(5); M = V through Ni) as well as the trinuclear and tetranuclear iron carbonyls Fe(3)(CS)(3)(CO)(n) (n = 9, 8, 7, 6) and Fe(4)(CS)(4)(CO)(n) (n = 12, 11, 10, 9). The substitution of one or two CO groups with CS groups to give less symmetrical structures leads to many more isomers. Structures in which a four-electron donor thiocarbonyl group uses its sulfur atom to bridge a metal-metal bond as a η(2)-μ-CS ligand are more favorable in binuclear metal thiocarbonyl chemistry than corresponding structures in metal carbonyl chemistry owing to the basicity of the sulfur atom. Six-electron donor thiocarbonyl groups bridging clusters of three or four iron atoms are also found in low-energy structures including a particularly favorable Fe(4)(CS)(4)(CO)(10) structure suggested as a possible target for future synthetic chemistry. In thiocarbonyl substitution products of simple binuclear metal carbonyls such as Fe(2)(CO)(9) [= Fe(2)(CO)(6)(μ-CO)(3)], Co(2)(CO)(8) [= Co(2)(CO)(6)(μ-CO)(2)], and Cp(2)Fe(2)(CO)(4) [= Cp(2)Fe(2)(CO)(2)(μ-CO)(2)], structures with bridging CS groups are invariably lower energy structures than isomeric structures with bridging CO groups.
Physical Chemistry Chemical Physics 08/2012; 14(43):14743-55. · 3.57 Impact Factor
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Berichte der deutschen chemischen Gesellschaft 07/2010; 2010(26):4175 - 4186. · 2.94 Impact Factor
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ABSTRACT: Isocarbonyl groups bonded to chromium through their oxygen atoms as well as the usual carbonyl groups bonded to carbon atoms have been considered as possible structural features for Cr(CO)(6), Cr(2)(CO)(n) (n = 11, 10, 9), and Cr(3)(CO)(16). In this connection, Cr(CO)(6) structures with one of the six CO groups bonded to the chromium either solely through its oxygen atom or side-on through both its carbon and oxygen atoms are predicted by density functional theory to lie >30 kcal/mol above the well-known Cr(CO)(6) structure, in which all six carbonyl groups are bonded to the chromium atom in the normal manner through their carbon atoms. The binuclear Cr(2)(CO)(11) structure of the type (OC)(5)Cr-C-O-Cr(CO)(5) with a linear bridging carbonyl group bonded to one chromium atom through its carbon atom and to the other chromium atom through its oxygen atom is of lower energy than previously studied Cr(2)(CO)(11) structures and indeed is viable with respect to dissociation into Cr(CO)(5) + Cr(CO)(6). Similar binuclear structures are found for Cr(2)(CO)(10) and Cr(2)(CO)(9) with linear bridging carbonyl groups. However, the Cr(2)(CO)(9) structure with a linear bridging carbonyl group, no Cr-Cr bond, and 16-electron chromium configurations is found to lie higher by 22 +/- 5 kcal/mol than the previously found Cr(2)(CO)(6)(mu-CO)(3) structure with three bridging carbonyl groups, a formal Cr[triple bond]Cr triple bond, and the favorable 18-electron chromium configuration. For the trinuclear Cr(3)(CO)(16), nearly degenerate trans- and cis-Cr(CO)(4)[OCCr(CO)(5)](2) structures are found that are viable with respect to dissociation into 2Cr(CO)(5) + Cr(CO)(6).
The Journal of Physical Chemistry A 03/2010; 114(13):4672-9. · 2.95 Impact Factor
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ABSTRACT: The structures of the mononuclear derivatives Ni(CS)(CO)(n) (n = 3, 2, 1, 0) and the binuclear derivatives Ni(2)(CS)(2)(CO)(n) (n = 5, 4, 3, 2) have been optimized by density functional theory for comparison with the corresponding structures of Ni(CO)(n+1) and Ni(2)(CO)(n+2), respectively. In the lowest energy structures for Ni(CS)(CO)(n) (n = 3, 2, 1), the nickel atom has approximate tetrahedral (n = 3), trigonal planar (n = 2), or bent coordination (n = 1) corresponding to 18-, 16-, and 14-electron metal configurations, respectively. The six lowest energy Ni(2)(CS)(2)(CO)(5) structures all have a single CE (E = S, O) bridge and a formal Ni-Ni single bond of length approximately 2.6 to approximately 2.7 A analogous to the lowest energy Ni(2)(CO)(7) structure. The Ni(2)(CS)(2)(CO)(5) structures with a bridging CS group are of lower energies than similar structures with a bridging CO group. Higher energy Ni(2)(CS)(2)(CO)(5) structures with a linear bridging CE group (E = O, S) and no Ni...Ni bond are also found with tetrahedral coordination for both nickel atoms. The lowest energy Ni(2)(CS)(2)(CO)(4) structures are doubly bridged structures with only two-electron donor CO and CS groups and Ni=Ni distances of approximately 2.5 A suggesting the formal double bond needed to give both nickel atoms the favored 18-electron configuration. For Ni(2)(CS)(2)(CO)(3) the structures with one four-electron donor bridging eta(2)-mu-CS group and a formal Ni=Ni double bond of approximately 2.4 to approximately 2.5 A are energetically preferred over triply bridged structures with a shorter Ni[triple bond]Ni distance of approximately 2.2 A, corresponding to a formal triple bond and similar to the lowest energy Ni(2)(CO)(5) structure. The lowest energy Ni(2)(CS)(2)(CO)(2) structures are generally derived from Ni(2)(CS)(2)(CO)(3) structures by removal of a carbonyl group. No formal quadruple bonds are found in any of the Ni(2)(CS)(2)(CO)(2) structures, as indicated by the absence of ultrashort Ni(-4)Ni distances.
The Journal of Physical Chemistry A 02/2010; 114(6):2365-75. · 2.95 Impact Factor
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ABSTRACT: The chromium carbonyl thiocarbonyls Cr(CS)(CO)(n) (n = 5, 4, 3) and Cr(2)(CS)(2)(CO)(n) (n = 9, 8, 7, 6) were studied by density functional theory (DFT). The expected octahedral structure was found for the known Cr(CS)(CO)(5). The structures for the unsaturated derivatives Cr(CS)(CO)(n) (n = 4, 3) are derived from the octahedral Cr(CS)(CO)(5) by removal of one or two carbonyl groups, respectively. The lowest energy structures for the binuclear derivatives Cr(2)(CS)(2)(CO)(n) (n = 9, 8, 7, 6) all contain four-electron donor bridging eta(2)-mu-CE (E = O, S) groups. For the formally saturated Cr(2)(CS)(2)(CO)(9), no chromium-chromium bond is then required to give the chromium atoms the favored 18-electron configuration. This leads to a uniquely linear Cr-C-O-->Cr arrangement or bent Cr-C-S-->Cr arrangement (C-S-->Cr angle of approximately 110 degrees ) with a long clearly nonbonding Cr...Cr distance. A similar structural feature is found in the known stable arene-chromium carbonyl thiocarbonyl (eta(6)-MeC(6)H(5))Cr(CO)(2)[CS-->Cr(CO)(5)]. The lowest energy structures for the formally unsaturated Cr(2)(CS)(2)(CO)(n) (n = 8, 7, 6) are predicted to have one (n = 8) or two (n = 7, 6) four-electron donor eta(2)-mu-CS groups with a Cr-Cr single bond (n = 8 and 7) or Cr horizontal lineCr double bond (n = 6) to give both chromium atoms the favored 18-electron configuration. The lowest energy structures for the binuclear Cr(2)(CS)(2)(CO)(n) (n = 9, 8, 7, 6) are all predicted to be stable with respect to fragmentation into mononuclear Cr(CS)(CO)(m) in contrast to the homoleptic Cr(2)(CO)(11). This suggests that there is a reasonable chance that at least some of the binuclear Cr(2)(CS)(2)(CO)(n) (n = 9, 8, 7, 6) derivatives will be synthesized as stable or at least detectable molecules.
The Journal of Physical Chemistry A 12/2009; 114(1):486-97. · 2.95 Impact Factor
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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.
Inorganic Chemistry 07/2009; 48(13):5973-82. · 4.60 Impact Factor
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ABSTRACT: Theoretical studies on Fe(3)(CS)(3)(CO)(9) show that the structure having an isosceles Fe(3) triangle with one edge bridged by two CS groups analogous to the Fe(3)(CO)(10)(mu-CO)(2) structure of Fe(3)(CO)(12) is energetically favored over structures of other types. However, the Fe(3)(CS)(3)(CO)(9) system is very highly fluxional with five distinct equilibrium structures lying within 6 kcal/mol of this global minimum. The lowest energy structures predicted for the unsaturated Fe(3)(CS)(3)(CO)(n) (n = 8, 7, 6) are very different from those previously predicted for the corresponding homoleptic carbonyls Fe(3)(CO)(n+3). Thus Fe(3)(CS)(3)(CO)(n) (n = 8, 7, 6) structures with four- and six-electron donor thiocarbonyl groups and only formal Fe-Fe single bonds are energetically preferred over structures with some iron-iron multiple bonding. For Fe(3)(CS)(3)(CO)(8) the lowest energy structures have a unique four-electron donor thiocarbonyl group bridging all three iron atoms. Similarly, for Fe(3)(CS)(3)(CO)(7) the lowest energy structures have a unique six-electron donor thiocarbonyl group bridging all three iron atoms similar to the remarkable six-electron donor carbonyl group in the known stable Cp(3)Nb(3)(CO)(6)(eta(2)-mu(3)-CO). For the even more unsaturated Fe(3)(CS)(3)(CO)(6), the lowest energy structures have both a six-electron donor thiocarbonyl group bridging all three iron atoms and a four-electron donor thiocarbonyl group bridging one of the Fe-Fe edges. Thus all of these structures of the unsaturated derivatives Fe(3)(CS)(3)(CO)(n) (n = 8, 7, 6) require only formal Fe-Fe single bonds for each iron atom to have the favored 18-electron configuration. From the wide range of formal Fe-Fe single bonds found in these structures the lengths of doubly bridged single bonds are seen to be approximately 2.5 to 2.6 A whereas unbridged single bonds are significantly longer at approximately 2.7 to 2.8 A.
Inorganic Chemistry 06/2009; 48(13):6167-77. · 4.60 Impact Factor
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ABSTRACT: Density functional theory (DFT) studies on Fe(CS)(CO)(4) using the B3LYP and BP86 methods show the axially and equatorially substituted trigonal bipyramidal structures to be essentially degenerate, in accord with the experimental observation of an equilibrium of these two isomers in Fe(CS)(CO)(4) synthesized from Na(2)Fe(CO)(4) and SCCl(2). Furthermore, the apically substituted square pyramidal structure of Fe(CS)(CO)(4) lies approximately 5 kcal/mol above the trigonal bipyramidal structures, implying a highly fluxional system. The lowest energy structures for the unsaturated Fe(CS)(CO)(n) (n = 3, 2) can be derived from the trigonal bipyramidal or square pyramidal structures of Fe(CS)(CO)(4) by removal of one or two carbonyl groups, respectively. For the binuclear Fe(2)(CS)(2)(CO)(n) (n = 7, 6, 5, 4) derivatives there is a clear energetic preference for bridging CS groups over bridging CO groups in most cases. Thus, the global minimum for Fe(2)(CS)(2)(CO)(7) is a triply bridged structure analogous to Fe(2)(CO)(9) but with two bridging CS groups and one bridging CO group. The lowest energy structures for the unsaturated Fe(2)(CS)(2)(CO)(n) (n = 6, 5, 4) also contain two bridging CS groups, including at least one four-electron donor eta(2)-mu-CS group bonded to the iron atom not only through the carbon atom but also through the sulfur atom as indicated by relatively short Fe-S distances of approximately 2.6 A. The FeFe distances of approximately 2.4 A in the highly unsaturated Fe(2)(CS)(2)(CO)(n) (n = 5, 4) derivatives with one or two four-electron donor bridging CS groups, respectively, suggest a formal bond order no higher than two, which is sufficient to give both iron atoms the favored 18-electron configuration.
Inorganic Chemistry 04/2009; 48(5):1974-88. · 4.60 Impact Factor
