Iron−Gold (or −Mercury) Carbide Clusters Derived from [Fe₆C(CO)₁₆]^2-. X-ray Crystal Structures of (NEt₄)[Fe₆C{AuPPh₃}(CO)₁₆] and [Fe₄C{AuPPh₃}(CO)₁₁(NO)]

Abstract

The metal halide complexes ClAuPPh3 and ClHg(m) react in thf with [Fe6C(CO)16]2- affording the metal cluster compounds (NEt4)[Fe6C{μ3-AuPPh3}(CO)16] (1) and (NEt4)[Fe6C{Hg(m)}(CO)16] (m = Mo(CO)3Cp (2), W(CO)3Cp (3), and Mn(CO)5 (4)) in good yields. The cluster [{Fe6C(CO)16}2(Hg)]2- (5) is also isolated by reaction of this anion with Hg(NO3)2. The product obtained by treatment of 1 with NOBF4 depends on the stoichiometry of the reaction. Thus, with a 1:1 molar ratio the nitrosyl compound [Fe6C{AuPPh3}(CO)15(NO)] (6) was formed whereas the use of an excess of NOBF4 led to the pentametal cluster [Fe4C{AuPPh3}(CO)11(NO)] (7). The structures of 1 and 7 have been determined by X-ray diffraction methods. The electrochemical behavior of 2−5 has been investigated by cyclic voltammetry and coulometry. An extended Hückel molecular orbital study of the bonding capabilities of [Fe4C(CO)12]2- has been carried out in order to understand the structural differences between [Fe4C{AuPPh3}(CO)12]- and [HFe4C(CO)12]-.

Gold–Heterometal Interactions and Bonds

“…A structural diversity of heterodimetallic and -trimetallic cores was observed for the pentanuclear species containing Au-Fe [296][297][298][299][300][301][302][303][304][305][306][307][308][309], Au-Ru [267,272,[310][311][312][313][314][315][316][317][318][319][320][321][322][323][324][325] and Au-Os [326][327][328][329][330][331][332][333][334][335]. A (Ph 3 P)Au unit can bridge in a m 3 -fashion a face of a tetrahedral heterodimetallic (Fe 2 Ir 2 , Fe 2 Rh 2 , Ru 2 Rh 2 , Ru 3 Rh, Ru 3 Co) core [296,297,310,311,315] [311]…”

“…Related clusters in which the Au (PR 3 ) unit bridges in a m 3 -M,C,M 0 fashion a butterfly CM 4 (M ¼ Fe [305,306], Ru [324]) or CFe 3 Co (M 0 ¼ Co [307], Fe [308]) core are also known, for example (Ph 3 P)AuFe 4 (m 5 -C)(CO) 12 (NO) 228 [Au-Fe 2.820(2)/2.866(2) Å] (Figure 4.38a) [306].…”

“…Heptanuclear clusters with Au-Fe [160,306,[370][371][372][373]394], Au-Ru [264,319,328,[374][375][376][377][378][379][380][381][382][383][384][385][386][387][388][389][390] and Au-Os bonds [327,[391][392][393] have also been reported. Most common structures are based on C-centered [160,306,374,375] or B-centered [376][377][378][379] [160], (b) (Ph 3 P)AuOs 6 (m 6 -P)(CO) 18 253 [391], (c) [(Et 3 P)Au] 2 Fe 5 (m 6 -C)(CO) 14 254 [370], (d) (dppm)Au 2 Os 4 Ru(h 6 -C 6 H 6 )(CO) 12 [379].…”

“…Most common structures are based on C-centered [160,306,374,375] or B-centered [376][377][378][379] [160], (b) (Ph 3 P)AuOs 6 (m 6 -P)(CO) 18 253 [391], (c) [(Et 3 P)Au] 2 Fe 5 (m 6 -C)(CO) 14 254 [370], (d) (dppm)Au 2 Os 4 Ru(h 6 -C 6 H 6 )(CO) 12 [379]. A gold atom edge-bridged to an Ru-Ru bond in B-centered BRu 6 and cis-BRh 2 Ru 4 cores were found in some compounds [378,380,381] or in the cluster (Ph 3 P)AuRu 6 (m 6 -C)(mSePh)(CO) 15 252 [Au-Ru 2.7253(6)/2.8515(6) Å] [382].…”

“…38 (a) The structure of (Ph 3 P)AuFe 4 (m 4 -C)(CO)12 (NO) 228[306],andmetalframeworksin(b)[(Ph 3 P)Au] 2 Os 2 (m-H) 2 (CO)12 232[367], (c) [(dppe)Au 2 ]Os 4 (m-H) 4 (CO)11 233 [369], (d) [(Ph 2 MeP) Au] 2 Os 4 (CO)12 234 [368], (e) [(Et 3 P)Au] 2 Os 4 (m-CO)(CO)12 235[368],and (f) [(Ph 3 P)Au] 3 Ru 3 [m 3 -h 1 :h 1 :h 1 , h 2 -CCHCPh 2 OC(O)] (CO) 8 236 [362] (for clarity, ligands on Os and Ru are not shown). Depending on the saturated or the unsaturated nature of the cluster and the phosphine ligands used, different geometries of the hexanuclear Au 2 the (dppe)Au 2 unit bridges an edge of the Os 4 tetrahedron and the second Au atom coordinated to a third Os atom in [(dppe)Au 2 ]Os 4 (m-H) 4 (CO) 11 233 [Au-Os 2.699(3)-2.825(3) Å] (Figure 4.38c) [369]; (iii) open butterfly Os 4 core bicapped by two isolated m 3 -Au(PR 3 ) units in [(Ph 2 MeP)Au] 2 Os 4 (CO) 12 234 [Au-Os 2.784 (2)-2.831(2) Å] (Figure 4.38d) [368], or (iv) diedge-bridged tetrahedral Os 4 core in [(Et 3 P)Au] 2 Os 4 (m-CO)(CO) 12 235 [Au-Os 2.739(1)-2.863(1) Å]…”