A Carbonyl Group Bridging Four Metal Atoms in a Homoleptic Carbonylmetal Cluster: The Remarkable Case of ­Co₄(CO)₁₁

Abstract

The unsaturated Co4(CO)11 is predicted by density functional theory (B3LYP and BP86 functionals) to have a structure with one μ4‐CO group bridging all four cobalt atoms in a Co4 butterfly, with five Co–Co bonds in the range 2.44–2.56 Å. This μ4‐CO group is predicted to have a relatively long C–O bond of 1.226 Å (BP86) with a correspondingly low ν(CO) frequency of 1636 cm–1. Co4(CO)11 structures of higher energy have Co4 tetrahedra (6 Co–Co bonds) or Co4 butterflies (5 Co–Co bonds) with a collection of terminal, edge‐bridging, and face‐bridging CO groups forming a total of 15 or 16 Co–C bonds. The predicted molecular structures show no signs of cobalt–cobalt multiple bonding. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Interactions of a Diplumbyne with Dinuclear Transition Metal Carbonyls to Afford Metalloplumbylenes

“…The structure of compound 3 conforms to Wade’s rules, which predict a nido structure for the tetracobalt tetrahedron core as it has n + 2 ( n = number of vertices) skeletal electron pairs for cluster bonding. , The edge-bridging Pb–Co bonds are 2.5008(7) and 2.5150(6) Å while the average of the face-bridging Pb–Co distances is 2.5750(8) Å, which is slightly longer than the edge-bridging distance as expected for the higher lead coordination number. The Co–Co lengths are similar to those of the Co–Co bonds (2.441(14)–2.527(10) Å) in cobalt carbonyl clusters except that the Co(1)–Co(4) distance bridged by the PbAr i Pr 6 moiety is 2.7472(9) Å, which is much longer than an average Co–Co bond (2.499(1) Å). − The calculated structure of the unsaturated compound Co 4 (CO) 11 reported by King and co-workers was predicted to have a μ 4 -CO group bridging all four cobalt atoms, where the structure of 3 resembles one of the predicted structures with a butterfly array of cobalt atoms. The calculated structure indicated a long Co···Co distance between the two wingtips cobalt atoms of 2.974 (B3LYP) or 3.105 Å (BP86) in the Co 4 butterfly, which is 0.2–0.3 Å longer than Co(1)–Co(4) in the structure of 3 .…”

“…reported by King and coworkers 42 was predicted to have a μ 4 -CO group bridging all four cobalt atoms, where the structure of 3 resembles one of the predicted structures with a butterfly array of cobalt atoms. The calculated structure indicated a long Co···Co distance between the two wingtips cobalt atoms of 2.974 Å (B3LYP) or 3.105 Å (BP86), in the Co 4 butterfly, 0.2~0.3 Å longer than Co(1)-Co(4) in the structure of 3.…”

“…The CO stretching frequencies of 2 were calculated to be 1893, 1921, 1967, and 2008 cm –1 . The IR spectrum of 3 showed similarities with the calculated (BP86) vibrational frequencies of the theoretical butterfly complex Co 4 (CO) 11 , where the vibrational frequencies have relatively low wavenumber values of 1820 and 1849 cm –1 that can be attributed to the bridging carbonyl groups, and those at 2008 (m) and 2035 (m) cm –1 that can be attributed to the terminal carbonyl groups (2020 (s), 2026 (s), 2032 (s)) …”

“…butterfly complex Co 4 (CO) 11 , where the vibrational frequencies have relatively low wavenumber values of 1820 cm -1 and 1849 cm -1 , which can be attributed to the bridging carbonyl groups, and that 2008(m) cm -1 and 2035(m) cm -1 to the terminal carbonyl groups(2020(s), 2026(s), 2032(s)). 42…”

Trinuclear and tetranuclear cyclopentadienyl vanadium carbonyl clusters: unusual carbonyl groups in Herrmann's (C5H5)4V4(CO)4 exhibiting low CO stretching frequencies

“…bridge either a V-V edge, a V 3 triangular face, or all four vanadium atoms in the two butterfly structures. 33 These latter m 4 -CO groups do not have metal-oxygen bonds to the m 4 -CO groups and exhibit higher n(CO) frequencies of 1654, 1704, and 1636 cm À1 , respectively.…”