Pentamethylcyclopentadienyl derivatives of transition metals

Photogeneration of dinuclear metal carbonyls containing a metal-metal triple bond

“…The thermolysis of IX apparen tly proceeds cleanly according to reaction ( 9 ) giving VIII in good yield along wi th bibenzyl . Reaction ( 9 ) gives Ylli in…”

Binuclear Carbonylheptalenechromium Complexes: Partition of Heptalene into a Complexed Heptafulvene Subunit and an Uncomplexed 1,3‐Diene Subunit for Coordination to a Multiply Bonded Pair of Chromium Atoms

“…The global minimum for C 12 H 10 Cr 2 (CO) 3 by the BP86 method is the singlet cis-C 12 H 10 Cr 2 (CO) 2 (η 2 -μ-CO) structure 3S-2 in contrast to the triplet 3T-1 global minimum by the B3LYP method. This is consistent with the tendency for the B3LYP method to favor higher spin states, as discussed by Reiher et al [35] In such cases, the M06L functional always predicts an intermediate energy between the energies predicted by B3LYP and BP86.…”

“…[1] The analogous chromium compound (Me 5 C 5 ) 2 -Cr 2 (CO) 4 was subsequently synthesized in 1973. [2] Shortly thereafter (Me 5 C 5 ) 2 Cr 2 (CO) 4 was shown by X-ray diffraction [3] to have an unusually short CrϵCr distance of 2.24 Å, as compared with a much longer Cr-Cr single bond length [4] of 3.281 Å in (C 5 H 5 ) 2 Cr 2 (CO) 6 ( Figure 1). The short CrϵCr distance in (Me 5 C 5 ) 2 Cr 2 (CO) 4 suggests the formal triple bond required to give each chromium atom the favored 18-electron configuration.…”

“…The global minima for the more highly unsaturated C 12 H 10 Cr 2 (CO) n (n = 4, 3) complexes are predicted to have a four-electron donor bridging η 2 -μ-CO group as indicated by short Cr-O distances consistent with a direct bond and a low ν(CO) frequency consistent with a low formal C-O formal bond order. discovered [5] instability of (C 5 H 5 ) 2 Cr 2 (CO) 5 with respect to disproportionation into (C 5 H 5 ) 2 Cr 2 (CO) 6 with a Cr-Cr single bond and (C 5 H 5 ) 2 Cr 2 (CO) 4 with a CrϵCr triple bond. This reaction is an unusual example of the disproportionation of a M=M double bonded derivative into a M-M single bonded derivative and the corresponding MϵM triple bonded derivative.…”

“…X-ray diffraction shows the latter to have a Cr-Cr single bond length of 3.26 Å, which is very close to the Cr-Cr single-bond length of 3.28 Å in (η 5 -C 5 H 5 ) 2 Cr 2 (CO) 6 , discussed above. [2,3] However, efforts to synthesize unsaturated binuclear azulene carbonylchromium derivatives C 10 H 8 Cr 2 (CO) n (n Ͻ 6) have been unsuccessful; such species might be candidates for structures with chromium-chromium multiple bonds. Recent theoretical studies [9] predict a tetracarbonyl structure (η 5 ,η 5 -C 10 H 8 )Cr 2 (CO) 3 (μ-CO) with one bridging carbonyl group and a short enough ca.…”