Unsaturation and variable hapticity in binuclear azulene manganese carbonyl complexes

Abstract

Azulene is reported to react with Mn(2)(CO)(10) to give trans-C(10)H(8)Mn(2)(CO)(6), which has been shown by X-ray crystallography to have a bis(pentahapto) structure with no metal-metal bond. This structure is found by density functional theory to be the lowest energy C(10)H(8)Mn(2)(CO)(6) structure. However, a corresponding bis(pentahapto) cis-C(10)H(8)Mn(2)(CO)(6) structure, also without an Mn···Mn bond, lies within ~1 kcal mol(-1) of this global minimum. The lowest energy C(10)H(8)Mn(2)(CO)(5) structure is singlet cis-η(5),η(5)-C(10)H(8)Mn(2)(CO)(5) with an Mn→Mn dative bond from the Mn(CO)(3) group to the Mn(CO)(2) group. However, a singlet cis-η(6),η(4)-C(10)H(8)Mn(2)(CO)(5) structure with a normal Mn-Mn single bond lies within ~6 kcal mol(-1) of this global minimum. The lowest energy structures of the more highly unsaturated C(10)H(8)Mn(2)(CO)(n) (n = 4, 3, 2) systems all have cis geometries and manganese-manganese bonds of various orders. The corresponding global minima are triplet cis-η(5),η(3)-C(10)H(8)Mn(2)(CO)(3)(η(2)-μ-CO) for the tetracarbonyl with a four-electron donor bridging carbonyl group, singlet cis-η(5),η(5)-C(10)H(8)Mn(2)(CO)(3) for the tricarbonyl, and triplet cis-η(6),η(4)-C(10)H(8)Mn(2)(CO)(η(2)-μ-CO) for the dicarbonyl.

Metal–Metal (MM) Bond Distances and Bond Orders in Binuclear Metal Complexes of the First Row Transition Metals Titanium Through Zinc

“…BP86 predictions for the azulene series (C 10 H 8 )Mn 2 (CO) n (n = 5, 4, 3, and 2) 319 show mainly η 5 ,η 5 -coordination modes for the bicyclic ligand, except for two triplet minima (Table 18). The (C 10 H 8 )Mn 2 (CO) 5 system 09 has two singlet minima with The remaining results of this subsection are compiled from computational (BP86) results where some consistent trends are discernible in Tables 16 to 18 for various series of binuclear manganese carbonyl complexes.…”

“…BP86 predictions for the azulene series (C 10 H 8 )­Mn 2 (CO) n ( n = 5, 4, 3, and 2) show mainly η 5 ,η 5 -coordination modes for the bicyclic ligand, except for two triplet minima (Table ). The (C 10 H 8 )­Mn 2 (CO) 5 system 09 has two singlet minima with long Mn–Mn single bonds of lengths 3.025 and 2.969 Å.…”

“…The pentalene ligand series (Table ) gives the ranges: 2.85 ± 0.11 Å for single bonds (one long interaction aside), 2.52 ± 0.08 Å for double bonds, 2.26 ± 0.01 Å for triple bonds, and 2.289 Å for the sole example of a dipolar quadruple bond. The azulene series (Table ) has the ranges: 2.76 ± 0.01 Å for single bonds (weak interactions apart), 2.68 ± 0.08 Å for double bonds, and 2.359 Å for the sole example of a triple bond.…”

Binuclear heptalene iron carbonyl complexes: Comparison with related azulene and pentalene complexes

“…In binuclear azulene metal carbonyls the five-membered ring is almost always bonded to a metal atom as a pentahapto ligand as shown by both experimental [1] and theoretical [11,12] studies. However, the hapticity of the azulene seven-membered ring is variable as shown by both experimental and theoretical studies.…”

Effect of Spectator Ligands on Haptotropic Rearrangements of Metal‐Azulene Complexes

“…The metal centre can bond to both rings simultaneously, forming η 5 + 1 , η 5 + 2 and η 7 + 2 bonds. [15,[34][35][36][37] Korichi et al have reported the relative energy of the isomers of several mononuclear Az complexes. Their results do not show a clear trend on the preference of the metal for one of the two rings.…”