The hexamethylpentalene dianion and other reagents for organometallic pentalene chemistry

Abstract

Novel permethylated pentalenide anions are reported which offer exciting new opportunities for the future development of organometallic pentalene chemistry.

Binuclear Pentalene Iron Carbonyl Complexes

“…The resulting pentalene metal complexes exhibit a diverse array of coordination modes, thereby showing great flexibility in adapting to the electronic requirements of the metal center. [18] Examples of such complexes include the mononuclear transition metal derivatives (C 8 H 6 )V(C 9 H 7 ), (η 8 -C 8 H 6 )M(η 5 -C 5 H 5 ) (M = V, Ti, Zr), (η 8 -C 8 H 6 ) 2 M (M = Ti, Zr, Hf) and (η 3 -C 3 H 5 ) 2 Zr(η 8 -C 8 H 6 ) having a pentalene ligand bonded to a single metal atom as an octahapto ligand, [19][20][21][22] as well as the binuclear pentalene metal carbonyl derivatives cis-(η 5 ,η 5 -C 8 H 6 )Fe 2 (CO) 5 , [6] trans-(η 5 ,η 5 -C 8 H 6 )[M(CO) 3 ] 2 (M = Mn, Re), [7] and Ru 2 (MMe 3 ) 2 (CO) 4 (C 8 H 6 ). [5] Within the last few years the chemistry of pentalene metal complexes has expanded with the development by O'Hare and co-workers of methods for the synthesis of permethylpentalene precursors in quantity.…”

“…[5] Within the last few years the chemistry of pentalene metal complexes has expanded with the development by O'Hare and co-workers of methods for the synthesis of permethylpentalene precursors in quantity. [18] This has allowed the synthesis of stable hexameth-ylpentalene metal carbonyl complexes [4] including the metal carbonyl derivatives cis-(η 5 ,η 5 -C 8 Me 6 )Fe 2 (CO) 5 and cis-(η 5 ,η 5 -C 8 Me 6 )Co 2 (CO) 4 [4] as well as the bis(hexamethylpentalene)metal derivatives (C 8 Me 6 ) 2 M 2 (M = V, Cr, Mn, Co, Ni). [23] In addition Cloke and co-workers [24][25][26] Among the pentalene metal carbonyl derivatives, the pentalene iron carbonyls (Figure 1) have been studied in the greatest detail.…”

Zirconium and Hafnium Permethylpentalene Compounds

“…9 However, in 2005, Ashley and co-workers reported a homogeneous, highyielding synthesis of suitable precursors for permethylpentalene (Pn*; C 8 Me 6 ), 10,11 and this ligand has been subsequently used in early d-block and f-block organometallic chemistry. 12 −14 Recently we reported the synthesis of "(η 8 -Pn*)MX 2 " (M = Ti, Zr, Hf) synthons, 15 which we used to make mixed sandwich complexes that demonstrate very high activity for α-olefin polymerization.…”

Unusual B4N2C2 Ligand in a Ruthenium Pseudo‐Triple‐Decker Sandwich Complex Displaying Three Reversible Electron‐Transfer Steps

“…Despite its very similar geometry, the 8-π-electron heterocyclic ligand in 3 is not a direct analogue of the 10-π-electron pentalenediyl. 7,8 A crystal structure was determined for 3(tmeda)2, revealing that the planar B4N2C2 ligand was coordinated by two potassium ions each supporting a TMEDA molecule, in a centrosymmetric arrangement (Fig. 2).…”

“…The recent synthesis of hexamethylpentalene is a promising development in this area. 8 Heterocyclic rings, particularly those containing boron, have a higher tendency to coordinate bifacially and generate stacked sandwich compounds. 9 The largest multidecker sandwich compounds known to date contain six decks and feature dianionic cyclic ligands with B2C3 and B3C2 frameworks.…”