Bis(η⁵-cyclopentadienyl)[μ-(4b,5,5a-η³:9b,10,10a-η³)-2,3,7,8-tetrakis(trimethylsilyl)benzo[3,4]cyclobuta[1,2-b]biphenylene]-syn-dicobalt (Co–Co), a Dinuclear π-Complex of the Linear [3]Phenylene Framework

Abstract

The title compound was made by the reaction of the CpCo-complex of 2,3,7,8-tetrakis(trimethylsilyl) linear [3]phenylene, in which the metal coordinates one of the cyclobutadiene rings, with CpCo(C₂H₄)₂. Because of its relative stability, a syn-dicobalt-bound configuration is indicated rather than its anti alternative.

Key words

aromaticity - cobalt - complexation - dinuclear complexes - phenylenes

Publication History

Received: 03 September 2021

Accepted after revision: 01 October 2021

Accepted Manuscript online:
01 October 2021

Article published online:
14 October 2021

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• 11 2,3,7,8-Tetrakis(trimethylsilyl) linear [3]phenylene(CpCo)₂ 6In a glovebox, 2,3,7,8-tetrakis(trimethylsilyl) linear [3]phenylene(CpCo) 1 (85 mg, 0.133 mmol) and CpCo(C₂H₄)₂ (25 mg, 0.139 mmol) were added to a Schlenk flask. The flask was taken out of the glove box, and freshly distilled degassed benzene (15 mL) was added under N₂. The mixture was heated to 70 °C in an oil bath for 23 h and then cooled to r.t. The solvent was removed in vacuo, furnishing a black residue that was filtered rapidly through a plug of neutral alumina (activity III; 2.5 × 3.5 cm), eluting with hexanes–THF (100:1) under N₂. The solvents were again removed in vacuo, and the ensuing black residue was crystallized from acetone–EtOAc (100:1) at –78 °C to give reddish-black crystals; yield: 57 mg (56%). ¹H NMR (400 MHz, acetone-d ₆): δ = 7.36 (s, 4 H), 4.89 (m, 4 H), 4.81 (s, 2 H), 0.39 (s, 36 H). ¹³C NMR (100 MHz, acetone-d ₆): δ = 150.5, 145.4, 125.9, 82.8, 57.1, 53.7, 2.66. MS (FAB): m/z = 762 ([M⁺]). HRMS (EI, 70 eV): m/z [M⁺] calcd for C₄₀H₅₂Co₂Si₄: 762.1810; found: 762.1791. UV/Vis (hexane): λ_max (log ε) = 221 (3.36, sh), 244 (3.44), 286 (3.63), 386 (2.79, sh), 439 nm (2.58).