Trinuclear Cluster Complexes Containing the Furyne Ligand:  Synthesis, Structure, and Properties of the Cycloalkyne Complexes (CpCo)n(Cp*Co)3-n(CO)(μ3-η2-C4H4O) (n = 3, 2)

Document Type

Article

Publication Date

3-13-1997

Publication Title

Organometallics

DOI

10.1021/om960867z

ISSN

1520-6041

Abstract

Cyclopentadienyl-based tricobalt clusters containing the cyclic furyne ligand, CH2C⋮CCH2O, have been prepared by the pyrolysis of the butynediol complexes (CpCo)3(CO)(RCCR), 1, and (CpCo)2(Cp*Co)(CO)(RCCR), 2 (R = CH2OH). The solid state structures of the furyne complexes, (CpCo)3(CO)(μ3-η2-CH2C⋮CCH2O), 3, and (CpCo)2(Cp*Co)(CO)(μ3-η2-CH2C⋮CCH2O), 4, verify the presence of the five-membered heterocycle, which formally contains an alkyne group interacting with the tricobalt framework. Chemically and electrochemically reversible one-electron oxidative and reductive couples are observed for 3 at +0.235 and −1.466 V (CH2Cl2 solution, Pt electrode, Fc0/+1 = +0.482 V), respectively, which are similar to redox features observed for noncyclic analogues. At 171 K, the methylene signals of the furyne ligand in 4 are observed as doublets, indicating that furyne rotation is slow at this temperature. Reversible coalescence of the methylene signals occurs at 195 K, and at room temperature, a single sharp methylene resonance is observed. Total line shape analysis of the coalescing spin system yields the activation parameters for the motion of the furyne ring:  ΔG⧧ (300 K) = 39.4(2) kJ/mol, ΔS⧧ = −18(2) J/mol, and ΔH⧧ = 34.0(4) kJ/mol.

Link to Full Text

Share

COinS