Dinitrogen binding, P4-activation and aza-Büchner ring expansions mediated by an isocyano analogue of the CpCo(CO) fragment. Issue 37 (2nd August 2016)

• Record Type: Journal Article
• Authors: Mokhtarzadeh, Charles C.; Rheingold, Arnold L.; Figueroa, Joshua S.
• Is Part Of: Dalton transactions. Volume 45:Issue 37(2016)
• Page Start: 14561
• Page End: 14569
• Publication Date: 2016-08-02
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c6dt02789j
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : Synthetic studies targeting an m -terphenyl isocyanide analogue of the unstable 16e −, S = 1 complex CpCo(CO) are reported (Cp = η 5 -C5 H5 ). Abstract : Synthetic studies targeting an m -terphenyl isocyanide analogue of the unstable 16e −, S = 1 complex CpCo(CO) are reported (Cp = η 5 -C5 H5 ). The m -terphenyl isocyanide CNAr Dipp2 (Ar Dipp2 = 2, 6-(2, 6-(i-Pr)2 C6 H3 )2 C6 H3 ) is shown to readily bind to both CpCoI2 and Cp*CoI2 fragments (Cp* = η 5 -C5 Me5 ) and provide mono-isocyanide starting materials that are suitable for chemical reduction. Treatment of CpCoI2 (CNAr Dipp2 ) with KC8 produces the bridging isocyanide dimer, [CpCo(μ-CNAr Dipp2 )]2, thereby indicating that the steric combination of Cp and CNAr Dipp2 ligands does not allow for the production of mononuclear complexes. However, Cp*CoI2 (CNAr Dipp2 ) with KC8 under an N2 atmosphere results in the formation of the complex, Cp*Co(N2 )(CNAr Dipp2 ), which is a unique two-legged piano stool complex featuring a coordinated dinitrogen ligand. The N2 ligand in Cp*Co(N2 )(CNAr Dipp2 ) is shown to be labile and, upon removal by application of vacuum, leads to the production of an η 4 -coordinated 1-azabenz[ b ]azulene complex by aza-Büchner cyclization of the CNAr Dipp2 ligand. This cyclization reaction is rationalized via the intermediacy of the unobserved 16e − species [Cp*Co(CNAr Dipp2 )]. While this intramolecular aza-Büchner cyclization prevents isolation of [Cp*Co(CNAr Dipp2 )], the dinitrogen complex Cp*Co(N2 )(CNAr Dipp2 ) is shown to serve as a reliable synthon for this 16e − species upon reaction with small molecule substrates. Both free CNAr Dipp2 and diphenylacetylene react with Cp*Co(N2 )(CNAr Dipp2 ) to form two-legged piano stool complexes. In addition, Cp*Co(N2 )(CNAr Dipp2 ) reacts readily with 0.5 and 1.0 equivalents of P4 to produce poly-phosphorus products resulting from P–P single bond cleavage.