Synthesis of 1,2-bis(di- tert-butylphosphino)ethane (dtbpe) complexes of nickel: radical coupling and reduction reactions promoted by the nickel(I) dimer [(dtbpe)NiCl] 2

Abstract

Tetrahydrofuran solutions of (dtbpe)NiCl 2 (dtbpe=1,2-bis(di- tert-butylphosphino)ethane) are reduced by KC 8 to afford the dimeric Ni(I) complex [(dtbpe)NiCl] 2 ( 1) in 73% yield. Reaction of 1 with [FeCp 2][PF 6] effects a one-electron oxidation to give the mixed-valent Ni(I,II) binuclear species [{(dtbpe)NiCl} 2][PF 6], [ 1][PF 6]. Complex 1 reacts with the radicals NO and TEMPO (2,2,6,6-tetramethyl-1-piperidine- N-oxyl) to give the diamagnetic Ni(0) nitrosyl (dtbpe)Ni(Cl)(NO) ( 2) and the Ni(II) complex (dtbpe)Ni(Cl)( O, N:η 2-TEMPO) ( 3). Reduction of the SS bond of diphenyldisulfide by 1 results in formation of the Ni(II) arylthiolate complex (dtbpe)NiCl(SPh) ( 4). The radical anions NaOCPh 2 and KN 2Ph 2 react cleanly with 1 to afford (dtbpe)Ni(η 2-OCPh 2) ( 5) and (dtbpe)Ni(η 2-N 2Ph 2) ( 6). Phenylacetylide CC bond coupling is effected by reaction of 1 with LiCCPh to form [(dtbpe)Ni( C, C′:η 2-CCPh)] 2 ( 7). In addition to standard spectroscopic (IR, NMR, EPR) and magnetic measurements, complexes 1, [ 1][PF 6], 3, and 5 were also characterized by single-crystal X-ray diffraction methods.