The coordination chemistry of copper(i) in liquid ammonia, trialkyl and triphenyl phosphite, and tri-n-butylphosphine solution

Abstract

The coordination chemistry of the solvate complexes of the relatively soft electron-pair acceptor copper(I) has been studied in solution and solid state in seven solvents with strong electron-pair donor properties, liquid ammonia, trimethyl, triethyl, triisopropyl, tri-n-butyl and triphenyl phosphite, and tri-n-butylphosphine. The solvate complexes have been characterised by means of EXAFS and ⁶³Cu NMR spectroscopy, and in some cases also by ⁶⁵Cu NMR spectroscopy. The copper(I) ion is three-coordinated, most probably in a coplanar trigonal fashion, in liquid ammonia with a mean Cu–N bond distance of 2.00(1) Å. No ⁶³Cu NMR signal has been detected from the ammonia solvated copper(I) ion in liquid ammonia, which supports a three-coordination. The phosphite and phosphine solvated copper(I) ions are tetrahedral with Cu–P bond distances in the range 2.24–2.28 Å in both solution and solid state as determined by EXAFS spectroscopy. The tetrahedral configuration of these complexes has been confirmed by ⁶³Cu and ⁶⁵Cu NMR spectroscopy through the J(⁶³Cu–³¹P) and J(⁶⁵Cu–³¹P) couplings. The fact that two of the investigated complexes, [Cu(P(OC₆H₅)₃)₄]⁺ and [Cu(P(C₄H₉)₃)₄]⁺, are ⁶³Cu and ⁶⁵Cu NMR silent is probably caused by a significantly angular distorted tetrahedral configuration.