π‐Complexes of Copper(I) with Terminal Alkynes. Synthesis and Crystal Structure of [(HC≡CCH 2 NH 3 )(Cu 2 Br 3 )] π‐Complex

Crystals of the zwitterionic copper(I) π‐complex [(HC≡CCH 2 NH 3 )Cu 2 Br 3 ] have been synthesized by interaction of CuBr with [HC≡CCH 2 NH 3 ]Br in aqueous solution (pH < 1) and X‐ray studied. The crystals are monoclinic: space group P 2 1 / n , a = 6.722(4), b = 12.818(8), c = 9.907(3) Å, β = 100.25(4)°, V = 840.0(8) Å 3 , Z = 4, R = 0.0592 for 3015 reflections. The crystal structure of the π‐complex contains isolated [(HC≡CCH 2 NH 3 ) + (Cu 2 Br 3 ) − ] 2 units which are incorporated into a framework by strong hydrogen N–H···Br and C≡C–H···Br bonds. The length of π‐coordinated propargylammonium C≡C bond is equal 1.216(8) Å and Cu(I)–(C≡C) distance equals 1.958(5) Å.