Linkage isomerism of two benzoato-copper(I) complexes containing bis(diphenylphosphino)methane bridging ligands. Crystal structures, TSDC measurements and reactivities of [Cu 2(μ-dppm) 2(O 2CPh) 2] and [Cu 2(μ-dppm) 2(O 2CPh)(μ-O 2CPh)]·H 2O

Abstract

Here we report the molecular structures and reactivities of the two complexes [{Cu(O 2CPh)dppm} 2] ( A) and [{Cu(O 2CPh)dppm} 2]·H 2O ( B), containing isomeric dibenzoato copper(I) moieties doubly bridged by dppm ligands (dppm=bis(diphenylphosphino)methane). In the isomeric unit [{Cu(O 2CPh)dppm} 2] of B, the two metal atoms are also bridged by one of the two benzoato ligands and a significant shortening of the transannular Cu…Cu distance (2.994(2) Å in B versus 3.359(2) Å in A) is observed. The eight-membered Cu 2P 4C 2 ring adopts an approximate chair conformation in A and a saddle conformation in B. The structures of A and B have been determined by single crystal X-ray diffraction method. The crystals of A are triclinic, space group P 1 , with Z = 1 in a unit cell of dimensions a = 11.841(2), b = 11.366(2), c = 10.769(2) Å, α = 100.68(2), β = 101.45(2) and γ = 93-37(2)°. The crystals of B are monoclinic, space group P2 1/ a, with Z = 4 in a unit cell of dimensions a = 21.295(3), b = 13.295(2), c = 22.068(3) Å and β = 114.72(2)°. Final R was 0.032 (2553 reflections) for A and 0.058 (3909 reflections) for B. Bulky anions react with A and B metathetically removing one of the benzoato groups or, when coordinating, both of them. The characteristics of the new anions modulate the conformation of the Cu 2(dppm) 2 unit. Thermally stimulated depolarization current (TSDC) measurements have also been performed on B to study the electric polarization phenomena induced by reorientation of dipole moments of the crystallization water molecules in the temperature range 100 ⩽ T ⩽ 350 K. The reorientation ability of the dipole water molecules is probably favoured by the dynamic disorder of the atoms, which surround the water molecules in the crystal lattice.