Synthesis and characterization of a novel complex: Mo(CO)4[2-(2′pyridyl)quinoxaline]. An insight based on experimental and theoretical data

Abstract

Synthesis and characterization of the new complex Mo(CO)₄(2,2′-pq), where 2,2′-pq = 2-(2′pyridyl)quinoxaline, 1, is presented. The ligand 2,2′-pq, 2, belongs to the general class of quinoxalines, natural products yielding a rich coordination chemistry. This is the first reference for its coordination with Mo. Complex 1 crystallizes in space group P2₁/n with a = 9.621(4), b = 16.748(7), c = 10.343(4) Å, Z = 4 and V = 1626.4(12) ų. The octahedral geometry of the metal centre is distorted due to the bending of the axial carbonyls from the ligand 2. This bending is associated with the extensive solvatochromism of the MLCT band of complex 1 and related complexes as our semi-empirical calculations (ZINDO) and comparison with other complexes of Mo(CO)₄L indicate. Moreover Oshika–Bayliss–McRae's formalism is employed in order to depict the solvation factors that influence the solvatochromism of 1. The latter one is attributed to the enhanced π-backbonding in 1, the polarization of the valence electrons of 2 and to the contribution of COs in the HOMO.