Abstract
The synthesis, characterization, structural and computational studies of Re(I) tricarbonyl bromo complexes bearing alkyl-substituted 1,4-diazabutadiene ligands, [Re(CO)3(1,4-DAB)Br], where 1,4-DAB = N,N-bis(2,4-dimethylbenzene)-1,4-diazabutadiene, 2,4-Me2DAB (1); N,N-bis(2,4-dimethylbenzene)-2,3-dimethyl-1,4-diazabutadiene, 2,4-Me2DABMe (2); N,N-bis(2,4,6-trimethylbenzene)-1,4-diazabutadiene, 2,4,6-Me3DAB (3); and N,N-bis(2,6-diisopropylbenzene)-1,4-diazabutadiene, 2,6-ipr2DAB (4) are reported. The complexes were characterized by different spectroscopic methods such as FT-IR, 1H-NMR, 13C-NMR, and elemental analyses and their solid-state structures were confirmed by X-ray diffraction. In each complex, the Re(I) centre shows a distorted octahedral shape with a facial geometry of carbonyl groups. The gas phase geometry of the complexes was identified by density functional theory. Interesting intermolecular n…π* interactions of complexes 1 and 3 were investigated by non-covalent interaction index (NCI), and natural bond orbital (NBO) analyses. The intramolecular n…σ*, σ…π*, π…σ* interactions were also studied in complexes 3 and 4.
Highlights
Transition metal carbonyl complexes have become one of the most important classes of coordination compounds in inorganic chemistry
It has been demonstrated that M–CO(lone pair)· · · π interactions are relevant in the structures of a number of transition metal carbonyl complexes, and they have important effects on their internal geometry in the related complexes and supramolecular interactions of metal carbonyl complexes [33,34]
The new [(NN)Re(CO)3 X] (NN = diazabutadiene) complexes were synthesized via substitution reaction from the DAB ligands and Re(CO)5 Br in a mixture of CH2 Cl2 and toluene under reflux condition
Summary
Transition metal carbonyl complexes have become one of the most important classes of coordination compounds in inorganic chemistry. It has been demonstrated that M–CO(lone pair)· · · π interactions are relevant in the structures of a number of transition metal carbonyl complexes, and they have important effects on their internal geometry in the related complexes and supramolecular interactions of metal carbonyl complexes [33,34] In spite of their inherently weak nature, M–CO(lone pair)· · · π* interactions stabilize precise molecular conformations that maximize the overlap between the involved donor and acceptor orbitals in the interaction and can provide a measure of stability to their crystal structures and lead to supramolecular architectures [35]. In continuation of our work on synthesis, characterization, structural chemistry, and computational studies of transition metal-carbonyl complexes [39,40], we here report the synthesis, spectroscopic, structural and computational studies of new Re(I)-tricarbonyl bromo complexes bearing 1,4-diazabutadiene as non-heterocyclic diimine ligands, namely: N,N-bis(2,4-dimethylbenzene)-1,4-diazabutadiene, 2,4-Me DAB (1); N,N-bis(2,4-dimethylbenzene)-2,3-dimethyl-1,4-diazabutadiene, 2,4-Me 2 DABMe
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