Synthesis and characterization of triply-bonded titanium-iron complexes supported by 2-(diphenylphosphino)pyrrolide ligands

The synthesis of several titanium-iron multiply bonded complexes supported by a 2-(diphenylphos-phino) pyrrolide (NP) ligand is reported. Treatment of the homoleptic, 8-coordinate Ti(NP)(4) monometallic precursors with FeCl2 and KC8 yielded the tetragonally-symmetric heterobimetallic complex Ti(mu(2)-NP)(4)Fe, 2. X-ray crystallographic analysis reveals a short metal-metal distance (2.021(2) and 2.028(2) angstrom for two independent molecules in the asymmetric unit) consistent with a Fe-Ti triple bond. Theoretical calculations also indicate 3 bonding interactions. Further reduction of 2 by 2 electrons with KC8 results in the isolation of the dianion, [K-2][(kappa(1)-NP)Ti(mu(2)-NP)(3)Fe], 3, where one phosphine arm has decoordinated from Fe, and the Fe-Ti triple bond has shortened to 1.9474(7) angstrom. This shortening results from the local ligand field change about Fe from tetragonal to trigonal, which allows for significantly better orbital overlap with Ti. (C) 2016 Elsevier B.V. All rights reserved.