title: Adducts of nitrogenous ligands with rhodium(II) tetracarboxylates and tetraformamidinate: NMR spectroscopy and density functional theory calculations.
abstract: Complexation of tetrakis(μ2-N,N'-diphenylformamidinato-N,N')-di-rhodium(II) with ligands containing nitrile, isonitrile, amine, hydroxyl, sulfhydryl, isocyanate, and isothiocyanate functional groups has been studied in liquid and solid phases using (1)H, (13)C and (15)N NMR, (13)C and (15)N cross polarisation-magic angle spinning NMR, and absorption spectroscopy in the visible range. The complexation was monitored using various NMR physicochemical parameters, such as chemical shifts, longitudinal relaxation times T1 , and NOE enhancements. Rhodium(II) tetraformamidinate selectively bonded only unbranched amine (propan-1-amine), pentanenitrile, and (1-isocyanoethyl)benzene. No complexation occurred in the case of ligands having hydroxyl, sulfhydryl, isocyanate, and isothiocyanate functional groups, and more expanded amine molecules such as butan-2-amine and 1-azabicyclo[2.2.2]octane. Such features were opposite to those observed in rhodium(II) tetracarboxylates, forming adducts with all kind of ligands. Special attention was focused on the analysis of Δδ parameters, defined as a chemical shift difference between signal in adduct and corresponding signal in free ligand. In the case of (1)H NMR, Δδ values were either negative in adducts of rhodium(II) tetraformamidinate or positive in adducts of rhodium(II) tetracarboxylates. Experimental findings were supported by density functional theory molecular modelling and gauge independent atomic orbitals chemical shift calculations. The calculation of chemical shifts combined with scaling procedure allowed to reproduce qualitatively Δδ parameters.
authors: Institute of Organic Chemistry PAS, ul. Kasprzaka 44/52, 01-224, Warsaw, Poland.
authors: Piotr
authors: P
authors: Cmoch
authors: Rafał
authors: R
authors: Głaszczka
authors: Jarosław
authors: J
authors: Jaźwiński
authors: Bohdan
authors: B
authors: Kamieński
authors: Elżbieta
authors: E
authors: Senkara
mesh_terms: D000588:Amines / Q000737:chemistry; D002264:Carboxylic Acids / Q000737:chemistry*; D005559:Formamides / Q000737:chemistry*; D017953:Isocyanates / Q000737:chemistry; D017879:Isothiocyanates / Q000737:chemistry; D008024:Ligands; D009570:Nitriles / Q000737:chemistry; D009942:Organometallic Compounds / Q000737:chemistry*; D011789:Quantum Theory; D012238:Rhodium / Q000737:chemistry*
chemical_list: D000588:Amines; D002264:Carboxylic Acids; D005559:Formamides; D017953:Isocyanates; D017879:Isothiocyanates; D008024:Ligands; D009570:Nitriles; D009942:Organometallic Compounds; D012238:Rhodium
keywords: 13C CPMAS NMR; 15N CPMAS NMR; DFT calculations; NMR; Rhodium(II) tetraformamidinate; complexation