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Au(III) chloride compounds with 7,8-benzoquinoline (bqn) – [Au(bqn)Cl3] and [Au(bqn∗)Cl2] (bqn∗ being deprotonated, at the C(10) carbon, monoanionic form of bqn) were studied by 1H–13C, 1H–15N HMQC and HMBC–NMR. 1H, 13C and 15N coordination shifts were discussed in relation to the molecular structures, revealing characteristic variability patterns. Analogous NMR measurements were performed for the new (bqnH+)2(AuCl4−)Cl− salt, studied also by single crystal X-ray diffraction. All compounds exhibited fluorescence.

An update of a review paper published in 2013 (L. Pazderski, 15N and 31P NMR coordination shifts in transition metal complexes with nitrogen- and phosphorus-containing heterocycles, Annu. Rep. NMR Spectr. 80 (2013) 33–180), devoted to 15N NMR and covering years 2012–20 (till June), with 184 references. It collects 15N NMR data for 407 complexes or organometallics of such transition metal ions as Ni(II), Pd(II), Pt(II), Pt(IV), Rh(I), Ir(I), Co(III), Rh(III), Ir(III), Fe(II), Ru(II), Os(II), Cu(I), Ag(I), Au(I), Au(III), Zn(II), Cd(II) and Hg(II) with nitrogen-containing heterocycles (azines, azoles, purines and 1,2,4-triazolo-[1,5a]-pyrimidines). 15N NMR coordination shifts, i.e., differences between 15N chemical shifts of the same nitrogen in the molecules of the complex or organometallic and the ligand ( Δ 15 N coord = δ 15 N compl / organomet − δ 15 N lig ) are discussed in relation to some structural features of the reviewed coordination compounds, mainly to the type of the metal central ion and the donor atom in trans-position in respect to the concerned N atom.

(1)H, (13)C and (15)N NMR studies of iron(II), ruthenium(II) and osmium(II) bis-chelated cationic complexes with 2,2':6',2″-terpyridine ([M(terpy)(2) ](2+) ; M = Fe, Ru, Os) were performed. Significant shielding of nitrogen-adjacent H(6) and deshielding of H(3'), H(4') protons were observed, both effects being mostly expressed for Fe(II) compounds. The metal-bonded nitrogens were shielded, this effect being much larger for the outer N(1), N(1″) than the inner N(1') atoms, and enhanced in the Fe(II) → Ru(II) → Os(II) series.

(1)H, (13)C, (15)N and (195)Pt NMR studies of gold(III) and platinum(II) chloride organometallics with N(1),C(2')-chelated, deprotonated 2-phenylpyridine (2ppy*) of the formulae [Au(2ppy*)Cl(2)], trans(N,N)-[Pt(2ppy*)(2ppy)Cl] and trans(S,N)-[Pt(2ppy*)(DMSO-d(6))Cl] (formed in situ upon dissolving [Pt(2ppy*)(micro-Cl)](2) in DMSO-d(6)) were performed. All signals were unambiguously assigned by HMBC/HSQC methods and the respective (1)H, (13)C and (15)N coordination shifts (i.e. differences between chemical shifts of the same atom in the complex and ligand molecules: Delta(1H)(coord) = delta(1H)(complex) - delta(1H)(ligand), Delta(13C)(coord) = delta(13C)(complex) - delta(13C)(ligand), Delta(15N)(coord) = delta(15N)(complex) - delta(15N)(ligand)), as well as (195)Pt chemical shifts and (1)H-(195)Pt coupling constants discussed in relation to the known molecular structures. Characteristic deshielding of nitrogen-adjacent H(6) protons and metallated C(2') atoms as well as significant shielding of coordinated N(1) nitrogens is discussed in respect to a large set of literature NMR data available for related cyclometallated compounds.

1H, 13C and 15N nuclear magnetic resonance studies of gold(III), palladium(II) and platinum(II) chloride complexes with phenylpyridines (PPY: 4-phenylpyridine, 4ppy; 3-phenylpyridine, 3ppy; and 2-phenylpyridine, 2ppy) having the general formulae [Au(PPY)Cl3], trans-/cis-[Pd(PPY)2Cl2] and trans-/cis-[Pt(PPY)2Cl2] were performed and the respective chemical shifts (delta1H, delta13C and delta15N) reported. 1H, 13C and 15N coordination shifts (i.e. differences between chemical shifts of the same atom in the complex and ligand molecules: Delta(coord)(1H) = delta(complex)(1H)-delta(ligand)(1H), Delta(coord)(13C) = delta(complex)(13C)-delta(ligand)(13C), Delta(coord)(15N) = delta(complex)(15N)-delta(ligand)(15N)) were discussed in relation to the type of the central atom (Au(III), Pd(II) and Pt(II)), geometry (trans-/cis-) and the position of a phenyl group in the pyridine ring system.

(1)H, (13)C and (15)N NMR studies of gold(III), palladium(II) and platinum(II) chloride complexes with picolines, [Au(PIC)Cl(3)], trans-[Pd(PIC)(2)Cl(2)], trans/cis-[Pt(PIC)(2)Cl(2)] and [Pt(PIC)(4)]Cl(2), were performed. After complexation, the (1)H and (13)C signals were shifted to higher frequency, whereas the (15)N ones to lower (by ca 80-110 ppm), with respect to the free ligands. The (15)N shielding phenomenon was enhanced in the series [Au(PIC)Cl(3)] Pt(II) replacement, but decreased upon the trans --> cis-transition. Experimental (1)H, (13)C and (15)N NMR chemical shifts were compared to those quantum-chemically calculated by B3LYP/LanL2DZ + 6-31G**//B3LYP/LanL2DZ + 6-31G*.

trans-[Co(py)4Cl2]Cl·6H2O, mer-[Co(py)3Cl3] and mer-[Co(py)3(CO3)Cl] were studied by UV-Vis, far-IR and 1H, 13C, 15N NMR. The formation of Co-N bonds lead to variable in sign and magnitude changes of 1H NMR chemical shifts, heavily dependent on proton position, coordination sphere geometry and character of auxiliary ligands. 13C nuclei were deshielded upon Co(III) coordination, while 15N NMR studies exhibited ca. 85–110 ppm shielding effects (ca. 15–25 ppm more expressed for nitrogens trans to N than trans to Cl or O). 13C and 15N CPMAS spectra revealed a slight inequivalency of formally identical Co-py bonds in trans-[Co(py)4Cl2]Cl·6H2O and mer-[Co(py)3Cl3], suggesting for the latter complex an existence of distortion isomers. In chloroform, a spontaneous trans-[Co(py)4Cl2]Cl → mer-[Co(py)3Cl3] + py reaction was monitored by 1H NMR and UV-Vis. This process of py → Cl substitution allowed the design of a more convenient and efficient method of mer-[Co(py)3Cl3] preparation.

A series of Pd(II) and Pt(II) complexes with 6-mercaptopurine (6-Hmp) of formulae Pd(6-Hmp) 2 Cl 2 ( 1 ), Pd(6-mp) 2 ·2H 2 O ( 2 ), Pt(6-mp) 2 ·2H 2 O ( 3 ), Pt(6-mp)(dmso)Cl ( 4 ) was synthesized and studied by IR, far-IR, 1 H, 13 C, 15 N NMR. ( 1 ) has an ionic character and consists of distinct [Pd(6-Hmp) 2 ] 2+ cations and uncoordinated Cl − anions, whereas ( 2,3 ) are neutral species with central atoms bis-chelated by the deprotonated 6-mp − ligands. NMR studies suggest that S and N(7) are the complexation sites, while far-IR spectra indicate the square-planar geometry of Pd(II) or Pt(II). In ( 4 ) the Pt(II) atom is coordinated by one chelating 6-mp − anion, S-bonded dmso molecule and a terminal chloride. The antiproliferative activity in vitro of ( 2–4 ) was tested against human leukaemia HL-60 cells, being exhibited for ( 2 ) at the level ca. six times lower than in case of cisplatin.

The zinc triad metal chloride complexes with pyridazine of [M(pyridazine)Cl2]n type, M=Zn(II) (1), Cd(II) (2), Hg(II) (3), were synthesized. The crystal and molecular structures of 2 and 3 were studied by single crystal X-ray diffraction. They are isostructural polymers of formulae catena[bis(μ2-chloro)-(μ2-pyridazine-N,N′)]cadmium(II) and catena[bis(μ2-chloro)-(μ2-pyridazine-N,N′)]mercury(II). They crystallize in the orthorhombic Imma space group (2: a=7.056(1), b=7.447(1), c=13.113(1) A; 3: a=7.129(1), b=7.398(1), c=13.073(2) A). The central atoms have the geometry of square bipyramid and are bridged by axial pyridazines and equatorial chlorides. The Cd–N and Hg–N bonds are 2.371(3) and 2.407(5) A, the Cd–Cl and Hg–Cl being 2.6279(7) and 2.6626(12) A, respectively. The X-ray powder diffractograms suggest 1 has a similar structure, being different from the monomeric species Zn(pyridazine)2Cl2 (4), already described by several authors as the sole product of ZnCl2+pyridazine reaction. The 15N CPMAS-NMR measurements of 1–3 reveal significant shielding (65–90 ppm) of nitrogen nuclei upon the formation of coordination bondings, the observed low-frequency shifts decreasing with the atomic mass of the metal.

Platinum(II) complexes with 1,2,4-triazolo[1,5-a]pyrimidines of general formula trans-[PtCl2(dmso)(L)], where L=1,2,4-triazolo[1,5-a]pyrimidine (tp), 5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine (dmtp), 5,7-diphenyl-1,2,4-triazolo[1,5-a]pyrimidine (dptp), 5,7-ditertbutyl-1,2,4-triazolo[1,5-a]pyrimidine (dbtp) have been prepared by direct reaction between cis-[PtCl2(dmso)2] and respective 1,2,4-triazolo[1,5-a]pyrimidine in molar ratio M:L=1:1. All new platinum(II) compounds were characterized by 1H, 13C, 15N, 195Pt NMR and IR. Significant 15N NMR upfield shifts (75–87 ppm) were observed for N(3) atom indicating this nitrogen atom as a coordination site. Crystal structure of trans-[PtCl2(dmso)(dmtp)] (2) has been determinated. The molecular structure indicates that Pt(II) ion has the square-planar geometry with N(3) bonded dmtp, S-bonded dimethylsulfoxide and two trans chloride anions.

Palladium(II) complexes of formula [Pd(tp)2Cl2] 1, [Pd(dmtp)2Cl2]·H2O 2, [Pd(dptp)2Cl2]·H2O 3, [Pd(dbtp)2Cl2] 4a, 4b, where tp = 1,2,4-triazolo[1,5-a]pyrimidine, dmtp = 5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine, dptp = 5,7-diphenyl-1,2,4-triazolo[1,5-a]pyrimidine, dbtp = 5,7-di-tert-butyl-1,2,4-triazolo[1,5-a]pyrimidine, were prepared. The crystal structure of [Pd(dbtp)2Cl2]·0.5 C2H5OH 4c was resolved by X-ray diffraction analysis, exhibiting monomeric, nearly square-planar cis geometry and N(3) co-ordination. A small tetrahedral distortion from the co-ordination plane was observed. The Pd–Cl distances are 2.276(1) and 2.283(1) A, and Pd–N 2.042(3) and 2.040(3) A. Spectroscopic measurements (UV-VIS, IR, NMR) suggested analogous structures for 1, 2 and 3. Compounds 4a and 4b are most likely rotational isomers in solution and distortional isomers in the solid state. 15N–1H heteronuclear correlation NMR was measured for 2, 4a and 4b whereas 1 and 3 were characterized with 13C and 15N CP MAS. Significant shielding of the co-ordinated N(3) and adjacent C(2) or C(3a) nuclei was observed.

Copper(II) complexes of formula Cu2(CH2ClCOO)4(dmtp)2 (1) and Cu2(CN2ClCOO)4(dptp)2 (2), wheredmtp=5,7-dimethyl-1,2,4-triazolo-[1,5-α]-pyrimidine anddptp=5,7-diphenyl-1,2,4-triazolo-[1,5-α]-pyrimidine, were obtained. The X-ray diffraction analysis of 1 exhibited the dimeric structure with chloroacetate bridges. The coordination sphere of Cu(II) ion is a slightly distorted square pyramid, with 4 equatorial carboxylic oxygens and anaxially N(3) bonded dmtp molecule. The distance Cu–Cu is 2.7035(7) Aand the distance between Cu and O4 plane is 0.239(1) A(towards the axial ligand). The distances Cu–O are 1.954(2)–1.981(2) A,Cu–N 2.150(1) A. The angles O–Cu–O are 87.88(8)–90.56(8)° and166.04(6)–166.07(5)°, O–Cu–N 90.08(7)–103.76(7)°. The O4 plane is not perpendicular to the Cu · · · Cu line, the angles O–Cu–Cu being 82.04(5)–84.00(5)° and N–Cu–Cu169.54(4)°. Spectroscopic (IR, UV, EPR) and magnetic studies suggested that 2 has the analogous structure to 1.

Pd(II) and Pt(II) chloride organometallics with the deprotonated, N(1), C(2′)-chelating form of 2-phenylpyridine (2ppy*), i.e. [Pd(2ppy*)(μ-Cl)]2 (1) and [Pt(2ppy*)(μ-Cl)]2 (2), were studied by 1H, 13C, 15N, and 195Pt NMR in DMF-d7 and by 15N CP/MAS in the solid state. Both dimers immediately decompose in DMSO-d6, however, the products of this process are entirely different for 1 and 2. The cleavage of 1 is unusual among all described [M(2ppy*)(μ-X)]2 dimeric compounds as it yields, most likely, the [Pd(2ppy*)(DMSO-d6)2]+ [Pd(2ppy*)Cl2]− ionic pair, whereas 2 is known to undergo a more classical conversion into trans(S,N)-[Pt(2ppy*)(DMSO-d6)Cl]. The conclusions formulated for the above ionic pair were supported by quantum-chemical NMR calculations, calibrated specifically for this class of compounds (geometry optimization tested on molecular cluster, calibration of exact-exchange admixture in the PBE0 functional). The proposed computational approach is shown to be valid and suitable also for similar systems.

A review with 351 references. It collects the 15N and 31P NMR data for ca. 390 and ca. 340, respectively, complexes of transition metal ions such as Ni(0), Pd(0), Pt(0), Ni(II), Pd(II), Pt(II), Pd(IV), Pt(IV), Co(− 1), Rh(− 1), Rh(I), Ir(I), Co(III), Rh(III), Ir(III), Fe(− 2), Ru(− 2), Fe(II), Ru(II), Os(II), Cu(I), Ag(I), Au(I), Au(III), Zn(II), Cd(II), and Hg(II) with nitrogen-containing heterocycles (azines, azoles and azoloazines like purines or 1,2,4-triazolo-[1,5a]-pyrimidines), and their phosphorus analogues (phosphinines and phospholes). The 15N and 31P NMR coordination shifts, that is, the differences between 15N or 31P chemical shifts of the same nitrogen or phosphorus in the molecules of the complex and the ligand (Δ15Ncoord = δ15Ncompl − δ15Nlig; Δ31Pcoord = δ31Pcompl − δ31Plig), have been discussed in relation to some structural features of the reviewed coordination compounds, mainly to the type of the metal central ion and the donor atom in trans-position in respect to the concerned 15N or 31P nucleus.

(1)H, (13)C and (15)N NMR studies of gold(III), palladium(II) and platinum(II) chloride complexes with dimethylpyridines (lutidines: 2,3-lutidine, 2,3lut; 2,4-lutidine, 2,4lut; 3,5-lutidine, 3,5lut; 2,6-lutidine, 2,6lut) and 2,4,6-trimethylpyridine (2,4,6-collidine, 2,4,6col) having general formulae [AuLCl(3)], trans-[PdL(2)Cl(2)] and trans-/cis-[PtL(2)Cl(2)] were performed and the respective chemical shifts (delta(1H), delta(13C), delta(15N)) reported. The deshielding of protons and carbons, as well as the shielding of nitrogens was observed. The (1)H, (13)C and (15)N NMR coordination shifts (Delta(1H) (coord), Delta(13C) (coord), Delta(15N) (coord); Delta(coord) = delta(complex) - delta(ligand)) were discussed in relation to some structural features of the title complexes, such as the type of the central atom [Au(III), Pd(II), Pt(II)], geometry (trans- or cis-), metal-nitrogen bond lengths and the position of both methyl groups in the pyridine ring system.

1H, 13C and 15N NMR studies of iron(II), ruthenium(II) and osmium(II) tris-chelated cationic complexes with 2,2′-bipyridine and 1,10-phenanthroline of the general formula [M(LL)3]2+ (M = Fe, Ru, Os; LL = bpy, phen) were performed. Inconsistent literature 1H signal assignments were corrected. Significant shielding of nitrogen-adjacent protons [H(6) in bpy, H(2) in phen] and metal-bonded nitrogens was observed, being enhanced in the series Ru(II) → Os(II) → Fe(II) for 1H, Fe(II) → Ru(II) → Os(II) for 15N and bpy → phen for both nuclei. The carbons are deshielded, the effect increasing in the order Ru(II) → Os(II) → Fe(II). Copyright © 2010 John Wiley & Sons, Ltd.

A series of Pd and Pt chloride complexes with pyridine (py), 2,2'-bipyridine (bpy) and 1,10-phenanthroline (phen), of general formulae trans-/cis-[M(pY)(2)Cl-2], [M(py)(4)]Cl-2, trans-/cis-[M(py)(2)Cl-4], [M(bpy)Cl-2], [M(bPy)Cl-4], [M(phen)Cl-2], [M(phen)Cl-4], where M = Pd, Pt, was studied by H-1, Pt-195, and N-15 NMR. The 90-140 ppm low-frequency N-15 coordination shifts are discussed in terms of such structural features of the complexes as the type of platinide metal, oxidation state, coordination sphere geometry and the type of ligand. The results of quantum-chemical NMR calculations were compared with the experimental N-15 coordination shifts, well reproducing their magnitude and correlation with the molecular structure.