Gregory J. Grant

Heteroleptic platinum(II) complexes of macrocyclic thioethers and halides: the crystal structures of [Pt(9S3)Cl2], [Pt(9S3)Br2], and [Pt(9S3)I2]

Abstract The synthesis, spectroscopic, and crystal structures of three heteroleptic thioether/halide platinum(II) (Pt(II)) complexes of the general formula [Pt(9S3)X2] (9S3=1,4,7-trithiacyclononane, X=Cl−, Br−, I−) are presented. All three 9S3/dihalo complexes form very similar structures in which the Pt(II) center is surrounded by a cis arrangement of two halides and two sulfur atoms from the 9S3 ligand. The third sulfur from the 9S3 forms a long distance interaction with the Pt center resulting in an elongated square pyramidal structure with a S2X2+S1 coordination geometry. The distances between the Pt(II) center and axial sulfur shorten with larger halide ions (Cl−=3.260(3) A>Br−=3.243(2) A>I−=3.207(2) A). These distances are consistent with the halides functioning as π donor ligands, and their PtS axial distances fall intermediate between Pt(II) thioether complexes involving π acceptor and σ donor ligands. The 195Pt NMR chemical shift values follow a similar trend with an increased shielding of the platinum ion with larger halide ions. The 9S3 ligand is fluxional in all of these complexes, producing a single carbon resonance. Additionally, a related series of homoleptic crown thioether complexes have been studied using 195Pt NMR, and there is a strong correlation between the chemical shift and complex structure. Homoleptic crown thioethers show the anticipated upfield chemical shifts with increasing number of coordinated sulfurs. Complexes containing four coordinated sulfur donors have chemical shifts that fall in the range of −4000 to −4800 ppm while a value near −5900 ppm is indicative of five coordinated sulfurs. However, for S4 crown thioether complexes, differences in the stereochemical orientation of lone pair electrons on the sulfur donors can greatly influence the observed 195Pt NMR chemical shifts, often by several hundred ppm.

Synthesis and complexation studies of mesocyclic and macrocyclic polythioethers XIV. Crown thioether complexes of palladium(II) and platinum(II)

Abstract This paper describes the synthesis and characterization of several crown thioether complexes of Pt(II) and Pd(II). We wish to report the syntheses and X-ray crystal structures of both the Pd(II) and Pt(II) complexes with the macrocyclic thioether complex, 1,4,7,11,14,17-hexathiacycloeicosane (20S6). Crystal data for [Pd(20S6)](PF6)2: C14H28F12P2PdS6; monoclinic, space group P2 1 c ; a = 12.910(3) A , b = 9.810(20) A , c = 22.103(6) A , β = 102.170(20)°, V = 2700.39 A 3 ; Z = 4; R = 0.055; D = 1.931 g cm −3 ; 6346 reflections measured. Crystal data for [Pt(20S6)](PF6)2·CH3NO2: C15H31F12NO2P2PtS6; monoclinic, space group Cc; a = 12.321(5) A , b = 14.608(7) A , c = 17.032(5) A ; β = 98.15(3)°, V= 3034.55 A 3 ; Z= 4; R = 0.036; D = 2.045 g cm −3 ; 2777 reflections measured. Neither complex exhibits any significant electrochemistry or any visible absorption bands. Both complexes crystallize in the same linkage isomer where the metal ion is surrounded by a distorted square planar arrangement of four sulfur atoms. Two sulfur atoms that are adjacent to each other in the macrocyclic ring remain uncoordinated. 13C NMR spectroscopy reveals the presence of additional isomers in solution. We also wish to report the synthesis and X-ray crystal structure of the crown thioether complex, bis(1,4,7-trithiacyclodecane)platinum(II) hexafluorophosphate, [Pt(10S3)2](PF6)2. The two 10S3 ligands are arranged around the platinum in pseudooctahedral fashion to yield the meso stereoisomer. Four of the six sulfur atoms from the 10S3 ligands form a square planar arrangement around the platinum (mean Pt-Sequatorial bond distance = 2.30 A). The remaining two sulfurs are coordinated axially at a much greater distance from the Pt (Pt-Saxial = 3.21 A). Crystal data for [Pt(10S3)2](PF6)2·2CH3NO2: C16H34PdS6P2F12N2O4; monoclinic, space group C2 c ; a = 22.473(9) A , b = 12.071(4) A , c = 11.186(3) A ; β = 94.14(3)°, V= 3026.53 A 3 ; Z = 4; R = 0.046; D = 1.991 g cm −3 ; 2836 reflections measured. Cyclic voltammetry measured in acetonitrile showed a single, reversible oxidation wave at +0.324 V versus F c F c + . Variable temperature 13C NMR spectroscopy shows no solvent-complex interactions, in contrast to the Pd(II) analog. The palladium(II) complex, [Pd(ttn)2](PF6)2, which contains the acyclic thioether 2,5,8-trithianonane (ttn) was also prepared.

Crown thioether complexes of trivalent transition metal ions. The crystal structure of [Cr(18S6)Cl3]☆

Abstract The structure of the macrocyclic complex, [Cr(18S6)Cl 3 ] (18S6=1,4,7,10,13,16-hexathiacyclooctadecane), has been determined by single-crystal X-ray diffraction, the first Cr(III)-thioether coordination complex to be structurally characterized. An octahedral environment of three sulfur atoms and three chlorine atoms around the Cr(III) center is observed in the complex, and the stereoisomer obtained in our case is the one in which only three adjacent sulfur atoms in the 18S6 ligand are bonded to the CrCl 3 moiety. This is also the first reported structure of this atypical coordination mode for the 18S6 ligand which typically coordinates in hexadentate fashion or as a bridging ligand. The syntheses, characterization, and electronic spectra of a series of eleven additional thioether complexes of Cr(III) are described. All twelve Cr complexes have the general formula CrLCl 3 and potentially tetra-, penta- and hexadentate thioether ligands all function as tridentate ligands coordinating to a single metal center. The electronic spectra for the Cr complexes are all similar and enable ligand field parameters readily to be calculated. The thioethers function as weak field ligands, and there is a substantial reordering in their spectrochemical series when compared to the series obtained with softer metal ions such as Ni(II) or Fe(II). In addition, the synthesis and characterization of two novel V(III) complexes with the general formula VLCl 3 where L = 1,4,7-trithiacyclononane (9S3) or 1,4,7-trithiacyclodecane (10S3) are described. These are the first two reported examples of thioether complexes of vanadium(III). The reaction between 9S3 and the anion [Re 2 Cl 8 ] −2 has also been investigated.

Synthesis and structure of a platinum(II) molecular square incorporating four fluxional thiacrown ligands: The crystal structure of [Pt4([9]aneS3)4(4,4′-bipy)4](OTf)8

A Pt(II) molecular square containing four fluxional trithiacrown ligands at the corners is prepared by transition metal-mediated self-assembly.

Heteroleptic platinum(II) complexes with crown thioether and phosphine ligands: the crystal structures of [Pt(9S3)(PPh3)Cl](PF6)·CH3NO2 and [Pt(10S3)(PPh3)Cl](PF6)

Abstract We wish to report the synthesis, spectroscopic properties, and crystal structures of two Pt(II) heteroleptic complexes with triphenylphosphine (PPh3), chloride, and the crown trithioethers 9S3 (1,4,7-trithiacyclononane) or 10S3 (1,4,7-trithiacyclodecane). Both complexes have the general formula [Pt(L)(PPh3)Cl](PF6) (L=9S3 or 10S3) and form similar structures in which the Pt(II) center is surrounded by a cis arrangement of the chloride, the P donor from the phosphine, and two sulfur atoms from the 9S3 ligand. The third sulfur in each structure forms a longer interaction with the platinum resulting in an elongated square pyramidal structure. The 195Pt NMR chemical shifts for both complexes show a value near −4100 ppm, consistent with a cis-PtS2PCl coordination sphere. The trithioethers in both complexes are fluxional, resulting in relatively simple 13C NMR spectra for them (9S3, one line; 10S3, four lines). Although the fluxional behavior of the 9S3 ligand in platinum group metal complexes is well-documented, our NMR and structural data confirm definite fluxional behavior of the 10S3 ligand for the first time.

Homoleptic Group 12 metal complexes of macrocyclic thioethers: the crystal structures of bis(1,4,7-trithiacyclodecane)M(II) perchlorate: M(II)=zinc(II), cadmium(II), mercury(II) ☆

Abstract We wish to report the crystal structures for a series of homoleptic complexes involving the three Group 12 family members with the crown thioether 1,4,7-trithiacyclodecane (10S3). The ligand coordinates in tridentate fashion and readily forms bis complexes with the d10 metal ions, Zn(II), Cd(II), and Hg(II). The three compounds have the general formula [M(10S3)2](ClO4)2 and are isostructural. The three crystal structures show the two 10S3 ligands arranged in a trans or anti fashion around the metal center in a distorted octahedral fashion to yield the meso stereoisomer. All three complexes show hexakis(thioether) octahedral coordination which is unusual for these Group 12 metal ions. The mean M–S bond distances increase as one moves down the family although there is only a modest increase between the Cd and Hg complexes (Zn: 2.4965(10) A, Cd: 2.6523(6) A, Hg: 2.6870(16) A). In sharp contrast to crown thioether complexes of other metal ions, the majority of the M–S bond lengths in these 10S3 complexes are shorter than those found in their 9S3 analogs. A simple four line 13C{1H} NMR spectrum is obtained for the three complexes. Variable temperature 13C{1H} NMR experiments performed on the Hg(II) complex suggest a rapid intermolecular exchange of the 10S3 ligands is occurring. The Cd complex shows a singlet in its 113Cd{1H} NMR spectrum with a chemical shift at 612 ppm, in agreement with a hexakis(thioether) coordination environment.

Synthetic, electrochemical, and structural studies on heterobimetallic crown thioether complexes with Group 10 metals: the crystal structures of [Pt(9S3)(dppf)](PF6)2·CH3NO2 and [Pd(9S3)(dppf)](PF6)2·CH3NO2

Abstract The syntheses, electrochemistry, and crystal structures for two new Pt(II) and Pd(II) heteroleptic bimetallic complexes with the crown trithioether 1,4,7-trithiacyclononane (9S3) and the diphosphine ligand, 1,1′-bis(diphenylphosphino)ferrocene (dppf) are reported. Both complexes have the general formula [M(9S3)(dppf)](PF6)2 (M=Pt or Pd) and exhibit the anticipated structure forming a distorted cis square planar array of two sulfur atoms from the 9S3 and two phosphorus atoms. These are, to our knowledge, the first reported examples of dppf transition metal complexes involving a thioether as the ancillary ligand. The dppf ligand functions as a bidentate chelator to a single metal center, and the third 9S3 sulfur atom does interact with the metal ion from a greater distance (PtS=2.8167(8) A; PdS=2.7916(5) A) to yield an elongated square pyramidal geometry. The two structures are isomorphous with very similar bond distances and angles. The values for the 31P-NMR chemical shifts (Pt=15.09 ppm, Pd=−0.47 ppm), the 195Pt-NMR chemical shift for the Pt(II) complex (−4353 ppm) and 1J(195Pt–31P) coupling constants (3511 Hz) are all consistent with a cis-MS2P2 square planar coordination sphere. The 9S3 ligand is fluxional in solution for both complexes. The electrochemistry of both complexes is dominated by a reversible Fe(II)/Fe(III) couple from the ferrocene moiety (E1/2=+721 mV for Pt(II), +732 mV for Pd(II), both versus Fc/Fc+).

The synthesis and structure of bis(1,4,7-trithiacyclodecane)-ruthenium (II) perchlorate: the meso diastereoisomer☆

The synthesis of the Ru(II) crown thioether complex, bis(1,4,7-trithiacyclodecane) ruthenium (II) perchlorate, [Ru(10S3)2](ClO4)2, and a study of its properties utilizing single crystal X-ray diffraction, electronic spectroscopy, 13C NMR spectroscopy and cyclic voltammetry is reported. The crystal structure shows the two 10S3 ligands are arranged in a trans or anti fashion around the ruthenium (II) center in nearly octahedral fashion to yield the meso stereoisomer. 13C NMR spectroscopy demonstrates that this stereoisomer is also the predominant one observed in solution, in contrast to the Co(III) and Fe(II) complexes. The electronic absorption spectrum is similar to other previously observed hexakis (thioether) ruthenium (II) complexes with d-d transitions at 346 and 297 nm. The electrochemical behavior is also similar to related Ru(II) complexes and shows a single quasi-reversible oxidation wave at + 1.37 V versus Fc/Fc+. Crystal data for [Ru(10S3)2](ClO4)2: C14H28Cl2O8RuS6; monoclinic, space group P21/c; a = 7.391(2), b = 9.480(2), c = 17.351(3) A; β = 97.10(2)0, V = 1206.4(5) A3; Z = 2; R = 0.0521; D = 1.896 g cm−3; 3211 reflections measured. The properties of the complex are compared with the congeneric Fe complex.

Transition metal complexes with macrocyclic oxathiaethers

Abstract Complexation studies with Ni(II), Co(III), Co(II), Cd(II), and Cu(II) for the two mixed oxathia crown ligands 1-oxa-4,7-dithiacyclononane (9S2O) and 1,10-dioxa-4,7,13,16-tetrathiacyclooctadecane (18S4O2) are reported. These ten complexes have been characterized by a variety of means including electronic spectroscopy, cyclic voltammetry, and nuclear magnetic resonance spectroscopy. Furthermore, the complexes [Ni(18S4O2](BF4)2, [Cu(9S2O)2](BF4)2 and [Ni(9S2O)2](ClO4)2, have been characterized by single crystal X-ray diffraction. For the complex [Ni(18S4O2](BF4)2 the diastereoisomer obtained is the one which contains the two oxygen atoms trans to each other and a meridional positioning of the diethylene SOS moiety. Selectivity for this particular stereoisomer is also supported by NMR data for the Cd(II) and Co(III) complexes, and this selectivity arises from the conformational preferences of the individual CO and CS bonds in the macrocycle. Both the nickelsulfur and nickeloxygen bonds in the complex are highly compressed due to the rigid macrocyclic structure and are among the shortest of these types of bonds found in any crown Ni(II) complex. The copper(II) complex, [Cu(9S2O)2](BF4)2, shows an interesting Jahn–Teller distortion from an octahedral geometry resulting in coordinate bonds which are all remarkably similar in length (CuS(4) 2.3293(6); CuS(7) 2.3336(6); and CuO(1) 2.355(2) A). The oxygen atoms are found in a trans position around the copper(II) center, and the axial CuO bonds are elongated due to the Jahn–Teller distortion. In all of these complexes, the two oxathiaether ligands function as much weaker field ligands than do their crown thioether analogs. Also, cyclic voltammetric experiments reveal that the oxathia crowns do not have the ability to stabilize less common metal oxidation states, a common property of many crown thioether ligands.

Complexation and conformational analysis studies of 11-membered ring crown trithioethers

Abstract We wish to report the synthesis of a series of transition metal complexes with two isomeric 11-membered ring trithioethers, 1,4,7-trithiacycloundecane (11S3-147) and 1,4,8-trithiacycloundecane (11S3-148). With respect to Ni(II), Fe(II), Co(II), Co(III), and Ru(II), the two function as relatively strong field ligands, but their ligand field strengths fall between the stronger field and smaller ring trithioether ligands such as 1,4,7-trithiacyclononane(9S3) and the larger ring and weaker field ligand, 1,5,9-trithiacyclododecane(12S3). Complexes of both ligands with first row transition metals are much more sensitive to solvolysis reactions than the analogous 9S3 complexes. 13 C NMR spectroscopy shows that there is little stereoisomer selectivity between the cis and trans diastereoisomers for the bis complexes of 11S3-147. The complex [Pd(11S3-147) 2 ] 2+ does not display the unusual spectroscopic and electrochemical properties observed in smaller ring Pd(II) complexes. Its absorption spectrum does not show any d–d transitions and an irreversible ligand-centered oxidation is observed. A conformational analysis study for both macrocycles showed that neither has a lowest energy conformation suitable for tridentate coordination. The effects of the lack of pre-organization dominate the complexation behavior of the two macrocyclic ligands.