Coordination-induced keto–enol tautomerization in the formation of Ni2+ and Cu2+complexes of a fluorinated keto-diol

The fluorinated keto-diol (CF3)2C(OH)CH2C(=O)CH2C(CF3)2OH forms stable, neutral, 1:1 complexes of Ni2+ (6a) and Cu2+ (6b) with tetramethylethylenediamine (TMED) as coligand. The structure of each complex has been determined crystallographically; they are isomorphous and isostructural, monoclinic with space group Cc (No. 9). Complex 6a, C15H20F12N2NiO3, has a = 11.495(2), b = 15.516(2), c = 12.323(2) Å, β = 99.88(1)°, V = 2165.4(6) Å3Z = 4. Complex 6b, C15H20CuF12N2O3, has a = 11.603(2) b = 15.661(2), c = 12.276(2) Å, β = 99.75(2)°, V = 2198.5(6) Å Z = 4. In each, the metal is in square-planar geometry bonded to two alkoxide groups and two N atoms of TMED. A previous assignment of a zwitterionic structure to these complexes has been shown to be incorrect. Instead, the ligand is coordinated as the di-ionized enol tautomer (CF3)2C(–O−)CH2C(–O−)=CHC(CF3)2OH, the C=C double bond being external to the six-membered chelate ring. The remaining OH group of the ligand forms part of a second six-membered ring held together by hydrogen bonding.

Metal-selenolate chemistry: stereochemistry of adamantane-type clusters of formula [(μ-SePh)6(MSePh)4]2− (M = Zn and Cd)

The structures of three tetramethylammonium salts containing anions of formula [(μ-SePh)6(MSePh)4]2− (M = Zn and Cd) were determined by single crystal X-ray diffraction techniques. The Zn salt crystallizes in different space groups depending upon the solvent combination used in the synthesis. Thus crystals of (Me4N)2[Zn4(SePh)10], 1, grown from a mixture of methanol, acetonitrile, and acetone are triclinic, space group [Formula: see text] with cell dimensions a = 13.214(2), b = 23.859(2), c = 13.072(1) Å, α = 91.134(8), β = 113.350(8), γ = 79.865(9)°, and Z = 2. In the absence of acetone, a solvated crystal (Me4N)2[Zn4(SePh)10]•CH3CN, 2, is formed, which belongs to the monoclinic space group P21/n with a = 14.248(1), b = 39.722(2), c = 13.408(1) Å, β = 97.132(5)°, and Z = 4. The Cd salt (Me4N)2[Cd4(SePh)10], 3, crystallizes in the monoclinic space group P21/c, with a = 20.830(2), b = 14.282(1), c = 25.872(1) Å, β = 99.626(6)°, and Z = 4. These three salts are the first examples of homoleptic, tetranuclear selenolatometal(II) anions with (μ-Se)6M4 cages of adamantane-type stereochemistry. In each case the phenyl substituents of the bridging ligands adopt the configuration [aae, aae, aee, aee], which has the minimum number of two 1,3-axial–axial non-bonding substituent interactions. Keywords: selenolate complexes, synthesis, X-ray crystallography, isomerism, adamantane stereochemistry.

Synthesis, multinuclear magnetic resonance spectra, and chemistry of some complexes [(μ-SR)6(MX)4]2− (R = alkyl; M = Zn or Cd; X = Cl, Br, or I) and the X-ray structural analysis of (Et4N)2[(μ-SPri)6(CdBr)4]

The self-assembly method has been used to prepare a wide range of new adamantane-like anions of the type [(μ-SR)6(MX)4]2− (M = Zn or Cd; R = alkyl or benzyl; X = Cl, Br, or I) as their Et4N+ salts. Metal (111 or 113Cd) NMR data have been measured for the cadmium complexes, and also for many of the possible mixed-metal complexes [(μ-SR)6(CdX)n(ZnX)4−n]2−. In the complexes with mixed metals, the effects of Zn substitution on the metal chemical shifts are generally larger for the alkyl- and benzyl-thiolate complexes than for related benzenethiolate complexes. However, for [(μ-SPri)6(CdX)n(CdX′)4−n]2− (X/X′ = Cl/Br, Cl/I, or Br/I), substituent effects are no larger than found in some PhS−-bridged complexes. The reaction of [(μ-SPri)6(CdX)4]2− (X = Cl, Br, or I) with E′8 (E′ = S or Se) in CH2Cl2 gives [Cd4(μ4-E′) (μ-SPri)12(CdX)4]2− as the major species detectable by metal, 13C, and, where applicable, 77Se NMR. However, the reaction does not occur stoichiometrically. The compound (Et4N)2[(μ-SPri)6(CdBr)4] crystallizes in the monoclinic space group P21/c with cell dimensions a = 24.079(3) Å, b = 11.365(2) Å, c = 22.561(3) Å, β = 113.89(1), and Z = 4. The structure was refined to R(Rw) = 0.0663(0.0703) with the use of 2669 unique data with I > 2.5σ(I). The anion contains an adamantane-type (μ2-S)6Cd4 cage composed of a nearly regular Cd4 tetrahedron and a distorted S6 octahedron, the irregularity of which is caused by 1,3-interactions of the substituent groups on the sulfur atoms. The axial or equatorial dispositions of the six alkyl groups in the four fused M3S3 rings are [aae, aae, aee, aee]. For the zinc-group elements, this is the first example of an adamantane-like (μ-Salkyl)6M4 cage that has been characterized crystallographically. Keywords: cadmium complex, cadmium-111/113 NMR, thiolate complex, X-ray analysis, zinc complex.

Synthesis and multinuclear magnetic resonance study of some tin(IV) complexes of pyridine-2-thiolate and related ligands, and the X-ray structural analysis of Sn(C5H4NS)4•C5H5NS

Tin metal reacts with 2,2′-dithiobis (pyridine) in refluxing toluene to give the pyridine-2-thiolate complex Sn(C5H4NS)4, 1a. Multinuclear (77Se, 119Sn) magnetic resonance shows that ligand redistribution occurs in 1a:Sn(EPh)4 (E = S or Se) mixtures to give Sn(EPh)4−x(C5H4NS)x. From the pattern of the 119Sn chemical shifts of these series, compared with that of Sn(EPh)4−x(SR)x (R = simple alkyl or aryl group), the complexes are shown to be five-coordinate Sn(EPh)3(C5H4NS-N,S) when x = 1 and six-coordinate Sn(EPh)4−x(C4H4NS-S)x−2(C5H4NS-N,S)2 when x = 2–4. Reaction of Sn(SPh)2 and (C5H4NS)2 yields pure Sn(SPh)2(C5H4NS)2. The 13C NMR spectrum of Sn(C5H4NS-S)2 (C5H4NS-N,S)2 is an exchange average down to 178 K, probably as a result of fluxionality. The series Sn(EPh)4−x,(L′)x (E = Se, L′ =5-nitropyridine- or quinoline-2-thiolate, x = 0–4; E = S or Se, L′ = pyridine-2-thiolate-N-oxide, x = 0–2) can be prepared insitu by redox between Sn(EPh)4 and the disulfide (L′)2. Treatment of 1a with X2 (X = Br or E- gives SnX4−x(C5H4NS-N,S)x(x = 2 or 3), which have been characterized by NMR, and provides a new synthesis of the known dihalo complexes.In a recrystallization of 1a from CH2Cl2:hexane Sn(C5H4NS)4•C5H5NS, 2, was obtained, probably as a result of hydrolysis. The structure of 2 has been solved by single crystal X-ray diffraction techniques. The compound crystallizes in the orthorhombic space group Pbca (No. 61) with a unit cell of dimensions a = 17.132(2) Å, b = 15.337(2) Å, c = 21.268(3) Å, and Z = 8. Full-matrix least-squares on F led to agreement factors R = 0.0439 and Rw = 0.0426 for 3145 independent reflections with Fo > 2.5σ (Fo) and 206 variables. The molecule Sn(C5H4NS-S)2(C5H4NS-N,S)2 has highly distorted octahedral coordination about the tin atom, with the monodentate ligands in cis positions and the bidentate ligands attached with mutually cis nitrogen atoms. The Sn—S distances are 2.463(2)–2.542(2) Å and the Sn—N distances are 2.332(2) and 2.324(2) Å. The N—Sn—S angles in the chelate rings are 64.2(2) and 65.1(1)°. The molecule of pyridine-2-thione in the lattice is hydrogen-bonded to the N atom of one of the monodentate ligands in the tin complex, with a [Formula: see text] hydrogen bond distance of 1.92(7) Å. Keywords: pyridine-2-thiolate, selenium-77 NMR, tin-119 NMR, tin(IV) complexes, X-ray analysis.

Halogen and pseudohalogen substitution of some adamantanoid chalcogenate clusters [(μ-EPh)6(MEPh)4]2− using methylmercury and triphenyltin derivatives. A multinuclear nuclear magnetic resonance study

Multinuclear nmr (1H, 77Se, 111/113Cd, 119Sn, 199Hg, as appropriate) has been used to study Y−−EPh− exchange in Me2CO or MeCN between RnM′Y (RnM′ = Ph3Sn or MeHg; Y = Cl, Br, I, NCO, or NCS) and the adamantane-like anions [(μ-EPh)6(MEPh)4]2− (E = S, M = Zn, Cd, or Co; E = Se, M = Zn or Cd), as their tetraalkylammonium salts. Quantitative terminal substitution of the clusters occurs in most cases, giving [(μ-EPh)6(MEPh)4 − x(MY)x]2−(x = 1–4). However, reaction is incomplete for M = Cd, E = S or Se, RnM′Y = Ph3SnNCO or Ph3SnNCS and for M = Zn or Co, E = S, RnM′Y = MeHgI. Differences in the extents of reaction for Ph3SnY and MeHgY are consistent with the position of equilibrium in MeHgY:Ph3SnEPh mixtures.Group interchange provides a convenient alternative synthesis of the known halogen-substituted clusters [(μ-EPh)6(MY)4]2−(M = Zn or Cd, Y = Cl, Br, or I; M = Co, Y = Cl), and the first syntheses of [(μ-SPh)6(CoY)4]2− (Y = Br or I) and various pseudohalogen-substituted adamantanoid anions. The nuclei used for full direct nmr characterization of the new clusters in solution were: 77Se and 113Cd for [(μ-SePh)6(CdSePh)4 − x(CdY)x]2− (x = 1–4; Y = NCO or NCS); 77Se for [(μ-SePh)6(ZnSePh)4 − x(ZnY)x]2− (x = 1–4, Y = NCO or NCS); 113Cd for [(μ-SPh)6(CdSPh)4 − x(CdY)x]2−(x = 1–4; Y = NCO or NCS); 1H for [(μ-SPh)6(CoY)4]2− (Y = Br, I, NCO, or NCS). The first solution 1H nmr spectrum of [(μ-SPh)6(CoCl)4]2− is also reported.

Synthesis of 31P nmr spectroscopic study of [Ag(μ-R2PCH2PR2)3Ag]2+ (R = Me or Ph). Observation of an intramolecular "end-over-end" exchange of bridging R2PCH2PR2

Reaction of AgAsF6 with R2PCH2PR2 (R = Ph or Me) in a 2:3 ratio in MeNO2 or Me2CO produces the new compounds [Ag2(R2PCH2PR2)3](AsF6)2, which have been isolated in good yield. The analogous 107Ag-enriched compounds are produced using 107AgAsF6. The 2:3 compounds have interesting variable temperature 31P nmr spectra which have been studied in detail using the 107Ag-enriched compounds. The 31P nmr spectra of [107Ag2(Ph2PCH2PPh2)3](AsF6)2:[107Ag2(Me2PCH2PMe2)3](AsF6)2 mixtures at ambient probe temperature show the formation of the mixed ligand binuclear cations [107Ag2(Ph2PCH2PPh2)3−x(Me2PCH2PMe2)x]2+ (x = 1 or 2). By analogy, the two parent complexes also contain binuclear cations, and the limiting low temperature 31P nmr spectra of these can be interpreted in terms of the manxane structure, [107Ag(μ-R2PCH2PR2)3107Ag]2+. With increase in temperature, the 31P nmr spectra of the parents provide evidence for an intramolecular exchange process which is faster for R = Ph than for R = Me and which is shown to involve "end-over-end" exchange of bridging R2PCH2PR2. This type of exchange has not been observed previously for these ligands. With Me2CO as solvent, an approximate value of the enthalpy of activation for exchange is 59 kJ mol−1 for [107Ag((μ-Ph2PCH2PPh2)3107Ag]2+ and 50 kJ mol−1 for [107Ag(μ.-Me2PCH2PMe2)3107Ag]2+.

Syntheses and X-ray structural analyses of [(C6H5)4As][Sn(EC6H5)3], E = S and Se

Stannous chloride, in solutions containing at least three mole equivalents of NaEC6H5, E = S and Se, forms triligated anions which crystallize readily as the tetraphenylarsonium salts, [(C6H5)4As[Sn(SC6H5)3], 1, and [(C6H5)4As][Sn(SeC6H5)3], 2. The crystals so formed are isomorphous, and their structures have been determined by single crystal X-ray diffractometry techniques. The salts crystallize in the monoclinic space group P21/c, with four formula units in unit cells of dimensions a = 10.760(1), b = 17.515(2), c = 20.247(3) Å, β = 104.71(1)° for 1, and a = 10.885(2), b = 17.587(2), c = 20.612(2) Å, β = 105.47(1)°, for 2. The structures have been refined by full-matrix least-squares techniques on F to agreement factors R = 0.024 (4780 observations with Fo > 3σ(Fo)) for 1, and R = 0.030 (3442 observations with Fo > 3σ(Fo)) for 2. The discrete [Sn(EC6H5)3]− anions are isostructural; the three S or Se atoms form the base of a triangular pyramid whose apex is occupied by the Sn atom. Two Sn—S distances in 1 are 2.532(1) and the third 2.552(1) Å, while in 2 the Sn—Se distances are 2.649(1), 2.650(1), and 2.671(1) Å. Angles at the Sn atom are 89.91(3), 90.55(3), and 96.73(3)° in 1, and 88.74(3), 89.72(3), and 97.27(3)° in 2. In both anions all three phenyl groups adopt a propeller-like conformation and are disposed in equatorial positions above the basal plane of chalcogen atoms. These salts represent the first thiolato- and sele-nolatostannates(II) to be characterized structurally. Tin-119 nmr spectra confirm that the [Sn(EC6H5)3]− ions are the same anionic Sn(II) species recently prepared insitu in solution.