Adriana Lorenzotti

Group 12 metal complexes of tetradentate N2O2–Schiff-base ligands incorporating pyrazole: Synthesis, characterisation and reactivity toward S-donors, N-donors, copper and tin acceptors

Abstract New [M(Q)2(X)] derivatives (where M=Zn, Cd or Hg; Q=1-phenyl-3-methyl-4-R(C=O)-pyrazolon-5-ato; in detail: QL, R=C6H5; QB, R=CH2C(CH3)3; QS, R=CH(C6H5)2; X=EtOH or H2O) have been synthesised and characterised. These compounds undergo a condensation reaction with the appropriate diamine in ethanol, affording novel Schiff-base metal derivatives [M(diaquo)bis(1-phenyl-3methyl-4-R(C=N)-pyrazolone)(CH2)ndiimmine] (LnH2, R=C6H5, n=2, 3 or 4; BnH2, R=CH2C(CH3)3, n=2, 3 or 4; SnH2, R=CH(C6H5)2, n=2 or 3; M=Zn, Cd or Hg). These compounds possess a six-coordinate metal environment. A 113Cd NMR study has been carried out on cadmium derivatives. The derivative [Zn(L2)(H2O)2] reacted with CuCl2 and with Cu(ClO4)2 affording [Cu(QL)2] and [Cu(en)2](ClO4)2 (en=ethylendiamine), respectively, upon breaking of the C=N bond in the Schiff-base donor. In addition [Zn(L2)(H2O)2] reacted with 1,10-phenanthroline (phen), yielding the derivative [Zn(QL)2(phen)]. Whereas when [Zn(L2)(H2O)2] reacted with CdCl2, formation of [Cd(L2)(H2O)2] due to exchange of the metal centre was observed. Finally the derivative [Zn(L2)(Hmimt)], likely containing a five-coordinate ZnN2O2S central core, has been obtained from the exchange reaction between [Zn(L2)(H2O)2] and 1-methylimidazolin-2-thione (Hmimt).

Organotin derivatives of 4-acyl-5-pyrazolones. Crystal structure of trans-di(t-butyl)bis(1-phenyl-3-methyl-4-benzoyl-pyrazolon-5-ato)tin(IV)

Abstract Stable, six-coordinated Q 2 SnRX compounds have been prepared where QH is 1-phenyl-3-methyl-4-R′C(O)-pyrazol-5-one (R′ = Me, Ph) X = Cl or R, and R = Cl, Me, Et, i-Pr, n- and t-Bu, vinyl, benzyl or phenyl. They are not fluxional when X = Cl or Ph or X = R = t-Bu. The 119 Sn NMR chemical shift is a function of the number of chloride groups. Owing to crowding of the ligands, in the title molecule the CSnC axis is bent (150.0(5)°) and the SnC bonds and two of the four SnO bonds are long; 2.20(1) for the SnC, 2.381(7) and 2.461(6) vs. 2.145(5) and 2.135(6) A for SnO.

Synthesis and spectroscopic investigations (IR, NMR and Mössbauer) of tin(IV) and organotin(IV) derivatives of bis(pyrazol-1-yl) alkanes: X-ray crystal structures of bis(4-methylpyrazol-1-yl) methane and its dimethyltin(IV) dichloride adduct

A series of 1:1 adducts of the type [(L)RnSnX4−n]·zH2O (L ≡ bis(4-methylpyraazol-1-yl)ethane (L4), bis(3,4,5-timethylpyrazol-1-yl)methane (LT), 1,2-bis(pyrazol-1-yl)ethane (LA) or 1,2-bis(3,5-dimethylpyrazol-1-yl)ethane (LB); R ≡ Me, Et, Bu or Ph; X ≡ I, Br or Cl; n = 0, 1 or 2; z = 1, 1.5 or 2), and the likely polynuclear [(LA)5(SnCl4)4]·(H2O)5 and [(LB)2(SnCl4)3]·12[Et2O] have been characterized in the solid state and in solution by analyses, spectral (IR, Mossbauer, and 1H, 13C and 119Sn NMR) data and conductivity measurements. When LT reacts with SnCl4, cleavage of a carbon (sp3)-nitrogen bond was observed and the adduct [(3,4,5-trimethyl-pyrazole)2SnCl4] was obtained. The diorganotin(IV) complexes generally dissociate in chloroform or in acetone solution, while the trichlorotin(IV) and tetrachlorotin(IV) adducts probably retain the hexacoordinate configuration. The crystal structures of L4 and of the adduct [(L4)(CH3)2SnCl2] have been determined by X-ray analysis. In the adduct the tin atom is coordinated to two halide atoms, two methyl groups and two N atoms, with trans-(CH3)2Sn in a slightly distorted octahedral configuration. The long SnN bond distance (2.436(6)A) indicated weak donor ability of the N2 donor L4. Comparison is made with the X-ray crystal structures of several R2SnX2N2-type compounds.

Tin(IV) and organotin(IV) derivatives of novel β-diketones: II. Mono- and diaryltin(IV) complexes of 1-phenyl-3-methyl-4-R(CO)-pyrazol-5-one (R=CCl3, OCH3, OC2H5). Crystal and molecular structure of trans-dibenzylbis(1-phenyl-3-methyl-4-methoxycarbonyl-pyrazolon-5-ato)tin(IV), (C7H7)2Sn(QOMe)2

Abstract A series of new tin(IV) and organotin(IV) derivatives has been synthesized. In basic (triethylamine) chloroform solution five- [R 2 SnCl(Q * )] and six-coordinate [R 2 Sn(Q * ) 2 ] tin(IV) derivatives (HQ * =1-phenyl-3-methyl-4-trichloroacetylpyrazol-5-one; R=Ph, Bz) are obtained. In basic (KOH) alcoholic R′OH solution (R′=Me, Et) [R 2 Sn( Q O R ′ ) 2 ] and [RSnCl 2 ( Q O R ′ )] derivatives (Q OR =1-phenyl-3-methyl-4-alkoxycarbonyl-pyrazolon-5-ato) are obtained, upon cleavage of the C–CCl 3 bond in the starting HQ * donor. From interaction between HQ * and SnCl 4 in refluxing dichloromethane the adduct SnCl 4 (HQ * ) was isolated. Additionally the donor HQ * reacts with RSnCl 3 (R=Ph, Bu n ) in basic (triethylamine) tetrachloromethane solution to form the salt-like products [Et 3 NH] + [RSnCl 3 (Q * )] − . All the compounds were characterized by analytical and spectral (IR, far-IR, 1 H, 13 C and 119 Sn NMR) data. The diffraction study of the complex Bz 2 Sn(Q OMe ) 2 shows a six-coordinate tin in a distorted octahedral frame, with the Bz groups trans to each other. The Bz–Sn–Bz bond angle is 164.5(4)° and the Sn–O distances are 2.105(6) and 2.359(7) A in one ligand and 2.109(7) and 2.329(7) A in the other. We find that in bis(pyrazolonate)diorganotin complexes structural features such as bite angle, difference of Sn–O bond length and O–Sn–O bond angles are functions of the organometallic C–Sn–C bond angle.

Adducts from mercury(I) and mercury(II) compounds with Bispyrazolylalkanes.X-Ray crystal structure of Bis(3,5-dimethylpyrazol-l-yl)methane(dicyano)-mercury(II)

Abstract The 1:1 adducts between thebis(3,5-dimethylpyrazol-1-yl)methane (L′-L′) or 2,2′-bis(pyrazol- 1-yl)propane (L″L″) ligand and HgX 2 (with X = Cl, CN or CO 2 CF 3 ) have been obtained as well as [(L′L′) 2 ]Hg(ClO 4 ) 2 and the mercury(I) derivative (ligand) 2 Hg 2 (ClO 4 ) 2 . The adducts have been characterized from analytical and spectral data (IR, proton and 13 C NMR). Four-coordinated mercury is present in (L′L′)Hg(CN) 2 , in which the metal-(NN) 2 C ring adopts an asymmetric boat form. The molecular parameters are significantly different for the two independent molecules, the CHgC angles and the two Hg-N distances being 163.1(9)°and 2.55(1) plus 2.70(1) A in the one case, and 148.2(8)° and 2.40(1) plus 2.51(1) A, in the other; correspondingly the N-Hg-N angle, the ‘bite’ of the ligand, ranges from 79.0(5)° to 71.7(4)°, a value outside the range previously reported.

Tin(IV) and organotin(IV) adducts of bis(3,5-dimethylpyrazol-1-yl)methane or of 2,2′-bis(pyrazol-1-yl)propane and their behaviour in solution

Abstract Adducts of bis(3,5-dimethylpyrazol-1-yl)methane or 2,2′-bis(pyrazol-1-yl)propane with tin(IV), trimethyl-, or triphenyl-tin(IV) halides as well as of the former ligand with diphenyl-, or dimethyl-tin(IV) halides have been isolated and characterized. Solution data ( 1 H, 13 C, 119 Sn NMR spectra, conductivity measurements and molecular weight determinations) show that the adducts from the less acidic acceptors [(Me 2 pz) 2 CH 2 ] 3 (Me 2 SnCl 2 ) 2 and [(Me 2 pz) 2 CH 2 ]Ph 2 SnCl 2 undergo extensive dissociation.

Silver derivatives of various bis(pyrazol-1-yl)alkanes: their behaviour in solution and X-ray crystal structure of [{Me2C(pz)2}2Ag]ClO4

Abstract Various bis(pyrazol-1-yl)alkanes, (pz)2ClR2 (R  Me and pzH = pyrazole; R  H, pzH = pyrazole, 3,5- dimethylpyrazole or 4-nitropyrazole (L3)), give 1:1 adducts with silver(I) nitrate or methanesulphonate and 2:1 adducts with silver perchlorate or fluoroborate. In [{Me2}C(pz)2}2Ag]ClO4 four coordination is found but rarely tetrahedral because of the steric misfit of the ligand which forms NAgN angles of 82.6 or 83.8(1)°; the AgN distances range from 2.247 to 2.432(4) A. In solution, according to combined evidence from spectra (1H and 13C), conductivity and molecular weight determinations, the (pz)2CR2 ligand is not displaced by acetone, is partially displaced by dimethyl sulphoxide or, in the case of (L3)2AgNO3, by nitrate, in agreement with the peculiar behaviour of L3.

Synthesis, characterization and reactivity of coordination compounds of group 12 metals containing the N2-donor ligand bis(3,4,5-trimethylpyrazol-1-yl)methane

Abstract The interaction between bis(3,4,5-trimethylpyrazol-1-yl)methane, LT, and several MX2, salts, gives 1:1 [LT]MX2 (M = Zn, Cd or Hg; X = Cl, Br or I; M = Zn, X = trifluoraccetate, M = Hg, X = CN, SCN or saccharinate) and 2:1 [LT]2MX2 adducts (M = Zn, X = NO3, ClO4, BF4, B(C6H5)4 or CF3SO3; M = Cd, X = NO3, ClO4 or BF 4; M = Hg, X = ClO4) which are air- and thermally stable, while the reaction of LT with Hg(CF3COO)2 gives the basic salt [LT]Hg(CF3COO)2· 5 4 HgO. The adduct [LT]ZnCl2 readily reacted with 1-phenyl-3-methyl-4-benzoyl-pyrazol-5-one (Q′H), in the presence of a base, to yield the mixed-ligand complex [LT(Q′)2Zn], whereas (Q′)2Cd·[H2O] and (Q′)2Hg·[Et2O] were obtained when a similar reaction was carried out with [LT]CdI2 and [LT]HgCl2, respectively, as starting materials. The compounds [LTZnCl2 related with the anionic pyrazolato ligand (pz−) and with the neutral 1-methylimidazole (ImH′) yielding the complexes (pz)2Zn and (ImH′)2ZnCl2, respectively. Displacement of the ligand LT was observed also from the reaction of [LT]CdBr2 with 4-phenylimizadole (ImH∗) and from the reaction of [LT]ZnCl2 and [LT]ZnBr2 with 2,2′-bipyridyl (Bipy), while no interaction was observed with pyridine (py), pyrazole,(pzH), 4-bromopyrazole (4-BrpzH) or 3,5-dimethylpyrazole (3,5-Me2pzH). All the compounds obtained were characterized from analytical and spectral data (IR, far-IR, 1H and 13C).

Adducts Between Bis(1,2,4-Triazol-1-yl)Methane and Group 11, 12, or 14 Compounds

Abstract The title ligand gave adducts with silver(I), zinc(II), cadmium(II), mercury(II), mercury(I), and tin(IV) where it must be exopolydentate. The 1H and 13C nmr spectra, electrical conductivity, and molecular weights were determined in dimethylsulphoxide.

Tin (IV) and organotin (IV) complexes containing mono or bidentate N-donor ligands. V. Imidazole and imidazoline-2-thione derivatives: synthesis and spectroscopic characterization. Comparison with other imidazole tin (IV) complexes

Abstract The reactions of imidazole (L1), benzimidazole (L2), 2-phenylimidazole (L3), 1-acetylimidazole (L4), imidazoline-2 (1,3H)-thione (L5) and 1-methyl-imidazoline-2 (3H)-thione (L6) with RnSnCl4−n (R=Me, Bun or Ph; n=1, 2 or 3) were investigated. Twenty-seven novel adducts were obtained and characterized by analytical (elemental analysis, conductivity and vaporimetric molecular weight measurements) and spectral (IR, far IR, 1 H and 119 Sn NMR) data. The ligands L 1, L 2, L 3 and L 4 behave in the monodentate N-donor fashion, whereas L 5 and L 6 behave as monodentate S-donor molecules. Breaking of the N–CO bonds and protonation of imidazolate moiety occurred when the donor L 4 reacts with organotin acceptors in not rigorously anhydrous conditions. The behavior of the adducts in acetone and chlorinated solvents is also discussed. Comparison was made with related organotin (IV) complexes of imidazoles.