Dante Leonesi

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).

Tin(IV) and organotin(IV) derivatives of novel β-diketones. III Diorgano- and dihalotin(IV) complexes of 1,3-dimethyl-4-R(CO)-pyrazol-5-one (R=CH3, C6H5) and the crystal structure of trans-dicyclohexylbis(1,3-dimethyl-4-acetylpyrazolon-5-ato)tin(IV)

Abstract Several diorgano- and dihalotin(IV) derivatives of new β-diketonate donors, 1,3-dimethyl-4-R(CO)pyrazol-5-ones (R=Me, QDH; R=Ph, QMH) have been synthesized and characterized with analytical and spectroscopic methods. They are stable monomeric species, very soluble not only in aromatic and chlorohydrocarbon solvents, but also in alcohols and hydroalcoholic solutions. In the solid state, the diorganotin(IV) derivatives adopt a skewed trapezoidal bipyramidal geometry. The X-ray structure of bis(1,3-dimethyl-4-acetylpyrazolon-5-ato)dicyclohexyltin(IV) shows marked distortion of the organometallic C–Sn–C angle (155°) and two different sets of Sn–O distances. The factors affecting the distortion of this type of complex are discussed. The dihalotin(IV) derivatives (Q)2SnX2 (X=F, Cl, Br and I) are likely cis octahedral in the solid state, whereas in solution they exist as a mixture of cis and trans isomers. 119Sn-NMR solution data are discussed and related to electronic and steric properties of the β-diketonate donor, and also to the nature of the halo and organic groups bound to tin.

Synthesis, characterization and spectroscopic investigations of tin(IV) and organotin(IV) derivatives of 4-aroyl-5-pyrazolones. Crystal structure of trans-dimethylbis[1-phenyl-3-methyl-4-(4-bromobenzoyl)- pyrazolon-5-ato]tin(IV)

Abstract Stable six-coordinate derivatives [(Q)2SnRX] [QH is 1-phenyl-3-methyl-4-R′C(O)-pyrazol-5-one (R′  4-BrC6H4 {QBrH}, 4-FC6H4 {QFH}, 4-ClC6H4 {QClH}, 4-IC6H4{QIH}, or 4-C7H15 -C6H4 {QRH}), X  Cl or R, and R  Cl, Me, nBu, tBu, Ph, vinyl or benzyl] and 1:1 adducts [(QH) SnRnX4−n]·xS [QH = 1-phenyl-3-methyl-4-R′C(O)-pyrazol-5-one (R′  4-BrC6H4, 4-FC6H4 or 4-C7H15-C6H4; X  Cl or R and R  Cl, Me, or Ph; x = 0, 1 2 , or 1; S  CH2Cl 2, H2O, or Et2O] have been synthesized and characterized by analysis and spectral (IR, and 1H, 13C, and 119Sn NMR) data. The diffraction study of the complex [(QBr)2SnMe2] shows the metal to be six-coordinate in a skewed trapezoidal bipyramidal (STB-6) geometry; SnO distances are 2.104(4) and 2.099(4) A, and 2.385(5) and 2.436(5) A and the Me SnMe bond angle is 154.5(3)°. In QBr, 4-bromophenyl and the pyrazolone rings are nearly coplanar. This co-planarity is opposed by an intramolecular repulsive force between one ortho H atom of the bromophenyl moiety and one O atom of the chelate ring. This feature appears related to the small bite of the ligand QBr (OSnO bond angles of 78.5(2)° and 79.5(2)°) which may be responsible for the STB-6 geometry.

Tin(IV) and organotin(IV) adducts of bis(1-pyrazolyl)methane

Abstract Bis(pyrazol-1-yl)methane, (L-L), reacts with tin(IV) or organotin(IV) halides yielding (L-L)SnX m R −m (X = Cl, Br, I; m = 4,3 or 2 but not 1; R = methyl or phenyl). NMR spectra show that the compounds are fluxional, while combined molecular weight determinations and conductivity data show that in acetone solution the molecules obtained dissociate readily into the starting materials.

Silver(I) and gold(I) complexes of hydrotris(3,5-dimethylpyrazol-1-yl)borate: synthesis, spectroscopic and structural characterization, and reactivity toward C-, N- and S-donor ligands.

Abstract Reaction of Ag(NO3) with 1 equiv of K[HB(3,5-Me2pz)3] (pzH=pyrazole) and 1 equiv of PR3 (R OPh or C6F5) in methanol provides two new air stable derivatives {[HB(3,5-Me2pz)3]Ag(PR3)}. When the interaction between Ag(O3SCF3), CNR (R But or cyclohexyl), and K[HB(3,5-Me2pz)3] was carried out in CH2Cl2 at 0°C the air stable neutral compounds {[HB(3,5-Me2pz)3]Ag(CNR)} were obtained. The borderline monodentate imidazole (ImH) reacts with the dinuclear {[HB(3,5-Me2pz)3]Ag}2 yielding the mixed-ligand complex {[HB(3,5-Me2pz)3]Ag(ImH)}. On the other hand when the soft donor 1-methyl-2-mercaptoimidazole (Hmimt) was employed, no stable compound was obtained. We also synthesized [Phen2Ag](O3SCF3) (Phen=1,10-phenanthroline) and its reaction with K[HB(3,5-Me2pz)3] yielded the complex {Phen[HB(3,5-Me2pz)3]Ag}, which is not fluxional in solution. Instead only unmanageable material was obtained from the reaction between (Hmimt)2Ag(O3SCF3) and K[HB(3,5-Me2pz)3]. Finally, the gold(I) complex [HB(3,5-Me2pz)3]Au(PPh3)2 was obtained when the reaction between PPh3AuCl and [HB(3,5-Me2pz)3] was carried out in presence of 1 equiv of PPh3. The solid state structures of {[HB(3,5-Me2pz)3]Ag(PPh2Me)} and {[HB(3,5-Me2pz)3]Ag(P-o-tolyl3)}, show that the silver(I) atoms are in a strongly distorted tetrahedral environment, with the [HB(3,5-Me2pz)3]− donor acting in the tridentate form. The Ag–P and Ag–N bond distances in {[HB(3,5-Me2pz)3]Ag(PPh2Me)} are 2.336(2) A and 2.316(6), 2.336(5) and 2.329(6) A, respectively; they are shorter than in the more sterically hindered {[HB(3,5-Me2pz)3]Ag(P-o-tolyl3)} (Ag–P: 2.375(2) A; Ag–N: 2.361(4) A). The ligand bite N–Ag–N ranges from 82.1(2)° to 84.8(2)°, whereas the N–Ag–P angle ranges from 125.1(1) to 134.1(1)°.

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.

Synthesis and characterization of derivatives of copper(I) with n-donor ligands—I. Azole and bis(azolyl)alkane compounds. Crystal structure of nitrato bis(tri-p-tolylphosphine)copper(I)

Abstract Several new complexes of the type [Cu(NO 3 )(PPh 3 ) 2 (L) m ] (L = 3-methylpyrazole, 4-methylpyrazole, 3,5-dimethylpyrazole, 4-bromopyrazole or bis(4-methylpyrazol-1-yl)methane, m = 1; L = pyrazole, 1,2,4-triazole or 2-methylimidazole, m = 2), [Cu(NO 3 )(PPh 3 )] (L = 3,4,5-trimethylpyrazole or 4-phenylimidazole), [Cu(NO 3 ) (PAr 3 ) n (L) 3 ] (Ar = p - or m -tolyl, n = 0 or 1, L = pyrazole), [CuX(PPh 3 ) 2 (L)] (X = Cl, Br or I, L = pyrazole or 3,5-dimethylpyrazole) and [CuX(PPh 3 )(L)] (X = Cl or Br, L = bis (pyrazol-1-yl)methane, bis(3,5-dimethylpyrazol-1-yl)methane or bis(triazol-1-yl)methane) have been prepared and characterized by analytical and spectral data. The compounds [CuX(PPh 3 ) 2 (L)] (X = Cl, Br or I, L = pyrazole or 3,5-dimethylpyrazole) are fluxional at temperature above 240 K. The dinuclear compound [Cu 2 (PPh 3 ) 3 (pzH) 2 ] was obtained when the reaction between [CuI(PPh 3 ) 3 ] and pyrazole (pzH) was carried out in methanol containing alkali. In the crystal structure of the title compound, the copper atom is found in a strongly distorted tetrahedral coordination [PCuP: 128.0(1)°] with two long CuO distances [2.217(9) and 2.184(9) A].

Synthesis and characterization of some zinc, cadmium and mercury(II) derivatives of bis(4-methylpyrazol-1-yl) alkanes

Abstract The interaction between bis(4-methylpyrazol-1-yl)methane, L, and various MX2 (M = Zn, X = Cl, Br or I; M = Cd, X = Cl, I or NO3; M = Hg, X = Cl, Br, I, CN or SCN) gives the 1:1 adducts [L]MX2, which are air- and thermally stable. The ligand also gives 2:1 {[L]2Zn(CF3SO3)2·2H2O, [L]2Zn(NO3)2·3H2O, [L]2Cd(ClO4)2·H2O, [L]2Hg(CF3CO2)2} and 3:1 {[L]3Zn(ClO4)2, [L]3Zn(BF4)2, [L]3Zn(CF3CO2)2·H2O, [L]3Cd(BF4)2·H2O, [L]3Hg(ClO4)2·H2O} adducts with good acceptors. All the complexes have been characterized from analytical and spectral (IR, far-IR, 1H and 13C NMR) data. The adduct [L]HgCl2, stable in pyridine solution, readily reacts with PPh3 and 2,2′-bipyridyl (Bipy) to yield (PPh3)2HgCl2 and (Bipy)HgCl2, respectively. Comparison is made with results obtained with group 12 derivatives of other poly(azol-l-yl)alkanes.

Synthesis and characterization of copper(I) derivatives with nitrogen-donor ligands—II. Dihydridobis- and tetrakis(1H-pyrazol-1-YL)borate. The X-ray cyrstal structure of [pz2B-(μ-pz)2-Cu(PPh3)2]☆

Abstract Bis(triarylphosphine)copper(I) derivatives with the anionic tetrakis(1H-pyrazol-1-yl)borato (pzTp) or dihydridobis(1H-pyrazol-l-yl)borato (Bp) have been prepared from (Ar3P)2CuNO3 and KpzTp or KBp, and characterized through IR and 1H, 13C and 31p NMR. The complexes contain tetrahedral CuI and a bidentate ligand. The pzTp ones are fluxional in solution with all pyrazolyl groups equivalent down to ∼ −60°C. The X-ray crystal structure of (Ph3P)2CupzTp has been resolved. The CuI atom has distorted tetrahedral cordination and shows CuN distances of 2.087(3), 2.051(3) A and CuP distances of 2.273(1), 2.359(1) A; the NCuN and PCuP angles are 92.6(1)° and 119.82(4)°, respectively, whereas the NCuP angles range from 99.21(9) to 119.76(9)°. The six-membered B(NN)2Cu ring adopts the boat form.

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.