Augusto Cingolani

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).

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. 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.

Tin(IV) and organotin(IV) derivatives of novel β-diketones I. Dialkyltin(IV) complexes of 1-phenyl-3-methyl-4-R′(CO)-pyrazol-5-one (R′ = CCl3, OCH3, OC2H5, OiC3H7, OC7H7). Crystal and molecular structure of trans-dimethylbis]1-phenyl-3-methyl- 4-i-propoxycarbonyl-pyrazolon-5-ato]tin(IV)

Abstract Stable six-coordinate tin(IV) and organotin(IV) derivatives R2SnQ∗*2 (R = Me, Et, Bun, Bu1) ( HQ ∗* = 1- phenly -3- methyl -4- trichloracetyl-pyrazol -5- one ) have been synthesized in basic (triethylamine0 solution of chloroform. These complexes have been characterized by elemental analysis and spectroscopic (IR and far-IR, 1H, 13C and 119Sn NMR) data. In basic (KOH) alcoholic R′OH solutions (R′ = Me, Et, Pri, benzyl), the tin acceptor induces cleavage of the CCCl3 bond in the donor (Q∗*)− and the new derivatives bis(1-phenyl-3-methyl-4-alkoxycarbonyl-pyrazolon-5-ato)R2Sn(IV) (R = Me, Et, Bu1 or Bua) and (1-phenyl-3-methyl-4-ethoxycarbonyl-pyrazolon-5-ato)-Me2Sn(IV)Cl have been obtained. Structural information has been derived from 119Sn NMR parameters such as 1 J( 119 Sn  13 C ), 2 J( 119 Sn  1 H ) and δ(119Sn). The diffraction study of the complex [Me2Sn(1-phenyl-3-methyl-4(COOPr1)-pyrazolon-5-ato)2] shows the metal to be six-coordinate in a skewed trapezoidal bipyramidal (STB) geometry; SnO distances are 2.10(1) and 2.39(1) A in one ligand, and 2.09(1) and 2.39(1) A in the other ligand, and the MeSnMe bond angle is 157.0(8)°. The title compound crystals are monoclinic, space group P21/c, cell parameters: a = 11.489(4), b = 14. 558(7), c = 18.973(8) A , β = 77.14(3)° .

Tin(IV) and organotin(IV) complexes containing the anion of some substituted-3-methyl-4-acyl-5-pyrazolones. Crystal structure of dimethylbis(1-phenyl-3-methyl-4-benzoyl pyrazolon-5-ato)tin(IV)

Abstract Six-coordinate [(Q) 2 SnRX] compounds, where QH is 1-R′-3-methyl-4-R″C(O)-5-pyrazolone (QpH: R′= p -NO 2 C 6 H 4 , R″= C 6 H 5 ; Q M H: R′= CH 3 , R″ = C 6 H 5 ; Q F H: R′= C 6 H 5 , R″ = CF 3 ), X = Cl or R, R = Cl or CH 3 , have been prepared and characterized by analyses, spectral (IR, 1 H-, 13 C- and 119 Sn-NMR data) and conductivity measurements. The crystal structure of [(Q′) 2 Sn(CH 3 ) 2 ] (Q′H is 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone) was also determined: the sterically demanding ligand gives rise to severe distortion of the six-coordinate [(Q′) 2 Sn(CH 3 ) 2 ] compound, similar to that noted in [(Q′) 2 Sn(t-C 4 H 9 ) 2 ] and I(Q′) 2 Sn(n-C 4 H 9 ) 2 ]. The CSnC axis is bent (153.3(3)°) and two of the four SnO bonds are exceptionally long (2.337(4) and 2.412(4) A) whereas the other two SnO bonds are normal (2.104(3) and 2.103(4), A).

Organotin(IV) derivatives of novel β-diketones ☆: Part V. Synthesis and characterization of di- and triorganotin(IV) derivatives of 4-acyl-5-pyrazolones modified in position 3 of the pyrazole. Crystal structure of (1,3-diphenyl-4-benzoyl-pyrazolon-5-ato)triphenyltin(IV)

Abstract The interaction between R 3 SnCl, (R 3 Sn) 2 O, R 2 SnO or R 2 SnCl 2 acceptors (R=Me, n Bu or Ph) and the two novel β-diketone proligands (LH=1,3-diphenyl-4-R 4 (CO)-pyrazol-5-one: L 1 H, R 4 =Ph; L 2 H, R 4 =Me) yields complexes [SnR 3 (L)(H 2 O)] (R=Me or n Bu, L=L 1 or L 2 ), [SnPh 3 (L)] and [SnR 2 (L) 2 ] (L=L 1 or L 2 ). The phenyl substituent on position 3 induces instability of the triorganotin derivatives in solution with the formation of SnR 2 (L) 2 and SnR 4 compounds. Moreover, diorganotin derivatives partially dissociate in solution yielding [SnR 2 (L)(solvent)] 2+ species. When compared with the related 3-methyl species, the crystal structure of (1,3-diphenyl-4-benzoyl-pyrazolon-5-ato)triphenyltin(IV) is not modified by the 3-phenyl substitution. The chemical instability generated by the Ph in position 3 is greater than in positions 1 and 4. In addition, the Ph in position 3 of the pyrazole influences the solution behavior of the free neutral 4-acyl-5-pyrazolones stabilizing a novel amino-diketo tautomeric form.

Synthesis and spectroscopic characterization of new Cu(I) complexes containing triaryl- tricycloalkylphosphines and heterocyclic anionic or neutral N-donor ligands. Crystal and molecular structure of [(Cy3P)2(pzH)Cu]ClO4.CH3OH (Cy = cyclohexyl, pzH = pyrazole).

The reaction of (PPh3)4CuClO4, (PPh3)2CuCl, (Cy3P)2CuNO3 and (Cy3P)2CuClO4 with an excess of monodentate heterocyclic N-donor ligand (QH in general, in detail: ImH=imidazole, 1-MeimH=1-methylimidazole, 2-MeimH=2-methylimidazole, 4-Phim=4-phenylimidazole, BimH=benzimidazole, 1-BzimH=1-benzylimidazole, pzH=pyrazole, pz′H=3,5-dimethylpyrazole) in diethyl ether or benzene resulted in the formation of new 2:2:1 [(PPh3)2(QH)2Cu]ClO4 (QH=ImH, 1-MeimH, 2-MeimH, 4-PhimH, BimH, pzH) and [(PCy3)2(QH)2Cu]NO3 (QH=4-PhimH, BimH), 1:3:1 [(PPh3)(1-BzimH)3Cu]ClO4, [(PCy3)(1-MeimH)3Cu]ClO4 and [(PCy3)(QH)3Cu]NO3 (QH=ImH, 1-MeimH, pzH), 2:1:1 [(PPh3)2O(QH)CuCl] (QH=ImH, 2-MelmH, 4-PhimH, BimH, 1-BzimH), [(PCy3)2 (QH)Cu]NO3 (QH=1-BzimH, pz′H) and [(PCy3)2 (QH)Cu]ClO4 (QH=2-MeimH, 4-PhimH, BimH, 1-BzimH, pzH, pz′H), 1:2:1 [(PCy3)(2-MeimH)2Cu]NO3and [(PCy3)(ImH)2Cu]ClO4 and 1:1:1 [(PPh3) (1-MeimH)CuCl] adducts. With the bidentate donors bis(pyrazol)-1-yl)methane (L1), bis(3,5-dimethylpyrazol-1-yl)methane (L2) and bis(4-methylpyrazol-1-yl)methane (L4), 2:1:1 [(PPh3)2(L)Cu]ClO4 and 1:1:1 [(PCy3)(L)Cu]ClO4 complexes were obtained, whereas the exopolydentate bis (1,2,4-triazol-l-yl) methane (L3) in similar conditions yielded 1:1:1 [(PPh3)(L3)Cu]ClO4 and [(PCy3)(L3)Cu]NO3, and 1:2:1 [(PCy3)(L3)2Cu]ClO4 derivatives. Breaking of the bridging C(sp3)-N bond in the bidentate bis (pyrazol-1-yl)methane occurred when the reaction between L1 and (PCy3)2CuNO3 was carried out in diethyl ether under aerobic conditions, the derivative [(PCy3)(pzH)3Cu]NO3 being formed. In methanol in the presence of base, ImH, 2-MeimH, 4-PhimH and BimH react with (PPh3)2CuCl giving the sparingly soluble complexes [(PPh3)2(Im)Cu]·1/2H2O, [(PPh3)2(2-Meim)Cu]·H2O, [(PPh3)(4-Phim)Cu] and [(PPh3)(Bim)Cu], respectively. Reaction of [(PPh3)2(ImH)2Cu]ClO4 with PCy3, PBz3 (Bz=benzyl), P(p-tolyl)3, and (Ph2PCH2)2 (abbreviated Diphos) resulted in the formation of compounds [(PPh3)(PCy)3(ImH)2Cu]ClO4, [(PPh3)(PBz3)(ImH)Cu]ClO4, [(PPh3)P(p-tolyl)3(ImH)2Cu]ClO6 and [(Diphos)2Cu]ClO4, respectively, whereas reaction with 1,10-phenanthroline (Phen) and 2,2′-bipyridyl (Bipy) produced [(PPh3)2(ImH)(Phen)Cu]ClO4 and [(PPh3)2(ImH)(Bipy)Cu]ClO4, respectively. While PCy3, PBz3 and P(p-tolyl)3 were not able to displace the triphenylphosphine from [(PPh3)2(L1)Cu]ClO4, Phen and Bipy in the same conditions formed the derivatives [(PPh3)2(Phen)Cu]ClO4 and [(PPh3)2(Bipy)Cu]ClO4. All of the complexes were characterized by IR and far-IR data, conductivity, 1H NMR and in some cases also with UV, 13C and 31P NMR and molecular weight measurements. The structure of [(Cy3P)2(pzH)Cu]ClO4·CH3OH was determined by single crystal X-ray diffraction: monoclinic, space group Pn,Z=2,a=9.949(7),b=13.128(4),c=16.588(8) A, β=91.15(7)°. The copper atom exhibited a distorted ideal trigonal planar geometry involving two phosphine groups (CuP:2.262(9) and 2.272(6) A; PCuP: 132.3(7)°) and one pyrazole ligand (CuN:2.047(18)A) coordinating through a pyridine-like nitrogen atom. The pyrazole donor of one molecule was hydrogen bonded to a molecule of methanol, which in turn was hydrogen bobded to the ionic perchlorato group.

Tin(IV) and organotin(IV) complexes containing mono or bidentate N-donor ligands: III. 1-methylimidazole derivatives: synthesis, spectroscopic and structural characterization

Abstract A series of adducts of the type [(L # ) y R n SnX 4− n ]· z H 2 O (L # =1-methylimidazole, y =1 or 2, R=Me, Et, Bu n or Ph, n =1, 2 or 3, X=Cl, Br or I, z =0, 1/2 or 1) has been characterized in the solid state and in solution by analyses, spectral (IR, 119 Sn Mossbauer, and 1 H, 13 C and 119 Sn NMR) data and conductivity measurements. The molecular weight determinations and the NMR data indicate that these organotin(IV) complexes partly dissociate in chloroform and acetone solution. The donor L # interacts with [(CH 3 ) 3 SnNO 3 ], yielding the 2:1 ionic complex [(L # ) 2 (CH 3 ) 3 Sn]NO 3 . The derivative [(L # ) 2 (CH 3 ) 2 SnCl 2 ] reacts with NaClO 4 , AgNO 3 , NaBPh 4 and KSCN in ethanol and diethyl ether giving the complexes [(L # ) 2 (CH 3 ) 2 Sn(ClO 4 ) 2 ], [(L # )(CH 3 ) 2 Sn(NO 3 ) 2 (H 2 O)], [(L # )(CH 3 ) 2 SnCl(H 2 O) 2 ]BPh 4 and [(L # ) 2 (CH 3 ) 2 Sn(NCS) 2 ], respectively, whereas when [(L # )(CH 3 ) 3 SnCl] interacts with an equimolar quantity of NaClO 4 , [(L # ) 2 (CH 3 ) 3 Sn]ClO 4 ·1/2H 2 O and (CH 3 ) 3 Sn(ClO 4 ) in 1:1 ratio are obtained. The stability towards self-decomposition of the complexes obtained decreases with increasing number of the Sn-bonded aryl or alkyl groups. The derivative [(L # ) 2 (CH 3 ) 2 SnBr 2 ] reacts with 1,10-phenanthroline (Phen), yielding immediately the complex [(Phen)(CH 3 ) 2 SnBr 2 ], whereas from the reaction between [(L # ) 2 (CH 3 ) 2 Sn(ClO 4 ) 2 ] and Phen, the mixed ligand complex [(L # )(Phen)(CH 3 ) 2 Sn](ClO 4 ) 2 is obtained. A different behaviour has been shown from the diiodide complex [(L # ) 2 (C 2 H 5 ) 2 SnI 2 ] which reacts with Phen, yielding the compound with the 3:2 stoichiometry [(Phen) 3 {(C 2 H 5 ) 2 SnI 2 } 2 ]. Both the crystal structures of [(L # ) 2 (CH 3 ) 2 SnBr 2 ] and [(L # ) 2 (C 2 H 5 ) 2 SnI 2 ] show the tin atom in an all- trans octahedral regular configuration, whereas in [(L # )(C 6 H 5 ) 3 SnCl] the tin atom exhibits a distorted trigonal bipyramidal geometry, with the phenyl groups in the equatorial positions. A comparison was made with structural data of other R 3 SnXN-type derivatives. The molecular parameters of 1-methylimidazole in the tin(IV) complexes were used, together with other structural data in literature, to derive empirical rules concerning the imidazole donor.

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.

Synthesis and characterization of some Tin(II) and Tin(IV) derivatives of 4-acyl-5-pyrazolones. Crystal structure of bis(1-phenyl-3-methyl-4-acetyl-pyrazolon-5-ato)Tin(II)

Abstract Stable, four-coordinated (Q)2Sn compounds have been prepared, where QH is 1-phenyl-3-methyl-4-RC( O)-pyrazol-5-one (R = CH3, CF3, n-C6H13, C6H5,pF-C6H4,p-Cl-C6H4,p-Br-C6H4,p-I-C6H4,p-NO2-C6H4,p-CH3O-C6H4). They have been characterized through analytical data, IR and1H,13C and119Sn NMR spectroscopy. In the crystal structure of the title compound (8), the tin atom is found in a distorted ψ trigonal bipyramidal environment, with the tin lone pair occupying an equatorial site. The diaxial angle O Sn O is bent [149.8(2)°] and two sets of Sn O distances are found [Sn O(1) = 2.141 (5)A˚; Sn O(3) = 2.133 (5)A˚; Sn O(2) = 2.296 (6)A˚; Sn O(4) = 2.313 (6)A˚]. Oxidative addition of iodomethane or dihalogens (Br2 or I2) to (Q)2Sn provides a route to new (Q)2RnSnIVX2-n compounds (where X = Br or I;R = CH3 or X).