Patrizio Cecchi

Organotin(IV) polypyrazolylborates. III, Tris(3,5-dimethylpyrazolyl)borates

Abstract The compounds RnSnX3-nQ where R = Me, Et, Bu or Ph; X = Cl or Br: n = 0, 1, or 2 and Q is the sterically demanding title ligand have been shown to be stable and non-fluxional and to contain six-coordinated tin(IV) and the tridentate ligand Q.

A Mössbauer study of some iron(II) and iron(III) poly(pyrazolyl)borates. The x-ray crystal structures of iron(II)bis[hydridotris(3-methyl-1H-pyrazol-1-yl)borate] and iron(II)bis[hydridotris(1H-pyrazol-1-yl)borate] tetrafluoroborate

Abstract A series of iron(II) or iron(III) complexes of type FeL2 or [FeL2]+ X−(X = BF4 or BPh4) with L = hydridotris(1H-pyrazol-1-yl)borate(L0), tetrakis(1H-pyrazol-1-yl)borate(L0′), hydridotris(-methyl-1H-pyrazol1-yl)borate(L1), hydridotris(3,5-dimethyl-1H-pyrazol-1-yl)borate(L2), hydridotris(4-chlor-3,5-dimethyl-1H-pyrazol-1-yl)borate(L2Cl), hydridotris(3,4,5-trimethyl-1H-pyrazol-1-yl)borate(L3), hydridotris(1,2,4-1H-triazol-1-yl)borate(Ltz) and hydridotris(3a,7a-benzo-1,2,3-1H-triazol-1-yl)borate(Lbtz) has been prepared. The series has been characterized mainly by th 57Fe Mossbauer effect. The X-ray crystal structures of iron(II)bis[hydridotris(3-methyl-1H-pyrazol-1-yl)borate] (3) and iron(III)bis[hydridotris(1H-pyrazol-1-yl)borate] tetrafluroborate (9) have been resolved. Discrete units with octahedral FeIIN6 or FeIII sites are present in each. The Fen bond length ranges from 2.197(4) to 2.215(4) A in 3 and from 1.948(6) to 1.964(6) A in 9. The bond angle ranges from 86.4(2)° to 93.7(2)° in 3 and from 88.3(4)° to 90.9(5)° in 9.

Synthesis and characterization of copper(I) derivatives with N-donor ligands—III. Hydridotris (1H-pyrazol-1-yl)borate. The X-ray crystal structure of [HB-(μ-pz)3-Cu(PPh3)]

Abstract (Triarylphosphine)copper(I) derivatives containing anionic tris(1 H -pyrazol-1-yl)borato have been prepared from (Ar 3 P) 2 CuNO 3 and KTp, KTp ∗ , KTp Me and KTp ∗Cl and characterized through IR and 1 H, 13 C and 31 P NMR spectra. The complexes contain tetrahedral Cu I and a tridentate ligand. The X-ray single crystal analysis of the (PPh 3 )CuTp complex is reported. Four-coordinate Cu 1 is present in a distorted tetrahedral configuration owing to the bulky PPh 3 and Tp groups: NCuN angles range from 88.4(2) to 91.8(2)°; NCuP angles range from 120.6(2) to 127.3(1)°. The CuN distances are 2.081(5), 2.065(5) and 2.083(5) A and the CuP distance is 2.153(2) A.

The effect of the 3-trifluoromethyl substituent in polypyrazolylborato complexes on the iron(II) spin state; X-ray diffraction and absorption and Mössbauer studies ☆

Abstract A series of bis(polypyrazolylborato)iron(II) complexes (with Tp 3CF 3 , Tp 4Me , Tp 4Br , and pzTp 4Me ) has been prepared and characterised by 57 Fe Mossbauer spectroscopy. In addition, the Tp 3CF 3 has been studied and compared with Tp 3CH 3 by X-ray absorption investigation. The X-ray crystal structure of iron(II)bis(3-trifluoromethyl-1 H -pyrazol-1-yl)borato has been resolved. In Fe(Tp 3CF 3 ) 2 the coordination geometry around the Fe centre is distorted octahedral, with the FeN bond distances in the range 2.219(3)–2.251(3) A that are slightly longer than typical distances for high-spin iron(II) complexes. A close comparison of the Tp 3CF 3 and Tp 3CH 3 has revealed small but nonetheless significant differences as evidenced from low-temperature Mossbauer studies and from X-ray absorption near-edge structure approach. At variance with Fe(Tp 3CHF 3 ) 2 , the high spin state for Fe(Tp 3CF 3 ) 2 is to be taken as the most stable one.

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.

Organotin(IV) polypyrazolylborates. XII. Hydridotris(4-bromo-1H-pyrazol-1-yl) borates: characterization, Mössbauer study and X-ray crystal structure of MeCl2Sn(4-BrPz)3BH

A series of tin(IV) and organotin(IV) hydridotris(4-bromo-1H-pyrazol-1-yl)borates has been prepared. The compounds of general formula RnSnCl4−n−1[HB(4-Br-pz)3] (where R = Me or Ph, n = 0, 1, 2, or 3) are rigid in solution and contain a six-coordinate tin(IV) site with a tridentate ligand. They were characterised by IR, 1H, 13C, 119Sn NMR, and 119Sn Mossbauer spectroscopy. Their stability towards self-decomposition decreases with increasing number of Sn-bonded aryl or alkyl groups. The compound MeCl2Sn[HB(4-Br-pz)3] crystallises in the space group (no. 148), trigonal, with .

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.

Organotin(IV) polypyrazolylborates VII. Hydridotris (3,4,5-trimethyl-1 H-pyrazol-1-yl) borates. X-ray crystal structures of K(HB(3,4,5-Me3Pz)3] and [HB(3,4,5-Me3Pz)3 SnMeCl2]

Abstract Tin(IV) and organotin(IV) compounds containing hydridotris(3,4,5-trimethyl-1 H-pyrazol-1-yl)borate (L3), [RnSnCl4-n-1L3] (R=Me, n = 0–2) have been synthesised and studied by NMR (1H, 13C, 119Sn) spectroscopic techniques. The compounds are not fluxional and contain six-coordinate tin(IV) with a tridentate ligand. X-ray crystal structure of [MeSnCl2L3] is reported together with that of the parent potassium hydridotris(3,4,5-trimethyl-1 H-pyrazol-1-yl)borate, K(C18H28N6B) and comparisons are made.

Tris(4-bromo-1H-pyrazol-1-yl)borato derivatives of first-row transition and group 12 and 14 metals. X-ray crystal structure of [HB(4-Brpz)3]2 Cd. 113Cd solution NMR study of bis[poly(pyrazolyl)borato]cadmium complexes

Abstract A series of metal complexes M[HB(4-Brpz)3]2 [HB(4-Brpz)3 = hydridotris(4-bromo-1H-pyrazol-1-yl)borate and M = Mn, Fe, Co, Ni, Cu, Zn, Cd, Pb] were obtained from reaction of K[HB(4-Brpz)3] and the appropriate metal salt in aqueous solution. These air-stable complexes are sparingly soluble in most common solvents; they have been investigated through elemental analysis, conductivity measurements, IR, UV-vis and, in the case of diamagnetic compounds, 1H and 13C NMR spectroscopy. The X-ray crystal structure of cadmium(II) bis[hydridotris(4-bromo-1H-pyrazol-1-yl)borate] has been resolved. Six-coordinate cadmium is present in a slightly distorted octahedron with the axes not linear [angles 176.8(3), 177.2(3) and 178.7(3)°]. The ‘bite’ of the ligand, i.e. NCdN angle, lies in the range 81.6(2)–84.1(3)° (weighted average 82.4(4)°). The CdN distances vary from 2.298(8) to 2.329(8) A (weighted average 2.317(5) A). The geometry around the B atom is tetrahedral. The NBN angles range from 105.8(8) to 110.5(7)° (weighted average 108.5(7)°); the BN bond distances vary from 1.53(2) to 1.62(1) A (weighted average 1.58(1) A). We report and discuss also the 113Cd NMR solution data of several cadmium poly(pyrazol-1-yl)borates).

First-row transition- and group 12- and 14-metal(II) bis[hydridotris(3-Me-1H-pyrazol-1-yl) borate]. The X-ray crystal structure of the nickel derivative

Abstract Several thermally stable M[L]2 complexes were obtained from the appropriate metal chlorides in aqueous solution (M = Mn, Fe, Co, Ni, Cu, Zn, Cd, Pb) with potassium hydridotris[(3-Me-1H-pyrazol-1-yl)borate]. They have been investigated by elemental analysis, conductivity measurements, IR spectroscopy and, where possible, by 1H and 13C NMR. The X-ray crystal structure of nickel(II)bis[hydridotris(3-Me-1H-pyrazol-1-yl)borate] has been resolved. Two discrete units with octahedral NiN6 sites are present. The NiN bond lengths range from 2.097(5) to 2.134(4) A and the NNiN bond angles from 87.8(2) to 92.4(2)°.