L. Sacconi

Structural correlations and NMR properties of mononuclear cyclic triphosphorus complexes

Abstract The [(triphos)Ni(η-P 3 )BF 4 · C 2 H 5 OH compound has been synthesized by treating Ni(BF 4 ) 2 · 6H 2 O with P 4 S 3 , in the presence of the triphos ligand (triphos = 1,1,1-tris(diphenylphosphinomethyl)ethane). The crystal structure of the complex and that of the previously obtained platinum isomorph have been investigated by X-ray diffraction. Correlations are drawn within the series of the monocationic [(triphos)M(η 3 -P 3 )] + (M = Ni, Pd, Pt) complexes and that of the neutral [(triphos)M(η 3 -P 3 )] (M = Co, Rh, Ir) compounds, as well as between the two series. Phosphorus NMR data are reported for the compounds of the two sets and trends are analyzed in terms of simple models of the bonding.

Hydridodinitrogen and hydrido complexes of iron(II) with the linear tetratertiary phosphine hexaphenyl-1,4,7,10-tetraphosphadecane. Crystal structure of the complex [FeH(N2)((C6H5)2PC2H4P(C6H5)C2H4P(C6H5)C2H4P(C6H5)2]Br · C2H5OH

Abstract Treatment of the chromophore [FeX(P4)]+, where X = Br, I and P4 is the tetradentate open-chain ligand hexaphenyl-1,4,7,10-tetraphoshadecane, with sodium tetrahydroborate under helium or nitrogen gave cationic hydrido- or hydrido-dinitrogen-iron(II) complexes of formula [FeH(P4]X and [FeH(N2)(P4)]X. The structure of the [FeH(N2)(P4)]Br · C2H5OH complex was determined from three dimensional X-ray data collected by counter methods. The crystals are triclinic, space group P1- with cell dimensions a = 15.392(8), b = 16.109(10), c = 9.914(5) ]A, α = 69.57(8), β = 78.43(9), γ = 68.46(9)°. The structure was solved the heavy atom technique to a final conventional R factor of 0.053 over 1631 independent observed reflections. The structure consists of [FeH(N2)(P4)]+ cations, bromide anions, and solvating C2H5OH molecules. The metal atom is octahedrally coordinated with the four phosphorus atoms of the ligand in the equatorial plane and weith the hydrogen atom and one atom of the dinitrogen molecule in the axial positions.

Halo-, hydrido- and dinitrogen-complexes of iron(II) with tritertiary phosphines

Abstract From the five-coordinate iron(II) complexes [FeXL] BPh 4 , (L = tris(2-diphenylphosphinoethyl)amine, np 3 , and tris(2-diphenylphosphinoethyl)phosphine, pp 3 ) hydrido and hydrido dinitrogen complexes have been obtained; these have formula [FeH(pp 3 )]BPh 4 and [FeHN 2 L]BPh 4 (L = np 3 , PP 3 . In the latter complexes the dinitrogen molecule may be replaced by other neutral ligands such as CO, CH 3 CN, C 6 H 5 CN.

Metal-assisted reaction of carbon disulfide with the tris(tertiary phosphine) 1,1,1-tris(diethylphosphinomethyl)ethane. Synthesis and structure of the complex [MeC(CH2PEt2)3Fe{S2C(PEt2CH2)2CMe2}](BF4)2

Abstract Carbon disulfide reacts with iron(II) tetrafluoroborate in the presence of 1,1,1-tris(diethylphosphinomethyl)ethane, etriphos, to give the complex [MeC(CH 2 PEt 2 ) 3 Fe{S 2 C(PEt 2 CH 2 ) 2 CMe 2 }](BF 4 ) 2 . This is the first example of a diamagnetic five-coordinate iron(II) complex. Its molecular structure has been determined from counter diffraction data. The crystals are monoclinic belonging to space group P 2 1 / c with four molecules in the unit cell of dimensions a 18.964(7), b 18.016(7), c 14.033(5) A, β 109.1(1)°. The structure has been solved by three-dimensional Patterson and Fourier syntheses and refined by least-squares techniques to final R and R W factors of 0.074 and 0.073, respectively. The iron atom is five-coordinated by the three phosphorus atoms of the etriphos ligand and the two sulfur atoms of the zwitterionic ligand in a distorted square pyramidal geometry.

Synthesis, properties and x-ray structural determination of cationic five-coordinate σ-triphenylstannylnickel (II) complexes with poly(tertiary phosphines)

Abstract Cationic five-coordinate nickel(II) complexes containing a nickel—tin σ-bond with the general formula [Ni(SnPh 3 )(L)]BPh 4 (L  tris(2-diphenylphosphinoethyl)amine, np 3 ; tris(2-diphenylphosphinoethyl)phosphine, pp 3 ) were synthesized by reaction of the five-coordinate complexes [NiCl(L)]BPh 4 with LiSnPh 3 . The structure of the [Ni(SnPh 3 )(np 3 )]BPh 4 derivative was determined by X-ray diffraction. The crystals are monoclinic, space group P 2 1 c with cell dimensions a 18.88(1), b 38.53(2), c 18.93(1) A, β 93.3(1)°, D c 1.34 g cm -3 for Z  8. The structure was solved by three-dimensional Patterson and Fourier syntheses and refined by least-squares techniques to a final conventional R factor of 0.088. The structure consists of trigonal bipyramidal [Ni(SnPh 3 )(np 3 )] + cations and BPh 4 - anions, with a Ni—Sn bond distance (av) of 2.556(15) A.

Cationic η3-Triphenylcyclopropenylnickel complexes with tridentate ligands containing N, P, As as the donor atoms. Molecular structure of η3-triphenylcyclopropenyl-1,1,1-tris(diphenylphosphinomethyl)ethanenickel perchlorate

Abstract The [(C 3 Ph 3 )Ni(PPh 3 ) 2 ]ClO 4 complex reacts with the tridentate ligands, 1,1,1-tris(dimethylphosphinomethyl)ethane, 1,1,1-tris(diphenylphosphinomethyl)ethane, (bis(2-diphenylphosphino)ethyl)phenylphosphine, (bis(2-diphenylphosphino)ethyl)-n-propylamine, and 1,1,1-tris(diphenylarsinomethyl)ethane to give cationic η 3 -triphenylcyclopropenyl complexes of formula [(C 3 Ph 3 )NiL]Y (Y = ClO 4 , BPh 4 ). An uncharged derivative with the formula [(C 3 Ph 3 )Ni(hb(3,5-me 2 Pz) 3 )] (hb(3,5-me 2 Pz) 3 = hydrotris(3,5-dimethyl-1-pyrazolyl)borate) has also been prepared. The molecular structure of [(C 3 Ph 3 )Ni(triphos)]ClO 4 has been determined from counter diffraction data. The crystals are monoclinic, space group P 2 1 / n with cell dimensions: a 17.750(5), b 17.629(5), c 16.509(4) A; β 92-59(9)°, D c = 1.359 g cm −3 for Z = 4. Full matrix least-squares refinement led to the conventional R factor of 0.064 for 2556 observed reflections. The molecular structure consists of [(C 3 Ph 3 )Ni(triphos)] + cations and ClO 4 − anions. The nickel atom is coordinated to the three phosphorus atoms of the triphos ligand, and to the C 3 Ph 3 fragment in a symmetric η 3 fashion.

Paramagnetic carbonyl cobalt(II) complexes. Molecular structure of bromocarbonyl-1,1,1-tris(diphenylphosphinomethyl)ethanecobalt(II) tetraphenylborate

Carbon monoxide or cyclohexyl isonitrile (L) react with the dinuclear five-coordinated derivatives of 1,1,1-tris(diphenylphosphinomethyl)ethane, (triphos), [(triphos)Co(μ-X)2Co(triphos)](BPh4)2 (X = halide) to give complexes of formula [(triphos)Co(L)X]BPh4. The latter are rare examples of paramagnetic cobalt(II) carbonyl complexes. The molecular structure of [(triphos)Co(CO)Br]BPh4 has been determined from counter diffraction data. The crystals are monoclinic, space group P21/a with cell dimensions a 20.225(8), b 20.664(9), c 13.301(5); β 97.24(5)°, Dc = 1.338 g cm−3 for Z = 4. Full-matrix least squares refinement led to the conventional R factor of 0.057 for 3648 observed reflections. The molecular structure consists of five-coordinate [(triphos)Co(CO)Br]+ cations of intermediate geometry and BPh−4 anions.

π-Polyolefin and π-acetylene cobalt(I) complexes with the tris(tertiary phosphine) 1,1,1-tris(diphenylphosphinomethyl)ethane. X-ray structure of [(triphos)Co(η4-C7H8)]ClO4 · O.5 CH2Cl2

Abstract Cationic cobalt(I) complexes with the general formula [(triphos)Co(L)]Y (triphos  1,1,1-tris(diphenylphosphinomethyl) ethane; L  1,3-butadiene, isoprene, 1,3-cyclohexadiene, 1,3,5-cycloheptatriene, 1,3,5,7-cyclooctatetraene, phenylacetylene, diphenylacetylene) have been obtained by reaction of cobalt perchlorate with a variety of conjugated polyolefins or with acetylenes in the presence of the triphos ligand. The crystal structure of the complex [(triphos)Co(C7H8)]ClO4 · 0.5 CH2Cl2 has been determined by an X-ray analysis using diffractometric data. The crystals are monoclinic, space group P21/c with cell dimensions a 10.514(3), b 15.041(5), c 54.795(12) A, β 92.61(3)°, Z  8. The structure was solved by direct methods and refined by least-squares techniques to a final conventional R factor of 0.091. The structure, which consists of [(triphos)Co(C7H8)]+ cations, perchlorate anions, and interposed CH2-Cl2 solvent molecules, shows that the cycloheptatriene molecule acts as a tetrahapto ligand. The coordination polyhedron can be regarded either as a distorted square pyramid or as a distorted octahedron. The coordination geometries of all complexes have been assigned on the basis of this structure determination and of IR and NMR data.

Trimeric nickel(II) complexes with bridging triphosphine ligand 1,1,1-tris(diphenylphosphinoethyl)ethane (etp3). X-ray structure of the complex [Ni3Cl6(etp3)2]·0.7CHCl3

Abstract The tripod-like triphosphine (PPh2CH2CH2)3CCH3, etp3, forms with nickel(II) halides trinuclear complexes of formula [Ni3X6(etp3)2] (X = Cl, Br, I), where the etp3 phosphine acts as trimetallic ligand, its three phosphorus atoms being linked to the three different nickel atoms. The chloroderivative has been studied by X-ray analysis, using diffractometer data. The crystal are monoclinic, space group P21/a, a = 26.27(1), b = 28.84(2), c = 11.91(1), β = 99.0(2)°, dm = 1.36 g cm−3, dc = 1.354 g cm−3 for Z = 4. The structure has been solved by three-dimensional Patterson and Fourier syntheses and refined by least-squares techniques to final R and Rw factors of 0.072 and 0.073 respectively. The complex molecule is trinuclear, with three four-coordinate nickel ions, bridging two etp3 ligands.

POLARIZED SPECTRA OF THE TRIGONAL BIPYRAMIDAL CoNP3Br CHROMOPHORE

Abstract The electronic spectra of high-spin pentacoordinate cobalt(II) complexes have been tentatively assigned on the basis of a ligand field approach.1–3 A controversy has arisen about the assignment of the spectrum of a typical chromophore, CoN4Br, having strictly C 3v symmetry in the compound [CoBr(Me6tren)]Br, where Me6tren is N[CH2CH2N(CH3)2]3. This spectrum shows four distinct bands well separated from charge transfer bands at 5.7, 12.3, 16.1 and 19.2–19.8 kK.4 Ciampolini and Bertini2 assigned these bands to transitions from the 4 A 2(F) ground state to the 4 E(F), 4 E E, 4 A 2(P), and 4 E(P) excited states whereas Wood3 assigned the second band to a spin forbidden transition, the third band to a transition to the 4 E(F) level and the last band to the two transitions to the highest two levels. Because of the cubic symmetry of the crystal lattice of this compound,5 polarized spectra were of no aid in deciding the correct assignment.