Paolo Innocenti

Synthesis and molecular structure of hydrido(tetrahydroborato)(1,1,1-tris(diphenylphosphinomethyl)ethane)-iron(II)

Abstract Sodium tetrahydroborate reacts with iron(II) tetrafluoroborate and 1,1,1-tris(diphenylphosphinomethyl)ethane (triphos) to give the complex (triphos)-FeH(BH4) whose molecular structure, determined from X-ray data consists of monomolecular units in which the iron atom is six-coordinated by the three phosphorus atoms of the ligand, two hydrogen atoms of the BH4 group, and a hydridic hydrogen atom. Variable temperature 31P NMR spectra reveal stereochemical non-rigidity of the complex in solution.

Phosphato complexes of beryllium(II): a 31P and 9Be nuclear magnetic resonance study

Abstract 31 P and 9 Be NMR spectra of mixtures of beryllium(II) and phosphoric acid have been interpreted to support the speciation previously proposed on the basis of potentiometric measurements. Nine 31 P lines were observed at ≈0.4, −3.67, −4.51, −5.57, −6.5, −7.08, −8.81, −9.3 and −11.0 ppm relative to 85% phosphoric acid as external standard. The signal in the range 0.36–0.56 was assigned to rapidly exchanging H 3 PO 4 , H 2 PO 4 − with a further contribution from Be 3 O(H 2 PO 4 ) 6 2− . The peaks at −3.67 and −4.51 ppm were ascribed to isomers of Be(H 2 PO 4 ) 2 . The species Be(H 2 PO 4 ) + also gives a signal centred at −4.51 ppm. The peak at −6.5 ppm was assigned to Be 3 (OH) 3 (H 2 PO 4 ) 3 . The peaks at −5.58, −8.81 and −9.3 ppm are tentatively assigned to isomers of the complex Be 2 (OH)(H 2 PO 4 ) 2+ . Signals observed at −7.08 and −11.0 ppm could not be assigned to any of the complexes proposed by potentiometry. The 9 Be NMR data are also consistent with the model previously proposed.

Dynamic nuclear magnetic resonance studies of the η3-triphenylcyclopropenyl complexes [M(η3-C3Ph3)L]PF6[M = Ni, Pd or Pt; L = MeC(CH2PPh2)3]. Crystal structure of the platinum derivative

The dynamic behaviour of the three complexes [M(η3-C3Ph3)L]PF6[M = Ni 1, Pd 2 or Pt 3; L = 1,1,1-tris(diphenylphosphinomethyl)ethane] has been investigated through 13C-{1H} variable-temperature NMR spectroscopy. The spectra indicate a temperature-dependent fluxionality of the cyclopropenyl ring, with the rotational barrier increasing in the order Ni < Pd < Pt. The molecular structure of 3, established by single-crystal X-ray diffraction studies, shows that the co-ordination geometry of the platinum complex is fully comparable with that of the nickel analogue, indicating no correlation between structural parameters and fluxional behaviour. Crystal data for 3: monoclinic, space group P21/n, a= 17.129(3), b= 17.517(3), c= 17.968(7)A, β= 95.11 (3)°, Z= 4, R= 0.037.

Synthesis and X-ray crystal structure of the asymmetric trinuclear complex [Ni3(µ3-S)2(H2O)(PPh3)5][PF6]2

By reaction of H2S and PPh3 with [Ni(H2O)6]2+ the trinuclear complex cation [Ni3(µ3-S)2(H2O)(PPh3)5]2+ is formed. The molecular structure of [Ni3(µ3-S)2(H2O)(PPh3)5][PF6]2 was determined from three-dimensional X-ray data collected by counter methods. The crystals are monoclinic, space group Pn, with a= 24.235(14), b= 13.892(8), c= 14.141 (8)A, β= 91.45(7)°, and Z= 2. The inner core of the cation consists of a triangle of nickel atoms capped above and below by two triply bridging sulphur atoms. Two nickel atoms are co-ordinated by two triphenylphosphine ligands, whereas the third is linked to a triphenylphosphine and to one water molecule. The mean value of the nickel–nickel bond distances, 2.95(5)A, seems to exclude any direct metal–metal interaction; the geometry may be therefore described as three square-planar nickel(II) moieties sharing two triply bridging sulphur ligands.

Reactions of polysulphide with metal–phosphine species. Synthesis and X-ray crystal structure of [{Ni(bppte)(µ-OH)}2][ClO4]2·(CH3)2CO

The reaction of [Ni(H2O)6][ClO4]2 in the presence of 1,1,1-tris(diphenylphosphinomethyl)ethane, tppme, with [Sn]2– leads to the formation of the dimeric hydroxo-complex [{Ni(bppte)(µ-OH)}2][ClO4]2·(CH3)2CO, bppte = PPh2SCH2C(CH3)(CH2PPh2)2, which was structurally characterized by X-ray diffraction. Crystal data are: a= 19.046(7), b= 18.195(6), c= 13.349(5)A, β= 97.76(4)°, space group P21/a, and Z= 2. In the centrosymmetric dimeric hydroxo-bridged cation each metal atom displays square-planar co-ordination, the third arm of the ligand, PPh2SCH2, being unco-ordinated. The unexpected formation of hydroxo complexes is discussed.

Reactivity of diphosphines towards methyl- and phenyl-mercury(II) ions. Crystal structure of [Hg(Ph2PCH2CH2PPh2)2][O3SCF3]2

Methyl-and phenyl-mercury(II) ions reacted, in the molar ratio 2 : 1, with bidentate phosphines L–L to give binuclear complexes of general formula [RHg(L–L)HgR]2+. [L–L = Ph2P(CH2)nPPh2, n= 1–3]. When an excess of the phosphine ligand is present an intermolecular exchange process occurs which leads to the formation of the symmetrically substituted compounds, HgR2 and [Hg(L–L)2]2+. The reactions in solution have been studied by multinuclear NMR spectroscopy; the structure of the bimetallic species was deduced with the aid of computer simulation. The single-crystal structure of [Hg(Ph2PCH2CH2PPh2)2][O3SCF3]2[orthorhombic, space group Pbcn, a= 17.141(3), b= 20.158(3), c= 15.614(9)A, Z= 4] showed the mercury atom to be in a distorted-tetrahedral configuration.

Synthesis, X-ray crystal structure and NMR characterization of a tetrahedral methylmercury complex with the tripod ligand N(CH2CH2PPh2)3

The complex [Hg(np3)Me]CF3SO3, which is the first example of a methylmercury complex in an almost regular tetrahedral coordination, is obtained by the reaction of np3[N(CH2CH2PPh2)3] with (HgMe)CF3SO3; the complex has been studied by X-ray analysis in the solid state and NMR spectroscopy in solution.

Synthesis, characterization, and structure of the complex [FeH(H2BH2){CH3C(CH2PPh2)3}]

By reaction of [Fe(H2O)6][BF4]2 with 1,1,1-tris(diphenylphosphinomethyl)ethane, tppme, and an excess of sodium tetrahydroborate, in boiling tetrahydrofuran, the red crystalline complex [FeH(H2BH2)(tppme)] has been synthesized. Its crystal structure has been determined from counter diffraction data [orthorhombic, space group Pn21a, a= 20.803(7), b= 16.964(5), c= 10.242(3)A, and Z= 4] and refined by full-matrix least squares to R and R′ of 0.042 and 0.041 respectively for 1 191 reflections having I 3σ(I). The iron atom is six-co-ordinated by the three phosphorus atoms of the ligand, two hydrogen atoms of the BH4 group, and a hydridic hydrogen atom. Variable-temperature 1H and 31P n.m.r. studies have shown that at low temperature (<253 K) the molecule is rigid also in solution. On raising the temperature, scrambling of the three metal-bound hydrogens occurs and the ligand phosphorus atoms, co-ordinated to the metal, become magnetically equivalent.

Synthesis and dynamic stereochemistry of the complexes [Pt{CH3C(CH2PPh2)3}(SR)(H)](R = H or Ph)

The cis square-planar hydrido mercapto derivatives [Pt(triphos)(SH)(H)] and [Pt(triphos)(SPh)(H)][triphos = CH3C(CH2PPh2)3] have been prepared by reaction of [Pt(triphos)(PPh3)] with H2S or HSPh. Analysis of the 1H and 31P NMR data for the two complexes over a temperature range encompassing slow- and fast-exchange limits characterizes these molecules as stereochemically non-rigid on the NMR time-scale. The fluxional behaviour can be explained on the basis of intramolecular exchange of the unco-ordinated phosphorus atom of triphos with the phosphorus atom co-ordinated in cis position to the hydride ligand. At higher temperature, a complete scrambling of the three phosphorus atoms occurs, and at the fast-exchange limit the spin correlation between the phosphorus atoms and platinum metal is retained. The related complexes [Pt(dppp)(SH)(H)](dppp = Ph2PCH2CH2CH2PPh2), [Pt(triphos)Cl2] and [Pt(triphos)(SH)2] have been prepared in order to clarify the mechanism of the fluxionality for [Pt(triphos)(SR)(H)](R = H or Ph).

Alkali-metal complexes with tris(2-diphenylphosphorylethyl)amine. Crystal structures of [Li2{N(CH2CH2POPh2)3}2][Li{N(CH2CH2POPh2)3}]2[BPh4]4 and [Na{N(CH2CH2POPh2)3}(H2O)(BuOH)]BPh4

By oxidation of N(CH2CH2PPh2)3 with H2O2 the ligand N(CH2CH2POPh2)3·3H2O was synthesized. In CH2Cl2 with MBPh4 in butanol, where M = Li or Na, the new ligand gives complexes of formula [Li2{N(CH2CH2POPh2)3}2][Li{N(CH2CH2POPh2)3}]2[BPh4]4, (1), and [Na{N(CH2CH2POPh2)3}(H2O)(BuOH)] BPh4, (2). The crystal structures of these compounds have been determined from counter diffraction data: (1), triclinic, space group P, a= 19.958(11), b= 17.767(9), c= 17.880(9)A, α= 87.63(8), β= 64.38(8), γ= 86.25(8)°, and Z= 1; (2), triclinic, space group P, a= 16.958(9), b= 14.341(8), c= 14.200(8)A, α= 97.39(8), β= 109.43(9), γ= 94.78(8)°, and Z= 2. The structure of (1) consists of two distinct complex cations, in which the lithium atom exhibits different environments, tetrahedral and trigonal respectively. In (2) the sodium atom is surrounded in a tetrahedral fashion by two oxygen atoms of the phosphine ligand, and by the oxygen atoms of one water and one butanol molecule.