A. M. Piazzesi

Metals in orgranic syntheses : VII. The isolation of trans-[PtCl(COPr-n)(PPh3)2] (I) and trans-[Pt(SnCl 3)(COPr-n)(PPh 3) 2] (II), active intermediates in the hydroformylation of propene catalyzed by a [PtCl 2(PPh 3) 2]-SnCl2, precursor. The crystal and molecular structure of complex i and a comparison with its palladium analog

Trans -[PtCl(COPr-n)(PPh 3 ) 2 ] (I) has been isolated in good yield from the mixtures obtained by treating a mixture of propene, cis -[PtCl 2 (PPh 3 ) 2 ] and SnCl 2 · H 2 O with carbon monoxide in the presence or absence of hydrogen in an alcohol in which no significant hydroformylation or hydroxycarboalkylation actually occurs. The cis -[PECl 2 (PPh 3 2 ]-SnCl 2 · 2 H 2 O system is highly active in the catalytic hydroformylation in methyl isobutyl ketone, and from reaction mixtures in this medium trans -[Pt(SnCl 3 )(COPr-n)(PPh 3 ) 2 ] (II) has been isolated (33% yield). The presence of a PtSn bond in a complex of type II plays a key role in promoting the formation of the aldehyde from the acyl derivative, but it is not necessary for the formation of intermediate I, since this can be isolated in good yield even in the absence of the tin compound. The higher regioselectivity observed using intermediate I or II, compared with that when the precursor is used is discussed in terms of steric effects of the ligands competing for coordination to the platinum atom. The catalytic properties of complex I are compared also with those of its palladium analog, which catalyzes only the hydrocarbo-

Metals in organic syntheses. XIII. The isolation and molecular structure of trans-[PdCl(COC6H13-n)(PPh3)2], an intermediate in the hydrocarboalcoxylation of 1-hexene catalyzed by the precursor trans-[PdCl2(PPh3)2]

Abstract The complex trans-[PdCl(COC6H13-n)(PPh3)2] has been isolated in the course of 1-hexene hydrocarboalkoxylation catalyzed by the precursor trans-[PdCl2(PPh)3)2] in EtOH. The catalytic activity of the precursor and that of the acyl complex are practically the same, thus suggesting that the latter complex is an intermediate in the catalysis. The IR spectrum of the acyl complex shows ν(CO) at 1685 cm−1. The crystal and molecular structure of the complex was determined from three dimensional X-ray diffractometer data. The complex crystallizes in the triclinic space group P 1 . Cell parameters were: a = 17.330(8), b = 11.963(7), c = 10.100(7) », α = 112.4(1), β = 97.7(1), γ = 99.8(1)°, Z = 2. Full-matrix least-squares refinement converged at R = 0.067. The coordination about the metal significantly deviates from planarity towards a tetrahedral configuration. No unusual dimensions were shown.

Metals in organic syntheses

Abstract The complex trans -[PtCl(COC 6 H 13 -n)(PPh 3 ) 2 ] (I) has been synthesized by treating cis -[PtCl 2 (PPh 3 ) 2 ] and 1-hexene with carbon monoxide under pressure in EtOH at 100°C. When in combination with SnCl 2 -2H 2 O, complex I is an intermediate precursor in the highly regioselective catalytic hydroformylation of 1-hexene, which readily occurs in a solvent such as a ketone. The crystal and molecular structure of complex I has been determined from three dimensional X-ray diffractometer data. The complex crystallizes in the triclinic space group P 1 . Cell parameters are as follows: a 15.869(8), b 12.306(8), c 11.437(7) A, α 109.8(1), β 76.6(1), γ 112.9(1)°, Z  2. Fullmatrix least-squares refinement converged at R  0.058 ( R w  0.064). The structure has approximately square planar geometry, and shows no unusual dimensions.

The crystal structure of dichlorobis(N-methylimidazole)dimethyltin(IV)

Abstract The structure of the complex dichlorobis( N -methylimidazole)dimethyltin(IV), Me 2 SnCl 2 ( N Miz) 2 , has been determined from three-dimensional X-ray diffraction data. The compound crystallizes in the triclinic space group P 1 , and the cell parameters are: a 7.218(2), b 7.441(3), c 7.972(3) A, α 114.1(1), β 104.05(10), γ 97.8(1)°, Z = 1. The coordination geometry about the tin atom is all- trans octahedral; the N Miz. ligands are bonded to the metal through their pyridine-like nitrogen atom. The SnC, SnCl and SnN bond distances are 2.118(5), 2.571(3) and 2.329(5) A, respectively. The 1 H NMR spectra are consistent with the presence of a trans -octahedral structure for Me 2 SnCl 2 ( N Miz) 2 in solution, also.

Crystal and molecular structure of trans-(methyl)chlorobis(triphenylphosphine)platinum(II)

Abstract The crystal and molecular structure of trans -Pt(CH 3 )Cl(PPh 3 ) 2 has been determined. Crystals are monoclinic, space group P 2 1 / n , a = 11.813(7), b = 23.523(9), c = 12.306(7) A , β = 111.7(1)°, Z = 4.2676 observed reflections were measured with a diffractometer; the structure was solved by Patterson-Fourier methods and refined by full-matrix least-squares to a final conventional R of 0.049 ( R w = 0.041). The crystal contains discrete neutral trans -Pt(CH 3 )Cl(PPh 3 ) 2 molecules, separated by normal van der Waals contacts. The complex is a typical square-planar Pt(II) species. Structural parameters: PtCl = 2.431(3), PtC = 2.08(1) PtP = 2.295(3) and 2.298(3) A ; P(1)PtCl = 88.1(1), P(1)PtC(1) = 92.3(4), P(2)PtCl = 88.1(1) and P(2)PtC(1) = 91.6(4)°.

Crystal and molecular structure of cis-Dichlorobis(N,N-dimethyl O-ethylthiocarbamate)platinum(II)

The structure of cis -dichlorobis(N,N-dimethyl-O-ethylthiocarbamate)platinum(II) has been determined from three-dimensional X-ray data. The complex crystallizes in the orthorhombic system, space group P bca , with molecules in a unit cell of dimensions a = 14.681(5), b = 17.136(6), c = 14.357(5) A . A full-matrix least-squares refinement has led to a value of the conventional R index (on F) of 0.044 for the 1501 observed reflections with I ⩾ 3σ(I). The complex is a typical square-planar Pt(II) species. Structural parameters: PtCl 2.320(4) and 2.321(4); PtS 2.285(4) and 2.291(4) A ; Cl(1)PtCl(10) 90.5(2), S(1)PtS(10) 87.1(2), Cl(1)PtS(1) 91.1(2) and Cl(10)PtS(10) 91.8(2)°.

Crystal and molecular structure of trans-dithiocyanatobis(N-methyl O-ethylthiocarbamate)palladium(II)

Abstract Trans -dithiocyanatobis(N-methyl O-ethylthiocarbamate)palladium(II) has been prepared and studied by IR and visible spectroscopy. Its molecular structure has been determined from three-dimensional X-ray data. The complex crystallizes in the triclinic system, space group P 1 with one molecule in a unit cell of dimensions a = 9.522(7), b = 8.352(7), c = 5.658(6) A , α = 93.1(1), β = 96.5(1), γ = 88.8(1)°. Full-matrix least squares refinement has led the conventional R index (on F) to 0.029 for the 900 observed reflections having I ⩾ 2.5 σ(I). The complex is a typical square-planar Pd(II) species. Relevant structural parameters are: PdS 2.319(1) and 2.331(2) A S(1)PdS(2) 82.9(1)°.

Preparation, spectroscopic characterization and anion binding studies of a mononuclear Co(II) derivative of Carcinus maenas hemocyanin

Abstract The binuclear copper in the active site of Carcinus maenas hemocyanin has been substituted with one EDTA-resistant Co(II) per 75 000 M r by reconstitution of the apo protein. Specific cobalt substitution at the copper binding site is demonstrated from the optical spectral changes directly correlated with the amount of Co(II) bound to the protein, the ellipticity in CD spectra in the near UVVis region, and the efficiency of tryptophan fluorescence quenching. The optical absorption spectrum of the cobalt-substituted protein is characterized by a band pattern attributable to d-d transitions of the metal ion. Both the position of the wavelength maximum (568 nm) and the molar extinction coefficient (≅300 M -1 cm -1 ) are typical of a four-coordinate, pseudo-tetrahedral Co(II) center. Optical titrations indicate that Cl - , Br - , N 3 - , SCN - , and CN - bind to Co(II)Hc, each with a stoichiometry of 1:1 per metal center. The apparent stability constants determined from Hill plots of titration data decrease in the order CN - » N 3 - ≅ SCN - >Cl - >Br - . Low temperature EPR studies demonstrate that at pH 7, the cobalt is high spin both in the presence and absence of anionic ligands. A low spin species is formed at pH 9 in the presence of cyanide. The spectrum of this latter complex exhibits superhyperfine structure indicative of metal ligation to 14 N supplied by the protein. Direct ligation of cyanide to cobalt is demonstrated by additional spectral splitting observed when this complex is formed using 13 C-labelled CN - .

1:3 Platinum(II) halide complexes with thiocarbamic esters. The crystal and molecular structure of chloro-tris(N-propyl-O-ethylthiocarbamate)platinum(II) chloride

Abstract The complexes {[PtL 3 X]X}, where L = N-ethyl O-ethylthiocarbamate (ETC), N-propyl O-ethylthiocarbamate (PTC) and X = Cl, Br, were prepared and characterized by IR spectroscopy. The structure of {[Pt(PTC) 3 Cl]Cl} was determined from three-dimensional X-ray diffractometer data. The complex crystallized in the triclinic system, space group P 1 with two molecules in a unit cell of dimensions: a = 16.935(4), b = 10.697(3), c = 8.949(3) », a = 114.1(1), β = 83.4(1), γ = 98.4(1)°. Full-matrix least-squares refinement converged at R = 0.056 ( R w = 0.061). The structure consist of separated molecules, each containing the [Pt(PTC) 3 Cl] + cation which holds the Cl − anion by hydrogen bonds through the NH groups of the three PTC molecules.

Reactivity of functionalized halo-derivatives with transition metal complexes. Synthesis and x-ray diffraction study of [Ph3P(CH2CH2COCH3)]+[PdCl3(PPh3)]− obtained by reaction of trans-[PdCl2(PPh3)2] with CH3COCH2CH2Cl

Abstract The complex [PdCl3(PPh3)]−[Ph3P(CH2CH2COCH3)]+ (I) was prepared by reacting trans-[PdCl2(PPh3)2] with CH3COCH2CH2Cl in boiling ethanol. The i.r. spectrum of (I) shows a band of strong intensity at 1717 cm−1 for v(CO) and bands attributable to v(PdCl) at 343(s), 301(w) and 277(m) cm−1. The crystal and molecular structure of complex (I) has been determined from three-dimensional X-ray diffractometer data. The complex crystallizes in the monoclinic space group P21/n. Cell parameters are as follows: a = 18.849(9), b = 21.301(9), c = 9.156(7) A, β = 92.8(1)°, Z = 4. Full-matrix least-squares refinement converged at R = 0.063 (Rw = 0.055). The anion [PdCl3(PPh3)]− has approximately square planar geometry. The cation [Ph3P(CH2CH2COCH3)]+ shows the usual angular distortions from the tetrahedral value at the phosphorus atom.