E. A. V. Ebsworth

The preparation and properties of some iridium-substituted difluorophosphines: synthesis of some PF2-bridged heterometal complexes

Abstract Reaction between trans -Ir(CO)X(PEt 3 ) 2 and PF 2 X (X = Cl) at 193 K gives Ir(CO)X(PEt 3 ) 2 PF 2 X, which rearranges at 298 K to form Ir(CO)X 2 (Pet 3 ) 2 PF 2 (Z). When X = Br or I, product Z is formed at room temperature, but only traces of the intermediate are detected when X = Br, and none at all when X = I. The end-products have been isolated and characterised by NMR and IR spectroscopy and by analysis, and by reactions with O 2 , S 8 , Se; with B 2 H 6 ; with [M(arene)Cl 2 ] 2 (M = Ru or Os); and with PtCl 2 (COD). Reaction with H 2 G (G = O, S, Se) gives Ir(CO)X 2 (PEtP 3 ) 2 P′FH(G). Crystal structures are reported for Ir(CO)Cl 2 (PEt 3 ) 2 P′F 2 O, for Ir(CO)Cl 2 (PEt 3 ) 2 -μ-(P′F 2 )RuCl 2 ( p -cymene), and for [Ir(CO)Cl 2 (PEt 3 ) 2 -μ-(P′F 2 )] 2 PtCl 2 . In each molecule the angle IrP′Q (Q = O, Ru, Pt) is unusually wide.

Platinum complexes of silylacetylene and silyl perfluoromethyl acetylene

Silylacetylene and silyl perfluoromethyl acetylene react with trans-HPt(PEt3)2Cl to give complexes of the form trans-YCCSiH2Pt(PEt3)2X(Y H, CF3). The same acetylenes react with trans-I2Pt(PEt3)2 at 243 K; the initial products are complexes of 6-coordinated platinum, HPt(SiH2CCY) (PEt3)2I2, which decompose to give YCCSiHIPt(PEt3)2I. There was no evidence of interaction between the acetylenic groups and platinum. The compounds have all been detected spectroscopically, and in most cases by analysis; 195Pt and 31P chemical shifts were determined by heteronuclear double resonance.

Crystal structure of tris(Z-trimethylsilylprop-1-enyl)borane, [CH3CHCSi(CH3)3]3B

The structure of tris(Z-trimethylsilylprop-1-enyl)borane was determined by single-crystal X-ray diffraction. Coordination about boron is trigonal planar with an average CBC angle of exactly 120.0°. Crystal data: C18H39BSi3, Mr, 350.6; space group P1, a 10.311(3), b 13.693(3), c 19.033(3) A; α 70.592(17)°, 13 85.426(21)°, β 79.628(21)°; U 2492.4 A3; Z = 4, Dc 0.934 g cm−3 Mo-Kα radiation, λ 0.71069 A; μ Mo-Kα, 1.83 cm−1; F(000) = 776, T 20°C, R = 0.061 calculated from 3422 observed reflections.

Crystal and molecular structures of silyl isocyanate (at –135 °C) and of germyl isocyanate (at –95 °C)

Crystals of the title compounds are orthorhombic, space group Pnma, with Z= 4. For silyl isocyanate, a= 7.96, b= 6.52, and c= 7.10 A(at –135 °C), while for germyl isocyanate a= 8.01, b= 6.67 and c= 6.97 A(at –95°C); 0.3% estimated standard deviations are assumed. Crystals have been grown ‘in situ’ on a Weissenberg goniometer fitted with low-temperature equipment, and microdensitometer intensities obtained from films exposed using Cu-Kα radiation. The structures have been refined to R= 0.034 over 329 reflections for silyl isocyanate, and R= 0.049 over 266 reflections for germyl isocyanate. The compounds have similar crystal structures, involving crystallographic Cs(m) molecular symmetry and bent (zigzag) heavy-atom skeletons. Important molecular parameters are: for silyl isocyanate, Si–N 1.720(6)A, Si–N–C 158.4(5), and N–C–O 176.4(6)°; for germyl isocyanate, Ge–N 1.856(8)A, Ge–N–C 147.0(7) and N–C–O 173.8(9)°. Both structures contain M ⋯ N and M ⋯ O intermolecular interactions. The nitrogen interactions result in linear N ⋯ M–N groupings and may be responsible for an apparent increase in the M–N bond length as compared with molecules in the gas phase. A quantitative method for estimating the increases to M–N bond lengths is described in the Appendix.

Photoelectron spectrum and bonding in SiF3Mn(CO)5

Abstract The He I photoelectron spectrum of pentacarbonyltrifluorosilylmanganese contains a band attributable to the Si-Mn bonding level, at a binding energy of 10.4 eV. The corresponding band for the SiH 3 - derivative is probably obscured by the stronger bands near 9 eV due to the Mn 3d levels.

Reactions of phosphine, arsine, and stibine with carbonylbis(triethylphosphine)iridium(I) halides. Part 1. Reactions in toluene; X-ray crystal structures of [Ir(CO)ClH(PEt3)2(AsH2)] and [Ir(CO)XH(PEt3)2(µ-ZH2)RuCl2(η6-MeC6H4CHMe2-p)](X = Br, Z = P; X = Cl, Z = As)

trans-[Ir(CO)X(PEt3)2](X = Br or Cl) reacts with ZH3(Z = P, As, or Sb) in toluene at 180 K to give [Ir(CO)XH(PEt3)2(ZH2)]. When Z = P or As, the product is monoisomeric, but with Z = Sb two isomers are formed. [Ir(CO)BrH(PEt3)2(P′H2)](4) reacts with Cl2 to give [Ir(CO)BrClH (PEt3)2]; with Se, [Ir(CO)BrH(PEt3)2(P′H2Se)] is the product. Reaction with HCl at 200 K gives [Ir(CO)BrH(PEt3)2(P′H3)]+, but as the solution is allowed to warm PH3 is displaced by Cl, and a similar reaction with H2Se leads to the formation of [Ir(CO)BrH(PEt3)2(SeH)]. Boron trifluoride does not interact with (4), but B2H6 reacts to give a BH3 adduct that is stable in solution at room temperature. Compound (4) reacts with [{RuCl2(η6-MeC6H4CHMe2-p)}2], forming [Ir(CO)BrH(PEt3)2(µ-P′H2)RuCl2(η6-MeC6H4CHMe2-p)]. Reactions of [Ir(CO)ClH(PEt3)2(AsH2)](5) are similar, except that treatment with Se leads to decomposition. The crystal structures of (5) and the complexes formed by both (4) and (5) with [{RuCl2(η6-MeC6H4CHMe2-p)}2] are reported.

Preparation and properties of silyl- and germyl-trifluoromethylacetylenes (1,1,1-trifluoro-4-silabut-2-yne and 1,1,1-trifluoro-4-germabut-2-yne), and molecular structure of silyltrifluoromethylacetylene determined by electron diffraction

Abstract The compounds MH 3 CCCF 3 (M = Si, Ge) and their fully deuterium-substituted analogues have been prepared by reaction of silyl or germyl halides with the Grignard reagent derived from CF 3 CCH. They have been characterised by a variety of physical and spectroscopic measurements, including a full vibrational analysis and electron diffraction and microwave studies of SiH 3 CCCF 3 .

An electron diffraction determination of the gas-phase molecular structures of 1-silacyclopent-3-ene, 1,1-difluoro-1-silacyclopent-3-ene and 1,1-dichloro-1-silacyclopent-3-ene

Abstract The molecular structures of 1-silacyclopent-3-ene and 1,1-difluoro- and 1,1-dichloro-substituted species have been studied by electron diffraction. All three molecules have structures of C 2v symmetry, but there are apparent deviations from planarity of the rings caused by ring-puckering vibrations, the amplitudes of which are greatest for the fluoride, and smallest for the chloride. For 1-silacyclopent-3-ene important parameters ( r a ) are as follows: r (SiC) = 189.9(3) pm; r (CC) = 153.3(4) pm; r (CC) = 135.9(6) pm; ∠ (CCC) = 118.4(2)°. For 1,1-difluoro-1-silacyclopent-3-ene, r (SiF) = 158.3(3) pm; r (SiC) = 184.7(3) pm; r (CC) = 137.8(7) pm; ∠ (CCC) = 117.9(3)°. For 1,1-dichloro-1-silacyclopent-3-ene, r (SiCl) = 206.6(4) pm; r (SiC) = 187.6(6) pm; r (CC) = 152.6(7) pm; r (CC) = 133.0(10) pm; ∠ (CCC) = 120.3(10)°; ∠ (ClSiCl) = 103.9(5)°.

Structure/reactivity relationships for cationic (phosphenium) iron tetracarbonyl complexes

Abstract An X-ray crystal structure of [(Et 2 N) 2 PFe(CO) 4 ] + , reveals shortening of the PFe and CO eq bonds and lengthening of the FeC eq bonds, possibly suggesting that the CO lability of cationic (phosphenium)iron tetracarbonyl complexes is due to the strong π-acceptor character of the phosphenium ligand.

Photoelectron spectra and bonding of (N–B)-2,8,9-trioxa-5-aza-1-borabicyclo[3.3.3]undecane (boratran) and some 2,8,9-trioxa-5-aza-1-silabicyclo[3.3.3]undecanes (silatrans)

The He(I) photoelectron spectra of silatrans [N(CH2CH2O)3]SiR, (I: R = H, Me, or OEt), and boratran [N-(CH2CH2O)3]B, (II), are compared with those of the non-cage triethoxy-compounds and with that of the parent tris(2-hydroxyethyl)amine. The shifts observed in the N 2p lone-pair band are discussed in relation to internal σ-donation to the empty p orbital of boron or d orbitals of silicon and to interaction with oxygen lone-pair levels.