Andrew J. Thorne

Carbene complexes: XX. Electron-rich carbeneiron(0) trigonal bipyramidal carbonyls and their germanium(II) and tin(II) analogues [Fe(CO)3(L)(L′)] (L = CN(Me)(CH2)2NMe, L′ = PEt3, 3 CO's equatorial; or L = M(OAr)2 (equatorial: M = Ge OR Sn, Ar = C6H2But2-2,6-Me-4), L′ = CO)☆

Abstract The first bis(aryloxo)-main Group 14 metal(II)-transition-metal complexes eq -[Fe(CO) 4 ){M(OAr) 2 }] ( eq - denotes equatorial, Ar = C 6 H 2 Bu t 2 -2,6-Me-4, and M = Ge (II) or Sn (III)) have been prepared, from [Fe 2 (CO) 9 ] and the appropriate aryloxide M(OAr) 2 . X-ray structures of the complexes II and III show them to have the unusual (for a trigonal bipyramidal (tbp) [Fe(CO) 4 L] complex) eq -distorted tbp configuration. The related carbene complex [Fe(CO) 3 (L Me )(PEt 3 )] (I) [L Me = CN(Me)(CH 2 ) 2 N Me] has the tbp- rans -configuration in the crystal. The stereochemical integrity of each of I–III is maintained in solution. The exceptionally short Fe-Ge and Fe-Sn distances, and the relatively small deviation from coplanarity of the MO 2 plane and the Fe(CO) ax M planes are consistent with the ligands M(OAr) 2 being good π-acceptors but poor σ-donors in complexes II or III. By contrast, the X-ray data for complex I support the view the L Me is a strong σ-donor but weak π-acceptor. For a series of tbp- trans -[Fe(CO) 3 (L)(L′)] complexes, a comparison of Fe-C carb and Fe-P distances shows that the trans -influence of a ligand L falls in the sequence L = CO ρ PR 3 ρ L Me .

Chemistry, including the X-ray structure, of bis[bis(trimethylsilyl)methylgermanium(II)], R2GeGeR2[R = CH(SiMe3)2], a stable compound having a metal–metal ‘double bond,’ a dimetallene

Reaction of MgClR(OEt2)[R = CH(SiMe3)2] with GeCl2· dioxane in OEt2 yields the bright yellow crystalline Ge2R4[having a trans-folded C2h Ge2C4 framework with a fold angle of 32°, a germanium environment intermediate between pyramidal and planar (sum of angles at Ge = 348°) and a GeGe bond length of 2.347(2)A(ca. 4% shorter than in elemental germanium)], which behaves chemically as a singlet germylene eR2.

SYNTHESIS AND CHARACTERISATION OF SOME MESOGENIC MONONUCLEAR AND MULTINUCLEAR PHTHALOCYANINES

Abstract Octa-substituted phthalocyanines carrying either one or two hydroxyalkyl chains have been synthesised and their liquid crystalline behaviour characterised by polarised light microscopy and differential scanning calorimetry. The compounds form discotic columnar mesophases with hexagonal or rectangular symmetry. Examples have been used as precursors for the synthesis of mesogenic di-nuclear and tri-nuclear phthalocyanines, ie derivatives containing two or three phthalocyanine rings. These compounds have been characterised by elemental analysis and low resolution field desorption mass spectrometry, FD-MS. 1H NMR spectroscopy and gel permeation chromatography of selected examples provide supporting data. Visible region spectroscopy of dilute solutions of the multinuclear phthalocyanines in cyclohexane (down to a concentration of 5 × 10−7 mol dm−3 where intermolecular aggregation is expected to be minimal) suggests that the compounds exist as an equilibrium between a ‘closed’ conformer where the two rings are arranged cofacially (broad band centred at ca 645nm) and an open form having an absorption band similar to that of the simpler precursor phthalocyanines, λmax ca. 730 nm. The closed conformer is favoured in more polar media eg 10% toluene - 90% ethanol. Examples have been deposited as spin coated films of even thickness on glass slides.

The molecular structure of gaseous bis(trimethylsilyl)methane, CH2(Si(CH3)3)2, as determined by electron diffraction: An unusually large SiCSi angle

Abstract Steric interaction between trimethylsilyl groups in the title compound is relieved by opening the SiCSi angle (123.2° (9)), by stretching the central CSi bonds slightly (1.889-(4) A) and by a torsional displacement of the methyl groups from staggered positions (25° (5)). The compound is compared to other strained t-butyl or trimethylsilyl substituted methanes and silanes.

Synthesis and characterisation of 2, 4, 6-tri-t-butylphenylphosphines; X-ray structure of [P(C6H2But3-2,4,6)S]3

Whereas treatment of phosphorus(III) chloride with an equimolar portion of LiAr (Ar = C6H2But3-2, 4, 6) affords PArCl2, with 2LiAr there is obtained ArPPAr, which has Low-lying MO′s (photoelectron spectroscopy) and a LUMO (reversible electrochemical 1-electron reduction); other reactions of LiAr lead to PAr(Cl)X [X - CH(SiMe3)2(and a 1-phosphabenzocyclopentene therefrom), Ph, C6H2Me3-2, 4, 6(interesting variable temperature n.m.r. spectra), or OC6H2But3-2, 4, 6], or the puckered six-membered (PS)3 cyclic title compound (ring torsion angles all 80° with the S atoms 1.0 A out of the P3 plane ) which with PPh3 yields ArPPAr.

Novel two-coordinate germanium(II) arylamides: Ge(NHAr)2, ArN[Ge(NHAr)]2(µ-NAr) and [Ge(µ-NAr)]2 2, and the X-ray structures of 2 and Sn(NHAr)2(Ar = C6H2But3-2,4,6)

Depending on reaction conditions, treatment of GeCl2(1,4-dioxane) with [Li(µ-NHAr)(L)]2(L = OEt2 or OC4H8) yields Ge(NHAr)21 or the first binuclear group 14 element(II) amides [Ge(µ-NAr)]22 or ArN[Ge(NHAr)]2(µ-NAr)3; X-ray structural data are presented on the tin analogue of 1 and on the germetane 2.

Molecular structures of bis(trimethylsilyl)methyl-lithium [(LiR)n, R = CH(SiMe3)2] in the vapour (gas-phase electron diffraction: a monomer, n= 1) and the crystal (X-ray: a polymer, n=∞)

Gaseous bis(trimethylsilyl)methyl-lithium (LiR) at ca. 413K is a monomer with Li–C 2.03(6)A and the SiMe3 groups only slightly distorted from an eclipsed conformation with respect to each other; crystalline LiR is a polymer, having three ‘molecules’ of monomer in the asymmetric unit, the Li–C distances range from 2.14(3) to 2.27(2)A and average 2.19(5)A, <CLiC angles are 147(1), 151(1), and 152(1)°, and <LiCLi angles are 152(1)–153(1)°.

Metal secondary amides derived from the highly hindered 2,4,6-tri-t-butylaniline; X-ray crystal structure of trans-[Li(µ-NHAr)(OEt2)]2(Ar = C6H2But3-2,4,6)

Treatment of 2,4,6-tri-t-butylaniline (NH2Ar) with LiBun in OEt2 yields the white crystalline trans-[Li(µ-NHAr)(Oet2)]2, (2), which in turn furnishes the orange Sn(NHAr)2(with SnCl2) or a mixture of NiI/NiIIamides {using [Nil2(PPh3)2]} which with CO affords colourless crystalline cis-[Ni(Co)2(NHAr)2];the lithium amide(2) has a centrosymmetric four- membered planar LiNLiN ring with the substituents at N arranged in a transoid fashion: Li–N = 2.041(6) and 1.987(5)A, Li–O = 1.906(5)A, and ∠NLiN = 102.2(2)°

Liquid crystalline polymeric phthalocyanines

The first examples of phthalocyanine linear mainchain polymers showing liquid crystal properties are described.

Molecular structures of the main group 4 metal(II) bis(trimethylsilyl)-amides M[N(SiMe3)2]2 in the crystal (X-ray) and vapour (gas-phase electron diffraction)

The group 4 metal(II) bis(trimethylsilyl)amides, M[N(SiMe3)2]2, are V-shaped monomers both in the crystal (M = Sn or Pb) at 140 K and the vapour (M = Ge, Sn, or Pb) at ca. 380 K, with ∠NMN in the vapour being 101(1.5), 96, or 91(2)° for M = Ge, Sn, or Pb respectively [but 104.7(2)(M = Sn) or 103.6(7)°(M = Pb) in the solid].