Volume 46, Issue 7

Thermal reaction of Me 2 Si[Cp′M(CO) 3 ] 2 (M = Mo, W; Cp′ = C 5 H 4 ) with tetramethyldiphosphane and -diarsane gives oxidative coupling products with bridging EMe 2 -groups (E = P, As). With E = P discrete binuclear compounds are obtained, which on further thermolysis afford new species of the general formula {Me 2 Si(Cp′M) 2 (CO) 3 (μ-PMe 2 ) 2 } (5). X-Ray structure determination of 5 a (M = Mo) and NMR data show a PMP-heteroallylic system which is bound to the second metal. In the case of M = W a second compound with a mixed hydrido and dimethylphosphido bridge can be isolated, which shows fluxionality in solution. However, the oxidative additions with tetramethyldiarsane lead to insoluble products which are assumed to be polymeric with Cp′–SiMe 2 –Cp′ as well as AsMe 2 bridges linking the metal centers.

By the addition of iminoboranes RB≡NR′ (1a—d) to the corresponding diazadiboretidines (RBNR′) 2 (2a—d), a ring expansion is observed, borazines (RBNR′) 3 (3a—d) being formed. The particular iminoborane iPrB≡NiPr (la) can be added to the diazadiboretidines 2c—g to give borazines B 3 N 3 R 2 R′ 2 iPr 2 with an unsymmetrical set of ligands. From PhB=NtBu (1j) and (PhBNtBu) 2 (2j), the Dewar borazine 3j′ is formed, which crystallizes in the space group P2,/c. The diazadiboretidines 2b—i, the borazines 3b—d,f, and the Dewar borazine 3e′ are split into the corresponding iminoboranes RB≡NtBu at 500-600 °C in the gas phase. The molten borazines 3b—d,f and Dewar borazines 3e′, j′ are contracted to the corresponding diazadiboretidines 2b—f, j at 160-320 °C. [Ligands R/R′: iPr/iPr (a), Me/tBu (b), Et/tBu (c), Pr/tBu (d), ¡Pr/ tBu (e), Bu/tBu (f), iBu/tBu (g), tBu/tBu (h), tBu(Me 3 Si)N/tBu (i), Ph/tBu (j).]

Borontrichloride reacts with two equivalents of z-3-diethylboryl-4-triethylstannylhex-3-en (2) to give the intermediate 3. In situ ethylation of 3 yields the bis(z-3-diethylborylhex-3-en-4-yl)ethylboran (4). Reactions of 4 with cyclopentadienylcobaltbis(ethen) or molybdenumhexacarbonyl lead to the mononuclear complexes 5 and 6. Their constitution is derived from NMR and MS data, and confirmed for 6 by an X-ray structure analysis.

A number of aminotetraphosphetanes could be obtained by reductive dehalogenation of dichlorophosphines with magnesium as well as by elimination of chlorotrimethylsilane from vicinal chlorosily-functionalized biphosphines and from [2+2]-cyclodimerization of aminodiphosphenes, respectively. The molecular structures of several tetraphosphetanes are reported and discussed. The torsion-angle of the four-membered rings varies from 22.5° to 45.7°, depending on the size and electronegativity of the exocyclic ligands.

The methyltrifluoromethyliodonium salts CH 3 ICF 3 + MF 6 - are prepared by methylation of CF 3 I with CH 3 OSO+MF 6 - (M = As, Sb) in liquid SO 2 . The compounds have been characterized by Raman and NMR spectroscopy. Attempts to prepare the analogous bromonium compounds were not successful.

The reaction of nitrile solvate complexes [(C 5 H 5 )(P(OCH 3 )3) 2 (NCCH 3 )Fe]PF 6 (Ia) and [(C 5 H 5 )(DPPE)(NCCH 3 )Fe]PF 6 (Ib, DPPE = [(C 6 H 5 ) 2 PCH 2 ] 2 ) with halogenophosphanes, -arsines or -stibines L′ afford the cationic complexes [(C 5 H 5 )(L 2 )(L′)Fe]PF 6 (II, L 2 = (P(OCH 3 ) 3 ) 2 , L′ = PCl 3 , P(CH 3 )Cl 2 , P(t-C 4 H 9 )Cl 2 , P(C 6 H 5 )Cl 2 , P(C 6 H 5 ) 2 Cl, PBr 3 , AsCl 3 , SbCl 3 ; III, L 2 = DPPE, L′ = PCl 3 , AsCl 3 , SbCl 3 ) in high yield. Spectroscopic data are given together with the characterization of [(C 5 H 5 )(P(OCH 3 ) 3 ) 2 (P(t-C 4 H 9 )Cl 2 )Fe]PF 6 (IIc) by single crystals X-ray diffraction analysis. Through reduction of coordinated P– Cl ligands in selected complexes II and III complexes bearing PH 3 , P(C 6 H 5 )H 2 and P(C 6 H 5 ) 2 H ligands are available. With anhydrous KF in acetonitrile solution in the presence of dibenzo-18-crown-6, the coordinated P– Cl ligands in selected complexes II and HIII undergo Cl/F-exchange with formation of related complexes with P(CH 3 )ClF, P(CH 3 )F 2 , PF 2 Cl and PF 3 ligands.

[Li(tmed)] 3 [Sm(CH 3 )6] reacts with tert-butanol in diethyl ether to give [Li 5 Sm(O–t-C 4 H 9 ) 8 ] (1), the structure of which has been elucidated by X-ray structure analysis. 1 crystallizes tetragonally with a = 1703(4) and c = 3178(1) pm, space group P4 1 2 1 2, Z = 8. The structure was refined to R = 0.042 for 4082 observed reflections (F o > 6σ(F o )).

Tris(oxinato) complexes of aluminium(III) and gallium(III) have been prepared from 8-oxyquinoline (OxH) and its six C-methylated derivatives from aqueous solutions of the metal chlorides or nitrates and an ammonium acetate buffer. Crystalline monohydrates or (upon precipitation with methanol) mono-methanol adducts are obtained. Single crystal X-ray diffraction studies reveal a meridional tris(chelate) structure for the two (isomorphous) tris(oxinates) Al(Ox) 3 · MeOH and Ga(Ox) 3 · MeOH with distinct differences in the individual dimensions. (The MeOH molecules form strong hydrogen bonds with one of the oxygen atoms.) For these species and those of the substituted ligands 3-MeOx, 4-MeOx, 5-MeOx, 6-MeOx, and 7-MeOx a similar meridional structure was confirmed by low temperature 1 H NMR spectroscopy, which showed three inequivalent sets of ligands in each case. The collaps of these signals at elevated temperatures indicates a ligand-equilibrating process, with the mechanism probably comprising a dissociation of a pyridine function from the metal, to give a fluctional pentacoordinate species with free rotation about the intact M—O bond, and an M—N recombination at a random octahedral site. For the 2-MeOx ligands, however, the facial structure is preferred at lower temperature, but with the meridional isomer present as a component of an equilibrium. This indicates the strong steric influence of substituents in 2-position of the 8-oxy-quinoline.

Pyrazole, 1,2,4-triazole, and 8-amino-quinoline form complexes as neutral ligands with silver nitrate in slightly acidic aqueous medium. With pyrazole a 2:1 complex (1) is obtained. The crystal structure determination revealed an ionic structure with independent NO 3 - anions and centrosymmetrical (pyr) 2 Ag + cations with a linear coordination geometry at the silver atoms. The reactions with 1,2,4-triazole and 8-amino-quinoline yield dimeric 1:1 complexes (2,3), in which the silver atoms are bridged by the ligands and have short contacts with nitrate oxygen atoms. The coordination geometry of the metals can thus be described as distorted tetrahedral. A 1:1 complex with 2,3-diphenyl-1,2,4-triazole (2a) and a 2:1 complex with 8-hydroxy-quinoline (4) have also been prepared, but not characterized in detail.

From solutions of TeBr 4 in concentrated aqueous HBr red needles of the crystalline hexabromotellurous acid with the stoichiometric composition H 2 TeBr 6 · 8H 2 O (1) were isolated (space group P2 1 /n, a = 7.662(5), b = 9.796(6), c = 11.987(8) Å, β = 91.35(4)° at 259 Κ). If the HBr:TeBr 4 concentration ratio in the system TeBr 4 /HBr/H 2 O was kept low, a novel acid with formal composition HTe 3 Br 13 ·4 H 2 O (2) could be prepared (space group Cm, a = 13.501(5), b = 15.453(6), c = 9.153(3) Å, β = 138.11(2)° at 140 Κ). The X-ray structural analysis of 1 shows the acid to contain, besides regular octahedral [TeBr 6 ] 2- ions (Te-Br: 2.671(4)-2.716(4) Å), [Η 9 Ο 4 ] + hydroxonium ions (O ··· O: 2.48(3)-2.62(3) Å). The [H 9 O 4 ] + units are linked through a hydrogen bond system (O ··· O: 2.80(3)-2.97(4) Å) to form a three-dimen-sional network. The formula has to be written as [H 9 O 4 ] 2 [TeBr 6 ]. 2 is the first acid in this class with a trinuclear anion. Its structural formula is [H 9 O 4 ][Te 3 Br 13 ]. As a fragment of the Te 4 Br, 6 cube the anion consists of three edge-sharing octahedra with a central triply bridging Br. The mean bond distances are 2.515 Å for terminal Te-Br, 2.944 Å for Te-μ 2 Br and 3.077 Å for Te—μ 3 Br. The Ο···Ο distances in the isolated [H 9 O 4 ] + hydroxonium ions are 2.45(3)-2.57(2) A. Raman spectra of both acids are reported.

Hexachlorocyclotrisiloxane (2) and octachlorocyclotetrasiloxane (4) were prepared by reaction of SiCl 4 with O 2 at 955 °C. Their mass spectra are compared with those of the isoelectronic cyclophosphazenes. The vibrational spectra of 2 and 4 are very similar and closely related to that of (PNCl 2 ) 3 , but clearly different from that of the puckered (PNCl 2 ) 4 molecule. The X-ray examination of 2 and 4 reveals planarity of the (SiO) n , n = 3 and 4 ring systems, with d(Si—O) on average 1.619(4) and 1.584(3) A, respectively.

Tricarbonyl(η 5 -2,4-pentadienyl)manganese (1) and tricarbonyl(η 5 -2,4-dimethyl-2,4-pentadienyl)manganese (2) photochemically add 2,3-dimethyl-1,3-butadiene (3). Mediated by manganese, 6,7-dimethyl-2,6-cyclononadiene-1-yl and 1,3,6,7-tetramethyl-2,6-cyclononadiene-1-yl complexes are formed. Η-shifts from the methyl groups of the substituted CC double bonds convert the primary products into tricarbonyl-η 3:CH -l-methylene-2-methyl-6-cyclononen-2-ylmanganese (4), and tricarbonyl-η 3:CH -1-methylene-2,5,7-trimethyl-6-cyclononen-2-yl-manganese (6), respectively. In addition tetracarbonyl-η 3 -1-methylene-2-methyl-6-cyclononen-2-yl-manganese (5), and tetracarbonyl-η 3 -1-methylene-2,5,7-trimethyl-6-cyclononen-2-ylmanganese (7) are obtained. The latter are also formed from 4 and 6 by addition of CO under ambient conditions. In the complexes 4 and 6 the hydrocarbon ligands are coordinated by enyl units, encompassing C 1, C2, and the exocyclic methylene group, and by a C-H-Mn 2-electron-3-center bond of the 2-methyl group to the manganese. They exhibit temperature dependent 1 H NMR spectra due to a hindered rotation of the 2-methyl group with a barrier of activation of AG* = 40-43 kJ · mol -1 . There is evidence for an equilibrium of the complexes 4 and 6 with the isomers tricarbonyl-η 3:CH -1-methylene-2-methyl-5-cyclononen-2-yl-manganese (4′), and tricarbonyl-η 3:CH -1-methylene-2,5,7-trimethyl-5-cyclononen-2-yl-manganese (6′). At higher temperatures the isomers 4, 4′ and 6, 6′ are interconverted by a 1,4-H shift with a barrier of activation of AG* = 75 kJ · mol -1 . The crystal and molecular structure of 4 was determined by X-ray structure analysis. The constitutions of the complexes 4-7 were deduced from IR and 1 H NM R spectra.

Two new flavones grantionin 1 and grantioidinin 2 have been isolated from Inula grantioides and their structures were determined as 7-hydroxy-6,3′,5′-trimethoxy flavone 1 and 5-hydroxy-3,6,7,8,2′,5′-hexamethoxy flavone 2 along with a known dinorsequiterpene pluchidione 3.

Butadiyn- and hexatriynamines 1 a - g, bearing silyl-, trichlorvinyl- and amino groups, resp. in the ω-position of their acetylenic system add nitrile oxides 3 at their first C/C-triple bond to give the 5-aminoisoxazoles 4, whereas the analogous oligoynamines 1 i-l, bearing a hydrogen in the ω-position, add the nitrile oxides 3 at their terminal C/C-triple bond to give the (5-isoxazolyl)ethynyl- or -1,3-butadiynyl-amines 7. The latter ones react with a second molecule of nitrile oxide 3 to give the bis(isoxazoles) 8. In two cases, keton oximes 6e,j are formed as the products of a 1,3-addition.

3-O-Methylpannaric acid is a new dibenzofuran from the lichen Roccella capensis (Roccellaceae); its structure has been established by spectroscopic and chemical methods.