Alan D. Redhouse

Synthesis of coordinatively unsaturated diphosphine nickel(II) and palladium(II)β-agostic ethyl cations: X-ray crystal structure of [Ni{But2P(CH2)2PBut2}(C2H5)][BF4]

Protonation of [M(L2)(η2-C2H4)](L2= chelating diphosphine; M = Ni, Pd) with HBF4 affords a series of cations [M(L2)(C2H5)]+ characterized as β-agostic ethyl complexes by NMR spectroscopy and X-ray structure analysis.

The crystal structure of (HOMe2Si)2O

Abstract X-Ray crystallography shows that in the solid state, molecules of(HOMe 2 Si) 2 O are extensively hydrogen bonded together to form zig-zag double chains with no bonding between the chains.

Molecular iodoalkane complexes: preparation of the complexes [(η5-C5H5)Ru(PPh3)(CNtBu)(IR)]PF6, (R = CH3, CH2SiMe3), and the crystal structures of [(η5-C5H5Ru(PPh3)(CNtBu)I] and [(η5-C5H5)Ru(PPh3)(CNtBu)(ICH3)]PF6

Abstract Reaction of the molecular hydrogen complex [(η5-C5H5)Ru(PPh3(CNt+Bu)(η2-H2)]PF6 (1) with CH3I and Me3SiCH2I leads to the iodoalkane complexes [(η5-C5H5)Ru(PPh3)(CN+Bu)(IR)]PF6 (R = CH3 (2) and R = CH2SiMe3 (3)), respectively. Treatment of the neutral iodide [(η5-C5H5)Ru(PPh3)(CNtBu)I] (4) with MeSO3CF3 gave 2 as the triflate salt. The crystal structures of 2 and 4 have been determined.

3H-Azepines and related systems. Part 5. Photo-induced ring expansions of o-Azidobenzonitriles to 3-Cyano- and 7-Cyano-3H- azepin-2(1H)-ones

Abstract Unlike other aryl azides bearing electron-withdrawing ortho-substituents, o-azidobenzonitriles on photolysis in aqueous-tetrahydrofuran yield mixture of the expected 3-cyano- and the unexpected 7-cyano-3H-azepin-2(1H)-ones. In one instance ring-contraction to a 2-azabicyclo[3.2.0]hept-6-ene-3-one is noted. X-Ray crystallographic data for 7-cyano- and 4-chloro-7-cyano-3H-azepin-2-one, and for the azabicycloheptenone, are presented.

Synthesis of Pt(II)-η3-benzyl complexes: crystal structure of [Pt(Bu2tP(CH2)3PBu2t)(η3-anti-1-MeCHC6H4Br-4)][BF4]

Abstract Treatment of bis(1,5-cyclooctadiene)platinum with 1,3-bis(di-t-butylphosphino)propane and various styrenes and subsequent protonation of the resultant platinum(0) alkene complexes affords a series of cationic complexes [Pt(Bu2tP(CH2)3PBu2t)(η3-anti-1-MeCHC6H4X)][BF4] (X = Br-3, Br-4 (2b), H, Me-4, MeO-4). These have been characterized by NMR spectroscopy and, in the case of 2b, by a single-crystal X-ray diffraction study.

1,3-dipolar cycloadditions of 2-ethoxy- and 2-(ethylthio)-1-azetines with nitrile oxides, nitrile ylides and nitrilimines : an unexpected 1,2,4-triazole formation

Abstract 2-Ethoxy- and 2-(ethylthio)-1-azetines readily undergo 1,3-dipolar cycloadditions with nitrile oxides and nitrile ylides to give stable 4,5-bicyclic cycloadducts. With nitrilimines, however, the expected 1,3-dipolar cycloadducts and/or unexpected ring-opened products, namely 1,2,4-triazoles, are formed depending on the nature of the nitrilimine N -substituent. In contrast, the azetines fail to react with nitrile sulphides, azomethine ylides, nitrones, aryl azides, and various dienes. X-ray crystallographic data on the nitrile oxide, nitrile ylide, and nitrilimine cycloadducts, and on the 1,2,4-triazoles, are presented. Also a mechanistic rationale for triazole formation is offered.

Synthesis and crystal structure of the six-coordinate ruthenium nitrosyl complex [(η5-C5H5)Ru(PPh3)(NO)(Cl)]PF6

Abstract Reaction of [(η 5 -C 5 H 5 )Ru(PPh 3 ) 2 Cl] ( 1 ) with sodium nitrite in hot acidified ehtanol followed by anion exchange gave the red crystalline solid [(η 5 -C 5 H 5 )Ru(PPh 3 (NO)(Cl]PF 6 ( 2 ) in good yield. Compound 2 has been crystallographically characterised and shows a large interligand angle at ruthenium between the chloride and nitrosyl ligands. The dication {[(η 5 -C 5 H 5 )Ru(PPh 3 )(CN t Bu)(NO)][BF 4 ] 2 } ( 4 ) has been prepared from [(η 5 -C 5 H 5 )Ru(PPh 3 )(CN t Bu)(Cl)] ( 3 ) and nitrosinium tetrafluoroborate.

2H-benzimidazoles (isobenzimidazoles). Part 9. Synthesis and reactions of 4,6-dibromo-2H-benzimidazole-2-spirocyclohexane

Abstract The title compound 1 was prepared by condensation of 3,5-dibromo- o -phenylenediamine 10 with cyclohexanone and oxidation of the resulting 4,6-dibromo-1,3-dihydro-2 H -benzimidazole-2-spirocyclohexane 5 with manganese dioxide. With sodium 2,3-dichlorophenoxide, sodium benzenesulfinate, or piperidine it reacts by loss of bromine, to give the 6-substituted derivatives 2 , 3 , and 4 , respectively. Morpholine, however, gives 5,7-dibromo-4-morpholino-2 H -benzimidazole-2-spirocyclohexane 15 whilst pyrid-2(1 H )-thione and pyrimidin-2(1 H )-thione give 4-bromo-1,3-dihydro-6-(pyridin-2-ylthio)-2 H -benzimidazole-2-spirocyclohexane 6 and 5,7-dibromo-1,3-dihydro-4-(pyrimidin-2-ylthio)-2 H -benzimidazole-2-spirocyclohexane 14 , respectively. In the presence of 1 or 2 mol equiv. of sodium methoxide an aryne mechanism appears to operate, leading to the formation of either a mixture of 5-bromo-6-methoxy- 11 and 6-bromo-4-methoxy-2 H -benzimidazole-2-spirocyclohexane 12 or 5,6-dimethoxy-2 H -benzimidazole-2-spirocyclohexane 13 , respectively. Oxidation of the title compound 1 with m -chloroperoxybenzoic acid yields the 1-oxide 7 exclusively, which reacts with piperidine and morpholine by loss of the 4-bromine atom, to give compounds 16 and 17 , respectively, in the latter case with concomitant loss of oxygen.

Synthesis of amidines and attempted synthesis of imidazoazines by reactions of lithiated β-aminoazines with nitriles

Abstract Deprotonation of 3-aminopyridine, followed by reaction of aromatic nitriles, gives N-(3-pyridyl)-benzamidines, and other β-aminoazines (pyridines, quinolines, pyrazines, pyrimidines) react similarly. Attempts to cyclise the amidines to, for example, 2-aryl-1H-imidazol[4,5-b]pyridines (5) met with limited success.

Carbon–carbon bond cleavages in agostic cations formed by protonation of cobalt–diene complexes

The fluxional, agostic, norborn-5-en-2-ylcobalt(III) cations [Co(η-C5R5)(2 : 5,6-η-C7H9)]+(R = H,Me) undergo C–C bond cleavage at –20 °C to give 4-vinylcyclopentenylcobalt(III) complexes [Co(η-C5R5)(1-3 : 6,7-η-CH2CH[graphic omitted]H2)]+[R = H (4)(structurally characterized by X-ray crystallography), Me (7)], which react with LiAIH4 or LiBHEt3 to give neutral 4-vinylcyclopentenecobalt(I) complexes [Co(η-C5R5)(1,2 : 6,7-η-CH2CH[graphic omitted]H2)][R = H (8), Me (9a)]; (9a) is protonated at 0 °C to give the 4-ethylcyclopentenyl complex [Co(η-C5Me5){1-3-η-C5H6(endo-Et-4)}]+(11), which is stabilized by an agostic interaction between cobalt and the endo-hydrogen–carbon bond of the 5-position, and readily undergoes conrotatory ring-opening to afford [Co(η-C5Me5){η-C5H6(syn-Et-5)}]+(12) containing an acyclic 5-ethylpentadienyl ligand, as shown by X-ray crystallography.