Paul D. Hempstead

Mesomorphic stilbazole complexes of silver octyl sulfate. Crystal and molecular structure of bis[4-(4-methoxystyryl)pyridinato]silver(I) octyl sulfate hemihydrate

Reaction of the salts bis[4-(4-alkoxystyryl)pyridinato]silver(I) trifluoromethanesulfonate {[Ag(n-OPhVPy)2][CF3SO3]} with sodium octyl sulfate (NaOS) in acetone leads to the metathesised product [Ag(n-OPhVPy)2][OS] in good yield. These octylsulfate salts are mesomorphic showing a nematic phase at short chain lengths and SC and SA phases at longer chain lengths. The single-crystal X-ray structure of the methoxy homologue has four molecules in the unit cell which are arranged as two crystallographically independent, centrosymmetric pairs linked by a hydrogen-bonded water molecule. Each pair of silver atoms is bridged by two sulfate groups with Ag — O distances longer than those normally associated with covalent bonds.

Synthesis and crystal structure of a first-generation model for the trinuclear copper site in ascorbate oxidase and of a dinuclear silver precursor

The synthesis and X-ray crystal structure of a disilver complex [Ag2L1][BF4]2 of a bibracchial tetraimine Schiff-base macrocycle derived from the silver-templated cyclocondensation of 2,6-diacetylpyridine and tris(2-aminoethyl)amine are reported. The complex crystallises in the monoclinic space group P21/n(a non-standard setting of P21/c, no. 14) and has unit-cell dimensions a= 11.660(22), b= 28.14(4), c= 12.158(21)A, β= 107.94(13)° with Z= 4. Functionalisation of the pendant arms with salicylaldehyde followed by transmetallation with CuII leads to the formation of a trinuclear copper(II) complex [Cu3L4-(OH)][ClO4]3·2H2O in which there is a single CuII atom 4.9 and 5.9 A distant from a pair of CuII atoms which are 3.6 A apart and hydroxy-bridged. The complex, which crystallises in the monoclinic space group P21(no. 4) and has unit cell dimensions a= 13.997(24), b= 16.043(9), c= 14.353(11)A, β= 118.97(10)° with Z= 2, may be regarded as a first-generation model for ascorbate oxidase. A study of the magnetic properties shows that the trinuclear copper(II) complex can be regarded as a mononuclear site non-interacting with a moderately coupled copper pair (2J=–202 cm–1).

Attempted functionalisation of a mononuclear barium complex of a 24-membered bibracchial tetraimine Schiff-base macrocycle derived from tris(2-aminoethyl)amine using salicylaldehyde

Functionalisation of a mononuclear barium Complex of a 24-membered bibracchial tetraimine Schiff-base Macrocycle (L1) derived from the barium-templated cyclocondensation of 2,6-diacetylpyridine and tris(2-aminoethyl)amine was attempted using salicylaldehyde. The reaction leads to the isolation of the tripodal ligand tris[2-(salicylideneamino)ethyl]amine (L2) and the complex BaL22(ClO4)2. The crystal structures of the parent macrocyclic complex, [BaL1][ClO4]2[monoclinic, space group P21/c(no. 14), a= 11.755(7), b= 21.733(17), c= 15.621(15)A, β= 90.50(7)°, Z= 4], and BaL22(ClO4)2[monoclinic, space group P21/c(C2h5, no. 14), a= 12.299(15), b= 9.530(15), c= 25.798(32)A, β= 108.679(9)°, Z= 2] have been determined.

Hydrogen loss from pentamethylcyclopentadienyl–ruthenium complexes; the synthesis and X-ray structure of [Ru(C5Me4CH2Cl)Cl3(Me2S)]

Reaction of [{C5Me5RuCl2}2] with Me2SO (in air in CHCl3) gives [(C5Me4CH2)RuCl2(Me2SO)], 2a; this reacts with HCl to give [(C5Me4CH2Cl)RuCl3(Me2S)](also in high yield), characterised by an X-ray structure determination.

Chiral annulated cyclopentadienyl ligands: Synthesis and crystal structure of both exo and endo Rh{η5-Cp′}(cod)} [Cp′=(4S,7R)-1,2,3-triphenyl-4,8,8-trimethyl-1H,4,5,6,7-tetrahydro-4,7-methanoindenyl]

Abstract The title homochiral cyclopentadiene ligand C 31 H 30 (i.e., Cp′H, 5 ) has been synthesised from camphor in four steps. The lithium salt of this ligand reacted with [Rh(cod)Cl] 2 to give predominantly racemic ( η 4 -cycloocta-1,5-diene)[ η 5 -1,2,3-triphenyl-4-methyl-7-isopropyl-1H-indenyl]rhodium although the desired RhCp′(cod) complex was formed in 20% yield as an equal mixture of endo 7a and exo 7b isomers. The X-ray structures of 7a and 7b have been determined at room temperature with use of Mo-K α radiation ( λ =0.71069 A). Both compounds crystallise in the orthorhombic space group P 2 1 2 1 2 1 ( D 2 4 , No. 19); for compound 7a , a =13.549(23) A, b =14.490(25) A, c =15.909(14) A, V =3123(8) A 3 , Z =4 and D c =1.303 g cm −3 and the structure was refined to R =0.0488 on the basis of 2545 independent reflections. For the exo isomer 7b , a =13.301(18) A, b =15.599(32) A, c =14.436(19) A, V =2995(10) A 3 , Z =4 and D c =1.359 g cm −3 ; the structure was refined to R =0.0362 on the basis of 4620 independent reflections. Bromine reacts with the compounds 7a and 7b to give the corresponding [{Rh(Cp′)} 2 ( μ -Br 3 )]Br 3 .

Chiral tetraphenylcyclopentadienyl complexes of ruthenium and palladium; crystal structure of [Ru(η5-C5Ph4R1*)(CO)2Br](R1*= menthyl)

The compound (–)-bromomenthyltetraphenylcyclopentadiene has been synthesised. It reacts with [Ru3(CO)12] to give [Ru(η5-C5Ph4R1*)(CO)3]Br (R1*= menthyl) which on heating yields [Ru(η5-C5Ph4R1*)(CO)2Br]1. Alternatively complex 1 may be prepared by treating bromoform with [Ru(η5-C5Ph4R1*)(CO)2H], generated from [Ru3(CO)12] and C5Ph4R1*H. A crystal structure of complex 1 shows that the crystals are monoclinic, space group P21(C22, no. 4), Z= 4, with a= 13.783(4), b= 17.799(5), c= 14.974(3)A, β= 107.05(2)°, U= 3512.0 A3., the structure has been refined to R 0.0777 for 3931 unique reflections in the range 3.5 < 2θ < 45°(Mo-Kα radiation). The corresponding complex [Pd(η5-C5Ph4R2*)(η3-C3H5)](R2*= neomenthyl)2 has been synthesised by the reaction of Li[C5Ph4R2*] with [{Pd(η3-C3H5)Cl}2].

A triangulo-copper(II) cluster compound derived from a bibracchial tetraimine Schiff base macrocycle : a first generation model for ascorbate oxidase ?

The synthesis and X-ray crystal structure of a triangulo-copper(II) complex which may be regarded as a first generation model for the triangular copper(II) site in ascorbate oxidase is described.

Ring contraction in schiff base macrocycles: The X-Ray crystal structure of an imidazolidine-containing macrocycle

Cyclocondensation of benzene-1,3-dicarbaldehyde and 3-azapentane-1,5-diaminein acetonitrile leads to isolation of an 18-membered imidazolidine-containing Schiff base macrocycle rather than the anticipated 24-membered tetraimine Schiff base macrocycle. This has occurred as a consequence of internal nucleophilic addition of the secondary amine functions across adjacent azomethine bonds. The X-ray crystal structure of the imidazolidine-containing Schiff base macrocycle is reported.

The interaction of organotransition metal fragments with oxaazamacrocycles. Synthesis and X-ray crystal structure of Mo(CO)3[O-en-N-pyn-H4]·CH2Cl2

The reaction of fac-Mo(NCMe)3(CO)3 with [O-en-N-pyn-H4] in CH2Cl2 gives fac-Mo(CO)3[O-en-N-pyn-H4]·CH2Cl2, whose X-ray crystal structure is monoclinic, a = 10.448(20), b = 14.975(23), c = 16.598(27) A,β = 100.57(14)°. The macrocycle is bonded confacially to a trigonally elongated octahedral molybdenum through one pyridinyl nitrogen, one amino nitrogen and one oxygen donor.

Cyclopentadienone complexes of molybdenum: synthesis of carbonyl, acetonitrile, phosphine and phosphido-bridged derivatives

Reaction of [Mo(CO)6] with 2 equivalents of tetraphenylcyclopentadienone (tetracyclone) in refluxing toluene gives [Mo(CO)2(η4-C4Ph4CO)2]1a in ca. 95% yield. With 1 equivalent of tetracyclone in boiling heptane, [{Mo(CO)3(σ:η4-C4Ph4CO)}2]2 is produced as well as 1a. This dimeric complex has been crystallographically characterised [triclinic, space group P(no. 2), a= 8.980(3), b= 11.332(4), c= 13.526(5)A; α= 77.55(3), β= 71.94(3), γ= 81.02(3)°, Z= 2 monomer units]; each molybdenum is in a distorted-octahedral environment, co-ordinated by the η4-diene ligand, three carbonyl ligands, and the ketonic carbonyl of the other centrosymmetrically related tetracyclone. Another convenient route into the chemistry of tetracyclone molybdenum complexes is provided by [Mo(CO)3(NCMe)(η4-C4Ph4CO)]5 which is formed in high yield by treating [Mo(CO)3(NCMe)3] with tetracyclone. One (but only one) of the tetracyclone ligands of complex 1a can be displaced by chelating phosphines to give [Mo(CO)2(L–L)(η4C4Ph4CO)](L–L = Ph2PCH2PPh2 or Ph2PCH2CH2PPh2); the stereochemistry and fluxionality of these complexes is briefly discussed. Thermal reaction of 1a with monodentate phosphines (L = PPh3 or PPh2Me) yields [Mo(CO)3L(η4-C4Ph4CO)]7 by a carbonyl redistribution process; the same compounds can be prepared from 5 by displacement of the labile acetonitrile ligand, as can an analogous species with L = PPh2H. Thermolysis of [Mo(CO)3(PPh2H)(η4-C4Ph4CO)] or thermal reaction of 1a with PPh2 H gives the phosphido-bridged complex [Mo2(CO)3(µ-PPh2)(µ-σ:η5-C4Ph4COH)]8. The crystal structure of 8 has also been determined [triclinic, space group P(Ci′1 no. 2), a= 12.806(10), b= 14.173(8), c= 17.958(7)A, α= 83.75(4), β= 86.92(5), γ= 71.57(5)°, Z= 2] and reveals a formal MoMo double bond [2.923(2)A] bridged by a diphenylphosphido group and a tetracyclone ligand bonded in a σ:η5 manner. The other tetracyclone is bonded as an η5-hydroxytetraphenylcyclopentadienyl ligand, having taken up the proton released by oxidative addition of the P–H bond.