Owen S. Mills

Carbon compounds of the transition metals IX. Evidence for and structure of dicyclopentadienyltricarbonyldirhodium

Abstract The product of the ultraviolet-light irradiation of a pentane solution of monomeric cyclopentadienyldicarbonylrhodium is show to be dicyclopentadienyltricarbonyldirhodium. The structure is unusual in that it contains a single bridging carbonyl group. The crystals are triclinic with a = 8.08 ± 0.04, b = 8.95 ± 0.05, c = 9.46 ± 0.05 A, α = 73° 8′ ± 10′, β = 80° 33′ ± 10′, γ = 83° 9′ ± 10′. The RhRh distance is 2.68 A, RhC(ring) 2.26 A, RhC(terminal carbonyl) 1.87 A and RhC-(bridging carbonyl) 2.01 A.

Carbon compounds of the transition metals : V. The structure of bis(cyclopentadienyldicarbonyl-rutheium)

Abstract The structure of bis(cyclopentadienyldicarbonylruthenium) has been determined in the solid at room temperature. The crystals are monoclinic with a = 7.10, b = 12.48, c = 8.04» and β = 104.33°. The cell dimensions, space-group and structure are compared with those of bis(cyclopentadienyldicarbonyliron). The Ru-Ru distance is 2.73 », Ru-C(terminal CO) 1.86 », Ru-C(bridging) CO) 1.99 » and Ru-C(ring) 2.26 ». In the solid structure is centrosymmetrical.

Carbon compounds of the transition metals VIII. The structure of tris(π-cyclopentadienylcarbornylrhodium)

Abstract The structure of tris(cyclopentadienylcarbonylrhodium) in the solid state has been determined by X-ray diffraction methods. The crystals are monoclinic with a = 7.06, b = 12.92, c = 9.47 A and β = 94°45′. The structure consists of a triangular arrangement of rhodium atoms with π-cyclopentadienyl groups displaced to one side of the triangle and bridging carbonyl groups on the other. The RhRh distance is 2.62 A, RhC(ring) 2.24 A and RhC(carbonyl) 2.00 A.

The crystal and molecular structure of cis-diammine-1,1-cyclobutanedicarboxoplatinum(II) [cis-Pt(NH3)2CBDCA]. Dynamic puckering of the cyclobutane ring

Abstract C6H12N2O4Pt, Mr = 371.27, orthorhombic, Pnma, a = 7.724(2), b = 10.464(3), c = 11.176(2) A, V = 903.29 A3, Z = 4, DX = 2.73 Mg m−3, μ (Mo Kα) = 16.32 mm−1, λ = 0.71069 A. Final R = 0.029 for 856 reflexions. A mirror plane containing the platinum and average cyclobutane ring bisects the molecule. One of the cyclobutane carbon atoms shows excessive thermal motion, which is interpreted in terms of a dynamically puckering ring.

Carbon compounds of the transition metals X. The structure of tetracyclopentadienylhydrido-trirhodium

Abstract The structure of tetracyclopentadienylhydridotrirhodium has been determined by X-ray analysis of the solid. The black crystals belong to the orthorhombic system with spacegroup Pnma and a = 12.82, b = 14.96 and c = 8.86 A. The rhodium atoms are arranged in an almost equilateral triangle with mean edge 2.72 A. Three π-cyclopentadienyl groups, one attached to each rhodium atom, are displaced to one side of the rhodium triangle and the fourth cyclopentadienyl group lies parallel to the triangle on the opposite side to the other three. The mean rhodium-carbon distance of the three rings is 2.23 A. The shortest rhodium-carbon distance to the fourth ring is 2.09 A. NMR measurements are consistent with the hydridic proton being situated near the centre of the rhodium triangle.

A [2 + 2] photo-adduct of 8-methoxypsoralen and thymine: X-ray crystal structure; a model for the reaction of psoralens with DNA in the phototherapy of psoriasis

Ultaviolet irradiation of a mixture of 8-methoxypsoralen and thymine in an ice-methanol matrix in the presence of benzopenone affords a [2 + 2] adduct which is shown by X-ray crystallography to result from cis-bonding of the 4′- and 5′-(furan) positions of the 8-methoxypsoralen to, respectively, the 5- and 6-positions of the thymine.

Synthesis of 2,3,5,6-tetrahydro-1h,4h,11ch-3a,6a,11b-triazabenz[de] anthracene (5) and x-ray crystal structure determinations of (5), hexahydro-1h,4h,7h,9bh-3a,6a,9a-triazaphenalene (1), benzo[b]-1,5,9-triazadodecane n,n',“n-tritosylamide, and of 1,5.9-triazadodecane n,n',n”-tritosylamide

Abstract The synthesis of 2,3,5,6-tetrahydro-1H,4H,11cH-3a,6a,11b-triazabenz [de]anthracene (5) is described. X-ray crystal structure deteminations on hexahydro-1H,4H,7H,9bH-3a,6a,9a-triazaphenalene (1) and its benzoanalogue (5) show them to adopt differing conformations; the reasons for this are discussed.

The crystal and molecular structure of tetracarbonyl(hexamethylbicyclo[2.2.0]hexa-2,5-diene)chromium a transition metal complex of a substituted dewar benzene

Abstract The crystal and molecular structure of tetracarbonyl(hexamethylbicyclo-[2.2.0]hexa-2,5-diene)chromium (CH 3 ) 6 C 6 Cr(CO) 4 has been determined from 804 independent non-zero single-crystal X-ray intensities collected photographically. The structure has been refined by standard Fourier and least-squares techniques to a conventional R value of 0.111 (isotropic temperature factors for the light atoms). The crystals are orthorhombic, spacegroup Pnma, a =12.73(3), b =11.25(2), c =11.57(2) A, Z =4. The molecule possesses idealized mm 2 ( C 2 v ) symmetry and can be described as an octahedral complex of chromium in which the ligand occupies two positions cis to one another. The Dewar benzene nucleus consists of two fused cyclobutene rings with a dihedral angle of 113°. The CC (double-bond) distances in the ligand are 1.36(1) A, the C (bridge) distance is 1.55(2) A and the remaining CC (ligand) distances have an average value of 1.53(2) A. The steric strain in the molecule causes the CrC (ligand) bonding distances to be unusually large viz. 2.33 (1) and 2.34 (1) A.

Phosphite complexes of copper(II) carboxylates and their derivatives. Crystal structure of penta-µ-acetato-bis(triethyl phosphite)tricopper-(I,II)

Copper(II) alkanecarboxylates, [Cu2(O2CR1)4](R1= Me, Et, or Prn), react with trialkyl phosphites, P(OR2)3(R2= Me, Et, or Pri), in equimolar proportions in alcohol (R2OH) solution to form pale blue-green [Cu2(O2CR1)5{P(OR2)3}2] complexes, which have been characterised by microanalysis, spectroscopic (i.r., 1H and 31P n.m.r., e.s.r., u.v.–visible), and magnetic susceptibility measurements. The crystal structure of [Cu3(O2CMe)5{P(OEt)3}2] has been determined from X-ray diffractometer data by Patterson and Fourier methods. Crystals are monoclinic, space group Cc, with Z= 4 in a unit cell of dimensions a= 13.77(4), b= 19.10(3), c= 17.08(4)A, and β= 125.6(2)°. The structure was refined by least-squares methods to R 0.10 for 651 reflections. The structure shows that a Cu2(O2CMe)4 unit provides a monoatomic syn-anti bridge through oxygen to a Cu(O2CMe){P(OEt)3}2 unit, the acetate group of which provides an anti-anti bridge between Cu2(O2CMe)4 units to form a polymeric chain. In alcohol solution the chain is broken and the solvated fluxional monomeric [Cu3(O2CMe)5{P(OR2)3}2](R2= Me or Et) units rearrange so that the copper(I) atom is connected to one of the copper(II) atoms through two unidentate bridging acetates. In alcohol solution [Cu3(O2CMe)5{P(OR2)3}2](R = Me or Et) reacts with unidentate oxygen- or nitrogen-donor ligands, L, to form [Cu2(O2CMe)4L2] and [{Cu(O2CMe)[P(OR2)3]2}2]. The dimeric copper(I) complexes react with bidentate nitrogen- and phosphorus-donor ligands, L′, to form [Cu(O2CMe){P(OR2)3}L′][L′= 2,2′-bipyridine, 1,10-phenanthroline, 1,2-diaminoethane, or 1,2-bis(diphenylphosphino)ethane] which exist as fluxional monomers in solution.

Preparation and properties of some crown ethers incorporating stable carbocations

Reaction of 1,3-xylyl-18-C5[12(n= 3)] and 1,3-xylyl-21-C6[12(n= 4)] with diazomethane yields mixtures of crown ethers incorporating cycloheptatrienes, and these have been converted to crown ethers incorporating tropylium ions 5(n= 3 and 4) by hydride abstraction with triphenylcarbenium tetrafluoroborate. These compounds have pKR+≈ 3.8. Crown ethers containing the 1,8-dioxyxanthone residue, 22(n= 3–5), have been prepared by alkylation of 1,8-dihydroxyxanthone with polyethylene glycol dibromides. These have been converted into the corresponding xanthydrols, 16(n= 3–5). The conjugate acids of the ketones have –2.14 < pKa < –1.94. The alcohols exist in equilibrium with the bridged 9-xanthylium cations and have 0.78 < pKR+ < 1.08. For 1,8-diethoxyxanthone and 1,8-diethoxyxanthydrol, the corresponding values are pKa=–1.93 and pKR+= 1.38. The possibility that crown ethers incorporating relatively stable carbocationic centres may catalyse amide hydrolyses is briefly discussed.