Glen B. Robertson

Isolation of a co-ordinated ketol intermediate in the hydrolysis of PF6– initiated by the labile cations [Ru(η6-arene)(acetone)3]2+; X-ray crystal structure of acetone(4-hydroxy-4-methylpentan-2-one)(η6-mesitylene)ruthenium bistetrafluoroborate

Formation of the tri-µ-difluorophosphato complexes [Ru2(µ-PO2F2)3(η6-arene)2][PF6] from [Ru(η6-arene)(acetone)3][PF6]2 proceeds via di-cations [Ru(η6-arene)(4-hydroxy-4-methylpentan-2-one)(acetone)]2+; the mesitylene complex has been isolated as its BF4– salt and characterised by single crystal X-ray analysis.

Sulphur chromium complexes: syntheses and crystal structures of (η5C5H5)2Cr2(CO)4S and (η5-C5H5)2Cr2(CO)5S2

The facile reaction of dicyclopentadienylhexacarbonyldichromium with stoicheiometric amounts of elemental sulphur in tetrahydrofuran or toluene at ambient temperature produces (η5-C5H5)2Cr2(CO)4S (1) and (η5-C5H5)2Cr2(CO)5S2(2) in isolated yields of 100 and 90%, respectively.

Mearsine, a unique isoquinuclidine alkaloid: x-ray crystal structure of mearsine picrate

Abstract X-ray crystallography shows that mearsine, a minor alkaloid of the north Queensland plant Peripentadenia mearsii , has the novel isoquinuclidine structure 1, which permits charge transfer to take place between carbonyl and an azomethine group.

The nature of ‘Pt(Ph2PCH2CH2PPh2).’ A platinum(I)–platinum(I) dimer containing bridging cyclometallated 1,2-bis(diphenylphosphino)-ethane; X-ray crystal structure

Single-crystal X-ray structural analysis of a complex of empirical formula [pt(dppe)](dppe = Ph2PCH2CH2PPh2) formed by heating [Pt(OH)Me(dppe)]in methanol shows that it should be formulated as [Pt-µ-{o-C6H4P(Ph)CH2PPh2}]2 and that it contains cyclometallated dppe ligands bridging a Pt1–Pt1 bond.

Conformational effects in the absorption spectra and photochemistry of [2,n](9,10)anthracenophanes (n = 2,3)

Abstract The absorption spectra of [2.2](9,10)anthracenophane (1) and [2.3](9,10)anthracenophane (II), in condensed media, contain overlapping contributions from two conformational isomers with quite different spectra. The spectra of the two conformations of I and of one conformation of II have been separately determined by a solid state method. This involved the incorporation of the photoisomers of I (1,2,7,8,-tetrahydro-2a,6b[1′,2′]:8a, 12b[1″,2″] -dibenzenodibenzo [a,c] dicyclo- buta[e.g]cyclooctene) and II (1,2,8,9-tetrahydro-2a,6b[1′,2′]:9a,13b[1″,2″]-dibenzeno-7H-dibenzo[a,e]cyclobuta[c]-cyclopenta[g]cyclooctene) in host single crystals of the photoisomer of 1,3-di(9-anthryl)propane, I and II were then obtained by thermal dissociation and their spectra measured at 8 K. The two conformers of 1 were separated by photoselection, the rotated conformer being between 4 and 5 times more photoreactive than the translated conformer. A modified molecular force field program was used to simulate the environment around the guest molecule (I) and the resultant geometries and orientations in the (disordered) site of the host crystal are in excellent agreement with the polarization analysis of the absorption spectra. Two crystal orientations of the rotated conformer were found. For II, the rotated conformation, with two orientations, dominates the absorption spectrum and the translated conformer could not be obtained by photoselection. The force field program was used to calculate the molecular geometries (gas phase) of both conformations of I and II and their photoisomers, I was also obtained by ultraviolet photodissociation of its photoisomer at 8 K. Both conformers were obtained with the same ratio as for the thermally treated crystals. This result considered with the photoselection experiments, demonstrates that the reversible photoisomerization does not proceed via biradical intermediate.

Coupling of cyclooctyne with carbon monoxide on divalent molybdenum and tungsten. Crystal and molecular structure of a bis(hexamethylene)cyclopentadienonetungsten complex, W(S2CNMe2)2(CO){(C8H12)2CO}

Cyclooctyne (C8H12) in excess reacts with the dialkyldithiocarbamato complexes M(S2CNR2)2(CO)2 (R = Me, Et; M == Mo, L = PPh3; M = W, L = CO, PPh3) to give a mixture of two complexes, M(S2CNR2)2)(CO){(C8H12)2CO} (1–4) and M(S2CNR2)2(C8H12){(C5H12)2CO} (5–8). These contain tetrahapto-bis-(hexamethylene)cyclopentadienone, (C8H12CO, formed by the condensation of two molecules of cyclooctyne with one molecule of CO. Crystals of W(S2CNMe2)2(CO){(C8H12)2CO} (3) are monoclinic, space group P21/n, with a 15.132(1), b 15.705(2), c 11.346(1) A, β 93.68(2)°, and Z = 4. The structure was solved by heavy-atom methods and refined by least-squares methods to R = 0.027 (Rw = 0.045) for 5811 unique data [I ≧ 3σ(I)]. The molecule is approximately pentagonal bipyramidal, with terminal CO and one sulphur atom of a bidentate Me2NCS2 ligand in the axial positions. The equatorial sites are occupied by the other sulphur atom of this Me2NCS2 ligand, the second bidentate Me2NCS2 ligand, and the mid-points of the coordinated CC bonds of η4-(C8H12CO. As in other cyclopentadienone complexes, the CC distances in the η4-dienone are almost equal (av. 1.45 A) and the CO group is bent away from the plane of the ring (dihedral angle 17.6°). Infrared and NMR (1H, 13C) data suggest that complexes 5–8 are similar to 1–4, with cyclooctyne acting as a 2π-electron donor in place of CO.

Solid state photochemistry and photophysics of 1,3-di(9-anthryl)propane in its photoisomer single crystal

Abstract The photoisomer (2,3,8,9-tetrahydro-3a,8[1′,2′] : 9,13b[1″,2″]-dibenzeno-1H-dibenzo[a,e]cyclopenta[c]cyclootene; APAPI) crystal of 1,3-di(9-anthryl) propane (APA) is monoclinic with a = 10.016(2), b = 13.432(3), c = 25.307(6)A, β = 113.08(2)° P2 1 /c and Z = 6. Four of the molecules in the unit cell are ordered and two are disordered. Irradiation by ultraviolet light, at about 10 K, gave APA with different molecular conformations in the two types of site. Their absorption spectra have been obtained by photoselection. The APA in the ordered site is about 8 times more photoreactive (conversion to APAPI) than the APA in the disordered site. Both types of APA are non-fluorescent. A molecular force field calculation has been modified to allow the prediction of the conformation of the APA in each site. For the ordered site, two closely related topochemical conformations were predicted and for the disordered site, one translated conformation was predicted in agreement with spectroscopic analysis. Polarization analysis showed the absence of out of plane absorption intensity in both cases. Consideration of the relative yields of photoreaction of both APA and APAPI in the two sites, under exactly the same experimental conditions, does not support a biradical photomechanism.

Deprotonation and metallation of an olefinic tertiary phosphine by planar d8 divalent metal complexes; the crystal structure of [PtCl(o-Ph2 PC6 H4 C=CHC6 H4 PPh2 -o)]

Summary The reaction of 2,2′-bis (diphenylphosphino)stilbene with halide salts or complexes of Ni II , Pd II , or Pt II results in the elimination of hydrogen halide and the formation of complexes [MCI ( o -Ph 2 PC 6 H 4 C=CHC 6 H 4 PPh 2 - o )] in which the tridentate phosphine ligand is bonded to the metal via two M-P σ-bonds and one M-C σ-bond.

The structure of [{(π-c6H5)P(C6H5)2}Cr(CO)2]2; a complex with a

Abstract The structure of [{(π-C6H5)P(C6H5)2}Cr(CO)2]2 has been determined by X-ray methods; each dimer consists of two Cr atoms bridged by two triphenylphosphine groups while each triphenylphosphine group is P-bonded to one Cr-atom, and is involved in π-arene bonding to the second Cr atom.

Formation and X-ray crystal structure of an A-frame µ-methylene diplatinum complex containing bridging cyclometallated 1,2-bis(diphenylphosphino)ethane

The 1 : 1 adduct of the PtI–PtI dimer [Pt-µ-{o-C6H4P(Ph)CH2 CH2PPh2}]2 with methyl iodide is deprotonated by sodium methoxide to give a µ-methylenediplatinum(II) complex [Pt2-µ-{o-C6H4P(Ph)CH2CH2PPh2}2(µ-CH2)], characterised by single-crystal X-ray structural analysis; the latter complex reacts with [Me3O]PF6 to give an ethyldiplatinum(II) cation which retains the bridging cyclometallated dppe ligands.