A case study of campus‐based flexible learning using the World Wide Web and computer conferencing

This paper explores the use of the World Wide Web (WWW) integrated with computer conferencing as a teaching and learning tool. The aim of the study described was to evaluate the effectiveness of the use of online materials designed in a flexible learning format and integrated with a computer conference. It was hoped that this would create additional opportunity for group discourse between campus‐based students. The paper is divided in the following way: a discussion of the context to new developments in teaching and learning is followed by an introduction to the case study. Finally the findings of the case study are discussed with reference to research from the field of collaborative systems (Orlikowski, 1992; Grudin, 1994) as a framework for reflection. Some tentative conclusions are made for future work

cyclo-Tetra-μ-oxido-tetrakis[3-nitro-4-hydroxyphenylarsenic(III)]

The title compound, [As₄O₄(C₆H₄NO₃)₄], has an eight-membered As₄O₄ ring with a slightly twisted boat-chair conformation. The aryl groups complete the threefold coordination for each As atom. Each OH group forms a strong intramolecular O-H⋯O hydrogen bond to the adjacent NO₂ group, with only weak C-H⋯O, O⋯As [3.036 (6)-3.184 (6) Å] and O⋯O [2.921 (10)-2.930 (10) Å] interactions between tetramers

New complexes with M-Si-O or M-Si-S linkages (M = Fe or Co)

Ph2XSiFe(CO)2Cp [X = p-tolylS (1a), MeO (1b)] and Ph[2-MeOC6H4]XSiFe(CO)2Cp [X = Cl (2a), OMe (2b)] have been fully characterised, including X-ray crystal structure determinations for 1a, 1b and 2a. None of the examples showed any tendency for migration of the X groups from silicon to iron, with elimination of silylene. However very ready loss of the X groups was seen in the electrospray mass spectra, suggesting formation of the cationic silylene-iron complex ions is favoured. This was especially so for 2a and 2b, where intramolecular stabilisation of the silicon centre from the 2-OMe group is possible.The stable siloxane O[SiPh2{Co(CO)4}]2 was also characterised; the X-ray crystal structure analysis shows a Si-O-Si bond angle of 153°

Novel polyoxometalates: Is antimony the new molybdenum?

Polyoxometalates based on Mo, W or V have been known for a long time and present a diverse range of structures, with the [XMo₁₂O₄₀]ⁿ⁻ Keggin ions (X = P, Si ,…) perhaps the best known.¹ They are still subject to intense research with >4000 papers published in the past five years. Following on from our study² of aryl arsonic acids RAsO₃H₂, which are straightforward molecular species based on four-coordinate As(V), we became interested in the corresponding antimony compounds. Although aryl stibonic acids of nominal formula RSbO₃H₂ have been known for over 100 years,³ their composition has remained uncertain, as they form only amorphous solids, have complicated titration behaviour and only limited solubility. The presumption has been that they are polymeric, based on 5- or 6-coordinate Sb with Sb-O-Sb linkages, though direct evidence is sparse.⁴ Recently, it has been shown by Beckman that if very bulky R groups are used, then relatively simple dimers such as (2,6-Mes₂C₆H₃Sb₂O₂(OH)₄(Mes=mesityl) can be isolated, but these represent a special case.

Anomalous reaction of an aryl silane with Co₂ (CO)₂; characterisation of Me ₂NC₆H₄Si[Co(CO)₄][OCCo₃(CO)₉]₂

Reaction of Me₂NC₆H₄SiH₃ with Co₂(CO)₈ gave Me₂NC₆H₄Si[Co(CO)₄][OCCo₃(CO)₉]₂ which was shown to have one –Co(CO)₄ group and two –OCCo₃(CO)₉ cluster units bonded to the silicon atom

Characterisation of the first authenticated organomercury hydroxide, 4-Me₂NC₆H₄HgOH

4-Me₂NC₆H₄HgOH was prepared from 4-Me₂NC₆H₄HgOAc. Full characterisation showed that it crystallises as discrete molecules, the first example of a true organomercury hydroxide in the solid state. The structures of 4-Me₂NC₆H₄HgOAc and (4-Me₂NC₆H₄)₂Hg are also discussed. 4-Me₂NC₆H₄HgOH has been characterised spectroscopically and crystallographically as a true organomercury hydroxide

Tris(tert-butylisonitrile)hexacarbonyl- 3-ethylidyne-triangulo-tricobalt(I)(3 Co-Co)

The title molecule, [Co3(C2H3)(C5H9N)3(CO)6] or [Co3(3-CCH3)(CNtBu)3(CO)6], lies on a threefold rotation axis. The three isonitrile ligands each occupy an equatorial site on each of the three Co atoms. The average Co-Co bond length is 2.4769 (6) Å. The tert-butyl groups are disordered over two orientations, with site occupancies of ca 0.6:0.4

Platinum(II), palladium(II), nickel(II), and gold(I) complexes of the “electrospray-friendly” thiolate ligands 4-SC₅H₄N- and 4-SC₆H₄OMe-

The series of platinum(II), palladium(II), and nickel(II) complexes [ML₂(dppe)] [M = Ni, Pd, Pt; L = 4-SC₅H₄N or 4-SC₆H₄OMe; dppe = Ph₂PCH₂CH₂PPh₂] containing pyridine-4-thiolate or 4-methoxybenzenethiolate ligands, together with the corresponding gold(I) complexes [AuL(PPh3)], were prepared and their electrospray ionization mass spectrometric behavior compared with that of the thiophenolate complexes [M(SPh)₂(dppe)] (M = Ni, Pd, Pt) and [Au(SPh)(PPh₃)]. While the pyridine-4-thiolate complexes yielded protonated ions of the type [M + H]+ and [M + 2H]²+ ions in the Ni, Pd, and Pt complexes, an [M + H]+ ion was only observed for the platinum derivative of 4-methoxybenzenethiolate. Other ions, which dominated the spectra of the thiophenolate complexes, were formed by thiolate loss and aggregate formation. The X-ray crystal structure of [Pt(SC₆H₄OMe-4)₂(dppe)] is also reported

Reactions of isonitriles with [Fe₃(CO)₁₂] and [Ru₃(CO)₁₂] monitored by electrospray mass spectrometry: structural characterisation of [Fe₃(CO)₁₀(CNPh)₂] and [Ru₄(CO)₁₁(μ₃-η²-CNPh)₂(CNPh)]

The reactions of [Fe₃(CO)₁₂] or [Ru₃(CO) ₁₂] with RNC (R=Ph, C₆H₄OMe-p or CH₂SO₂C₆H₄Me-p) have been investigated using electrospray mass spectrometry. Species arising from substitution of up to six ligands were detected for [Fe₃(CO)₁₂], but the higher-substituted compounds were too unstable to be isolated. The crystal structure of [Fe₃(CO)₁₀(CNPh)₂] was determined at 150 and 298 K to show that both isonitrile ligands were trans to each other on the same Fe atom. For [Ru₃(CO)₁₂] substitution of up to three COs was found, together with the formation of higher-nuclearity clusters. [Ru₄(CO)₁₁(CNPh)₃] was structurally characterised and has a spiked-triangular Ru₄ core with two of the CNPh ligands coordinated in an unusual μ₃-η² mode. The substitution reactions of [M₃(CO)₁₂] by RNC have been investigated by electrospray mass spectrometry showing up to six COs can be replaced. [Fe₃(CO)₁₀(CNPh)₂] has both PhNC axially on the same Fe atom, and [Ru₄(CO)₁₁(μ₃-η²-CNPh)₂(CNPh)] has a spiked-triangular cluster core with two PhNC ligands in an unusual coordination mode

Synthesis and characterization of nickel(II) maltolate complexes containing ancillary bisphosphine ligands

Cationic nickel(II) complexes containing chelating O,O'-donor maltolate or ethyl maltolate ligands in conjunction with bidentate bisphosphine ligands Ph₂P(CH₂)nPPh₂ were prepared by a one-pot reaction starting from nickel(II) acetate, bisphosphine, maltol (or ethyl maltol), and trimethylamine, and isolated as their tetraphenylborate salts. An X-ray structure determination of [Ni(maltolate)(Ph₂PCH₂CH₂PPh₂)]BPh₄ shows that the maltolate ligand binds asymmetrically to the (slightly distorted) square-planar nickel(II) center. The simplicity of the synthetic method was extended to the synthesis of the known platinum(II) maltolate complex [Pt(maltolate)(PPh₃)₂]BPh₄ which was obtained in high purity