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

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

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

The cycloauration of pyridine-2-thiocarboxamide ligands

Reactions of H[AuCl₄] with N-substituted 2-pyridine thiocarboxamide ligands 2-(C₅H₄N)C(S)NHR (R= p-C₆H₄Me, CH₂Ph, Me, p-C₆H₄OMe) gave cycloaurated derivatives {(C₅H₄N)C(S)NR}AuCl₂, with the ligand bonded as the thiol tautomer through the deprotonated SH group and the pyridine N atom to give a five-membered metallacyclic ring. The X-ray structure determination of the R = CH₂Ph derivative shows a square-planar gold(III) complex that dimerises in the solid state by weak Au...S intermolecular interactions. In contrast, in the reaction of H[AuCl₄] with 2-(C₅H₄N)C(S)NHR where R = 2-pyridyl, the ligand was oxidised to give a 1,2,4-thiadiazolo[2,3-a]pyridinium heterocyclic ring that was crystallographically characterised

The formation of mixed germanium–cobalt carbonyl clusters: an electrospray mass spectrometric study, and the structure of a high-nuclearity [Ge₂Co₁₀(CO)₂₄]²⁻ anion

The reaction of [µ₄-Ge{Co₂(CO)₇}₂] with [Co(CO)₄]⁻ has been monitored by electrospray mass spectrometry to detect the cluster anions generated. Conditions giving known mixed Ge–Co carbonyl clusters were established, and a new high nuclearity cluster anion, [Ge₂Co₁₀(CO)₂₄]²⁻ was detected. Conditions for its formation were optimised and it was subsequently isolated as its [Et₄N]⁺ salt and characterised by single-crystal X-ray crystallography. The Ge₂Co₁₀ cluster core has a novel geometry with the two germanium atoms in semi-encapsulated positions, forming seven formal Ge–Co bonds. There are also eighteen formal Co–Co bonds. Corresponding reactions of [µ₄-Si{Co₂(CO)₇}₂] with [Co(CO)₄]⁻ were also investigated

Synthesis and reactivity of gold(III) complexes containing cycloaurated iminophosphorane ligands

Transmetallation reactions of ortho-mercurated iminophosphoranes (2-ClHgC₆H₄)Ph₂P NR with [AuCl₄]⁻ gives new cycloaurated iminophosphorane complexes of gold(III) (2-Cl₂AuC₆H₄)Ph₂P NR [R = (R,S)- or (S)-CHMePh, p-C₆H₄F, tBu], characterised by NMR and IR spectroscopies, ESI mass spectrometry and an X-ray structure determination on the chiral derivative R = (S)-CHMePh. The chloride ligands of these complexes can be readily replaced by the chelating ligands thiosalicylate and catecholate; the resulting derivatives show markedly higher anti-tumour activity versus P388 murine leukaemia cells compared to the parent chloride complexes. Reaction of (2-Cl₂AuC₆H₄)Ph₂P NPh with PPh₃ results in displacement of a chloride ligand giving the cationic complex [(2-Cl(PPh₃)AuC₆H₄)Ph₂P NPh]⁺, indicating that the P N donor is strongly bonded to the gold centre

Bis[μ-bis(diphenylphosphino)methane-К²P:P’]bis[(saccharinato-КN)- palladium(I)] dichloromethane solvate

The dimeric palladium(I) saccharinate complex [Pd₂(sac)₂(dppm)₂], has been characterized as its di¬chloro¬methane solvate, i.e. [Pd₂(C₇H₄NO₃S)₂(C₂₅H₂₂P₂)₂]•CH₂Cl₂. The complex features a Pd—Pd bond bridged by two dppm ligands, with the saccharinate ligands N-bonded trans to the Pd—Pd bond

(p -Cymene)thioglycollatoruthenium(II) dimer; a complex with an ambi-basic S,O-donor ligand

The title compound was prepared from the (p-cymene)ruthenium chloride dimer and thioglycollic acid. The structure is a centrosymmetric dimer bridged by the soft-base S atoms, with the hard-base O atoms of the carboxylate group chelating to form a five-membered twisted-ring. The coordination of the ruthenium atoms is completed by a η6-p-cymene ligand, giving an 18-electron count. The Ru–S bonds are essentially equal at 2.396(1) Å