A comprehensive study of the reactivity of Lewis bases with dihalodiboranes(4) is presented. Diaryldihalodiboranes provide rearranged monoadducts when treated with cyclic (alkyl)(amino)carbenes, but halide-bridged adducts when treated with a range of pyridyl bases. Alternatively, the combination of diaminodihalodiboranes with strong carbene donors leads to boraborenium salts. The reduction and halide-abstraction reactivity of these adducts was also explored, leading to intramolecular C-H activation and the first 1,2-bis(borenium) dication.

Reaction of a N-heterocyclic silylene (NHSi) with PhBX (X=Cl, Br) readily afforded six-membered silaborinines through an insertion/ring expansion sequence. Increasing the sterics of the borane from phenyl to duryl enabled the selective generation and isolation of the highly colored silylborane intermediates. Theoretical studies on the mechanism and energetics of the silaborinine formation were fully consistent with the experimental observations.

Reactions of an aryldihydroborane with a Pt(0) complex lead to a range of novel products, including complexes with bridging diborene and diborane(3) ligands and a complex with both borylene and borane (M → B) ligands. The products imply varying degrees of dehydrogenation of the boron centers with concomitant formation of boron-boron bonds, which in one case is later broken. These reactions show that although the dehydrocoupling of dihydroboranes is not a straightforward process in this case, the reactions are capable of connecting boron atoms in unusual ways, leading to unprecedented bonding motifs.

In recent years, numerous computer assisted learning (CAL) programmes based on new teaching methods, as for example the principles of cognitive apprenticeship and problem based learning, have euphorically been developed for various medical fields. However, many of these programmes failed due to either low acceptance, economic inefficiency, or, most seriously, problems with the implementation and evaluation in medical curricula. In 1999, the practical training course 'Dermatology 2000', an interactive multimedia programme for dermatological education, was developed and completely integrated into the regular dermatological curriculum of five German medical schools. The formative evaluation of an implemented relational database revealed contemporary information about the programme's quantity of use. So far, 3050 students have participated in 6557 lessons. The evaluation of two online questionnaires showed a high learner acceptance regarding the programme's instructional design, ergonomics, and didactical presentation and, after completion of Dermatology 2000, an increased interest in medical education software. A comparison of the objective learning outcome illustrated that Dermatology 2000 students (n = 31) not only outperformed non-participants (n = 7) but also showed a (10%) lower rate of errors in a conventional knowledge test. Additionally, single-case studies demonstrated the increased ability of participating students to apply the acquired knowledge to diagnostic problems. We conclude that the implementation of CAL in present medical curricula can contribute to reformations of medical education. The instructional design of Dermatology 2000 is well accepted and suitable to provide both theoretic biomedical knowledge and clinical skills.

A reactivity study on a series of platinum boryl complexes was performed. The first stable base adducts of cationic haloboryl complexes of the form trans-[Pt{B(Br)-(NMe 2 )}(NCMe)(PCy 3 ) 2 ] + were isolated and fully characterized. The dianion [B 12 Cl 12 ] 2− was introduced as a weakly coordinating anion to complex chemistry forming a A 2 X salt. Through the reaction of trans-[Pt{B(Br)(tBu)}Br(PCy 3 ) 2 ] with BBr 2 tBu, the first highly soluble dinuclear platinum boryl complex, [Pt{B(Br)(tBu)}(μ-Br)(PCy 3 )] 2 , could be synthesized with concomitant buildup of the corresponding phosphine-borane adduct. In contrast to this observation, reaction of trans-[Pt{B(Br)(Mes)}Br(PCy 3 ) 2 ] with BBr 3 leads to the formation of the cationic borylene complex trans-[Pt(BMes)Br(PCy 3 ) 2 ] + by abstraction of the bromo ligand bound mutually trans to the boryl ligand in the precursor and concomitant buildup of [BBr 4 ] − . Reaction of [Pt(PCy 3 ) 2 ] with BCl 3 and subsequent abstraction of the platinum-bound chloro ligand enabled the structural characterization of trans-[Pt(BCl 2 )(PCy 3 ) 2 ] + , which is isoelectronic with the metal-only Lewis pair trans-[Pt(BeCl 2 )(PCy 3 ) 2 ]. The bonding situation in both systems was investigated in detail using quantum chemical calculations. A T-shaped cationic complex, trans-[Pt{B(Br)(Fc)}(PiPr 3 ) 2 ] + , and its precursor trans-[Pt{B(Br)(Fc)}Br(PiPr 3 ) 2 ], both with reduced steric bulk at the phosphine ligands compared with their PCy 3 derivatives, were fully characterized.

(2016) New outcomes of Lewis base addition to diboranes(4): electronic effects override strong steric disincentives. Chemical Communications, 52

A series of iridium dihydroborate complexes [(tBuPOCOP)­IrH­(κ2-H2BHR)] (tBuPOCOP = κ3-C6H3-1,3-[OPtBu2]2; R = Mes = 2,4,6-Me3C6H2; R = Dur = 2,3,5,6-Me4C6H) and [LIrH­(κ2-H2BHDur)] (L = tBuPCP = κ3-C6H3-1,3-[CH2PtBu2]2, L = η5-C5Me5) and an osmium dihydroborate compound [OsH­(κ2-H2BHDur)­(CO)­(PiPr3)2] have been prepared by using two different synthetic strategies. The first approach is based on direct borane coordination to the metal center, whereas the second is based on a salt-elimination protocol using the lithium salts Li­[H3BR] (R = Mes or Dur) and the corresponding metal halides. The compounds have been characterized by multinuclear NMR and IR spectroscopy and X-ray diffraction analysis. The results constitute the first syntheses of κ2-σ:σ-dihydroborate complexes featuring bulky aryl groups.

The reaction of PF with [(Cy P) Pt] gave the PF complex trans-[(Cy P) PtF(PF )][PF ], which was characterized by single-crystal X-ray diffraction, multinuclear NMR spectroscopy, and elemental analysis. To the best of our knowledge, this reaction is the first example of the oxidative addition of a P-F bond to a transition metal and is a rare example of an activation of a main-group-element-fluorine bond by a metal. Relativistic DFT calculations showed that the formation of the Lewis pair [(Cy P) Pt→PF ], which was not observed even at low temperatures, represents the initial step of the reaction. From this key intermediate, the cation trans-[(Cy P) PtF(PF )] was furnished by a two-step mechanism involving, successively, a second and a third PF molecule.