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Biomedical subjects

Holger Braunschweig

Publications and source records attributed to Holger Braunschweig.

28 records · Page 2Linked to original sources
PubMed2005

Heterodinuclear bridged borylene complexes.

Heterodinuclear bridged borylene complexes are synthesized via oxidative addition of the B-Br bond of bromoboryl complex precursors to an electron-rich palladium species. The synthetic protocol grants access to the first compound featuring the reactive bromoborylene ligand.

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PubMed2004

Novel organocycloborates via Grignard reagents.

An unprecedented cyclisation reaction of alpha,omega-borylbromoalkanes is seen upon treatment with magnesium turnings, forming organocycloborates in high yield. The novel boratacyclopentanes and -hexanes have been characterised by X-ray crystallography.

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PubMed2004

Synthesis and structure of boron-bridged constrained geometry complexes of titanium.

The boron-bridged constrained geometry titanium complexes [Ti[eta5:eta1-(C5H4)B(NR2)NPh](NMe2)2][R = iPr (3), SiMe3(4)] and [Ti[eta5:eta1-(C9H6)B(NiPr2)NPh](NMe2)2](12) have been prepared in good yields by amine elimination reaction from [Ti(NMe2)4]. Subsequent deamination-chlorination with excess Me3SiCl yielded the corresponding dichloro-complexes (5, 6, 13). Reaction of the analogous ligand precursors (C5H5)B(NiPr2)N(H)R (R = Cy, tBu) with [Ti(NMe2)4] did not result in the expected bridged compounds, but rather in the half-sandwich complexes [Ti[(eta5-C5H4)B(NiPr2)N(H)R](NMe2)3][R = Cy (9), tBu (10)]. All compounds were fully characterised by means of multinuclear NMR spectroscopy. Thorough investigation of substituent effects was achieved by comparative X-ray diffraction studies on complexes 3, 5, 6 and 12.

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PubMed2003

Formation, structure and reactivity of boryloxycarbyne complexes of group 6 metals.

Reaction of the diborane(4) B(2)(NMe(2))(2)I(2) with two equivalents of K[(eta(5)-C(5)H(5))M(CO)(3)] (M=Cr, Mo, W) yielded the dinuclear boryloxycarbyne complexes [[(eta(5)-C(5)H(5))(OC)(2)M(triple bond)CO](2)B(2)(NMe(2))(2)] (4 a, M=Mo; b, M=W; c, M=Cr), which were fully characterised in solution by multinuclear NMR methods. The Mo and W complexes 4 a, b proved to be kinetically favoured products of this reaction and underwent quantitative rearrangement in solution to afford the complexes [[(eta(5)-C(5)H(5))(OC)(2)M(triple bond)CO]B(NMe(2))B(NMe(2))[M(CO)(3)(eta(5)-C(5)H(5))]] (5 a, M=Mo; b, M=W); 5 a was characterised by X-ray crystallography in the solid state. Corresponding reactions of B(2)(NMe(2))(2)I(2) with only one equivalent of K[(eta(5)-C(5)H(5))M(CO)(3)] (M=Mo, W) initially afforded 1:1 mixtures of the boryloxycarbyne complexes 4 a, b and unconsumed B(2)(NMe(2))(2)I(2). This mixture, however, yielded finally the diborane(4)yl complexes [(eta(5)-C(5)H(5))(OC)(3)M[B(NMe(2))B(NMe(2))I]] (6 a, M=Mo; b, M=W) by [(eta(5)-C(5)H(5))(OC)(3)M] transfer and rearrangement. Density functional calculations were carried out for 4 c and 5 a, b.

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PubMed2003

Unprecedented reactivity of the bridged borylene complexes [mu-BCl((eta(5)-C(5)H(4)Me)Mn(CO)(2))(2)] toward pyridine.

The reactivity of the bridged chloroborylene complex [mu-BCl((eta(5)-C(5)H(4)Me)Mn(CO)(2))(2)] (1) toward pyridine was investigated under various conditions. In the presence of protic reagents such as H[Co(CO)(4)] or H[BF(4)], the formation of the aminoborylene complex [1-(mu-B)-4-H-(NC(5)H(5))((C(5)H(4)Me)Mn(CO)(2))(2)] (2) was observed. Compound 2 represents the product of an unprecedented formal 1,4-hydroboration of pyridine. Corresponding reactions of 1 with pyridine and Tl[PF(6)] afforded 2 in similar yields, thus providing evidence that the abstraction of the boron bound chloride initiates the observed reaction. Complex 2 was fully characterized in solution and in the crystal.

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