Macropolyhedral boron-containing cluster chemistry. Ligand-induced two-electron variations of intercluster bonding intimacy. Structures of nineteen-vertex[(eta(5)-C5Me5) HIrB18H19(PMe2Ph)] and the related carbene complex [(eta(5)-C5Me5)HIrB18H19{C(NHMe)(2)}]

Addition of PMe2Ph to fused-cluster syn-[(η5-C5Me5)IrB18H20] 1 to give [(η5-C5Me5)HIrB18H19(PMe2Ph)] 3 entails a diminution in the degree of intimacy of the intercluster fusion, rather than retention of inter-subcluster binding intimacy and a nido → arachno conversion of the character of either of the subclusters. Reaction with MeNC gives [(η5-C5Me5)HIrB18H19{C(NHMe)2}] 4 which has a similar structure, but with the ligand now being the carbene {:C(NHMe)2}, resulting from a reductive assembly reaction involving two MeNC residues and the loss of a carbon atom

Macropolyhedral boron-containing cluster chemistry: two-electron variations in intercluster bonding intimacy. Contrasting structures of 19-vertex [(eta(5)-C5Me5)HIrB18H19(PHPh2)] and [(eta(5) -C5Me5)IrB18H18(PH2Ph)]

Fused double-cluster [(5-C5Me5)IrB18H18(PH2Ph)]8, from syn-[(5-C5Me5)IrB18H20] 1 and PH2Ph, retains the three-atoms-in-common cluster fusion intimacy of 1, in contrast to [(5-C5Me5)HIrB18H19(PHPh2)]6, from PHPh2 with 1, which exhibits an opening to a two atoms-in-common cluster fusion intimacy. Compound 8 forms via spontaneous dihydrogen loss from its precursor [(5-C5Me5)HIrB18H19(PH2Ph)]7, which has two-atoms-in-common cluster-fusion intimacy and is structurally analogous to 6

The two most common histological subtypes of malignant germ cell tumour are distinguished by global microRNA profiles, associated with differential transcription factor expression.

BACKGROUND: We hypothesised that differences in microRNA expression profiles contribute to the contrasting natural history and clinical outcome of the two most common types of malignant germ cell tumour (GCT), yolk sac tumours (YSTs) and germinomas. RESULTS: By direct comparison, using microarray data for paediatric GCT samples and published qRT-PCR data for adult samples, we identified microRNAs significantly up-regulated in YSTs (n = 29 paediatric, 26 adult, 11 overlapping) or germinomas (n = 37 paediatric). By Taqman qRT-PCR we confirmed differential expression of 15 of 16 selected microRNAs and further validated six of these (miR-302b, miR-375, miR-200b, miR-200c, miR-122, miR-205) in an independent sample set. Interestingly, the miR-302 cluster, which is over-expressed in all malignant GCTs, showed further over-expression in YSTs versus germinomas, representing six of the top eight microRNAs over-expressed in paediatric YSTs and seven of the top 11 in adult YSTs. To explain this observation, we used mRNA expression profiles of paediatric and adult malignant GCTs to identify 10 transcription factors (TFs) consistently over-expressed in YSTs versus germinomas, followed by linear regression to confirm associations between TF and miR-302 cluster expression levels. Using the sequence motif analysis environment iMotifs, we identified predicted binding sites for four of the 10 TFs (GATA6, GATA3, TCF7L2 and MAF) in the miR-302 cluster promoter region. Finally, we showed that miR-302 family over-expression in YST is likely to be functionally significant, as mRNAs down-regulated in YSTs were enriched for 3' untranslated region sequences complementary to the common seed of miR-302a~miR-302d. Such mRNAs included mediators of key cancer-associated processes, including tumour suppressor genes, apoptosis regulators and TFs. CONCLUSIONS: Differential microRNA expression is likely to contribute to the relatively aggressive behaviour of YSTs and may enable future improvements in clinical diagnosis and/or treatment.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are

Periodic trends and easy estimation of relative stabilities in 11-vertex nido-p-block-heteroboranes and -borates

Density functional theory computations were carried out for 11-vertex nido-p-block-hetero(carba)boranes and -borates containing silicon, germanium, tin, arsenic, antimony, sulfur, selenium and tellurium heteroatoms. A set of quantitative values called “estimated energy penalties” was derived by comparing the energies of two reference structures that differ with respect to one structural feature only. These energy penalties behave additively, i.e., they allow us to reproduce the DFT-computed relative stabilities of 11-vertex nido-heteroboranes in general with good accuracy and to predict the thermodynamic stabilities of unknown structures easily. Energy penalties for neighboring heteroatoms (HetHet and HetHet′) decrease down the group and increase along the period (indirectly proportional to covalent radii). Energy penalties for a five- rather than four-coordinate heteroatom, [Het5k(1) and Het5k(2)], generally, increase down group 14 but decrease down group 16, while there are mixed trends for group 15 heteroatoms. The sum of HetHet′ energy penalties results in different but easily predictable open-face heteroatom positions in the thermodynamically most stable mixed heterocarbaboranes and -borates with more than two heteroatoms

B(C6F5)3 as C6F5 Transfer Agent in Zirconium Chemistry: Borole Sandwich and Borole-Bridged Triple-Decker Complexes

Treatment of Cp‘‘Zr(C6F5)(OEt2){?5-(3-RC4H3BC6F5)} ( 1H , R = H; 1Me , R = Me; Cp‘‘ = 1,3-C5H3(SiMe3)2) in toluene with nitriles R‘CN gives rise to the adducts Cp‘‘Zr(C6F5)(NCR‘){?5-(3-RC4H3BC6F5)} ( 2H , R = H, R‘ = Me; 3H , R = H, R‘ = tBu; 3Me , R = Me, R‘ = tBu) in high yields. The reaction of 1H and 1Me with a 4-fold excess of tert-butylisocyanide in toluene at -20 °C leads to the formation of Cp‘‘Zr(C6F5)(CNtBu)2{?5-(3-RC4H3BC6F5)} ( 4H , R = H; 4Me , R = Me), while warming to room temperature results in the insertion of one molecule of isocyanide into the zirconium-C6F5 bond to give the ?2-iminoacyl complexes Cp‘‘Zr{?2-(C6F5CNtBu)}(CNtBu){?5-(3-RC4H3BC6F5)} ( 5H , R = H; 5Me , R = Me). The structures of 3H and 5H were confirmed by X-ray diffraction. The reaction of the diene complexes CpRZr(?3-crotyl)(?4-butadiene) ( 6a , CpR = C5H4SiMe3; 6b , C5H4Me; 6c , Cp; 6d , Cp‘‘) with B(C6F5)3 in toluene solution at room temperature proceeds quantitatively with C-H activation, butene elimination, and C6F5 transfer to generate CpRZr(C6F5){?4-CH2CHCHCHB(C6F5)2} ( 7a - d ). These boryldiene complexes are thermally unstable and smoothly rearrange to give the triple-decker complexes Zr2(CpR)2(C6F5)2{µ-?5:?5-C4H4BCH2-?3,?F-CHCHCHB(C6F5)3} ( 8a - d ). The formation of these complexes involves the complete transfer of all three C6F5 substituents of one B(C6F5)3 molecule, as well as C-H activation and the loss of one C6F5 group as pentafluorobenzene. The triple-decker complexes feature a Zr2C4B core, a zwitterionic structure, and an unusually strong Zr-F donor interaction. On activation with methylalumoxane (MAO), 8a - d polymerize ethene

fac,cis-bromidotricarbonylbis(tribenzylphosphine)rhenium(I)

Crystals of the title compound, fac,cis-[ReBr(C21H21P)2(CO)3], were obtained by recrystallization of a sample from CHCl3 layered with hexane. The geometry about the d6 ReI centre is (distorted) octa­hedral with the three CO ligands fac and the two tribenzyl­phosphine ligands cis. In accordance with the trans influence, the Re-C bond trans to Br is significantly shorter than those trans to the organophos­phine ligands

The reactivity of trimethylsilyliminophosphines towards titanium and zirconium halides

Zirconium tetrachloride reacted with C2H4(Ph2P=NSiMe3)2-1,2 1 under C–H activation to give the NCN chelate complex ZrCl3{?3-N,C,N'-C2H3(Ph2P=NSiMe3)2}, while the reaction with C5H3N(Ph2P=NSiMe3)2-2,6 gave an N-donor adduct. Cp*TiCl3 reacts with trimethylsilyliminophosphines under dehalosilylation in all cases. In contrast to 1, the potentially C–N chelating benzylphosphinimine (4-ButC6H4CH2)Ph2P=NSiMe3 undergoes dehalosilylation with TiCl4 in preference to C–H activation, while prolonged reflux with ZrCl4 affords the salt [4-ButC6H4CH2P(Ph)2NHSiMe3]2[Zr2Cl10]. The molecular structures of the latter, ZrCl3{C2H3(Ph2PNSiMe3)2}, C5H3N(Ph2P=NTiCl2Cp*)2-2,6, and TiCl2Cp*{N=PPh2CH2C6H4But-4} have been determined by X-ray diffraction