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1. Bis(diiminate)-based boron difluoro complexes: e?ective synthon for bis(borenium) cations.

Author

Parveen, Darakshan, Yadav, Rahul Kumar, Mondal, Bijan, Dallon, Marie, Sarazin, Yann, and Roy, Dipak Kumar

Subjects
CATIONS, BORON, ACIDS
Abstract

A series of boron difluoro bis(diiminate) complexes have been prepared and used to obtain triflate substituted fluoroborane complexes. The corresponding well-defined bis(borenium) cations were subsequently synthesized and structurally authenticated. We are also presenting the first experimental and theoretical study of bis(borenium) cations that are derivative of cationic borinic acid. [ABSTRACT FROM AUTHOR]

Published
2024
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3. A comparison of peak bone mass of European causasian and South Asian women residing in the United Kingdom

Author

Roy, Dipak Kumar

Subjects
612
Abstract

Aims: To characterise the distribution of peak bone mass at the total hip, lumbar spine (LS) and total body (TB) sites of women from one European Caucasian (EC) and two South Asian populations, namely Pakistani Muslims (PM) and Gujarati Hindus (GH), residing in the UK, and to explore whether variations of lifestyle and other non-genetic putative risk factor characteristics may explain any variation in peak bone mass between the EC and South Asian groups. Methods: Women, aged 18 years to 36 years, were recruited from primary care age-sex registers from practices located within Greater Manchester. Women were mailed a screening questionnaire concerning various lifestyle factors. Those women who replied, were invited to attend for a more detailed interview-assisted lifestyle questionnaire, assessments of height, weight and waist-to-hip ratio, bone density (BMD) at the total hip, LS and TB, fat mass (FM) and lean mass (LM) and blood tests for serum calcium, parathyroid hormone (PTH) and 25 hydroxyvitamin D (25 OHD). Results: The participation rates for BMD screening, were 19%, 9% and 14% for EC, PM and GH women respectively. EC and GH women who completed the screening questionnaire were slightly older than those who did not. Based on a study comparing responses to the screening questionnaire, differences in characteristics between those who attended for BMD screening and those who did not, for all three ethnic groups , were generally small and the direction inconsistent in terms of benefit or detriment to BMD. BMD data was available on 118 EC, 98 PM and 28 GH women. Compared to PM, EC had significantly higher BMD at the hip (0.962 g/cm2 vs 0.916 g/cm2 ), LS (1.031 g/cm2 vs 0.984 g/cm2) and TB (1.096 g/cm2 vs 1.058 g/cm2). Although BMD at all three sites were higher among EC compared with GH, differences were small and non-significant. There were no significant differences in LS BMAD (calculated by dividing areal BMD by subject height), between EC and either South Asian group. When comparing EC and PM women, adjusting for age and separately for height, LM, maximum non-pregnant weight, serum 25 OHD, PTH, dietary calcium consumption or vitamin D consumption, eliminated significant BMD differences at all three sites, adjusting for weight eliminated differences at the hip and LS, while adjusting for hormonal contraception use eliminated differences at the hip only. In multivariate models, at the hip, after adjusting for age, weight, height, 25 OHD, PTH, dietary calcium consumption and hormonal contraception use, at the LS, after adjusting for these characteristics (other than hormonal contraception use) and at the TB, after adjusting for age, height, LM, 25 OHD, PTH and dietary calcium consumption, BMD was significantly higher in PM women (b coefficient for PM with EC as referent = 0.063, 0.064 at the hip, LS and TB respectively).

Published
2003

20. Toward Transition-Metal-Templated Construction of Arylated B4 Chains by Dihydroborane Dehydrocoupling

Author

Lenczyk, Carsten, Roy, Dipak Kumar, Oberdorf, Kai, Nitsch, Jörn, Dewhurst, Rian D., Radacki, Krzysztof, Halet, Jean-François, Marder, Todd B., Bickelhaupt, F.M., Braunschweig, Holger, Lenczyk, Carsten, Roy, Dipak Kumar, Oberdorf, Kai, Nitsch, Jörn, Dewhurst, Rian D., Radacki, Krzysztof, Halet, Jean-François, Marder, Todd B., Bickelhaupt, F.M., and Braunschweig, Holger

Abstract

Contains fulltext : 214624.pdf (publisher's version ) (Open Access), The reactivity of a diruthenium tetrahydride complex towards three selected dihydroboranes was investigated. The use of [DurBH2] (Dur=2,3,5,6-Me4C6H) and [(Me3Si)2NBH2] led to the formation of bridging borylene complexes of the form [(Cp*RuH)2BR] (Cp*=C5Me5; 1?a: R=Dur; 1?b: R=N(SiMe3)2) through oxidative addition of the B?H bonds with concomitant hydrogen liberation. Employing the more electron-deficient dihydroborane [3,5-(CF3)2-C6H3BH2] led to the formation of an anionic complex bearing a tetraarylated chain of four boron atoms, namely Li(THF)4[(Cp*Ru)2B4H5(3,5-(CF3)2C6H3)4] (4), through an unusual, incomplete threefold dehydrocoupling process. A comparative theoretical investigation of the bonding in a simplified model of 4 and the analogous complex nido-[1,2(Cp*Ru)2(?-H)B4H9] (I) indicates that there appear to be no classical σ-bonds between the boron atoms in complex I, whereas in the case of 4 the B4 chain better resembles a network of three B?B σ bonds, the central bond being significantly weaker than the other two.

Published
2019

21. Steric Effects Dictate the Formation of Terminal Arylborylene Complexes of Ruthenium from Dihydroboranes

Author

Lenczyk, Carsten, Roy, Dipak Kumar, Nitsch, J., Radacki, Krzysztof, Rauch, Florian, Dewhurst, Rian D., Bickelhaupt, F.Matthias, Marder, Todd B., Braunschweig, H., Lenczyk, Carsten, Roy, Dipak Kumar, Nitsch, J., Radacki, Krzysztof, Rauch, Florian, Dewhurst, Rian D., Bickelhaupt, F.Matthias, Marder, Todd B., and Braunschweig, H.

Abstract

Contains fulltext : 208131.pdf (publisher's version ) (Open Access)

Published
2019

22. Isolation and Reactivity of an Antiaromatic s‐Block Metal Compound.

Author

Roy, Dipak Kumar, Tröster, Tobias, Fantuzzi, Felipe, Dewhurst, Rian D., Lenczyk, Carsten, Radacki, Krzysztof, Pranckevicius, Conor, Engels, Bernd, and Braunschweig, Holger

Subjects
*METAL compounds, *BERYLLIUM, *ALKALINE earth compounds, *HETEROCYCLIC compounds synthesis, *CHEMICAL reduction, *ANTIAROMATICITY
Abstract

The concepts of aromaticity and antiaromaticity have a long history, and countless demonstrations of these phenomena have been made with molecules based on elements from the p, d, and f blocks of the periodic table. In contrast, the limited oxidation‐state flexibility of the s‐block metals has long stood in the way of their participation in sophisticated π‐bonding arrangements, and truly antiaromatic systems containing s‐block metals are altogether absent or remain poorly defined. Using spectroscopic, structural, and computational techniques, we present herein the synthesis and authentication of a heterocyclic compound containing the alkaline earth metal beryllium that exhibits significant antiaromaticity, and detail its chemical reduction and Lewis‐base‐coordination chemistry. [ABSTRACT FROM AUTHOR]

Published
2021
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23. Isolierung und Reaktivität eines s‐Block‐Metall‐Antiaromaten.

Author

Roy, Dipak Kumar, Tröster, Tobias, Fantuzzi, Felipe, Dewhurst, Rian D., Lenczyk, Carsten, Radacki, Krzysztof, Pranckevicius, Conor, Engels, Bernd, and Braunschweig, Holger

Subjects
*BERYLLIUM
Abstract

Das Konzept der Aromatizität und der Antiaromatizität ist seit langem bekannt, und zahlreiche Belege für dieses Phänomen wurden durch Moleküle, welche auf Elementen des p‐, d‐ und f‐Blocks des Periodensystems der Elemente (PSE) basieren, geliefert. Aufgrund der begrenzten Varianz des Oxidationszustandes von s‐Block‐Metallen konnten diese bisher nicht mit komplexen π‐Bindungssystemen interagieren. Daher gibt es keine bzw. nur schlecht beschriebene Beispiele für antiaromatische Systeme mit s‐Block‐Metallen. Durch die Verwendung von spektroskopischen, strukturanalytischen und quantenchemischen Methoden konnte eine heterocyclische Verbindung hergestellt und charakterisiert werden, welche das Erdalkalimetall Beryllium enthält und signifikante Antiaromatizität aufweist. Weiterhin beschreiben wir die Reaktivität gegenüber Lewis‐Basen und die chemische Reduktion dieser Verbindung. [ABSTRACT FROM AUTHOR]

Published
2021
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28. Toward Transition‐Metal‐Templated Construction of Arylated B4 Chains by Dihydroborane Dehydrocoupling.

Author

Lenczyk, Carsten, Roy, Dipak Kumar, Oberdorf, Kai, Nitsch, Jörn, Dewhurst, Rian D., Radacki, Krzysztof, Halet, Jean‐François, Marder, Todd B., Bickelhaupt, Matthias, and Braunschweig, Holger

Subjects
*BORON, *OXIDATIVE addition, *TRANSITION metals, *BORON isotopes, *HYDROGEN bonding, *CONSTRUCTION
Abstract

The reactivity of a diruthenium tetrahydride complex towards three selected dihydroboranes was investigated. The use of [DurBH2] (Dur=2,3,5,6‐Me4C6H) and [(Me3Si)2NBH2] led to the formation of bridging borylene complexes of the form [(Cp*RuH)2BR] (Cp*=C5Me5; 1 a: R=Dur; 1 b: R=N(SiMe3)2) through oxidative addition of the B−H bonds with concomitant hydrogen liberation. Employing the more electron‐deficient dihydroborane [3,5‐(CF3)2‐C6H3BH2] led to the formation of an anionic complex bearing a tetraarylated chain of four boron atoms, namely Li(THF)4[(Cp*Ru)2B4H5(3,5‐(CF3)2C6H3)4] (4), through an unusual, incomplete threefold dehydrocoupling process. A comparative theoretical investigation of the bonding in a simplified model of 4 and the analogous complex nido‐[1,2(Cp*Ru)2(μ‐H)B4H9] (I) indicates that there appear to be no classical σ‐bonds between the boron atoms in complex I, whereas in the case of 4 the B4 chain better resembles a network of three B−B σ bonds, the central bond being significantly weaker than the other two. [ABSTRACT FROM AUTHOR]

Published
2019
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