Ulrich Pidun

THE BONDING OF ACETYLENE AND ETHYLENE IN HIGH-VALENT AND LOW-VALENT TRANSITION METAL COMPOUNDS

Abstract The equilibrium geometries of the transition metal compounds WCl 4 L, WCl 5 L − and W(CO) 5 L (L = acetylene, ethylene) are theoretically predicted at the HF and MP2 levels of theory using a relativistic effective core potential for tungsten and valence shell basis sets of DZ + P quality. The WL dissociation energies are calculated at the CCSD(T) level of theory. The calculated geometries are in very good agreement with experimental values. The WC acetylene and WC ethylene bond distances of WCl 4 L are much shorter than bond lengths of W(CO) 5 L. However, the (CO) 5 WL bond dissociation energies are higher than or comparable in magnitude with the Cl 4 WL bond energies. This result can be explained by the different nature of the tungsten-carbon bonds in W(CO) 5 L and WCl 4 L, as revealed by the charge decomposition analysis (CDA) of the compounds. The WC bonds of the low-valent carbonyl complexes have donor-acceptor character and the binding can be understood in terms of the Dewar-Chatt-Duncanson model. The tungsten-carbon bonds of WCl 4 L are polar covalent bonds which are formally formed from the triplet states of WCl 4 and L. The dissociation energies of WCl 4 L are very low, because the energy which is necessary to promote acetylene and ethylene into the lowest lying triplet state is very high. The CDA results for WCl 5 L − suggest that the anions might also be considered as complexes which can be discussed in terms of closed-shell orbital interactions. The Cl 5 W − L bond energies are rather low, because there is strong repulsion between the occupied orbitals of the fragments. The breakdown of the donor-acceptor interactions into orbital contributions shows that acetylene is a four-electron donor in WCl 5 (HCCH) − , while it is a two-electron donor in W(CO) 5 (HCCH). The donation from the out-of-plane CC-bonding π orbital of acetylene is the reason why WCl 5 (HCCH) − is a stable (isolable) compound. This orbital is not available for ethylene, and thus WCl 5 (C 2 H 4 ) is predicted to have a weak tungsten-ethylene bond.

Corporate Portfolio Management: Theory and Practice

Forty years after the introduction of the BCG growth-share matrix, some version of corporate portfolio management (CPM) is employed by most large multibusiness companies. But little is known about the current practices of CPM. Which processes have companies adopted, and which executives in a company tend to be the main participants? What are the major corporate uses of CPM? And how satisfied are todays companies with their approaches?. To answer these questions, The Boston Consulting Group, in collaboration with Freiberg University in Germany, conducted a comprehensive global survey on the practices of corporate portfolio management that involved more than 200 senior executives at the largest companies worldwide. These survey responses were supplemented by interviews with 50 senior executives of global multibusiness companies as well as a systematic review of more than 100 major client projects that BCG conducted between 2004 and 2009. One major focus of the survey was the concept of parenting advantage.- Defined in terms of a particular company being the best possible owner of a particular business, the concept offers a clear framework for identifying the four most important ways in which management can use the principles and methods of CPM to create value for its businesses:. While fostering synergies and realizing advantage through centralization of functions and services were considered relevant by about half of the companies responding to the survey, the most important drivers of corporate value added by CPM were said to be the direct influence of the parents expertise and active portfolio monitoring. But even so, only 40% of recent divestiture decisions and 23% of recent acquisitions were said to be triggered by portfolio considerations, suggesting a significant gap between the effort put into CPM processes and their role in corporate-level decision-making.

The calculation of bond dissociation energies of transition metal complexes using isostructural reactions

Abstract The metal-ligand bond dissociation energies (CO) n M-L are theoretically predicted at the HF, MP2 and CCSD(T) levels of theory using effective core potentials for the metals for M = Cr, Mo, W, Ni, Pd, Pt and for L = CO, NO + , CN − , NC − , CS, SiO, N 2 . The bond energies at the HF level are too low and the MP2 values are too high, while the CCSD(T) results are in good agreement with experimental data. The bond energies at MP2 show the same trend as the CCSD(T) values and may therefore be used for the prediction of relative bond dissociation energies. The absolute values for the bond energies calculated at MP2 are significantly improved when they are corrected using the energies of isostructural reactions M(CO) n + L → M(CO) n −1 L + CO.

[HRh(CO)4]-Catalyzed Hydrogenation of Co: A Systematic Ab Initio Quantum-Chemical Investigation of the Reaction Mechanism

Some earlier assumptions must be dismissed, and a number of experimental observations are explained, following our systematic theoretical investigation of intermediates and transition states of the [HRh(CO)4]-catalyzed hydrogenation of carbon monoxide. The formyl complex 1 and the formaldehyde complex 2 are found to be the key intermediates.

How to assess the corporate parenting strategy? A conceptual answer

Purpose – The major purpose of this paper is the development of a theoretical framework that can be used by corporate practitioners to understand the implicit parenting strategy of their company, assess its performance, and adjust it for improving the net corporate value creation.Design/methodology/approach – In this paper, a three‐dimensional framework is developed that accounts for corporate‐to‐business and business‐to‐business interactions, value‐adding and value‐destroying activities, and strategic and operational levers. The framework is operationalized by assigning a broad set of individual activities to these levers.Findings – The paper delivers a robust, systematic, and operational framework to assess the net benefits to a given business of being part of a corporate portfolio, and to identify and evaluate implicit parenting strategies in corporate practice. While previous studies mainly focused on broad parenting approaches with low granularity this framework now allows earlier observations to be ...

Corporate Portfolio Analysis Tools Revisited: Assessing Causes that May Explain Their Scholarly Disdain

While prominent corporate portfolio analysis tools such as the BCG Growth-Share Matrix took centre stage in the field of strategic management from the 1960s to the mid‐1980s, this review of the literature shows that they have since then largely disappeared from the academic agenda, despite their practical relevance and widespread application. There may be two independent reasons for this apparent scholarly disdain: corporate portfolio analysis tools (a) may have been recognized as unsuitable owing to inherent flaws or superior alternative concepts or (b) may have become obsolete because of proof that corporate diversification is inferior to market diversification. Thus, this assessment is based on an extensive review of the most relevant academic literature on corporate portfolio analysis tools and on the constitutive diversification – performance link published in leading management journals over the past five decades. The review reveals that research to date has not produced advanced tools based on an objective criticism of the original matrices, nor has corporate diversification – as a precondition for corporate portfolio analysis – proved to be inferior to market‐based co‐ordination mechanisms. Thus, this literature review constitutes a call for further academic research in the field of corporate portfolio analysis tools as well as corporate diversification.

Corporate portfolio management applications: role of firm characteristics and impact on corporate processes

Corporate portfolio management (CPM) approaches emerged over 40 years ago in response to the rise of large corporations with diversified portfolios of partly unrelated business units. Their initial purpose and main application area was to support corporate management in defining the boundaries of a firm, allocating resources and assigning specific roles and targets for each business unit. Today, CPM is still regarded as highly relevant, but little is known about the application of CPM instruments in corporate practise. Based on a survey among 196 executives of the largest companies worldwide, we identified three distinct CPM user-types: corporate developers, business unit steerers and passive portfolio managers. These CPM application patterns are traced back to a set of distinct company characteristics. Moreover, it is demonstrated that the CPM user type has a significant influence on the characteristics of the implemented CPM processes and on the integration of CPM with other corporate processes.

Parenting Approaches in Corporate Strategy an Exploratory Study on the Impact of Portfolio Structure and Culture

We empirically analyze the parenting advantage concept’s relevance for corporate strategy, identify different types of parenting approaches, and investigate the actual application of parenting advantage in corporate portfolio management. We find that parenting advantage is considered highly relevant for corporate strategy and portfolio management; that there are distinct types of parenting approaches in corporate practice; that portfolio structure and cultural differences strongly affect a company’s choice of parenting approach; and that the main deterrent to more effectively applying the parenting advantage concept for corporate-level management is a lack of operationalization that specifies sources of parenting advantage, and which evaluates the effectiveness of different parenting approaches.

Transforming the business portfolio

Purpose – The major purpose of this paper is to investigate antecedents, outcomes and processes of business portfolio transformations, including diversifying, refocusing and repositioning portfolio restructurings. Design/methodology/approach – The paper conducts a longitudinal study on the process of business portfolio transformations among the largest 100 European and 100 North American firms during the period of 1998-2010. A newly developed metric is applied that allows a business portfolio transformation to be identified and quantified and process-related research to be conducted. Findings – The study confirms and expands prior literature that postulates that poor performance and over-diversification are key motivations for portfolio restructuring. However, the majority of transformations were not successful, with firm performance further deteriorating in the course of the transformation. The analysis of the transformation process itself reveals that the average transformation took 2.6 years and change...

Recent developments in the application of theory to structural problems in coordination chemistry

The development of molecular orbital techniques and their applications to structural problems in co-ordination chemistry will be reviewed. Initially semi-empirical molecular orbital methods were used to supplement symmetry based arguments in structural chemistry. This led to significant generalisations concerning the stereochemistries of co-ordination compounds and cluster compounds. Recently more sophisticated Density Functional Theory calculations have become available which enable theoretical chemists to accurately predict the structures of co-ordination and organometallic compounds . This review provides a brief background to Density Functional Theory calculations and illustrates their application to a number of topical problems.