Contributions to the enantioselective Heck reaction using MeO-Biphep ligands : the case against dibenzylidene acetone

It is shown that the Pd-catalyzed enantioselective Heck reaction of p-XC(6)H(4)OTf, X = OMe, H, CO(2)Me, with dihydrofuran gives higher enantioselectivities when the chelating diphosphine MeO-Biphep, 1a, is replaced with its disubstituted analogue 3,5-di-tert-butyl MeO-Biphep, 1b. The phenylation of 5-methyl-2,3-dihydrofuran produces a new dihydrofuran containing a quaternary stereogenic center(ee, >98% with 1b, ca. 20%, with 1a). Catalytic results for the reaction of phenyl triflate with dhf, together with stoichiometric oxidative addition reactions of aryl halides on Pd complexes of 1, show that the use of Pd(dba)(1), dba = dibenzylidene acetone, slows the oxidative addition relative to the reaction in which the Pd(0) precursor is generated from PdCl(2)(1) + NaBH(4). The solid-state structures for two PdI-(aryl)(1a), 3, derivatives, aryl = p-MeOOC-C(6)H(4) (3a) and C(6)F(5) (3b) are reported

Structural distortions in Pd-MeO-Biphep and Pd-Binap aryl complexes : anomalies induced via electronic effects

The four-coordinate complexes [PdBr(p-NCC6H4)(MeO-Biphep)], 1 [MeO-Biphep = 6,6'-dimethoxy-2,2'-bis(diphenylphosphino)-1,1'-biphenyl], and [PdBr(p-NCC6H4)(p-tol-Binap)], 2 [p-tol-Binap = 2,2'-bis(di-p-tolylphosphino)-1,1'-binaphthyl], both distort markedly, with the former no longer square-planar, and the latter, possessing the longest recorded Pd-P bond length

New chiral complexes of palladium(0) containing P,S- and P,P-bidentate ligands

New chiral complexes of Pd(O) containing either the bis(phosphine) (6,6'-dimethoxybiphenyl-2,2'-diyl)bis(3,5-di-tert -butylphenylphosphine) (MeO-BIPHEP, 1) or the phosphine-sulfur chelate (2,3,4,6-tetra-O-acetyl-1-{(2-diphenylphosphino)benzyl)thio) -beta-D-glucopyranose ((2-Ph2PC6H4CH2) -S-CHCH(OAc)CH(OAc)CH(OAc)CH(CH2OAc)O,2) have been prepared, and the solid-state structure of one of these, Pd(benzoquinone)(2), has been determined. These Pd(O) complexes reveal interesting solution dynamics, as shown by 2-dimensional exchange spectroscopy. For the MeO-BIPHEP derivatives, one can obtain useful structural insights based on the observed restricted rotation around the aryl(3,5-di-tert-butylphenl)P-C bonds

Visualisation of KPIs in zero emission neighbourhoods for improved stakeholder participation using Virtual Reality

This paper addresses the role of virtual reality in addressing the specific challenge of the increasing complexity and decreasing usability when dealing with the level of detail required to model a zero emission neighbourhood (ZEN).[1] In such neighbourhoods, there is a need to handle both 'top down' neighbourhood level data with 'bottom up' building and material level data. This can quickly become overwhelming particularly when dealing with non expert users such as planners, architects, researchers and citizens who play a key part in the design process of future ZENs. Visualisation is an invaluable means to communicate complex data in an interactive way that makes it easier for diverse stakeholders to engage in decision making early and throughout the design process. The main purpose of this work has been to make ZEN key performance indicators (KPIs) more easily comprehensible to a diverse set of stakeholders who need to be involved in the early design phase. The paper investigates how existing extended reality (XR) technologies, such as virtual reality, can be integrated with an existing dynamic LCA method in order to provide visualise feedback on KPIs in early phase design of sustainable neighbourhoods. This existing method provides a dynamic link between the REVIT Bim and the ZEB Tool using a Dynamo plugin.[2] The results presented in this paper demonstrate how virtual reality can help to improve stakeholder participation in the early design phase and more easily integrate science-based knowledge on GHG emissions and other KPIs into the further development of the user-centered architectural and urban ZEN toolbox for the design and planning, operation and monitoring of ZENs. [3

Electronically and sterically induced structural distortions in square-planar d(8) complexes

The solid-state structure of the cationic MeO-Biphep Rh(I) compound [Rh((S)-MeO-Biphep)-(P{OMe}(3))(2))]BF4 (3) has been determined by X-ray diffraction. The four P-donors deviate markedly from square-planar geometry, with the phosphite ligands P2 and P2' ca. +/-0.61(7) Angstrom from the P1-Rh-P1' plane. This distortion resembles that found for PdBr(p-NCC6H4)-((S)-MeO-Biphep) (1). Density functional calculations on a series of systematically varied models of 1 reveal three major components to be responsible for the observed distortion from square-planar geometry: (i) attractive aromatic ring pi-pi interactions, (ii) electronic stabilization of coplanar aromatic rings in pseudo-trans positions, and (iii) P-phenyl and MeO-Biphep-phenyl intraligand repulsive steric interactions. Additional DFT studies on the p-tolyl-Binap analogue of i, PdBr(p-NCC6H4)((R)-p-Tol-Binap) (2), explain the source of the extremely long Pd-PB bond distance, 2.437(1) Angstrom, in 2. Despite the structural similarity between 1 and 2, the calculations rationalize the observation of a pronounced distortion from a square-planar geometry in the former that is essentially absent in the latter