scholarly journals Asymmetric Coordination

2020 ◽  
pp. 127-131
2022 ◽  
Vol 0 (0) ◽  
Author(s):  
Christoph Ludwig Teske ◽  
Huayna Terraschke ◽  
Sebastian Mangelsen ◽  
Wolfgang Bensch

Abstract The title compounds were prepared by precipitation from acidic solutions of the reactants in acetone/water. Bi(S2CNH2)2Cl (1) crystallizes in the non-centrosymmetric trigonal space group P32 with a = 8.6121(3) and c = 11.1554(4) Å, Z = 3; Bi(S2NH2)2SCN (2) in P21/c (monoclinic) with a = 5.5600(2), b = 14.3679(5), c = 12.8665(4) Å, and β = 90.37(3)°. In the crystal structure of 1 Bi3+ is in a sevenfold coordination of two bidentate and one monodentate S2CHNH2 − anions with an asymmetric coordination pattern of five Bi–S and two Bi–Cl− bonds. The linkage of these polyhedra via common Cl–S edges leads to a 1D polymeric structure with undulated chains propagating in the direction [001]. These chains are linked by strong and medium strong hydrogen bonds forming the 3D crystal structure. In the crystal structure of 2 the Bi3+ cation is in an eightfold coordination. The polyhedron can be described as a significantly distorted tetragonal anti-prism, capped by an additional S atom. Two of these prisms share a common quadrilateral face to form a “prism-double” (Bi2S10N2). These building units are linked by common edges, and the resulting 1D infinite angulated chains propagate along [100]. By contrast to organo-dithiocarbamate compounds, where C–H···X bridges are dominant, the interchain connections in the crystal structures of 1 and 2 are formed exclusively via N–H···S, N–H···Cl, and N–H···N interactions, generating the 3D networks. A significant eccentricity of the Bi3+ cation in the crystal structures of both complexes is observed. Both compounds emit light in the orange range of the electromagnetic spectrum.


2019 ◽  
Vol 16 (02) ◽  
pp. 1950008
Author(s):  
Fuhai Zhang ◽  
Jiadi Qu ◽  
He Liu ◽  
Yili Fu

The paper develops a multi-priority control method of asymmetric coordination for a redundant dual-arm robot. A novel dual-arm coordination impedance is introduced to the multi-priority control, and then the performance of the object tracking and the redundant joints is improved by the regulation of the relative Cartesian errors between two arms. The control of asymmetric coordination is divided into the main task and the secondary task. The control of the main task can regulate the two end-effectors’ errors and the relative errors by building the model of spatial parallel spring and damping (SPSDM), which establishes the dual-arm coordination impedance relation in Cartesian space. The control of the secondary task optimizes the performance of the redundant joint impedance and joint limit avoidance in null space. Finally, a typical asymmetric coordination experiment of peg-in-hole is carried out to verify the validity and feasibility of the proposed method. The results indicate that the proposed dual-arm coordination impedance can regulate the relative tracking errors between two objects directly, and in the context of the external impact force applied to the two end-effectors, the peg-in-hole dual-arm task can be achieved successfully.


1976 ◽  
Vol 29 (11) ◽  
pp. 2541 ◽  
Author(s):  
BF Hoskins ◽  
CD Pannan

Various forms of asymmetry in the lengths of the bond between the central atom and sulphur, found in differing coordination environments of 1,1-dithiolate compounds involving main group atoms, have been successfully rationalized by considering both the valence shell electron pair repulsion theory and the effect of the restricted ligand bite distance.


2014 ◽  
Vol 70 (4) ◽  
pp. m133-m133 ◽  
Author(s):  
Martin Reichelt ◽  
Hans Reuter

The title compound, [Sn(C4H9)2(C2O4)]n, an unexpected side product in the reaction of di-tert-butyltin(IV) oxide with nitric acid, represents the first diorganotin(IV) oxalate to be structurally characterized. The SnIVatom of the one-dimensional coordination polymer is located on a mirror plane and is coordinated by two chelating oxalate ions with two rather different Sn—O bond lengths of 2.150 (1) and 2.425 (1) Å, and twot-butyl groups with Sn—C bond lengths of 2.186 (2) and 2.190 (2) Å. The coordination polyhedron around the SnIVatom is a distorted tetragonal disphenoid. The centrosymmetric oxalate ion also has an asymmetric coordination geometry, as reflected by the two slightly different C—O bond lengths of 1.242 (2) and 1.269 (2) Å. The chains of the polymer propagate along theb-axis direction. Only van der Waals interactions are observed between the chains.


2009 ◽  
Vol 362 (9) ◽  
pp. 3231-3237 ◽  
Author(s):  
Hai Fu ◽  
Yang-Guang Li ◽  
Yong-Hui Wang ◽  
Xin-Long Wang ◽  
Xiao-Jia Feng ◽  
...  

2010 ◽  
Vol 122 (43) ◽  
pp. 8127-8129 ◽  
Author(s):  
Lei Gong ◽  
Zhijie Lin ◽  
Klaus Harms ◽  
Eric Meggers

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