Distorted square pyramidal

All the OsNX4 complexes are distorted square pyramids (with N-Os-X angles of 103.7 to 104.5°) [188]. The stability of an osmium(VI) to iodine bond is unusual and is presumably owing to the extensive Os=N 7r-bonding reducing the positive charge on the metal and stabilizing it to reduction. 

Extended-Hiickel calculations have been carried out [185] for systems such as IrCl4(NO)2-, based on a slightly distorted square pyramid of C4v symmetry (crystallographically studied 5-coordinate systems do not have a planar base but exhibit this slight distortion). Figure 2.104 shows how the... 

A crystal-structure determination on [Ni(PhCH2CS2)2] showed evidence of a Ni-Ni bond (Ni—Ni distance, 256 pm) in a bridging, acetate-cage, binuclear complex (363). Each nickel atom is 5-coordinate and is in a tetragonally distorted, square-pyramid spectroscopic evidence for a Ni-Ni bond has been obtained (364). The polarized crystal spectra showed more bands than predicted for a mononuclear, diamagnetic, square-planar nickel(Il), and the spectra are indicative of substantial overlap of the d-orbitals between the two nickel atoms. The bis(dithiobenzation)nickeKII) complex was found to exhibit unusual spectrochemical behavior (365). 

If the BF2 groups in Ni(dmg-BF2)2 are substituted by BPh2 units (122), the complex also adopts the saddle-shaped conformation of type D (Fig. 32), in which the two dimethylglyoxime fragments are bent down from the N4 plane with a dihedral angle of about 27° between the two least-squares planes of the dioxime units. The coordination geometry around the nickel ion is distorted square-pyramidal, but there are no intermolecular Ni Ni interactions [167]. 

Kawashima reported the structure of 1-phenyl-l//-phosphirene 102 which has a distorted square-pyramidal structure (Scheme 35) [82, 83], The observed elongation of the C=C bond has been interpreted in terms of the tt-o interaction in similar ways by Regitz [39] for cyclic phosphirene and by Clark [14] for phosphirenium ions 17. 

The structural analyses reveal distorted square pyramidal coordination with a nearly linear Cl( 1)—Ru—Cl(2) angle (168.62 and 170.42 for 12 and 13,... 

The solid state structure of complex 7b is shown in Figure 25.1. Similar to parent chelating ether complex [9b], the solid-state structure of 7b shows a distorted square-pyramidal structure with the benzylidene moiety at the apical position. The N-aryl ring is located above the benzylidene moiety resulting in the relatively close contact of the benzylidene proton with the 7r-aromatic system of the mesityl group. 

Macrocycles attached to redox responsive groups such as ferrocene (78) can give selective transition metal ion receptors. The X-ray structure reveals a five-coordinate zinc with distorted square-pyramidal geometry bound to the four macrocycle nitrogens and an iodide. In the solid state the two ferrocenyl groups are positioned on the same side of the ligand with distances to the metal center of 5.347(7) and 6.120(8) A and these distances can be related to the redox behavior.689... 

CH3OH)]2 has a distorted square-pyramidal zinc center with the iodide in the apical position and a Zn—Ba distance of 3.736(1) A. The iodide can be removed by treatment with a silver salt. 

Methyl pyruvate thiosemicarbazone in the presence of zinc chloride or acetate resulted in the formation of complexes with the ligand hydrolyzed or transesterified. The complexes with pyruvate thiosemicarbazone, ZnL2, or ethyl pyruvate thiosemicarbazone, ZnLCl2 were structurally characterized by single-crystal X-ray crystallography showing respectively a distorted octahedral and distorted square pyramidal geometry.874... 

Pentacoordinated Pc complexes with planar macrocycle are very scarce. Very recently, Galezowski and Kubicki [25] reported a o-bonded ComPc(CH3CH2) (2) with an alkyl group as axial ligand. Investigation of its crystal structure revealed that the solid consists of centrosymmetric face-to-face dimers. The cobalt atom in 2 is pentacoordinated and has a distorted square pyramidal geometry. The cobalt atom... 

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