Bite distance

The Ni—N bond distances, N—N bite distances, and N—M—N bite angles of Ni11 macrocyclic complexes depend on the coordination number of the metal ion and the type of macrocycle. These... 

The protein sequences from six different sources have been determined and compared to attempt identification of possible ligands (Gatti et al., 1989). The conserved consensus sequence around the cysteines is shown in Fig. 19. Clearly, there are several possible combinations of cysteines and histidines that fit established bite distances in other Fe S proteins. On the basis of preferred sequences, bite distances, and the required order of ligands, we suggest that Cys-129-Cys-134 for the ferric... 

The Ni—N bond distances, N-N bite distances, and N-M-N bite angles of Ni(II) macrocyclic complexes depend on the coordination number of the metal ion and the type of macrocycle. These structural parameters influence the electronic spectra and the electrochemical data. In general, Ni—N bond distances of square-planar complexes are shorter than those of the octahedral complexes because of the absence of electrons in dx2 . Furthermore, as the Ni—N bond distance in-... 

Complex Ni Ni-L4 Chelate rings Bite distances (A) Bite angles1 (deg) Ref. 

Displacement of Ni atom from NiN4 plane (A). 4 Average Ni—N bond distance (A). c N-N bite distances (A). d Bite (NMN) angles. 

Related to jS-diketones are metalla-/ -diketones, whose distinctive chemistry is a recent development. In these, the methine group of a conventional diketonate is replaced with an organometallic moiety such as m-Mn(CO)4, m-Re(CO)4, /<2c-Mn(CO)3(RNC) or C5H5Fe(CO).519 Exemplary is Al Mn(MeCO)2(CO)4 3, which is prepared in a two-step synthesis. Addition of methyllithium to Mn(CO)5COMe forms Li[Mn(MeCO)2(CO)4] which, when treated with aluminum chloride, provides the tris(chelate) compound.520 An X-ray study showed that the MnC202Al ring is essentially planar with Mn—C(acyl) bond distances indicative of a bond order of ca. 1.2. The O—O bite distance, 2.73 A, is about the same as that of acetylacetonate in Al(MeCOCHCOMe)3.521 As in the... 

Fig. 12. Definition of solid state structural parameters for tris chelate complexes with D3 symmetry 0 is the twist angle and is the projection of the bite angle a onto the plane which is perpendicular to the C3 symmetry axis, 0 is the pitch angle and is the angle subtended by the plane of the chelate ring and the C3 symmetry axis r, d, s and h are the metal ligand distance, bite distance, triangle edge, and the distance between the triangles, respectively. From Ref.82 ...

A] bond distances. The restricted bite distances of the xanthate ligands [the S—M—S chelate angles are 73.50(6) and 69.77(4)°, respectively] are most the likely source for the deviations from the ideal octahedral geometries. The distortions are best seen in the twists of the triangular faces, that is, 40.27(7) and 46.43(5)° for the gallium and indium structures, respectively, compared to the ideal octahedral angle of 60°. Enantiomeric pairs associate in their respective crystal lattices via S- -S contacts of 3.598(4) and 3.592(2) A, respectively. 

Fabbrizzi and co-workers have demonstrated the use of bis-copper(II) cryptates to sense ambidentate anions [49]. On titrating molecule 71 with NaN3 in aqueous solution, the colour changed from pale blue to bright green and an anion-metal LMCT absorption appeared at 400 nm. X-ray diffraction studies have shown that the azide anion is held colinear with the two Cu(II) centres, coordinated through the two terminal sp2-hybridised nitrogen atoms. Stability constants for 71 with a variety of anions in aqueous solution were calculated and the selectivity of this anion sensor was found to be controlled by the bite distance between the two copper atoms (Fig. 1). 

Among the bridging ligands with the shortest bite distance are the oxygen-donor anions sulfate, hydrogen phosphate and acetate. The sulfate... 

The fact that only Pt111 dimers have been isolated for quadruply-bridged sulfate, phosphate, acetate, and acetamidate complexes indicates that the short bite distance of these ligands destabilizes the Pt2 state, which requires a much longer Pt-Pt distance. 

Fig. 2. Correlation diagram of the Pt(III)—Pt(III) distance and the Mo(II)—Mo(II) distance vs the ligand bite distance.

Before further discussion, some technical terms relevant to the structural discussions are described here. Bite distance B) is the distance... 

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