Six-coordinate compounds

The participation of phosphoms d orbitals in the five- and six-coordinate compounds provides increased polarizabiUty, nucleophilicity, and ionic character. In fact, compounds such as phosphoms pentachloride [10026-13-8] 5) thought to have considerable ionic character. The CJ-bond orders between the phosphoms atom and its constituents in the higher coordinate compounds maybe less than one. 

Rhenates, tetraevanodtoxy-six-coordinate compounds structure, 1, 53 Rhenium... 

Site symmetry symbols, I, 128 Six-coordinate compounds stereochemistry, 1, 49-69 Six-membered rings metal complexes, 2, 79 Skeletal muscle sarcoplasmic reticulum calcium pump, 6, 565 Slags... 

DNA polymerases, 5, 1007 Trans effect, 1,16, 26, 315 metal complexes, 2, 705, palladium(II) amine complexes, 5, 1115 platinum complexes, 5, 353, 493 six-coordinate compounds. 1, 49 T ransestcrification metal alkoxide synthesis, 2, 340 Transferases zinc, S, 1002... 

Four-coordinate complexes exhibit lower isomer shifts than six-coordinate compounds. Metal-ligand bonds are shorter and more covalent if the coordination number is smaller because of less steric hindrance and less overlap with antibonding 2g orbitals in the case of four as compared to six bonds. 

Konig and others published in the 1970s an impressive series of studies on six-coordinate iron(II)-bis-phenanthroline complexes [160-164] for which they inferred 5=1 from thorough magnetic susceptibility and applied-field Mossbauer measurements. Criteria for the stabilization of the triplet ground state for six-coordinate compounds with tetragonal ( >4 ) and trigonal ( >3 ) symmetry were obtained from LFT analyses [163], The molecular structures, however, were not known because the materials could not be crystallized. 

The range of cyclic systems for four-, five-, and six-coordinate compounds synthesized up to 1995 is summarized in <1996CHEC-II(8)1135>. This chapter aims to review advances in synthesis, characterization, reactivity studies, and applications of compounds containing a spiro phosphorus atom since 1995. 

Various manganese complexes have also been investigated. In one study, six-coordinate compounds of type [MnXL]+ and seven-coordinate species of type [MnX2L] [where L = (293) and X is one of a range of... 

Complexes of SB (73) are five-coordinate in solution and normally show no tendency to coordinate a basic ligand to form six-coordinate compounds.725 The formation of adducts depends on the chelate ring, as in (70). With electronegative groups in the aromatic ring, e.g. 5-N02salen (73 RI = R2 = H, R = 5-N02), electronic and CD spectra show hexacoordinate adducts, and solid adducts were obtained with py and DMSO.725... 

All the monomeric molybdenum(III) complexes are paramagnetic, and in Table l5 the magnetic moments of some typical examples are given. For six-coordinate compounds the values lie between 3.53 and 3.86 BM, with most in the region 3.7 to 3.8 BM as predicted for octahedral d3 complexes.37 The value of 1.73 BM in ELt[Mo(CN)7] 2H20 is consistent with a spin-doublet ground state d3 system.3S... 

Kummer et al.374 found addition compounds of Si2Cl6 and Si2Cl4me2 with bipyridyl. They postulate a six-coordinated compound. 

Reaction of carbastannatrane 442b (Hal = Cl) with AgBF4 yields the tetrafluorobo-rate salt [N(CH2CH2CH2)3Sn]+BF4. Its ionic structure in solution was confirmed by 119Sn NMR chemical shift (103 ppm), which indicate a tetracoordinate tin atom827,876. However, reactions of azastannatranes 445 (R = Me, w-Bu, Ph) with BF3 Et20 lead to six-coordinated compounds 448 (equation 75)877. 

The electrochemistry of a number of such six-coordinate compounds [MnXL]+ and seven-coordinate compounds [MX2L] (with L = (203), R,R = Me and X = halide, water, triphenylphosphine oxide, imidazole, 1-methylimidazole or pyridine) has been investigated.551 The redox behaviour of these compounds was of interest because it was considered that the potentially -acceptor macrocycle (203 R = R = Me) may promote the formation of Mn° or Mn1 species or may yield a metal-stabilized ligand radical with the manganese remaining in its divalent state. For a number of macrocyclic ligand systems, it has been demonstrated that the redox behaviour can be quite dependent on axial ligation it was also of interest to study whether this was the case for the present systems. 

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