Noble gases, coordination compounds

Noble gas(VIII) compounds, 316 Noble gases, 311-321 carbon ligands, 316 coordination compounds, 312 coordination geometry, 312 halogen ligands, 313-316 nitrogen ligands, 319... 

A recent structure determination has shown that the compound I(OS02F)2l has the characteristic T-shaped coordination with the I" —I distance of 2.678 A in the equatorial position and two I—O axial distances of 2.09 and 2.26 A with O—I—angles of 91.0 and 85.3 . A secondary I O bond of 3.05 A completes a coordination similar to that in the [XeFs] ion described earlier. The only noble gas compound of this class is Xe(OTeF5)4, prepared from the interaction of Xep4 and B(OTeF5)3, for which the Raman spectrum supports the square planar arrangement. ... 

The nohle gas elements (He, Ne, Ar, BCr, Xe, and Rn) are unreactive only recently have compounds of these elements been prepared. It has long been recognized that compounds in which each atom can, by electron sharing with other atoms, gather around itself a number of electrons equal to that foimd in a noble gas also tend to be very stable. Professor N. V. Sidgwick of Oxford University applied this observation to metal complexes. He postulated the central metal would surround itself with sufficient ligands so that the total number of electrons around the metal would be the same as that in the next noble gas. The number of electrons surrounding the coordinated metal is... 

All noble gas compounds (except for proton adducts such as the gas-phase species HeH" ") are hypervalent that is, they have more than eight eleeflons in the noble gas valence shell. In addition, XeF4 and XeF are susceptible to nucleophilic attack by F , which further increases their coordination number. Fluoride ligands are also common leaving or migrating groups in much of xenon chemistry. 

Nickel is the only metal to react directly with carbon monoxide at room temperature at an appreciable rate, although iron does so on heating under pressure. Cobalt affords HCo(CO)4 with a mixture of hydrogen and carbon monoxide (p. 387). In general, therefore, direct reaction does not provide a route to metal carbonyls. The metal atom technique (p. 313) has been used to prepare carbonyls of other metals in the laboratory e.g. Cr(CO)g, but it offers no advantages over the reduction method discussed below. When metal vapours are cocondensed with carbon monoxide in frozen noble gas matrices at very low temperatures (4-20K) the formation of carbonyl complexes is observed. These include compounds of metals which do not form any stable isolable derivatives e.g. Ti(CO), Nb(CO) and Ta(CO)g as well as Pd(C0)4 and Pt(C0)4. Vibrational spectra of the matrix show that coordinatively unsaturated species such as Ni(CO) n = 1-3) or Cr(CO) (n = 3-5) are also formed under these conditions. 

When one or more of the vertices of a carborane are replaced by metal (M) atoms or metaUo (ML ) groups, a metaUocarborane is formed. Transition metal atoms in these cluster compounds are considered to be pseudo-octahedrally coordinated with valence shells having 18 electrons, corresponding to noble gas configuration. When this assumption is combined with Wades 2 + 2 rules, we can readily arrive at a general formula for the number of valence electrons C for the skeleton of a metaUocarborane ... 

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