M n complexes

We have seen that metal-carbene complexes polarized in this way, M =C , are Schrock carbenes. Thus, the reactivity of the M=0 and M=N complexes resembles that of early transition-metal complexes of nucleophilic alkylidene complexes, which has consequences in organic chemistry and catalysis (see Part IV). It is indeed possible to transfer the O and NR ligands in the same way as alkylidene ligands of early transition-metal complexes were transferred. 

McPhalen, C. A., James, M. N. G. Structural comparison of two serine proteinase-protein inhibitor complexes Eglin-C-Subtilisin Carlsberg and CI-2-subtilisin novo. Biochemistry 27 (1988) 6582-6598... 

James, M.N.G., et al. Structures of product and inhibitor complexes of Streptomyces griseus protease A at 1.8 A resolution. A model for serine protease catalysis. 

Comparison of the photoelectron spectra and electronic structures of M-NS and M-NO complexes, e.g., [CpCr(CO)2(NX)] (X = S, O), indicates that NS is a better a-donor and a stronger r-acceptor ligand than NO. This conclusion is supported by " N and Mo NMR data, and by the UV-visible spectra of molybdenum complexes. 

Transition-metal complexes of the thionylimide anion exhibit characteristic vibrations in the regions 1260-1120, 1090-1010 and 630-515 cm , which are assigned to Oas(NSO), Os(NSO) and <5(NSO), respectively. X-ray structural data for several M-NSO complexes reveal N-S and S-O bond lengths of ca. 1.46 0.04 A indicative of double bond character in both of these bonds. 

The hydrolytic sensitivity of thionylimines is also displayed by L M-RNSO complexes, which produce the corresponding LnM-S02 complexes. The ease of hydrolysis of these metal complexes follows the order o-(5)-pyramidal > o-(5)-trigonal > 7c(N,S). ... 

MCl3(NS)(PPh3)2]. In the few complexes for which X-ray structural data are available the M-N-S group is essentially linear (170-177°) (see p. 453 and refs. 233, 235) but spectroscopic data on others suggest that bent and even ij -bridging modes may be possible. 

Komplex-erz, n. complex ore, -ion, n. complex ion. -salz, n. complex salt. -stahli m. complex alloy steel, -verbindung, /. complex compound. 

They resemble the oxygen-bridged [M2OC1io]4- (section 1.3.6) (Figure 1.75) with M-N stretching frequencies similar to those in the mononuclear complexes (1108 cm-1 in [Os2N(NH3)gCl2]Cl3). 

Moseley found that each K spectrum of Barkla contains two lines, Ka and K(3, and that the L spectra are more complex. Later important work, especially by Siegbahn,38 has shown that M, N, and O spectra exist and are more complex in their turn. Relatively numerous low-intensity lines are now known to exist in all series. Fortunately, the analytical chemist can afford to ignore most of these low-intensity lines in his practical applications of x-ray methods at present. It generally suffices for him to know that x-ray spectra at their most complex are enormously simpler than emission spectra involving valence electrons, and that most x-ratr lines are satisfactorily accounted for on the basis of the simple selection rules that govern electron transitions between energy states. 

At concentrations above 10 M a complex series of reactions, ending with the formation of 4,4-methylenebis (N,N-dimethylaniIine), occur. The extra methylene group comes from a further molecule of starting material. Finally, at even higher concentrations, the product becomes the dye, crystal violet or its leuco-form. 

Polysulfides with two-valent complex cations, e.g., [M(N-methyhmida-zole)6]Ss have been prepared with M = Mn, Fe, Ni, Mg [51]. 

Murray, D.L. and Schoeninger, M.J. 1988 Diet, status and complex social structure in iron age Central Europe some contributions ofbone chemistry. In Gibson, D.B. and Geselowitz, M.N., eds.. Tribe and Polity in Late Prehistoric Europe. New York, Plenum 155-176. 

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