Single-Crystal X-Ray Structures

The sec-NH configurations of a number of macrocyclic systems, previously used in photochemical studies, have now been established as well as those for linear polyamines. It is also pleasing to see several structures of Cr(III) complexes containing biologically active ligands. 

The solution stereochemistry of the chelate rings in Cr(III) edta-type complexes, as determined by NMR spectroscopy, has now been correlated with X-ray structural parameters. Structures of chromate esters, long postulated as intermediates in the oxidation of alcohols by Cr(VI), have also been determined. 

[Cr(cida)(H20)2]-3H20 cida = (9). The unsymmetrical quadridentate tripodal ligand adopts configuration (10) rather than (11). Cr-N = 2.082(4)  

The mechanistic significance of the difference in Cr—Cl bond lengths for [CrCl(NH3)5]Cl2 and [CrCl(MeNH2)5]Cl2 is discussed in the Introuduction. 

CrS04-5H20 ) Isomorphous with CUSO4 5H2O. Cr-OHjCeq) = 2.05(1) Cr—OHjCax) = 2.43(1). 

KCrp4 Contains CrjF9 units with three different Cr—F distances of 1.860, 1.943, and 1.926. 

Cr-N (mean) = 2.081(14) A(AA) plus A(S5) cations. See Reference 1, Table 6.1, for a compilation of other Cr-F bond distances. 

Protons marked are acidic and seven-coordinate Cr(lll) complexes with deprotonated forms (DAPSC-H) of this quinquidentate ligand can be isolated.Donor atoms are underlined. 

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Addition of lithiated Ar-(4-methylphenylsulfonyl)-S-phenyl-S -(2-propenyl)sulfoximine to acyclic enones gives exclusively 1,4-a-adducts in high diastereomeric purity. The configuration of the adduct (R2 = R3 = C6H5) has been determined by a single crystal X-ray structure determination27. 

From single-crystal X-ray structural analysis the ground-state conformation of (.S )-2-(4-meth-ylphenylsulfinyl)-2-cyclopentenone was shown to have the sulfoxide bond orientated anti to the carbonyl bond, as expected for minimization of electrostatic interactions13. 

Wells et al. characterized group 13-stibine adducts by single crystal X-ray structure analyses first in 1997 [35]. The solid state structures of three borane-stibine adducts of the type X3B—Sb(Tms)3 (X = Cl 6, Br 7, I 8), obtained by reaction of boron trihalides BX3 and Sb(Tms)3 in n-pentane, were determined. 

Single crystal X-ray structure analyses of analogously substituted adducts confirmed the applicability of this model. Adducts of the type EtaAl—E(Tms)3 and f-BuaAl—E(i-Pr)3 (E = P, As, Sb, Bi) were structurally characterized [50], allowing detailed comparisons of their solid state structural parameters. The trends observed for the average Al—C bond lengths and the C— Al—C bond angular sums are summarized in Figs. 5 and 6. 

Figure 3.12 Single crystal X-ray structure of O-adduct with o-chloranil.

As discussed in Section II. A, theoretical studies predicted that phospha-silenes with silyl substituents attached to phosphorus should have planar, trigonally coordinated silicon, with the Si—P w-bonds strengthened by the hyperconjugative influence of the silyl group.16 Recently, this was proved by a single-crystal X-ray structure determination of the derivative... 

We also performed a single-crystal X-ray structure analysis of this lead compound. The solid state structure of this compound depicted in Fig. 3-15 shows a half-boat-like ( sofa ) conformation with the 9-phenanthryl group in a quasi-axial or r/Mf/.v/-flagpole position, and the a, 3-unsaturated exocyclic ester in a s-cis conformation. This cleft-like conformation is advantageous for the creation of centers with a high recognition ability, since one enantiomer fits in better than the other thus leading to selectivity. 

The zinc teflate Zn(OTeF5)2 has been synthesized and characterized by IR and 19F NMR spectroscopy. The interaction with a number of weakly coordinating solvents was studied and the single-crystal X-ray structures determined for nitrobenzene derivatives [Zn(OTeF5)2 (PhN02)2]2 and Zn(0TeF5)2(PhN02)3.428... 

Zinc boryloxides with a tetrameric Zn404 core (45) have only recently been characterized. The single-crystal X-ray structure and multinuclear NMR spectroscopy studies were used as a basis for discussion of deformation of the central core.435 Alkali metal zinc orthoborates MZn4(B03)3 (M = K, Rb, Cs) have been synthesized and single-crystal X-ray structures determined for M = K and Rb.436... 

Methyl- l-[methyl-(2-pyridin-2-yl-ethyl)amino]propane-2-thiol (108) is a tridentate N2S ligand with an aliphatic thiolate ligand. The single-crystal X-ray structures demonstrate that the zinc complexes are close structural analogs of the His2Cys site found in peptide deformylase.873... 

The specific features of the cluster compounds of technetium are such, that practically each new compound must be studied using single crystal X-ray structural analysis, because their complex structures do not allow the interpretation of the results from other physico-chemical methods of investigation. Therefore, the synthesis of single crystals suitable for X-ray structural analysis is the main and most laborious chemical task. 

A single crystal X-ray structure analysis of 8 (Fig. 4) confirms the molecular constitution of the compound deduced by spectroscopic methods and shows further structural details. The molecule is dimeric with a Mn-C15 ( -carbyne) bond length of 1.857(2) A and a Mn-Mn bond distance of 2.565(1) A the latter one is typical for a Mn-Mn single bond [13]. The Mn-C15 (carbyne) bond is short compared to known Mn-C single bonds, for example that in (OC)4Mn-C(C00Et)C(HgBr)C(0Et)0 is found to be 2.051(26) A [13b], For the acyclic carbyne complex [Cp(CO)2Mn = C-CH=CPh2]+ BF4 the MnC distance is 1.665(5) A [14] comparable values for... 

Reaction of the carbonyl complex 26 with the mercury diazomethane 27 gives the highly reactive 17e intermediate carbyne complex 28 which dimerizes to form the / -biscarbyne complex 30. In this case, the intermediate terminal carbyne complex 28 has been trapped by reaction with the mercury diazomethane 29 to form the cyclic vinylidene complex 31. 31 was also characterized by a single crystal X-ray structure analysis. 

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