Selected benzoic acid derivatives and related substances were used as additives to 2,5-dihydroxybenzoic acid (2,5DHB) and the performance of the mixtures in matrix-assisted laser desorption/ionization mass spectrometry was investigated. Using benzoic acid derivatives substituted at position 2 and/or 5 or related substances as a co-matrix in the 1-10% range with 2,5DHB results in improved ion yields and signal-to-noise ratio of analyte molecules, especially for the high-mass range. The enhanced performance is prominent for 2-hydroxy-5metboxybenzoic acid and exists for both proteins and oligosaccharides. It is suggested that the improvement is caused by a disorder in the 2,5DHB crystal lattice allowing 'softer' desorption. Charge transfer from matrix ions to additive molecules at the expense of analyte ionization gives a simple explanation for the deteriorating effects of some tested additives.

Lithium cyclopentadienide adds to a variety of isocyanates [R−NCO, R = tert-butyl (a), n-butyl (b), cyclohexyl (c), phenyl (d), 3-pyridyl (e), 2-tetrahydropyranyl (f), adamantyl (g)] to yield the monocarbamoyl-substituted cyclopentadienides C5H4CONHR- 3 admixed with varying amounts of the respective 1,2-dicarbamoyl-substituted C5H3(CONHR)2 - systems 4 and a corresponding quantity of the C5H5 - starting material. Subsequent treatment of these reaction mixtures with anhydrous FeCl2 gave the 1,1‘-dicarbamoylferrocenes 6 and the corresponding monocarbamoylferrocenes 5, which were easily separated by chromatography. The carbamoylferrocenes 5b, 5c, and 6d were characterized by X-ray crystal structure analyses. The (N-phenyl- and (N-adamantylcarbamoyl)cyclopentadienides were treated with CpTiCl3 to give the carboxamide-substituted titanocene dichloride complexes [Cp(C5H4CONHR)TiCl2] 8a (R = Ph) and 8b (R = adamantyl), respectively. Complex 8b was also characterized by X-ray diffraction. The valine ester-derived isocyanate reacts with lithium cyclopentadienide to give the N-valinyl-substituted carbamoylcyclopentadienide 3h. Subsequent treatment with FeCl2 or FeCl2/CpLi, respectively, produces the 1,1‘-difunctionalized ferrocene 6h or the monofunctionalized ferrocene 5h. Both complexes were characterized by X-ray crystal structure analyses.

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COMMUNICATIONS x Fig. 2. Crystal structure of Zb [I 11. Selected distances [A] and angles [ 1: CLC2 140.0(7). C5-C6 15(1.6(7). C6-C7 149.0(8). Zr-CI 244.2(1): C5-C6-C7 114 l(4). C4-C5-C6 127 7(5), CI-Zr-CI 97.95(5).largest observed in these compounds. As in 2 a the dihedral angles in the bridges of 2 b (38.6(7) and 20.7(8)") indicate an approximately eclipsed configuration of the five-membered rings.Owing to the molecular structure of the new rigid zirconocenophane 2 b, catalytic activity for the stereoselective polymerization of alkenes can be anticipated for this compound or substituted chiral derivatives. Moreover, application of complexes of type 2 b appears promising for C -C bond-forming reactions with metallocene derivatives from the fourth subgroup, which are currently of interest.[I6] as well as for the synthesis of novel metaIIacycIes.