Heterobinuclear Complexes of Manganese and Molybdenum Containing Amino Acidato and Related O,N and S,N Bridges

Abstract

The addition of NaOMe to [MnMo(CO) 6 (µ-S 2 CPCy 3 )(µ-Br)] (1) produces [MnMo(CO) 6 (µ-S 2 CPCy 3 )(µ-OMe)] (2), containing a methoxide bridge between Mn and Mo. Compound 2 reacts with R-amino acids to yield, upon elimination of MeOH, the complexes [MnMo(CO) 5 -(µ-S 2 CPCy 3 ){µ-OC(O)CR 1 R 2 NR 3 2 }] (3a-f), in which the oxygen atom of the carboxylato group acts as a bridge between Mn and Mo, while the amino function coordinates the molybdenum atom, displacing one carbonyl ligand. In a similar reaction, the addition of ethanolamine to 2 affords the µ 2 (O)-η 2 (O,N)-aminoethanolato complex [MnMo(CO) 5 (µ-S 2 CPCy 3 )(µ-OCH 2 CH 2 -NH 2 )] (4). Reaction of 2 with cysteine methyl ester hydrochloride and NaOMe affords [MnMo-(CO) 5 (µ-S 2 CPCy 3 ){µ-SCH 2 C(COOMe)NH 2 }] (5), with the sulfur atom in the bridging position. The new complexes have been characterized by analytical and spectroscopic methods, and their structures have been determined by X-ray crystallography for 2, 3e (2,2-dimethylaminobutyrato), and 4.

Molybdenum carbonyl complexes with pyridylimino acidato ligands

“…The structure of 2a shows an interesting arrangement of anion/cation pair dimers, which will be described in detail together with those found in other iminocarboxylate complexes prepared in this work (see below). On the other hand, the high value of the Flack parameter for the structure [0.42 (7)] suggests that a nearly total racemization of the chiral a-carbon occurs in the formation of 2a.…”

“…The choice of the chiral space group P1 was suggested by the XPREP subroutine of SHELXTL on the basis of the value of the mean |EE* −1 | = 0.795. The Flack parameter was refined with the instruction TWIN, and converged to 0.42 (7), indicating the presence of two enantiomers in the lattice. Alternatively, the structure was solved and refined on the centrosymmetric space group P 1.…”

“…5 On the other hand, the continuing interest on amino acids as ligands for metal complexes, or as building blocks in organometallic chemistry is stimulated by the expectations of attaching the resulting complexes to biological molecules. 6 We have described recently the use of amino acidate anions as bridging ligands in heterobinuclear complexes containing manganese and molybdenum, 7 and explored the metalation of benzodiazepines in ruthenium complexes. 8 In the course of current studies focussed on pyridyl imino ligands we became interested in using amino acids as convenient blocks to build chelate N-N ligands containing a side arm with a carboxylate functionality.…”