The capability of donor-substituted alkynes to link different metal ions in a side-on carbon donor-chelate coordination mode is extended from the donor centers S and P to the second period element N. The complex [Tp'W(CO)2 {η(2) -C2 (S)(NHBn)}] (Tp'=hydrido-tris(3,5-dimethylpyrazolyl)borate, Bn=benzyl) bearing a terminal sulfur atom and a secondary amine substituent is accessible by a metal-template synthesis. Subsequent deprotonation allowed the formation of remarkably stable heterobimetallic complexes with the [(η(5) -C5 H5 )Ru(PPh3 )] and the [Ir(ppy)2 ] moiety. Electrochemical and spectroscopic investigations (cyclic voltammetry, IR, UV/Vis, luminescence, EPR), as well as DFT calculations, and X-ray structure determinations of the W-Ru complex in two oxidation states reveal a strong metal-metal coupling but also a limited delocalization of excited states.

No abstract

No abstract

The synthesis and reactivity of a W(ii) C2I2 complex towards various nucleophiles are described. Soft, aprotic nucleophiles like 4-dimethylaminopyridine (DMAP) lead to substitution of one CO at tungsten, whereas reaction with an excess of benzylamine results in a dual nucleophilic substitution at the alkyne moiety involving the rearrangement to a novel cationic amidinium carbyne complex.

This paper is dedicated to Professor Barry Trost for the outstanding importance of his work in the field of homogeneous catalysis.

Recently, alkyne complexes with terminal thiolate/ amide substitution have been shown to act as S,N-chelate ligands in dinuclear complexes. In this study, the detailed synthesis and reactivity of W(II) alkyne complexes bearing different amino groups in the α-position are reported. The preparative scheme starts with cationic alkyne complexes [Tp′W(CO) 2 -η 2 -C,C′-C 2 Br(SR)]PF 6 {Tp′ = hydridotris(3,5-dimethylpyrazolyl)borate, R = benzyl (Bn), C 2 H 4 SiMe 3 }, which are obtained by applying free bromo alkynes. Subsequent nucleophilic substitution of the bromine substituent led to unsymmetrical substituted alkyne complexes [Tp′W(CO) 2 -η 2 -C,C′-C 2 (SR)(NHBn)]PF 6 with S,N substitution in the α position of the coordinated alkyne. Depending on the base used, deprotonation of the secondary amine resulted in either neutral iminoketenyl complexes [Tp′W(CO) 2 -η 2 -C,C′-C 2 (SR)(NBn)] or a zwitterionic PF 5 adduct. Reductive removal of the benzyl protective group was primarily observed at the imine substituent, causing a side-on/end-on rearrangement to the cyanide substituted carbene complex K[Tp′W(CO) 2 -η 1 -C(CN)(SBn)]. The reversibility of the rearrangement was proven with HBF 4 /Et 2 O, because double protonation led to [Tp′W(CO) 2 -η 2 -C,C′-C 2 (SR)(NH 2 )]BF 4 exhibiting an unprecedented primary amine substitution at the coordinated alkyne. The reaction sequence starting with the thiol SC 2 H 4 SiMe 3 derivative leading to the desired [Tp′W(CO) 2 -η 2 -C,C′-C 2 S(NHBn)] with a terminal S atom as well as the bonding situation in those complexes is discussed based on full spectroscopic characterization including X-ray structure analyses. Finally, a trinuclear complex assembled by homoleptic coordination of Pd(II) by two anionic S,N-chelates [Tp′W(CO) 2 -η 2 -C,C′-C 2 S(NBn)] − is presented.

No abstract