The use of 1,2-dipiperidinoacetylene for the preparation of monometallic diaminoacetylene and homo- or heterobimetallic diaminodicarbene ruthenium(ii) complexes

摘要

The reaction of the ynediamine 1,2-dipiperidinoacetylene (1) with [(η~2-COE)Cr(CO)_5], [(THF)W(CO)_5] and [RuCl_2(η~6-cymene)]_2 afforded homobimetallic complexes 2a, 2b and 3, in which the diaminoacetylene 1 acts as a bis(aminocarbene) ligand by bridging two complex fragments Cr(CO)_5 (in 2a), W(CO)_5 (in 2b) and RuCl_2(η~6- cymene) (in 3). The reaction of 1 with [RuCl_2(PPh_3) _3] gave trans-[(1)RuCl(PPh_3)_2]Cl, [4]Cl, in which the alkyne 1 coordinates as a 4-electron donor ligand. The cation 4 represents a rare example of a square-planar Ru(ii) complex with a low-spin ground state (S = 0), and its stability can be ascribed to the strong alkyne-metal π-interaction as confirmed by DFT calculations. Treatment with one or two equivalents of NaBPh_4 in acetonitrile gave [4]BPh _4 and the dicationic [(1)Ru(PPh_3)_2(CH _3CN)_2](BPh_4)_2, [5](BPh _4)_2. [4]Cl can be used for the preparation of heterobimetallic Ru-Pd bis(aminocarbene) complexes by reaction with [(MeCN) _2PdCl_2], resulting in the formation of bimetallic 6 and tetrametallic 7.