Novel Cr(iii) catalysts supported by linear phosph(iii)azanes of the type R(1)R(2)N-P(Ph)-NR(3)-P(Ph)-NR(4)R(5) have been prepared, all of which, upon activation with MMAO-3A, are highly active for ethene tri-/tetramerization with considerable selectivity. The effect of ligand substitution as well as solvent on the catalytic performance has been examined.

What is the most significant result of this study? Our paper reports on novel P-N-P-containing compounds which can be prepared by reducing N,N-bis{chloro(aryl)-phosphino}-amines. Due to the variation of the substituents at the phosphorus or nitrogen centers, the solvents and reducing agents, we were able to develop selective syntheses for several cyclic compounds. We consider the formation of new PN rings as the essence of this paper.

The cleavage of P-P σ bonds has long been a subject of interest and is investigated widely. P-P bonds can be cleaved homolytically to yield phosphinyl radicals, which can be persistent and stable for long periods or undergo further reactions. P-P bonds that exhibit polarization owing to different substitution can be opened heterolytically. Furthermore, it is possible to activate them through metal interactions. Both processes can [a] 3009 Scheme 2. Different ways to prepare 2 and the competitive reaction to form 3 (pip = piperidine).Scheme 3. The selective insertion of acetonitrile (left) or benzonitrile (right) into one (P-P) bond of the ligand leads to 4 or 5, respectively.