SYNTHESIS AND EVALUATION OF THE BONDING PROPERTIES OF A POTENTIALLY TRIDENTATE LIGAND - -(DIPHENYLOPHOSPHINO)-2-ETHOXY-1-(2-PYRIDYL)ETHANE

The trifunctional ligand 1 (diphenylphosphino)-2-ethoxy-1-(2-pyridyl)e thane (pepye) has been prepared and its bonding properties toward Mo0, Rh(I) and Ru(II) metallic centres evaluated. The complex fac-[Mo(CO)3 (pepye)] in which the ligand is P,N,O bonded in solution evolves to ci s-[Mo(CO)4-(pepye)] where it is P,N bonded. In the complex [Rh(cod)(pe pye)]ClO4 (cod = cycloocta-1,5-diene) the ligand is P,N bonded. The cy cloocta-1,5-diene can be displaced by carbon monoxide, and [Rh(CO)2(pe pye)]ClO4 and [{Rh(CO)(pepye)}2] [ClO4]2 have been isolated. In the fo rmer the ligand is P,N bonded and in the latter the two rhodium atoms are bridged by the phosphine and ether functions of each ligand. The c omplex all-cis-[RuCl2(pepye)2] has been isolated in two diastereoisome ric forms in a 6:4 ratio. In polar solvents it evolves to [RuCl(pepye) 2]+ in which one of the ligands is P,N,O bonded and the two diastereoi somers have been isolated as their tetraphenylborate salts. The bonded ether arm of the ligand can be displaced by carbon monoxide leading t o [RuCl(CO)(pepye)2]BPh4. This reaction can be reversed in boiling ace tone, more or less easily, depending upon the diastereoisomers.