Ligand Dependence of the Indenyl Ring Slippage in [(η5-Ind)MoL2(CO)2]0,+ Complexes: Experimental and Theoretical Studies

The reaction of a series of cationic and neutral complexes [(η5-Ind)Mo(CO)2L2]0,+ (1, L = NCMe; 2, L = CNMe; 3, L = OPPh3; 4, L = OP(OMe)3; 5, L = PMe3; 6, L2 = (PhSCH2)2; 7, L2 = (O2CCF3)-; 8, L2 = (O2CCH3)-; 9, L2 = (O2CPh)-; 10, L2 = [(NPh)2CH]-; 11, L2 = [(N-p-tolyl)2CH]-; 12, L2 = (S2CNEt2)-; 13, L2 = (S2P(OEt)2)-; 14, L2 = acac-; 15, L2 = MeC(O)CHC(NPh)CMe) with acetonitrile produces the ring-slipped adducts [(η3-Ind)MoL2(NCMe)(CO)2]0,+ only in the cases where L = NCMe, OPPh3, OP(OMe)3 or L2 = (O2CCF3)-, acac-. The adducts are labile and have been characterized by means of the distinctive chemical shift of the central pseudo-allylic proton of the η3-indenyl ligand. In the other cases no ring slippage is observed. In NCMe solvent 6 undergoes substitution to give 1, but the macrocycle trithiacyclononane (ttcn) reacts with 1 to give [(η3-Ind)Mo(CO)2(κ3-ttcn)]+ as the BF4- salt. PMe3 reacts with 1 to give substitution products in a stepwise fashion. [(η5-Ind)Mo(NCMe)(PMe3)(CO)2]BF4 is formed instantaneo...