Synthesis and reactions of alkyne complexes [MoCl(GeCl3)-(CO)(NCMe)(PPh3)(η2-RC2R)](R = Me or Ph) containing six different monodentate ligands

Abstract

The complex [MoCl(GeCl₃)(CO)₂(NCMe)₂(PPh₃)] reacts with RC₂R (R = Me or Ph) in CH₂Cl₂ to give alkyne complexes [MoCl(GeCl₃)(CO)(NCMe)(PPh₃)(η²-RC₂R)](R = Me 1 or Ph 2) containing six different monodentate ligands. Reaction of 1 with an equimolar quantity of L [L = PPh₃, PPh₂(C₆H₁₁), PMe₂Ph, imidazole or 2-methylimidazole] afforded complexes [MoCl(GeCl₃)(CO)L(PPh₃)(η²-MeC₂Me)] in high yield. Equimolar quantities of 1 and L–L {L–L = Ph₂P(CH₂)_nPPh₂(n= 1–6), [Fe(η⁵-C₅H₄PPh₂)₂], (C₆H₁₁)NCHCHN(C₆H₁₁), 2,2′-bipyridine, 1,10-phenanthroline, 4,7-dimethyl-1,10-phenanthroline, 5,6-dimethyl-1,10-phenanthroline, S₂CP(C₆H₁₁)₃ or Ph₂P(CH₂)₂PPh(CH₂)₂PPh₂} gave [MoCl(GeCl₃)(CO)(PPh₃){σ-Ph₂P(CH₂)PPh₂}(η²-MeC₂Me)] and the cationic complexes [Mo(GeCl₃)(CO)(PPh₃)(L–L)(η²-MeC₂Me)]Cl in good yield. The cationic nature of several of these complexes was confirmed by exchange with Na[BPh₄] to afford complexes with tetraphenylborate as the counter anion. The fluxionality of some of the complexes was detertmined by variable-temperature ¹H NMR spectroscopy. Solution and solid-state ¹³C NMR spectroscopy was used to confirm that the alkyne ligand in several of these complexes is donating four electrons to the molybdenum.