THIOLATE AND THIOETHER FUNCTIONS AS DONOR GROUP-X, GROUP-Y IN TRIPOD LIGANDS RCH2C(CH2PPH2)(CH2X)(CH2Y) - SYNTHESIS AND COORDINATION CHEMISTRY

Tripod ligands RCH2C(CH2PPh2) (CH2X)(CH2Y) (1) with X, Y = SAlkyl, SBz l selectively undergo reductive cleavage of the SBzl function with Li/ NH3/THF at -40 degrees C to produce RCH2C(CH2PPh2)(CH2X)(CH2Y) (2) (X, Y = SAlkyl, SH). In these mixed donor set ligands the SH functions ar e the least coordinative ones such that [eta(2)-{CH3C(CH2PPh2)(CH2SEt) (CH2SH)}(CO)(4)Mo] (5) is a stable compound with an uncoordinated SH f unction at the dangling arm of the ligand. If the SH functions of a po tential tripod ligand are deprotonated the resulting thiolate function s are found to strongly coordinate in compounds such as [eta(3) {CH3C( CH2PPh2)(2)(CH(2)s)}(CO)(3)Mo](-) which are obtained as their lithium and sodium salts 6. These highly reactive species may be stabilized by encapsulating their alkali counter ions in cryptands and the correspo nding salts with [2,1,1]cryptand (7a) and [2,2,2]cryptand (7b) are far easier to handle than the cryptand-free progeners 6. Alkylation of th e coordinatively bound thiolate function in 6 leads to the correspondi ng thioether derivatives [eta(3)-{CH3C(CH2PPh2)(2)(CH2SR)}(CO)(3)Mo] ( 8).