Solution-State Interactions of Bis(pentamethylcyclopentadienyl)ytterbium, Cp*2Yb, with Trialkylphosphines and R3PX Complexes (X = O, NR', CHR'')
作者:David J. Schwartz、Richard A. Andersen
DOI:10.1021/om00009a039
日期:1995.9
The interactions formed between Cp*Yb-2 (1) and phosphines and R(3)PX derivatives (X = O, NR', CHR'') in solution have been investigated using multinuclear (H-1, C-13, P-31, Yb-171) and variable-temperature NMR spectroscopy. Intermolecular exchange can be slowed at low temperature for 1:1 and 1:2 phosphine adducts, with a (1)J(YbP) value of ca. 950 Hz for Cp*Yb-2(PEt(3)) (3) and Cp*Yb-2(PMe(3)) (4) and ca. 600 Hz for Cp*Yb-2(PMe(3))(2) (2), Cp*Yb-2(dmpm) (dmpm = Me(2)PCH(2)PMe(2)) (5), and Cp*Yb-2(1,2-(PMe(2))(2)C6H4) (6) Adducts of 1 with Me(3)PO and Et(3)PNH undergo slow intermolecular exchange in solution at 25 degrees C (NMR time scale); both 1:1 adducts (Cp*Yb-2(OPMe(3)), 7; Cp*Yb-2(HNPEt(3)), 9) and 1:2 adducts (Cp*Yb-2(OPMe(3))(2), 8; Cp*Yb-2(HNPEt(3))(2), 10) have been isolated. The spectroscopic properties of two ylide adducts, Cp*Yb-2(Me(2)PhPCHSiMe(3)) (12) and Cp*Yb-2(Me(2)LPhPCH(2)) (13), have also been investigated. Intermolecular exchange can be slowed at low temperature in both cases; in the former complex a second process, resulting in inequivalent Cp* rings and inequivalent P-bound methyl groups, can also be slowed at lower temperatures. The nature of this process is discussed in detail. The solid-state structure of 12 has been determined. The NMR values for all of the complexes are discussed in detail. In addition, the Yb-171 chemical shifts for 6, 7, and 12 have been measured, via H-1/Yb-171 indirect detection utilizing long-range J(YbH) coupling, and are discussed.