HYDROTRIS(PYRAZOLYL)BORATE CHEMISTRY OF URANIUM(III) AND URANIUM(IV) - SYNTHESIS OF DELTA-HYDROCARBYL DERIVATIVES OF URANIUM(IV) AND REACTIVITY OF UCL2R[HB(3,5-ME2PZ)3] (R = CH2SIME3, CH(SIME3)2) AND UCL2[HB(3,5-ME2PZ)3] TOWARD KETONES AND ALDEHYDES

The tetravalent uranium hydrocarbyl compounds UCl2[CH(SiMe3)2]L (L* = HB(3,5-Me2-pz)3) and UCl3-x(CH2SiMe3)(x)L (x = 1-3) have been prepar ed by salt metathesis from UCl3L (THF) and the appropriate lithium al kyls. The reactivity of the carbyls UCl2[CH(SiMe3)2]L (1) and UCl2(CH 2SiMe3)L (2) toward ketones has been studied. Compound 2 reacts with acetone and 3-pentanone in stoichiometric amount to yield the correspo nding tertiary alkoxide compounds UCl2[OC(R)2CH2SiMe3]L (R = Me, Et), as a result of insertion of the ketones into the U-C bond. Addition o f excess acetone to 2 affords the uranium aldolate UCl2[OC(Me)2-CH2C(O )Me]L, while excess 3-pentanone yields only the insertion compound. F or compound 1 the corresponding insertion products are not formed, but addition of excess acetone yields the uranium aldolate. This compound is also obtained by reacting the U(III) compound (UCl2L)x with exces s acetone. Compound 2 reacts with aldehydes RCHO (R = Me, Ph) in a sto ichiometric ratio, yielding the secondary alkoxides UCl2[OC(H)(R)CH2Si Me3]L (R = Me, Ph), due to insertion of the aldehydes into the U-C bo nd. Similar reactions in 1:2 stoichiometric ratio yield the compounds UCl2[OC(H)(R)NNC5H7]L(R = Me, Ph). The same compounds can be obtained by reacting carbyl 1 or (UCl2L)x with aldehydes. The analogous compo und UCl2[OC(Me)2NNC5H7] L was obtained during slow recrystallization of the uranium aldolate. The molecular structures of the following com pounds were determined by single-crystal X-ray diffraction: UCl2[OC(Me )2CH2SiMe3]L, orthorhombic, space group P2(1)2(1)2(1), a = 10.672(1) angstrom, b = 16.158(1) angstrom, c = 17.531(1) angstrom, V = 3023(1) angstrom3, Z = 4; UCl2[OC(H)(Me)NNC5H7]L, monoclinic, space group P2( 1)/n, a = 9.662(2) angstrom, b = 16.093(2) angstrom, c = 18.527(3) ang strom, beta = 93.28(1)degrees, V = 2876(1) angstrom3, Z = 4; UCl2[OC(H )(Ph)NNC5H 7]L, monoclinic, space group P2(1)/n, a = 11.588(3) angstr om, b 19.376(4) angstrom, c = 14.707(4) angstrom, beta = 101.90(2)degr ees, V = 3231(3) angstrom3, Z = 4; UCl2[OC(Me)2NNC5H7]L, orthorhombic , space group Pbca, a = 17.766(1) angstrom, b = 18.059(1) angstrom, c = 18.196(2) angstrom, V = 5838(1) angstrom3, Z = 8.