Synthesis and characterization of new mixed allyl–alkoxo-complexes of uranium(IV). The crystal and molecular structure of di-µ-isopropoxo-bis[di(η-allyl)isopropoxouranium(IV)]

Abstract

New complexes of general formula [U(q-C,H,),(OR),][R = Et (1). Pri (2), or But (3)] have been prepared by reaction of [U(-q-C,H,),] with ROH. The crystal structure of (2) has been determined from single-crystal X-ray diffraction data (Mo-K, radiation). The complex crystallizes in the space group P2Jc with unit-cell dimensions a = 12.324(7), b = 8.535(1), c = 17.897(9) A, = 126.71 (3)". Z = 4, and R 0.030 for 1 408 independent observations. In the dimeric molecular structure, with 7 crystallographic site symmetry, two uranium atoms are joined by two alkoxide bridges. The co-ordination polyhedron of the uranium can be regarded as a distorted pentagonal bipyramid, whose equatorial plane is defined by the terminal carbons of the 3-ally1 ligands and by a bridging oxygen. The axial positions of the bipyramid are occupied by the remaining bridging oxygen and by a terminal oxygen. The latter shows a linear co-ordination [U-0-C 178.0( 1 O)"]. Other relevant bond distances are : U-O(bridging) 2.271 (10) and 2.41 3(10) ; U-O(termina1) 2.056(13) ; and U-C(mean) 2.679( 14) A. Infrared data for (1)-( 3) suggest that the uranium-ally1 x bond is predominantly ionic; this is consistent with some structural peculiarities of the allyl ligands in (2). Hydrogen-1 n.m.r. results indicate monomeric structures in tetrahydrofuran [(1)-( 3)] and dimeric ones in toluene solution for (1) and ( 2).THE synthesis of tetra-allyluranium [U(-q-C,H,)J, and its performance as a catalyst for the homogeneous polymerization of diolefins, have been previously re-p0rted.l Uranium alkoxides, however, more readily available and more stable than the tetra-allyluranium derivatives, in combination with AlR, and a Lewis acid give very active and highly stereospecific catalysts., In this case, we believe that a q-ally1 intermediate is formed ' in s i t N ' when the catalyst is prepared in the presence of This feature seems to be peculiar to uranium organo-10-15y0. metallic c o m p o ~n d s . ~

Uranium-Mediated Ring Opening of Tetrahydrofuran. Crystal Structure of UI2(OCH2CH2CH2CH2I)2(Ph3PO)2

“…The IR spectrum of 1 is similar to compounds of the general formula UX 4 (Ph 3 PO) 2 (X = I, 2 ; Br, 3 ; Cl, 4 ), except for the added appearance of a very strong band at 1063 cm -1 , which is assigned to the ν C - O stretch . Strong IR active bands in the 1100 cm -1 region have been assigned to the C−O stretching mode observed in uranium−alkoxide complexes …”

Sterically Demanding Aryloxides as Supporting Ligands in Organoactinide Chemistry. Synthesis, Structural Characterization, and Reactivity of Th(O-2,6-t-Bu2C6H3)2(CH2SiMe3)2 and Formation of the Trimeric Thorium Hydride Th3H6(O-2,6-t-Bu2C6H3)6

“…Th−O bond distances in 2 are statistically indistinguishable (2.147(10) and 2.127(11) Å) and are comparable to those found in Th(O-2,6- t -Bu 2 C 6 H 3 ) 2 (CH 2 -py-6-Me) 2 (2.190(9) Å) 16b and Th(O-2,6- t -Bu 2 C 6 H 3 ) 4 (2.189(6) Å) . Th−C distances of 2.438(16) and 2.485(18) Å are similar to those found in other crystallographically characterized thorium alkyl complexes and can be compared to the average Th−C distances of 2.55(1), 2.47(1), 2.54(1), 2.49(2), and 2.58(1) Å found in Th(O-2,6- t -Bu 2 C 6 H 3 ) 2 (CH 2 -py-6-Me) 2 ,16b (η-C 5 Me 5 ) 2 Th(CH 2 SiMe 2 CH 2 ), (η-C 8 H 8 )(η-C 5 Me 5 )Th[CH(SiMe 3 ) 2 ], (η-C 5 Me 5 ) 2 Th(CH 2 SiMe 3 ) 2 27a and (η-C 5 Me 5 )Th(CH 2 C 6 H 5 ) 3 ,27b respectively. Th−O−C angles are almost linear (162.1(10) and 176.9(8)°) and are typical of those seen in other transition-metal complexes bearing bulky aryloxide ligands .…”

“…Having noted the extensive series of investigations by Rothwell and co-workers in which aryloxide-supported alkyl complexes of groups 4 and 5 have been found to mediate a number of catalytic and stoichiometric reactions, we wished to investigate whether thorium complexes of the type Th(OAr) 2 R 2 (Ar = 2,6- t -Bu 2 C 6 H 3 ) would exhibit similar reactivity. There have been a limited number of reports in the literature of alkoxide and aryloxide moieties being utilized as supporting ligands for actinide σ-alkyl complexes, but reactivity studies of these species have not been undertaken. This paper describes the synthesis and structural characterization of the bis(alkyl) complex Th(OAr) 2 (CH 2 SiMe 3 ) 2 (Ar = 2,6- t -Bu 2 C 6 H 3 ) and compares its reactivity with that of both cyclopentadienyl-supported actinide alkyls as well as alkyl−aryloxide derivatives of the group 4 transition metals.…”

Dinuclear uranium alkoxides. Preparation and structures of KU2(OCMe3)9, U2(OCMe3)9, and U2(OCHMe2)10, containing [uranium(IV), uranium(IV)], [uranium(IV), uranium(V)], and [uranium(V), uranium(V)], respectively

“…(2) O(9) 0.360 (2) K(1) 0.0549 (9) C (12) 0.028 (3) C (11) 0.078 (4) C a In this and the following tables, starred atoms were refined isotropically. There are no intermolecular bonding interactions, and it is thus not surprising that this compound, even though formally ionic, dissolves readily in nonpolar solvents such as hexane.…”