Synthesis and crystal structure of the volatile monocyclopentadienyl uranium complex (η-C₅H₅)U(BH₄)₃

Uranocene. The First Member of a New Class of Organometallic Derivatives of the f Elements

“…Their first publication on organouranium chemistry in 1985, on the synthesis and crystal structure of the volatile C 5 H 5 U(BH 4 ) 3 , 94 reported a uranium borohydride, a compound type which was to be crucial in their subsequent successful development of mono-C 8 H 8 -uranium chemistry. Further studies on cyclopentadienyl and substituted-cyclopentadienyl uranium compounds followed.…”

f‐Element Half‐Sandwich Complexes: A Tetrasilylcyclobutadienyl–Uranium(IV)–Tris(tetrahydroborate) Anion Pianostool Complex

“…TheU ÀCdistances in 3 span the range 2.477(11) to 2.549 (12) ,w hich is 0.12-0.18 shorter than the U À Cdistances in I [6a] reflecting their terminal and bridging natures, [16] respectively,and the U À C cent distance is 2.290 (15) .I ti si nstructive to compare the average U À C distances in 3 (2.513 )t ot hose of [U(h 5 -C 5 H 5 )(BH 4 ) 3 ] (2.656 ) [17] and [U(h 6 -C 6 Me 6 )(BH 4 ) 3 ](2.927 ) [18] since each complex features a{ U(BH 4 ) 3 }u nit in ap ianostool half-sandwich structural motif;t he trend of increasing U À C distances nicely illustrates the effect on moving from formally dianionic (C 4 R 4 ) 2À to monoanionic (C 5 R 5 ) 1À to neutral (C 6 R 6 ) 0 ligands,adjusting for the increasing ring sizes and the fact that the uranium component of 3 is ac harge-rich anion and the hexamethylbenzene complex incorporates uranium(III) rather than uranium(IV). Thec yclobutadienyl ring C À C distances span the range 1.452(16) to 1.488 (17) ,w hich is typical of metal coordinated cyclobutadienyl ligands. [8] The four SiMe 3 groups are displaced out of the C 4 plane of the cyclobutadienyl core,and all bend away from the uranium ion with displacements ranging from 0.452 to 0.566 ;t his is comparable to the magnitude of out of plane displacements for methyl groups in sterically crowded tris(cyclopentadienyl) complexes, [19] but the anion component of 3 is not obviously sterically overloaded, and we address ap ossible electronic reason for this below.T he UÀHd istances span the range 2.34(10) to 2.51(10) ,but, as is inherent to X-ray diffraction, those bond metrics are not determined with great precision invalidating any detailed discussion, and so perhaps am ore meaningful metric is the U [17] and [U-(h 6 -C 6 Me 6 )(BH 4 ) 3 ](range:2.49(4) to 2.69(3) ).…”

f‐Element Half‐Sandwich Complexes: A Tetrasilylcyclobutadienyl–Uranium(IV)–Tris(tetrahydroborate) Anion Pianostool Complex

“…Thes alient features of the uranium anion component of 3 are the coordination of one h 4 -cyclobutadienyl and three k 3 -tetrahydroborate ligands to uranium in ap ianostool half-sandwich structure (the hydrides were located in the Fourier Difference Map but refined with restraints). TheU ÀCdistances in 3 span the range 2.477(11) to 2.549 (12) ,w hich is 0.12-0.18 shorter than the U À Cdistances in I [6a] reflecting their terminal and bridging natures, [16] respectively,and the U À C cent distance is 2.290 (15) .I ti si nstructive to compare the average U À C distances in 3 (2.513 )t ot hose of [U(h 5 -C 5 H 5 )(BH 4 ) 3 ] (2.656 ) [17] and [U(h 6 -C 6 Me 6 )(BH 4 ) 3 ](2.927 ) [18] since each complex features a{ U(BH 4 ) 3 }u nit in ap ianostool half-sandwich structural motif;t he trend of increasing U À C distances nicely illustrates the effect on moving from formally dianionic (C 4 R 4 ) 2À to monoanionic (C 5 R 5 ) 1À to neutral (C 6 R 6 ) 0 ligands,adjusting for the increasing ring sizes and the fact that the uranium component of 3 is ac harge-rich anion and the hexamethylbenzene complex incorporates uranium(III) rather than uranium(IV). Thec yclobutadienyl ring C À C distances span the range 1.452(16) to 1.488 (17) ,w hich is typical of metal coordinated cyclobutadienyl ligands.…”

“…Thec yclobutadienyl ring C À C distances span the range 1.452(16) to 1.488 (17) ,w hich is typical of metal coordinated cyclobutadienyl ligands. [8] The four SiMe 3 groups are displaced out of the C 4 plane of the cyclobutadienyl core,and all bend away from the uranium ion with displacements ranging from 0.452 to 0.566 ;t his is comparable to the magnitude of out of plane displacements for methyl groups in sterically crowded tris(cyclopentadienyl) complexes, [19] but the anion component of 3 is not obviously sterically overloaded, and we address ap ossible electronic reason for this below.T he UÀHd istances span the range 2.34(10) to 2.51(10) ,but, as is inherent to X-ray diffraction, those bond metrics are not determined with great precision invalidating any detailed discussion, and so perhaps am ore meaningful metric is the U···B distances (range:2 .537(19) to 2.594 (17) ), which compare well to the U···B distances in [U(h 5 -C 5 H 5 )(BH 4 ) 3 ]( range:2 .46(4) to 2.57(5) ) [17] and [U-(h 6 -C 6 Me 6 )(BH 4 ) 3 ](range:2.49(4) to 2.69(3) ). [18] Lastly,the [Li(THF) 4 ] + cation is unremarkable so is not discussed any further.…”

“…TheU ÀCdistances in 3 span the range 2.477(11) to 2.549 (12) ,w hich is 0.12-0.18 shorter than the U À Cdistances in I [6a] reflecting their terminal and bridging natures, [16] respectively,and the U À C cent distance is 2.290 (15) .I ti si nstructive to compare the average U À C distances in 3 (2.513 )t ot hose of [U(h 5 -C 5 H 5 )(BH 4 ) 3 ] (2.656 ) [17] and [U(h 6 -C 6 Me 6 )(BH 4 ) 3 ](2.927 ) [18] since each complex features a{ U(BH 4 ) 3 }u nit in ap ianostool half-sandwich structural motif;t he trend of increasing U À C distances nicely illustrates the effect on moving from formally dianionic (C 4 R 4 ) 2À to monoanionic (C 5 R 5 ) 1À to neutral (C 6 R 6 ) 0 ligands,adjusting for the increasing ring sizes and the fact that the uranium component of 3 is ac harge-rich anion and the hexamethylbenzene complex incorporates uranium(III) rather than uranium(IV). Thec yclobutadienyl ring C À C distances span the range 1.452(16) to 1.488 (17) ,w hich is typical of metal coordinated cyclobutadienyl ligands. [8] The four SiMe 3 groups are displaced out of the C 4 plane of the cyclobutadienyl core,and all bend away from the uranium ion with displacements ranging from 0.452 to 0.566 ;t his is comparable to the magnitude of out of plane displacements for methyl groups in sterically crowded tris(cyclopentadienyl) complexes, [19] but the anion component of 3 is not obviously sterically overloaded, and we address ap ossible electronic reason for this below.T he UÀHd istances span the range 2.34(10) to 2.51(10) ,but, as is inherent to X-ray diffraction, those bond metrics are not determined with great precision invalidating any detailed discussion, and so perhaps am ore meaningful metric is the U···B distances (range:2 .537(19) to 2.594 (17) ), which compare well to the U···B distances in [U(h 5 -C 5 H 5 )(BH 4 ) 3 ]( range:2 .46(4) to 2.57(5) ) [17] and [U-(h 6 -C 6 Me 6 )(BH 4 ) 3 ](range:2.49(4) to 2.69(3) ).…”