Allyl(carbaborane) complexes of Group 6 metals: preparation and reactivity

Abstract

Treatment of thf (tetrahydrofuran) solutions of [MBr(CO),(NCMe),(q3-C3H5)] (M = Mo or W) with Na,[7,8-C,BgH,R',] (R' = H or Me), followed by addition of [N(PPh,),]CI or [NEtJCI, afforded the salts [Y][M(CO),(q3-C3H5)(q5-7,8-C,BgH,R',)] [Y = N(PPh,),, R' = Me, M = M o l a or W 1b; Y = NEt,, R' = H, M = Mo 1 c] in high yield. These species may be synthesised, but in lower yield, from allyl bromide and TI,[M(C0)3(q5-7,8-C,BsHsR'2)] generated in situ. Protonation of the salts 1 a and 1 b with HBF,*Et,O in the presence of CO or PPh, yielded the compounds [ M (CO),L,(q5-7.8-C,BgHgMe2)] ( M = Mo 2a or W

Balancing Steric and Electronic Effects in Carbonyl–Phosphine Molybdacarboranes

“…We therefore targeted complexes [3,3,3‐(CO) 3 ‐3‐PPh 3 ‐3,1,2‐ closo ‐MoC 2 B 9 H 11 ] and [3,3‐(CO) 2 ‐3,3‐(PPh 3 ) 2 ‐3,1,2‐ closo ‐MoC 2 B 9 H 11 ] (the latter as either or both the cis ‐ and trans ‐isomers) for synthesis and structural study. Although these specific compounds were previously unknown, the related cage‐C‐methylated analogues [1,2‐Me 2 ‐3,3,3‐(CO) 3 ‐3‐PPh 3 ‐3,1,2‐ closo ‐MoC 2 B 9 H 9 ] ( I ) and [1,2‐Me 2 ‐3,3‐(CO) 2 ‐3,3‐(PPh 3 ) 2 ‐3,1,2‐ closo ‐MoC 2 B 9 H 9 ] ( II ) were reported by Stone et al in 1993 . Interestingly, both I and II are afforded by the protonation of [PNP][1,2‐Me 2 ‐3,3‐(CO) 2 ‐3‐(η‐C 3 H 5 )‐3,1,2‐ closo ‐MoC 2 B 9 H 9 ] {PNP = [N(PPh 3 ) 2 ] + } in the presence of excess PPh 3 .…”

Transition Metal Metallacarbaboranes

“…230 (M = Cr, Mo, W) have also been prepared, 128 as have several novel copper species having Cu-Cu bonds, including a "pinwheel" cluster incorporating a Cu 3 triangle ( Figure 21). 188 ' 190 ' 1 " Straightforward syntheses of other classes of monometallic (ligand) x M(R 1 R 2 C 2 B 9 H 9 ) organometallacarbaboranes in which the ligand is arene, 1 0 ' 1 1 "' 1 *' 1 5 0 ' 1 5 1 ' 1 5 7 allyl, 198 and diphosphacyclobutadiene 220 have been described. Hawthorne and co-workers have prepared metallacarbaborane-pyrazolylborate 185 and -porphyrin 192 complexes, thereby linking carbaborane chemistry to these two large fields.…”

Metal complexes of monocarbon carboranes bearing C-amine or -amino substituents

“…One alkyne then rearranges to a vinylidene group which inserts into a B-H bond following which the second alkyne also transforms to a rhenium bound vinylidene group which inserts into the nearby C-H bond at the boron-bound terminus of the B-C(H)‚C(H)Bu t group to yield 43. Vinylidene-metal species have been implicated in the chemistry of molybdena-and ruthena-dicarbollide systems where alkynes RC"CH insert into cage B-H bonds [29,[40][41][42]. …”

“…Our unsuccessful attempt to prepare an allylmolybdenum monocarbollide complex [NEt 4 ] 2 [1-NHBu t -2-(g 3 -C 3 H 5 )-2,2-(CO) 2 -closo-2,1-MoCB 10 H 10 ], analogous to the dicarbollide species [NEt 4 ][3-(g 3 -C 3 H 5 )-3,3-(CO) 2 -closo-3,1,2-MoC 2 B 9 H 11 ] [29], was mentioned above. The sequence of reactions designed to give the desired allyl complex yielded instead compound 15a, because the allyl bromide oxidized the intermediate trianion [1-NHBu t -2,2,2-(CO) 3 -closo-2,1-MoCB 10 H 10 ] 3À instead of forming the target species.…”

“…Some years ago we prepared a useful allylmolybdenum dicarbollide reagent [NEt 4 ][3-(g 3 -C 3 H 5 )-3,3-(CO) 2 -closo-3,1,2-MoC 2 B 9 H 11 ] by treating Tl 2 [3,3,3-(CO) 3 -closo-3,1,2-MoC 2 B 9 H 11 ] with CH 2 ‚CHCH 2 Br, followed by addition of [NEt 4 ]Cl [29]. We anticipated that we might prepare an analogous dianionic monocarbollide species [1-NHBu t -2-(g 3 -C 3 H 5 )-2,2-(CO) 2 -closo-2,1-MoCB 10 H 10 ] 2À by deprotonating 7-NH 2 Bu t -nido-7-CB 10 H 12 [30] with 3 equivalents of LiBu n to generate [7-NHBu t -nido-7-CB 10 It was subsequently found that 15a could be more straightforwardly prepared and in better yield by the interaction of the lithium salt of the monoanionic species [7-NHBu t -nido-7-CB 10 H 12 ] À [24] with [Mo(CO) 6 ] in refluxing NCMe, followed by addition of [N(PPh 3 ) 2 ]Cl [31].…”