Synthesis of Nickel−Monocarbollide Complexes by Oxidative Insertion

Abstract

Treatment of the 11-vertex carborane anion [closo-2-CB(10)H(11)](-) with Ni(0) reagents in tetrahydrofuran (THF) affords-via oxidative insertion reactions-12-vertex Ni(II) complexes, isolated as the salts [N(PPh(3))(2)][2,2-L(2)-closo-2,1-NiCB(10)H(11)] (L = CO (1a), CNBu(t) (1b), and CNXyl (1c; Xyl = C(6)H(3)Me(2)-2,6); L(2) = cod (1d; cod = 1,2:5,6-eta-cyclo-octa-1,5-diene)). One CO ligand in 1a is readily replaced by donors L' in the presence of Me(3)NO to give the species [N(PPh(3))(2)][2-CO-2-L'-closo-2,1-NiCB(10)H(11)] (L' = PEt(3) (1e), PPh(3) (1f), CNBu(t) (1g), and CNXyl (1h)). The anionic complexes themselves readily react with hydride abstracting reagents in the presence of donor ligands to yield zwitterionic complexes in which boron vertexes bear substituents that are bound through C, N, or O atoms. Thus, for example, 1c with H(+) and CNXyl gives [2,2,7-(CNXyl)(3)-closo-2,1-NiCB(10)H(10)] (2b), while 1f with Me(+) in the presence of OEt(2) affords [2-CO-2,11-{mu-PPh(2)(C(6)H(4)-o)}-7-OEt(2)-closo-2,1-NiCB(10)H(9)] (4), in which an additional cycloboronation of one phosphine phenyl ring has occurred. In contrast, 1f with Me(+) in the presence of NCMe gives a mixture of the isomers [2-CO-2-PPh(3)-7-{(X)-N(Me)=C(H)Me}-closo-2,1-NiCB(10)H(10)] (X identical with E (5c) and Z (5d)). X-ray diffraction analyses of compounds 1a, 2b, 4, and 5c confirmed their important structural features.

Synthesis and Reactivity of 10-Vertex arachno-Platinacarboranes

“…Attempts to synthesize 4 from 3 by direct reaction with CNBu t were unsuccessful, and given the low yield of 4 , it is unwise to speculate upon its precise mechanism of formation. We note, however, that similar B−CNBu t substitution has been reported in the synthesis of bis(isocyanide) derivatives of {NiCB 10 } clusters using {Ni 0 (CNBu t ) 2 } synthons …”

“…We note, however, that similar B-CNBu t substitution has been reported in the synthesis of bis(isocyanide) derivatives of {NiCB 10 } clusters using {Ni 0 (CNBu t ) 2 } synthons. 20 The 11 B{ 1 H} NMR spectrum for 4 shows a separate resonance for each of the eight boron atoms. Unresolved coupling to the platinum nucleus allows the peak at δ 13.2 to be assigned to B(4), and the resonance at δ -24.0 can be assigned to the isocyanide-substituted boron atom, B( 8), as no coupling to a hydrogen nucleus is apparent for this peak in the proton-coupled Phosphine-substituted 10-vertex arachno-platinacarborane species similar to 1-3 have been identified previously, 16,17 .…”

B–N bond formation at stanna-closo-dodecaborate

“…40,44,58,59 The B-N bond lengths are common in a variety of nitrogen substituted borane clusters and the C-N bond lengths are in consistency with the double bond character in 2 and 6 and the single bonds in the hydrogenation product 4. 30,32,[36][37][38][39] The B-B distances in the clusters do not significantly change due to introduction of…”

“…Transition metal complexes of the monocarbollide and dicarbollide ligands react with a mixture of acetonitrile and CF 3 SO 3 Me to give the hydroboration product with the N(Me)vC(H)Me group connected via the nitrogen atom at the boron cluster. [36][37][38][39] We are investigating the chemistry of group 14 heteroboranes and especially of the mono-and di-hetero-closo-dodecaborates of germanium and tin. [40][41][42][43][44][45][46][47][48][49][50][51][52] In the last few years we have published our results on the coordination properties of the germanium and tin ligands [GeB 11 H 11…”

Boron

“…81 The anion nido-[CB 10 H 11 ] À has been reacted with a range of Ni 0 precursors to form the closo complex anions [{L 2 Ni}-1-NiCB 10 H 11 ] (L ¼ CO, PEt 3 , PPh 3 , CNBu t , and CN-C 6 H 3 Me 2 ; L 2 ¼ cod). 82 The reactive chemistry of the charge compensated triruthenium monodicarbollide cluster {(Z 5 -1-Me 2 S-CB 10 H 8 )Ru(CO) 2 }Ru 2 (CO) 6 towards the phosphine ligands PMe 3 , PCy, 1,1 0 (Ph 2 P) 2 -fc, and 1,2-(Ph 2 P) 2 -1,2-C 2 B 10 H 10 has been published. The reactivity of the triruthenium cluster towards t Bu-SS-t Bu and t Bu-CQCH has also been discussed.…”