Alkyne coupling at a rhenium-monocarborane substrate: synthesis of Re,B-eta2:sigma-butadienyl complexes

Treatment of 7-NH(2)Bu(t)-nido-7-CB(10)H(12) in tetrahydrofuran (THF) with LiBu(n)(3 equiv) and then [ReBr(CO)(3)(THF)(2)] gives the rhenacarborane dianion [1-NHBu(t)-2,2,2-(CO)(3)-closo-2,1-ReCB(10)H(10)](2-), isolated as the bis-[N(PPh(3))(2)](+) salt (4). Iodine oxidation of this Re(I) intermediate gives the Re(III) complex [1,2-mu-NHBu(t)-2,2,2-(CO)(3)-closo-2,1-ReCB(10)H(10)] 6 in which the carborane functions formally as an 8-electron (6pi+ 2sigma) donor. Reaction of with ligands L in the presence of Me(3)NO gives substituted products [1,2-mu-NHBu(t)-2,2-(CO)(2)-2-L-closo-2,1-ReCB(10)H(10)][L = PPh(3)(7a), CNXyl (7b; Xyl = C(6)H(3)Me(2)-2,6), or Bu(t)C triple bond CH (7c)]. Formation of complex 7c is unexpectedly accompanied by [1,2-mu-NHBu(t)-2,2-(CO)(2)-3,2-sigma:eta(2)-{C(=CHBu(t))-CH=CHBu(t)}-closo-2,1-ReCB(10)H(9)] 8a, in which an alkyne-derived dienyl group is bound to both the rhenium centre and to an adjacent boron vertex. Complex 8a is also obtained from 7c with Bu(t)C triple bond CH and Me(3)NO. The same reaction of 7c, using PhC triple bond CH or CNXyl instead of Bu(t)C triple bond CH, gives, respectively, [1,2-micro-NHBu(t)-2,2-(CO)(2)-3,2-sigma:eta(2)-{C(=CHBu(t))-CH=CHPh}-closo-2,1-ReCB(10)H(9)] 8b and [1,2-micro-NHBu(t)-2-Bu(t)C triple bond CH-2-CO-2-CNXyl-closo-2,1-ReCB(10)H(10)] 9. Addition of donors L to results in displacement from rhenium of the pendant dienyl moiety, yielding [1,2-mu-NHBu(t)-2,2-(CO)(2)-2-L-3-{C(=CHBu(t))-CH=CHBu(t)}-closo-2,1-ReCB(10)H(9)][L = PMe(3)(10a), CNBu(t)(10b)]. Single-crystal X-ray diffraction analyses have confirmed the novel structural features of compounds 6, 7c, 8b and 9.     

Facile two-electron reduction of a closo-rhodathiadecaborane

Closo-to-arachno redox flexibility in metallaheteroboranes may be viewed as a metal-to-ligand cooperative action with application in catalysis. The treatment of [PSH][arachno-4-SB(8)H(11)] with [RhCl(PPh(3))(3)] affords, after chromatography, three new 10-vertex rhodathiaboranes, [2,2,2-(H)(PPh(3))(2)-closo-2,1-RhSB(8)H(8)] (3), [6,6,9-(PPh(3))(3)-arachno-6,5-RhSB(8)H(9)] (4) and [2,2,2-(Cl)(H)(PPh(3))-6-(PPh(3))-closo-2,1-RhSB(8)H(7)] (5). 3 reacts quantitatively with PPh(3) to form 4, which, in turn, reacts with chlorinated solvents to give the chloro-ligated cluster 5. Kinetic studies demonstrate that the reaction of 3 with PPh(3) obeys a second-order rate law, with an associative mechanism. The Lewis acidity of 3 is quite remarkable, and, given its closo-to-arachno structural and electronic response, this cluster is expected to exhibit a rich chemistry.     

Synthesis of nickel-monocarbollide complexes by oxidative insertion

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.     

Substitution, cage functionalization, and oxidation of the charge-compensated triruthenium monocarbollide cluster complex [1-SMe2-2,2-(CO)2-7,11-(mu-H)2-2,7,11-{Ru2(CO)6}-closo-2,1-RuCB10H8

The compound [1-SMe2-2,2-(CO)2-7,11-(mu-H)2-2,7,11-{Ru2(CO)6}-closo-2,1-RuCB10H8] 1a reacts with PMe3 or PCy3(Cy = cyclo-C6H11) to give the structurally different species [1-SMe2-2,2-(CO)2-7,11-(mu-H)2-2,7,11-{Ru2(CO)5(PMe3)}-closo-2,1-RuCB10H8] 4 and [1-SMe2-2,2-(CO)2-11-(mu-H)-2,7,11-{Ru2(mu-H)(CO)5(PCy3)}-closo-2,1-RuCB10H8]5, respectively. A symmetrically disubstituted product [1-SMe2-2,2-(CO)2-7,11-(mu-H)2-2,7,11-{Ru2(CO)4(PMe3)2}-closo-2,1-RuCB10H8] 6 is obtained using an excess of PMe3. In contrast, the chelating diphosphines 1,1'-(PPh2)2-Fe(eta-C5H4)2 and 1,2-(PPh2)2-closo-1,2-C2B10H10 react with 1a to yield oxidative-insertion species [1-SMe2-2,2-(CO)2-11-(mu-H)-2,7,11-{Ru2(mu-H)(micro-[1',1'-(PPh2)2-Fe(eta-C5H4)2])(CO)4}-closo-2,1-RuCB10H8] 7 and [1-SMe2-2,2-(CO)2-11-(mu-H)-2,7,11-{Ru2(mu-H)(CO)4(1',2'-(PPh2)2-closo-1',2'-C2B10H10)}-closo-2,1-RuCB10H8] 8, respectively. In toluene at reflux temperatures, 1a with Bu(t)SSBu(t) gives [1-SMe2-2,2-(CO)2-7-(mu-SBu(t))-11-(mu-H)-2,7,11-{Ru2(mu-H)(mu-SBu(t))(CO)4}-closo-2,1-RuCB10H8] 9, and with Bu(t)C [triple bond] CH gives [1-SMe2-2,2-(CO)2-7-{mu:eta2-(E)-CH=C(H)Bu(t)}-11-{mu:eta2-(E)-CH=C(H)Bu(t)}-2,7,11-{Ru2(CO)5}-closo-2,1-RuCB10H8] 10. In the latter, two alkyne groups have inserted into cage B-H groups, with one of the resulting B-vinyl moieties involved in a C-H...Ru agostic bond. Oxidation of 1a with I2 or HgCl2 affords the mononuclear ruthenium complex [1-SMe2-2,2,2-(CO)3-closo-2,1-RuCB10H10] 11.     

Synthesis of a bimetallic platinum-tungsten complex with a bridging micro-diboranyl-oxycarbyne moiety

The novel bimetallic micro-diboranyl-oxycarbyne bridged platinum-tungsten complex [W{eta(1),micro-CO-B(NMe(2))-B(NMe(2))-(eta(5)-C(5)H(4))}(CO)(2){Pt(PPh(3))(2)}] (W-Pt) () has been synthesised by a two-step reaction, starting from the dilithiated half-sandwich compound Li[W(eta(5)-C(5)H(4)Li)(CO)(3)] () via the ansa-diboranyl-oxycarbyne tungsten complex [W{eta(1)-CO-B(NMe(2))B(NMe(2))(eta(5)-C(5)H(4))}(OC)(2)] () by use of stoichiometric amounts of B(2)(NMe(2))(2)Br(2) and [Pt(eta(2)-C(2)H(4))(PPh(3))(2)], respectively.     

Photochemical synthesis and reactivity studies of dirhenacarboranes

Ultraviolet irradiation of [PPh(4)][closo-1-CB(8)H(9)] with [Re(2)(CO)(10)] in THF (tetrahydrofuran) at ambient temperature affords the dirhenacarborane anion [6,10-{Re(CO)(4)}-10-(micro-H)-6,6,6-(CO)(3)-closo-6,1-ReCB(8)H(8)]-, isolated as its [PPh(4)]+ salt (1). Further irradiation of 1 yields a second isomeric anion [6,10-{Re(CO)(4)}-6-(micro-H)-10,10,10-(CO)(3)-closo-10,1-ReCB(8)H(8)]- that was characterized as a [N(PPh(3))(2)]+ salt (2). Reaction of 1 with NOBF(4) produces the neutral dirhenacarborane compound [8,10-{Re(CO)(4)}-8,10-(micro-H)2-6,6-(CO)(2)-6-NO-closo-6,1-ReCB(8)H(7)] (3). Compounds 1-3 all consist of a central {closo-ReCB(8)} cluster with a second rhenium center which is exo-polyhedral. Attempts to substitute the carbonyl ligands of 3 with other donor ligands such as phosphines, isocyanides, or alkynes resulted in loss of the exo-polyhedral rhenium moiety and formation of a monorhenium anion, [6,6-(CO)(2)-6-NO-closo-6,1-ReCB(8)H(9)]-, isolated as its [N(PPh(3))(2)]+ salt (4). The heterometallic dimetallacarborane species, [6,7,10-{Cu(PPh(3))}-7,10-(micro-H)2-6,6-(CO)(2)-6-NO-closo-6,1-ReCB(8)H(7)] (5) and [6,7-{Au(PPh(3))}-7-(micro-H)-6,6-(CO)(2)-6-NO-closo-6,1-ReCB(8)H(8)] (6) were formed from reactions of 4 with {Cu(PPh(3))}+ and {Au(PPh(3))}+, respectively. Similarly, reaction of 4 with {Ir(CO)(PPh(3))(2)}+ afforded two products, [6,10-{Ir(micro-PPh(2))(Ph)(CO)(PPh(3))}-10-(micro-H)-6-CO-6-NO-closo-6,1-ReCB(8)H(8)] (7) and [6,9,10-{Ir(micro-PPh(2))(H)(PPh(3))}-9-(micro-H)-6-CO-6-NO-10-Ph-closo-6,1-ReCB(8)H(8)] (8). The solid-state structures of compounds 1-8 were all unequivocally established by single-crystal X-ray diffraction experiments.     

Formation of intramolecular rings in ferramonocarbollide complexes

Addition of PPh 2Cl and Tl[PF 6] to CH 2Cl 2 solutions of [N(PPh 3) 2][6,6,6-(CO) 3- closo-6,1-FeCB 8H 9] ( 1) affords the isomeric B-substituted species [6,6,6-(CO) 3- n-(PHPh 2)- closo-6,1-FeCB 8H 8] [ n = 7 ( 2a) or 10 ( 2b)]. Deprotonation (NaH) of the phosphine ligand in 2a, with subsequent addition of [IrCl(CO)(PPh 3) 2] and Tl[PF 6], yields the neutral, zwitterionic complex [6,6,6-(CO) 3-4,7-mu-{Ir(H)(CO)(PPh 3) 2PPh 2}- closo-6,1-FeCB 8H 7] ( 3), which contains a B-P-Ir- B ring. Alternatively, deprotonation using NEt 3, followed by addition of HC[triple bond]CCH 2Br, affords [6,6,6-(CO) 3-7-(PPh 2CCMe)- closo-6,1-FeCB 8H 8] ( 4). Addition of [Co 2(CO) 8] to CH 2Cl 2 solutions of the latter gives [6,6,6-(CO) 3-7-(PPh 2-{(mu-eta (2):eta (2)-CCMe)Co 2(CO) 6})- closo-6,1-FeCB 8H 8] ( 5), which contains a {C 2Co 2} tetrahedron. In the absence of added substrates, deprotonation of the PHPh 2 group in compounds 2, followed by reaction of the resulting anions with CH 2Cl 2 solvent, affords [6,6,6-(CO) 3- n-(PPh 2CH 2Cl)- closo-6,1-FeCB 8H 8] [ n = 7 ( 6a) or 10 ( 6b)] plus [6,6-(CO) 2-6,7-mu-{PPh 2CH 2PPh 2}- closo-6,1-FeCB 8H 8] ( 7, formed from 2a), of which the latter species possesses an intramolecular B-P-C-P- Fe ring. Addition of Me 3NO to CH 2Cl 2 solutions of 2a causes loss of an Fe-bound CO ligand and formation of [6,6-(CO) 2-6,7-mu-{NMe 2CH 2PPh 2}- closo-6,1-FeCB 8H 8] ( 8), which incorporates a B-P-C-N- Fe ring. A similar reaction in the presence of ligands L yields [6,6-(CO) 2-6-L-7-(PPh 2CH 2Cl)- closo-6,1-FeCB 8H 8] [L = PEt 3 ( 9) or CNBu (t) ( 10)], in addition to 8.     

Electronic structures of ruthenium and osmium complexes of 9,10-phenanthrenequinone

The reaction of 9,10-phenanthrenequinone (PQ) with [M(II)(H)(CO)(X)(PPh(3))(3)] in boiling toluene leads to the homolytic cleavage of the M(II)-H bond, affording the paramagnetic trans-[M(PQ)(PPh(3))(2)(CO)X] (M = Ru, X = Cl, 1; M = Os, X = Br, 3) and cis-[M(PQ)(PPh(3))(2)(CO)X] (M = Ru, X = Cl, 2; M = Os, X = Br, 4) complexes. Single-crystal X-ray structure determinations of 1, 2·toluene, and 4·CH(2)Cl(2), EPR spectra, and density functional theory (DFT) calculations have substantiated that 1-4 are 9,10-phenanthrenesemiquinone radical (PQ(?-)) complexes of ruthenium(II) and osmium(II) and are defined as trans-[Ru(II)(PQ(?-))(PPh(3))(2)(CO)Cl] (1), cis-[Ru(II)(PQ(?-))(PPh(3))(2)(CO)Cl] (2), trans-[Os(II)(PQ(?-))(PPh(3))(2)(CO) Br] (3), and cis-[Os(II)(PQ(?-))(PPh(3))(2)(CO)Br] (4). Two comparatively longer C-O [average lengths: 1, 1.291(3) ?; 2·toluene, 1.281(5) ?; 4·CH(2)Cl(2), 1.300(8) ?] and shorter C-C lengths [1, 1.418(5) ?; 2·toluene, 1.439(6) ?; 4·CH(2)Cl(2), 1.434(9) ?] of the OO chelates are consistent with the presence of a reduced PQ(?-) ligand in 1-4. A minor contribution of the alternate resonance form, trans- or cis-[M(I)(PQ)(PPh(3))(2)(CO)X], of 1-4 has been predicted by the anisotropic X- and Q-band electron paramagnetic resonance spectra of the frozen glasses of the complexes at 25 K and unrestricted DFT calculations on 1, trans-[Ru(PQ)(PMe(3))(2)(CO)Cl] (5), cis-[Ru(PQ)(PMe(3))(2)(CO)Cl] (6), and cis-[Os(PQ)(PMe(3))(2)(CO)Br] (7). However, no thermodynamic equilibria between [M(II)(PQ(?-))(PPh(3))(2)(CO)X] and [M(I)(PQ)(PPh(3))(2)(CO)X] tautomers have been detected. 1-4 undergo one-electron oxidation at -0.06, -0.05, 0.03, and -0.03 V versus a ferrocenium/ferrocene, Fc(+)/Fc, couple because of the formation of PQ complexes as trans-[Ru(II)(PQ)(PPh(3))(2)(CO)Cl](+) (1(+)), cis-[Ru(II)(PQ)(PPh(3))(2)(CO)Cl](+) (2(+)), trans-[Os(II)(PQ)(PPh(3))(2)(CO)Br](+) (3(+)), and cis-[Os(II)(PQ)(PPh(3))(2)(CO)Br](+) (4(+)). The trans isomers 1 and 3 also undergo one-electron reduction at -1.11 and -0.96 V, forming PQ(2-) complexes trans-[Ru(II)(PQ(2-))(PPh(3))(2)(CO)Cl](-) (1(-)) and trans-[Os(II)(PQ(2-))(PPh(3))(2)(CO)Br](-) (3(-)). Oxidation of 1 by I(2) affords diamagnetic 1(+)I(3)(-) in low yields. Bond parameters of 1(+)I(3)(-) [C-O, 1.256(3) and 1.258(3) ?; C-C, 1.482(3) ?] are consistent with ligand oxidation, yielding a coordinated PQ ligand. Origins of UV-vis/near-IR absorption features of 1-4 and the electrogenerated species have been investigated by spectroelectrochemical measurements and time-dependent DFT calculations on 5, 6, 5(+), and 5(-).     

Reactions of manganese and rhenium complexes with organic azides: preparation of tetraazabutadiene derivatives

Azide complexes [M(RN(3))(CO)(3)P(2)]BPh(4)[M = Mn, Re; R = C(6)H(5)CH(2), 4-CH(3)C(6)H(4)CH(2), C(6)H(5), 4-CH(3)C(6)H(4), C(5)H(9); P = PPh(OEt)(2), PPh(2)(OEt)] were prepared by allowing tricarbonyl MH(CO)(3)P(2) hydride complexes to react first with Br?nsted acid (HBF(4), CF(3)SO(3)H) and then with organic azide in the dark. In sunlight the reaction yielded tetraazabutadiene [M(eta(2)-1,4-R(2)N(4))(CO)(2)P(2)]BPh(4) complexes or, with benzyl azide, imine [M{eta(1)-NH[double bond, length as m-dash]C(H)Ar}(CO)(3)P(2)]BPh(4)(Ar = C(6)H(5), 4-CH(3)C(6)H(4)) derivatives. Tetraazabutadiene [M(eta(2)-1,4-R(2)N(4))(CO)(2)P(2)]BPh(4) complexes were also prepared by reacting dicarbonyl MH(CO)(2)P(3) species first with Br?nsted acid and then with an excess of organic azide. Complexes were characterised spectroscopically (IR, (1)H, (31)P, (13)C, (15)N NMR data) and by the X-ray crystal structure determination of complex [Re{eta(2)-1,4-(C(6)H(5)CH(2))(2)N(4)}(CO)(2){PPh(OEt)(2)}(2)]BPh(4)(). Strong evidence for coordination of the organic azide was obtained from the (15)N NMR spectra of labelled [M(C(6)H(5)CH(2)(15)NN(15)N)(CO)(3)P(2)]BPh(4) derivatives.     

Supraicosahedral and icosahedral nickelacarbaboranes bearing exopolyhedral metal fragments

Treatment of the isomeric 12-vertex nickelacarbaborane salts [NEt(4)][3-(eta3)-C(3)H(5))-closo-3,1,2-NiC(2)B(9)H(11)] and [NEt(4)][2-(eta3)-C(3)H(5))-closo-2,1,7-NiC(2)B(9)H(11)] with [CuCl(PPh(3))](4) and Tl[PF(6)] affords the zwitterionic bimetallic species [3-(eta3)-C(3)H(5))-3,4,8-[Cu(PPh(3))]-4,8-(mu-H)(2)-closo-3,1,2-NiC(2)B(9)H(9)] and [2-(eta3)-C(3)H(5))-2,6,11-(Cu(PPh(3)))-6,11-(mu-H)(2)-closo-2,1,7-NiC(2)B(9)H(9)], respectively. Similarly, the 13-vertex nickelacarbaborane [NEt(4)][4-(eta3)-C(3)H(5))-closo-4,1,6-NiC(2)B(10)H(12)] reacts with sources of mono-cationic metal fragments to form [4-(eta3)-C(3)H(5))-7,8,13-(Cu(PPh(3)))-7,8,13-(mu-H)(3)-4,1,6-closo-NiC(2)B(10)H(9)], [4-(eta3)-C(3)H(5))-3,8-(Rh(PPh(3))(2))-3,8-(mu-H)(2)-4,1,6-closo-NiC(2)B(10)H(10)] and [4-(eta3)-C(3)H(5))-3,7,8-(RuCl(PPh(3))(2))-3,7,8-(mu-H)(3)-4,1,6-closo-NiC(2)B(10)H(9)]. The molecular structures of these five new bimetallic compounds were determined by X-ray diffraction studies, confirming that exopolyhedral Cu, Rh and Ru fragments are attached to the cluster via B-H[right harpoon up]M agostic-type interactions and, in the case of the (NiC(2)B(9)) species, by a metal-metal bond.     

Osmium-mediated C--H and C--C bond cleavage of a phenolic substrate: p-quinone methide and methylene arenium pincer complexes

The diphosphine 2,4,6-(CH(3))(3)-3,5-(iPr(2)PCH(2))(2)C(6)OH (1) reacts with [OsCl(2)(PPh(3))(3)] in presence of an excess of triethylamine to yield the isomeric para-quinone methide derivatives [Os{4-(CH(2))-1-(O)-2,6-(CH(3))(2)-3,5-(iPr(2)PCH(2))(2)C(6)}(Cl)(H)(PPh(3))] (2 and 3), which differ in the positions of the mutually trans hydride and chloride ligands. Complex 2 reacts with CO to afford the dicarbonyl species [Os{1-(O)-2,4,6-(CH(3))(3)-3,5-(iPr(2)PCH(2))(2)C(6)}(Cl)(CO)(2)] (4), which results from hydride insertion into the quinonic double bond. Protonation of 2 and 3 leads to the formation of the methylene arenium derivative [Os{4-(CH(2))-1-(OH)-2,6-(CH(3))(2)-3,5-(iPr(2)PCH(2))(2)C(6)}(Cl)(H)(PPh(3))][OSO(2)CF(3)] (5 a). The diphosphine 1 reacts with [OsCl(2)(PPh(3))(3)] at 100 degrees C under H(2) to afford [Os{1-(OH)-2,6-(CH(3))(2)-3,5-(iPr(2)PCH(2))(2)C(6)}(Cl)(H(2))(PPh(3))] (6), a PCP pincer complex resulting formally from C(sp(2))--C(sp(3)) cleavage of the C--CH(3) group in 1. C--C hydrogenolysis resulting in the same complex is achieved by heating 2 under H(2) pressure. Reaction of the diphosphine substrate with [OsCl(2)(PPh(3))(3)] under H(2) at lower temperature allows the observation of a methylene arenium derivative resulting from C--H activation, [Os{4-(CH(2))-1-(OH)-2,6-(CH(3))(2)-3,5-(iPr(2)PCH(2))(2)C(6)}(Cl)(2)(H)] (7). This compound reacts with PPh(3) in toluene to afford the ionic derivative [Os{4-(CH(2))-1-(OH)-2,6-(CH(3))(2)-3,5-(iPr(2)PCH(2))(2)C(6)}(Cl)(H)(PPh(3))]Cl (5 b). X-ray diffraction studies have been carried out on compounds 2, 3, 4, 5 b, 6, and 7, which allows the study of the structural variations when going from methylene arenium to quinone methide derivatives.     

Dithiocarboxylate complexes of ruthenium(II) and osmium(II)

The ruthenium(II) complexes [Ru(R)(κ(2)-S(2)C·IPr)(CO)(PPh(3))(2)](+) (R = CH=CHBu(t), CH=CHC(6)H(4)Me-4, C(C≡CPh)=CHPh) are formed on reaction of IPr·CS(2) with [Ru(R)Cl(CO)(BTD)(PPh(3))(2)] (BTD = 2,1,3-benzothiadiazole) or [Ru(C(C≡CPh)=CHPh)Cl(CO)(PPh(3))(2)] in the presence of ammonium hexafluorophosphate. Similarly, the complexes [Ru(CH=CHC(6)H(4)Me-4)(κ(2)-S(2)C·ICy)(CO)(PPh(3))(2)](+) and [Ru(C(C≡CPh)=CHPh)(κ(2)-S(2)C·ICy)(CO)(PPh(3))(2)](+) are formed in the same manner when ICy·CS(2) is employed. The ligand IMes·CS(2) reacts with [Ru(R)Cl(CO)(BTD)(PPh(3))(2)] to form the compounds [Ru(R)(κ(2)-S(2)C·IMes)(CO)(PPh(3))(2)](+) (R = CH=CHBu(t), CH=CHC(6)H(4)Me-4, C(C≡CPh)=CHPh). Two osmium analogues, [Os(CH=CHC(6)H(4)Me-4)(κ(2)-S(2)C·IMes)(CO)(PPh(3))(2)](+) and [Os(C(C≡CPh)=CHPh)(κ(2)-S(2)C·IMes)(CO)(PPh(3))(2)](+) were also prepared. When the more bulky diisopropylphenyl derivative IDip·CS(2) is used, an unusual product, [Ru(κ(2)-SC(H)S(CH=CHC(6)H(4)Me-4)·IDip)Cl(CO)(PPh(3))(2)](+), with a migrated vinyl group, is obtained. Over extended reaction times, [Ru(CH=CHC(6)H(4)Me-4)Cl(BTD)(CO)(PPh(3))(2)] also reacts with IMes·CS(2) and NH(4)PF(6) to yield the analogous product [Ru{κ(2)-SC(H)S(CH=CHC(6)H(4)Me-4)·IMes}Cl(CO)(PPh(3))(2)](+)via the intermediate [Ru(CH=CHC(6)H(4)Me-4)(κ(2)-S(2)C·IMes)(CO)(PPh(3))(2)](+). Structural studies are reported for [Ru(CH=CHC(6)H(4)Me-4)(κ(2)-S(2)C·IPr)(CO)(PPh(3))(2)]PF(6) and [Ru(C(C≡CPh)=CHPh)(κ(2)-S(2)C·ICy)(CO)(PPh(3))(2)]PF(6).     

Synthesis of N-heterocyclic carbene rhenium(I) carbonyl complexes

Reaction of aminophosphinimine [RHN(CH(2))(2)N[double bond, length as m-dash]PPh(3)] (R = H, Et) with Re(2)(CO)(10) provided the NH-functionalized carbene rhenium complex [Re(2)(CNHCH(2)CH(2)NR)(CO)(9)] (3a, R = H, 3b, R = Et). Treatment of 3 with Br(2) provided the mono nuclear [Re(CNHCH(2)CH(2)NR)(CO)(4)Br] (1, R = H, 2, R = Et). However, NH-functionalized carbene complexes 1-3 did not undergo N-alkylation with alkyl halides to yield the N-substituted NHC complexes. The direct ligand substitution of [Re(CO)(5)Br] with a carbene donor was employed to prepare [Re(IMes(2))(CO)(4)Br] (6a, IMes(2) = 1,3-di-mesitylimidazol-2-ylidene; 6b, IMes(2) = 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene). Analyses of spectroscopic and crystal data of 6a and 6b show similar corresponding data among these complexes, suggesting the saturated and unsaturated NHCs have similar bonding with Re(I) metal centers. Reduction of 6a and 6b with LiEt(3)BH yielded the corresponding hydrido complexes 7a-b [ReH(CO)(4)(IMes(2))], but not 1 and 2. Ligand substitution of 1, 6a and 6b toward 2,2'-bipyridine (bipy) was investigated. Crystal structures of 1, 3a-b, 6a-b and 7b were determined for characterization and comparison.     

Reactions of the dianion [1,1,1-(CO)3-2-Ph-closo-1,2-MnCB9H9]2- with transition-metal cations: facile insertion and then extrusion of cluster vertexes

The manganacarborane dianion in [N(PPh(3))(2)][NEt(4)][1,1,1-(CO)(3)-2-Ph-closo-1,2-MnCB(9)H(9)] (1b) reacts with cationic transition metal-ligand fragments to give products in which the electrophilic metal groups (M') are exo-polyhedrally attached to the {closo-1,2-MnCB(9)} cage system via three-center two-electron B-H --> M' linkages and generally also by Mn-M' bonds. With {Cu(PPh(3))}(+), the Cu-Mn-Cu trimetallic species [1,6-{Cu(PPh(3))}-1,7-{Cu(PPh(3))}-6,7-(mu-H)(2)-1,1,1-(CO)(3)-2-Ph-closo-1,2-MnCB(9)H(7)] (3a) is formed, whereas reactions with {M'(dppe)}(2+) (M' = Ni, Pd; dppe = Ph(2)PCH(2)CH(2)PPh(2)) give [1,3-{Ni(dppe)}-3-(mu-H)-1,1,1-(CO)(3)-2-Ph-closo-1,2-MnCB(9)H(8)] (5a) and [1,3,6-{Pd(dppe)}-3,6-(mu-H)(2)-1,1,1-(CO)(3)-2-Ph-closo-1,2-MnCB(9)H(7)] (5b), both of which contain M'-Mn bonds. The latter reaction with M' = Pt affords [3,6-{Pt(dppe)}-3,6-(mu-H)(2)-1,1,1-(CO)(3)-2-Ph-closo-1,2-MnCB(9)H(7)] (6), which lacks a Pt-Mn connectivity. Compound 6 itself spontaneously converts to [1-Ph-2,2,2-(CO)(3)-8,8-(dppe)-hypercloso-8,2,1-PtMnCB(9)H(9)] (7b) and thence to [3,6,7-{Mn(CO)(3)}-3,7-(mu-H)(2)-1-Ph-6,6-(dppe)-closo-6,1-PtCB(8)H(6)] (8). This sequence occurs via initial insertion of the {Pt(dppe)} unit and then extrusion of {Mn(CO)(3)} and one {BH} vertex. In the presence of alcohols ROH, compound 6 is transformed to the 7-OR substituted analogues of 7b. X-ray diffraction studies were essential in elucidating the structures encountered in compounds 5-8 and hence in understanding their behavior.     

Iridium-iron-monocarborane clusters from oxidative insertion reactions of [IrCl(CO)(PPh3)2] with ferracarborane anions

The nine-vertex ferracarborane salt [N(PPh3)2][7,7,7-(CO)3-closo-7,1-FeCB7H8] (1) reacts with an excess of [IrCl(CO)(PPh3)2] in the presence of Tl[PF6] to form, successively, the bimetallic species [7,7,9,9,9-(CO)5-7-PPh3-closo-7,9,1-IrFeCB6H7] (3), in which one {BH}- vertex has formally been subrogated by an {Ir(CO)2(PPh3)} unit, and the trimetallic complex [6,7,9-{Ir(CO)(PPh3)2}-7,9-(mu-H)2-7,9,9-(CO)3-7-PPh3-closo-7,9,1-IrFeCB6H6] (5), which contains an {FeIr2} triangle. The {FeIrCB6} core in 5 resembles that in 3 with, in addition, the Fe...Ir connectivity being spanned by an {Ir(CO)(PPh3)2} fragment and the consequent Fe-Ir and Ir-Ir bonds bridged by hydrido ligands. In contrast to the above, treatment of the 10-vertex diferracarborane salt [N(PPh3)2][6,6,6,10,10,10-(CO)6-closo-6,10, 1-Fe2CB7H8] (2) with the same reagents yields two very different, trimetallic complexes, namely [8,10-{Ir(mu-PPh2)(Ph)(CO)(PPh3)}-8-(mu-H)-6,6,6,10,10-( CO)5-closo-6,10,1-Fe2CB7H7] (6) and [6,7,10-{Fe(CO)3}-6-(mu-H)-6,10,10,10-(CO)4-6-PPh3-closo-6,10,1-IrFeCB7H7] (7). In 6, an exo-polyhedral {IrPh(CO)(PPh3)} moiety is attached to a {closo-6,10,1-Fe2CB7} framework via a PPh2-bridged Fe-Ir bond and a B-HIr agostic-type linkage, the iridium center formally having inserted into one P-Ph bond of a PPh3 unit. Complex 7 contains an {IrFeCB7} cluster core, with an exo-polyhedral {Fe(CO)3} moiety bridging a {BIrFe} triangular face and with an additional Ir-H-Fe bridge. However, this metal atom arrangement reveals that iridium and iron moieties have exchanged exo- and endo-polyhedral sites with respect to the 10-vertex metallacarborane. X-ray diffraction studies upon 3, 5, 6, and 7 confirmed their novel structural features; some preliminary reactivity studies upon these compounds are also reported.     

Syntheses of functionalized ferratricarbadecaboranyl complexes

The reactions of nitriles (RCN) with arachno-4,6-C(2)B(7)H(12)(-) provide a general route to functionalized tricarbadecaboranyl anions, 6-R-nido-5,6,9-C(3)B(7)H(9)(-), R = C(6)H(5) (2(-)), NC(CH(2))(4) (4(-)), (p-BrC(6)H(4))(Me(3)SiO)CH (6(-)), C(14)H(11) (8(-)), and H(3)BNMe(2)(CH(2))(2) (10(-)). Further reaction of these anions with (eta(5)-C(5)H(5))Fe(CO)(2)I yields the functionalized ferratricarbadecaboranyl complexes 1-(eta(5)-C(5)H(5))-2-C(6)H(5)-closo-1,2,3,4-FeC(3)B(7)H(9) (3), 1-(eta(5)-C(5)H(5))-2-NC(CH(2))(4)-closo-1,2,3,4-FeC(3)B(7)H(9) (5), 1-(eta(5)-C(5)H(5))-2-[(p-BrC(6)H(4))(Me(3)SiO)CH]-closo-1,2,3,4-FeC(3)B(7)H(9) (7), 1-(eta(5)-C(5)H(5))-2-C(14)H(11)-closo-1,2,3,4-FeC(3)B(7)H(9) (9), and 1-(eta(5)-C(5)H(5))-2-H(3)BNMe(2)(CH(2))(2)-closo-1,2,3,4-FeC(3)B(7)H(9) (11). Reaction of 11 with DABCO (triethylenediamine) resulted in removal of the BH(3) group coordinated to the nitrogen of the side chain, giving 1-(eta(5)-C(5)H(5))-2-NMe(2)(CH(2))(2)-closo-1,2,3,4-FeC(3)B(7)H(9) (12). Crystallographic studies of complexes 3, 5, 7, 9, and 11 confirmed that these complexes are ferrocene analogues in which a formal Fe(2+) ion is sandwiched between the cyclopentadienyl and tricarbadecaboranyl monoanionic ligands. The metals are eta(6)-coordinated to the puckered six-membered face of the tricarbadecaboranyl cage, with the exopolyhedral substituents bonded to the low-coordinate carbon adjacent to the iron.     

Ruthenium mediated C-H activation of 2-(arylazo)phenols: characterization of an intermediate and the final organoruthenium complex

Reaction of 2-(arylazo)phenols with [Ru(PPh(3))(2)(CO)(2)Cl(2)] affords a family of organometallic complexes of ruthenium(II) of type [Ru(PPh(3))(2)(CO)(CNO-R)], where the 2-(arylazo)phenolate ligand (CNO-R; R = OCH(3), CH(3), H, Cl, and NO(2)) is coordinated to the metal center as tridentate C,N,O-donor. Another group of intermediate complexes of type [Ru(PPh(3))(2)(CO)(NO-R)(H)] has also been isolated, where the 2-(arylazo)phenolate ligand (NO-R) is coordinated to the metal center as bidentate N,O-donor. Structures of the [Ru(PPh(3))(2)(CO)(NO-OCH(3))(H)] and [Ru(PPh(3))(2)(CO)(CNO-OCH(3))] complexes have been determined by X-ray crystallography. All the complexes are diamagnetic and show characteristic (1)H NMR signals and intense MLCT transitions in the visible region. Both the [Ru(PPh(3))(2)(CO)(NO-R)(H)] and [Ru(PPh(3))(2)(CO)(CNO-R)] complexes show two oxidative responses on the positive side of SCE.     

Synthesis and reactivity of fluorinated ferracarborane anions

The ferracarborane [N(PPh3)2][6,6,6,10,10,10-(CO)6-closo-6,10,1-Fe2CB7H8] reacts in CH2Cl2 with 3 molar equivalents of Ag[PF6] to yield the trifluoro-substituted species [N(PPh3)2][7,8,9-F3-6,6,6,10,10,10-(CO)6-closo-6,10,1-Fe2CB7H5]. Compound undergoes structural rearrangement in toluene at reflux temperatures, forming [N(PPh3)2][8,9,10-F3-6,6,6,7,7,7-(CO)6-closo-6,7,1-Fe2CB7H5]. Alternatively, reaction of either or with a 10-fold excess of Ag[PF6] in CH2Cl2 forms two species: namely, [N(PPh3)2][2,7,9,10-F4-6,6,6,8,8,8-(CO)6-closo-6,8,1-Fe2CB7H4], in which one further B-F substitution has occurred and the {Fe2CB7} cluster core has rearranged, plus a mono-iron co-product, [N(PPh3)2][3,8,9-F3-7,7,7-(CO)3-closo-7,1-FeCB7H5] that is formed by polyhedral contraction. Treatment of with [NO][BF4] in CH2Cl2 results in CO substitution at the 4-connected iron vertex [Fe10], producing the zwitterionic complex [7,8,9-F3-6,6,6,10,10-(CO)5-10-NO-closo-6,10,1-Fe2CB7H5]. Addition of Me3NO to a mixture of and PEt3 in CH2Cl2 also results in CO substitution, forming the isomeric species [N(PPh3)2][7,8,9-F3-6,6,m,10,10-(CO)5-n-PEt3-closo-6,10,1-Fe2CB7H5] [m=6, n=10; m=10, n=6] in a 5:1 ratio. Treatment of with [NO][BF4] and then CNBut in CH2Cl2 allows further, successive CO substitution at Fe10 to yield first a neutral, zwitterionic complex [7,8,9-F3-6,6,6,10-(CO)4-10-NO-10-PEt3-closo-6,10,1-Fe2CB7H5] and then [7,8,9-F3-6,6,6-(CO)3-10-CNBut-10-NO-10-PEt3-closo-6,10,1-Fe2CB7H5]. The molecular structures of compounds and have been established by X-ray diffraction.     

Synthesis and characterization of a new family of square-planar nickel(II) carbonyl derivatives

The reaction of [NBu(4)](2)[Ni(C(6)F(5))(4)] (1) with solutions of dry HCl(g) in Et(2)O results in the protonolysis of two Nibond;C(6)F(5) bonds giving [NBu(4)](2)[[Ni(C(6)F(5))(2)](2)(mu-Cl)(2)] (2 a) together with the stoichiometrically required amount of C(6)F(5)H. Compound 2 a reacts with AgClO(4) in THF to give cis-[Ni(C(6)F(5))(2)(thf)(2)] (3). Reacting 3 with phosphonium halides, [PPh(3)Me]X, gives dinuclear compounds [PPh(3)Me](2)[[Ni(C(6)F(5))(2)](2)(mu-X)(2)] (X=Br (2 b) or I (2 c)). Solutions of compounds 2 in CH(2)Cl(2) at 0 degrees C do not react with excess CNtBu, but do react with CO (1 atm) to split the bridges and form a series of terminal Ni(II) carbonyl derivatives with general formula Qcis-[Ni(C(6)F(5))(2)X(CO)] (4). The nu(CO) stretching frequencies of 4 in CH(2)Cl(2) solution decrease in the order Cl (2090 cm(-1))>Br (2084 cm(-1))>I (2073 cm(-1)). Compounds 4 revert to the parent dinuclear species 2 on increasing the temperature or under reduced CO pressure. [NBu(4)]cis-[Ni(C(6)F(5))(2)Cl(CO)] (4 a) reacts with AgC(6)F(5) to give [NBu(4)][Ni(C(6)F(5))(3)(CO)] (5, nu(CO)(CH(2)Cl(2))=2070 cm(-1)). Compound 5 is also quantitatively formed ((19)F NMR spectroscopy) by 1:1 reaction of 1 with HCl(Et(2)O) in CO atmosphere. Complex 3 reacts with CO at -78 degrees C to give cis-[Ni(C(6)F(5))(2)(CO)(2)] (6, nu(CO)(CH(2)Cl(2))=2156, 2130 cm(-1)), which easily decomposes by reductive elimination of C(6)F(5)bond;C(6)F(5). Compounds 3 and 6 both react with CNtBu to give trans-[Ni(C(6)F(5))(2)(CNtBu)(2)] (7). The solid-state structures of compounds 3, 4 b, 6, and 7 have been established by X-ray diffraction methods. Complexes 4-6 are rare examples of square-planar Ni(II) carbonyl derivatives.     

Unexpected formation of a trinuclear complex containing a Ta(IV)-Ta(IV) bond in the reactions of Bu(t)N=Ta(NMe2)3 with silanes

A new trinuclear species containing a Ta(IV)-Ta(IV) bond, Ta(3)(μ-H)(μ-NMe(2))(μ=NBu(t))(2)(=NBu(t))(NMe(2))(5), has been formed by reductive elimination of H(2). Ta(2)H(2)(μ-NMe(2))(2)(NMe(2))(2)(=NBu(t))(2) has also been isolated. O(2) oxidizes the Ta(IV)-Ta(IV) bond to yield Ta(3)(μ(3)-O)(H)(μ=NBu(t))(μ-NMe(2))(2)(NMe(2))(4)(=NBu(t))(2) under ligand exchange. Delocalization of d electrons is discussed.