Molecular nitrides containing group 4 and 5 metals: single and double azatitanocubanes

Treatment of [[Ti(eta(5)-C(5)Me(5))(micro-NH)](3)(micro(3)-N)] (1) with the imido complexes [Ti(NAr)Cl(2)(py)(3)] (Ar=2,4,6-C(6)H(2)Me(3)) and [Ti(NtBu)Cl(2)(py)(3)] in toluene affords the single azatitanocubanes [[Cl(2)(ArN)Ti]( micro(3)-NH)(3)[Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)]].(C(7)H(8)) (2.C(7)H(8)) and [[Cl(2)Ti](micro(3)-N)(2)(micro(3)-NH)[Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)]] (3), respectively. Similar reactions of complex 1 with the niobium and tantalum imido derivatives [[M(NtBu)(NHtBu)Cl(2)(NH(2)tBu)](2)] (M=Nb, Ta) in toluene give the single azaheterometallocubanes [[Cl(2)(tBuN)M](micro(3)-N)(micro(3)-NH)(2)[Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)]] (M=Nb (4), Ta (5)), both complexes react with 2,4,6-trimethylaniline to yield the analogous species [[Cl(2)(ArN)M](micro(3)-N)(micro(3)-NH)(2)[Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)]].(C(7)H(8)) (Ar=2,4,6-C(6)H(2)Me(3), M=Nb (6.C(7)H(8)), Ta (7.C(7)H(8))). Also the azaheterodicubanes [M[micro(3)-N)(2)(micro(3)-NH)](2)[Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)](2)].2C(7)H(8) [M=Ti (8.2C(7)H(8)), Zr (9.2C(7)H(8))], and [M[(micro(3)-N)(5)(micro(3)-NH)][Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)](2)].2 C(7)H(8) (Nb (10.2C(7)H(8)), Ta (11.2C(7)H(8))) were prepared from 1 and the homoleptic dimethylamido complex [M(NMe(2))(x)] (x=4, M=Ti, Zr; x=5, M=Nb, Ta) in toluene at 150 degrees C. X-ray crystal structure determinations were performed for 6 and 10, which revealed a cube- and double-cube-type core, respectively. For complexes 2 and 4-7 we observed and studied by DNMR a rotation or trigonal-twist of the organometallic ligands [[Ti(eta(5)-C(5)Me(5))(micro-NH)](3)(micro(3)-N)] (1) and [(micro(3)-N)(micro(3)-NH)(2)[Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)]](1-). Density functional theory calculations were carried out on model complexes of 2, 3, and 8 to establish and understand their structures.     

Titanium alkali metal nitrido complexes

Treatment of [(Ti(eta5-C5Me5)(mu-NH))3(mu3-N)] with alkali metal bis(trimethylsilyl)amido reagents in toluene afforded the complexes [M(mu3-N)(mu3-NH)2[Ti3(mu5-C5Me5)3(mu3-N)]]2 (M = Li (2), Na, (3), K (4)). The molecular structures of 2 and 3 have been determined by X-ray crystallographic studies and show two azaheterometallocubane cores [MTi3N4] linked by metal-nitrogen bonds. Reaction of the lithium derivative 2 with chlorotrimethylsilane or trimethyltin chloride in toluene gave the incomplete cube nitrido complexes [Ti3(eta5-C5Me5)3(mu-NH)2(mu-NMMe3)(mu3-N)] (M = Si (5), Sn (6)). A similar reaction with indium(I) or thallium(I) chlorides yielded cube-type derivatives [M(mu3-N)(mu3-NH)2[Ti(eta5-C5Me5)3(mu3-N)] (M=In (7), Tl (8)).     

Amido-bridged double-cube nitrido complexes containing titanium and magnesium/calcium

Treatment of the single cube nitrido complexes [(thf)x((Me3Si)2N)M((mu3-N)(mu3-NH)2Ti3(eta5-C5Me5)3(mu3-N))](M = Mg, x= 0; Ca, x= 1) with one equivalent of anilines NH2Ar in toluene affords the arylamido complexes [(ArHN)M((mu3-N)(mu3-NH)2Ti3(eta5-C5Me5)3(mu3-N))]n[M = Mg (3), n= 1, Ar = 4-MeC6H4; Ca (4), n= 2, Ar = 2,4,6-Me3C6H2]. The magnesium complex 3 has a single-cube structure whereas the X-ray crystal structure of the analogous calcium derivative 4 shows two cube-type azaheterometallocubane moieties Ca((mu3-N)(mu3-NH)2Ti3(eta5-C5Me5)3(mu3-N)) held together by two mu-2,4,6-trimethylanilido ligands. Complexes 3 and 4 react with chloroform-d1 at room temperature to give the metal halide adducts [Cl2M((mu3-NH)3Ti3(eta5-C5Me5)3(mu3-N))](M = Mg, Ca). A solution of 3 in n-hexane gave complex [(Mg2(mu3-N)(mu3-NH)5[Ti3(eta5-C5Me5)3(mu3-N)]2)(mu-NHAr)3] which shows three mu-4-methylanilido ligands bridging two [MgTi3N4] cube type cores according to an X-ray crystal structure determination.     

Molecular nitrides with titanium and rare-earth metals

A series of titanium-group 3/lanthanide metal complexes have been prepared by reaction of [{Ti(η(5)-C(5)Me(5))(μ-NH)}(3)(μ(3)-N)] (1) with halide, triflate, or amido derivatives of the rare-earth metals. Treatment of 1 with metal halide complexes [MCl(3)(thf)(n)] or metal trifluoromethanesulfonate derivatives [M(O(3)SCF(3))(3)] at room temperature affords the cube-type adducts [X(3)M{(μ(3)-NH)(3)Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-N)}] (X = Cl, M = Sc (2), Y (3), La (4), Sm (5), Er (6), Lu (7); X = OTf, M = Y (8), Sm (9), Er (10)). Treatment of yttrium (3) and lanthanum (4) halide complexes with 3 equiv of lithium 2,6-dimethylphenoxido [LiOAr] produces the aryloxido complexes [(ArO)(3)M{(μ(3)-NH)(3)Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-N)}] (M = Y (11), La (12)). Complex 1 reacts with 0.5 equiv of rare-earth bis(trimethylsilyl)amido derivatives [M{N(SiMe(3))(2)}(3)] in toluene at 85-180 °C to afford the corner-shared double-cube nitrido compounds [M(μ(3)-N)(3)(μ(3)-NH)(3){Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-N)}(2)] (M = Sc (13), Y (14), La (15), Sm (16), Eu (17), Er (18), Lu (19)) via NH(SiMe(3))(2) elimination. A single-cube intermediate [{(Me(3)Si)(2)N}Sc{(μ(3)-N)(2)(μ(3)-NH)Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-N)}] (20) was obtained by the treatment of 1 with 1 equiv of the scandium bis(trimethylsilyl)amido derivative [Sc{N(SiMe(3))(2)}(3)]. The X-ray crystal structures of 2, 7, 11, 14, 15, and 19 have been determined. The thermal decomposition in the solid state of double-cube nitrido complexes 14, 15, and 18 has been investigated by thermogravimetric analysis (TGA) and differential thermal analysis (DTA) measurements, as well as by pyrolysis experiments at 1100 °C under different atmospheres (Ar, H(2)/N(2), NH(3)) for the yttrium complex 14.     

Rhodium/iridium-titanium azaheterometallocubanes

Treatment of [[Ti(eta5-C5Me5)(mu-NH)]3(mu3-N)] (1) with the diolefin complexes [[MCl(cod)]2] (M = Rh, Ir; cod = 1,5-cyclooctadiene) in toluene afforded the ionic complexes [M-(cod)(mu3-NH)3Ti3(eta5-C5Me5)3(mu3-N)]Cl [M = Rh (2), Ir (3)]. Reaction of complexes 2 and 3 with [Ag(BPh4)] in dichloromethane leads to anion metathesis and formation of the analogous ionic derivatives [M(cod)(mu3-NH)3Ti3-(eta5-C5Me5)3(mu3-N)][BPh4] [M = Rh (4), Ir (5)]. An X-ray crystal structure determination for 5 reveals a cube-type core [IrTi3N4] for the cationic fragment, in which 1 coordinates in a tripodal fashion to the iridium atom. Reaction of the diolefin complexes [[MCl(cod))2] (M = Rh, Ir) and [[RhCl(C2H4)2]2] with the lithium derivative [[Li(mu3-NH)2(mu3-N)-Ti3(eta5-C5Me5)3(mu3-N)]2] x C7H8 (6 C7H8) in toluene gave the neutral cube-type complexes [M(cod)(mu-NH)2(mu3-N)Ti3-(eta5-C5Me5)3(mu3-N)] [M = Rh (7), Ir (8)] and [Rh(C2H4)2(mu3-NH)2(mu3-N)Ti3(eta5-C5Me5)3(mu3-N)] (9), respectively. Density functional theory calculations have been carried out on the ionic and neutral azaheterometallocubane complexes to understand their electronic structures.     

Ammonolysis of mono(pentamethylcyclopentadienyl) titanium(IV) derivatives

Ammonolyses of mono(pentamethylcyclopentadienyl) titanium(IV) derivatives [Ti(eta5-C5Me5)X3] (X = NMe2, Me, Cl) have been carried out in solution to give polynuclear nitrido complexes. Reaction of the tris(dimethylamido) derivative [Ti(eta5-C5Me5)(NMe2)3] with excess of ammonia at 80-100 degrees C gives the cubane complex [[Ti(eta5-C5Me5)]4(mu3-N)4] (1). Treatment of the trimethyl derivative [Ti(eta5-C5Me5)Me3] with NH3 at room temperature leads to the trinuclear imido-nitrido complex [[Ti(eta/5-CsMes)(mu-NH)]3(mu3-N)] (2) via the intermediate [[Ti(eta5-C5Me5)Me]2(mu-NH)2] (3). The analogous reaction of [Ti(eta5-C5Me5)Me3] with 2,4,6-trimethylaniline (ArNH2) gives the dinuclear imido complex [[Ti(eta5-C5Me5)Me])2(mu-NAr)2] (4) which reacts with ammonia to afford [[Ti(eta5-C5Me5)(NH2)]2(mu-NAr)2] (5). Complex 2 has been used, by treatments with the tris(dimethylamido) derivatives [Ti(eta5-C5H5-nRn)(NMe2)3], as precursor of the cubane nitrido systems [[Ti4(eta5-C5Me5)3(eta5-C5H5-nRn)](mu3-N)4] [R = Me n = 5 (1), R = H n = 0 (6), R = SiMe3 n = 1 (7), R = Me n = 1 (8)] via dimethylamine elimination. Reaction of [Ti(eta5-C5Me5)Cl3] or [Ti(eta5-C5Me5)(NMe2)Cl2] with excess of ammonia at room temperature gives the dinuclear complex [[Ti2(eta5-C5Me5)2Cl3(NH3)](mu-N)] (9) where an intramolecular hydrogen bonding and a nonlineal nitrido ligand bridge the "Ti(eta5-C5Me5)Cl(NH3)" and "Ti(eta5-C5Me5)Cl2" moieties. The molecular structures of [[Ti(eta5-C5Me5)Me]2 (mu-NAr)2] (4) and [[Ti2(eta5-C5Me5)2Cl3(NH3)](mu-N)] (9) have been determined by X-ray crystallographic studies. Density functional theory calculations also have been conducted on complex 9 to confirm the existence of an intramolecular N-H...Cl hydrogen bond and to evaluate different aspects of its molecular disposition.     

Encapsulation of a trinuclear silver(I) cluster by two imido-nitrido metalloligands [{Ti(eta5-C5Me5)(micro-NH)}3(micro3-N)

Treatment of the metalloligand [{Ti(eta(5)-C(5)Me(5))(micro-NH)}(3)(micro(3)-N)] with silver(i) trifluoromethanesulfonate in different molar ratios gives the ionic compounds [Ag{(micro(3)-NH)(3)Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)}(2)][O(3)SCF(3)] and [Ag{(micro(3)-NH)(3)Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)}][O(3)SCF(3)] or the triangular silver cluster [(CF(3)SO(2)O)(3)Ag(3){(micro(3)-NH)(3)Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)}(2)] in which each face is capped by a metalloligand.     

Synthetic and theoretical study of the incorporation of metal halides in [{Ti(eta5-C5Me5)(mu-NH)}3(mu3-N)

The capacity of the imido-nitrido organometallic ligand [{Ti(eta5-C5Me5)(mu-NH)}3(mu3-N)] (1) to entrap main group metal halides MXn has been investigated. Treatment of 1 with metal halides in toluene or dichloromethane afforded several soluble adducts [MXn(L)] (L=1) in good yields. The reaction of 1 with one equivalent of Group 1 and 13 monohalides MX afforded single cube-type complexes [XM{(mu3-NH)3Ti3(eta5-C5Me5)3(mu3-N)}] (M=Li, X=Br (2), I (3); M=Na, X=I (4); M=In, X=I (5); M=Tl, X=I (6)). Analogous treatment of 1 with Group 2 and 14 dihalides MX(2) gave the corresponding adducts [I2M{(mu3-NH)3Ti3(eta5-C5Me5)3(mu3-N)}] (M=Mg (7), Ca (8), Sr (9)) and [Cl(2)M{(mu3-NH)3Ti3(eta5-C5Me5)3(mu3-N)}] (M=Sn (10), Pb (11)). The treatment of 1 with SnI2 or the reaction of 10 with MeI at 60 degrees C afforded two azametallocubane units linked by two bridging iodine atoms [{ISn(mu3-NH)3Ti3(eta5-C5Me5)3(mu3-N)}2(mu-I)2] (12). Indium triiodide reacted with 1 in toluene to form the adduct [I3In(mu3-NH)3Ti3(eta5-C5Me5)3(mu3-N)] (13). Density functional theory calculations have been carried out to study these processes and evaluate the influence of the solvent. X-ray crystal structure determinations have been performed for complexes 10, 12, and 13.     

Cube-type nitrido complexes containing titanium and zinc/copper

Several azaheterometallocubane complexes containing [MTi3N4] cores have been prepared by the reaction of [{Ti(eta5-C5Me5)(mu-NH)}3(mu3-N)] (1) with zinc(II) and copper(I) derivatives. The treatment of 1 with zinc dichloride in toluene at room temperature produces the adduct [Cl2Zn{(mu3-NH)3Ti3(eta5-C5Me5)3(mu3-N)}] (2). Attempts to crystallize 2 in dichloromethane gave yellow crystals of the ammonia adduct [(H3N)Cl2Zn{(mu3-NH)Ti3(eta5-C5Me5)3(mu-NH)2(mu3-N)}] (3). The analogous reaction of 1 with alkyl, (trimethylsilyl)cyclopentadienyl, or amido zinc complexes [ZnR2] leads to the cube-type derivatives [RZn{(mu3-N)(mu3-NH)2Ti3(eta5-C5Me5)3(mu3-N)}] (R = CH2SiMe3 (5), CH2Ph (6), Me (7), C5H4SiMe3 (8), N(SiMe3)2 (9)) via RH elimination. The amido complex 9 decomposes in the presence of ambient light to generate the alkyl derivative [{Me3Si(H)N(Me)2SiCH2}Zn{(mu3-N)(mu3-NH)2Ti3(eta5-C5Me5)3(mu3-N)}] (10). The chloride complex 2 reacts with lithium cyclopentadienyl or lithium indenyl reagents to give the cyclopentadienyl or indenyl zinc derivatives [RZn{(mu3-N)(mu3-NH)2Ti3(eta5-C5Me5)3(mu3-N)}] (R = C5H5 (11), C9H7 (12)). Treatment of 1 with copper(I) halides in toluene at room temperature leads to the adducts [XCu{(mu3-NH)3Ti3(eta5-C5Me5)3(mu3-N)}] (X = Cl (13), I (14)). Complex 13 reacts with lithium bis(trimethylsilyl)amido in toluene to give the precipitation of [{Cu(mu4-N)(mu3-NH)2Ti3(eta5-C5Me5)3(mu3-N)}2] (15). Complex 15 is prepared in a higher yield through the reaction of 1 with [{CuN(SiMe3)2}4] in toluene at 150 degrees C. The addition of triphenylphosphane to 15 in toluene produces the single-cube compound [(Ph3P)Cu{(mu3-N)(mu3-NH)2Ti3(eta5-C5Me5)3(mu3-N)}] (16). The X-ray crystal structures of 3, 8, 9, and 15 have been determined.     

Yttrium and erbium halide complexes with [{Ti(eta5-C5Me5)(mu-NH)}3(mu3-N)] as a neutral tridentate ligand

Treatment of [{TiCp*(mu-NH)} 3(mu 3-N)] ( 1; Cp* = eta (5)-C 5Me 5) with yttrium and erbium halide complexes [MCl 3(THF) 3.5] and [MCpCl 2(THF) 3] (Cp = eta (5)-C 5H 5) gives cube-type adducts [Cl 3M{(mu 3-NH) 3Ti 3Cp* 3(mu 3-N)}] and [CpCl 2M{(mu 3-NH) 3Ti 3Cp* 3(mu 3-N)}]. An analogous reaction of 1 with [{MCp 2Cl} 2] in toluene affords [Cp 3M(mu-Cl)ClCpM{(mu 3-NH) 3Ti 3Cp* 3(mu 3-N)}] (M = Y, Er).     

Electrophilic attack on trinuclear titanium imido-nitrido systems

Alkylation of [{Ti(η(5)-C(5)Me(5))(μ-NH)}(3)(μ(3)-N)] with MeOTf occurs at the imido ligands to produce the methylamido derivative [Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-N)(μ-NH)(2)(μ-NHMe)(OTf)] which readily rearranges to form the methylimido complex [Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-N)(μ-NH)(μ-NH(2))(μ-NMe)(OTf)].     

Interplay of cubic building blocks in (et6-arene)ruthenium-containing tungsten and molybdenum oxides

A series of molybdenum and tungsten organometallic oxides containing [Ru(arene)]2+ units (arene =p-cymene, C6Me6) was obtained by condensation of [[Ru(arene)Cl2]2] with oxomolybdates and oxotungstates in aqueous or nonaqueous solvents. The crystal structures of [[Ru(eta6-C6Me6]]4W4O16], [[Ru(eta6-p-MeC6H4iPr]]4W2O10], [[[Ru-(eta6-p-MeC6H4iPr)]2(mu-OH)3]2][[Ru(eta6-p-MeC6H4iPr)]2W8O28(OH)2[Ru(eta6-p-MeC6H4iPr)(H2O)]2], and [[Ru(eta6-C6Me6)]2M5O18[Ru(eta6-C6Me6)(H2O)]] (M = Mo, W) have been determined. While the windmill-type clusters [[Ru(eta6-arene)]4(MO3)4(mu3-O)4] (M = Mo, W; arene =p-MeC6H4iPr, C6Me6), the face-sharing double cubane-type cluster [[Ru(eta6-p-MeC6H4iPr)]4(WO2)2(mu3-O)4(mu4-O)2], and the dimeric cluster [[Ru(eta6-p-MeC6H4iPr)(WO3)3(mu3-O)3(mu3-OH)Ru(eta6-pMeC6H4iPr)(H2O)]2(mu-WO2)2]2- are based on cubane-like units, [(Ru(eta6-C6Me6)]2M5O18[Ru(eta6-C6Me6)(H2O)]] (M = Mo, W) are more properly described as lacunary Lindqvist-type polyoxoanions supporting three ruthenium centers. Precubane clusters [[Ru(eta6-arene)](MO3)2(mu-O)3(mu3-O)]6- are possible intermediates in the formation of these clusters. The cluster structures are retained in solution, except for [[Ru(eta6-p-MeC6H4iPr)]4Mo4O16], which isomerizes to the triple-cubane form.     

Synthesis, characterisation, crystal structures, reactivity, and electrochemistry of ruthenium-nitrido, ruthenium-cobalt-imido and ruthenapyrrolidone carbonyl clusters containing alkyne ligands

Thermolysis of [Ru3(CO)9(mu3-NOMe)(mu3-eta2-PhC2Ph)] (1) with two equivalents of [Cp*Co(CO)2] in THF afforded four new clusters, brown [Ru5(CO)8(mu-CO)3(eta5-C5Me5)(mu5-N)(mu4-eta2-PhC2Ph)] (2), green [Ru3Co2(CO)7(mu3-CO)(eta5-C5Me5)2(mu3-NH)[mu4-eta8-C6H4-C(H)C(Ph)]] (3), orange [Ru3(CO)7(mu-eta6-C5Me4CH2)[mu-eta3-PhC2(Ph)C(O)N(OMe)]] (4) and pale yellow [Ru2(CO)6[mu-eta3-PhC2(Ph)C(O)N(OMe)]] (5). Cluster 2 is a pentaruthenium mu5-nitrido complex, in which the five metal atoms are arranged in a novel "spiked" square-planar metal skeleton with a quadruply bridging alkyne ligand. The mu5-nitrido N atom exhibits an unusually low frequency chemical shift in its 15N NMR spectrum. Cluster 3 contains a triangular Ru2Co-imido moiety linked to a ruthenium-cobaltocene through the mu4-eta8-C6H4C(H)C(Ph) ligand. Clusters 4 and 5 are both metallapyrrolidone complexes, in which interaction of diphenylacetylene with CO and the NOMe nitrene moiety were observed. In 4, one methyl group of the Cp* ring is activated and interacts with a ruthenium atom. The "distorted" Ru3Co butterfly nitrido complex [Ru3Co(CO)5(eta5-C5Me5)(mu4-N)(mu3-eta2-PhC2Ph)(mu-I)2I] (6) was isolated from the reaction of 1 with [Cp*Co(CO)I2] heated under reflux in THF, in which a Ru-Ru wing edge is missing. Two bridging and one terminal iodides were found to be placed along the two Ru-Ru wing edges and at a hinge Ru atom, respectively. The redox properties of the selected compounds in this study were investigated by using cyclic voltammetry and controlled potential coulometry. 15N magnetic resonance spectroscopy studies were also performed on these clusters.     

Synthesis and reactivity of calix[4]arene-supported group 4 imido complexes

New mononuclear titanium and zirconium imido complexes [M(NR)(R'(2)calix)] [M=Ti, R'=Me, R=tBu (1), R=2,6-C(6)H(3)Me(2) (2), R=2,6-C(6)H(3)iPr(2) (3), R=2,4,6-C(6)H(2)Me(3) (4); M=Ti, R'=Bz, R=tBu (5), R=2,6-C(6)H(3)Me(2) (6), R=2,6-C(6)H(3)iPr(2) (7); M=Zr, R'=Me, R=2,6-C(6)H(3)iPr(2) (8)] supported by 1,3-diorganyl ether p-tert-butylcalix[4]arenes (R'(2)calix) were prepared in good yield from the readily available complexes [MCl(2)(Me(2)calix)], [Ti(NR)Cl(2)(py)(3)], and [Ti(NR)Cl(2)(NHMe(2))(2)]. The crystallographically characterised complex [Ti(NtBu)(Me(2)calix)] (1) reacts readily with CO(2), CS(2), and p-tolyl-isocyanate to give the isolated complexes [Ti[N(tBu)C(O)O](Me(2)calix)] (10), [[Ti(mu-O)(Me(2)calix)](2)] (11), [[Ti(mu-S)(Me(2)calix)](2)] (12), and [Ti[N(tBu)C(O)N(-4-C(6)H(4)Me)](Me(2)calix)] (13). In the case of CO(2) and CS(2), the addition of the heterocumulene to the Ti-N multiple bond is followed by a cycloreversion reaction to give the dinuclear complexes 11 and 12. The X-ray structure of 13.4(C(7)H(8)) clearly establishes the N,N'-coordination mode of the ureate ligand in this compound. Complex 1 undergoes tert-butyl/arylamine exchange reactions to form 2, 3, [Ti(N-4-C(6)H(4)Me)(Me(2)calix)] (14), [Ti(N-4-C(6)H(4)Fc)(Me(2)calix)] (15) [Fc=Fe(eta(5)-C(5)H(5))(eta(5)-C(5)H(4))], and [[Ti(Me(2)calix)](2)[mu-(N-4-C(6)H(4))(2)CH(2)]] (16). Reaction of 1 with H(2)O, H(2)S and HCl afforded the compounds [[Ti(mu-O)(Me(2)calix)](2)] (11), [[Ti(mu-S)(Me(2)calix)](2)] (12), and [TiCl(2)(Me(2)calix)] in excellent yields. Furthermore, treatment of 1 with two equivalents of phenols results in the formation of [Ti(O-4-C(6)H(4)R)(2)(Me(2)calix)] (R=Me 17 or tBu 18), [Ti(O-2,6-C(6)H(3)Me(2))(2)(Me(2)calix)] (19) and [Ti(mbmp)(Me(2)calix)] (20; H(2)mbmp=2,2'-methylene-bis(4-methyl-6-tert-butylphenol) or CH(2)([CH(3)][C(4)H(9)]C(6)H(2)-OH)(2)). The bis(phenolate) compounds 17 and 18 with para-substituted phenolate ligands undergo elimination and/or rearrangement reactions in the nonpolar solvents pentane or hexane. The metal-containing products of the elimination reactions are dinuclear complexes [[Ti(O-4-C(6)H(4)R)(Mecalix)](2)] [R=Me (23) or tBu (24)] where Mecalix=monomethyl ether of p-tert-butylcalix[4]arene. The products of the rearrangement reaction are [Ti(O-4-C(6)H(4)Me)(2) (paco-Me(2)calix)] (25) and [Ti(O-4-C(6)H(4)tBu)(2)(paco-Me(2)calix)] (26), in which the metallated calix[4]arene ligand is coordinated in a form reminiscent of the partial cone (paco) conformation of calix[4]arene. In these compounds, one of the methoxy groups is located inside the cavity of the calix[4]arene ligand. The complexes 24, 25 and 26 have been crystallographically characterised. Complexes with sterically more demanding phenolate ligands, namely 19 and 20 and the analogous zirconium complexes [Zr(O-4-C(6)H(4)Me)(2)(Me(2)calix)] (21) and [Zr(O-2,6-C(6)H(3)Me(2))(2)(Me(2)calix)] (22) do not rearrange. Density functional calculations for the model complexes [M(OC(6)H(5))(2)(Me(2)calix)] with the calixarene possessing either cone or partial cone conformations are briefly presented.     

Phosphato, chromato, and perrhenato complexes of titanium(IV) and zirconium(IV) containing Kläui's tripodal ligand

Treatment of titanyl sulfate in dilute sulfuric acid with 1 equiv of NaL(OEt) (L(OEt)(-) = [(eta(5)-C(5)H(5))Co{P(O)(OEt)(2)](3)](-)) in the presence of Na(3)PO(4) and Na(4)P(2)O(7) led to isolation of [(L(OEt)Ti)(3)(mu-O)(3)(mu(3-)PO(4))] (1) and [(L(OEt)Ti)(2)(mu-O)(mu-P(2)O(7))] (2), respectively. The structure of 1 consists of a Ti(3)O(3) core capped by a mu(3)-phosphato group. In 2, the [P(2)O(7)](4-) ligands binds to the two Ti's in a mu:eta(2),eta(2) fashion. Treatment of titanyl sulfate in dilute sulfuric acid with NaL(OEt) and 1.5 equiv of Na(2)Cr(2)O(7) gave [(L(OEt)Ti)(2)(mu-CrO(4))(3)] (3) that contains two L(OEt)Ti(3+) fragments bridged by three mu-CrO(4)(2-)-O,O' ligands. Complex 3 can act as a 6-electron oxidant and oxidize benzyl alcohol to give ca. 3 equiv of benzaldehyde. Treatment of [L(OEt)Ti(OTf)(3)] (OTf(-) = triflate) with [n-Bu(4)N][ReO(4)] afforded [[L(OEt)Ti(ReO(4))(2)](2)(mu-O)] (4). Treatment of [L(OEt)MF(3)] (M = Ti and Zr) with 3 equiv of [ReO(3)(OSiMe(3))] afforded [L(OEt)Ti(ReO(4))(3)] (5) and [L(OEt)Zr(ReO(4))(3)(H(2)O)] (6), respectively. Treatment of [L(OEt)MF(3)] with 2 equiv of [ReO(3)(OSiMe(3))] afforded [L(OEt)Ti(ReO(4))(2)F] (7) and [[L(OEt)Zr(ReO(4))(2)](2)(mu-F)(2)] (8), respectively, which reacted with Me(3)SiOTf to give [L(OEt)M(ReO(4))(2)(OTf)] (M = Ti (9), Zr (10)). Hydrolysis of [L(OEt)Zr(OTf)(3)] (11) with Na(2)WO(4).xH(2)O and wet CH(2)Cl(2) afforded the hydroxo-bridged complexes [[L(OEt)Zr(H(2)O)](3)(mu-OH)(3)(mu(3)-O)][OTf](4) (12) and [[L(OEt)Zr(H(2)O)(2)](2)(mu-OH)(2)][OTf](4) (13), respectively. The solid-state structures of 1-3, 6, and 11-13 have been established by X-ray crystallography. The L(OEt)Ti(IV) complexes can catalyze oxidation of methyl p-tolyl sulfide with tert-butyl hydroperoxide. The bimetallic Ti/ Re complexes 5 and 9 were found to be more active catalysts for the sulfide oxidation than other Ti(IV) complexes presumably because Re alkylperoxo species are involved as the reactive intermediates.     

1,1-ethylenedithiolato complexes of palladium(II) and platinum(II) with isocyanide and carbene ligands

The reactions of [Tl(2)[S(2)C=C[C(O)Me](2)]](n) with [MCl(2)(NCPh)(2)] and CNR (1:1:2) give complexes [M[eta(2)-S(2)C=C[C(O)Me](2)](CNR)(2)] [R = (t)Bu, M = Pd (1a), Pt (1b); R = C(6)H(3)Me(2)-2,6 (Xy), M = Pd (2a), Pt (2b)]. Compound 1b reacts with AgClO(4) (1:1) to give [[Pt(CN(t)Bu)(2)](2)Ag(2)[mu(2),eta(2)-(S,S')-[S(2)C=C[C(O)Me](2)](2)]](ClO(4))(2) (3). The reactions of 1 or 2 with diethylamine give mixed isocyanide carbene complexes [M[eta(2)-S(2)C=C[C(O)Me](2)](CNR)[C(NEt(2))(NHR)]] [R = (t)Bu, M = Pd (4a), Pt (4b); R = Xy, M = Pd (5a), Pt (5b)] regardless of the molar ratio of the reagents. The same complexes react with an excess of ammonia to give [M[eta(2)-(S,S')-S(2)C=C[C(O)Me](2)](CN(t)Bu)[C(NH(2))(NH(t)Bu)]] [M = Pd (6a), Pt (6b)] or [M[eta(2)-(S,S')-S(2)C=C[C(O)Me](2)][C(NH(2))(NHXy)](2)] [M = Pd (7a), Pt (7b)] probably depending on steric factors. The crystal structures of 2b, 4a, and 4b have been determined. Compounds 4a and 4b are isostructural. They all display distorted square planar metal environments and chelating planar E,Z-2,2-diacetyl-1,1-ethylenedithiolato ligands that coordinate through the sulfur atoms.     

Cubane-type heterometallic sulfido clusters: incorporation of two metal fragments into a dinuclear ReS(mu-S)2ReS core affording bimetallic M2Re2(mu 3-S)4 clusters (M = Ru,Pt, Cu) or trimetallic MM'Re2(mu 3-S)4 clusters via incomplete cubane-type MRe2(mu 3-S)(mu 2-S)3 intermediates (M = Ru,Rh, Ir; M' = Mo,W, Pd,Ru, Rh)

Reactions of a dirhenium tetra(sulfido) complex [PPh(4)](2)[ReS(L)(mu-S)(2)ReS(L)] (L = S(2)C(2)(SiMe(3))(2)) with a series of group 8-11 metal complexes in MeCN at room temperature afforded either the cubane-type clusters [M(2)(ReL)(2)(mu(3)-S)(4)] (M = CpRu (2), PtMe(3), Cu(PPh(3)) (4); Cp = eta(5)-C(5)Me(5)) or the incomplete cubane-type clusters [M(ReL)(2)(mu(3)-S)(mu(2)-S)(3)] (M = (eta(6)-C(6)HMe(5))Ru (5), CpRh (6), CpIr (7)), depending on the nature of the metal complexes added. It has also been disclosed that the latter incomplete cubane-type clusters can serve as the good precursors to the trimetallic cubane-type clusters still poorly precedented. Thus, treatment of 5-7 with a range of metal complexes in THF at room temperature resulted in the formation of novel trimetallic cubane-type clusters, including the neutral clusters [[(eta(6)-C(6)HMe(5))Ru][W(CO)(3)](ReL)(2)(mu(3)-S)(4)], [(CpM)[W(CO)(3)](ReL)(2)(mu(3)-S)(4)] (M = Rh, Ir), [(Cp*Ir)[Mo(CO)(3)](ReL)(2)(mu(3)-S)(4)], [[(eta(6)-C(6)HMe(5))Ru][Pd(PPh(3))](ReL)(2)(mu(3)-S)(4)], and [(Cp*Ir)[Pd(PPh(3))](ReL)(2)(mu(3)-S)(4)] (13) along with the cationic clusters [(Cp*Ir)(CpRu)(ReL)(2)(mu(3)-S)(4)][PF(6)] (14) and [(Cp*Ir)[Rh(cod)](ReL)(2)(mu(3)-S)(4)][PF(6)] (cod = 1,5-cyclooctadiene). The X-ray analyses have been carried out for 2, 4, 7, 13, and the SbF(6) analogue of 14 (14') to confirm their bimetallic cubane-type, bimetallic incomplete cubane-type, or trimetallic cubane-type structures. Fluxional behavior of the incomplete cubane-type and trimetallic cubane-type clusters in solutions has been demonstrated by the variable-temperature (1)H NMR studies, which is ascribable to both the metal-metal bond migration in the cluster cores and the pseudorotation of the dithiolene ligand bonded to the square pyramidal Re centers, where the temperatures at which these processes proceed have been found to depend upon the nature of the metal centers included in the cluster cores.     

Does dinitrogen hydrogenation follow different mechanisms for [(eta5-C5Me4H)2Zr]2(mu2,eta2,eta2-N2) and {[PhP(CH2SiMe2NSiMe2CH2)PPh]Zr}2(mu2,eta2,eta2-N2) complexes? A computational study

The mechanisms of dinitrogen hydrogenation by two different complexes--[(eta(5)-C(5)Me(4)H)(2)Zr](2)(mu(2),eta(2),eta(2)-N(2)), synthesized by Chirik and co-workers [Nature 2004, 427, 527], and {[P(2)N(2)]Zr}(2)(mu(2),eta(2),eta(2)-N(2)), where P(2)N(2) = PhP(CH(2)SiMe(2)NSiMe(2)CH(2))(2)PPh, synthesized by Fryzuk and co-workers [Science 1997, 275, 1445]--are compared with density functional theory calculations. The former complex is experimentally known to be capable of adding more than one H(2) molecule to the side-on coordinated N(2) molecule, while the latter does not add more than one H(2). We have shown that the observed difference in the reactivity of these dizirconium complexes is caused by the fact that the former ligand environment is more rigid than the latter. As a result, the addition of the first H(2) molecule leads to two different products: a non-H-bridged intermediate for the Chirik-type complex and a H-bridged intermediate for the Fryzuk-type complex. The non-H-bridged intermediate requires a smaller energy barrier for the second H(2) addition than the H-bridged intermediate. We have also examined the effect of different numbers of methyl substituents in [(eta(5)-C(5)Me(n)H(5)(-)(n))(2)Zr](2)(mu(2),eta(2),eta(2)-N(2)) for n = 0, 4, and 5 (n = 5 is hypothetical) and [(eta(5)-C(5)H(2)-1,2,4-Me(3))(eta(5)-C(5)Me(5))(2)Zr](2)(mu(2),eta(2),eta(2)-N(2)) and have shown that all complexes of this type would follow a similar H(2) addition mechanism. We have also performed an extensive analysis on the factors (side-on coordination of N(2) to two Zr centers, availability of the frontier orbitals with appropriate symmetry, and inflexibility of the catalyst ligand environment) that are required for successful hydrogenation of the coordinated dinitrogen.     

Construction of titanasiloxanes by incorporation of silanols to the metal oxide model [(Ti(eta 5-C5Me5)(mu-O))3(mu3-CR)]: DFT elucidation of the reaction mechanism

A family of novel titanasiloxanes containing the structural unit {[Ti(eta(5)-C(5)Me(5))O](3)} were synthesized by hydron-transfer processes involving reactions with equimolecular amounts of mu(3)-alkylidyne derivatives [{Ti(eta(5)-C(5)Me(5))(mu-O)}(3)(mu(3)-CR)] (R=H (1), Me (2)) and monosilanols, R(3)'Si(OH), silanediols, R(2)'Si(OH)(2), and the silanetriol tBuSi(OH)(3). Treatment of 1 and 2 with triorganosilanols (R'=Ph, iPr) in hexane affords the new metallasiloxane derivatives [{Ti(eta(5)-C(5)Me(5))(mu-O)}(3)(mu-CHR)(OSiR(3)')] (R=H, R'=Ph (3), iPr (4); R=Me, R'=Ph (5), iPr (6)). Analogous reactions with silanediols, (R'=Ph, iPr), give the cyclic titanasiloxanes [{Ti(eta(5)-C(5)Me(5))(mu-O)}(3)(mu-O(2)SiR'(2))(R)] (R=Me, R'=Ph (7), iPr (8); R=Et, R'=Ph (9), iPr (10)). Utilization of tBuSi(OH)(3) with 1 or 2 at room temperature produces the intermediate complexes [{Ti(eta(5)-C(5)Me(5)) (mu-O)}(3)(mu-O(2)Si(OH)tBu)(R)] (R=Me (11), Et(12)). Further heating of solutions of 11 or 12 affords the same compound with an adamantanoid structure, [{Ti(eta(5)-C(5)Me(5))(mu-O)}(3)(mu-O(3)SitBu)] (13) and methane or ethane elimination, respectively. The X-ray crystal structures of 3, 4, 6, 8, 10, 12, and 13 have been determined. To gain an insight into the mechanism of these reactions, DFT calculations have been performed on the incorporation of monosilanols to the model complex [{Ti(eta(5)-C(5)H(5))(mu-O)}(3)(mu(3)-CMe)] (2 H). The proposed mechanism consists of three steps: 1) hydron transfer from the silanol to one of the oxygen atoms of the Ti(3)O(3) ring, forming a titanasiloxane; 2) intramolecular hydron migration to the alkylidyne moiety; and 3) a mu-alkylidene ligand rotation to give the final product.     

The preparation and characterisation of hetero- and homobimetallic complexes containing bridging naphthalene-1,8-dithiolato ligands

Homo- and heterobimetallic complexes of the form [(PPh(3))(2)(mu(2)-1,8-S(2)-nap){ML(n)}] (in which (1,8-S(2)-nap)=naphtho-1,8-dithiolate and {ML(n)}={PtCl(2)} (1), {PtClMe} (2), {PtClPh} (3), {PtMe(2)} (4), {PtIMe(3)} (5) and {Mo(CO)(4)} (6)) were obtained by the addition of [PtCl(2)(NCPh)(2)], [PtClMe(cod)] (cod=1,5-cyclooctadiene), [PtClPh(cod)], [PtMe(2)(cod)], [{PtIMe(3)}(4)] and [Mo(CO)(4)(nbd)] (nbd=norbornadiene), respectively, to [Pt(PPh(3))(2)(1,8-S(2)-nap)]. Synthesis of cationic complexes was achieved by the addition of one or two equivalents of a halide abstractor, Ag[BF(4)] or Ag[ClO(4)], to [{Pt(mu-Cl)(mu-eta(2):eta(1)-C(3)H(5))}(4)], [{Pd(mu-Cl)(eta(3)-C(3)H(5))}(2)], [{IrCl(mu-Cl)(eta(5)-C(5)Me(5))}(2)] (in which C(5)Me(5)=Cp*=1,2,3,4,5-pentamethylcyclopentadienyl), [{RhCl(mu-Cl)(eta(5)-C(5)Me(5))}(2)], [PtCl(2)(PMe(2)Ph)(2)] and [{Rh(mu-Cl)(cod)}(2)] to give the appropriate coordinatively unsaturated species that, upon treatment with [(PPh(3))(2)Pt(1,8-S(2)-nap)], gave complexes of the form [(PPh(3))(2)(mu(2)-1,8-S(2)-nap){ML(n)}][X] (in which {ML(n)}[X]={Pt(eta(3)-C(3)H(5))}[ClO(4)] (7), {Pd(eta(3)-C(3)H(5))}[ClO(4)] (8), {IrCl(eta(5)-C(5)Me(5))}[ClO(4)] (9), {RhCl(eta(5)-C(5)Me(5))}[BF(4)] (10), {Pt(PMe(2)Ph)(2)}[ClO(4)](2) (11), {Rh(cod)}[ClO(4)] (12); the carbonyl complex {Rh(CO)(2)}[ClO(4)] (13) was formed by bubbling gaseous CO through a solution of 12. In all cases the naphtho-1,8-dithiolate ligand acts as a bridge between two metal centres to give a four-membered PtMS(2) ring (M=transition metal). All compounds were characterised spectroscopically. The X-ray structures of 5, 6, 7, 8, 10 and 12 reveal a binuclear PtMS(2) core with PtM distances ranging from 2.9630(8)-3.438(1) A for 8 and 5, respectively. The napS(2) mean plane is tilted with respect to the PtP(2)S(2) coordination plane, with dihedral angles in the range 49.7-76.1 degrees and the degree of tilting being related to the PtM distance and the coordination number of M. The sum of the Pt(1)coordination plane/napS(2) angle, a, and the Pt(1)coordination plane/M(2)coordination plane angle, b, a+b, is close to 120 degrees in nearly all cases. This suggests that electronic effects play a significant role in these binuclear systems.