Synthesis, structural characterization, reactivity, and thermal stability of [eta(5):sigma-Me2C(C5H4)(C2B10H10)]Ti(R)(NMe2)

Reaction of [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]TiCl(NMe2) (1) with 1 equiv of PhCH2K, MeMgBr, or Me3SiCH2Li gave corresponding organotitanium alkyl complexes [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti(R)(NMe2) (R = CH2Ph (2), CH2SiMe3 (4), or Me (5)) in good yields. Treatment of 1 with 1 equiv of n-BuLi afforded the decomposition product {[eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti}2(mu-NMe)(mu:sigma-CH2NMe) (3). Complex 5 slowly decomposed to generate a mixed-valence dinuclear species {[eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti}2(mu-NMe2)(mu:sigma-CH2NMe) (6). Complex 1 reacted with 1 equiv of PhNCO or 2,6-Me2C6H3NC to afford the corresponding monoinsertion product [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti(Cl)[eta(2)-OC(NMe2)NPh] (7) or [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti(Cl)[eta(2)-C(NMe2)=N(2,6-Me2C6H3)] (8). Reaction of 4 or 5 with 1 equiv of R'NC gave the titanium eta(2)-iminoacyl complexes [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti(NMe2)[eta(2)-C(R)=N(R')] (R = CH2SiMe3, R' = 2,6-Me2C6H3 (9) or tBu (10); R = Me, R' = 2,6-Me2C6H3 (11) or tBu (12)). The results indicated that the unsaturated molecules inserted into the Ti-N bond only in the absence of the Ti-C(alkyl) bond and that the Ti-C(cage) bond remained intact. All complexes were fully characterized by various spectroscopic techniques and elemental analyses. Molecular structures of 2, 3, 6-8, and 10-12 were further confirmed by single-crystal X-ray analyses.     

Synthesis and structure of boron-bridged constrained geometry complexes of titanium

The boron-bridged constrained geometry titanium complexes [Ti[eta5:eta1-(C5H4)B(NR2)NPh](NMe2)2][R = iPr (3), SiMe3(4)] and [Ti[eta5:eta1-(C9H6)B(NiPr2)NPh](NMe2)2](12) have been prepared in good yields by amine elimination reaction from [Ti(NMe2)4]. Subsequent deamination-chlorination with excess Me3SiCl yielded the corresponding dichloro-complexes (5, 6, 13). Reaction of the analogous ligand precursors (C5H5)B(NiPr2)N(H)R (R = Cy, tBu) with [Ti(NMe2)4] did not result in the expected bridged compounds, but rather in the half-sandwich complexes [Ti[(eta5-C5H4)B(NiPr2)N(H)R](NMe2)3][R = Cy (9), tBu (10)]. All compounds were fully characterised by means of multinuclear NMR spectroscopy. Thorough investigation of substituent effects was achieved by comparative X-ray diffraction studies on complexes 3, 5, 6 and 12.     

Dicarbollylamine ligand as a tunable template for sigma,sigma- and pi,sigma-bonding modes: syntheses, structures, and theoretical studies of eta5:eta1-coordinated constrained-geometry group 13 metal complexes

A series of group 13 main group complexes with pi,sigma-type bonding interaction of the formula [{(eta (5)-RC 2B 9H 9)(CH 2)(eta (1)-NMe 2)}MMe] (M = Al, R = H 5, Me 6; Ga, R = H 7, Me 8; In, R = H 9, Me 10) was produced by the reaction of group 13 metal alkyls (MMe 3; M = Al, Ga, In) with the dicarbollylamine ligands, nido-8-R-7,8-C 2B 9H 10-7-(CH 2)NHMe 2 (R = H 1, Me 2). The reactions of 1 and 2 with AlMe 3 in toluene initially afforded tetra-coordinated aluminum complexes with sigma,sigma-type bonding interaction, [{(eta (1)-RC 2B 9H 10)(CH 2)(eta (1)-NMe 2)}AlMe 2] (R = H 3, Me 4), which readily underwent further methane elimination to yield the corresponding constrained geometry complexes (CGCs, 5 and 6) of aluminum with pi,sigma-bonding interaction. However, the reactions between 1 and 2 and MMe 3 (M = Ga, In) in toluene produced gallium and indium pi,sigma-CGCs of 7 and 10 directly, not proceeding through sigma,sigma-intermediates. The structures of group 13 metal CGCs were established by X-ray diffraction studies of 5, 6, and 8, which authenticated a characteristic eta (5):eta (1)-coordination mode of the dicarbollylamino ligand to the group 13 metals. A similar pi,sigma-bonding interaction was also established in ethylene-bridged dicarbollylethylamine series. Thus, aluminum pi,sigma-CGCs of dicarbollylethylamine, [{(eta (5)-RC 2B 9H 9)(CH 2) 2(eta (1)-NBz 2)}AlMe] (R = H 17, Me 18), were prepared by the trans-metalation of the [{(eta (5)-RC 2B 9H 9)(CH 2) 2(eta (1)-NBz 2)}Ti(NMe 2) 2] (R = H 15, Me 16) with AlMe 3. However, only sigma,sigma-bonded complexes of the formula [{(eta (1)-RC 2B 9H 9)(CH 2) 2(eta (1)-NBz 2)}AlMe 2] (R = H 13, Me 14) were isolated by the reaction between [ nido-7-8-R-7,8-C 2B 9H 10-(CH 2) 2HNBz 2] (R = H 11, Me 12) and AlMe 3. When methane-elimination reactions between metal alkyls and dicarbollylamines were carried out with either the gallium atom or monobenzyl aminoethyl tethered ligands, [ nido-7-H 2NBz(CH 2) 2-8-R-7,8-C 2B 9H 10] (R = H 21, Me 22), desired pi,sigma-CGCs, [{(eta (5)-RC 2B 9H 9)(CH 2) 2(eta (1)-NBz 2)}GaMe] (R = H 19, Me 20) or [{(eta (5)-RC 2B 9H 9)(CH 2) 2(eta (1)-NHBz)}AlMe] (R = H 23, Me 24), were generated, respectively. DFT calculation on 5 provides evidence of existence of pi,sigma-bonding of dicarbollylamine ligand to the aluminum atom: pi-bonding interaction of a dicarbollyl unit becomes intensified in the presence of a weak sigma-bonding amine-tethered group. Furthermore, preference for the formation of pi,sigma-bonding was predicted by optimizing a reaction profile including sigma,sigma- and pi,sigma-structures as well as transition state structures for each methylene- and ethylene-spaced ligand system, 3-5 and 14- 18, to reveal that pi,sigma-bonding interaction is more favorable in the case of a methylene-tethered ligand system.     

Synthesis, structure, and reactivity of Group 4 metallacycles incorporating a Me2C-linked cyclopentadienyl-carboranyl ligand

Group 4 metallacycles [eta5:sigma-Me2C(C5H4)(C2B10H10)]Ti[eta2-N(Me)CH2CH2N(Me)] (1a), [eta5:sigma-Me2C(C5H4)(C2B10H10)]Zr[eta2-N(Me)CH2CH2N(Me)](HNMe2) (1b) and [eta5:sigma-Me2C(C5H4)(C2B10H10)]M[eta2-N(Me)CH2CH2CH2N(Me)] (M = Ti (2a), Zr (2b), Hf (2c)) were synthesized by reaction of [eta5:sigma-Me2C(C5H4)(C2B10H10)]M(NMe2)(2) (M = Ti, Zr, Hf) with MeNH(CH2)(n)NHMe (n = 2, 3). These metal complexes reacted with unsaturated molecules such as 2,6-Me2C6H3NC, PhNCO and PhCN to give exclusively M-N bond insertion products. The M-C(cage) bond remained intact. Such a preference of M-N over M-C(cage) insertion is suggested to most likely be governed by steric factors, and the mobility of the migratory groups plays no obvious role in the reactions. This work also shows that the insertion of unsaturated molecules into the metallacycles is a useful and effective method for the construction of very large ring systems.     

Silver as an exopolyhedral auxiliary to the rhenacarborane anion [Re(CO)3(eta5-7,8-C2B9H11)]-

The rhenacarborane salt Cs[Re(CO)3(eta5-7,8-C2B9H11)] (1) has been used to synthesize the tetranuclear metal complex [[ReAg(mu-10-H-eta5-7,8-C2B9H10)(CO)3]2[mu-Ph2P(CH2)2PPh2]] (3) where two [ReAg(mu-10-H-eta5-7,8-C2B9H10)(CO)3] fragments have been shown by X-ray crystallography to be bridged by a single 1,2-bis(diphenylphosphino)ethane ligand. Reaction of 1 with Ag[BF4] in the presence of the ligands bis- or tris(pyrazol-1-yl)methane yields the complexes [ReAg(mu-10-H-eta5-7,8-C2B9H10)(CO)3[kappa2-CH2(C3H3N2-1)2]] (4) or [[ReAg(mu-10-H-eta5-7,8-C2B9H10)(CO)3]2[mu-kappa1,kappa2-CH(C3H3N2-1)3]] (5), respectively. From X-ray studies, the former comprises a Re-Ag bond bridged by the carborane cage and with the bis(pyrazol-1-yl)methane coordinating the silver(I) center in an asymmetric kappa(2) mode. Complex 5 was unexpectedly found to contain a tris(pyrazol-1-yl)methane bridging two [ReAg(mu-10-H-eta5-7,8-C2B9H10)(CO)3] fragments in a kappa1,kappa2 manner. Treatment of 1 with Ag[BF4] in the presence of 2,2'-dipyridyl and 2,2':6',2' '-terpyridyl yields [ReAg(mu-10-H-eta5-7,8-C2B9H10)(CO)3[kappa2-(C5H4N-2)(2)]] (6) and [ReAg(mu-10-H-eta5-7,8-C2B9H10)(CO)3[kappa3-C5H3N(C5H4N-2)2-2,6]] (7). The X-ray structure determination of 7 revealed an unusual pentacoordinated silver(I) center, asymmetrically ligated by a kappa3-2,2':6',2' '-terpyridyl molecule. The same synthetic procedure using N,N,N',N'-tetramethylethylenediamine gave a tetranuclear metal complex [[ReAg(mu-10-H-eta5-7,8-C2B9H10)(CO)3]2[mu-Me2N(CH2)2NMe2]2] (8) which is believed, in the solid state, to be bridged between the silver atoms by two of the diamine molecules. The salt 1 with Ag[BF4] in the absence of any added ligand gave the tetrameric cluster [ReAg[mu-5,6,10-(H)3-eta5-7,8-C2B9H8](CO)3]4 (9) where, in the solid state, four [ReAg(mu-10-H-eta5-7,8-C2B9H10)(CO)3] units are held together by long interunit B-H right harpoon-up Ag bonds.     

Mild mono and double demethylation in dimethylsulfonium substituted ruthenacarborane complexes. A regioselective reaction

Reaction of [RuCl(2)(eta(6)-C(6)H(6))](2) with [10-(CH(3))(2)S-7,8-nido-C(2)B(9)H(10)](-) or [9-(CH(3))(2)S-7,8-nido-C(2)B(9)H(10)](-) afforded the expected cationic complexes [Ru(eta(5)-n-(CH(3))(2)S-7,8-C(2)B(9)H(10))(eta(6)-C(6)H(6))](+)(n= 10, (1); 9, (3)), but also the unexpected neutral Ru(eta(5)-10-HS-7,8-C(2)B(9)H(10))(eta(6)-C(6)H(6))(2) or Ru(eta(5)-9-(CH(3))S-7,8-C(2)B(9)H(10))(eta(6)-C(6)H(6))(4) by double and mono demethylation of the (CH(3))(2)S moiety, respectively.     

Insertion, reduction, and carbon-carbon coupling induced by monomeric aluminum hydride compounds bearing substituted pyrrolyl ligands

A monomeric aluminum hydride complex bearing substituted pyrrolyl ligands, AlH[C(4)H(3)N(CH(2)NMe(2))-2](2) (1), was synthesized and structurally characterized. To further confirm the presence of Al--H bonds, the compound AlD[C(4)H(3)N(CH(2)NMe(2))-2](2) ([D]1) was synthesized by reacting LiAlD(4) with [C(4)H(4)N(CH(2)NMe(2))-2]. Compound 1 and [D]1 react with phenyl isothiocyanate yielding Al[C(4)H(3)N(CH(2)NMe(2))-2](2)[eta(3)-SCHNPh] (2) and Al[C(4)H(3)N(CH(2)NMe(2))-2](2)[eta(3)-SCDNPh] ([D]2) by insertion. The reactions of 1 with 9-fluorenone and benzophenone generated the unusual aluminum alkoxide complexes 3 and 4, respectively, through intramolecular proton abstraction and C-C coupling. A mechanistic study shows that 9-fluorenone coordinates to [D]1 and releases one equivalent of HD followed by C-C coupling and hydride transfer to yield the final product. Reduction of benzil with 1 affords aluminum enediolate complex 5 in moderate yield. Mechanistic studies also showed that the benzil was inserted into the aluminum hydride bond of [D]1 through hydroalumination followed by proton transfer to generate the final product [D]5. All new complexes have been characterized by (1)H and (13)C NMR spectroscopy and X-ray crystallography.     

Sequential protonation and methylation of a hydride-osmium complex containing a cyclopentadienyl ligand with a pendant amine group

Complex OsH{eta5-C5H4(CH2)2NMe2}(P(i)Pr3)2 (1) reacts with 1 equiv of trifluoromethanesulfonic acid (HOTf) and trifluoromethanesulfonic acid-d1 (DOTf) to produce the dihydride and hydride-deuteride complexes, [OsHE{eta5-C5H4(CH2)2NMe2}(P(i)Pr3)2]OTf (E = H (2), D (2-d1), respectively. Treatment of 2 and 2-d1 with a second equivalent of HOTf gives [OsHE{eta5-C5H4(CH2)2NHMe2}(P(i)Pr3)2][OTf]2 (E = H (3), D (3-d1) as a result of the protonation of the nitrogen atom. While the hydride and deuteride ligands of 2, 2-d1, 3, and 3-d1 do not undergo any H/D exchange process with the solvent, in acetone-d6, the NH proton of 3 and 3-d1 changes places with a deuterium atom of the solvent to yield [OsHE{eta5-C5H4(CH2)2NDMe2}(P(i)Pr3)2][OTf]2 (E = H (3-Nd1), D (3-d2)). Complex 3-Nd1 can also be obtained from the treatment of complex 2 with DOTf in dichloromethane. No exchange process between the hydride and the ND positions in 3-Nd1 or between the deuteride and NH positions in 3-d1 has been observed. Treatment of 3-Nd1 and 3-d1 with sodium methoxide results in a selective reaction of the base with the ammonium group to regenerate 2 and 2-d1, respectively. Complex 1 also reacts with methyl and methyl-d3 trifluoromethanesulfonate (CH3OTf and CD3OTf, respectively) to give [OsH{eta5-C5H4(CH2)2NMe2CE3}(P(i)Pr3)2]OTf (E = H (4), D (4-d3)) as a result of the addition of the CE3 (E = H, D) group to the nitrogen atom. Complex 4 has been characterized by an X-ray diffraction analysis. It reacts with a second molecule of CH3OTf or CD3OTf to produce [OsH{eta5-C5H4(CH2)2NMe3}{CH2CH(CH3)P(i)P2}(P(i)Pr3)[OTf]2 (5). Similarly, complex 4-d3 reacts with a second molecule of CH3OTf or CD3OTf to yield [OsH{eta5-C5H4(CH2)2NMe2CD3}{CH2CH(CH3)P(i)P2}(P(i)Pr3)[OTf]2 (5-d3). In acetonitrile, complex 5 evolves to an equilibrium mixture of the acetonitrile adducts [Os{eta5-C5H4(CH2)2NMe3}(NCCH3)(P(i)Pr3)2][OTf]2 (7) and [Os{eta5-C5H4(CH2)2NMe3}(NCCH3)2(P(i)Pr3)][OTf]2 (8). In methanol or methanol-d4, complex 4 is not stable and loses trimethylamine to give the vinylcyclopentadienyl derivatives [OsHE(eta5-C5H4CH=CH2)(P(i)Pr3)2]OTf (E = H (9), D (9-d1)) as a result of the protonation or deuteration of the metallic center and a subsequent Hofmann elimination. Protonation of 4 with HOTf gives the dihydride-trimethylammonium derivative [OsH2{eta5-C5H4(CH2)2NMe3}(P(i)Pr3)2][OTf]2 (10). Treatment of 9 with sodium methoxide produces OsH(eta5-C5H4CH=CH2)(P(i)Pr3)2 (11).     

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.     

Solution structures and dynamic properties of chelated d(0) metal olefin complexes [eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]Ti(OCMe(2)CH(2)CH(2)CH=CH(2))(+) (R = H, Me): Models for the [eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]Ti(R')(olefin)(+) intermediates in "constrained geometry" catalysts.

To model the Ti-olefin interaction in the putative [eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]Ti(R')(olefin)(+) intermediates in "constrained geometry" Ti-catalyzed olefin polymerization, chelated alkoxide olefin complexes [eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]Ti(OCMe(2)CH(2)CH(2)CH=CH(2))(+) have been investigated. The reaction of [eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]TiMe(2) (1a,b; R = H, Me) with HOCMe(2)CH(2)CH(2)CH=CH(2) yields mixtures of [eta(5)-C(5)R(4)SiMe(2)NH(t)Bu]TiMe(2)(OCMe(2)CH(2)CH(2)CH=CH(2)) (2a,b) and [eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]TiMe(OCMe(2)CH(2)CH(2)CH=CH(2)) (3a,b). The reaction of 2a/3a and 2b/3b mixtures with B(C(6)F(5))(3) yields the chelated olefin complexes [[eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]Ti(OCMe(2)CH(2)CH(2)CH=CH(2))][MeB(C(6)F(5))(3)] (4a,b; 71 and 89% NMR yield). The reaction of 2b/3b with [Ph(3)C][B(C(6)F(5))(4)] yields [[eta(5): eta(1)-C(5)Me(4)SiMe(2)N(t)Bu]Ti(OCMe(2)CH(2)CH(2)CH=CH(2))][B(C(6)F(5))(4)] (5b, 88% NMR yield). NMR studies establish that 4a,b and 5b exist as mixtures of diastereomers (isomer ratios: 4a/4a', 62/38; 4b/4b', 75/25; 5b/5b', 75/25), which differ in the enantioface of the olefin that is coordinated. NMR data for these d(0) metal olefin complexes show that the olefin coordinates to Ti in an unsymmetrical fashion primarily through C(term) such that the C=C pi bond is polarized with positive charge buildup on C(int). Dynamic NMR studies show that 4b/4b' undergoes olefin face exchange by a dissociative mechanism which is accompanied by fast inversion of configuration at Ti ("O-shift") in the olefin-dissociated intermediate. The activation parameters for the conversion of 4b to 4b' (i.e., 4b/4b' face exchange) are: DeltaH = 17.2(8) kcal/mol; DeltaS = 8(1) eu. 4a/4a' also undergoes olefin face exchange but with a lower barrier (DeltaH = 12.2(9) kcal/mol; DeltaS = -2(3) eu), for the conversion of 4a to 4a'.     

Reduction of bis

The reduction of symmetric, fully-substituted titanocene dichlorides bearing two pendant omega-alkenyl groups, [TiCl2(eta5-C5Me4R)2], R = CH(Me)CH= CH2 (1a). (CH2)2CH=CH2 (1b) and (CH2)3CH=CH2 (1c), by magnesium in tetrahydrofuran affords bis(cyclopentadienyl)titanacyclopentanes [Ti(IV)[eta1:eta1: eta5:eta5-C5Me4CH(Me)CH(Ti)CH2CH(CH2(Ti))CH(Me)C5Me4]] (2a), [Ti(IV)[eta1:eta1:eta5: eta5-C5Me4(CH2)2CH(Ti)(CH2)2CH(Ti)(CH2)2C5Me4]] (2b) and [Ti(IV)[eta1:eta1:eta5:eta5-C5Me4(CH2)2CH(Ti)CH(Me)CH(Me)CH(Ti)(CH2)2C5Me4]](2c), respectively, as the products of oxidative coupling of the double bonds across a titanocene intermediate. For the case of complex 1c, a product of a double bond isomerisation is obtained owing to a preferred formation of five-membered titanacycles. The reaction of the titanacyclopentanes with PbCl2 recovers starting materials 1a from 2a and 1b from 2b, but complex 2c affords, under the same conditions, an isomer of 1c with a shifted carbon - carbon double bond, [TiCl[eta5-C5Me4(CH2CH2CH=CHMe)]2] (1c'). The titanacycles 2a-c can be opened by HCl to give ansa-titanocene dichlorides ansa-[[eta5:eta5-C5Me4CH(Me)CH2CH2CH(Me)CH(Me)C5Me4]TiCl2] (3a), ansa-[[eta5:eta5-C5Me4(CH2)8C5Me4]TiCl2] (3b), along with a minor product ansa-[[eta5:eta5-C5Me4CH2CH=CH(CH2)5C5Me4]TiCl2] (3b'), and ansa-[[eta5:eta5-CsMe4(CH2)3CH(Me)CH(Me)CH=CHCH2C5Me4]TiCl2] (3c), respectively, with the bridging aliphatic chain consisting of five (3a) and eight (3b, 3b' and 3c) carbon atoms. The course of the acidolysis changes with the nature of the pendant group; while the cyclopentadienyl ring-linking carbon chains in 3a and 3b are fully saturated, compounds 3c and 3b' contain one asymetrically placed carbon-carbon double bond, which evidently arises from the beta-hydrogen elimination that follows the HCl addition.     

2-Aminopyrrolines: new chiral amidinate ligands with a rigid well-defined molecular structure and their coordination to Ti(IV)

The use of an amino-oxazolinate (NN(ox) = kappa2-2,6-dimethylphenylamido-4(S)-isopropyloxazoline) as a chiral analogue to amidinate ligands in the chemistry of titanium was found to lead to undesired side reactions. The reaction of 2,6-dimethylphenylamido-4(S)-isopropyloxazoline with [Ti(NMe2)4] afforded the bis(amidinato) complex [Ti(NN(ox))2(NMe2)2] (2) which was thermally converted to the ring-opened decomposition products [Ti(NN(ox)){kappa3-N(2,6-C6H3Me2)C(NMe2)NC(iPr)CH2O}(NMe2)] (3) and [Ti{kappa3-N(2,6-C6H3Me2)C(NMe2)-NC(iPr)CH2O}2] (4). The NMR spectra of 4 recorded at low temperature displayed two sets of resonances corresponding to two symmetric isomers in a 2:5 ratio, the probable geometries of which were established by ONIOM (QM/MM) simulations. To suppress ring opening of the oxazolines, their oxygen atom was formally replaced by a CH2 group in the synthesis of a series of amino-pyrroline protioligands 2-RN(H)(5-C4H5NR') (HN(R)N(R')). Their reaction with [Ti(NMe2)4] gave the thermally stable complexes [Ti(N(R)N(R'))2(NMe2)2], of which three derivatives were characterized by X-ray diffraction. They are stereochemically dynamic and undergo reversible ligand rearrangements in solution, for which the activation parameters were determined by variable-temperature (1)H NMR spectroscopy.     

Organometallic building blocks with amino-substituted cyclopentadienyl and boratabenzene ligands for the synthesis of heterometallic complexes and clusters

A comparative study of the reactivity of isolobal rhenium and molybdenum carbonylmetallates containing a borole, in [Re(eta5-C4H4BPh)(CO)3]- (2), a boratanaphthalene, in [Mo(eta5-2,4-MeC9H6BMe)(CO)3]- (4a) and [Mo(eta5-2,4-MeC9H6BNi-Pr2)(CO)3]- (4b), a boratabenzene, in [Mo(eta5-3,5-Me2C5H3BNi-Pr2)(CO)3]- (6) or a dimethylaminocyclopentadienyl ligand, in [Mo(eta5-C5H4NMe2)(CO)3]- (7), toward palladium(II), gold(I), mercury(II) and platinum(II) complexes has allowed an evaluation of the role of these pi-bonded ligands on the structures and unprecedented coordination modes observed in the resulting metal-metal bonded, heterometallic complexes. The new metallate 6 was reacted with [AuCl(PPh3)], and with 1 or 2 equiv. HgCl2, which afforded the new heterodinuclear complexes [Au{Mo(eta5-3,5-Me2C5H3BNi-Pr2)(CO)3}(PPh3)] (Mo-Au) (10) and [Hg{Mo(eta5-3,5-Me2C5H3BNi-Pr2)(CO)3}Cl] (Hg-Mo) (11) and the heterometallic chain complex [Hg{Mo(eta5-3,5-Me2C5H3BNi-Pr2)(CO)3}2] (Mo-Hg-Mo) (12), respectively. Reactions of the new metallate 7 with HgCl2, trans-[PtCl2(CNt-Bu)2] and trans-[PtCl2(NCPh)2] yielded the heterodinuclear complex [Hg{Mo(eta5-C5H4NMe2)(CO)3}Cl] (Mo-Hg) (15), the heterotrinuclear chain complexes trans-[Pt{Mo(eta5-C5H4NMe2)(CO)3}2(CNt-Bu)2] (Mo-Pt-Mo) (16) and trans-[Pt{Mo(eta5-C5H4NMe2)(CO)3}2(NCPh)2] (Mo-Pt-Mo) (17), the mononuclear complex [Mo(eta5-C5H4NMe2)(CO)3Cl] (18), the lozenge-type cluster [Mo2Pt2(eta5-C5H4NMe2)2(CO)8] (19) and the heterodinuclear complex [[upper bond 1 start]Pt{Mo(eta5-C5H4N[upper bond 1 end]Me2)(CO)3}(NCPh)Cl](Mo-Pt) (20), respectively. The complexes 11, 16, 17.2THF, 18 and 20 have been structurally characterized by X-ray diffraction and 20 differs from all other compounds in that the dimethylaminocyclopentadienyl ligand forms a bridge between the metals.     

Reactions of tris(amino)phosphines with arylsulfonyl azides: product dependency on tris(amino)phosphine structure

The Staudinger reaction of N(CH2CH2NR)3P [R = Me (1), Pr (2)] with 1 equiv of N3SO2C6H4Me-4 gave the ionic phosphazides [N(CH2CH2NR)3PN][SO2C6H4Me-4] [R = Me (3), R = Pr (5a)], and the same reaction of 2 with N3SO2C6H2Me3-2,4,6 gave the corresponding aryl sulfinite 5b. On the other hand, the reaction of 1 with 0.5 equiv of N3SO2Ar (Ar = C6H4Me-4) furnished the novel ionic phosphazide [[N(CH2CH2NMe)3P]2(mu-N3)][SO2Ar] (6). Data that shed light on the mechanistic pathway leading to 3 were obtained by low temperature 31P NMR spectroscopy. A crystal and molecular structure analysis of the phosphazide sulfonate [N(CH2CH2NMe)3PN3][SO3C6H4Me-4] (4), obtained by atmospheric oxidation of 3, indicated an ionic structure, the cationic part of which is stabilized by a transannular P-N bond. A crystal and molecular structure analysis of 6 also indicated an ionic structure in which the cation features two untransannulated N(CH2CH2NMe)3P cages bridged by an azido group in an eta 1: mu: eta 1 fashion. The reaction of P(NMe2)3 with N3SO2Ar (Ar = C6H4Me-4) in a 1:0.5 molar ratio furnished [[(Me2N)3P]2(mu-N3)][SO2-Ar] (11) in quantitative yield. On the other hand, the same reaction involving a 1:1 molar ratio of P(NMe2)3 and N3SO2Ar produced a mixture of 11, [(Me2N)3PN3][SO2Ar] (12), and the iminophosphorane (Me2N)3P=NSO2Ar (10). In contrast, the bicyclic tris(amino)phosphines MeC(CH2NMe)3P (7) and O=P(CH2NMe)3P (8) reacted with N3SO2-Ar (Ar = C6H4Me-4) to give the iminophosphorane MeC(CH2NMe)3P=NSO2Ar (14) (structured by X-ray means) and O=P(CH2NMe)3P=NSO2Ar (16) via the intermediate phosphazides MeC(CH2NMe)3PN3SO2Ar (13) and O=P(CH2NMe)3PN3SO2Ar (15), respectively. The variety of products obtained from the reactions of arylsulfonyl azides with proazaphosphatranes (1 and 2), acyclic P(NMe2)3, bicyclic tris(amino)phosphines 7 and 8 are rationalized in terms of steric and basicity variations among the phosphorus reagents.     

Tantalum amido and imido complexes supported by tris[(2-indolyl)methyl]amine,a tetradentate trianionic ligand with reduced pi-donor character

Tris[(2-indole)methyl]amine, N(CH2inH)3, may be readily obtained by reaction of methyl 2-bromomethyl-1-indolecarboxylate with NH3 followed by deprotection with NaOMe/MeOH. In its deprotonated form, [N(CH2in)3]3- is an efficient tetradentate trianionic ligand for tantalum, as illustrated by the isolation and structural characterization of [eta 4-N(CH2in)3]Ta(NAr)(NMe2H) (Ar = 2,6-C6H3Pri2), [eta 4-N(CH2in)3]Ta(NMe2)2 and [eta 4-N(CH2in)3]Ta(NMe2)Cl. The [N(CH2in)3]3- ligand has a structural similarity to that of [N(CH2CH2NR)3]3-, but differs electronically from the latter due to its reduced pi-donor capability, a direct result of the nitrogen being a component of the aromatic pi-system of the indolyl fragment.     

Reaction of nido-7,8-C(2)B(9)H(13) with Dicobalt Octacarbonyl: Crystal Structures of the Complexes [Co(2)(CO)(2)(eta(5)-7,8-C(2)B(9)H(11))(2)], [Co(2)(CO)(PMe(2)Ph)(eta(5)-7,8-C(2)B(9)H(11))(2)], and [CoCl(PMe(2)Ph)(2)(eta(5)-7,8-C(2)B(9)H(11))

The compounds [Co(2)(CO)(8)] and nido-7,8-C(2)B(9)H(13) react in CH(2)Cl(2) to give a complex mixture of products consisting primarily of two isomers of the dicobalt species [Co(2)(CO)(2)(eta(5)-7,8-C(2)B(9)H(11))(2)] (1), together with small amounts of a mononuclear cobalt compound [Co(CO)(2)(eta(5)-10-CO-7,8-C(2)B(9)H(10))] (5) and a charge-compensated carborane nido-9-CO-7,8-C(2)B(9)H(11) (6). In solution, isomers 1a and 1b slowly equilibrate. However, column chromatography allows a clean separation of 1a from the mixture, and a single-crystal X-ray diffraction study revealed that each metal atom is ligated by a terminal CO molecule and in a pentahapto manner by a nido-C(2)B(9)H(11) cage framework. The two Co(CO)(eta(5)-7,8-C(2)B(9)H(11)) units are linked by a Co-Co bond [2.503(2) ?], which is supported by two three-center two-electron B-H right harpoon-up Co bonds. The latter employ B-H vertices in each cage which lie in alpha-sites with respect to the carbons in the CCBBB rings bonded to cobalt. Addition of PMe(2)Ph to a CH(2)Cl(2) solution of a mixture of the isomers 1, enriched in 1b, gave isomers of formulation [Co(2)(CO)(PMe(2)Ph)(eta(5)-7,8-C(2)B(9)H(11))(2)] (2). Crystals of one isomer were suitable for X-ray diffraction. The molecule 2a has a structure similar to that of 1a but differs in that whereas one B-H right harpoon-up Co bridge involves a boron atom in an alpha-site of a CCBBB ring coordinated to cobalt, the other uses a boron atom in the beta-site. Reaction between 1b and an excess of PMe(2)Ph in CH(2)Cl(2) gave the complex [CoCl(PMe(2)Ph)(2)(eta(5)-7,8-C(2)B(9)H(11))] (3), the structure of which was established by X-ray diffraction. Experiments indicated that 3 was formed through a paramagnetic Co(II) species of formulation [Co(PMe(2)Ph)(2)(eta(5)-7,8-C(2)B(9)H(11))]. Addition of 2 molar equiv of CNBu(t) to solutions of either 1a or 1b gave a mixture of two isomers of the complex [Co(2)(CNBu(t))(2)(eta(5)-7,8-C(2)B(9)H(11))(2)] (4). NMR data for the new compounds are reported and discussed.     

Synthesis, structures, and DFT bonding analysis of new titanium hydrazido(2-) complexes

The reaction of 1,1-diphenylhydrazine with Ti(NMe2)2Cl2 produced the monomeric terminal titanium hydrazido(2-) species Ti(NNPh2)Cl2(HNMe2)2 (1) in near-quantitative yield. The reaction of Ti(NMe2)2Cl2 with the less sterically demanding ligand precursors 1,1-dimethylhydrazine or N-aminopiperidine gave the dimeric mu-eta2,eta1-bridged compounds Ti2(mu-eta2,eta1-NNMe2)2Cl4(HNMe2)2 (2) and Ti2[mu-eta2,eta1-NN(CH2)5]2Cl4(HNMe2)3 (3). The X-ray structures of 2 and 3 showed the formation of N-H...Cl hydrogen bonded dimers or chains, respectively. The reaction of 1 with an excess of pyridine formed [Ti(NNPh2)Cl2(py)2]n (4, n = 1 or 2). The reaction of the tert-butyl imido complex Ti(N(t)Bu)Cl2(py)3 with either 1,1-dimethylhydrazine or N-aminopiperidine again resulted in the formation of hydrazido-bridged dimeric complexes, namely Ti2(mu-eta2,eta1-NNMe2)2Cl4(py)2 (5, structurally characterized) and Ti2[mu-eta2,eta1-NN(CH2)5]2Cl4(py)2 (6). Compounds 1 and 4 are potential new entry points into terminal hydrazido(2-) chemistry of titanium. Compound 1 reacted with neutral fac-N3 donor ligands to form Ti(NNPh2)Cl2(Me3[9]aneN3) (7), Ti(NNPh2)Cl2(Me3[6]aneN3) (8), Ti(NNPh2)Cl2[HC(Me2pz)3] (9, structurally characterized), and Ti(NNPh2)Cl2[HC(n)Bupz)3] (10) in good yields (Me3[9]aneN3 = trimethyl-1,4,7-triazacyclononane, Me3[6]aneN3 = trimethyl-1,3,5-triazacyclohexane, HC(Me2pz)3 = tris(3,5-dimethylpyrazolyl)methane, and HC((n)Bupz)3 = tris(4-(n)butylpyrazolyl)methane). DFT calculations were performed on both the model terminal hydrazido compound Ti(NNPh2)Cl2[HC(pz)3] (I) and the corresponding imido compounds Ti(NMe)Cl2[HC(pz)3] (II) and Ti(NPh)Cl2[HC(pz)3] (III). The NNPh2 ligand binds to the metal center in an analogous manner to that of terminal imido ligands (metalligand triple bond), but with one of the Ti=N(alpha) pi components significantly destabilized by a pi interaction with the lone pair of the N(beta) atom. The NR ligand sigma donor ability was found to be NMe > NPh > NNPh2, whereas the overall (sigma + pi) donor ability is NMe > NNPh2 > NPh, as judged by fragment orbital populations, Ti-N atom-atom overlap populations, and fragment-charge analysis. DFT calculations on the hydrazido ligand in a mu-eta2,eta1-bridging mode showed involvement of the N=N pi electrons in donation to one of the Ti centers. This TiN2 interaction is best represented as a metallocycle.     

Preparation and properties of cyclopentadienyl- and pentamethylcyclopentadienyl-titanium(IV) complexes with the C8H4S8 ligand, electrical conductivities of their oxidized species, and X-ray crystal structure of Ti(C5Me5)2(C8H4S8)

Ti(C5H5)2(C8H4S8) (1), Ti(C5Me5)2(C8H4S8) (2), [NMe4][Ti(C5H5)(C8H4S8)2] (3), and [NMe4][Ti(C5Me5)(C8H4S8)2] (4) [C8H4S8(2-) = 2-(4,5-ethylenedithio)-1,3-dithiole-2-ylidene)-1,3-dithiole-4,5- dithiolate(2-)] were prepared by reaction of Ti(C5H5)2Cl2, Ti(C5Me5)2Cl2, Ti(C5H5)Cl3, or Ti(C5Me5)Cl3 with Li2C8H4S8 or [NMe4]2[C8H4S8] in THF. They were oxidized by iodine, the ferrocenium cation, or TCNQ (7,7,8,8-tetracyano-p-quinodimethane) in CH2Cl2 or in acetone to afford one-electron-oxidized and over-one-electron-oxidized species, [Ti(C5H5)2(C8H4S8)].I3, [Ti(C5H5)2(C8H4S8)][PF6], [Ti(C5Me5)2(C8H4S8)].I3, [Ti(C5Me5)2(C8H4S8)][PF6], [Ti(C5H5)(C8H4S8)2].I0.9, [Ti(C5H5)(C8H4S8)2][TCNQ]0.3, [Ti(C5Me5)(C8H4S8)2].I2.4, and [Ti(C5Me5)(C8H4S8)2][TCNQ]0.3, with the C8H4S8 ligand-centered oxidation. They exhibited electrical conductivities of 1.6 x 10(-1) to 7.6 x 10(-4) S cm-1 measured for compacted pellets at room temperature. The crystal structure of 2 was clarified to consist of isolated dimerized units of the molecules through some sulfur-sulfur nonbonded contacts: monoclinic, P2(1)/c, a = 9.534(2) A, b = 18.227(2) A, c = 17.775(2) A, beta = 94.39(1) degrees, Z = 4.     

Synthesis, characterization and ethylene reactivity of 2-diphenylphosphanylbenzamido nickel complexes

Addition of primary amines to N-[2-(diphenylphosphanyl)benzoyloxy]succinimide affords 2-diphenylphosphanylbenzamides, Ph2PC6H4C(O)NHR (R = C(CH3)3, 3; R = H, 4; R = CH2CH2CH3, 5; R = CH(CH3)2, 6). Addition of NiCl(eta3-CH2C6H5)(PMe3) to the deprotonated potassium salts of the amides and subsequent treatment of two equivalents of B(C6F5)3 to the resulting products furnishes eta3-benzyl zwitterionic nickel(II) complexes, [Ph2PC6H4C(O)NR-kappa2N,P]Ni(eta3-CH2C6H5) (R = C6H5, 9; R = C(CH3)3, 10; R = H, 11; R = CH2CH2CH3, 12; R = CH(CH3)2, 13). Solid structures of 9, 11, 13 and the intermediate eta1-benzyl nickel(II) complexes, [Ph2PC6H4C(O)NR-kappa2N,P]Ni(eta1-CH2C6H5)(PMe3) (R = C6H5, 7; R = C(CH3)3, 8) were determined by X-ray crystallography. When ethylene is added to the eta3-benzyl zwitterionic nickel(II) complexes, butene is obtained by the complexes 9-12 but complex 13 provides very high molecular-weight branched polyethylene (Mw, approximately 1300000) with excellent activity (up to 5200 kg mol-1 h-1 at 100 psi gauge).     

A highly efficient titanium-based olefin polymerisation catalyst with a monoanionic iminoimidazolidide pi-donor ancillary ligand

The titanium complex Cp[1,3-(2',6'-Me2C6H3)2(CH2N)2C=N]Ti(CH2Ph)2, with a monoanionic eta 1-iminoimidazolidide ancillary ligand, is shown to be a highly efficient catalyst for olefin polymerisation when activated with the Lewis acid B(C6F5)3.