Synthetic and structural investigations of monomeric dilithium boraamidinates and bidentate NBNCN ligands with bulky N-bonded groups

The dilithiated boraamidinate complexes [Li(2)[PhB(NDipp)(2)](THF)(3)] (7a) (Dipp = 2,6-diisopropylphenyl) and [Li(2)[PhB(NDipp)(N(t)Bu)](OEt(2))(2)] (7b), prepared by reaction of PhB[N(H)Dipp][N(H)R'] (6a, R' = Dipp; 6b, R' = (t)Bu) with 2 equiv of (n)BuLi, are shown by X-ray crystallography to have monomeric structures with two terminal and one bridging THF ligands (7a) or two terminal OEt(2) ligands (7b). The derivative 7a is used to prepare the spirocyclic group 13 derivative [Li(OEt(2))(4)][In[PhB(NDipp)(2)](2)] (8a) that is shown by an X-ray structural analysis to be a solvent-separated ion pair. The monoamino derivative PhBCl[N(H)Dipp] (9a), obtained by the reaction of PhBCl(2) with 2 equiv of DippNH(2), serves as a precursor for the synthesis of the four-membered BNCN ring [[R'N(H)](Ph)B(mu-N(t)Bu)(2)C(n)Bu] (10a, R' = Dipp). The X-ray structures of 6a, 9a, and 10a have been determined. The related derivative 10b (R' = (t)Bu) was synthesized by the reaction of [Cl(Ph)B(mu-N(t)Bu)(2)C(n)Bu] with Li[N(H)(t)Bu] and characterized by (1)H, (11)B, and (13)C NMR spectra. In contrast to 10a and 10b, NMR spectroscopic data indicate that the derivatives [[DippN(H)](Ph)B(NR')(2)CR(NR')] (11a: R =( t)Bu, R' = Cy; 11b: R = (n)Bu, R' = Dipp) adopt acyclic structures with three-coordinate boron atoms. Monolithiation of 10a produces the novel hybrid boraamidinate/amidinate (bamam) ligand [Li[DippN]PhB(N(t)Bu)C(n)Bu(N(t)Bu)] (12a).     

In search of the [PhB(mu-N(t)Bu)2]2As. radical: experimental and computational investigations of the redox chemistry of group 15 bis-boraamidinates

DFT calculations for the group 15 radicals [PhB(mu-N(t)Bu)2]2M. (M = P, As, Sb, Bi) predict a pnictogen-centered SOMO with smaller contributions to the unpaired spin density arising from the nitrogen and boron atoms. The reactions of Li 2[PhB(mu-NR)2] (R = (t)Bu, Dipp) with PCl 3 afforded the unsolvated complex LiP[PhB(mu-N(t)Bu)2] 2 ( 1a) in low yield and ClP[PhB(mu-NDipp)2] (2), both of which were structurally characterized. Efforts to produce the arsenic-centered neutral radical, [PhB(mu-N (t) Bu) 2] 2As., via oxidation of LiAs[PhB(mu-N(t)Bu)2]2 with one-half equivalent of SO 2Cl 2, yielded the Zwitterionic compound [PhB(mu-N (t) Bu) 2As(mu-N(t)Bu)2B(Cl)Ph] (3) containing one four-coordinate boron center with a B-Cl bond. The reaction of 3 with GaCl3 produced the ion-separated salt, [PhB(mu-N(t)Bu)2] 2As (+)GaCl 4 (-) ( 4), which was characterized by X-ray crystallography. The reduction of 3 with sodium naphthalenide occurred by a two-electron process to give the corresponding anion [{PhB(mu-N(t)Bu)2} 2As] (-) as the sodium salt. Voltammetric investigations of 4 and LiAs[PhB(mu-N (t) Bu) 2] 2 ( 1b) revealed irreversible processes. Attempts to generate the neutral radical [PhB(mu-N(t)Bu)2] 2As. from these ionic complexes via in situ electrolysis did not produce an EPR-active species.     

Syntheses, structures and reactions of a series of beta-diketiminatoyttrium compounds

This paper describes the synthesis and selected reactions of a series of crystalline mono(beta-diiminato)yttrium chlorides , , , , , , and . The X-ray structure of each has been determined, as well as of [YCl()(2)] (), [Y()(2)OBu(t)] () and [Y{CH(SiMe(3))(2)}(thf)(mu-Cl)(2)Li(OEt(2))(2)(mu-Cl)](2) (). The N,N'-kappa(2)-beta-diiminato ligands were [{N(R)C(Me)}(2)CH](-) [R = C(6)H(4)Pr(i)-2 (); R = C(6)H(4)Bu(t)-2 (); R = C(6)H(3)Pr(i)(2)-2,6 ()], [{N(SiMe(3))C(Ph)}(2)CH)](-) () and [{N(C(6)H(3)Pr(i)(2)-2,6)C(H)}(2)CPh](-) (). Equivalent portions of Li[L(x)] and YCl(3) in Et(2)O under mild conditions yielded [Y(mu-Cl)(L(x))(mu-Cl)(2)Li(OEt(2))(2)](2) [L(x) = () or ()] and [Y(mu-Cl)()(mu-Cl)Li(OEt(2))(2)(mu-Cl)](2) () or its thf (instead of Et(2)O) equivalent . Each of the Li(OEt(2))(2)Cl(2) moieties is bonded in a terminal () or bridging () mode with respect to the two Y atoms; the difference is attributed to the greater steric demand of than or . Under slightly more forcing conditions, YCl(3) and Li() (via) gave the lithium-free complex [YCl(2)()(thf)(2)] (). Two isoleptic compounds and (having in place of in , and , respectively) were obtained from YCl(3) and an equivalent portion of K[] and Na[], respectively; under the same conditions using Na[], the unexpected product was [YCl()(2)] () (i.e. incorporating only one half of the YCl(3)). A further unusual outcome was in the formation of from and 2 Li[CH(SiMe(3))(2)]. Compound [Y(){N(H)C(6)H(3)Pr(i)(2)-2,6}(thf)(mu(3)-Cl)(2)K](2).4Et(2)O (), obtained from and K[N(H)C(6)H(3)Pr(i)(2)-2,6], is noteworthy among group 3 or lanthanide metal (M) compounds for containing MClKCl (M = Y) moieties.     

Preparation and x-ray structures of alkali-metal derivatives of the ambidentate anions [tBuN(E)P(mu-NtBu)2P(E)NtBu]2- (E = S, Se) and [tBuN(Se)P(mu-NtBu)2PN(H)tBu)]-

The ambidentate dianions [(t)BuN(E)P(mu-N(t)Bu)(2)P(E)N(t)Bu](2)(-) (5a, E = S; 5b, E = Se) are obtained as their disodium and dipotassium salts by the reaction of cis-[(t)Bu(H)N(E)P(mu-N(t)Bu)(2)P(E)N(H)(t)Bu] (6a, E = S; 6b, E = Se), with 2 equiv of MN(SiMe(3))(2) (M = Na, K) in THF at 23 degrees C. The corresponding dilithium derivative is prepared by reacting 6a with 2 equiv of (t)BuLi in THF at reflux. The X-ray structures of five complexes of the type [(THF)(x)()M](2)[(t)BuN(E)P(mu-N(t)Bu)(2)P(E)N(t)Bu] (9, M = Li, E = S, x = 2; 11a/11b, M = Na, E = S/Se, x = 2; 12a, M = K, E = S, x = 1; 12b, M = K, E = Se, x = 1.5) have been determined. In the dilithiated derivative 9 the dianion 5a adopts a bis (N,S)-chelated bonding mode involving four-membered LiNPS rings whereas 11a,b and 12a,b display a preference for the formation of six-membered MNPNPN and MEPNPE rings, i.e., (N,N' and E,E')-chelation. The bis-solvated disodium complexes 11a,b and the dilithium complex 9 are monomeric, but the dipotassium complexes 12a,b form dimers with a central K(2)E(2) ring and associate further through weak K.E contacts to give an infinite polymeric network of 20-membered K(6)E(6)P(4)N(4) rings. The monoanions [(t)Bu(H)N(E)P(mu-N(t)Bu)(2)P(E)N(t)Bu)](-) (E = S, Se) were obtained as their lithium derivatives 8a and 8b by the reaction of 1 equiv of (n)BuLi with 6a and 6b, respectively. An X-ray structure of the TMEDA-solvated complex 8a and the (31)P NMR spectrum of 8b indicate a N,E coordination mode. The reaction of 6b with excess (t)BuLi in THF at reflux results in partial deselenation to give the monolithiated P(III)/P(V) complex [(THF)(2)Li[(t)BuN(Se)P(mu-N(t)Bu)(2)PN(H)(t)Bu]] 10, which adopts a (N,Se) bonding mode.     

The synthesis and characterization of mono and dinuclear group 13 complexes derived from a Schiff base

The coordination preferences of the tetradentate Schiff base, N,N'-ethylenebis(acetylacetoimine), H(2)L, with a variety of group 13 precursors, led to the formation of a series of mono and binuclear products. The reaction of H(2)L with AlMe(3) and Me(2)GaCl afforded the binuclear complexes, [L{Al(Me)(2)}(2)] 1 and [H(2)L{GaCl(Me)(2)}(2)], 3, the latter an adduct of the neutral ligand. Treatment of 1 with iodine generated the cationic Al(III) complex, [LAl(thf)(2)]I, 2, while the addition of n-BuLi to H(2)L, followed by reaction with GaCl(3) and InCl(3) led to an ionic complex [{LGaCl}(2)(μLi)]GaCl(4), 4, an In(III) dimer, [LInCl](2), 5 and monomeric [LInCl(thf)], 6. In contrast, the reaction of [In{N(SiMe(3))(2)}(3)] with H(2)L yielded a homoleptic, air stable, indium complex, [L(3)In(2)], 7. All products were definitively characterized by X-ray crystallography and their structures confirmed by pertinent spectroscopic techniques.     

Synthesis and luminescence studies of mono- and C3-symmetric, tris(ligand) complexes of Sm(III), Y(III) and Eu(III) with sulfur-bridged binaphtholate ligands

A series of trivalent mono- and tris(ligand) lanthanide complexes of a sulfur-bridged binaphthol ligand [1,1'-S(2-HOC(10)H(4)Bu(t)(2)-3,6)(2)] H(2)L(SN), have been prepared and characterised both structurally and photophysically. The H(2)L(SN) ligand provides an increased steric bulk and offers an additional donor atom (sulfur) as compared with 1,1'-binaphthol (BINOL), a ligand commonly used to complex Lewis acidic lanthanide catalysts. Reaction of the diol H(2)L(SN) with [Sm[N(SiMe(3))(2)](3)] affords silylamido- and amino- derivatives [Sm(L(SN))[N(SiMe(3))(2)][HN(SiMe(3))(2)]] and the crystallographically characterised [Sm(L(SN))[N(SiMe(3))(2)](thf)(2)] with different degrees of structural rigidity, depending on the presence of coordinating solvents. The binaphthyl groups of the L(SN) ligand act as sensitisers of the metal centred emission, which is observed for the Eu(III) and Sm(III) complexes studied. We have therefore sought to use emission spectroscopy as a non-invasive technique to monitor a monomer-dimer equilibrium in these complexes. A dramatic difference between the emission properties of the unreactive dimeric Sm(III) aryloxide complex, the solvated monomeric analogues and the amido adduct demonstrated the potential use of such a technique. For a few representative lanthanides (Ln = Sm, Eu and Y) the reaction of the dilithium salt Li(2)L(SN) with either [Ln[N(SiMe(3))(2]3)] or [LnCl(3)(thf)(3)] affords only the homoleptic complex [Li(S)(3)][LnL(SN)(3)](S = thf or diethyl ether); we report the structural characterisation of the Sm complex. However, the reactions of this dipotassium salt K(2)L(SN) with [Sm[N(SiMe(3))(2)](3)] or [SmCl(3)(thf)(3)] give only [SmL(SN)N(SiMe(3))(2)], or intractable mixtures respectively, in which no (tris)binaphtholate is observed. The only isolable lanthanide-L(SN) halide adduct so far is [YbL(SN)I(thf)].     

Synthesis and structures of aluminum and magnesium complexes of tetraimidophosphates and trisamidothiophosphates: EPR and DFT investigations of the persistent neutral radicals {Me2Al[(mu-NR)(mu-NtBu)P(mu-NtBu)2]Li(THF)2}(*) (R = SiMe3, tBu)

Reactions of (RNH)(3)PNSiMe(3) (3a, R = (t)()Bu; 3b, R = Cy) with trimethylaluminum result in the formation of {Me(2)Al(mu-N(t)Bu)(mu-NSiMe(3))P(NH(t)()Bu)(2)]} (4) and the dimeric trisimidometaphosphate {Me(2)Al[(mu-NCy)(mu-NSiMe(3))P(mu-NCy)(2)P(mu-NCy)(mu-NSiMe(3))]AlMe(2)} (5a), respectively. The reaction of SP(NH(t)Bu)(3) (2a) with 1 or 2 equiv of AlMe(3) yields {Me(2)Al[(mu-S)(mu-N(t)Bu)P(NH(t)()Bu)(2)]} (7) and {Me(2)Al[(mu-S)(mu-N(t)()Bu)P(mu-NH(t)Bu)(mu-N(t)Bu)]AlMe(2)} (8), respectively. Metalation of 4 with (n)()BuLi produces the heterobimetallic species {Me(2)Al[(mu-N(t)Bu)(mu-NSiMe(3))P(mu-NH(t)()Bu)(mu-N(t)()Bu)]Li(THF)(2)} (9a) and {[Me(2)Al][Li](2)[P(N(t)Bu)(3)(NSiMe(3))]} (10) sequentially; in THF solutions, solvation of 10 yields an ion pair containing a spirocyclic tetraimidophosphate monoanion. Similarly, the reaction of ((t)BuNH)(3)PN(t)()Bu with AlMe(3) followed by 2 equiv of (n)BuLi generates {Me(2)Al[(mu-N(t)Bu)(2)P(mu(2)-N(t)Bu)(2)(mu(2)-THF)[Li(THF)](2)} (11a). Stoichiometric oxidations of 10 and 11a with iodine yield the neutral spirocyclic radicals {Me(2)Al[(mu-NR)(mu-N(t)Bu)P(mu-N(t)Bu)(2)]Li(THF)(2)}(*) (13a, R = SiMe(3); 14a, R = (t)Bu), which have been characterized by electron paramagnetic resonance spectroscopy. Density functional theory calculations confirm the retention of the spirocyclic structure and indicate that the spin density in these radicals is concentrated on the nitrogen atoms of the PN(2)Li ring. When 3a or 3b is treated with 0.5 equiv of dibutylmagnesium, the complexes {Mg[(mu-N(t)()Bu)(mu-NH(t)()Bu)P(NH(t)Bu)(NSiMe(3))](2)} (15) and {Mg[(mu-NCy)(mu-NSiMe(3))P(NHCy)(2)](2)} (16) are obtained, respectively. The addition of 0.5 equiv of MgBu(2) to 2a results in the formation of {Mg[(mu-S)(mu-N(t)()Bu)P(NH(t)Bu)(2)](2)} (17), which produces the hexameric species {[MgOH][(mu-S)(mu-N(t)()Bu)P(NH(t)Bu)(2)]}(6) (18) upon hydrolysis. Compounds 4, 5a, 7-11a, and 15-17 have been characterized by multinuclear ((1)H, (13)C, and (31)P) NMR spectroscopy and, in the case of 5a, 9a.2THF, 11a, and 18, by X-ray crystallography.     

Reactions of Li- and Yb-coordinated N,N'-bis(trimethylsilyl)-beta-diketiminates: one- and two-electron reductions, deprotonation, and C-N bond cleavage

The synthesis and characterisation of novel Li and Yb complexes is reported, in which the monoanionic beta-diketiminato ligand has been (i) reduced (SET or 2 [times] SET), (ii) deprotonated, or (iii) C-N bond-cleaved. Reduction of the lithium beta-diketiminate Li(L(R,R'))[L(R,R')= N(SiMe(3))C(R)CHC(R')N(SiMe(3))] with Li metal gave the dilithium derivative [Li(tmen)(mu-L(R,R'))Li(OEt(2))](R = R'= Ph; or, R = Ph, R[prime or minute]= Bu(t)). When excess of Li was used the dimeric trilithium [small beta]-diketiminate [Li(3)(L(R,R[prime or minute]))(tmen)](2)(, R = R'= C(6)H(4)Bu(t)-4 = Ar) was obtained. Similar reduction of [Yb(L(R,R'))(2)Cl] gave [Yb[(mu-L(R,R'))Li(thf)](2)](, R = R[prime or minute]= Ph; or, R = R'= C(6)H(4)Ph-4 = Dph). Use of the Yb-naphthalene complex instead of Li in the reaction with [Yb(L(Ph,Ph))(2)] led to the polynuclear Yb clusters [Yb(3)(L(Ph,Ph))(3)(thf)], [Yb(3)(L(Ph,Ph))(2)(dme)(2)], or [Yb(5)(L(Ph,Ph))(L(1))(L(2))(L(3))(thf)(4)] [L(1)= N(SiMe(3))C(Ph)CHC(Ph)N(SiMe(2)CH(2)), L(2)= NC(Ph)CHC(Ph)H, L(3)= N(SiMe(2)CH(2))] depending on the reaction conditions and stoichiometry. The structures of the crystalline complexes 4, 6x21/2(hexane), 5(C(6)D(6)), and have been determined by X-ray crystallography (and have been published).     

Synthesis, structures and reactivity of ruthenium nitrosyl complexes containing Kläui's oxygen tripodal ligand

Ruthenium nitrosyl complexes containing the Kl?ui's oxgyen tripodal ligand L(OEt)(-) ([CpCo{P(O)(OEt)(2)}(3)](-) where Cp = η(5)-C(5)H(5)) were synthesized and their photolysis studied. The treatment of [Ru(N^N)(NO)Cl(3)] with [AgL(OEt)] and Ag(OTf) afforded [L(OEt)Ru(N^N)(NO)][OTf](2) where N^N = 4,4'-di-tert-butyl-2,2'-bipyridyl (dtbpy) (2·[OTf](2)), 2,2'-bipyridyl (bpy) (3·[OTf](2)), N,N,N'N'-tetramethylethylenediamine (4·[OTf](2)). Anion metathesis of 3·[OTf](2) with HPF(6) and HBF(4) gave 3·[PF(6)](2) and 3·[BF(4)](2), respectively. Similarly, the PF(6)(-) salt 4·[PF(6)](2) was prepared by the reaction of 4·[OTf](2) with HPF(6). The irradiation of [L(OEt)Ru(NO)Cl(2)] (1) with UV light in CH(2)Cl(2)-MeCN and tetrahydrofuran (thf)-H(2)O afforded [L(OEt)RuCl(2)(MeCN)] (5) and the chloro-bridged dimer [L(OEt)RuCl](2)(μ-Cl)(2) (6), respectively. The photolysis of complex [2][OTf](2) in MeCN gave [L(OEt)Ru(dtbpy)(MeCN)][OTf](2) (7). Refluxing complex 5 with RNH(2) in thf gave [L(OEt)RuCl(2)(NH(2)R)] (R = tBu (8), p-tol (9), Ph (10)). The oxidation of complex 6 with PhICl(2) gave [L(OEt)RuCl(3)] (11), whereas the reduction of complex 6 with Zn and NH(4)PF(6) in MeCN yielded [L(OEt)Ru(MeCN)(3)][PF(6)] (12). The reaction of 3·[BF(4)](2) with benzylamine afforded the μ-dinitrogen complex [{L(OEt)Ru(bpy)}(2)(μ-N(2))][BF(4)](2) (13) that was oxidized by [Cp(2)Fe]PF(6) to a mixed valence Ru(II,III) species. The formal potentials of the RuL(OEt) complexes have been determined by cyclic voltammetry. The structures of complexes 5,6,10,11 and 13 have been established by X-ray crystallography.     

Formation of N-I charge-transfer bonds and ion pairs in polyiodides with imidotellurium cations

[((t)BuNH)Te(mu-N(t)Bu)(2)Te(N(t))Bu)][OSO(2)CF(3)] (4a) is obtained in quantitative yields by the treatment of [((t)BuN)Te(mu-N(t)Bu)(2)Te(N(t)Bu)] (1) with HCF(3)SO(3). The reaction of 4a with LiI and iodine in the molar ratio 1:1:4.5 affords a product that, upon recrystallization from acetonitrile, was found to be a solid solution of [((t)BuNH)Te(mu-N(t)Bu)(2)Te(N(t)Bu)](2)I(20) (5a) and [((t)BuNH)Te(mu-N(t)Bu)(2)Te(NH(t)Bu)](2)I(18) (5b). Consequently, the crystal structure is disordered, containing 88.3(1)% of 5a.2MeCN and 11.7(1)% of 5b.2MeCN. The I(20) framework is involved in two symmetry-equivalent N-I-I-I-I fragments, two I(3)(-) ions, and three I(2) molecules that are linked together by I...I secondary bonding interactions. The bonding in the N-I-I-I-I fragment can be considered in terms of the lp(N) --> sigma*(I(2)) and pi(I(2)) --> sigma*(I(2)) charge-transfer interactions involving one [((t)BuNH)Te(mu-N(t)Bu)(2)Te(N(t)Bu)](+) cation and two I(2) units. The N-I bond length of 2.131(7) A, the I-I distances of 3.118(1), 3.095(2), and 2.788(2) A, and the angle I(2)-I(2) angle of 84.75(4) degrees are consistent with this bonding scheme. The I-I bond distances in the two symmetry-equivalent I(3)(-) ions are 3.113(1) and 2.792(2) A, and those in two crystallographically independent I(2) molecules are 2.736(2) and 2.743(1) A. The formal I(18)(4)(-) anion in 5b.2MeCN consists of four I(3)(-) anions and three I(2) molecules linked by I...I secondary bonds. One crystallographically independent I(3)(-) anion is connected to the [((t)BuNH)Te(mu-N(t)Bu)(2)Te(HN(t)Bu)](2+) cation by two hydrogen bonds [H...I = 2.823(5) and 2.983(5) A; N...I = 3.697(8) and 3.857(9) A]. The I(3)(-) anions and I(2) molecules in 5b show virtually identical bond parameters to those in 5a. The treatment of 1 with iodine and the reactions of its methylated derivatives, [((t)BuNMe)Te(mu-N(t)Bu)(2)Te(N(t)()Bu)][OSO(2)CF(3)] and [((t)BuNMe)Te(mu-N(t)Bu)(2)Te(MeN(t)Bu)][OSO(2)CF(3)](2), with LiI and iodine also afford highly moisture-sensitive polyiodides, either by the formation of N-I charge-transfer complexes or by ionic interactions. The crystal structures of the partially hydrolyzed products, [((t)BuIN)Te(mu-N(t))Bu)(2)Te(mu-O)](2)(I(3))(2) (3), [((t)BuMeN)Te(mu-N(t)Bu)(2)Te(mu-O)](2)(I(3))(2) (6), and 6.2MeCN, are also reported.     

The beta-dialdiminato ligand [{N(C6H3Pri(2)-2,6)C(H)}2CPh]-: the conjugate acid and Li, Al, Ga and In derivatives

The synthesis of the following crystalline complexes is described: [Li(L)(thf)2] (), [Li(L)(tmeda)] (), [MCl2(L)] [M=Al (), Ga ()], [In(Cl)(L)(micro-Cl)2Li(OEt2)2] (), [In(Cl)(L){N(H)C6H3Pri(2)-2,6}] (), [In(L){N(H)C6H3Pri(2)-2,6}2] (), [{In(Cl)(L)(micro-OH)}2] (), [L(Cl)In-In(Cl)(L)] () (the thf-solvate, the solvate-free and the hexane-solvate), [{In(Cl)L}2(micro-S)] () and [InCl2(L)(tmeda)] () ([L]-=[{N(C6H3Pri(2)-2,6)C(H)}2CPh]-). From H(L) (), via Li(L) in Et2O, and thf, tmeda, AlCl3, GaCl3 or InCl3 there was obtained , , , or , respectively in excellent yield. Compound was the precursor for each of , and [{InCl3(tmeda)2{micro-(OSnMe2)2}}] () by treatment with one () or two () equivalents of K[N(H)(C6H3Pri(2)-2,6)], successively Li[N(SiMe3)(C6H3Pri(2)-2,6)] and moist air (), Na in thf (), tmeda (), or successively tmeda and Me3SnSnMe3 (). Crystals of (with an equivalent of In) and were obtained from InCl or thermolysis of [In(Cl)(L){N(SiMe3)(C6H3Pri(2)-2,6)}] () {prepared in situ from and Li[N(SiMe3)(C6H3Pri(2)-2,6)] in Et2O}, respectively. Compound was obtained from a thf solution of and sulfur. X-Ray data for crystalline , , , , , and are presented. The M(L) moiety in each (not the L-free ) has the monoanionic L ligated to the metal in the N,N'-chelating mode. The MN1C1C2C3N2 six-membered M(L) ring is pi-delocalised and has the half-chair (, and ) or boat (, and ) conformation.     

Synthesis and structures of the [benzamidinato]3- complexes Li3(tmeda)(L1)]2 and [Li(thf)4][Li5(L2)(OEt2)2] [L1 = N(SiMe3)C(Ph)N(SiMe3) and L2 = N(SiMe3)C(C6H4-4)NPh

Reduction at ambient temperature of each of the lithium benzamidinates [Li(L(1))(tmeda)] or [{Li(L(2))(OEt(2))(2)}(2)] with four equivalents of lithium metal in diethyl ether or thf furnished the brown crystalline [Li(3)(L(1))(tmeda)] (1) or [Li(thf)(4)][Li(5)(L(2))(2)(OEt(2))(2)] (2), respectively. Their structures show that in each the [N(R(1))C(R(3))NR(2)](3-) moiety has the three negative charges largely localised on each of N, N' and R = Aryl); a consequence is that the "aromatic" 2,3- and 5,6-CC bonds of R(3) approximate to being double bonds. Multinuclear NMR spectra in C(6)D(6) and C(7)D(8) show that 1 and 2 exhibit dynamic behaviour. [The following abbreviations are used: L(1) = N(SiMe(3))C(Ph)N(SiMe(3)); L(2) = N(SiMe(3))C(C(6)H(4)Me-4)N(Ph); tmeda = (Me(2)NCH(2)-)(2); thf = tetrahydrofuran.] This reduction is further supported by a DFT analysis.     

Lithiation of tris(alkyl- and arylamido)orthophosphates EP[N(H)R]3 (E = O,S, Se): imido substituent effects and P=E bond cleavage

In the solid state, OP[N(H)Me](3) (1a) and OP[N(H)(t)Bu](3) (1b) have hydrogen-bonded structures that exhibit three-dimensional and one-dimensional arrays, respectively. The lithiation of 1b with 1 equiv of (n)BuLi generates the trimeric monolithiated complex (THF)[LiOP(N(t)Bu)[N(H)(t)Bu](2)](3) (4), whereas reaction with an excess of (n)BuLi produces the dimeric dilithium complex [(THF)(2)Li(2)OP(N(t)Bu)(2)[N(H)(t)Bu]](2) (5). Complex 4 contains a Li(2)O(2) ring in an open-ladder structure, whereas 5 embraces a central Li(2)O(2) ring in a closed-ladder arrangement. Investigations of the lithiation of tris(alkyl or arylamido)thiophosphates, SP[N(H)R](3) (2a, R = (i)Pr; 2b, R = (t)Bu; 2c, R = p-tol) with (n)BuLi reveal interesting imido substituent effects. For the alkyl derivatives, only mono- or dilithiation is observed. In the case of R = (t)Bu, lithiation is accompanied by P-S bond cleavage to give the dilithiated cyclodiphosph(V/V)azane [(THF)(2)Li(2)[((t)BuN)(2)P(micro-N(t)Bu)(2)P(N(t)Bu)(2)]] (9). Trilithiation occurs for the triaryl derivatives EP[N(H)Ar](3) (E = S, Ar = p-tolyl; E = Se, Ar = Ph), as demonstrated by the preparation of [(THF)(4)Li(3)[SP(Np-tol)(3)]](2) (10) and [(THF)(4)Li(3)[SeP(NPh)(3)]](2) (11), which are accompanied by the formation of small amounts of 10.[LiOH(THF)](2) and 11.Li(2)Se(2)(THF)(2), respectively.     

Lithiation of (tBuNH)3PNSiMe3 and formation of tetraimidophosphate complexes containing M3O3 rings (M = Li, K): X-ray structure of the stable radical [(Me3SiN)P(mu3-N(t)Bu)3[mu3-Li(THF)]3(OtBu))

The reaction of ((t)BuNH)(3)PNSiMe(3) (1) with 1 equiv of (n)BuLi results in the formation of Li[P(NH(t)Bu)(2)(N(t)Bu)(NSiMe(3))] (2); treatment of 2 with a second equivalent of (n)BuLi produces the dilithium salt Li(2)[P(NH(t)Bu)(N(t)Bu)(2)(NSiMe(3))] (3). Similarly, the reaction of 1 and (n)BuLi in a 1:3 stoichiometry produces the trilithiated species Li(3)[P(N(t)Bu)(3)(NSiMe(3))] (4). These three complexes represent imido analogues of dihydrogen phosphate [H(2)PO(4)](-), hydrogen phosphate [HPO(4)](2)(-), and orthophosphate [PO(4)](3)(-), respectively. Reaction of 4 with alkali metal alkoxides MOR (M = Li, R = SiMe(3); M = K, R = (t)Bu) generates the imido-alkoxy complexes [Li(3)[P(N(t)Bu)(3)(NSiMe(3))](MOR)(3)] (8, M = Li; 9, M = K). These compounds were characterized by multinuclear ((1)H, (7)Li, (13)C, and (31)P) NMR spectroscopy and, in the cases of 2, 8, and 9.3THF, by X-ray crystallography. In the solid state, 2 exists as a dimer with Li-N contacts serving to link the two Li[P(NH(t)Bu)(2)(N(t)Bu)(NSiMe(3))] units. The monomeric compounds 8 and 9.3THF consist of a rare M(3)O(3) ring coordinated to the (LiN)(3) unit of 4. The unexpected formation of the stable radical [(Me(3)SiN)P(mu(3)-N(t)Bu)(3)[mu(3)-Li(THF)](3)(O(t)Bu)] (10) is also reported. X-ray crystallography indicated that 10 has a distorted cubic structure consisting of the radical dianion [P(N(t)Bu)(3)(NSiMe(3))](.2)(-), two lithium cations, and a molecule of LiO(t)Bu in the solid state. In dilute THF solution, the cube is disrupted to give the radical monoanion [(Me(3)SiN)((t)BuN)P(mu-N(t)Bu)(2)Li(THF)(2)](.-), which was identified by EPR spectroscopy.     

Bis(alkylamido)phenylborane complexes of zirconium,hafnium, and vanadium

The coordination chemistry of the bis(tert-butylamido)phenylborane ligand, [(t)BuN-B(Ph)-N(t)Bu](2)(-), is developed. The ligand can be delivered to metals of groups 4 and 5 from its dilithio salt. The reactions of PhB((t)BuNLi)(2), 1, with metal halides of zirconium, hafnium, and vanadium generate complexes of the general formulas ((t)BuN-B(Ph)-N(t)Bu)(2)M(THF) (M = Zr (2), Hf (3)), Li(2)[M((t)BuN-B(Ph)-N(t)Bu)(3)] (M = Zr (4), Hf (5)), and M((t)BuN-B(Ph)-N(t)Bu)(2) (M = V (6)). (1)H and (11)B[(1)H] NMR and single-crystal X-ray analysis show that these amido metal complexes are structurally analogous to amidinates.     

Unexpected reactivity and coordination in gallium(III) and indium(III) chloride complexes with geometrically constrained thio- and selenoether ligands

Reaction of GaCl(3) with 1 mol equiv of [14]aneS(4) in anhydrous CH(2)Cl(2) gives the exocyclic chain polymer [GaCl(3)([14]aneS(4))] (1) whose structure confirms trigonal bipyramidal coordination at Ga with a planar GaCl(3) unit. In contrast, using [16]aneS(4) and GaCl(3) or [16]aneSe(4) and MCl(3) (M = Ga or In) in either a 1:1 or a 1:2 molar ratio produces the anion-cation complexes [GaCl(2)([16]aneS(4))][GaCl(4)] (2) and [MCl(2)([16]aneSe(4))][MCl(4)] (M = Ga, 3 and M = In, 4) containing trans-octahedral cations with endocyclic macrocycle coordination. The ligand-bridged dimer [(GaCl(3))(2){o-C(6)H(4)(SMe)(2)}] (5) is formed from a 2:1 mol ratio of the constituents and contains distorted tetrahedral Ga(III). This complex is unusually reactive toward CH(2)Cl(2), which is activated toward nucleophilic attack by polarization with GaCl(3), producing the bis-sulfonium species [o-C(6)H(4)(SMeCH(2)Cl)(2)][GaCl(4)](2) (6), confirmed from a crystal structure. In contrast, the xylyl-based dithioether gives the stable [(GaCl(3))(2){o-C(6)H(4)(CH(2)SEt)(2)}] (8). However, replacing GaCl(3) with InCl(3) with o-C(6)H(4)(CH(2)SEt)(2) preferentially forms the 4:3 In:L complex [(InCl(3))(4){o-C(6)H(4)(CH(2)SEt)(2)}(3)] (9) containing discrete tetranuclear moieties in which the central In atom is octahedrally coordinated to six bridging Cl's, while the three In atoms on the edges have two bridging Cl's, two terminal Cl's, and two mutually trans S-donor atoms from different dithioether ligands. GaCl(3) also reacts with the cyclic bidentate [8]aneSe(2) to form a colorless, extremely air-sensitive adduct formulated as [(GaCl(3))(2)([8]aneSe(2))] (10), while InCl(3) gives [InCl(3)([8]aneSe(2))] (14). Very surprisingly, 10 reacts rapidly with O(2) gas to give initially the red [{[8]aneSe(2)}(2)][GaCl(4)](2) (11) and subsequently the yellow [{[8]aneSe(2)}Cl][GaCl(4)] (12). The crystal structure of the former confirms a dimeric [{[8]aneSe(2)}(2)](2+) dication, derived from coupling of two mono-oxidized {[8]aneE(2)}(+?) cation radicals to form an Se-Se bond linking the rings and weaker transannular 1,5-Se···Se interactions across both rings. The latter (yellow) product corresponds to discrete doubly oxidized {[8]aneSe(2)}(2+) cations (with a primary Se-Se bond across the 1,5-positions of the ring) with a Cl(-) bonded to one Se. Tetrahedral [GaCl(4)](-) anions provide charge balance in each case. These oxidation reactions are clearly promoted by the Ga(III) since [8]aneSe(2) itself does not oxidize in air. The new complexes have been characterized in the solid state by IR and Raman spectroscopy, microanalysis, and X-ray crystallography where possible. Where solubility permits, the solution characteristics have been probed by (1)H, (77)Se{(1)H}, and (71)Ga NMR spectroscopic studies.     

Synthesis and characterization of pentachlorophenyl-metal derivatives with d0 and d10 electron configurations

By reaction of [TiCl(3)(thf)(3)] with LiC(6)Cl(5), the homoleptic organotitanium(III) derivative [Li(thf)(4)][Ti(III)(C(6)Cl(5))(4)] (1) has been prepared as a paramagnetic (d(1), S = 1/2, g(av) = 1.959(2)), extremely air-sensitive compound. Oxidation of 1 with [N(C(6)H(4)Br-4)(3)][SbCl(6)] gives the diamagnetic (d(0)) organotitanium(IV) species [Ti(IV)(C(6)Cl(5))(4)] (2). Compounds 1 and 2 are also electrochemically related (E(1/2) = 0.05 V). The homoleptic, diamagnetic (d(10)) compounds [N(PPh(3))(2)][Tl(C(6)Cl(5))(4)] (3) and [Sn(C(6)Cl(5))(4)] (4) have also been prepared. Nearly tetrahedral environments have been found for the d(0), d(10), and d(1) metal centers in the molecular structures of compounds 2-4 as well as in that of [Li(thf)(2)(OEt(2))(2)][Ti(III)(C(6)Cl(5))(4)].CH(2)Cl(2) (1') (X-ray diffraction). The reaction of the heavier Group 4 metal halides, MCl(4) (M = Zr, Hf) with LiC(6)Cl(5) in the presence of [NBu(4)]Br gives, in turn, the heteroleptic species [NBu(4)][M(C(6)Cl(5))(3)Cl(2)] (M = Zr (5), Hf (6)). Compounds 5 and 6 are isomorphous and isostructural, with the metal center in a trigonal-bipyramidal (TBPY-5) environment defined by two axial Cl ligands and three equatorial C(6)Cl(5) groups (X-ray diffraction). No redox features are observed for compounds 3-6 in CH(2)Cl(2) solution between -1.6 and +1.6 V.     

Syntheses and structures of quinuclidine-stabilized amido- and azidogallanes

Quinuclidine-stabilized amido- and azidogallanes, HGa[N(TMS)2]2(quin) (1), H2Ga[N(TMS)2](quin) (2), HGa-[N(H)(2,6-iPr2C6H3)]2(quin) (3), and H2GaN3(quin) (4), were synthesized from the quinuclidine adducts of mono- and dichlorogallane. Structural determinations revealed that all compounds were monomeric with four-coordinate gallium centers. Reactions of the five-coordinate compound, HGaCl2(quin)2, with 2 equiv of Li[N(TMS)2] or Li[N(H)(2,6-iPr2C6H3)] resulted in the isolation of compound 1 or 3. A ligand redistribution during the reaction of H2GaCl(quin) with Li[N(H)(2,6-iPr2C6H3)] produced compound 3 and H3Ga(quin) in a 1:1 molar ratio.     

The distinct affinity of cyclopentadienyl ligands towards trivalent uranium over lanthanide ions. Evidence for cooperative ligation and back-bonding in the actinide complexes

The mono and bis(cyclopentadienyl) compounds [M(C5H4Bu t)I2] and [M(C5H4Bu t)2I](M = U, La, Ce, Nd) were formed in thf by comproportionation reactions of [M(C5H4Bu t)3] and LnI3 or [UI3(L)4](L = thf or py) in the molar ratio of 1 : 2 and 2 : 1, respectively, while treatment of [UI(3)(py)(4)] or LnI(3)(Ln = La, Ce, Nd) with 1 or 2 mol equivalents of LiC5H4Bu t in thf afforded the [M(C5H4Bu t)I2] and [M(C5H4Bu t)2I2]- compounds, respectively. The X-ray crystal structures of [M(C5H4Bu t)I2(py)3](M = U, La, Ce, Nd), [{Ce(C5H4Bu t)2(mu-I)}2] and [M(C5H4Bu t)2I(py)2](M = U, Nd) have been determined; the differences between the average M-C distances in the mono(cyclopentadienyl) complexes correspond to the variation in the ionic radii of the trivalent uranium and lanthanide ions while the U-N and U-I bond lengths seem to be smaller than those predicted from a purely ionic bonding model. The distinct affinity of the cyclopentadienyl ligands towards Ln(III) and U(III) was revealed by two series of competing reactions: the ligand exchange reactions between [Ln(C5H4Bu t)(n')I(3-n')](Ln = La, Ce, Nd) and [U(C5H4Bu t)(n')I(3-n')] species (1 < or = n'+n' =n < or = 5), and the addition of n mol equivalents of LiC(5)H(4)Bu(t)(1 [less-than-or-equal]n[less-than-or-equal] 5) to a 1 : 1 mixture of LnI3 and [UI3(thf)4] or [UI3(py)4]. The stability of the [M(C5H4Bu t)I2] species was found to vary in the order Nd > Ce > U > La, a trend which is in accord with an electrostatic bonding model. However, the bis and tris(cyclopentadienyl) complexes of uranium are more stable than their lanthanide analogues. This difference can be accounted for by a higher degree of covalency in the U-C5H4Bu t bond, resulting from the late appearance of back-bonding which would emerge only after the first cyclopentadienyl ligand is bound.     

Synthesis and structures of some new types of lithium beta-diketiminates

The tetracyclic dilithio-Si,Si'-oxo-bridged bis(N,N'-methylsilyl-beta-diketiminates) 2 and 3, having an outer LiNCCCNLiNCCCN macrocycle, were prepared from [Li{CH(SiMe(3))SiMe(OMe)(2)}](infinity) and 2 PhCN. They differ in that the substituent at the beta-C atom of each diketiminato ligand is either SiMe(3) (2) or H (3). Each of and has (i) a central Si-O-Si unit, (ii) an Si(Me) fragment N,N'-intramolecularly bridging each beta-diketiminate, and (iii) an Li(thf)(2) moiety N,N'-intermolecularly bridging the two beta-diketiminates (thf = tetrahydrofuran). Treatment of [Li{CH(SiMe(3))(SiMe(2)OMe)}](8) with 2Me(2)C(CN)(2) yielded the amorphous [Li{Si(Me)(2)((NCR)(2)CH)}](n) [R = C(Me)(2)CN] (4). From [Li{N(SiMe(3))C(Bu(t))C(H)SiMe(3)}](2) (A) and 1,3- or 1,4-C(6)H(4)(CN)(2), with no apparent synergy between the two CN groups, the product was the appropriate (mu-C(6)H(4))-bis(lithium beta-diketiminate) 6 or 7. Reaction of [Li{N(SiMe(3))C(Ph)=C(H)SiMe(3)}(tmeda)] and 1,3-C(6)H(4)(CN)(2) afforded 1,3-C(6)H(4)(X)X' (X =CC(Ph)N(SiMe3)Li(tmeda)N(SiMe3)CH; X' = CN(SiMe3)Li(tmeda)NC(Ph)=C(H)SiMe3)(9). Interaction of A and 2[1,2-C(6)H(4)(CN)(2)] gave the bis(lithio-isoindoline) derivative [C6H4C(=NH)N{Li(OEt2)}C=C(SiMe3)C(Bu(t))=N(SiMe3)]2 (5). The X-ray structures of 2, 3, 5 and 9 are presented, and reaction pathways for each reaction are suggested.