Crystalline metal (Li, Mg, Ca, Sr, Ba, Sn, Pb) complexes of the new chelating N,N'-dianionic [1,2-N(R)C6H4(CH2NR)](2-) ligand (R = SiMe3, CH2Bu(t)).

2-Aminomethylaniline was converted into the N,N'-bis(pivaloyl) (1) or -bis(trimethylsilyl) (2) derivative, using 2 Bu(t)C(O)Cl or 2 Me(3)SiCl (≡ RCl), respectively, with 2 NEt(3), or for 2 from successively using 2 LiBu(n) and 2 RCl. N,N'-Bis(neopentyl)-2-(aminomethyl)aniline (3) was prepared by LiAlH(4) reduction of 1. From 2 or 3 and 2 LiBu(n), the appropriate dilitiodiamide {2-[{N(Li)R}C(6)H(4){CH(2)N(Li)R}(L)](2) (L absent, 4a; or L = THF, 4b) or the N,N'-bis(neopentyl) analogue (5) of 4a was prepared. Treatment of 4a with 2 Bu(t)NC, 2 (2,6-Me(2)C(6)H(3)NC) or 2 Bu(t)CN (≡ L') furnished the corresponding adduct [2-N{Li(L')R}C(6)H(4){CH(2)N(Li)R}] (4c, 4d or 4e, respectively), whereas 4b with 2 PhCN afforded [2-{N(Li)R}C(6)H(4){CH(2)C(Ph) = NLi(NCPh)}] (6). The dimeric bis(amido)stannylene [Sn{N(R)C(6)H(4)(CH(2)NR)-1,2}](2) (7) was obtained from 4a and [Sn(µ-Cl)NR(2)](2), while the N,N'-bis(neopentyl) analogue 8 of 7 was similarly derived from [Sn(µ-Cl)NR(2)](2) and 5. Reaction of two equivalents of the diamine 2 with Pb(NR(2))(2) yielded 9, the lead homologue of 7. Oxidative addition of sulfur to 7 led to the dimeric bis(diamido)tin sulfide 10. Treatment of 2 successively with 'MgBu(2)' in C(5)H(12) and THF gave [Mg{N(R)C(6)H(4)(CH(2)NR)}(THF)](2) (11a), which by displacement of its THF by an equivalent portion of Bu(t)CN or PhCN produced [Mg{N(R)C(6)H(4)(CH(2)NR)}(CNR')(n)] [R' = Bu(t), n = 1 (11b); R' = Ph, n = 2 (11c)]. The Ca (12), Sr (13) or Ba (14) analogues of the Mg compound 11a were isolated from 2 and either the appropriate compound M(NR(2))(2) (M = Ca, Sr, Ba), or successively 2 LiBu(n) and 2 M(OTos)(2). The new compounds 1-14 were characterized by microanalysis (C, H, N; not for 1, 2, 3, 5), solution NMR spectra, ν(max) (C≡N) (IR for 4c, 4d, 4e, 6, 11b, 11c), selected EI-MS peaks (for 1, 2, 3, 7, 8, 9, 10), and single crystal X-ray diffraction (for 4a, 4b, 11a).

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.

Crystalline di- or trianionic metal (Al, Sm) beta-diketiminates.

The new [Al(L(Tol))Br(2)] (1) and the known [Al(L(Ph))Me(2)] (2) were prepared as potential precursors to more novel aluminium compounds. In the event, only the latter was effective. Thus 2 and two equivalents of potassium was the source of [{Al(L(Ph))Me(2)K(2)(OEt(2))}(2)] (3). The complexes [{KSm(L(Ph))(2)}(2)] (4), [Sm(2)(L(Dph))(3)] (5) and [Sm(L(Tol,Ad))(L(Tol,Ad)-H)] (6) were obtained from SmI(2) and two equivalents of the appropriate potassium beta-diketiminate [L(Ph) or L(Tol) or L(Dph) = {N(SiMe(3))C(Ar)}(2)CH, Ar = Ph or C(6)H(4)Me-4 or C(6)H(4)Ph-4; L(Tol,Ad) = N(SiMe(3))C(C(6)H(4)Me-4)C(H)C(Ad)NSiMe(3), L(Tol,Ad)-H = N(SiMe(3))C(C(6)H(4)Me-4)C(H)C(Ad)NSiMe(2)CH(2), Ad = 1-adamantyl]. Crystalline complexes 3-6 were isolated in very low (4, 5) or satisfactory (3, 6) yield and characterised by X-ray diffraction. From comparisons of the M-N, N-C, C-C and C-C(Ar) bond lengths with suitable standards, complexes 3-5 are assigned as containing Al(3+)/(L(Ph))(3-) for 3, Sm(3+)/(L(Ph))(-)/(L(Ph))(3-) for 4, and {Sm(3+)}(2)/(L(Dph))(-)/(L(Dph))(2-)/(L(Dph))(3-) for 5. Complex 6 is best formulated as a Sm(3+) compound with one "normal" (L(Tol,Ad))(-) and one deprotonated (L(Tol,Ad)-H)(2-) ligand.

Crystalline amidocerium(IV) oxides and a side-on bridging dioxygen complex.

Complexes [Ce(NR(2))(3)] (1) or [Ce(NR''(2))(3)] (2) were cerium(III) precursors to the X-ray characterised crystalline oligomeric oxygen-containing amidocerium(IV) compounds [{Ce(NR(2))(2)(mu-O)}(n)] (3, n = 2; 4, n = 3), [{Ce(NR''(2))(2)(mu-O)}(4)] (5), [{(R(2)N)(3)Ce}(2)(mu-[upper bond 1 start]OMOM[upper bond 1 end])] (6, M = Na; 7, M = K), [{(R(2)N)(3)CeOCe(NR(2))(2)}(2)(mu-[upper bond 1 start]OKOK[upper bond 1 end])] (8), and [{Ce(NR(2))(3)}(2)(mu-eta(2):eta(2)-O(2))].2C(n)H(2n+2) (9, n = 6; 9', n = 5) [R = SiMe(3), NR''(2) = TMP = [upper bond 1 start]NC(Me)(2)(CH(2))(3)C[upper bond 1 end]Me(2)]. Each was isolated in low, or for 5 very low, yield. Except for 4, the oxidising agent was O(2) at -27 degrees C in hexane (3, 6, 7, 8, 9), pentane (9'), or toluene (5), and a co-reagent for the alkali metal bis(trimethylsilyl)amido(oxy)cerate(iv)s was NaNR(2) (8) or KNR(2) (7, 8). From 1 and an equivalent portion of 2,6-(t)Bu(2)-benzoquinone after 5 weeks in pentane there was obtained the bis(amido)cyclotricer(IV)oxane 4. The NMR spectral solution chemical shifts for NR(2) groups of 3, 4, and 6-9 were consistent with each sample being diamagnetic and hence a Ce(IV) species. A transient amidocerium(IV) superoxide Ce(NR(2))(3)(eta(2)-O(2)) (J), or its TMP analogue, is considered to be the common first-formed intermediate in each case, while 4 is believed to have arisen from the adventitious hydrolysis of [{Ce(NR(2))(3)O}(2)((t)Bu(2)C(6)H(2)-1,4)].

Varied reactions of [M(L)]3 with HgCl2, FeBr2, CeCl3, AgOTf; ligand transfer, nucleophilic attack with recombination and/or fragmentation [M = Li or Na; L = N(SiMe3){C(H)N}3SiMe3].

The crystalline compounds [Hg{N(R)C(H)NR}(2)] (1), [Fe(L)(2)](2) (2), [Ce(L)(2)Cl](2) (3), [(AlMe(2))(3){(N(R)C(H)NC(H)N)(2)C(H)NC(H)NR}] (4), and [Ag(8)Na{(N(R)C(H)N)(2)(C(H)N)(4)R}(3)] (5) were obtained from [Li(L)](3) (A) (for 1) or [Na(L)](3) (B) and HgCl(2), FeBr(2), CeCl(3), Al(Cl)Me(2), and AgOTf, respectively [L = N(R){C(H)N}(3)R; R = SiMe(3)]. Compounds 1, 2, 3, and 5 were prepared in tetrahydrofuran (THF) at 20 degrees C; for 4, it was C(6)H(14) at -78 degrees C. NMR data for 1 showed only a single SiMe(3) environment for 1, implicating a fast exchange process. Single crystal X-ray data showed dinuclear structures for 2 and 3. Each ligand [L](-) in crystalline 2 was bound to each of the two Fe atoms in a kappa(1)- or kappa(2)-fashion, respectively, with one NSiMe(3) group of the former unattached; this was consistent with VT (1)H NMR spectral data indicative of fast exchange (at 313 K) between axial kappa(1)- and equatorial kappa(2)-N,N'-coordination to Fe. The magnetic moment for 2 in C(6)H(6) was appropriate for high-spin octahedral Fe(II). The ligands [L](-) in crystalline 3 are arranged in a helical fashion. The NMR spectra of 4 in C(6)D(5)CD(3) showed that there is an equilibrium between two asymmetric structures; minor co-products were 4', assigned as a symmetrical isomer of 4, and N(R)C(H)NR(2). The anion of 5 is proposed to be identical to that of 4'. Routes to the ligands of 1, 4, 4', and 5 are suggested; the key feature is that the ligand [L](-), unless tethered in an appropriate metal-containing matrix (as in A, B, 2, or 3), is labile because of SiMe(3) mobility, fragmentation, and/or recombination.

Synthesis and structures of beta-dialdiminatoantimony(III) halides and beta-dialdiminium hexahalogenoantimoniates.

From SbCl3, SbBr3 or SbI3 and an equivalent portion of the -dialdiminatopotassium compound K[{N(C6H3Pri2-2,6)C(H)}2CPh] [[triple bond]K(L)] in Et2O there was obtained in good yield the crystalline yellow [SbCl2(L)].(0.5thf).(0.5Et2O) (1) and the bis(bromo) analogue 2, or the orange [{SbI(L)(mu-I)}2].(0.5Et2O) (3). Each of 1-3 was treated with the appropriate dihalogen (X2) in Et2O. Thus, whereas 1 or 2 furnished the corresponding -dialdiminium hexahalogenoantimoniate [Et2O...H(L)H...OEt2][SbX6] (4, X = Cl; 6, X = Br), the iodo compound 3 afforded the known pyrazolium salt [N(C6H3Pri2-2,6)C(H)C(Ph)C(H)N(C6H3Pri2-2,6)][I5]. It is suggested that the source of the additional 2HX, required to convert 1 or 2 with X2 in Et2O into 4 or 6, was derived from halogenation of the N-aryl groups of L. The formation of 4 or 6 was achieved by the alternative synthesis from equivalent portions of [H2(L)]X, SbX3 and X2 in diethyl ether. The X-ray structures of the isomorphous compounds 1 and 2 and 4 and 6, as well as of 3, are reported.

Synthesis and characterisation of twelve Sn(IV) diaryls and formation of a Sn(III) triaryl.

Ten new crystalline compounds of formula (i) [{Sn(Ar(N2))(2)(micro-E)}(2)] [E = O (), S (), Se (), Te ()], (ii) [Sn(Ar(N2))(2)(ER)(2)] [ER = SCH(2)Ph (), SePh (), TePh ()], (iii) [Sn(Ar(N2))(2)(Br)R] [R = CH(SiMe(3))(2) (), Bu(t) ()] and (iv) [Sn(Ar(N2))(2){CH(SiMe(3))(2)}][BPh(4)] [Ar(N2) = C(6)H(3)(NMe(2))(2)-2,6 ()] have been prepared and identified by microanalysis, EI-mass spectrometry and multinuclear NMR spectroscopy, and for , , , and by single crystal X-ray diffraction. Whereas in the solid state, each of the latter five has only one of its two NMe(2) substituents of each [Ar(N2)](-) ligand close to the tin atom (<3.1 A), in solution at ambient temperature the NMe(2) groups are characterised by a single (1)H and (13)C signal. The known compounds [Sn(Ar(N2))(2)(NCE)(2)] [E = O (), S ()] were synthesised by a new route: the redox reaction between [Sn(Ar(N2))(2)] () and 2AgNCE. Irradiation of a toluene solution of at 298 K afforded a persistent radical assigned as [ Sn(Ar(N2))(3)] ().

Heteroleptic ytterbium(II) complexes supported by a bulky beta-diketiminato ligand.

Heteroleptic beta-diketiminatoytterbium(ii) complexes [{Yb(L)(mu-I)(thf)}(2)] [: L = {N(Ar*)C(Me)}(2)CH = L(1), : L = {N(SiMe(3))C(Ph)}(2)CH = L(2); Ar* = C(6)H(3)(i)Pr(2)-2,6] were prepared by a salt elimination [from YbI(2)(thf)(2) and KL] or by a ligand redistribution [from YbI(2)(thf)(2) and YbL(2)] reaction. Complexes and were convenient precursors to some new Yb(ii) heteroleptic compounds. Thus, reaction of and with KN(SiMe(3))(2) yielded the mononuclear amido compounds [Yb(L){N(SiMe(3))(2)}(thf)] (: L = L(1) and : L = L(2)). Similarly, with K{N(H)Ar*} gave [Yb(L(1)){N(H)Ar*}(thf)] (). Complex was also obtained via a protolytic reaction of [Yb{N(SiMe(3))(2)}(2)(thf)(2)] with HL(1) at an elevated temperature. Treatment of with slightly less than a stoichiometric amount of K{CH(SiMe(3))(2)} afforded [Yb(L(1)){CH(SiMe(3))(2)}(thf)] (), while using even a small excess of the alkyl reagent resulted in the deprotonation of the beta-diketiminato ligand and the formation of the known dimer [{Yb(L(3))(thf)}(2)] [, L(3) = N[combining macron](Ar*)C(Me)C(H)C(C[combining macron]H(2))N(Ar*)]. Compounds or reacted with KCPh(3) in thf yielding [Yb(L(1)){eta(5)-C(6)H(5)CPh(2)}(thf)] () or [Yb(CPh(3))(2)(thf)(2)] (), respectively; the latter has two differently coordinated CPh(3) ligands. The molecular structures of 1, 2, 4, 5, 6, 8 and 9 were determined by X-ray diffraction.

beta-Diiminato complexes of arsenic including the formally AsI compound [As3L3] [L = [N(C6H3Pri2-2,6)C(H)]2CPh].

The reaction of the potassium beta-diiminate KL (L = [[N(Ar)C(H)](2)CPh](-); Ar = C(6)H(3)Pr(i)(2)-2,6) with AsI(3) gave [AsI(2)L] (1), which upon reduction with KC(8) produced [(kappa(1)-L)(2)As-As[double bond, length as m-dash]As(kappa(2)-L)] (2), having a unique bent chain of the three arsenic atoms in the formal oxidation states +2, 0 and +1.

Synthesis and structures of halides and pseudohalides of bis[2,6-bis(dimethylamino)phenyl]tin(IV).

Oxidative addition reactions of Sn{C6H3(NMe2)(2)-2,6}2 [ identical with Sn(ArN2)2] () with XeF2, HgCl2 or TeCl4, dabco.2Br2, I2, or SiMe3N3 afforded [Sn(ArN2)2F2] (), [Sn(ArN2)2Cl2] (), [Sn(ArN2)2Br2] (), [Sn(ArN2)2I2] (), or [Sn(ArN2)2{N(SiMe3)2}N3] (), respectively. Compound was also obtained from and aqueous KF. Treatment of , under phase transfer conditions using [NBnEt3]Cl in H2O, with NaN3, KOCN, or KSCN yielded [Sn(ArN2)2(N3)2] (), [Sn(ArN2)2(NCO)2] (), or [Sn(ArN2)2(NCS)2] (), respectively. Alternative pathways to are suggested. Excellent (, and ) and satisfactory () yields were recorded; each compound was characterised by C, H, N microanalysis, mass spectra and multinuclear NMR solution spectra at ambient temperature, which invariably showed equivalent NMe2(1)H and 13C signals for the two NMe2 groups. The X-ray structures of crystalline [Sn(ArN2)Cl] (), , , , and showed that only one of the 2- and 6-Me2N substituents of an (ArN2) group was in a close SnN contact. Reaction of with Li[AlMe4] or LiMe gave [Sn(ArN2)(micro-Me)2AlMe2] () or c-(SnMe2)6, respectively.

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 3a, 3b, 4a, 4b, 5a, 5b, 5c and 9. The X-ray structure of each has been determined, as well as of [YCl(L4)(2)] (6), [Y(L1)(2)OBu(t)] (7) and [Y{CH(SiMe(3))(2)}(thf)(mu-Cl)(2)Li(OEt(2))(2)(mu-Cl)](2) (8). The N,N'-kappa(2)-beta-diiminato ligands were [{N(R)C(Me)}(2)CH](-) [R = C(6)H(4)Pr(i)-2 (L1); R = C(6)H(4)Bu(t)-2 (L2); R = C(6)H(3)Pr(i)(2)-2,6 (L3)], [{N(SiMe(3))C(Ph)}(2)CH)](-) (L4) and [{N(C(6)H(3)Pr(i)(2)-2,6)C(H)}(2)CPh](-) (L5). 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) = (L1(3a)) or (L1(3b))] and [Y(mu-Cl)(L3)(mu-Cl)Li(OEt(2))(2)(mu-Cl)](2) (4a) or its thf (instead of Et(2)O) equivalent 4b. Each of the Li(OEt(2))(2)Cl(2) moieties is bonded in a terminal (3) or bridging (4) mode with respect to the two Y atoms; the difference is attributed to the greater steric demand of L3 than L1 or L2. Under slightly more forcing conditions, YCl(3) and Li(L2) (via 3b) gave the lithium-free complex [YCl(2)(L2)(thf)(2)] (5b). Two isoleptic compounds 5a and 5c (having in place of L2 in 5b, L3 and L5, respectively) were obtained from YCl(3) and an equivalent portion of K[L3] and Na[L5], respectively; under the same conditions using Na[L4], the unexpected product was [YCl(L4)(2)] (6) (i.e. incorporating only one half of the YCl(3)). A further unusual outcome was in the formation of 8 from 3a and 2 Li[CH(SiMe(3))(2)]. Compound [Y(L5){N(H)C(6)H(3)Pr(i)(2)-2,6}(thf)(mu(3)-Cl)(2)K](2).4Et(2)O (9), 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.

Synthesis and structures of crystalline Li, Al and Sn(II) 1-azaallyls and beta-diketiminates derived from [Li{mu,eta3-N(SiMe3)C(Ad)C(H)SiMe3}]2 (Ad = 1-adamantyl).

The crystalline dimeric 1-azaallyllithium complex [Li{mu,eta(3-N(SiMe3)C(Ad)C(H)SiMe3}]2 (1) was prepared from equivalent portions of Li[CH(SiMe3)2] and 1-cyanoadamantane (AdCN). Complex was used as precursor to each of the crystalline complexes 2-8 which were obtained in good yield. By 1-azaallyl ligand transfer, 1 afforded (i) [Al{eta3-N(SiMe3)C(Ad)C(H)SiMe3}{kappa1-N(SiMe3)C(Ad)=C(H)SiMe3-E}Me] (5) with [AlCl2Me](2), (ii) [Sn{eta3-N(SiMe3)C(Ad)C(H)SiMe3}2] (7) with Sn[N(SiMe3)2]2, and (iii) [Li(N{C(Ad)=C(H)SiMe3-E}{Si(NN)SiMe3})(thf)2] (8) with the silylene Si[(NCH(2)Bu(t))2C6H(4)-1,2] [= Si(NN)]. By insertion into the C[triple bond, length as m-dash]N bond of the appropriate cyanoarene RCN, gave the beta-diketiminate [Li{mu-N(SiMe3)C(Ad)C(H)C(R)NSiMe3}]2 [R = Ph (2), C(6)H(4)Me-4 (3)], and yielded [Al{kappa2-N(SiMe3)C(Ad)C(H)C(Ph)NSiMe3}{kappa1-N(SiMe3)C(Ad)=C(H)SiMe3-E}Me] (6). The beta-diketiminate [Al{kappa2-N(SiMe3)C(Ad)C(H)C(Ph)NSiMe3}Me2] (4) was prepared from 2 and [AlClMe2]2. The X-ray structures of 1 and 3-8 are presented. Multinuclear NMR spectra in C6D6 or C6D5CD3 have been recorded for each of 1-8; such data on 8 revealed that in solution two minor isomers were also present.

Specific insertion reactions of a germylene, stannylene and plumbylene into the unique P-P bond of the hexaphospha-pentaprismane cage, P6C4tBu4: crystal and molecular structures of P6C4tBu4ER2 (E = Ge, Sn, R = N(SiMe3)2; E = Pb, R = (C6H3(NMe2)2 -2,6).

Treatment of the cage compound P6C4(t)Bu4 with M(N(SiMe3)2)2 (M = Ge or Sn) or Pb(C6H3(NMe2)2- 2,6) at room temperature results in their specific insertion into the P-P bond connecting the two 5-membered P3C2(t)Bu2 rings. The products were fully characterised by multinuclear NMR spectroscopy and single crystal X-ray diffraction studies.

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.

Synthesis and theoretical studies on rare three-coordinate lead complexes.

A series of beta-diketiminate lead halide complexes has been synthesised LPbCl (2), LPbBr (3) and LPbI (4) (L = {N(2,6-(i)Pr(2)C(6)H(3))C(Me)}2CH]), which includes a rare example of a three-coordinate lead iodide (4). The chloride and bromide complexes, 2 and 3, are relatively stable in both the solid and solution states, only slowly decomposing to elemental lead over the course of a month in solution, the lead iodide 4 appears to be less stable and decomposes after 3 d in the solid state at ambient temperatures. The lead chloride complex 2 was treated with KN(SiMe3)2 to yield an unusual terminal lead amide complex LPbN(SiMe3)2 (5). Unlike three-coordinate beta-diketiminate transition metal-halide complexes, the ligands are present in a pyramidal arrangement around the lead centre, commonly attributed to the presence of a stereochemically active lone pair. We have investigated the influence of this lone pair on the geometry of the metal halide complexes 2-4, as well as the isostructural germanium and tin complexes (6 and 7, respectively) using DFT calculations. The lone pair in the lead complexes is significantly more diffuse than in the tin and germanium analogues and only a small amount of hybridisation between the 6s and 6p orbitals is observed.

Synthesis of the 2,4,5-tri-tert-butyl-1,3-diphospholide anion by phosphinidene elimination from 2,4,6-tri-tert-butyl-1,3,5-triphosphabenzene on treatment with the amide Li[NPh(SiMe3)].

Treatment of the lithium amide Li[NPh(SiMe3)] with 2,4,6-tri-tert-butyl-1,3,5-triphosphabenzene, P(3)C(3)tBu(3), in a 1:2 ratio afforded equimolar amounts of the lithium salt of the five-membered 2,4,5-tri-tert-butyl-1,3-diphospholide anion, LiP(2)C(3)tBu(3) (isolated as its N,N,N',N'-tetramethylethylenediamine (TMEDA) adduct), and the tricyclic compound 6-[phenyl(trimethylsilyl)amino]-3,5,7-tri-tert-butyl-1,2,4,6-tetraphosphatricyclo[3.2.0.0(2,7)]hept-3-ene. Both compounds have been structurally characterised by single-crystal X-ray diffraction studies. The mechanism of this remarkable reaction has been elucidated by theoretical methods at the B3LYP/6-311+G** level of theory. The reaction involves a hitherto unobserved aminophosphinidene, which was formed by abstraction of a phosphorus atom from triphosphabenzene. The intermediate aminophosphinidene, which is further stabilised by the solvent THF, shows, in agreement with previous theoretical predictions, enhanced stability and reacts then with a second molecule of triphosphabenzene.

beta-Diiminato ligand (L) transformations in reactions of KL with PI3 and I2 [L = {N(C6H3Pr(i)2-2,6)C(H)}2CPh].

The reaction of the potassium beta-diiminate KL (L = [{N(Ar)C(H)}(2)CPh](-); Ar = C(6)H(3)Pr(i)(2)-2,6) with PI(3) unexpectedly produced a phosphenium salt of the intermolecularly C,C-coupled ligand [P(I){N(Ar)CH}(2)C(C(6)H(4)-4)C(Ph)(CH[double bond, length as m-dash]NAr)(2)](+)[I(3)](-), while an intramolecularly N,N-coupled salt [N[upper bond 1 start](Ar)C(H)C(Ph)C(H)N[upper bond 1 end](Ar)](+)[I(5)](-) was isolated from KL + I(2).

Synthesis and structures of selected benzamidinates of Li, Na, Al, Zr and Sn(II) using the C1-symmetric ligands [N(SiMe3)C(C6H4Me-4 or Ph)NPh]-.

Several compounds based on the C(1)-symmetric ligands [N(R)C(Ar)NPh]- [abbreviated as B1 (Ar = C(6)H(4)Me-4) or B2 (Ar = Ph), R = SiMe(3)] are reported. They are the crystalline metal benzamidinates [Li(mu:kappa2-B1)(OEt2)](2) (1), [Al(kappa2-B1)2Me] (2), [Al(kappa2-B1)2X] [X = Cl/Me, 1 : 1 (3)], [Sn(kappa2-B1)2] (4), Zr(kappa2-B1)2Cl2 (5), [Zr(kappa2-B1)3Cl] (6), [Na(mu:kappa2-B1)(tmeda)]2 (7), K[B1] (8), Li(B2)(OEt2) (9) and Zr(kappa2-B1)3Cl (10) and the known benzamidine Z-H2NC(C6H4Me-4) = NPh (11). They were prepared by (i) insertion of the nitrile 4-MeC6H4CN (1, 7, 8, 11) or PhCN (9) into the appropriate M-N(R')Ph [R' = R and M = Li (1, 9), Na (7), K (8)] bond and subsequent hydrolysis for 11 [R' = H and M = Li], or (ii) a ligand transfer reaction using the lithium amidinate 1 and Al(Me)2Cl (2, 3), SnCl2 (4) or ZrCl4 (5, 6), or Li(B2) and ZrCl4 (10). The X-ray structures of 1, 2, 3, 4, 6b (i.e..3PhMe) 7, and 11 are presented. Exploratory polymerisation experiments are described, using 2, 5 or 6 as a procatalyst with methylaluminoxane (MAO) (Al : Zr ca. 500 : 1) as promoter. Thus toluene solutions were exposed to C2H4 under ambient conditions; while 2 was unresponsive, 5 and 6 showed modest activity in the formation of polyethylene.