Synthesis and photophysical properties of cyclometalated platinum(II) 1,2-benzenedithiolate complexes and heterometallic derivatives obtained from the addition of [Au(PCy3)]+ units

The cyclometalated compounds [Pt(C^N)(HC^N)Cl] [HC^N = 2-phenylpyridine (Hppy; 1a), 1-(4-tert-butylphenyl)isoquinoline (Htbpiq; 1b)] react with 1,2-benzenedithiol, t-BuOK, and Bu(4)NCl in a 1:1:2:1 molar ratio in CH(2)Cl(2)/MeOH to give the complexes Bu(4)N[Pt(C^N)(bdt)] [bdt = 1,2-benzenedithiolate; C^N = ppy (Bu(4)N2a), tbpiq (Bu(4)N2b)]. In the absence of Bu(4)NCl, the same reactions afford solutions of K2a and K2b, which react with [AuCl(PCy(3))] to give the neutral heterometallic derivatives [Pt(C^N)(bdt){Au(PCy(3))}] [C^N = ppy (3a), tbpiq (3b)]. The cationic derivatives [Pt(C^N)(bdt){Au(PCy(3))}(2)]ClO(4) [C^N = ppy (4a), tbpiq (4b)] are obtained by reacting 3a and 3b with acetone solutions of [Au(OClO(3))(PCy(3))]. The crystal structures of 3b and 4b reveal the formation of short Pt···Au metallophilic contacts in the range 2.929-3.149 ?. Complexes 3b, 4a, and 4b undergo dynamic processes in solution that involve the migration of the [Au(PCy(3))](+) units between the S atoms of the dithiolate. Complexes Bu(4)N2a and 2b display a moderately solvatochromic band in their electronic absorption spectra that can be ascribed to a transition of mixed ML'CT/LL'CT character (M= metal; L = bdt; L' = C^N; CT = charge transfer), while their emissions are assignable to transitions of the same orbital parentage but from triplet excited states. The successive addition of [Au(PCy(3))](+) units to the anions 2a and 2b results in an increase in the absorption and emission energies attributable to lower highest occupied molecular orbital energies. Additionally, the characteristics of the absorption and emission spectra of the heterometallic derivatives indicate a gradual loss of LL'CT character in the involved electronic transitions, with a concomitant increase of the L'C and ML'CT contributions.     

Synthesis, structure, and luminescence of di- and trinuclear palladium/gold and platinum/gold complexes with (2,7-di-tert-butylfluoren-9-ylidene)methanedithiolate

Acetone solutions of [Au(OClO3)(PCy3)] react with complexes [M{S2C=(t-Bu-fy)}2]2- [t-Bu-fy=2,7-di-tert-butylfluoren-9-ylidene; M=Pd (2a), Pt (2b)] or [M{S2C=(t-Bu-fy)}(dbbpy)] [dbbpy=4,4'-di-tert-butyl-2,2'-bipyridyl; M=Pd (3a), Pt (3b)] to give the heteronuclear complexes [M{S2C=(t-Bu-fy)}2{Au(PCy3)}2] [2:1 molar ratio; M=Pd (4a), Pt (4b)], [M{S2C=(t-Bu-fy)}(dbbpy){Au(PCy3)}]ClO4 [1:1 molar ratio; M=Pd (5a), Pt (5b)], or [M{S2C=(t-Bu-fy)}(dbbpy){Au(PCy3)}2](ClO4)2 [2:1 molar ratio; M=Pd (6a), Pt (6b)]. The crystal structures of 3a, 4a, 4b, 5b, and 6a have been solved by single-crystal X-ray studies and, in the cases of the heteronuclear derivatives, reveal the formation of short Pd...Au or Pt...Au metallophilic contacts in the range of 3.048-3.311 A. Compounds 4a and b and 5a and b undergo a dynamic process in solution that involves the migration of the [Au(PCy3)]+ units between the sulfur atoms of the dithiolato ligands. The coordination of 2a and b and 3a and b to [Au(PCy3)]+ units results in important modifications of their photophysical properties. The dominant effect in the absorption spectra is an increase in the energy of the MLCT (4a and b) or charge transfer to diimine (5a, b, 6a, b) transitions because of a decrease in the energies of the mixed metal/dithiolate HOMOs. The Pd complexes 2a and 4a are luminescent at 77 K, and the features of their emissions are consistent with an essentially metal-centered 3d-d state. The Pt/Au complexes are also luminescent at 77 K, and their emissions can be assigned as originating from a MLCT triplet state (4b) or a mixture of charge transfer to diimine and diimine intraligand pi-pi* triplet states (5b and 6b).     

Cyclo- and carbophosphazene-supported ligands for the assembly of heterometallic (Cu2+/Ca2+, Cu2+/Dy3+, Cu2+/Tb3+) complexes: synthesis, structure, and magnetism

The carbophosphazene and cyclophosphazene hydrazides, [{NC(N(CH(3))(2))}(2){NP{N(CH(3))NH(2)}(2)}] (1) and [N(3)P(3)(O(2)C(12)H(8))(2){N(CH(3))NH(2)}(2)] were condensed with o-vanillin to afford the multisite coordination ligands [{NC(N(CH(3))(2))}(2){NP{N(CH(3))N═CH-C(6)H(3)-(o-OH)(m-OCH(3))}(2)}] (2) and [{N(2)P(2)(O(2)C(12)H(8))(2)}{NP{N(CH(3))N═CH-C (6)H(3)-(o-OH)(m-OCH(3))}(2)}] (3), respectively. These ligands were used for the preparation of heterometallic complexes [{NC(N(CH(3))(2))}(2){NP{N(CH(3))N═CH-C(6)H(3)-(o-O)(m-OCH(3))}(2)}{CuCa(NO(3))(2)}] (4), [{NC(N(CH(3))(2))}(2){NP{N(CH(3))N═CH-C(6)H(3)-(o-O)(m-OCH(3))}(2)}{Cu(2)Ca(2)(NO(3))(4)}]·4H(2)O (5), [{NC(N(CH(3))(2))}(2){NP{N(CH(3))N═CH-C(6)H(3)-(o-O)(m-OCH(3))}(2)}{CuDy(NO(3))(4)}]·CH(3)COCH(3) (6), [{NP(O(2)C(12)H(8))}(2){NP{N(CH(3))N═CH-C(6)H(3)-(o-O)(m-OCH(3))}(2)}{CuDy(NO(3))(3)}] (7), and [{NP(O(2)C(12)H(8))}(2){NP{N(CH(3))N═CH-C(6)H(3)-(o-O)(m-OCH(3))}(2)}{CuTb(NO(3))(3)}] (8). The molecular structures of these compounds reveals that the ligands 2 and 3 possess dual coordination pockets which are used to specifically bind the transition metal ion and the alkaline earth/lanthanide metal ion; the Cu(2+)/Ca(2+), Cu(2+)/Tb(3+), and Cu(2+)/Dy(3+) pairs in these compounds are brought together by phenoxide and methoxy oxygen atoms. While 4, 6, 7, and 8 are dinuclear complexes, 5 is a tetranuclear complex. Detailed magnetic properties on 6-8 reveal that these compounds show weak couplings between the magnetic centers and magnetic anisotropy. However, the ac susceptibility experiments did not reveal any out of phase signal suggesting that in these compounds slow relaxation of magnetization is absent above 1.8 K.     

Experimental observation of spin delocalisation onto the aryl-alkynyl ligand in the complexes [Mo(C≡CAr)(Ph2PCH2CH2PPh2)(η-C7H7)]+ (Ar = C6H5, C6H4-4-F; C7H7 = cycloheptatrienyl): an EPR and ENDOR investigation

The paramagnetic aryl-alkynyl complexes [Mo(C≡CAr)(dppe)(η-C(7)H(7))](+) (dppe = Ph(2)PCH(2)CH(2)PPh(2); Ar = C(6)H(5), [1](+); C(6)D(5), [2](+); C(6)H(4)-4-F, [3](+); C(6)H(4)-4-Me, [5](+)) and [Mo(C≡CBu(t))(dppe)(η-C(7)H(7))](+) [4](+), have been investigated in a combined EPR and ENDOR study. Direct experimental evidence for the delocalisation of unpaired spin density over the framework of an aryl-alkynyl ligand has been obtained. The X-band solution EPR spectrum of the 4-fluoro derivative, [3](+), exhibits resolved hyperfine coupling to the remote para position of the aryl group [a(iso)((19)F) = 4.5 MHz, (1.6 G)] in addition to couplings attributable to (95/97)Mo, (31)P and (1)H of the C(7)H(7) ring. A full analysis of the (1)H ENDOR spectra is restricted by the low g anisotropy of the system which prevents the use of orientation selection. However, inter-comparison of the (1)H cw-ENDOR frozen solution spectra of [1](+), [2](+), [4](+) and [5](+), combined with spectral simulation informed by calculated values derived from DFT investigations, has facilitated estimation of the experimental a(iso)((1)H) hyperfine couplings of [1](+) including the ortho, ±3.7 MHz (±1.3 G) and para, ±3.9 MHz (±1.4 G) positions of the C(6)H(5) substituent of the aryl-alkynyl ligand.     

Silver(I) Ethynide Coordination Networks and Clusters Assembled with tert-Butylphosphonic Acid

Variation of the reaction conditions with AgC≡CR (R = Ph, C(6)H(4)OCH(3)-4, (t)Bu), (t)BuPO(3)H(2), and AgX (X = NO(3), BF(4)) as starting materials afforded four new silver(I) ethynide complexes incorporating the tert-butylphosphonate ligand, namely, 3AgC≡CPh·Ag(2)(t)BuPO(3)·Ag(t)BuPO(3)H·2AgNO(3) (1), 2AgC≡CC(6)H(4)OCH(3)-4·Ag(2)(t)BuPO(3)·2AgNO(3) (2), [{Ag(5)(NO(3)@Ag(18))Ag(5)}((t)BuC≡C)(16)((t)BuPO(3))(4)(H(2)O)(3)][{Ag(5)(NO(3)@Ag(18))Ag(5)} ((t)BuC≡C)(16)((t)BuPO(3))(4)(H(2)O)(4)]·3SiF(6)·4.5H(2)O·3.5MeOH (3), and [{Ag(8)(Cl@Ag(14))}((t)BuC≡C)(14)((t)BuPO(3))(2)F(2)(H(2)O)(2)]BF(4)·3.5H(2)O (4). Single-crystal X-ray analysis revealed that complexes 1 and 2 display different layer-type coordination networks, while 3 and 4 contain high-nuclearity silver(I) composite clusters enclosing nitrate and chloride template ions, respectively, that are supported by (t)BuPO(3)(2-) ligands.     

Organic triplet emissions of arylacetylide moieties harnessed through coordination to [Au(PCy(3))]+. Effect of molecular structure upon photoluminescent properties

A family of mono- and binuclear Cy(3)P-supported gold(I) complexes containing various pi-conjugated linear arylacetylide ligands, including the two homologous series (Cy(3)P)Au(Ctbd1;CC(6)H(4))(n)()(-)(1)(Ctbd1;CPh) and (Cy(3)P)Au(Ctbd1;CC(6)H(4))(n)()Ctbd1;CAu(PCy(3)) (n = 1-4), have been prepared. X-ray crystal analyses revealed no intermolecular aurophilic interactions in their crystal lattice. The lowest-energy singlet transitions are predominately intraligand in nature and exhibit both phenyl and acetylenic (1)(pipi) character. Strong photoluminescence is detected in solid and solution states under ambient conditions, with lifetimes in the microsecond regime. For complexes with a single arylacetylide group, only phosphorescence from the arylacetylide (3)(pipi) state is observed. Vibrational spacings in the solid-state emission spectra can be attributed to a combination of phenyl ring deformation and symmetric phenyl ring and Ctbd1;C stretches. Additional delayed-fluorescence emission is recorded for complexes with multiple p-arylacetylide units, and this is attributed to a triplet-triplet annihilation process. The phosphorescence energy of these complexes are readily modified by altering the length of the conjugated arylacetylide system, while the intensity of phosphorescence relative to fluorescence decreases when the p-arylacetylide chain is elongated. Information regarding the nature and relative energies of arylacetylide singlet and triplet excited states has been derived from the two homologous series and extrapolated to polymeric arylacetylide species. The (3)(pipi) excited-state reduction potentials E degrees [Au(+)/Au] (Au = 1a, 2, and 4) are estimated to be -1.80, -1.28, and -1.17 V versus SSCE, respectively.     

Influence of the electronic characteristics of N-donor ligands in the excited state of heteronuclear gold(I)-copper(I) systems

By reaction of the heterometallic gold-silver complexes [{AuAg(C(6)F(5))(2)(N≡C-Me)}(2)](n) or [{AuAg(C(6)Cl(5))(2)(N≡C-Me)}(2)](n) and CuCl in the presence of pyrimidine and different nitrile ligands (acetonitrile, benzonitrile, and cinnamonitrile), the heteronuclear complexes {[Au(C(6)X(5))(2)][Cu(L)(μ(2)-C(4)H(4)N(2))]}(n) (X = F and L = N≡C-Me (1), L = N≡C-Ph (2) or N≡C-CH═CH-Ph (3); X = Cl and L = N≡C-Me (4), N≡C-Ph (5), N≡C-CH═CH-Ph (6)) have been prepared. The crystal structures of complexes {[Au(C(6)X(5))(2)][Cu(L)(μ(2)-C(4)H(4)N(2))]}(n) (X = F; L = N≡C-CH═CH-Ph (3), X = Cl; L = N≡C-Ph (5)) have been determined by X-ray diffraction studies. The crystal structures of both complexes consists of polymeric chains formed by the repetition of [Au(C(6)X(5))(2)][Cu(L)(μ(2)-C(4)H(4)N(2))] units through copper-pyrimidine bonds. Complexes 1, 2, 4, and 5 are brightly luminescent in the solid state at room temperature and at 77 K with lifetimes in the microseconds range. These compounds are also luminescent in solution, displaying different photophysical behaviors depending on the donor characteristics of the solvents used. The distortion in the excited state allows an associative attack by donor solvents quenching one of the emitting excited states. DFT optimizations of the ground (S(0)) and lowest triplet excited state (T(1)) display the structure distortion of the complexes upon electronic excitation. The molecular orbitals involved in the electronic transitions responsible for the phosphorescence in the case of the complexes 1, 2, 4, and 5 are related to metal (gold-copper) to ligand (pyrimidine) charge transfer transitions, while in the case of the nonluminescent complexes 3 and 6, the nonradiative electronic transition arises from metal (gold-copper) to ligand (cinnamonitrile) charge transfer transitions.     

DFT/TDDFT investigation on bis-cyclometalated alkynylgold(III) complex: Comparison of absorption and emission properties

absorption and phosphorescent mechanism of three Au(III) complexes, Au(2,5-F2C6H3-C^C^C)(C≡C-C6H4N(C6H5)2 [Au25FPh], Au(3,5-F2C6H3-C^C^C)(C≡C-C6H4N(C6H5)2 [Au35FPh], and Au(3,5-F2C6H3-C^C^C)(C≡C-C6H4N(1H-indole)2 [Au35FID], are calculated and compared using density functional theory (DFT) and time-dependent DFT (TDDFT). The calculated results reveal that enlarging the center C^C^C ligand will result in the enhanced LMCT participation. This theoretical contribution allows design of new Au(Ⅲ) complexes with higher phosphorescence efficiency.     

Gold(I) phosphido complexes: synthesis, structure, and reactivity

Deprotonation of the phosphine complexes Au(PHR(2))Cl with aqueous ammonia gave the gold(I) phosphido complexes [Au(PR(2))](n)() (PR(2) = PMes(2) (1), PCy(2) (2), P(t-Bu)(2) (3), PIs(2) (4), PPhMes (5), PHMes (6); Mes = 2,4,6-Me(3)C(6)H(2), Is = 2,4,6-(i-Pr)(3)C(6)H(2), Mes = 2,4,6-(t-Bu)(3)C(6)H(2), Cy = cyclo-C(6)H(11)). (31)P NMR spectroscopy showed that these complexes exist in solution as mixtures, presumably oligomeric rings of different sizes. X-ray crystallographic structure determinations on single oligomers of 1-4 revealed rings of varying size (n = 4, 6, 6, and 3, respectively) and conformation. Reactions of 1-3 and 5 with PPN[AuCl(2)] gave PPN[(AuCl)(2)(micro-PR(2))] (9-12, PPN = (PPh(3))(2)N(+)). Treatment of 3 with the reagents HI, I(2), ArSH, LiP(t-Bu)(2), and [PH(2)(t-Bu)(2)]BF(4) gave respectively Au(PH(t-Bu)(2))(I) (14), Au(PI(t-Bu)(2))(I) (15), Au(PH(t-Bu)(2))(SAr) (16, Ar = p-t-BuC(6)H(4)), Li[Au(P(t-Bu)(2))(2)] (17), and [Au(PH(t-Bu)(2))(2)]BF(4) (19).     

Synthesis and luminescent properties of cis bis-N-heterocyclic carbene platinum(II) bis-arylacetylide complexes

A series of luminescent N-heterocyclic carbene platinum(II) complexes, [(pmim)Pt(C≡C-R)(2)] (R = C(6)H(5) (2), C(6)H(4)OMe (3), C(6)H(2)(OMe)(3) (4), C(6)H(4)NMe(2) (5), C(4)H(3)S (6), C(6)H(4)C≡CC(6)H(5) (7), 1-pyrenyl (8), and C(6)H(4)F (9)), were successfully synthesized using the precursor (pmim)PtI(2), 1 (pmim = 1,1'-dipentyl-3,3'-methylene-diimidazoline-2,2'-diylidene). The X-ray crystal structures of 1, 4, 5, and 7 have been determined. These complexes showed long-lived emission in solution at room temperature. The emission origin of the complexes is tentatively assigned to be from triplet states of predominantly intraligand (IL) character with some mixing of metal-to-ligand charge-transfer (MLCT) character. TD-DFT and DFT calculations have been performed on most of the complexes to ascertain the nature of the excited state. Changes in the alkynyl ligands lead to a change in the absorption and emission maxima seen for these complexes in a potentially predictable way.     

Synthetic and structural chemistry of amidinate-substituted boron halides

The following new amidinate-substituted boron halides are reported: [PhC{N(SiMe(3))}(2)]BCl(2)(6), [MeC{NCy}(2)]BCl(2)(10), [Mes*C{NCy}(2)]BCl(2)(11), [MeC{N(i)Pr}(2)]BCl(2)(12), and [FcC{NCy}(2)]BBr(2)(13). Compound 6 was prepared via the trimethylsilyl chloride elimination reaction of BCl(3) with N,N,N'-tris(trimethylsilyl)benzamidine, and compounds 10-12 were prepared by salt metathesis between the lithium amidinates [RC(NR')(2)]Li and BX(3). Compound 13 was prepared via the insertion of 1,3-dicyclohexylcarbodiimide into the B-C bond of ferrocenyldibromoborane FcBBr(2). The molecular structures of 6, 10, 11, 13 and the known compound [PhC{N(SiMe(3))}(2)]BBr(2)(1) were established by single-crystal X-ray diffraction.     

Ruthenium agostic (phosphinoaryl)borane complexes: multinuclear solid-state and solution NMR, X-ray, and DFT studies

The reactivity of the (o-phosphinophenyl)(amino)borane compound HB(N(i)Pr(2))C(6)H(4)(o-PPh(2)) prepared from Li(C(6)H(4))PPh(2) and HBCl(N(i)Pr(2)) toward the bis(dihydrogen) complex RuH(2)(H(2))(2)(PCy(3))(2) (1) was studied by a combination of DFT, X-ray, and multinuclear NMR techniques including solid-state NMR, a technique rarely employed in organometallic chemistry. The study showed that the complex RuH(2){HB(N(i)Pr(2))C(6)H(4)(o-PPh(2))}(PCy(3))(2) (3), isolated in excellent yield as yellow crystals and characterized by X-ray diffraction, led in solution to PCy(3) dissociation and formation of an unsaturated 16-electron complex RuH(2){HB(N(i)Pr(2))C(6)H(4)(o-PPh(2))}(PCy(3)) (4), with a hydride trans to a vacant site. In both cases, the (phosphinoaryl)(amino)borane acts as a bifunctional ligand through the phosphine moiety and a Ru-H-B interaction, thus featuring an agostic interaction.     

Supramolecular luminescent gold(I)-copper(I) complexes: self-assembly of the Au(x)Cu(y) clusters inside the [Au3(diphosphine)3]3+ triangles

The reactions between diphosphino-alkynyl gold complexes (PhC2Au)PPh2(C6H4)(n)PPh2(AuC2Ph) (n = 1, 2, 3) with Cu(+) lead to formation of the heterometallic aggregates, the composition of which may be described by a general formula [{Au(x)Cu(y)(C2Ph)2x}Au3{PPh2(C6H4)(n)PPh2}3](3+(y-x)) (n = 1, 2, 3; x = (n + 1)(n + 2)/2; y = n(n + 1)). These compounds display very similar structural patterns and consist of the [Au(x)Cu(y)(C2Ph)2x](y-x) alkynyl clusters "wrapped" in the [Au3(diphosphine)3](3+) triangles. The complex for n = 1 was characterized crystallographically and spectrally, the larger ones (n = 2, 3) were investigated in detail by NMR spectroscopy. Their luminescence behavior has been studied, and a remarkably efficient emission with a maximum quantum yield of 0.92 (n = 1) has been detected. Photophysical experiments demonstrate that an increase of the size of the aggregates leads to a decrease in photostability and photoefficiency. Computational studies have been performed to provide additional insight into the structural and electronic properties of these supramolecular complexes. The theoretical results obtained are in good agreement with the experimental data, supporting the proposed structural motif. These studies also suggest that the observed efficient long-wavelength luminescence originates from metal-centered transitions within the heterometallic Au-Cu core.     

Highly luminescent octanuclear Au(I)-Cu(I) clusters adopting two structural motifs: the effect of aliphatic alkynyl ligands

Reactions of the homoleptic (AuC(2)R)(n) precursors with stoichiometric amount of diphosphine ligand PPh(2)C(6)H(4)PPh(2) (P^P) and Cu(+) ions lead to an assembly of a new family of bimetallic clusters [Au(6)Cu(2)(C(2)R)(6)(P^P)(2)](2+) (type I; R=9-fluorenolyl (1), diphenylmethanolyl (2), 2,6-dimethyl-4-heptanolyl (3), 1-cyclohexanolyl (4), Cy (5), tBu (6)). In the case of R=1-cyclohexanolyl, a structurally different complex [Au(6)Cu(2)(C(2)C(6)H(11)O)(6)(P^P)(3)](2+) (7, type II) could be obtained by treatment of 4 with one equivalent of the diphosphine, while for R=isopropanolyl only the latter type of cluster [Au(6)Cu(2)(C(2)C(3)H(7)O)(6)(P^P)(3)](2+) (8) was detected. Steric bulkiness of the alkynyl ligands and O···H-O hydrogen bonding are suggested to play an important role in stabilizing the type I and type II cluster structural motif, respectively. All the complexes exhibit intense photoluminescence in solution with emission parameters that depending on the geometrical arrangement of the octanuclear metal core. The clusters 1-4 and 6 show single emission band in a blue region (469-488 nm) with maximum quantum yield of 94% (4), while structurally different 7 and 8 emit yellow-orange (590 nm) with unity quantum efficiency. The theoretical DFT calculations of the electronic structures have been carried out to demonstrate that the metal-centered triplet emission within the heterometallic core plays a key role for the observed phosphorescence.     

Triplet electronic states in d(2) and d(8) complexes probed by absorption spectroscopy: a CASSCF/CASPT2 analysis of [V(H2O)6]3+ and [Ni(H2O)6]2+

Octahedral complexes of transition metal ions with d(2) and d(8) electron configurations have triplet electronic states with identical T(2g), A(2g), T(1g)((3)F), and T(1g)((3)P) symmetry labels. CASSCF and CASPT2 calculations indicate the predominant electronic configurations for each triplet state. The two (3)T(1g) states show strong configuration mixing in the d(8) complex [Ni(H(2)O)(6)](2+), but much weaker mixing occurs between these states in the d(2) compound [V(H(2)O)(6)](3+). Calculated vibrational frequencies and equilibrium geometries for the triplet states are used to obtain theoretical absorption spectra that are in agreement with the experimental data.     

Acrylonitrile polymerization by Cy3PCuMe and (Bipy)2FeEt2

Cy(3)PCuMe (1) undergoes reversible ligand redistribution at low temperature in solution to form the tight ion pair [Cu(PCy(3))(2)][CuMe(2)] (3). The structure of 3 was assigned on the basis of (i) the stoichiometry of the 1 = 3 equilibrium, (ii) the observation of a triplet for the PCy(3) C1 (13)C NMR resonance due to virtual coupling to two (31)P nuclei, and (iii) reverse synthesis of 1 by combining separately generated Cu(PCy(3))(2)(+) and CuMe(2)(-) ions. Complex 1 and [Cu(PCy(3))(2)][PF(6)] (5) coordinate additional PCy(3) to form (Cy(3)P)(2)CuMe and [Cu(PCy(3))(3)][PF(6)], respectively, while 3 does not. Complex 1, free PCy(3), and (bipy)(2)FeEt(2) (2) each initiate the polymerization of acrylonitrile. In each case, the polyacrylonitrile contains branches that are characteristic of an anionic polymerization mechanism. The major initiator in acrylonitrile polymerization by 1 is PCy(3), which is liberated from 1. A transient iron hydride complex is proposed to initiate acrylonitrile polymerization by 2.     

Coordination chemistry of the cyclo-(P(5)tBu(4))(-) ion: monomeric and oligomeric copper(I), silver(I) and gold(I) complexes

[Na{cyclo-(P(5)tBu(4))}] (1) reacts with [CuCl(PCyp(3))(2)] (Cyp=cyclo-C(5)H(9)) and [CuCl(PPh(3))(3)] (1:1) to give the corresponding copper(I) complexes with a tetra-tert-butylcyclopentaphosphanide ligand, [Cu{cyclo- (P(5)tBu(4))}(PCyp(3))(2)] (2) and [Cu{cyclo-(P(5)tBu(4))}(PPh(3))(2)] (3). The CuCl adduct of 2, [Cu(2)(mu-Cl){cyclo-(P(5)tBu(4))}(PCyp(3))(2)] (4), was obtained from the reaction of 1 with [CuCl(PCyp(3))(2)] (1:2). Compounds 2 and 3 rearrange, even at -27 degrees C, to give [Cu(4){cyclo- (P(4)tBu(3))PtBu}(4)] (5), in which ring contraction of the [cyclo-(P(5)tBu(4))](-) anion has occurred. The reaction of 1 with [AgCl(PCyp(3))](4) or [AgCl(PPh(3))(2)] (1:1) leads to the formation of [Ag(4){cyclo-(P(4)tBu(3))PtBu}(4)] (6). Intermediates, which are most probably mononuclear, "[Ag{cyclo-(P(5)tBu(4))}(PR(3))(2)]" (R=Cyp, Ph) could be detected in the reaction mixtures, but not isolated. Finally, the reaction of 1 with [AuCl(PCyp(3))] (1:1) yielded [Au{cyclo-(P(5)tBu(4))}(PCyp(3))] (7), whereas an inseparable mixture of [Au(3){cyclo-(P(5)tBu(4))}(3)] (8) and [Au(4){cyclo-(P(4)tBu(3))PtBu}(4)] (9) was obtained from the analogous reaction with [AuCl(PPh(3))]. Complexes 3-7 were characterised by (31)P NMR spectroscopy, and X-ray crystal structures were determined for 3-9.     

Luminescent mu-ethynediyl and mu-butadiynediyl binuclear gold(I) complexes: observation of (3)(pi pi*) emissions from bridging C(n)(2-) units.

The synthesis and X-ray structural and spectroscopic characterization for LAuC triple bond CAuL x 4CHCl(3) and LAuC triple bond C--C triple bond CAuL x 2CH(2)Cl(2) (1 x 4CHCl(3) and 2 x 2CH(2)Cl(2), respectively; L = PCy(3), tricyclohexylphosphine) are reported. The bridging C(n)(2-) units are structurally characterized as acetylene or diacetylene units, with C triple bond C distances of 1.19(1) and 1.199(8) A for 1 x 4CHCl(3) and 2 x 2CH(2)Cl(2), respectively. An important consequence of bonding to Au(I) for the C(n)(2-) moieties is that the lowest-energy electronic excited states, which are essentially acetylenic (3)(pi pi*) in nature, acquire sufficient allowedness via Au spin-orbit coupling to appear prominently in both electronic absorption and emission spectra. The origin lines for both complexes are well-defined and are observed at 331 and 413 nm for 1 and 2, respectively. Sharp vibronic progressions corresponding to v(C triple bond C) are observed in both emission and absorption spectra. The acetylenic (3)(pi pi) excited state of 2 has a long lifetime (tau(0) = 10.8 mus) in dichloromethane at room temperature and is a powerful reductant (E degrees [Au(2)(+)/Au(2)] < or = -1.85 V vs SSCE).     

Bis(alpha-diimine)nickel complexes: molecular and electronic structure of three members of the electron-transfer series [Ni(L)(2)](z)() (z = 0, 1+, 2+) (L = 2-Phenyl-1,4-bis(isopropyl)-1,4-diazabutadiene). A combined experimental and theoretical study

From the reaction of Ni(COD)(2) (COD = cyclooctadiene) in dry diethylether with 2 equiv of 2-phenyl-1,4-bis(isopropyl)-1,4-diazabutadiene (L(Ox))(0) under an Ar atmosphere, dark red, diamagnetic microcrystals of [Ni(II)(L*)(2)] (1) were obtained where (L*)(1-) represents the pi radical anion of neutral (L(Ox))(0) and (L(Red))(2-) is the closed shell, doubly reduced form of (L(Ox))(0). Oxidation of 1 with 1 equiv of ferrocenium hexafluorophosphate in CH(2)Cl(2) yields a paramagnetic (S = 1/2), dark violet precipitate of [Ni(I)(L(Ox))(2)](PF(6)) (2) which represents an oxidatively induced reduction of the central nickel ion. From the same reaction but with 2 equiv of [Fc](PF(6)) in CH(2)Cl(2), light green crystals of [Ni(II)(L(Ox))(2)(FPF(5))](PF(6)) (3) (S = 1) were obtained. If the same reaction was carried out in tetrahydrofuran, crystals of [Ni(II)(L(Ox))(2)(THF)(FPF(5))](PF(6)) x THF (4) (S = 1) were obtained. Compounds 1, 2, 3, and 4 were structurally characterized by X-ray crystallography: 1 and 2 contain a tetrahedral neutral complex and a tetrahedral monocation, respectively, whereas 3 contains the five-coordinate cation [Ni(II)(L(Ox))(2)(FPF(5))](+) with a weakly coordinated PF(6)(-) anion and in 4 the six-coordinate monocation [Ni(II)(L(Ox))(2)(THF)(FPF(5))](+) is present. The electro- and magnetochemistry of 1-4 has been investigated by cyclic voltammetry and SQUID measurements. UV-vis and EPR spectroscopic data for all compounds are reported. The experimental results have been confirmed by broken symmetry DFT calculations of [Ni(II)(L*)(2)](0), [Ni(I)(L(Ox))(2)](+), and [Ni(II)(L(Ox))(2)](2+) in comparison with calculations of the corresponding Zn complexes: [Zn(II)((t)L(Ox))(2)](2+), [Zn(II)((t)L(Ox))((t)L*)](+), [Zn(II)((t)L*)(2)](0), and [Zn(II)((t)L*)((t)L(Red))](-) where ((t)L(Ox))(0) represents the neutral ligand 1,4-di-tert-butyl-1,4-diaza-1,3-butadiene and ((t)L*)(1-) and ((t)L(Red))(2-) are the corresponding one- and two-electron reduced forms. It is clearly established that the electronic structures of both paramagnetic monocations [Ni(I)(L(Ox))(2)](+) (S = 1/2) and [Zn(II)((t)L(Ox))((t)(L*)](+) (S = 1/2) are different.     

Syntheses of highly unsaturated isocyanides via organometallic pathways

The carbon carbon coupling reaction by nucleophilic attack of (CO)(5)Cr(CN-CF=CF(2)) 1 by lithium or Grignard compounds 2a-i yields the isocyanide complexes (CO)(5)Cr(CN-CF=CF-R) 3a-i (a R = CH=CH(2), b R = CH=CF(2), c R = C≡CH, d R = C≡C-SiMe(3), e R = C≡C-Ph, f R = C≡C-C(6)F(4)OMe, g R = C≡C-C(6)H(3)(CF(3))(2), h R = C(6)F(5), i R = C(6)H(3)(CF(3))(2)) as mixtures of E and Z isomers. The dinuclear complexes 5a-c are obtained from the reaction of 1 with the dilithio or dimagnesium compound 4a-c as the Z,Z-, E,Z- and E,E-isomers, respectively. (CO)(5)Cr(CN-CF=CF-C≡C-C≡C-CF=CF-NC)Cr(CO)(5)7 is obtained as a mixture of Z,Z-, Z,E- and E,E-isomers from (CO)(5)Cr(CN-CF=CF-C≡C-H 3d by Eglington-Glaser coupling. (CO)(5)Cr(CN-CF=CF-C≡C-CF=CF-NC)Cr(CO)(5)6 and (CO)(5)Cr(CN-CF=CF-C=C-C≡C-CF=CF-NC)Cr(CO)(5)7 react with octacarbonyldicobalt forming the cluster compounds Z,Z-[{η(2)-μ(2)-(CO)(5)Cr(CN-CF=CF-C≡C-CF=CF-NC)Cr(CO)(5)}Co(2)(CO)(6)] Z,Z-8, E,Z-[{η(2)-μ(2)-(CO)(5)Cr(CN-CF=CF-C≡C-CF=CF-NC)Cr(CO)(5)}Co(2)(CO)(6)] E,Z-8 and E,E-[{η(2)-μ(2)-(CO)(5)Cr(CN-CF=CF-C≡C-CF=CF-NC)Cr(CO)(5)}Co(2)(CO)(6)] E,E-8 and Z,Z-[{η(2)-μ(2)-(CO)(5)Cr(CN-CF=CF-C≡C-C≡C-CF=CF-NC)Cr(CO)(5)}{Co(2)(CO)(6)}(2)] Z,Z-9, E,Z-[{η(2)-μ(2)-(CO)(5)Cr(CN-CF=CF-C≡C-C≡C-CF=CF-NC)Cr(CO)(5)}{Co(2)(CO)(6)}(2)] E,Z-9 and E,E-[{η(2)-μ(2)-(CO)(5)Cr(CN-CF=CF-C≡C-C≡C-CF=CF-NC)Cr(CO)(5)}{Co(2)(CO)(6)}(2)] Z,Z-9, respectively. The crystal and molecular structures of E-3d, Z-3h, Z,Z-8, E,Z-8 and Z,Z-9 were elucidated by single-crystal X-ray crystallography.