Coordination Chemistry of thecyclo-(P5tBu4)− Ion: Monomeric and Oligomeric Copper(I), Silver(I) and Gold(I) Complexes

Cyclo-Tetrakis(μ-diphenylphosphido)-1,5-bis(tri-tert-butylphosphine)-Tetracopper

Copper phosphido compound Cu4(μ-PPh2)4(PtBu3)2 was synthesized by three synthetic methods and structurally characterized by X-ray diffraction and 1H, 31P, 13C and 31P HMBC NMR spectroscopy. Cu4(μ-PPh2)4(PtBu3)2 was also demonstrated to be a hydrophosphination pre-catalyst.

Gold(I) Complexes of Tetra-tert-butylcyclotetraphosphane

The reaction of tetra-tert-butylcyclotetraphosphane cyclo-(PtBu)4 (L) with one to four equivalents [AuCl(tht)] (tht = tetrahydrothiophene) leads to the gold(I) complexes [(AuCl)nL] (n = 1–4, 1–4) in which the ligand coordinates...

Facile synthesis of cyclo-(P4tBu3)-containing oligo- and pnictaphosphanes

The cyclo-(P₄^tBu₃) synthon [Li{cyclo-(P₄^tBu₃)}(thf)(tmeda)] (1) (thf = tetrahydrofuran, tmeda = N,N,N',N'-tetramethylethane-1,2-diamine) is readily accessible in a one-pot synthesis from P₄ and Li^tBu. The use of 1 as a cyclo-(P₄^tBu₃) building block enables the rational synthesis of cyclo-(P₄^tBu₃)-containing oligophosphanes, namely {cyclo-(P₄^tBu₃)}₂ (2), {cyclo-(P₄^tBu₃)}₂P^tBu (3) and {cyclo-(P₄^tBu₃)}₂CH₂ (4), C_3v-symmetric pnictaphosphanes E{cyclo-(P₄^tBu₃)}₃ (E = Bi, Sb, As; 5-7) as well as AsCl{cyclo-(P₄^tBu₃)}₂ (8). Compounds 5 and 6 represent the first neutral homoleptic bismuthane and stibane that contain only bonds to phosphorus. All new compounds were isolated in moderate to good yields and fully characterised. The ³¹P{¹H} NMR spectral data of 1, 2, 4, and 8 have been determined by automated line-shape analysis.

Non-conventional Behavior of a 2,1-Benzazaphosphole: Heterodiene or Hidden Phosphinidene?

The titled 2,1-benzazaphosphole (1) (i. e. ArP, where Ar=2-(DippN=CH)C6 H4 , Dipp=2,6-iPr2 C6 H3 ) showed a spectacular reactivity behaving both as a reactive heterodiene in hetero-Diels-Alder (DA) reactions or as a hidden phosphinidene in the coordination toward selected transition metals (TMs). Thus, 1 reacts with electron-deficient alkynes RC≡CR (R=CO2 Me, C5 F4 N) giving 1-phospha-1,4-dihydro-iminonaphthalenes 2 and 3, that undergo hydrogen migration producing 1-phosphanaphthalenes 4 and 5. Compound 1 is also able to activate the C=C double bond in selected N-alkyl/aryl-maleimides RN(C(O)CH)2 (R=Me, tBu, Ph) resulting in the addition products 7-9 with bridged bicyclic [2.2.1] structures. The binding of the maleimides to 1 is semi-reversible upon heating. By contrast, when 1 was treated with selected TM complexes, it serves as a 4e donor bridging two TMs thus producing complexes [μ-ArP(AuCl)2 ] (10), [(μ-ArP)4 Ag4 ][X]4 (X=BF4 (11), OTf (12)) and [μ-ArP(Co2 (CO)6 )] (13). The structure and electron distribution of the starting material 1 as well as of other compounds were also studied from the theoretical point of view.

Versatile Coordination Chemistry of Hexa-tert-butyl-octaphosphine

The octaphosphine {cyclo-(P₄^tBu₃)}₂ (1) possesses a multifaceted coordination chemistry. The predominant binding mode is a P,P-chelate, e.g., in the monometallic chelate complex [MLL'(1-κ²P²,P^4')] in which the ligand 1 adopts a gauche conformation. Examples include square-planar (M = Rh^I, L = CO, L' = Cl (2), M = Pd^II, L = L' = Cl (3), M = Pt^II, L = L' = Cl (9)), tetrahedral (M = Co^-I, L = NO, L' = CO (4)), and trigonal-planar complexes [ML(1-κ²P²,P^4')] (M = Pd⁰, L = PPh₃, (5), M = Cu^I, L = Br (6)). With 2 equiv of [CuBr(SMe₂)], a dinuclear complex [(CuBr)₂(1-κ²P²,P^2',κ²P⁴,P^4')] (7) was obtained which features a synperiplanar conformation of the octaphosphine. A second coordination mode was also observed in [PtCl₂(1-κ²P¹,P^2')] (10) in which the bridge phosphorus atom in octaphosphine 1 is involved in the chelation, with the ligand in an antiperiplanar conformation. Thermolysis of selected complexes showed them to be suitable candidates for the generation of phosphorus-rich metal phosphides MP_x (x > 1).

P-P Condensation and P-N/P-P Bond Metathesis: Facile Synthesis of Cationic Tri- and Tetraphosphanes

[LC R P((PhP)2 C2 H4 )][OTf] (4 a,b[OTf]) and [LC iPr P(PPh2 )2 ][OTf] (5 b[OTf]) were prepared from the reaction of imidazoliumyl-substituted dipyrazolylphosphane triflate salts [LC R P(pyr)2 ][OTf] (3 a,b[OTf]; a: R=Me, b=iPr; LC R =1,3-dialkyl-4,5-dimethylimidazol-2-yl; pyr=3,5-dimethylpyrazol-1-yl) with the secondary phosphanes PhP(H)C2 H4 P(H)Ph) and Ph2 PH. A stepwise double P-N/P-P bond metathesis to catena-tetraphosphane-2,3-diium triflate salt [(Ph2 P)2 (LC Me P)2 ][OTf]2 (7 a[OTf]2 ) is observed when reacting 3 a[OTf] with diphosphane P2 Ph4 . The coordination ability of 5 b[OTf] was probed with selected coinage metal salts [Cu(CH3 CN)4 ]OTf, AgOTf and AuCl(tht) (tht=tetrahydrothiophene). For AuCl(tht), the helical complex [{(Ph2 PPLC iPr )Au}4 ][OTf]4 (9[OTf]4 ) was unexpectedly formed as a result of a chloride-induced P-P bond cleavage. The weakly coordinating triflate anion enables the formation of the expected copper(I) and silver(I) complexes [(5 b)M(CH3 CN)3 ][OTf]2 (M=Cu, Ag) (10[OTf]2 , 11[OTf]2 ).

Synthesis of metallophosphaalkenes by reaction of organometallic nucleophiles with a phosphaethynolato-borane

We describe the reaction of a phosphaethynolato-borane [B]OCP ([B] = N,N'-bis(2,6-diisopropylphenyl)-2,3-dihydro-1H-1,3,2-diazaboryl) with the organometallic nucleophile Na[Cp*Fe(CO)2] (Cp* = pentamethylcyclopentadienyl). The electrophilic character of [B]OCP allows for a new route towards the formation metal-phosphorus bonds affording a metallophosphaalkene that can be functionalised at both the oxygen and phosphorus atoms depending on the reagents employed.

Silylphosphido complexes of gold(I) coordinated with NHC ligands

The N-heterocyclic carbenes IPr (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) and iPr2-bimy (iPr2-bimy = 1,3-di-isopropylbenzimidazole-2-ylidene) were utilized as a basis for the preparation of four gold–silylphosphido complexes: [(IPr)AuP(Ph)SiMe3] (1), [(IPr)AuP(SiMe3)2] (2), [(iPr2-bimy)AuP(Ph)SiMe3] (3), and [(iPr2-bimy)AuP(SiMe3)2] (4). These complexes represent rare examples of terminally bonded Au–PR2 and the first examples where phosphorus retains reactive P-SiMe3 moieties. The reactivity of the P–Si bonds in 1 and 3 was explored via the addition of PhC(O)Cl. The products of these reactions were the formation of the phosphido-bridged [(IPrAu)2(μ-PPhC(O)Ph)][AuCl2] (5) and, in the case of the smaller N-heterocyclic carbenes, the tertiary phosphine PPh(C(O)Ph)2 (6) was isolated together with the known gold complex [(iPr2-bimy)AuCl]. Both reactions proceed via the elimination of ClSiMe3.

Coinage metal coordination chemistry of stable primary, secondary and tertiary ferrocenylethyl-based phosphines

Ferrocene-based phosphines constitute an important auxiliary ligand in inorganic chemistry. Utilizing the (ferrocenylethyl)phosphines (FcCH2CH2)3-nHnP (Fc = ferrocenyl; n = 2, 1; n = 1, 2; n = 0, 3) the synthesis of a series of coordination complexes [(FcCH2CH2)3-nHnPCuCl]4 (n = 2, 1-CuCl; n = 0, 3-CuCl), [(FcCH2CH2)2HPCuCl] (2-CuCl), {[(FcCH2CH2)H2P]2AgCl}2 (1-AgCl), [(FcCH2CH2)2HPAgCl] (2-AgCl), [(FcCH2CH2)3PAgCl]4 (3-AgCl), [(FcCH2CH2)3PM(OAc)]4 (M = Cu, 3-CuOAc M = Ag, 3-AgOAc), [(FcCH2CH2)3-nHnPAuCl] (n = 1, 2-AuCl; n = 0, 3-AuCl), via the reaction between the free phosphine and MX (M = Cu, Ag and Au; X = Cl, OAc), is described. The reaction between the respective phosphine with a suspension of metal-chloride or -acetate in a 1 : 1 ratio in THF at ambient temperature affords coordinated phosphine-coinage metal complexes. Varying structural motifs are observed in the solid state, as determined via single crystal X-ray analysis of 1-CuCl, 3-CuCl, 1-AgCl, 3-AgCl, 3-CuOAc, 3-AgOAc, 2-AuCl and 3-AuCl. Complexes 1-CuCl and 3-CuCl are tetrameric Cu(i) cubane-like structures with a Cu4Cl4 core, whereas silver complexes with primary and tertiary phosphine reveal two different structural types. The structure of 1-AgCl, unlike the rest, displays the coordination of two phosphines to each silver atom and shows a quadrangle defined by two Ag and two Cl atoms. In contrast, 3-AgCl is distorted from a cubane structure via elongation of one of the ClAg distances. 3-CuOAc and 3-AgOAc are isostructural with step-like cores, while complexes 2-AuCl and 3-AuCl reveal a linear geometry of a phosphine gold(i) chloride devoid of any aurophilic interactions. All of the complexes were characterized in solution by multinuclear (1)H, (13)C{(1)H} and (31)P NMR spectroscopic techniques; the redox chemistry of the series of complexes was examined using cyclic voltammetry. This class of complexes has been found to exhibit one reversible Fe(ii)/Fe(iii) oxidation couple, suggesting the absence of electronic communication between the ferrocenyl units on individual phosphine ligands as well as between different phosphines on the polymetallic cores.

Assembly and stabilization of {E(cyclo-P3)2} (E = Sn, Pb) as a bridging ligand spanning two triaryloxyniobium units

Complexes (THF)0-2E[P3Nb(ODipp)3]2 (E = Sn, Pb; Dipp = 2,6-(i)Pr2C6H3) were isolated (>90%) from the salt metathesis of [Na(THF)3][P3Nb(ODipp)3] with E(2+) salts. The reaction of (THF)Sn[P3Nb(ODipp)3]2 with pyridine-N-oxide was investigated as a method to deposit a new SnP6 phase. Additionally, the neutral complex P3Nb(ODipp)2(py)2 (py = pyridine) was prepared from [Na(THF)3][P3Nb(ODipp)3] in the presence of pyridine and salts of coordinating cations (Mg(II), Sn(II), Pb(II), Ge(II), Hg(II) and Ag(I)). P3Nb(ODipp)2(py)2 was found to successfully produce AsP3 upon treatment with AsCl3. The characterization of complexes (THF)0-1Sn[P3Nb(ODipp)3]2, (THF)2Pb[P3Nb(ODipp)3]2 and P3Nb(ODipp)2(py)2, including their solid state structures, is discussed.

Remarkably stable chelating bis-N-heterocyclic carbene adducts of phosphorus(i) cations

Treatment of triphosphenium precursors with bidentate bis-N-heterocyclic carbenes generates remarkably stable phosphamethine cyanine dyes with useful chemical and physical properties.

The reactivity of silylated amino(dichloro)phosphanes in the presence of silver salts

New cyclic and acylic phosphorus-nitrogen compounds have been synthesized in reactions of Hyp-N(SiMe3)PCl2 (hypersilyl = Hyp = (Me3Si)3Si) with silver salts of the perfluorinated anions [CF3CO2](-), [CF3SO3](-), and [C6F5](-). Depending on the choice of the silver salt, not only AgCl but also Me3SiCl elimination could be observed, leading to a transient highly reactive 1,3 dipole molecule. This 1,3 dipole molecule was found to be a key species, which can undergo [3 + 2] cyclization, when a dipolarophile such as acetonitrile is present. Also, dimerization or even cyclo-tetramerization are observed. The occurrence of different reaction channels demonstrates that the hypersilyl moiety can act as a highly reactive functional group. All new compounds have been characterized by single-crystal X-ray diffraction studies.

Platinum(II) tetramesityltetraphosphane-1,4-diides

[Na(2)(thf)(4)(P(4)Mes(4))] () (Mes = 2,4,6-Me(3)C(6)H(2)) reacts with one equivalent of [PtCl(2)(cod)] (cod = 1,5-cycloctadiene) or [PtCl(2)(dppe)] (dppe = bis(diphenylphosphino)ethane) to give the corresponding platinum(II) tetramesityltetraphosphane-1,4-diide complexes [Pt(P(4)Mes(4))(cod)] () and [Pt(P(4)Mes(4))(dppe)] (). The Pt-P bonds of these complexes proved to be extraordinarily stable and did not react with insertion reagents such as tert-butyl isocyanide or cyclohexyl isocyanide. Instead, ligand transfer occurred to give [Pt(P(4)Mes(4))(C[triple bond, length as m-dash]NBu(t))(2)] () and [Pt(P(4)Mes(4))(C[triple bond, length as m-dash]NCy)(2)] (). Further reactions of with CO, CS(2), white phosphorus, MeI and ethyl diazoacetate led either to formation of cyclo-P(4)Mes(4) and cyclo-P(3)Mes(3) or to unidentified products, in which no evidence of insertion of these reagents into the Pt-P bond was observed.