Temperature-Assisted Generation of Arylmethyl Radicals from Bis(arylmethyl)tin Dichlorides: Efficient Reagents for C s p 3 ${{{\bf C}}_{{{\bf s p}}

The oxidative-addition reaction between an arylmethyl chloride (RCH2 Cl; R=1-C10 H7 , 2,4,6-Me3 C6 H2 , 4-MeC6 H4 , 3-MeC6 H4 , C6 H5 , 4-ClC6 H4 ) and tin powder in boiling toluene produces bis(arylmethyl)tin dichlorides, [(RCH2 )2 SnCl2 ] in good yields. At 160 °C in mesitylene bis(1-naphthylmethyl)tin dichloride undergoes Sn-C homolytic cleavage to generate two 1-naphthylmethyl radicals (1-C10 H7 CH2 ⋅) which were trapped by TEMPO (C9 H8 NO⋅). Subsequently, the radicals (RCH2 ⋅) produced in this manner were utilized for efficient substitution reactions with electron-rich arenes (R'H; R'=2,4,6-Me3 C6 H2 , 1,2,4,5-Me4 C6 H, 1,2,3,4,5-Me5 C6 ) to obtain a variety of unsymmetrical diarylmethanes (RR'CH2 ). The addition of one equivalent of iodine (I2 ) to the reaction mixture resulted in a significant increase in the yields of coupled products.

1-Hy-droxy-4-methyl-pyridinium chloride.

The title salt, C6H8NO+·Cl-, contains two cations and two anions in the asymmetric unit. The components are linked by O-H⋯Cl and C-H⋯Cl hydrogen bonds, leading to tetra- (square-planar) or penta-coordinated (square-pyramidal) chloride ions. The title salt is isostructural with its bromide analogue.

s-Block metal complexes of PC(H)P-bridged chalcogen-centred methanides: comparisons with isoelectronic PNP-bridged monoanions.

The chemistry of the chalcogen-centred methanides [HC(PR2E)2]- (E = S, Se, Te; R = alkyl, aryl) (PC(H)P-bridged anions) is less well-developed than that of the isoelectronic imidodiphosphinates [N(PR2E)2]-, which are PNP-bridged analogues. The objective of this Perspective is to compare the chemistry of s-block metal complexes of the PC(H)P- and PNP-bridged anions in the context of synthetic approaches, X-ray (solid-state) structures, multinuclear NMR spectra, redox behaviour, and applications in coordination and inorganic heterocyclic chemistry. The related monochalcogeno-centred anions [HC(PR2)(PR2E)]- and [N(PR2)(PR2E)]- (E = S, Se, Te; R = alkyl, aryl) are also included in the discussion. Consideration of the similarities and, especially, the differences in the properties and reactions of the methanides with those of their imidodiphosphinate analogues reveals a number of areas in which the significance of the PC(H)P-bridged anions could be advanced.

Synthesis of a labile sulfur-centred ligand, [S(H)C(PPh2S)2](-): structural diversity in lithium(i), zinc(ii) and nickel(ii) complexes.

A high-yield synthesis of [Li{S(H)C(PPh2S)2}]2 [Li2·(3)2] was developed and this reagent was used in metathesis with ZnCl2 and NiCl2 to produce homoleptic complexes 4 and 5b in 85 and 93% yields, respectively. The solid-state structure of the octahedral complex [Zn{S(H)C(PPh2S)2}2] (4) reveals notable inequivalence between the Zn-S(C) and Zn-S(P) contacts (2.274(1) Å vs. 2.842(1) and 2.884(1) Å, respectively). Two structural isomers of the homoleptic complex [Ni{S(H)C(PPh2S)2}2] were isolated after prolonged crystallization processes. The octahedral green Ni(ii) isomer 5a exhibits the two monoprotonated ligands bonded in a tridentate (S,S',S'') mode to the Ni(ii) centre with three distinctly different Ni-S bond lengths (2.3487(8), 2.4500(9) and 2.5953(10) Å). By contrast, in the red-brown square-planar complex 5b the two ligands are S,S'-chelated to Ni(ii) (d(Ni-S) = 2.165(2) and 2.195(2) Å) with one pendant PPh2S group. DFT calculations revealed that the energetic difference between singlet and triplet state octahedral and square-planar isomers of the Ni(ii) complex is essentially indistinguishable. Consistently, VT and (31)P CP/MAS NMR spectroscopic investigations indicated that a mixture of isomers exists in solution at room temperature, while the singlet state square-planar isomer 5b becomes favoured at -40 °C.

Spirocyclic, macrocyclic and ladder complexes of coinage metals and mercury with dichalcogeno P2N2-supported anions.

Metathetical reactions of alkali-metal derivatives of the dianion [(t)BuN(Se)P(µ-N(t)Bu)2P(Se)N(t)Bu](2-) ((2Se2-)) with Ag(NHC)Cl, Ag[BF4], AuCl(THT) and HgCl2, as well as the reaction of 2S(2-) with AuCl(THT) were investigated. The observed products all incorporate the monoprotonated ligands 2SeH(-) or 2SH(-) in a variety of structural arrangements around the metal centres, including tetrameric and trimeric macrocycles [Ag and Au (E = Se)], a ladder (Au, E = S) and a spirocycle (Hg); the ladder contains both the dianion 2S(2-) and the monoanion 2SH(-) as ligands linking three Au2 units. All complexes have been characterised in the solid state by single crystal X-ray analyses and in solution by multinuclear ((1)H, (31)P and (77)Se) NMR spectra.

1,1'-(Diselanediylbis{[P,P-diphenyl-N-(tri-methyl-sil-yl)phospho-rimido-yl]methanylyl-idene})bis-[1,1-diphenyl-N-(tri-methyl-sil-yl)-λ(5)-phosphanamine] pentane disolvate.

The title compound, C62H78N4P4Se2Si4·2C5H12, is made up of two [SeC(PPh2NSiMe3)(PPh2NHSiMe3)] units related by an inversion center situated at the mid-point of the diselenide bond. It crystallized with two disordered mol-ecules of pentane used as solvent of crystallization. It is a rare example of an anti-periplanar diselenide and exhibits a long Se-Se bond of 2.4717 (8) Å. The Se-C bond length of 1.876 (5) Šis short in comparison with the range of values found for other diselenides (1.91-1.97 Å). The mol-ecule exhibits two intra-molecular N-H⋯N hydrogen bonds. In the crystal, there are no significant inter-molecular inter-actions present. One of the Me3Si- groups is disordered over two positions with a refined occupancy ratio of 0.708 (8):0.292 (8). The contribution of the disordered solvent to the scattering was removed with the SQUEEZE option of PLATON [Spek (2009 ▶). Acta Cryst. D65, 148-155]. The solvent contribution has been included in the reported mol-ecular weight and density.

A planar dianionic ditelluride and a cyclic tritelluride supported by P2N2 rings.

Oxidation of alkali metal derivatives of [Te((t)BuN)P(µ-N(t)Bu)(2)P(N(t)Bu)Te](2-) with I(2) produces the intermediate ditelluride dianion [Te((t)BuN)P(µ-N(t)Bu)(2)P(N(t)Bu)Te](2)(2-) with a planar PTeTeP conformation and, subsequently, the cyclic tritelluride [((t)BuN)P(µ-N(t)Bu)(2)P(N(t)Bu)(µ-TeTeTe)].

Planar P(6)E(6) (E = Se, S) macrocycles incorporating P(2)N(2) scaffolds.

Oxidation of alkali metal derivatives of the dianions [E((t)BuN)P(µ-N(t)Bu)(2)P(N(t)Bu)E](2-) (E = S, Se) with I(2) produces 15-membered macrocycles in which a planar P(6)E(6) motif is stabilised by perpendicular P(2)N(2) scaffolds.

PCP-bridged chalcogen-centred anions: coordination chemistry and carbon-based reactivity.

Since the discovery of the stabilising influence of thiophosphinoyl groups in methanediides by Le Floch et al. (Angew. Chem. Int. Ed., 2004, 43, 6382), numerous transition metal, lanthanide and actinide complexes of bis(thiophosphinoyl) carbene ligands have been investigated with an emphasis on the electronic structure and reactivity of the metal-carbon bonds. This Perspective begins by discussing main group (s- and p-block) complexes of this ligand and draws attention to differences compared to their d and f-block analogues. Investigations targeting the heavy chalcogen analogues of the Le Floch ligand have revealed an unusual carbon-based reactivity that led to the discovery of novel multidentate chalcogen-centred ligands as both monomers and, upon oxidation, dimers linked by dichalcogenido functionalities. Studies of main group and coinage metal complexes have established the flexibility and redox-activity of these novel anionic ligands.

S,C,S-Pnictogen bonding in pincer complexes of the methanediide [C(Ph2PS)2](2-).

The metathetical reactions of Li(2)[C(Ph(2)PS)(2)] with MCl(3) (M = Sb, Bi) in a 1:1 molar ratio in toluene afford the complexes {MCl[C(Ph(2)PS)(2)]}(2), which dimerise through weak MS interactions; the S,C,S-coordination of the tridentate ligand to the metal in the monomeric units incorporates a polar M-C single bond and a three-centre two-electron S-M-S bond.

Coordination polymers containing ferrocene backbone. Synthesis, structure and electrochemistry.

The reaction of 1,1'-ferrocenedicarboxylic acid (LH(2)) with bis(triphenyltin) oxide afforded a molecular heterobimetallic compound [(Ph(3)Sn)(2)L]. In the latter the two carboxylate units of [L](2-) are involved in an anisobidentate chelating coordination mode to two triphenyl tin units. The reaction of LH(2) with trimethyltin hydroxide or bis(tri-n-butyltin) oxide afforded 2D-coordination polymers [(Me(3)Sn)(2)L](n) and [(n-Bu(3)Sn)(2)L](n) which are formed as a result of anisobidentate bridging coordination action of the two carboxylate units of [L](2-). Interestingly the 2D-coordination polymers contain 24-membered macrocycles each of which is comprised of four trialkyl tin units. The coordination unsaturation of [(Ph(3)Sn)(2)L] can be utilized to form coordination polymers. Accordingly the reaction of LH(2) with bis(triphenyltin) oxide in the presence of ditopic nitrogen ligands such as 4,4'-bipyridine, 4,4'-trimethylenebipyridine or 4,4'-vinylenebipyridine afforded one-dimensional coordination polymers which contain in their backbone three distinct structural components viz., two triorganotin units, a ferrocenyl unit and a bridging nitrogen ligand unit. The coordination polymers, however, do not retain their structural integrity in solution and fall apart to their monomeric units. Electrochemical studies on these hybrid orgaonotin/ferrocene systems reveal that most of them exhibit a single quasi-reversible oxidation peak.

Halide-capped tellurium-containing macrocycles.

The reaction of 1,1,2,3,3-pentamethyltrimethylenephosphinic acid (cycPO(2)H) with bis(p-methoxyphenyl)tellurium dichloride (1) affords a 12-membered macrocycle [((p-MeOC(6)H(4))(2)Te)(2)(mu-O)(mu-cycPO(2))(mu(4)-Cl)](2) x C(6)H(6) (2) in good yield. The latter reacts with sodium iodide to give [((p-MeOC(6)H(4))(2)Te)(2)(mu-O)(mu-cycPO(2))(mu(4)-I)](2) x 4 C(6)H(6) (3). 2 and 3 are isostructural dicationic macrocycles and contain a Te(4)P(2)O(6) framework. An interesting aspect of both of these structures is that two counter halide atoms are present as capping ligands above and below the macrocyclic plane enabled by Te-X interactions. In contrast to the macrocyclic product obtained with diorganotellurium dihalide the reaction of diphenyltin dichloride with cycPO(2)H resulted in the formation of an oxygen-capped cluster [(PhSn)(3)(mu(3)-O)(mu-cycPO(2))(3)(mu-OH)(3)][cycPO(2)] x CH(3)CN. The latter is formed by a Sn-Ph cleavage reaction.

Tellurasiloxane cages containing Te(6)Si(4)O(12) and Te(6)Si(6)O(15) frameworks.

Reaction of the silanetriol t-BuSi(OH)(3) with (p-Me(2)NC(6)H(4))(2)TeO in a 4:6 ratio resulted in the formation of [((p-Me(2)NC(6)H(4))(2)Te)(6)(t-BuSiO(3))(4)].1.5 C(7)H(8) (1.1.5C(7)H(8)). In contrast, the reaction of tetrahydroxy-1,3-disiloxane, [t-BuSi(OH)(2)](2)O with (p-MeOC(6)H(4))(2)TeO in a 3:6 ratio afforded [((p-MeOC(6)H(4))(2)Te)(6)(t-BuSi)(6)O(15)] . 2 C(7)H(8) (2.2C(7)H(8)). 1 possesses a tetrahedron cage structure in which the vertices of the tetrahedron are occupied by silicon atoms. Each pair of silicon atoms is connected to each other by a R(2)TeO(2) motif. The six O-Te-O bridges occupy the edges of the tetrahedron. In contrast to 1, the structure of 2 can be described as a trigonal prismatic cage. The latter consists of two Te(3)Si(3)O(6) rings that are interconnected to each other through three Si-O-Si linkages. The structure of 2 is reminiscent of a double-six-ring (D6R) secondary building unit (SBU) framework found in zeolites such as faujasite. Reaction of (p-Me(2)NC(6)H(4))(2)TeO or (p-MeOC(6)H(4))(2)TeO with the disiloxane-1,3-diol, [Ph(2)Si(OH)](2)O in a 2:2 ratio afforded [((p-Me(2)NC(6)H(4))(2)Te)(OPh(2)Si-O-SiPh(2)O)](2) (3) and [((p-MeOC(6)H(4))(2)Te)(OPh(2)Si-O-SiPh(2)O)](2).CH(3)CN (4.CH(3)CN). In contrast to 1 and 2, the compounds 3 and 4 contain puckered 12-membered Te(2)Si(4)O(6) rings.