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The complexes [Pt(mdt)2] (4; mdt = methyl dithiolene, [Me2C2S2]n-), [Pt(adt)2] (5; adt = p-anisyldithiolene, [(MeO-p-C6H4)2C2S2]2-), and [Pd(adt)2] (10) have been prepared in yields of ≥ 90% via transmetalation reactions with the corresponding [R2Sn(S2C2R'2)] complexes (R = "Bu, R' = Me; R = Me, R' = C6H4-p-OMe, 3). Intrahgand C--S and C--CchclaIe bond lengths (~1.71 and ~1.40 A, respectively) obtained by X-ray crystallography show these compounds to be comprised of radical monoanions mdt*- and adt*- . The six-coordinate octahedral adducts [Pt(adt)2(dppe)J [6; dppe = 1,2-bis(diphenylphosphino)ethane], trans-[Pt(adt)2(PMe3)2] (8), and frans-[Pt(mdt)2(PMe3)2] (9) have also been prepared, and crystal structures reveal dithiolene ligands that are fully reduced ene-l,2-dithiolates (C--S and C--Cchelate = ~1.77 and 1.35 A, respectively). Reduction of the dithiolene ligand thus occurs to accommodate the +IV oxidation state typical of octahedral sixcoordinate platinum. The cyclic voltammogram of 5 shows twofully reversible reductions at --0.11 and --0.84 V in CH2C12 (vs Ag/AgCl), attributed to successive (adt*- + e- → adt2-) processes, and a reversible oxidation at +1.01 V. The cyclic voltammogram of 9 shows two reversible oxidations at +0.38 and +0.86 V, which are assigned as successive (adt2- &#8594 adt*- + e-) oxidations. Consistent with their formulation as having fully reduced dithiolene ligands, the UV--vis spectra for 6, 8, and 9 show no low-energy absorptions below 700 nm, and the S K-edge XAS spectra of 6 and 8 show dithiolene sulfur that is reduced relative to that in 5. The introduction of PMe3 to 10 did not produce the palladium analogue of 8 but rather [Pd(adt)(PMe3)2] (11) . The reaction of [PdCl2(PPh3)2] with Li2(mdt) produced a mixture of [Pd(mdt)(PPh3)2] (12, 20%) and [(Ph3P)Pd(p-l,2-mdt- S,S':S)2Pd(PPh3)] (13, 28%), with the latter having C2 symmetry with a Pd2S2 core structure folded along the S…S axis. [ABSTRACT FROM AUTHOR]

A series of reports describing the syntheses and structures of [MCl2(diazadiene)] (M = Cr, Mo, W) complexes is reassessed in the context of known chemistry of low-valent Group VI metal complexes, crystallographic trends such as M--CI bond lengths and unit cell volumes, and calculated metal--ligand bond lengths. Crystallographic data and computational results are inconsistent with any of these species being second or third row transition metal complexes. A review of the crystallographic information files accompanying the [MCl2(diazadiene)] (M = Mo, W) published structures reveals that the metal atoms were inappropriately treated with partial site occupancy factors (0.775 for Mo; 0.4005 and 0.417 for W), the effect of which was to manifest lighter-element behavior and better refinement in accord with the metal atoms' correct identity. A deliberate synthesis and characterization by X-ray diflraction of [ZnCl2(MesdadMe)] (MesdadMe = l,4-bis(2,4,6-trimethylphenyl)-2,3-dimethyl-l,4-diaza-1,3-butadiene) are reported. Refinement of this structure with the same combination of second or third row metal and offsetting partial site occupancy is shown to provide final refinement statistics essentially the same as with the correct model employing M = Zn at site occupancy 1.00. Use of the published method for synthesis of [WCl2(diazadiene)] with MesdadMe and [WBr4(MeCN)2] in lieu of [WCl4MeCN2] is shown to produce [ZnBr2(MesdadMe)], which has also been characterized by X-ray diffraction. It is concluded that the unusual putative 12-electron [MCl2(diazadiene)] (M = Cr, Mo, W) complexes are in all cases the corresponding [ZnCl2(diazadiene)] complexes, Zn having been commonly employed as reducing agent in their synthesis. [ABSTRACT FROM AUTHOR]

In order to assess the sensitivity and complementarity of X-ray absorption and emission spectroscopies for determining changes in the metal ligation sphere, a systematic experimental and theoretical study of iron model complexes has been carried out. A series of high-spin ferrous complexes, in which the ligation sphere has been varied from a three-coordinate complex, [LtBuFe(SPh)] (1) (where LtBu = bulky β-diketiminate ligand; SPh = phenyl thiolate) to four-coordinate complexes [LtBuFe(SPh)(X)] (where X = CNtBu (2); 1-methylimidazole (3); or N,N-dimethylformamide (DMF) (4)), has been investigated using a combination of Fe K-edge X-ray absorption (XAS) and Kβ X-ray emission (XES) spectroscopies. The Fe K XAS pre-edge and edge of all four complexes are consistent with a high-spin ferrous assignment, with the largest differences in the pre-edge intensities attributed to changes in covalency of the fourth coordination site. The X-ray emission spectra show pronounced changes in the valence to core region (V2C) as the identity of the coordinated ligand is varied. The experimental results have been correlated to density functional theory (DFT) calculations, to understand key molecular orbital contributions to the observed absorption and emission features. The calculations also have been extended to a series of hypothetical high-spin iron complexes to understand the sensitivity of XAS and XES techniques to different ligand protonation states ([LtBuFeII(SPh)(NHn)]3-n (n = 3, 2, 1, 0)), metal oxidation states [LtBuFe(SPh)(N)]n- (n = 3, 2, 1), and changes in the ligand identity [LtBuFeIV(SPh)(X)]n-(X = C4-, N3-, O2-; n = 2, 1, 0). This study demonstrates that XAS pre-edge data have greater sensitivity to changes in oxidation state, while valence to core (V2C) XES data provide a more sensitive probe of ligand identity and protonation state. The combination of multiple X-ray spectroscopic methods with DFT results thus has the potential to provide for detailed characterization of complex inorganic systems in both chemical and biological catalysis. [ABSTRACT FROM AUTHOR]

A new, high yield synthesis of [Ni(S[sub2]C[sub2]Me[sub2])[sub2]] (3) is described using 4,5-dimethyl-1 ,3-dithiol-2-one, Me[sub2]C[sub2]S[sub2]C==O (1), as dithiolene ligand precursor. Reaction of (Me[sub2]C[sub2]S[sub2])Sn[supn]Bu[sub2], 2, with WCI[sub6] produces tris(dithiolene) [W(S[sub2]C[sub2]Me[sub2])[sub3]] (6) and demonstrates the potential synthetic utility of this compound in metallodithiolene synthesis. The series of compounds [W(S[sub2]C[sub2]Me[sub2])[subx](CO)[sub6-2x]] (x = 1 -3), obtained as a mixture via the reaction of [Ni(S[sub2]C[sub2]Me[sub2])[sub2]] with [W(MeCN)[sub3](CO)[sub3]], has been characterized structurally. A trigonal prismatic geometry is observed for [W(S[sub2]C[sub2]Me[sub2])(CO)[sub4]) (4) and confirmed by a DFT geometry optimization to be lower in energy than an octahedron by 5.1 kcal/mol. The tris(dithiolene) compound [W(S[sub2]C[sub2]Me[sub2])[sub3]] crystallizes in disordered fashion upon a 2-fold axis in C2/c, a different space group than that observed for its molybdenum homologue (P¯1), which is attributed to a slightly smaller chelate fold angle, α, in the former. The reactivity of 4 and [W(S[sub2]C[sub2]Me[sub2])[sub2](CO)[sub2]] (5) toward PMe[sub3] has been examined. Compound 4 yields only [W(S[sub2]C[sub2]Me[sub2])(CO)[sub2](PMe[sub3])[sub2]] (7), while 5 produces either [W(S[sub2]C[sub2]Me[sub2])[sub2](CO)(PMe[sub3])] (8) or [W(S[sub2]C[sub2]Me[sub2])[sub2](PMe[sub3])[sub2]] (9) depending upon reaction conditions. Crystallographic characterization of 5, 8, and 9 reveals a trend toward greater reduction of the dithiolene ligand (i.e., more ene1 ,2-dithiolate character) across the series, as manifested by C-C and C-S bond lengths. These structural data indicate a profound effect exerted by the π-acidic CO ligands upon the apparent state of reduction of the dithiolene ligand in compounds with ostensibly the same oxidation state. [ABSTRACT FROM AUTHOR]

The reactions of cyclodiphosphazane cis-[tBuNP(OC6H4OMe-o)]2 (1) with 2 equiv of CuX in acetonitrile afforded one-dimensional CuI coordination polymers [Cu2X2{tBuNP(OC6H4OMe-o)}2]n (2, X = Cl; 3, X = Br; 4, X = I). The crystal structures of 2 and 4 reveal a zigzag arrangement of [P(μ-N)2P] and [Cu(u-X)2Cu] units in an alternating manner to form one-dimensional CuI coordination polymers. The reaction between 1 and CuX in a 2:1 ratio afforded mononuclear tricoordinated copper(l) complexes of the type [CuX{(tBuNP(OC6H4OMe-o))2}2] (5, X = Cl; 6, X = Br; 7, X = I). The single-crystal structures were established for the mononuclear copper(l) complexes 5 and 6. When the reactant ratios are 1:1, the formation of a mixture of polymeric and mononuclear products was observed. The CuI polymers (2-4) were converted into the mononuclear complexes (5-7) by reacting with 3 equiv of 1 in dimethyl sulfoxide. Similarly, the mononuclear complexes (5-7) were converted into the corresponding polymeric complexes (2-4) by reacting with 3 equiv of copper(l) halide under mild reaction conditions. [ABSTRACT FROM AUTHOR]

Ether- and thioether-functionalized cyclodiphosphazanes cis-[tBuNP(OCH2CH2EMe)]2 (E = O, 1; E = S, 2) react with 2 equiv of elemental sulfur or selenium to produce dichalcogenides cis-[tBuNP(E)(OCH2CH2EMe)]2 (4-6), whereas the similar reaction of amine-functionalized cyclodiphosphazane cis-[tBuNP(OCH2CH2NMe2)12 (3) with elemental chalcogen results in the formation of thio- or selenophosphates trans-[tBuNP(O)(ECH2CH2NMe2)]2 (E = 5, 7; E = Se, 8) through [1,3]-sigmatropic rearrangement. The X-ray crystal structure of 8 confirms the rearranged product as the trans isomer with a planar P2N2 ring. The equimolar reaction of P(OCH2CH2OMe)3 (9) with elemental sulfur or selenium produces the simple sulfide and selenide E=P(OCH2CH2OMe)3 (E = 5, 11; E = Se, 12) derivatives, respectively. In contrast, the reaction between P(OCH2CH2NMe2)3 (10) and S or Se furnishes the rearranged products (13 and 14). The rearrangement reaction was monitored by 31PNMR spectroscopy, which confirms the formation of selenophosphinic acid as the first step of the rearrangement. The [1,3]-sigmatropic rearrangement presumably takes place through chalcogen-nitrogen interactions. [ABSTRACT FROM AUTHOR]

Cyclodiphosphazanes having hemilabile ponytails such as cis-[tBuNP(OC6H4OMe-o)]2 (2), cis-[tBuNP(OCH2CH2-OMe)]2 (3), cis-[tBuNP(OCH2CH2SMe)]2 (4), and cis-[tBuNP(OCH2CH2NMe2))2 (5) were synthesized by reacting cis-[tBuNPCl]2 (1) with corresponding nucleophiles. The reaction of 2 with [M(COD)Cl2] afforded cis-[MCl2(2)2] derivatives (M = Pd (6), Pt (7)), whereas, with [Pd(NCPh)2C]2], trans-[MCl2(2)2] (8) was obtained. The reaction of 2 with [Pd(PEt3)Cl2]2, [Ru(η6p-cymene)Cl2]2, and [M(COD)Cl]2 (M = Rh, Ir) afforded mononuclear complexes of Pd(II) (9), Ru(II) (11), Rh(I) (12), and Ir(l) (13) irrespective of the stoichiometry of the reactants and the reaction condition. In the above complexes the cyclodiphosphazane acts as a monodentate ligand. The reaction of 2 with [PdCl(η³-C3H5))2 afforded binuclear complex [(PdCl(η³-C3H5))2{(tBuNP(OC6H4OMe-o))2-κP}] (10). The reaction of ligand 3 with [Rh(CO)2Cl]2 in 1:1 ratio in CH3CN under reflux condition afforded tetranuclear rhodium(1) metallamacrocycle (14), whereas the ligands 4 and 5 afforded bischelated binuclear complexes 15 and 16, respectively. The crystal structures of 8, 9, 12, 14, and 16 are reported. [ABSTRACT FROM AUTHOR]

Dimetallic compounds I(P-P)M(S2C6H2S2)M(P-P)] (M=Ni, Pd; P-P=chelating bis(phosphine), 3a-3f) are prepared from OCS2C6H2S2CO or nBu2SnS2C6H2S2SnnBu2, which are protected forms of 1,2,4,5-benzenetetrathiolate. Selective monodeprotections of OCS2C6H2S2CO or nBu2SnS2C6H2S2SnnBu2 lead to [(P-P)Ni(S2C6- H2S2CO)] or [(P-P)Ni(S2C6H2S2SnnBu2)]; the former is used to prepare trimetallic compounds [(dcpe)Ni(S2C6H2S2)M(S2C6H2S2)Ni(dcpe)] (M = Ni (6a) or Pt (6b); dcpe = 1 ,2-bis(dicyclohexylphosphino)ethane). Compounds 3a-3f are redox active and display two oxidation processes, of which the first is generally reversible. Dinickel compound [(dcpe)Ni(S2C6H2S2)Ni(dcpe)] (3d) reveals two reversible oxidation waves with ΔE½=0.66 V, corresponding to κC of 1.6 x 1011 for the mixed valence species. Electrochemical behavior is unstable to repeated scanning in the presence of [Bu4N][PF6] electrolyte but indefinitely stable with Na[BArF24] (BArF24 = tetrakis(3, 5-bis(frifluoromethyl)phenyl)borate), suggesting that the radical cation generated by oxidation is vulnerable to reaction with PF6-. Chemical oxidation of 3d with [Cp2Fe][BArF24] leads Information of [3d][BArF24]. Structural identification of [3d][BArF24] reveals appreciable shortening and lengthening of C-S and C-C bond distances, respectively, within the tetrathioarene fragment compared to charge neutral 3d, indicating this to be the redox active moiety. Attempted oxidation of [(dppb)Ni(S2C6H2S2)Ni(dppb)] (3c) (dppb = 1 ,2-bis(diphenylphosphino)benzene) with AgBArF24 produces [[(dppb)Ni(S2C6H2S2)Ni(dppb)]2(μ-Ag2)][BArF24]2, [4c][BArF24]2, in which no redox chemistry has occurred. Crystal structures of bis(disulfide)-linked compounds [(P-P)Ni(S2C6H2(u-S2)2C6H2S2)Ni(P-P)] are reported. Near IR spectroscopy upon cationic [3d]+ and neutral 6a reveals multiple intense absorptions in the 95O-14OO nm region. Time-dependent density functional theory (DFT) calculations on a 6a model compound indicate that these absorptions are transitions between ligand-based π-type orbitals that have significant contributions from the sulfur p orbitals. [ABSTRACT FROM AUTHOR]