OR Ligands Research Articles

Reactions of W 2(H)(OR) 7, W 2(OR) 6(py) 2 and W 4(OCH 2cC 4H 7) 12 compounds (R = Pr i, CH 2Bu t, cC 5H 9) with azobenzene, 1,2-diphenylhydrazine and 1,1-dimethylhydrazine

The reaction of W 2(H)(OR) 7, W 2(OR) 6(py) 2 and W 4(OCH 2 cC 4H 7) 12 compounds ( R = Pr i , CH 2Bu t, cC 5H 9) in hydrocarbon solvents with azobenzene, 1,2-diphenylhydrazine and 1,1-dimethylhydrazine have been studied. The tetranuclear cluster proved to be inert while W 2(H)(OR) 7 was the most kinetically labile. In all cases where a reaction was observed the dinuclear center was ultimately oxidized with the formation of imido (NR 2−) or hydrazido (NNR 2 2−) ligands being formed. These were isolated as compounds of W(6+) supported by four OR ligands. These products require alkoxide group scrambling and no compound from which OR groups were lost was detected. Studies of the reactions between W 2(H)(OR) 7 compounds and hydrazines by low-temperature NMR spectroscopy indicate the initial formation of 1:1 adducts followed by elimination of H 2 and ROH as the hydrazine is activated. The following compounds were isolated and crystallographically characterized by single crystal studies: [W(OPr i) 4NPh] 2, [W 3(μ 3-H)(OPr i) 9(NPh (py)], [W(Opr i) 4(NpH)(pyl)] and [W(OPr i) 4(NNMe 2)((py)]. The trinuclear tungsten compound is noteworthy in being a rare, if not the only, example of a 12-electron triangular metal cluster capped by a hydrido ligand. In the other structures the W(6+) center is in a distorted octahedral coordination and the imido or hydrazido(2−) ligand is terminal with significant contribution from the resonance form having a W-N triple bond.

Synthesis and Structure of Lanthanide Complexes Derived from the O,N-Chelating, Bis(methylpyridine)-Substituted Alcohol HOC(CMe3)(2-CH2NC5H3Me-6)2

Hydrolysis of the product formed by reacting 2 equiv of 2-(lithiomethylene)-6-methylpyridine with trimethylacetyl chloride gives the alcohol HOC(CMe{sub 3})(2-CH{sub 2}NC{sub 5}H{sub 3}Me-6){sub 2}, (1) (HOR), in 44% yield. Three equivalents of (1) reacts with Yb[N(SiMe{sub 3}){sub 2}]{sub 3} to form Yb(OR){sub 3} (2a). The analogous 2 equiv reaction generates Yb(OR){sub 2}[N(SiMe{sub 3}){sub 2}], (3). X-ray diffraction studies were successful on (3) and on (2b), the Sm analog of (2a). Two of the alkoxide ligands in Sm(OR){sub 3}, (2b), are bidentate such that each has an uncomplexed nitrogen donor atom oriented away from the metal. These chelates occupy basal positions in the distorted square pyramidal geometry around the metal center in (2b) such that the oxygen donors are trans. The axial position is occupied by the third alkoxide which is monodentate through its oxygen donor atom. This leaves a total of four unattached pyridine functionalities available for further coordination. The ligand arrangement in (3) is very similiar to that in (2b) except that the monodentate alkoxide in (2b) is replaced by a N(SiMe{sub 3}){sub 2} group. A ligand fragmentation product, (R{prime}O){sub 2}Sm({mu}-OR){sub 2}Na, (4), containing the chelating bidentate pyridine enolate ligand [OC(CMe{sub 3})(=2CHNC{sub 5}H{sub 3}Me-6)](OR{prime}), formed by loss of a 2,6-dimethylpyridinemore » group from OR, was also isolated in the course of these studies. Each OR ligand in (4) has its oxygen atom bridging Sm and Na, one pyridine nitrogen coordinated to Na, and one pyridine nitrogen which is not connected to any metal. The samarium center in (4) has a distorted octahedral geometry generated by two chelating R{prime}O groups and the two bridging oxygens from the OR groups. The nitrogen donor atoms of the R{prime}O groups have a cis orientation and are trans to the bridging ligands.« less

DINUCLEAR METAL(O) COMPLEXES CONTAINING BRIDGING OR LIGANDS. SYNTHESIS, CRYSTAL STRUCTURE AND CYCLIC VOLTAMMETRY OF DINUCLEAR Mo AND W COMPLEXES, [Et4N]3[M2(CO)6(μ-OPh)3] (M = Mo,W)

Abstract The reaction of M(CO)6 (M = Mo,W) with tetraethyl ammonium phenoxide affords the dinuclear M(O) complexes containing bridging OR ligands, [Et4N]3[M2(CO)6(OPh)3] (M = Mo (1), W (2)). The X-ray structures of 1 and 2 have been determined. 1.3MeCN crystallizes in the monoclinic space group P21/n with a = 11.971(5), b = 19.326(9), c = 26.492(8)A;β = 102.26(3)° V = 5989A3; Z = 4; R 1 = 0.083, R 2 = 0.098. 2.2MeCN crystallizes in the orthorhombic space group P212121 with a = 17.610(8), b = 26.712(15), c = 11.822(4)A; V = 5561.2A3; Z = 4; R1 = 0.058, R 2 = 0.087. The structures of both the anions of 1 and 2 possess three μ-OPh ligands and three terminal carbonyls on each M atom resulting in pseudo-C 3v symmetry. M-M distances are 3.315(3) and 3.3035(9)A for 1 and 2, respectively. The CV of 1 and 2 is discussed.

Synthesis and crystal and molecular structure of Mo4O(OCH2But)10(py): A 12-electron butterfly cluster

From the reaction between Mo2(OCH2But)6 and water (1/2 equiv) in toluene solution in the presence of pyridine the oxo-alkoxide tetranuclear cluster Mo4O(OCH2But)10(py) has been isolated as a dark crystalline compound. Crystal data at −121°C:a=24.762(12) A,b=24.799(9) A,c=23.021(9) A,Z=8,d caled=1.27 g cm−3 in space group 14/m. The compound contains a Mo4 butterfly with a hinge angle of 137° between the two Mo3 triangles. The molecule has a crystallographically-imposed mirror plane of symmetry that contains the wing-tip Mo atoms. One wing-tip Mo atom is in an octahedral environment being bonded to two terminal and two-bridging OR ligands, and one pyridine ligand that is trans to a μ3-oxo bridge. The other Mo atoms are each coordinated to only four oxygen atoms. The backbone Mo atoms have one terminal and two bridging OR ligands and form one bond each to the μ3-oxo group. The other wing-tip Mo atom is coordinated to two terminal and two bridging OR groups. The five Mo-Mo distances span the range 2.43–2.59 A. The1H and13C{1H} NMR spectra in benzene-d6 are consistent with the presence of this structure in solution. The present results are compared to earlier findings for 12-electron alkoxide clusters of Mo and W.

ChemInform Abstract: SOME SQUARE‐PLANAR ALKOXO‐ AND HYDROXO‐COMPLEXES OF GROUP 8‐ PREPARATION, BONDING, AND NOVEL CONDENSATION REACTIONS WITH ACTIVE METHYL COMPOUNDS

AbstractDie Methoxokomplexe (I) und (III) wurden durch metathetische Reaktion der entsprechenden Chloroverbindungen (II) mit Na‐methoxid dargestellt.

Some square-planar alkoxo- and hydroxo-complexes of Group 8: preparation, bonding, and novel condensation reactions with active methyl compounds

A series of mononuclear methoxo-complexes. cis- and trans-[MR(OMe)(PPh3)2](M = Pd or Pt; R = aryl or alkenyl) has been prepared by metathesis of [MR(Cl)(PPh3)2] with Na(OMe). Hydrolysis of the methoxo-complexes gives corresponding hydroxo-complexes. trans-[MR(OH)(PPh3)2], which are also obtained from [MR(OCMe2)(PPh3)2]+ and [OH]–. The stability and nature of the M–OR bond (R = H or Me) are influenced markedly by the identity of the metal and the trans ligand, R. The anionic character of the OH or OR ligand increases in the orders Pt < Pd and C6F5 < CClCCl2 < CHCCl2 < Ph. The hydroxo-complexes react with PhCOMe and MeNO2 to give the corresponding condensates. trans-[PtR(CH2X)(PPh3)2](X = COPh or NO2). The condensation reaction is facilitated by the increase in anionic character of the OH ligand.