John G. Watkin

Synthesis and characterization of a mixed-ring bis-cyclopentadienyl derivative of neodymium. X-ray crystal structures of (η-C5Me5)NdI2(py)3 and (η-C5Me5)(η-C5H4SiMe3)NdI(py)

Abstract Reaction of neodymium metal with 1.5 equiv of elemental iodine in iso-propanol, followed by crystallization from THF, leads to isolation of NdI3(THF)x (1). Compound 1 reacts with one equiv of KC5Me5 to produce the mono-pentamethylcyclopentadienyl derivative (η-C5Me5)NdI2(THF)3 (2) in moderate yield. Treatment of 2 with an excess of pyridine in toluene leads to displacement of the THF ligands and formation of the tris-pyridine adduct (η-C5Me5)NdI2(py)3 (3). Compound 3 reacts with one equiv of KC5H4SiMe3 to yield the mixed-ring complex (η-C5Me5)(η-C5H4SiMe3)NdI(py) (4). Single crystal X-ray diffraction studies have been performed on complexes 3 and 4. (η-C5Me5)NdI2(py)3 (3) adopts a pseudo-octahedral geometry in the solid state, with the cyclopentadienyl ligand occupying one coordination site, the three pyridine ligands in a mer-configuration, and the iodide ligands trans to one another. The Nd–I distance is 3.1603(5) A, while Nd–N bond lengths to the pyridine ligands are 2.631(4) and 2.678(6) A. The solid state structure of (η-C5Me5)(η-C5H4SiMe3)NdI(py) (4) features a typical bent metallocene Cp2MX2 geometry with Nd–I and Nd–N distances of 3.0664(4) and 2.555(4) A, respectively.

Synthesis and X-ray crystal structures of the samarium mono(pentamethylcyclopentadienyl) aryloxide complexes (η-C5Me5)Sm(O-2,6-t-Bu2C6H3)2(THF) and [(η-C5Me5)Sm(O-2,6-i-Pr2C6H3)3Li(THF)]. Differences in metathesis chemistry of 2,6-di-iso-propylphenoxide and 2,6-di-tert-butylphenoxide ligands

Abstract The reaction of SmCl3 with three equivalents of KO-2,6-t-Bu2C6H3 in THF produces the tris(aryloxide) complex Sm(OAr)3(THF) (Ar=2,6-t-Bu2C6H3, 1). Complex 1 undergoes clean metathesis reaction with one equivalent of LiC5Me5 to form the mono(pentamethylcyclopentadienyl) aryloxide derivative (η-C5Me5)Sm(OAr)2(THF) (2). In contrast, an analogous reaction of LiC5Me5 with the 2,6-di-iso-propylphenoxide complex Sm(OAr*)3(THF)2 (Ar*=2,6-i-Pr2C6H3, 3) leads to overall addition of the alkali metal reagent, and isolation of the lithium-containing ‘ate’ complex [(η-C5Me5)Sm(OAr*)(μ-OAr*)2Li(THF)] (4). Compounds 2 and 4 have been subjected to single-crystal X-ray diffraction studies. Complex 2 features a three-legged piano-stool geometry, with Sm–O distances to the aryloxide ligands of 2.133(6) and 2.188(6) A, and a Sm–O(THF) distance of 2.435(7) A. Complex 4 also exhibits a three-legged piano-stool geometry, with two of the aryloxide oxygen atoms coordinated to a lithium metal center. A THF ligand completes the coordination sphere of the lithium. The Sm–O bond lengths to the lithium-coordinated aryloxide oxygens (2.250(6) and 2.247(5) A) are longer than the distance to the terminal aryloxide (Sm–O=2.144(6) A). The Li–O distances range from 1.876(17) to 1.945(18) A.

New developments in actinide alkoxide chemistry

Abstract Much new information on the synthesis, physicochemical properties, solid state structures, and reaction chemistry of actinide alkoxide complexes has begun to emerge in the last decade. We have developed several new starting materials that facilitate easy entry into thorium and uranium alkoxide chemistry. Synthetic pathways employed in our laboratories to obtain alkoxide and aryloxide complexes of the actinides include (1) metathesis of the iodide ligands in Ul 3 (THF) 4 and Thl 4 (THF) 4 with potassium salts of the desired ligand, or (2) protonolysis of metal-nitrogen or metal-carbon bonds by alcohols or phenols. The rich structural and reaction chemistry of these new complexes is described along with prospects for future developments in the field.

Ytterbium trichloride-catalyzed allylation of aldehydes with allyltrimethylsilane

Abstract Ytterbium chloride (YbCl 3 ) is found to be an effective catalyst for the allylation of both aromatic and aliphatic aldehydes using allyltrimethylsilane.

Synthesis and energetic content of red oil

Abstract ‘Red oil’ materials, resembling those produced during destructive incidents at Hanford and Savannah River, have been prepared following prolonged heating of uranyl nitrate, nitric acid, tributylphosphate (TBP) and a hydrocarbon diluent either under reflux conditions or within a high-pressure bomb reactor. Phase inversions, a characteristic feature of ‘red oil’ formation, were observed only when a cyclic hydrocarbon diluent was employed and were not observed when a straight chain hydrocarbon was used. The energetic content of the ‘red oil’ materials was found to be in the range from 30 to 444 J g −1 (7.2–106.1 cal g −1 ) as determined by DSC in open pans in the temperature range 20–350°C, with a typical value being 200 J g −1 (47.8 cal g −1 ). A ‘baseline’ Purex solution of UO 2 (NO 3 ) 2 (TBP) 2 released 120 J g −1 (28.7 cal g −1 ) upon heating through the same temperature range.

Metal complexes based on an upper-rim calix[4]arene phosphine ligand

Abstract A new upper-rim phosphacalix[4]arene 5,17-bis(diphenylphosphinomethyl)-25,26,27,28-tetrapropoxycalix[4]arene ( 4 ) has been prepared starting from commercially available tert -butyl calix[4]arene. Treatment of 4 with (COD)PdMeCl and (COD)PtCl 2 gives polymeric phosphine-coordinated Pd(II) and Pt(II) species, respectively. 4 reacts with [(COD)RhCl] 2 to give a di-rhodium complex that is an active catalyst for the hydroformylation of 1-octene and styrene.

STRUCTURAL CHARACTERIZATION AND REACTIVITY STUDIES OF THE SAMARIUM ARYLOXIDE COMPLEX SM(O-2,6-PR2IC6H3)3(THF)2

Abstract Reaction of the samarium aryloxide bis-THF adduct Sm(OAr) 3 (THF) 2 ( 1 ; Ar = 2,6-Pr 2 i C 6 H 3 ) with two equivalents of pyridine produces the bis-pyridine complex Sm(OAr) 3 py 2 ( 2 ) in 85% yield. Compound 1 also reacts with an excess of pyridine to form the tris-pyridine adduct Sm(OAr) 3 py 3 ( 3 ) in excellent yield. Addition of one equivalent of KOAr to 1 leads to the isolation of the potassium salt K[Sm(OAr) 4 ] ( 4 ) in high yield. The salt 4 reacts with one equivalent of pyridine to form the mono-pyridine adduct K[Sm(OAr) 4 py] ( 5 ). Compounds 1–5 have been characterized by 1 H NMR and IR spectroscopy, elemental analysis and, in the case of 1 , by a single-crystal X-ray diffraction study. In the solid state, 1 adopts a trigonal bipyramidal structure in which THF ligands occupy axial sites. Sm O distances to the aryloxide ligands average 2.14(2)A˚, while those to THF ligands average 2.45(2)A˚.

Neutral and anionic transition metal complexes supported by decafluorodiphenylamido ligands: X-ray crystal structures of {Na(THF)2} {Ti[N(C6F5)2]4}, {K(η6-C6H5Me)2} {ZrCl2[N(C6F5)2]3}, K{VCl[N(C6F5)2]3}, Fe[N(C6F5)2]2(THF)2 and Co[N(C6F5)2]2(py)2

Abstract Reaction of MN(C6F5)2 (M=Na, K) with transition metal halides results in the formation of transition metal complexes incorporating decafluorodiphenylamido ligands. TiCl3(THF)3 reacts with 3 equiv. NaN(C6F5)2 to yield the ‘metallate’ complex {Na(THF)2}{Ti[N(C6F5)2]4} (1). Single crystal X-ray diffraction studies reveal a tetrahedral titanium center complexed by four decafluorodiphenylamido ligands; while two THF ligands and four fluorine atoms coordinate the sodium cation. ZrCl4 reacts with 3 equiv. KN(C6F5)2 to give {K(η6-C7H8)2}{ZrCl2[N(C6F5)2]3} (2). The 19F NMR spectrum of 2 reveals phenyl resonances in a 2:1 ratio, consistent with a trigonal bipyramidal structure being maintained in solution. The crystal structure of 2 reveals a pseudo-octahedral structure, with the sixth-coordination site being completed by a weak ZrF interaction with a pentafluorophenyl group of an amido ligand. The potassium counterion interacts in an η6 fashion with two toluene rings in addition to a fluorine atom arising from one of the pentafluorophenyl groups. The reaction of VCl3 with 3 equiv. KN(C6F5)2 generates the ‘metallate’ complex K{VCl[N(C6F5)2]3} (3); the solid state structure of 3 reveals a distorted trigonal bipyramid with the coordination sphere being completed by a weak V–F interaction with the ortho-fluorine of one of the fluorophenyl amido ligands. Exposure of FeCl3 to 3 equiv. KN(C6F5)2 results in reduction of the metal center and the formation of the Fe(II) species Fe[N(C6F5)2]2(THF)2 (4). Compound 4 is tetrahedral in the solid state with none of the weak MF contacts observed for 1, 2, 3 and 5. CoI2 reacts with 2 equiv. NaN(C6F5)2 in the presence of pyridine to produce the expected product Co[N(C6F5)2]2(py)2 (5); X-ray crystallography reveals a five-coordinate species in the solid state which is additionally stabilized by a weak CoF interaction.

Plutonium(III)-catalyzed Meerwein–Ponndorf–Verley reactions

Abstract The reactivity of Th(IV), U(III), U(IV), Pu(III) and Pu(IV) iso -propoxide in the Meerwein–Ponndorf–Verley reduction of ketones by iso -propanol have been examined. Plutonium(III) iso -propoxide is found to be an effective catalyst for the reduction of a range of substituted aryl-alkyl ketones, while An(IV) iso -propoxides (An=Th, U, Pu) are found to be inactive. U(III) was found to oxidize under the reaction conditions to a U(IV) complex, which was also catalytically inactive.

Crystal structure of the zerovalent niobium complex Nb (η-C6H5Me)2

Abstract The crystal structure of Nb(η-C 6 H 5 Me) 2 ( 1 ), prepared by co-condensation of niobium metal atoms with toluene vapor, has been determined. The toluene rings lie parallel to one another on either side of the niobium metal center ( Nb−C = 2.334(5) A av. ), with methyl groups almost perfectly eclipsed. Crystal data for 1 (at −50 °C): orthorhombic, space group Pbcn , a =13.706(3), b =11.977(2), c =13.753(3) A, V=2257.6 A 3 , D calc =1.631 g cm −3 , Z=8, R=0.0421, R w =0.0612 .