Steffen Blaurock

Facile Access to Tetravalent Cerium Compounds: One-Electron Oxidation Using Iodine(III) Reagents

Readily accessible and easy-to-use phenyliodine(III) dichloride, PhICl(2), has been established as an innovative and superior reagent for the one-electron oxidation of cerium(III) complexes, comprising amide, amidinate, and cyclopentadienyl derivatives. Its use allowed the successful synthesis and structural characterization of the first members of three new classes of chloro-functionalized (organo)cerium(IV) compounds, including the long sought-after Cp(3)CeCl.

Molybdenum tetracarbonyl complexes with functionalised aminophosphine ligands: cis-[Mo(CO)4(PPh2NHR)2] (R=Ph, But) — molecular structures of PMes2NHPh (Mes=2,4,6-Me3C6H2), PPh2NHBut and cis-[Mo(CO)4(PPh2NHBut)2]

Abstract The aminophosphines PPh2NHR [R=Ph (1a), But (1b)] react readily with cis-[Mo(CO)4(NCEt)2] to give cis-[Mo(CO)4(PPh2NHR)2] [R=Ph (2), But (3)] in high yield, while the bulky aminophosphine PMes2NHPh (1c) (Mes=2,4,6-Me3C6H2), obtained from LiNHPh and PMes2Cl, does not react even at elevated temperature. Compounds 1c, 2 and 3 were characterised spectroscopically (IR; 1H, 31P, 13C NMR), 2 and 3 also by MS, and crystal structure determinations were carried out on 1b, 1c and 3; for 3, this showed the presence of the cis isomer. Complexes 2 and 3 do not react with [Cp2ZrCl2]/NEt3 or with [Cp2ZrMe2].

A Wittig Reaction with 2-Furyl Substituents at the Phosphorus Atom: Improved (Z) Selectivity and Isolation of a Stable Oxaphosphetane Intermediate

Wittig reactions with ylides bearing one, two or three 2-furyl groups directly bound to the phosphorus atom have been studied. Greatly improved (Z)-alkene selectivities of up to 98:2 could be observed if 2-furyl groups were present. Monitoring of the reactions by NMR spectroscopy revealed only oxaphosphetane intermediates, which became more stable with increasing number of 2-furyl substituents bound to the phosphorus atom. Oxaphosphetane 10d, with three furyl groups, was successfully isolated, and the results of a crystal structure analysis are presented. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Metallatriphos complexes: synthesis and molecular structure of [TpZr(OCH2PPh2)3] (Tp=tris(pyrazolyl)hydroborate) and formation of the heterodinuclear complex [TpZr(μ-OCH2PPh2)3Mo(CO)3] with bridging phosphinoalkoxide ligands

Abstract [TpZr(OCH2PPh2)3] (1) is obtained from [TpZrCl3] and LiOCH2PPh2 in THF. Complex 1 reacts with [Mo(CO)3(NCEt)3] to give the heterodinuclear complex [TpZr(μ-OCH2PPh2)3Mo(CO)3] (2). Complexes 1 and 2 were characterised spectroscopically. Crystal structure determinations were carried out on 1 and on HOCH2PPh2. The former showed that the lone pairs of the P atoms appear to be suited ideally for coordination to a second metal centre.

Unprecedented Bending and Rearrangement of f-Element Sandwich Complexes Induced by Superbulky Cyclooctatetraenide Ligands

The use of the superbulky cyclooctatetraenide dianion ligand [C(8)H(6)(SiPh(3))(2)](2-) (= COT(BIG)) in organo-f-element chemistry leads to unprecedented effects such as the formation of a significantly bent anionic Ce(III) sandwich complex, a novel cerocene formed by sterically induced SiPh(3) group migration, as well as the first example of a bent uranocene.

Synthesis and coordination properties of 1-tert-butylchlorophosphino- and 1,2-bis(tert-butylchlorophosphino)-1,2-dicarba-closo-dodecaborane(12)—molecular structures of rac- and meso-1,2-(PtBuCl)2C2B10H10 and (R,R,R,R/S,S,S,S)-[{Cu{1,2-(PtBuCl)2C2B10H10}(μ-Cl)}2]

Abstract 1-tert-Butylchlorophosphino-1,2-dicarba-closo-dodecaborane(12) (1) and a mixture of stereoisomers of rac- and meso-1,2-bis(tert-butylchlorophosphino)-1,2-dicarba-closo-dodecaborane(12) (2a, b; 2a:2b=1:1) are readily obtained from tBuPCl2 and 1-lithio- and 1,2-dilithio-1,2-dicarba-closo-dodecaborane(12), respectively. The stereoisomers of 2a, b were separated by column chromatography. Compounds 1 and 2a, b react with [AuCl(tht)] (tht=tetrahydrothiophene) to yield [AuCl(1-PtBuClC2B10H11)] (3) and [AuCl{1,2-(PtBuCl)2C2B10H10}] (4). A mixture of 2a and 2b reacts with CuCl in THF to give (R,R,R,R/S,S,S,S)-[{Cu{1,2-(PtBuCl)2C2B10H10}(μ-Cl)}2] (5) in 48% yield. Compounds 1–5 were characterised spectroscopically (1H, 31P, 11B, 13C NMR; IR), and X-ray structure determinations were carried out on 2a, b and 5.

Organometallic tantalum complexes with phosphine, phosphanido and phosphinidene ligands. Syntheses and crystal structures of [Sp′TaCl4[PH2(2, 4, 6-Pri3C6H2)]], [Cp′Ta(μ-PPh2)(PPh2)]2·C7H8 and [Cp′TaCl[μ-P(2, 4, 6-Pri3C6H2)]]2· C7H8(Cp′ =C5H4Me)

Abstract The rreaction of [Cp′TaCl4] (Cp′ =C5H4Me) with KPPh2 (dioxane)2 (1 : 1) in diethyl ether at room temperature gave the phosphanido-bridge tantalum(III) complex [Cp′Ta(μ-PPh2)(PPh2)]2 (1) · C7H8 as black crystals. [Cp′TaCl4] reacted with 2, 4, 6-triisopropylphenylphosphine with formation of the adduct [Cp′TaCl4[PH2(2, 4, 6-Pr3iC6H2)]] (2). Attempts to eliminate HCl from 2 with DBU (DBU= 1, 8-diazabicyclo-[5, 4, 0]-undec-7-ene) gave the phosphinidene-bridged tantalum(IV) complex [Cp′TaCl[μ-P(2, 4, 6-Pr3iC6H2)]]2 (3)·C7H8. It was shown independently that DBU acts as a base and a reducing agent. 1–3 were characterized spectroscopically (IR, MS, NMR) as well as by crystal structure determinations.

Syntheses, Crystal Structures and Reactivity of Organometallic Tantalum(IV) Phosphinidene Complexes: trans‐[{Cp*TaCl(μ‐PR)}2] (Cp* = C5Me5, R = Cy, tBu, Ph), cis‐ and trans‐[{Cp*TaCl(μ‐PMes)}2] (Mes = 2,4,6‐Me3C6H2) and cis‐[{Cp′TaCl(μ‐PMes)}2] (Cp′ = C5H4Me)

The reaction of [Cp*TaCl4] (Cp* = C5Me5) with LiPHR (1:1 or 1:2) gives the phosphinidene-bridged tantalum(IV) complexes trans-[{Cp*TaCl(μ-PR)}2] [R = Cy (1), tBu (2), Ph (3), 2,4,6-Me3C6H2 (Mes) (4b)]. When the reaction with LiPHMes is carried out in a 1:1 ratio, cis-[{Cp*TaCl(μ-PMes)}2] (4a) is also formed besides 4b. For comparison, cis-[{Cp′TaCl(μ-PMes)}2] (5) was prepared from [Cp′TaCl4] (Cp′ = C5MeH4) and LiPHMes (1:1). 1−5 are diamagnetic and were characterised spectroscopically (IR, MS; 1 H, 31P, 13C NMR). Crystal structure determinations on 1−5 showed the presence of dimeric phosphinidene-bridged TaIV complexes. The phosphinidene-bridged complexes 1, 3 and 4b do not react with acetone, benzophenone, acetonitrile, CS2 (1, 3), acetaldehyde (4b), or ethylaluminum dichloride (3). 3 reacts with moist acetone in the presence of traces of air to give the trinuclear cluster [{Cp*TaCl(μ2−O)}3(μ3-O)(μ2-O2PHPh)}] (6) in very low yield. With an excess of CyNC, 3 gives [Cp*TaCl(CNCy)4]Cl (7), which was characterised by 1H and 13C NMR spectroscopy and by crystal structure determination. As a minor product, [(Cp*TaCl2)2(μ2-O)(η2,μ2-P2Cy2)] (8) was also obtained in the reaction of [Cp*TaCl4] with LiPHCy. 6 and 8 were only characterised by crystal structure determination. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Unerwartete Reduktion von [Cp*TaCl4(PH2R)] (R = But, Cy, Ad, Ph, 2,4,6‐Me3C6H2; Cp* = C5Me5) durch Reaktion mit DBU – Molekülstruktur von [(DBU)H][Cp*TaCl4] (DBU = 1,8‐Diazabicyclo[5.4.0]undec‐7‐en)

[Cp*TaCl4(PH2R)] (R = But, Cy, Ad, Ph, 2,4,6-Me3C6H2 (Mes); Cp* = C5Me5) reagieren mit DBU in einer intramolekularen Redoxreaktion unter Bildung von [(DBU)H][Cp*TaCl4] (1) (DBU = 1,8-Diazabicyclo[5.4.0]undec-7-en) und dem entsprechenden Diphosphan (P2H2R2) bzw. Zersetzungsprodukten hiervon. 1 wurde spektroskopisch und rontgenstrukturanalytisch charakterisiert. Im Festkorper wird eine Wasserstoffbruckenbindung zwischen dem (DBU)H-Kation und einem Chloroliganden des Anions beobachtet. Unexpected Reduction of [Cp*TaCl4(PH2R)] (R = But, Cy, Ad, Ph, 2,4,6-Me3C6H2; Cp* = C5Me5) by Reaction with DBU – Molecular Structure of [(DBU)H][Cp*TaCl4] (DBU = 1,8-diazabicyclo[5.4.0]undec-7-ene) [Cp*TaCl4(PH2R)] (R = But, Cy, Ad, Ph, 2,4,6-Me3C6H2 (Mes); Cp* = C5Me5) react with DBU in an internal redox reaction with formation of [(DBU)H][Cp*TaCl4] (1) (DBU = 1,8-diazabicyclo[5.4.0]undec-7-ene) and the corresponding diphosphane (P2H2R2) or decomposition products thereof. 1 was characterised spectroscopically and by crystal structure determination. In the solid state, hydrogen bonding between the (DBU)H cation and one chloro ligand of the anion is observed.

Explosive Werner-type cobalt(III) complexes

A series of potentially explosive Werner-type cobalt(III) complexes comprising the anions azotetrazolate, nitrotetrazolate, picrate and dipicrylamide were prepared via simple metathetical routes. Treatment of [Co(NH3)5NO2]Cl2, trans-[Co(NH3)4(py)NO2]Cl2 (py = pyridine), trans-[Co(NH3)4(NO2)2]Cl, and [Co(NH3)5N3]Cl2 with equimolar amounts of disodium azotetrazolate, (Na2C2N10·5H2O, 1), in aqueous solutions afforded new cobalt(III) azotetrazolate salts [Co(NH3)5NO2](C2N10)·2H2O (2), trans-[Co(NH3)4(py)NO2](C2N10)·2H2O (3), trans-[Co(NH3)4(NO2)2]2(C2N10) (4), and [Co(NH3)5N3](C2N10)·H2O (5) in moderate to excellent yields (46–88%). Similar treatment of trans-[Co(NH3)4(NO2)2]Cl with 1 equiv. of sodium 5-nitrotetrazolate dihydrate (= NaNT, 6) afforded the novel cobalt(III) 5-nitrotetrazolate derivative trans-[Co(NH3)4(NO2)2](NT)·H2O (7) as orange, rectangular prismatic crystals in 64% yield. Two complex cobalt(III) picrates, trans-[Co(NH3)4(NO2)2](picrate)·H2O (9) and [Co(NH3)5N3](picrate)2 (10), were prepared in a similar manner from the corresponding chloride precursors and equimolar amounts of sodium picrate. The reaction of trans-[Co(NH3)4(NO2)2]Cl with sodium dipicrylamide (= NaDPA) in a 1 : 1 molar ratio gave the first cobalt(III) dipicrylamide, trans-[Co(NH3)4(NO2)2](DPA)·H2O (12). Finally, the highly explosive, dark blue-green dichroitic non-electrolyte complex mer-[Co(en)(py)(N3)3] (13) was formed upon treatment of [Co(en)(py)2(NH3)Cl]Cl2·H2O with excess NaN3 in hot water (93% yield). The molecular and crystal structures of 2, 3, 4, 5, 7, 9, 10, 12, and 13 were determined by single-crystal X-ray diffraction. In the solid state, all compounds comprised extensive hydrogen-bonded supramolecular networks. Representative studies of the energetic properties (impact and friction sensitivity, combustion) revealed that some of the new compounds can be classified as primary explosives.