Jose M. Goicoechea

Synthesis and Isolation of [Fe@Ge10]3−: A Pentagonal Prismatic Zintl Ion Cage Encapsulating an Interstitial Iron Atom

Reaction of an ethylenediamine (en) solution of the Zintl phase precursor K(4)Ge(9) with FeAr(2) (Ar = 2,6-Mes(2)C(6)H(3)) in the presence of 2,2,2-crypt (4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane) yielded the endohedral Zintl ion [Fe@Ge(10)](3-) (1) which was crystallographically characterized as a [K(2,2,2-crypt)](+) salt in [K(2,2,2-crypt)](3)[Fe@Ge(10)]*2en. This unprecedented Zintl ion exhibits a pentagonal prismatic 10-atom germanium cage with an interstitial iron atom in the central cavity. Confirmation of the existence of the cluster anion in solution was corroborated by positive and negative ion mode electrospray mass spectrometry.

The 2‐Phosphaethynolate Anion: A Convenient Synthesis and [2+2] Cycloaddition Chemistry

Hip to be square: Direct carbonylation of solutions of the heptaphosphide trianion (P7(3-)) afforded the phosphaethynolate anion in moderate yields. This species undergoes [2+2] cycloaddition reactions with diphenylketene and bis(2,6-diisopropylphenyl)carbodiimide to yield the anionic four-membered heterocycles P[C(O)]2C(C6H5)2(-) and PC(O)(CNDipp)NDipp(-) .

E–H Bond Activation of Ammonia and Water by a Geometrically Constrained Phosphorus(III) Compound

The synthesis of a phosphorus(III) compound bearing a N,N-bis(3,5-di-tert-butyl-2-phenoxy)amide ligand is reported. This species has been found to react with ammonia and water, activating the E–H bonds in both substrates by formal oxidative addition to afford the corresponding phosphorus(V) compounds. In the case of water, both O–H bonds can be activated, splitting the molecule into its constituent elements. To our knowledge, this is the first example of a compound based on main group elements that sequentially activates water in this manner.

Phosphinecarboxamide: A Phosphorus-Containing Analogue of Urea and Stable Primary Phosphine

Reactions of the 2-phosphaethynolate anion (PCO(-), 1) with ammonium salts quantitatively yielded phosphinecarboxamide (PH2C(O)NH2, 2). The molecular structure and chemical properties of 2 were studied by single-crystal X-ray diffraction and multielement NMR spectroscopy. This phosphorus-containing analogue of urea is a rare example of an air-stable primary phosphine.

Transition Metal Complexes of Anionic N-Heterocyclic Dicarbene Ligands†

The development of N-heterocylic carbene (NHC) chemistry has advanced enormously since the pioneering work of Wanzlick and Schçnherr, and that of fele. Arguably, one of the most significant breakthroughs in this area was the isolation of the first stable N-heterocyclic carbene (NHC), 1,3-bis(adamantyl)-imidazol-2-ylidene, by Arduengo and coworkers. Since this species was first reported, NHCs have gone from chemical curiosities to ubiquitous ligands in the span of just twenty years. Their use as supporting ligands for the formation of transition metal complexes with varied chemical properties has been extensively documented. Similarly, the exploitation of their strong sigma-donor ability has been used in main-group chemistry for the stabilization of numerous low-coordinate complexes containing elements in low oxidation states, including the remarkable group 14 and 15 diatomic species E2 (E = Si, Ge, P, As) [5–8] and P2 . The chemistry of NHCs is dominated by ligand coordination through the C2 atom in the so-called classical mode (A, Figure 1). However, following the discovery of the first transition metal complex of an abnormal NHC (aNHC, B, Figure 1) by Crabtree and co-workers, numerous additional examples of such abnormally bonded species have been isolated, including the first example of an isolated metalfree abnormal carbene. A closely related, metal-free mesoionic carbene was also isolated by Bertrand and coworkers. More recently, Robinson and co-workers reported the first example of an anionic N-heterocyclic dicarbene, that is, an NHC in which one of the sites of the imidazol-2-ylidene backbone has been deprotonated, giving rise to an NHC capable of coordinating through the C2 and C4 positions simultaneously (NHDC, C, Figure 1). A related anionic NHC which can be rationalized as an adduct of a dicarbene and B(C6F5)3 was also recently reported. [15] Whereas lanthanide complexes of an N-heterocyclic dicarbene have previously been isolated, to our knowledge no examples of transition metal complexes of N-heterocyclic dicarbenes have been reported to date. Related neutral dicarbenes based on 1,2,4-triazole-3,5-diylidenes were first identified in coordination polymers of silver(I) salts. Herein, we report the first example of a transition metal complex containing anionic N-heterocyclic dicarbene ligands K[{DC[N(2,6-iPr2C6H3)]2(CH)C}2Mn(mes)(thf)]·THF (2). Reaction of 1,3-bis(2,6-diisopropylphenyl)-imidazol-2-ylidene (IPr) with Mn3(mes)6 in diethylether afforded the complex [Mn(IPr)(mes)2] (1; Figure 2) as an insoluble offwhite solid in near quantitative yields. Crystals suitable for single crystal X-ray diffraction could be obtained by slow diffusion of diethylether into a pyridine solution of 1 at 4 8C. Analogous reactions giving rise to related three

Phosphide Delivery to a Cyclotrisilene

The reactivity of the 2-phosphaethynolate anion (PCO−) towards a cyclic trisilene (cSi3(Tip)4) is reported. The result is the net activation of the P=C and Si=Si multiple bonds of the precursors affording a heteroatomic bicyclo[1.1.1]pentan-2-one analogue ([P(CO)Si3(Tip)4]−; 1). This reaction can be interpreted as the formal addition of a phosphide and a carbonyl across the Si=Si double bond. Photolytic decarbonylation of 1 results in the incorporation of the phosphide vertex into the cyclotrisilene scaffold, yielding a congener of the cyclobutene anion with considerable allylic character.

Synthesis and characterization of [Ru@Ge12]3-: an endohedral 3-connected cluster.

The 12-vertex endohedral cluster [Ru@Ge12](3-) reveals an unprecedented D2d-symmetric 3-connected polyhedral geometry. The structure contrasts dramatically with the known deltahedral or approximately deltahedral geometries of [M@Pb12](2-) (M = Ni, Pd, Pt) and [Mn@Pb12](3-) and is a result of extensive delocalization of electron density from the transition-metal center onto the cage.

Reductive cleavage of Zn–C bonds by group 14 Zintl anions: synthesis and characterisation of [E9ZnR]3− (E = Ge, Sn, Pb; R = Mes, iPr)

The reaction of ethylenediamine solutions of K(4)E(9) (E = Ge, Sn, Pb) with diaryl and dialkyl organozinc reagents ZnMes(2) and Zn(i)Pr(2) yielded the functionalized Zintl ions, closo-[E(9)ZnR](3-) (R = Mes: E = Ge (1), Sn (2), Pb (3); R = (i)Pr: E = Ge (4), Sn (5), Pb (6)). These reactions proceed via reductive zinc-carbon bond activation of the organometallic reagents by the free solvated electrons present in ethylenediamine solutions of intermetallic Zintl phases. The functionalized cluster anions 1, 2 and 4-6 were characterized in the solid-state as [K(2,2,2-crypt)](+) salts by single-crystal X-ray diffraction and elemental analysis, while the presence of all six cluster anions in solution was confirmed by (1)H and (13)C{(1)H} NMR spectroscopy and electrospray mass spectrometry.

Coupling reactions of functionalized Zintl ions [E9Cd(C6H5)]3- (E = Sn, Pb) with tributyltinhydride: synthesis and isolation of {Sn9CdSn[(CH2)3CH3]3}3-.

Reaction of ethylenediamine solutions of K(4)E(9) (E = Sn, Pb) with diphenylcadmium yielded the Cd(C(6)H(5))-functionalized Zintl ions, closo-[E(9)Cd(C(6)H(5))](3-) (E = Sn (1); Pb (2)). Solution reactivity studies of 1 with tributyltinhydride in pyridine revealed that the cluster is capable of undergoing a coupling reaction to yield the tributyltin-functionalized cluster, closo-{Sn(9)CdSn[(CH(2))(3)CH(3)](3)}(3-) (3). In-situ monitoring of this reaction by (1)H and (13)C{(1)H} NMR spectroscopy reveals the formation of the tributyltin functionalized cluster anion in addition to free benzene. Species 1-3 were characterized in the solid-state as [K(2,2,2-crypt)](+) salts by single crystal X-ray diffraction and elemental analysis, while the presence of all three cluster anions in solution was confirmed by (1)H and (13)C{(1)H} NMR spectroscopy and electrospray mass-spectrometry.

[Hg3(Ge9)4]10−: a nanometric molecular rod precursor to polymeric mercury-linked cluster chains

Reaction of an ethylenediamine solution of K(4)Ge(9) with Hg(C(6)H(5))(2) yielded [Hg(3)(Ge(9))(4)](10-), an unprecedented mercury-linked molecular rod consisting of four nine-atom germanium clusters.