Hydropnictination Reactions of Carbodiimides and Isocyanates with Protonated Heptaphosphide and Heptaarsenide Zintl Ions

By following a similar procedure to that employed for the synthesis of [HP7]2- (1), the synthesis and characterization of the hydrogenheptaarsenide dianion [HAs7]2- (2) was achieved. Building on previous research that has shown that [HP7]2- can react with carbodiimides to yield amidine-functionalized cluster anions [P7C(NHR)(NR)]2-, we have found that the analogous hydroarsination reactions are also possible by reaction of 2 with RC=N=CR to yield [As7C(NHR)(NR)]2- [R = Dipp (3), iPr (4) and Cy (5); Dipp = 2,6-diisopropylphenyl]. Furthermore, we also demonstrate that such hydropnictination reactions can be extended to other heteroallenes such as isocyanates (O=C=NAd; Ad = adamantyl) to afford the amide-derivatized cluster anions [E7C(CO)(NHAd)]2- [E = P (6) and As (7)]. All new compounds were characterized by multinuclear NMR spectroscopy, elemental analyses and electrospray mass spectrometry. Clusters 2, 4, 6 and 7 were also characterized by single-crystal X-ray diffraction of [K(18-crown-6)] 2[2], [K(18-crown-6)]2[4], [K(18-crown-6)] 2[6]·py (py = pyridine) and [K(18-crown-6)] 2[7]·py. Crystal structures confirming composition and connectivity were also obtained for anions 3 and 5. Copyright © 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim

Hydrophosphination of Carbodiimides Using Protic Heptaphosphide Cages: A Unique Effect of the Bimodal Activity of Protonated Group 15 Zintl Ions

Direct reaction of the hydrogen heptaphosphide dianion, [HP 7] 2- (1), with carbodiimides RN=C=NR (R = Dipp (2,6-diisopropylphenyl), iPr, Cy) afforded the amidine-functionalized Zintl ions [P 7C(NHR)(NR)] 2- (R = Dipp (2), iPr (3), and Cy (4)). The bimodal activity of 1, which contains both negatively charged phosphide vertices alongside "electron-precise" phosphine-like nuclei allows for the direct hydrophosphination of the carbodiimides without need for an external proton source. Further reaction of the bis(2,6- diisopropylphenyl)amidine-functionalized cluster 2 with a proton source such as [NH 4][BPh 4] or [H(OEt 2) 2][BAr F4] affords the protonated monoanionic species [HP 7C(NHDipp)(NDipp)] - (5). As with 1, species 5 also has bimodal character, and additional hydrophosphination reactions are possible by reacting 5 with RN=C=NR to yield the bis-functionalized monoanions {[P 7[C(NHDipp)(NDipp)][C(NHR)(NR)]} - (R = Dipp (6), iPr (7), and Cy (8)). All species were characterized by multielement NMR spectroscopy and electrospray mass spectrometry. In addition clusters 3, 5, and 6-8 were characterized by single-crystal X-ray diffraction in [K(18-crown-6)] 2[3], [K(2,2,2-crypt)][5], [K(2,2,2-crypt)][6] •THF, [K(2,2,2-crypt)][7]•hex, and [K(2,2,2-crypt)][8]•0. 65THF•0.35hex, respectively. Density functional theory level calculations were conducted on all anionic species to probe their electronic structure. © 2012 American Chemical Society

Hydropnictination Reactions of Carbodiimides and Isocyanates with Protonated Heptaphosphide and Heptaarsenide Zintl Ions

By following a similar procedure to that employed for the synthesis of [HP7]2- (1), the synthesis and characterization of the hydrogenheptaarsenide dianion [HAs7]2- (2) was achieved. Building on previous research that has shown that [HP7]2- can react with carbodiimides to yield amidine-functionalized cluster anions [P7C(NHR)(NR)]2-, we have found that the analogous hydroarsination reactions are also possible by reaction of 2 with RC=N=CR to yield [As7C(NHR)(NR)]2- [R = Dipp (3), iPr (4) and Cy (5); Dipp = 2,6-diisopropylphenyl]. Furthermore, we also demonstrate that such hydropnictination reactions can be extended to other heteroallenes such as isocyanates (O=C=NAd; Ad = adamantyl) to afford the amide-derivatized cluster anions [E7C(CO)(NHAd)]2- [E = P (6) and As (7)]. All new compounds were characterized by multinuclear NMR spectroscopy, elemental analyses and electrospray mass spectrometry. Clusters 2, 4, 6 and 7 were also characterized by single-crystal X-ray diffraction of [K(18-crown-6)] 2[2], [K(18-crown-6)]2[4], [K(18-crown-6)] 2[6]·py (py = pyridine) and [K(18-crown-6)] 2[7]·py. Crystal structures confirming composition and connectivity were also obtained for anions 3 and 5. Copyright © 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim

'Classical' and 'Abnormal' Bonding in Tin (II) N-Heterocyclic Carbene Complexes

Reaction of Sn(OTf)2 (OTf-≤OSO2CF3-) with one and two equivalents of the N-heterocyclic carbene (NHC) 1,3-bis(2,6-diisopropylphenyl)-imidazol-2-ylidene (IPr) yielded the complexes [Sn(IPr)(OTf)2] (1) and [Sn(IPr)(aIPr)(OTf)][OTf] (2), respectively. Both species were characterised by single crystal X-ray diffraction, multi-element NMR spectroscopy, and elemental analysis. Both compounds display an NHC ligand bonded to the tin(ii) metal centre via the C2 carbon in a 'classical' mode, while 2 also contains an 'abnormal' C4/C5-bonded carbene (aIPr). These observations highlight the subtle steric and electronic effects affecting the coordination modes of these ligands. Solution phase NMR experiments on 1 and 2 reveal complex behaviour resulting in the protonation of the IPr ligands to yield the 1,3-bis(2,6-diisopropylphenyl)-imidazolium cation via an unidentified reaction mechanism

Group 12 Metal Complexes of N-Heterocyclic Ditopic Carbanionic Carbenes

Reaction of the N-heterocyclic carbene 1,3-bis(2,6-diisopropylphenyl) imidazol-2-ylidene (IPr) with M(mes)2 (M = Zn, Cd) in diethyl ether afforded the Lewis acid-base adducts [M(IPr)(mes)2] (M = Zn (1), Cd (2)) in quantitative yields. An analogous reaction between Hg(mes)2 and IPr failed to form the desired 1:1 adduct, [Hg(IPr)(mes)2], as evidenced by NMR spectroscopy. Reduction of 1 and 2 with KC8 afforded K+ salts of the anionic complexes [{:C[N(2,6-iPr 2C6H3)]2(CH)C}2M(mes)] - (M = Zn (3), Cd (4)). By contrast, reduction of a THF solution of a mixture of Hg(mes)2 and IPr gave rise to the homoleptic anionic species [{:C[N(2,6-iPr2C6H3)] 2(CH)C}3Hg]- (5). Species 3-5 display abnormally bonded anionic N-heterocyclic "dicarbene" ligands (or ditopic carbanionic carbenes) in which IPr has been deprotonated at the C4/C5 position. The vacant C2 atoms retain carbenic character, allowing for further coordination to Lewis acids. This was demonstrated by reaction of 3 with H 3B:SMe2, AlEt3, and CO2 (in the presence of the appropriate cation-sequestering agents), which afforded salts of the [{LA:C[N(2,6-iPr2C6H3)] 2(CH)C}2Zn(mes)]- anions (LA = BH3 (6), AlEt3 (7), and CO2 (8)). © 2013 American Chemical Society

Synthesis and Characterization of Free and Coordinated 1,2,3-Tripnictolide Anions

We have investigated the chemical reactivity of heptaatomic anionic clusters of the group 15 elements ([E7]3-/[HE 7]2-, E = P, As) toward the symmetric and asymmetrically substituted alkynes diphenylacetylene and phenylacetylene. The results reported herein, alongside a previous report on the reactivity of such clusters toward acetylene, describe a versatile route by which to access otherwise elusive 1,2,3-tripnictolide anions of the general formula [E3C 2RR′]- (R = R′ = H, E = P (1), As (2); R = R′ = C6H5, E = P (3) As (4); R = H, R′ = C6H5, E = P (5), As (6)). These species can be isolated as [K(18-crown-6)]+ or [K(2,2,2-crypt)]+ salts. All anions were characterized by multielement NMR spectroscopy and electrospray mass spectrometry. In addition, single-crystal X-ray diffraction structures of the novel species [K(18-crown-6)(THF)2][3], [K(2,2,2-crypt)][4] ·xTHF (x = 0, 0.5), and [K(18-crown-6)THF][6] were also obtained. The chemical reactivity of these group 15 cyclopentadienyl analogues has been explored in a series of ligand displacement reactions with Mo(CO) 3(L)3 (L = CO, CH3CN) to yield the complex anions [(η5-E3C2H2)Mo(CO) 3]- (E = P (7), As (8)), [{η5-E 3C2(C6H5)2}Mo(CO) 3]- (E = P (9), As (10)), and [{η5-E 3C2H(C6H5)}Mo(CO)3] - (E = P (11), As (12)). © 2013 American Chemical Society