Alkaline earth complexes of a sterically demanding guanidinate ligand

The synthesis of the guanidine MesN{C(NCy2)}N(H)Mes (LH; Mes = 2,4,6-Me3C6H2, Cy = cyclohexyl), and its use as a proligand for the synthesis of alkaline earth metal complexes are reported. Described herein are (i) an unusual Hauser base cubane, (ii) a homoleptic and a base-stabilized magnesium complex featuring the same guanidinate ligands, and (iii) the comparison of a series of alkaline earth (Mg, Ca, Sr, Ba) bis(guanidinate) complexes, which allows the opportunity to compare the changing trends in bonding as the Group is descended. The reaction between LH and MeMgI(OEt2)2 yields the Hauser base as a mixture of the tetramer [Mg4L4(μ3-I)4] (1a) and dimer [Mg2L2(μ-I)2(OEt2)2] (1b), and the reaction with two equivalents of MgnBu2 leads to the formation of four-coordinate [MgL2] (2), which features a square-planar geometry for the magnesium cation, or five-coordinate [MgL2(THF)] (3), depending on the solvent used. 1a is the first crystallographically-characterized cubane structure to consist of four LAeX (L = ligand, X = halide) units. The complexes [AeL2(THF)2] (Ae = Ca, 4; Ae = Sr, 5) and [BaL2] (6) were synthesized via redox transmetallation/ligand exchange reactions. Complex 6 is the first example of a homoleptic, monomeric barium complex of the NCN ligand family, with the structure stabilized by a number of barium-arene interactions in the solid state

Tuning coordination in s-block carbazol-9-yl complexes

1,3,6,8-Tetra-tert-butylcarbazol-9-yl and 1,8-diaryl-3,6-di(tert-butyl)carbazol-9-yl ligands have been utilized in the synthesis of potassium and magnesium complexes. The potassium complexes (1,3,6,8-tBu4carb)K(THF)4 (1; carb=C12H4N), [(1,8-Xyl2-3,6-tBu2carb)K(THF)]2 (2; Xyl=3,5-Me2C6H3) and (1,8-Mes2-3,6-tBu2carb)K(THF)2 (3; Mes=2,4,6-Me3C6H2) were reacted with MgI2 to give the Hauser bases 1,3,6,8-tBu4carbMgI(THF)2 (4) and 1,8-Ar2-3,6-tBu2carbMgI(THF) (Ar=Xyl 5, Ar=Mes 6). Structural investigations of the potassium and magnesium derivatives highlight significant differences in the coordination motifs, which depend on the nature of the 1- and 8-substituents: 1,8-di(tert-butyl)-substituted ligands gave π-type compounds (1 and 4), in which the carbazolyl ligand acts as a multi-hapto donor, with the metal cations positioned below the coordination plane in a half-sandwich conformation, whereas the use of 1,8-diaryl substituted ligands gave σ-type complexes (2 and 6). Space-filling diagrams and percent buried volume calculations indicated that aryl-substituted carbazolyl ligands offer a steric cleft better suited to stabilization of low-coordinate magnesium complexes

A monomeric, heterobimetallic complex with an unsupported Mg−Fe bond

The phosphinimine, trimethylsilyl-substituted BIPM ligand [BIPM = bis(iminophosphorano)methanide] has been used to stabilise CH(Ph2PNSiMe3)2MgFe(η5-C5H5)(CO)2 (1), which is a structurally authenticated complex exhibiting a direct, unsupported bond between an alkaline earth metal and a transition metal. The FTIR-measured carbonyl stretching frequencies for this complex suggest that there is a polarisation of charge from the transition metal fragment to the magnesium centre. The presence of a polar metal-metal bond in 1 is confirmed by DFT calculations, which suggest that the Mg−Fe bond is predominantly ionic in nature

Dynamic Permutational Isomerism in a closo-Cluster

Permutational isomers of trigonal bipyramidal [W2RhIr2(CO)9(η(5)-C5H5)2(η(5)-C5HMe4)] result from competitive capping of either a W2Ir or a WIr2 face of the tetrahedral cluster [W2Ir2(CO)10(η(5)-C5 H5)2] from its reaction with [Rh(CO)2(η(5)-C5HMe4)]. The permutational isomers slowly interconvert in solution by a cluster metal vertex exchange that is proposed to proceed by Rh-Ir and Rh-W bond cleavage and reformation, and via the intermediacy of an edge-bridged tetrahedral transition state. The permutational isomers display differing chemical and physical properties: replacement of CO by PPh3 occurs at one permutational isomer only, while the isomers display distinct optical power limiting behavior.We thank the Australian Research Council (Discovery Grant to M.G.H. and M.P.C., ARC Australian Research Fellowship to M.P.C.) for financial support. J.F. was the recipient of a China Scholarship Council ANU Postgraduate Scholarship

Alkaline Earth Complexes of a Sterically Demanding Guanidinate Ligand: Alkaline Earth Guanidinate Complexes

The synthesis of the guanidine MesN{C(NCy2)}N(H)Mes (LH; Mes = 2,4,6-Me3C6H2, Cy = cyclohexyl), and its use as a proligand for the synthesis of alkaline earth metal complexes are reported. Described herein are (i) an unusual Hauser base cubane, (ii) a homoleptic and a base-stabilized magnesium complex featuring the same guanidinate ligands, and (iii) the comparison of a series of alkaline earth (Mg, Ca, Sr, Ba) bis(guanidinate) complexes, which allows the opportunity to compare the changing trends in bonding as the Group is descended. The reaction between LH and MeMgI(OEt2)2 yields the Hauser base as a mixture of the tetramer [Mg4L4(?3-I)4] (1a) and dimer [Mg2L2(?-I)2(OEt2)2] (1b), and the reaction with two equivalents of MgnBu2 leads to the formation of four-coordinate [MgL2] (2), which features a square-planar geometry for the magnesium cation, or five-coordinate [MgL2(THF)] (3), depending on the solvent used. 1a is the first crystallographically-characterized cubane structure to consist of four LAeX (L = ligand, X = halide) units. The complexes [AeL2(THF)2] (Ae = Ca, 4; Ae = Sr, 5) and [BaL2] (6) were synthesized via redox transmetallation/ligand exchange reactions. Complex 6 is the first example of a homoleptic, monomeric barium complex of the NCN ligand family, with the structure stabilized by a number of barium-arene interactions in the solid state

Synthesis and characterisation of magnesium complexes containing sterically demanding N,N' -bis(aryl)amidinate ligands

Condensation reactions of carboxylic acids and anilines in the presence of polyphosphoric acid trimethylsilyl ester (PPSE) afforded a range of sterically demanding N,N′-bis(aryl)amidines, RN{C(R′)}N(H)R [R = Mes (Mes = 2,4,6-trimethylphenyl), R′ =

Mixed-metal cluster chemistry. 39. Syntheses and X-ray structures of Mo 3 Ir 3 (μ 4 -η 2 -CO)(μ 3 -CO)(CO) 10 (η 5 -C 5 H 5 ) 3 and Mo 3 RhIr 3 (μ-CO) 4 (CO) 7 (η 5 -C 5 H 5 ) 3 (η 5 -C 5 Me 5 )

We thank the Australian Research Council (ARC) for support ofthis work. J.F. was the recipient of a China Scholarship Council ANUPostgraduate Scholarship and M.D.R. was the recipient of anAustralian Postgraduate Awar

Syntheses and Optical Properties of Azo-Functionalized Ruthenium Alkynyl Complexes

We thank the Australian Research Council (ARC), the National Natural Science Foundation of China (51432006), and the Chinese Government Ministry of Education and State Administration of Foreign Experts Affairs (111 Project: B13025) for financial support. M.P.C. thanks the ARC for an Australian Research Fellowship

Synthesis, Optical, Electrochemical, and Theoretical Studies of Dipolar Ruthenium Alkynyl Complexes with Oligo(phenylenevinylene) Bridges

We thank the Australian Research Council (ARC), the National Natural Science Foundation of China (51432006), the Chinese Government Ministry of Education, and the Chinese Government State Administration of Foreign Experts Affairs (111 Project: B13025). M.P.C. thanks the ARC for an Australian Research Fellowship and C.Q. thanks CONICYT (Chile) for a Chile PhD Scholarship Abroad

Ligand influences on homoleptic Group 12 m-terphenyl complexes

Three m-terphenyl ligands 2,6-Ar2C6H3 – [Ar = 2,6-Me2C6H3 (2,6-Xyl); 3,5-Me2C6H3 (3,5-Xyl); 2,3,4,5,6-Me5C6 (Pmp)] have been used to stabilise three series of two-coordinate Group 12 diaryl complexes; (2,6-Ar2C6H3)2M [M = Zn, Cd, Hg; Ar = 2,6-Xyl 1-3; 3,5-Xyl 4-6; Pmp 7-9], where differing steric demands on the metal centres are imparted. These are the first homoleptic d-block complexes featuring any of these ligands. Complexes 1-9 have been characterised in solution and the solid state; the analysis of structural changes produced by differences in ligand properties is reported. In particular, complexes 4-6 show smaller C–M–C bond angles and contain secondary ligand interactions that are not seen in the analogous complexes 1-3 and 7-9