Alkaline-Earth Chalcogenolates: Exploration of Synthetic Strategies and Structural Chemistry

Barium thiolates and selenolates: syntheses and structural principles

The synthesis and structural characterization of a family of barium thiolates and selenolates is described. The thiolates were synthesized by metallation of thiols, the selenolates by reductive insertion of the metal into the selenium-selenium bond of diorganodiselenides. Both reaction sequences were carried out by using barium metal dissolved in ammonia; this afforded barium thiolates and selenolates in good yield and purity. The structural principles displayed in the target compounds span a wide range of solid-state formulations, including monomeric and dimeric species, and separated ion triples, namely [Ba(thf)4(SMes*)2] (1; Mes* = 2,4,6-tBU3C6H2), [Ba(thf)4(SeMes*)2] (2), [Ba([18]crown-6)(hmpa)2][(SeMes*)2] (3), the dimeric [(Ba(py)3(thf)(SeTrip)2)2] (4; py = pyridine, Trip = 2,4.6-iPr3C6H2), and [Ba([18]crown-6)(SeTrip)2] (5). The full range of association modes is completed by [Ba([18]crown-6)(hmpa)SMes*][SMes*] (6) communicated earlier by this group. In the solid state, this compound displays an intermediate ion coordination mode: one anion is bound to the metal, while the second one is unassociated. Together these compounds provide structural information about all three different association modes for alkaline earth metal derivatives. This collection of structural data allows important conclusions about the influence of solvation and ligation on structural trends.

Syntheses, structures, and reactivities of heteroleptic magnesium amide thiolates

The syntheses and characterizations of a family of novel heteroleptic magnesium amide thiolates are presented. The compounds are synthesized by ligand redistribution chemistry involving reactions of equimolar amounts of magnesium amides and magnesium thiolates. Utilization of the smaller thiolates [Mg(SPh)2]n and [Mg(S-2,4,6-iPr3C6H2)2]n results in the isolation of dimeric species, [Mg(THF)(N(SiMe3)2)(mu-SR)]2 (R = Ph (1), 2,4,6-iPr3C6H2 (2)), with four-coordinate metal centers and bridging thiolate functions. The sterically more encumbered thiolate S-2,4,6-tBu3C6H2 induces the formation of the four-coordinate, monomeric species Mg(THF)2(N(SiMe3)2)(S-2,4,6-tBu3C6H2) (3)). Careful choice of reaction conditions allows the successful syntheses of pure heteroleptic compounds; however, it remains difficult to obtain the compounds in high yields, since a tendency toward product symmetrization and ligand redistribution under re-formation of the starting materials is prevalent. One of these symmetrized products is also included in this report: the dimeric, four-coordinate magnesium thiolate [Mg-(THF)(S-2,4,6-tBu3C6H2)(mu-S-2,4,6-tBu3C6H2)]2 (4), isolated as the product of the reaction between [Mg-(N(SiMe3)2)2]2 and Mg(THF)2(S-2,4,6-tBu3C6H2)2. All compounds were characterized by NMR and IR spectroscopy, elemental analyses, and X-ray crystallography. Crystal data obtained with Mo K alpha (lambda = 0.710 73 A) radiation are as follows. 1: C16H31MgNOSSi2, a = 11.2100(1) A, b = 17.4512(3) A, c = 11.2999(2) A, beta = 97.952(1) degrees, V = 2189.32(6) A3, Z = 4, monoclinic, space group P2(1)/n, R1 (all data) = 0.0934. 2: C25H49MgNOSSi2, a = 11.1691(1) A, b = 11.0578(1) A, c = 26.0671(4) A, beta = 99.906(1) degrees, V = 3171.44(6) A3, Z = 4, monoclinic, space group P2(1)/c, R1 (all data) = 0.0557. 3: C36H71MgNO3SSi2, a = 42.8293(16) A, b = 10.9737(5) A, c = 16.8305(7) A, beta = 98.755(3) degrees, V = 7818.1(6) A3, Z = 8, monoclinic, space group C2/c, R1 (all data) = 0.1331. 4: C80H132Mg2O2S4, a = 18.8806(2) A, b = 19.3850(2) A, c = 27.3012(4) A, beta = 97.250(1) degrees, V = 9912.4(2) A3, Z = 4, monoclinic, space group P2(1)/n, R1 (all data) = 0.1023.

Formation of Separated versus Contact Ion Triplets in Magnesium Thiolates. Synthesis and Characterization of [Mg(15-crown-5)(SCPh(3))(2)] and [Mg(15-crown-5)(THF)(2)][S-2,4,6-tBu(3)C(6)H(2))](2)

The synthesis and structural characterization of two magnesium thiolate complexes are described. Both compounds were prepared by analogous reactions routes, namely, alkane elimination and transamination, but using differently sized ligands. Utilization of the smaller HSCPh(3), resulted in the formation of [Mg(15-crown-5)(SCPh(3))(2)], 1, displaying a seven-coordinate magnesium center with two magnesium-sulfur bonds. Employment of the sterically more encumbered HS-2,4,6-tBu(3)C(6)H(2) yielded a separated cation and anions as displayed in [Mg(15-crown-5)(THF)(2)][S-2,4,6-tBu(3)C(6)H(2)](2), 2. Compound 2 exhibits a seven-coordinate cation, completing its coordination environment with five metal-crown-ether interactions in addition to two tetrahydrofuran (THF) contacts. The compounds were characterized by IR and NMR spectroscopy in addition to X-ray crystallography. Crystal data with Mo Kalpha (lambda = 0.710 73 Å) are as follows: 1, C(48)H(50)MgO(5)S(2), a = 8.4785(4) Å, b = 9.3595(5) Å, c = 13.8306(6) Å, alpha = 87.332(1) degrees, beta = 85.929(1) degrees, gamma = 68.733(1) degrees, Z = 1, triclinic; 2, C(54)H(94)MgO(7)S(2), a = 13.6755(2) Å, b = 12.8045(6) Å, c = 32.7127(12) Å, beta = 97.87(1) degrees, Z = 4, monoclinic.