Preparation and Properties of Group 13 (Ga, In, Tl) Heterometallic Single and Corner-Shared Double Cube Derivatives of [Mo(3)S(4)(H(2)O)(9)](4+) and Related Studies.

New routes are described for the preparation of cuboidal complexes [Mo(3)InS(4)(H(2)O)(12)](5+), [Mo(3)GaS(4)(H(2)O)(12)](5+), and [Mo(6)InS(8)(H(2)O)(18)](8+) from the incomplete cuboidal [Mo(3)S(4)(H(2)O)(9)](4+). A comparison of the aqueous solution properties of the single cubes, [Mo(3)GaS(4)(H(2)O)(12)](5+) and [Mo(3)InS(4)(H(2)O)(12)](5+), and the double cubes, [Mo(6)InS(8)(H(2)O)(18)](8+) and [Mo(6)TlS(8)(H(2)O)(18)](8+), the total listing of group 13 derivatives, is reported. The single cube [Mo(3)InS(4)(H(2)O)(12)](5+) can be quantitatively converted into the double cube by reductive (H(3)PO(2) or BH(4)(-)) addition of [Mo(3)S(4)(H(2)O)(9)](4+). The double cubes are O(2) sensitive, much more so in HCl than Hpts (pts(-) = p-toluenesulfonate), and are oxidized by H(+) in HCl solutions with the formation of H(2) (detected by gas chromatography). The single cubes are less reactive in air, and are only oxidized by H(+) at higher ( approximately 4 M) levels. Stoichiometry measurements with [Co(dipic)(2)](-) and [Fe(H(2)O)(6)](3+) as 1e(-) oxidants were used to confirm charges on the clusters. In the absence of reduction potentials, rate constants for outer-sphere [Co(dipic)(2)](-) oxidations give a measure of redox properties. Oxidation of [Mo(6)InS(8)(H(2)O)(18)](8+) with [Co(dipic)(2)](-) provides a route back to the single cube [Mo(3)InS(4)(H(2)O)(12)](5+). Properties of [W(3)InS(4)(H(2)O)(12)](5+) and [Mo(6)InO(2)S(6)(H(2)O)(18)](8+) obtained from [W(3)S(4)(H(2)O)(9)](4+) and [Mo(3)OS(3)-(H(2)O)(9)](4+) are also considered. The single cube [W(3)InS(4)(H(2)O)(12)](5+) is >10(3) times more reactive with [Co(dipic)(2)](-) than [Mo(3)InS(4)(H(2)O)(12)](5+), consistent with reducing properties W > Mo. No evidence was obtained in these studies for [Mo(3)TlS(4) (H(2)O)(12)](5+), [Mo(6)GaS(8)(H(2)O)(18)](8+), or the recently proposed 6+ analogue of [Mo(3)GaS(4)(H(2)O)(12)](5+).

Preparation and Solution Properties of Chalcogenide-Rich Clusters [Mo(3)Y(7)(H(2)O)(6)](4+) (Y = S, Se): Kinetics of PR(3)(3-) Abstraction of Y from &mgr;-(Y(2)(2-)) and H(2)O Substitution by Cl(-) and Br(-).

The chalcogenide-rich trinuclear Mo(IV)(3) clusters [Mo(3)Y(7)(H(2)O)(6)](4+), containing single &mgr;(3)-(Y(2)(-)) and three &mgr;-(Y(2)(2)(-)) core ligands, have been obtained for the first time from polymeric {Mo(3)Y(7)Br(4)}(x)() via [Mo(3)Y(7)Br(6)](2)(-) (Y = S, Se). ICP analyses of 2 M HCl solutions give Mo:S and Mo:Se ratios consistent with the formulas indicated, and on reaction with concentrated HBr, 85% recovery of (Et(4)N)(2)[Mo(3)S(7)Br(6)], the structure of which is known, has been achieved. Abstraction of S and Se with PPh(3) (two-phase system), or the water-soluble phosphine (3-SO(3)C(6)H(4))(3)P(3)(-) (PR(3)(3)(-)), gives quantitative formation of [Mo(3)S(4)(H(2)O)(9)](4+) and [Mo(3)Se(4)(H(2)O)(9)](4+). With CN(-), both abstraction of S (or Se) and CN(-) replacement of H(2)O is observed, giving [Mo(3)S(4)(CN)(9)](5)(-) and [Mo(3)Se(4)(CN)(9)](5)(-) as products. It was possible to assign which atom of the sideways eta(2),eta(2) &mgr;-(S(2)(2)(-)) and &mgr;-(Se(2)(2)(-)) ligands is abstracted using the structurally characterized [Mo(3)S(4)Se(3)(H(2)O)(6)](4+) cluster. Thus it was demonstrated that with the phosphines the equatorial (to the Mo(3) plane) Se atoms of the three &mgr;-(SSe(2)(-)) groups are removed with formation of the Mo(3)S(4)(4+) core. Kinetic studies on the reactions of [Mo(3)S(7)(H(2)O)(6)](4+) and [Mo(3)Se(7)(H(2)O)(6)](4+) with PR(3)(3)(-) give approximately 10(3) faster abstraction rate constants (k(a)/M(-)(1) s(-)(1)) for S than Se. The rate law k(a) = k(1)[H(+)] + k(-)(1)[H(+)](-)(1) is explained by the involvement of protonated &mgr;-(Y(2)(2)(-)) (k(1)) and an H(2)O conjugate-base form (k(-)(1)). Equilibration rate constants for X(-) = Cl(-) and Br(-) substitution of H(2)O on [Mo(3)S(7)(H(2)O)(6)](4+) and [Mo(3)Se(7)(H(2)O)(6)](4+) are however independent of [H(+)] in the range 0.5-2.0 M investigated. With X(-) concentrations up to 1.3 M (S cluster) and 0.3 M (Se), the uniphasic reactions are assigned as substitution of the H(2)O cis to &mgr;(3)-(Y(2)(-)) at each Mo. At 25 degrees C formation rate constants 10(4)k(f)/M(-)(1) s(-)(1) are as follows for [Mo(3)S(7)(H(2)O)(6)](4+): Cl(-) (1.83); Br(-) (2.07). The same rate constants are as follows for [Mo(3)Se(7)(H(2)O)(6)](4+): Cl(-) (6.7); Br(-) (33). Formation rate constants for Cl(-) are surprisingly 2 x 10(6) times slower than for the reaction of [Mo(3)S(4)(H(2)O)(9)](4+) with Cl(-). Reactions of Mo(3)S(7)(4+) with three metals (Sn, Ni, In) were studied briefly.

Aqueous Solution Chemistry of the Mo(3)PdS(4) Cube: Substitution Reactions and the Double to Single Cube Interconversion Induced by CO, Two Phosphines, Cl(-), Br(-), and NCS(-).

The kinetics of conversion of an edge-linked double cube, in this case [{Mo(3)PdS(4)(H(2)O)(9)}(2)](8+), to the corresponding single cube [Mo(3)(PdX)S(4)(H(2)O)(9)](4+), has been studied for the first time. Reaction is induced by six reagents X = CO, two water-soluble phosphines, Cl(-), Br(-), and NCS(-), which complex at the tetrahedral Pd. The first stage of reaction is fast and is accompanied by color changes, e.g. purple to dark blue in the case of Cl(-), assigned as double to single cube conversion. With X = CO and the two phosphines, when absorbance changes are intense enough for stopped-flow monitoring with reactants at Pd-SCN. On removal of e.g. Cl(-) by chromatography or addition of Ag(+), the double cube re-forms.

Preparation and Properties of the Corner-Shared Double Cube [Mo(6)BiS(8)(H(2)O)(18)](8+) as a Derivative of [Mo(3)S(4)(H(2)O)(9)](4+) in Aqueous Acidic Solutions.

The reaction of [Mo(3)S(4)(H(2)O)(9)](4+) with Bi(III) in the presence of BH(4)(-) (rapid), or with Bi metal shot (3-4 days), gives a heterometallic cluster product. The latter has been characterized as the corner-shared double cube [Mo(6)BiS(8)(H(2)O)(18)](8+) by the following procedures. Analyses by ICP-AES confirm the Mo:Bi:S ratio as 6:1:8. Elution from a cation-exchange column by 4 M Hpts (Hpts = p-toluenesulfonic acid), but not 2 M Hpts (or 4 M HClO(4)), is consistent with a high charge. The latter is confirmed as 8+ from the 3:1 stoichiometries observed for the oxidations with [Co(dipic)(2)](-) or [Fe(H(2)O)(6)](3+) yielding [Mo(3)S(4)(H(2)O)(9)](4+) and Bi(III) as products. Heterometallic clusters [Mo(6)MS(8)(H(2)O)(18)](8+) are now known for M = Hg, In, Tl, Sn, Pb, Sb, and Bi and are a feature of the P-block main group metals. The color of [Mo(6)BiS(8)(H(2)O)(18)](8+) in 2.0 M Hpts (turquoise) is different from that in 2.0 M HCl (green-blue). Kinetic studies (25 degrees C) for uptake of a single chloride k(f) = 0.80 M(-)(1) s(-)(1), I = 2.0 M (Hpts), and the high affinity for Cl(-) (K > 40 M(-)(1)) exceeds that observed for complexing at Mo. A specific heterometal interaction of the Cl(-) not observed in the case of other double cubes is indicated. The Cl(-) can be removed by cation-exchange chromatography with retention of the double-cube structure. Kinetic studies with [Co(dipic)(2)](-) and hexaaqua-Fe(III) as oxidants form part of a survey of redox properties of this and other clusters. The Cl(-) adduct is more readily oxidized by [Co(dipic)(2)](-) (factor of approximately 10) and is also more air sensitive.

Ligand Substitution Reactions at the Nickel of [Mo(3)NiS(4)(H(2)O)(10)](4+) with Two Water Soluble Phosphines, CO, Br(-), I(-), and NCS(-) and the Inertness of the 1,4,7-Triazacyclononane (L) Complex [Mo(3)(NiL)S(4)(H(2)O)(9)](4+).

Comparisons (25 degrees C) are made of substitution reactions, X replacing H(2)O, at the tetrahedral Ni of the heterometallic sulfido cuboidal cluster [Mo(3)NiS(4)(H(2)O)(10)](4+), I = 2.00 M (LiClO(4)). Stopped-flow formation rate constants (k(f)/M(-)(1) s(-)(1)) for six X reagents, including two water soluble air-stable phosphines, 1,3,5-triaza-7-phosphaadamantane PTA (119) and tris(3-sulfonatophenyl)phosphine TPPTS(3)(-) (58), and CO (0.66), Br(-) (14.6), I(-) (32.3), and NCS(-) (44) are reported alongside the previous value for Cl(-) (9.4). A dependence on [H(+)] is observed with PTA, which gives an unreactive form confirmed by NMR as N-protonated PTA (acid dissociation constant K(a) = 0.61 M), but in no other cases with [H(+)] in the range 0.30-2.00 M. The narrow spread of rate constants for all but the CO reaction is consistent with an I(d) dissociative interchange mechanism. In addition NMR studies with H(2)(17)O enriched solvent are too slow for direct determination of the water-exchange rate constant indicating a value <10(3) s(-)(1). Equilibrium constants/M(-)(1) for 1:1 complexing with the different X groups at the Ni are obtained for PTA (2040) and TPPTS(3)(-) (8900) by direct spectrophotometry and from kinetic studies (k(f)/k(b)) for Cl(-) (97), Br(-) (150), NCS(-) (690), and CO (5150). No NCS(-) substitution at the Ni is observed in the case of the heterometallic cube [Mo(3)Ni(L)S(4)(H(2)O)(9)](4+), with tridentate 1,4,7-triazacyclononane(L) coordinated to the Ni. Substitution of NCS(-) for H(2)O, at the Mo's of [Mo(3)NiS(4)(H(2)O)(10)](4+) and [Mo(3)(NiL)S(4)(H(2)O)(9)](4+) are much slower secondary processes, with k(f) = 2.7 x 10(-)(4) M(-)(1) s(-)(1) and 0.94 x 10(-)(4) M(-)(1) s(-)(1) respectively. No substitution of H(2)O by TPPTS(3)(-) or CO is observed over approximately 1h at either metal on [Mo(3)FeS(4)(H(2)O)(10)](4+), on [Mo(4)S(4)(H(2)O)(12)](5+) or [Mo(3)S(4)(H(2)O)(9)](4+).