Preparation, Structure, and Properties of the Arsenic-Containing Corner-Shared Double Cube [Mo₆AsS₈(H₂O)₁₈]⁸⁺:  Metal−Metal Bonding and a Classification of Different Cluster Types

Abstract

The trinuclear MoIV 3 incomplete cuboidal cluster [Mo3S4(H2O)9]4+ in 2 M HCl reacts rapidly (green to intense blue-green color change) with AsO2 - or HAsO4 2- in the presence of H3PO2 as reductant to give the new air-sensitive corner-shared double cube [Mo6AsS8(H2O)18]8+. Purification by Dowex 50W-X2 cation-exchange chromatography requires 4 M H(pts) (pts = p-toluenesulfonic acid) for elution, consistent with a high charge. The X-ray structure has been determined for crystals obtained from 4 M H(pts) solution, full formula [Mo6AsS8(H2O)18](pts)8·28H2O. The Mo6AsS8 core structure was confirmed from ICP elemental analysis for Mo, As, and S (6:1:8) and the 8+ charge from the 3:1 stoichiometries with [Co(dipic)2]- and [Fe(H2O)6]3+ as oxidant. Rate constants for the oxidation of [Mo6AsS8(H2O)18]8+ with [Co(dipic)2]- have been determined and indicate strong reduction properties as compared to other heteroatom clusters. The existence of short (bonding) Mo−Mo separations, 2.716 Å average, and long (nonbonding) Mo−As separations at 3.554 A, together with similar features for other heteroatom clusters, has led to a classification of the clusters into different categories. The nine 8+ double cubes, most of which contain a main group heteroatom M, are classified as (Mo3S4 4+)2 M0, with retention of two metal−metal bonded Mo3S4 4+ units. The single cubes, on the other hand, can be classified as Mo3S4 4+M0, with M a transition metal, or Mo3S4 4+M x , with M a main group element (x depends on group involved).

Preparation, Structure, and Reactivity of Heterometallic Sn-Containing Single- and Double-Cube Derivatives of [Mo3Se4(H2O)9]4+ and [W3Se4(H2O)9]4+

“…Important features are the short Mo−Mo distances (mean 2.788 Å), indicative of metal−metal bonding and long Mo−Sn separations (mean 3.870 Å), nonbonding for the single cube; and corresponding Mo−Mo (mean 2.732 Å) bonding and Mo−Sn (mean 3.858 Å) nonbonding separations in the double cube. These features are consistent with the formalism Mo 3 Se 4 4+ Sn 2+ and (Mo 3 Se 4 4+ ) 2 Sn 0 previously referred to . The NCS - ligands are coordinated through the nitrogen atoms, with N and S atoms clearly distinguished by their different X-ray scattering powers, and by N−C and C−S bond lengths.…”

Preparation, Structure, and Reactivity of Heterometallic Sn-Containing Single- and Double-Cube Derivatives of [Mo3Se4(H2O)9]4+ and [W3Se4(H2O)9]4+

“…Important features are the short Mo−Mo distances (mean 2.788 Å), indicative of metal−metal bonding and long Mo−Sn separations (mean 3.870 Å), nonbonding for the single cube; and corresponding Mo−Mo (mean 2.732 Å) bonding and Mo−Sn (mean 3.858 Å) nonbonding separations in the double cube. These features are consistent with the formalism Mo 3 Se 4 4+ Sn 2+ and (Mo 3 Se 4 4+ ) 2 Sn 0 previously referred to . The NCS - ligands are coordinated through the nitrogen atoms, with N and S atoms clearly distinguished by their different X-ray scattering powers, and by N−C and C−S bond lengths.…”

Preparation, Structure, and Reactivity of Ge-Containing Heterometallic Cube Derivatives of [M3E4(H2O)9]4+ (M = Mo, W; E = S, Se)

“…There is no disorder in compound 3 , for which hydrogen atoms were located and refined. This compound is isostructural with the corresponding arsenic-containing double cube 1 Crystallographic Data for [Mo 6 GeS 8 (H 2 O) 18 ](pts) 8 ·28H 2 O ( 1 ), [W 6 GeS 8 (H 2 O) 18 ](pts) 8 ·23H 2 O ( 2 ), and [Mo 6 GeSe 8 (H 2 O) 18 ](pts) 8 ·8H 2 O ( 3 ) 1 2 3 empirical formula C 56 H 148 GeMo 6 O 70 S 16 C 56 H 138 GeW 6 O 65 S 16 C 56 H 108 GeMo 6 O 50 S 8 Se 8 fw 3102.9 3540.3 3118/9 cryst syst triclinic triclinic monoclinic space group P 1̄ P 1̄ P 2 1 / c a , Å 13.5499(10) 13.6001(13) 12.3558(5) b , Å 14.0334(10) 13.9790(14) 34.0069(13) c , Å 18.4296(13) 18.4290(18) 11.9249(5) α, deg 92.984(2) 92.715(2) 90 β, deg 104.680(2) 104.859(2) 92.437(2) γ, deg 118.056(2) 117.882(2) 90 V , Å 3 2930.8(4) 2935.4(5) 5006.1(3) Z 1 1 2 ρ calc , g cm -1 12.6 64.8 41.9 μ, cm -1 12.6 64.8 41.9 T , °C −113 −113 −113 R a 0.0595 0.0816 0.0377 R w b 0.1438 0.2097 0.0762 data, parameters 13214, 876 10174, 790 11466, 666 a Conventional R = ∑|| F o | − | F c ||/∑| F o | for “observed” reflections having F o 2 > 2σ( F o 2 ).…”

Preparation and Properties of Group 13 (Ga, In, Tl) Heterometallic Single and Corner-Shared Double Cube Derivatives of [Mo3S4(H2O)9]4+ and Related Studies

“…Linear dependencies of k obs on [Co III ] gave second-order rate constants k a with I ) 2.00 M (LiCl) and k b with I ) 2.00 M (Lipts), Table 2. As in previous studies 1,2 no dependence of k a or k b on [H + ], range 0.50-2.00 M, was observed (Figure 6). The reactions can accordingly be assigned as outer-sphere electron transfer.…”

“…At 4 °C, 3 mM solutions can be stored for 3 days without full decay, consistent with the high activation energy (79 kJ mol -1 ) for reaction with H + . A possible explanation is that in Hpts solutions the cluster is protected by outer-sphere association with pts - , and formation of a network of H bonds as in crystal structures . No similar protection is observed in HCl solutions.…”

Preparation, Structure, and Reactivity of Heterometallic Sn-Containing Single- and Double-Cube Derivatives of [Mo3Se4(H2O)9]4+ and [W3Se4(H2O)9]4+

“…Important features are the short Mo−Mo distances (mean 2.788 Å), indicative of metal−metal bonding and long Mo−Sn separations (mean 3.870 Å), nonbonding for the single cube; and corresponding Mo−Mo (mean 2.732 Å) bonding and Mo−Sn (mean 3.858 Å) nonbonding separations in the double cube. These features are consistent with the formalism Mo 3 Se 4 4+ Sn 2+ and (Mo 3 Se 4 4+ ) 2 Sn 0 previously referred to . The NCS - ligands are coordinated through the nitrogen atoms, with N and S atoms clearly distinguished by their different X-ray scattering powers, and by N−C and C−S bond lengths.…”

Preparation, Structure, and Reactivity of Ge-Containing Heterometallic Cube Derivatives of [M3E4(H2O)9]4+ (M = Mo, W; E = S, Se)

“…There is no disorder in compound 3 , for which hydrogen atoms were located and refined. This compound is isostructural with the corresponding arsenic-containing double cube 1 Crystallographic Data for [Mo 6 GeS 8 (H 2 O) 18 ](pts) 8 ·28H 2 O ( 1 ), [W 6 GeS 8 (H 2 O) 18 ](pts) 8 ·23H 2 O ( 2 ), and [Mo 6 GeSe 8 (H 2 O) 18 ](pts) 8 ·8H 2 O ( 3 ) 1 2 3 empirical formula C 56 H 148 GeMo 6 O 70 S 16 C 56 H 138 GeW 6 O 65 S 16 C 56 H 108 GeMo 6 O 50 S 8 Se 8 fw 3102.9 3540.3 3118/9 cryst syst triclinic triclinic monoclinic space group P 1̄ P 1̄ P 2 1 / c a , Å 13.5499(10) 13.6001(13) 12.3558(5) b , Å 14.0334(10) 13.9790(14) 34.0069(13) c , Å 18.4296(13) 18.4290(18) 11.9249(5) α, deg 92.984(2) 92.715(2) 90 β, deg 104.680(2) 104.859(2) 92.437(2) γ, deg 118.056(2) 117.882(2) 90 V , Å 3 2930.8(4) 2935.4(5) 5006.1(3) Z 1 1 2 ρ calc , g cm -1 12.6 64.8 41.9 μ, cm -1 12.6 64.8 41.9 T , °C −113 −113 −113 R a 0.0595 0.0816 0.0377 R w b 0.1438 0.2097 0.0762 data, parameters 13214, 876 10174, 790 11466, 666 a Conventional R = ∑|| F o | − | F c ||/∑| F o | for “observed” reflections having F o 2 > 2σ( F o 2 ).…”

Preparation and Properties of Group 13 (Ga, In, Tl) Heterometallic Single and Corner-Shared Double Cube Derivatives of [Mo3S4(H2O)9]4+ and Related Studies

“…Linear dependencies of k obs on [Co III ] gave second-order rate constants k a with I ) 2.00 M (LiCl) and k b with I ) 2.00 M (Lipts), Table 2. As in previous studies 1,2 no dependence of k a or k b on [H + ], range 0.50-2.00 M, was observed (Figure 6). The reactions can accordingly be assigned as outer-sphere electron transfer.…”

“…At 4 °C, 3 mM solutions can be stored for 3 days without full decay, consistent with the high activation energy (79 kJ mol -1 ) for reaction with H + . A possible explanation is that in Hpts solutions the cluster is protected by outer-sphere association with pts - , and formation of a network of H bonds as in crystal structures . No similar protection is observed in HCl solutions.…”

Preparation, Structure, and Reactivity of Heterometallic Sn-Containing Single- and Double-Cube Derivatives of [Mo3Se4(H2O)9]4+ and [W3Se4(H2O)9]4+

“…Important features are the short Mo−Mo distances (mean 2.788 Å), indicative of metal−metal bonding and long Mo−Sn separations (mean 3.870 Å), nonbonding for the single cube; and corresponding Mo−Mo (mean 2.732 Å) bonding and Mo−Sn (mean 3.858 Å) nonbonding separations in the double cube. These features are consistent with the formalism Mo 3 Se 4 4+ Sn 2+ and (Mo 3 Se 4 4+ ) 2 Sn 0 previously referred to . The NCS - ligands are coordinated through the nitrogen atoms, with N and S atoms clearly distinguished by their different X-ray scattering powers, and by N−C and C−S bond lengths.…”

Preparation, Structure, and Reactivity of Ge-Containing Heterometallic Cube Derivatives of [M3E4(H2O)9]4+ (M = Mo, W; E = S, Se)

“…There is no disorder in compound 3 , for which hydrogen atoms were located and refined. This compound is isostructural with the corresponding arsenic-containing double cube 1 Crystallographic Data for [Mo 6 GeS 8 (H 2 O) 18 ](pts) 8 ·28H 2 O ( 1 ), [W 6 GeS 8 (H 2 O) 18 ](pts) 8 ·23H 2 O ( 2 ), and [Mo 6 GeSe 8 (H 2 O) 18 ](pts) 8 ·8H 2 O ( 3 ) 1 2 3 empirical formula C 56 H 148 GeMo 6 O 70 S 16 C 56 H 138 GeW 6 O 65 S 16 C 56 H 108 GeMo 6 O 50 S 8 Se 8 fw 3102.9 3540.3 3118/9 cryst syst triclinic triclinic monoclinic space group P 1̄ P 1̄ P 2 1 / c a , Å 13.5499(10) 13.6001(13) 12.3558(5) b , Å 14.0334(10) 13.9790(14) 34.0069(13) c , Å 18.4296(13) 18.4290(18) 11.9249(5) α, deg 92.984(2) 92.715(2) 90 β, deg 104.680(2) 104.859(2) 92.437(2) γ, deg 118.056(2) 117.882(2) 90 V , Å 3 2930.8(4) 2935.4(5) 5006.1(3) Z 1 1 2 ρ calc , g cm -1 12.6 64.8 41.9 μ, cm -1 12.6 64.8 41.9 T , °C −113 −113 −113 R a 0.0595 0.0816 0.0377 R w b 0.1438 0.2097 0.0762 data, parameters 13214, 876 10174, 790 11466, 666 a Conventional R = ∑|| F o | − | F c ||/∑| F o | for “observed” reflections having F o 2 > 2σ( F o 2 ).…”

Preparation and Properties of Group 13 (Ga, In, Tl) Heterometallic Single and Corner-Shared Double Cube Derivatives of [Mo3S4(H2O)9]4+ and Related Studies

“…Linear dependencies of k obs on [Co III ] gave second-order rate constants k a with I ) 2.00 M (LiCl) and k b with I ) 2.00 M (Lipts), Table 2. As in previous studies 1,2 no dependence of k a or k b on [H + ], range 0.50-2.00 M, was observed (Figure 6). The reactions can accordingly be assigned as outer-sphere electron transfer.…”

“…At 4 °C, 3 mM solutions can be stored for 3 days without full decay, consistent with the high activation energy (79 kJ mol -1 ) for reaction with H + . A possible explanation is that in Hpts solutions the cluster is protected by outer-sphere association with pts - , and formation of a network of H bonds as in crystal structures . No similar protection is observed in HCl solutions.…”