THE CRYSTAL AND MOLECULAR STRUCTURES OF TWO DERIVATIVES OF WERNER'S HEXOL CLUSTER CATION: [Co{(OH)₂Co(NH₃)₄}₃](NO₃)₅ (OH) · 4H₂O(I) AND [Co{(OH)₂Co(NH₃)₄}₃](NO₃)₆ · 2H₂O(II)

Abstract

Crystals of compound (I) and (II) are black in reflected light and brown-black in transmitted light. The 'H-nmr of the cations of (I), recorded in D6-DMSO, show peaks, relative to the 'H of D6-DMSO, at + 0.46 ppm(re1. int. = 3); +0.85 ppm(re1. int. = 1.2); + 1.80 ppm (rel. int. = 3); and -4.18 ppm(re1. int.=l). The magnetic susceptibility of (I) is C', (293.18 K ) = 588.45 x c.g.s. units, which corresponds to a &*=0.295 B.M. per Co ion; however, the small shifts and sharp 'H-nmr lines in the DMSO spectrum preclude the presence of paramagnetic clusters. Cyclic voltametry of the cation present in (I) shows highly distorted, irreversible, oxidation and reduction waves which indicate the lack of stability of any oxidized or reduced form -a fact which accords with the sharp lines of the N M R spectra; e.g., no stable paramagnetic species are present in (I). Compound ( l ) , M.W.=941.24, crystallizes in P21/n (No. 14), with cell constants a= 11.789(2), 6 = 13.855(2), c = 21.534(3) A, p = 91.94(1)"; V = 3515.44 A3, d (meas; z= 4) = 1.778gm-~m-~. A total of 4705 data were collected in the range 4" 5 2 8 5 50". They were corrected for absorption (p = 19.562cm-'; rel. trans. coeK range=0.8642 to 0.9997); of these, 2623 were unique and had I > 340. The structure was solved by direct methods, none of the hydrogens of the amine ligands were found experimentally at sensible positions; thus, they were left out. Refinement of the heavy atoms (anisotropic) ied to final residuals of R(F)=O.O637 and 0.0771. Compound (10, M.W.=950.20, crystallizes in space group P1 (bar; No. 2), with cell constants a= 12.858(3 , b = 12.475(2), c = 12.1 14(2)A, a=96.63(1), p=91.94(1) and y = in the range 4" 5 2 8 5 50". They were corrected for absorption (p=21.301cn-'; rel. trans. coeff. range = 0.7372 to 0.9998); of these, 4456 were unique and had I 2 340. The structure was 61.71(2)"; V = 1615.68 A ' , d(meas; z=2)= 1.953 g m -~m -~. A total of 5657 data were collected *In Memoriam Alfred Werner: On the 109th Anniversary of the Presentation of his $Participant in the Undergraduate Special Studies Program. Habilitationschnft, October, 1891. 185 Downloaded by [The University of Manchester Library] at 08:05 14 October 2014 186 I. BERNAL et al. solved by direct methods, the majority of the hydrogens of the amine ligands were found experimentally at sensible positions, the rest were calculated at idealized positions (N-H = 0.95A). The hydrogens of the OH ligands were located experimentally in a final difference Fourier map. Refinement of the heavy atoms (anisotropic) with fixed hydrogens (B= 5.00 8') led to final residuals of R(F) = 0.0348 and 0.0440. Precisely as visualized by Werner, the hexol cations consist of a central Co(II1) cation surrounded by three [Co(NH&(OH),] ' + ligands. In (I), the 0-Col -0 angles are acute (av. value = 82.97"), as expected from the electrostatic repulsion of the Co(II1) central cation and the monopositive ligands surrounding it. Consequently, the Co. . . .Co distances are long (2.896, 2.888 and 2.889 A; on average, 2.891 ...

Stable Heterometallic Cluster Ions based on Werner's Hexol

“…[13,14] We sought to use the acid-lability of carbonate ligands as ar oute to control condensation reactions,a nd we demonstrate this strategy by extending the hexol scaffold to incorporate other metal ions (Scheme 1). Integration allowed for the assignment of the downfield signals to protons on the two types of ammine ligands (cis and trans to the hydroxide bridges) and the upfield signal was assigned to the bridging hydroxide protons.T he spectrum obtained for CoAl had many similarities to what is observed for the all-cobalt hexol cluster, [17] showing that they adopt asimilar structure in solution. To produce the cluster containing aluminum, Al[(m-OH) 2 Co(NH 3 ) 4 ] 3 (NO 3 ) 6 (CoAl), an aqueous solution of Al(NO 3 ) 3 was added dropwise to an Scheme 1.…”

“…[17,18] At the center is as ixcoordinate Al 3+ ion, bound with bridging hydroxide ligands that connect it to the outer [Co(NH 3 ) 4 ] 3+ units.T he -NH 3 ligands are split into two chemical environments:either cis to bridging hydroxide ligands or trans to the hydroxide ligands, which can be distinguished in solution (see below). [17,18] At the center is as ixcoordinate Al 3+ ion, bound with bridging hydroxide ligands that connect it to the outer [Co(NH 3 ) 4 ] 3+ units.T he -NH 3 ligands are split into two chemical environments:either cis to bridging hydroxide ligands or trans to the hydroxide ligands, which can be distinguished in solution (see below).…”

“…Using am etal nitrate salt to effect the dissociation of the carbonato ligand could also make this approach applicable to the incorporation of other metal ions,given the acidic nature of most metal nitrate salts.A lthough only Group 13 metal ions were tested here,i ti st hought that this approach could apply to any metal acidic enough to affect the dissociation of the carbonato ligand.Thed ata from single-crystal XRD shows that the aluminum analog adopts as imilar structure as the original hexol cluster that contained only cobalt. [17,18] At the center is as ixcoordinate Al 3+ ion, bound with bridging hydroxide ligands that connect it to the outer [Co(NH 3 ) 4 ] 3+ units.T he -NH 3 ligands are split into two chemical environments:either cis to bridging hydroxide ligands or trans to the hydroxide ligands, which can be distinguished in solution (see below). The overall charge on the cluster is balanced with six outer-sphere nitrate ions (Figure 1).One advantage of preparing clusters with diamagnetic Co III and Al III ions is the use of 1 H-NMR and DOSY to understand their solution behavior.T he spectrum obtained for the hexol-type clusters was surprisingly simple,w hich indicated that apure species with high symmetry was present in solution.…”

“…Thet wo downfield resonances,a t 3.68 ppm and 3.15 ppm, both integrated to 18 protons,a nd the upfield resonance at 1.09 ppm represented 6p rotons. Integration allowed for the assignment of the downfield signals to protons on the two types of ammine ligands (cis and trans to the hydroxide bridges) and the upfield signal was assigned to the bridging hydroxide protons.T he spectrum obtained for CoAl had many similarities to what is observed for the all-cobalt hexol cluster, [17] showing that they adopt asimilar structure in solution. Surprisingly,the same spectrum could be collected in D 2 Ow ith similar integration ratios to that in [D 6 ]DMSO and confirmed the stability of the cluster at ca.…”

“…Thed ata from single-crystal XRD shows that the aluminum analog adopts as imilar structure as the original hexol cluster that contained only cobalt. [17,18] At the center is as ixcoordinate Al 3+ ion, bound with bridging hydroxide ligands that connect it to the outer [Co(NH 3 ) 4 ] 3+ units.T he -NH 3 ligands are split into two chemical environments:either cis to bridging hydroxide ligands or trans to the hydroxide ligands, which can be distinguished in solution (see below). The overall charge on the cluster is balanced with six outer-sphere nitrate ions (Figure 1).…”