Mixed Metal Frameworks

There are still only a few examples of mixed metal-transition metal clusters containing boron atoms. The first to be reported was Cp2Co2Fe(CO)4B3H3 (92). This cluster results from the photolysis of 2-CpCoB4Hg [a basally substituted isolobal analog of pentaborane(9)] with Fe(CO)5. NMR spectroscopic data are consistent with the proposed structure shown in Fig. 17. 

The auraferraboranes and auraruthenaboranes of types M4(CO),2 Aux(PR3)xBH3 x (M = Fe or Ru jc = 1, 2, or 3) may be included here for completeness, but a full discussion is more appropriate in Section IV. As described in detail above, each is formed from the interaction of the anion [HM4(CO)i2BH] with R3PAuC1 or in the case of M = Fe and jc = 3, the reaction of 16 with [(Ph3PAu)30][BF4].  

The reaction of the mono-, di-, or trianion of 15 with [Rh(CO)2Cl]2 is the means of preparing the first example of a c/aso-metalloborane cluster, namely, [Fe4Rh2(CO)i6B] . Monitoring the reaction by 11B-NMR spectroscopy shows that the pathway proceeds via the formation of cis-[Fe4Rh2(CO)16B]- ( B NMR 8 +205, = 23.3 Hz) foUowed by iso- 

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JH Robson, BC Ream, H Soo. Monoalkylene Glycol Production Using Mixed Metal Framework Compositions. US Patent 4,967,018, October 30, 1990. 

A recent discovery shows that the lone pair electrons of the chlorine atom can also facilitate the formation of NCS frameworks. A novel family of salt-containing, mixed-metal sihcates (CU-14), Ba6Mii4Sii2034Cl3 and Ba6Fe5Sin034Cl3, was synthesized via the BaCl2 salt-inclusion reaction [6 a]. These compounds crystallize in the NCS space group Pmcli (No. 26), adopting one of the 10 polar, non-... 

Over the last few years, we have made a number of novel discoveries using reactive salt fluxes in the crystal growth experiment of mixed-metal oxides. The most important outcome that these salt-inclusion solids have demonstrated is the propensity for structure- directing effects of the employed salt. These hybrid solids have revealed fascinating solid-state structures ranging from nanoclusters to three-dimensional open frameworks of current interest. Solids featuring mag-... 

HjOss(CO)i0, whose structure is shown in 3, has been extensively used by Stone and co-workers (67, 68) in synthesizing mixed-metal clusters that contain the Os3 framework. Several of these reactions, including the adaptation with Co4(CO)u of Johnson et al. (23), are summarized in Scheme 1. X-Ray structural analyses demonstrated that Os3PtH2(CO)10(PCy3) (67) and OssCoHs(CO)12 (25) have tetrahedral structures. 

A common feature of metal clusters is their stereochemical nonrigidity, in which carbonyl and hydride ligands exchange their coordination sites. Mixed-metal clusters are ideally suited for studies of the fluxional processes in clusters because of the low symmetry inherent in their metal framework. In such clusters, the majority of the ligands are in chemically nonequivalent positions and should thus be distinguishable by NMR... 

Organically templated 3d-4f mixed metal sulfates of the formula [C2N2H10][La2M(H2O)2(SO4)6] (M = Co, Ni), have been recently synthesized by Clearfield et alP The three-dimensional anionic framework is formed by the bridging of La(lli) and divalent transition metal ions by the sulfate anions. 8-Membered ring tunnels run along the c-axis, which are occupied by the protonated organic cations. 

A new class of mixed open-framework materials consisting of both the phosphate and the oxalate units has been synthesized in the presence of structuredirecting agents [51-54], The solids thus prepared usually contain sheets made on metal phosphates, which are pillared by the oxalate units. In addition to the interesting architectures exhibited by them, the phosphate-oxalates also show remarkable adsorptive and other properties. In the case of the transition metal phosphate-oxalates, interesting magnetic properties have also been observed. We will discuss some select cases of the phosphate-oxalates of iron in the following. 

Answer. l,5- Re(CO)3 2Pt3(PlBu3)3 has a eve = 62 (2Re + 6 CO + 3 Pt + 3 PR3 = 14 + 12 + 30 + 6 = 62 whereas a normal trigonal bipyramid exhibits 72. Even taking into account the two to four lower eve count of many late metal clusters, this mixed metal cluster is distinctly electronically unsaturated. Addition of six H atoms to the framework adds six electrons for a eve count of 68, four less that the normal count but acceptable for a Pt cluster. This hydrogenation reaction is formal reduction of an electronically unsaturated cluster by the addition of three moles of H2. 

We may note, finally, that nickel and platinum form various mixed clusters, some very large, as in the case of the [Ni3gPt( (CO)4gHmedium size cluster, [Nic,Pt3(CO)2iH]3 , has been structurally characterized. The metal framework is as shown in (16-XXV). 

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