Synthesis and Spectroscopic Characterization of Novel Heterotermetallic Isopropoxides: X-ray Crystal Structures of ICd{M2(OPri)9} and [{Cd(OPri)3}Ba{M2(OPri)9}]2 (M = Ti, Hf)

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Abstract
Metathesis reactions between CdI2 and KM2(OPri)9 (M = Ti, Hf) in toluene produce monomeric iodo−heterobimetallic isopropoxides ICdM2(OPri)9 (1, M = Ti; 2, M = Hf) which have been characterized by solution (1H, 13C, and 113Cd) and solid state (13C and 113Cd) CP MAS NMR spectroscopy, microanalysis, cryoscopic molecular weight determination, and single crystal X-ray diffraction study. Both 1 and 2 in the solid state represent the first structurally characterized examples of halide heterobimetallic alkoxides based on {Ti2(OPri)9}- and {Hf2(OPri)9}- bioctahedral subunits, respectively. The overall molecular geometry of 1 and 2 can be viewed formally as an interaction of the CdI+ fragment with {M2(OPri)9}- substructures via two terminal and two bridging (μ2-) isopropoxy groups. Reaction of 1 and 2 with equimolar KBa(OPri)3 in toluene afforded novel heterotermetallic isopropoxides [{Cd(OPri)3}Ba{M2(OPri)9}]2 (3, M = Ti; 4, M = Hf). Formation of heterotermetallic frameworks involves an interesting rearrangement of the central metal atoms between the two precursor molecules, which is probably commanded by the tendency of barium to achieve higher coordination numbers. The dimeric forms of 3 and 4 as shown by cryoscopy and 113Cd solution and solid state CP MAS NMR studies are confirmed by crystallography. The X-ray crystal structures of 3 and 4 reveal, as a common feature, a central Ba(μ2-OPri)2Cd(μ2-OPri)2Cd(μ2-OPri)2Ba unit formed by a spirocyclic linking of two LBa(OPri)2 (3, L = Ti2(OPri)9; 4, L = Hf2(OPri)9) units to a four membered, Cd2(OPri)2, ring. Crystal data: for 1, monoclinic, space group P21/m, a = 11.71(2) Å, b = 15.78(3) Å, c = 12.16(2) Å, β = 116.69(14)°, Z = 2; for 2, triclinic, space group P1̄, a = 9.825(2) Å, b = 11.428 Å, c = 20.619 Å, α = 95.619(12)°, β = 99.915(11)°, γ = 111.347(11)°, Z = 2; for 3, monoclinic, space group P21/c, a = 22.68(2) Å, b = 12.603(11) Å, c = 19.00(2) Å, β = 96.83(8)°, Z = 2; for 4, monoclinic, space group P21/c, a = 23.197(5) Å, b = 12.886(3) Å, c = 19.378(4) Å, β = 97.18(3)°, Z = 2.

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