ABSTRACT
The pnictogen-centered nucleophiles LiE(SiMe3)2 (E = N, P, or As) substitute a cyclopentadienide ligand of chromocene (Cp2Cr), with elimination of lithium cyclopentadienide, to give the series of pnictogen-bridged compounds [(µ:η(2):η(5)-Cp)Cr{µ-N(SiMe3)2}2Li] (1) and [(η(5)-Cp)Cr{µ-E(SiMe3)2}]2, with E = P (2) or E = As (3). Whereas 1 is a heterobimetallic coordination polymer, 2 and 3 are homometallic dimers, with the differences being due to a structure-directing influence of the hard or soft character of the bridging group 15 atoms. For compound 1, the experimental magnetic susceptibility data were accurately reproduced by a single-ion model based on high-spin chromium(II) (S = 2), which gave a g-value of 1.93 and an axial zero-field splitting parameter of D = -1.83 cm(-1). Determinations of phosphorus- and arsenic-mediated magnetic exchange coupling constants, J, are rare: in the dimers 2 and 3, variable-temperature magnetic susceptibility measurements identified strong antiferromagnetic exchange between the chromium(II) centers, which was modeled using the spin Hamiltonian H = -2J(S(CrA)·S(CrB)), and produced large coupling constants of J = -166 cm(-1) for 2 and -77.5 cm(-1) for 3.
ABSTRACT
Manganocene reacts with LiE(SiMe(3))(2) (E = P or As) to give [(η(5)-Cp)Mn{µ-E(SiMe(3))(2)}](2), where E = P (1) or As (2). The temperature dependence of the magnetic susceptibility in 1 and 2 is due to antiferromagnetic exchange and to spin-crossover (SCO). Compound 2 shows two-step SCO with hysteresis, involving high-spin (S = 5/2) and intermediate-spin S = (3/2) Mn(II).
ABSTRACT
Slow diffusion reactions of the pentaphosphaferrocene [Cp*Fe(η(5)-P(5))] (Cp*=η(5)-C(5)Me(5) (1)) with CuX (X=Cl, Br, I) in different stoichiometric ratios and solvent mixtures result in the formation of one- and two-dimensional polymeric compounds 2-6 with molecular formula [{Cu(µ-X)}{Cp*Fe(µ(3),η(5):η(1):η(1)-P(5))}](n) (X=Cl (2a), I (2'c)), [{Cu(µ-I)}{Cp*Fe(µ(3),η(5):η(1):η(1)-P(5))}](n) (3), [{CuX}{Cp*Fe(µ(4),η(5):η(1):η(1):η(1)-P(5))}](n) (X=Cl (4a), Br (4b), I (4c), Br (4'b), I (4'c)), [{Cu(3)(µ-I)(2)(µ(3)-I)}{Cp*Fe(µ(5),η(5):η(1):η(1):η(1):η(1)-P(5))}](n) (5) and [{Cu(4)(µ-X)(4)(CH(3)CN)}{Cp*Fe(µ(7),η(5):η(2):η(1):η(1):η(1):η(1):η(1)-P(5))}](n) (X=Cl (6a), Br (6b)), respectively. The polymeric compounds have been characterised by single-crystal X-ray diffraction analyses and, for selected examples, by magic angle spinning (MAS) NMR spectroscopy. The solid-state structures demonstrate the versatile coordination modes of the cyclo-P(5) ligand of 1, extending from two to five coordinating phosphorus atoms in either σ or σ-and-π fashion. In compounds 2a, 2'c and 3, two phosphorus atoms of 1 coordinate to copper atoms in a 1,2 coordination mode (2a, 2'c) and an unprecedented 1,3 coordination mode (3) to form one-dimensional polymers. Compounds 4a-c, 4'b, 4'c and 5 represent two-dimensional coordination polymers. In compounds 4, three phosphorus atoms coordinate to copper atoms in a 1,2,4 coordination mode, whereas in 5 the cyclo-P(5) ligand binds in an unprecedented 1,2,3,4 coordination mode. The crystal structures of 6a,b display a tilted tube, in which all P atoms of the cyclo-P(5) ligand are coordinated to copper atoms in σ- and π-bonding modes.
ABSTRACT
The one-pot reactions of the tin(II) halides SnX(2) (X = F, Cl, Br, I) with lithium hexamethyldisilazide, [Li(hmds)], and benzotriazole, (bta)H, produce contrasting outcomes. Tin(II) fluoride does not react with [Li(hmds)] and (bta)H, the outcome being the formation of insoluble [Li(bta)](∞). Tin(II) chloride and tin(II) bromide react with [Li(hmds)] and (bta)H in toluene to produce the hexadecametallic tin(II)-lithium cages [(hmds)(8)Sn(8)(bta)(12)Li(8)X(4)]·(n toluene) [X = Cl, 3·(8 toluene); X = Br, 4·(3 toluene)]. The reaction of tin(II) iodide with [Li(hmds)] and (bta)H in thf solvent produces the ion-separated species [{(thf)(2)Li(bta)}(3){Li(thf)}](2)[SnI(4)]·(thf), [5](2)[SnI(4)]·(thf), the structure of which contains a cyclic trimeric unit of lithium benzotriazolate and a rare example of the tetraiodostannate(II) dianion.
