The First Triple-Decker Complex with a Carbenium Center, [CpCo(µ-C3 B2 Me5 )RuC5 Me4 CH2 ]+ : Synthesis, Reactivity, X-Ray Structure, and Bonding.

The first derivative of the methylium cation with the triple-decker substituent, [CpCo(C3 B2 Me5 )RuC5 Me4 CH2 ]PF6 (2PF6 ), was synthesized from the reaction of the triple-decker complex CpCo(C3 B2 Me5 )RuCp* (1) with the salt of the trityl cation [CPh3 ]+ . The X-ray crystal structure of 2PF6 reveals that the methylium carbon is bound to the ruthenium with Ru-C bond length of 2.259 Šand corresponds to the description of its structure as η6 -fulvene-ruthenium. Reactions of 2PF6 with nucleophiles OH- , Ph3 P, Et3 N led to the corresponding derivatives of 1 in high yields. Aromatic amines PhNEt2 and 4-MeC6 H4 NH2 react with 2PF6 to give the electrophilic aromatic substitution products quantitatively. Chemical reduction of 2PF6 with Zn powder in tetrahydrofuran leads to the formation of the bis(triple-decker) derivative (CpCo(C3 B2 Me5 )RuC5 Me4 CH2 )2 (10) with a CH2 CH2 -bridge. The structures of complexes 4, 7-10 were determined by X-ray diffraction. Density functional calculations support the crystallographically determined geometry of 2 and allow rationalization of some characteristics of its structure, spectroscopy, and reactivity.

Fusion of a 1,3-diboraruthenocene to form a slipped mu-hexahydrotetraboranaphthalene triple-decker complex with two axial C--H bonds.

Colliding double deckers: Addition of zinc to a reaction mixture of [{Cp*RuCl}(4)]/pentamethyl-2,3-dihydro-1,3-diborole (C(3)B(2)Me(5)H) in THF leads to three known double- and triple-decker complexes of [C(3)B(2)Me(5)](-), and unexpectedly to the slipped triple-decker (see picture) with two fused diborole rings. The endo C--H bonds of two MeC--H groups donate two additional electrons to achieve the stable 34 VE configuration.

Diboryl and diboranyl porphyrin complexes: synthesis, structural motifs, and redox chemistry: diborenyl porphyrin or diboranyl isophlorin?

The syntheses of diboryl porphyrin complexes [(BX2)2(ttp)] (ttp: dianion of tetra-p-tolylporphyrin) and the B-B single-bond diboranyl complexes [(BX)2(ttp)] (X=F, Cl, Br, I) are given. The former are prepared from the reactions of BX3 (X=F, Cl) with [Li2(ttp)] and the latter from B(2)Cl(4) (X=Cl), the reaction of SbF3 with [(BCl)2(ttp)] (for X=F), and, in the cases of X=Br or I, in a remarkable reductive coupling reaction resulting directly from the reaction of BBr3 or BI3 with [Li2(ttp)]. Density functional theory (DFT) calculations on the thermochemical parameters for the reductive coupling reactions (and those calculated for related dipyrromethene complexes) indicate that a combination of the reducing ability of bromide and iodide ions combined with the constrained environment of the porphyrin ligand contribute to the driving force. The reductive coupling is also observed in the reaction of [(BCl2)2(ttp)] with nBuLi to give [(BnBu)2(ttp)], which was characterised crystallographically. The reaction of [(BCl)2(ttp)] with catechol gives a boron catecholato porphyrin complex, [B2(O(2)C(6)H(4))(ttp)]. Chloride abstraction from [(BCl)2(ttp)] gives the planar dication [B2(ttp)]2+, whereas chemical reduction of [(BCl)2(ttp)] by using magnesium anthracenide gives a neutral complex, [B(2)(ttp)], in which the TTP ligand has been reduced by two electrons to give an unusual example of an isophlorin complex. The cationic and neutral complexes [B2(ttp)]2+ and [B2(ttp)] were characterised through a combination of spectroscopic data that is supported by DFT calculations on the porphine analogues.

A "tetrameric" 3,4-di-p-tolyl-1,2,5-oxadiborole derivative.

In the title compound, 1,1,6a,7,9a,10-hexachloro-2,3,5,6,8,9,11,12-octa-p-tolyl-1,6a,9a,12a-tetraborata-3a,4a,7,10-tetrabora-4a(1),6b,9b,12b-tetraoxonia-4-oxatetracyclopenta[1,2-a:2,1,5-de:1,2-g:1,2-i]naphthalene dichloromethane pentasolvate, C(64)H(56)B(8)Cl(6)O(5).5CH(2)Cl(2), two condensed oxadiborole rings are attached to two further oxadiborole rings in a type of donor-acceptor bonding, thus forming a ten-membered alternating (B-O)(5) naphthalene-like arrangement as the central building block.

Coordinated B2 Bridges in Porphyrins-Unexpected Formation of a Diborane(4)- from a Diborylporphyrin.

Fitting B2 bridges in porphyrins can be achieved by reaction of dilithiated porphyrins with B2 Cl4 as well as by reductive elimination from diborylporphyrins. Coordination takes place under rectangular distortion of the porphyrin framework.

Blue Tetrakis(diisopropylamino)-cyclo-tetraborane and Yellow Tetrakis(tetramethylpiperidino)tetrabora-tetrahedrane.

The colored boranes closo-1 and cyclo-2 are obtained upon dehalogenation of sterically hindered diaminodichlorodiborane(4) 3. The TMP groups of 1 cause the formation of a tetrahedrane, whereas in 2 the diisopropylamino substituents stabilize the bent four-membered ring. TMP=2,2,6,6-tetramethylpiperidino.

A Boron-Bridged Tetrathiaporphyrinogen.

Lewis acid and Lewis base centers are simultaneously present in the boron-bridged thiophene-containing porphyrinogen 1 that has been synthesized in high yield. Its crystal structure reveals a nonplanar macrocycle; this and the colorless aspect suggest the absence of a delocalized π-electron system. R = NiPr2 .

Apically Linked Small Metallacarborane Clusters. Directed Synthesis and Structural Characterization of 7,7'-[CpCo(2,3-Et(2)C(2)B(4)H(3)](2) and [CpCo(2,3-Et(2)C(2)B(4)H(3)-7)](2)X Complexes (X = MeCH, HC=CH, C&tbd1;C)(,)(1).

A series of novel bis(cobaltacarboranyl) (CoC(2)B(4))(2)X dicluster complexes whose B(7) (apex) atoms are linked by organic moieties involving sp-, sp(2)-, or sp(3)-hybridized carbon, or by a direct B(7)-B(7') bond, has been prepared by extension of the recently described "recapitation" method (Curtis, M. A.; et al. Inorg. Chem. 1996, 35, 6703) that entails treatment of 6-vertex nido-CoC(2)B(3) dianions with monoboron reagents. Reactions of Li(2)[nido-CpCo(Et(2)C(2)B(3)H(3))] in toluene with MeCH(BCl(2))(2) and with cis-(BCl(2))C(2)H(2) gave, respectively, [CpCo(2,3-Et(2)C(2)B(4)H(3)-7-)](2)MeCH (5) and cis-[CpCo(2,3-Et(2)C(2)B(4)H(3)-7-)](2)C(2)H(2) (6a) following chromatographic separation. Ultraviolet irradiation of 6a induced partial conversion to the trans isomer 6b, affording a 46:54 trans/cis equilibrium mixture in 84 h. Reactions of the same cobaltacarborane dianion with bis(catecholboryl)acetylene and with bis(catecholdiboryl) gave [CpCo(2,3-Et(2)C(2)B(4)H(3)-7-)](2)C(2) (7) and [CpCo(2,3-Et(2)C(2)B(4)H(3)-7-)](2) (8), respectively. The new complexes were isolated as air-stable, crystalline orange solids and were characterized from their (1)H, (11)B, and (13)C NMR, IR, UV-visible, and mass spectra, supported by X-ray crystallographic studies of 5, 6a, 7, and 8. Crystal data for 5: space group P2(1)ca (orthorhombic); a = 14.220(10) Å, b = 15.690(10) Å, c = 16.860(10) Å, Z = 4; R = 0.041 for 7485 independent reflections. Crystal data for 6a: space group C2/c (monoclinic); a = 12.849(6) Å, b = 11.435(6) Å, c = 25.619(13) Å, beta = 96.230(10) degrees; Z = 4; R = 0.036 for 5440 independent reflections. Crystal data for 7: space group P2(1)/n (monoclinic); a = 17.298(12) Å, b = 13.932(10) Å, c = 30.82(2) Å, beta = 96.34(5) degrees; Z = 8; R = 0.070 for 9632 independent reflections. Crystal data for 8: space group P&onemacr; (triclinic); a = 9.150(10) Å, b = 10.270(10) Å, c = 10.340(10) Å, alpha = 84.52(5) degrees, beta = 78.05(5) degrees, gamma = 68.6(5) degrees; Z = 1; R = 0.056 for 5154 independent reflections.

Electron-poor 2,3-Dihydro-1,3-Diborolyl Complexes of Iron and Ruthenium: Synthesis, Reactivity, and Crystal and Electronic Structures of an Iron Sandwich Complex.

The addition product of sodium hydride and the 2,3-dihydro-1,3-diborole (CiPr)2 (BEt)2 CHMe (3c) reacted with [{(C5 Me5 )FeCl}x ] to produce the green sandwich complex [(C5 Me5 )Fe{n5 -(CiPr)2 (BEt)2 CMe}] (2 c), which formally contains 16 valence electrons (VE). Complex 2c has unexpected structural properties in the solid state: the 1,3-diborolyl ring is extremely folded (41°), and the Fe-C2 distance is short (1.90 Å). Analogously, violet Ru complexes 4a,c,d were obtained from 3a,c, NaH or tBuLi, and [{(C5 Me5 )RuCl}4 ]. With the less bulky heterocycles 3 b,e the new 30 VE triple-decker complexes [(C5 Me5 )Ru{µ,n5 -(CR1 )2 (BR2 )2 CMe}RuH(C5 Me5 )] (5b,e) were formed, which contain a Ru-H bond. Cyclic voltammetric studies revealed the existence of stable anions 2c- and 4d- formed by reversible one-electron reduction at -1.26 and -1.40 V, respectively (vs. SCE). The red-brown anions were further characterized by ESR spectroscopy following stepwise reduction of the neutral species with potassium in THF. Addition of CO to 4a and 4d led to formation of the monocarbonyl complexes [(C5 Me5 )Ru(CO){n5 -(CR1 )2 -(BR2 )2 CMe}] (6a,d), and 6d was characterized by X-ray structure analysis. The heterocycle in 6d is less folded (19°) than in 2 c. Its CO ligand causes a 28.5° tilt of the cyclic ligands. Reaction of CO with 2 c yielded a red product of unknown structure. The electronic structure of 2 was studied by EH-MO theory, which revealed a unique bonding in the sandwich. The s̀ electron density of the B-C bonds participates in the bonding to the iron atom; this demonstrates that the number of bonding electrons is the same as in ferrocene. Thus, the complexes 2 actually have 18 VE.