Synthetic and NMR Studies of Neutral and Cationic Dinuclear Fulvalene Zirconium Complexes Containing the “Zr₂(μ-CN^tBu)” Unit

Abstract

Methylation of the previously described isocyanide-bridged complex [{Zr(η 5 -C 5 H 5 )Cl} 2 (µ-CN t Bu)(µ-η 5 -C 5 H 4 -η 5 -C 5 H 4 )] with 2 equiv of MgClMe in toluene at 80 °C afforded the dinuclear dimethyl complex [{Zr(η 5 -C 5 H 5 )(CH 3 )} 2 (µ-CN t Bu)(µ-η 5 -C 5 H 4 -η 5 -C 5 H 4 )], 1. The same reaction with 1 or 2 equiv of MgClMe at room temperature gave a mixture of compounds containing the dimethyl derivative 1 and two isomers of the monomethyl derivative [{Zr(η3, isolated by reaction of the zirconium(III) derivative [{Zr(η 5 -1,3-t Bu 2 C 5 H 3 )(µ-Cl)} 2 (µ-η 5 -C 5 H 4 -η 5 -C 5 H 4 )] with 1 equiv of CN t Bu in toluene, gave a mixture of unidentified compounds. Treatment of the dimethyl complex [{Zr(η 5 -C 5 H 5 )(CH 3 )} 2 (µ-CN t Bu)(µ-η 5 -C 5 H 4 -η 5 -C 5 H 4 )], 1, with 1 equiv of the Lewis acid B(C 6 F 5 ) 3 in dichloromethane at -78 °C affords the new yellow crystalline zirconium cationic derivative [{Zr(η 5 -C 5 H 5 )} 2 (µ-CH 3 )(µ-CN t Bu)(µ-η 5 -C 5 H 4 -η 5 -C 5 H 4 )]-[BMe(C 6 F 5 ) 3 ], 4. Hydrolysis of the µ-methyl compound 4 led to the µ-hydroxo cationic derivative [{Zr(η 5 -C 5 H 5 )} 2 (µ-OH)(µ-CN t Bu)(µ-η 5 -C 5 H 4 -η 5 -C 5 H 4 )][BMe(C 6 F 5 ) 3 ], 5. Compound 4 reacts with an excess of isocyanides CNR in dichloromethane at -78 °C to give the cationic species [{Zr(η 5 -C 5 H 5 )} 2 (CH 3 )(CNR)(µ-CNR)(µ-η 5 -C 5 H 4 -η 5 -C 5 H 4 )][BMe(C 6 F 5 ) 3 ] (R ) t Bu, 6; 2,6-Me 2 C 6 H 3 , 7). All of the reported compounds were characterized by the usual analytical and NMR spectroscopic methods, which are discussed.

High-Vacuum Pyrolysis of Zr(2,3,7,8,12,13,17,18-Octaethylporphyrin)(PhC⋮CPh) as a Route to Novel Zr Species: X-ray Structure of a Hetero-Triply Bridged Species, [(OEP)Zr(μ-Cl)]2(μ-O)

“…Indeed, a number of oxo- or hydroxo-bridged Zr(por) and Hf(por) species have been generated via, usually unintended, hydrolysis of organometallic derivatives . Hydrolysis of methylene and methyl bridging units has been observed for Zr(IV) derivatives in other coordination environments as well . The oxo-bridged dimer 3 is stable in air in the crystalline form, but its solutions undergo a change of color, indicative of further hydrolysis, ultimately yielding a mixture of [Zr(OEP)(μ-OH)] 2 (μ-O) and [Zr(OEP)(μ-O)] 2 as the major products.…”

Mono- and Dinuclear Cyclopentadienylsiloxo Titanium Complexes: Synthesis, Reactivity, and Catalytic Polymerization Applications

“…54 The substitution of the benzyl by a halide bridge occurring in halogenated solvents is clearly favored by the π-donating ability of this substituent, which increases the electron density, reducing their positive charge. [54][55][56] Cationic dinuclear group 4 complexes with halide bridges have also been formed by rearrangement of mononuclear cationic derivatives in halogenated solvents. 53,57,58 The dinuclear nature of compound 1c could be helpful to synthesize dinuclear dicationic derivatives by abstraction of one benzyl substituent from each titanium atom.…”

A Trimetallic Fulvalene‐Bridged Dizirconocene–Gallium Complex

“…[11] The Ga(1)-Zr (2) The diamagnetic nature of 1 is supported by the fact that this compound is EPR-inactive. [19] Other 1 H NMR signals for bridging zirconium hydrides range from d = À5.32 to 0.95 ppm, [20][21][22][23] whereas terminal zirconium hydride 1 H NMR signals may range from d = 3.03 to 7.25 ppm. This value compares well with the value of d = À4.67 ppm reported for the bridging hydride ligand in [(C 10 H 8 )(CpZr) 2 (m-Cl)(m-H)(CH 2 CCSiMe 3 )]-[BMe(C 6 F 5 ) 3 ].…”

“…[19] Other 1 H NMR signals for bridging zirconium hydrides range from d = À5.32 to 0.95 ppm, [20][21][22][23] whereas terminal zirconium hydride 1 H NMR signals may range from d = 3.03 to 7.25 ppm. [19,26] We did not observe a Ga À H IR stretch in the expected region (1800-2100 cm À ). The characteristically broad Zr À H IR stretch (ñ = 1150-1500 cm À1 ) was obscured in the spectrum of 1.…”