Tris borate, reaction with iron

It is noteworthy that carbene function may be manifested in the derivatives of tris(imidazol-l-yl)borate 44 (96AGE310). Its reaction first with n-butyllithium, then with iron(II) chloride, and finally with sodium tetraphenylborate gives the iron(III) carbene derivative 45. 

The tris(mercaptophenylimidazolyl)borate iron and cobalt complexes [(Tmph)2M] (M = Fe, Co) have been synthesized by reaction of (Tmph)Tl with MI2.156 Structural characterization by X-ray diffraction demonstrates that the potentially tridentate Tmph binds through only two sulfur donors in these sandwich complexes and that the tetrahedral metal centers supplement the bonding by interactions with two BH groups. Comparison of the structures of [(Tmph)2M] with those of related tris(pyrazolyl)borate counterparts indicates that the Tm favors lower primary coordination number in divalent metal complexes. 

The reactions of cyclopropenium ions with nucleophiles have led to several interesting observations. In the carbohydrate area, diphenylcyclopropenium perchlorate has been employed in an improved oligosaccharide synthesis based on the glycosylation of sugar diphenylcyclopropenyl ethers. With certain cyclopenta-dienyl-co-ordinated metal carbonyls (Mo, W), tri-t-butylcyclopropenium tetrafluoro-borate affords products derived from electrophilic attack of the cyclopropenium ion on the co-ordinated cyclopentadienyl anion, while for the analogous co-ordinated iron species attack at a carbonyl ligand occurs. With the cyclopentadienyl or indenyl anion, cyclopropenium ion (225) yields the tripolar mesomeric compounds (227), and... 

The iron carbonyl complexes are most easily obtained via reaction of a suitable salt of [Fe(CO)4] and an appropriate dihalo-group 13 element complex X2ER, but reaction of a neutral iron carbonyl compound with (RE) may also be used. The syntheses of the known Fe(CO)4 compounds arc presented in Equations (11)-(14). The R group attached to E can also be a donor ligand such as tris(pyrazolyl)borate (Equation (14)). ... 

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