Syntheses and Structural Characterizations of Ferra- and Cobaltacarborane Complexes Derived from the arachno-6-R-5,6,7-C3B7H12 [R- = NCCH2-, MeOC(O)CH2-, MeC(O)CH2-] Tricarbaborane1

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Abstract
A series of ferratricarbaboranyl complexes, closo-1-(η-C5H5)FeRC3B7H9 [R- = H-, NCCH2-, MeOC(O)CH2-], have been generated by the reactions of (η-C5H5)Fe(CO)2I with tricarbaboranyl arachno-6-R-5,6,7-C3B7H11- anions. Structural characterizations of closo-1-(η-C5H5)Fe-2-(NCCH2)-2,3,4-C3B7H9, 1c, closo-1-(η-C5H5)Fe-3-(NCCH2)-2,3,4-C3B7H9, 1d, closo-1-(η-C5H5)Fe-2-(MeCH3OC(O)CH2)-2,3,4-C3B7H9, 2b, and closo-1-(η-C5H5)Fe-3-(MeOC(O)CH2)-2,3,4-C3B7H9, 2c, show the ferratricarbaboranyl cages in these complexes have closo-octadecahedral structures containing carbon atoms in the two four-coordinate positions closest to the iron. Other isolated products arise from further reactions of the side chain groups, with crystallographically characterized products including the multicage complex (μ2,12‘-CH2)[closo-1-(η-C5H5)Fe-2,3,4-C3B7H9][arachno-5‘-(NCCH2)-5‘,7‘,9‘,12‘,11‘-C4NB7H10], 1e, and the first polyboron metallapentacarbaborane nido-2-(η-C5H5)Fe-7-Me-7,8,9,10,12-C5B6H10, 3c. Cobaltatricarbaboranes of general formula 1-(η-C5H5)Co(NCCH2)C3B7H9, 4b−d, along with the unique multimetal cluster commo-Co-[closo-1-Co-8,9-((η-C5H5)Co)2-2,3,5-C3B7H10][closo-2‘-Co-3‘-(NCCH2CH2)-1‘,10‘-C2B7H8], 4e, were isolated from the reaction of cobalt chloride with a mixture of the arachno-6-NCCH2-5,6,7-C3B7H11- and cyclopentadienyl anions.