Irida-, rhoda-, nickela-, and cuprapentaboranes derived from the arachno-[B4H9]- ion. Crystal structure of [Ir(.eta.4-B4H9)(CO){P(CH3)2C6H5}2], an analog of arachno-B5H11 and [Ir(.eta.4-C4H6)(CO){P(CH3)2C6H5}2]+

Structure and decomposition of [HFe(CO)4(B2H5)], a revised behavior of an old uncharacterized complex

“…2). In fact, the isomer D can be viewed as a result of a weak interaction between B 2 H 6 and [Fe(CO) 4 …”

“…On the other hand, since its discovery by Poliakoff and Turner [21] more than 30 years ago, [Fe(CO) 4 ] and its spin multiplicity has been the continuing subject of numerous studies [22e36] (The metal carbonyl is denoted in our paper by 4 to explicitly denote the number of CO groups, cf. 1 4 ¼ Fe(CO) 4 singlet and 3 4 ¼ Fe(CO) 4 triplet).…”

“…1 4 ¼ Fe(CO) 4 singlet and 3 4 ¼ Fe(CO) 4 triplet). Although theory early showed that the C 2v triplet ground state 3 4 ( 3 B 2 ) is energetically slightly favoured over the singlet [23e26], the multiplicity behavior of Fe(CO) 4 in different reaction environments is still a subject of controversy. It was shown that 3 4 could be converted to 1 4$L (L ¼ Xe, CH 4 ) by the photolysis of [Fe (CO) 5 ] in low temperature matrixes according to the reaction 3 4 þ L / 1 4 L, the reverse pathway could be brought about with low activation energies [27e30].…”

“…Nevertheless this suggestion did not receive complete agreement [31] since numerous studies suggested that the interaction of 1 4 with the solvent (benzene, cyclohexane, heptanes) stabilizes the derived complex to be lower than 3 4, with no evidence for the uncomplexed singlet state 1 4 [23e35]. In gas phase a singlet pathway is expected including the formation of the intermediate [Fe (CO) 4 ] via dissociation of an excited singlet state [Fe(CO) 5 ] yielding the lowest 1 4 ( 1 A 1 ) [36]. The same result has been noticed by ultrafast electron diffraction spectroscopy showing clearly that the elimination of CO from [Fe(CO) 5 ] leads to the major transient 1 4 ( 1 A 1 state) [37].…”

“…Relative B3PW91/LANL2TZ(f)/6-311þG** energies DE in kcal/mol of all minima for HM(CO)4 B 2 H 5 (M ¼ Os, Ru, Fe). Values in normal font are for M ¼ Fe, in italics for M ¼ Ru and in parentheses are for M ¼ Os.…”