Contribution of the o-carboranyl fragment to the chemical stability and the ~(31)P-NMR chemical shift in closo-carboranylphosphines. Crystal structure of bis(1-yl-2-methyl-1,2-dicarba-closo-dodecaborane)phenylphosphine

摘要

Closo-carboranylphosphines behave differently from closo-monothiocarboranes or other organophosphorus compounds. They tend to lose one boron by reacting with a nucleophile such as OH~- with hydrolysis of the C-P bond. On the other hand, they are less basic than similar organophosphorus compounds, and less reactive both towards oxygen and some metal ions. Many or all of these characteristics can be attributed to the carborane cluster. Its influence on the phosphorus has been revealed by studying the ~(31)P chemical shifts of a series of P(L)R_2 and P(L)_2R phosphines, where L are different carboranyl fragments. If the series P(L)Ph_2 is considered, where a phosphorus atom is surrounded by two phenyl groups and one o-carboranyl moiety carbon bonded to the phosphorus, it is observed that the capacity to shift the ~(31)P-NMR resonances of P(L)Ph_2 to lower field follows the trend: 1-yl-1,2-dicarba-closo-dodecaborane > 1-yl-2-phenyl-1,2-dicarba-closo-dodecaborane > 1-yl-2-methyl-1,2-dicarba-closo-dodecaborane. These trends are valid for any P(L)R_2 series tested so far. It is also found that the absolute value of the ~1J(P-C(1)) coupling constants, where C(1) is the cluster carbon bonded to P atom, also displays the same trend. The molecular structure of bis(1-yl-2-methyl-1,2-dicarba-closo-dodecaborane)phenylphosphine is presented in this paper.