Robert C. Dobbie

Reactions of Me3P, Me3N and R2NH with the small closo-carboranes C2BxHx+2) (x = 3, 4, 5)

Abstract The reactivity of the small carboranes with Me3L (L = P or N) follows the order 1,5-C2B3H5 > 1,6-C2B4H6 > 2,4-C2B5H7. The smallest cage forms unstable adducts whereas 1,6-C2B4H6 gives the dipolar Me3Lue5f8C2B4H6-. The largest cage does not react with Me3L, but Me2NH readily cleaves C2B5H7 to give Me2NH - BH3, a nonvolatile polymer which probably has the basic structure A, Me2NBHMe, and other volatile products that can formally be accounted for in terms of a disproportionation of the latter compound.

Reactions of closo-1,5-C2B3H5 with Cl2 and with BMe3

Reaction of closo-1,5-C2B3H5 with Cl2 under reduced temperatures in an inert solvent gives 2-Cl-1,5-C2B3H4. Using a hot/cold reactor a mixture of BMe3 and 1,5-C2B3H5 is converted to a combination of B-mono-, di-, and tri-methyl derivatives of this smallest closo carborane. In addition, B-mono-, di-, tri-, and tetramethyl derivatives of 2,2-C2B3H4ue5f8C2B3H4, as well as the parent dimer, are produced.

Trifluoromethylphosphine complexes of tricarbonylnitrosylcobalt

The reaction of P(CF3)nX3–n(L; n= 1 or 2, X = F, Cl, Br, or I) with [Co(CO)3(NO)] at room temperature gives [Co(CO)2(NO)L] as the major product in ail cases except P(CF3)I2. The chloro- and fluoro-phosphines can additionally form [Co(CO)(NO)L2] and the fluorophosphines give intermediates of sufficient thermal stability to allow total substitution of CO under more forcing conditions, giving [Co(NO)L3]. Exchange reactions between free ligand (L′) and the co-ordinated phosphine (L) in [Co(CO)2(NO)L] enable the construction of the following displacement series: P(CF3)F2∼ P(CF3)F > P(CF3)Cl2∼ P(CF3)2Cl > PBr(CF3)2 > P(CF3)H2 > P(CF3)2I > PBr2(CF3). The reactivity of the P–X bond in the co-ordinated phosphines is much lower than that in the corres-pondingfree phosphine.

Reactions of a terminal phosphido-group in an organoiron complex. Part III. Complexes containing two metal atoms with a single phosphido-bridge

The phosphido-complex [Fe(cp)(CO)2{P(CF3)2}](L)(cp =η-cyclopentadienyl) acts as a Lewis base towards metal carbonyls and nitrosyls, forming the monosubstituted complexes [Ni(CO)3L], [Co(CO)2(NO)L], [Fe(CO)(NO)2L], [Fe(CO)4L], [Mn(CO)3(NO)L], and trans-[Mn(CO)4(H)L]. With [Co2(CO)8], (L) forms the tetranuclear complex [Co2(CO)6L2]. I.r. studies suggest that the donor–acceptor ability of (L) is intermediate between that of triarylphosphines and trialkyl phosphites. In the i.r. spectra, [Co(CO)2(NO)L] and [Mn(CO)3(NO)L] show more than one ν(NO) band and additional ν(CO) bands compared to the other complexes, the presence of which is attributed to rotational isomerism about the P–Co and P–Mn bond respectively.

Hydrolysis and methanolysis of the small closo-carbaboranes 1,5-dicarbapentaborane, 1,6-dicarbahexaborane, and 2,4-dicarbaheptaborane. The preparation of 1,3,5-triborapentane derivatives, (RO)2BCH2B(OR)CH2B(OR)2(R = Me or H)

The order of reactivity toward methanol and water for three small closo-carbaboranes is B3C21,5H5 > B5C22,4H7 > B4C21,6H6. The smallest carbaborane reacts rapidly with both reagents to form initially the triborapentane. (RO)2BCH2B(OR)CH2B(OR)2(R = Me or H). The other two carbaboranes give smaller cleavage products, B(OR)3, BMe(OR)2, and (RO)2BCH2B(OR)2. The mass spectra of (MeO)2BCH2B(OMe)CH2B(OMe)2 and (MeO)2BCH2B(OMe)2 are discussed.

Preparation and properties of iodo(trifluoromethyl)phosphine and exchange reactions of some simple trifluoromethylphosphines

Iodo(trifluoromethyl)phosphine, F3CP(H)I, can be prepared by the reaction of iodine with F3CPH2, or by exchange between F3CPH2 and F3CPl2 with which it is in equilibrium. Chlorine reacts with F3CPH2 to give F3CP(H)Cl, (F3CPH)2, and HCl. Replacement reactions of iodine in F3CP(H)I with silver(I) and mercury(II) halides lead to the preparation of mixtures containing F3CP(H)Cl and of pure F3CP(H)Br. With Ag[CN] and Hg[CN]2, F3CP(H)I gives (F3CP)4 and F3CP(CN)2 respectively; in the latter case there is evidence for a mercury–phosphorus intermediate. The diphosphane (F3CPH)2 can be prepared by reduction of F3CP(H)I with mercury or by its reaction with SbF3, CdF2, or NaF. Reactions between all possible pairs of compounds F3CPX2–F3CPY2(X or Y = F, Cl, Br, I, H, or CN) give the mixed species F3CP(X)Y, characterised by n.m.r. spectroscopy, in all cases except when X = F and Y = H, I or CN, although the reaction is often more complex than simple exchange. The vibrational spectra of F3CP(H)X and F3CP(D)X (X = Br or I) have been analysed in terms of group vibrations.