The adducts 2D,B,C14 are formed by direct reaction of diboron tetrachloride with D = Me,N, C,H,N, MeCN, and HCN; these are involatile and thermally stable and do not react with olefins. Addition of hydrogen chloride can give diborates, e.g., ~e,NH], [B,Cl,], and the methyl cyanide adduct adds trimethylamine with only partial displacement of the cyanide, suggesting formation of [Me,N],[B,Cl,(CN),]. With D = (CH,*NMe,),, a 1: 1 adduct is formed which is polymeric; with D = N,H4, NH,*NMe,, and (CH,*NH,) 2, elimination of hydrogen chloride as the hydrochloride follows donation and polymeric B-N compounds containing boron-boron bonds are formed. D = Me,NH gives a mixture of B(NMe,),, B,(NMe,),, and polymeric BNMe,.PREVIOUS studies of the reactions of diboron tetrachloride with ammonia and amines and with cyanogen have shown that both boron atoms act as acceptors, giving 2 : 1 adducts. When the donor molecule contains reactive hydrogen, elimination of hydrogen chloride as the hydrochloride of the donor base follows, e.g. :We now report the reactions of diboron tetrachloride with both mono-and bi-dentate nitrogen-donor molecules.
EXPERIMENTALDonor substances were prepared (where necessary) by conventional methods and purified by fractionation in the vacuum-system. In a typical reaction, measured amounts of diboron tetrachloride and the donor were mixed a t liquid-nitrogen temperature and the mixture was allowed to warm until reaction was observed (usually at the m. p. of the donor) ; the reaction temperature was kept as low as possible to minimise decomposition of the unchanged diboron tetrachloride. Decomposition was, however, often catalysed by the donor, and hence precise reaction ratios could not always be observed. When reaction was complete, the excess of donor was removed and measured, together with any volatile products which were separated and identified. The reaction product was examined (a) by hydrolysis in a sealed tube (evolved hydrogen and chloride ion were determined, but accurate boron determinations were usually nullified by interference of the donor base in the titrations), (b) by heating it in a sealed tube, volatile products being removed as before, (c) by addition of ethylene or but-2-ene, and ( d ) by addition of hydrogen chloride or trimethylamine. The decomposition of diboron tetrachloride during reaction with a donor yielded boron trichloride and polymeric BCl, the latter being red or yellow; separate experiments indicated that the rate of reaction of (BCl). with a donor was negligibly slow under the conditions used. Hence the main product was contaminated with small amounts of the donor-boron trichloride adduct and with (BCl),. Reaction of an excess B,CI, + 8Me,NH + B,(NMe,), + 4Me,NH,HCI Diboron tetrachloride was prepared and purified as previously described .3Urry, Wartik, Moore, and Schlesinger,
