The gas-phase ion chemistry of cyanamide (1) has been investigated by EI, positive- and negative-ion CI, ICR,\ud MIKE, and CAD mass spectrometry, as well as by theoretical calculations at the Gaussian-1 level. Attention\ud has been focused on the CH2N2'+ molecular ion, on the structure and the relative stability of the conjugate\ud acids of 1, and on the HNCN- ion. The experimental proton affinity (PA) of 1, 194.5 f 2 kcal mol-', deduced\ud from ICR equilibrium experiments is consistent with the Gaussian-1 value, 191.7 f 2 kcal mol-', which refers\ud to formation of the most stable protomer, identified as the HzN-CNH+ ion having the structure of cyanamide\ud protonated at the N atom of the cyano group. Calculations performed at the MP4/6-3 1 lG**//MP2/6-3 lG* + ZPE (RHF/6-3 1G*) level of theory have identified two additional protomers, having the structure of cyanamide\ud protonated at the amino group and at the C atom, less stable by 22.4 and 54.0 kcal mol-', respectively, than\ud the most stable HzN-CNH+ species. From the stability difference between cyanamide and carbodiimide, the\ud PA of the latter is estimated to be 198.1 f 2 kcal mol-'. The results of experiments aimed at evaluating the\ud acidity of 1 by the ICR equilibrium method give a gas-phase PA of the [HNCNI- anion of 349.8 f 4 kcal mol-',\ud in excellent agreement with the Gaussian-1 theoretical value of 347.8 * 2 kcal mol-'

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Gaseous (FCN)H+ ions were obtained by protonation of cyanuric fluoride by strong Brønsted acids such as H3 + (D3 +) and C n H5 + (n = 1, 2), and their structure and reactivity were examined by FT-ICR mass spectrometry and computational methods at the G2 level of theory. The results show that FCNH+ is considerably more stable than the HFCN+ protomer, the gap amounting to 360 kJ mol-1 at the G2 level. The gas-phase basicity (GB) of FCN was estimated by “bracketing” experiments by measuring the efficiency of H+ transfer from FCNH+ to reference bases. Utilizing a general correlation between the rate and the ΔG° change of the proton-transfer we obtain GB(FCN) = 668.4 ± 10 kJ mol-1, to be compared with the G2 computed GB of 651.8 ± 8 kJ mol-1, both values being referred to N protonation. The reactions of FCNH+ with isolated (C2H4) and conjugated (C6H6) π systems were also investigated. The ion behaves as a FC+ = NH electrophile promoting aromatic cyanation, e.g., yielding C6H5CNH+ from benzene. Consideration is given to the reaction mechanism and its correlation with solution-chemistry cyanation.

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Borate and polyborate anions have been studied in the gas phase by an approach involving, instead of vaporization of preformed ions, gas-phase synthesis of increasingly complex polyanions by stepwise addition of H3B03, followed by H 2 0 loss, to H2BO3-, obtained in turn from gaseous H3BO3 via dissociative electron attachment or by suitable ion-molecule reactions. Chemical ionization and ion-cyclotron resonance techniques demonstrate the formation, in addition to BO2-and H2BO3-, of polyanions belonging to three different classes, (Hn-~B,,Ozn)-, (Hn+lBn02n+l)-, and (H,,+3BnOzn+2)-, containing up to 11 B atoms. The results provide the first evidence for the existence as discrete entities in the gas phase of free polyanions, e.g., the triborate ion H4B307-and the pentaborate ion H4BSOIO-, whose salts exist in solid borates and in solution. Furthermore, previously unknown anions have been obtained, including gaseous HZBOs-, H&Os-, HsB409-, etc. The character of the H3BO3 acidity changes in passing from solution to the gas phase. In solution H3BO3 behaves exclusively as a Lewis acid, giving B(0H)d-upon ionization, whereas in the gas phase it behaves instead as a Bransted acid, as shown by the formation of its conjugate base H2BO3-and by its gas-phase Bransted acidity, 354 f 4 kcal mol-', typical of a relatively weak gaseous acid whose strength is comparable to that of HClO.