Title: The Case of "of"-Insertion 

Consider the illicit derivation in (1), comparing it to the grammatical (2).

(1) * [The gallery]i seemed [to [[the patrons] ti]] that the painting was a masterpiece.
(2) It seemed [to [the patrons] [of [the gallery]]] that the painting was a masterpiece.

The NP [[the patrons] [the gallery]] would under ordinary circumstances be converted to "the patrons of the gallery" by "of"-insertion. In (1), however, rather than receiving Case by "of"-insertion, the complement of N raises to a finite subject position in the same clause. All theta-roles are discharged appropriately and every NP receives case.

It is not difficult to come up with plausible reasons why (1) should be illicit, but it is not obvious which is correct. We will summarize some of the possibilities.

One approach would be to formulate "of"-insertion as a cyclic rule that must obligatorily have applied by the time a complex NP is complete. This would force insertion of  "of" before [NP the gallery] is able to raise to the matrix [Spec,TP], freezing it in place. A variant of this approach would take patrons to select/subcategorize for an  "of" PP directly, though one might question whether a selection/subcategorization violation could be sufficient to account for the severe deviance of (1) under the relevant interpretation. Another alternative would be to assume, following Chomsky (1986), that "of" marks an inherent Case which must obligatorily be assigned.

It is possible that raising of [NP the gallery] violates some formulation of the A-over-A constraint. In order to incorporate such a constraint into modern Minimalist theories, we would have to commit to the existence of "defective intervention" constraints, since the complex NP (having already received Case) could not itself raise to the matrix subject position.

In a similar vein, raising of [NP the gallery] could be taken to be a complex NP constraint violation. The formulation of a suitable constraint is a delicate matter, given the possibility of wh-movement out of the complement of "picture" NPs. It may be, as argued in Chomsky (1977, 113-114), that extraction out of PP complements of N depends on prior extraposition of the PP. Since there is no PP in (1), extraposition could not apply, so there would be no way of obviating the complex NP constraint.

A final possibility would be to appeal to the traditional idea that "it" in (2) is underlyingly an associate of the embedded clause. In modern terms, "it" would originate as a double of the clause and would raise to matrix [Spec,TP] to acquire Case (either for its own sake, or in order to "transmit" Case to its associate). In (2) this movement can proceed without obstacle, but a similar movement would be blocked in (1) by the NP "the gallery". On this account, the offending element would not be the chain headed by [NP the gallery], but rather some portion of the doubling constituent (either the clause or its NP associate).

References:
Chomsky, N. 1977. "On Wh-Movement." In Cullicover, P. W., Wasow, Thomas and Akmajian, Adrian (eds.), "Formal Syntax," New York: Academic Press.

Chomsky, N. 1986. "Knowledge of Language." New York: Praeger.